Red and near-infrared light-activated photoelectrochemical nanobiosensors for biomedical target detection.

Photoelectrochemical (PEC) nanobiosensors integrate molecular (bio)recognition elements with semiconductor/plasmonic photoactive nanomaterials to produce measurable signals after light-induced reactions. Recent advancements in PEC nanobiosensors, using light-matter interactions, have significantly improved sensitivity, specificity, and signal-to-noise ratio in detecting (bio)analytes. Tunable nanomaterials activated by a wide spectral radiation window coupled to electrochemical transduction platforms have further improved detection by stabilizing and amplifying electrical signals. This work reviews PEC biosensors based on nanomaterials like metal oxides, carbon nitrides, quantum dots, and transition metal chalcogenides (TMCs), showing their superior optoelectronic properties and analytical performance for the detection of clinically relevant biomarkers. Furthermore, it highlights the innovative role of red light and NIR-activated PEC nanobiosensors in enhancing charge transfer processes, protecting them from biomolecule photodamage in vitro and in vivo applications. Overall, advances in PEC detection systems have the potential to revolutionize rapid and accurate measurements in clinical diagnostic applications. Their integration into miniaturized devices also supports the development of portable, easy-to-use diagnostic tools, facilitating point-of-care (POC) testing solutions and real-time monitoring.

Revealing the ESIPT process in benzoxazole fluorophores within polymeric matrices through theory and experiment.

The impact of the polymeric matrix on the photophysical characteristics of monomeric dyes responsive to excited-state intramolecular proton transfer (ESIPT) was investigated through UV-Vis absorption as well as steady-state and time-resolved emission spectroscopies. For this purpose, two benzoxazole monomers (M1 and M2) with acryloyl groups at different positions in their molecular structures were employed to facilitate covalent bonding within a styrene chain. Our findings reveal significant variations in their excited-state properties due to the proximity of the acryloyl groups, which affects the energy barrier of the ESIPT reaction, the emission wavelength, and the balance between the normal and tautomeric forms. The experimental results were corroborated through theoretical investigations at the DFT/TDDFT level, specifically using the B3LYP-D3/def2-TZVP methodology. Three notable observations emerged: donor/acceptor groups at the meta/para positions induced electron distribution changes, causing red-shifted emission for M2; in the polymer film, particularly in PM1, intramolecular hydrogen bond deactivation favored N* emission over T* emission; and the zwitterionic character of the T* species. This study underscores the advantages of functionalization in polymers, which can lead to colorless films and prevalent N* or T* emission, and contributes valuable insights into molecular design strategies for tailoring the photophysical properties of polymeric materials.

Effect of Chitosan-Riboflavin Bioconjugate on Green Mold Caused by Penicillium digitatum in Lemon Fruit.

Penicillium digitatum is the causal agent of green mold, a primary postharvest disease of citrus fruits. This study evaluated the efficacy of a novel photoactive chitosan-riboflavin bioconjugate (CH-RF) to control green mold in vitro and in lemon fruit. The results showed total inhibition of P. digitatum growth on APDA supplemented with CH-RF at 0.5% (w/v) and a significant reduction of 84.8% at 0.25% (w/v). Lemons treated with CH-RF and kept under controlled conditions (20 °C and 90-95% relative humidity) exhibited a noteworthy reduction in green mold incidence four days post-inoculation. Notably, these effects persisted, with all treatments remaining significantly distinct from the control group until day 14. Furthermore, CH-RF showed high control of green mold in lemons after 20 days of cold storage (5 ± 1 °C). The disease incidence five days after cold storage indicated significant differences from the values observed in the control. Most CH-RF treatments showed enhanced control of green mold when riboflavin was activated by white-light exposure. These findings suggest that this novel fungicide could be a viable alternative to conventional synthetic fungicides, allowing more sustainable management of lemon fruit diseases.

Characterization data of cellulose modified by gamma irradiation to be used as template in the synthesis of a photoactive composite for environmental applications.

The following data provide evidence of the green functionalization process of a cellulose substrate by gamma radiation to be used as template in the preparation of photocatalyst composites. Functionalized cellulose, by gamma radiation treatment, improved its stability in water and exhibited a reduced size. Our data showed an intensification of carbonyl groups signal and a decrease in the thermal stability of the cellulose as result of the gamma radiation dose. Infrared and thermal data of the treated cellulose provide evidence of bond scission and the formation of functional groups that improved it is application as template. Finally, the conductive polymer poly(3,4-ethylenedioxythiophene) was deposited on the gamma irradiated cellulose to be used as photo-catalyze in the treatment of contaminated water with pharmaceutical compounds.

