Fluorescence/electrochemical dual-mode strategy for Golgi protein 73 detection based on molybdenum disulfide/ferrocene/palladium nanoparticles and nitrogen-doped graphene quantum dots.

Golgi protein 73 (GP73) is a new serum marker associated with early diagnosis and postoperative assessment of hepatocellular carcinoma (HCC). Herein, an electrochemical/fluorescence dual-signal biosensor was designed for determination of GP73 based on molybdenum disulfide/ferrocene/palladium nanoparticles (MoS2-Fc-PdNPs) and nitrogen-doped graphene quantum dots (NGQDs). GP73 aptamer (Apt) was labeled with NGQDs to form the NGQDs-Apt fluorescence probe. MoS2-Fc-PdNPs served not only as the fluorescence quencher but also as electrochemical enhancer. The sensing platform (NGQDs-Apt/MoS2-Fc-PdNPs) was formed based on the fluorescence resonance energy transfer (FRET) mechanism. In the presence of GP73, the specific binding of NGQDs-Apt to GP73 interrupted FRET, restoring the fluorescence of NGQDs-Apt at λex/em = 348/438 nm and enhancing the oxidation current of Fc in MoS2-Fc-PdNPs at 0.04 V through differential pulse voltammetry (DPV). Under the optimal conditions, the DPV current change and fluorescence recovery have a good linear relationship with GP73 concentration from 1.00 to 10.0 ng/mL. The calibration equation for the fluorescence mode was Y1 = (0.0213 ± 0.00127)X + (0.0641 ± 0.00448) and LOD was 0.812 ng/mL (S/N = 3). The calibration equation of the electrochemical mode was Y2 = (3.41 ± 0.111)X + (1.62 ± 0.731), and LOD of 0.0425 ng/mL (S/N = 3). The RSDs of fluorescence mode and electrochemical mode after serum detection were 1.62 to 5.21% and 0.180 to 6.62%, respectively. By combining the electrochemical and fluorescence assay, more comprehensive and valuable information for GP73 was provided. Such dual-mode detection platform shows excellent reproducibility, stability, and selectivity and has great application potential.

Sandwich-type supersensitive electrochemical aptasensor of glypican-3 based on PrGO-Hemin-PdNP and AuNP@PoPD.

A new sandwich-type electrochemical biosensing platform was developed by gold @polyphthalenediamine nanohybrids (AuNP@PoPD) as the sensing platform and phosphorus doped reduced graphene oxide-hemin-palladium nanoparticles (PrGO-Hemin-PdNP) as the signal amplifier for phosphatidylinositol proteoglycan 3 (GPC3). AuNP@PoPD, co-electrodeposited into the screen printed electrode with high conductivity and stability, is dedicated to assembling the primary GPC3 aptamer (GPC3Apt). The second GPC3Apt immobilized on the high conductivity and large surface area of PrGO-Hemin-PdNP was utilized as an electrochemical signal reporter by hemin oxidation (PrGO-Hemin-PdNP-GPC3Apt). In the range 0.001-10.0 ng/mL, the hemin oxidation current signal of the electrochemical aptasensor increased log-linearly with the concentration of GPC3, the lowest detection limit was 0.13 pg/mL, and the sensitivity was 2.073 µA/µM/cm2. The aptasensor exhibited good sensing performance in a human serum sample with the relative error of 4.31-8.07%. The sandwich sensor showed good selectivity and stability for detection GPC3 in human serum samples, providing a new efficient and sensitive method for detecting HCC markers.

A novel electrochemical aptasensor based on NrGO-H-Mn3O4 NPs integrated CRISPR/Cas12a system for ultrasensitive low-density lipoprotein determination.

