Silver nanoparticles have antibacterial properties, but their use has been a cause for concern because they persist in the environment. Here, we show that lignin nanoparticles infused with silver ions and coated with a cationic polyelectrolyte layer form a biodegradable and green alternative to silver nanoparticles. The polyelectrolyte layer promotes the adhesion of the particles to bacterial cell membranes and, together with silver ions, can kill a broad spectrum of bacteria, including Escherichia coli, Pseudomonas aeruginosa and quaternary-amine-resistant Ralstonia sp. Ion depletion studies have shown that the bioactivity of these nanoparticles is time-limited because of the desorption of silver ions. High-throughput bioactivity screening did not reveal increased toxicity of the particles when compared to an equivalent mass of metallic silver nanoparticles or silver nitrate solution. Our results demonstrate that the application of green chemistry principles may allow the synthesis of nanoparticles with biodegradable cores that have higher antimicrobial activity and smaller environmental impact than metallic silver nanoparticles.

Transfer of repetition effects across changes in the context and the surface form of words being read aloud is used to diagnose the degree of abstraction at which perceptual encoding operations take place during reading. Complete transfer is observed for changes from textually coherent to randomly scrambled word order and vice versa in Experiment 1 and for changes from typed to handwritten surface form and vice versa in Experiment 2. Experiment 3 extends the finding of complete transfer across changes in surface form to texts composed of unfamiliar pseudowords, showing that the abstraction effects of the previous experiment do not require lexical familiarity for their occurrence. Experiment 4 further extends this finding to a situation in which readers explicitly expect surface form to remain the same. The results are consistent with a perceptual system in which encoding operations are (a) very abstract with respect to properties of surface form and (h) relatively independent both of higher order comprehension processes, such as syntactic parsing and proposition formation, and of attended expectations about surface properties over which the operations project their categorizations of stimuli. We argue that the perceptual abstraction observed in these experiments depends on overlearned encoding operations established by reading many different instances of the typographical variations typical of a particular writing system.

Lignin nanoparticles can serve as biodegradable carriers of biocidal actives with minimal environmental footprint. Here we describe the colloidal synthesis and interfacial design of nanoparticles with tunable surface properties using two different lignin precursors, Kraft (Indulin AT) lignin and Organosolv (high-purity lignin). The green synthesis process is based on flash precipitation of dissolved lignin polymer, which enabled the formation of nanoparticles in the size range of 45-250 nm. The size evolution of the two types of lignin particles is fitted on the basis of modified diffusive growth kinetics and mass balance dependencies. The surface properties of the nanoparticles are fine-tuned by coating them with a cationic polyelectrolyte, poly(diallyldimethylammonium chloride). We analyze how the colloidal stability and dispersion properties of these two types of nanoparticles vary as a function of pH and salinities. The data show that the properties of the nanoparticles are governed by the type of lignin used and the presence of polyelectrolyte surface coating. The coating allows the control of the nanoparticles' surface charge and the extension of their stability into strongly basic regimes, facilitating their potential application at extreme pH conditions.

Highlights d S. epidermidis strains within-individual are diverse and evolved from multiple founders d Strain diversity is shaped by purifying selection and transmission events d Strain admixture can suppress virulence and alter metabolism at a population level d Horizontal gene transfer disseminates antibiotic resistance genes within individuals

The β-coronavirus SARS-CoV-2 has caused a global pandemic. Affinity reagents targeting the SARS-CoV-2 spike protein are of interest for the development of therapeutics and diagnostics. We used affinity selection–mass spectrometry for the rapid discovery of synthetic high-affinity peptide binders for the receptor binding domain (RBD) of the SARS-CoV-2 spike protein. From library screening with 800 million synthetic peptides, we identified three sequences with nanomolar affinities (dissociation constants K d = 80–970 nM) for RBD and selectivity over human serum proteins. Nanomolar RBD concentrations in a biological matrix could be detected using the biotinylated lead peptide in ELISA format. These peptides do not compete for ACE2 binding, and their site of interaction on the SARS-CoV-2-spike-RBD might be unrelated to the ACE2 binding site, making them potential orthogonal reagents for sandwich immunoassays. These findings serve as a starting point for the development of SARS-CoV-2 diagnostics or conjugates for virus-directed delivery of therapeutics.