Reduced bacterial adhesion with parylene coating: Potential implications for Micra transcatheter pacemakers

INTRODUCTION: Infections of cardiac implantable electronic devices remain a prevalent health concern necessitating the advent of novel preventative strategies. Based on the observation that bacterial infections of the Micra transcatheter pacemaker device are extremely rare, we examine the effect of parylene coating on bacterial adhesion and growth. METHODS: Bacterial growth was compared on polyurethane coated, bare, or parylene coated titanium surfaces. Eight test samples per bacterial species and material combination were incubated with Staphylococcus Aureus or Pseudomonas aeruginosa for 24 hours and then assayed for bacterial growth. The surface contact angle was also characterized by measuring the angle between the tangent to the surface of a liquid droplet made with the surface of the solid sample. RESULTS: The mean bacterial colony counts were significantly reduced for both parylene coated titanium versus bare samples (3.69 +/- 0.27 and 4.80 +/- 0.48 log[CFU/mL] respectively for S. aureus [P < .001] and 5.51 +/- 0.27 and 6.08 +/- 0.11 log[CFU/mL] respectively for P. aeruginosa [P < .001]), and for parylene coated titanium versus polyurethane samples (4.27 +/- 0.42 and 5.40 +/- 0.49 log[CFU/mL] respectively for S. aureus [P < .001] and 4.23 +/- 0.42 and 4.84 +/- 0.32 log[CFU/mL] respectively for P. aeruginosa [P = .006]). Parylene coated titanium samples had a higher contact angle compared with bare titanium, but lower compared with polyurethane (mean contact angle 87.5 +/- 3.1 degrees parylene, 73.3 +/- 3.7 degrees titanium [P < .001 vs parylene], and 94.8 +/- 3.7 degrees polyurethane [P = .002 vs parylene]). CONCLUSIONS: Parylene coating significantly reduced the ability of bacteria to grow in colony count assays suggesting that this could contribute to the reduction of bacterial infections of Micra transcatheter pacemakers.