Macrophage-membrane-coated hybrid nanoparticles with self-supplied hydrogen peroxide for enhanced chemodynamic tumor therapy.

Addressing the challenges of chemodynamic therapies (CDTs) relying on Fenton reactions in malignant tumors is an active research area. Here, we report a method to develop pH-responsive hybrid nanoparticles for enhanced chemodynamic tumor treatment. Reactive CaO2 nanoparticles (core) are isolated by biocompatible ZIF-8 doped with Fe2+ (shell), and then encapsulated by macrophage membranes (symbolized as CaO2@Fe-ZIF-8@macrophage membrane or CFZM), thus endowed with high stability under normal physiological conditions. Our design features active tumor-homing by the macrophage-membrane coating, tumor microenvironment (TME)-responsive cargo release, and self-supplied hydrogen peroxide for promotion of the Fenton reaction. We demonstrate the improved delivery/tumor cell uptake of CFZM, the efficient production of toxic ˙OH with self-supplied H2O2 in CFZM, and high-efficacy tumor ablation on BALB/c mice bearing CT26 tumor cells. This offers a translational strategy to develop active tumor-targeting and TME-responsive nanotherapeutics with enhanced CDT against malignant tumors.

Ciprofloxacin-Loaded, pH-Responsive PAMAM-Megamers Functionalized with S-Nitrosylated Hyaluronic Acid Support Infected Wound Healing in Mice without Inducing Antibiotic Resistance.

Antimicrobial-resistant bacterial infections threaten to become the number one cause of death by the year 2050. Since the speed at which antimicrobial-resistance develops is exceeding the pace at which new antimicrobials come to the market, this threat cannot be countered by making more, new and stronger antimicrobials. Promising new antimicrobials should not only kill antimicrobial-resistant bacteria, but also prevent development of new bacterial resistance mechanisms in strains still susceptible. Here, PAMAM-dendrimers are clustered using glutaraldehyde to form megamers that are core-loaded with ciprofloxacin and functionalized with HA-SNO. Megamers are enzymatically disintegrated in an acidic pH, as in infectious biofilms, yielding release of ciprofloxacin and NO-generation by HA-SNO. NO-generation does not contribute to the killing of planktonic Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa, but in a biofilm-mode of growth short-lived NO-assisted killing of both ciprofloxacin-susceptible and ciprofloxacin-resistant bacterial strains by the ciprofloxacin released. Repeated sub-culturing of ciprofloxacin-susceptible bacteria in presence of ciprofloxacin-loaded and HA-SNO functionalized PAMAM-megamers does not result in ciprofloxacin-resistant variants as does repeated culturing in presence of ciprofloxacin. Healing of wounds infected by a ciprofloxacin-resistant S. aureus variant treated with ciprofloxacin-loaded, HA-SNO functionalized megamers proceed faster through NO-assisted ciprofloxacin killing of infecting bacteria and stimulation of angiogenesis.

A Heterocatalytic Metal-Organic Framework to Stimulate Dispersal and Macrophage Combat with Infectious Biofilms.

Eradication of infectious biofilms is becoming increasingly difficult due to the growing number of antibiotic-resistant strains. This necessitates development of nonantibiotic-based, antimicrobial approaches. To this end, we designed a heterocatalytic metal-organic framework composed of zirconium 1,4-dicarboxybenzene (UiO-66) with immobilized Pt nanoparticles (Pt-NP/UiO-66). Pt-NP/UiO-66 enhanced singlet-oxygen generation compared with Pt nanoparticles or UiO-66, particularly in an acidic environment. Singlet-oxygen generation degraded phosphodiester bonds present in eDNA gluing biofilms together and therewith dispersed biofilms. Remaining biofilms possessed a more open structure. Concurrently, Pt-NP/UiO-66 stimulated macrophages to adapt a more M1-like, "fighting" phenotype, moving faster toward their target bacteria and showing increased bacterial killing. As a combined effect of biofilm dispersal and macrophage polarization, a subcutaneous Staphylococcus aureus biofilm in mice was more readily eradicated by Pt-NP/UiO-66 than by Pt nanoparticles or UiO-66. Therewith, heterocatalytic Pt-NP/UiO-66 metal-organic frameworks constitute a nonantibiotic-based strategy to weaken protective matrices and disperse infectious biofilms, while strengthening macrophages in bacterial killing.

