Polysaccharides to combat viruses (Covid-19) and microbes: New updates

COVID-19, which is speedily distributed across the world and presents a significant challenge to public health, is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Following MERS coronavirus (MERS-CoV) and SARS, this is the third severe coronavirus outbreak in less than 20 years. To date, there are no exact agents and vaccines available for the treatment of COVID-19 that are clinically successful. Antimicrobial medications are effective in controlling infectious diseases. However, the extensive use of antibiotics makes microbes more resistant to drugs and demands novel bioactive agents’ development. Polysaccharides are currently commonly used in the biomedical and pharmaceutical industries for their remarkable applications. Polysaccharides appear to have a wide range of anti-virus (anti-coronavirus) and antimicrobial applications. Polysaccharides are able to induce bacterial cell membrane disruption as they demonstrate potency in binding onto the surfaces of microbial cells. Here, the antiviral mechanisms of such polysaccharides and their success in the application of antiviral infections are reviewed. Additionally, this report provides a summary of current advancements of well-recognized polysaccharides as antimicrobial and anti-biofilm agents.

Cross Talk Between Zinc-Solubilizing Bacteria and Plants: A Short Tale of Bacterial-Assisted Zinc Biofortification

A contemporary approach to bacterially mediated zinc (Zn) biofortification offers a new dimension in the crop improvement program with better Zn uptake in plants to curb Zn malnutrition. The implication of Zn solubilizing bacteria (ZSB) represents an inexpensive and optional strategy for Zn biofortification, with an ultimate green solution to enlivening sustainable agriculture. ZSB dwelling in the rhizospheric hub or internal plant tissues shows their competence to solubilize Zn via a variety of strategies. The admirable method is the deposition of organic acids (OAs), which acidify the surrounding soil environment. The secretion of siderophores as a metal chelating molecule, chelating ligands, and the manifestation of an oxidative–reductive system on the bacterial cell membrane are further tactics of bacterially mediated Zn solubilization. The inoculation of plants with ZSB is probably a more effective tactic for enhanced Zn translocation in various comestible plant parts. ZSB with plant growth-enhancing properties can be used as bioelicitors for sustainable plant growth via the different approaches that are crucial for plant health and its productivity. This article provides an overview of the functional properties of ZSB-mediated Zn localization in the edible portions of food crops and provides an impetus to explore such plant probiotics as natural biofortification agents.

Antimicrobial and Anti-inflammatory Effects of a Novel Peptide From the Skin of Frog Microhyla pulchra

Brevinins are an important antimicrobial peptide (AMP) family identified in the skin of Ranidae frogs and generally contain a characteristic ranabox structure at their C-terminal sequence. Herein a novel AMP named brevinin-2MP has been identified from the skin of the frog Microhyla pulchra by molecular cloning. Brevinin-2MP (GVITDTLKGVAKTVAAELLRKAHCKLTNSC) with a high amphipathic α-helix in sodium dodecyl sulfate solutions can destroy bacterial cell membrane and kill microbes. Furthermore, brevinin-2MP has been found to inhibit the lipopolysaccharide (LPS)-induced expression of pro-inflammatory NO, MCP-1, IL-6, and TNF-α via binding unidentified targets on the cell membrane and consequently suppressing the activation of MAPK/NF-κB signaling cascades induced by LPS in RAW 264.7 cells. Consistently, brevinin-2MP significantly alleviates the acute inflammatory response in carrageenan-induced mice paw. In conclusion, brevinin-2MP with anti-inflammatory and antimicrobial properties will be an ideal candidate drug molecule for bacterial inflammation treatment.

Self-assembled nanoparticles containing photosensitizer and polycationic brush for synergistic photothermal and photodynamic therapy against periodontitis

Background Periodontitis is a chronic inflammatory disease in oral cavity owing to bacterial infection. Photothermal therapy (PTT) and photodynamic therapy (PDT) have many advantages for antibacterial treatment. As an excellent photosensitizer, indocyanine green (ICG) shows prominent photothermal and photodynamic performances. However, it is difficult to pass through the negatively charged bacterial cell membrane, thus limiting its antibacterial application for periodontitis treatment. Results In this work, self-assembled nanoparticles containing ICG and polycationic brush were prepared for synergistic PTT and PDT against periodontitis. First, a star-shaped polycationic brush poly(2-(dimethylamino)ethyl methacrylate) (sPDMA) was synthesized via atom transfer radical polymerization (ATRP) of DMA monomer from bromo-substituted β-cyclodextrin initiator (CD-Br). Next, ICG was assembled with sPDMA to prepare ICG-loaded sPDMA (sPDMA@ICG) nanoparticles (NPs) and the physicochemical properties of these NPs were characterized systematically. In vitro antibacterial effects of sPDMA@ICG NPs were investigated in porphyromonas gingivalis (Pg), one of the recognized periodontitis pathogens. A ligature-induced periodontitis model was established in Sprague–Dawley rats for in vivo evaluation of anti-periodontitis effects of sPDMA@ICG NPs. Benefiting from the unique brush-shaped architecture of sPDMA polycation, sPDMA@ICG NPs significantly promoted the adsorption and penetration of ICG into the bacterial cells and showed excellent PTT and PDT performances. Both in vitro and in vivo, sPDMA@ICG NPs exerted antibacterial and anti-periodontitis actions via synergistic PTT and PDT. Conclusions A self-assembled nanosystem containing ICG and polycationic brush has shown promising clinical application for synergistic PTT and PDT against periodontitis. Graphical Abstract

The Use of Innovative Materials in the Organization of Clinical Treatment in Dentistry

The article examines the features of the use of innovative materials in the organization of clinical treatment in dentistry. In modern conditions, solving the problem of patient safety is one of the main conditions for the functioning of medicine in general and dentistry in particular. For this reason, the search for innovations in the field of antimicrobial protection and, together with it, the functionality of various materials is one of the main tasks of researchers in the field of dentistry. Nanomaterials, which are made on the basis of graphene, are able to demonstrate excellent antimicrobial properties. These materials have the ability to disrupt the integrity of the bacterial cell membrane and produce reactive oxygen species (ROS). These materials are widely used in the manufacture of dentures, they are incorporated in the composition of composite resins and luting cements in the organization of restorative treatment, are used for the manufacture of adhesive materials. Many experts recognize that these materials are the future of dental practice, since they have the ability to provide a high level of functionality and safety.

