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The Mimosa pudica leaf has motor organs allowing movements driven by cell osmotic changes in the parenchyma cells in response to various stimuli. Short white light pulses induce rapid and large seismonastic‐like movements (denoted “photostimulation”) of the primary pulvini in various leaves within 120 s after the onset of light. An early event recorded is a wavelength‐related modification of the plasma membrane difference: potential depolarization under white, blue, green, and red wavelengths, and hyperpolarization under far red wavelengths (and also in darkness). The photoreactivity of the pulvini is controlled by a circadian rhythm and modulated by the applied diurnal photoperiod cycle (photophase ranging from 6 to 18 h). The reactivity varied among plants and even between leaves on the same plant. The level of reactivity is related to the photon fluence rate in the range from 10 to 140 μmol m−2 s−1 under white light and to the experimental temperature in the range 15°C–35°C. An “accommodation” to light supply is evidenced by a modulation of the reactivity in relation to the schedule of light application under low fluence rates and the introduction of short darkness intervals during the first 30‐s light pulse. The blue light‐induced photostimulation is under phytochrome control. [ABSTRACT FROM AUTHOR]

Photobiomodulation (PBM), previously known as low-level laser light therapy, represents a noninvasive form of phototherapy that utilizes wavelengths in the red light (RL, 620-700 nm) portion of the visible light (VL, 400-700 nm) spectrum and the near-infrared (NIR, 700-1440 nm) spectrum. PBM is a promising and increasingly used therapy for the treatment of various dermatologic and nondermatologic conditions. Photons from RL and NIR are absorbed by endogenous photoreceptors including mitochondrial cytochrome C oxidase (COX). Activation of COX leads to the following changes: modulation of mitochondrial adenosine triphosphate (ATP), generation of reactive oxygen species (ROS), and alterations in intracellular calcium levels. The associated modulation of ATP, ROS and calcium levels promotes the activation of various signaling pathways (eg, insulin-like growth factors, phosphoinositide 3-kinase pathways), which contribute to downstream effects on cellular proliferation, migration, and differentiation. Effective PBM therapy is dependent on treatment parameters (eg, fluence, treatment duration and output power). PBM is generally well-tolerated and safe with erythema being the most common and self-limiting adverse cutaneous effect. [ABSTRACT FROM AUTHOR]

Advancements in optoelectronic biointerfaces have revolutionized healthcare by enabling targeted stimulation and monitoring of cells, tissues, and organs. Photostimulation, a key application, offers precise control over biological processes, surpassing traditional modulation methods with increased spatial resolution and reduced invasiveness. This perspective highlights three approaches in non-genetic optoelectronic photostimulation: nanostructured phototransducers for cellular stimulation, micropatterned photoelectrode arrays for tissue stimulation, and thin-film flexible photoelectrodes for multiscale stimulation. Nanostructured phototransducers provide localized stimulation at the cellular or subcellular level, facilitating cellular therapy and regenerative medicine. Micropatterned photoelectrode arrays offer precise tissue stimulation, critical for targeted therapeutic interventions. Thin-film flexible photoelectrodes combine flexibility and biocompatibility for scalable medical applications. Beyond neuromodulation, optoelectronic biointerfaces hold promise in cardiology, oncology, wound healing, and endocrine and respiratory therapies. Future directions include integrating these devices with advanced imaging and feedback systems, developing wireless and biocompatible devices for long-term use, and creating multifunctional devices that combine photostimulation with other therapies. The integration of light and electronics through these biointerfaces paves the way for innovative, less invasive, and more accurate medical treatments, promising a transformative impact on patient care across various medical fields. Highlights: • Non-genetic optoelectronic biointerfaces revolutionize healthcare by enabling precise biological stimulation and monitoring. • Key methods include nanostructured phototransducers, micropatterned arrays, and thin-film flexible electrodes. • Future advancements will integrate imaging, develop wireless devices, and create multifunctional therapies, transforming patient care. [ABSTRACT FROM AUTHOR]

Abstract In this paper the photobiomodulation on isolated mitochondria of bovine liver is studied as a thermodynamic process of conversion of energy. This analysis is conducted by considering a particular set-up for the photobiomodulation experiments of interest. It allows, in particular, the computation of the electromagnetic field and the related energetic quantities in the stimulated organelles. The measurements of the excess of biochemical power density produced by the illuminated mitochondria are performed at regular time intervals after the experiments. The calculations and the measurements finally allow us to obtain the first results on the efficiency of the process of conversion of electromagnetic energy into excess of biochemical energy released by the isolated organelles.

In this paper the photobiomodulation on isolated mitochondria of bovine liver is studied as a thermodynamic process of conversion of energy. This analysis is conducted by considering a particular set-up for the photobiomodulation experiments of interest. It allows, in particular, the computation of the electromagnetic field and the related energetic quantities in the stimulated organelles. The measurements of the excess of biochemical power density produced by the illuminated mitochondria are performed at regular time intervals after the experiments. The calculations and the measurements finally allow us to obtain the first results on the efficiency of the process of conversion of electromagnetic energy into excess of biochemical energy released by the isolated organelles. [ABSTRACT FROM AUTHOR]

The two leading causes of blindness in the developed world are age-related macular degeneration and retinitis pigmentosa. The photostimulation of remaining retinal neurons using a photodiode in a proposed subretinal prosthesis is one of the solutions that hopes to restore vision. In this paper, we envision a better result through device simulation and modeling of a graphene-based photodiode that yields high-performance, wire-free, and light-induced retina implants. This study shows how the characteristics of graphene-based photodiodes have an improved result in terms of low threshold requirements for the activation of neurons. Graphene-based photodiode responsiveness is significantly improved in the visible and near-infrared ranges. Using a graphene photoconductive layer in a silicon photodiode can significantly decrease contact resistance, reduce dark current up to 20-fold, and lower the induced thermal effect and spontaneous emission by orders of magnitude of 103 and 106, respectively, compared to its Si counterparts. This advancement highlights graphene's potential for optimizing metal–semiconductor interfaces, offering improved precision and sensitivity for high-resolution retinal prosthesis applications requiring enhanced signal-to-noise ratio and finer control. We offered a range of sizes for graphene-based photodiode arrays, including [5 × 5], [6 × 6], [6 × 7], and [7 × 6], to ensure the subretinal prostheses meet thermal safety standards. Physics-based modeling and simulation of graphene-based devices help us understand charge transfer mechanisms, improve operating bias, and achieve proper band gap modulation, which ushers in the development of graphene-like 2D materials for photostimulating neurons in projected retinal prostheses. [ABSTRACT FROM AUTHOR]

