Poly-L-Lysine is a synthetic polymer widely used in cell culture as a coating agent to enhance cell adhesion to surfaces like glass or plastic, particularly for hard-to-culture cells such as neurons, in research and diagnostic applications. In biotechnology, it facilitates DNA and protein immobilization on solid supports, including microarray production, for efficient sample analysis. It is also employed in medical applications as a component in drug or vaccine delivery systems to improve cellular uptake and immune response. Additionally, in the food industry, it acts as a natural antimicrobial preservative to extend product shelf life. In cosmetics, it enhances formulation texture and stability.