A sensitive label-free immunosensor for detection α-Fetoprotein in whole blood based on anticoagulating magnetic nanoparticles

Biosensing of Alpha-Fetoprotein: A Key Direction toward the Early Detection and Management of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is currently one of the most prevalent cancers worldwide. Associated risk factors include, but are not limited to, cirrhosis and underlying liver diseases, including chronic hepatitis B or C infections, excessive alcohol consumption, nonalcoholic fatty liver disease (NAFLD), and exposure to chemical carcinogens. It is crucial to detect this disease early on before it metastasizes to adjoining parts of the body, worsening the prognosis. Serum biomarkers have proven to be a more accurate diagnostic tool compared to imaging. Among various markers such as nucleic acids, circulating genetic material, proteins, enzymes, and other metabolites, alpha-fetoprotein (AFP) is a protein marker primarily used to diagnose HCC. However, current methods need a large sample and carry a high cost, among other challenges, which can be improved using biosensing technology. Early and accurate detection of AFP can prevent severe progression of the disease and ensure better management of HCC patients. This review sheds light on HCC development in the human body. Afterward, we outline various types of biosensors (optical, electrochemical, and mass-based), as well as the most relevant studies of biosensing modalities for non-invasive monitoring of AFP. The review also explains these sensing platforms, detection substrates, surface modification agents, and fluorescent probes used to develop such biosensors. Finally, the challenges and future trends in routine clinical analysis are discussed to motivate further developments.

Progress in Procalcitonin Detection Based on Immunoassay

Procalcitonin (PCT) serves as a crucial biomarker utilized in diverse clinical contexts, including sepsis diagnosis and emergency departments. Its applications extend to identifying pathogens, assessing infection severity, guiding drug administration, and implementing theranostic strategies. However, current clinical deployed methods cannot meet the needs for accurate or real-time quantitative monitoring of PCT. This review aims to introduce these emerging PCT immunoassay technologies, focusing on analyzing their advantages in improving detection performances, such as easy operation and high precision. The fundamental principles and characteristics of state-of-the-art methods are first introduced, including chemiluminescence, immunofluorescence, latex-enhanced turbidity, enzyme-linked immunosorbent, colloidal gold immunochromatography, and radioimmunoassay. Then, improved methods using new materials and new technologies are briefly described, for instance, the combination with responsive nanomaterials, Raman spectroscopy, and digital microfluidics. Finally, the detection performance parameters of these methods and the clinical importance of PCT detection are also discussed.

Recent Advances in Metallic Nanostructures-assisted Biosensors for Medical Diagnosis and Therapy

The field of nanotechnology has witnessed remarkable progress in recent years, particularly in its application to medical diagnosis and therapy. Metallic nanostructures-assisted biosensors have emerged as a powerful and versatile platform, offering unprecedented opportunities for sensitive, specific, and minimally invasive diagnostic techniques, as well as innovative therapeutic interventions. These biosensors exploit the molecular interactions occurring between biomolecules, such as antibodies, enzymes, aptamers, or nucleic acids, and metallic surfaces to induce observable alterations in multiple physical attributes, encompassing electrical, optical, colorimetric, and electrochemical signals. These interactions yield measurable data concerning the existence and concentration of particular biomolecules. The inherent characteristics of metal nanostructures, such as conductivity, plasmon resonance, and catalytic activity, serve to amplify both sensitivity and specificity in these biosensors. This review provides an in-depth exploration of the latest advancements in metallic nanostructures-assisted biosensors, highlighting their transformative impact on medical science and envisioning their potential in shaping the future of personalized healthcare.

Detection of Alpha Fetoprotein Based on AIEgen Nanosphere Labeled Aptamer Combined with Sandwich Structure of Magnetic Gold Nanocomposites

As a biomarker, alpha-fetoprotein (AFP) is valuable for detecting some tumors in men, non-pregnant women, and children. However, the detection sensitivity in some methods needs to be improved. Therefore, developing a simple, reliable, and sensitive detection method for AFP is important for non-malignant diseases. An aptamer binding was developed based on aggregation-induced emission luminogen (AIEgen) nanosphere labeled with Fe3O4@MPTMS@AuNPs. AFP was detected with a sandwich structure of AuNPs magnetic composite particles. An aggregation-induced emission (AIE) molecule and polystyrene (PS) nanosphere complex were assembled, enhancing the fluorescence and improving the sensitivity of detection. The limit of detection (LOD) was at a given level of 1.429 pg/mL, which can best be achieved in serum samples. Finally, the results obtained showed the complex to be promising in practical applications.

