Detection and Difference Analysis of the Enzyme Activity of Colloidal Gold Nanoparticles With Negatively Charged Surfaces Prepared by Different Reducing Agents

Nanozymes are particles with diameters in the range of 1–100 nm, which has been widely studied due to their biological enzyme-like properties and stability that natural enzymes do not have. In this study, several reducing agents with different structures (catechol (Cc), hydroquinone (Hq), resorcinol (Rs), vitamin C (Vc), pyrogallic acid (Ga), sodium citrate (Sc), sodium malate (Sm), and sodium tartrate (St)) were used to prepare colloidal gold with a negative charge and similar particle size by controlling the temperature and pH. The affinity analysis of the substrate H2O2 and TMB showed that the order of activities of colloidal gold Nanozymes prepared by different reducing agents was Cc, Hq, Rs, Vc, Ga, Sc, Sm, St. It was also found that the enzyme activity of colloidal gold reduced by benzene rings is higher than that of the colloidal gold enzyme reduced by linear chains. Finally, we discussed the activity of the colloidal gold peroxidase based on the number and position of isomers and functional groups; and demonstrated that the nanozymes activity is affected by the surface activity of colloidal gold, the elimination of hydroxyl radicals and the TMB binding efficiency.

Development of Immunochromatographic Assay for the Rapid Detection of Mycoplasma capricolum subsp. capripneumoniae Antibodies

Mycoplasma capricolum subsp. capripneumoniae (Mccp) is the cause of contagious caprine pleuropneumonia (CCPP), which is a highly significant respiratory disease in goats leading to significant economic losses in Africa and Asia. Currently available procedures for the diagnosis of CCPP have some limitations in sensitivity, specificity, operation time, requirement of sophisticated equipment or skilled personnel, and cost. In this study, we developed a rapid, sensitive, and specific colloidal gold-based immunochromatographic assay (GICA) strip for the efficient on-site detection of antibodies against Mccp in the serum within 10 min. For the preparation of this colloidal GICA strip, recombinant P20 protein, the membrane protein of Mccp, was expressed by Escherichia coli prokaryotic expression system after purification was used as the binding antigen in the test. The rabbit anti-goat immunoglobulin G labeled with the colloidal gold was used as the detection probe, whereas the goat anti-rabbit immunoglobulin G was coated on the nitrocellulose membrane as the control line. The concentration of the coating antibody was optimized, and the effectiveness of this colloidal GICA strip was evaluated. Our results proved that the detection limit of the test strip was up to 1:64 dilutions for the Mccp antibody-positive serum samples with no cross-reactivity with other pathogens commonly infecting small ruminants,including goat pox virus, peste des petits ruminants virus, foot-and-mouth disease virus type A, or other mycoplasmas. Moreover, the colloidal GICA strip was more sensitive and specific than the indirect hemagglutination assay for the detection of Mccp antibodies. The 106 clinical serum samples were detected by the colloidal GICA strip compared with the complement fixation test, demonstrating an 87.74% concordance with the complement fixation test. This novel colloidal GICA strip would be an effective tool for the cost-effective and rapid diagnosis of CCPP in the field.

Emergence and Genomic Characterization of a KPC-2-, NDM-1-, and IMP-4-Producing Klebsiella michiganensis Isolate

A rectal swab sample was collected from a patient with Guillain–Barré syndrome and enriched in lysogeny broth. Carbapenem-resistant bacteria were selected by China Blue agar plates containing 0.3 μg/ml meropenem. Carbapenemase-producing Klebsiella michiganensis was identified and characterized by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF), immune colloidal gold technique, a conjugation experiment, PCR analysis, and antimicrobial susceptibility testing. The genome of K. michiganensis was determined by whole genome sequencing. Antimicrobial susceptibility testing showed that the K. michiganensis was resistant to imipenem, meropenem, ertapenem, cefmetazole, ceftazidime, cefotaxime, piperacillin/tazobactam, sulbactam/cefoperazone, ceftazidime/avibactam, cefepime, and aztreonam while susceptible to polymyxin B, ciprofloxacin, tigecycline, and amikacin. Immune colloidal gold technique suggested that this strain co-produced three different carbapenemases [Klebsiella pneumoniae carbapenemase (KPC), New Delhi metallo-beta-lactamase (NDM), and Imipenem (IMP)]. Whole genome sequencing analysis indicated that this strain belonged to ST91, and blaKPC–2, blaNDM–1, and blaIMP–4 were carried on different conjugative plasmids. Besides, the co-existence and transferability of blaKPC–2, blaNDM–1, and blaIMP–4 in K. michiganensis facilitates the potential horizontal dissemination and nosocomial spread of resistance genes among multidrug-resistant organisms.

Boosting the catalytic behavior and stability of a gold catalyst with structure regulated by ceria

In this work, a series of colloidal gold nanoparticles with controllable sizes and CeO2 promotion were anchored on carbon nanotubes (CNT) for the aerobic oxidation of benzyl alcohol.

