A platinum glutamate acid complex as a peroxidase mimic: high activity, controllable chemical modification, and application in biosensors.

Recent strides in nanotechnology have given rise to nanozymes, nanomaterials designed to emulate enzymatic functions. Despite their promise, challenges such as batch-to-batch variability and limited atomic utilization persist. This study introduces Pt(Glu)2, a platinum glutamic acid complex, as a versatile small-molecule peroxidase mimic. Synthesized through a straightforward method, Pt(Glu)2 exhibits robust catalytic activity and stability. Steady-state kinetics reveal a lower Km value compared to that of natural enzymes, signifying strong substrate affinity. Pt(Glu)2 was explored for controllable chemical modification and integration into cascade reactions with natural enzymes, surpassing other nanomaterials. Its facile synthesis and seamless integration enhance cascade reactions beyond the capabilities of nanozymes. In biosensing applications, Pt(Glu)2 enabled simultaneous detection of cholesterol and alkaline phosphatase in human serum with high selectivity and sensitivity. These findings illustrate the potential of small molecule mimetics in catalysis and biosensing, paving the way for their broader applications.

Economic burden attributable to healthcare-associated infections at western China hospitals: 6 Year, prospective cohort study.

OBJECTIVES: Healthcare-associated infections (HAIs) represent a major threat to patient safety and are associated with significant economic burden. Calculating the costs attributable to HAIs is challenging given the various sources of bias. Although HAIs as a reasonably preventable medical harm should have been closely linked to medical insurance incentives, there was little linkage between HAIs and medicare in western China owing to the lack of economic evaluation data. The present study aimed to generate estimates of the attributable costs associated with HAIs and the magnitude of costs growth. METHODS: In this cohort study designed horizontally and vertically from 2016 to 2022, we compared outcomes of randomly sampling patients with HAIs and individually matched patients without HAIs in two cohorts at a 6-year interval at 34 hospitals in western China. The primary outcome was the direct medical cost for the entire hospital stay, converted to US dollars ($ for the benchmark year), discounted at 3% annually, and estimated separately in the full analysis set (FAS) and the per protocol set (PPS). We used multiple linear regression to adjust the discounted costs and to assess subgroups effects within each cohort. We nested a dynamic vertical comparison of costs attributable to HAIs between the front and rear cohorts. RESULTS: A total of 230 patients with HAIs in 2016 and 204 patients with HAIs in 2022 were enrolled. After a 1:1 match, all 431 pairs were recruited as FAS, of which 332 pairs as PPS met all matching restrictions. Compared to the 2016 cohort in FAS, the patients with HAIs in 2022 had a significantly older age (64.40 ± 16.45 years), higher repeat hospitalization rate (65 [32.02%] of 203), and lower immune function (69 [33.99%] of 203). The discounted costs and adjusted-discounted costs for patients with HAIs in the 2022 cohort were found to be significantly higher than those of patients without HAIs (discounted costs: $5484.60 [IQR 8426.03] vs $2554.04(4530.82), P < 0.001; adjusted-discounted costs: $5235.90 [3772.12] vs $3040.21(1823.36), P < 0.001, respectively), and also higher than those of patients with HAIs in the 2016 cohort (discounted costs: $5484.60 [8426.03] vs $3553.00 [6127.79], P < 0.001; adjusted-discounted costs: $5235.90 [3772.12] vs $3703.82 [3159.14], P < 0.001, respectively). In vertical comparison of PPS, the incremental costs of the 2022 cohort are 1.48 times higher than those of the 2016 cohort ($964.63(4076.15) vs $652.43 [2533.44], P = 0.084). CONCLUSIONS: This meticulously designed study in western China has successfully and accurately examined the economic burden attributable to HAIs. Their rapidly increasing tendency poses a serious challenge to patients, hospitals, and the medical insurance. A closer linkage between HAIs and ongoing motivating system changes is urgently needed in western China.

Enhancement and inactivation effect of CRISPR/Cas12a via extending hairpin activators for detection of transcription factors.

