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The MyMass
mass photometer enables researchers to quickly verify sample quality before proceeding to cryo-EM, native MS, BLI, SPR and other demanding experimental workflows.
Compact, all-in-one mass photometer helps researchers verify sample quality before proceeding to cryo-EM, native MS, BLI, SPR, and other costly experiments.
Oxford, UK – 18 March 2026 – Refeyn, developer of pioneering mass photometry technology, announces the launch of MyMass mass photometer (MyMassMP), a compact instrument designed to answer a critical research question: Is the sample good enough for further analysis?
Structure-based drug design and AI-driven therapeutic development are transforming how new medicines are discovered, but depend on high-quality samples. Structural and biophysical workflows, such as cryo-EM, native mass spectrometry (MS), bio-layer interferometry (BLI), and surface plasmon resonance (SPR), are time-consuming and costly, and poor sample quality remains one of the main reasons they fail. MyMassMP gives researchers a fast, accurate assessment of purity, homogeneity, and oligomerization state in solution before committing to resource-intensive experiments.
Built on the same proven technology as Refeyn’s TwoMP mass photometer, which is already trusted across leading structural biology and biotherapeutics labs worldwide, MyMassMP brings this quality check capability into a simpler, self-contained benchtop instrument. Featuring an integrated display and computer for onboard data analysis, and dedicated consumables, it offers an intuitive workflow from sample to result.
“Structural biology and AI-driven drug discovery are moving fast, but they’re only as good as the samples that drive them. MyMassMP directly addresses that challenge and marks a significant step forward for Refeyn, putting the power of mass photometry within reach of more researchers than ever before,”
– Gerry Mackay, Refeyn CEO
“In recent years, our users have consistently shown us how valuable mass photometry is for quickly assessing sample quality before committing to more complex experiments. With MyMassMP, we’re making this capability even more accessible – empowering researchers to confidently answer a simple but critical question: Are my samples ready?”
– Fiona Coats, Chief Product and Marketing Officer at Refeyn
MyMassMP is available now. Learn more at: refeyn.com/mymass
About Refeyn
Refeyn (www.refeyn.com) specializes in the development, production, and distribution of mass photometry for industry and academia. Enabling accurate mass measurement of single molecules in their native state, and without labels, Refeyn’s products deliver crucial analytics faster and use less sample than conventional methods. The company’s vision is to accelerate discovery through innovation, empowering the latest scientific breakthroughs in basic research and transforming biotherapeutic development and manufacturing.
Contact:
Catie Lichten – Scientific Communications Manager
[email protected]
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]]>The post Leading CROs and CDMOs turn to mass photometry for rapid protein, mRNA and viral vector analytics appeared first on Refeyn.
]]>As CROs and CDMOs expand their role in biopharma development and manufacturing, fast, accurate bioanalytic technologies remain critical to biotherapeutic affordability
Refeyn’s Samux benchtop mass photometer enables rapid analysis of adeno-associated virus (AAV) samples.
Oxford, UK – 2 March 2026 – Refeyn, developer of pioneering mass photometry technology, expands its global adoption across contract research organizations (CROs) and contract development and manufacturing organizations (CDMOs). To showcase this development, Refeyn has launched a new webpage that highlights how leading CROs and CDMOs are redefining process development and manufacturing workflows with mass photometry, and provides researchers with an interactive tool to locate and partner with these organizations.
Mass photometry’s rapid adoption reflects rising demand for fast, reliable, and cost-effective analytics for protein and mRNA characterization, antibody development, and viral vector analysis. Introduced just eight years ago, the technology is now cited in nearly 1,500 scientific publications and is used by 90% of top biopharma companies. With GMP-compliant software for AAV analytics and recognition from regulatory bodies – including the US Pharmacopeia, China’s NIFDC, and the British Pharmacopeia – mass photometry can be deployed confidently from early development through manufacturing and QC.
Leading CROs and CDMOs use mass photometry to deliver rapid, label-free insights into critical quality attributes – AAV capsid purity (full/empty/partial ratios), mRNA integrity and purity– and emerging antibody modalities. This enables clients to make earlier, better-informed development decisions while reducing sample consumption and turnaround times, tackling analytical challenges that are difficult with traditional methods.
“Adding mass photometry to the analytical panel reduces the overall cost of new therapies by accelerating development and manufacturing,” said Gabriella Kiss, PhD, Director of Market Development at Refeyn. “By working with partners around the world, we’re expanding access to this technology – whether organizations invest in their own instruments or use trusted service providers – ultimately helping shorten the path from discovery to patients.”
CROs and CDMOs can partner with Refeyn to differentiate their analytics and meet growing demand for faster, higher-quality data, while biopharma teams can access mass photometry through the expanding partner network.
To learn more about Refeyn’s CRO/CDMO partnerships and discover how CROs and CDMOs are using mass photometry, visit: https://refeyn.com/cro-cdmo-mass-photometry-services.
Register to meet one of our partners, Franklin Biolabs, in an upcoming webinar, Accelerating GMP Quality Control with Mass Photometry from Development to Release – presented by Ray Zhang, Associate Director, QC Analytics on Thursday, March 26, 2026.
About Refeyn
Refeyn Ltd. (www.refeyn.com) specializes in the development, production, and distribution of mass photometry for industry and academia. Enabling accurate mass measurement of single particles in solution, in their native state, and without labels, Refeyn’s products deliver crucial analytics faster and use less sample than conventional methods.
The company’s vision is to accelerate discovery through innovation, empowering the latest scientific breakthroughs in basic research and transforming biotherapeutic development and manufacturing.
Applications of mass photometry include: Characterization of sample purity and heterogeneity, adeno-associated viral (AAV) vector empty/full analysis, assessment of protein oligomerization and interactions, analysis of antibody aggregation and binding, and mRNA sample characterization.
For more information, contact:
Catie Lichten – Scientific Communications Manager, Refeyn
[email protected]
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]]>The post Comparing analytical approaches for AAV characterization (2026) appeared first on Refeyn.