Abstract Alzheimer’s disease (AD) is an age-related neurodegenerative disorder that poses a significant burden on socio-economic and healthcare systems worldwide. However, the currently available therapy of AD is limited, and new strategies are needed to enhance the clearance of β-amyloid (Aβ) protein and improve cognitive function. Photobiomodulation (PBM) is a non-invasive and effective therapeutic method that has shown promise in treating various brain diseases. Here, we demonstrate that 1267-nm PBM significantly alleviates cognitive decline in the 5xFAD mouse model of AD and is safe as it does not induce a significant increase in cortical temperature. Moreover, with the combination of 3D tissue optical clearing imaging and automatic brain region segmentation, we show that PBM-mediated reductions of Aβ plaques in different subregions of prefrontal cortex and the hippocampus are different. The PBM-induced lymphatic clearance of Aβ from the brain is associated with improvement of memory and cognitive functions in 5xFAD mice. Our results suggest that the modulation of meningeal lymphatic vessels (MLVs) should play an important role in promoting Aβ clearance. Collectively, this pilot study demonstrates that PBM can safely accelerate lymphatic clearance of Aβ from the brain of 5xFAD mice, promoting improvement of neurocognitive status of AD animals suggesting that PBM can be an effective and bedside therapy for AD. Graphical Abstract

In afterglow phosphors, luminescence appears and can be observed with the naked eye for minutes to hours or more, even after photoexcitation ceases. Red afterglow and photostimulated luminescence (PSL) at 650 nm are studied in CaS:Eu2+, Mn2+ phosphors. Infrared light at 980 nm from a laser diode induces the red PSL for 990 s. Two types of trap states are found to be present in the phosphors by using thermoluminescence (TL). Deep trap states are reflected in a TL peak in the temperature region of 520 K, and are related to PSL. Shallow trap states reflected in the other TL peak at 250 K are related to afterglow. The intensity dependence of photoexcitation on PSL shows that carriers are more easily accumulated in the deep trap states than shallow trap states. Experiments of electron paramagnetic resonance are conducted to discuss the possible origins of PSL and the afterglow. [ABSTRACT FROM AUTHOR]

This research paper explores the contribution of optical resolution to the spatial precision of two-photon optogenetic photostimulation in neurobiology. The study conducted controlled experiments to assess the impact of altering the axial spread of the optical point spread function (OPSF) on the spatial precision of photostimulation in the mouse neocortex. The results indicate that optical resolution is not always the limiting factor in achieving spatial precision, and other factors such as cell size and shape play a significant role. The findings provide valuable insights for future research in improving the precision of all-optical interrogation in neuroscience. [Extracted from the article]

Alzheimer's disease (AD) is an age-related neurodegenerative disorder that poses a significant burden on socio-economic and healthcare systems worldwide. However, the currently available therapy of AD is limited, and new strategies are needed to enhance the clearance of β-amyloid (Aβ) protein and improve cognitive function. Photobiomodulation (PBM) is a non-invasive and effective therapeutic method that has shown promise in treating various brain diseases. Here, we demonstrate that 1267-nm PBM significantly alleviates cognitive decline in the 5xFAD mouse model of AD and is safe as it does not induce a significant increase in cortical temperature. Moreover, with the combination of 3D tissue optical clearing imaging and automatic brain region segmentation, we show that PBM-mediated reductions of Aβ plaques in different subregions of prefrontal cortex and the hippocampus are different. The PBM-induced lymphatic clearance of Aβ from the brain is associated with improvement of memory and cognitive functions in 5xFAD mice. Our results suggest that the modulation of meningeal lymphatic vessels (MLVs) should play an important role in promoting Aβ clearance. Collectively, this pilot study demonstrates that PBM can safely accelerate lymphatic clearance of Aβ from the brain of 5xFAD mice, promoting improvement of neurocognitive status of AD animals suggesting that PBM can be an effective and bedside therapy for AD. [ABSTRACT FROM AUTHOR]

Optoelectronic biointerfaces have gained significant interest for wireless and electrical control of neurons. Three–dimentional (3D) pseudocapacitive nanomaterials with large surface areas and interconnected porous structures have great potential for optoelectronic biointerfaces that can fulfill the requirement of high electrode‐electrolyte capacitance to effectively transduce light into stimulating ionic currents. In this study, the integration of 3D manganese dioxide (MnO2) nanoflowers into flexible optoelectronic biointerfaces for safe and efficient photostimulation of neurons is demonstrated. MnO2 nanoflowers are grown via chemical bath deposition on the return electrode, which has a MnO2 seed layer deposited via cyclic voltammetry. They facilitate a high interfacial capacitance (larger than 10 mF cm−2) and photogenerated charge density (over 20 µC cm−2) under low light intensity (1 mW mm−2). MnO2 nanoflowers induce safe capacitive currents with reversible Faradaic reactions and do not cause any toxicity on hippocampal neurons in vitro, making them a promising material for biointerfacing with electrogenic cells. Patch‐clamp electrophysiology is recorded in the whole‐cell configuration of hippocampal neurons, and the optoelectronic biointerfaces trigger repetitive and rapid firing of action potentials in response to light pulse trains. This study points out the potential of electrochemically‐deposited 3D pseudocapacitive nanomaterials as a robust building block for optoelectronic control of neurons. [ABSTRACT FROM AUTHOR]

Stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs) represent a relatively common phenomenon recorded during a long-term electroencephalogram (EEG) monitoring allowing to capture the altered state and response to auditory, tactile or nociceptive stimulation in critically ill patients. It is a nosologically non-specific phenomenon, and its relation to ictal event remains debated. We present a clinical case in which SIRPIDs were recorded in the affected dominant hemisphere in response to low-frequency photostimulation in a 60-years-old woman recovering after middle cerebral artery stroke. No ictal events were recorded during routine EEG monitoring; the patient was not in critical condition.

Abstract Optoelectronic biointerfaces have gained significant interest for wireless and electrical control of neurons. Three–dimentional (3D) pseudocapacitive nanomaterials with large surface areas and interconnected porous structures have great potential for optoelectronic biointerfaces that can fulfill the requirement of high electrode‐electrolyte capacitance to effectively transduce light into stimulating ionic currents. In this study, the integration of 3D manganese dioxide (MnO2) nanoflowers into flexible optoelectronic biointerfaces for safe and efficient photostimulation of neurons is demonstrated. MnO2 nanoflowers are grown via chemical bath deposition on the return electrode, which has a MnO2 seed layer deposited via cyclic voltammetry. They facilitate a high interfacial capacitance (larger than 10 mF cm−2) and photogenerated charge density (over 20 µC cm−2) under low light intensity (1 mW mm−2). MnO2 nanoflowers induce safe capacitive currents with reversible Faradaic reactions and do not cause any toxicity on hippocampal neurons in vitro, making them a promising material for biointerfacing with electrogenic cells. Patch‐clamp electrophysiology is recorded in the whole‐cell configuration of hippocampal neurons, and the optoelectronic biointerfaces trigger repetitive and rapid firing of action potentials in response to light pulse trains. This study points out the potential of electrochemically‐deposited 3D pseudocapacitive nanomaterials as a robust building block for optoelectronic control of neurons.

