Graphene oxide@gold nanorods-based multiple-assisted electrochemiluminescence signal amplification strategy for sensitive detection of prostate specific antigen

Advances in surface plasmon resonance for analyzing active components in traditional Chinese medicine

The surface plasmon resonance (SPR) biosensor technology is a novel optical analysis method for studying intermolecular interactions. Owing to in-depth research on traditional Chinese medicine (TCM) in recent years, comprehensive and specific identification of components and target interactions has become key yet difficult tasks. SPR has gradually been used to analyze the active components of TCM owing to its high sensitivity, strong exclusivity, large flux, and real-time monitoring capabilities. This review sought to briefly introduce the active components of TCM and the principle of SPR, and provide historical and new insights into the application of SPR in the analysis of the active components of TCM.

Multiplexed Opto-Microfluidic Biosensing: Advanced Platform for Prostate Cancer Detection

Cancer stands as a prominent global cause of mortality, necessitating early detection to augment survival rates and alleviate economic burdens on healthcare systems. In particular, prostate cancer (PCa), impacting 1.41 million men globally in 2020, accentuates the demand for sensitive and cost-effective detection methods beyond traditional prostate-specific antigen (PSA) testing. While clinical techniques exhibit limitations, biosensors emerge as compact, user-friendly alternatives to traditional laboratory approaches. However, existing biosensors predominantly concentrate on PSA detection, prompting the necessity for advancing toward multiplex sensing platforms. This study introduces a compact opto-microfluidic sensor featuring a substrate of gold nanospikes, fabricated via electrodeposition, for enhanced sensitivity. Embedded within a microfluidic chip, this nanomaterial enables the precise and concurrent measurement of PSA, alongside two complementary PCa biomarkers, matrix metalloproteinase-2 (MMP-2) and anti-α-methylacyl-CoA racemase (anti-AMACR) in diluted human plasma, offering a comprehensive approach to PSA analysis. Taking advantage of the localized surface plasmon resonance principle, this biosensor offers robustness and sensitivity in real sample analysis without the need for labeling agents. With the limit of detection at 0.22, 0.37, and 0.18 ng/mL for PSA, MMP-2, and anti-AMACR, respectively, this biosensing platform holds promise for point-of-care analysis, underscoring its potential impact on medical diagnostics.

Biosensors for prostate cancer detection

Prostate cancer (PC) is one of the most common tumors and a leading cause of mortality among men, resulting in ~375 000 deaths annually worldwide. Various analytical methods have been designed for quantitative and rapid detection of PC biomarkers. Electrochemical (EC), optical, and magnetic biosensors have been developed to detect tumor biomarkers in clinical and point-of-care (POC) settings. Although POC biosensors have shown potential for detection of PC biomarkers, some limitations, such as the sample preparation, should be considered. To tackle such shortcomings, new technologies have been utilized for development of more practical biosensors. Here, biosensing platforms for the detection of PC biomarkers such as immunosensors, aptasensors, genosensors, paper-based devices, microfluidic systems, and multiplex high-throughput platforms, are discussed.

Electrochemical Biosensors for Whole Blood Analysis: Recent Progress, Challenges, and Future Perspectives

Whole blood, as one of the most significant biological fluids, provides critical information for health management and disease monitoring. Over the past 10 years, advances in nanotechnology, microfluidics, and biomarker research have spurred the development of powerful miniaturized diagnostic systems for whole blood testing toward the goal of disease monitoring and treatment. Among the techniques employed for whole-blood diagnostics, electrochemical biosensors, as known to be rapid, sensitive, capable of miniaturization, reagentless and washing free, become a class of emerging technology to achieve the target detection specifically and directly in complex media, e.g., whole blood or even in the living body. Here we are aiming to provide a comprehensive review to summarize advances over the past decade in the development of electrochemical sensors for whole blood analysis. Further, we address the remaining challenges and opportunities to integrate electrochemical sensing platforms.

Modern Electrochemical Biosensing Based on Nucleic Acids and Carbon Nanomaterials

To meet the requirements of novel therapies, effective treatments should be supported by diagnostic tools characterized by appropriate analytical and working parameters. These are, in particular, fast and reliable responses that are proportional to analyte concentration, with low detection limits, high selectivity, cost-efficient construction, and portability, allowing for the development of point-of-care devices. Biosensors using nucleic acids as receptors has turned out to be an effective approach for meeting the abovementioned requirements. Careful design of the receptor layers will allow them to obtain DNA biosensors that are dedicated to almost any analyte, including ions, low and high molecular weight compounds, nucleic acids, proteins, and even whole cells. The impulse for the application of carbon nanomaterials in electrochemical DNA biosensors is rooted in the possibility to further influence their analytical parameters and adjust them to the chosen analysis. Such nanomaterials enable the lowering of the detection limit, the extension of the biosensor linear response, or the increase in selectivity. This is possible thanks to their high conductivity, large surface-to-area ratio, ease of chemical modification, and introduction of other nanomaterials, such as nanoparticles, into the carbon structures. This review discusses the recent advances on the design and application of carbon nanomaterials in electrochemical DNA biosensors that are dedicated especially to modern medical diagnostics.

