Comparison of the Penetration Depth of 905 nm and 1064 nm Laser Light in Surface Layers of Biological Tissue Ex Vivo

A systematic review and meta-analysis of the effectiveness of high-intensity laser therapy in patients with carpal tunnel syndrome

OBJECTIVES

This systematic review aimed to evaluate the effects of high-intensity laser therapy (HILT) on pain intensity, disability, and electrophysiological parameters in individuals diagnosed with carpal tunnel syndrome (CTS).

DATA SOURCES AND SYNTHESIS

A search of electronic databases, including PubMed, Web of Science, Scopus, CINAHL, Science Direct, Cochrane Library, the PEDro database, and Google Scholar (updated until February 18, 2025), was conducted for randomized controlled trials (RCTs).

DATA EXTRACTION AND QUALITY ASSESSMENT

Data were extracted independently by three researchers. The quality of RCTs was assessed using the Cochrane Risk of Bias (RoB) 2.0 tool, while evidence certainty was evaluated with the GRADE approach. Primary outcomes included pain intensity, with secondary outcomes comprising electrophysiological parameters and disability.

RESULTS

Nine RCTs met inclusion criteria. Most studies exhibited a low risk of bias across RoB2 domains, except for outcome measurement, resulting in an overall RoB of 44%. Meta-analyses demonstrated that HILT, alone or combined with interventions such as splinting, exercise, TENS, vitamin B supplements, or ergonomic modifications, significantly reduced pain (SMD = 0.7 to 1.6) and disability (SMD = 0.68). Electrophysiological improvements included enhanced distal motor latency (SMD = 0.98) and sensory conduction velocity (SMD = 0.8), particularly when combined with median nerve gliding or splinting.

CONCLUSION

This review confirms HILT's effectiveness in reducing pain and disability and improving electrophysiological parameters in CTS. However, evidence certainty remains moderate to low. Future RCTs should standardize outcome measures to evaluate HILT's clinical impact beyond statistical significance, and comparative studies with LLLT are needed to refine laser therapy protocols.

SYSTEMATIC REVIEW REGISTRATION NUMBER

PROSPERO CRD42023470170 (October 17, 2023). CONTRIBUTION OF THE PAPER.

NIR-activated multifunctional agents for the combined application in cancer imaging and therapy

Anticancer therapies that combine both diagnostic and therapeutic capabilities hold significant promise for enhancing treatment efficacy and patient outcomes. Among these, agents responsive to near-infrared (NIR) photons are of particular interest due to their negligible toxicity and multifunctionality. These compounds are not only effective in photodynamic therapy (PDT), but also serve as contrast agents in various imaging modalities, including fluorescence and photoacoustic imaging. In this review, we explore the photophysical and photochemical properties of NIR-activated porphyrin, cyanine, and phthalocyanines derivatives as well as aggregation-induced emission compounds, highlighting their application in synergistic detection, diagnosis, and therapy. Special attention is given to the design and optimization of these agents to achieve high photostability, efficient NIR absorption, and significant yields of fluorescence, heat, or reactive oxygen species (ROS) generation depending on the application. Additionally, we discuss the incorporation of these compounds into nanocarriers to enhance their solubility, stability, and target specificity. Such nanoparticle-based systems exhibit improved pharmacokinetics and pharmacodynamics, facilitating more effective tumor targeting and broadening the application range to photoacoustic imaging and photothermal therapy. Furthermore, we summarize the application of these NIR-responsive agents in multimodal imaging techniques, which combine the advantages of fluorescence and photoacoustic imaging to provide comprehensive diagnostic information. Finally, we address the current challenges and limitations of photodiagnosis and phototherapy and highlight some critical barriers to their clinical implementation. These include issues related to their phototoxicity, limited tissue penetration, and potential off-target effects. The review concludes by highlighting future research directions aimed at overcoming these obstacles, with a focus on the development of next-generation agents and platforms that offer enhanced therapeutic efficacy and imaging capabilities in the field of cancer treatment.

Infrared Laser-Assisted Extraction of Bioactive Compounds from Rosa canina L

The extraction of bio-compounds from medicinal plants provides opportunities for using the plant extract for health benefits. Rosa canina L. is considered a "natural superfood", and the valorization of its active compounds requires an extraction technique that ensures a suitable extraction yield while preserving the compounds' activity. In our study, infrared laser irradiation (IRLIR) technology was used for the first time in the bioactive compound's extraction from Rosa canina L. Different solvents (water-ethanol, hexane-ethanol) and different extraction times were tested to obtain a high extraction yield. Chromatographic and spectrophotometry methods were used to monitor the profile of bioactive compounds and the antioxidant activity of the extracts. The results obtained for IRLIR were compared with those obtained by accelerated solvent extraction (ASE), an advanced extraction method. The IRLIR technology proved to be a more reliable analytical tool for the extraction of (+)-catechin, gallic acid, and lutein. In addition, a richer extract formula was obtained by IRLIR extraction with respect to ASE, with the IRLIR process ensuring a short extraction time, low volume of the extraction solvent, low energy consumption, and a less expensive device.

