Controlled Light Exposure Research Articles

Increase in polyunsaturated fatty acids and carotenoid accumulation in the microalga Golenkinia brevispicula (Chlorophyceae) by manipulating spectral irradiance and salinity.

Microalgal biotechnology offers a promising platform for the sustainable production of diverse renewable bioactive compounds. The key distinction from other microbial bioprocesses lies in the critical role that light plays in cultures, as it serves as a source of environmental information to control metabolic processes. Therefore, we can use these criteria to design a bioprocess that aims to stimulate the accumulation of target molecules by controlling light exposure. We study the effect on biochemical and photobiological responses of Golenkinia brevispicula FAUBA-3 to the exposition of different spectral irradiances (specifically, high-fluence PAR of narrow yellow spectrum complemented with low intensity of monochromatic radiations of red, blue, and UV-A) under prestress and salinity stress conditions. High light (HL) intensity coupled to salinity stress affected the photosynthetic activity and photoprotection mechanisms as shown by maximal quantum yield (Fv/Fm) and non-photochemical quenching (NPQmax) reduction, respectively. HL treatments combined with the proper dose of UV-A radiation under salinity stress induced the highest carotenoid content (2.75 mg g dry weight [DW]- 1) composed mainly of lutein and β-carotene, and the highest lipid accumulation (35.3% DW) with the highest polyunsaturated fatty acid content (alpha-linolenic acid (C18:3) and linoleic acid (C18:2)). Our study can guide the strategies for commercial indoor production of G. brevispicula for high-value metabolites.

Real-time observation of a metal complex-driven reaction intermediate using a porous protein crystal and serial femtosecond crystallography

Determining short-lived intermediate structures in chemical reactions is challenging. Although ultrafast spectroscopic methods can detect the formation of transient intermediates, real-space structures cannot be determined directly from such studies. Time-resolved serial femtosecond crystallography (TR-SFX) has recently proven to be a powerful method for capturing molecular changes in proteins on femtosecond timescales. However, the methodology has been mostly applied to natural proteins/enzymes and limited to reactions promoted by synthetic molecules due to structure determination challenges. This work demonstrates the applicability of TR-SFX for investigations of chemical reaction mechanisms of synthetic metal complexes. We fix a light-induced CO-releasing Mn(CO)3 reaction center in porous hen egg white lysozyme (HEWL) microcrystals. By controlling light exposure and time, we capture the real-time formation of Mn-carbonyl intermediates during the CO release reaction. The asymmetric protein environment is found to influence the order of CO release. The experimentally-observed reaction path agrees with quantum mechanical calculations. Therefore, our demonstration offers a new approach to visualize atomic-level reactions of small molecules using TR-SFX with real-space structure determination. This advance holds the potential to facilitate design of artificial metalloenzymes with precise mechanisms, empowering design, control and development of innovative reactions.

Exploring the metabolic implications of blue light exposure during daytime in rats

Excessive exposure to light is a global issue. Artificial light pollution has been shown to disrupt the body's natural circadian rhythm. To investigate the impacts of light on metabolism, we studied Sprague-Dawley rats chronically exposed to red or blue light during daytime or nighttime. Rats in the experimental group were exposed to extended light for 4 hours during daytime or nighttime to simulate the effects of excessive light usage. Strikingly, we found systemic metabolic alterations only induced by blue light during daytime. Furthermore, we conducted metabolomic analyses of the cerebrospinal fluid, serum, heart, liver, spleen, adrenal, cerebellum, pituitary, prostate, spermatophore, hypothalamus and kidney from rats in the control and blue light exposure during daytime. Significant changes in metabolites have been observed in cerebrospinal fluid, serum, hypothalamus and kidney of rats exposed to blue light during daytime. Metabolic alterations observed in rats encompassing pyruvate metabolism, glutathione metabolism homocysteine degradation, phosphatidylethanolamine biosynthesis, and phospholipid biosynthesis, exhibit analogous patterns to those inherent in specific physiological processes, notably neurodevelopment, cellular injury, oxidative stress, and autophagic pathways. Our study provides insights into tissue-specific metabolic changes in rats exposed to blue light during the daytime and may help explain potential mechanisms of photopathogenesis.

