Signal Labels Research Articles

ReS2@Au NPs as signal labels quenching steady photocurrent generated by NiCo2O4/CdIn2S4/In2S3 heterojunction for sensitive detection of CYFRA 21-1

In order to achieve rapid and sensitive detection of CYFRA 21-1, a signal-off photoelectrochemical (PEC) immunosensor was devised with NiCo2O4/CdIn2S4/In2S3 heterojunction photoactive materials as sensing platform and ReS2@Au NPs as the secondary antibody labels amplifying signal based on the energy band-matching cascade structure and double suppression effect. NiCo2O4 possessed a faster charge transfer rate due to the abundance of redox electron pairs (Co3+/Co2+ and Ni3+/Ni2+). To further improve the PEC properties of NiCo2O4 under visible light, CdIn2S4 with matching bandgap energy was selected to form heterojunction with NiCo2O4 and sensitized with In2S3. The proposed heterojunctions with well-matched band structure promoted the transfer of photo-generated carriers and were exploited as signal transducers for immobilization of antibodies and recognition of CYFRA 21-1. Furthermore, a novel urchin-like p-type ReS2 semiconductor nanostructure functionalized by Au NPs was firstly used as a nanolabel to quench the signal. On the one hand, the Schottky heterojunction generated by ReS2 and Au NPs could compete with the transducer substrate for both light and electron donors. On the other hand, the large space steric hindrance of ReS2 prevented contact between the matrix and AA. Subsequently, the sensor was sensitive in a wide range of concentrations for CYFRA 21-1 (0.0001–50 ng/mL), and the detection limit was 0.05 pg/mL.

Sandwich-Type Electrochemical Aptasensor for Highly Sensitive and Selective Detection of Pseudomonas Aeruginosa Bacteria Using a Dual Signal Amplification Strategy

An electrochemical aptasensor developed to realize the detection of Pseudomonas aeruginosa (P. aeruginosa) bacteria based on a signal amplification strategy. The carbon screen-printed electrode (CSPE) surface was modified by MIL-101(Cr)/Multi-walled carbon nanotubes (MWCNT), which significantly increased the effective surface area of the electrode, thus resulting in further F23 aptamer immobilization at the surface of the modified electrode. As a result, the P. aeruginosa can be efficiently captured onto the surface of the aptasensor. Moreover, aptamer immobilized on the two-dimensional graphitic carbon nitride complex with silver nanoparticles (AgNPs/c-g-C3N4/Apt) was used as an electrochemical signal label, connected to P. aeruginosa bacteria at the modified electrode. This strategy increased the aptamer surface density and the sensitivity for detecting P. aeruginosa. Also, the resultant material was thoroughly characterized using Fourier transform infrared (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) analysis techniques. A highly sensitive voltammetric aptasensor for P. aeruginosa detection was obtained via this strategy at the limit of detection of 1 Colony-forming unit (CFU)/mL (σ = 3). Therefore, this proposed strategy with dual signal amplification can be a promising platform for simple, practical, reliable, and sensitive method for P. aeruginosa.

An Enzyme-Free Sandwich Amperometry-Type Immunosensor Based on Au/Pt Nanoparticle-Functionalized Graphene for the Rapid Detection of Avian Influenza Virus H9 Subtype

Avian influenza virus H9 subtype (AIV H9) has contributed to enormous economic losses. Effective diagnosis is key to controlling the spread of AIV H9. In this study, a nonenzymatic highly electrocatalytic material was prepared using chitosan (Chi)-modified graphene sheet (GS)-functionalized Au/Pt nanoparticles (GS-Chi-Au/Pt), followed by the construction of a novel enzyme-free sandwich electrochemical immunosensor for the detection of AIV H9 using GS-Chi-Au/Pt and graphene–chitosan (GS-Chi) nanocomposites as a nonenzymatic highly electrocatalytic material and a substrate material to immobilize capture antibodies (avian influenza virus H9-monoclonal antibody, AIV H9/MAb), respectively. GS, which has a large specific surface area and many accessible active sites, permitted multiple Au/Pt nanoparticles to be attached to its surface, resulting in substantially improved conductivity and catalytic ability. Au/Pt nanoparticles can provide modified active sites for avian influenza virus H9-polyclonal antibody (AIV H9/PAb) immobilization as signal labels. Upon establishing the electrocatalytic activity of Au/Pt nanoparticles on graphene towards hydrogen peroxide (H2O2) reduction for signal amplification and optimizing the experimental parameters, we developed an AIV H9 electrochemical immunosensor, which showed a wide linear range from 101.37 EID50 mL−1 to 106.37 EID50 mL−1 and a detection limit of 100.82 EID50 mL−1. This sandwich electrochemical immunosensor also exhibited high selectivity, reproducibility and stability.