A novel electrochemical immunosensor that amplifies Poly(o-phenylenediamine) signal by pH-driven cascade reaction used for alpha-foetoprotein detection

The present protocol develops an electrochemical immunosensor with poly(o-phenylene diamine) attached gold nanoparticles (PPD@Au NPs) as the immune platform, polydopamine-loaded cobalt ions (Co²⁺-PDA) as the immune probe, and K₂S₂O₈ as the signal amplifying substance with pH-driven cascade reaction. The application of conventional immunosensors often leads to easy leakage of the current signal and increases the impedance due to assembly. However, this new immunosensor offers the following advantages: (1) The signal substance PPD is modified on the electrode surface, effectively reducing the signal loss and leakage of the immunosensor; (2) The pH response reduces the impedance of the immunosensor while destroying the Co²⁺-PDA secondary antibody label; (3) The pH response releases a small amount of Co²⁺, leading to SO₄^-· generation by K₂S₂O₈ through a cascade reaction, further amplifying the PPD response current signal; (4) The pH response generates excess Co²⁺ and the by-product PDA fragments can consume the SO₄^-· generated by K₂S₂O₈, so that the final response signal decreases with the increasing antigen concentration. The experimental results showed that the immunosensor exhibited good selectivity, long-term stability, and reproducibility for AFP detection in the range of 1 pg/mL-100 ng/mL, with a detection limit of 0.214 pg/mL. Interestingly, it is expected to be used for detecting AFP in actual blood samples.

Recent advances in nanotechnology-enhanced biosensors for α-fetoprotein detection

α-Fetoprotein (AFP) is a kind of fetal protein that is related to tumor, the increasing concentration of which gives birth to a large variety of diseases, such as liver cancer. Therefore, the detection method with super sensitivity, high selectivity, and less time consumption under trace concentrations in early stage of diseases is becoming a necessity. In recent years, nanomaterials have been regarded as significant resources for the exploration of efficient biosensors with high sensitivity, selectivity, speed, as well as simple process, due to their excellent optical, electrical, and chemical properties. In this paper, we reviewed the research progress of AFP biosensors with enhanced sensitivity and selectivity by nanoparticles. Representative examples have also been displayed in this paper to expound the nanotechnologies utilized in the early detection of AFP. Furthermore, challenges of the clinical application of AFP biosensors based on nanotechnology have been elaborated, as well as the development opportunity in this field in the future. This review provides a comprehensive overview on the various nano-biosensor for AFP detection based on functional nanotechnology.

Detection of Alpha-Fetoprotein Using Aptamer-Based Sensors

Alpha-fetoprotein (AFP) is widely-known as the most commonly used protein biomarker for liver cancer diagnosis at the early stage. Therefore, developing the highly sensitive and reliable method of AFP detection is of essential demand for practical applications. Herein, two types of aptamer-based AFP detection methods, i.e., optical and electrochemical biosensors, are reviewed in detail. The optical biosensors include Raman spectroscopy, dual-polarization interferometry, resonance light-scattering, fluorescence, and chemiluminescence. The electrochemical biosensors include cyclic voltammetry, electrochemical impedance spectroscopy, and giant magnetic impedance. Looking into the future, methods for AFP detection that are high sensitivity, long-term stability, low cost, and operation convenience will continue to be developed.

Electrochemical sensor based on micromotor technology for detection of Ox-LDL in whole blood

Detecting the concentration of oxidized low-density lipoprotein (Ox-LDL) in whole blood is of great significance for monitoring the development of atherosclerosis. In order to simplify the complex processing steps of blood sample before the detection, an electrochemical sensor based on micromotor technology was designed, which was called magnesium (Mg)-Fe₃O₄@ prussian blue (PB)@ antibody of Ox-LDL (Ab)@ bovine serum albumin (BSA). The active capture of Ox-LDL in whole blood can be realized by the help of the movement of Mg microsphere with the driving force of H₂. Then the captured Ox-LDL was collected on the surface of the magnetic glassy carbon electrode (MGCE) by self-made funnel device, and the content of Ox-LDL was detected by electrochemical workstation in the way of chronoamperometry (i-t). Due to the application of micromotor, the electrochemical sensor proposed in this study had good detection efficiency for Ox-LDL in whole blood with range from 1 × 10^-2 μg/mL to 10 μg/mL, and the limit of detection (LOD) towards Ox-LDL was 9.80 × 10^-4 μg/mL. The electrochemical sensor based on micromotor technology provides a rapid, effective, and sensitive method for the detection of Ox-LDL in whole blood.

