Bacteria biofilms in chronically infected wounds significantly increase the burden of healthcare costs and resources for patients and clinics. Because biofilms are such an effective barrier to standard antibiotic treatment, new methods of therapy need to be developed to combat these infections. Our group has demonstrated the potential of using Laser Generated Shockwaves as a potential therapy to mechanically disrupt the bacterial biofilms covering the wound. Previous studies have used rigid silica glass as the shockwave propagation medium, which is not compatible with the intended clinical application. This paper describes the exploration of five candidate flexible plastic films to replace the glass substrate. Each material measured 0.254 mm thick and was used to generate shockwaves of varying intensities. Shockwave characterization was performed using a high-speed Michelson displacement interferometer and peak stress values obtained in the flexible substrates were compared to glass using one-way nested Analysis of Variance and Tukey HSD post-hoc analysis. Results demonstrate statistically significant differences between substrate material and indicate that polycarbonate achieves the highest peak stress for a given laser fluence suggesting that it is optimal for clinical applications. Experiment and simulation of the spallation process," J. Appl. Phys. 74(4), 2388-2396 (1993). 18. V. Gupta and J. Yuan, "Measurement of interface strength by the modified laser spallation technique. II.Applications to metal/ceramic interfaces," J. Appl. Phys. 74(4), 2397-2404 (1993). 19. J. Yuan, V. Gupta, and A. Pronin, "Measurement of interface strength by the modified laser spallation technique.III. Experimental optimization of the stress pulse," J. Appl. Phys. 74(4), 2405-2410 (1993). 20. T. Požar, P. Gregorčič, and J. Možina, "A precise and wide-dymanic-range displacement-measuring homodyne quadrature laser interferometer," Appl. Phys. B 105(3), 575-582 (2011).

Objective: The goal of this paper is to demonstrate and evaluate the potential efficacy of laser-generated shockwave (LGS) therapy on biofilm infected tissue. Methods: To demonstrate proof of concept, Staphylococcus epidermidis was allowed to proliferate on ex vivo pigskin, until mature biofilm formation was achieved, and then subjected to LGS. Bacterial load between control and treated samples was compared using the swab technique and colony counting. Scanning electron microscopy (SEM) was then used to visualize the biofilm growth and resulting reduction in biofilm coverage from treatment. Images were false colored to improve contrast of biofilm, and percent biofilm coverage was computed, along with biofilm cluster size. Results: LGS reduced bacterial load by 69% (p = 0.008). Imaging showed biofilm coverage reduced by 52% and significantly reduced average cluster size (p < 0.001). Conclusion: LGS therapy reduced the burden of bacterial biofilm on ex vivo pigskin and can be visualized using SEM imaging. Significance: LGS therapy is a new treatment for infected wounds, allowing rapid disruption of biofilm to 1) remove bacteria and 2) increase susceptibility of remaining biofilm to topical antibiotics. This can lead to improved wound healing times, reduced patient morbidity, and decreased healthcare costs.

LGS enhances the efficacy of topical antibiotics in an in vitro model. This has significant implications for clinical applications in the management of chronic soft tissue infections and recalcitrant chronic rhinosinusitis. Lasers Surg. Med. 49:539-547, 2017. © 2017 Wiley Periodicals, Inc.

Taken together, LGS does not appear to have direct bacteriocidal properties, but rather by allowing for biofilm disruption and bacterial cell membrane permeabilization, both of which likely increase topical antibiotic delivery to pathogenic organisms. Insight into the mechanisms of LGS will allow for improved clinical applications and facilitate safe and effective translation of this technology. Lasers Surg. Med. © 2018 Wiley Periodicals, Inc.