Growing cultivated meat begins with a relatively small number of cells. Those cells have to multiply, often while attached to tiny particles suspended in culture media. The particles provide more surface area than a flat culture vessel, but they can create another problem later: if the microcarriers are not edible, the cells may need to be separated from them before the final product is made.
A recent study from researchers at the University of California, Davis examined whether soy protein microcarriers for cultivated meat could serve as both a cell-growth surface and a material that might eventually remain in the product. The team made microcarriers from soy protein isolate, modified some of the soy through sulfonation, and then followed how bovine satellite cells behaved on the particles over five days.
The CellScale MicroTester G2 appears early in that workflow. Before comparing cell expansion on the two soy formulations, the researchers compressed individual microcarriers to check whether sulfonation had also changed their stiffness. If the particles differed substantially in both chemistry and mechanics, it would be harder to work out what the cells were responding to.
Why Soy Protein Microcarriers for Cultivated Meat Are Being Studied
Most anchorage-dependent muscle cells will not simply grow while floating freely in a tank. They need a surface to attach to. Microcarriers supply that surface while allowing many particles and cells to be kept in suspension, which is one reason cultured meat microcarriers are being considered for larger-scale cell expansion.
Conventional products such as Cytodex 3 can support cell growth, but Cytodex 3 is made from dextran and coated with denatured collagen. For cultivated meat, a carrier that is not intended to be eaten may add a cell-recovery step. Edible microcarriers could change that workflow, at least in principle, because the cells and their growth surface might be processed together.
Soy is an interesting candidate for a few practical reasons. It is already used as a food ingredient, it contains protein, and researchers can process soy protein isolate into different forms. It has also been investigated as a cell-culture scaffold. Soy protein microcarriers for cultivated meat therefore sit somewhere between a bioprocessing material and a possible part of the food itself.
That does not mean any soy particle will work. The particles need to form at a useful size, remain intact in liquid, provide a surface for cell attachment, and have mechanical properties that make sense for the culture system. What happens at their surface matters too.
Sulfonating Soy Protein to Change the Microcarrier Surface
The researchers prepared an unmodified soy protein isolate material, referred to as SPI, and a sulfonated version called sSPI. Sulfonation added negatively charged sulfonate groups to the protein. In the resulting material, the authors measured changes in conductivity, surface charge, and water uptake.
There was a biological reason for making that change. Sulfated molecules in native extracellular matrix can interact with growth factors. The team wanted to see whether sulfonated soy might behave in a related way, particularly with basic fibroblast growth factor, or bFGF, which is used in muscle cell culture.
Surface modification can bring an experimental complication, though. It may change more than surface chemistry. It can also change swelling or mechanics, and cells are responsive to their mechanical microenvironment. This is why the compression measurements are more than a side note. For soy protein microcarriers for cultivated meat, comparing cell results is easier to interpret when the two soy groups do not also have a large difference in average stiffness.
How Soy Protein Microcarriers for Cultivated Meat Were Measured
Individual-Particle Compression Testing
The team formed SPI and sSPI microcarriers using a water-in-oil emulsion process. The resulting particles spanned approximately 70 to 300 micrometres in diameter. Samples this small cannot be handled like a conventional scaffold coupon, so the researchers tested the particles one at a time.
Each microcarrier was placed between parallel plates on the MicroTester G2 and compressed to 30% strain over 30 seconds. Testing was performed in phosphate-buffered saline containing 0.1% Tween 80, rather than after drying the particles. The compressive modulus was calculated at 10% strain.
For soy protein microcarriers for cultivated meat, this individual-particle test answers a more useful question than a bulk material measurement alone. It describes the mechanics of the carrier in the form and environment where cells will encounter it.
This is a direct form of micro-mechanical testing. Instead of testing a larger bulk soy gel and assuming that the finished microcarrier behaves the same way, the force and displacement response comes from an individual particle. The protocol also combines parallel-plate compression testing with testing while submerged in PBS, closer to the state in which the microcarriers were later used for cell culture.
Soy Microcarrier Stiffness Compared with Cytodex 3
The average compressive moduli were 28.4 ± 9.3 kPa for SPI microcarriers and 25.0 ± 20.0 kPa for sSPI microcarriers. Cytodex 3 measured 61.8 ± 17.8 kPa. Both soy groups were softer on average than Cytodex 3, while the two soy formulations had reasonably similar mean values.
Those values provide a direct stiffness comparison for soy protein microcarriers for cultivated meat and a commonly used commercial control. They do not tell the whole story of how a particle will behave in culture, but they make the mechanical difference between the groups visible.
The spread in the sSPI measurements is hard to miss. It suggests that individual particles were not mechanically uniform, even if the group average landed near that of SPI. So it would be too neat to call the formulations perfectly stiffness-matched. Still, there was not a large shift in their average compressive modulus after sulfonation. That gave the researchers a more workable comparison when they moved on to cell culture.
The setup resembles work previously described for compression testing of individual hydrated microbeads. In both cases, a single small particle is isolated, compressed between plates, and measured while wet. The application is different, but the practical question is similar: how does the actual particle respond under load?
How Bovine Cells Responded to Soy Protein Microcarriers for Cultivated Meat
Cell Attachment and Early Expansion
After characterizing the soy protein microcarriers for cultivated meat, the team seeded primary bovine satellite cells onto SPI, sSPI, and Cytodex 3 microcarriers. These are muscle-resident stem cells that can expand and later contribute to muscle tissue formation.
