Optical lens-microneedle array for percutaneous light delivery

Fully equipped CARs to address tumor heterogeneity, enhance safety, and improve the functionality of cellular immunotherapies

Although adoptive transfer of chimeric antigen receptor (CAR)-engineered T cells has achieved unprecedented response rates in patients with certain hematological malignancies, this therapeutic modality is still far from fulfilling its remarkable potential, especially in the context of solid cancers. Antigen escape variants, off-tumor destruction of healthy tissues expressing tumor-associated antigens (TAAs), poor CAR-T cell persistence, and the occurrence of functional exhaustion represent some of the most prominent hurdles that limit CAR-T cell ability to induce long-lasting remissions with a tolerable adverse effect profile. In this review, we summarize the main approaches that have been developed to face such bottlenecks, including the adapter CAR (AdCAR) system, Boolean-logic gating, epitope editing, the modulation of cell-intrinsic signaling pathways, and the incorporation of safety switches to precisely control CAR-T cell activation. We also discuss the most pressing issues pertaining to the selection of co-stimulatory domains, with a focus on strategies aimed at promoting CAR-T cell persistence and optimal antitumor functionality.

An Experimental Phototherapy Device for Studying the Effects of Blue Light on Patients with Raynaud's Phenomenon

Raynaud's phenomenon (RP) is a condition that causes decreased blood flow to areas perfused by small blood vessels (e.g., fingers, toes). In severe cases, ulceration, gangrene, and loss of fingers may occur. Most treatments focus on inducing vasorelaxation in affected areas by the way of pharmaceuticals. Recently, animal studies have shown that vasorelaxation can be induced by non-coherent blue light (wavelength ~ 430-460 nm) through the actions of melanopsin, a photoreceptive opsin protein encoded by the OPN4 gene. To study this effect in humans, a reliable phototherapy device (PTD) is needed. We outline the construction of a PTD to be used in studying blue light effects on Raynaud's patients. Our design addresses user safety, calibration, electromagnetic compatibility/interference (EMC/EMI), and techniques for measuring physiological responses (temperature sensors, laser Doppler flow sensors, infrared thermal imaging of the hands). We tested our device to ensure (1) safe operating conditions, (2) predictable, user-controlled irradiance output levels, (3) an ability for measuring physiological responses, and (4) features necessary to enable a double-blinded crossover study for a clinical trial. We also include in the Methods an approved research protocol utilizing our device that may serve as a starting point for clinical study. We introduced a reliable PTD for studying the effects of blue light therapy for patients suffering from Raynaud's phenomenon and showed that our device is safe and reliable and includes the required measurement vectors for tracking treatment effects throughout the duration of a clinical study.

Engineering vascularized skin-mimetic phantom for non-invasive Raman spectroscopy

Recent advances in Raman spectroscopy have shown great potential for non-invasive analyte sensing, but the lack of a standardized optical phantom for these measurements has hindered further progress. While many research groups have developed optical phantoms that mimic bulk optical absorption and scattering, these materials typically have strong Raman scattering, making it difficult to distinguish metabolite signals. As a result, solid tissue phantoms for spectroscopy have been limited to highly scattering tissues such as bones and calcifications, and metabolite sensing has been primarily performed using liquid tissue phantoms. To address this issue, we have developed a layered skin-mimetic phantom that can support metabolite sensing through Raman spectroscopy. Our approach incorporates millifluidic vasculature that mimics blood vessels to allow for diffusion akin to metabolite diffusion in the skin. Furthermore, our skin phantoms are mechanically mimetic, providing an ideal model for development of minimally invasive optical techniques. By providing a standardized platform for measuring metabolites, our approach has the potential to facilitate critical developments in spectroscopic techniques and improve our understanding of metabolite dynamics in vivo.

Improving flat fluorescence microscopy in scattering tissue through deep learning strategies

Intravital microscopy in small animals growingly contributes to the visualization of short- and long-term mammalian biological processes. Miniaturized fluorescence microscopy has revolutionized the observation of live animals' neural circuits. The technology's ability to further miniaturize to improve freely moving experimental settings is limited by its standard lens-based layout. Typical miniature microscope designs contain a stack of heavy and bulky optical components adjusted at relatively long distances. Computational lensless microscopy can overcome this limitation by replacing the lenses with a simple thin mask. Among other critical applications, Flat Fluorescence Microscope (FFM) holds promise to allow for real-time brain circuits imaging in freely moving animals, but recent research reports show that the quality needs to be improved, compared with imaging in clear tissue, for instance. Although promising results were reported with mask-based fluorescence microscopes in clear tissues, the impact of light scattering in biological tissue remains a major challenge. The outstanding performance of deep learning (DL) networks in computational flat cameras and imaging through scattering media studies motivates the development of deep learning models for FFMs. Our holistic ray-tracing and Monte Carlo FFM computational model assisted us in evaluating deep scattering medium imaging with DL techniques. We demonstrate that physics-based DL models combined with the classical reconstruction technique of the alternating direction method of multipliers (ADMM) perform a fast and robust image reconstruction, particularly in the scattering medium. The structural similarity indexes of the reconstructed images in scattering media recordings were increased by up to 20% compared with the prevalent iterative models. We also introduce and discuss the challenges of DL approaches for FFMs under physics-informed supervised and unsupervised learning.