Design and Study of a Photo-Switchable Polymeric System in the Presence of ZnS Nanoparticles under the Influence of UV Light Irradiation.

Recent progress in the field of photosensitive materials has prompted a need to develop efficient methods to synthesize materials with basic intermolecular architectural designs and novel properties. Accordingly, in this work we design and study a photoactive polymer as a photo-switchable polymeric system in the presence and absence of ZnS nanoparticles (average size < 10 nm) at 5 wt.%. The influence of UV light irradiation on its properties were also studied. The photoactive block copolymer was obtained from styrene (S) and methyl methacrylate (MMA) as monomers and 1-(2-hydroxyethyl)-3,3-dimethylindoline-6-nitrobenzopyran (SP) was grafted to the block copolymer backbone as a photochromic agent. Furthermore, the incorporation of ZnS (NPs) as photo-optical switch component into the system enhances the purple colored photo-emission, with the open form of the spiropyran derivative (merocyanine, MC). The ZnS stabilize the isomeric equilibrium in the MC interconversion of the photochromic agent. The photo-switchable properties of the PS-b-PMMA-SP in the presence of ZnS (NPs) were examined using UV-VIS spectroscopy, Photoluminescence (PL) spectroscopy, optical fluorescence and scanning electronic microscopy (SEM-EDX.). The observed changes in the absorbance, fluorescence and morphology of the system were associated to the reversible interconversion of the two states of the photochromic agent which regulates the radiative deactivation of the luminescent ZnS NPs component. After UV irradiation the photoactive polymer becomes purple in color. Therefore, these basic studies can lead to the development of innovative functional and nanostructured materials with photosensitive character as photosensitive molecular switches.

Exploring the Effect of the Irradiation Time on Photosensitized Dendrimer-Based Nanoaggregates for Potential Applications in Light-Driven Water Photoreduction.

Fourth generation polyamidoamine dendrimer (PAMAM, G4) modified with fluorescein units (F) at the periphery and Pt nanoparticles stabilized by L-ascorbate were prepared. These dendrimers modified with hydrophobic fluorescein were used to achieve self-assembling structures, giving rise to the formation of nanoaggregates in water. The photoactive fluorescein units were mainly used as photosensitizer units in the process of the catalytic photoreduction of water propitiated by light. Complementarily, Pt-ascorbate nanoparticles acted as the active sites to generate H2. Importantly, the study of the functional, optical, surface potential and morphological properties of the photosensitized dendrimer aggregates at different irradiation times allowed for insights to be gained into the behavior of these systems. Thus, the resultant photosensitized PAMAM-fluorescein (G4-F) nanoaggregates (NG) were conveniently applied to light-driven water photoreduction along with sodium L-ascorbate and methyl viologen as the sacrificial reagent and electron relay agent, respectively. Notably, these aggregates exhibited appropriate stability and catalytic activity over time for hydrogen production. Additionally, in order to propose a potential use of these types of systems, the in situ generated H2 was able to reduce a certain amount of methylene blue (MB). Finally, theoretical electronic analyses provided insights into the possible excited states of the fluorescein molecules that could intervene in the global mechanism of H2 generation.

Phenotypic Resistance in Photodynamic Inactivation Unravelled at the Single Bacterium Level.

Herein we report a simple fluorescence microscopy methodology that, jointly with four photosensitizers (PSs) and a cell viability marker, allows monitoring of phenotypic bacterial resistance to photodynamic inactivation (PDI) treatments. The PSs, composed of BODIPY dyes, were selected according to their ability to interact with the cell wall and the photoinactivating mechanism involved (type I or type II). In a first approach, the phenotypic heterogeneity allowing bacteria to persist during PDI treatment was evaluated in methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli as Gram-positive and Gram-negative models, respectively. By means of propidium iodide (PI), we monitored with spatiotemporal resolution cell viability at the single bacterium level. All the PSs were effective at inactivating pathogens; however, the cationic nonhalogenated PS (compound 1) surpassed the others and was capable of photoinactivating E. coli even under optimal growth conditions. Compound 1 was further tested on two other Gram-negative strains, Pseudomonas aeruginosa and Klebsiella pneumoniae, with outstanding results. All bacterial strains used here are well-known ESKAPE pathogens, which are the leading cause of nosocomial infections worldwide. Thorough data analysis of individual cell survival times revealed clear phenotypic variation expressed in the cell wall that affected PI permeation and thus its intercalation with DNA. For the same bacterial sample, death times may vary from seconds to hours. In addition, the PI incorporation time is also a parameter governed by the phenotypic characteristics of the microbes. Finally, we demonstrate that the results gathered for the bacteria provide direct and unique experimental evidence that supports the time-kill curve profiles.

