Violet LED induces vasodilation in rat aortic rings by soluble guanylate cyclase-dependent mechanism and increases SOD activity.

We found several studies that have used the aortic rings as an experimental model, mainly for the testing of new drugs or new therapies that try to reverse or prevent endothelial dysfunction or characterize its mechanism of action in a biological system, creating the knowledge necessary to obtain the treatment of those several diseases, where many of these treatments involve photobiomodulation therapies. We also found numerous wavelengths represented by different colors of LASER or LED in which frequently, the mechanism of action in biological systems is unknown. This study has as main objective to investigate the effects of the Violet LED Light (405 nm) by using isolated aortic rings, looking for nitric oxide (NO) release, and evaluating if Violet LED Light can modulate the superoxide dismutase (SOD) activity. We performed a vascular reactivity study in isolated aortic rings from normotensive rats with a single LED application. Besides it, the rings were pre-incubated with soluble guanylate cyclase (sGC) inhibitor or endothelial NO synthase inhibitor and subsequently underwent the application of the Violet LED. The cell viability and nitric oxide release in cell culture of human umbilical codon vein cells (HUVEC) were analyzed. In the vascular reactivity experiment, we observed a peak of vasodilation when applying light to the aortic rings. The soluble guanylate cyclase inhibitor abolished the relaxation induced by the Violet LED Light. However, the NO synthase inhibitor did not modify the Violet LED effect. In an isolated system, we verified that the Violet LED Light can increase SOD activity. Our results suggest that Violet LED Light induces vasodilation by a mechanism dependent on sGC activation, and not by NOS activation, and part of this effect could be due to the increase of SOD activity.

In vitro evaluation of physical and chemical parameters involved in aPDT of Aggregatibacter actinomycetemcomitans.

Periodontitis is an infectious disease characterized by the destruction of supporting tissues. Antimicrobial photodynamic therapy (aPDT) has been proposed as an improved method for eliminating microorganisms. Its efficiency depends on the correct use of physical and chemical parameters. Thus, these parameters and their relations were evaluated in this study with the purpose of establishing lethal conditions for combating bacterial agents. Diode lasers and light-emitting diodes (LEDs) were characterized to evaluate the absorption profile and resonance of methylene blue (MB) and toluidine blue O (TBO). The relations between light energy density and photosensitizer absorption were determined. Two methodologies were used to evaluate the effects of aPDT against Aggregatibacter actinomycetemcomitans. LED light exhibited a broad emission spectrum with a peak light wavelength of 637 nm and 99% purity. The resonance intensity of MB was higher with diode laser irradiation, and TBO showed higher resonance intensity with LED irradiation. There was no difference in the absorption profile of photosensitizers using diode lasers or LEDs, and variations in power density did not result in an increasing or decrease in light absorption. A. actinomycetemcomitans was susceptible to photodynamic processes. Emission spectra and peak light wavelengths of light sources combined with the absorption profiles of photosensitizers were the main parameters involved in determining the efficiency of photodynamic effects. Power density did not alter the light absorption of photosensitizers. The association between adequate irradiation characteristics and photosensitizer absorption results in complete inactivation of A. actinomycetemcomitans. In addition, the bactericidal effect was not altered by an increase in energy densities.

The Rationale for "Laser-Induced Thermal Therapy (LITT) and Intratumoral Cisplatin" Approach for Cancer Treatment.

Cisplatin is one of the most widely used anticancer drugs in the treatment of various types of solid human cancers, as well as germ cell tumors, sarcomas, and lymphomas. Strong evidence from research has demonstrated higher efficacy of a combination of cisplatin and derivatives, together with hyperthermia and light, in overcoming drug resistance and improving tumoricidal efficacy. It is well known that the antioncogenic potential of CDDP is markedly enhanced by hyperthermia compared to drug treatment alone. However, more recently, accelerators of high energy particles, such as synchrotrons, have been used to produce powerful and monochromatizable radiation to induce an Auger electron cascade in cis-platinum molecules. This is the concept that makes photoactivation of cis-platinum theoretically possible. Both heat and light increase cisplatin anticancer activity via multiple mechanisms, generating DNA lesions by interacting with purine bases in DNA followed by activation of several signal transduction pathways which finally lead to apoptosis. For the past twenty-seven years, our group has developed infrared photo-thermal activation of cisplatin for cancer treatment from bench to bedside. The future development of photoactivatable prodrugs of platinum-based agents injected intratumorally will increase selectivity, lower toxicity and increase efficacy of this important class of antitumor drugs, particularly when treating tumors accessible to laser-based fiber-optic devices, as in head and neck cancer. In this article, the mechanistic rationale of combined intratumor injections of cisplatin and laser-induced thermal therapy (CDDP-LITT) and the clinical application of such minimally invasive treatment for cancer are reviewed.

