Macrophages Modulated by Red/NIR Light: Phagocytosis, Cytokines, Mitochondrial Activity, Ca2+ Influx, Membrane Depolarization and Viability

Light-powered phagocytic macrophage microrobot (phagobot): both in vitro and in vivo

Micro/nanorobots based on immune cells show great potential for addressing challenging biological and biomedical conditions. However, their powerful innate immune functions, particularly the phagocytosis capabilities, remain a big challenge to fully leverage with the current designs of immune cell-based microrobots. Herein, we report a light-powered phagocytic macrophage microrobot (phagobot), which is capable of robotic navigation toward specific foreign bio-threats and executing precise phagocytosis of these targeted entities under light control. Without genetic modification or nanoengineering of macrophages, the phagobot's "wake-up" program is achieved through direct activation of a resting-state macrophage by a tightly focused near-infrared (NIR) light beam. The phagobot exhibits robotic steering and directional navigation controlled by optical manipulation of the extended pseudopodia within the activated macrophage. It can further execute targeted phagocytic clearance tasks via engulfing various foreign bio-threats, including nanoplastics, microbials, and cancer cell debris. Notably, the phagobot can be constructed in a living larval zebrafish through optical activation and manipulation of the endogenous macrophage, which also exhibits controllable navigation and targeted phagocytic capabilities in vivo. With the intrinsic immune functions of macrophages, our light-powered phagobot represents a novel form of intelligent immune cell-based microrobots, holding many new possibilities for precise immune regulation and treatment for immune-related diseases.

Enhanced Hair Regrowth Through Dual-Wavelength Low-Level Laser Therapy: A Comparative Study on Mice

Low-level laser therapy (LLLT) is a non-invasive treatment that uses low-power lasers or light sources to stimulate biological responses. Previous studies focused on single-wavelength effects on hair growth in mice. In this study, we investigated dual-wavelength combinations to enhance hair regrowth. Using light-emitting diodes (LEDs) at 670, 680, 780, and 880 nm, we assessed the correlation between different wavelength pairs and hair regrowth after shaving in mice. Phototherapy was conducted over 14 days, with results analyzed through surface image analysis and histological examination. Our findings indicate that dual-wavelength therapy is superior to single-wavelength treatment and significantly more effective than the untreated control, demonstrating its potential for improved hair regrowth.

Research status of biomaterials based on physical signals for bone injury repair

Bone defects repair continues to be a significant challenge facing the world. Biological scaffolds, bioactive molecules, and cells are the three major elements of bone tissue engineering, which have been widely used in bone regeneration therapy, especially with the rise of bioactive molecules in recent years. According to their physical properties, they can be divided into force, magnetic field (MF), electric field (EF), ultrasonic wave, light, heat, etc. However, the transmission of bioactive molecules has obvious shortcomings that hinder the development of the tissue-rearing process. This paper reviews the mechanism of physical signal induction in bone tissue engineering in recent years. It summarizes the application strategies of physical signal in bone tissue engineering, including biomaterial designs, physical signal loading strategies and related pathways. Finally, the ongoing challenges and prospects for the future are discussed.

Near-infrared light therapy normalizes amyloid load, neuronal lipid membrane order, rafts and cholesterol level in Alzheimer's disease

Cholesterol dysregulation, disorder of neuronal membrane lipid packing, and lipid rafts lead to the synthesis and accumulation of toxic amyloid-β (Aβ), contributing to the development of Alzheimer's disease (AD). Our study shows that near-infrared (NIR) transcranial photobiomodulation therapy (tPBMT) can reduce Aβ load and restore the properties of neuronal plasma membrane, including Aβ production, bilayer order, rafts, lipid content, and Ca2+ channels during AD. Mice in the experiments were exposed to 808-nm LED for 1 h daily over 3 months. In the APOE transgenic model with cholesterol dysregulation, the cholesterol levels increased by 22 times, causing healthy neurons to produce toxic Aβ three times faster, increasing its load by five times. Consequently, Aβ disrupts the membrane bilayer and prompts the formation of lipid rafts and pores. NIR-tPBMT can nearly half attenuate Aβ load, restore membrane lipid order and rigidity, reduce the number of lipid rafts, modulate cholesterol synthesis, normalize Ca2+ influx by activated endocytosis, and reduce neuronal death. The Ca2+ influx induced by light does not cause excitotoxicity but modulates Ca2+/calmodulin signaling involved in AD mechanisms and cell viability. The transcriptome analysis of the brain cortex and hippocampus shows that light can downregulate Ca2+/calmodulin-dependent AD-risk genes BACE, PSEN, and APP, and normalize cholesterol homeostasis via the HMGCR, DHCR7, and INSIG1 genes. Additionally, light enhances neuron resistance to the endoplasmic reticulum stress via activating transcription factors of the unfolded protein response. Thus, red/NIR light could be promising in combating AD, restoring synaptic plasticity in degenerating neurons and reducing Aβ load.

The Role of Photobiomodulation to Modulate Ion Channels in the Nervous System: A Systematic Review

Photobiomodulation (PBM) is a safe and effective neurotherapy that modulates cellular pathways by altering cell membrane potentials, leading to beneficial biological effects such as anti-inflammatory and neuroregenerative responses. This review compiles studies from PubMed up to March 2024, investigating the impact of light at wavelengths ranging from 620 to 1270 nm on ion channels. Out of 330 articles screened, 19 met the inclusion criteria. Research indicates that PBM can directly affect various ion channels by influencing neurotransmitter synthesis in neighboring cells, impacting receptors like glutamate and acetylcholine, as well as potassium, sodium channels, and transient receptor potential channels. The diversity of studies hampers a comprehensive meta-analysis for evaluating treatment strategies effectively. This systematic review aims to explore the potential role of optoelectronic signal transduction in PBM, studying the neurobiological mechanisms and therapeutic significance of PBM on ion channels. However, the lack of uniformity in current treatment methods underscores the necessity of establishing standardized and reliable therapeutic approaches.

