Functionalized polylysine biomaterials for advanced medical applications: A review

• Polylysine characteristics and it’s functionalization with composites. • Targeted release characteristics of polylysine for drug and gene delivery. • Interfacial cohesiveness of polylysine based bio-adhesives for tissue repairing. • Polylysine based bio-fibrous membranes for protein immobilization and wound dressings. Advancements in the biomedical sector are dominating due to evolutions in healthcare functions such as targeted drug and gene delivery, bio-adhesives for tissue transplantation, bio-fibers based wound dressing, and protein immobilization. Among the various polymeric materials, the polylysine is a special type of naturally occurring homo-polyamide ε-poly-L-lysine (PLL) showcasing significant results for numerous biomedical applications. Analysis of polylysine based biomaterials or hydrogels have been reported to exhibit promising performance due to properties such as water solubility, consumability, biocompatibility, no toxicity, and stimuli-responsive (pH, temperature, enzyme) characteristics of the material. PLL based targeted drug delivery systems have massive importance because of increased efficacy and decrement in toxicity level during the interactions with human body functions. It is crucial to facilitate higher loading efficiency of drugs, and effective targeting of drug molecules at the desired site. Polylysine is an excellent biocompatible carrier, utilized as selective functionalization material or nanoparticle along with silica nanoparticles or mesostructured silica, and triblock polymer formation. The emergence of polylysine hydrogel as a bio-adhesive has broad impact due to its excellent binding strength compared to conventional bioadhesive (fibril glue) in the market; it subdues adverse effects such as bleeding diatheses, weak adhesion, and risk of infection due to biological origin. It is applicable in the sector of tissue repairing, wound healing, and sports injuries by eliminating traditional time-consuming techniques such as end-to-end suture to reduce the possibility of foreign material involvement and incomplete nerve sealing. The primary cationic amine group of polylysine reacts with targeted tissue and mucus layer closely by undergoing ionic interaction, exhibiting improved tissue adhesive properties. Additionally, electrospun polylysine nano-fibers have evolved as a material for protein immobilization, immobilizing antigens/antibodies, vaccine preparation, and wound dressings. PLL functionalized electrospun materials exhibited enhanced antibacterial properties by reducing the number of tumor cells.