Optogenetic control of retinal cells transduced with light‐sensitive channelrhodopsins can enable restoration of visual perception in patients with vision loss. However, a light intensity orders of magnitude higher than ambient light conditions is required to achieve robust cell activation. Relatively bulky wearable light amplifiers are currently used to deliver sufficient photon flux (>1016 photons/cm2/s in a ±10° emission cone) at a suitable wavelength (e.g., 600 nm for channelrhodopsin ChrimsonR). Here, ultrahigh brightness organic light‐emitting diodes (OLEDs) with highly directional emission are developed, with the ultimate aim of providing high‐resolution optogenetic control of thousands of retinal cells in parallel from a compact device. The orange‐emitting phosphorescent OLEDs use doped charge transport layers, generate narrowband emission peaking at 600 nm, and achieve a luminance of 684 000 cd m–2 at 15 V forward bias. In addition, tandem‐stack OLEDs with a luminance of 1 152 000 cd m–2 and doubled quantum efficiency are demonstrated, which greatly reduces electrical and thermal stress in these devices. At the photon flux required to trigger robust neuron firing in genetically modified retinal cells and when using heat sinking and realistic duty cycles (20% at 12.5 Hz), the tandem‐stack OLEDs therefore show a greatly improved half‐brightness lifetime of 800 h. [ABSTRACT FROM AUTHOR]

The global number of people with Alzheimer's disease (AD) doubles every 5 years. It has been established that unless an effective treatment for AD is found, the incidence of AD will triple by 2060. However, pharmacological therapies for AD have failed to show effectiveness and safety. Therefore, the search for alternative methods for treating AD is an urgent problem in medicine. The lymphatic drainage and removal system of the brain (LDRSB) plays an important role in resistance to the progression of AD. The development of methods for augmentation of the LDRSB functions may contribute to progress in AD therapy. Photobiomodulation (PBM) is considered to be a non-pharmacological and safe approach for AD therapy. Here, we highlight the most recent and relevant studies of PBM for AD. We focus on emerging evidence that indicates the potential benefits of PBM during sleep for modulation of natural activation of the LDRSB at nighttime, providing effective removal of metabolites, including amyloid-β, from the brain, leading to reduced progression of AD. Our review creates a new niche in the therapy of brain diseases during sleep and sheds light on the development of smart sleep technologies for neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

Purpose: to investigate the changes of electrophysiological activity of healthy rabbit retina occurring in courses of fractal stimulation (FS) of varied duration in order to obtain new scientific data on how fractal visual signals of low intensity, self-similar with respect to time, affect the retina.Material and methods. 12 healthy Chinchilla rabbits (24 eyes), were examined before and after FS courses that lasted 1, 4 or 12 weeks, using electroretinographic (ERG), morphometric (optical coherence tomography) and biochemical methods (detection of dopamine in the tear). For FS of rabbits, a device with an LED emitter was developed, which generates nonlinear brightness fluctuation based on the Weierstrass — Mandelbrot fractal functions. The choice of fractal signal parameters used in the work was substantiated. Pattern ERG and ganzfeld ERG were registered according to ISCEV standards; also, photopic flicker ERG was recorded at 8.3, 10, 12, and 24 Hz.Results. No negative effects of a 12-month FS course on the activity and morphology of the retina, or on dopaminergic processes in the eye of a healthy animal were found, which confirms the safety of using low-intensity FS in the clinic. A statistically significant increase in the amplitude of low-frequency flicker ERGs, a shortening of peak latency, and an increase in the amplitude of the b-wave of the scotopic and photopic ERGs was noted.Conclusion. To assess possible therapeutic effects of FS, we need to continue the investigation on animal models and human patients with retinal pathology. Considering the changes of retinal activity as revealed in the present paper, we recommend the duration of FS courses from 1 week to 1 month for future studies.

Light is an emerging treatment approach that is being used to treat many diseases and conditions such as pain, inflammation, and wound healing. The light used in dental therapy generally lies in visible and invisible spectral regions. Despite many positive results in the treatment of different conditions, this therapy still faces some skepticism, which has prevented its widespread adoption in clinics. The main reason for this skepticism is the lack of comprehensive information about the molecular, cellular, and tissular mechanisms of action, which underpin the positive effects of phototherapy. However, there is currently promising evidence in support of the use of light therapy across a spectrum of oral hard and soft tissues, as well as in a variety of important dental subspecialties, such as endodontics, periodontics, orthodontics, and maxillofacial surgery. The merging of diagnostic and therapeutic light procedures is also seen as a promising area for future expansion. In the next decade, several light technologies are foreseen as becoming integral parts of modern dentistry practice. [ABSTRACT FROM AUTHOR]

The blood–brain barrier (BBB) limits the delivery of majority of cancer drugs and thereby complicates brain tumor treatment. The nasal-brain-lymphatic system is discussed as a pathway for brain drug delivery overcoming the BBB. However, in most cases, this method is not sufficient to achieve a therapeutic effect due to brain drug delivery in a short distance. Therefore, it is necessary to develop technologies to overcome the obstacles facing nose-to-brain delivery of promising pharmaceuticals. In this study, we clearly demonstrate intranasal delivery of liposomes to the mouse brain reaching glioblastoma (GBM). In the experiments with ablation of the meningeal lymphatic network, we report an important role of meningeal pathway for intranasal delivery of liposomes to the brain. Our data revealed that GBM is characterized by a dramatic reduction of intranasal delivery of liposomes to the brain that was significantly improved by near-infrared (1267 nm) photostimulation of the lymphatic vessels in the area of the cribriform plate and the meninges. These results open new perspectives for non-invasive improvement of efficiency of intranasal delivery of cancer drugs to the brain tissues using nanocarriers and near-infrared laser-based therapeutic devices, which are commercially available and widely used in clinical practice. [ABSTRACT FROM AUTHOR]

Red photostimulated luminescence (PSL) at 650 nm appears under the excitation by using an infrared (IR) light-emitting diode at 940 nm in CaS:Eu2+ afterglow phosphors. The effect of doping of Dy3+ ions, alkali metal ions or Clâˆ' ions in CaS:Eu2+ on afterglow or photostimulation is investigated. Afterglow temporal decays and thermoluminescence glow curves suggest that Dy3+ ions and alkali metal ions induce different types of defects in the phosphor, and enhance the afterglow independently. Doping of Clâˆ' ions is found to enhance the photostimulation by the IR excitation. Even if the phosphor is irradiated with IR light for some seconds, the afterglow decay curve is the same as when it is not irradiated with IR light. Trap states responsible for the photostimulation are different from those responsible for the afterglow. The red photostimulation appears under the excitation at 940 nm, after the phosphor is left in the dark for 60 min. Its intensity is 68% of the red PSL generated after being left in the dark for 10 min. It is considered that the PSL decreases little, when the sample is kept in the dark. [ABSTRACT FROM AUTHOR]

Modern poultry production systems use environmentally controlled houses providing only artificial illumination. The role of light in reproduction of poultry depends on light quality (photoperiod, intensity/brightness, and spectrum), which enables us to provide custom-made illumination, targeted for the elevation of reproductive activities. Artificial targeted illumination significantly affects poultry reproduction. This phenomenon is based on the mechanism of light absorption in birds, which consists of two main components: the eye (retinal photoreceptors) and brain extraretinal photoreceptors. Several experiments on turkey hens and broiler breeder males and females have shown that photostimulation of brain extraretinal photoreceptors, while maintaining retinal photoreceptors under non-photostimulatory conditions, elevates reproductive activity by increasing egg production of hens and semen quality of roosters. In addition, we found acceleration in all gonadal axis parameters, leading to the acceleration in the production rate. Furthermore, we studied the role of retinal activation in gonadal axis suppuration and identified the role of serotonin in this phenomenon. As for today, several broiler breeder farms use targeted illumination based on our studies with excellent results. [ABSTRACT FROM AUTHOR]

