Islet transplantation represents a promising treatment for Type 1 diabetes mellitus; however, approximately 60-70% of intrahepatic transplanted islets fail to engraft. Localised controlled delivery of immunomodulatory molecules offers potential to enhance islet survival, but achieving reproducible spatiotemporal delivery remains a significant challenge. This thesis investigated robust microfluidics-based approaches for fabricating uniform poly(lactic-co-glycolic acid) (PLGA) microparticles to provide predictable and controlled protein release, compared with conventional homogenisation methods. The hepatic targeting potential of these microparticles was also investigated by incorporating galactose, a ligand that binds to the asialoglycoprotein receptor (ASGPR) expressed on hepatocytes. Various microfluidic configurations were systematically evaluated, including two-chips-in-series, homogenisation with microfluidics, and customised one-step processes. Flow parameter mapping and interfacial tension studies guided material selection and process optimisation. The homogenisation with microfluidics approach generated particles with remarkably low polydispersity compared to conventional homogenisation methods and demonstrated scalability using a Telos® scale out microfluidics system (Dolomite Microfluidics). To evaluate the efficacy of these novel microparticles as controlled release protein delivery vehicles, protein encapsulation, release, and functionality retention was investigated using human serum albumin (HSA) as a model protein. Contrary to predictions, homogenisation-only-produced particles demonstrated a higher encapsulation efficiency compared to particles fabricated using a hybrid homogenisation with microfluidics method, highlighting a need for process optimisation. Additionally, the HSA release profiles were similar for both methods of fabrication. Nonetheless, the inter-particle variability in release of HSA with homogenisation-only PLGA microparticles was higher, attributed to the polydispersity of the microparticles themselves. Furthermore, the lower bulk shearing forces exerted during microfluidic fabrication compared to homogenisation, translated to superior preservation of protein integrity with the hybrid method. A poly(lactic-co-glycolic acid)-poly(ethylene glycol)-poly(lactic-co-glycolic acid) (PLGA-PEG-PLGA) triblock copolymer was incorporated to accelerate controlled protein release. Homogenisation-only particles with 30% (w/w) triblock demonstrated superior burst release control compared to homogenisation with microfluidics particles. In contrast, the homogenisation with microfluidics particles with 20% (w/w) triblock showed superior burst release control. This revealed a complex interplay between fabrication method, microparticle size, and PLGA-PEG-PLGA triblock interaction. Hepatic cell attachment studies investigated whether the incorporation of galactosylated-poly (vinyl alcohol) (Gal-PVA) enhanced specific hepatocyte attachment. Despite established galactose-ASGPR potential, no significant increase in specific hepatocyte attachment was observed with the inclusion of Gal-PVA. However, further analysis revealed that effective receptor-mediated particle retention may be influenced by variables such as particle size, triblock copolymer, and the method of galactose incorporation itself. This research challenges the conventional assumption that particle monodispersity directly correlates with improved release control and encapsulation efficiency. The findings demonstrate complex interactions between fabrication methodology and polymer composition that influence delivery performance and particle-cell interactions beyond particle size uniformity alone. These insights establish methodological foundations for developing controlled release systems to enhance islet transplantation outcomes for patients with Type 1 diabetes mellitus.
Krishna Kumar Patel (Thu,) studied this question.