Poly(allylamine hydrochloride) is widely used in various industrial and biomedical applications due to its cationic polymer properties. It is commonly employed as a flocculant in water treatment processes, where it helps in the aggregation and removal of suspended particles, improving water clarity. In the biomedical field, it is utilized in the development of drug delivery systems, particularly for creating polyelectrolyte complexes that enhance the stability and controlled release of therapeutic agents. Additionally, it serves as a coating material for medical devices, providing antimicrobial properties and improving biocompatibility. In the field of biotechnology, it is used in the immobilization of enzymes and proteins, facilitating various biochemical reactions and assays. Its ability to form thin films and multilayers also makes it valuable in the fabrication of sensors and biosensors, enhancing their sensitivity and selectivity.