Wenshu Zheng

Identification of Bacteria in Water by a Fluorescent Array

We report a method for the rapid and efficient identification of bacteria making use of five probes having fluorescent characteristics (F-array) and subsequent statistical analysis. Eight kinds of bacteria, including normal and multidrug-resistant bacteria, are differentiated successfully. Our easy-to-perform and time-saving method consists of mixing bacteria and probes, recording fluorescent intensity data by automated flow cytometry, and statistical analysis. No washing steps are required in order to identify the different bacteria simultaneously.

Recyclable Colorimetric Detection of Trivalent Cations in Aqueous Media Using Zwitterionic Gold Nanoparticles

This report describes a colorimetric assay for trivalent metal cations (M(3+)) using gold nanoparticles (AuNPs)-modified with oppositely charged thiols that can form intermolecular zwitterionic surfaces. Zwitterionic AuNPs (Zw-AuNPs) are stable in high-salt solutions and well-dispersed in a wide range of pH values. M(3+) including Fe(3+), Al(3+), and Cr(3+) can effectively trigger the aggregation of Zw-AuNPs by interfering with their surface potential, and aggregated AuNPs can be regenerated and recycled by removing M(3+). In our approach, the output signal can be observed by the naked eye within a micromolar (μM) concentration range. Uniquely, our assay is capable of discriminating Fe(3+) from Fe(2+), which is challenging using traditional approaches. More importantly, Zw-AuNPs can be stored stably at room temperature for a long period (3 months) with constant detection performance. Both the cost-effectiveness and the long shelf life make Zw-AuNPs ideal for detecting M(3+) in resource-poor and remote areas.

Composites of Bacterial Cellulose and Small Molecule-Decorated Gold Nanoparticles for Treating Gram-Negative Bacteria-Infected Wounds

Bacterial infections, especially multidrug-resistant bacterial infections, are an increasingly serious problem in the field of wound healing. Herein, bacterial cellulose (BC) decorated by 4,6-diamino-2-pyrimidinethiol (DAPT)-modified gold nanoparticles (Au-DAPT NPs) is presented as a dressing (BC-Au-DAPT nanocomposites) for treating bacterially infected wounds. BC-Au-DAPT nanocomposites have better efficacy (measured in terms of reduced minimum inhibition concentration) than most of the antibiotics (cefazolin/sulfamethoxazole) against Gram-negative bacteria, while maintaining excellent physicochemical properties including water uptake capability, mechanical strain, and biocompatibility. On Escherichia coli- or Pseudomonas aeruginosa-infected full-thickness skin wounds on rats, the BC-Au-DAPT nanocomposites inhibit bacterial growth and promote wound repair. Thus, the BC-Au-DAPT nanocomposite system is a promising platform for treating superbug-infected wounds.

Recent Progress of Colorimetric Assays Based on Gold Nanoparticles for Biomolecules

Abstract Biochemical analysis assays based on colorimetric methods using gold nanoparticles have many advantages such as high sensitivity, good selectivity, naked-eyes readout and complex instruments free. These methods have good prospects in applications. This review mainly focuses on colorimetric assays applying gold nanoparticles for biomolecules detection.

Colorimetric detection of Al(III) in vermicelli samples based on ionic liquid group coated gold nanoparticles

We synthesized ionic liquid (1-ethyl-3-methylimidazolium thiocyanate)-coated gold nanoparticles (IL-Au NPs) using a one-pot method and introduced them in the colorimetric assay for Al3+. IL-Au NPs showed good sensitivity and selectivity. They can determine the concentration of aluminum in vermicelli samples.

Double-Enzymes-Mediated Bioluminescent Sensor for Quantitative and Ultrasensitive Point-of-Care Testing

We report an ultrasensitive, quantitative, and rapid bioluminescent immunosensor (ABS) for point-of-care testing (POCT) of the disease biomarker in clinical samples using double enzymes including alkaline phosphatase (ALP) and luciferase. In the presence of the biomarker, the ALP attached on the surface of immuno-nanocomplex dephosphorylates adenine triphosphate (ATP), subsequently inhibiting the ATP-luciferin-luciferase bioluminescent reaction. The highly sensitive response of ATP (picomolar level) allows for ultrasensitive detection of biomarker via the effective change of the bioluminescence intensity through ALP- and luciferase-catalyzed reactions, which can be quantitatively determined by a portable ATP detector. This ABS fulfills the criteria for POCT that performs sensitive (femtomolar level of biomarkers) and quantitative measurement quickly (less than 1 h) with minimal equipment (portable detector).