Effects of Cultivation Stress on the Glaucophyte Cyanophora paradoxa and Bioactive Potential in Human Cancer Cell Lines

ABSTRACT The propensity to accumulate high-value metabolites under specific conditions makes microalgae promising candidates for commercial applications. Here, the freshwater microalga Cyanophora paradoxa CCAP 981/1 was cultivated under varying conditions (control, nitrogen limitation, NaCl supplementation and blue light exposure) and the biological activity of the corresponding biomass extracts was assessed against human breast (MCF-7) and lung (A549) cancer cell lines. The stress treatments hindered the growth of C. paradoxa, the control displaying the highest specific growth rate (0.16 d−1 ± 0.01). Biomass screening by GCMS and HPLC identified diverse bioactive compounds including pigments (chlorophylls, xanthophylls, carotenes) and fatty acids (e.g., EPA). The control cultivation conditions returned the highest yields of biomass (724 mg), zeaxanthin (6.8 mg g−1), EPA (1.1 mg g−1) and phycocyanin (113.9 mg g−1), while the blue light treatment enhanced the proportions of unsaturated forms of C18 (34.3%). Extracts of dried biomass obtained by cold maceration using solvents of increasing polarity were used in the treatment of MCF-7 and A549 cancer cells. Ethyl acetate extracts from nitrogen-limited cultures reduced MCF-7 viability (~70%) after 72 h. However, the diethyl ether and methanol extracts showed no impact on MCF-7 and A549 cell viability. Furthermore, acridine orange staining revealed no significant DNA damage in these cell lines upon exposure to C. paradoxa extracts. Overall, the minimal impacts on cell viability observed here supports considering C. paradoxa as a promising source of natural bioactive compounds with applications in various biotechnological sectors.

Current sleep interventions for shift workers: a mini review to shape a new preventative, multicomponent sleep management programme

IntroductionShift work can lead to sleep disturbances and insomnia during the sleeping period, as well as excessive sleepiness and fatigue during the waking period. While Cognitive Behavioral Therapy (CBT-i) is recommended as the first line of treatment for insomnia, key elements of CBT-i, such as maintaining a consistent sleep schedule, can be challenging for shift workers, highlighting the need for tailored sleep interventions. This mini review provides a narrative synthesis of non-pharmacological sleep interventions for shift workers and informs the development of a preventative, multicomponent sleep management programme.MethodAn informal review was conducted in line with Phase 1 of the Framework for the Development and Evaluation of Complex Interventions.ResultsA variety of strategies have been employed to help manage the impacts of shift work on sleep, including: CBT-i, adjusting shift schedules, controlled light exposure, sleep hygiene education, planned napping, caffeine consumption, and mind-body interventions (e.g., yogic relaxation).DiscussionRecommendations, limitations, and directions for future research are discussed; notably, the role of the family, the commute to and from the workplace, and the eating behaviors of employees appear to have been overlooked in current intervention efforts. Digital CBT-i platforms could help to provide an effective, scalable, and low-cost method of reducing insomnia in shift workers.

Effects of Photobiomodulation Using Near-Infrared Light on the Dentin and Periodontal Ligament in a Beagle Model

In this study, we investigated the effect of photobiomodulation (PBM) using near-infrared light on the dentin and periodontal ligament in a beagle model. We utilized a specific PBM device to irradiate NIR light with a wavelength of 810 nm and an energy density of 80.22 mJ/cm2. The device’s settings were optimized for a frequency of 300 Hz and a 30% duty cycle, allowing precise and controlled light exposure. Through a comprehensive analysis involving micro-computed tomography, scanning electron microscopy, and hematoxylin and eosin staining, we demonstrated increased odontoblast activity at the pulp–dentin interface in PBM-treated samples. This increased activity may be postulated to potentially contribute to alleviating dental hypersensitivity through the differentiation of dental pulp stem cells and the promotion of vascular development within the odontoblast layer. Moreover, our observations also indicated an improvement in the strength and integrity of fibrous connective tissue within the periodontal ligament. These findings highlight the potential of PBM with specific parameters applied using NIR as a valuable treatment method for tooth tissue regeneration. It shows particular promise in the treatment of dental diseases associated with dentin and periodontal ligament damage and offers a new perspective in the management of tooth hypersensitivity and other related dental diseases.

Optogenetic polymerization and assembly of electrically functional polymers for modulation of single-neuron excitability.