Recent Progress in Electrochemical Nano-Biosensors for Detection of Pesticides and Mycotoxins in Foods

Pesticide and mycotoxin residues in food are concerning as they are harmful to human health. Traditional methods, such as high-performance liquid chromatography (HPLC) for such detection lack sensitivity and operation convenience. Efficient, accurate detection approaches are needed. With the recent development of nanotechnology, electrochemical biosensors based on nanomaterials have shown solid ability to detect trace pesticides and mycotoxins quickly and accurately. In this review, English articles about electrochemical biosensors in the past 11 years (2011-2022) were collected from PubMed database, and various nanomaterials are discussed, including noble metal nanomaterials, magnetic metal nanoparticles, metal-organic frameworks, carbon nanotubes, as well as graphene and its derivatives. Three main roles of such nanomaterials in the detection process are summarized, including biomolecule immobilization, signal generation, and signal amplification. The detection targets involve two types of pesticides (organophosphorus and carbamate) and six types of mycotoxins (aflatoxin, deoxynivalenol, zearalenone, fumonisin, ochratoxin A, and patulin). Although significant achievements have been made in the evolution of electrochemical nano-biosensors, many challenges remain to be overcome.

Electrochemical aptasensor based on the target-induced strand displacement strategy-driven for T-2 toxin detection

Herein, an aptasensor based on target-induced strand displacement (TISD) strategy was developed for sensitive detection of T-2 toxin. Gold nanoparticles@ aminated manganese dioxide (AuNPs@NH₂-MnO₂) exhibited excellent electrical conductivity and provided more binding sites for aptamer (Apt). Besides, polyethyleneimine-reduced graphene oxide/gold‑platinum core-shell nanorods composites (PEI-rGO/Pt@Au NRs) were used to be carriers for signaling tags, as their sufficiently large specific surface area improved the loading capacity for signal molecules. In the presence of T-2, the Apt sequence was more inclined to form an Apt-T-2 complex, and the cDNA was displaced from the Apt-cDNA duplex, while the signal tag was released, resulting in a weakened MB signal, differential pulse voltammetry (DPV) was used to record the signal change. Under optimal conditions, the signal response of the constructed electrochemical aptasensor exhibited a good linear relationship with the concentration of T-2. The detection limit was 8.74 × 10^-7 ng mL^-1over a wide range of concentration from 5 × 10^-6 ng mL^-1 to 5 ng mL^-1. Furthermore, the proposed aptasensor had excellent specificity, good stability and can be well applied to the detection of real samples. It provided a new avenue for the research and development of sensitive aptasensors in food detection and analysis.

Hemin-graphene oxide-gold nanoflower-assisted enhanced electrochemiluminescence immunosensor for determination of prostate-specific antigen

An ultrasensitive luminol electrochemiluminescence (ECL) immunosensor was constructed for the detection of prostate specific antigen (PSA) using glucose oxidase-decorated hemin-graphene oxide-gold nanoflowers ternary nanocomposites as probes. Graphene oxide was first modified with hemin and then with gold nanoflowers through an in situ growth method, which has significantly boosted the catalytic activity of this graphene oxide-based peroxidase mimetics. The biocatalytical activity of this ECL immunosensor was thoroughly investigated to achieve selective recognition of the analyte molecules (PSA) by specific binding between antigens and antibodies. The limit of detection was calculated to be 0.32 pg mL^-1 with a signal-to-noise ratio of 3. A broad linear range from 7.5 × 10^-4 to 2.5 ng mL^-1 was obtained. Such step-by-step assembled biosensor showed controlled nanostructure and exhibited promising application in analysis of human serum samples with a recovery range of 90.6-111.8% and a RSD range of 3.9-5.5%.

Gold nanoparticle-based signal amplified electrochemiluminescence for biosensing applications

Since the content levels of biomarkers at the early stage of many diseases are generally lower than the detection threshold concentration, achieving ultrasensitive and accurate detection of these biomarkers is still one of the major goals in bio-analysis. To achieve ultrasensitive and reliable bioassay, it requires developing highly sensitive biosensors. Among all kinds of biosensors, electrogenerated chemiluminescence (ECL) based biosensors have attracted enormous attention due to their excellent properties. In order to improve the performance of ECL biosensors, gold nanoparticles (Au NPs) have been widely utilized as signal amplification tags. The introduction of Au NPs could dramatically enhance the performance of the constructed ECL biosensors via diverse ways such as electrode modification material, efficient energy acceptor in ECL resonant energy transfer (ECL-RET), reaction catalyst, surface plasmon resonance (SPR) enhancer, and as nanocarrier. Herein, we summarize recent developments and progress of ECL biosensors based on Au NPs signal amplification strategies. We will cover ECL applications of Au NPs as a signal amplification tag in the detection of proteins, metal ions, nucleic acids, small molecules, living cells, exosomes, and cell imaging. Finally, brief summary and future outlooks of this field will be presented.