In situ formation of peptidic nanofibers can fundamentally optimize the quality of immune responses against HIV vaccine

Herein, we report that the in situ formed peptidic nanofibers facilitate the induction of multiple crucial immunities against HIV DNA vaccine, including polyfunctional T cell response, broad IgG subclasses response, and V1/V2 loop-specific antibody response, all of which can hardly be triggered by HIV DNA vaccine alone. Such novel in situ formation fundamentally overcomes the big hurdle for the applications of such nanofibers, which previously can only trigger these crucial immune responses via adding exogenous alkaline phosphatase. Such robustness of peptidic nanofibers for inducing crucial immune responses may allow better inhibition against HIV than reported materials.

Skiving stacked sheets of paper into test paper for rapid and multiplexed assay

Stacked paper skiving paves the way for industrial manufacturing of paper-based analytical devices for barcode assays. This paper shows that stacked sheets of paper preincubated with different biological reagents and skiving them into uniform test paper sheets allow mass manufacturing of multiplexed immunoassay devices and simultaneous detection of multiplex targets that can be read out by a barcode scanner. The thickness of one sheet of paper can form the width of a module for the barcode; when stacked, these sheets of paper can form a series of barcodes representing the targets, depending on the color contrast provided by a colored precipitate of an immunoassay. The uniform thickness of sheets of paper allows high-quality signal readout. The manufacturing method allows highly efficient fabrication of the materials and substrates for a straightforward assay of targets that range from drugs of abuse to biomarkers of blood-transmitted infections. In addition, as a novel alternative to the conventional point-of-care testing method, the paper-based barcode assay system can provide highly efficient, accurate, and objective diagnoses.

Universal Coating from Electrostatic Self-Assembly to Prevent Multidrug-Resistant Bacterial Colonization on Medical Devices and Solid Surfaces

We provide a facile and scalable strategy for preparing gold nanoparticles (AuNPs)-based antibacterial coating on a variety of surfaces through electrostatic self-assembly. AuNPs conjugated with 4,6-diamino-2-pyrimidinethiol (DAPT, not antibacterial by itself), AuDAPT, can form stable coating on different substrates made from polyethylene (PS), polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), polydimethylsiloxane (PDMS), and SiO2 in one step. Such a coating can efficiently eradicate pathogenic Gram-negative bacteria and even multidrug-resistant (MDR) mutants without causing any side-effect such as cytotoxicity, hemolysis, coagulation, and inflammation. We show that immobilized AuDAPT, instead of AuDAPT released from the substrate, is responsible for killing the bacteria and that the antimicrobial components do not enter into the environment to cause secondary contamination to breed drug resistance. Advantages for such coating include applicability on a broad range of surfaces, low cost, stability, high antibacterial efficiency, good biocompatibility, and low risk in antibiotics pollution; these advantages may be particularly helpful in preventing infections that involve medical devices.

Rapid Detection of Copper in Biological Systems Using Click Chemistry

A fast (1 min), straightforward but efficient, click chemistry-based system that enables the rapid detection of free copper (Cu) ions in either biological fluids or living cells without tedious pretreatment is provided. Cu can quickly induce the conjugation between graphene oxide (GO) and a fluorescent dye via click reaction. On the basis of the high specificity of bioorthogonal reaction and the effective quenching ability of GO, the assay studied in this paper can respond to Cu ions in less than 1 min with excellent selectivity and sensitivity, which is the fastest sensor for Cu as far as it is known. In addition, the application of this system is verified by performing assays in living cells and untreated urine samples from patients suffering from Wilsons Disease. Such a Cu detection system shows great promises in both fundamental research and routine clinical diagnostics.