An amplified colorimetric method has been developed for the detection of protein and cancer cells based on the assembly of nucleic acids and proteins for the first time. In this process, the assembly of nucleic acids was triggered by a biotinylated DNA strand after a sandwich immunoreaction. The biotinylated DNA strand and sandwich immunocomplex were connected by streptavidin. Then, the assembly of biotinylated bovine serum albumin (Biotin-BSA) and streptavidin-horseradish peroxidase (SA-HRP) occurred at a node of the assembled products of nucleic acids through the biotin-streptavidin reaction. Under the catalysis of horseradish peroxidase, 3,3′,5,5′-tetramethylbenzidine (TMB) was oxidized by H2O2 and the oxidized product was analyzed by its UV–vis absorbance signal and sensitive colorimetric detection. This colorimetric sensor could not only achieve the quantitative determination of protein by UV–vis absorbance but could also be applied for semiquantitative determination by digital visualization. Using alpha-fetoprotein (AFP) as the model target, this proposed colorimetric method showed a wide linear range from 5 pg/mL to 1 ng/mL with a detection limit of 1.95 pg/mL by the instrument, and even 5 pg/mL target protein could be distinguished simply by the naked eye. This approach was then expanded to detect cancer cells based on the recognition of folic acid receptors that were over-expressed on the cancer cells by folic acid-tethered DNA. More importantly, this strategy can be further used as a universal colorimetric method for the determination of viruses or other proteins by changing the corresponding antibodies. 相似文献
In this work, a highly-sensitive and cost-effective detection approach based on the integration of tyramide signal amplification with a silver enhancement method (SEM-TSA) has been developed successfully. To demonstrate the feasibility of this approach, human IgG as a model target protein was employed and its concentration was assayed based on colorimetric detection. The analytical parameters including the concentrations of detection antibody, streptavidin-horseradish peroxidase, biotinyl tyramide, and streptavidin-nanogold were systematically optimized. The quantitative analysis was performed and a dynamic range was obtained from 0.18 ng/mL to 39.1 ng/mL, while no detectable images could be observed when the silver enhancement method (SEM) without TSA was used. The detection limits were 0.18 ng/mL and 21 ng/mL for SEM-TSA and SEM, respectively. The results showed that sensitivity of the presented colorimetric assay significantly increased by two-orders of magnitude. In addition, this method has been successfully applied in analyzing normal human serum samples. The results suggested the colorimetric detection method based on TSA-SEM has promising potential applications in biomedical analysis and clinical diagnosis. 相似文献
In this work, a very simple dual-readout lateral flow test strip (LFTS) platform was developed for sensitive detection of alkaline phosphatase (ALP) based on a portable device. In this assay, quantum dots (QDs) conjugated with bovine serum albumin (QDs-BSA) were chosen as fluorescence signal labels. In the absence of ALP, MnO2 nanosheets aggregate on the test line and exhibit an obvious brown color, which can be observed by naked eyes to realize semi-qualitative analysis. Meanwhile, fluorescence intensity of QDs-BSA can also be effectively quenched by MnO2 nanosheets due to inner-filter effect. Correspondingly, in the presence of ALP, ALP can catalyze the hydrolysis of ascorbic acid 2-phosphate (AAP) to generate L-ascorbic acid (AA), which can reduce MnO2 into Mn2+, accompanying with the obvious fluorescence recovery of the QDs. By simply monitoring the change of colorimetric and fluorescent signal on the test line, trace amount of ALP can be quantitatively detected. Under the optimal conditions, measurable evaluation of ALP was reached in a linear range from 1 U/L to 20 U/L with a detection limit of 0.7 U/L based on fluorescence signal. Furthermore, this colorimetric/fluorescent dual-readout assay was successfully applied to monitor ALP in human serum samples, showing its great potential as a point of care biosensor for clinical diagnosis. 相似文献
Lanthanide‐doped upconversion nanoparticles (UCNPs) have shown great promise in bioapplications. Exploring new host materials to realize efficient upconversion luminescence (UCL) output is a goal of general concern. Herein, we develop a unique strategy for the synthesis of novel LiLuF4:Ln3+ core/shell UCNPs with typically high absolute upconversion quantum yields of 5.0 % and 7.6 % for Er3+ and Tm3+, respectively. Based on our customized UCL biodetection system, we demonstrate for the first time the application of LiLuF4:Ln3+ core/shell UCNPs as sensitive UCL bioprobes for the detection of an important disease marker β subunit of human chorionic gonadotropin (β‐hCG) with a detection limit of 3.8 ng mL−1, which is comparable to the β‐hCG level in the serum of normal humans. Furthermore, we use these UCNPs in proof‐of‐concept computed tomography imaging and UCL imaging of cancer cells, thus revealing the great potential of LiLuF4:Ln3+ UCNPs as efficient nano‐bioprobes in disease diagnosis. 相似文献
Cardiac Troponin I (cTnI) is a preferred biomarker to diagnose acute myocardial infarction which is one of the leading risks to health globally due to its short term. However, clinical analyzers are difficult to achieve its on-site quantitative detection. A novel label-free aptasensor was constructed to realize ultrasensitive and rapid recognition of cTnI. A nanocubic AuNPs/In2O3 composite was designed to provide synergistic effects of abundant active sites and signal magnification for aptamers grafting. Relying on a conductance-dependence strategy, this aptasensor can achieve the quantitative detection within 10 min, which is much faster than state-of-the-art analyzers, as well as exhibiting an ultrawide linear range of 0.1–1000 ng/mL and a low detection limit of 0.06 ng/mL with an excellent selectivity in the analysis of human serum. 相似文献