]]>This post was first published in March 2023
Updated on 20 February 2026
Adeno-associated virus (AAV) sample characterization is critical for research, development, and manufacturing processes of gene therapies that involve these viral vectors (Fig. 1). At Refeyn, we have developed the Samux line of mass photometry products specifically for AAV analysis, featuring the SamuxMP and SamuxMP Auto mass photometers as well as dedicated consumables.
Here, we discuss the pros and cons of mass photometry when compared to other frequently used methods for AAV analytics, including electron microscopy (EM), analytical ultracentrifugation (AUC), charge detection mass spectrometry (CDMS), quantitative polymerase chain reaction (qPCR) combined with enzyme-linked immunosorbent assay (ELISA), and size exclusion chromatography combined with multi-angle light scattering (SEC-MALS). We aim to provide a straightforward overview of the key analytical techniques used in the AAV space, so you can understand how mass photometry would fit into your AAV analytics toolbox.
Figure 1. AAV samples can contain a mixture of different species. The main impurities in AAV samples are capsids with no genome content (empty) or that contain an incomplete copy of the recombinant DNA (partially filled). Other impurities like capsid fragments, free nucleic acids, and protein contaminants can be detected in the lower mass ranges. Finally, AAV samples may also contain higher-mass, overfilled capsids, which are still being investigated and are generally treated as impurities unless explicitly defined as part of the product.
Outline
How do AAV analysis techniques compare in terms of speed?
Sample characterization can become a bottleneck in AAV development processes. As a result, one practical consideration when choosing between AAV analysis methods is the time each measurement takes.
Techniques like CDMS, EM, and AUC deliver high-quality data, but their long turnaround times can slow development and hold up manufacturing decisions [1]–[4]. Others, like qPCR/ELISA or SEC-MALS, are significantly faster and are frequently used when time is a factor. Mass photometry is currently the fastest available technique for AAV analysis. Individual mass photometry measurements take less than five minutes, and the automated mass photometer SamuxMP Auto runs 24 samples in as little as 90 minutes without user intervention.
Mass photometry’s speed makes it practical not only for characterization, but also for at-line decision-making during process development and manufacturing, enabling rapid screening of conditions, timely fraction selection in downstream purification, faster troubleshooting, and tighter process control without adding delays to the workflow (Fig. 2).
Figure 2. Mass photometry provides valuable information throughout downstream AAV purification processes. At multiple purification stages, mass photometry can be used to quantify empty, partially filled, full, and overfilled capsids, as well as other impurities, enabling rapid, at-line checks across key unit operations during development and manufacturing.
Which AAV analysis techniques are best suited for in-house implementation?
Equipment, running costs, and expertise requirements are all important to consider when evaluating the suitability of an AAV analytical method for a given environment. Among frequently used techniques, both AUC and EM require specialized equipment and highly trained operators to acquire and analyze data. As a result, these techniques are often outsourced and/or reserved for specific characterization studies and later-stage release assays.[1]–[5].
Other AAV characterization approaches, such as qPCR-ELISA, SEC-MALS, and CDMS, can be run on benchtop instruments, which makes them easier to implement [1]–[4], [6], although CDMS requires an advanced native mass spectrometer and considerable expertise for instrument calibration, experimental set-up and data analysis.
Mass photometers fit on a benchtop, require as little as one day of training to operate (Fig. 3), and have running costs of less than $5 per measurement. This makes mass photometry easy to implement in-house for readily available AAV analytics.
Figure 3. Loading a sample onto a mass photometer. Only basic lab skills are required to use mass photometry. An operator simply pipettes the sample onto a sample carrier slide.
Which analytical technologies simplify the analysis of different AAV serotypes?
If your AAV development and manufacturing processes regularly include multiple capsid serotypes, it is necessary to consider whether that could affect your analytical workflow protocols. AAV characterization methods that depend on high molecular specificity, such as qPCR-ELISA or affinity chromatography, must be optimized for each serotype.
By contrast, methods based on intrinsic physical properties such as hydrodynamic size or particle mass tend to transfer more easily across AAV serotypes and typically require only modest method tuning compared to the methods mentioned above. These approaches include SEC-MALS, AUC, EM, CDMS, and mass photometry. Among them, mass photometry generally requires the least re-optimization across serotypes (Fig. 4)
Figure 4. Mass photometry accurately measures AAVs of different serotypes. These data from Wagner et al. (2023) [7] show how mass photometry and AUC output comparable results when quantifying empty, full, partially filled, and overfilled capsids of three different serotypes: AAV5 (a), AAV8 (b), and AAV9 (c). Measurements were taken on SamuxMP.
How do different techniques handle upstream AAV sample analysis?
Monitoring vector production, quality, and process performance during cell culture and harvest enables earlier decisions that reduce risk to development and production. Some analytical techniques, like ELISA/qPCR, can work on crude samples with minimal preparation. Others, like CDMS, EM, SEC-MALS, and AUC, require some sample processing before they can be applied. Mass photometry can also be used to get critical insights into crude AAV samples, with the added advantage that MP is compatible with quick cleanup protocols that take only 1 to 3 hours (in comparison to 24 hours for AUC).
Figure 5. Mass photometry can be used for upstream AAV characterization. Mass photometry analysis of a crude AAV sample during upstream processing (A) and after a simple cleanup step (B). The histograms show the mass ranges of empty (E), partially filled (P), and full (F) capsids. AAV capsids could not be resolved in the crude sample but could be quantified after the cleanup step. These data were collected by Généthon with SamuxMP.
What analytical techniques can resolve partially filled and overfilled AAVs?
In addition to empty and full AAVs, preparations may include capsids that contain genetic contaminants, such as truncated copies of the intended cargo or fragments of host cell DNA. These fragments are often smaller than the intended cargo, so the AAV capsids containing them are only partially filled in comparison to the ‘full’ capsids in the sample.
Capsids may also be overfilled – containing more cargo than is intended. To determine whether a sample contains partially filled or overfilled AAV capsids, it is important to choose a technique with enough resolution to differentiate capsids that differ in mass. Bulk analysis techniques such as qPCR-ELISA and SEC-MALS do not have this capability, as they measure average properties across the whole sample. Electron microscopy techniques, on the other hand, struggle to resolve the small electron density differences needed to identify heterogeneously loaded capsids [1], [3], [4], [6].