Application of Light-Responsive Nanomaterials in Bone Tissue Engineering

The application of light-responsive nanomaterials (LRNs) in bone tissue engineering shows broad prospects, especially in promoting bone healing and regeneration. With a deeper understanding of the mechanisms of bone defects and healing disorders, LRNs are receiving increasing attention due to their non-invasive, controllable, and efficient properties. These materials can regulate cellular biological reactions and promote bone cell adhesion, proliferation, and differentiation by absorbing specific wavelengths of light and converting them into physical and chemical signals. In addition, the unique surface morphology and biocompatibility of LRNs enable them to effectively load drugs in bone tissue engineering, achieve precise release, and optimize the bone regeneration process. Through photothermal and photodynamic therapy, these materials also possess antibacterial properties and can play an important role in the repair of infectious bone defects. Although LRNs have shown significant advantages in bone tissue regeneration, a series of challenges still need to be overcome to achieve their widespread and effective clinical applications. This article summarizes the basic principles, classification, and potential applications of LRNs in bone tissue regeneration, aiming to provide reference for future research and clinical applications.

Quality appraisal of systematic reviews on high-intensity laser therapy for musculoskeletal pain management: an umbrella review

Musculoskeletal pain (MSP) remains one of the leading causes of disability worldwide. Recent approaches to treating this condition have prompted the development of several systematic reviews investigating the efficacy of high-intensity laser therapy (HILT), whose analgesic mechanisms are based on photobiomodulation neural inhibition, endorphin and serotonin release and anti-inflammatory effects. To assess the methodological quality, reliability, and validity of the systematic reviews (SRs) on HILT in MSP. This study is an overview of SRs (umbrella review) with an observational, retrospective, and secondary design. The search considered PubMed, Scopus, Web of Science, CINAHL, Embase, Cochrane Library, ScienceDirect, and Google Scholar databases (updated October 23, 2024). The primary focus was on the methodological quality of the reviews and their reporting of pain intensity results. The HILT effects on pain intensity were reported using mean differences (MD) or standardized mean differences (SMD). The quality assessment was conducted using the A Measurement Instrument to Assess Systematic Reviews 2 checklist (AMSTAR-2), and the findings were synthesized narratively. The MD and SMD obtained from all reviews were presented using forest plots. The Shapiro-Wilk normality test assessed MD and SMD distributions for pain intensity across meta-analyses. The average MD and SMD, along with their respective confidence intervals (CI), were estimated and presented based on the aggregate study outcomes. Twenty SRs were included, fourteen of which conducted meta-analyses covering diverse musculoskeletal disorders such as knee osteoarthritis, epicondylalgia, myofascial pain, frozen shoulder, plantar fasciitis, neck, and low back pain. The primary databases used were PubMed, Web of Science, and the Cochrane Library. The AMSTAR-2 average score was 12.9 points (± 1.8), indicating varying methodological quality with one or two criteria resulting in low or critically low. HILT's best analgesic effects are observed in frozen shoulder disorder (MD = -2.23 cm; 95% CI:-3.3,-1.2; p < 0.01), knee osteoarthritis (MD = -1.9 cm; 95% CI:-2.0,-1.8;p < 0.01), low back pain (MD = -1.9 cm; 95% CI = -2.9,-1.0; p < 0.01), and myofascial pain (MD = -1.9 cm; 95% CI:-2.6,-1.2; p < 0.01). Largest effect sizes are for neck pain (SMD = 2.1; 95% CI = 1.2,3.0, p < 0.05) and low back pain (SMD = 1.1 (95% CI = 1.4,0.8; p < 0.01). This review underscores the generally low to critically low methodological quality of SRs on HILT, as assessed by AMSTAR-2. Key areas for improvement for future SRs of RCTs include addressing publication bias, disclosing funding sources, and enhancing search strategies and discussions on heterogeneity. The scarcity of RCTs for conditions such as temporomandibular disorders, carpal tunnel syndrome, and myofascial pain highlights the need for further research. SRs on spinal disorders, frozen shoulder, and neck pain demonstrated the most favorable analgesic effects, providing valuable insights for clinical practice and future RCTs.

