Novel In Vitro Study to Assess Microbial Barrier Properties of Polyurethane-Based Tissue Adhesives in Comparison to the Gold Standard Dermabond®

Abstract

Tissue adhesives as a physical barrier to microorganism penetration provide an alternative method with many advantages for wound closure in surgical settings compared to the clinical standard. This raises the need of developing and conducting in vitro methods that are sensitive and reproducible to assess their microbial barrier properties. In this study, three different polyurethane-based tissue adhesives with different physicochemical properties were evaluated in comparison to Dermabond® as a clinical gold standard for topical wound closure. Here, physicochemical properties varied in lactide concentration, viscosity, processing, and the full polymerization time. To evaluate the microbial barrier function, a 5 μl aliquot of E. coli Lux inoculum containing at least 1 × 10⁹ CFU/ml was applied to the surface of each test adhesive and sterile filter paper as the control that was placed on an agar plate and incubated at 37°C. Plates were observed for bacterial growth (morphology), the adhesion of the adhesive/filter paper, and bioluminescence after 24, 48, and 72 hours. The data presented in this in vitro model indicated that polyurethane-based tissue adhesives with lactide concentration ≥ 5% provided a suitable barrier against microbial penetration with 95% confidence of 99% efficacy for 72 h along with Dermabond®. Interestingly, the here described method was able to discriminate between the different physicochemical properties showing a better microbial barrier function with increasing lactide concentration of the adhesive. Overall, the results of this study showed the noninferiority between Dermabond® and the two abovementioned polyurethane-based tissue adhesives.

Figure 1

Experimental design. (a) Experimental design and group assignment. (b) T₀: characterization, inoculation, and application of E. coli Lux on the test articles, representative images of polyurethane-based tissue adhesive (PU-glue: AM1, AM2, and AM3), Dermabond®, filter paper (control) on the agar plate. T_24h, T_48h, T_72h: morphology observation and bioluminescence measurement using IVIS imaging system, representative images of PU-glue (upper row) and filter paper (lower row) from above at each time point.

Figure 2

Results of bioluminescence measurement taken from above converted into CFU/ml after inoculation with 5 μl of a 1 : 100 dilution of E. coli Lux culture at indicated time points: (a) AM1, (b) AM2, (c) AM3, and (b) Dermabond®. Values are means, and error bars represent SD.

Figure 3

Results of bioluminescence measurement taken from bottom site converted into CFU/ml after inoculation with 5 μl of a 1 : 100 dilution of E. coli Lux culture at indicated time points: (a) AM1, (b) AM2, (c) AM3, and (d) Dermabond®. Values are means, and error bars represent SD. ^∗∗∗ for p ≤ 0.001 and ^∗∗∗∗ for p ≤ 0.0001.

Figure 4

Results of bioluminescence measurement taken from cross-section converted into CFU/ml after inoculation with 5 μl of a 1 : 100 dilution of E. coli Lux culture at indicated time points: (a) AM1, (b) AM2, (c) AM3, and (d) Dermabond®. Values are means, and error bars represent SD.

Figure 5

Graphical illustration (bar chart) of the percent maintenance of the microbial barrier against bacterial growth for AM1, AM2, AM3, and Dermabond® based on total flux values upon different time points after removal of the tissue adhesives.