Effect of laser generated shockwaves 1 on ex-vivo pigskin

Biofilm dispersion: The key to biofilm eradication or opening Pandora's box?

Biofilms are extremely difficult to eradicate due to their decreased antibiotic susceptibility. Inducing biofilm dispersion could be a potential strategy to help combat biofilm-related infections. Mechanisms of biofilm dispersion can basically be divided into two groups, i.e. active and passive dispersion. Active dispersion depends on a decrease in the intracellular c-di-GMP levels, leading to the production of enzymes that degrade the biofilm matrix and promote dispersion. In contrast, passive dispersion relies on triggers that directly release cells from the biofilm. In the present review, several active and passive dispersion strategies are discussed. In addition, the disadvantages and possible consequences of using dispersion as a treatment approach for biofilm-related infections are also reviewed.

Safety of laser-generated shockwave treatment for bacterial biofilms in a cutaneous rodent model

Bacterial biofilms are often found in chronically infected wounds. Biofilms protect bacteria from antibiotics and impair wound healing. Surgical debridement is often needed to remove the biofilm from an infected wound. Laser-generated shockwave (LGS) treatment is a novel tissue-sparing treatment for biofilm disruption. Previous studies have demonstrated that LGS is effective in disrupting biofilms in vitro. In this study, we aim to determine the safety threshold of the LGS technology in an in vivo rodent model. To understand the in vivo effects of LGS on healthy cutaneous tissue, the de-haired dorsal skin of Sprague-Dawley rats were treated with LGS at three different peak pressures (118, 296, 227 MPa). These pressures were generated using a 1064 nm Nd/YAG laser (pulse duration 5 ns and laser fluence of 777.9 mJ) with laser spot size diameters of 2.2, 3.0, and 4.2 mm, respectively. Following treatment, the animals were observed for 72 h, and a small subset was euthanized at 1-h, 24-h, and 72-h post-treatment and assessed for tissue injury or inflammation under histology. Each treatment group consisted of 9 rats (n = 3/time point for 1-h, 24-h, 72-h post-treatment). An additional 4 control (untreated) rats were included in the analysis, for a total of 31 animals. Gross injuries occurred in 21 (77%) animals and consisted of minor erythema, with prevalence positively correlated with peak pressure (p < 0.05). Of injuries under gross observation, 94% resolved within 24 h. Under histological analysis, the injuries and tissue inflammation were found to be localized to the epidermis and superficial dermis. LGS appears to be well tolerated by cutaneous tissue for the laser energy settings shown to be effective against bacterial biofilm in vitro. All injuries incurred, at even the highest peak pressures, were clinically mild and resolved within 1 day. This lends further support to the overall safety of LGS and serves to translate LGS towards in vivo efficacy studies.

Effects of Different 980-nm Diode Laser Parameters in Hepatectomy

BACKGROUND AND OBJECTIVE

Despite the successful application of laser in animal experiments and clinics, the adjustment of laser parameters during surgery is still unclear. This study aimed to investigate the effect of different 980-nm diode laser parameters in hepatectomy. This could provide a clear protocol for using 980-nm diode laser in hepatectomy.

STUDY DESIGN/MATERIALS AND METHODS

In total, 48 Sprague-Dawley rats were used to explore the effects of different 980-nm diode laser parameters in hepatectomy, by setting different parameter combinations. The rats were randomly divided into eight groups, including the continuous wave group and quasi-continuous wave group. The effects were assessed in terms of liver resection speed, extent of intraoperative bleeding, and thermal damage.

RESULTS

In the quasi-continuous wave group, there was a significant difference in resection speed at the different laser parameters (P < 0.001); however, there was no significant difference in intraoperative bleeding and thermal damage. In the continuous wave group, there was a significant difference in resection speed, intraoperative bleeding, and thermal damage at different parameters.

