Inhibition of Bacterial Adhesion using Calcium Phosphate Microspheres Loaded with Protamine

Abstract

Bacterial adhesion to biomaterials remains a serious problem for use in medical devices. The increment of antibiotic resistant microorganisms has prompted interest in the use of antimicrobial peptides (AMPs). Protamine, a cationic antimicrobial peptide, has bactericidal properties against a range of Gram-positive and Gram-negative bacteria and pathogens. The immobilization of protamine on the biomaterial surface has been pursued as an alternative strategy for using antibiotics. In this study, calcium phosphate microspheres (CPMs) were prepared by an ultrasonic spray-pyrolysis (USSP) technique and the properties of protamine-adsorbed CPMs were analyzed. Calcium phosphate CPMs consisted of β-tricalcium phosphate (TCP) and hydroxyapatite (HAp). The adsorption of protamine to CPMs increased dose-dependently. The zeta potential of protamine-adsorbed CPMs also increased with protamine concentration. The adsorption would be driven by electrostatic interaction following the Langmuir model. The antimicrobial evaluation demonstrated that discs fabricated by protamine-loaded CPMs inhibited bacterial growth and biofilm formation. The interaction between protamine and bacteria could contribute to the antimicrobial activity. These results suggest that the immobilization of protamine on the surface of biomaterials could be used as an antimicrobial material for medical devices.