Tissue engineering is promising to treat osteoarthritis, an incurable, prevalent, painful and costly disease. It is well known that four factors determine its success: cell source, microenvironments, chemical and mechanical stimulants. These factors were regulated by pericellular matrix (PCM), a capsule structure surrounding the chondrocytes. However, current cell sources do not possess the natural PCM. Although many groups have regenerated the PCM in-vitro, there were some limitations. First, the regenerated PCM (neoPCM) was not biomimetic. Second, most of these studies neglected the negative dedifferentiation effects. Third, these methods cultured chondrocytes in bulk scaffolds. Therefore, when releasing the cells with neoPCM as a cell source, the extracellular matrix (ECM) was removed, which was opposite to the aim of tissue engineering, i.e. to grow new ECM to form the tissues. As a result, no cell sources have functional biomimetic neoPCM.

We encapsulated individual chondrocytes in cellular scale microgels to regenerate PCM, based on a central hypothesis that the microenvironments of microgels can regulate the neoPCM. As an early-stage project, this dissertation focused on the methodology development and the viability demonstration. First, we developed a novel microfluidic technique to fulfill the single-cell microencapsulation requirements. By exploiting the photocrosslinkable and biodegradable advantages of oxidized methacrylated alginate (OMA), this technique can photocrosslink OMA microgels with better monodispersity, degradation rate, cytocompatibility, and shape consistency than the widely employed ionic crosslinking methods. Our microuidic technique can be an alternative to manufacturing alginate microgels for biomedical applications. We also solved a common issue that scattered ultraviolet light induces clogging. Furthermore, we identified the effects of photocrosslinking process on the cell viability and justified the cytocompatibility our technique.

Second, we identified the viability of our microencapsulation method to regenerate PCM. We characterized the mechanical property, phenotype, and composition of neoPCM. We found that the microencapsulation did not affect the morphology of neoPCM but enhanced their mechanical strength/stiffness, comparing to bulk culture. We found that dedifferentiation and lack of intercellular interactions did not affect the PCM regeneration. We demonstrated this method is promising to provide a better cell source for cartilage tissue engineering by optimizing the microencapsulation parameters in future.