532-nm Light Research Articles

Surface plasmons on silver gratings transform pyrolytic carbon into luminescent graphitized carbon dots.

Plasmonic catalysis holds the promise of opening new reaction pathways that are inaccessible thermally or via direct UV-vis electronic transitions. Here, energetic carriers produced via the decay of surface plasmons excited by visible light at 532nm (2.33eV, green) on a Ag-grating-bearing pyrolytic carbon residue drive its transformation into light-emitting graphitized carbon dots. The pyrolytic carbon residue is detectable via high-magnification surface-enhanced Raman scattering but cannot be directly observed using optical, electron, atomic force, or helium ion microscopy. When a Ag-grating-bearing pyrolyzed residue is introduced into a high-purity O2-depleted gas environment (Ar, N2, and CO2) and excited with 532nm light, bright yellow luminescence emerges and is readily observed. Light emission is not observed without the pyrolytic carbon, without the excitation of plasmons, or in air or an Ar/O2 gas mixture. This process, driven by visible light and a nanostructured Ag surface bearing pyrolytic carbon, will be of interest to researchers involved in plasmonic catalysis, catalytic processes involving carbon, and luminescent plasmonic surfaces.

Spatiotemporal Control Over Protein Release from Artificial Cells via a Light-Activatable Protease.

The regulation of protein uptake and secretion by cells is paramount for intercellular signaling and complex multicellular behavior. Mimicking protein-mediated communication in artificial cells holds great promise to elucidate the underlying working principles, but remains challenging without the stimulus-responsive regulatory machinery of living cells. Therefore, systems to precisely control when and where protein release occurs should be incorporated in artificial cells. Here, a light-activatable TEV protease (LaTEV) is presented that enables spatiotemporal control over protein release from a coacervate-based artificial cell platform. Due to the presence of Ni2+-nitrilotriacetic acid moieties within the coacervates, His-tagged proteins are effectively sequestered into the coacervates. LaTEV is first photocaged, effectively blocking its activity. Upon activation by irradiation with 365nm light, LaTEV cleaves the His-tags from sequestered cargo proteins, resulting in their release. The successful blocking and activation of LaTEV provides control over protein release rate and triggerable protein release from specific coacervates via selective irradiation. Furthermore, light-activated directional transfer of proteins between two artificial cell populations is demonstrated. Overall, this system opens up avenues to engineer light-responsive protein-mediated communication in artificial cell context, which can advance the probing of intercellular signaling and the development of protein delivery platforms.

On-demand release of CO in dual-responsive nanocomposite hydrogels for wound dressing

Gaseous signaling molecules, especially carbon monoxide (CO), hold promising potential for disease management. The therapeutic efficacy of CO is closely tied to its concentration, however, maintaining it at optimal levels for both efficacy and safety is highly challenging. To address this, we designed a dual-responsive (pH/red light) nanocomposite hydrogel for on-demand CO release. We first synthesized a hybrid nanocomposite (CaCO3@AgCCN) comprising a CO2 donor (CaCO3) and a photocatalyst (Ag3PO4-decorated carbon dot g-C3N4, AgCCN) capable of converting CO2 to CO. The size of CaCO3 particles was approximately 40 nm, while that of AgCCN was around 150 nm in this nanocomposite. CaCO3@AgCCN was then incorporated into chitosan (CS) to form a nanocomposite hydrogel. This nanocomposite hydrogel could respond to a mildly acidic environment due to bacterial growth, generating CO2 exactly where it is needed (the wound site), which would be subsequently catalytically converted to CO by AgCCN under 630-nm red light illumination to facilitate wound healing. The generated CO, readily controlled by adjusting the CaCO3@AgCCN content in the nanocomposite hydrogel and the red-light illumination time (the CO concentration reaching 4.7 μM after 10-min illumination), has demonstrated strong bactericidal and anti-inflammatory effects, both essential in facilitating wound healing as shown in both in vitro and in vivo studies. Coupled with satisfactory biocompatibility, this dual-responsive nanocomposite hydrogel appears to hold great promise for safe and effective applications of CO in biomedical fields.

An Innovative Azobenzene-Based Photothermal Fabric with Excellent Heat Release Performance for Wearable Thermal Management Device.