Cyanobacteria-rich microbiomes may stand as a cost-effective source of pigments, as they exhibit improved stability in comparison to monocultures and do not require sterile media to grow. However, these bioproduct sources have not been thoroughly optimized for pigment production. The aim of the present study was to evaluate the effects of light quality and exposure time on pigment concentration and population distribution in 6 microbiomes rich in Synechococcus sp. and Synechocystis sp. A multivariable experimental design was implemented for selecting the optimal culture conditions in terms of light quality (white, red, green and blue) and exposure time (4 and 6 days). As a result, differential light quality exposures did not favor the growth of one species over another. Green light had a significantly positive effect on phycobiliprotein content in all microbiomes, with up to a 2.3-fold increase as compared to white light. Indeed, 4 days of exposure induced a change in phycobiliprotein composition in 5 microbiomes. Microbiome M11 was the best phycobiliprotein producer (content up to 145.5 mg gDW−1). Meanwhile, carotenoid contents above 1.8 mg gDW−1 were attained in all the microbiomes under optimized conditions. In conclusion, light quality modulation is a promising approach to stimulate the production of pigments in cyanobacteria-rich microbiomes. [Display omitted] • Unsterile cyanobacteria-rich microbiomes are a promising source of pigments. • 4-day light treatments were able to induce changes in pigment compositions. • Green light enhanced phycobiliprotein content in all the microbiomes studied. • Up to 145.5 mg gDW−1 phycobiliprotein content was produced under blue light. • Pigment production may be optimized by adjusting the duration of the growth phase. [ABSTRACT FROM AUTHOR]

Modern poultry production systems use environmentally controlled houses providing only artificial illumination. The role of light in reproduction of poultry depends on light quality (photoperiod, intensity/brightness, and spectrum), which enables us to provide custom-made illumination, targeted for the elevation of reproductive activities. Artificial targeted illumination significantly affects poultry reproduction. This phenomenon is based on the mechanism of light absorption in birds, which consists of two main components: the eye (retinal photoreceptors) and brain extraretinal photoreceptors. Several experiments on turkey hens and broiler breeder males and females have shown that photostimulation of brain extraretinal photoreceptors, while maintaining retinal photoreceptors under non-photostimulatory conditions, elevates reproductive activity by increasing egg production of hens and semen quality of roosters. In addition, we found acceleration in all gonadal axis parameters, leading to the acceleration in the production rate. Furthermore, we studied the role of retinal activation in gonadal axis suppuration and identified the role of serotonin in this phenomenon. As for today, several broiler breeder farms use targeted illumination based on our studies with excellent results.

In deep tissue imaging, pulsed near-infrared lasers commonly provide high peak powers needed for nonlinear absorption, but average power and linear absorption can be limiting factors for tissue damage through heat. We implemented intra-cavity dumping within a mode-locked Ti:Sapphire laser used for two-photon computer generated holography stimulation. This system enables photostimulation in which pulse energy, average power, and repetition rate can each be varied and harnessed as degrees of freedom. We demonstrate how this system provides a new dimension of temporal control in photostimulation experiments to alter the ratio of nonlinear to linear light-tissue interactions, namely by tuning the laser repetition rate between single-shot and ≈ 3 MHz. Repetition rates below 1 MHz, yielding pulse energies over 60 nJ, facilitated holographic projections with more regions of interest than the highest repetition rate of 3 MHz. Even lower repetition rates ( ≈ 10 kHz) diminished thermal load on the sample, as characterized by quantification of heat shock protein expression in zebrafish tissue.

Optoelectronic biointerfaces offer a wireless and nongenetic neurostimulation pathway with high spatiotemporal resolution. Fabrication of low‐cost and flexible optoelectronic biointerfaces that have high photogenerated charge injection densities and clinically usable cell stimulation mechanism is critical for rendering this technology useful for ubiquitous biomedical applications. Here, supercapacitor technology is combined with flexible organic optoelectronics by integrating RuO2 into a donor–acceptor photovoltaic device architecture that facilitates efficient and safe photostimulation of neurons. Remarkably, high interfacial capacitance of RuO2 resulting from reversible redox reactions leads to more than an order‐of‐magnitude increase in the safe stimulation mechanism of capacitive charge transfer. The RuO2‐enhanced photoelectrical response activates voltage‐gated sodium channels of hippocampal neurons and elicits repetitive, low‐light intensity, and high‐success rate firing of action potentials. Double‐layer capacitance together with RuO2‐induced reversible faradaic reactions provide a safe stimulation pathway, which is verified via intracellular oxidative stress measurements. All‐solution‐processed RuO2‐based biointerfaces are flexible, biocompatible, and robust under harsh aging conditions, showing great promise for building safe and highly light‐sensitive next‐generation neural interfaces. [ABSTRACT FROM AUTHOR]

Gq-coupled receptors regulate numerous physiological processes by activating enzymes and inducing intracellular Ca2+ signals. There is a strong need for an optogenetic tool that enables powerful experimental control over Gq signaling. Here, we present chicken opsin 5 (cOpn5) as the long sought-after, single-component optogenetic tool that mediates ultra-sensitive optical control of intracellular Gq signaling with high temporal and spatial resolution. Expressing cOpn5 in HEK 293T cells and primary mouse astrocytes enables blue light-triggered, Gq-dependent Ca2+ release from intracellular stores and protein kinase C activation. Strong Ca2+ transients were evoked by brief light pulses of merely 10 ms duration and at 3 orders lower light intensity of that for common optogenetic tools. Photostimulation of cOpn5-expressing cells at the subcellular and single-cell levels generated fast intracellular Ca2+ transition, thus demonstrating the high spatial precision of cOpn5 optogenetics. The cOpn5-mediated optogenetics could also be applied to activate neurons and control animal behavior in a circuit-dependent manner. cOpn5 optogenetics may find broad applications in studying the mechanisms and functional relevance of Gq signaling in both non-excitable cells and excitable cells in all major organ systems. [ABSTRACT FROM AUTHOR]

The blood-brain barrier (BBB) has a significant contribution to the protection of the central nervous system (CNS). However, it also limits the brain drug delivery and thereby complicates the treatment of CNS diseases. The development of safe methods for an effective delivery of medications and nanocarriers to the brain can be a revolutionary step in the overcoming this limitation. Here, we report the unique properties of the lymphatic system to deliver tracers and liposomes to the brain meninges, brain tissues, and glioma in rats. Using a quantum-dot-based 1267 nm laser (for photosensitizer-free generation of singlet oxygen), we clearly demonstrate photostimulation of lymphatic delivery of liposomes to glioma as well as lymphatic clearance of liposomes from the brain. These pilot findings open promising perspectives for photomodulation of lymphatic delivery of drugs and nanocarriers to the brain pathology bypassing the BBB. The lymphatic “smart” delivery of liposomes with antitumor drugs in the new brain tumor branches might be a breakthrough strategy for the therapy of gliomas.