Veni, Vidi, Vici: Immobilized Peptide-Based Conjugates as Tools for Capture, Analysis, and Transformation

Analysis of peptide biomarkers of pathological states of the organism is often a serious challenge, due to a very complex composition of the cell and insufficient sensitivity of the current analytical methods (including mass spectrometry). One of the possible ways to overcome this problem is sample enrichment by capturing the selected components using a specific solid support. Another option is increasing the detectability of the desired compound by its selective tagging. Appropriately modified and immobilized peptides can be used for these purposes. In addition, they find application in studying the specificity and activity of proteolytic enzymes. Immobilized heterocyclic peptide conjugates may serve as metal ligands, to form complexes used as catalysts or analytical markers. In this review, we describe various applications of immobilized peptides, including selective capturing of cysteine-containing peptides, tagging of the carbonyl compounds to increase the sensitivity of their detection, enrichment of biological samples in deoxyfructosylated peptides, and fishing out of tyrosine–containing peptides by the formation of azo bond. Moreover, the use of the one-bead-one-compound peptide library for the analysis of substrate specificity and activity of caspases is described. Furthermore, the evolution of immobilization from the solid support used in peptide synthesis to nanocarriers is presented. Taken together, the examples presented here demonstrate immobilized peptides as a multifunctional tool, which can be successfully used to solve multiple analytical problems.

Research progress of using micro/nanomotors in the detection and therapy of diseases related to the blood environment

Micro/nanomotors bring new possibilities for the detection and therapy of diseases related to the blood environment with their unique motion effect. This work reviews the research progress of using micro/nanomotors in the detection and therapy of diseases related to the blood environment. First, we outline the advantages of using micro/nanomotors in blood-related disease detection. To be specific, the motion capability of micro/nanomotors can increase plasma or blood fluid convection and accelerate the interaction between the sample and the capture probe. This allows the effective reduction of the amount of reagents and treatment steps. Therefore, the application of micro/nanomotors significantly improves the analytical performance. Second, we discuss the key challenges and future prospects of micro/nanomotors in the treatment of blood-environment related diseases. It is very important to design a unique treatment plan according to the etiology and specific microenvironment of the disease. The next generation of micro/nanomotors is expected to bring exciting progress to the detection and therapy of blood-environment related diseases.

Hedgehog-like Bi2S3 nanostructures: a novel composite soft template route to the synthesis and sensitive electrochemical immunoassay of the liver cancer biomarker

A new route was proposed to synthesize novel hedgehog-like Bi₂S₃nanostructure using CTAB-trimellitic acid as a composite soft template and thiourea as the sulfur source, which was used  to construct an effective electrochemical AFP immunosensor.

Fluorescence sensing strategy based on aptamer recognition and mismatched catalytic hairpin assembly for highly sensitive detection of alpha-fetoprotein

At present, alpha fetoprotein (AFP) is mainly used as a serum marker of primary Hepatocellular carcinoma. A simple, enzyme-free sensing strategy is introduced for highly sensitive fluorescence detection of AFP. This detection strategy is based on aptamer recognition and mismatched catalytic hairpin assembly (MCHA). At first, Trigger is locked by aptamer before the introduction of AFP in this aptamer-MCHA system. The aptamer preferentially combines with AFP via powerful attraction in the presence of AFP. This results in the release of trigger and initiation of MCHA cycle, thus forming the H1 and H2 double chain complexes (denoted as H1@H2). Finally, H1@H2 and double chain structure containing fluorophore and its quenched group- BHQ1 (denoted as F@Q) initiated displacement reaction, which caused double chain separation and fluorescence recovery. This assay produces a wide detection range, which is from 0.1 ng mL^-1 to 10 μg mL^-1 and the limit of detection as 0.033 ng mL^-1. The whole detection process was performed at 37 °C for 60 min. In addition, this assay had high anti-interference ability and could be used to detect AFP in clinical serum. This novel AFP detection strategy is able to screen of Hepatocellular carcinoma.