Azobenzene (azo)-based photothermal energy storage systems have garnered great interest for their potential in solar energy conversion and storage but suffer from limitations including rely on solvents and specific wavelengths for charging process, short storage lifetime, low heat release temperature during discharging, strong rigidity and poor wearability. To address these issues, an azo-based fabric composed of tetra-ortho-fluorinated photo-liquefiable azobenzene monomer and polyacrylonitrile fabric template is fabricated using electrospinning. This fabric excels in efficient photo-charging (green light) and discharging (blue light) under visible light range, solvent-free operation, long-term energy storage (706 days), and good capacity of releasing high-temperature heat (80-95 °C) at room temperature and cold environments. In addition, the fabric maintains high flexibility without evident loss of energy-storage performance upon 1500 bending cycles, 18-h washing or 6-h soaking. The generated heat from charged fabric is facilitated by the Z-to-E isomerization energy, phase transition latent heat, and the photothermal effect of 420nm light irradiation. Meanwhile, the temperature of heat release can be personalized for thermal management by adjusting the light intensity. It is applicable for room-temperature thermal therapy and can provide heat to the body in cold environments, that presenting a promising candidate for wearable personal thermal management.

Effect of 660-nm LED photobiomodulation on the proliferation and chondrogenesis of meniscus-derived stem cells (MeSCs)

Meniscus-derived stem cells (MeSCs), a unique type of MSC, have outstanding advantages in meniscal cytotherapy and tissue engineering, but the effects and molecular mechanisms of PBM on MeSCs are still unclear. We used 660-nm LED light with different energy densities to irradiate six human MeSC samples and tested their proliferation rate via cell counting, chondrogenic differentiation capacity via the DMMB assay, mitochondrial activity via the MTT assay, and gene expression via qPCR. The proliferation ability, chondrogenic capacity and mitochondrial activity of the 18 J/cm2 group were greater than those of the 4 J/cm2 and control groups. The mRNA expression levels of Akt, PI3K, TGF-β3, Ki67 and Notch-1 in the 18 J/cm2 group were greater than those in the other groups in most samples. After chondrogenic induction, the expression of Col2A1, Sox9 and Aggrecan in the 18 J/cm2 group was significantly greater than that in the 4 J/cm2 and control groups in most of the samples. The variation in the MTT values and Src, PI3K, Akt, mTOR and GSK3β levels decreased with time. The results showed that 660-nm LED red light promoted proliferation and chondrogenic differentiation and affected the gene expression of MeSCs, and the effects on gene expression and mitochondrial activity decreased with time.

Synergistic Modulation of π-π* and n-π* Transitions by In Situ Phenol-Like Structure Integration for Efficiently Wide-Spectrum Hydrogen Production of Ultrathin Carbon Nitride.

2D carbon nitride nanosheets, exemplified by g-C3N4, offers significant structural benefits and enhanced photocatalytic activity. Nonetheless, the quantum confinement effect prevalent in nanoscale photocatalysts would result in an enlarged bandgap, potentially restricting the spectral absorption range and impeding improvements in photocatalytic efficiency. Here, a high-performance 2D photocatalyst with an extended spectral response is achieved by incorporating a novel phenol-like structure into the conjugated framework of ultrathin g-C3N4 nanosheet. This novel strategy features targeted pyrimidine doping to create a conjugated carbon zone in heptazine structure, offering a thermodynamically favorable pathway for hydroxyl functionalization during the annealing exfoliation process. Consequently, the π-π* transition energy in the material is significantly decreased, and the active lone pair electrons in phenol-like structure induces a new n-π* transition with notably enhanced absorption from 500 to 650nm. The optimized material shows a dramatic enhancement in photocatalytic activity, achieving ≈72 times than the activity of bulk g-C3N4, and demonstrating a measurable H2 production rate of 6.57µmol g-1 h-1 under 650nm light. This study represents a significant step forward in the strategic design of 2D photocatalysts, with tailored electronic structures that significantly boost light absorption and photocatalytic efficiency.

Multiphoton-Driven Photocatalytic Defluorination of Persistent Perfluoroalkyl Substances and Polymers by Visible Light.