A biodegradable, flexible photonic patch for in vivo phototherapy

Diagnostic and therapeutic illumination on internal organs and tissues with high controllability and adaptability in terms of spectrum, area, depth, and intensity remains a major challenge. Here, we present a flexible, biodegradable photonic device called iCarP with a micrometer scale air gap between a refractive polyester patch and the embedded removable tapered optical fiber. ICarP combines the advantages of light diffraction by the tapered optical fiber, dual refractions in the air gap, and reflection inside the patch to obtain a bulb-like illumination, guiding light towards target tissue. We show that iCarP achieves large area, high intensity, wide spectrum, continuous or pulsatile, deeply penetrating illumination without puncturing the target tissues and demonstrate that it supports phototherapies with different photosensitizers. We find that the photonic device is compatible with thoracoscopy-based minimally invasive implantation onto beating hearts. These initial results show that iCarP could be a safe, precise and widely applicable device suitable for internal organs and tissue illumination and associated diagnosis and therapy.

The efficacy of LED microneedle patch on hair growth in mice

Light penetration depth in the scalp is a key limitation of low-level light therapy for the treatment of androgenetic alopecia (AGA). A novel light emitting diode (LED) microneedle patch was designed to achieve greater efficacy by enhancing the percutaneous light delivery. The study aimed to investigate the efficacy and safety of this device on hair growth in mice. Thirty-five male C57BL/6 mice which their dorsal skin was split into upper and lower parts to receive either LED irradiation alone or LED irradiation with a microneedle patch. Red (629 nm), green (513 nm), and blue light (465 nm) at an energy dose of 0.2 J/cm² were applied once daily for 28 days. Outcomes were evaluated weekly using digital photographs. Histopathological findings were assessed using a 6 mm punch biopsy. A significant increase in hair growth was observed in the green light, moderate in the red light, and the lowest in the blue light group. The addition of the microneedle patch to LED irradiation enhanced greater and faster anagen entry in all the groups. Histopathology showed an apparent increase in the number of hair follicles, collagen bundles in the dermis, angiogenesis, and mononuclear cell infiltration after treatment with the green-light LED microneedle patches. No serious adverse effects were observed during the experiment. Our study provides evidence that the newly developed green-light LED microneedle patch caused the optimal telogen-to-anagen transition and could lead to new approaches for AGA. Microneedle stimulation may aid percutaneous light delivery to the target hair follicle stem cells.

Dual-function microneedle array for efficient photodynamic therapy with transdermal co-delivered light and photosensitizers

Photodynamic therapy (PDT), as a globally accepted method for treating different forms of skin or mucosal disorders, requires efficient co-delivery of photosensitizers and corresponding therapeutic light. The adverse effects of intravenous injection of photosensitizers have been reduced by the development of microneedle arrays for transdermal local photosensitizer delivery. However, the drawbacks of the only available therapeutic light delivery method at the moment, which is directly applying light to the skin surface, are yet to be improved. This study presents a new strategy in which therapeutic light and photosensitizer were transdermally co-delivered into local tissues. A flexible dual-function microneedle array (DfMNA) which contains 400 microneedles was developed. Each microneedle consists of a dissolvable needle tip (140 μm in height) for delivering the photosensitizer and a transparent needle body (660 μm in height) for guiding therapeutic light. Using port-wine stains, which is a frequently occurring skin disorder caused by vascular malformation, as a model disease, the effectiveness of DfMNA mediated PDT has been verified on mice. Compared with the standard operation procedure of clinical PDT, the DfMNA decreases the amount of photosensitizer from 300 μg to 0.5 μg and reduces therapeutic light irradiance from 100 mW cm^-2 to 60 mW cm^-2 while realizing better treatment effects. As a result, the skin damage and the burden on the metabolic system have been alleviated. The DfMNA has a remarkably reduced photosensitizer amount and, for the first time, realized transdermal delivery of therapeutic light for PDT, thus avoiding the disadvantages of existing PDT methodologies.

Antimicrobial Blue Light for Prevention and Treatment of Highly Invasive Vibrio vulnificus Burn Infection in Mice