In this study, for the first time, red LED light radiation was applied to the fermentation process of table olives using the Negrinha de Freixo variety. Photostimulation using LED light emission (630 ± 10 nm) is proposed to shorten and speed up this stage and reduce time to market. Several physical-chemical characteristics and microorganisms (total microbial count of mesophilic aerobic, molds, yeasts, and lactic acid bacteria) and their sequence during fermentation were monitored. The fermentation occurred for 122 days, with two irradiation periods for red LED light. The nutritional composition and sensory analysis were performed at the end of the process. Fermentation under red LED light increased the viable yeast and lactic acid bacteria (LAB) cell counts and decreased the total phenolics in olives. Even though significant differences were observed in some color parameters, the hue values were of the same order of magnitude and similar for both samples. Furthermore, the red LED light did not play a relevant change in the texture profile, preventing the softening of the fruit pulp. Similarly, LED light did not modify the existing type of microflora but increased species abundance, resulting in desirable properties and activities. The species identified were yeasts - Candida boidinii , Pichia membranifaciens , and Saccharomyces cerevisiae , and bacteria - Lactobacillus plantarum and Leuconostoc mesenteroides , being the fermentative process dominated by S. cerevisiae and L. plantarum. At the end of fermentation (122 days), the irradiated olives showed less bitterness and acidity, higher hardness, and lower negative sensory attributes than non-irradiated. Thus, the results of this study indicate that red LED light application can be an innovative technology for table olives production. • Red LED light is an innovative technology to be applied to table olives. • Red LED light promoted a slightly faster decrease in the pH to the safe value. • Red LED light did not modify the type of microflora present in fermentation. • Red LED light was able to increase the abundance of desirable species. • The irradiated fruits were classified in the extra category. [ABSTRACT FROM AUTHOR]

Revealing the intricate logic of neuronal circuits and its connection to the physiopathology of living systems constitutes a fundamental question in neuroscience. Optogenetics offers the possibility to use light of specific wavelengths to study the activity of neurons with unprecedented spatiotemporal resolution. To make use of this technique at its full potential, bidirectional proteins may be expressed across the neuronal membrane to provoke both enhancement and inhibition of neuronal activity depending on the excitation wavelength. This generates the demand for light sources with high spatial precision, high operation speed, and multi‐color emission from the same location. To meet these requirements, the design, realization, and characterization of organic light‐emitting diodes (OLEDs) are presented with switchable bicolor emission, exhibiting high irradiance and good efficiency. The OLEDs can switch between blue and red/green light upon changing the voltage polarity, triggering both optogenetic inhibition and excitation in ND7/23 cells and Drosophila melanogaster larvae expressing bidirectional optogenetic proteins. This work shows the potential of engineering OLEDs to enable multicolor optogenetics with a single, organic device, and provides a new avenue towards bicolor optical brain stimulation in vivo. [ABSTRACT FROM AUTHOR]

The aim of this study is to highlight the favorable effect of photostimulation obtained in the methotrexate therapy on Walker 256 tumour. The method of selective tumour photostimulation follows the increase, in the malignant tissue, of the concentration of any specific substance for the neoplastic cell that can be administered "in bolus" for cytostatic treatment. This goal is achieved by exposing the tumour tissue to the optical field emitted by a specially designed equipment. On the other hand, in the case of chemotherapy, there are certain types of cytostatics that have a "positive photodynamic potential", thus, following the interaction between their molecules and the light radiation with the strictly determined parameters, free radicals are born that destroy the intracellular cytostatic fixation targets. This phenomenon is called the photodynamic activation of the cytostatic, the method is called Photostimulated Chemotherapy (PSChT), and the drug used in this study is Methotrexate (MTX).

In recent publications, positive results have been reported with the use of glasses with red protective filters in prematurely born infants with low body weight, which were presumably associated with a decrease in the levels of illumination of the environment of the child. However, to date, it has not been proven that a decrease in the amount of light reaching the retina of the newborn affects the frequency and severity of retinopathy of prematurity (RP). The analysis of the literature on the therapeutic effect of various modes of red and near infrared radiation on the retina is presented, which allowed a different look at the protective mechanisms of glasses-filters in premature babies. It has been suggested and substantiated that the observed effect may relate to the phenomenon of pre-conditioning photostimulation, which reduces the risk of developing RP and reduces the severity of the disease due to the induction of adaptive plastic reactions in the retina.

Much has been reported about optogenetic based cardiac arrhythmia treatment and the corresponding characterization of photostimulation parameters, but still, our capacity to interact with the underlying spatiotemporal excitation patterns relies mainly on electrical and/or pharmacological approaches. However, these well-established treatments have always been an object of somehow heated discussions. Though being acutely life-saving, they often come with potential side-effects leading to a decreased functionality of the complex cardiac system. Recent optogenetic studies showed the feasibility of the usage of photostimulation as a defibrillation method with comparatively high success rates. Although, these studies mainly concentrated on the description as well as on the comparison of single photodefibrillation approaches, such as locally focused light application and global illumination, less effort was spent on the description of excitation patterns during actual photostimulation. In this study, the authors implemented a multi-site photodefibrillation technique in combination with Multi-Lead electrocardiograms (ECGs). The technical connection of real-time heart rhythm measurements and the arrhythmia counteracting light control provides a further step toward automated arrhythmia classification, which can lead to adaptive photodefibrillation methods. In order to show the power effectiveness of the new approach, transgenic murine hearts expressing channelrhodopsin-2 ex vivo were investigated using circumferential micro-LED and ECG arrays. Thus, combining the best of two methods by giving the possibility to illuminate either locally or globally with differing pulse parameters. The optical technique presented here addresses a number of challenges of technical cardiac optogenetics and is discussed in the context of arrhythmic development during photostimulation. [ABSTRACT FROM AUTHOR]

Light perception in birds is composed of the retina and extraretinal sites, located in the brain. Previous studies indicate that selective photostimulation of the eye decreased reproductive performance, whereas extraretinal photostimulation increases it. Differential photostimulation of the retina and extraretinal sites is based on the retina's sensitivity to green wavelengths and on the red wavelengths' ability to penetrate body tissues.We previously found that short-day exposure to green light within a long-day exposure to red light increases reproductive activity in female turkeys and broiler breeder hens. Furthermore, in a study conducted recently in our laboratory, we found that blue light repressed expression of green light receptor in the retina, which can further enhance reproduction activity in broiler breeders. Here, we examined the “brain activate/eye deactivate” hypothesis on gonadal axis activity and reproductive performance in a broiler breeder flock.Broiler breeder hens and roosters (ROSS 308) were divided into 5 light-treatment groups (controlled rooms with light-emitting diodes [LED] lamps): warm white (control), long-day (14 h) red (630 nm) and short-day (6 h) green (514 nm) (red-green), long-day green and short-day red (green-red), long-day red and short-day blue (456 nm) (red-blue), and long-day blue and short-day red (blue-red). Birds were reared from 20 to 55 wk of age. Eggs were collected daily. Weekly egg production calculated. All eggs were incubated for fertility and hatchability examination. Blood was drawn monthly for plasma analysis. At 35 wk of age (after peak production) and 55 wk of age (end of the experiment), 10 hens from each treatment group were euthanized, and selected tissues and glands were taken for gene expression trials.Providing long-day red light to extraretinal photoreceptors while maintaining retinal photoreceptors on short day with blue or green light significantly improved reproductive activities, manifested by elevated egg production and gonadal axis activity compared with Controls and primary breeder recommendations. Long-day green light reduced reproductive performances. We suggest that targeted photostimulation enhances reproductive and gonadal axis activities in broiler breeders.