Coordination-induced self-assembly based carbon dot dendrimers as efficient signal labels for electrochemiluminescent immunosensor construction

In this work, an “on-off” electrochemiluminescent immunosensor for bone alkaline phosphatase (BALP) detection was constructed based on the carbon dot dendrimers (CD DRs) as signal labels and Pt nanoparticles functionalized Ni-phenolic coordination spheres (Pt@Ni-PCS) as quenching labels. The prepared CD DRs with low cytotoxicity were synthesized via coordination-induced self-assembly of carboxyl groups-rich N-doped carbon dots and zirconium oxygen clusters, of which the ECL efficiency was 2-fold enhancement than that of discrete N-doped carbon dots. Benefiting from the efficient quenching effect of Pt@Ni-PCS toward Zr-CD DRs/triethylamine-based ECL system, the prepared immunoassay for BALP detection exhibited a broad linear range with 1 pg/mL to 50 ng/mL and a low limit of detection of 24.9 fg/mL. Importantly, this highlights coordination-induced self-assembly as a tool for carbon dots enrichment to construct efficient ECL nanocomposites, which conceptualizes a pathway to expand the application of carbon dots in clinical ECL analysis technology.

An ultrasensitive electrochemical immunosensor for carcinoembryonic antigen detection based on two-dimensional PtPd/Cu-TCPP(Fe) nanocomposites.

Establishing an effective signal amplification strategy is the key to achieving sensitive detection of analytes by electrochemical immunoassay. In this work, a novel sandwich-type electrochemical immunosensor with dual-signal amplification was successfully constructed using PtPd/Cu-TCPP(Fe) as the sensing platform and mesoporous silicon dioxide as the signal amplifier. Firstly, two-dimensional wrinkled Cu-TCPP(Fe) nanomaterials loaded with PtPd nanoparticles have strong affinity for the immobilization of capture antibodies and can generate excellent electrochemical signals. Meanwhile, the mesoporous silicon dioxide with large steric hindrance was used as signal label to further improve the sensitivity of the immunosensor by increasing the difference of the current response signal. Under optimal experimental conditions, the electrochemical immunosensor exhibited a wide linear detection range from 0.1pg/mL to 1.0μg/mL, with a detection limit as low as 0.166fg/mL. The experimental results showed that the constructed immunosensor has a great application prospect in clinical biomarker detection.

Ratiometric fluorescent immunochromatography for simultaneously detection of two nitrofuran metabolites in seafoods

Competitive immunochromatographic assay (ICA) has been widely used in food safety on-site monitoring. However, traditional competitive ICA relies on the change of single-signal intensity to discriminate the results, leading to limited sensitivity and accuracy of naked-eye visual inspection. In this study, we developed a sensitive ratiometric fluorescent immunochromatographic assay (RFICA) judging results based on the color changes of fluorescence. Two different color quantum dot nanobeads (QBs) were introduced as signal labels for rapid and accurate detection of 3-amino-2-oxazolidinone (AOZ) and semicarbazide (SEM) in seafoods. Under the optimal conditions, the visual detection limit for 2-NPAOZ and 2-NPSEM reached up to 1 and 0.5 ng/mL, which were 5- and 14-fold lower than that of traditional single-signal response fluorescent ICA strips. In addition, the RFICA strips were applied to real samples with acceptable recoveries of 81.33 ∼ 99.23 %. These results demonstrate that the developed RFICA platform possesses considerable potential in the on-site detection.

Ultrasensitive sandwich-typed electrochemical immunoassay for detection of squamous cell carcinoma antigen based on highly branched PtCo nanocrystals and dendritic mesoporous SiO2@AuPt nanoparticles.