In contrast, AUC, CDMS, and mass photometry (Figs. 4 and 5) characterize the different species in a sample individually at high resolution, enabling detection of populations of empty, partially filled, full, and overfilled capsids [1]–[6]. In terms of accuracy, both AUC and CDMS are considered to have slightly higher mass resolution and lower variability than MP analysis, but results are seen as broadly comparable between the techniques, with MP having a practical advantage due to its fast measurements and ease of use [5], [7], [8].
What AAV analysis techniques can be implemented in GMP environments?
For processes involved in drug manufacturing, regulatory agencies establish a series of regulations known as good manufacturing practices (GMP), such as Title 21 CFR 11 by the US Food and Drug Administration (FDA) or GMP Annex 11 by the European Union. GMP compatibility is an important consideration when choosing your favorite AAV analysis technique, as it will continue to support your processes once you reach the manufacturing stage. Mass photometry, SEC-MALS, and qPCR/ELISA are all techniques with full GMP support from their manufacturers. EM and AUC are compatible with GMP, but their instrument manufacturers do not provide GMP-compliant software. Finally, CDMS is, for now, not suitable for use in GMP-regulated environments.
Summary comparison of common AAV analytical methods
Table 1. A summary of the advantages and disadvantages of different methodologies for AAV analytics.
To optimize your AAV development and production processes, it is important to choose AAV characterization technologies that streamline your analytical workflows. Factors to consider when choosing an approach to analyze AAV samples include measurement time, cost, ease of use, and what information it can provide about the capsid populations in the sample.
In this article, we have given an overview of the main techniques available for AAV characterization, comparing them based on their speed, ease of use, and analytical capabilities (see summary in Table 1).
Overall, mass photometry compares favorably to other methods. The information provided by mass photometry is comparable to that of powerful techniques like AUC or CDMS, but with lower time and expertise requirements, lower sample consumption and running costs, and a small instrument footprint. This makes mass photometry a powerful and versatile tool for AAV analytics that can be applied throughout development and manufacturing.
For more information:
To ask questions, get in touch with our mass photometry experts.
Further resources:
USP AAV standards to support quality testing and characterization
In this webinar, Dr. Anthony Blaszczyk (USP) discusses the first AAV reference materials released by the United States Pharmacopeia. In addition, Drs. Paul Getty and Lauren Tomlinson (Pharmaron) talk about Pharmaron’s strategy to use mass photometry for AAV process development and manufacturing.
Measuring AAV genome length with mass photometry
This application note – created in collaboration with AskBio – shows how mass photometry can be used to measure the encapsidated AAV genome length. The app note showcases how the SamuxMP and SamuxMP auto mass photometers easily detect and quantify empty and full AAV populations. You will also see example data from AAV samples of different serotypes showing expected vs measured AAV genome length, highlighting the precision of mass photometry.
Mass photometry in contract research and manufacturing
Refeyn’s mass photometry technology is trusted by research institutions and pharma organizations worldwide, including many CROs and CDMOs. Find out how its suitability for GMP environments and growing acceptance by regulatory authorities make it useful for teams working in process development or manufacturing.
Recent advances in purification techniques have enhanced AAV sample compatibility with mass photometry in upstream development. Watch this webinar to learn how to overcome the limitations of traditional characterization methods (e.g., AUC, SEC-MALS, TEM) and how mass photometry enhances GMP-regulated environments and process optimization.
BioProcess International Featured Report – February 2026
In the article on p17 Ray Zhang and Peter Lehman from Franklin Biolabs present their findings when they compare sedimentation-velocity analytical ultracentrifugation and mass photometry.
References
[1] M. Penaud-Budloo, A. François, N. Clément, and E. Ayuso, ‘Pharmacology of Recombinant Adeno-associated Virus Production’, Molecular Therapy – Methods & Clinical Development, vol. 8, pp. 166–180, Mar. 2018, doi: 10.1016/j.omtm.2018.01.002.
[2] J. C. Grieger, V. W. Choi, and R. J. Samulski, ‘Production and characterization of adeno-associated viral vectors’, Nature Protocols, vol. 1, no. 3, Art. no. 3, Aug. 2006, doi: 10.1038/nprot.2006.207.
[3] A. L. Gimpel et al., ‘Analytical methods for process and product characterization of recombinant adeno-associated virus-based gene therapies’, Molecular Therapy – Methods & Clinical Development, vol. 20, pp. 740–754, Mar. 2021, doi: 10.1016/j.omtm.2021.02.010.
[4] A. K. Werle et al., ‘Comparison of analytical techniques to quantitate the capsid content of adeno-associated viral vectors’, Molecular Therapy – Methods & Clinical Development, vol. 23, pp. 254–262, Dec. 2021, doi: 10.1016/j.omtm.2021.08.009.
[5] E. H. T. M. Ebberink, A. Ruisinger, M. Nuebel, M. Thomann, and A. J. R. Heck, ‘Assessing production variability in empty and filled adeno-associated viruses by single molecule mass analyses’, Molecular Therapy – Methods & Clinical Development, vol. 27, pp. 491–501, Dec. 2022, doi: 10.1016/j.omtm.2022.11.003.
[6] E. A. Green and K. H. Lee, ‘Analytical methods to characterize recombinant adeno-associated virus vectors and the benefit of standardization and reference materials’, Current Opinion in Biotechnology, vol. 71, pp. 65–76, Oct. 2021, doi: 10.1016/j.copbio.2021.06.025.
[7] Wagner C, Fuchsberger FF, Innthaler B, Lemmerer M, Birner-Gruenberger R. ‘Quantification of empty, partially filled and full adeno-associated virus vectors using mass photometry’. International journal of molecular sciences. Jul. 2023, 3;24(13):11033. https://doi.org/10.3390/ijms241311033.