Vibrio vulnificus is an invasive marine bacterium that causes a variety of serious infectious diseases. With the increasing multidrug-resistant variants, treatment of V. vulnificus infections is becoming more difficult. In this study, we explored antimicrobial blue light (aBL; 405 nm wavelength) for the treatment of V. vulnificus infections. We first assessed the efficacy of aBL against five strains of V. vulnificus in vitro. Next, we identified and quantified intracellular porphyrins in V. vulnificus to provide mechanistic insights. Additionally, we measured intracellular reactive oxygen species (ROS) production and bacterial membrane permeabilization following aBL exposures. Lastly, we conducted a preclinical study to investigate the efficacy and safety of aBL for the prevention and treatment of burn infections caused by V. vulnificus in mice. We found that aBL effectively killed V. vulnificus in vitro in both planktonic and biofilm states, with up to a 5.17- and 4.57-log₁₀ CFU reduction being achieved, respectively, following an aBL exposure of 216 J/cm². Protoporphyrin IX and coproporphyrins were predominant in all the strains. Additionally, intracellular ROS was significantly increased following aBL exposures (P < 0.01), and there was evidence of aBL-induced permeabilization of the bacterial membrane (P < 0.0001). In the preclinical studies, we found that female mice treated with aBL 30 min after bacterial inoculation showed a survival rate of 81% following 7 days of observation, while only 28% survival was observed in untreated female mice (P < 0.001). At 6 h post-inoculation, an 86% survival was achieved in aBL-treated female mice (P = 0.0002). For male mice, 86 and 63% survival rates were achieved when aBL treatment was given 30 min and 6 h after bacterial inoculation, respectively, compared to 32% survival in the untreated mice (P = 0.0004 and P = 0.04). aBL did not reduce cellular proliferation or induce apoptosis. We found five cytokines were significantly upregulated in the males after aBL treatment, including MCSF (P < 0.001), MCP-5 (P < 0.01), TNF RII (P < 0.01), CXCL1 (P < 0.01), and TIMP-1 (P < 0.05), and one in the females (TIMP-1; P < 0.05), suggesting that aBL may induce certain inflammatory processes. In conclusion, aBL may potentially be applied to prevent and treat V. vulnificus infections.

Light-Controllable Binary Switch Activation of CAR T Cells

Major challenges to chimeric antigen receptor (CAR) T cell therapies include uncontrolled immune activity, off-tumor toxicities and tumor heterogeneity. To overcome these challenges, we engineered CARs directed against small molecules. By conjugating the same small molecule to distinct tumor-targeting antibodies, we show that small molecule specific-CAR T cells can be redirected to different tumor antigens. Such binary switches allow control over the degree of CAR T cell activity and enables simultaneous targeting of multiple tumor-associated antigens. We also demonstrate that ultraviolet light-sensitive caging of small molecules blocks CAR T cell activation. Exposure to ultraviolet light, uncaged small molecules and restored CAR T cell-mediated killing. Together, our data demonstrate that a light-sensitive caging system enables an additional level of control over tumor cell killing, which could improve the therapeutic index of CAR T cell therapies.

Innovative light sources for phototherapy

The use of light for therapeutic purposes dates back to ancient Egypt, where the sun itself was an innovative source, probably used for the first time to heal skin diseases. Since then, technical innovation and advancement in medical sciences have produced newer and more sophisticated solutions for light-emitting sources and their applications in medicine. Starting from a brief historical introduction, the concept of innovation in light sources is discussed and analysed, first from a technical point of view and then in the light of their fitness to improve existing therapeutic protocols or propose new ones. If it is true that a “pure” technical advancement is a good reason for innovation, only a sub-system of those advancements is innovative for phototherapy. To illustrate this concept, the most representative examples of innovative light sources are presented and discussed, both from a technical point of view and from the perspective of their diffusion and applications in the clinical field.

Enhanced antimicrobial activity through the combination of antimicrobial photodynamic therapy and low-frequency ultrasonic irradiation

The rapid increase of antibiotic resistance in pathogenic microorganisms has become one of the most severe threats to human health. Antimicrobial photodynamic therapy (aPDT), a light-based regimen, has offered a compelling nonpharmacological alternative to conventional antibiotics. The activity of aPDT is based on cytotoxic effect of reactive oxygen species (ROS), which are generated through the photosensitized reaction between photon, oxygen and photosensitizer. However, limited by the penetration of light and photosensitizers in human tissues and/or the infiltration of oxygen and photosensitizers in biofilms, the eradication of deeply located or biofilm-associated infections by aPDT remains challenging. Ultrasound irradiation bears a deeper penetration in human tissues than light and, sequentially, can promote drug delivery through cavitation effect. As such, the combination of ultrasound and aPDT represents a potent antimicrobial strategy. In this review, we summarized the recent progresses in the area of the combination therapy using ultrasound and aPDT, and discussed the potential mechanisms underlying enhanced antimicrobial effect by this combination therapy. The future research directions are also highlighted.

Localised light delivery on melanoma cells using optical microneedles

Light-based therapy is an emerging treatment for skin cancer, which has received increased attention due to its drug-free and non-invasive approach. However, the limitation of current light therapy methods is the inability for light to penetrate the skin and reach deep lesions. As such, we have developed a polylactic acid (PLA) microneedles array as a novel light transmission platform to perform in vitro evaluation regarding the effect of light therapy on skin cancer. For the first time, we designed and fabricated a microneedle array system with a height fixation device that can be installed in a cell culture dish and an LED array for blue light irradiation. The effect of the blue light combined with the microneedles on cell apoptosis was evaluated using B16F10 melanoma cells and analyzed by Hoechst staining. Our results demonstrate that blue light can be transmitted by microneedles to skin cells and effectively affect cell viability.