Squamous cell carcinoma antigen (SCCA) is one of the common squamous cell carcinomas (SCC) in women, which usually works as a tumor biomarker for cervical cancer in diagnostic applications. Herein, bimetallic PtCo highly branched nanocrystals (PtCo BNCs) acted as electrode substrates to construct sandwich-typed electrochemical immunosensor for ultrasensitive detection of SCCA, by using dendritic mesoporous SiO2@AuPt nanoparticles (DM-SiO2@AuPt NPs) to adsorb electroactive thionine (Thi) as a signal label. The PtCo BNCs enlarged the loading of the primary antibody (Ab1), showing effective improvement in conductivity and sensitivity. The DM-SiO2 had abundant pores to incorporate more Thi, on which the decorated AuPt NPs created a great number of active sites to immobilize the secondary antibodies (Ab2), thereby obviously amplifying the detection signals. The prepared sensor exhibited a broader linear range (0.001-120ngmL-1) and a lower detection limit (0.33pgmL-1, S/N = 3), combined with high reproducibility, a low relative standard deviation (below 2.5%) and acceptable recovery (from 98.5 to 110.0%) even in diluted human serum samples. This research provides a substantial platform for clinical diagnosis of SCCA in practice.

Dual-mode immunosensor based on Cu-doped Mo2C nanosheets as signal labels

A method for detecting of Carcinoembryonic antigen(CEA) with improved accuracy is urgently needed. In this work, a dual-mode immunosensor for accurate detection of CEA was fabricated, which used a Cu-doped Mo2C co-catalyst as an enhancer. Especially, Cu-doped Mo2C presents a strong different pulse voltammetry (DPV) signal for the electron transfer between Cu2+ and Cu+, without the addition of K3[Fe(CN6)] and other electron transfer mediators, but also shows high electrocatalytic activity towards H2O2 redox reactions. So that detection sensitivity of the chronoamperometry (CA) was enhanced. Furthermore, characterized by excellent conductivity, highly ordered pore distribution and great surface area, Ti3C2 Mxenes can be effective in promoting electron transfer and loading a large number of AuNPs. In the meantime, AuNPs can also immobilize CEA-Ab1 through Au-N bonds. Based on a Cu-Mo2C-Au dual-signal indicator, Ti3C2 Mxene-Au as the matrix, the immunsosensor was developed to achieve dual-signal detection of CEA. Satisfactory detection ranges (1 fg.mL−1 to 40 ng.mL−1) were obtained with limits of detection of 0.33 fg.ml−1 (DPV) and 1.67 fg.ml−1 (CA), respectively. Therefore, the prepared electrochemical immunosensor has good application prospects for the detection of CEA.

High-Density Gold Nanoparticles Implanted on Mg/Fe LDH Nanoflowers Assisted Lateral Flow Immuno-Dipstick Assay for Visual Detection of Human Epididymal Protein 4.

The timelier and more accurate the diagnosis of the disease, the higher the patient’s survival rate. Human epididymal protein 4 (HE4) has great significance as a biomarker of concern for reflecting ovarian cancer. Herein, we prepared a novel optical label that can be used in lateral-flow immuno-dipstick assay (LFIA) for sensitive visual detection of HE4 by implanting hydrophobic gold nanoparticles (Au NPs) at high density in Mg/Fe LDH nanoflowers (MF NFs). MF NFs with large specific surface area, high porosity, abundant active binding sites, and stable structure were employed for the first time as templates to directly anchor Au NPs in the organic phase. After simple modification with an optimized amount of branched polyethyleneimine, not only could MF@Au NFs be dispersed in the aqueous phase, but also amino functional groups were introduced on its surface to facilitate subsequent antibody coupling steps. The limit of detection reaches 50 pM with a detection range of 50 to 1000 pM. This work initially explored how MF NFs can be used to load signal labels with ideal stability and signal amplification capabilities, which greatly improves the practicability of LFIA and highlights its important role in the field of rapid diagnostics.

