Probing the Formation of Reactive Oxygen Species by a Porous Self-Assembled Benzophenone Bis-Urea Host

Selected Extracts from High Mountain Plants as Potential Sunscreens with Antioxidant Capacity

The photoprotective and antioxidant activities of extracts of six species of plants collected in a high mountain ecosystem at 3150 m.a.s.l. were evaluated. In vitro photoprotection according to UVA-UVB absorption spectrum, Sun Protection Factor (SPF), UVA Protection Factor (UVAPF), (critical wavelength) λ_c and UVA/UVB Ratio were assessed. Also, the antioxidant activity was determined using the DPPH radical assay and the inhibition of lipid peroxidation in methyl linoleate (MeLo). Total anthocyanins content (TAC) and total polyphenolic content (TPC) were evaluated. Among the extracts evaluated, the extract of B. antioquensis, an endemic plant of Colombia, showed a significant photoprotection against UVA-UVB range, with SPF values of 15 ± 2 and UVAPF of 7 ± 1, λ_c : 378, UVA/UVB Ratio: 0.78. Furthermore, this extract presented an excellent antioxidant activity, with EC₅₀ of 0.17 ± 0.04 g of dry extract/mmol DPPH, a value of TPC of 464 ± 9 mg gallic acid equivalents (GAE)/g dry extract and significant inhibition of MeLo peroxidation. The results suggest that the extract of B. antioquensis has the best quality to be a source of new UV filters, with a broad spectrum of protection and antioxidant properties.

Visible-Light-Driven and Self-Hydrogen-Donated Nanofibers Enable Rapid-Deployable Antimicrobial Bioprotection

The novel coronavirus SARS-CoV-2 has prompted a worldwide pandemic and poses a great threat to public safety and global economies. Most present personal protective equipment (PPE) used to intercept pathogenic microorganisms is deficient in biocidal properties. Herein, we present green nanofibers with effective antibacterial and antiviral activities that can provide sustainable bioprotection by continuously producing reactive oxygen species (ROS). The superiority of the design is that the nanofibers can absorb and store visible light energy and maintain the activity under light or dark environment. Moreover, the nanofibers can uninterruptedly release ROS in the absence of an external hydrogen donor, acting as a biocide under all weather conditions. A facile spraying method is proposed to rapidly deploy the functional nanofibers to existing PPE, such as protective suits and masks. The modified PPE exhibit stable ROS production, excellent capacity for storing activity potential, long-term durability, and high bactericidal (>99.9%) and viricidal (>99.999%) efficacies.

From Incident Light to Persistent and Regenerable Radicals of Urea-Assembled Benzophenone Frameworks: A Structural Investigation

Herein we probe the effects of crystalline structure and geometry on benzophenone photophysics, self-quenching, and the regenerable formation of persistent triplet radical pairs at room temperature. Radical pairs are not observed in solution but appear via an emergent pathway within the solid-state assembly. Single crystal X-ray diffraction (SC-XRD) of two sets of constitutional isomers, benzophenone bis-urea macrocycles, and methylene urea-tethered dibenzophenones are compared. Upon irradiation with 365 nm light-emitting diodes (LEDs), each forms photogenerated radicals as monitored by electron paramagnetic resonance (EPR). Once generated, the radicals exhibit half-lives from 2 to 60 days before returning to starting material without degradation. Re-exposure to light regenerates the radicals with similar efficiency. Subtle differences in the structure of the crystalline frameworks modulates the maximum concentration of photogenerated radicals, phosphorescence quantum efficiency (φ), and n-type self-quenching as observed using laser flash photolysis (LFP). These studies along with the electronic structure analysis based on the time-dependent density functional theory (TD-DFT) suggest the microenvironment surrounding benzophenone largely dictates the favorability of self-quenching or radical formation and affords insights into structure/function correlations. Advances in understanding how structure determines the excited state pathway solid-state materials undertake will aid in the design of new radical initiators, components of OLEDs, and NMR polarizing agents.

Alternative methods of photodynamic therapy and oxygen consumption measurements-A review

Photooxidation generates reactive oxygen species (ROS) through the interaction of dyes or surfaces with light radiation of appropriate wavelength. The reaction is of wide utility and is highly effective in photodynamic therapy (PDT) of various types of cancer and skin disease. Understanding generation of singlet oxygen has contributed to the development of PDT and its subsequent use in vivo. However, this therapy has some limitations that prevent its use in the treatment of cancers located deep within the body. The limited depth of light penetration through biological tissue limits initiation of PDT action in deep tissue. Measurement of oxygen photo consumption is critical due to tumor hypoxia, and use of magnetic resonance imaging (MRI) is particularly attractive since it is non-invasive. This article presents bioluminescence (BL) and chemiluminescence (CL) phenomena based on publications from the last 20 years, and preliminary results from our lab in the use of MRI to measure oxygen concentration in water. Current work is aimed at improving the effectiveness of singlet oxygen delivery to deep tissue cancer.