Exploring the effect of photobiomodulation and gamma visual stimulation induced by 808 nm and visible LED in Alzheimer's disease mouse model

Although photobiomodulation (PBM) and gamma visual stimulatqion (GVS) have been overwhelmingly explored in the recent time as a possible light stimulation (LS) means of Alzheimer's disease (AD) therapy, their effects have not been assessed at once. In our research, the AD mouse model was stimulated using light with various parameters [continuous wave (PBM) or 40 Hz pulsed visible LED (GVS) or 40 Hz pulsed 808 nm LED (PBM and GVS treatment)]]. The brain slices collected from the LS treated AD model mice were evaluated using (i) fluorescence microscopy to image thioflavine-S labeled amy-loid-β (Aβ) plaques (the main hallmark of AD), or (ii) two-photon excited fluorescence (TPEF) imaging of unlabeled Aβ plaques, showing that the amount of Aβ plaques was reduced after LS treatment. The imaging results correlated well with the results of Morris water maze (MWM) test, which demonstrated that the spatial learning and memory abilities of LS treated mice were noticeably higher than those of untreated mice. The LS effect was also assessed by in vivo nonlinear optical imaging, revealing that the cerebral amyloid angiopathy decreased spe-cifically as a result of 40 Hz pulsed 808 nm irradiation, on the contrary, the angiopathy reversed after visible 40 Hz pulsed light treatment. The obtained results provide useful reference for further optimization of the LS (PBM or GVS) parameters to achieve efficient phototherapy of AD.

Monte Carlo based dosimetry of extraoral photobiomodulation for prevention of oral mucositis

Photobiomodulation therapy (PBMT) is recommended for prevention and treatment of oral mucositis, a painful condition that occurs in cancer patients. Intraoral PBMT is limited to treating distal oral mucosa and oropharynx. Extraoral PBMT may provide a more efficient intervention. The goal of this study was to develop a clinically viable protocol for extraoral PBMT. Monte Carlo modeling was used to predict the distribution of 850 nm light for four treatment sites, using anatomical data obtained from MRI and optical properties from the literature. Simulated incident light power density was limited to 399 mW/cm2 to ensure treatment safety and to prevent tissue temperature increase. The results reveal that total tissue thickness determines fluence rate at the oral mucosa, whereas the thickness of individual tissue layers and melanin content are of minor importance. Due to anatomical differences, the fluence rate varied greatly among patients. Despite these variations, a universal protocol was established using a median treatment time methodology. The determined median treatment times required to deliver efficacious dose between 1 and 6 J/cm2 were within 15 min. The developed PBMT protocol can be further refined using the combination of pretreatment imaging and the Monte Carlo simulation approach implemented in this study.

Comparing the Impact of NIR, Visible and UV Light on ROS Upregulation via Photoacceptors of Mitochondrial Complexes in Normal, Immune and Cancer Cells

The effect of UV/visible/NIR light (380/450/530/650/808/1064 nm) on ROS generation, mitochondrial activity and viability is experimentally compared in human neuroblastoma cancer cells. The absorption of photons by mitochondrial photoacceptors in Complexes I, III and IV is in detail investigated by sequential blocking with selective pharmaceutical blockers. Complex I absorbs UV/blue light by heme P450, resulting in a very high rate (14 times) of ROS generation leading to cell death. Complex III absorbs green light, by cytochromes b, c1 and c, and possesses less ability for ROS production (seven times), so that only irradiation lower than 10 mW cm^-2 causes an increase in cell viability. Complex IV is well-known as the primary photoacceptor for red/NIR light. Light of 650/808 nm at 10-100 mW cm^-2 generates a physiological ROS level about 20% of a basal concentration, which enhance mitochondrial activity and cell survival, while 1064 nm light does not show any distinguished effects. Further, ROS generation induced by low-intensity red/NIR light is compared in neurons, immune and cancer cells. Red light seems to more rapidly stimulate ROS production, mitochondrial activity and cell survival than 808 nm. At the same time, different cell lines demonstrate slightly various rates of ROS generation, peculiar to their cellular physiology.

Therapeutic Potential of Photobiomodulation for Chronic Kidney Disease

Chronic kidney disease (CKD) is a growing global public health problem. The implementation of evidence-based clinical practices only defers the development of kidney failure. Death, transplantation, or dialysis are the consequences of kidney failure, resulting in a significant burden on the health system. Hence, innovative therapeutic strategies are urgently needed due to the limitations of current interventions. Photobiomodulation (PBM), a form of non-thermal light therapy, effectively mitigates mitochondrial dysfunction, reactive oxidative stress, inflammation, and gut microbiota dysbiosis, all of which are inherent in CKD. Preliminary studies suggest the benefits of PBM in multiple diseases, including CKD. Hence, this review will provide a concise summary of the underlying action mechanisms of PBM and its potential therapeutic effects on CKD. Based on the findings, PBM may represent a novel, non-invasive and non-pharmacological therapy for CKD, although more studies are necessary before PBM can be widely recommended.