Antimicrobial blue light: A 'Magic Bullet' for the 21st century and beyond?

Over the past decade, antimicrobial blue light (aBL) at 400 - 470 nm wavelength has demonstrated immense promise as an alternative approach for the treatment of multidrug-resistant infections. Since our last review was published in 2017, there have been numerous studies that have investigated aBL in terms of its, efficacy, safety, mechanism, and propensity for resistance development. In addition, researchers have looked at combinatorial approaches that exploit aBL and other traditional and non-traditional therapeutics. To that end, this review aims to update the findings from numerous studies that capitalize on the antimicrobial effects of aBL, with a focus on: efficacy of aBL against different microbes, identifying endogenous chromophores and targets of aBL, Resistance development to aBL, Safety of aBL against host cells, and Synergism of aBL with other agents. We will also discuss our perspective on the future of aBL.

Phototherapy and optical waveguides for the treatment of infection

With rapid emergence of multi-drug resistant microbes, it is imperative to seek alternative means for infection control. Optical waveguides are an auspicious delivery method for precise administration of phototherapy. Studies have shown that phototherapy is promising in fighting against a myriad of infectious pathogens (i.e. viruses, bacteria, fungi, and protozoa) including biofilm-forming species and drug-resistant strains while evading treatment resistance. When administered via optical waveguides, phototherapy can treat both superficial and deep-tissue infections while minimizing off-site effects that afflict conventional phototherapy and pharmacotherapy. Despite great therapeutic potential, exact mechanisms, materials, and fabrication designs to optimize this promising treatment option are underexplored. This review outlines principles and applications of phototherapy and optical waveguides for infection control. Research advances, challenges, and outlook regarding this delivery system are rigorously discussed in a hope to inspire future developments of optical waveguide-mediated phototherapy for the management of infection and beyond.

Biocompatible and Biodegradable Polymer Optical Fiber for Biomedical Application: A Review

This article discusses recent advances in biocompatible and biodegradable polymer optical fiber (POF) for medical applications. First, the POF material and its optical properties are summarized. Then, several common optical fiber fabrication methods are thoroughly discussed. Following that, clinical applications of biocompatible and biodegradable POFs are discussed, including optogenetics, biosensing, drug delivery, and neural recording. Following that, biomedical applications expanded the specific functionalization of the material or fiber design. Different research or clinical applications necessitate the use of different equipment to achieve the desired results. Finally, the difficulty of implanting flexible fiber varies with its flexibility. We present our article in a clear and logical manner that will be useful to researchers seeking a broad perspective on the proposed topic. Overall, the content provides a comprehensive overview of biocompatible and biodegradable POFs, including previous breakthroughs, as well as recent advancements. Biodegradable optical fibers have numerous applications, opening up new avenues in biomedicine.

Translation of Polymeric Microneedles for Treatment of Human Diseases: Recent Trends, Progress, and Challenges

The ongoing search for biodegradable and biocompatible microneedles (MNs) that are strong enough to penetrate skin barriers, easy to prepare, and can be translated for clinical use continues. As such, this review paper is focused upon discussing the key points (e.g., choice polymeric MNs) for the translation of MNs from laboratory to clinical practice. The review reveals that polymers are most appropriately used for dissolvable and swellable MNs due to their wide range of tunable properties and that natural polymers are an ideal material choice as they structurally mimic native cellular environments. It has also been concluded that natural and synthetic polymer combinations are useful as polymers usually lack mechanical strength, stability, or other desired properties for the fabrication and insertion of MNs. This review evaluates fabrication methods and materials choice, disease and health conditions, clinical challenges, and the future of MNs in public healthcare services, focusing on literature from the last decade.

Single Polylactic Acid Nanowire for Highly Sensitive and Multifunctional Optical Biosensing

Nanowire-based optical biosensors with high sensitivity are highly desired for the detection of biological microenvironments and analysis of cellular processes. However, the current nanowire biosensors are mostly fabricated with metal and semiconductor materials, which are not suitable for long-term use in biological environments due to their incompatible and nondegradable properties. Biosensors based on biofriendly materials (e.g., spider silk) often do not have high enough sensitivity due to high losses or micron sizes. Here, polylactic acid (PLA), a polymer with high optical transparency, good biocompatibility, biodegradability, and flexibility, is used to fabricate nanowires using a directly drawing method for the first time. Because of the strong evanescent wave and abundant carboxyl groups on the surface of nanowires, an ultralow concentration sensing of cytochrome c is achieved with a limit of detection of 1.38 × 10^-17 M, which is much lower than other detection results using semiconductor/metal-based nanosensors (10^-6 to 10^-12 M). On this basis, a label-free and real-time monitoring of cell apoptosis is realized. In addition, by doping quantum dots, the functionalized PLA nanowires can also sense a change in pH. These results are suggestive of the potential for PLA nanowires applied in multifunctional biosensing and biodetection, pushing forward the photomedicine field.