Water-Soluble Ruthenium (II) Complex Derived From Optically Pure Limonene and Its Microencapsulation Are Efficient Tools Against Bacterial Food Pathogen Biofilms: Escherichia coli, Staphylococcus aureus, Enteroccocus faecalis, and Listeria monocytogenes

Bioactive aminooxime ligands based on optically pure (R)-limonene have been synthesized in two steps. Their ruthenium (II) cationic water-soluble complex was prepared by a reaction between dichloro (para-cymene) ruthenium (II) dimers and aminooxime ligands in a 1:2 molar ratio. Antibacterial and antibiofilm activities of the synthetized complex were assessed against Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Enterococcus faecalis. The results revealed that the ruthenium (II) complex has higher antibacterial and antibiofilm activities in comparison with free ligands or the enantiopure (R)-limonene. Moreover, microencapsulation of this complex reduced its cytotoxicity and improved their minimum inhibitory concentration and antibiofilm activity toward the considered bacteria. The ruthenium (II) complex targets the bacterial cell membrane, which leads to rapid leakage of intracellular potassium. Our study suggests that the developed ruthenium (II) complexes could be useful as an alternative to conventional disinfectants.

Antimicrobial activity and mode of action of 1,8-cineol against carbapenemase-producing Klebsiella pneumoniae

Antimicrobial resistance remains one of the most challenging issues that threatens the health of people around the world. Plant-derived natural compounds have received considerable attention for their potential role to mitigate antibiotic resistance. This study was carried out to assess the antimicrobial activity and mode of action of a monoterpene, 1,8-cineol (CN) against carbapenemase-producing Klebsiella pneumoniae (KPC-KP). Results showed that resazurin microplate assay and time-kill analysis revealed bactericidal effects of CN at 28.83 mg/mL. Zeta potential showed that CN increased the surface charge of bacteria and an increase of outer membrane permeability was also detected. CN was able to cause leakage of proteins and nucleic acids in KPC-KP cells upon exposure to CN and ethidium bromide influx/efflux experiment showed the uptake of ethidium bromide into the cell; this was attributed to membrane damage. CN was also found to induce oxidative stress in CN-treated KPC-KP cells through generation of reactive oxygen species which initiated lipid peroxidation and thus damaging the bacterial cell membrane. Scanning and transmission electron microscopies further confirmed the disruption of bacterial cell membrane and loss of intracellular materials. In this study, we demonstrated that CN induced oxidative stress and membrane damage resulting in KPC-KP cell death.

Effect of Silver Nanoparticles on Blue Light Phototoxicity against Fusobacterium nucleatum

A previous study showed that sub-lethal exposure of blue light caused cell membrane damage in Fusobacterium nucleatum (Fn). The aim of the present study was to test the combined effect of blue light and silver nanoparticles against Fn. Bacterial suspensions were exposed to blue light (400–500 nm) with or without silver nanoparticles (10 nm). Exposed and non-exposed samples were studied for malodor production (Odor judge scores), VSC levels (Halimeter), reactive oxygen species (ROS) production (fluorimeter), and bacterial cell membrane damage (fluorescence microscopy). The results showed that combining blue light exposure and silver nanoparticles significantly reduced malodor and VSC production by Fn concomitant with increased ROS levels and bacterial cell membrane damage. These results suggest that silver nanoparticles may increase blue light phototoxicity against Fn.

Listeriolysin S: A bacteriocin from Listeria monocytogenes that induces membrane permeabilization in a contact-dependent manner

Listeriolysin S (LLS) is a thiazole/oxazole–modified microcin (TOMM) produced by hypervirulent clones of Listeria monocytogenes. LLS targets specific gram-positive bacteria and modulates the host intestinal microbiota composition. To characterize the mechanism of LLS transfer to target bacteria and its bactericidal function, we first investigated its subcellular distribution in LLS-producer bacteria. Using subcellular fractionation assays, transmission electron microscopy, and single-molecule superresolution microscopy, we identified that LLS remains associated with the bacterial cell membrane and cytoplasm and is not secreted to the bacterial extracellular space. Only living LLS-producer bacteria (and not purified LLS-positive bacterial membranes) display bactericidal activity. Applying transwell coculture systems and microfluidic-coupled microscopy, we determined that LLS requires direct contact between LLS-producer and -target bacteria in order to display bactericidal activity, and thus behaves as a contact-dependent bacteriocin. Contact-dependent exposure to LLS leads to permeabilization/depolarization of the target bacterial cell membrane and adenosine triphosphate (ATP) release. Additionally, we show that lipoteichoic acids (LTAs) can interact with LLS and that LTA decorations influence bacterial susceptibility to LLS. Overall, our results suggest that LLS is a TOMM that displays a contact-dependent inhibition mechanism.