Lasers in Medical Science

Photobiomodulation is proposed as a non-linear process, and only low-level laser therapy (LLLT) is assumed to stimulate exposed cells, whereas high powered laser and fluences can cause negative effects, exhausting the cell’s energy reserve as a consequence of excessive photon-based stimulation. In our work, we investigated and compared the effects of 808-nm diode laser (CW) with a new flat-top handpiece. To this purpose, we tested the photobiomodulation effects of 1 and 3 J/cm2 fluence, both generated by 100 mW or 1 W of laser power and of 64 J/cm2 of fluence generated by 100 mW, 1 W, 1.5 W or 2 W, as expressed through oxygen consumption and ATP synthesis of Paramecium. Data collected indicates the incremental consumption of oxygen through irradiation with 3 J/cm2–100 mW or 64 J/cm2–1 W correlates with an increase in Paramecium ATP synthesis. The Paramecium respiration was inhibited by fluences 64 J/cm2–100 mW or 64 J/cm2–2 W and was followed by a decrease in the endogenous ATP concentration. The 1 J/cm2–100 mW or 1 W and 3 J/cm2–1 W did not affect mitochondrial activity. The results show that the fluence of 64 J/cm2–1 W more than the 3 J/cm2–100 mW causes greater efficiency in Paramecium mitochondria respiratory chain activity. Our results suggest that thanks to flat-top handpiece we used, high fluences by high-powered laser have to be reconsidered as an effective and non-invasive therapy. Possible associated benefits of deeper tissue penetration would increase treatment effectiveness and reduced irradiation time.

Cardiac arrhythmias can be treated by endocardial laser photocoagulation of arrhythmogenic foci. Transcatheter continuous wave Nd-YAG laser (1064 nm) photocoagulation was studied for impairment of atrioventricular (AV) conduction. First, studies on the dose-effect relation revealed that in vitro applications to ventricular endocardium produce dose-dependent coagulation necrosis. However, energy absorption varies in tissue specimens from different experimental animals and humans and may be dependent on differences in surfaces ultrastructure. Ten times more energy is required for human endocardial specimens than for canine endocardium. The long-term in vivo experiment demonstrates that the chronic laser-induced myocardial lesion size is proportional to the applied energy, exhibit no arrhythmogenic effects and may thus be suitable for the treatment of cardiac arrhythmias. Transcatheter laser application using a combined electrode-laser catheter reliably achieved a slowing of atrioventricular AV conduction (AV modification) or a complete AV block. Thus, the transcatheter application of Nd-YAG laser energy at the AV node may be useful for treatment of tachyarrhythmias in man.

. Laserneedles represent a new non-invasive optical stimulation method which is described for the first time in this paper. We investigated 27 healthy volunteers (mean age±SD: 25.15±4.12 years; range: 21–38 years; 14 female, 13 male) in a randomised cross-over trial to study differences between laserneedle acupuncture and manual needle acupuncture in specific cerebral parameters. Mean blood flow velocity (v m) showed specific and significant increases in the ophthalmic artery during laserneedle stimulation (p=0.01) and during manual needle stimulation (p<0.001) at vision-related acupoints. At the same time insignificant alterations in v m were found in the middle cerebral artery for both acupuncture methods. The eight laserneedles used in this study were arranged at the end of the optical fibres. Each fibre was connected to a semiconductor laser diode emitting at 685 nm with a primary output power of about 55 mW. Optical stimulation using properly adjusted laserneedles has the advantage that the stimulation can hardly be felt by the patient and the operator may also be unaware of whether the laserneedle system is active, and therefore true double blind studies in acupuncture research can be performed.

Various treatment modalities have been applied to atrophic scars. Fractional CO2 laser treatment has attracted increasingly more attention because of its quicker recovery time and fewer side effects. However, its limitation of sculpting the edge is an urgent shortcoming. In order to achieve a more effective result with fewer complications, we have integrated ultrapulse CO2 and fractional CO2 lasers to for the treatment of facial atrophic scars. The study included 25 patients (10 males and 15 females) diagnosed with moderate to severe atrophic scars between August 2020 and July 2022. All subjects underwent the same surgical treatment. The effects were assessed at baseline, 1 week, 1 month, and 3 months using photographic evidence. Objective evaluation of the results was conducted using a quartile grading scale, while the subjects’ satisfaction and any adverse events were also recorded. The patients in the study underwent more than two laser sessions (2–5), resulting in substantial improvement in their appearance. The time interval between each session was 3–6 months. The majority of the patients (19/25, 76%) had a significant or even excellent improvement. Any adverse events observed, such as erythema, superficial crusting, and PIH, were of a mild nature and temporary in duration. This treatment combined two CO2 lasers is an effective and safe choice for atrophic scars in Asians.