Metal-Support Interactions of Single-Atom Catalysts for Biomedical Applications.

The development of single-atom catalysts (SACs) has become a rapidly growing research field. It is a critical challenge to understand the interactions between the single-atom metal active sites and the support materials. Recently, original research reports of SACs in biomedical applications have emerged in the literature, yet this topic has seldom been reviewed. Here, this review focuses on the latest advances in single-atom catalysis for biomedical applications and highlights the keys for the design of SACs, such as understanding the interactions between metals and supports and classifying various enzyme-like activities. This review helps bridge the knowledge of multiple disciplines and provides prospects regarding the development of SACs for biomedicine.

Encapsulation of Photothermal Nanoparticles in Stealth and pH-Responsive Micelles for Eradication of Infectious Biofilms In Vitro and In Vivo.

Photothermal nanoparticles can be used for non-antibiotic-based eradication of infectious biofilms, but this may cause collateral damage to tissue surrounding an infection site. In order to prevent collateral tissue damage, we encapsulated photothermal polydopamine-nanoparticles (PDA-NPs) in mixed shell polymeric micelles, composed of stealth polyethylene glycol (PEG) and pH-sensitive poly(ß-amino ester) (PAE). To achieve encapsulation, PDA-NPs were made hydrophobic by electrostatic binding of indocyanine green (ICG). Coupling of ICG enhanced the photothermal conversion efficacy of PDA-NPs from 33% to 47%. Photothermal conversion was not affected by micellar encapsulation. No cytotoxicity or hemolytic effects of PEG-PAE encapsulated PDA-ICG-NPs were observed. PEG-PAE encapsulated PDA-ICG-NPs showed good penetration and accumulation in a Staphylococcus aureus biofilm. Penetration and accumulation were absent when nanoparticles were encapsulated in PEG-micelles without a pH-responsive moiety. PDA-ICG-NPs encapsulated in PEG-PAE-micelles found their way through the blood circulation to a sub-cutaneous infection site after tail-vein injection in mice, yielding faster eradication of infections upon near-infrared (NIR) irradiation than could be achieved after encapsulation in PEG-micelles. Moreover, staphylococcal counts in surrounding tissue were reduced facilitating faster wound healing. Thus, the combined effect of targeting and localized NIR irradiation prevented collateral tissue damage while eradicating an infectious biofilm.

Cationization of neutral small molecules by site-specific carboxylation of 10-phenyl-10H-phenothiazine in laser desorption/ionization.

It is a pre-requisite to ionize analyte molecules efficiently for detection by laser desorption/ionization mass spectrometry. Here, we report a conceptual demonstration of cationizing neutral small molecules which are typically difficult to be ionized with the traditional organic matrices due to their low proton/cation affinity values. Our strategy features generating radical cations from site-specifically carboxylated 10-(4-carboxyphenyl)-10H-phenothiazine-3,7-dicarboxylic acid (PTZ(A)2-Ph(A)) with a laser, and anchoring the chlorine ion from NaCl through covalent bond-like bridging interactions with the N/S atoms in the heterocyclic structure. This "Maverick" design allows a dramatic change of the energy landscape of analyte sodiation with an enhanced efficiency. We have synthesized two families of compounds based on the model structures of phenothiazine (PTZ) and phenoxazine (PXZ) and their carboxylated derivatives, and performed comparison between them or against the traditional organic matrices in a systematic format. We have demonstrated that PTZ(A)2-Ph(A) is outstanding as a novel MALDI matrix for the detection of oligosaccharides and amino acids, with an ultra-clean background baseline and high signal-to-noise ratios (up to dozens of times better than the traditional matrices). This work provides a new method for the cationization of neutral small molecules in a distinct mechanism, inspiring the development of next-generation matrices for sensitive detection of hard-to-be-ionized molecules by MALDI MS.

