Controlling the growth of Escherichia coli by layer-by-layer encapsulation

Effect of Salt on Synthetic Cationic Antimicrobial Polymer-Cell Interactions

Cationic antiseptics are deployed in a variety of settings, where salinity ranges from almost pure water to hypertonic salt. Here, we examine how dissolved NaCl affects the antimicrobial action of a model antimicrobial, polydiallyldimethylammonium chloride (PDADMAC) to the bacterium Escherichia coli (E. coli). Fluorescence microscopy is used to measure the time course of both the adsorption of PDADMAC to E. coli and the cell viability. NaCl decreases the density of adsorbed PDADMAC and diminishes its efficacy. At NaCl concentrations at or above 0.15 M, PDADMAC no longer kills bacteria but still prevents reproduction by halting the growth in cell length. Reproduction can be restarted if PDADMAC is removed. Fluorescence depolarization measurements show that PDADMAC rigidifies model membranes, but salt reduces the rigidity. We therefore attribute the halt in cell growth to reversible bridging by the polymer on the cell surface that prevents expansion of the cell membrane.

Scale-up construction of stable multifunctional hydrogel interfaces for large-scale purification of complex oil-water emulsions and oil recovery

Inspired by the multi-level structure of grass clumps in nature, a novel filter with plexiform-structured hydrogel interface was constructed using sepiolite-derived silica nanofiber (SiNF) as the supporter and crosslinked polyvinyl alcohol (cl-PVA) hydrogel as the coating. Experimental test, DFT and MD calculations have confirmed that the addition of SiNF can not only enhance oil-water separation efficiency, but also improve the stability of hydrogel coating. The hydrogel interface with excellent stability and superhydrophilic/underwater superoleophobicity can be manufactured on a large copper mesh (1 m × 1.2 m) to achieve large-scale production. The surface-engineered mesh (named cl-PVA/SiNF@Ag-Cu) can be assembled on a self-designed equipment for continuous purification of emulsion wastewater (processing capacity: 576.00 L/day), achieving a high separation efficiency of 99.7 % for complex oily emulsion only under the action of gravity, and can simultaneously recover oils. After being treated under extreme conditions such as strong acid/alkali, high/low temperature (100 °C, 200 °C, and -18 °C), high salt concentration, sandpaper wear, and long-term aging, the surface structure of cl-PVA/SiNF@Ag-Cu filter remains stable. The antifouling, antibacterial, and anticorrosion capabilities of the filter give it the potential for long-term and large-scale purification processes. Planting and breeding experiments have confirmed that purified water is harmless to animals and plants.

Chitosan-Based Biomaterials: Insights into Chemistry, Properties, Devices, and Their Biomedical Applications

Chitosan is a marine-origin polysaccharide obtained from the deacetylation of chitin, the main component of crustaceans’ exoskeleton, and the second most abundant in nature. Although this biopolymer has received limited attention for several decades right after its discovery, since the new millennium chitosan has emerged owing to its physicochemical, structural and biological properties, multifunctionalities and applications in several sectors. This review aims at providing an overview of chitosan properties, chemical functionalization, and the innovative biomaterials obtained thereof. Firstly, the chemical functionalization of chitosan backbone in the amino and hydroxyl groups will be addressed. Then, the review will focus on the bottom-up strategies to process a wide array of chitosan-based biomaterials. In particular, the preparation of chitosan-based hydrogels, organic–inorganic hybrids, layer-by-layer assemblies, (bio)inks and their use in the biomedical field will be covered aiming to elucidate and inspire the community to keep on exploring the unique features and properties imparted by chitosan to develop advanced biomedical devices. Given the wide body of literature that has appeared in past years, this review is far from being exhaustive. Selected works in the last 10 years will be considered.

The promotion mechanism of prebiotics for probiotics: A review

Prebiotics and probiotics play a positive role in promoting human nutrition and health. Prebiotics are compounds that cannot be digested by the host, but can be used and fermented by probiotics, so as to promote the reproduction and metabolism of intestinal probiotics for the health of body. It has been confirmed that probiotics have clinical or health care functions in preventing or controlling intestinal, respiratory, and urogenital infections, allergic reaction, inflammatory bowel disease, irritable bowel syndrome and other aspects. However, there are few systematic summaries of these types, mechanisms of action and the promotion relationship between prebiotics and probiotic. Therefore, we summarized the various types of prebiotics and probiotics, their individual action mechanisms, and the mechanism of prebiotics promoting probiotics in the intestinal tract. It is hoped this review can provide new ideas for the application of prebiotics and probiotics in the future.