Ionic conductivity and membrane capacitance are two foundational parameters that govern neuron excitability. Conventional optogenetics has emerged as a powerful tool to temporarily manipulate membrane ionic conductivity in intact biological systems. However, no analogous method exists for precisely manipulating cell membrane capacitance to enable long-lasting modulation of neuronal excitability. Genetically targetable chemical assembly of conductive and insulating polymers can modulate cell membrane capacitance, but further development of this technique has been hindered by poor spatiotemporal control of the polymer deposition and cytotoxicity from the widely diffused peroxide. We address these issues by harnessing genetically targetable photosensitizer proteins to assemble electrically functional polymers in neurons with precise spatiotemporal control. Using whole-cell patch-clamp recordings, we demonstrate that this optogenetic polymerization can achieve stepwise modulation of both neuron membrane capacitance and intrinsic excitability. Furthermore, cytotoxicity can be limited by controlling light exposure, demonstrating a promising new method for precisely modulating cell excitability.

Optimizing a Behavioral Sleep Intervention for Gynecologic Cancer Survivors: Study Design and Protocol

Sleep difficulties, particularly symptoms of insomnia and circadian disruption, are among the primary complaints of gynecologic cancer survivors before, during, and after treatment. Moreover, difficulty sleeping has been linked to poorer health-related quality of life and elevated symptom burden in this population. Although leading behavioral sleep interventions have demonstrated efficacy among cancer survivors, up to 50% of survivors are non-adherent to these treatments, likely because these interventions require labor-intensive behavior and lifestyle changes. Therefore, there is a need for more effective and acceptable approaches to diminish sleep disturbance among cancer survivors. This manuscript describes the methodology of a two-part study guided by the Multiphase Optimization Strategy (MOST) framework to identify a streamlined behavioral sleep intervention for gynecologic cancer survivors. Three candidate intervention components previously shown to decrease sleep disturbance will be evaluated, including sleep restriction, stimulus control, and systematic bright light exposure. Participants will be adult women with a history of non-metastatic gynecologic cancer who have completed primary treatment and who report current poor sleep quality. Fifteen participants will be recruited for Part 1 of the study, which will utilize qualitative methods to identify barriers to and facilitators of intervention adherence. Results will inform changes to the delivery of the candidate intervention components to promote adherence in Part 2, where 80 participants will be recruited and randomized to one of eight conditions reflecting every possible combination of the three candidate intervention components in a full factorial design. Participants will complete assessments at baseline, post-intervention, and 3-months post-intervention. Part 2 results will identify the combination of candidate intervention components that yields the most efficacious yet efficient 6-week intervention for diminishing sleep disturbance. This is the first known study to apply the MOST framework to optimize a behavioral sleep intervention and will yield a resource-efficient treatment to diminish sleep disturbance, improve health-related quality of life, and decrease symptom burden among gynecologic cancer survivors. ClinicalTrials.gov Identifier: NCT05044975.

Microscope-based light gradient generation for quantitative growth studies of photosynthetic micro-organisms.

Photosynthetic micro-organisms are equipped with molecular machineries that are designed to transform light into chemical or bioenergy, and help shape and balance the ecosystem of all life forms on earth. Recently, aquatic ecosystems have been disrupted by climate change, which leads to the frequent occurrence of harmful algal blooms (HABs). HABs endanger drinking water resources and harm the fishing and coastal recreation industries. Despite its urgency, mechanistic understanding of how key biophysical and biochemical parameters impact algal growth is largely unexplored. In this article, we developed a microscope-based light gradient generator for studies of photosynthetic micro-organisms under well-defined light intensity gradients. This technology utilized a commercially available microscope, allowed for controlled light exposure and imaging of cells on the same microscope platform, and can be integrated with any micrometer-scale device. Using this technology, we studied the role of light intensity in the growth of photosynthetic micro-organisms. A parallel study was also carried out using a 96-well plate. Our work revealed that the growth rate of the microalgae/cyanobacteria was significantly regulated by the light intensity and followed Monod or van Oorschot kinetic models. The measured half-saturation constants were compared with those obtained in macro-scale devices, and indicated that shading, light spectrum, and temperature may all play important roles in the light sensitivity of photosynthetic micro-organisms. This work highlighted the importance of analytical tools for quantitative understanding of biophysical parameters in the growth of photosynthetic micro-organisms, and knowledge learned will be critical in the design of future technologies for managing algal blooms or optimizing bioenergy production.

