Design and Optimization of Chitosan-Based Microparticles for Drug Delivery in Colorectal Therapies

Colorectal diseases, including inflammatory bowel diseases (IBDs) and colorectal cancer (CC), pose a significant clinical challenge due to their prevalence and the limitations of current therapeutic approaches. Surgical interventions, although often necessary, are associated with high morbidity and mortality, particularly due to postoperative complications such as infections, anastomotic leakage, and impaired wound healing. These complications not only hinder short-term recovery but also compromise long-term survival and the efficacy of adjuvant therapies. In this context, the development of advanced biomaterials for targeted drug delivery and tissue regeneration offers promising therapeutic potential. In particular, hydrogel-based scaffolds derived from natural polymers, such as gelatine methacryloyl (GelMA), are widely investigated for the regeneration of the colorectal mucosa. These biomaterials can be further loaded with polymeric carriers for in situ release of therapeutic agents. This thesis, developed within the European project TENTACLE, focuses on the design and optimization of chitosan-based microparticles (CMPs) for targeted drug delivery (e.g. antibiotics) in colorectal applications. Chitosan, a biocompatible and biodegradable polysaccharide, was selected for its mucoadhesive and antimicrobial properties, as well as its capacity for chemical modification. CMPs were synthesized via spray drying, a scalable and reproducible technique suitable for industrial applications. The process was optimized by varying chitosan concentration, tripolyphosphate (TPP) crosslinking ratio, and neomycin sulphate loading. The goal was to identify formulation limits and achieve desirable particle morphology and distribution, which was ultimately feasible by tuning different parameters of the spray drying and of the chitosan solution. Stability tests in various media (deionised water and buffer media) were performed to evaluate the potential of CMPs as drug carriers. These studies revealed that formulations containing only chitosan and TPP were unstable in every liquid solution, whereas the inclusion of neomycin significantly improved dispersion in water. To improve particle stability, particularly at physiological pH, both upstream and downstream formulation strategies were investigated. Tween 80 and genipin were each tested separately—the former as stabiliser coating agent, the latter to improve particle stability by covalent cross-linking. The two strategies were implemented in both stages: upstream, by incorporating them before the spray-dry process, and downstream, by applying them post-synthesis. This dual approach aimed to evaluate their respective effects on dispersion, structural integrity, and overall microparticle stability. However, Tween80 was found to compromise particle integrity and was discontinued, while genipin was successfully integrated upstream, improving structural stability, although it did not improve dispersion. The resulting microparticles were characterized using thermogravimetric analysis (TGA), scanning electron microscopy (SEM), dynamic light scattering (DLS), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR-ATR), confirming the formation of spherical, stable particles with tunable properties. CMPs were then incorporated into photocurable GelMA hydrogels to evaluate their performance in scaffolds for regenerative applications. Two aspects were assessed: (1) stability in GelMA precursor solution in DPBS, and (2) the maximum particle concent