CONCLUSION

The study showed that the average power determined hemostasis efficiency and thermal damage, and peak power determined the liver resection speed, whereas the pulse width and repetition frequency are not independent factors. When using 980-nm diode laser in hepatectomy, the average power should be decreased to prove hemostasis efficiency in delicate operations, and the peak power should be decreased to accelerate the procedure without worsening thermal damage. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

In-depth analysis of antibacterial mechanisms of laser generated shockwave treatment

Background and Objectives Laser generated shockwave (LGS) is a novel modality for minimally invasive disruption of bacterial biofilms. The objectives of this study are to determine the mechanisms behind LGS treatment and non-biofilm effects on bacterial disruption, including (1) comparing bacterial load with and without LGS in its planktonic form and (2) estimating bacterial cell permeability following LGS. Study Design/Materials and Methods For the first study, planktonic S. epidermidis were treated with gentamicin (0, 8, 16, 32, 64 μg/ml) with and without LGS (1064 nm Nd:YAG laser, 110.14 mJ/mm² , pulse duration 9 ns, spot size 3 mm, n = 8/group), and absorbances at 600 nm compared. For the second study, four samples of planktonic S. epidermidis were treated with LGS (same settings). Propidium iodide (PI) uptake via flow cytometry as a measure of cell permeability was measured at 0, 10, and 20 minutes following LGS. RESULTS: In comparing corresponding gentamicin concentrations within both LGS-treated samples and controls at 0 hours, there were no differences in absorbance (P = 0.923 and P = 0.814, respectively). Flow cytometry found modest PI uptake (10.4 ± 2.5%) immediately following LGS treatment, with time-dependent increase and persistence of the signal at 20 minutes (R²  = 0.449, P = 0.048). CONCLUSION: 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.

Laser-generated shockwaves enhance antibacterial activity against biofilms in vitro

BACKGROUND AND OBJECTIVES

Bacterial biofilm formation within chronic wound beds, which provides an effective barrier against antibiotics, is a known cause of recalcitrant infections and a significant healthcare burden, often requiring repeated surgical debridements. Laser-generated shockwaves (LGS) is a novel, minimally invasive, and nonthermal modality for biofilm mechanical debridement which utilizes compressive stress waves, generated by photonic absorption in thin titanium films to mechanically disrupt the biofilm. Prior studies have demonstrated LGS monotherapy to be selectively efficacious for biofilm disruption and safe for host tissues. In this study, we sought to determine if LGS can enhance the antimicrobial activity and biofilm disruption capability of topical antibiotic therapy.

STUDY DESIGN/MATERIALS AND METHODS

Staphylococcus epidermidis biofilms grown in vitro on glass were treated with topical gentamicin (31, 62, and 124 μg/ml) with and without LGS (n = 3-11/treatment group). Mechanical shockwaves were generated with a 1,064 nm Nd:YAG laser (laser fluence 110.14 mJ/mm² , pulse duration 5 ns, spot size 3 mm). Following a 24-hour incubation period, bacterial viability was assessed by determining the number of colony-forming units (CFU) via the Miles and Misra method. Residual biofilm bioburden was analyzed using the crystal violet biofilm assay.

RESULTS

With gentamicin monotherapy, CFU density (CFU/mm² ) at 31, 62, and 124 μg/ml were (282 ± 84) × 10⁴ , (185 ± 34) × 10⁴ , and (113 ± 9) × 10⁴ , respectively. With LGS and gentamicin therapy, CFU density decreased to (170 ± 44) × 10⁴ , (89 ± 24) × 10⁴ , and (43 ± 3) × 10⁴ , respectively (P = 0.1704, 0.0302, and 0.0004 when compared with gentamicin alone). Biofilm burden as measured by the assay in the gentamicin 31, 62, and 124 μg/ml groups was reduced by 80%, 95%, and 98% when LGS was added (P = 0.0102, >0.0001, and 0.0001 for all groups when compared with gentamicin alone). Furthermore, samples treated with LGS saw an increase in susceptibility to gentamicin, in terms of reduced biofilm bioburden and CFU densities.

CONCLUSION

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.

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

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.