A sensitive sandwich-type immunosensor for the detection of MCP-1 based on a rGO-TEPA-Thi-Au nanocomposite and novel RuPdPt trimetallic nanoalloy particles

Detection of tumor marker CA72-4 with an electrochemical immunosensor based on MnO2 nanosheets and HNM-AuPtPd nanocomposites

To accurately detect tumor marker carbohydrate antigen 72-4 (CA72-4) of serum samples is of great significance for the early diagnosis of malignant tumors. In the present study, MnO2/hollow nanobox metal-organic framework (HNM)-AuPtPd nanocomposites were prepared via multi-step synthesis and superposition method and a series of characterizations were carried out. A highly sensitive immunosensor Ab/MnO2/HNM-AuPtPd/GCE based on the composite nanomaterial was further prepared and used to detect the tumor marker CA72-4. The constructed immunosensor achieved signal amplification by increasing the electrocatalytic activity to H2O2 by means of the synergistic effect of MnO2 ultra-thin nanosheets (MnO2 UNs) and HNM-AuPtPd. At the same time, the electrochemical properties of the immunosensor were analyzed using cyclic voltammetry, electrochemical impedance, amperometry (with the test voltage of -0.4 V), and differential pulse voltammetry. The experimental results showed that the MnO2/HNM-AuPtPd nanocomposites were successfully prepared, and the immunosensor Ab/MnO2/HNM-AuPtPd/GCE demonstrated an excellent electrochemical performance. The electrochemical immunosensor had the highest detection sensitivity under the optimal experimental conditions, such as incubation pH of 7.0, incubation time of 60 min, with the addition of 15 μL of H2O2, and in the concentration range 0.001-500 U/mL. It had a low detection limit of 1.78×10-5 U/mL (S/N = 3). Moreover, the serum sample recovery were in the range from 99.38 to 100.52%. This study provides a new method and experimental basis for the detection of tumor markers in clinical practice.

Multimetal-Based Metal-Organic Framework System for the Sensitive Detection of Heart-Type Fatty Acid Binding Protein in Electrochemiluminescence Immunoassay

In this work, an electrochemiluminescence (ECL) quenching system using multimetal-organic frameworks (MMOFs) was proposed for the sensitive and specific detection of heart-type fatty acid-binding protein (H-FABP), a marker of acute myocardial infarction (AMI). Bimetallic MOFs containing Ru and Mn as metal centers were synthesized via a one-step hydrothermal method, yielding RuMn MOFs as the ECL emitter. The RuMn MOFs not only possessed the strong ECL performance of Ru(bpy)32+ but also maintained high porosity and original metal active sites characteristic of MOFs. Moreover, under the synergistic effect of MOFs and Ru(bpy)32+, RuMn MOFs have more efficient and stable ECL emission. The trimetal-based MOF (FePtRh MOF) was used as the ECL quencher because of the electron transfer between FePtRh MOFs and RuMn MOFs. In addition, active intramolecular electron transfer from Pt to Fe or Rh atoms also occurred in FePtRh MOFs, which could promote intermolecular electron transfer and improve electron transfer efficiency to enhance the quenching efficiency. The proposed ECL immunosensor demonstrated a wide dynamic range and a low detection limit of 0.01-100 ng mL-1 and 6.8 pg mL-1, respectively, under optimal conditions. The ECL quenching system also presented good specificity, stability, and reproducibility. Therefore, an alternative method for H-FABP detection in clinical diagnosis was provided by this study, highlighting the potential of MMOFs in advancing ECL technology.

A new sandwich-type electrochemiluminescence sensor based on HPSNs-NH2@Au NPs and AuPdPt NPs for determination of α(2,3)-sial-Gs

A novel sandwich-type "on-off" electrochemiluminescence (ECL) biosensor for the determination of α(2,3)-sial-Gs was designed. Specifically, amino-functionalized porous silica nanoparticles (HPSNs-NH2) were first prepared and then decorated with gold nanoparticles (Au NPs) to form HPSNs-NH2@Au NP nanocomposite, which exhibited a strong ability to enhance ECL intensity with K2S2O8 as co-reactant (signal-on) and could immobilize the target-specific binding molecules of maackia amurensis lectin (MAL). Additionally, AuPdPt trimetallic nanoparticles were prepared to serve as a quenched ECL signal indicator (signal-off) with the ability of capturing the target non-specific binding molecules of 3-aminophenylboronic acid (APBA) to form a signal label. The sandwich-type ECL biosensor was constructed based on the structure of MAL-α(2,3)-sial-Gs-APBA and achieved a determination toward α(2,3)-sial-Gs with a wide linear range from 1 fg mL-1 to 10 ng mL-1 and a low detection limit of 0.5 fg mL-1. Furthermore, the proposed ECL biosensor showed satisfactory selectivity, stability, and reproducibility for α(2,3)-sial-Gs determination.

