Simin Wei

Herein, photothermal AgNPs were synthesized using Mentha pulegium extract under UV radiation for treating MRSA-infected wounds, where small-sized AgNPs and their aggregates acted as the antibiotic and photothermal agent, respectively.

Due to the lower oxidation potential than natural nucleic acid bases, one-electron oxidation of DNA is usually funneled into the direction of intermediates for oxidized DNA damage like 8-oxo-7,8-dihydroadenine (8-oxoA) leading to a radical cation, which may undergo facile deprotonation. However, compared to the sophisticated studies devoted to natural bases, much less is known about the radical cation degradation behavior of an oxidized DNA base. Inspired by this, a comprehensive theoretical investigation is performed to illuminate the deprotonation of 8-oxoA radical cation (8-oxoA^•+) in both free and encumbered context by calculating the pK _a value and mapping the energy profiles. The calculative pK _a values of active protons in free 8-oxoA^•+ follow the order: N7-H < N9-H < N6-H1< N6-H2, suggesting the preference of proton departure in free 8-oxoA^•+. To further illustrate the preferred site and mechanism for 8-oxoA^•+ deprotonation, energy profiles are constructed to distinguish the possibility from that of all active protons in both contexts. The results show distinctly that 8-oxoA^•+ mainly suffers from the loss of proton from N9 due to the lowest energy barrier but deprotonates N7-H in real DNA as the connection of N9 and ribose. The energy barriers for the deprotonation of N7-H from 8-oxoA^•+ in free and encumbered contexts are 1.5 and 1.3 kcal/mol, respectively, indicating a fast deprotonation reaction. It is more interestingly that the N9-H proton transfer (PT, toward N3) to adjacent water follows a stepwise fashion rather than a one-step approach as previously reported. Furthermore, the PT behavior of free N9-H toward O8 is dramatically influenced by base pairing T, where it is localized at neighboring water without further PT to adjacent water in free 8-oxoA^•+ but migrated directly to adjacent water in the 8-oxoA^•+:T base pair. And the deprotonation of N6-H2 in 8-oxoA^•+:T is disturbed as the PT to O4 of the pairing T base is inhibited. It is warmly anticipated that these results could provide an in-depth perspective to understand the important role of 8-oxoA in mutation.

Clinical studies have continually referred to the involvement of drug carrier having dramatic negative influences on the biocompatibility, biodegradability, and loading efficacy of hydrogel. To overcome this deficiency, researchers have proposed to directly self-assemble natural herbal small molecules into a hydrogel without any structural modification. However, it is still a formidable challenge due to the high requirements on the structure of natural molecules, leading to a rarity of this type of hydrogel. Mangiferin (MF) is a natural polyphenol of C-glucoside xanthone with various positive health benefits, including the treatment of diabetic wounds, but its poor hydrosolubility and low bioavailability significantly restrict the clinical application. Inspired by these, with heating/cooling treatment, a carrier-free hydrogel (MF-gel) is developed by assembling the natural herbal molecule mangiferin, which is mainly governed through hydrogen bonds and intermolecular π–π stacking interactions. The as-prepared hydrogel has injectable and self-healing properties and shows excellent biocompatibility, continuous release ability, and reversible stimuli-responsive performances. All of the superiorities enable the MF-based hydrogel to serve as a potential wound dressing for treating diabetic wounds, which was further confirmed by both the vitro and vivo studies. In vitro, the MF-gel could promote the migration of healing-related cells from peripheral as well as the angiogenesis and displays the capacity of mediating inflammation response by scavenging the intracellular ROS. In vivo, the MF-gel accelerates wound contraction and healing via inflammatory adjustment, collagen deposition, and angiogenesis. This study provides a facile and effective method for diabetic wound management and emphasizes the direct self-assembly hydrogel from natural herbal small molecule.

A thorough theoretical investigation was performed to disclose the subtle influence of H-bonding on the reaction of HO˙ and G in the C(H⁺)GC motif, which shows strong structural dependency dramatically different from unencumbered G.

A DFT investigation was performed to illuminate the obscure mechanism of hydroxyl radical and guanine in G-quadruplex, where direct hydrogen abstraction from N2 of G to furnish neutral radical could compete with C8 addition.

The flower of safflower is widely used in Chinese herbal preparations and the non-medicinal parts have been applied to develop a sustainable green method, where AgNPs were generated using a mixture of leaf and stem after 12 h of incubation in the dark. In this study, we intend to improve the efficiency of the reduction reaction and optimize this green method by selecting other non-medicinal parts, such as the bud and the pure stem, evaluating the biosynthesis parameters and harnessing the assistance of ultrasonication. Visual observation and UV-vis spectroscopy confirmed that both safflower stem (SS) and bud (SB) mediated AgNPs (SS-AgNPs and SB-AgNPs, respectively) could be produced rapidly over time under ultrasonication. An alkaline solution could accelerate the formation of SS-AgNPs and SB-AgNPs with greater surface loads. SS-AgNPs and SB-AgNPs of small size could be obtained at pH 8.0 and 10.0, respectively. Large concentrations of SS and SB extract are also beneficial for forming AgNPs of small size. It is in acid and neutral solutions that monodispersed SS-AgNPs and SB-AgNPs can be generated. Characterization of selectively synthesized SS-AgNPs and SB-AgNPs demonstrated their spherical shape with the actual size below 30 nm covered by anions. Both SS-AgNPs and SB-AgNPs exhibited potent antioxidant and antibacterial activity. The MIC values of SS-AgNPs for S. aureus and E. coli were 12.5 and 25.0 μg mL⁻¹, respectively, slightly superior to SB-AgNPs. In an in vitro anticancer assay, both kinds of AgNPs show potent toxicity action against the SW620 cell line with IC₅₀ values of 5.4 and 10.6 μg mL⁻¹, respectively. However, only SS-AgNPs reveal an inhibitory action against the HeLa cell line, where the IC₅₀ is found to be 26.8 μg mL⁻¹. These results provide experimental proof that the assistance of ultrasonication and adjusting the process parameters are efficient methods for promoting the reduction reaction, and both SS and SB mediated AgNPs could serve as a promising antioxidant, antibacterial and anticancer agents.

A theoretical investigation was performed to disclose the transformation mechanism of 8‐oxo‐7,8‐dihydroguanine radical cation (8‐oxoG⋅⁺) to protonated 2‐amino‐5‐hydroxy‐7,9‐dihydropurine‐6,8‐dione (5‐OH‐8‐oxoG) in base pair. The energy profiles for three possible pathways of the events were mapped. It is shown that direct loss of H7 from base paired 8‐oxoG⋅⁺ is the only energetically favorable pathway to generate neutral radical, 8‐oxoG(‐H7)⋅. Further oxidation of 8‐oxoG(‐H7)⋅ : C to 8‐oxoG(‐H7)⁺ : C is exothermic. However, the 8‐oxoG(‐H7)⁺ : C deprotonation from all possible active sites is infeasible, indicating the inaccessible second proton loss and the lack of essential intermediate 2‐amino‐7,9‐dihydropurine‐6,8‐dione (8‐oxoG^OX). This makes 8‐oxoG(‐H7)⁺ act as the precursor of hydration leading to the generation of protonated 5‐HO‐8‐oxoG by stepwise fashion in base pair, which would initiate the step down guanidinohydantoin (Gh) pathway. These results clearly specify the structure‐dependent transformation for 8‐oxoG⋅⁺ and verify the emergence of protonated 5‐HO‐8‐oxoG in base pair.