Perfluoroalkyl substances (PFASs) and fluorinated polymers (FPs) have been extensively utilized in various industries, whereas their extremely high stability poses environmental persistence and difficulty in waste treatment. Current decomposition approaches of PFASs and FPs typically require harsh conditions such as heating over 400 °C. Thus, there is a pressing need to develop a new technique capable of decomposing them under mild conditions. Here, we demonstrated that perfluorooctanesulfonate (PFOS), known as a "persistent chemical," and Nafion, a widely utilized sulfonated FP for ion-exchange membranes, can be efficiently decomposed into fluorine ions under ambient conditions via the irradiation of visible LED light onto semiconductor nanocrystals (NCs). PFOS was completely defluorinated within 8-h irradiation of 405-nm LED light, and the turnover number of the C-F bond dissociation per NC was 17200. Furthermore, 81 % defluorination of Nafion was achieved for 24-h light irradiation, demonstrating the efficient photocatalytic properties under visible light. We revealed that this decomposition is driven by cooperative mechanisms involving light-induced ligand displacements and Auger-induced electron injections via hydrated electrons and higher excited states. This study not only demonstrates the feasibility of efficiently breaking down various PFASs and FPs under mild conditions but also paves the way for advancing toward a sustainable fluorine-recycling society.

Boosting the Cell Harvesting Performance of Poly(di(ethylene glycol)methyl ether methacrylate) Cell Release Layers via Copolymerization of Photo- and Thermoresponsive Monomers.

The performance of the cell-selective thermoresponsive poly(di(ethylene glycol)methyl ether methacrylate) (PDEGMA) cell harvest system is shown to be drastically enhanced by exploiting the combination of photoresponsive spiropyran derivates and PDEGMA in copolymerized brushes. The analysis of copolymerized 1'-(2-methacryloxyethyl)-3',3'-dimethyl-6-nitrospiro(2H-1-benzopyran-2,2'-indoline) (SPMA) (DEMGA) di(ethylene glycol)methyl ether methacrylate brushes revealed that a minor adjustment of the SPMA/DEGMA ratios results in a significant alternation of wettability as well as protein adsorption, when switching the temperature from 37 to 22°C and alternately irradiating using different light wavelengths (from 530 to 365nm). Thin P(SPMA-co-DEGMA) layers supported pancreatic tumor PaTu 8988t cells with high cell viability. Copolymer layers with 2.5% SPMA/DEGMA led to the highest efficiency of enzyme-free cell release with very good cell viability. The release is induced by cooling the cell culture medium to 22°C and irradiating the surface with 365nm light. Compared to neat PDEGMA, the P(SPMA-co-DEGMA) layers showed a threefold increase in the speed of the change of cell morphology of the attached cells and a >5 times increased fraction of detached cells, which underlines the potential of these dual responsive PDEGMA systems for optimized performance in the facile capture, culture, and release of different cell lines.

Photocatalysis-promoted tumor ferroptosis enabled by MOF-derived black TiO2

Ferroptosis has emerged as a novel approach to suppress tumor growth through the iron-dependent accumulation of lipid peroxides, providing new opportunities for cancer therapy. However, the effectiveness of ferroptosis is impeded by the substantial neutralization of reactive oxygen species (ROS), generated through the Fenton reaction, by the high level of glutathione in cancer cells. Here we report a titanium metal–organic frameworks (MOFs)-derived method to create black TiO2 nanoparticles with excellent photocatalytic performance. The nanoparticle has a narrow bandgap of 1.02 eV, multiple discrete gap states, and a high density of oxygen vacancies (46.2 %), facilitating ROS generation under 1064-nm light irradiation. When coated with a tannic acid/Fe3+ layer, the resulting nanocomposite possesses the ability to deplete glutathione concentration, preventing the newly generated ROS from being neutralized and promoting ferroptotic cancer cell death. Complemented by photothermal and chemodynamic effects, in vivo experiments demonstrate a high tumor inhibition rate of 89.8 %. The utilization of MOF-derived nanomaterials represents a universal strategy, offering a solution for ferroptosis-based therapy in solid tumors and contributing to the development of smart, optically active materials with diverse applications in biological contexts.

Crosslinking Vinyl-Addition Polynorbornenes via Difunctional Diazirines to Generate Low Dielectric-Constant and Low Dielectric-Loss Thermosets.

