Bi-layer sandwich film for antibacterial catheters

Abstract

Background: Approximately one quarter of all nosocomial infections can be attributed to the urinary tract. The infections are supposed to be mainly caused by implantations of urethral catheters and stents. A new catheter design is introduced with the aim to lower the high number of nosocomial urethral infections. In order to avoid limitations to use, the design is first applied to conventional commercially available balloon catheters. Results: The main feature of the design is a sandwich layer on both sides of the catheter wall, which is composed of a fragmented base layer of silver capped by a thin film of poly(p-xylylene). This top layer is mainly designed to release a controlled amount of Ag+ ions, which is bactericidal, but not toxic to humans. Simultaneously, the lifetime is prolonged to at least one year. The base layer is electrolessly deposited applying Tollens’ reagens, the cap layer is deposited by using chemical vapor deposition. Conclusion: The three main problems of this process, electroless deposition of a fragmented silver film on the surface of an electrically insulating organic polymer, irreproducible evaporation during heating of the precursor, and exponential decrease of the layer thickness along the capillary, have been solved trough the application of a simple electrochemical reaction and two standard principles of physics: Papin’s pot and the principle of Le Chatelier.

Internal Coating of Ureteral Stents with Chemical Vapor Deposition of Parylene

“…The Gorham CVD process occurs in a reactor which is extensively described elsewhere [6,22]. Briefly, the reactor (Plasma Parylene Systems, Rosenheim, Germany) had a volume of 91 l and was flanged to an evaporator and cracker via a gate on the left, referred to as the front door (Figure 3).…”

“…Because PPX belongs to the group of organic polymers which passed the approval of the FDA, it has been in use as a coating film on implantates for human beings for more than 40 years [4,5]. This quality especially attracted our interest, and we deposited very thin films of parylene on the inner and outer surface of urethral balloon catheters and ureteral stents to add antibacterial activity to them [6].…”

“…Whereas the silver acts as antibacterial reagent, its release rate can be moderated by a very thin top layer of parylene. This coating also improves the tribological properties and, last but not least, also hampers the proceeding of bacteria [6].…”

An Evaluation of Parylene Thin Films to Prevent Encrustation for a Urinary Bladder Pressure MEMS Sensor System

“…Innovative approaches involving Ag-Au nanoparticle-coated stents offer prolonged antibacterial and biofilm-resistant qualities [7]. Additionally, Franz et al [8] proposed a sandwich layer with a silver base layer and parylene film to gradually release non-toxic, bactericidal Ag ions. Early antimicrobial coating studies involved soaking urological stents in antibiotics and drying them for a coated effect; combining such coated stents with systemic antibiotics yielded bacteriostatic effects.…”

Vapor-based polymers: from films to nanostructures

“…The absence of small molecule compounds or solvents in CVD films mitigates the risk of potential leakage of hazardous residues from the coating material, which, in turn, often results in superior biocompatibility [ 10 ]. This, together with the conformal character of the coating, is of importance in a novel antibacterial catheter introduced by Franz et al [ 11 ] Here, poly( p -xylylene), which is deposited via chemical vapor deposition, is used as a top layer above an electro-deposited silver coating, ensuring the prolonged release of antibacterial silver ions.…”