A flexible and bright surface-enhanced electrochemiluminescence film constructed from efficient aggregation-induced emission luminogens for biomolecular sensing

A bright surface-enhanced electrochemiluminescence film (SEEF) was fabricated from an organic luminogen with aggregation-induced emission (AIEgen) features on flexible substrates. Flexible carbonous substrates including carbon fiber cloth (GCFC) and carbon fiber paper (GCFP) were decorated with gold nanoparticles (AuNPs) through electrochemical deposition methods, followed by facilely casting AIEgen solutions. The resulting SEEF had a low driving potential of +0.84 V, and its electrochemiluminescence (ECL) was readily observed by the naked eye. The systematic investigation showed that the bright ECL was associated with the promoted electrochemical oxidation and radiative decay of excited AIEgens enhanced by AuNP deposition. Intriguingly, the ECL intensity of the film was linearly enhanced by increasing AIEgen loadings, which allowed tuning of ECL brightness on demand. Moreover, the SEEF was flexible and immune to folding. The ECL intensity rarely changed even when consecutively folding the film 20 times due to the strong interaction between the AIEgen and substrate. The SEEF was further used to sense biomolecules in aqueous media. The ECL of the film was linearly quenched in the presence of dopamine (DA) in the range of 10^-15-10^-6 M with a record-low limit of detection of 3.16 × 10^-16 M. Furthermore, a simple method based on grayscale analysis of ECL images (GAEI) was used for visual sensing of DA. This work provides a kind of novel bright ECL film, useful for the ultrasensitive monitoring of biomolecules in aqueous media.

Cancer Diagnostics and Early Detection Using Electrochemical Aptasensors

The detection of early-stage cancer offers patients the best chance of treatment and could help reduce cancer mortality rates. However, cancer cells or biomarkers are present in extremely small amounts in the early stages of cancer, requiring high-precision quantitative approaches with high sensitivity for accurate detection. With the advantages of simplicity, rapid response, reusability, and a low cost, aptamer-based electrochemical biosensors have received considerable attention as a promising approach for the clinical diagnosis of early-stage cancer. Various methods for developing highly sensitive aptasensors for the early detection of cancers in clinical samples are in progress. In this article, we discuss recent advances in the development of electrochemical aptasensors for the early detection of different cancer biomarkers and cells based on different detection strategies. Clinical applications of the aptasensors and future perspectives are also discussed.

Ultrasensitive Immunosensor for Prostate-Specific Antigen Based on Enhanced Electrochemiluminescence by Vertically Ordered Mesoporous Silica-Nanochannel Film

Ultrasensitive and specific detection of prostate-specific antigen (PSA) in complex biological samples is crucial for early diagnosis and treatment of prostate-related diseases. Immunoassay with a simple sensing interface and ultrahigh sensitivity is highly desirable. Herein, a novel electroluminescence (ECL) immunosensing platform is demonstrated based on the equipment of vertically ordered mesoporous silica-nanochannel films (VMSFs) with PSA antibody, which is able to realize ultrasensitive detection of PSA in human serum. Through the electrochemically assisted self-assembly (EASA) method, the VMSF is easily grown on an indium tin oxide (ITO) electrode in a few seconds. Owing to a large surface area and the negatively charged surface, VMSF nanochannels display strong electrostatic attraction to the positively charged ECL luminophores (tris(2,2-bipyridyl) dichlororuthenium (II), (Ru(bpy)₃²⁺), leading to two orders-of-magnitude enhancement of ECL emission compared with that of the bare ITO electrode. The outer surface of the VMSF is functionalized with reactive epoxy groups, which further allows covalent attachment of PSA antibody (Ab) on the entry of nanochannels. As the combination of PSA with Ab decreases the ECL signal by hindering the mass transfer of ECL luminophores and coreactant, the developed immunosensor can achieve ultrasensitive detection of PSA ranging from 1 pg ml⁻¹ to 100 ng ml⁻¹ with a limit of detection (LOD) of 0.1 pg ml⁻¹. Considering the antifouling ability of the VMSF, sensitive detection of PSA in human serum is also realized. The proposed nanochannel-based immunosensor may open up a new way for the facile development of the universal immunosensing platform for rapid and ultrasensitive detection of disease markers.

