Organic-Inorganic Interfacial Dipole Induced by Energy Level Alignment for Efficient Photocatalytic Sterilization.

Photocatalytic molecules are considered to be one of the most promising substitutions of antibiotics against multidrug-resistant bacterial infections. However, the strong excitonic effect greatly restricts their efficiency in antibacterial performance. Inspired by the interfacial dipole effect, a Ti3C2 MXene modified photocatalytic molecule (MTTTPyB) is designed and synthesized to enhance the yield of photogenerated carriers under light irradiation. The alignment of the energy level between Ti3C2 and MTTTPyB results in the formation of an interfacial dipole, which can provide an impetus for the separation of carriers. Under the role of a dipole electric field, these photogenerated electrons can rapidly migrate to the side of Ti3C2 for improving the separation efficiency of photogenerated electrons and holes. Thus, more electrons can be utilized to produce reactive oxygen species (ROS) under light irradiation. As a result, over 97.04% killing efficiency can be reached for Staphylococcus aureus (S. aureus) when the concentration of MTTTPyB/Ti3C2 was 50 ppm under 660 nm irradiation for 15 min. A microneedle (MN) patch made from MTTTPyB/Ti3C2 was used to treat the subcutaneous bacterial infection. This design of an organic-inorganic interface provides an effective method to minimize the excitonic effect of molecules, further expanding the platform of inorganic/organic hybrid materials for efficient phototherapy.

Symmetrical Localized Built-in Electric Field by Induced Polarization Effect in Ionic Covalent Organic Frameworks for Selective Imaging and Killing Bacteria.

Photocatalytic materials are some of the most promising substitutes for antibiotics. However, the antibacterial efficiency is still inhibited by the rapid recombination of the photogenerated carriers. Herein, we design a cationic covalent organic framework (COF), which has a symmetrical localized built-in electric field due to the induced polarization effect caused by the electron-transfer reaction between the Zn-porphyrin unit and the guanidinium unit. Density functional theory calculations indicate that there is a symmetrical electrophilic/nucleophilic region in the COF structure, which results from increased electron density around the Zn-porphyrin unit. The formed local electric field can further inhibit the recombination of photogenerated carriers by driving rapid electron transfer from Zn-porphyrin to guanidinium under light irradiation, which greatly increases the yield of reactive oxygen species. This COF wrapped by DSPE-PEG2000 can selectively target the lipoteichoic acid of Gram-positive bacteria by electrostatic interaction, which can be used for selective discrimination and imaging of bacteria. Furthermore, this nanoparticle can rapidly kill Gram-positive bacteria including 99.75% of Staphylococcus aureus and 99.77% of Enterococcus faecalis at an abnormally low concentration (2.00 ppm) under light irradiation for 20 min. This work will provide insight into designing photoresponsive COFs through engineering charge behavior.

Injectable thermosensitive hydrogel to enhance the photothermal ablation and systemic immunotherapy of breast tumors.

As the high-frequency tumor in women around the world, breast cancer has high mortality due to metastasis tumors making it difficult to cure. Herein, we report a near-infrared (NIR) activated bio-multifunctional thermosensitive hydrogel (denoted as AMDR) with powerful cell killing and immunogenicity amplifying ability. Based on the molecular engineering strategy, a photothermal agent (M-4) with 52.4% conversion efficiency was synthesized. Accordingly, the designed injectable thermosensitive hydrogel AMDR is simply fabricated by the employment of the M-4 photothermal agent, doxorubicin hydrochloride (DOX) as the antitumor drug, and imiquimod (R837) as the immunologic adjuvant by self-assembly. Under NIR irradiation, the AMDR hydrogel can generate local mild heat to release DOX for synergistic killing of tumor cells with little damage to normal cells. The immunogenic cell death induced by potent in situ killing combined with heat-released R837 can trigger robust immune response to inhibit and kill metastasis tumors. The developed AMDR hydrogel is successfully applied in the treatment of primary tumors and inhibition of distal tumors of tumor-bearing mice. The study provides a novel strategy and platform for complete treatment of breast cancer and also offers ideas for designing high-efficiency photothermal agents.