An enhancement effect for the activation of CRISPR/Cas12a (CRISPR = clustered regularly interspaced short palindromic repeats; Cas = CRISPR-associated) was discovered. That was, a hairpin model with dangling 5' end complementary to crRNA (CRISPR RNA) greatly improved the activity of CRISPR/Cas12a after extention of two random sequences. But, the corresponding intact hairpin without PAM (protospacer adjacent motif) or suboptimal PAM sequences was completely inactive to CRISPR/Cas12a because of the superhigh stability of intact hairpin. According to the finding, a CRISPR/Cas12a-based strategy coupled with a signal reported system was designed for transcription factors detection. By using mono-labeled ssDNA (single-stranded DNA) as reporter and two newly synthesized N-C (nitrogen-doped carbon) nanosheets as scavenger to eliminate the fluorescent background, the strategy realized the detection of NF-ĸB p50 (p50 subunit of nuclear factor kappa-B) with a linear detection range of 0.8 - 2000.0 pM and a LOD of 0.5 pM. The discovery of "enhancement and inactivation effect" not only deepened insight into CRISPR/Cas12a but also broadened the practical application of CRISPR/Cas systems for the molecular detection and disease diagnostics.

A dual-mode strategy based on ß-galactosidase and target-induced DNA polymerase protection for transcription factor detection using colorimetry and a glucose meter.

In this work, we report a novel dual-mode method for the highly specific and sensitive detection of transcription factors (TFs) via the integration of Klenow polymerase protection induced by target-specific recognition, cascade-signal amplification using the hybridization chain reaction (HCR) and CRISPR/Cas12a system, and dual-signal transduction mediated by ß-galactosidase (ß-gal) and two substrates. A dual-mode signal-sensing interface was constructed by immobilizing the oligo DNA probe (P1) tethered ß-gal in a 96-well plate. A hairpin H1 with the ability to initiate HCRs was designed to contain the TF binding site. The binding between the TF and H1 protected the H1 from being extended by the Klenow fragment. After thermal denaturation, the reserved H1 launched the HCR and the HCR products activated CRISPR/Cas12a to cleave P1 and reduce the ß-gal on the sensing interface, and thus the contents of the TFs and the corresponding signals mediated by the catalysis of ß-gal showed a correlation. This work was the first attempt at utilizing ß-gal for dual-signal transduction. It is a pioneering study to utilize the HCR-CRISPR/Cas12a system for dual-mode TF sensors. It revealed that DNA polymerase protection through the binding of TF and DNA could be applied as a new pattern to develop TF sensors.

Multifunctional Gold-Silver-Carbon Quantum Dots Nano-Hybrid Composite: Advancing Antibacterial Wound Healing and Cell Proliferation.

The urgent need for innovative materials that effectively eliminate bacteria while promoting cell growth to accelerate wound healing has led to the exploration of new options, as current antimicrobial nanoparticles often exhibit high cytotoxicity, which hinders wound closure. In this study, a nano-hybrid composite, named gold-silver-carbon quantum dots (AuAg-CDs), was prepared by embedding gold and silver nanoclusters into carbon dots. The AuAg-CDs nano-hybrid composite demonstrates remarkable biocompatibility, displays potent antibacterial activity, and possesses a unique capability to promote cell proliferation. By physically disrupting bacterial membranes and promoting mammalian cell proliferation, this composite emerges as a highly promising material for wound healing applications. The underlying mechanism of the multifunctional AuAg-CDs was investigated through comprehensive analyses encompassing cell morphology, bacterial membrane potential, levels of reactive oxygen species (ROS), and adenosine triphosphate (ATP) production in both bacterial and mammalian cells. Additionally, AuAg-CDs were incorporated into alginate to create a hydrogel wound dressing, which underwent evaluation using animal models. The results underscore the remarkable potential of the AuAg-CDs wound dressing in facilitating the proliferation of wound fibroblasts and combating bacterial infections. The significance of designing multifunctional nanomaterials to address the challenges associated with pathogenic bacterial infections and regenerative medicine is highlighted by this study, paving the way for future advancements in these fields.