Thermosets having low dielectric constant (Dk < 3) and low dielectric dissipation factor (Df < 0.003), high glass transition temperature (Tg > 150 °C), and good adhesion to copper are desirable for the low loss layers of the copper clad laminates (CCL) in next generation printed circuit boards. Three different difunctional diazirines are evaluated for both thermal and photochemical crosslinking of a high Tg vinyl-addition polynorbornene resin: poly(5-hexyl-1-norbornene) (poly(HNB)). The substrate polymer, crosslinked by the carbenes generated from the activated diazirines, forms thermosets with Dk < 2.3 and Df < 0.001 at 10GHz depending on the identity of the diazirine and the loading. The Dk and Df values for one composition are stable for 1600h at 125 °C in air and for 1400h at 85 °C and 85% relative humidity, suggesting good long-term reliability of this thermoset. Adhesion of poly(HNB) to copper can be enhanced by priming the copper surface with a diazirine prior to high temperature lamination; peel strength values of greater than 7.5 N cm-1 are achieved. Negative-tone photopatterning of poly(HNB) with diazirines upon exposure to 365nm light is demonstrated.

HiPorfin photodynamic therapy for vaginal high-grade squamous intraepithelial lesion

PurposeWe aimed to evaluate the efficacy and safety of HiPorfin-photodynamic therapy (PDT) in women with vaginal high-grade squamous intraepithelial Lesion (HSIL).MethodsRetrospective analysis of eighteen patients with vaginal HSIL received HiPorfin-PDT between June 2019 and May 2023. Illumination with a 630-nm laser light was applied to the lesions 48–72 h after intravenous injection of 2 mg/kg HiPorfin®. The light dose to the lesions was 150 J/cm2.ResultsThe mean age of the 18 patients was 45.8 years (range, 24 to 63). The complete response (CR) rate was 66.7% (12/18), 83.3% (15/18) and 83.3% (15/18) at 3, 6 and 12 months after PDT, respectively. Patients who achieved CR showed no signs of recurrence during long-term follow-up. There were three cases of persistent disease showing partial response (PR) and the lesion area was significantly reduced more than 50%. One patient with persistent disease then underwent thermocoagulation one time and subsequently showed no evidence of HSIL. Pre-treatment, 100% (18/18) patients were high-risk human papilloma virus (HR-HPV)-positive. HPV eradication rate was 16.7% (3/18), 22.2% (4/18) and 44.4% (8/18) after PDT at 3, 6 and 12 months, respectively. Before treatment, liquid-based cytology test ≥ atypical squamous cells of undetermined significance (ASCUS) was 94.4% (17/18). Negative conversion ratio of cytology was 47.1% (8/17), 52.9% (9/17) and 76.5% (13/17) at 3, 6 and 12 months, respectively. There were no serious adverse effects during and after PDT.ConclusionsHiPorfin-PDT may be an effective alternative treatment for vaginal HSIL for organ-saving and sexual function protection.

Kinetic isotope effect reveals rate-limiting step in green-to-red photoconvertible fluorescent proteins.

Photoconvertible fluorescent proteins (pcFPs) undergo a slow photochemical transformation when irradiated with blue light. Since their emission is shifted from green to red, pcFPs serve as convenient fusion tags in several cutting-edge biological imaging technologies. Here, a pcFP termed the Least Evolved Ancestor (LEA) was used as a model system to determine the rate-limiting step of photoconversion. Perdeuterated histidine residues were introduced by isotopic enrichment and chromophore content was monitored by absorbance. pH-dependent photoconversion experiments were carried out by exposure to 405-nm light followed by dark equilibration. The loss of green chromophore correlated well with the rise of red, and maximum photoconversion rates were observed at pH 6.5 (0.059 ± 0.001 min-1 for red color acquisition). The loss of green and the rise of red provided deuterium kinetic isotope effects (DKIEs) that were identical within error, 2.9 ± 0.9 and 3.8 ± 0.6, respectively. These data indicate that there is one rate-determining step in the light reactions of photoconversion, and that CH bond cleavage occurs in the transition state of this step. We propose that these reactions are rate-limited on the min time scale by the abstraction of a proton at the His62 beta-carbon. A conformational intermediate such as a twisted or isomerized chromophore is proposed to slowly equilibrate in the dark to generate the red form. Additionally, His62 may shuttle protons to activate Glu211 to serve as a general base, while also facilitating beta-elimination. This idea is supported by a recent X-ray structure of methylated His62.

