The development of a robust and portable biosensor for the detection of pathogenic bacteria could impact areas ranging from water-quality monitoring to testing of pharmaceutical products for bacterial contamination. Of particular interest are detectors that combine the natural specificity of biological recognition with sensitive, label-free sensors providing electronic readout. Evolution has tailored antimicrobial peptides to exhibit broad-spectrum activity against pathogenic bacteria, while retaining a high degree of robustness. Here, we report selective and sensitive detection of infectious agents via electronic detection based on antimicrobial peptide-functionalized microcapacitive electrode arrays. The semiselective antimicrobial peptide magainin I--which occurs naturally on the skin of African clawed frogs--was immobilized on gold microelectrodes via a C-terminal cysteine residue. Significantly, exposing the sensor to various concentrations of pathogenic Escherichia coli revealed detection limits of approximately 1 bacterium/μL, a clinically useful detection range. The peptide-microcapacitive hybrid device was further able to demonstrate both Gram-selective detection as well as interbacterial strain differentiation, while maintaining recognition capabilities toward pathogenic strains of E. coli and Salmonella. Finally, we report a simulated "water-sampling" chip, consisting of a microfluidic flow cell integrated onto the hybrid sensor, which demonstrates real-time on-chip monitoring of the interaction of E. coli cells with the antimicrobial peptides. The combination of robust, evolutionarily tailored peptides with electronic read-out monitoring electrodes may open exciting avenues in both fundamental studies of the interactions of bacteria with antimicrobial peptides, as well as the practical use of these devices as portable pathogen detectors.

The antimicrobial peptide microcin J25 (MccJ25) is posttranslationally matured from a linear preprotein into its native lasso conformation by two enzymes. One of these enzymes cleaves the preprotein and the second enzyme installs the requisite isopeptide bond to establish the lasso structure. Analysis of a mimic of MccJ25 that can be cyclized without the influence of the maturation enzymes suggests that MccJ25 does not spontaneously adopt a near-lasso structure. In addition, we conducted atomistically detailed replica-exchange molecular dynamics simulations of pro-microcin J25 (pro-MccJ25), the 21-residue uncyclized analog of MccJ25, to determine the conformational ensemble explored in the absence of the leader sequence or maturation enzymes. We applied a nonlinear dimensionality reduction technique known as the diffusion map to the simulation trajectories to extract two global order parameters describing the fundamental dynamical motions of the system, and identify three distinct pathways. One path corresponds to the spontaneous adoption of a left-handed lasso, in which the N-terminus wraps around the C-terminus in the opposite sense to the right-handed topology of native MccJ25. Our computational and experimental results suggest a role for the MccJ25 leader sequence and/or its maturation enzymes in facilitating the adoption of the right-handed topology.

Antibody-dependent enhancement (ADE) exists in several kinds of virus. It has a negative influence on antibody therapy for viral infection. This effect was first identified in dengue virus and has since also been described for coronavirus. To date, the rapid spread of the newly emerged coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causing coronavirus disease 2019 (COVID-19), has affected over 3.8 million people across the globe. The novel coronavirus poses a great challenge and has caused a wave of panic. In this review, antibody-dependent enhancements in dengue virus and two kinds of coronavirus are summarized. Possible solutions for the effects are reported. We also speculate that ADE may exist in SARS-CoV-2.

The crosslinking of the core of nanoparticles composed of polystyrene-block-poly(ethylene oxide) copolymers can be achieved through encapsulation of a small molecule aryl diazide, 4,4 0diazidobiphenyl, and subsequent photolysis. The core-crosslinked nanoparticles exhibited high stability under thermal challenge. These stabilized nanoparticles have potential to serve as a nanobead for the polymerase chain reaction (PCR). We also demonstrated that this crosslinker can endow thin films of polystyrene with solvent resistance. NMR studies on these films provided evidence that crosslinking was occurring via insertion of the nitrene formed by photolysis of the azide into the methylene or methine groups in the backbone of polystyrene.

Extracellular vesicles (EV)-based delivery of therapeutic mRNAs is challenged by the low loading efficiency. In this study, we designed a DNA aptamer consisting of two parts: the single strand part recognized the AUG region of target mRNA, preventing mRNA from translation and ribosome assembly; and the double strand part containing the elements recognized by the CD9-ZF (zinc finger) motifs, sorting DNA aptamer-mRNA complex into CD9-ZF engineered EVs. In vitro and in vivo studies revealed that the system could efficiently load functional mRNAs to the EVs. Furthermore, adipose specific delivery of loaded Pgc1α mRNA via the strategy could efficiently induce white adipocyte browning. Similarly, delivery of interleukin-10 (Il-10) mRNA via the strategy had potent anti-inflammatory effect in inflammatory bowel disease (IBD) mouse model. Together, our study has proposed an efficient strategy to load therapeutic mRNAs of interest into EVs, which could be used as a promising strategy for gene therapy.