Localized Delivery of Theranostic Nanoparticles and High-Energy Photons using Microneedles-on-Bioelectronics

The low delivery efficiency of light-responsive theranostic nanoparticles (NPs) to target tumor sites, particularly to brain tumors due to the blood-brain barrier, has been a critical issue in NP-based cancer treatments. Furthermore, high-energy photons that can effectively activate theranostic NPs are hardly delivered to the target region due to the strong scattering of such photons while penetrating surrounding tissues. Here, a localized delivery method of theranostic NPs and high-energy photons to the target tumor using microneedles-on-bioelectronics is presented. Two types of microneedles and flexible bioelectronics are integrated and mounted on the edge of surgical forceps. Bioresorbable microneedles containing theranostic NPs deliver the NPs into target tumors (e.g., glioblastoma, pituitary adenoma). Magnetic resonance imaging can locate the NPs. Then, light-guiding/spreading microneedles deliver high-energy photons from bioelectronics to the NPs. The high-energy photons activate the NPs to treat tumor tissues by photodynamic therapy and chemotherapy. The controlled thermal actuation by the bioelectronics accelerates the diffusion of chemo-drugs. The proposed method is demonstrated with mouse tumor models in vivo.

A highly robust approach to fabricate the mass-customizable mold of sharp-tipped biodegradable polymer microneedles for drug delivery

A skin-perforable dissolving microneedle is a promising mediator for painlessly delivering active pharmaceutical compounds across the skin. All the microneedle manufacturing processes so far, however, are much sensitive to input variation and unfavorable for make-to-order approach. Here, a robust method for fabricating mass-customizable master molds is developed to prepare sharp-tipped biodegradable polymer microneedles. Our approach combines the predrying and chip casting (PCC) of an ultrathick photoresist layer with a substrateless, inclined, and rotational exposure (SIR exposure). The PCC achieves the uniform reduction of solvent across the photoresist thickness which is critically required for the formation of a sharp tip; the SIR exposure creates master molds whose geometry is easily customizable and virtually insensitive to a variation in ultraviolet (UV) exposure dose. A theoretical model for the spatiotemporal distribution of UV dose under SIR exposure is established to show the technological superiority of our method. Next, our method's applicability is proven by fabricating a set of poly(lactic-co-glycolic) acid (PLGA) microneedles and performing both porcine skin penetration test and their in vitro degradation test. Our approach is verified to be robust in manufacturing mass-customizable molds for skin-perforable dissolving microneedles and to have high compatibility with almost all existing biodegradable polymers. The findings of this study lead to both a significant growth of dissolving microneedle-mediated drug delivery and better understanding of drug release kinetics.

Potentiated antimicrobial blue light killing of methicillin resistant Staphylococcus aureus by pyocyanin

As antimicrobial resistance continues to threaten the efficacy of conventional antibiotic therapy, it is paramount that we investigate innovative approaches to treat infectious diseases. In this study, we investigated the antimicrobial capabilities of the innovative combination of antimicrobial blue light (aBL; 405 nm wavelength) with the Pseudomonas aeruginosa pigment pyocyanin against methicillin resistant Staphylococcus aureus (MSRA. We explored the effects of different radiant exposures of aBL and increasing concentrations of pyocyanin against planktonic cells and those within biofilms. In addition, we investigated the effect of the aBL/pyocyanin on the endogenous staphyloxanthin pigment, as well as the role of hydrogen peroxide and singlet oxygen scavenging in the efficacy of this combination. Lastly, we investigated the potential for the aBL/pyocyanin to reduce the MRSA burden within a proof-of-principle mouse abrasion infection model. We found pyocyanin to be a powerful potentiator of aBL activity under all in vitro conditions tested. In addition, we serendipitously discovered the capability of the aBL/pyocyanin combination to bleach staphyloxanthin within colonies of MRSA. Furthermore, we established that singlet oxygen is an important mediator during combined aBL/pyocyanin exposure. Moreover, we found that the combination of aBL and pyocyanin could significantly reduce the viability of MRSA within a proof-of-principle early onset MRSA skin abrasion infection. Exposure to the treatment did not have deleterious effects on skin tissue. In conclusion, the combination of aBL and pyocyanin represents a potentially powerful therapeutic modality for the treatment of infections caused by MRSA.

Cryptochrome 1 is modulated by blue light in human keratinocytes and exerts positive impact on human hair growth

Photoactivation of cryptochrome-family proteins by blue light is a well-established reaction regulating physiology of plants, fungi, bacteria, insects and birds, while impact of blue light on cryptochrome synthesis and/or activity in human non-visual cells remains unknown. Here, we show that 453 nm blue light induces cryptochrome 1 (CRY1) accumulation in human keratinocytes and the hair follicle. CRY1 is prominently expressed in the human anagen hair follicle, including epithelial stem cells. Specific silencing of CRY1 promotes catagen, while stimulation of CRY1 by KL001 prolongs anagen ex vivo by altering the expression of genes involved in apoptosis and proliferation. Together, our study identifies a role for CRY1 in sustaining human hair growth. Previously, we demonstrated positive effects of 453 nm blue light on hair growth ex vivo. Taken all together, our study suggests that CRY1 might mediate blue light-dependent positive effects on hair growth.