Microbial reduction of prebagged human plasma using 405 nm light and its effects on coagulation factors

Bacterial contamination is the most prevalent infectious complication of blood transfusion in the developed world. To mitigate this, several ultraviolet light-based pathogen reduction technologies (PRTs), some of which require photo-chemicals, have been developed to minimize infection transmission. Relative to UV light, visible 405-nm light is safer and has shown potential to be developed as a PRT for the in situ treatment of ex vivo human plasma and platelet concentrates, without the need for photo-chemicals. This study investigates the effect of 405-nm light on human plasma, with focus on the compatibility of antimicrobial light doses with essential plasma clotting factors. To determine an effective antimicrobial dose that is compatible with plasma, prebagged human plasma (up to 300 mL) was seeded with common microbial contaminants and treated with increasing doses of 405-nm light (16 mW cm−2; ≤ 403 J cm−2). Post-exposure plasma protein integrity was investigated using an AOPP assay, in vitro coagulation tests, and ELISA-based measurement of fibrinogen and Protein S. Microbial contamination in 300 mL prebagged human plasma was significantly reduced (P ≤ 0.05) after exposure to ≤ 288 J cm−2, with microbial loads reduced by > 96.2%. This dose did not significantly affect the plasma protein quality parameters tested (P > 0.05). Increased doses (≥ 345 J cm−2) resulted in a 4.3% increase in clot times with no statistically significant change in protein activity or levels. Overall, this study has demonstrated that the effective microbicidal 405 light dose shows little to no negative effect on plasma quality.

Enhanced antimicrobial efficacy and energy efficiency of low irradiance 405-nm light for bacterial decontamination

Due to its increased safety over ultraviolet light, there is interest in the development of antimicrobial violet-blue light technologies for infection control applications. To ensure compatibility with exposed materials and tissue, the light irradiances and dose regimes used must be suitable for the target application. This study investigates the antimicrobial dose responses and germicidal efficiency of 405 nm violet-blue light when applied at a range of irradiance levels, for inactivation of surface-seeded and suspended bacteria. Bacteria were seeded onto agar surfaces (101–108 CFUplate−1) or suspended in PBS (103–109 CFUmL−1) and exposed to increasing doses of 405-nm light (≤ 288 Jcm−2) using various irradiances (0.5–150 mWcm−2), with susceptibility at equivalent light doses compared. Bacterial reductions ≥ 96% were demonstrated in all cases for lower irradiance (≤ 5 mWcm−2) exposures. Comparisons indicated, on a per unit dose basis, that significantly lower doses were required for significant reductions of all species when exposed at lower irradiances: 3–30 Jcm−2/0.5 mWcm−2 compared to 9–75 Jcm−2/50 mWcm−2 for low cell density (102 CFUplate−1) surface exposures and 22.5 Jcm−2/5 mWcm−2 compared to 67.5 Jcm−2/150 mWcm−2 for low density (103 CFUmL−1) liquid exposures (P ≤ 0.05). Similar patterns were observed at higher densities, excluding S. aureus exposed at 109 CFUmL−1, suggesting bacterial density at predictable levels has minimal influence on decontamination efficacy. This study provides fundamental evidence of the greater energy efficacy of 405-nm light for inactivation of clinically-significant pathogens when lower irradiances are employed, further supporting its relevance for practical decontamination applications.

Multi-scale tissue fluorescence mapping with fiber optic ultraviolet excitation and generative modeling

Cellular imaging of thick samples requires physical sectioning or laser scanning microscopy, which can be restrictive, involved, and generally incompatible with high-throughput requirements. We developed fiber optic microscopy with ultraviolet (UV) surface excitation (FUSE), a portable and quantitative fluorescence imaging platform for thick tissue that enabled quick sub-cellular imaging without thin sections. We substantially advanced prior UV excitation approaches with illumination engineering and computational methods. Optical fibers delivered &lt;300nm light with directional control, enabling unprecedented 50× widefield imaging on thick tissue with sub-nuclear clarity, and 3D topography of surface microstructure. Probabilistic modeling of high-magnification images using our normalizing flow architecture FUSE-Flow (made freely available as open-source software) enhanced low-magnification imaging with measurable localized uncertainty via variational inference. Comprehensive validation comprised multi-scale fluorescence histology compared with standard H&amp;E histology, and quantitative analyses of senescence, antibiotic toxicity, and nuclear DNA content in tissue models via efficient sampling of thick slices from entire murine organs up to 0.4×8×12mm and 1.3 million cells per surface. This technology addresses long-standing laboratory gaps in high-throughput studies for rapid cellular insights.

