Yuqing Wu

Regulation on the aggregation-induced emission (AIE) of DNA-templated silver nanoclusters by BSA and its hydrolysates

The aggregation-induced emission (AIE) phenomenon of the metal nanoclusters (NCs) has been discovered quite recently, which is considered to be creative to improve the optical properties of NCs upon ligand aggregation. In the present study, we report an AIE system for double-stranded DNA-templated silver nanoclusters (AgNCs-dsDNA) by using bovine serum albumin (BSA) in solution, which induce a moderate emission enhancement of AgNCs (5-fold) and a blue-shift through a loosen interaction. In addition, significant luminescence enhancement (30-fold) is further stimulated by the addition of digestive enzyme to the system by altering the surface structure of the aggregated particles. The processes are observed directly through transmission electron microscopy (TEM), where the dispersed AgNCs spheres are aggregated in a large incompact sheet-like film by BSA; while further trypsin addition lead them into larger particles (>50nm) with higher density. And the intrinsic mechanism is explained well by UV-vis absorption and time-resolved luminescence spectra. The observed luminescence enhancement in step-II is attributed to the AIE through stronger interaction between the hydrolysates of BSA and the ligand dsDNA. Therefore, the optical properties of AgNCs-dsDNA are regulated well by the addition of BSA and trypsin in different amounts, which relates directly to the degree of aggregation and can be extended to other metal nanoclusters by employing the pairs of protein and related enzyme.

Co-assembly of polyoxometalates and peptides towards biological applications

The synergistic self-assembly of biomolecules with polyoxometalates (POMs) has recently been considered as an effective approach to construct nano-biomaterials with diverse structures and morphologies towards applications in drug delivery, controlled release, tissue engineering scaffolds, and biomineralization, due to the unique features of the clusters in addition to many well-known inorganic nanoparticles. This review presents an overview of recent work focusing on the noncovalent co-assembly of peptides and POMs as well as their biological applications. In the co-assemblies triggered by the interaction between the components significant advantages are observed that POMs or peptides alone do not possess; examples include chiral recognition of hybrid metal oxides, the quick hydrolysis of peptides, and enhanced inhibition of Aβ aggregation. Finally, we outline a brief perspective on possible unresolved issues and future opportunities in this field.

Thermally prepared ultrabright adenosine monophosphate capped gold nanoclusters and the intrinsic mechanism

Gold nanoclusters (AuNCs) have been widely applied in fluorescence sensing, bioimaging and phototherapy. Although great progress has been made, the relatively low quantum yield (QY, <10%) in most currently reported AuNCs limits their application greatly. In the present study, adenosine monophosphate (AMP) capped gold nanoclusters (AuNC@AMP) are prepared by using a newly developed heating method in a short time (within 60 min), and are found to show a strong and stable luminescence emission in a relative high QY (14.52%). In addition, an in-depth investigation by employing infrared, 1H and 31P NMR spectroscopy has attributed the origin of such a high luminescence to both the binding of the purine ring and/or the phosphate moiety of AMP as well as their orientations at the gold core surface. In addition, electron-rich atoms such as nitrogen and oxygen, or group moieties such as -NH2 in the ligands can largely promote the luminescence emission of AuNCs. The present study reveals the intriguing generation of ultrabright luminescence from metal nanoclusters, and it will stimulate more research both on the fabrication and practical applications of luminescent metal NCs. With regard to the high QY of these AuNCs, they have great potential for biological applications as adenine is crucially important in life sciences.

Disperse magnetic solid phase microextraction and surface enhanced Raman scattering (Dis-MSPME-SERS) for the rapid detection of trace illegally chemicals

The technique of solid phase micro-extraction (SPME) is an important method for sample pretreatment in analytical chemistry, especially for the analysis in micro-systems. Surface enhanced Raman scattering (SERS) is an ultra-sensitive and fast detection technique. Both are particularly important in qualitative analysis of trace amount of substance. In this study, combining the magnetic nanoparticles with magnetic SPME device, we develop a high efficient new pretreatment method named as disperse magnetic solid phase micro-extraction (Dis-MSPME). In comparison to the traditional SPME, the proposed Dis-MSPME realizes solid phase micro-extraction from dispersive system, which improved the extraction efficiency largely. Conjunction the advantages both of Dis-MSPME and SERS is proposed as Dis-MSPME-SERS as a new detection method, which realize enrichment, magnetic separation and detection all-in-one. Making it a simpler, more efficient and sensitive approach in identifying the illegal additives. Sildenafil citrate (SC) in 500μL health wine as an example of illegal additive was successfully detected in a LOD of 1.0 × 10-8M. Moreover, comparative study on the extract efficient of Dis-MSPME-SERS with SPME-SERS shows it takes only 10min to detect sildenafil citrate in the health wine, from enrichment to detection by Dis-MSPME-SERS.

