On the function of biosynthesized cellulose as barrier against bacterial colonization of VAD drivelines

Abstract

Bacterial colonization of drivelines represents a major adverse event in the implantation of left ventricular assist devices (L-VADs) for the treatment of congestive heart failure. From the external driveline interface and through the skin breach, pathogens can ascend to the pump pocket, endangering the device function and the patient's life. Surface Micro-Engineered Biosynthesized cellulose (BC) is an implantable biomaterial, which minimizes fibrotic tissue deposition and promotes healthy tissue regeneration. The topographic arrangement of cellulose fibers and the typical material porosity support its potential protective function against bacterial permeation; however, this application has not been tested in clinically relevant animal models. Here, a goat model was adopted to evaluate the barrier function of BC membranes. The external silicone mantle of commercial L-VAD drivelines was implanted percutaneously with an intervening layer of BC to separate them from the surrounding soft tissue. End-point evaluation at 6 and 12 weeks of two separate animal groups revealed the local bacterial colonization at the different interfaces in comparison with unprotected driveline mantle controls. The results demonstrate that the BC membranes established an effective barrier against the bacterial colonization of the outer driveline interface. The containment of pathogen infiltration, in combination with the known anti-fibrotic effect of BC, may promote a more efficient immune clearance upon driveline implantation and support the efficacy of local antibiotic treatments, therefore mitigating the risk connected to their percutaneous deployment.

Figure 1

Experimental animal wearing a protective vest to secure the integrity of wound dressings.

Figure 2

Application of biosynthesized cellulose (BC) to the silicone mantle (s.d.m) of L-VAD-drivelines and implantation process. (A) Original s.d.m. wrapped in BC. Both ends of overlapping BC were trimmed to the length of the s.d.m. (B) Surgical site at the end of the procedure. S.d.m. are secured at the exit sites by a single purse string suture. (C) Preparation of subcutaneous tunnels and insertion of s.d.m. Arrangement of implants at the animals flank. Dotted line represents future incision for the explantation of the s.d.m.

Figure 3

In vitro test of BC barrier function. (A) Experimental settings. A test BC membrane separates two chambers assembled with an airtight seal. A dispersion of microparticles is loaded into the upper chamber and let to diffuse for 24 h. (B) Direct evaluation of microparticle penetration (Dextran beads) across BC membranes. The upper surface of the BC membrane is reported as positive control (upper panel). The lower surface of the BC membrane upon incubation with Dextran beads (middle panel). The lower surface of BC membrane upon incubation with distilled water, reported as negative control (lower panel). (C) Bacterial colonization of pristine (upper left) and punctured BC membranes (lower left) and of the underlying agar substrate (right). A blue circle (lower right) indicates bacterial colonization underneath punctured BC membranes.

Figure 4

Microbiologic results after sonication and subsequent plating. Observed implant colonization rate (bacterial growth) in the 6- and 12-week-group. In both groups, bacterial colonization rate of BC was higher than for the underlying BCB-s.d.m. No corresponding BCB-s.d.m. colonization was observed in 50% and 37,5% of the cases in the 6- and 12-week group, respectively. The control group (B-s.d.m.) is reported as control.