Atherosclerosis cardiovascular disease (ASCVD) has become one of the leading death causes in humans. Low-density lipoprotein (LDL) is an important biomarker for assessing ASCVD risk level. Thus, monitoring LDL levels can be an important means for early diagnosis of ASCVD. Herein, a novel electrochemical aptasensor for determination LDL was designed based on nitrogen-doped reduced graphene oxide-hemin-manganese oxide nanoparticles (NrGO-H-Mn3O4 NPs) integrated with clustered regularly interspaced short palindromic repeats and associated proteins (CRISPR/Cas12a) system. NrGO-H-Mn3O4 NPs not only have a large surface area and remarkable enhanced electrical conductivity but also the interconversion of different valence states of iron in hemin can provide an electrical signal. Nonspecific single-stranded DNA (ssDNA) was bound to NrGO-H-Mn3O4 NPs to form a signaling probe and was immobilized on the electrode surface. The CRISPR/Cas12a system has excellent trans-cleavage activity, which can be used to cleave ssDNA, thus detaching the NrGO-H-Mn3O4 NPs from the sensing interface and attenuating the electrical signal. Significant signal change triggered by the target was ultimately obtained, thus achieving sensitive detection of the LDL in range from 0.005 to 1000.0 nM with the detection limit of 0.005 nM. The proposed sensor exhibited good stability, selectivity, and stability and achieved reliable detection of LDL in serum samples, demonstrating its promising application prospects for the diagnostic application of LDL.

Reduced graphene oxide-persimmon tannin/Pt@Pd nanozyme-based cascade colorimetric sensor for detection of 1,5-anhydroglucitol.

1,5-anhydroglucitol (1,5-AG) is of considerable clinical relevance as a biochemical marker of glucose metabolism in the assessment and monitoring of diabetes. Herein, a simple colorimetric biosensor was constructed for the identification and detection of 1,5-AG by using pyranose oxidase (PROD) enzyme cascaded with reduced graphene oxide/persimmon tannin/Pt@Pd (RGO-PT/Pt@Pd NPs) nanozyme. The as-prepared RGO-PT/Pt@Pd NPs had excellent peroxidase-like activity and can be applied as a nanozyme. First, PROD enzyme reacts with the target 1,5-AG, decomposing 1,5-AG into 1,5-anhydrofuctose (1,5-AF) and H2O2. At this point, the highly catalytic RGO-PT/Pt@Pd NPs nanozyme produces a cascade with PROD enzyme which catalyzes the decomposition of H2O2 to produce O2. This in turn oxidizes the substrate 3,3',5,5'-tetramethylbenzidine (TMB) and produces a color change in the solution. Finally, the detection of 1,5-AG was achieved by measuring the absorption peak at 652 nm with an ultraviolet visible (UV-vis) spectrophotometer. Under optimal conditions, the linear operating range of the 1,5-AG enzyme cascade colorimetric sensor was 1.0-100.0 µg/mL, and the limit of detection (LOD) was 0.81 µg/mL. The proposed colorimetric biosensor was successfully applied to detect 1,5-AG in spiked human serum samples with the recoveries of 97.2-103.9% and RSDs of 1.94-4.48%. It provides a promising developmental assay for clinical detection of 1,5-AG.

H-rGO-Pd NPs Nanozyme Enhanced Silver Deposition Strategy for Electrochemical Detection of Glypican-3.

Glypican-3 (GPC3), as an emerging biomarker, has been shown to be beneficial for the early diagnosis and treatment of hepatocellular carcinoma (HCC). In this study, an ultrasensitive electrochemical biosensor for GPC3 detection has been constructed based on the hemin-reduced graphene oxide-palladium nanoparticles (H-rGO-Pd NPs) nanozyme-enhanced silver deposition signal amplification strategy. When GPC3 specifically interacted with GPC3 antibody (GPC3Ab) and GPC3 aptamer (GPC3Apt), an "H-rGO-Pd NPs-GPC3Apt/GPC3/GPC3Ab" sandwich complex was formed with peroxidase-like properties which enhanced H2O2 to reduce the silver (Ag) ions in solution to metallic Ag, resulting in the deposition of silver nanoparticles (Ag NPs) on the surface of the biosensor. The amount of deposited Ag, which was derived from the amount of GPC3, was quantified by the differential pulse voltammetry (DPV) method. Under ideal circumstances, the response value was linearly correlated with GPC3 concentration at 10.0-100.0 µg/mL with R2 of 0.9715. When the GPC3 concentration was in the range from 0.01 to 10.0 µg/mL, the response value was logarithmically linear with the GPC3 concentration with R2 of 0.9941. The limit of detection was 3.30 ng/mL at a signal-to-noise ratio of three and the sensitivity was 1.535 µAµM-1cm-2. Furthermore, the electrochemical biosensor detected the GPC3 level in actual serum samples with good recoveries (103.78-106.52%) and satisfactory relative standard deviations (RSDs) (1.89-8.81%), which confirmed the applicability of the sensor in practical applications. This study provides a new analytical method for measuring the level of GPC3 in the early diagnosis of HCC.