Posterior laryngofissure using a surgical contact diode laser: an experimental feasibility study.

To evaluate the feasibility of a 980-nm contact diode laser (CDL) as a method for creating a posterior laryngofissure in live pigs. Twenty-eight Landrace pigs (15-20 kg) were anesthetized, intubated, ventilated, and submitted to a cervical tracheostomy. An anterior and posterior midline longitudinal laryngofissure incision was created according to randomization-control (n = 4), posterior laryngofissure with a scalpel blade; electrocautery (n = 12), posterior laryngofissure by electrocautery (10, 15, 20, 25 W powers); CDL (n = 12), posterior laryngofissure by the CDL (10, 15, 20, 25 W peak powers in pulsed mode). Larynx and proximal trachea were excised, prepared for histopathology, and digital morphometric analysis. Measurements in and within each group were analyzed (Kruskal-Wallis and Dunn test) with a level of significance of p < 0.05. Incision width was not different between the groups, as well as in the powers used in CDL (p = 0.161) and electrocautery group (p = 0.319). The depth of the incisions was smaller in the Laser group compared to control (p = 0.007), and in the electrocautery compared to control (p = 0.026). Incision area was smaller in CDL compared with the control (p = 0.027), and not different between laser and electrocautery groups (p = 0.199). The lateral thermal damage produced by electrocautery was the largest, with a significant difference between laser and electrocautery (p = 0.018), and between electrocautery and control (p = 0.004), whereas the comparison between laser and control showed no significant differences (p = 0.588). The posterior laryngofissure incision using a 980-nm CDL is feasible resulting in smaller incisional area and less lateral thermal damage.

Effects of diode laser setting for laryngeal surgery in a rabbit model.

PURPOSE: To study the damaging effect of different diode laser settings on vocal folds 7 days after injury in a rabbit model. METHODS: Twenty-one male New Zealand white rabbits were randomized into three groups with seven animals per group. A 980-nm diode laser was used to create a single spot injury in each vocal fold. Different modulation frequencies (10 Hz versus 1000 Hz) in pulsed mode, different powers (3 W versus 5 W), and distinct wave modes of radiation (pulsed versus continuous) were compared. RESULTS: The extent of the inflammatory infiltrate and ablation crater were greater when using 5-W optical power compared with 3 W. The extent and depth of the inflammatory infiltrate, and the width and depth of the ablation crater were greater with continuous wave mode compared with pulsed mode. The density of collagen fibers only increased when using the laser in continuous wave mode. CONCLUSION: The use of the 980-nm diode laser with an output power of 5 W produced an increased extent of thermal injury compared to an output power of 3 W and, more importantly, using continuous rather than pulsed wave mode significantly increased the extent and depth of thermal injury in rabbit vocal folds.

Comparison between contact diode laser with 980 nm and 1470 nm wavelengths for posterior laryngofissure in pigs.

To compare two different wavelengths of the surgical contact diode laser (CDL) for producing a posterior laryngofissure in in-vivo pigs. Anesthetized pigs underwent a tracheostomy and an anterior laryngofissure through a cervicotomy. They were randomly selected for the CDL wavelength and Power, according to the peak of Power set at device (980nm wavelength: Ppeak power of 10 W, 15 W, and 20 W, or 1470 nm wavelength: Ppeak 3 W, 5 W, 7 W, 10 W). At the end of the experiment, the laryngotracheal specimen was extracted and sent for histology and morphometry measurements (incision size, depth, area, and lateral thermal damage). Hemodynamic data and arterial blood gases were recorded during the incisions. Statistical analysis of the comparisons between the parameters and groups had a level of significance of p < 0.05. Twenty-six pigs were divided into CDL 980 nm (n = 11) and 1470 nm (n = 15). There was a greater incision area at the thyroid level in the 980 nm CDL and a wider incision at the trachea level, with a larger distance between mucosa borders. There were no significant differences in the area of lateral thermal damage between the two groups and neither difference among the power levels tested. Both wavelengths tested showed similar results in the various combinations of power levels without significant differences in the lateral thermal damage. The posterior laryngofissure incision can be performed by either of the wavelengths at low and medium power levels without great difference on lateral thermal damage.

Prompt Inactivation of Coronavirus Using a 280 nm Light-Emitting Diode Cluster Device.