Development and optical characterisation of agarose-based phantoms mimicking biological tissues for studies of light penetration in the brain

Searching for materials that accurately mimic the optical properties of biological tissues is essential, particularly for transcranial photobiomodulation (PBM) research, where it is necessary to comprehend how light propagates through the head tissues. In this research, we characterised, in the 500-1200 nm range, the transmittance spectra of porcine tissues (skin, muscle, cranium, brain, and cerebellum) and different agarose-based phantoms. These phantoms were developed using different combinations of titanium dioxide (TiO2), India ink, organometallic compounds, and laser-ablated gold and zinc oxide nanoparticles. The surface and mechanical properties of these phantoms were also characterized. The results showed that an increased TiO2 concentration decreased the optical transmittance of the phantoms. However, when TiO2 was added to the India ink and laser-ablated nanoparticles' phantoms, not only did it reduce transmittance amplitude, but it also flattened its spectra. Comparing the phantoms and biological tissues' results, the spectral profiles of TiO2 samples appeared similar to those of muscle, skin, and brain/cerebellum; organometallic compounds replicated the skin and muscle curves; India ink emulated skin and cranium; and the laser-ablated nanoparticles mimicked the muscle. Although it was possible to establish qualitative similarities between the phantoms and the biological tissues' optical transmittance spectra, there is a need for further studies with different components' combinations to ascertain curves that more closely mimic the biological tissues.

Ultrasound-assisted laser therapy for selective removal of melanoma cells

The current study explores the potential of ultrasound-assisted laser therapy (USaLT) to selectively destroy melanoma cells. The technology was tested on an ex vivo melanoma model, which was established by growing melanoma cells in chicken breast tissue. Ultrasound-only and laser-only treatments were used as control groups. USaLT was able to effectively destroy melanoma cells and selectively remove 66.41% of melanoma cells in the ex vivo tumor model when an ultrasound peak negative pressure of 2 MPa was concurrently applied with a laser fluence of 28 mJ/cm2 at 532 nm optical wavelength for 5 min. The therapeutic efficiency was further improved with the use of a higher laser fluence, and the treatment depth was improved to 3.5 mm with the use of 1,064 nm laser light at a fluence of 150 mJ/cm2. None of the laser-only and ultrasound-only treatments were able to remove any melanoma cells. The treatment outcome was validated with histological analyses and photoacoustic imaging. This study opens the possibility of USaLT for melanoma that is currently treated by laser therapy, but at a much lower laser fluence level, hence improving the safety potential of laser therapy.

Advancements in Photothermal Therapy Using Near-Infrared Light for Bone Tumors

Bone tumors, particularly osteosarcoma, are prevalent among children and adolescents. This ailment has emerged as the second most frequent cause of cancer-related mortality in adolescents. Conventional treatment methods comprise extensive surgical resection, radiotherapy, and chemotherapy. Consequently, the management of bone tumors and bone regeneration poses significant clinical challenges. Photothermal tumor therapy has attracted considerable attention owing to its minimal invasiveness and high selectivity. However, key challenges have limited its widespread clinical use. Enhancing the tumor specificity of photosensitizers through targeting or localized activation holds potential for better outcomes with fewer adverse effects. Combinations with chemotherapies or immunotherapies also present avenues for improvement. In this review, we provide an overview of the most recent strategies aimed at overcoming the limitations of photothermal therapy (PTT), along with current research directions in the context of bone tumors, including (1) target strategies, (2) photothermal therapy combined with multiple therapies (immunotherapies, chemotherapies, and chemodynamic therapies, magnetic, and photodynamic therapies), and (3) bifunctional scaffolds for photothermal therapy and bone regeneration. We delve into the pros and cons of these combination methods and explore current research focal points. Lastly, we address the challenges and prospects of photothermal combination therapy.

Photobiomodulation's potential as a non-invasive therapy for alzheimer's disease and minimal cognitive impairment: A 12-week investigation

BACKGROUND

Alzheimer's Disease (AD), undergoing a faster increase in occurrence than any other type of dementia, lacks a curative remedy despite advanced discoveries. To explore the realm of non-pharmacologic therapies, our study evaluates the 12-week impact of non-invasive Photobiomodulation (PBM) on cognitive and psychological aspects in individuals with AD and minimal cognitive impairment (MCI). The urgency of exploring innovative interventions is underscored by the rising occurrence of AD, particularly in regions with aging populations like Iran.

METHOD

13 patients (6 case patients and 7 control patients) participated in the study. Sham treatment was administered to seven individuals, while another six received PBM treatment over 12 weeks, with daily at-home LED (810 nm wavelength) device usage lasting 20 min. Initially, the patient and their caregiver participated in two hospital sessions to acquaint them with the device's operation.

RESULTS

The mean reduction of Hamilton's anxiety questionnaire score was 3.33±6.08 in the intervention group and 2.00±3.46 in the control group (p-value=0.836). The mean score reduction of the Hamilton depression questionnaire was 3.16±3.86 in the intervention group and 4.85±6.20 in the control group (p-value=0.836). The mean score of the DAD questionnaire in the intervention group before the study was 25.50±13.13 and after the intervention was 29.83±12.12 (p-value=0.084) and in the control group it was 29.71±8.19 and after the study was 29±0.972 (p-value = 0.526). The mean changes in the DAD questionnaire score in the intervention group increased by 4.33±4.92 and decreased by 0.71±2.81 in the control group (p-value=0.041).