Much has been reported about optogenetic based cardiac arrhythmia treatment and the corresponding characterization of photostimulation parameters, but still, our capacity to interact with the underlying spatiotemporal excitation patterns relies mainly on electrical and/or pharmacological approaches. However, these well-established treatments have always been an object of somehow heated discussions. Though being acutely life-saving, they often come with potential side-effects leading to a decreased functionality of the complex cardiac system. Recent optogenetic studies showed the feasibility of the usage of photostimulation as a defibrillation method with comparatively high success rates. Although, these studies mainly concentrated on the description as well as on the comparison of single photodefibrillation approaches, such as locally focused light application and global illumination, less effort was spent on the description of excitation patterns during actual photostimulation. In this study, the authors implemented a multi-site photodefibrillation technique in combination with Multi-Lead electrocardiograms (ECGs). The technical connection of real-time heart rhythm measurements and the arrhythmia counteracting light control provides a further step toward automated arrhythmia classification, which can lead to adaptive photodefibrillation methods. In order to show the power effectiveness of the new approach, transgenic murine hearts expressing channelrhodopsin-2 ex vivo were investigated using circumferential micro-LED and ECG arrays. Thus, combining the best of two methods by giving the possibility to illuminate either locally or globally with differing pulse parameters. The optical technique presented here addresses a number of challenges of technical cardiac optogenetics and is discussed in the context of arrhythmic development during photostimulation.

The blood–brain barrier (BBB) limits the delivery of majority of cancer drugs and thereby complicates brain tumor treatment. The nasal-brain-lymphatic system is discussed as a pathway for brain drug delivery overcoming the BBB. However, in most cases, this method is not sufficient to achieve a therapeutic effect due to brain drug delivery in a short distance. Therefore, it is necessary to develop technologies to overcome the obstacles facing nose-to-brain delivery of promising pharmaceuticals. In this study, we clearly demonstrate intranasal delivery of liposomes to the mouse brain reaching glioblastoma (GBM). In the experiments with ablation of the meningeal lymphatic network, we report an important role of meningeal pathway for intranasal delivery of liposomes to the brain. Our data revealed that GBM is characterized by a dramatic reduction of intranasal delivery of liposomes to the brain that was significantly improved by near-infrared (1267 nm) photostimulation of the lymphatic vessels in the area of the cribriform plate and the meninges. These results open new perspectives for non-invasive improvement of efficiency of intranasal delivery of cancer drugs to the brain tissues using nanocarriers and near-infrared laser-based therapeutic devices, which are commercially available and widely used in clinical practice.

ABSTRACT: Previous findings have reported that providing light during incubation can affect hatchability and chick quality. This study was conducted to investigate the effects of providing light during incubation on posthatch broiler production parameters, thermoregulation and immune response. Lights with different wavelengths were used over the course of four separate hatches. Ross 308 broiler hatching eggs were randomly distributed into 4 lighting treatments for each hatch. The incubation lighting treatments included: dark as control, white, red, or blue lights for 12 h d−1 (200 lux at egg level). Broilers hatched from each incubator with the same gender were placed into one of 8 sets of pens (3 pens/set) and raised under 18 h d−1 photoperiod. Six birds per pen were immunized intraocularly with AviPro ND-IB Polybanco vaccine on d 10 and 21 posthatch. Chicks hatched under white and blue lights had heavier (P < 0.05) body weight and higher (P < 0.05) feed consumption than the control group during the first 6 h postplacement. No differences in vent temperature were found among treatments at 24 h posthatch (P > 0.05). Chicks hatched with light stimulation however had more stable (P < 0.05) cloaca temperature at 36 h posthatch. No differences in average body weight gain, feed consumption or feed conversion ratio were found among lighting treatments between d 7 and d 35. On d 14 of age, birds hatched from red light had higher (P < 0.05) total IgG concentration than those hatched under dark, blue or white light. These results indicated that in ovo light stimulation with different wavelengths did not affect growth parameters of broilers at market age. Providing photoperiodic blue and white light during incubation improved the production parameters of broilers during the first week posthatch.

ABSTRACT: Providing lighting schedule during incubation has been shown to improve chick quality and reduce stress posthatch. This study was conducted to evaluate the effects of providing light of different colors during incubation on embryo development, air cell temperature, the spread of hatch, and hatching performance. Four batches of eggs (n = 2,176, 1,664, 1,696 and 1,600) from Ross 308 broiler breeders were used in the experiment. In each trial, eggs were randomly distributed into 4 lighting treatments. The incubation lighting treatments included: incubated under dark as control, illuminated with white, red or blue lights for 12 h daily. There were no incubation lighting treatment differences in embryo development, the spread of hatch, hatchability, embryo mortality, hatch weight, chick length, navel closure quality, yolk-free body weight, or relative spleen weight. However, embryos incubated under red light had lower average air cell temperature than those in dark, white or blue light treatments. This finding may suggest higher melatonin secretion during the scotophase when illuminated with red light. Male chicks incubated under dark had a higher bursa of Fabricius weight than males illuminated with blue light. In conclusion, these results suggest that the red, white and blue light stimulation during incubation had no negative effects on hatchability, embryo mortality, spread of hatch or day-old chick quality, but may have potential impacts on immunity and energy metabolism in broiler embryos.

This paper presents the design and the utilization of a wireless electro-optic platform to perform simultaneous multimodal electrophysiological recordings and optogenetic stimulation in freely moving rodents. The developed system can capture neural action potentials (AP), local field potentials (LFP) and electromyography (EMG) signals with up to 32 channels in parallel while providing four optical stimulation channels. The platform is using commercial off-the-shelf components (COTS) and a low-power digital field-programmable gate array (FPGA), to perform digital signal processing to digitally separate in real time the AP, LFP and EMG while performing signal detection and compression for mitigating wireless bandwidth and power consumption limitations. The different signal modalities collected on the 32 channels are time-multiplexed into a single data stream to decrease power consumption and optimize resource utilization. The data reduction strategy is based on signal processing and real-time data compression. Digital filtering, signal detection, and wavelet data compression are used inside the platform to separate the different electrophysiological signal modalities, namely the local field potentials (1–500 Hz), EMG (30–500 Hz), and the action potentials (300–5,000 Hz) and perform data reduction before transmitting the data. The platform achieves a measured data reduction ratio of 7.77 (for a firing rate of 50 AP/second) and weights 4.7 g with a 100-mAh battery, an on/off switch and a protective plastic enclosure. To validate the performance of the platform, we measured distinct electrophysiology signals and performed optogenetics stimulation in vivo in freely moving rondents. We recorded AP and LFP signals with the platform using a 16-microelectrode array implanted in the primary motor cortex of a Long Evans rat, both in anesthetized and freely moving conditions. EMG responses to optogenetic Channelrhodopsin-2 induced activation of motor cortex via optical fiber were also recorded in freely moving rodents.