The composite of bismuth oxyiodide-bismuth/nitrogen-doped carbon for photoreduction and electrochemical/photoelectrochemical dual-model sensing of Cr(VI).

A porous bismuth oxyiodide-metal bismuth/nitrogen-doped carbon (BiOI-Bi/N-C) composite composed of BiOI nanosheets, N-C sheets, and metallic Bi nanoparticles was prepared. BiOI-Bi/N-C exhibited remarkable cathodic photoelectrochemical activity and rapid adsorption capacity for Cr(VI) ions. Interestingly, the photocatalytic process of BiOI-Bi/N-C toward Cr(VI) was pH dependent. Under acidic medium, the synthesized material displayed efficient photocatalysis and achieved 95.0% photoreduction efficacy for Cr(VI) ions to Cr3+ within 30 min under visible light irradiation. Under neutral medium, Cr(VI) state showed a different photocatalytic process, and Cr(OH)3 as a product covered on BiOI-Bi/N-C, which decreased the electrochemical (EC) and photoelectrochemical (PEC) performance of BiOI-Bi/N-C. Based on the findings, BiOI-Bi/N-C was utilized as EC/PEC dual-model sensing interface for the detection of Cr(VI) ions. The presented dual-model sensing method displayed an ultralow limit of detection down to 6.8 pM for EC and 3.2 pM for PEC. It demonstrated the practical application potential for the assay of Cr(VI) in real samples.

Dual-mode photoelectrochemical/electrochemical sensor based on Z-scheme AgBr/AgI-Ag-CNTs and aptamer structure switch for the determination of kanamycin.

A "signal-on" dual-mode aptasensor based on photoelectrochemical (PEC) and electrochemical (EC) signals was established for kanamycin (Kana) assay by using a novel Z-scheme AgBr/AgI-Ag-CNTs composite as sensing platform, an aptamer structure switch, and K3[Fe(CN)6] as photoelectron acceptor and electrochemical signal indicator. The aptamer structure switch was designed to obtain a "signal-off" state, which included an extended Kana aptamer (APT), one immobilized probe (P1), and one blocking probe (P2) covalently linked with graphdiyne oxide (GDYO) nanosheets. P1, P2, and aptamer formed the double helix structure, which resulted in the inhibited photocurrent intensity because of the weak conductivity of double helix layer and serious electrostatic repulsion of GDYO towards K3[Fe(CN)6]. In the presence of Kana, APT specifically bound to the target and dissociated from P1 and P2, and thus, a "signal-on" state was initiated by releasing P2-GDYO from the platform. Based on the sensing platform and the aptamer structure switch, the dual-mode aptasensor realized the linear determination ranges of 1.0 pM-2.0 µM with a detection limit (LOD) of 0.4 pM (for PEC method) and 10 pM-5.0 µM with a LOD of 5 pM (for EC method). The aptasensor displayed good application potential for Kana test in real samples.

Sensitive fluorescence detection of pathogens based on target nucleic acid sequence-triggered transcription.

Accurate identification of mutant pathogens derived from genetic polymorphisms is highly desired in clinical diagnosis. However, current detection methods based on Watson-Crick hybridization suffers from false positives due to the cross-reactivity of wild-type sequences. In this study, we developed an accurate identification of mutant pathogens by combining programmable DNAzyme and target nucleic acid sequence-triggered transcription. Single nucleotide variants (SNVs) are the most plentiful type of mutations in the genome. High specificity to discriminate SNV was first achieved by rational design of dual-hairpin DNA structure and DNAzyme's capability of site-specific cleavage. T7 RNA polymerase-mediated transcription amplification was introduced to exponentially increase the sensitivity by encompassing T7 promoter sequence into the dual-hairpin DNA structure. The design of this biosensor is fast and straightforward without many computational steps, and the highly sensitive biosensor can detect not only SNVs but also occasional insertions and large deletions in the genome. We showed that the assay could rapidly detect COVID-19 variant and methicillin-resistant Staphylococcus aureus (MRSA), and the limit of detection is 0.96 copy/µL. The modular design of functional DNA enables this biosensor be easily reconfigured and is useful diagnosis of emerging infectious diseases caused by mutant pathogens.