In this study, a bimetallic nanomaterial‐based electrochemical immunosensor was developed for the detection of carcinoembryonic antigen (CEA) and vascular endothelial growth factor (VEGF) cancer biomarkers at the same time. CEA and VEGF biomarkers are indicators for colon and breast cancers and stomach cancers, respectively. During the study, gold nanoparticle (AuNp), lead nanoparticle (PbNp), copper nanoparticle (CuNp) and magnetic gamma iron(III)oxide (γFe2O3 Np) were synthesized, characterized and used together for the first time in the structure of an electrochemical biosensor based on anti‐CEA and anti‐VEGF. For this purpose, Au SPE based sandwich immunosensor was fabricated by using labeled anti‐CEA (labeled with Pb+2) and labeled anti‐VEGF (labeled with Cu+2). As a result, CEA and VEGF biomarkers were detected following the oxidation peaks of label metals (Pb+2 and Cu+2) by using differential pulse voltammetry. After the experimental parameters were optimized, the linear range was found in the concentration range between 25 ng/mL and 600 ng/mL with the relative standard deviation (RSD) value of (n=3 for 600 ng/mL) 3.33 % and limit of detection (LOD) value of 4.31 ng/mL for CEA biomarker. On the other hand, the linear range was found in the concentration range between 0.2 ng/mL and 12.5 ng/mL with the RSD value of (n=3 for 12.5 ng/mL) 5.31 % and LOD value of 0.014 ng/mL for VEGF biomarker. Lastly, sample application studies for synthetic plasma sample and interference studies with dopamine, ascorbic acid, BSA, cysteine and IgG were carried out. 相似文献
Diethylstilbestrol (DES) is a synthetic estrogen that has ever been used worldwide. Polyclonal antibodies (PAbs) were used in immunoassay for detection of DES residues in environmental and agricultural samples in previous paper. In this paper, an indirect competitive enzyme-linked immunosorbent assay (icELISA) was developed based on monoclonal antibody (MAb) for the determination of diethylstilbestrol. Mono-o-carboxypropyldiethylstilbestrol (DES-CP) and mono-o-carboxymethyldiethylstilbestrol (DES-CME) were synthesized to be haptens. DES-CP was coupled to bovine serum albumin (BSA) to be an immunogen in BALB/c female mouse for MAb production. The MAb was characterized for specificity and affinity to DES in icELISA. Under the optimum condition, the icELISA showed an ICs0 of 9.8 ng/mL, the limit of detection (IC20) of 2.3 ng/mL and a working range of 2-42 ng/mL. Hexestrol and dienestrol exhibited cross-reactivity values were 44% and 27%, respectively. Cross-reactivity of natural estrogen 17β-estradiol was less than 0.1%. The influences of some factors such as salt concentration, pH and organic solvent concentration on the assay were evaluated. The concentrations of DES in the fortified water samples determined by the assay were correlated well with the fortification levels. The results were conf'm'ned with analysis by HPLC. 相似文献
In this paper, we present a new colorimetric technique as a novel assay for the easy and direct detection of α-amylase activity. This detection system utilizes the interaction of α-amylase with starch that is supporting copper/gold (Cu/Au) nanoclusters. The Cu/Au nanoclusters are synthesized using starch as a stabilizing agent at room temperature. These nanoclusters show robust peroxidase-like activity and are able to catalyze the oxidation of TMB (3,3,5,5-tetramethylbenzidine) in the presence of hydrogen peroxide (H2O2), leading to the generation of a blue-colored solution. The α-amylase detection mechanism is based on the digestion of the starch by α-amylase, which results in nanocluster aggregation, leading to increased nanoparticle size and thus decreased peroxidase-like activity of the Cu/Au NCs. Experiments showed that the gradual addition of α-amylase causes the peroxidase activity to decrease step by step in a linear fashion. Using this method, colorimetric sensing of α-amylase was achieved with a detection limit (LOD) of 0.04 U/mL and a linear range of 0.1–10 U/mL. This method is significantly selective for α-amylase and could be affordably and conveniently applied to the detection of α-amylase in blood serum.
A rapid and sensitive liquid chromatography method with amperometric detection has been developed for the determination of
propafenone in serum. Sample preparation based on single extraction with dichloromethane using bupivacaine hydrochloride as
internal standard. The compounds were separated on C-18 reversed-phase analytical column with the mobile phase composed of
methanol-acetonitrile-10 mM K2HPO4 (45: 25: 30, v/v/v). Analytes were detected electrochemically with the use of amperometric detector. The quantification limit
for propafenone in serum was 10 ng/mL. Linearity of the method was confirmed in the range of 10–500 ng/mL with correlation
coefficient of 0.9998. Inter-day relative standard deviations (RSD) ranged from 0.27 to 11.9% and intra-day RSD equalled from
1.1 to 9.7%. The newly developed method was applied for the monitoring of the drug in blood levels with 18 healthy volunteers
taking tablet with propafenone. 相似文献
High performance liquid chromatography coupled with electrochemical detection (HPLC-EC) method has been developed for the determination of benzidine and its related congeners in wastewater at the low ng/mL level. With a µ-Bondapak C18 column, 53% acetonitrile (pH 4.7), and electrochemical detection at +1.0 V applied potential, the detection limits range from 3 ng/mL for benzidine to 10 ng/mL for 3,3′-dichlorobenzidine, assuming a 100 µL injection. The detection limits can be further lowered to the sub-ng/mL level by incorporating a short precolumn into the HPLC system for on-line sample enrichment. Recoveries are generally greater than 80% — except for benzidine and 3,3′-diaminobenzidine which give 50–70% recoveries. Industrial wastewater samples from a coke-plant and a plant producing 3,3′-dichlorobenzidine based dyes were successfully studied via this method. 相似文献