Absence of Light Exposure Increases Pathogenicity of Pseudomonas aeruginosa Pneumonia-Associated Clinical Isolates.

Simple SummaryAn often-overlooked factor when designing an experiment is light exposure. Bacterial cultures are usually grown in an uncontrolled light environment, subject to natural daylight conditions. However, light as an abiotic factor has been described as a trigger for the switch from environmental to a pathogenic host-associated lifestyle. Pseudomonas aeruginosa possesses features that allow it to sense light and adapt its behavior accordingly. In this study, clinical isolates of P. aeruginosa from the sputum of pneumonia-diagnosed patients were assayed in two extreme light exposure conditions: constant illumination and intensity of full-spectrum light, and complete absence of light. The aim was to understand the influence of this factor on P. aeruginosa pathogenic potential, studied in interface with a human pulmonary epithelial cell line model. The preliminary findings here described evidenced that growth in the dark, which would more closely mimic the conditions in the lung microenvironment, was associated with a higher cytotoxicity against host cells, concordant with an increased pathogenic potential. Given the importance of accurately interpreting bacterial responses in in vitro studies, this study raises awareness of the need to control light exposure conditions to be as similar as possible to in vivo parameters.Pseudomonas aeruginosa can alter its lifestyle in response to changes in environmental conditions. The switch to a pathogenic host-associated lifestyle can be triggered by the luminosity settings, resorting to at least one photoreceptor which senses light and regulates cellular processes. This study aimed to address how light exposure affects the dynamic and adaptability of two P. aeruginosa pneumonia-associated isolates, HB13 and HB15. A phenotypic characterization of two opposing growth conditions, constant illumination and intensity of full-spectrum light and total absence of light, was performed. Given the nature of P. aeruginosa pathogenicity, distinct fractions were characterized, and its inherent pathogenic potential screened by comparing induced morphological alterations and cytotoxicity against human pulmonary epithelial cells (A549 cell line). Growth in the dark promoted some virulence-associated traits (e.g., pigment production, LasA proteolytic activity), which, together with higher cytotoxicity of secreted fractions, supported an increased pathogenic potential in conditions that better mimic the lung microenvironment of P. aeruginosa. These preliminary findings evidenced that light exposure settings may influence the P. aeruginosa pathogenic potential, likely owing to differential production of virulence factors. Thus, this study raised awareness towards the importance in controlling light conditions during bacterial pathogenicity evaluation approaches, to more accurately interpret bacterial responses.

Site-specific targeting of a light activated dCas9-KillerRed fusion protein generates transient, localized regions of oxidative DNA damage.

DNA repair requires reorganization of the local chromatin structure to facilitate access to and repair of the DNA. Studying DNA double-strand break (DSB) repair in specific chromatin domains has been aided by the use of sequence-specific endonucleases to generate targeted breaks. Here, we describe a new approach that combines KillerRed, a photosensitizer that generates reactive oxygen species (ROS) when exposed to light, and the genome-targeting properties of the CRISPR/Cas9 system. Fusing KillerRed to catalytically inactive Cas9 (dCas9) generates dCas9-KR, which can then be targeted to any desired genomic region with an appropriate guide RNA. Activation of dCas9-KR with green light generates a local increase in reactive oxygen species, resulting in "clustered" oxidative damage, including both DNA breaks and base damage. Activation of dCas9-KR rapidly (within minutes) increases both γH2AX and recruitment of the KU70/80 complex. Importantly, this damage is repaired within 10 minutes of termination of light exposure, indicating that the DNA damage generated by dCas9-KR is both rapid and transient. Further, repair is carried out exclusively through NHEJ, with no detectable contribution from HR-based mechanisms. Surprisingly, sequencing of repaired DNA damage regions did not reveal any increase in either mutations or INDELs in the targeted region, implying that NHEJ has high fidelity under the conditions of low level, limited damage. The dCas9-KR approach for creating targeted damage has significant advantages over the use of endonucleases, since the duration and intensity of DNA damage can be controlled in "real time" by controlling light exposure. In addition, unlike endonucleases that carry out multiple cut-repair cycles, dCas9-KR produces a single burst of damage, more closely resembling the type of damage experienced during acute exposure to reactive oxygen species or environmental toxins. dCas9-KR is a promising system to induce DNA damage and measure site-specific repair kinetics at clustered DNA lesions.