A highly sensitive strategy for glypican-3 detection based on aptamer/gold carbon dots/magnetic graphene oxide nanosheets as fluorescent biosensor.

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related deaths in China. Glypican-3 (GPC3) is a specific antigen related to HCC, which is widely used in clinical detection as a reliable marker of HCC. In this paper, a highly sensitive homogeneous apatasensor was designed for GPC3 detection based on fluorescence resonance energy transfer (FRET) where the GPC3 aptamer labelled gold carbon dots (AuCDs-GPC3Apt) are used as a donor and magnetic graphene oxide (Fe3O4/GO) nanosheets are used as an acceptor. A one-step hydrothermal method was used to synthesize AuCDs to provide sufficient fluorescence. The FRET phenomenon exists between AuCDs-GPC3Apt and Fe3O4/GO, which weakens the fluorescence intensity of the whole system. When the target GPC3 is added to the FRET system, the fluorescent AuCDs-GPC3Apt binds to the GPC3 and forms a folded structure, which leads to AuCDs-GPC3Apt separation from Fe3O4/GO nanosheets. The Fe3O4/GO is then magnetically separated so that the fluorescence of free labelled AuCDs-GPC3Apt is restored. Under the optimum conditions, the fluorescence recovery rate is linearly correlated with the concentration of GPC3 (5-100 ng·mL-1) and the detection limit is 3.01 ng·mL-1 (S/N = 3). This strategy shows recoveries from 98.76 to 101.29% in real human serum samples and provides an immediate and effective detection method for the quantification of GPC3 with great potential applications for early diagnosis of HCC. A sensitive homogeneous FRET-based apatasensor was designed for GPC3 detection where the AuCDs-GPC3Apt is a donor and Fe3O4/GO nanosheets are an acceptor. The GPC3 fluorescent aptasensor combines wider output range with low cost, high specificity, and good anti-interference.

Colorimetric biosensor for visual determination of Golgi protein 73 based on reduced graphene oxide-carboxymethyl chitosan-Hemin/platinum@palladium nanozyme with peroxidase-like activity.

A Golgi protein 73 (GP73) colorimetric biosensor based on the reduced graphene oxide-carboxymethyl chitosan-hemin/platinum@palladium nanoparticles (RGO-CMCS-Hemin/Pt@Pd NPs) with peroxidase-like activity was constructed. The RGO-CMCS-Hemin/Pt@Pd NPs with high peroxidase-like activity were successfully synthesized under mild conditions. Then, the aminylated GP73 aptamer (Apt) was bound to the RGO-CMCS-Hemin/Pt@Pd NPs to form the recognition probe. Another unmodified GP73 aptamer (AptI) was served as the capture probe. In the presence of target GP73, the capture probe and the recognition probe specifically bind to GP73 and form a RGO-CMCS-Hemin/Pt@Pd NP-Apt/GP73/AptI sandwich-type structure, which can oxidase the colorless 3,3',5,5'-tetramethylbenzidine (TMB) into blue oxTMB in the presence of H2O2. GP73 detection was achieved by measuring the peak UV absorption at 652 nm. Under the optimum conditions, the GP73 concentration was linearly related to the absorbance intensity in the range 10.0-110.0 ng/mL, and the limit of detection (LOD) was 4.7 ng/mL. The proposed colorimetric biosensor was successfully applied to detect GP73 in spiked human serum samples with recoveries of 98.2-107.0% and RSDs of 1.90-5.44%, demonstrating the excellent potential for highly sensitive GP73 detection in clinical detection. A colorimetric biosensor for visual determination of GP73 based on RGO-CMCS-Hemin/Pt@Pd NPs nanozyme with peroxidase-like activity was designed. The GP73 biosensor responses linearly from 10.0-110.0 ng/mL with LOD of 4.7 ng/mL, and shows acceptable specificity and good recovery.

The research of aptamer biosensor technologies for detection of microorganism.