A Smartphone-Based Detection Method of Colloidal Gold Immunochromatographic Strip

The outbreak of the new coronavirus (SARS-CoV-2) infection has become a global public health crisis. Antigen detection strips (colloidal gold) can be widely used in novel coronavirus clinical screening and can even be extended to home self-testing, which provides a practical and effective way for people to obtain health status information away from the crowd. In this paper, a colloidal gold detection system without complex devices is proposed, which is based on smartphone usage along with a mobile-phone software embedded with normalization algorithms and a special designed background paper. The basic principle of the device relies on image processing. First, the data of the green channel of the image captured by a smartphone are selected to be processed. Second, the calibration curves are established using standard black and white card, and the calibration values under different detection environments are obtained by calibration curves. Finally, to verify the validity of the proposed method, various standard solutions with different concentrations are tested. Results show that this method can eliminate the influence of different environments on the test results, the test results in different detection environments have good stability and the variation coefficients are less than 5%. It fully proves that the detection system designed in this paper can detect the result of colloidal gold immunochromatographic strip in time, conveniently and accurately in different environments.

Development and Performance verification of colloidal gold labeled SARS-CoV-2 antigen detection method for routine popular screening of COVID-19 with clinical samples in Poland and China

In this research, we have constructed and optimized the colloidal gold labeled lateral flow strip (LFS) for rapid detection of antigen of SARS-CoV-2 and rapid screening of COVID-19. Based on the constructed and optimized colloidal gold lateral flow strip, the parameters of the LFS have been well evaluated with the clinical samples in the professional labs. The screening performance have also been evaluated from the aspects including the CT values, age distribution and onset of symptoms. Finally, based on the detection results of 420 clinical samples, the LFS can achieve the screening of COVID-19 with the positive percentage agreement (PPA, sensitivity), negative percent agreement (NPA, specificity), the positive predictive value (PPV) and the negative predictive value (NPV) of 96.8%, 100%, 100% and 96.6%, respectively, indicating the powerful potential for practical screening applications in pandemic control. Of great significance, this developed SARS-CoV-2 antigen detection method has also been successfully utilized for screening of delta-variant of SARS-CoV-2.

Merino Becomes Noble: A study of nanogold, wool and nanogold–wool composites

<p>Our research group, led by Professor J. H. Johnston, has developed a novel approach for dyeing merino wool with nanogold [gold nanoparticles (AuNPs)] by coupling the chemistry of gold with that of wool fibres. This utilises the plasmonic properties of nanogold to create attractive fabric colours ranging from pink to purple to grey. The newly created fabric benefits from the synergistic effect of the unique properties of strong merino wool and valuable gold, i.e. the innovative product is intensely coloured, colour fast, naturally hydrophobic, anti-microbial, anti-static as well as having first-rate wearing comfort. This innovation has attracted substantial interest from industry resulting in the collaboration of our research group with leading fabric manufacturers and designers. However, the colour range of this unique high-value product is limited. It was desirable to enlarge the colour range by developing new strategies to create wash fast nanogold–wool composites with a broad colour spectrum. Thus my research aimed to identify and understand the fundamental principles that govern the formation of nanogold–wool composites. Based on the derived knowledge, it was aimed to develop a methodology to covalently link pre-synthesised AuNPs of various colours to the surface of New Zealand merino wool fibres in order to obtain wash fast nanogold–wool composites with a broad colour spectrum. This involved the synthesis, functionalisation and characterisation of colloidal AuNPs, and their application as colourants for wool. The methodology followed three general steps: (1) synthesis of colloidal gold, (2) preparation of the wool surface for the colouring processes, and (3) production of nanogold–wool composites. Each work stage was accompanied by thorough analysis and characterisation of the intermediate and final products. Studying colloidal gold systems and nanogold–wool composites which were previously reported provided the insights that were necessary to develop new methodologies to strongly link AuNPs to wool. For instance, nanogold stabilised by oleylamine produces especially bright pink nanogold–wool composites; however, the AuNP–wool bond is relatively weak. Hence, several AuNP–wool bond types were intensively studied, and as a result of combining the knowledge gained, two approaches were developed to provide a proof-of-concept for the creation of wash fast nanogold–wool composites. These approaches involved a specifically designed, in-house-synthesised capping agent for AuNPs as well as a crosslinker that binds functionalised AuNPs to the reactive sites of wool. In addition to achieving the project aims, my work produced three new systems of colloidal gold in aqueous medium which stand out due to their properties. Specifically, these properties were: (1) being stable without significant electrostatic or steric stabilisation, (2) having a unique surface functionalisation allowing for selective chemistry, and (3) having an intense blue colour as a result of controlling the AuNP shape during synthesis. All three systems show application potential for wool colouration, ligand exchange reactions, surface-enhanced Raman spectroscopy (SERS), and in the field of biomedicine.</p>