Seasonal weight changes in laboratory ferrets.

Ferrets (Mustela putorius furo) are a valuable animal model used in biomedical research. Like many animals, ferrets undergo significant variation in body weight seasonally, affected by photoperiod, and these variations complicate the use weight as an indicator of health status. To overcome this requires a better understanding of these seasonal weight changes. We provide a normative weight data set for the female ferret accounting for seasonal changes, and also investigate the effect of fluid regulation on weight change. Female ferrets (n = 39) underwent behavioural testing from May 2017 to August 2019 and were weighed daily, while housed in an animal care facility with controlled light exposure. In the winter (October to March), animals experienced 10 hours of light and 14 hours of dark, while in summer (March to October), this contingency was reversed. Individual animals varied in their body weight from approximately 700 to 1200 g. However, weights fluctuated with light cycle, with animals losing weight in summer, and gaining weight in winter such that they fluctuated between approximately 80% and 120% of their long-term average. Ferrets were weighed as part of their health assessment while experiencing water regulation for behavioural training. Water regulation superimposed additional weight changes on these seasonal fluctuations, with weight loss during the 5-day water regulation period being greater in summer than winter. Analysing the data with a Generalised Linear Model confirmed that the percentage decrease in weight per week was relatively constant throughout the summer months, while the percentage increase in body weight per week in winter decreased through the season. Finally, we noted that the timing of oestrus was reliably triggered by the increase in day length in spring. These data establish a normative benchmark for seasonal weight variation in female ferrets that can be incorporated into the health assessment of an animal’s condition.

Combined Photosensitization and Vaccination Enable CD8 T-Cell Immunity and Tumor Suppression Independent of CD4 T-Cell Help.

Cytotoxic T lymphocytes (CTLs) are key players in fighting cancer, and their induction is a major focus in the design of therapeutic vaccines. Yet, therapeutic vaccine efficacy is limited, in part due to the suboptimal vaccine processing by antigen-presenting cells (APCs). Such processing typically takes place via the MHC class II pathway for CD4 T-cell activation and MHC class I pathway for activation of CD8 CTLs. We show that a combination of skin photochemical treatment and immunization, so-called photochemical internalization (PCI) facilitated CTL activation due to the photochemical adjuvant effect induced by photosensitizer, oxygen, and light. Mice were immunized intradermally with antigen and photosensitizer, followed by controlled light exposure. PCI-treated mice showed strong activation of CD8 T cells, with improved IFN-γ production and cytotoxicity, as compared to mice immunized without parallel PCI treatment. Surprisingly, the CD8 T-cell effector functions were not impaired in MHC class II- or CD4 T-cell-deficient mice. Moreover, PCI-based vaccination caused tumor regression independent of MHC class II or CD4 T cells presence in melanoma bearing mice. Together, the data demonstrate that PCI can act as a powerful adjuvant in cancer vaccines, even in hosts with impaired T-helper functions.

Perceptual and Physiological Consequences of Dark Adaptation: A TMS-EEG Study.

Existing literature on sensory deprivation suggests that short-lasting periods of dark adaptation (DA) can cause changes in visual cortex excitability. DA cortical effects have previously been assessed through phosphene perception, i.e., the ability to report visual sensations when a transcranial magnetic stimulation (TMS) pulse is delivered over the visual cortex. However, phosphenes represent an indirect measure of visual cortical excitability which relies on a subjective report. Here, we aimed at overcoming this limitation by assessing visual cortical excitability by combining subjective (i.e., TMS-induced phosphenes) and objective (i.e., TMS-evoked potentials - TEPs) measurements in a TMS-EEG protocol after 30min of DA. DA effects were compared to a control condition, entailing 30min of controlled light exposure. TMS was applied at 11 intensities in order to estimate the psychometric function of phosphene report and explore the relationship between TEPs and TMS intensity. Compared to light adaptation, after DA the slope of the psychometric function was significantly steeper, and the amplitude of a TEP component (P60) was lower, only for high TMS intensities. The perceptual threshold was not affected by DA. These results support the idea that DA leads to a change in the excitability of the visual cortex, accompanied by a behavioral modification of visual perception. Furthermore, this study provides a first valuable description of the relationship between TMS intensity and visual TEPs.