The activities and transmissions of microorganisms are closely related to human, and all kinds of diseases caused by pathogenic microorganisms have attracted attention in the world and brought many challenges to human health and public health. The traditional microbial detection technologies have characteristics of longer detection cycle and complicated processes, therefore, which can no longer meet the detection requirements in the field of public health. At present, it is the focus to develop and design a novel, rapid, and simple microbial detection method in the field of public health. Herein, this article summarized the development of aptamer biosensor technologies for detection of microorganism in the aspect of bacteria, viruses, and toxins in detail, including optical aptamer sensors such as fluorometry and colorimetry, electrochemical aptamer sensors, and other technologies combined with aptamer. KEY POINTS: • Aptamer biosensor is a good platform for microbial detection. • Aptamer biosensors include optical sensors and electrochemical sensors. • Aptamer sensors have been widely used in the detection of bacteria, viruses, and other microorganisms.

Glypican-3 electrochemical aptamer nanobiosensor based on hemin/graphene nanohybrids peroxidase-like catalytic silver deposition.

A Glypican-3 (GPC3) electrochemical aptamer nanobiosensor based on hemin/graphene nanohybrids (HGNs) peroxidase-like catalytic silver deposition and GPC3 aptamer has been constructed for the determination of GPC3. The HGNs were prepared by an one-step reduction method. Fourier transform infrared spectroscopy (FT-IR), ultraviolet spectroscopy (UV-vis), and transmission electron microscopy (TEM) were used to study the structure and morphological characteristics of the HGNs. The GPC3 electrochemical aptamer nanobiosensor was constructed using HGNs-aptamer (HGNs-Apt) as the signal probe and GPC3 aptamer as the capture probe. With the help of the catalytic action of peroxidase-like properties of HGNs, H2O2 reduces the silver (Ag) ions in solution to metallic Ag, which deposit on the surface of the electrode. The amount of deposited Ag, which was derived from the amount of GPC3, was quantified by differential pulse voltammetry (DPV). Under optimal conditions, the current response of Ag had a good positive correlation with the GPC3 concentration in the range 10.0-100.0 µg mL-1 with a correlation coefficient of 0.9958. The detection limit was 3.16 µg mL-1 at a signal-to-noise ratio of 3, and the sensitivity was calculated to be 0.807 µA µM-1 cm-2. The method is validated by analyzing spiked human serum samples with good recovery ranging from 101 to 122%. In addition, the GPC3 electrochemical aptamer nanobiosensor has acceptable selectivity, stability, and reproducibility. Graphical abstract A Glypican-3 electrochemical aptamer nanobiosensor based on hemin/graphene nanohybrids (HGNs) peroxidase-like catalytic silver deposition and GPC3 aptamer has been constructed for the determination of GPC3. The electrochemical aptamer nanobiosensor exhibits high selectivity, acceptance reproducibility, and good recovery performances.

Protecting HaCaT cells from ionizing radiation using persimmon tannin-Aloe gel composite.

Context: Persimmon tannin (extract of Diospyros kaki L.f [Ebenaceae]) and Aloe gel (extract of Aloe vera (L.) Burm.f. [Asphodelaceae]) are known as anti-radiation agents. However, radiation resistance of the persimmon tannin-Aloe gel composite remains inconclusive.Objective: To investigate the capacity of the persimmon tannin-Aloe gel composite to protect against ionising radiation at the cellular level.Materials and methods: HaCaT (human epidermal keratinocytes) cells were pre-treated with PT-A-1 (the mass ratio of persimmon tannin and Aloe gel was 2:1) or the single component (persimmon tannin or Aloe gel) at various concentrations (0, 50, 100, 200, 400, 800 µg/mL. Control group: medium with no HaCaT cells), and then radiated with X-rays (radiation dose: 4, 8, 12, 16, and 20 Gy). Cell viability, cell apoptosis, and radiation-induced intracellular reactive oxygen species (ROS) generation were analysed by CCK-8, Hoechst 33258 staining/flow cytometry, and 2',7'-dichlorfluorescein diacetate (DCFH-DA) assay, respectively, for 12 or 24 h incubation after radiation.Results: The optimal radiation dose and post-radiation incubation period were determined to be 8 Gy and 12 h. CCK-8 activity detection showed that the cell activity was 77.85% (p < 0.05, IC50 = 55.67 µg/mL). The apoptotic rate was the lowest (4.32%) at 200 µg/mL of PT-A-1 towards HaCaT cells. ROS production was the most effectively suppressed by 200 µg/mL PT-A-1 towards HaCaT cells.Discussion and conclusions: The persimmon tannin-Aloe gel composite has good radioprotective effect, and which will facilitate its clinic application as a potential natural anti-radiation agent in future.