Tumor penetrating Janus prodrug nanoassemblies for enhanced synergistic chemotherapy and photodynamic therapy of colon cancer

Intelligent nanodrug delivery systems that respond to tumor microenvironment have been extensively utilized in cancer therapy research. However, the passive diffusion of prodrug nanoparticles is hindered due to the absence of capillaries and dense extracellular matrix in the tumor microenvironment, resulting in low efficiency of anti-tumor drug delivery. In this study, we developed a metal matrix proteinase 2 (MMP2) and glutathione (GSH) responsive Janus prodrug nanoassemblies targeted towards tumors. The Janus prodrug nanoassemblies consist of targeted micelles and prodrug nanoaggregates linked by click chemistry. The size of the nanoassemblies can be reduced within the tumor microenvironment of high concentrations of MMP2. Active targeting and size shrinkage synergistically enhance cell uptake efficiency and tumor penetration capacity of nanoassemblies. The release of camptothecin (CPT) occurs in a GSH-dependent manner, while under irradiation with 660-nm red light, the photosensitizer introduced in the prodrug generates reactive oxygen species (ROS) to induce tumor cell death. Fluorescence imaging results demonstrate enhanced tumor targeting capabilities of Janus prodrug assemblies. As a theranostic agent for tumors, Janus prodrug assemblies achieve desirable synergistic chemotherapy and photodynamic therapy for colon cancer treatment. This work would provide a novel strategy for cancer diagnosis and treatment.

Photo-controlled programmable logic gate via self-powered Cu2O/BiFeO3/TiO2 ferroelectric heterojunction photodetectors

The increased demands for high integration, fast computation, and a wide range of data processing in digital logic circuits have triggered an interest in programmable logic gates that can run different logic operations. Photodetectors (PDs) based on ferroelectric materials can obtain different ferroelectric polarization states utilizing pre-biased voltage regulation to achieve programmable logic functions, but low photoelectric conversion efficiency and slow photoresponse speed are still key problems to be addressed for programmable logic gate devices. Herein, the Cu2O/BiFeO3(BFO)/TiO2 ferroelectric heterojunction PDs were constructed by introducing a p-type hole transport layer Cu2O on the BFO/TiO2 ferroelectric heterojunction films, which not only broadens the photoresponse spectra range to the red light, but also forms a stepped energy band structure at the heterojunction interface, and the interfacial electric field promotes the separation and transport of photogenerated carriers, improving the self-powered photodetection performance of the devices. The Cu2O/BFO/TiO2 PDs demonstrate a responsivity of 3.0 mA/W and a photoresponse rise time/decay time of 2.3/23.9 ms at 420 nm light illumination. The Cu2O/BFO/TiO2 PD can be polarized in different states by pre-biased voltage and outputs different electrical signal values under the ultraviolet (365 nm) and visible (420 nm) monochromatic light or the mixed light irradiation, thus the device can realize the "AND" gate output in the positive bias polarization state and the "OR" gate output in the negative bias polarization state, which shows that the ferroelectric heterojunction PDs has a great potential application in the field of photo-controlled programmable logic gate circuits.

Linear dichroism transition and polarization-sensitive photodetector of quasi-one-dimensional palladium bromide

Perpendicular optical reversal of the linear dichroism transition has promising applications in polarization-sensitive optoelectronic devices. We perform a systematical study on the in-plane optical anisotropy of quasi-one-dimensional PdBr2 by using combined measurements of the angle-resolved polarized Raman spectroscopy (ARPRS) and anisotropic optical absorption spectrum. The analyses of ARPRS data validate the anisotropic Raman properties of the PdBr2 flake. And anisotropic optical absorption spectrum of PdBr2 nanoflake demonstrates distinct optical linear dichroism reversal. Photodetector constructed by PdBr2 nanowire exhibits high responsivity of 747 A⋅W−1 and specific detectivity of 5.8 × 1012 Jones. And the photodetector demonstrates prominent polarization-sensitive photoresponsivity under 405-nm light irradiation with large photocurrent anisotropy ratio of 1.56, which is superior to those of most of previously reported quasi-one-dimensional counterparts. Our study offers fundamental insights into the strong optical anisotropy exhibited by PdBr2, establishing it as a promising candidate for miniaturization and integration trends of polarization-related applications.

