This PDF file contains the front matter associated with SPIE Proceedings Volume 11221, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

In the presence of diabetes mellitus (DM), the wound healing process is interrupted, and chronic wounds develop. DM affects the wound healing response and leads to early apoptosis and reduced number/function of fibroblast cells. In this study we investigated the hypothesis that photobiomodulation (PBM) initiates healing through reduced apoptosis and increased cell survival in diabetic wounded fibroblast (WS1) cells. Cells were irradiated using a diode laser at a wavelength of 660 nm, power output of 100 mW/cm² and a fluence of 5 J/cm² . Non-irradiated cells were used as controls. Irradiated cells were incubated for 48 h, after which assays for cell viability (Trypan blue exclusion assay), proliferation (5-Bromo-2′-deoxyuridine-BrdU), apoptosis (Annexin V/PI) and the expression of B-Cell Lymphoma 2- Bcl2 (ELISA) were done. PBM at a wavelength of 660 nm, power output of 100 mW/cm² and a fluence of 5 J/cm² significantly increased cell survival through reduced apoptosis in diabetic wounded fibroblast cells. The PBM effects observed in this study are critical in the wound healing process.

One of the promising therapeutic effects of photobiomodulation is the ability to modulate the redox homeostasis of a cell. While this effect may be beneficial in treating chronic or infected wounds by boosting the antimicrobial capabilities of neutrophils, it is poorly understood how the redox state of bacteria is altered due to exposure to the red or near-infrared light. To address this, we present the effects of 690 nm light on the response of S. aureus to exogenous hydrogen peroxide at a range of different optical parameters including irradiance and fluence.

Photobiomodulation therapy (PBMt) has played beneficial roles as non-invasive modalities for pain relief, wound healing, skin rejuvenation, hair regrowth, treatment for oral mucositis, and etc. for more than 50 years. Recently, there have been many PB Mt clinical trials for brain care. Recent results of PBMt clinical trials performed at Dankook University using red and near infrared LEDs include fat loss and reduction of symptoms on allergic rhinitis. Detailed processes, conditions of PBMt applications, and test results are summarized. PBMt using red and near infrared LEDs were found effective for fat loss and relief from allergic rhinitis. A potential application of PBMt using red and near infrared LEDs for brain care is also proposed.

Fluorescent Light Energy (FLE) is a unique form of photobiomodulation that stimulates healing, reduces inflammation, and alleviates pain. The system works by exciting a chromophore in a topical substrate, which emits FLE with a broad spectral range (~400-700 nm) that is delivered to the target tissue below. Results from in vivo and in vitro studies have shown FLE modulates inflammation via down-regulation of pro-inflammatory cytokines such as IL-6 and TNF-α and stimulates mitochondria biogenesis¹.

A recent study showed FLE-stimulated cells responded more potently compared to cells treated with light from an LED light source (“Mimicking Lamp”) designed to generate the same emission spectra and power intensity profile as FLE². FLE-treated human dermal fibroblasts (HDF) experienced up-regulated collagen production, while a minor and nonsignificant effect was observed for the Mimicking Lamp-treated HDFs. These results suggest that photons generated by FLE either penetrate tissue differently or are absorbed differently compared to photons from a LED light source. Photonic properties of FLE that could impact tissue penetration or absorption may include polarity or coherency, leading to different cellular responses.

To investigate if light polarity may influence cellular responses to FLE stimulation, the present study applied linear and circular-polarizing filters to investigate the influence of FLE’s polarity on immune parameters. The data suggest that FLE polarity contributes to its impact on biological systems. Furthermore, the immunemodulatory impact of FLE was investgated in a pilot study on a human ex vivo skin model suggesting that central myeloid immune surface markes are modulated by FLE.

Transcranial laser stimulation (TLS) is a neural type of photobiomodulation that has been shown beneficial effects on neurons. However, previous research in this field has used multiple wavelengths in the red to near-infrared range. It remains unclear which wavelength is optimal to stimulate the brain. In this study, Monte Carlo simulations are conducted to exposit the efficiencies of three representative wavelengths (660 nm, 810 nm and 1064 nm) in delivering photon energy into the brain. The results indicate that 1064 nm is the optimal, benefiting from its reduced tissue scattering.

Photobiomodulation (PBM) describes the enhancement of cellular functions following exposure to low irradiance visible or NIR light. Although these effects are not well understood, PBM has been shown to enhance the synthesis of ATP so the mitochondrion is the hypothesized target for the processes of photobiomodulation. More specifically, cytochromecontaining enzyme complexes of the electron transport chain (ETC) in the mitochondria are expected to be the primary photoabsorbers of the light thought to induce PBM. Recently, our group found light-induced changes in the activity of complex III (cytochrome c reductase) in isolated mitochondria. In this study, we use femtosecond transient absorption spectroscopy (TAS) to study the excited state dynamics of the electronic transitions in complex III as well as reduced cytochrome c. To investigate the potential for inducing PBM effects in these proteins, TAS experiments are performed without, and with, low irradiance light exposures during the scanning procedure choosing from blue (450 nm), red (635 nm), and near-infrared (808 nm) laser diodes. The TAS experiments with and without light exposures during the procedure are compared to determine if PBM effects were induced. Understanding illumination induced changes in the excited state dynamics of proteins can help to better characterize the molecular processes caused by PBM and lead to a more optimized treatment for the enhancement of human performance and therapy.