[8] Townsend JA, Li S, Sweezy L, Liu N, Rosconi MP, Pyles EA, Zhi L, Liu D, Wu Z, Qiu H, Shameem M. Comparative analysis of empty and full adeno-associated viruses under stress conditions by anion-exchange chromatography, analytical ultracentrifugation, and mass photometry. Journal of Pharmaceutical Sciences. Feb. 2025;114(2):1237-44. https://doi.org/10.1016/j.xphs.2025.01.005.
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]]>Monitoring AAV quality in upstream workflows has historically been limited by slow or downstream-only analytical methods. Mass photometry overcomes these barriers through single-particle mass measurement in solution, providing detailed capsid composition – including partially filled and overfilled species — in minutes. This infographic outlines how upstream implementation supports better process control, reduces batch variability, and enhances overall product quality. If you have any questions then please contact us – we’re always here to help.
Further resources:
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Refeyn’s SamuxMP benchtop mass photometer enables rapid analysis of adeno-associated virus samples. Image courtesy of Refeyn Ltd.
Oxford, UK – 26 January 2026 – Refeyn, the company behind pioneering mass photometry technology, has been named in The Sunday Times 100 Tech 2026, an annual ranking of the fastest-growing private technology companies in the UK.
The Sunday Times 100 Tech list recognizes companies based on three-year revenue growth, highlighting businesses that have demonstrated sustained commercial momentum and technological impact. Refeyn ranked 39th in the hardware category, reflecting revenue growth of approximately 40% over the last three years.
The ranking places Refeyn among a cohort of high-growth UK technology firms spanning sectors including the life sciences, energy and sustainability, telecommunications, and digital technology.
“Being recognized in The Sunday Times 100 Tech list is an important milestone for the company,” said Gerry Mackay, Refeyn’s CEO. “It reflects the impact our technology has had, the trust we have established among our customers, and the dedication of our staff as we continue to build the business.”
“This recognition validates our focus on delivering meaningful value to the scientists using our tools – across academia, contract research and manufacturing, and biopharma,” added Fiona Coats, Refeyn’s Chief Product and Marketing Officer.
Spun out of Oxford University in 2018, Refeyn develops bioanalytical instruments that feature its innovative mass photometry technology. The company works with customers in academia and industry – including in the development and manufacturing of mRNA, cell and gene, and antibody therapeutics. Mass photometry has been widely adopted and has been used in more than 1,400 scientific publications. Refeyn is headquartered in Oxford, UK, with a US headquarters in Waltham, Massachusetts, and additional sites across Europe, Asia and the US.
The Sunday Times 100 Tech recognition follows on Refeyn’s announcement earlier this month that they had been recognized as a Top Employer for 2026 in the UK.
About Refeyn
Refeyn Ltd. (www.refeyn.com) specializes in the development, production, and distribution of mass photometry for industry and academia. Enabling accurate mass measurement of single particles in solution, in their native state, and without labels, Refeyn’s products deliver crucial analytics faster and use less sample than conventional methods.
The company’s vision is to accelerate discovery through innovation, empowering the latest scientific breakthroughs in basic research and transforming biotherapeutic development and manufacturing.
Refeyn has been recognized for its unique approach to biomolecular analysis through multiple awards, including in the Royal Society of Chemistry Emerging Technologies Competition. It has recently been recognized as a Top Employer in the UK and accredited as an Inclusive Employer.
Applications of mass photometry include: Characterization of sample purity and heterogeneity, adeno-associated viral (AAV) vector empty/full analysis, assessment of protein oligomerization and interactions, analysis of antibody aggregation and binding, and mRNA sample characterization.
For more information, contact:
Catie Lichten – Scientific Communications Manager, Refeyn
E: [email protected];
T: +44 (0)1865 800 175
Or
Ric Kositzke – Senior Director, Marketing, Refeyn
E: [email protected];
T: +1 (971) 368-1755
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Oxford, UK – 15 January 2026 – Today, Refeyn Ltd is pleased to announce it has been recognized as a Top Employer in the UK for 2026 by Top Employers Institute. The Certification demonstrates Refeyn’s ability to create a high-performing workplace through data-driven people strategies, independent validation, and a clear focus on practices that drive business performance, employee engagement and growth.
Active in 131 countries/regions, Top Employers Institute is the global authority in HR certification, benchmarking and advisory. Its Programme certifies organisations based on the results of its HR Best Practices Survey which covers six domains including People Strategy, Work Environment, Talent Acquisition, Learning, Diversity, Equity & Inclusion, and Wellbeing.
Top Employers Institute CEO Adrian Seligman commented: “Achieving a Country Top Employer Certification for 2026 reflects Refeyn’s dedication to building an outstanding workplace that enables sustained business performance. Their strong alignment between people strategy and organizational goals, combined with a commitment to continuous improvement, demonstrates the impact of their transformative practices. We are proud to recognize Refeyn for their meaningful contribution to a better world of work in the UK.”
The Country Certification gives organizations access to globally benchmarked insights, data-driven recommendations, expert validation, and proven best practices to strengthen their people strategy. Certified companies benefit from enhanced employer branding, clearer strategic focus, improved decision making, and a stronger ability to demonstrate impact to leaders, boards and talent markets. They also gain opportunities to connect with a global community of certified Top Employers.
In 2025, the Programme certified and recognized nearly 2,500 Top Employers in 131 countries/regions, positively impacting over 14 million employees globally.
Editor’s notes
About Top Employers Institute
Top Employers Institute is the global authority on recognizing excellence in People Practices. We help accelerate these practices to enrich the world of work. Through the Top Employers Programme, participating companies can be certified and recognized as an employer of choice. The certification is awarded to organizations based on the participation and results of the HR Best Practices Survey covering six HR domains consisting of 20 topics such as People Strategy, Work Environment, Talent Acquisition, Learning, Diversity & Inclusion, and Wellbeing.
In 2025, Top Employers Institute certified nearly 2,500 organizations in 131 countries/regions. These certified Top Employers positively impact the lives of over 14 million employees globally.
About Refeyn
Refeyn Ltd. specializes in the development, production, and distribution of mass photometry for industry and academia. Mass photometry and macro mass photometry are unique bioanalytical technologies pioneered by Refeyn. By quantifying light scattering from particles in solution, mass photometry enables mass measurement at the single-particle level while macro mass photometry enables simultaneous measurement of viral vector size and contrast (a proxy for mass).