ABSTRACT: Artificial targeted illumination has a pivotal role in reproductive processes of poultry. The light-absorption mechanism in birds consists of 2 main components: the eye (retinal photoreceptors) and extraretinal photoreceptors located in the brain. Previous studies conducted on hens have shown that photostimulation of brain extraretinal photoreceptors elevates reproductive activity, whereas retinal photostimulation suppresses it. We tested the effect of targeted differential photostimulation (TDP) on reproductive activities of broiler breeder males. Fifty broiler breeder roosters (Ross), 21 wk of age, were divided into 5 environmentally controlled light-treatment rooms (n = 10) equipped with individual cages. Rooms 1 and 2 had 2 parallel lighting systems consisting of red light (630 nm) and green light (514 nm), and rooms 3 and 4 had parallel red and blue (456 nm) lighting systems. Room 5, illuminated with white light, served as the control. Birds of all groups were kept under short day (6L:18D) for 2 wk with both lighting systems in each treatment room turned on. At 23 wk of age, birds were photostimulated by gradually increasing one of the lighting systems to 14 h of light in each room, while the other lighting system was left on short day (6L:18D). Weekly semen samples were collected until 65 wk of age and analyzed for volume, motility, concentration and vitality. Monthly blood samples were drawn for plasma hormone assays. At 65 wk of age, roosters were euthanized and hypothalamus, pituitary gland, retina and testes samples were taken for mRNA expression analysis. TDP using long-day red light and short-day green light significantly increased reproductive performance, manifested by higher semen volume, motility and concentration, and testis weight; furthermore, this group had higher plasma testosterone levels, higher GnRH mRNA expression in the hypothalamus, lower levels of aromatase in the testes, and lower mRNA expression of hypothalamic serotonin transporter, and of pituitary prolactin and its receptors in the testes. This is the first study showing a positive effect of TDP on reproduction of broiler breeder roosters.

Light-activated biointerfaces provide a non-genetic route for effective control of neural activity. InP quantum dots (QDs) have a high potential for such biomedical applications due to their uniquely tunable electronic properties, photostability, toxic-heavy-metal-free content, heterostructuring, and solution-processing ability. However, the effect of QD nanostructure and biointerface architecture on the photoelectrical cellular interfacing remained unexplored. Here, we unravel the control of the photoelectrical response of InP QD-based biointerfaces via nanoengineering from QD to device-level. At QD level, thin ZnS shell growth (∼0.65 nm) enhances the current level of biointerfaces over an order of magnitude with respect to only InP core QDs. At device-level, band alignment engineering allows for the bidirectional photoelectrochemical current generation, which enables light-induced temporally precise and rapidly reversible action potential generation and hyperpolarization on primary hippocampal neurons. Our findings show that nanoengineering QD-based biointerfaces hold great promise for next-generation neurostimulation devices.

This paper presents the design and the utilization of a wireless electro-optic platform to perform simultaneous multimodal electrophysiological recordings and optogenetic stimulation in freely moving rodents. The developed system can capture neural action potentials (AP), local field potentials (LFP) and electromyography (EMG) signals with up to 32 channels in parallel while providing four optical stimulation channels. The platform is using commercial off-the-shelf components (COTS) and a low-power digital field-programmable gate array (FPGA), to perform digital signal processing to digitally separate in real time the AP, LFP and EMG while performing signal detection and compression for mitigating wireless bandwidth and power consumption limitations. The different signal modalities collected on the 32 channels are time-multiplexed into a single data stream to decrease power consumption and optimize resource utilization. The data reduction strategy is based on signal processing and real-time data compression. Digital filtering, signal detection, and wavelet data compression are used inside the platform to separate the different electrophysiological signal modalities, namely the local field potentials (1–500 Hz), EMG (30–500 Hz), and the action potentials (300–5,000 Hz) and perform data reduction before transmitting the data. The platform achieves a measured data reduction ratio of 7.77 (for a firing rate of 50 AP/second) and weights 4.7 g with a 100-mAh battery, an on/off switch and a protective plastic enclosure. To validate the performance of the platform, we measured distinct electrophysiology signals and performed optogenetics stimulation in vivo in freely moving rondents. We recorded AP and LFP signals with the platform using a 16-microelectrode array implanted in the primary motor cortex of a Long Evans rat, both in anesthetized and freely moving conditions. EMG responses to optogenetic Channelrhodopsin-2 induced activation of motor cortex via optical fiber were also recorded in freely moving rodents. [ABSTRACT FROM AUTHOR]

Light-activated biointerfaces provide a non-genetic route for effective control of neural activity. InP quantum dots (QDs) have a high potential for such biomedical applications due to their uniquely tunable electronic properties, photostability, toxic-heavy-metal-free content, heterostructuring, and solution-processing ability. However, the effect of QD nanostructure and biointerface architecture on the photoelectrical cellular interfacing remained unexplored. Here, we unravel the control of the photoelectrical response of InP QD-based biointerfaces via nanoengineering from QD to device-level. At QD level, thin ZnS shell growth (∼0.65 nm) enhances the current level of biointerfaces over an order of magnitude with respect to only InP core QDs. At device-level, band alignment engineering allows for the bidirectional photoelectrochemical current generation, which enables light-induced temporally precise and rapidly reversible action potential generation and hyperpolarization on primary hippocampal neurons. Our findings show that nanoengineering QD-based biointerfaces hold great promise for next-generation neurostimulation devices. [ABSTRACT FROM AUTHOR]

Abstract Background Photostimulation using low-power laser had been used for nervous repair with interesting results. This study aimed to evaluate the influence of 20 mW low-power He-Ne laser on the regeneration of a peripheral sciatic nerve after trauma using the Albino rabbit as an animal model for experimental treatment. Methods Six adult male rabbits were randomly assigned into two equal groups (control- and laser-treated). General anesthesia was administered intramuscularly, and exploration of the sciatic nerve was done in the lateral aspect of the legs. Complete longitudinal and reverse sections of the nerve were performed, which was followed by crushing of the neural sheath. Treatment was carried out directly after the trauma. Irradiation doses of low-level laser therapy (LLLT-31.5 J/cm2 ) with once a day application for 10 consecutive days and observed for 30 days. The animals were followed up for an extra 2 weeks. Two important factors were examined histopathology and functionality of the nerve. Results Compared to the control group, significant variations in regeneration were observed, including thicker nerve fibers, and more regular myelin layers in the treated group. Conclusions The results of the present study suggest that laser therapy may be a viable approach for nerve regeneration and repair.

