Thermoplastic Molding of Chitosan to Form Living Plastic Materials

Numerous approaches for the solution-based fabrication of chitosan-based materials are reported, but most often result in materials with limitations in terms of stability in aqueous systems and mechanics unless chemical cross-linking is utilized. In the present study, a thermomechanical compression method is presented for solid-state processing of chitosan powders into dense bulk plastic-like materials where the mechanical and physical properties can be tailored. To achieve this outcome, chitosan-citrate complexes, formed through ionic cross-linking and amidation, undergo thermal fusion at high temperature and pressure to generate robust materials with retention of the inherent properties of chitosan, including biodegradability and cytocompatibility. The chitosan-based plastics can be doped with enzymes and antibiotics with retention of bioactivity and are also explored as living materials when microbial cells (e.g., Pseudomonas putida) are included in the process and subsequently shown to maintain metabolic functions to degrade organic pollutants. This thermoplastic approach for solid-state processing of chitosan enables the development of a variety of new materials and composites with embedded biomolecules for enhanced functions. This solid-state fabrication of chitosan bulk materials approach eliminates the need for conventional solution-based processing, enabling rapid material production via compression molding while reducing costs, minimizing waste, and improving overall manufacturing efficiency.