Spun out of Oxford University in 2018, the company aims to make its technology accessible to all in the scientific community, enabling users to achieve new and better outcomes. Refeyn has been recognized for its unique approach to biomolecular analysis through multiple awards, including the Royal Society of Chemistry Emerging Technologies Competition. Applications of mass photometry include: Characterization of samples of biomolecules and adeno-associated viral (AAV) vectors, and analysis of protein oligomerization, biomolecular interactions, and antibody aggregation. Utilizing mass photometry and macro mass photometry, Refeyn’s products are capable of accurate analysis of single particles in solution, in their native state, and without the need for labels, opening up new possibilities for bioanalytics.
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]]>Mass photometry and macro mass photometry are powerful bioanalytical techniques that are being adopted across the life sciences. From academic researchers to CDMOs and leading biopharma companies, many have harnessed mass photometry technologies to gain vital information about their samples. Could they make a difference for you, too? Read on to learn about key applications and comparisons to other technologies.
Mass photometry technologies are based on the principle of interferometric scattering microscopy. They measure the interference between the light reflected by a glass surface (e.g. a coverslip) and the light scattered by particles in contact with the surface. Mass photometry and macro mass photometry each work slightly differently but, at their core, what they both offer is simple:
They report the different particle populations in your sample and their relative proportions in solution, with no labels or complex prep, and using up little of your valuable time or sample.
The information provided by mass photometry technologies can be valuable in a very broad range of situations, as it can readily detect impurities, oligomerization, capsid loading, aggregates or complexes with different stoichiometries. There are a number of applications where the unique strengths of mass photometry technologies really shine. Let’s look at several use cases and what mass photometry technologies offer for each, and how they overcome challenges that other techniques struggle to address.
1. Protein-protein interactions
The study of protein-protein interactions can be challenging, as they often involve multiple components, complex, dynamic equilibria or a high sensitivity to experimental conditions.
Why use mass photometry?
Mass photometry is a powerful tool for analyzing protein-protein interactions. Unlike techniques like size-exclusion chromatography (SEC) and biolayer interferometry (BLI), it works in solution with no columns or immobilization.
Mass photometry provides single-particle information rather than the bulk information reported by techniques such as dynamic light scattering (DLS), providing high-resolution information on complex formation, oligomerization behavior, stoichiometry and binding affinity.
The preparation for mass photometry measurements requires only a simple dilution to nanomolar concentrations. This captures the behavior of proteins in native-like concentrations and avoids the denaturation induced by SDS-PAGE. If measurements at higher concentrations are needed, the MassFluidix HC microfluidics add-on can be used to measure samples in the micromolar concentration range.
Finally, as mass photometry measurements are fast and consume little sample, it is easy to quickly test different experimental conditions.
Case study
This paper explains in detail how to use mass photometry to determine the mass distribution of a protein sample, revealing the complexes formed and relative abundance of each species, and, accordingly, the dissociation constant(s) (KD) of interactions.
Mass photometry measurement of interactions between protein A, human IgG and Bovine IgG. Panel A shows the overlapped individual measurements for each species, panel B shows overlapped measurements of 1:1 mixes of protein A and human IgG or bovine IgG. Mass photometry detects each individual species and the multiple human IgG-protein A complexes. As expected, bovine IgG does not bind to protein A and shows a small number of aggregates. Figure 1 from Kofinova et al. (2024).
2. Structural biology
Cutting-edge analytical techniques for structural biology such as cryo-EM are amazingly powerful, revealing intricate details about protein structure and interactions. However, instrument time is very valuable, and sample preparation is tricky, so it is critical to make sure proteins are monodisperse and in their desired oligomeric state before the measurement.
Why use mass photometry?
Mass photometry reports purity, stability and oligomeric states of samples with low time and sample volume requirements. The information it provides is on par with negative-stain electron microscopy (nsEM), and more detailed than techniques like SEC, DLS and SDS-PAGE. In addition, mass photometry requires very little time and sample, making it an ideal way to check samples before using precious cryo-EM time.
Case study
Protein quaternary structures in solution are a mixture of multiple forms (Marciano et al., 2022)
The authors of this paper evaluated the oligomeric state of 17 different bacterial proteins across a broad range of protein concentrations and solutions by native mass spectrometry, mass photometry, SEC, and small-angle X-ray scattering (SAXS), finding that most exhibit several oligomeric states at the same time. For approximately half of the proteins, the predicted oligomeric forms described in publicly available databases underestimated the complexity of protein quaternary structures in solution.
3. mRNA characterization
mRNA is the active payload for many gene therapies, but therapeutic mRNA sequences are difficult and expensive to produce. They require careful characterization to ensure the final product is safe and effective. As mRNA molecules are highly charged and quite large compared to most biologics, their analysis can be challenging.
Why use mass photometry?
Mass photometry can readily measure mRNA molecules and report on key attributes of the sample. As it reports the mass distribution of particles in the sample, it provides an overview of the lengths of the mRNA molecules present. A key advantage is that it can be used for mRNA of up to ~10,000 bases in length or more, depending on characteristics of each sample and buffer. A mass photometry measurement quickly shows if the transcript is intact and detects impurities such as aggregation or dsRNA. As it is fast, consumes little sample and has low operating costs, mass photometry enables frequent, at-line characterization of mRNA products without slowing down critical processes.
Case study
This paper reports on the use of mass photometry to directly measure RNA length, showing that it can address some of the current challenges in mRNA analytics and can serve as a useful orthogonal technique.
4. Antibody binding and aggregation
The discovery, development and production of antibody-based therapeutics require careful, repeated bioanalytical characterization of both the antibody candidates and their target antigens. New antibody modalities come with their own analytical challenges, as their complex interactions with multiple antigens make them harder to characterize with techniques like nanoparticle tracking analysis (NTA) or biolayer interferometry (BLI).
Why use mass photometry?
Mass photometry offers key advantages that make it an invaluable tool to derisk antibody development and production. It provides data comparable to gold-standard methods such as SEC but with minimal acquisition time (one minute) and sample consumption (15 – 30 ng), making it ideal for repeated, at-line analyses without slowing down processes.