Microtrap-assisted microfluidic magnetic separation and concentration for ultrasensitive immunoassays of biomarkers

Precise and accurate quantitation of important biomarkers is significant, especially in early-stage diseases diagnosis. To realized effective biosample preparation and trace-level biomarker detection, a microtrap-assisted microfluidic magnetic immunoassays (μMI) method was developed in this work. A microtrap was fabricated inside the straight microchannel of μMI device to help magnetic separation and concentration of immunocomplexes. These immunocomplexes were enriched in microtrap of μMI device to accomplish selective and sensitive biomarker detection. Horseradish peroxidase-labeled magnetic beads were employed to evaluate assay feasibility and microtrap effect on assay sensitivity. The microtrap-assisted μMI was then applied for model biomarkers detection. The limits of detection of μMI were 0.025 pg/mL for monocyte chemoattractant protein-1 (MCP-1) and 0.021 pg/mL for matrix metalloproteinase-9 (MMP-9), which corresponded up to 2014-fold sensitivity improvement compared to their standard microwell enzyme-linked immunosorbent assay (ELISA) results. In addition, the selectivity and reproducibility of microtrap-assisted μMI were confirmed. In clinical serum sample analysis, recoveries of 91.3%-106.7% with relative standard deviations less than 6.1% were obtained for MCP-1 and MMP-9, and method accuracy was verified by commercial ELISA kit. The developed μMI can accomplish ultratrace biomarker detection offering practical tool for laboratorial and clinical research.

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 (0.001-120 ng mL^-1) and a lower detection limit (0.33 pg mL^-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.

Biodetection Techniques for Quantification of Chemokines

Chemokines are a class of cytokine whose special properties, together with their involvement and relevant role in various diseases, make them a restricted group of biomarkers suitable for diagnosis and monitoring. Despite their importance, biodetection techniques dedicated to the selective determination of one or more chemokines are very scarce. For some years now, the critical diagnosis of inflammatory diseases by detecting both cytokine and chemokine biomarkers, has had a strong impact on the development of multiple detection platforms. However, it would be desirable to implement methodologies with a higher degree of selectivity for chemokines, in order to provide more precise information. In addition, better development of biosensor technology applied to this specific field would make it possible to address the main challenges of detection methods for several diseases with a high incidence in the population, avoiding high costs and low sensitivity. Taking this into account, this review aims to present the state of the art of chemokine biodetection techniques and emphasize the role of these systems in the prevention, monitoring and treatment of various diseases associated with chemokines as a starting point for future developments that are also analyzed throughout the article.

An electrochemical immunosensor based on reduced graphene oxide/multiwalled carbon nanotubes/thionine/gold nanoparticle nanocomposites for the sensitive testing of follicle-stimulating hormone

Follicle-Stimulating Hormone (FSH) is a kind of gonadotropin which can promote human reproduction and development. Abnormal FSH levels may lead to endocrine disorders and infertility. Sensitive determination of FSH is very significant for the clinical diagnosis of these diseases. Here, an electrochemical immunosensor based on a screen-printed electrode (SPE) was developed for the detection of FSH. Nanocomposites, compounded with reduced graphene oxide (rGO), multiwalled carbon nanotubes (MWCNTs), thionine (Thi) and gold nanoparticles (AuNPs), were used for increasing the specific surface area to adsorb molecules and amplify signals. The rGO/MWCNTs/Thi/AuNP nanocomposites, anti-FSH and BSA were successively assembled onto a SPE to fabricate the immunosensor. Electrochemical performance of the modified immunosensor was studied by differential pulse voltammetry (DPV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). FSH testing was based on the principle that the insulating FSH antigen-antibody immunocomplex could retard the electron transfer of Thi which led to the decrease of the DPV current response. Under optimum conditions, the rGO/MWCNTs/Thi/AuNP modified immunosensor exhibited high sensitivity and accuracy for the determination of FSH in a linear range from 1 mIU mL^-1 to 250 mIU mL^-1, and the detection limit was 0.05 mIU mL^-1 at a signal-to-noise ratio of 3. The immunosensor was successfully applied for the determination of quality serum samples with a recovery of 94.0-109.8%. The electrochemical immunosensor could be utilized for testing other gonadotropins.

An electrochemical biosensor based on hemin/G-quadruplex DNAzyme and PdRu/Pt heterostructures as signal amplifier for circulating tumor cells detection

Metastasis due to circulating tumor cells (CTCs) shed from the original tumor accounts for the majority of cancer-related death. Efficient CTCs detection is pivotal to the diagnosis of early cancer metastasis. In this work, Platinum nanoparticles (PtNPs) decorated hyperbranched PdRu nanospines (PdRu/Pt) hierarchical structures were firstly synthesized to detect CTCs with the assistance of DNAzyme. Meanwhile, Super P and gold nanoparticles (AuNPs) acted as sensing medium to improve electrical conductivity and immobilization of anti-EpCAM antibody to specifically capture model CTCs. After immune-conjugation of anti-EpCAM-MCF-7-signal probes on the gold electrode, PtNPs, PdRu nanospines (PdRuNSs) and hemin/G-quadruplex co-catalyzed substrate H₂O₂ to realize multiplexed signal amplification, which significantly improves the analytical performance of the electrochemical biosensor. As-proposed biosensor reached a limit of detection (LOD) down to 2 cells mL^-1 and showed a wide detection range of 2 to 10⁶ cells mL^-1. Application of the biosensor to detect MCF-7 cells spiked human blood samples further demonstrated the feasibility for early cancer evaluation in clinic.

