Edible Sulfonated Soy Protein Microcarriers for Cultivated Meat Cell Expansion

Microcarriers are essential in large-scale cell expansion for applications such as cultivated meat but are typically composed of non-edible materials, requiring additional cell retrieval steps. The ability to incorporate microcarriers into a final product would reduce cost and potentially add nutritional value. Additionally, substrate biophysical properties influence muscle cell adhesion and proliferation. We developed edible, functionalized soy microcarriers by sulfonating soy protein isolate (sSPI). Sulfonation introduced sulfonate groups in a controllable manner, enhancing sSPI conductivity and water uptake. Myoblasts adhered to soy protein gels in serum-free conditions, and cell adhesion on sulfonated and non-sulfonated soy substrates was mediated by integrin β1. Additionally, we interrogated the ability of sulfonated soy protein to mimic growth factor binding characteristic of sulfated glycosaminoglycans in the extracellular matrix. Sulfonated soy microcarriers adsorbed 17-fold more basic fibroblast growth factor (bFGF) than non-sulfonated counterparts after 24 h. Sulfonated soy microcarriers accelerated proliferation of primary bovine satellite cells at early timepoints compared to cells on Cytodex 3 microcarriers and supported cell expansion over 5 days, similar to unmodified soy protein microcarriers. Collectively, this study demonstrates that sulfonation induces physiochemical changes in soy protein, generating a functionalized substrate that can be used to fabricate microcarriers for satellite cell expansion and improved growth factor retention.