Distribution of dissolved iron and bacteria producing the photoactive siderophore, vibrioferrin, in waters off Southern California and Northern Baja.

Phytoplankton blooms can cause acute effects on marine ecosystems due either to their production of endogenous toxins or to their enormous biomass leading to major impacts on local economies and public health. Despite years of effort, the causes of these Harmful Algal Blooms are still not fully understood. Our hypothesis is that bacteria that produce photoactive siderophores may provide a bioavailable source of iron for phytoplankton which could in turn stimulate algal growth and support bloom dynamics. Here we correlate iron concentrations, phytoplankton cell counts, bacterial cell abundance, and copy numbers for a photoactive siderophore vibrioferrin biosynthesis gene in water samples taken from 2017 cruises in the Gulf of California, and the Pacific Ocean off the coast of northern Baja California as well as during a multiyear sampling at Scripps Pier in San Diego, CA. We find that bacteria producing the photoactive siderophore vibrioferrin, make up a surprisingly high percentage of total bacteria in Pacific/Gulf of California coastal waters (up to 9%). Vibroferrin's unique properties and the widespread prevalence of its bacterial producers suggest that it may contribute significantly to generating bioavailability of iron via photoredox reactions.

Biopelículas fotoactivas: material de empaque en alimentos sensibles a la oxidación / Photoactive biofilms: packaging materials in oxidation sensitive foods

RESUMEN La contaminación, a causa de residuos plásticos, es uno de los principales problemas ambientales, emergentes del siglo XX. Particularmente, el uso de envases plásticos para alimentos y bebidas ocupa el 50% de su producción total. La producción de empaques bioplásticos, a partir de materias primas renovables, surge como alternativa de bajo impacto ambiental en la industria de alimentos, sensibles a la oxidación, conservando su calidad organoléptica y nutricional. Esta investigación tuvo como objetivo la elaboración de biopelículas, a partir de almidón residual esterificado de papa, anclado a sustancias fotoactivas, con diferentes rangos de absorción electromagnética: betalaína, rutina y riboflavina, capaces de disminuir los procesos oxidativos inducidos por la luz, en muestras de carne bovina. Se evaluaron las propiedades fisicoquímicas, mecánicas y de eficacia fotoactiva. Los resultados mostraron que el anclaje de las sustancias fotoactivas al almidón esterificado, optimizó los valores de solubilidad en agua, transparencia, estabilidad ácido-base y resistencia a la ruptura de las biopelículas. La mayor protección fotoactiva, se obtuvo con la biopelícula de rutina, reduciendo en un 66,6% y 57,3% la degradación oxidativa de proteínas y lípidos de la carne. Se concluye, que la esterificación del almidón residual de papa y su posterior anclaje de sustancias fotoactivas, le confiere un uso potencial en la producción de envases biodegradables para alimentos.

ABSTRACT Pollution caused by plastic waste is one of the main emerging environmental problems of the 20th century. Particularly the use of plastic containers for food and beverages that occupies almost 50% of its total production. The elaboration of bioplastics from renewable raw materials emerges as an alternative of low environmental impact in the food industry sensitive to oxidation, conserving its organoleptic and nutritional quality. The aim of this research was to prepare biofilms from residual esterified potato starch, anchored to photoactive substances with different ranges of electromagnetic absorption: Betalaine, Rutin and Riboflavin, able to reduce oxidative processes induced by light in bovine meat samples. The physicochemical, mechanical and photoactive efficiency properties were evaluated. The results showed that the anchoring of the photoactive substances to the esterified starch optimizes the values of water solubility, transparency, acid-base stability and resistance to rupture of the biofilms. The greater photoactive protection was obtained with the biofilm of Rutin, reducing in 66.6% and 57.3% the oxidative degradation of proteins and lipids respectively. It is concluded that the esterification of residual potato starch and its subsequent anchoring of photoactive substances confers a potential use in the production of biodegradable food packaging.