Optical Waveguides and Integrated Optical Devices for Medical Diagnosis, Health Monitoring and Light Therapies

Optical waveguides and integrated optical devices are promising solutions for many applications, such as medical diagnosis, health monitoring and light therapies. Despite the many existing reviews focusing on the materials that these devices are made from, a systematic review that relates these devices to the various materials, fabrication processes, sensing methods and medical applications is still seldom seen. This work is intended to link these multidisciplinary fields, and to provide a comprehensive review of the recent advances of these devices. Firstly, the optical and mechanical properties of optical waveguides based on glass, polymers and heterogeneous materials and fabricated via various processes are thoroughly discussed, together with their applications for medical purposes. Then, the fabrication processes and medical implementations of integrated passive and active optical devices with sensing modules are introduced, which can be used in many medical fields such as drug delivery and cardiovascular healthcare. Thirdly, wearable optical sensing devices based on light sensing methods such as colorimetry, fluorescence and luminescence are discussed. Additionally, the wearable optical devices for light therapies are introduced. The review concludes with a comprehensive summary of these optical devices, in terms of their forms, materials, light sources and applications.

Dual-wavelength photo-killing of methicillin-resistant Staphylococcus aureus

With the effectiveness of antimicrobials declining as antimicrobial resistance continues to threaten public health, we must look to alternative strategies for the treatment of infections. In this study, we investigated an innovative, drug-free, dual-wavelength irradiation approach that combines 2 wavelengths of light, 460 nm and 405 nm, against methicillin-resistant Staphylococcus aureus (MRSA). MRSA was initially irradiated with 460-nm light (90-360 J/cm2) and subsequently irradiated with aliquots of 405-nm light (54-324 J/cm2). For in vivo studies, mouse skin was abraded and infected with approximately 107 CFUs of MRSA and incubated for 3 hours before irradiating with 460 nm (360 J/cm2) and 405 nm (342 J/cm2). Naive mouse skin was also irradiated to investigate apoptosis. We found that staphyloxanthin, the carotenoid pigment in MRSA cells, promoted resistance to the antimicrobial effects of 405-nm light. In addition, we found that the photolytic effect of 460-nm light on staphyloxanthin attenuated resistance of MRSA to 405-nm light killing. Irradiation of 460 nm alone did not elicit any antimicrobial effect on MRSA. In a proof-of-principle mouse skin abrasion infection model, we observed significant killing of MRSA using the dual-wavelength irradiation approach. However, when either wavelength of light was administered alone, no significant decrease in bacterial viability was observed. Moreover, exposure of the dual-wavelength irradiation to naive mouse skin did not result in any visible apoptosis. In conclusion, a dual-wavelength irradiation strategy may offer an innovative, effective, and safe approach for the treatment of skin infections caused by MRSA.

Printed Soft Optical Waveguides of PLA Copolymers for Guiding Light into Tissue

The application of optical technologies in treating pathologies and monitoring disease states requires the development of soft, minimal invasive and implantable devices to deliver light to tissues inside the body. Here, we present soft and degradable optical waveguides from poly(d,l-lactide) and derived copolymers fabricated by extrusion printing in the desired dimensions and shapes. The obtained optical waveguides propagate VIS to NIR light in air and in tissue at penetration depths of tens of centimeters. Besides, the printed waveguides have elastomeric properties at body temperature and show softness and flexibility in the range relevant for implantable devices in soft organs. Printed waveguides were able to guide light across 8 cm tissue and activate photocleavage chemical reactions in a photoresponsive hydrogel (in vitro). The simplicity and flexibility of the fiber processing method and the optical and mechanical performance of the obtained waveguides exemplify how rational study of medically approved biomaterials can lead to useful inks for printing cost-effective and flexible optical components for potential use in medical contexts.

Recent Advances in Bioplastics: Application and Biodegradation

The success of oil-based plastics and the continued growth of production and utilisation can be attributed to their cost, durability, strength to weight ratio, and eight contributions to the ease of everyday life. However, their mainly single use, durability and recalcitrant nature have led to a substantial increase of plastics as a fraction of municipal solid waste. The need to substitute single use products that are not easy to collect has inspired a lot of research towards finding sustainable replacements for oil-based plastics. In addition, specific physicochemical, biological, and degradation properties of biodegradable polymers have made them attractive materials for biomedical applications. This review summarises the advances in drug delivery systems, specifically design of nanoparticles based on the biodegradable polymers. We also discuss the research performed in the area of biophotonics and challenges and opportunities brought by the design and application of biodegradable polymers in tissue engineering. We then discuss state-of-the-art research in the design and application of biodegradable polymers in packaging and emphasise the advances in smart packaging development. Finally, we provide an overview of the biodegradation of these polymers and composites in managed and unmanaged environments.