Objective: We report on the development and characterization of a UV-C light-emitting diode (LED) 280 nm cluster prototype device designed for the rapid disinfection of SARS-CoV-2 coronaviruses. The device was evaluated against the Betacoronavirus mouse hepatitis virus-3 strain, and its virucidal capacity was probed as a function of different applied UV-C doses versus different situations concerning irradiation distances. Background: UV-C LEDs are light emitters that offer advantages over low-pressure mercury lamps, such as quasimonochromaticity, lower electrical power consumption, instant on/off with the instant full-power operation, unlimited on/off cycles for disinfection schemes, and a much longer lifetime operation, in addition to portability aspects, as well as UV-C LEDs do not contain heavy metal in its composition such as mercury, found in ultraviolet germicidal irradiation (UVGI) lamps. Results: This novel device reached a 99.999% elimination rate at a distance of 9 cm at all the tested irradiation times (dose dependence), demonstrating that it took only 30 sec to achieve this inactivation rate. Its virucidal effectivity in rapid virus inactivation was demonstrated. Conclusions: We conclude that the HHUVCS cluster device (λp = 280 nm) provides a rapid virucidal effect against the SARS-CoV-2 coronavirus. The current research should encourage further advances in UV-C LED-based devices designed for the inactivation of SARS-CoV-2 virus on surfaces, in air, and in liquids.

Fast inactivation of coronavirus in filtering-facepiece respirators in a reflective cylindrical UV-C chamber.

Objective: We report on the development and characterization of a UV-C (λ  =  200 - 280 nm, λpeak = 254 nm) chamber designed for the rapid disinfection of N95 class filtering-facepiece respirators contaminated with SARS-CoV-2 coronaviruses. The device was evaluated against Betacoronavirus strain MHV-3 and its virucidal capacity was evaluated as a function of different applied UV-C doses (UV-C exposure times of 60 s, 120 s, 180 s, and 240 s) using two types of respirators geometry (shell and two-panel shapes, 3M 8801 H and 9920 H, respectively), at eight points of the respirators. Background: Most chemical disinfection methods are not recommended for N95 masks. UV-C light provided by UVGI lamps (254 nm) is an effective physical agent against viruses and bacteria due to direct photochemical harming effect on DNA/RNA, and can provide rapid disinfection for personal protective equipment such as N95/PFF2 masks. Results: The device reached a mean elimination rate of 99.9999% of MHV-3 inoculated into all the assessed different points on the tested PFF2 respirator models in a UV-C cycle of just 60 s. Statistical analysis performed through Person´s chi-square test showed no correlation between the viral infectivity reduction and the viral inoculation point (p = 0.512) and the tested respirator models (p = 0.556). However, a correlation was found between the exposure time and the viral infectivity reduction (p = 0.000*), between UV-C and no UV-C exposure. All the tested UV-C exposure times (60 s, 120 s, 180 s, and 240 s) provided the same reduction in infection rates. Therefore, 60 s was confirmed as the minimum exposure time to achieve a 99.9999% or 6 Log reduction in MHV-3 coronavirus infection rates in the PFF2 samples tested in the device. Conclusions: We conclude that the assessed UV-C chamber for the inactivation of MHV-3 coronavirus in N95/PFF2 standard masks can be a promising tool for effective and rapid disinfection of coronaviruses, including SARS-CoV-2 virus.

Application of a 980-nanometer diode laser in neuroendoscopy: a case series.

OBJECTIVE: Ventricular neuroendoscopy represents an important advance in the treatment of hydrocephalus. High-power (surgical) Nd:YAG laser and low-level laser therapy (using 685-nm-wavelength diode laser) have been used in conjunction with neuroendoscopy with favorable results. This study evaluated the use of surgical 980-nm-wavelength diode laser for the neuroendoscopic treatment of ventricular diseases. METHODS: Nine patients underwent a neuroendoscopic procedure with 980-nm diode laser. Complications and follow-up were recorded. RESULTS: Three in-hospital postoperative complications were recorded (1 intraventricular hemorrhage and 2 meningitis cases). The remaining 6 patients had symptom improvement after endoscopic surgery and were discharged from the hospital within 24-48 hours after surgery. Patients were followed for an average of 14 months: 1 patient developed meningitis and another died suddenly at home. The other patients did well and were asymptomatic until the last follow-up consultation. CONCLUSIONS: The 980-nm diode laser is considered an important therapeutic tool for endoscopic neurological surgeries. This study showed its application in different ventricular diseases.