At the present time, photodynamic inactivation (PDI) is receiving considerable interest for its potential as an antimicrobial therapy. The results of our study indicate that enhancement of the phototoxic effect on Pseudomonas aeruginosa can be achieved by combination of tetrasulfonated hydroxyaluminum phthalocyanine (AlPcS4) and bimetallic gold/silver nanoparticles (Au/Ag-NPs) synthesized by the cell-free filtrate of Aureobasidium pullulans. The bimetallic nanoparticles were characterized by a number of techniques including UV-vis, XPS, TEM, and SEM-EDS to be 14 ± 3 nm spherical particles coated with proteins. The effect of diode lasers with the peak-power wavelength ʎ = 650 nm (output power of 10 and 40 mW; radiation intensity of 26 and 105 mW/cm2) in combination with the AlPcS4 and the bimetallic nanoparticles mixture on the viability of P. aeruginosa rods was shown. Particularly high efficiency of killing bacterial cells was obtained for the light intensity of 105 mW/cm2, after 20, 30, and 40 min of irradiation corresponding to 126, 189, and 252 J/cm2 energy fluences. For AlPcS4+Au/Ag-NPs treatment, the viable count reduction were equal to 99.90, 99.96, and 99.975%, respectively. These results were significantly better than those accomplished for irradiated separated assays of AlPcS4 and Au/Ag-NPs.

The introduction of light emitting diode (LED) devices as a novel treatment for pain relief in place of low-level laser warrants fundamental research on the effect of LED devices on one of the potential explanatory mechanisms: peripheral neurophysiology in vivo. A randomised controlled study was conducted by measuring antidromic nerve conduction on the peripheral sural nerve of healthy subjects (n=64). One baseline measurement and five post-irradiation recordings (2-min interval each) were performed of the nerve conduction velocity (NCV) and negative peak latency (NPL). Interventional set-up was identical for all subjects, but the experimental group (=32) received an irradiation (2 min at a continuous power output of 160 mW, resulting in a radiant exposure of 1.07 J/cm2) with an infrared LED device (BIO-DIO preprototype; MDB-Laser, Belgium), while the placebo group was treated by sham irradiation. Statistical analysis (general regression nodel for repeated measures) of NCV and NPL difference scores, revealed a significant interactive effect for both NCV (P=0.003) and NPL (P=0.006). Further post hoc LSD analysis showed a time-related statistical significant decreased NCV and an increased NPL in the experimental group and a statistical significant difference between placebo and experimental group at various points of time. Based on these results, it can be concluded that LED irradiation, applied to intact skin at the described irradiation parameters, produces an immediate and localized effect upon conduction characteristics in underlying nerves. Therefore, the outcome of this in vivo experiment yields a potential explanation for pain relief induced by LED.

In this paper, we use the laser biophotometry for in vivo investigations, searching the most sensitive interactions of the near-infrared spectrum with different tissues. The experimental methods are based on the average reflection coefficient (ARC) measurements. For healthy persons, ARC is the average of five values provided by the biophotometer. The probe is applied on dry skin with minimum pilosity, in five regions: left–right shank, left–right forearm, and epigastrium. For the pathological tissues, the emitting terminal is moved over the suspected area, controlling the reflection coefficient level, till a minimum value occurs, as ARC-Pathological. Then, the probe is moved on the symmetrical healthy region of the body to read the complementary coefficient from intact tissue, ARC-Intact, from the same patient. The experimental results show an ARC range between 67 and 59 mW for intact tissues and a lower range, up to 58–42 mW, for pathological tissues. The method is efficient only in those pathological processes accompanied by variable skin depigmentation, water retention, inflammation, thrombosis, or swelling. Frequently, the ARC ranges are overlapping for some diseases. This induces uncertain diagnosis. Therefore, a statistical algorithm is adopted for a differential diagnosis. The laser biophotometry provides a quantitative biometric parameter, ARC, suitable for fast diagnosis in the internal and emergency medicine. These laser biophotometry measurements are representatives for the Romanian clinical trials.

Photodynamic therapy (PDT) is considered a promising new strategy for liver cancer treatment. Three elements of PDT—optical output power, irradiation time, and photosensitizer concentration—play important roles in promoting cell death. This research aimed to characterize the effects of hematoporphyrin monomethyl ether (HMME)-based PDT on hepatocellular carcinoma cells HepG2 and thus elucidate the relationship between cell death and the three elements mentioned earlier. Furthermore, in this study, we present a parameter that represents the cumulative effects of these elements. The accumulation of HMME in HepG2 cells was observed by fluorescence microscopy. The absorption spectrum of HMME was detected using fluorescence spectral analysis. The viability of the treated cells was determined using the MTT assay, and cell apoptosis was evaluated using flow cytometry. We found that the fluorescence intensity was positively correlated with the incubation time for up to 2 h. The cell growth inhibition rate was significantly high and gradually increased with increasing concentrations of HMME or increasing light intensity, which was calculated as optical output power × irradiation time. Further analysis revealed an e-exponential decay of the cell survival rate to the product of the HMME concentration and the light intensity. We defined the product as parameter B (B = optical output power × irradiation time × HMME concentration). Similarly, the rate of cell apoptosis showed roughly e-exponential growth to parameter B. In conclusion, HMME-mediated PDT can significantly kill HepG2 cells, and the killing effect was related to the cumulative effects of the optical output power, the irradiation time, and the HMME concentration. Therefore, the newly defined parameter B, as a comprehensive physical quantity, may be of great significance for the regulation of light and photosensitizer according to patient-specific conditions in clinical practice.