Strategies to decrease social jetlag: Reducing evening blue light advances sleep and melatonin.

The timing of sleep is under the control of the circadian clock, which uses light to entrain to the external light-dark cycle. A combination of genetic, physiological and environmental factors produces individual differences in chronotype (entrained phase as manifest in sleep timing). A mismatch between circadian and societal (e.g., work) clocks leads to a condition called social jetlag, which is characterized by changing sleep times over work and free days and accumulation of sleep debt. Social jetlag, which is prevalent in late chronotypes, has been related to several health issues. One way to reduce social jetlag would be to advance the circadian clock via modifications of the light environment. We thus performed two intervention field studies to describe methods for decreasing social jetlag. One study decreased evening light exposure (via blue-light-blocking glasses) and the other used increased morning light (via the use of curtains). We measured behaviour as well as melatonin; the latter in order to validate that behaviour was consistent with this neuroendocrinological phase marker of the circadian clock. We found that a decrease in evening blue light exposure led to an advance in melatonin and sleep onset on workdays. Increased morning light exposure advanced neither melatonin secretion nor sleep timing. Neither protocol led to a significant change in social jetlag. Despite this, our findings show that controlling light exposure at home can be effective in advancing melatonin secretion and sleep, thereby helping late chronotypes to better cope with early social schedules.

Dynamic PEG-Peptide Hydrogels via Visible Light and FMN-Induced Tyrosine Dimerization.

Photoresponsive hydrogels have become invaluable 3D culture matrices for mimicking aspects of the extracellular matrix. Recent efforts have focused on using ultraviolet (UV) light exposure and multifunctional macromers to induce secondary hydrogel crosslinking and dynamic matrix stiffening in the presence of cells. This contribution reports the design of a novel yet simple dynamic poly(ethylene glycol)-peptide hydrogel system through flavin mononucleotide (FMN) induced di-tyrosine crosslinking. These di-tyrosine linkages effectively increase hydrogel crosslinking density and elastic modulus. In addition, the degree of stiffening in hydrogels at a fixed PEG macromer content can be readily tuned by controlling FMN concentration or the number of tyrosine residues built-in to the peptide linker. Furthermore, tyrosine-bearing pendant biochemical motifs can be spatial-temporally patterned in the hydrogel network via controlling light exposure through a photomask. The visible light and FMN-induced tyrosine dimerization process produces a cytocompatible and physiologically relevant degree of stiffening, as shown by changes of cell morphology and gene expression in pancreatic cancer and stromal cells. This new dynamic hydrogel scheme should be highly desirable for researchers seeking a photoresponsive hydrogel system without complicated chemical synthesis and secondary UV light irradiation.

Photoactivatable Adhesive Ligands for Light-Guided Neuronal Growth.

Neuro-regeneration after trauma requires growth and reconnection of neurons to reestablish information flow in particular directions across the damaged tissue. To support this process, biomaterials for nerve tissue regeneration need to provide spatial information to adhesion receptors on the cell membrane and to provide directionality to growing neurites. Here, photoactivatable adhesive peptides based on the CASIKVAVSADR laminin peptidomimetic are presented and applied to spatiotemporal control of neuronal growth to biomaterials in vitro. The introduction of a photoremovable group [6-nitroveratryl (NVOC), 3-(4,5-dimethoxy-2-nitrophenyl)butan-2-yl (DMNPB), or 2,2'-((3'-(1-hydroxypropan-2-yl)-4'-nitro-[1,1'-biphenyl]-4-yl)azanediyl)bis(ethan-1-ol) (HANBP)] at the amino terminal group of the K residue temporally inhibited the activity of the peptide. The bioactivity was regained through controlled light exposure. When used in neuronal culture substrates, the peptides allowed light-based control of the attachment and differentiation of neuronal cells. Site-selective irradiation activated adhesion and differentiation cues and guided seeded neurons to grow in predefined patterns. This is the first demonstration of ligand-based light-controlled interaction between neuronal cells and biomaterials.