Foveal Retinal Ganglion Cells Develop Altered Calcium Dynamics Weeks After Photoreceptor Ablation

Objective or purposePhysiological changes in retinal ganglion cells (RGCs) have been reported in rodent models of photoreceptor (PR) loss but this has not been investigated in primates. By expressing both a calcium indicator (GCaMP6s) and an optogenetic actuator (ChrimsonR) in foveal RGCs of the macaque, we reactivated RGCs in vivo and assessed their response in the weeks and years following PR loss. DesignWe used an in vivo calcium imaging approach to record optogenetically evoked activity in deafferented RGCs in primate fovea. Cellular scale recordings were made longitudinally over a 10 week period following photoreceptor ablation and compared to responses from RGCs that had lost photoreceptor input more than two years prior. ParticipantsThree eyes received photoreceptor ablation, OD of a male Macaca mulatta (M1), OS of a female Macaca fascicularis (M2) and OD of a male Macaca fascicularis (M3). Two animals were used for in vivo recording, one for histological assessment.Methods: Cones were ablated with an ultrafast laser delivered through an adaptive optics scanning light ophthalmoscope (AOSLO). A 0.5 s pulse of 25Hz 660nm light optogenetically stimulated RGCs, and the resulting GCaMP fluorescence signal was recorded using AOSLO. Measurements were repeated over 10 weeks immediately after PR ablation, at 2.3 years and in control RGCs. Main Outcome measuresThe calcium rise time, decay constant and sensitivity index of optogenetic mediated RGC were derived from GCaMP fluorescence recordings from 221 RGCs (Animal M1) and 218 RGCs (Animal M2) in vivo. ResultsFollowing photoreceptor ablation, the mean decay constant of the calcium response in RGCs decreased 1.5 fold (1.6±0.5 s to 0.6±0.3 s SD) over the 10 week observation period in subject 1 and 2.1 fold (2.5±0.5 s to 1.2±0.2 s SD) within 8 weeks in subject 2. Calcium rise time and sensitivity index were stable. Optogenetic reactivation remained possible 2.3 years after PR ablation. ConclusionsAltered calcium dynamics developed in primate foveal RGCs in the weeks after photoreceptor ablation. The mean decay constant of optogenetic mediated calcium responses decreased 1.5-2-fold. This is the first report of this phenomenon in primate retina and further work is required to understand the role these changes play in cell survival and activity.

222 nm far-UVC light markedly reduces the level of infectious airborne virus in an occupied room

An emerging intervention for control of airborne-mediated pandemics and epidemics is whole-room far-UVC (200–235 nm). Laboratory studies have shown that 222-nm light inactivates airborne pathogens, potentially without harm to exposed occupants. While encouraging results have been reported in benchtop studies and in room-sized bioaerosol chambers, there is a need for quantitative studies of airborne pathogen reduction in occupied rooms. We quantified far-UVC mediated reduction of aerosolized murine norovirus (MNV) in an occupied mouse-cage cleaning room within an animal-care facility. Benchtop studies suggest that MNV is a conservative surrogate for airborne viruses such as influenza and coronavirus. Using four 222-nm fixtures installed in the ceiling, and staying well within current recommended regulatory limits, far-UVC reduced airborne infectious MNV by 99.8% (95% CI: 98.2–99.9%). Similar to previous room-sized bioaerosol chamber studies on far-UVC efficacy, these results suggest that aerosolized virus susceptibility is significantly higher in room-scale tests than in bench-scale laboratory studies. That said, as opposed to controlled laboratory studies, uncertainties in this study related to airflow patterns, virus residence time, and dose to the collected virus introduce uncertainty into the inactivation estimates. This study is the first to directly demonstrate far-UVC anti-microbial efficacy against airborne pathogens in an occupied indoor location.