As a single-particle technique, mass photometry detects all the populations in a sample within its mass range, even those present in small quantities, allowing it to readily detect aggregation. The working concentrations of mass photometry are ideal to study aggregation behavior in relevant conditions, such as the low concentrations found inside IV bags. A microfluidics add-on, MassFluidix HC, makes it possible to measure samples at micromolar concentrations, enabling comparison to SEC.
A mass photometry measurement detects, in a single measurement, free antigens and antibodies as well as their complexes, and quantifies their abundance. This information can be used to assess antigen quality and determine antibodies’ preferred stoichiometries and binding affinities. Mass photometry is modality-agnostic and can also be applied to more complex samples (including bispecifics and multispecifics) with no additional preparation or method development. Combined with its low time and sample consumption, the strengths of mass photometry make it ideal for work with large antibody libraries and new modalities.
Case study
This study (currently still a preprint) used mass photometry and kinetic modelling to analyze the interactions between the bispecific antibody ivonescimab and its targets (VEGF and PD-1), quantifying the complexes formed and their affinities. They confirmed that VEGF induced ivonescimab to oligomerize and revealed dimers as the most stable structure – not higher-order structures, as previously thought.
Mass photometry analysis of ivonescimab:VEGF interactions. The mass photometry histograms show ivonescimab:VEGF complex formation for mixtures with 1:1, 1:2 and 1:4 antibody:antigen concentration ratios, at equilibrium, after 40 min incubation. Mass photometry detects and quantifies the multiple antibody-antigen complexes (see schematics above the histograms), helping understand how ivonescimab interacts with its targets. Figure 2B from Jajcanin Jozic et al. (2025).
5. Membrane proteins
To study membrane proteins, they need to be embedded in membrane mimetics to preserve the structure of their hydrophobic domains. Developing the right protocol for membrane protein preparation can be challenging, and it often comes down to trial and error.
Why use mass photometry?
Unlike other techniques, mass photometry is compatible with most membrane mimetics, and its low sample and time requirements are amenable to repeated analysis while developing protocols.
Case study
Mass Photometry of Membrane Proteins (Olerinyova et al., 2021)
This paper demonstrates how mass photometry can be used to study proteins solubilized using different types of membrane mimetics, providing information on the heterogeneity of samples and the functional state of the studied proteins.
6. Protein-DNA interactions
Some research (e.g. the study of DNA repair mechanisms) requires characterizing protein-DNA interactions. This is not straightforward, since protein-DNA complexes can be very heterogeneous in size and have variable charge-to-mass ratios due to variation in the number of proteins bound specifically and non-specifically to DNA.
Why use mass photometry?
Mass photometry enables the detection of protein-DNA and protein-protein interactions in solution without the need for labels or tags and without disruptive sample preparation. This is useful for studying the dynamic assembly and disassembly of protein-DNA complexes, which may involve transient interactions between multiple proteins.
Case study
This structural study used mass photometry along with other techniques and structure modeling to study the stimulation of S. cerevisiae Dna2 by RPA. They found that the large RPA subunit Rfa1 alone can promote the Dna2 nuclease activity and that different domains of Rfa1 regulate Dna2 recruitment, and its nuclease and helicase activities.
7. AAV analytics
Producing safe and effective AAV-based therapeutics requires screening samples for impurities that may impact safety and immunogenicity. One concern when producing AAV-based products is the presence of impurities in the form of capsids that do not contain the recombinant genomic payload, carry only a partial copy, or are overfull.
Why use mass photometry?
Current techniques available to characterize AAV capsid loading suffer from several disadvantages. Analytical ultracentrifugation (AUC) provides excellent resolution, but takes time, requires large amounts of sample and often needs to be outsourced. Other techniques like qPCR/ELISA or SEC-MALS have disadvantages including poor resolution and serotype specificity.
Mass photometry reports on multiple relevant attributes of AAV samples. Thanks to its single-molecule mass measurements, it readily quantifies the proportions of empty/full/partially filled capsids and detects overfull capsids and aggregation. In addition genome size can be estimated from the difference in mass between full and empty capsids. The information provided by mass photometry is on par with AUC, but its throughput, mass consumption, operating costs and instrument footprint are drastically lower, allowing for frequent, in-house analyses.
With a short cleanup step, mass photometry can also analyze AAV samples after upstream processing. In addition, Refeyn offers software that supports analysis in GMP-compliant environements to provide fast, informative analytics that support AAV-based therapeutic manufacturing.
Case study
A comparison of mass photometry and AUC measurements of different AAV serotypes. This study showed that mass photometry results are comparable to those from AUC, while requiring much less time and sample. Figure 6 from Wagner et al. (2023).
8. Large viral vector and VLP characterization
The safety and efficacy of therapeutics using vectors such as adenoviruses (AdVs), lentiviruses (LVVs) and virus-like particles (VLPs) require careful characterization to make sure the final product is pure and stable.
Why use macro mass photometry?
Among the challenges of current techniques are difficulties detecting and distinguishing different populations in the sample, including the critically important empty and full vectors. Those able to distinguish populations suffer from long measurement times, high operating costs or high sample consumption.
The single-particle, multiparametric analyses performed by macro mass photometry distinguish and quantify the different populations in the sample. This includes not only empty and full vectors, but other relevant components of the sample like aggregates, process-related impurities and helper virus populations in the case of AdV. Moreover, macro mass photometry delivers all this information in minutes, with minimal sample consumption and very low operating costs. This makes macro mass photometry ideal for frequent, in-house analyses of viral vector samples, speeding up process development and derisking production.
Case study
Quantifying adenovirus packaging with macro mass photometry
This application note from Refeyn – created in collaboration with the Jenner Institute at the University of Oxford – shows how macro mass photometry can be used to quickly evaluate adenovirus packaging. It also shows that macro mass photometry can distinguish adenoviral vectors from helper virus populations. Results are compared to expected values as well as to results from orthogonal techniques, including AUC and nsEM.
Think mass photometry may be right for you? For more information, do not hesitate to contact us.
