Engineering the Protein Corona Structure on Gold Nanoclusters Enables Red‐Shifted Emissions in the Second Near‐infrared Window for Gastrointestinal Imaging

Antibacterial Nanomaterials: Mechanisms, Impacts on Antimicrobial Resistance and Design Principles

Antimicrobial resistance (AMR) is one of the biggest threats to the environment and health. AMR rapidly invalidates conventional antibiotics, and antimicrobial nanomaterials have been increasingly explored as alternatives. Interestingly, several antimicrobial nanomaterials show AMR-independent antimicrobial effects without detectable new resistance and have therefore been suggested to prevent AMR evolution. In contrast, some are found to trigger the evolution of AMR. Given these seemingly conflicting findings, a timely discussion of the two faces of antimicrobial nanomaterials is urgently needed. This review systematically compares the killing mechanisms and structure-activity relationships of antibiotics and antimicrobial nanomaterials. We then focus on nano-microbe interactions to elucidate the impacts of molecular initiating events on AMR evolution. Finally, we provide an outlook on future antimicrobial nanomaterials and propose design principles for the prevention of AMR evolution.

Industrialization’s eye view on theranostic nanomedicine

The emergence of nanomedicines (NMs) in the healthcare industry will bring about groundbreaking improvements to the current therapeutic and diagnostic scenario. However, only a few NMs have been developed into clinical applications due to a lack of regulatory experience with them. In this article, we introduce the types of NM that have the potential for clinical translation, including theranostics, multistep NMs, multitherapy NMs, and nanoclusters. We then present the clinical translational challenges associated with NM from the pharmaceutical industry’s perspective, such as NMs’ intrinsic physiochemical properties, safety, scale-up, lack of regulatory experience and standard characterization methods, and cost-effectiveness compared with their traditional counterparts. Overall, NMs face a difficult task to overcome these challenges for their transition from bench to clinical use.

Synthesis of gold nanoclusters-loaded lysozyme nanoparticles for ratiometric fluorescent detection of cyanide in tap water, cyanogenic glycoside-containing plants, and soils

The modification of protein-stabilized gold nanoclusters with fluorophores has been intensively applied for the ratiometric detection of biomolecules, metal ions, and anions. This study developed a straightforward strategy to prepare lysozyme nanoparticle-encapsulated gold nanoclusters (LysNP-AuNCs) as a dual-emission probe for the ratiometric sensing of cyanide through fluorescence resonance energy transfer (FRET) without the conjugation of additional fluorophores. The reduction of gold ion precursors with lysozyme generated lysozyme-stabilized AuNCs under an alkaline pH, which were demonstrated to self-assemble into nanoaggregates during the formation of AuNCs. The aggregated lysozyme molecules on the AuNCs were treated with glutaraldehyde, triggering the conversion of the aggregated lysozymes into blue-emitting lysozyme nanoparticles. As a result, the AuNCs were well distributed inside a single lysozyme nanoparticle, as demonstrated by transmission electron microscopy. The presence of cyanide triggered the etching of the AuNCs in the LysNP-AuNCs, leading to the suppression of FRET from lysozyme nanoparticle to AuNCs. The LysNP-AuNC probe was implemented for FRET detection of cyanide with a linear range of 3-100 μM. Additionally, the selectivity of the LysNP-AuNC probe for cyanide toward other anions was remarkably high. The practicality of the proposed probe was evaluated by quantifying cyanide in tap water and soils and monitoring the liberation of hydrogen cyanide from cyanogenic glycoside-containing foods.

Protein adsorption onto nanomaterials engineered for theranostic applications

The key role of biomolecule adsorption onto engineered nanomaterials for therapeutic and diagnostic purposes has been well recognized by the nanobiotechnology community, and our mechanistic understanding of nano-bio interactions has greatly advanced over the past decades. Attention has recently shifted to gaining active control of nano-bio interactions, so as to enhance the efficacy of nanomaterials in biomedical applications. In this review, we summarize progress in this field and outline directions for future development. First, we briefly review fundamental knowledge about the intricate interactions between proteins and nanomaterials, as unraveled by a large number of mechanistic studies. Then, we give a systematic overview of the ways that protein-nanomaterial interactions have been exploited in biomedical applications, including the control of protein adsorption for enhancing the targeting efficiency of nanomedicines, the design of specific protein adsorption layers on the surfaces of nanomaterials for use as drug carriers, and the development of novel nanoparticle array-based sensors based on nano-bio interactions. We will focus on particularly relevant and recent examples within these areas. Finally, we conclude this topical review with an outlook on future developments in this fascinating research field.

Water-Dispersible Gold Nanoclusters: Synthesis Strategies, Optical Properties, and Biological Applications

Atomically precise gold nanoclusters (AuNCs) are an emerging class of quantum-sized nanomaterials. Intrinsic discrete electronic energy levels have endowed them with fascinating electronic and optical properties. They have been widely applied in the fields of optoelectronics, photovoltaics, catalysis, biochemical sensing, bio-imaging, and therapeutics. Nevertheless, most AuNCs are synthesized in organic solvents and do not disperse in aqueous solutions; this restricts their biological applications. In this review, we focus on the recent progress in the preparation of water-dispersible AuNCs and their biological applications. We first review different methods of synthesis, including direct synthesis from hydrophilic templates and indirect phase transfer of hydrophobic AuNCs. We then discuss their photophysical properties, such as emission enhancement and fluorescence lifetimes. Next, we summarize their latest applications in the fields of biosensing, biolabeling, and bioimaging. Finally, we outline the challenges and potential for the future development of these AuNCs.

Activatable NIR-II Fluorescent Probes Applied in Biomedicine: Progress and Perspectives

With the advantage of inherent responsiveness that can change the spectroscopic signals from "off" to "on" state in responding to targets (e. g. biological analytes/microenvironmental factors), activatable fluorescent probes have attracted extensive attention and made significant progress in the field of bioimaging and biosensing. Due to the high depth of tissue penetration, minimal tissue damage and negligible background signal at longer wavelengths, the development of second near-infrared window (NIR-II) fluorescent materials provides a new opportunity to develop activable fluorescent probes. Here, we summarized properties, advantages and disadvantages of mainly NIR-II fluorophores (such as rare earth-doped nanoparticles, quantum dots, single-walled carbon nanotubes, small molecule dyes, conjugated polymers and gold nanoclusters), then overviewed current role and development of activatable NIR-II fluorescent probes (AFPs) for biomedical applications including biosensing, bioimaging and therapeutic. The potential challenges and perspectives of AFPs in deep-tissue imaging and clinical application are also discussed.