Antifouling and antimicrobial coating with intelligent pH-responsive charge-switching capability prevents catheter-associated obstructions and infection

Catheter-related infections and obstructions are the primary causes of treatment failure and discontinuation in peritoneal dialysis (PD), constituting a major challenge in the renal replacement therapy for patients with renal failure thereby compromising their treatment. To address the challenge of balancing antimicrobial and anti-fouling properties on medical catheter surfaces, we propose a method that by introducing a slightly positive charge into the anti-fouling matrix to integrate antimicrobial and anti-fouling functions via smart switching behavior. Herein, we developed a polymeric zwitterionic-dominant coating with slightly positive charges (isoelectric point, IEP = 7.69), named PZ-SPC. By forming a hydration layer on the catheter surface, the polymeric zwitterionic hydrogel matrix effectively resisted the non-specific adhesion of proteins, bacteria, and cells on the catheters, thereby preventing bacterial biofilm formation. By adjusting the proportion of organosilicon quaternary ammonium salts (providing long alkyl chains and positive charges) introduced into the matrix, the IEP was precisely tuned to 7.69, which is slightly above the physiological pH (7.4). In a normal peritoneal dialysate environment, the PZ-SPC coating provided a weak net positive charge and hydration layer, thereby exerting a "defensive mode" for effective antifouling function. The adhesion of bovine serum albumin and fibrinogen is reduced by 76.58% and 70.57% respectively. In an acidic biofilm microenvironment, the PZ-SPC coating provided a stronger positive charge to enhance the permeabilization of the bacterial membrane, triggering a "killing mode" for effective antimicrobial action. The bactericidal rate of PD@PZ-SPC against both Gram-negative and Gram-positive bacteria achieves over 99.9% in acidic conditions. We established a peritoneal dialysis catheter-associated peritonitis model in rats to validate the <i>in vivo</i> efficacy of PD@PZ-SPC. The results showed that the PD@PZ-SPC effectively reduced catheter obstruction and alleviated the severity of peritonitis. This coating strategy achieves an optimal balance between "anti-fouling" and "contact sterilization" via intelligent pH-responsive charge switching behavior, providing a practical engineering guideline for developing surfaces to combat diverse contaminants in complex biological environments.