A fluorometric aptamer nanoprobe for alpha-fetoprotein by exploiting the FRET between 5-carboxyfluorescein and palladium nanoparticles.

Alpha-fetoprotein (AFP) is a reliable clinical marker of hepatocellular carcinoma (HCC). A highly sensitive fluorometric aptamer nanoprobe is described for AFP detection. It is based on fluorescence resonance energy transfer (FRET) between AFP aptamer labelled with 5-carboxyfluorescein (FAM) and palladium nanoparticles (PdNPs). The PdNPs quench the green fluorescence of the FAM-AFP aptamer via interactions between nitrogen functional groups of the AFP aptamer and PdNPs. When AFP was introduced into the FAM-AFP aptamer-PdNPs FRET system, the AFP aptamer preferentially combines with AFP. This results in a conformational change and weakens the interaction between the aptamer and the PdNPs. Thus, the fluorescence of FAM recovers. The fluorescence recovery of FAM increases linearly in the 5.0-150 ng·mL-1 AFP concentration range and has a 1.4 ng·mL-1 detection limit. The assay was applied to the analysis of spiked diluted human serum. The recovery values ranged from 98.3 to 112.9%, with relative standard deviations of <1.1%. This biosensing strategy provides a reliable and ultrasensitive protocol for the quantification of biomarkers with relevant antigens and aptamers. Graphical abstract Schematic presentation of a fluorometric aptamer nanoprobe for AFP assay based on fluorescence resonance energy transfer (FRET) between AFP aptamer labelled with 5-carboxyfluorescein (FAM) and palladium nanoparticles (PdNPs).

A composite prepared from carboxymethyl chitosan and aptamer-modified gold nanoparticles for the colorimetric determination of Salmonella typhimurium.

An aptamer-based assay is described for the determination of Salmonella typhimurium (S. typh). Carboxymethyl chitosan was loaded with amino-modified aptamer against S. typh, and then adsorbed on gold nanoparticles by electrostatic interaction to form a composite that acts as the molecular recognition element. In the presence of S. typh, it will be bound by the aptamer, and this changes the structure of the recognition element. On addition of salt solution, the gold nanoparticles agglomerate so that the color of the solution changes from red to blue. S. typh can be detected via measurement of the absorbance at 550 nm. Absorbance increases linearly with the logarithm of the S. typh concentration in the range from 100 to 109 cfu·mL-1. The limit of detection is 16 cfu·mL-1. The specificity and practicability of the assay were evaluated. The recoveries of S. typh from spiked milk samples are between 92.4 and 97.2%. The analytical results are basically consistent with those of a plate counting method. Graphical abstract Schematic representation of the colorimetric assay for Salmonella typhimuium (S. typh) using carboxymethyl chitosan (CMCS)-aptamer (Apt)-gold nanoparticles (AuNPs) composites.

Label-free electrochemical aptasensor for detection of alpha-fetoprotein based on AFP-aptamer and thionin/reduced graphene oxide/gold nanoparticles.

Sensitive and accurate detection of tumor markers is critical to early diagnosis, point-of-care and portable medical supervision. Alpha fetoprotein (AFP) is an important clinical tumor marker for hepatocellular carcinoma (HCC), and the concentration of AFP in human serum is related to the stage of HCC. In this paper, a label-free electrochemical aptasensor for AFP detection was fabricated using AFP-aptamer as the recognition molecule and thionin/reduced graphene oxide/gold nanoparticles (TH/RGO/Au NPs) as the sensor platform. With high electrocatalytic property and large specific surface area, RGO and Au NPs were employed on the screen-printed carbon electrode to load TH molecules. The TH not only acted as a bridging molecule to effectively capture and immobilize AFP-aptamer, but as the electron transfer mediator to provide the electrochemical signal. The AFP detection was based on the monitoring of the electrochemical current response change of TH by the differential pulse voltammetry. Under optimal conditions, the electrochemical responses were proportional to the AFP concentration in the range of 0.1-100.0 µg/mL. The limit of detection was 0.050 µg/mL at a signal-to-noise ratio of 3. The proposed method may provide a promising application of aptamer with the properties of facile procedure, low cost, high selectivity in clinic.

Optimization of Synthesis and Modification of ZnSe/ZnS Quantum Dots for Fluorescence Detection of Escherichia coil.