Photobiomodulation (PBM) is an umbrella term for positive biological effects induced by low irradiance exposures of visible to near infrared light. Though therapeutic and protective benefits of PBM are increasingly well documented in the scientific literature, the molecular mechanisms underlying these effects remain poorly understood. The putative chromophore for these effects is cytochrome c oxidase, also known as complex IV (C-IV) of the mitochondrial electron transport chain (ETC). It is generally held that light absorption at C-IV initiates a cascade of events involving nitric oxide and reactive oxygen species (ROS) which subsequently results in increased ATP generation and improved cellular robustness. However, little is known about the mechanisms by which these pathways are initiated, and how they establish the observed beneficial outcomes. To probe these mechanisms, we have conducted low irradiance exposures of isolated mitochondria at a range of wavelengths and radiant exposures. We utilized a spectrophotometric method to make in vitro measurements of ETC complex enzyme activities, by observing changes in the redox state of the small electron carrier protein, cytochrome c. Specifically, we analyzed the enzyme kinetics of cytochrome c reductase, also known as complex III (C-III), and C-IV, with and without exposure to low irradiance light. Additionally, by utilizing C-III and C-IV inhibitors (Antimycin A and sodium cyanide, respectively) we are able to distinguish between effects acting directly on one complex or the other. In summary, this research represents a unique look at the earliest stages of PBM induction in the mitochondria, and its associated molecular mechanisms.

Photobiomodulation (PBM), once known as low level laser therapy (LLLT), is a technique that uses light in the red and near infrared (NIR) range (600-900 nm) to elicit a beneficial physiological change in tissue. These physiological changes are thought to originate in the mitochondria by altering the metabolic rate for the electron transport chain (ETC). Resonance Raman spectroscopy at 532 nm was used to determine the reduction/oxidation (redox) state of cytochrome c in isolated mitochondria after exposure to low irradiance visible light. Mitochondria from porcine heart tissue were isolated and placed in a succinate buffer and then exposed to NIR (808 nm) light. Some enzymes involved in the ETC were selectively individually blocked and the resonance Raman spectra of cytochrome c redox state was measured before and after being illuminated by light representing photobiomodulation. By combining data on the cytochrome c redox state with the effects of inhibiting important enzymes, we can see what the impact of each enzyme in the ETC has on the effects we see from photobiomodulation. This method provides a better understanding on the underlying effects of photobiomodulation on the mitochondria, which can help direct efforts for targeted effects.

“Precision photomedicine: biomarkers for clinical translation of PBM therapy” was recorded at Photonics West BiOS 2020 held in San Francisco, California, United States.

Photobiomodulation (PBM) treatment using light-emitting diodes (LEDs) has become an attractive alternative to using lasers in recent years. Two arrays of 54 LEDs at 850 nm were used to apply PBM at three different irradiances for 5 minutes to the forearms of 11 human subjects in a placebo-controlled experiment. Near-infrared spectroscopy was used in vivo to track changes in hemoglobin and mitochondrial markers over the course of the treatments. A non-linear biphasic response in these markers was observed with respect to irradiance and time, which suggests that there is an optimal dosimetry for PBM treatment as theorized by the Arndt-Schultz Law.

Alzheimer’s disease (AD) not only takes an emotional toll on the individual with the disease, their families, relatives, and caretakers, it also has immense socioeconomic consequences on the health care system and society. Moreover, the socioeconomic consequences are expected to increase significantly, thus reducing the social and economic cost of AD is of high importance. Recently, exposure to 40 Hz stroboscopic light therapy, for one hour a day, resulted in slowing the progression of AD in mice and has a considerable potential for treatment in humans. However, exposure to such stroboscopic light carries its own consequences being that it is difficult to implement in a patient’s daily routine, irksome to use, and can cause visual discomfort which may result in a lack of patient adherence.

Here, we demonstrate a novel technology based on controlling multiple single-color LEDs to produce white light where its spectral composition alternates at a given modulation frequency without visible flicker. We coin this technique as Invisible Spectral Flicker (ISF). We present 40 Hz invisible spectral flicker light as a potential alternative in reducing discomfort compared to 40 Hz stroboscopic light, whilst still entraining oscillations in various areas of the brain. Furthermore, we demonstrate a distinct way to generate a 40 Hz metameric light source with the presented color mixing scheme, and validate that the CIE 1931 (x, y) coordinates match for two different spectral power distributions. Finally, we illustrate the light characteristics of seven 40 Hz color fusion light sources and two 40 Hz stroboscopic light sources. The technology presented here will lead to new, and hopefully improved, designs of light therapy systems for the treatment of Alzheimer’s and dementia.