A paper-based SERS assay for sensitive duplex cytokine detection towards the atherosclerosis-associated disease diagnosis

Atherosclerosis (AS) is the most common factor causing many cardiovascular and cerebrovascular diseases and has received considerable attention. The occurrence mechanism of AS is uncertain because it is a choronically pathological process that is influenced by multi-aspects, among which cytokines play the key roles in regulating the processes of the immune system. For example, two key cytokines, namely, IL-10 and MCP-1 (chemokine), which are involved in AS progression with varied levels, can be used for AS status monitoring and early diagnosis of AS-associated diseases. Hence, a new paper-based, surface-enhanced Raman spectroscopy (SERS) sensing platform was established for the detection of these two key cytokines. By combining a nanoporous networking membrane as the substrate and SERS nanotags as the probe for signal reading, together with a sandwich design, sensitive and specific identification and quantification of cytokine targets in human serum were achieved with excellent sensing characteristics. The lowest detectable concentration was determined to be 0.1 pg mL-1 for both IL-10 and MCP-1 in human serum. The assay also exhibits high specificity towards target cytokine detection, with low-nonspecific binding and acceptable cross-reactivity in the presence of other structurally similar targets. Finally, the practicability was validated by performing duplex detection in human serum, which further demonstrates the high specificity of the assay for the detection of target cytokines. Taken together, these promising results illustrate that this developed sensing assay is a candidate for clinical multi-target analysis in real environments.

Nanocomposites based on quasi-networked Au1.5Pt1Co1 ternary alloy nanoparticles and decorated with poly-L-cysteine film for the electrocatalytic application of hydroquinone sensing

A mildly one-pot method is developed for the synthesis of quasi-networked Au_1.5Pt₁Co₁ ternary alloy nanoparticles (TANPs) at room temperature through the co-reduction of AuCl₄^-, PtCl₆^- and Co²⁺ with hydrazine hydrate. Characterizations of XRD, XPS, HRTEM, EDS and SAED successfully reveal the crystal structure, composition, valence and morphology of Au_1.5Pt₁Co₁ TANPs, respectively. The glassy carbon electrode (GCE) modified by Au_1.5Pt₁Co₁ TANPs with good dispersion and multi-density surface defects occupies the optimal electrochemical active surface area (ECSA). After the coated poly-L-cysteine (P-L-Cys) film on the Au_1.5Pt₁Co₁/GCE surface, the morphology, element mapping and surface roughness of the P-L-Cys/Au_1.5Pt₁Co₁/GCE are investigated via FESEM and AFM to verify continuous electrode modification processes. The electrochemical behaviors of the composite electrode for hydroquinone (HQ) are evaluated by cyclic voltammetry (CV) with interfacial properties of adsorption and diffusion. Differential pulse voltammetry (DPV) for HQ electrochemical sensing at 0.10 V (vs. SCE) exhibits two linear response ranges from 0.1 to 30 and 30-200 μM, respectively. A low detection limit (S/N = 3) of 0.045 μM is obtained with a sensitivity of 4.247 μA μM^-1·cm^-2. The resulting P-L-Cys/Au_1.5Pt₁Co₁/GCE also presents ascendant selectivity, repeatability, reproducibility and stability. In addition, the established method is applied to the assessment of the HQ level in real water samples (mineral water, tap water and lake water) with the satisfactory results of spiked recoveries. The sensor may become a promising tool for the trace analysis of the electroactive substance in food or environmental samples.

A dual recognition strategy for accurate detection of CTCs based on novel branched PtAuRh trimetallic nanospheres

Accurate detection of circulating tumor cells (CTCs) has a pivotal role in the metastasis monitoring and prognosis of tumor. In this work, an ultrasensitive electrochemical cytosensor was developed based on excellent electrocatalytic materials and a dual recognition strategy. Herein, novel branched PtAuRh trimetallic nanospheres (b-PtAuRh TNS) were synthesized for the first time by a facile one-pot method, which had a huge specific surface area and outstanding catalytic activity. B-PtAuRh TNS linked with aptamers targeting mucin1 (MUC1) were served as signal tags to amplify the signal. As electrode modified material, the nanocomposites of Cabot carbon black (BP2000) and AuNPs were used to improve the electron transfer efficiency of electrode. In addition to using b-PtAuRh TNS labeled anti-MUC1 aptamers as signal probes, anti-EpCAM antibodies were worked as capture probes to achieve dual recognition of target cells. In other words, only cells expressing both MUC1 and EpCAM could produce electrochemical signal. The constructed cytosensor presented a wide linear range (5 - 1 × 10⁶ cells mL^-1) and a low detection limit (1 cell mL^-1). It was worth noting that the proposed cytosensor could detect CTCs in clinical blood samples. To sum up, the developed cytosensor might become a promising detection platform for cancer diagnosis and tumor metastasis.