Double-layer robust broad logistic regression for detecting weak pulse signal in chaotic interference

Owing to the extreme complexity of detecting weak signals submerged in chaotic interference, traditional neural network detection methods based on hypothesis testing are difficult to sufficiently portray the data and chaotic noise evolution characterization for achieving high effective training, and the hypothesis test usually has the shortcomings of poor generalization performance. In this article, a double-layer robust broad logistic regression (DRBLR) is proposed to overcome the aforementioned issues and achieve highly accurate detection. The proposed method reconstructs the observation signal into a high-dimensional phase space with fixed-size tuples, and it extracts both the chaotic evolution trend and nonlinear structure from these spatiotemporal sequences by broad enhancement and manifold embedding operation of the Robust Manifold Broad Learning System. After that, the weights in Logistic Regression with two layers can be trained based on the obtained features and their corresponding pulse signal labels. The strategy of the DRBLR model leads to a robust learning paradigm and obtains better generalization performance. Experiments to detect weak pulse signals are conducted using Lorenz and sunspot datasets. Simulation results illustrate that the proposed method can better capture the characteristics of the chaotic interference evolution and effectively detect the weak pulse signal in the chaotic noise background.

Electrochemical immunosensor for individual and simultaneous determination of Cytokeratin fragment antigen 21-1 and Neuron-specific enolase using carbon dots-decorated multiwalled carbon nanotube electrode

In this approach, we fabricated a sandwich-type electrochemical immunosensor for individual and simultaneous sensing of cytokeratin fragment antigen 21-1 (CYFRA 21-1) and neuron-specific enolase (NSE) using the multiple-label concept. In this report, carbon dots (CDs) were prepared from citric acid and ethylenediamine (EDA). A hybrid EDA-CDs-MWCNTs composites were prepared and then decorated with gold nanoparticles (AuNPs). The obtained hybrid composites were used as an immunosensing platform. Furthermore, AuNPs decorated EDA-CDs-MWCNTs was carefully loaded with reactive dye (orange G and carminic acid) and utilized as signal labels. The surface morphology and the electrochemical properties of the modified SPCE were studied carefully. The linear range for the individual and simultaneous detection was 0.002–10 ng mL−1 for the CYFRA 21-1 and NSE and the detection limits (LODs) were 0.22 pg mL−1 and 0.15 pg mL−1 for the individual detection while 0.25 pg mL−1 and 0.20 pg mL−1 for simultaneous detection, respectively. This developed immunoassay was utilized for the assessment of two markers in the serum sample with reasonable consequences.

Dual-color aggregation-induced emission nanoparticles for simultaneous lateral flow immunoassay of nitrofuran metabolites in aquatic products

Nitrofurans such as furaltadone and nitrofurantoin are a type of synthetic broad-spectrum antibiotics. Various fluorescent nanomaterials have been used as labeling materials in immunochromatographic assays (ICAs) for nitrofurans detection. However, previous fluorescent nanomaterials can undergo aggregation-caused quenching, leading to a decrease in the detection sensitivity. In this study, we developed a multiplex immunochromatographic assay (mICA) based on dual-color aggregation-induced emission nanoparticles (AIENPs) as signal labels for the simultaneous detection of 3-amino-5-morpholino-methyl-1,3-oxazolidinone (AMOZ) and 1-aminohydantoin (AHD), which were the metabolites of furaltadone and nitrofurantoin, respectively. Under optimal conditions, the cut-off values of the mICA for derivatized AMOZ (2-NP-AMOZ) and AHD (2-NP-AHD) reached up to 3 and 5 ng/mL, respectively. These values are at least 166-and 200-fold higher than those of the commercial gold nanoparticles (GNPs)-based test strip, respectively. Furthermore, the test strip was successfully applied to the samples, with acceptable recoveries in the range of 83.0–98.2%.

Pd@Pt Nanodendrites as Peroxidase Nanomimics for Enhanced Colorimetric ELISA of Cytokines with Femtomolar Sensitivity.