Tunable graphdiyne for DNA surface adsorption: affinities, displacement, and applications for fluorescence sensing.

Graphdiyne (GDY) adsorbed DNA probes have been used as a fluorescent sensing platform, but topics including DNA adsorption affinities, DNA probe displacement, and fluorescence quenching ability were rarely researched. Herein, the adsorption affinity of single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) on a tremella-like GDY was tuned by modulating the surface chemistry of GDY. The fluorescence quenching ability of GDY with different oxidation degrees was compared. The nonspecific displacement of DNA probes on GDY was studied. Under the same concentrations, GDY with low oxidation degree exhibited stronger adsorption affinity and higher adsorption capacity to both ssDNA and dsDNA than highly oxidized GDY. DNA adsorbed on low-oxidized GDY was more resistant to displacement by other DNAs. Protein showed strong interaction with different GDY and could displace DNA probes on GDY. Based on these findings, an ideal GDY with proper oxidation degree, exhibiting high surface affinity for ssDNA and low affinity for dsDNA, was used as scavenger of redundant ssDNA fluorescent probe in an enzyme-assisted amplification system for sensitive ochratoxin (OTA) detection. This study has enhanced our fundamental understanding of DNA adsorption by GDY. It also provided a rational way to apply GDY for fluorescence sensing in a complicated system.

Visual Quantitative Detection of Glutathione and Cholesterol in Human Blood Based on the Thiol-Ene Click Reaction-Triggered Wettability Change of the Interface.

Herein, we proposed an innovative visual quantitative sensing strategy based on thiol-ene click chemistry and the capillary action principle. A triethoxyvinylsilane (VTEO)- or mercaptopropylsilatrane (MPS)-modified interface was prepared for analyte recognition. Target analyte molecules containing thiol groups or C═C double bonds are coupled to the VTEO- or MPS-modified inner surface of the glass capillary tube via a thiol-ene click reaction, respectively. Then, the molecular recognition events were transformed into the wettability change of the inner wall of the glass capillary. The concentration of the target molecules was quantified by reading the height change of the water column in the capillary tube. As a proof of concept, this strategy was successfully used to build visual quantitative sensors for detecting glutathione and cholesterol. In addition, this strategy showed a good anti-interference ability to complex biological fluids and realized sensitive glutathione (GSH) and cholesterol detection in real human blood samples.

A cathode photoelectrochemical assay of terminal deoxynucleotidyl transferase activity based on Ag-AgI-CNTs composite and surface multisite strand displacement amplification.

Photocathode-based assay is anti-interference for real sample detection. Photocathode produces low photocurrent signal and gives rise to poor sensitivity. Herein, a novel cathode photoelectrochemical (CPEC) sensing platform based on Ag-AgI-CNTs as photocathode material and K3[Fe(CN)6] as photoelectron acceptor was established. Since [Fe(CN)6]3- effectively accepted photoelectrons from Ag-AgI-CNTs, it greatly enhanced the CPEC response. Combining a surface multisite strand displacement amplification (SMSDA) strategy, the CPEC platform was applied for the activity assay of terminal deoxynucleotidyl transferase (TdT). In this proposal, oligo dT primer tethered on CPEC platform was in-situ extended to generate a polyA tail. Then the polyA tail formed a stable multi-point hybrid structure with the adjacent oligo dT. After launching the SMSDA, the CPEC platform was covered by more elongated polynucleotide chains and network, which acutely hampered the photoelectron transfer (eT) between photocathode and electron acceptor and caused a reduced photocurrent. The CPEC sensor possessed a satisfactory linear response from 6 × 10-5-0.1 U and a low detection limit of 1.1 × 10-5 U. The strategy offered a more specific and sensitive method for TdT activity assay. It was feasible in the field of TdT-based biochemical research, drug screening, and disease diagnosis.