Label-free detection of biomarker alpha fetoprotein in serum by ssDNA aptamer functionalized magnetic nanoparticles

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in the clinic, with the characteristics of occult onset, rapid progression, and high degree of malignancy. Alpha fetoprotein (AFP) is the most important biomarker of HCC, which is widely used in early screening, diagnosis, and prognosis observation. A series of immunoassays have been developed and frequently used in the detection of AFP based on antibodies. Unfortunately, the shortcomings of antibodies, such as thermal unstable and fluctuant activity by batches, lead to the inaccuracy in the detection of AFP. In this study, aptamers instead of antibodies were adopted as the specific recognition element for AFP, aiming to seek an alternative strategy to immunoassays. An AFP-specific ssDNA aptamer was grafted to magnetic nanoparticles (Fe₃O₄@SiO₂) via avidin-biotin interaction, and the resultant aptamer functionalized magnetic nanoparticles (Ap-MNPs) were adequately characterized and tested. The Ap-MNPs in solution exhibited a fast response to the outer magnetic field, and can be completely separated in several minutes. It was found that Ap-MNPs have good specificity to the target AFP, as the recovery of AFP (87.0%) was much higher than the competitive proteins IgG (38.9%), HSA (18.5%), and FIB (11.4%). A convenient and efficient label-free detection method of AFP in serum was developed based on Ap-MNPs in combination with high-performance liquid chromatography. The linearity of this method was over a range of 1-50 μg ml^-1 with a correlation coefficient of 0.9999, and the limit of detection was 0.27 μg ml^-1. This study indicated that aptamers are an ideal tool for the recognition and detection of biomarkers, and thus will find wide applications in clinical practice.

A ratiometric electrochemiluminescence method using a single luminophore of porous g-C3N4 for the ultrasensitive determination of alpha fetoprotein

In this work, we report a simple ratiometric electrochemiluminescence method for ultra-sensitive immunoanalysis.

Facile synthesis of novel reduced graphene oxide@polystyrene nanospheres for sensitive label-free electrochemical immunoassay

Nanosized reduced graphene oxide@polystyrene nanospheres were first synthesized and further exploited for highly sensitive label-free electrochemical immunoassay applications.

Implication of Magnetic Nanoparticles in Cancer Detection, Screening and Treatment

During the last few decades, magnetic nanoparticles have been evaluated as promising materials in the field of cancer detection, screening, and treatment. Early diagnosis and screening of cancer may be achieved using magnetic nanoparticles either within the magnetic resonance imaging technique and/or sensing systems. These sensors are designed to selectively detect specific biomarkers, compounds that can be related to the onset or evolution of cancer, during and after the treatment of this widespread disease. Some of the particular properties of magnetic nanoparticles are extensively exploited in cancer therapy as drug delivery agents to selectively target the envisaged location by tailored in vivo manipulation using an external magnetic field. Furthermore, individualized treatment with antineoplastic drugs may be combined with magnetic resonance imaging to achieve an efficient therapy. This review summarizes the studies about the implications of magnetic nanoparticles in cancer diagnosis, treatment and drug delivery as well as prospects for future development and challenges of magnetic nanoparticles in the field of oncology.

A dual-responsive biosensor for blood lead detection

Simple and accurate detection of trace heavy metals in blood is very important. A novel dual-responsive electrochemical/fluorescent biosensor based on magnetic hyperbranched polyamide with heparin modification (MHPAM-H) for blood lead detection has been successfully developed. Upon conjugated with blood lead ions, dual-biosensor could not only display electrochemical signal but also fluorescence signal owing to the enriched amino groups, cavity structure, and good fluorescence properties of HPAM. Blood biocompatibility, construction of the dual-responsive biosensor, electrochemical/fluorescent detection of lead ions in water phase and blood condition, selectivity and stability of the dual-responsive biosensor were investigated in detail. The proposed dual-responsive biosensor displays good linear relationship (1.5 pM- 4.8 × 10³ pM for electrochemical detection and 0.5 pM-4.8 × 10³ pM for fluorescent detection) with low detection limit (4.4 pM for electrochemical detection and 1.0 pM for fluorescent detection) for blood lead, providing potential application for blood lead detection in the future.

Nanostructures for nonlabeled and labeled electrochemical immunosensors: Simultaneous electrochemical detection of cancer markers: A review

The simultaneous electrochemical determination of multiple tumor antigens has attracted a great deal of attention, which can effectively enhance the capability and accuracy of the analysis. Nanostructured materials mostly played a key major role in the electrochemical immunosensors fabrication and operation improvement. This review focused mainly on the protocols for using nanostructures to fabricate electrochemical (nonlabeled@label-free and labeled@sandwich-type) immunosensors. Furthermore, this review has also described the diverse classes of electroactive nanospecies which are a complementary part of any immunosensor that assists to reach the selectivity for the target antigen. Finally, the important analytical characteristics of the published immunosensors were discussed (electrochemical detection technique, linear range, and detection limit). Studies published between the years 2009-2018 have been included in this review.

