Fluorescence Quenchers Manipulate the Peroxidase-like Activity of Gold-Based Nanomaterials

The roles of templates consisting of amino acids in the synthesis and application of gold nanoclusters

Gold nanoclusters (AuNCs) with low toxicity, high photostability, and facile synthesis have attracted great attention. The ligand is of great significance in stabilizing AuNCs and regulating their properties. Ligands consisting of amino acids (proteins and peptides) are an ideal template for synthesizing applicative AuNCs due to their inherent bioactivity, biocompatibility, and accessibility. In this review, we summarize the correlation of the template consisting of amino acids with the properties of AuNCs by analyzing different peptide sequences. The selection of amino acids can regulate the fluorescence excitation/emission and intensity, size, cell uptake, and light absorption. By analyzing the role played by AuNCs stabilized by proteins and peptides in the application, universal rules and detailed performances of sensors, antibacterial agents, therapeutic reagents, and light absorbers are reviewed. This review can guide the template design and application of AuNCs when selecting proteins and peptides as ligands.

Development of Optical Differential Sensing Based on Nanomaterials for Biological Analysis

The discrimination and recognition of biological targets, such as proteins, cells, and bacteria, are of utmost importance in various fields of biological research and production. These include areas like biological medicine, clinical diagnosis, and microbiology analysis. In order to efficiently and cost-effectively identify a specific target from a wide range of possibilities, researchers have developed a technique called differential sensing. Unlike traditional "lock-and-key" sensors that rely on specific interactions between receptors and analytes, differential sensing makes use of cross-reactive receptors. These sensors offer less specificity but can cross-react with a wide range of analytes to produce a large amount of data. Many pattern recognition strategies have been developed and have shown promising results in identifying complex analytes. To create advanced sensor arrays for higher analysis efficiency and larger recognizing range, various nanomaterials have been utilized as sensing probes. These nanomaterials possess distinct molecular affinities, optical/electrical properties, and biological compatibility, and are conveniently functionalized. In this review, our focus is on recently reported optical sensor arrays that utilize nanomaterials to discriminate bioanalytes, including proteins, cells, and bacteria.

Protein encapsulation of nanocatalysts: A feasible approach to facilitate catalytic theranostics

Enzyme-mimicking nanocatalysts, also termed nanozymes, have attracted much attention in recent years. They are considered potential alternatives to natural enzymes due to their multiple catalytic activities and high stability. However, concerns regarding the colloidal stability, catalytic specificity, efficiency and biosafety of nanomaterials in biomedical applications still need to be addressed. Proteins are biodegradable macromolecules that exhibit superior biocompatibility and inherent bioactivities; hence, the protein modification of nanocatalysts is expected to improve their bioavailability to match clinical needs. The diversity of amino acid residues in proteins provides abundant functional groups for the conjugation or encapsulation of nanocatalysts. Moreover, protein encapsulation can not only improve the overall performance of nanocatalysts in biological systems, but also bestow materials with new features, such as targeting and retention in pathological sites. This review aims to report the recent developments and perspectives of protein-encapsulated catalysts in their functional improvements, modification methods and applications in biomedicine.

The recognition of aristolochic acid I based on fluorescence quenching of bovine serum albumin-stabilized gold nanoclusters

Aristolochic acid I (AAI) is one of the nephrotoxic derivatives present in genera Aristolochia and Asarum. Although some detection strategies for monitoring AAI have been reported, the application of these methods is limited because they involve tedious preparation and require professional operation. In this work, bovine serum albumin (BSA) has been introduced as a reducing agent and stabilizing agent to synthesize gold nanoclusters with strong red fluorescence for the rapid and effective detection of AAI. Under excitation at 328 nm, the fluorescence intensity at the maximum emission wavelength of the bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs) decreased with the addition of AAI, and the degree of quenching showed a linear relationship with the concentration of AAI from 0.1-12.8 μg mL^-1. The obtained BSA-AuNCs were stable, and quenching in the presence of AAI could be achieved within 10 seconds. Here, we have focused on the application of these gold nanoclusters as an optical sensing material for AAI in rat urine samples, including a discussion on the detection mechanism. The detection result of the fluorescent probe was consistent with that of the HPLC method. In view of this reality, the reported protein-AuNCs sensing platform can serve as a convenient detection strategy in toxicological analyses.