Life-threatening infections occur far too frequently when our natural barriers of defense are broken by surgery, trauma, medical instrumentation, or disease.Local wound environments, with dead and damaged tissues ("cracks & crevices"), facilitate microbial growth and invasion.Systemic antibiotics and topical antiseptics are not enough.A-BlocksTM (Amicrobe block copolypeptides) represent a new class of biomaterials designed to fill the treatment "gap".These long-chain synthetic copolypeptides are composed of one block of cationic amino acids (typically 100 or more) and one block of hydrophobic amino acids (typically 10-60).They self-assemble into microstructures such as fibrils or micelles in aqueous media.A-Blocks are engineered to: (1) kill microbes directly; (2) fill & coat tissue spaces; and (3) be safe for direct application to exposed tissues.They show broad-based antimicrobial activity against Gram-pos. bacteria (e.g., S. aureus, S. epidermidis), Gram-neg. bacteria (e.g., P. aeruginosa, E. coli) and yeast.In animal models, they demonstrate direct antimicrobial activity, as well as antimicrobial barrier function.It is anticipated that A-Block hydrogels and solutions will be applied directly to the exposed tissues of surgery and trauma to help prevent and treat infections.