De Novo Development of a Universal Biosensing Platform by Rapid Direct Native Protein Modification.

An innovative biosensing assay was developed for simplified, cost-effective, and sensitive detection. By rapid, direct treatment of target proteins with iron porphyrin (TPPFe) in situ, a carboxyl group of amino acid conjugates with an Fe atom of the TPPFe molecule, forming a stable protein complex. We have shown that this complex not only maintains the integrity and functions of original proteins but also acquires peroxidase activity that can turn TMB to a comparably visible signal like that in ELISA. This study is unique since such conversion is difficult to achieve with standard chemical modification or molecular biology methods. In addition, the proposed immunoassay is superior to traditional ELISA as it eliminates an expensive and complicated cross-linking process of an enzyme-labeled antibody. From a practical point of view, we extended this assay to rapid detection of clinically relevant proteins and glucose in blood samples. The results show that this simple immunoassay provides clinical diagnosis, food safety, and environmental monitoring in an easy-to-implement manner.

Monitoring biothiols dynamics in living cells by ratiometric fluorescent gold carbon dots.

Changes in biothiols, including glutathione (GSH) and cysteine, are closely related to a variety of diseases and cellular functions. Real-time monitoring intracellular GSH and cysteine dynamics in living cells are important for understanding pathophysiological processes. In this study, a stable heterostructure of dual-emission fluorescent gold carbon dots (GCDs) consisting of carbon skeleton and gold nanoclusters was prepared, which emits strong blue fluorescence and weak yellow-orange fluorescence. The blue fluorescence of the as-prepared GCDs has no response to biothiols including GSH and cysteine, but a turn-on yellow-orange fluorescence would be appeared accompanied by the biothiols reacting with the GCDs. Ratiometric fluorescent bioimaging therefore may be established based on the unique GCDs to detect GSH and cysteine levels in living cells. Moreover, real time monitoring GSH and cysteine levels in various cell lines in living cells at different growth stages was realized. The concentration of GSH in cancer cells is higher than that of normal cells, however, the level of cysteine in normal cells is consistently higher than in cancer cells at different stages of cell growth. The fluorescent GCDs probe provides a promising tool for tracking on regulation of GSH and cysteine dynamics by physiological environments due to the capability for real-time quantitation of GSH and cysteine.

Selectively monitoring glutathione in human serum and growth-associated living cells using gold nanoclusters.

Glutathione (GSH) plays a variety of vital functions in biological systems. Growth-associated change of GSH level in cells might be critical for cell survival and monitoring of GSH in living cells are of great significance for understanding the dynamic link between GSH and some diseases. In this work, chitason micelles templated gold nanoclusters (CM-Au NCs) emitting red fluorescence were prepared with a simple and rapid method, which shows interesting phenomenon of aggregation induced emission (AIE) affected by the size of the chitosan micelles. The unique CM-Au NCs can be used to develop turn-off fluorescent probe for detecting GSH in human serum and living cells based on the reverse process of AIE of CM-Au NCs, completely different from the principle of aggregation caused quenching (ACQ) effect, which can distinguish GSH from other biothiols (cysteine and homocysteine) and quantitatively detect GSH concentration of human serum in healthy people and cancer patients with high sensitivity. The practical application of fluorescent CM-Au NCs for cellular imaging and detecting GSH level indicates ultra-trace changes of GSH levels in normal and cancer cells could be monitored at different growth stages, which reveals that the levels of GSH in cancer cells was always higher than that of normal cells. Compared with commercial GSH assay kits for detection GSH in human serum and living cells, the proposed method was verified to be accuracy and precision. The results not only reflect the changes of GSH during cell growth at different stages, but also demonstrate the feasibility of reverse process of AIE of CM-Au NCs for detection GSH. This strategy would provide a platform to understand the dynamic link between GSH and disease to clarify the disease mechanism.

