Copper ion-loaded surface charge-convertible coatings on implant: Antibacterial and tunable cell adhesion properties

With rapid increase in implant surgeries, failure of implantation due to implant infection has increased. Although the problem of implant infections can be addressed by coating of implants with antibacterial materials, the fabrication of a versatile coating platform with high antibacterial performance, low toxicity, and tunable biofunctions for diverse implant applications, still remains a challenge. Herein, we report the fabrication of a biocompatible copper ion (Cu2+)-loaded surface charge-convertible antibacterial coating, which can transform from a positively-charged sterilized coating to an electro-neutral coating with anti-biofouling property by a facile acid trigger. First, a Cu2+ loaded positively-charged coating based on a copolymer with pendent carboxybetaine-tert-butyl ester groups was prepared on the surface of Ti implant. The positively-charged coating exhibited high and long-term in-vitro bactericidal effect through synergistic Cu ions-killing and contact-killing antimicrobial mechanisms. It also possessed, excellent cytocompatibility, favorable cell adhesion and growth behavior, promote osteogenesis, and was shown to reduce the inflammatory response and promote tissue healing in an in-vivo orthopedic implantation experiment. After acid treatment, the positively-charged coating was facilely transferred to an electro-neutral zwitterionic coating, which also exhibited high and long-term in-vitro bactericidal ability through synergistic Cu ions-killing and anti-biofouling antimicrobial mechanisms, and an inhibiting cell adhesion behavior. Therefore, this surface charge-convertible antibacterial coating may find applications for various implants, such as orthopedic implants and vascular catheters.