To learn more, check out these comprehensive resources:
Mass photometry handbook – Refeyn
Curious how mass photometry delivers accurate results – fast? Whether you’re new to the technique or looking to get more from your experiments, our handbook Understanding Mass Photometry is your essential guide.
Discover how it works and how to maximize its potential. Find out how it compares to other light scattering techniques, how it’s being used across the life sciences, and what others have to say about this unique technology.
Why is mass photometry appearing in over 1300 scientific studies and being adopted by Pfizer, GSK and Astra Zeneca? In this webinar, a Refeyn expert explains what it is that makes mass photometry such a powerful and versatile technique.
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]]>Refeyn, a leading life science instrumentation company pioneering mass photometry, announced today that Dr. Susan Altschuller has been appointed a Non-Executive Director of Refeyn, effective October 1st, 2025.
Dr. Susan Altschuller
Chief Financial Officer of Climb Bio, Inc.
Dr. Susan Altschuller is a seasoned biotechnology executive with over two decades of experience in the life sciences. She currently serves as Chief Financial Officer of Climb Bio, Inc.
Previously, Dr. Altschuller was CFO of Cerevel Therapeutics until its acquisition by AbbVie in 2024, and CFO of ImmunoGen, where she supported the commercial launch of an antibody-drug conjugate for ovarian cancer. She also held senior leadership roles at Alexion, Biogen, and Bioverativ, after beginning her career as a consultant with the Frankel Group.
Dr. Altschuller holds a BSE in Biomedical Engineering with Honors from Tulane University, a Ph.D. in Biomedical Engineering from the Illinois Institute of Technology, and an MBA from the MIT Sloan School of Management. She serves as Audit Chair on the Boards of Vestaron and Refeyn, and is a founding Board member of the HNRNP Family Foundation.
“We are pleased to welcome Susan to Refeyn’s Board,” said Jean-Paul Mangeolle, Refeyn’s Chairman. “Her financial expertise and deep understanding of both emerging biotech and global pharmaceutical companies will provide valuable insight as we scale and grow our presence in the life sciences tools market.”
To learn more about Refeyn’s Board of Directors, visit: About Us – Refeyn
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Natalia Markova
New to Refeyn’s Scientific Advisory Board
Refeyn is pleased to announce that Natalia Markova has joined its Scientific Advisory Board (SAB). With a genuine interest in the design and application of label-free biophysical technologies sparked during her PhD at Lund University, Natalia has built a career advancing microcalorimetry, biosensors, and particle characterization tools for structural biology, drug discovery, and biologics development. Known for fostering strategic collaborations, she has held senior roles across academia and industry, including at Pharmacia-Biovitrum, the Structural Genomics Consortium, CRO iNovacia, GE Healthcare, and Malvern Panalytical. Her recent focus is on fit-for-purpose analytics for nucleic acid–based drugs.
Bringing together trusted advisors from academia and industry, Refeyn’s SAB helps guide the development of mass photometry applications across biopharma discovery, development, and manufacturing.
To learn more about Refeyn’s SAB, visit: About Us – Refeyn
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]]>This post was first published in November 2021
Updated on 15th August 2025
Mass photometry is a way to measure the mass of biomolecules and small viral capsids in solution without labels. It works by quantifying the interference between the light scattered by an individual molecule in contact with a measurement surface and the light reflected by that surface. The resulting signal – or ’contrast’ – is directly proportional to the molecule’s mass [1], [2] (read more about how mass photometry works).
The single-molecule nature of mass photometry makes it a powerful bioanalytical technique. It allows you to detect and quantify different populations of species in a sample. For example, it can be used to quantify protein oligomers (monomers, dimers, trimers, etc.) (see Fig. 2 below), to characterize protein-protein interactions and calculate binding affinities, and to quantify populations of empty, partially filled and full adeno-associated virus (AAV) capsids.
Mass photometers report the data they obtain – profiles of the mass distribution of the components of a sample – as histograms. Knowing how to interpret a mass histogram is essential for making sense of mass photometry. Here, we explain how mass histograms are generated, and how to read and understand them.
How do mass photometers analyze data?
Mass photometry data is simply a series of images (Fig. 1). For each image in the series, the average of N frames is taken and divided by the average of the N subsequent frames to reveal how much the signal changed when a particle landed on the glass surface. When molecules and other small particles land on the glass surface, they produce signals in these ratiometric frames that are detected and counted. These signals are reported in the mass histogram.
Figure 1 Generation of the mass photometry signal. Images of the glass surface, taken over time, are divided into two stacks of N consecutive frames (typically N=5). These stacks are averaged to calculate a single ratiometric frame. The process is repeated for stacks of frames shifted by one frame at a time, generating a ratiometric movie that shows when particles land on the glass surface as well as their contrast signal.
What information is available in a single mass peak?
The typical mass photometry measurement lasts for one minute, and hundreds to thousands of landing events can be detected by the mass photometer during that time. Histograms are a helpful way to visualize those many single-molecule measurements (Fig. 2).
Figure 2 Mass photometry data of a sample of the antibody 2G12. The scatter plot (bottom) shows the mass measurements associated with the many landing events recorded over a 160-second time period. The mass photometry histogram (top) presents the data as a histogram, with the peaks fit by Gaussian curves. In this example, the peaks correspond to monomers, dimers and trimers of 2G12 IgG, a monoclonal antibody against the HIV envelope glycoprotein gp120.
In histograms, the measurements of single-particle landing events are grouped into narrow mass ranges (‘bin’) to make the data easier to interpret. Each bin is represented by a vertical bar, and the height of the bar (the ‘counts’) tells you how many measurements fell into that particular range. If a bar is tall, it means that the mass photometer counted many landing events within that mass range.
As for most biological data, repeated measurements of molecules with the same mass will produce data with some variability that is centered on the true value. In a mass photometry histogram, such data will appear as peaks made up of several bars. Each peak can be fit by a Gaussian curve (Fig. 2) – a straightforward statistical approach that is implemented in DiscoverMP, the custom-built data analysis software that works with Refeyn’s mass photometry instruments.