Polydopamine nanospheres loaded with l-cysteine-coated cadmium sulfide quantum dots as photoelectrochemical signal amplifier for PSA detection.

A sandwich-type photoelectrochemical (PEC) immunosensor was constructed for sensitive detection of prostate specific antigen (PSA). It was based on electrochemically reduced graphene oxide-TiO2 (ERGO-TiO2) as photoelectrochemical platform to immobilize capture antibody (Ab1). Then, quinone-rich polydopamine nanospheres (PDANS) loaded detection antibody (Ab2) and photocurrent signal label, l-cysteine-coated cadmium sulfide quantum dots (CdSQDs). ERGO-TiO2 displayed greatly improved photocurrent response to white light. CdSQDs conjugated with PDANS further amplified photocurrent signal because of the good conductivity of PDANS and ERGO. The increased photocurrent showed a linear correlation with PSA in the concentration range from 0.02 pg mL-1 to 200 ng mL-1 with the detection limit of 6.8 fg mL-1. It also revealed high selectivity and good stability.

Aptamer based ratiometric electrochemical sensing of 17ß-estradiol using an electrode modified with gold nanoparticles, thionine, and multiwalled carbon nanotubes.

Gold nanoparticles (AuNPs) with a size of ~3 nm were placed on a thionine-multiwalled carbon nanotube (Thi-CNTs) conjugate to form a novel AuNP-Thi-CNTs nanocomposite. Its morphology and composition were characterized by transmission electron microscopy, atomic force microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The nanocomposite was placed on an electrode and used as a redox-active signaling interface to fabricate a ratiometric electrochemical aptasensor for 17ß-estradiol (E2). The potentiostatic insertion method was applied to insert an aptamer against E2 into a thin alkane monolayer to warrant an adequate distance between aptamers. The aptamer against E2 acts as both a collector and separator to specifically bind E2. The electrode displays two peak signals (at +0.50 V vs. SCE for E2; and at -0.32 V for Thi) which increase and decrease, respectively, in the 12 pM to 60 nM E2 concentration range. Therefore, the current ratio can be used to reliably, reproducibly, and sensitively quantify the concentration of E2. Graphical abstract Schematic presentation of a novel AuNP-Thi-CNTs nanocomposite. AuNP-Thi-CNTs showed good electrocatalytic oxidation to E2. AuNP-Thi-CNTs was used as self-redox signal interface to fabricate aptasensor. Dual signals of extrinsic E2 and inner Thi was applied to monitor the concentration of E2.

Single Primer Based Multisite Strand Displacement Reaction Amplification Strategy for Rapid Detection of Terminal Deoxynucleotidyl Transferase Activity.

A fluorescence-based multisite strand displacement reaction (MSSDR) amplification strategy is developed for the rapid, sensitive, and selective detection the activity of terminal deoxynucleotidyl transferase (TdT). Oligo dT primer was used for the TdT extension reaction, then the left oligo dT primers were hybridized to the TdT extension reaction product by end to end tiled style and initiated the MSSDR by Klenow polymerase, subsequently, 3' terminals of these single-strand DNA produced by MSSDR are folded back to complement themselves with the adjacent sequences, and Klenow polymerase makes it into double-stranded DNA (dsDNA). The final dsDNA products were analyzed via dsDNA specific fluorescent dye. This method enables rapid (less than 100 min) and sensitive (limit of detection, LOD, 1.35 × 10-5 U) detection and has been demonstrated to work well using a real biosample. Our design would not only serve as a new prototype for high-throughput automated analysis and clinic diagnostic application but also has promising potential for improving the sensitivity of those TDT related biosensing system.

Enhanced Mimetic Enzyme Activity of Phosphorylated Porphyrin Nanocomposite Induced by Localized Surface Plasmon Resonance for Colorimetric Assay.