Colorimetric enzyme-linked immunosorbent assay (ELISA) has been widely applied as the gold-standard method for cytokine detection over decades. However, it has become a critical challenge to further improve the detection sensitivity of ELISA as limited by the catalytic activity of enzymes. Herein, we report an enhanced colorimetric ELISA for ultrasensitive detection of interleukin-6 (IL-6, as a model cytokine for demonstration) using core@shell nanodendrites ( NDs) as peroxidase nanomimics (named " ND ELISA"), pushing the sensitivity up to femtomolar level. Specifically, the NDs are rationally engineered by depositing Pt atoms on Pd nanocubes (NCs) to generate rough dendrite-like Pt skins on the Pd surfaces via Volmer-Weber growth mode. They can be produced on a large scale with highly uniform size, shape, composition, and structure. They exhibit significantly enhanced peroxidase-like catalytic activity with catalytic constants () more than 2000-fold higher than those of horseradish peroxidase (HRP, an enzyme commonly used in ELISA). Using NDs as the signal labels, the ND ELISA presents strong colorimetric signals for the quantitative determination of IL-6 with a wide dynamic range of 0.05-100 pg mL-1 and an ultralow detection limit of 0.044 pg mL-1 (1.7 fM). This detection limit is 21-fold lower than that of conventional HRP-based ELISA. The reproducibility and specificity of the ND ELISA are excellent. More significantly, the ND ELISA was validated for analyzing IL-6 in human serum samples with high accuracy and reliability through recovery tests. Our results demonstrate that the colorimetric ND ELISA is a promising biosensing tool for ultrasensitive determination of cytokines and thus is expected to be applied in a variety of clinical diagnoses and fundamental biomedical studies.

Molecular Recognition-Triggered Aptazyme Sensor Using a Co-MOF@MCA Hybrid Nanostructure as Signal Labels for Adenosine Triphosphate Detection in Food Samples.

Developing rapid detection technology for adenosine triphosphate (ATP) is crucial in quality supervision and food safety. Herein, an electrochemical aptasensor based on an aptazyme-catalyzed signal amplification strategy is constructed for ATP detection using polyethyleneimine-functionalized molybdenum disulfide (PEI-MoS2)/Au@PtPd nanobipyramids (MoS2/Au@PtPd NBPs) as a modification material. Additionally, a novel kind of nitrogen-rich covalent organic framework (COF) is prepared using melamine and cyanuric acid (MCA). We synthesize MCA and the Co-based metal organic framework (Co-MOF) as the signal label. Due to the fact that π-π stacking interactions of Co-MOF@MCA can expand the load efficiency and surface concentration of the signal label, the signal response is an order of magnitude higher than that of Co-MOF or MCA as the signal label. Target ATP changes the conformation of the aptazyme, and it becomes activated. With the assistance of metal ions, the signal label is circularly cleaved, causing an amplification of the signal. Among them, MoS2/Au@PtPd NBPs have a large specific surface area and good electrical conductivity and can carry substantial DNA strands and amplify the redox signal of methylene blue (MB). Under optimal conditions, the aptasensor can detect ATP from 10 pM to 100 μM with a low limit of detection of 7.37 × 10-10 μM. Therefore, the novel aptasensor has extensive application prospects in quality supervision and food safety.

Picomolar glutathione detection based on the dual-signal self-calibration electrochemical sensor of ferrocene-functionalized copper metal-organic framework via solid-state electrochemistry of cuprous chloride

Chemical biosensing techniques are essential for food analysis and disease diagnosis. Nanomaterials with redox activity show great potential in electrochemical analysis, acting as signal labels or signal amplification unit, which can reflect the targets concentration in foods and biological samples. Here, an ultra-sensitive dual-signal intrinsic self-calibration electrochemical platform for GSH was firstly fabricated based on the novel electroactive nanomaterial of ferrocene-functionalized copper metal–organic framework (Fc-Cu-MOF). Due to the solid-state electrochemical property of cuprous chloride (CuCl), a sharp characteristic peak with an increased signal appears with the coexistence of chloride ions in solution. The stronger specific affinity between Cu+ and GSH than that of Cu+ and Cl- triggers a “crowding effect” that causes the current signal of CuCl decrease greatly. Meanwhile, the peak current of ferrocene keeps unchanged as an internal reference. Based on the ratio of the peak current variation (ΔICu/ΔIFc) as the signal output, Fc-Cu-MOF modified electrode showed wider linear range in 0.1 nM −1 μM for GSH with the detection limit as low as 0.025 nM. And the sensor was successfully applied in the determination of GSH with excellent recoveries in various real samples such as food and serum samples, providing good prospect in application of bioanalysis and food screening.