This fitting yields two key values: The mean of the peak and its standard deviation. The mean is the mean mass of the particles whose data formed the peak, while the standard deviation indicates how spread out the values are – an indicator of the uncertainty in the measurement.
Interpreting multiple mass peaks
Often, a mass photometry histogram will have multiple peaks, indicating that there are multiple species present in the sample. Indeed, the single-molecule nature of mass photometry means that you can characterize samples containing many different species across a broad mass range. The different species can be detected provided they differ enough in mass (the mass differences must be above the resolution of the instrument – learn more about mass photometry resolution).
As an example consider a sample containing the antibody 2G12, which is known to form oligomers. In the histogram, we can see three peaks, indicating that there were three protein species, each with different mass, in the sample (Fig. 2). From the mean of each peak (which tells us the mass of the molecules in that subpopulation), we can conclude that the peaks correspond to 2G12 monomers, dimers and trimers.
We can also use the mass histogram information to assess the relative abundance of the different species detected. Already, from just a quick glance at the sizes of the peaks, we can see that the monomers were the most abundant, followed by dimers and then trimers. But going beyond that quick glance, by looking at the number of counts that contributed to each peak, we can quantify those abundances.
You can even use the information on the relative abundances to determine proteins’ binding affinities [3].
Example: A mass photometry histogram for bispecific antibody binding
There are numerous examples in the literature of mass photometry being used for protein characterization, including in research into hemoglobin scavenging [4], R2TP chaperones [5], antifungal drug targets [6] and many other areas. It is also increasingly used to study other types of biomolecules like nucleic acids [7] and AAVs [8].
Mass photometry gives a detailed overview of the contents of a sample while requiring little time investment and sample consumption. These strengths make it especially useful in the context of pharmaceutical development, where critical quality attributes of samples need to be frequently characterized. Here we show an example – extracted from a larger collaboration with Absolute Antibody – of what information a mass photometry histogram can provide.
Fig. 3 shows mass photometry analyses of samples of a bispecific antibody mixed with the HER2 antigen – one of its targets – at five different concentrations. At each concentration, the mass photometry histograms showed each of the isolated components of the sample (the antibody and antigen), as well as antibody-antigen complexes with different stoichiometries. As mass photometry also quantifies the relative proportions of each species, it is possible to calculate the binding affinities of the different complexes present in the sample, even in cases where multiple interactions are present.
Figure 3 Mass photometry resolves complex bsAb-antigen interactions. The concentration of bsAb-A was kept constant at 5 nM, while the HER2 concentration was varied (0.0, 2.5, 5.0, 10 and 20 nM). Mass photometry histograms (measured at equilibrium) show peaks and corresponding counts for each individual species as well as 1:1 HER2-bsAb complexes and 2:1 HER2-bsAb complexes. As the HER2 concentration increases, the peaks corresponding to free antigen and the 2:1 complex become more prominent, indicating that populations of those species are increasing.
In summary
- Mass photometry is a powerful bioanalytical method which allows the characterization of biomolecules and small viral capsids on a single-particle level.
- Mass photometry data are typically presented as histograms, where each peak of the histogram represents a population with a particular mass.
- Analysis of the peaks yields the mass of each population and its relative abundance.
Further resources
If you would like to learn more about mass photometry, we recommend the following resources:
Webinar: Quantifying protein-protein interactions by molecular counting with mass photometry
Fabian Soltermann from the University of Oxford talks about his work on mass photometry and the quantification of protein-protein interactions in antibody-antigen systems. Fabian shows how we go from counting single molecules with mass photometry to obtaining information on the purity of samples, as well as on stoichiometry, affinity and binding kinetics.
Refeyn’s TwoMP mass photometer is optimized for characterizing proteins and nucleic acids, as well as their interactions. With its high sensitivity, the TwoMP is ideally suited for measurements at physiological (i.e. low) concentrations, with measurements at higher concentrations enabled by the MassFluidix HC add-on. The high dynamic range intrinsic to single molecule counting techniques ensures low-abundance species are still captured accurately.
References
[1] G. Young et al., ‘Quantitative mass imaging of single biological macromolecules’, Science, vol. 360, no. 6387, pp. 423–427, Apr. 2018, doi: 10.1126/science.aar5839.
[2] G. Young and P. Kukura, ‘Interferometric Scattering Microscopy’, Annu. Rev. Phys. Chem., vol. 70, no. 1, pp. 301–322, Jun. 2019, doi: 10.1146/annurev-physchem-050317-021247.
[3] F. Soltermann et al., ‘Quantifying Protein–Protein Interactions by Molecular Counting with Mass Photometry’, Angew. Chem. Int. Ed., vol. 59, no. 27, pp. 10774–10779, 2020, doi: 10.1002/anie.202001578.
[4] S. Tamara, V. Franc, and A. J. R. Heck, ‘A wealth of genotype-specific proteoforms fine-tunes hemoglobin scavenging by haptoglobin’, Proc. Natl. Acad. Sci., vol. 117, no. 27, pp. 15554–15564, Jul. 2020, doi: 10.1073/pnas.2002483117.
[5] T. V. Seraphim et al., ‘Assembly principles of the human R2TP chaperone complex reveal the presence of R2T and R2P complexes’, Structure, vol. 0, no. 0, Sep. 2021, doi: 10.1016/j.str.2021.08.002.
[6] S. M. H. Chua et al., ‘Structural features of Cryptococcus neoformans bifunctional GAR/AIR synthetase may present novel antifungal drug targets’, J. Biol. Chem., p. 101091, Aug. 2021, doi: 10.1016/j.jbc.2021.101091.
[7] Schmudlach A, et al., ‘Mass photometry as a fast, facile characterization tool for direct measurement of mRNA length’, Biology Methods and Protocols, Biol. Methods Protoc., 2025;10(1):bpaf021, doi:10.1093/biomethods/bpaf021
[8] C. Wagner et al., ‘Quantification of empty, partially filled and full adeno-associated virus vectors using mass photometry’, Int. J. Mol. Sci., 3;24(13):11033, Jul. 2023, doi: 10.3390/ijms241311033.
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