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).

Multiple Drug Delivery from Mesoporous Coating Realizing Combination Therapy for Bare Metal Stents

The simultaneous loading of multifunctional drugs has been regarded as one of the major challenges in the drug delivery system. Herein, a mesoporous silica coating was constructed on a bare metal stent surface by an evaporation-induced self-assembly method, in which both hydrophilic and hydrophobic drugs (heparin and rapamycin) were encapsulated by a one-pot method for the first time, and the release behaviors of these drugs were studied. The releasing mechanisms of these drugs were investigated in detail. Rapid release of heparin can achieve anticoagulation and endothelialization, whereas slow release of rapamycin can realize antiproliferative therapy for long term. In vitro hemocompatibility and promotion for proliferation of vein endothelial cells and the inhibition of smooth muscle cells were conducted. In vivo stent implantation results verify that the mesoporous silica coating with both heparin and rapamycin can successfully accelerate the endothelialization process and realize the antiproliferative therapy for as long as 3 months. These results indicate that this multifunctional mesoporous coating containing both hydrophilic and hydrophobic drugs might be a promising stent coating in the future.

A Rapid Method for the Detection of Sarcosine Using SPIONs/Au/CS/SOX/NPs for Prostate Cancer Sensing

BACKGROUND

Sarcosine is an amino acid that is formed by methylation of glycine and is present in trace amounts in the body. Increased sarcosine concentrations in blood plasma and urine are manifested in sarcosinemia and in some other diseases such as prostate cancer. For this purpose, sarcosine detection using the nanomedicine approach was proposed. In this study, we have prepared superparamagnetic iron oxide nanoparticles (SPIONs) with different modified surface area. Nanoparticles (NPs) were modified by chitosan (CS), and sarcosine oxidase (SOX). SPIONs without any modification were taken as controls. Methods and Results: The obtained NPs were characterized by physicochemical methods. The size of the NPs determined by the dynamic light scattering method was as follows: SPIONs/Au/NPs (100⁻300 nm), SPIONs/Au/CS/NPs (300⁻700 nm), and SPIONs/Au/CS/SOX/NPs (600⁻1500 nm). The amount of CS deposited on the NP surface was found to be 48 mg/mL for SPIONs/Au/CS/NPs and 39 mg/mL for SPIONs/Au/CS/SOX/NPs, and repeatability varied around 10%. Pseudo-peroxidase activity of NPs was verified using sarcosine, horseradish peroxidase (HRP) and 3,3',5,5'-tetramethylbenzidine (TMB) as a substrate. For TMB, all NPs tested evinced substantial pseudo-peroxidase activity at 650 nm. The concentration of SPIONs/Au/CS/SOX/NPs in the reaction mixture was optimized to 0⁻40 mg/mL. Trinder reaction for sarcosine detection was set up at 510 nm at an optimal reaction temperature of 37 °C and pH 8.0. The course of the reaction was linear for 150 min. The smallest amount of NPs that was able to detect sarcosine was 0.2 mg/well (200 µL of total volume) with the linear dependence y = 0.0011x - 0.0001 and the correlation coefficient r = 0.9992, relative standard deviation (RSD) 6.35%, limit of detection (LOD) 5 µM. The suggested method was further validated for artificial urine analysis (r = 0.99, RSD 21.35%, LOD 18 µM). The calculation between the detected and applied concentrations showed a high correlation coefficient (r = 0.99). NPs were tested for toxicity and no significant growth inhibition was observed in any model system (S. cerevisiae, S. aureus, E. coli). The hemolytic activity of the prepared NPs was similar to that of the phosphate buffered saline (PBS) control. The reaction system was further tested on real urine specimens. Conclusion: The proposed detection system allows the analysis of sarcosine at micromolar concentrations and to monitor changes in its levels as a potential prostate cancer marker. The whole system is suitable for low-cost miniaturization and point-of-care testing technology and diagnostic systems. This system is simple, inexpensive, and convenient for screening tests and telemedicine applications.