Controllable surface engineered three-dimensional porous graphene based electrode for ultrasensitive flexible electrochemical sensing

The cost effective synthesis of ultrasensitive micro-electrodes with excellent biocompatibility, conductibility, specific surface area, long-term stability and flexibility is a challenge in diverse portable sensing electronics device. Herein, a flexible nanogold modified graphene-based porous electrode with exceptionally powerful loading capacity and electro-conductibility was developed through the laser-scribing, dipping, and electro-deposition processes. Benefited from laser-induced photothermal conversion, the graphene-based electrode presented three-dimensional framework structure with abundant oxygen-containing groups and nitrogen doping, which improved electron transport and superficial area. Further performance enhancements of the electrode were enabled by mild organic acids/alcohols-catalyzed chemically reduction and nanogold electro-deposition. The resistance of the functionalized graphene-based electrode decreased by 3.9 times and the specific surface area increased by 2.5 times compared with the original laser-induced graphene. The corresponding mechanism was investigated systematically. Based on the prepared electrodes, a flexible electrochemical sensing chip integrating Cu2+-assembled reticular-structured signal label and Zn2+-activated DNAzyme was constructed for quantitative detecting Cu2+ and Zn2+, which presented low detection limit of 0.32 nM (Cu2+) and 0.34 nM (Zn2+), excellent stability and flexibility. The investigation reveals that the dipping treatment and nanogold electrodeposition for porous laser-induced graphene are the promising approaches for the flexible electrochemical sensing applications.

Biomimetic synthesis of protein-DNA-CaHPO4 hybrid nanosheets for biosensing: Detection of thrombin as an example

Traditional strategies for coupling of proteins with DNA involve the additional modifications on protein or DNA to construct protein-DNA conjugates, resulting in complex or time-consuming coupling process. This study presented a biomimetic synthesis strategy to elaborately synthesize a new type of biomolecule-inorganic hybrid nanosheets. Horseradish peroxidase (HRP) and DNA aptamer can be easily combined with CaHPO4 via coprecipitation simultaneously to form all-inclusive HRP-aptamer-CaHPO4 hybrid (HAC) nanosheets integrating bifunction of biorecognition and signal amplification, which was proceeded in the green environment at room temperature and required no additional modifications on CaHPO4, protein and DNA. Therefore, it avoided tedious linking and purification procedures. The HAC nanosheets were then employed as the signal labels and showed excellent performance for detecting thrombin. This bioinspired approach provides great possibilities to facile and efficient immobilization of protein, DNA or even other types of biomolecules (e.g., RNA and peptide) on inorganic nanomaterials and endows great potential in the preparation of a variety of multifunctional biomolecule-CaHPO4 two-dimensional (2D) nanobiohybrids for various applications extending from biosensing to energy, biomedicine, environmental science and catalysis.

Ag2S quantum dots loaded dendritic mesoporous silica nanospheres as signal amplification labels for ultrasensitive electrochemical immuno-biosensor for Staphylococcus aureus