PAMAM dendrimers with dual-conjugated vancomycin and Ag-nanoparticles do not induce bacterial resistance and kill vancomycin-resistant Staphylococci.

The effective life-time of new antimicrobials until the appearance of the first resistant strains is steadily decreasing, which discourages incentives for commercialization required for clinical translation and application. Therefore, development of new antimicrobials should not only focus on better and better killing of antimicrobial-resistant strains, but as a paradigm shift on developing antimicrobials that prevent induction of resistance. Heterofunctionalized, poly-(amido-amine) (PAMAM) dendrimers with amide-conjugated vancomycin (Van) and incorporated Ag nanoparticles (AgNP) showed a 6-7 log reduction in colony-forming-units of a vancomycin-resistant Staphylococcus aureus strain in vitro, while not inducing resistance in a vancomycin-susceptible strain. Healing of a superficial wound in mice infected with the vancomycin-resistant S. aureus was significantly faster and more effective by irrigation with low-dose, dual-conjugated Van-PAMAM-AgNP dendrimer suspension than by irrigation with vancomycin in solution or a PAMAM-AgNP dendrimer suspension. Herewith, dual-conjugation of vancomycin together with AgNPs in heterofunctionalized PAMAM dendrimers fulfills the need for new, prolonged life-time antimicrobials killing resistant pathogens without inducing resistance in susceptible strains. Important for clinical translation, this better use of antibiotics can be achieved with currently approved and clinically applied antibiotics, provided suitable for amide-conjugation.

Structure and Role of BCOR PUFD in Noncanonical PRC1 Assembly and Disease.

Polycomb repression complex 1 (PRC1) is a multiprotein assembly that regulates transcription. The Polycomb group ring finger 1 protein (PCGF1) is central in the assembly of the noncanonical PRC1 variant called PRC1.1 through its direct interaction with BCOR (BCL-6-interacting corepressor) or its paralog, BCOR-like 1 (BCORL1). Previous structural studies revealed that the C-terminal PUFD domain of BCORL1 is necessary and sufficient to heterodimerize with the RAWUL domain of PCGF1 and, together, form a new protein-protein binding interface that associates with the histone demethylase KDM2B. Here, we show that the PUFD of BCOR and BCORL1 differ in their abilities to assemble with KDM2B. Unlike BCORL1, the PUFD of BCOR alone does not stably assemble with KDM2B. Rather, additional residues N-terminal to the BCOR PUFD are necessary for stable association. Nuclear magnetic resonance (NMR) structure determination and 15N T2 relaxation time measurements of the BCOR PUFD alone indicate that the termini of the BCOR PUFD, which are critical for binding PCGF1 and KDM2B, are disordered. This suggests a hierarchical mode of assembly whereby BCOR PUFD termini become structurally ordered upon binding PCGF1, which then allows stable association with KDM2B. Notably, BCOR internal tandem duplications (ITDs) leading to pediatric kidney and brain tumors map to the PUFD termini. Binding studies with the BCOR ITD indicate the ITD would disrupt PRC1.1 assembly, suggesting loss of the ability to assemble PRC1.1 is a critical molecular event driving tumorigenesis.

Circumventing antimicrobial-resistance and preventing its development in novel, bacterial infection-control strategies.