Soft and Stretchable Polymeric Optical Waveguide-Based Sensors for Wearable and Biomedical Applications

The past decades have witnessed the rapid development in soft, stretchable, and biocompatible devices for applications in biomedical monitoring, personal healthcare, and human-machine interfaces. In particular, the design of soft devices in optics has attracted tremendous interests attributed to their distinct advantages such as inherent electrical safety, high stability in long-term operation, potential to be miniaturized, and free of electromagnetic interferences. As the alternatives to conventional rigid optical waveguides, considerable efforts have been made to develop light-guiding devices by using various transparent and elastic polymers, which offer desired physiomechanical properties and enable wearable/implantable applications in optical sensing, diagnostics, and therapy. Here, we review recent progress in soft and stretchable optical waveguides and sensors, including advanced structural design, fabrication strategies, and functionalities. Furthermore, the potential applications of those optical devices for various wearable and biomedical applications are discussed. It is expected that the newly emerged soft and stretchable optical technologies will provide a safe and reliable alternative to next-generation, smart wearables and healthcare devices.

Polymeric biomaterials for biophotonic applications

With the growing importance of optical techniques in medical diagnosis and treatment, there exists a pressing need to develop and optimize materials platform for biophotonic applications. Particularly, the design of biocompatible and biodegradable materials with desired optical, mechanical, chemical, and biological properties is required to enable clinically relevant biophotonic devices for translating in vitro optical techniques into in situ and in vivo use. This technological trend propels the development of natural and synthetic polymeric biomaterials to replace traditional brittle, nondegradable silica glass based optical materials. In this review, we present an overview of the advances in polymeric optical material development, optical device design and fabrication techniques, and the accompanying applications to imaging, sensing and phototherapy.

Strong magnetochiral dichroism in chiral/magnetic layered heterostructures

In this Letter, we propose a nonreciprocal heterostructure which combines magnetism and chirality in a simple, easy-to-fabricate design and exhibits at least two orders of magnitude larger magnetochiral dichroism, compared to other proposed metamaterials. This effect stems from the simultaneous lack of time-reversal and space-inversion symmetries and is enhanced by collective slow-photon modes originating from the strong bending of the photonic bands at the Brillouin zone boundaries. We investigate the optical properties of this bianisotropic multilayer heterostructure, consisting of consecutive bilayers of chiral and magnetic materials, embedded in air, and discuss the associated photonic band structure and transmission/absorption spectra obtained by means of full electrodynamic calculations.

Light-Guiding Biomaterials for Biomedical Applications

Optical techniques used in medical diagnosis, surgery, and therapy require efficient and flexible delivery of light from light sources to target tissues. While this need is currently fulfilled by glass and plastic optical fibers, recent emergence of biointegrated approaches, such as optogenetics and implanted devices, call for novel waveguides with certain biophysical and biocompatible properties and desirable shapes beyond what the conventional optical fibers can offer. To this end, exploratory efforts have begun to harness various transparent biomaterials to develop waveguides that can serve existing applications better and enable new applications in future photomedicine. Here, we review the recent progress in this new area of research for developing biomaterial-based optical waveguides. We begin with a survey of biological light-guiding structures found in plants and animals, a source of inspiration for biomaterial photonics engineering. We describe natural and synthetic polymers and hydrogels that offer appropriate optical properties, biocompatibility, biodegradability, and mechanical flexibility have been exploited for light-guiding applications. Finally, we briefly discuss perspectives on biomedical applications that may benefit from the unique properties and functionalities of light-guiding biomaterials.

Characterization of the Optical Properties of Turbid Media by Supervised Learning of Scattering Patterns

Fabricated tissue phantoms are instrumental in optical in-vitro investigations concerning cancer diagnosis, therapeutic applications, and drug efficacy tests. We present a simple non-invasive computational technique that, when coupled with experiments, has the potential for characterization of a wide range of biological tissues. The fundamental idea of our approach is to find a supervised learner that links the scattering pattern of a turbid sample to its thickness and scattering parameters. Once found, this supervised learner is employed in an inverse optimization problem for estimating the scattering parameters of a sample given its thickness and scattering pattern. Multi-response Gaussian processes are used for the supervised learning task and a simple setup is introduced to obtain the scattering pattern of a tissue sample. To increase the predictive power of the supervised learner, the scattering patterns are filtered, enriched by a regressor, and finally characterized with two parameters, namely, transmitted power and scaled Gaussian width. We computationally illustrate that our approach achieves errors of roughly 5% in predicting the scattering properties of many biological tissues. Our method has the potential to facilitate the characterization of tissues and fabrication of phantoms used for diagnostic and therapeutic purposes over a wide range of optical spectrum.

Antimicrobial blue light inactivation of pathogenic microbes: State of the art

As an innovative non-antibiotic approach, antimicrobial blue light in the spectrum of 400-470nm has demonstrated its intrinsic antimicrobial properties resulting from the presence of endogenous photosensitizing chromophores in pathogenic microbes and, subsequently, its promise as a counteracter of antibiotic resistance. Since we published our last review of antimicrobial blue light in 2012, there have been a substantial number of new studies reported in this area. Here we provide an updated overview of the findings from the new studies over the past 5 years, including the efficacy of antimicrobial blue light inactivation of different microbes, its mechanism of action, synergism of antimicrobial blue light with other angents, its effect on host cells and tissues, the potential development of resistance to antimicrobial blue light by microbes, and a novel interstitial delivery approach of antimicrobial blue light. The potential new applications of antimicrobial blue light are also discussed.

