Analysis of flexible substrates for clinical translation of laser-generated shockwave therapy

Abstract

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).

Laser-Generated Shockwaves as a Treatment to Reduce Bacterial Load and Disrupt Biofilm

“…This material was selected based on results of previous shockwave characterization experiments [18]. Confinement was created by manually applying a thin layer (200 μ m) of water—glass on the titanium surface.…”

“…In the LGS process, a short-pulsed laser ablates a thin metal film layered between an acoustic backing and a carrier substrate. This configuration causes a focused compressive shockwave to travel through a coupling medium to the biofilm layer [18]. When the pressure wave reaches the biofilm—tissue interface, acoustic impedance mismatch causes a portion of the compressive wave to reflect as a tensile wave, while the rest of the compressive wave transmits through and disperses within the tissue.…”

Laser-generated shockwaves enhance antibacterial activity against biofilmsin vitro

“…A 0.5 μm layer of titanium was deposited onto a 0.1 mm thick polycarbonate plastic via RF sputtering, as described previously for plastics sample preparation . A 15 μm layer of waterglass was manually applied to the titanium side of the polycarbonate and allowed to dry for 20 minutes.…”

“…Laser‐generated shockwave (LGS) therapy is a novel, minimally invasive, and non‐thermal method for the removal of bacterial biofilms . LGS utilizes compressive stress waves generated by laser ablation of a thin titanium film to mechanically disrupt the biofilm, without damaging the underlying tissue (Fig.…”

“…Another study by Krespi et al showed that LGS therapy alone can be effective in removing Pseudomonas aeruginosa biofilms in vitro from commonly used prosthetic materials used in otolaryngology, such as sutures, screws, and tympanostomy tubes . The technology is analogous to, but disparate from extracorporeal shockwave therapy (ESWT), as it can generate peak pressures of 200 MPa with rise times of 2 ns, and without a tensile component . The presence of tensile in ESWT and other high intensity focused ultrasound technologies limits their translation for biofilm treatment.…”