Accelerated light protection performance measurement technology validated for dairy milk packaging design

We report an accelerated measurement technology for prediction of light protection performance of milk packaging by quantifying the ability of a package to preserve a light‐sensitive nutrient present in milk. This measurement technology consists of a light exposure instrument and a detection approach to track changes to the light‐sensitive nutrient, riboflavin (RF), in a light‐exposed solution sample. The light exposure instrument provided an intense, controlled light exposure and a consistent sample environment for an aqueous RF marker solution. Coupled with the light exposure instrument, two alternative detection approaches were used to determine the RF concentration of light‐exposed marker solutions: an accelerated ex situ (AES) approach by high‐performance liquid chromatography or an accelerated in situ (AIS) approach by ultraviolet–visible spectrometry. The capability of each RF determination method was confirmed using measurement systems analysis, and their statistical equivalency was demonstrated. To explore application of the measurement technology for use in package design, a set of high‐density polyethylene packages incorporating surface‐treated TiO2 pigments was evaluated for light protection performance by AES and AIS. For the same package set, experiments monitoring RF degradation in extended‐shelf‐life milk products under retail dairy storage conditions showed strong correlation with the AIS method (R2 > 0.97). Riboflavin retention increased under both retail and accelerated light exposure conditions for package designs containing greater loadings of surface‐treated TiO2 confirming its light protection efficacy. This research illustrates the utility of the accelerated methods to quantitatively evaluate package designs for light protection performance for nutrient preservation.

PCI-based vaccination: a novel method for targeting of MHC class I antigen presentation and stimulation of antigen-specific cytotoxic T cells

Abstract Cytotoxic CD8+ T cells are key players in fighting cancer and infectious diseases, hence, the design of therapeutic vaccines focuses on ways to prime strong cytotoxic immune responses. Yet, current vaccines efficacy is limited mainly due to the default processing of exogenous antigens via the MHC class II pathway and the activation of CD4+ and not CD8+ T cells. Photochemical internalization (PCI) is a novel intracellular delivery approach, able to circumvent the MHC class II processing. Briefly, after endocytosis of antigen and photosensitizer by antigen presenting cells, light activation of the photosensitizer causes disruption of endosomal membrane and antigen release into the cytosol, resulting in stimulation of MHC class I-restricted CD8+ T cells. Wild type and MHC class II-deficient mice were immunized intradermally with protein antigens and photosensitizer, followed by controlled light exposure for activation of the photosensitizer. The effectiveness of the PCI to stimulate CD8+ T cells was analyzed by measuring frequency, phenotype, and function of antigen-specific T cells in blood and spleens. PCI-treated mice showed a strong activation and proliferation of specific CD8+ T cells, with improved functions in terms of IFN-g production and cytotoxic capacity. The CD8+ T cell effector functions were not impaired in MHC class II-deficient or in CD4+ T cell-depleted mice, suggesting that the PCI-mediated antigen processing is independent of MHC class II and CD4+ T helper cells. Our data demonstrate that PCI–based vaccination can stimulation strong and functional cytotoxic CD8+ T cells, making PCI a potential method for use in therapeutic vaccines against cancer and infectious diseases.

Programmed Emission Transformations: Negative‐to‐Positive Patterning Using the Decay‐to‐Recovery Behavior of Quantum Dots

Positive and negative photoluminescent photopattern contrasts arising from intrinsic modification of quantum dot (QD) emission (decay or recovery) upon exposure to light are reported. The ability to fabricate a variety of photo­pattern types using a single type of quantum dot is due to a two‐step decay‐to‐recovery evolution upon light exposure. It is shown that high‐contrast photopatterns spanning mm2 areas can be fabricated within seconds with a facile one‐step process, representing a drastic reduction in the time required to develop an emissive pattern in a QD‐polymer film (from hours to seconds). Furthermore, the controlled light exposure allows for a programmed transformation of the emissive pattern contrast, with a reversal of the bright/dark regions of the QD‐polymer photopattern demonstrated. Finally, it is shown that the photopatterns can be stored over a period of time and then “recharged” using simple light exposure to partially recover the intensity and contrast of aged photopatterns. The outlined patterning strategies open up new pathways for facile, one‐step parallel fabrication of anti‐counterfeiting emitting labels and light sensors, as well as for gain‐loss parity‐time systems where an emission contrast is required but where physical patterning may not be appropriate.