Ultrasensitive analysis of heat shock protein 90α with antibodies orderly arrayed on a novel type of immunoprobe based on magnetic COFs

The early diagnosis of liver cancer by target biomarkers is of great significance for improving the survival rate of cancer patients. However, it is still a challenging task to sensitively detect circulating protein biomarkers due to decreased binding activity of antibodies originating from uncontrolled orientation of immobilization on the surface of a solid matrix. In this work, a novel immunoaffinity probe, Fe₃O₄@TpBD-DSS-Ab-MEG, based on magnetic COFs with ordered arrangement of anchored antibodies has been developed and applied for the first time to detection of a cancer biomarker, heat shock protein 90alpha (Hsp90α). The fabricated composites possess favorable features from magnetic cores and COF shells, including strong magnetic responses (7.96 emu g^-1), ordered active groups, a large amount of immobilized antibodies (111.7 μg/mg), good solvent and thermal stability. Fe₃O₄@TpBD-DSS-Ab-MEG demonstrated low detection limit (50 pg/mL), high selectivity (Hsp90α:BSA = 1:1000), desirable repeatability and good stability for Hsp90α immunocapture. Compared with other immunoprobes, our materials showed higher selectivity and sensitivity, which were mainly attributed to regular arrays of surface antibodies. Furthermore, samples containing Hsp90α at the concentration of 1 µg/mL in human plasma were used to test our immunoprobe, and 2 peptides of Hsp90α were successfully observed. The proposed non-invasive immunoassay strategy offers enhanced ability to control the orientation of immobilized antibodies and great promise for accurate analysis of the liver cancer biomarker Hsp90α in a complicated biological matrix. In addition, the facile preparation of magnetic COFs support and the satisfactory analytical performance made the newly developed immunoprobe a potential tool for sensitive detection of other cancer biomarkers in clinical diagnosis.

A redox cycling-amplified electrochemical immunosensor for α-fetoprotein sensitive detection via polydopamine nanolabels

A sandwich-type electrochemical immunosensor for sensitive detection of a tumor marker, α-fetoprotein (AFP), was fabricated by employing polydopamine-detection antibody nanoparticles (PDANPs-Ab2) as selective redox cycling-based signal amplifiers on an electrodeposited nano-gold electrode. In this research, PDANPs prepared through oxidative polymerization of dopamine were found to amplify the oxidation charge transfer of the electrochemical mediator (1,1'-ferrocene dimethanol, FDM), which was supported by cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS) investigation. Therefore, PDANPs were utilized as label materials of electrochemical immunosensors to enhance sensitivity for the first time. Meanwhile, the nano-gold electrode was used as a platform to accelerate electron transfer and immobilize capture antibody (Ab1). The electrochemical performance of the AFP immunosensor was investigated in PBS containing FDM with CV. Under optimal conditions, the constructed AFP immunosensor exhibited a wide linear range from 1 pg mL-1 to 50 ng mL-1 and a low detection limit of 0.3 pg mL-1, as well as excellent stability, reproducibility and selectivity. Measurements of AFP in human serum gave excellent correlation with the clinical standard Chemiluminescence Microparticle Immuno Assay (CMIA). These results indicated that the developed immunosensor may have promising application in the clinical diagnosis of AFP and other tumor markers.

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.

Construction and Potential Applications of Biosensors for Proteins in Clinical Laboratory Diagnosis

Biosensors for proteins have shown attractive advantages compared to traditional techniques in clinical laboratory diagnosis. In virtue of modern fabrication modes and detection techniques, various immunosensing platforms have been reported on basis of the specific recognition between antigen-antibody pairs. In addition to profit from the development of nanotechnology and molecular biology, diverse fabrication and signal amplification strategies have been designed for detection of protein antigens, which has led to great achievements in fast quantitative and simultaneous testing with extremely high sensitivity and specificity. Besides antigens, determination of antibodies also possesses great significance for clinical laboratory diagnosis. In this review, we will categorize recent immunosensors for proteins by different detection techniques. The basic conception of detection techniques, sensing mechanisms, and the relevant signal amplification strategies are introduced. Since antibodies and antigens have an equal position to each other in immunosensing, all biosensing strategies for antigens can be extended to antibodies under appropriate optimizations. Biosensors for antibodies are summarized, focusing on potential applications in clinical laboratory diagnosis, such as a series of biomarkers for infectious diseases and autoimmune diseases, and an evaluation of vaccine immunity. The excellent performances of these biosensors provide a prospective space for future antibody-detection-based disease serodiagnosis.

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.

A sandwich-type electrochemical biosensor for alpha-fetoprotein based on Au nanoparticles decorating a hollow molybdenum disulfide microbox coupled with a hybridization chain reaction

In this work, a sensitive sandwich-type biosensor for detecting alpha-fetoprotein (AFP) is developed by using a target-triggered hybridization chain reaction strategy.