Pain is a burden for orthodontic patients. The use of phototherapy has been reported in Orthodontics mainly due to its effects on pain, inflammation and on both bone and soft tissue repair. The aim of this study was to assess the effectiveness of LED phototherapy on pain relief following the process of tooth separation in humans. This longitudinal randomized controlled clinical trial was carried out in four observational times and was carried out in 40 patients whom were randomly divided into two groups: G1 (LED, AsGaAl, λ850 ± 10 nm, 150 mW, 20 J/cm², 64s per session) and G2 (Non irradiated Control). All patients were submitted to tooth separation using elastomeric separators. The pain level was measured by using a visual analogue scale (VAS) immediately after insertion (T1) of the elastic, at 48 (T2), 96 (T3) hours and 6 days (T4). It was observed an increase of the pain on the Control group from T1 to T2, with statistical significance. Pain levels in the LED group was always significantly lower (<0.001), except for T1. According with the results of the present study it may be concluded that, LED phototherapy, was effective in reducing the pain level after dental separation process when compared to the control group.

Antimicrobial Photodynamic Therapy (AmPDT) is an alternative to conventional treatments of local infections such as the use of antibiotics, which may lead to the development of resistance. AmPDT in addition of requiring the use of a photosensitizer it also needs a light source executed. In search of an efficient and cheap procedure, we aimed to assess the efficacy of using 1,9-dimethylmethylene blue (DMMB) as photosensitizer associated with the use of either Laser (λ660 nm), LED (λ632 ± 2 nm) or a multispectral polarized light (λ400 – 2000 nm) using different energy densities to kill E. faecalis (Laser or LED) or S. aureus (PL) in vitro. For this, 300 (S. aureus) or 3.32 ηg/ml (E. faecalis) of DMBB and energy densities of 5 (PL) or 18 J/cm² (Laser/LED) were used. Five minutes of pre-incubation time was used. CFU count (S. aureus) or the most probable number method (MPN) (E. faecalis) were used as assessment methods. The results showed a 99.97 % reduction on CFU counts of S. aureus and 99.999998 % reduction on E. faecalis (using both light sources). It is concluded that AmPDT carried out with 1,9-dimethylmethylene blue associated with either Laser, LED or Polarized light was efficacious on the reduction, in vitro, of the counts of aerobes and aerotolerant anaerobes Gram-positive bacteria.

Photobiomodulation (PBM) is the use of light in a specific wavelength and irradiance to induce some process in the cells such as death or division. One possible way to follow the light effects is through the optical redox ratio (ORR). ORR is an established microscope optical technique that uses the endogenous fluorescence of NADH (reduced form of nicotinamide adenine dinucleotide) and FAD (flavin adenine dinucleotide) to verify the metabolic route of a cell. The purpose of this study was to measure the effect of light on the ORR of Candida albicans cells, growing in aerobic and anaerobic conditions. Standardized C. albicans suspensions were adjusted in a spectrophotometer to 10⁷ colony forming units per milliliter (CFU/mL) (540 nm) after growing 12 or 24 hours under aerobic and anaerobic conditions. The anaerobic state was achieved using an airtight jar with a candle inside. Then, the PBM was performed using a LED device emitting at 450 nm with an irradiance of 44 mW/cm² and a total fluence rate of 200 J/cm². The ORR was evaluated through confocal laser microscopy using laser excitation of 755 nm (NADH excitation) or 860 nm (FAD excitation), and images were acquired in the channel mode of the microscope with 440 - 480 nm (NADH fluorescence) or 500 - 550 nm (FAD fluorescence) wavelength range, respectively. The ORR images were created by computing pixel-wise ratios of FAD/(NADH+FAD) fluorescence. Cell viability was quantified by CFU/mL assay. According to the viability test, the anaerobic suspensions (12 and 24 h) showed lower growth in comparison with the aerobic suspensions (12 and 24 h). The ORR is statistically the same in aerobic and anaerobic conditions, and lower after the illumination. In conclusion, our preliminary study demonstrated that it is possible to measure the ORR in C. albicans cells and the effects of PBM in these cells.

Studies of the physiological response of human half-body illumination by a specially designed bed comprising large number of LEDs emitting in the red and near infrared spectral range were carried out in a group of 32 volunteers comprising healthy subjects and hypertension patients. Blood pressure, heart rate and arterial blood oxygen saturation, as well as the bed surface temperature were continuously monitored during the measurement sessions with and without aluminum foil cover on the bed surface. None of the volunteers exhibited any notable changes in the heart rate and blood oxygenation during the procedures. The LightStim LED-bed session did not produce changes of arterial pressure in normotensive group, while decreased blood pressure exhibited 2/3 of hypertensive patients. The thermal emission from the bed may serve as a dominant contributor to the observed effects on cardiovascular system.