An electrochemical immuno-biosensor based on Ag 2 S/DMSNs labels was established to detect S. aureus . • An electrochemical immuno-biosensor based on Ag 2 S/DMSNs labels was established to detect S. aureus . • Using DMSNs for Ag 2 S QDs enrichment and signal amplification to improve the detection sensitivity. • A wide linear detection range from 10 to 10 8 CFU mL −1 , with a detection limit of 2 CFU mL −1 . • The immuno-biosensor showed excellent selectivity and stability. • The immuno-biosensor was successfully applied to detect actual samples. Developing novel signal amplification labels in electrochemical immuno-biosensors for ultrasensitive, fast and selective detection of foodborne pathogen is urgent and significant for people's health and life safety. Herein, dendritic mesoporous silica nanospheres (DMSNs) loaded with silver sulfide quantum dots (Ag 2 S QDs) were fabricated and employed as signal amplification labels for highly sensitive electrochemical detection of Staphylococcus aureus ( S. aureus ). DMSNs were treated with 3-aminopropyltrioxysilane to introduce amino group on surfaces to facilitate the immobilization of Ag 2 S QDs. Benefiting from the highly accessible surface areas and large pore channels characteristics given by the unique radial flower-like structure of DMSNs, large amount of Ag 2 S QDs were loaded into the surfaces and pores of the DMSNs to form Ag 2 S/DMSNs. To specifically recognize S. aureus cells, Ag 2 S/DMSNs were modified by anti- S. aureus antibody (Ab) to form Ab-Ag 2 S/DMSNs. When the sandwich-type electrochemical immuno-biosensor operated, Ag(Ⅰ) ions were released from the Ag 2 S/DMSNs label by HNO 3 leaching, and the detection of S. aureus was realized by the differential pulse voltammetry. The electrochemical signal of the prepared immuno-biosensor was substantially magnified when compared to the immuno-biosensor employing Ag 2 S QDs as signal label, since much more Ag 2 S QDs were labeled to each bacterial cell due to the high loading of Ag 2 S QDs on the DMSNs. As a consequence, the developed immuno-biosensor was capable of detecting S. aureus cells down to a limit of 2 colony forming units per mL (CFU mL −1 ) and exhibited a wide linear detection range from 10 CFU mL −1 to 10 8 CFU mL −1 . In addition, the immuno-biosensor showed excellent selectivity and stability for the detection of S. aureus , and was successfully applied to detected S. aureus in milk samples.

Novel colorimetric aptasensor based on MOF-derived materials and its applications for organophosphorus pesticides determination

For the visual detection of four organophosphorus pesticides (OPs), a colorimetric aptasensor was developed based on aptamer-mediated bimetallic metal-organic frameworks (MOFs) nano-polymers. Fe-Co magnetic nanoparticles (MNPs) and Fe-N-C nanozymes were prepared based on pyrolytic reaction, and were labeled with broad spectrum aptamers and complementary chains of organophosphorus pesticides respectively. The hybridization of aptamers and complementary chains led to the formation of nano-polymers. In the presence of target pesticides, they competed with complementary chains for aptamers on Fe-Co MNPs, resulting in a large number of Fe-N-C nanozymes signal labels being released into the supernatant. Fe-N-C nanozymes showed similar activity to peroxidase and catalyzed the 3,3′,5,5′-tetramethylbenzidine-hydrogen peroxide (TMB-H2O2) color system to turn the solution blue-green under mild conditions. The magnetic probes had good selectivity and sensitivity, and were easily separated by magnetic absorption. The sensor functioned well under optimal conditions, demonstrating good stability and specificity for four pesticides: phorate, profenofos, isocarbophos and omethoate, and the detection limits of four pesticides were as low as 0.16 ng/mL, 0.16 ng/mL, 0.03 ng/mL and 1.6 ng/mL respectively, and the recovery rate of OPs residue in vegetable samples was satisfactory. The work described here provided a simple, rapid and sensitive way to construct a biosensor.

Optical fiber peptide-sensor for ultrasensitive detection of prostate specific antigen

We develop the first optical fiber-based peptisensor with chemiluminescent detection, and apply it for ultrasensitive detection of prostate-specific antigen (PSA), an important biomarker for early diagnosis of prostate disease. Optical fiber is used not only as the carrier of the biological recognition elements (the specific biotinylated peptides, bio-KQLKSSHC), but also for the excellent light conduction for chemiluminescence signal output. The peptisensor is easily fabricated and gold nanoparticles (AuNPs) modified with horseradish peroxidase (HRP) are employed as the signal label for chemiluminescent detection. By combining the streptavidin-biotin system and the large surface area of AuNPs, both the peptide loading amount and the chemiluminescence signal are enhanced, thus the response of the peptisensor is greatly improved with a wide linear range of 0.80 pg/mL −100 ng/mL (2.42 ×10−9-3.03 ×10−4 nmol) and a low limit-of-detection of 0.30 pg/mL (9.09 ×10−10 nmol). The HRP@AuNPs@peptide optical fiber peptisensor exhibiting good reproducibility and selectivity for PSA assays. Our study indicates that the optical fiber-based peptisensors would be of value for sensitive detection of biomarkers with advantages of low-cost, easy operation and possibly for miniaturization, thus would they have great potential application in vitro diagnosis.