Beneficial impacts of fermented celery (Apium graveolens L.) juice on obesity prevention and gut microbiota modulation in high-fat diet fed mice.

Metabolic syndrome caused obesity has long been recognized as a risk of health. Celery and celery extracts have various medicinal properties, such as anti-diabetes and anti-inflammatory properties and blood glucose and serum lipid reduction. However, the effect of probiotic fermentation on celery juice and the association between fermented celery juice (FCJ) and obesity were unclear. This study aimed to evaluate the beneficial effects of FCJ on high-fat diet (HFD) induced obesity and related metabolic syndromes. C57BL/6 mice were randomly divided into six groups (n = 15 per group) fed either a normal diet (ND) or HFD with or without CJ/FCJ (10 g kg-1 day-1) by oral gavage for 12 weeks. Here we demonstrated that the probiotic fermentation of celery juice (CJ) could enhance the active ingredients in celery, such as total polyphenols, flavonoids, vitamin C and SOD. Compared to the slight improvement induced by CJ ingestion, FCJ intake significantly inhibited body weight gain, prevented dyslipidemia and hyperglycemia, and suppressed visceral fat accumulation. Furthermore, 16S rRNA sequencing analysis revealed that FCJ intake altered the composition of gut microbiota, increasing the ratio of Firmicutes/Bacteroidetes and the relative abundance of beneficial bacteria (Lactobacillus, Ruminococcaceae_UCG-014, Faecalibaculum and Blautia), and decreasing the relative abundance of harmful bacteria (Alloprevotella and Helicobacter). These findings suggest that FCJ can prevent HFD-induced obesity and become a novel gut microbiota modulator to prevent HFD-induced gut dysbiosis and obesity-related metabolic disorders.

A hybrid model of molecular regulation and population dynamics for yeast autophagy.

Autophagy is an evolutionarily conserved lysosome-based degradation process that is involved in maintaining cellular homeostasis and stress responses. Dysregulation of autophagy is known to associate with many diseases. In this paper, we establish a Hybrid model of Molecular regulation and Population dynamics (HMP model) for yeast autophagy to study how autophagy regulation at molecular level affects the cell population dynamics under the stress of starvation. The model includes interactions between amino acids, TORC1, Atg1 complex, and Atg8 lipidation at the molecular level, and cell death and division at the cell behavior level. Two feedback loops are involved in autophagy induction, in which the negative feedback of TORC1 activation has been known previously, and the positive feedback between TORC1 and Atg1 complex formation is introduced according to the similarity of Drosophila and mammalian cells. We demonstrate that the two feedback loops play distinct roles in autophagy regulation. The positive feedback is pro-survival, whereas the negative feedback has little effect on the survival of population during starvation. In addition, autophagy deficient cells can be rescued from starvation by amino acid exchanges from their neighboring wild type cells.

Effects of elongation delay in transcription dynamics.

In the transcription process, elongation delay is induced by the movement of RNA polymerases (RNAP) along the DNA sequence, and can result in changes in the transcription dynamics. This paper studies the transcription dynamics that involved the elongation delay and effects of cell division and DNA replication. The stochastic process of gene expression is modeled with delay chemical master equation with periodic coefficients, and is studied numerically through the stochastic simulation algorithm with delay. We show that the average transcription level approaches to a periodic dynamics over cell cycles at homeostasis, and the elongation delay can reduce the transcription level and increase the transcription noise. Moreover, the transcription elongation can induce bimodal distribution of mRNA levels that can be measured by the techniques of flow cytometry.

A mathematical model of cell population dynamics with autophagy response to starvation.

In this paper, we study the role of autophagy in yeast cell population dynamics in response to starvation by a mathematical model based on the logistic growth model. We analytically study the boundedness of solutions, and the existence and stability of equilibrium states under general biologically acceptable assumptions. Finally, we perform numerical studies for Saccharomyces cerevisiae response to starvation with autophagy. The results show that autophagy is valuable in maintaining cell population in starvation, and attenuating population fluctuations in response to perturbations in environmental nutrients. Furthermore, we show that proper level autophagy promotes cell survival through the inhibition of cell death by autophagy as well as the secretion of nutrients from autophagic cells, however excessive autophagy can decrease cell population due to autophagic cell death.