Application of Hexanoyl Glycol Chitosan as a Non-cell Adhesive Polymer in Three-Dimensional Cell Culture

Preparation of Highly Functional Spheroid of Endocrine Cells Based on Thermosensitive Glycol Chitosan

BACKGROUND

Pancreatic islet transplantation holds great potential as a therapeutic approach for treating type 1 diabetes mellitus (T1D). However, large islets suffer from hypoxia due to the limited diffusion distance of oxygen, leading to cell loss. Therefore, smaller spheroids are needed for better transplantation outcomes. This study aims to develop a method for forming highly functional islet spheroids using glycol chitosan (GC) derivatives, such as N-acetylated glycol chitosan (AGC) and N-hexanoyl glycol chitosan (HGC).

METHODS

Thermogelling polymers were produced by performing N-acylation of GC using the correspondingly carboxylic anhydrides. Islet spheroids were formed using a dual application with AGC-coated plates and HGC gelation. The AGC solution was applied to the plate for coating and evenly distributed using a 1 mL syringe. Then, the HGC encapsulated with islet single cells was cultured on top of it. Spheroid viability and functionality were evaluated using CCK-8 assay and glucose-stimulated insulin secretion assay.

RESULTS

The aqueous solutions of AGC (4%, w/v) and HGC (36% hexanoylation) (2%, w/v) demonstrated a sol-gel transition temperature around 37 °C, suitable for the physiological environment. These polymers also showed no cytotoxicity to intact islets. Islet single cells were cultured on HGC gels with varying degrees of hexanoylation (DH) values, where higher DH values led to smaller and more uniform spheroids. The resulting spheroids formed on AGC-coated plates and HGC36 gelation were smaller and more uniform than those formed on untreated plates. These spheroids exhibited significantly improved glucose responsiveness, with superior insulin secretion.

CONCLUSION

The optimized method using AGC and HGC offers a more efficient way to produce smaller, uniform, and functional spheroids.

The Role of Intermediate Water in Enhancing Blood and Cellular Compatibility of Chitosan-Based Biomaterials

Tissue engineering and regenerative medicine require biomaterials that balance blood compatibility with cell adhesion, proliferation, and differentiation. Chitosan and its derivatives, owing to their biocompatibility, biodegradability, and functional versatility, have been extensively explored for biomedical applications, including vascular grafts and tissue engineering scaffolds. This study investigates the effect of chemical modifications on the water state of chitosan derivatives─specifically, free water (FW), intermediate water (IW), and nonfreezing water (NFW)─and their implications for protein interactions, platelet adhesion, and mesenchymal stem cell (MSC) behavior. By incorporating hydrophilic and hydrophobic groups, the hydration of chitosan derivatives was precisely controlled, which significantly influenced blood compatibility and cell adhesion. Hexanoyl glycol chitosan (HGC) demonstrated reduced platelet adhesion, low fibrinogen denaturation, and favorable MSC adhesion, making it a promising candidate for applications requiring both enhanced blood compatibility and regenerative potential. These findings underscore the importance of hydration water modulation in designing advanced biomaterials for blood-contacting and regenerative medicine applications.

Robust and customizable spheroid culture system for regenerative medicine

Three-dimensional cell spheroids show promise for the reconstruction of native tissues. Herein, we report a sophisticated, uniform, and highly reproducible spheroid culture system for tissue reconstruction. A mesh-integrated culture system was designed to precisely control the uniformity and reproducibility of spheroid formation. Furthermore, we synthesized hexanoyl glycol chitosan, a material with ultralow cell adhesion properties, to further improve spheroid formation efficiency and biological function. Our results demonstrate improved biological function in various types of cells and ability to generate spheroids with complex structures composed of multiple cell types. In conclusion, our spheroid culture system offers a highly effective and widely applicable approach to generating customized spheroids with desired structural and biological features for a variety of biomedical applications.

A promising breakthrough in pancreatic cancer research: The potential of spheroids as 3D models

Pancreatic ductal adenocarcinoma (PDAC) stands as the fourth leading cause of cancer-related deaths, primarily attributable to its resistance to chemotherapy, resulting in a nearly universal fatality rate. Despite the promise exhibited by numerous drugs in preclinical studies, their subsequent failure in clinical trials underscores the inherent limitations of conventional two-dimensional cell culture models commonly employed in early drug screening endeavors. The inadequacies of two-dimensional (2D) models prompted the exploration of three-dimensional (3D) culture systems, which more faithfully recapitulate the native tumor microenvironment. These 3D systems have distinct advantages over 2D models in morphology, proliferation, drug response, and protein expression. Among these 3D platforms, tumor organoids and spheroids, generated through different methodologies, have emerged as next-generation models that closely mirror aspects of pancreatic tumor biology. This comprehensive review scrutinizes pancreatic cancer spheroids' techniques, tissue sources, and applications, offering a nuanced analysis of their advantages and limitations. By comparing these distinct 3D culture systems, researchers gain valuable insights to inform the selection of optimal model designs aligned with their specific experimental objectives. The utilization of these advanced models holds significant promise for enhancing the clinical relevance of both in vitro and in vivo cancer research, thereby contributing to the development of improved therapeutics against pancreatic cancer.

Recent Development of Functional Chitosan-Based Hydrogels for Pharmaceutical and Biomedical Applications

Chitosan is a promising naturally derived polysaccharide to be used in hydrogel forms for pharmaceutical and biomedical applications. The multifunctional chitosan-based hydrogels have attractive properties such as the ability to encapsulate, carry, and release the drug, biocompatibility, biodegradability, and non-immunogenicity. In this review, the advanced functions of the chitosan-based hydrogels are summarized, with emphasis on fabrications and resultant properties reported in literature from the recent decade. The recent progress in the applications of drug delivery, tissue engineering, disease treatments, and biosensors are reviewed. Current challenges and future development direction of the chitosan-based hydrogels for pharmaceutical and biomedical applications are prospected.