Rhythmic light stimulation can alter the electrical activity of the human and animal brain. Moreover, the brain response to certain flicker frequencies significantly exceeds the responses to neighboring frequencies. This phenomenon is thought to be related with the effect of resonance, as evidenced by the coincidence of one of the maxima in the profile of the response to flashes with the frequency of the alpha rhythm. However, other frequencies that cause an increased response to flashes are not reflected in electroencephalogram (EEG) as dominant oscillations. The goal of this study was to reveal the relationship between local maxima in the profile of the responses to flashes of different frequencies and dominant brain oscillations recorded in electrocorticogram (ECoG) of rhesus monkeys without stimulation. The study was carried out on four male rhesus monkeys Macaca mulatta. In three animals, peak responses were elicited by flickers at 8 and 16 Hz, while one monkey showed the second peak in the 22–30 Hz range. The first maximum (8–10 Hz) in the profile of the response to rhythmic photostimulation coincided with the dominant rhythm recorded in the occipital and parietal regions at rest. The second maximum at 16 Hz coincided with the dominant ECoG rhythm in one of the primates when it was in the state of emotional arousal, which may account for the resonant origin of the increase in responses in this frequency range. The data obtained indicate that dominant brain rhythms, including latent rhythms revealed only by rhythmic photostimulation, can coincide in frequency in monkeys and humans. The mechanisms behind the selective sensitivity of neural networks to different frequencies of photostimulation are discussed. [ABSTRACT FROM AUTHOR]

Photoactive organic semiconductor substrates are envisioned as a novel class of bioelectronic devices that transduce light into stimulating biological signals with relevance for retinal implants or guided cellular differentiation. The direct interface between the semiconductor and the electrolyte gives rise to different competing optoelectronic transduction mechanisms. A detailed understanding of such faradaic or capacitive processes and the underlying material science is necessary to develop and optimize future devices. Here, the problem in organic photoelectrodes is addressed based on a planar p‐n junction containing phthalocyanine (H2Pc) and N,N′‐dimethyl perylenetetracarboxylic diimide (PTCDI). The detailed characterization of photoelectrochemical current transients is combined with spectroscopic measurements, impedance spectroscopy, and local photovoltage measurements to establish a model that predicts quantitatively faradaic or capacitive current transients. The decisive elements of the model are the energy levels present at the interface and the voltage building up in the photoelectrode. The result of the efforts is a comprehensive model of photocapacitive and photofaradaic effects that can be applied to developing wireless bioelectronic photostimulation devices. [ABSTRACT FROM AUTHOR]

The protocol of optogenetic ChR2-mediated activation of astrocytes was used in a model of artificial neurogenic niche, neurospheres implanted into ex vivo organotypic cultures of mouse hippocampus. The electrophysiological characteristics of the hippocampus and expression of molecules involved in the mechanisms of activation of astrocytes and microglia (GFAP, CD38, C3/C3b, Cx43, CD11b, and CD18) were evaluated. Photoactivation of astrocytes led to activation of neurogenesis and changes in the expression of molecules (Cx43 and CD38) that determine bioavailability of NAD+ to ensure proliferative activity of cells in the neurogenic niche. Implantation of neurospheres into organotypic slices of the hippocampus caused an increase in C3/C3b expression and suppression of the synaptic plasticity of hippocampal neurons. [ABSTRACT FROM AUTHOR]

A growing number of studies document circadian phase-shifting after exposure to millisecond light flashes. When strung together by intervening periods of darkness, these stimuli evoke pacemaker responses rivaling or outmatching those created by steady luminance, suggesting that the circadian system's relationship to light can be contextualized outside the principle of simple dose-dependence. In the current review, we present a brief chronology of this work. We then develop a conceptual model around it that attempts to relate the circadian effects of flashes to a natural integrative process the pacemaker uses to intermittently sample the photic information available at dawn and dusk. Presumably, these snapshots are employed as building blocks in the construction of a coherent representation of twilight the pacemaker consults to orient the next day's physiology (in that way, flash-resetting of pacemaker rhythms might be less an example of a circadian visual illusion and more an example of the kinds of gestalt inferences that the image-forming system routinely makes when identifying objects within the visual field; i.e., closure). We conclude our review with a discussion on the role of cones in the pacemaker's twilight predictions, providing new electrophysiological data suggesting that classical photoreceptors—but not melanopsin—are necessary for millisecond, intermediate-intensity flash responses in ipRGCs (intrinsically photosensitive retinal ganglion cells). Future investigations are necessary to confirm this “Cone Sentinel Model” of circadian flash-integration and twilight-prediction, and to further define the contribution of cones vs. rods in transducing pacemaker flash signals.

Substrate engineering for steering cell growth is a wide and well‐established area of research in the field of modern biotechnology. Here we introduce a micromachining technique to pattern an inert and transparent polymer matrix blended with a photoactive polymer. We demonstrate that the obtained scaffold combines the capability to align with that to photostimulate living cells. This technology can open up new and promising applications, especially where cell alignment is required to trigger specific biological functions, e.g., generate powerful and efficient muscle contractions following an external stimulus.

We present a series of cationic membrane-targeted azobenzene molecules, with the aim to understand how variations in molecular architecture influence the relative optical and biological properties. 1,4-Amino-substituted azobenzene was chosen as the switching unit while the number of linked alkyl chains and their cationic end-group were systematically varied. Their photophysics, membrane partitioning, and electrophysiological efficacy were studied. We found that the polar end group is a key-factor determining the interaction with the phospholipid heads in the plasma membrane bilayer and consequently the ability to dimerize. The monosubstituted photoswitch with a pyridinium-terminated alkyl chain was found to be the best candidate for photostimulation. This study provides a structure-property investigation that can guide the chemical engineering of a new generation of molecular photo-actuators.

A growing number of studies document circadian phase-shifting after exposure to millisecond light flashes. When strung together by intervening periods of darkness, these stimuli evoke pacemaker responses rivaling or outmatching those created by steady luminance, suggesting that the circadian system's relationship to light can be contextualized outside the principle of simple dose-dependence. In the current review, we present a brief chronology of this work. We then develop a conceptual model around it that attempts to relate the circadian effects of flashes to a natural integrative process the pacemaker uses to intermittently sample the photic information available at dawn and dusk. Presumably, these snapshots are employed as building blocks in the construction of a coherent representation of twilight the pacemaker consults to orient the next day's physiology (in that way, flash-resetting of pacemaker rhythms might be less an example of a circadian visual illusion and more an example of the kinds of gestalt inferences that the image-forming system routinely makes when identifying objects within the visual field; i.e., closure). We conclude our review with a discussion on the role of cones in the pacemaker's twilight predictions, providing new electrophysiological data suggesting that classical photoreceptors—but not melanopsin—are necessary for millisecond, intermediate-intensity flash responses in ipRGCs (intrinsically photosensitive retinal ganglion cells). Future investigations are necessary to confirm this "Cone Sentinel Model" of circadian flash-integration and twilight-prediction, and to further define the contribution of cones vs. rods in transducing pacemaker flash signals. [ABSTRACT FROM AUTHOR]