In vivo photothermal treatment with real-time monitoring by optical fiber-needle array

Photothermal treatment (PTT) using gold nanoshells (gold-NSs) is accepted as a method for treating cancer. However, owing to restrictions in therapeutic depth and skin damage caused by excessive light exposure, its application has been limited to lesions close to the epidermis. Here, we demonstrate an in vivo PTT method that uses gold-NSs with a flexible optical fiber-needle array (OFNA), which is an array of multiple needles in which multimode optical fibers are inserted, one in each, for light delivery. The light for PTT was directly administrated to subcutaneous tissues through the OFNA, causing negligible thermal damage to the skin. Enhancement of light energy delivery assisted by the OFNA in a target area was confirmed by investigation using artificial tissues. The ability of OFNA to treat cancer without causing cutaneous thermal damage was also verified by hematoxylin and eosin (H&E) staining and optical coherence tomography in cancer models in mice. In addition, the OFNA allowed for observation of the target site through an imaging fiber bundle. By imaging the activation of the injected gold-NSs, we were able to obtain information on the PTT process in real-time.

In Vivo Investigation of Antimicrobial Blue Light Therapy for Multidrug-resistant Acinetobacter baumannii Burn Infections Using Bioluminescence Imaging

Burn infections continue to be an important cause of morbidity and mortality. The increasing emergence of multidrug-resistant (MDR) bacteria has led to the frequent failure of traditional antibiotic treatments. Alternative therapeutics are urgently needed to tackle MDR bacteria. An innovative non-antibiotic approach, antimicrobial blue light (aBL), has shown promising effectiveness against MDR infections. The mechanism of action of aBL is not yet well understood. It is commonly hypothesized that naturally occurring endogenous photosensitizing chromophores in bacteria (e.g., iron-free porphyrins, flavins, etc.) are excited by aBL, which in turn produces cytotoxic reactive oxygen species (ROS) through a photochemical process. Unlike another light-based antimicrobial approach, antimicrobial photodynamic therapy (aPDT), aBL therapy does not require the involvement of an exogenous photosensitizer. All it needs to take effect is the irradiation of blue light; therefore, it is simple and inexpensive. The aBL receptors are the endogenous cellular photosensitizers in bacteria, rather than the DNA. Thus, aBL is believed to be much less genotoxic to host cells than ultraviolet-C (UVC) irradiation, which directly causes DNA damage in host cells. In this paper, we present a protocol to assess the effectiveness of aBL therapy for MDR Acinetobacter baumannii infections in a mouse model of burn injury. By using an engineered bioluminescent strain, we were able to noninvasively monitor the extent of infection in real time in living animals. This technique is also an effective tool for monitoring the spatial distribution of infections in animals.

A new path in defining light parameters for hair growth: Discovery and modulation of photoreceptors in human hair follicle

BACKGROUND AND OBJECTIVE

Though devices for hair growth based on low levels of light have shown encouraging results, further improvements of their efficacy is impeded by a lack of knowledge on the exact molecular targets that mediate physiological response in skin and hair follicle. The aim of this study was to investigate the expression of selected light-sensitive receptors in the human hair follicle and to study the impact of UV-free blue light on hair growth ex vivo.

MATERIAL AND METHODS

The expression of Opsin receptors in human skin and hair follicles has been characterized using RT-qPCR and immunofluorescence approaches. The functional significance of Opsin 3 was assessed by silencing its expression in the hair follicle cells followed by a transcriptomic profiling. Proprietary LED-based devices emitting two discrete visible wavelengths were used to access the effects of selected optical parameters on hair growth ex vivo and outer root sheath cells in vitro.

RESULTS

The expression of OPN2 (Rhodopsin) and OPN3 (Panopsin, Encephalopsin) was detected in the distinct compartments of skin and anagen hair follicle. Treatment with 3.2 J/cm² of blue light with 453 nm central wavelength significantly prolonged anagen phase in hair follicles ex vivo that was correlated with sustained proliferation in the light-treated samples. In contrast, hair follicle treatment with 3.2 J/cm² of 689 nm light (red light) did not significantly affect hair growth ex vivo. Silencing of OPN3 in the hair follicle outer root sheath cells resulted in the altered expression of genes involved in the control of proliferation and apoptosis, and abrogated stimulatory effects of blue light (3.2 J/cm² ; 453 nm) on proliferation in the outer root sheath cells.

CONCLUSIONS

We provide the first evidence that (i) OPN2 and OPN3 are expressed in human hair follicle, and (ii) A 453 nm blue light at low radiant exposure exerts a positive effect on hair growth ex vivo, potentially via interaction with OPN3. Lasers Surg. Med. 49:705-718, 2017. © 2017 Wiley Periodicals, Inc.