The study first looked at attachment more broadly using C2C12 mouse myoblasts on flat soy protein gels. Cells adhered to both SPI and sSPI in serum-free conditions. Blocking integrin β1 reduced attachment, which points to integrin-mediated adhesion on the soy surfaces rather than attachment that depended entirely on serum proteins coating the material.
For the microcarrier experiment, the more useful comparison is the bovine cell count over five days. Between days 1 and 3, the relative increase in cell number was greatest on sSPI. That early change is interesting for soy protein microcarriers for cultivated meat, particularly because the sulfonated particles were not stiffer on average than the unmodified soy particles.
Why the Day-Five Results Need Context
By day 5, the pattern was less simple. Cytodex 3 had the highest cell number. SPI also had more cells than sSPI at that timepoint, although both soy formulations supported bovine satellite cell expansion over the culture period. In other words, sulfonation was associated with faster early proliferation, but it did not leave sSPI with the largest cell population at the end of the five-day experiment.
That distinction is important when discussing soy protein microcarriers for cultivated meat. The experiment does not identify one formulation as the obvious winner. It shows that both soy materials supported attachment and expansion, while the timing of cell growth differed between them.
Do Soy Protein Microcarriers for Cultivated Meat Retain More bFGF?
The researchers then exposed SPI and sSPI microcarriers to bFGF for 24 hours. They measured how much growth factor remained in the surrounding liquid and used a heparin solution to recover bFGF that had adsorbed to the particles.
Far more bFGF was recovered from sSPI. On a microcarrier-mass basis, the sulfonated particles retained about 17 times more recoverable bFGF than unmodified SPI. For soy protein microcarriers for cultivated meat, this was the clearest effect of sulfonation in the study.
There is still some room for caution. The assay shows that more bFGF could be recovered from the sSPI microcarriers after adsorption. It does not, on its own, show that every retained molecule remained biologically active or that stronger retention will always improve long-term cell expansion. The cell-count data were not that tidy. The sSPI group grew quickly early on, then had fewer cells than SPI and Cytodex 3 by day 5.
For soy protein microcarriers for cultivated meat, growth-factor retention may still be useful. A carrier that holds bFGF near the cell surface could affect how growth factors are delivered or how often media must be supplemented. That possibility would need more work, including longer cultures and a closer look at release and bioactivity.
What the Study Adds to Edible Microcarrier Development
The paper connects three parts of the microcarrier problem that are often discussed separately: food-compatible material selection, the mechanics of individual particles, and cell behaviour on the finished carrier. Soy protein microcarriers for cultivated meat have to be considered across all three, since changing the material can also change the surface and mechanics that cells encounter.
The soy particles were softer than Cytodex 3 under the reported compression conditions. SPI and sSPI had similar average moduli, even though the sSPI data were variable. That mechanical comparison gave the later biological experiments a clearer starting point. Differences in cell number could be considered alongside the change in surface chemistry without a major average stiffness difference between the soy groups.
These particles are small, but they still act as cell-growth supports. Their mechanics belong to the broader question of how researchers evaluate the mechanical properties of cell culture scaffolds. Shape, surface chemistry, swelling, stiffness, and stability in culture may all influence whether a material remains practical as a microcarrier.
There are limits to what can be inferred here. The culture ran for five days, and the researchers did not demonstrate a finished cultivated meat product containing the carriers. The study also did not test performance in a production-scale bioreactor. Soy protein microcarriers for cultivated meat remain a developing material concept, not a ready-made replacement for every commercial carrier.
Even so, the work gives a concrete example of how edible microcarriers can be evaluated. Rather than looking only at whether cells attach, the researchers asked what the particles were made from, how individual particles deformed in liquid, whether surface modification changed average stiffness, how bovine cells expanded over time, and whether the material retained a soluble growth factor.
Measuring Soy Protein Microcarriers for Cultivated Meat with the MicroTester
The MicroTester is a low-force mechanical testing system used with small specimens such as microtissues, spheroids, fibres, particles, hydrogels, and other soft biomaterials. In a compression test, a specimen is positioned between a fixed surface (anvil) and a platen (microbeam). As the platen moves, the system records force and displacement so the sample response can be calculated over the selected strain range.
In this study, that meant placing one hydrated microcarrier between the platen and anvil, compressing it at a controlled rate, and calculating modulus from the early part of the force-displacement response. The measurement came from the finished particle rather than a bulk material made from the same protein.
That distinction can matter for soy protein microcarriers for cultivated meat. Particle fabrication introduces its own geometry, surface structure, and particle-to-particle variation. Testing the individual carrier provides information about the object the cells actually encounter in culture.
Beyond microcarriers, the same general approach is used when researchers need controlled tension or compression measurements from specimens that are too small or too compliant for a conventional mechanical tester. The fixtures and test setup change with the specimen, but the basic workflow remains hands-on: mount or position the sample, apply a defined motion, record the force response, and calculate the mechanical quantity relevant to the experiment.
Citation
, , , , and , “ Edible Sulfonated Soy Protein Microcarriers for Cultivated Meat Cell Expansion,” Journal of Biomedical Materials Research Part A 114, no. 7 (2026): e70116, https://doi.org/10.1002/jbm.a.70116.