This study prepared an innovative 3-mercaptopropionic acid modified ZnSe/ZnS core/shell quantum dots (MPA-ZnSe/ZnS QDs), and established a rapid fluorescence method to detect the E. coli cells count by using MPA-ZnSe/ZnS QDs as fluorescence probe. The formulation variables and process were optimized using the response surface methodology (RSM). Fluorescence microscopy was used to obtain fluorescence microscope images of MPA-ZnSe/ZnS QDs that bind to bacteria. The fluorescence peak intensity increases with increasing cells count in the range of 101-108 CFU/mL. Compared with the traditional based on fluorescent detection methods, this method is more convenient and useful in the bacterial count determination.

Preparation and characterization of a novel polyethyleneimine cation-modified persimmon tannin bioadsorbent for anionic dye adsorption.

A novel and recyclable bioadsorbent (PTP) has been prepared by the cationization of persimmon tannin (PT) using polyethyleneimine (PEI) for application in the removal of the anionic dye methyl orange (MO) from aqueous solution. The physicochemical properties of the prepared PTP were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, Zeta potential measurements, Brunauer-Emmett-Teller and thermogravimetric analysis. Systematic batch adsorption experiments were carried out with pH, bioadsorbent dosage, initial MO concentration and contact time. Kinetic regression analysis indicated that the adsorption processes followed the pseudo-second order model. The equilibrium isotherm was in good fit with the Freundlich model with a maximum adsorption capacity of 225.74 mg/g. Thermodynamics data revealed that the adsorption of MO onto PTP was feasible, spontaneous and endothermic. A possible biosorption mechanism was presented where electrostatic interactions, hydrogen bonding, and π-π interactions dominated the adsorption of MO onto PTP. Moreover, the regeneration of the PTP was easily achieved and MO removal efficiency remained high (81.47%) after six cycles. The actual sewage treatment simulation was evaluated and the PTP had a good preference to adsorption MO. All these results indicated that PTP could be considered a high performance and promising candidate for the effective removal of anionic dyes from aqueous solutions.

A Fe3O4@Au-basedpseudo-homogeneous electrochemical immunosensor for AFP measurement using AFP antibody-GNPs-HRP as detection probe.

In this study, a Fe3O4@Au-based pseudo-homogeneous electrochemical immunosensor was prepared for detection of alpha fetoprotein (AFP), a well-known hepatocellular carcinoma biomarker. The primary antibody (Ab1) was immobilized on Fe3O4@Au NPs as the capture probe. Horseradish peroxidase (HRP) and secondary antibody (Ab2) were conjugated on gold nanoparticles (GNPs) through electrostatic adsorption to form signal-amplifying labels. In the presence of AFP, a sandwich immunocomplex was formed via specific recognition of antigen-antibody in a Fe3O4@Au-basedpseudo-homogeneousreaction system. After the immunocomplex was captured to the surface of magnetic glassy carbon electrode (MGCE), the labeling HRP catalyzed the decomposition of H2O2, resulting in a substantial current for the quantitative detection of AFP. The amperometric (i-t) method was employed to record the response signal of the immunosensor based on the catalysis of the immobilized HRP toward the reduction of H2O2 with hydroquinone (HQ) as the redox mediator. Under the optimal conditions, the amperometric current response presented a linear relationship with AFP concentration over the range of 20 ng/mL-100 ng/mLwith a correlation coefficient of 0.9940, and the detection limit was 0.64 ng/mL at signal/noise [S/N] = 3. Moreover, the electrochemical immunosensor exhibited higher anti-interference ability, acceptable reproducibility and long-term stability for AFP detection.

Application of CRISPR/Cas13a-based biosensors in serum marker detection.

The detection of serum markers is important for the early diagnosis and monitoring of diseases, but conventional detection methods have the problem of low specificity or sensitivity. CRISPR/Cas13a-based biosensors have the characteristics of simple detection methods and high sensitivity, which have a certain potential to solve the problems of conventional detection. This paper focuses on the research progress of CRISPR/Cas13a-based biosensors in serum marker detection, introduces the principles and applications of fluorescence, electrochemistry, colorimetric, and other biosensors based on CRISPR/Cas13a in the detection of serum markers, compares and analyzes the differences between the above CRISPR/Cas13a-based biosensors, and looks forward to the future development direction of CRISPR/Cas13a-based biosensors.

A dual-signal output electrochemical aptasensor for glypican-3 ultrasensitive detection based on reduced graphene oxide-cuprous oxide nanozyme catalytic amplification strategy.