A highly selective and sensitive fluorescent probe for lactate dehydrogenase based on ultrabright adenosine monophosphate capped gold nanoclusters

Ultrabright adenosine monophosphate (AMP) capped gold nanoclusters (AuNCs@AMP) were used as a novel fluorescent probe to detect lactate dehydrogenase (LDH), an important biomarker of common injuries and diseases. The fluorescence emission of AuNCs@AMP is quenched linearly in the presence of a wide concentration range of LDH (50–1000 nM), covering the range for clinical diagnosis. Particularly, the detection is very sensitive with an extremely low detection limit of 0.2 nM (26 pg μL−1, 0.8 U L−1), being more sensitive than the previously reported ones. However, the proposed probe does not response to other commercially available proteins with different isoelectric points, which shows a high selectivity toward LDH. In addition, the response mechanism is also investigated in detail, where the quenching response is attributed to the binding of AuNCs to the free thiol groups at the LDH surface. Therefore, the present study supplies a cost-effective, fast and easily performed approach to detect LDH with high selectivity and sensitivity, which has potential use in clinical diagnosis in future.

Hydrothermal synthesis of novel photosensitive gold and silver bimetallic nanoclusters protected by adenosine monophosphate (AMP)

Herein, a rapid and effective hydrothermal synthesis method was employed for the preparation of Au and Ag bimetallic nanoclusters protected by adenosine monophosphate (Au–AgNCs@AMP); the Au–AgNCs@AMP show large Stokes shift (∼200 nm) and strong luminescence emission with a high quantum yield (QY = 8.46%). Moreover, to the best of our knowledge, it is for the first time that the hydrothermal synthesis method has been employed to prepare bimetal nanoclusters protected by small molecules, which is a simple, easy-to-operate, one-pot, and time saving method. Through employing gold nanoclusters as seed and monitoring the preparation process, it can be understood that Au–AgNCs@AMP are formed with a core–shell structure, where gold atoms serve as the core and silver atoms are distributed on the surface as a shell. In addition, the Au–AgNCs@AMP show an obvious color change and turned from colorless to orange accompanied by a slight luminescence quenching upon exposure to sunlight; moreover, a new absorption peak appears between 400 and 500 nm, which gradually increases with the exposure time, and the mean particle size of the products also increases from 2.25 to 10.0 nm. The intrinsic mechanism of the novel photosensitivity has been attributed to the hydroxyl groups on the sugar ring of AMP that react with silver ions on the surface of the bimetal nanoclusters and induce an increase in the particle size. Herein, we have presented a new and feasible synthesis method for small molecule-protected bimetal nanoclusters to improve their luminescence properties.

Two-dimensional correlation spectroscopy in protein science, a summary for past 20 years

Two-dimensional correlation spectroscopy (2DCOS) has been widely used to Infrared, Raman, Near IR, Optical Activity (ROA), Vibrational Circular Dichroism (VCD) and Fluorescence spectroscopy. In addition, several new developments, such as 2D hetero-correlation analysis, moving-window two-dimensional (MW2D) correlation, model based correlation (βν and kν correlation analyses) have also well incorporated into protein research. They have been used to investigate secondary structure, denaturation, folding and unfolding changes of protein, and have contributed greatly to the field of protein science. This review provides an overview of the applications of 2DCOS in the field of protein science for the past 20 year, especially to memory our old friend, Dr. Boguslawa Czarnik-Matusewicz, for her great contribution in this research field. The powerful utility of 2DCOS combined with various analytical techniques in protein studies is summarized. The noteworthy developments and perspective of 2DCOS in this field are highlighted finally.

Cell receptor screening for human papillomavirus invasion by using a polyoxometalate-peptide assembly as a probe

The present study constructed a competitive recognition system using cell receptor screening for human papillomavirus (HPV) invasion by using the hybrid-assembly of polyoxometalates (POMs) and cationic peptides as a platform. The fine tuning both of the surface charge of POMs and peptide sequence were precisely performed to develop a luminescence switch of POMs, leading to the establishment of a ternary system to identify which types of glycosaminoglycans (GAGs) are potential cell receptors for HPV infection. In addition, the method was successfully applied to construct a hybrid-assembly with the recombined HPV 16 L1 pentamers from Escherichia coli and perform GAGs screening, which validated the systems potential for practical applications. In particular, the intrinsic mechanism for each competitive partner in the system was explained well by using isothermal titration calorimetry (ITC) and time-resolved fluorescence spectra. The present method will be helpful to extend the protocol to other systems by using peptides and POMs with similar properties, and ultimately, we hope it will promote the development of anti-viral agents.