Enzymatic poly(gallic acid)-grafted α-l-lysine inhibits Staphylococcus aureus and Escherichia coli strains with no cytotoxicity for human cells

The α-l-Lysine (LL) grafting onto the enzymatic poly(gallic acid) (PGAL) produces a helicoidal brush-like antimicrobial polymer containing outer positive-charged moieties. Best results are found with ca. 16 mol% α-LL-grafting for the inhibition of gram-positive Staphylococcus aureus and gram-negative Escherichia coli strains. Membrane permeability, confocal and scanning electron microscopy studies suggest a pore-formation and translocation mechanisms by initial electrostatic interaction of positive charged polymer at the negatively charged bacterial membranes. The attained polymer displays high concentration of hemolysis (Hc) in erythrocytes, and no lymphocyte mitochondrial activity. Interestingly, PGAL-LL is not cytotoxic on human dermal fibroblast. The antioxidant activity after the LL hybridization is also demonstrated by DPPH, ORAC, FRAP and hydroxyl radical scavenging, which enhances the preservation of human cells in addition to antimicrobial for this polymer.

Valorisation of plastic waste via metal-catalysed depolymerisation

Metal-catalysed depolymerisation of plastics to reusable building blocks, including monomers, oligomers or added-value chemicals, is an attractive tool for the recycling and valorisation of these materials. The present manuscript shortly reviews the most significant contributions that appeared in the field within the period January 2010–January 2020 describing selective depolymerisation methods of plastics. Achievements are broken down according to the plastic material, namely polyolefins, polyesters, polycarbonates and polyamides. The focus is on recent advancements targeting sustainable and environmentally friendly processes. Biocatalytic or unselective processes, acid–base treatments as well as the production of fuels are not discussed, nor are the methods for the further upgrade of the depolymerisation products.

Efficient conversion of polyamides to ω-hydroxyalkanoic acids: a new method for chemical recycling of waste plastics

An efficient transformation of polyamides to ω-hydroxy alkanoic acids was achieved. Treatment of nylon-12 with supercritical MeOH in the presence of glycolic acid gave methyl ω-hydroxydodecanoate in 85% yield and the alcohol/alkene selectivity in the product was enhanced to up to 9.5:1. The use of (18)O-enriched acetic acid for the reaction successfully introduced an (18)O atom at the alcoholic OH group in the product. This strategy may provide a new and economical solution for the chemical recycling of waste plastics.

Review: mass spectrometry of step-growth polymers

For at least two decades different mass spectrometric techniques have been applied for polymer analysis, including the qualitative determination of chemical compositions, end group identification, functionality type distribution and the determination of the cyclisation extend at each degree of polymerisation. Molecular weights exceeding 100 KDa are provable by MALDI-ToF mass spectrometry. Further, molecular weight distributions are determined by MADLI-ToF. However, there are some hints that, there is a discrimination against higher molecular weight species in samples with polydispersity of more than 1.2. Furthermore, pathways for dendritic and hyper-branched polymers, supramolecular polymers and nano condensates are analysed by help of mass spectrometry.