CONCLUSION

In general, PBM appears to hold promise as a potentially safe method for enhancing the cognitive, functional, and psychological status of individuals with Alzheimer's disease, though further research with larger sample size and cautious interpretation are warranted.

A Preliminary Study on Quantitative Analysis of Collagen and Apoptosis Related Protein on 1064 nm Laser-Induced Skin Injury

To investigate the associated factors concerning collagen and the expression of apoptosis-related proteins in porcine skin injuries induced by laser exposure, live pig skin was irradiated at multiple spots one time, using a grid-array method with a 1064 nm laser at different power outputs. The healing process of the laser-treated areas, alterations in collagen structure, and changes in apoptosis were continuously observed and analyzed from 6 h to 28 days post-irradiation. On the 28th day following exposure, wound contraction and recovery were notably sluggish in the medium-high dose group, displaying more premature and delicate type III collagen within the newly regenerated tissues. The collagen density in these groups was roughly 37-58% of that in the normal group. Between days 14 and 28 after irradiation, there was a substantial rise in apoptotic cell count in the forming epidermis and granulation tissue of the medium-high dose group, in contrast to the normal group. Notably, the expression of proapoptotic proteins Bax, caspase-3, and caspase-9 surged significantly 14 days after irradiation in the medium-high dose group and persisted at elevated levels on the 28th day. During the later stage of wound healing, augmented apoptotic cell population and insufficient collagen generation in the newly generated skin tissue of the medium-high dose group were closely associated with delayed wound recovery.

Efficacy of 1064 nm Photobiomodulation Dosimetry Delivered with a Collimated Flat-Top Handpiece in the Management of Peripheral Facial Paralysis in Patients Unresponsive to Standard Treatment Care: A Case Series

Peripheral facial paralysis (PFP) is a common condition where oxidative stress (OS) is involved in the pathophysiology of facial paralysis, inhibiting peripheral nerve regeneration, which can be featured in Bell's palsy, Ramsay Hunt syndrome and Lyme disease. The current standard care treatments lack consensus and clear guidelines. Hence, the utilization of the antioxidant immunomodulator photobiomodulation (PBM) can optimize clinical outcomes in patients who are unresponsive to standard care treatments. Our study describes three unique cases of chronic PFP of various origins that were unresponsive to standard care treatments, but achieved a significant and complete recovery of facial paralysis following PBM therapy. Case presentations: Case #1: a 30-year-old male who presented with a history of 12 years of left-side facial paralysis and tingling as a result of Bell's palsy, where all the standard care treatments failed to restore the facial muscles' paralysis. Eleven trigger and affected points were irradiated with 1064 nm with an irradiance of ~0.5 W/cm2 delivered with a collimated prototype flat-top (6 cm2) in a pulsed mode, with a 100 µs pulse duration at a frequency of 10 Hz for 60 s (s) per point. Each point received a fluence of 30 J/cm2 according to the following treatment protocol: three times a week for the first three months, then twice a week for another three weeks, and finally once a week for the following three months. The results showed an improvement in facial muscles' functionality (FMF) by week two, whereas significant improvement was observed after 11 weeks of PBM, after which the House-Brackmann grading scale (HBGS) of facial nerve palsy dropped to 8 from 13 prior to the treatment. Six months after PBM commencement, electromyography (EMG) showed sustainability of the FMF. Case #2: A five-year-old female who presented with a 6-month history of severe facial paralysis due to Lyme disease. The same PBM parameters were utilized, but the treatment protocol was as follows: three times a week for one month (12 consecutive treatment sessions), then the patient received seven more sessions twice a week. During the same time period, the physiotherapy of the face muscles was also delivered intensively twice a week (10 consecutive treatments in five weeks). Significant improvements in FMF and sustainability over a 6-month follow-up were observed. Case #3: A 52-year-old male who presented with severe facial palsy (Grade 6 on HBGS) and was diagnosed with Ramsay Hunt syndrome. The same laser parameters were employed, but the treatment protocol was as follows: three times a week for three weeks, then reduced to twice a week for another three weeks, then weekly for the next three months. By week 12, the patient showed a significant FMF improvement, and by week 20, complete FMF had been restored. Our results, for the first time, showed pulsed 1064 nm PBM delivered with a flat-top handpiece protocol is a valid and its treatment protocol modified, depending on the origin and severity of the condition, which is fundamental in optimizing facial paralysis recovery and alleviating neurological symptoms. Further extensive studies with large data are warranted to validate our PBM dosimetry and treatment protocols.