Single-step fabrication of catechol-e-poly-L-lysine antimicrobial paint that prevents superbug infection and promotes osteoconductivity of titanium implants

Prevention of infection and promotion of osteoconduction are the key factors to achieve long-term success in orthopaedic implants. In this work, an effective antimicrobial and osteoconductive coating is facilely prepared by the cross-linking of epsilon-poly-L-lysine (EPL) and catechol (abbreviated as EPLC) via a one-step mussel-inspired chemistry. A series of EPLC paints were prepared by catechol (15 mM) and varying concentrations of EPL (30, 40, and 50 mM) and named as EPLC1, EPLC2, and EPLC3. The coatings were easy to paint on implants. EPLC3 with the highest EPL concentration exhibited the most potent antimicrobial activity (greater than 99.99%) against both Gram-negative bacteria Escherichia coli (E. coli) and Gram-positive "superbug" methicillin-resistant Staphylococcus aureus (MRSA), and inhibited the biofilm formation of MRSA up to one week. Furthermore, the EPLC3 painted Ti implant was capable of reducing more than 3-log bacterial burden in a rodent subcutaneous infection model infected by MRSA. More interestingly, EPLC3 coating increased the osteoconductivity of Ti surfaces by promoting mouse pre-osteoblast MC3T3-E1 adhesion and proliferation. And the EPLC3 painted Ti surfaces could induce hydroxyapatite (HAp) formation after incubation in simulating human body fluids (SBF) within two weeks. Overall, the mussel-inspired EPLC paint can be easily applied to orthopaedic implants, and uendowed Ti with antimicrobial activity and promoted its osteoconductivity, which will benefit the long-term success of Ti implants.