Plasmon-enhanced light harvesting has been of great interest to enhance the catalytic efficiency of some composites or hybrids. The enhanced peroxidase-like activity of phosphorylated iron(III) porphyrin (TPPFe(III))-based nanocomposite, induced by localized surface plasmon resonance for a colorimetric assay, was developed in this study. Firstly, a phosphate group modification strategy was adopted to synthesize water-soluble iron(III) porphyrin materials. Then, the as-synthesized TPPFe(III) was covalently attached to core-shell gold nanorods (GNRs), GNR@Au2S/AuAgS, to form TPPFe(III)-GNR@Au2S/AuAgS nanocomposite, which shows greatly enhanced peroxidase-like activity compared to TPPFe(III). A mechanism for the enhanced peroxidase-like activity of TPPFe(III)-GNR@Au2S/AuAgS was proposed, which results from a synergic effect of hot electrons excited by localized surface plasmon resonance and photogenerated electrons of the TPPFe(III), verified by experiments. Furthermore, a fast colorimetric assay for the detection of H2O2 and glucose was established based on the unique property of TPPFe(III)-GNR@Au2S/AuAgS. This colorimetric assay was applied to determine practical human serum samples; satisfactory results demonstrate this method has high accuracy. The present study would not only provide some insights into the mechanism of plasmon-activated enzyme-like reactions, but also offer new strategies for improving the catalytic activity of a mimetic enzyme.

Fabricating and regulating peroxidase-like activity of eggshell membrane-templated gold nanoclusters for colorimetric detection of staphylococcal enterotoxin B.

Fluorescent eggshell membrane-templated gold nanoclusters (Au-ESM) can be obtained in a facile and low-cost manner in this study. The fluorescence of the Au-ESM may be significantly quenched by mercapto-compounds and peroxidase-like activity of Au-ESM could be regulated by the reaction process with glutathione. Moreover, the catalytic activity of the mimetic enzyme membrane could be modulated by immunoreactions. An immunoassay for colorimetric determination of staphylococcal enterotoxins B (SE-B) using colored gold nanoparticles was established based on the catalytic activity adjusted by the target molecules. This colorimetric assay can detect SE-B at the concentration range of 0.4-20 ng/mL and the limit of detection (LOD) is 0.12 ng/mL. As a practical application, the proposed colorimetric assay was further utilized to detect SE-B in food samples such as flour, corn and rice, requiring very low volume of sample and exhibiting great sensitivity and high accuracy, which provides promising platform for development of point-of-care diagnostic devices with biomedical and food safety applications.

Prompting peroxidase-like activity of gold nanorod composites by localized surface plasmon resonance for fast colorimetric detection of prostate specific antigen.

The interaction between incident light and surface electrons in conductive nanoparticles produces localized plasmon oscillations with a resonant frequency that strongly depends on the composition, size, geometry, and dielectric environment. Hybrid heterostructure materials combining two or more materials in one structure represent a powerful way to achieve unique properties and multifunctionality compared to those of the individual nanoparticle components. Hybrid gold nanorods and gold nanoclusters (GNR/AuNCs) heterostructures prepared by intimate integration of GNRs with AuNCs exhibit both localized surface plasmon resonance (LSPR) property and peroxidase-like activity. It is found that the catalytic activity of the AuNC/GNR heterostructure could be remarkably enhanced by LSPR induced by photon-plasmon coupling in the visible to near-infrared (NIR) region. Meanwhile, the catalytic activity of enzyme-like AuNC/GNRs may be regulated by immunoreactions to realize specific recognition of a target analyte. Accordingly, a fast colorimetric assay within 5 min for the detection of prostate specific antigen (PSA) was developed based on a AuNC/GNRs heterostructure mask regulated by the target molecule under photon-plasmon coupling. The color intensity is inversely proportional to the PSA concentration, and quantitative analysis may be achieved in a range of 10 and 200 pg mL-1. This sensor was practically applied to detect PSA levels in prostate cancer serum samples and the determined values agreed well with those measured by the hospital using standard methods. This indicates that the AuNC/GNRs heterostructure-based assay has high accuracy for the analysis of practical samples. Moreover, the new method has the advantages of very fast determination and low sample volume requirements.