INTRODUCTION: Development of new antimicrobials with ever 'better' bacterial killing has long been considered the appropriate response to the growing threat of antimicrobial-resistant infections. However, the time-period between the introduction of a new antibiotic and the appearance of resistance amongst bacterial pathogens is getting shorter and shorter. This suggests that alternative pathways than making ever 'better' antimicrobials should be taken. AREAS COVERED: This review aims to answer the questions (1) whether we have means to circumvent existing antibiotic-resistance mechanisms, (2) whether we can revert existing antibiotic-resistance, (3) how we can prevent the development of antimicrobial-resistance against novel infection-control strategies, including nano-antimicrobials. EXPERT OPINION: Relying on relieving antibiotic-pressure and natural outcompeting of antimicrobial-resistant bacteria seems an uncertain way out of the antibiotic-crisis facing us. Novel, non-antibiotic, nanotechnology-based infection control-strategies are promising. At the same time, rapid development of new resistance mechanisms once novel strategies is taken into global clinical use, may not be ruled out and must be closely monitored. This suggests focusing research and development on designing suitable combinations of existing antibiotics with new nano-antimicrobials in a way that induction of new antimicrobial-resistance mechanisms is avoided. The latter suggestion, however, requires a change of focus in research and development.

Sensitive detection of caspase-3 enzymatic activities and inhibitor screening by mass spectrometry with dual maleimide labelling quantitation.

There is a great need to develop sensitive and specific methods for quantitative analysis of caspase-3 activities in cell apoptosis. Herein, we report a new method for sensitive detection of caspase-3 enzyme activities and inhibitor screening based on dual maleimide (DuMal) labeling quantitation and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Evaluation of caspase-3 activities is performed using MS analysis of the enzymatic product of the peptide probe, which fuses a caspase-3 cleavable peptide segment (DEVD) and a quantifiable "ID tag" (a peptide segment of FRGLRGFKC labeled by maleimide). The DuMal labeling technique features non-isotopic tagging, rapid reactions, and reproducible quantitation. We have achieved quantitative analysis of the enzyme activities with a limit of detection (LOD) and limit of quantitation (LOQ) of caspase-3 down to 0.11 nM and 0.29 nM respectively and a proof-of-concept demonstration of its inhibitor screening. Our method has further been tested for caspase-3 activities in a Parkinson's disease cellular model, suggesting a useful tool for protease activity research.

Surfactant-Free Preparation of Au@Resveratrol Hollow Nanoparticles with Photothermal Performance and Antioxidant Activity.

Nanocomposites based on hollow Au nanostructures have gained considerable attention in theranostics applications because of their unique plasmonic structures and attractive physicochemical properties. The exploration of feasible and facile methods for constructing multifunctional nanocomposites combined with bioactive molecules is greatly needed for the development of multifunctional theranostics platforms. In this work, resveratrol, a natural polyphenol with antioxidant activity and cancer-chemopreventive propertyies is employed as the reducing agent cum coating agent for the surfactant-free preparation of Au@resveratrol hollow NPs (Au@Res HNPs). The as-prepared Au@Res HNPs were found to present good photothermal performance and chemical inhibition for cancer therapy. In vitro experiments indicated that the Au@Res HNPs can block cell cycles to inhibit cell division and lead to cell apoptosis after 808-nm laser irradiation. Because no toxic surfactants are introduced, the current protocol avoids the tedious surfactant separation and surface modification processes that are necessary for most theranostics materials.

Depolymerization of Free-Radical Polymers with Spin Migrations.

The mechanism of depolymerization is one of the most essential issues in chemical engineering and materials science. In this work, we investigate the depolymerization reactions of three typical free-radical poly(alpha-methylstyrene) tetramers by using first-principles density functional theory. The calculated results show that these reactions all need to overcome the energy barriers in the range of 0.58 to 0.77 eV, and that breaking the C-C bond at the chain end leads to the dissociation of alpha-methylstyrene monomers from the polymers. Electronic-structure analysis indicates that the reactions occur easily at the CR3 unsaturated end, and that the frontier molecular orbitals that participate in the reactions are mainly localized at the unsaturated ends. Meanwhile, spin population analysis presents the unique net spin-transfer process in free-radical depolymerization reactions. We hope the current findings can contribute to understanding the free-radical depolymerization mechanism and help guide future experiments.