Glypican-3 (GPC3) is an essential reference target for hepatocellular carcinoma detection, follow-up and prediction. Herein, a dual-signal electrochemical aptasensor based on reduced graphene oxide-cuprous oxide (RGO-Cu2O) nanozyme was developed for GPC3 detection. The RGO-Cu2O nanoenzyme displayed excellent electron transport effect, large specific surface area and outstanding peroxidase-like ability. The differential pulse voltammetry (DPV) signal of Cu2O oxidation fraction and the chronoamperometry (i-t) signal of H2O2 decomposition catalyzed by RGO-Cu2O nanozyme were used as dual-signal detection. Under optimal conditions, the log-linear response ranges were 0.1 to 500.0 ng/mL with the limit of detection 0.064 ng/mL for DPV technique, and 0.1-50.0 ng/mL for i-t technique (detection limit of 0.0177 ng/mL). The electrochemical aptasensor has remarkably analytical performance with wide response range, low detection limit, excellent repeatability and specificity, good recovery in human serum samples. The two output signals of one sample achieve self-calibration of the results, effectively avoiding the occurrence of possible leakage and misdiagnosis of a single detection signal, suggesting that it will be a promising method in the early biomarker detection.

Competitive electrochemical aptasensor for high sensitivity detection of liver cancer marker GP73 based on rGO-Fc-PANi nanocomposites.

Golgi protein 73 (GP73) is a novel tumor marker in the early diagnosis and prognosis of hepatocellular carcinoma (HCC). Herein, a competitive electrochemical aptasensor for detecting GP73 was constructed using reduced graphene oxide-ferrocene-polyaniline nanocomposite (rGO-Fc-PANi) as the biosensing platform. The rGO-Fc-PANi had larger specific surface area, excellent conductivity and outstanding electroactive performance, which served as nanocarrier for GP73 aptamer (GP73Apt) binding and as redox nanoprobe for record electrical signal. Then, a complementary chain (cDNA) was fixed to the electrode by hybridization with GP73Apt. When GP73 was present, a competitive process happened among cDNA, GP73Apt and GP73, formed the GP73-GP73Apt stable chemical structure and made cDNA detach from the sensing electrode, resulting in enhancement of electrical signal. The difference in the corresponding peak current before and after the competition can be used to indicate the quantitative of GP73. Under optimal conditions, the DPV current response showed a good log-linear relationship with GP73 concentrations (0.001 âˆ¼ 100.0 ng/mL) with a detection limit of 0.15 pg/mL (S/N = 3). It was successfully used for GP73 detection in human serum with RSDs ranging from 1.08 % to 6.96 %. Therefore, the aptasensor could provide an innovative technology platform and hold a great potential in clinical application.

Fluorescent "turn-on" aptamer sensor for sensitive and reliable detection of Golgi glycoprotein 73 based on nitrogen-doped graphene quantum dots and molybdenum disulfide nanosheets.

The sensitivity and specificity of Golgi glycoprotein 73 (GP73) are very important for early diagnosis of hepatocellular carcinoma. Herein, we constructed a new-fashioned fluorescent aptamer sensor for GP73 determination based on nitrogen-doped graphene quantum dots (N-GQDS) and molybdenum disulfide (MoS2) nanosheets. N-GQDs with high fluorescence intensity and good stability were screened out, and GP73 aptamer (GP73Apt) is labeled with N-GQDs to form the N-GQDs-GP73Apt fluorescence probe. MoS2 nanosheets can quench the fluorescence of N-GQDs-GP73Apt owing to fluorescence resonance energy transfer mechanisms. After introducing GP73 into the biosensing system, the N-GQDs-GP73Apt specifically bound with GP73 to form the deployable structures, making N-GQDs-GP73Apt far away from MoS2, blocking the fluorescence energy transfer process, and restoring the fluorescence of N-GQDs-GP73Apt. When the GP73 concentration was in the extent of 2.5 ng/mL∼100 ng/mL, the relative fluorescence recovery is linearly relevant to the concentration of GP73, and the limit of detection (LOD) was 1.29 ng/mL (S/N = 3). Moreover in the application of actual serum sample detection, the recovery was range 98.85∼100.55 %. The fluorescent aptamer sensor can rapidly detect and analyze the serum marker GP73 with the characteristics of low-cost, high sensitivity, good specificity and recovery.