Crystal-reconstructed BiVO4 semiconductor photoelectrochemical sensor for ultra-sensitive tumor biomarker detection

In this study, we developed a crystal-reconstructed-BiVO₄ aptamer photoelectrochemical (PEC) biosensor by a high-energy laser treatment technique. This biosensor achieves a limit of detection (LOD) (0.82 ag mL^-1), linear detection range (1 ag mL^-1 to 2 ng mL^-1), and resolution ratio (∼18 molecules per mL) for prostate-specific antigen (PSA) tumor biomarker detection. Furthermore, reconstructed surface microstructure and oxygen vacancy doping energy formation after crystal reconstruction induce the stereo-hindrance effect and photogenerated hole energy is reduced during PSA target detection. In this case, a photocurrent inhibition phenomenon for PSA detection is noticed. Based on this photocurrent inversion phenomenon, some dysoxidizable nucleonic acid tumor (miRNA-21) and virus biomarkers (RdRp-COVID) can be detected with a LOD level of ∼10^-16 M by linking the corresponding base paring probe on the surface of the crystal-reconstructed photoanode. In addition to high sensitivity, this PEC biosensor presents high detection specificity, stability, and accuracy in clinical verification. Thus, this crystal-reconstructed PEC biosensor shows application potential in the fields of multi-tumor or viral biomarker detection.

Integrating potential-resolved electrochemiluminescence with molecularly imprinting immunoassay for simultaneous detection of dual acute myocardial infarction markers

A novel potential-resolved molecularly imprinted electrochemical luminescence (ECL) immunosensor has been developed for the first time for the dual sensitive detection of markers of acute myocardial infarction (AMI): cardiac troponin I (cTnI) and myoglobin (Mb). In this work, cost-effective and robust molecularly imprinted polymer (MIP) as biomimetic antibody was used to construct the immunosensors through electropolymerization and elution to form polydopamine (PDA)-MIP modified electrode. In the presence of AMI biomarkers, two ECL probes including Ru(bpy)₃²⁺@ MOCs and MoS₂ QDs functionalized by cTnI antibody and Mb aptamer could be specifically captured respectively. And two potential distinct ECL signals will be generated in one potential scan. The intensity of ECL reflects the concentrations of cTnI and Mb. The two ECL probes were characterized with field emission scanning electron microscopy, X-ray diffraction, FT-IR spectrum and UV-Vis diffuse reflectance spectroscopy. The prepared sensor exhibited a wide linear range (0.05-10⁴ ng/mL) and a low detection limit (0.0184 ng/mL for cTnI and 0.0492 ng/mL for Mb). Additionally, the MIP-ECL sensor displayed excellent anti-interference, sensitivity and stability to detect cTnI and Mb. Therefore, it will be conducive to accelerate more precise and credible early diagnosis for AMI.

A photoelectrochemical biosensor based on methylene blue sensitized Bi5O7I for sensitive detection of PSA

Herein, bismuth oxyiodide (Bi₅O₇I) was used as a signal probe to construct an effective sensitization structure with methylene blue (MB), combined with protein conversion strategy, and a photoelectrochemical (PEC) biosensor was constructed for sensitive detection of prostate-specific antigen (PSA). The designed biosensor had a high sensitivity and a low detection limit (LOD) of 0.047 fg mL^-1, which opened up a simple way for the detection of PSA and showed a good application prospect in clinical and medical fields.

Advances in Optical Aptasensors for Early Detection and Diagnosis of Various Cancer Types

Cancer is a life-threatening concern worldwide. Sensitive and early-stage diagnostics of different cancer types can make it possible for patients to get through the best available treatment options to combat this menace. Among several new detection methods, aptamer-based biosensors (aptasensors) have recently shown promising results in terms of sensitivity, identification, or detection of either cancerous cells or the associated biomarkers. In this mini-review, we have summarized the most recent (2016-2020) developments in different approaches belonging to optical aptasensor technologies being widely employed for their simple operation, sensitivity, and early cancer diagnostics. Finally, we shed some light on limitations, advantages, and current challenges of aptasensors in clinical diagnostics, and we elaborated on some future perspectives.

Cobalt metal-organic framework modified carbon cloth/paper hybrid electrochemical button-sensor for nonenzymatic glucose diagnostics

In the growing pandemic, family healthcare is widely concerned with the increase of medical self-diagnosis away from the hospital. A cobalt metal-organic framework modified carbon cloth/paper (Co-MOF/CC/Paper) hybrid button-sensor was developed as a portable, robust, and user-friendly electrochemical analytical chip for nonenzymatic quantitative detection of glucose. Highly integrated electrochemical analytical chip was successfully fabricated with a flexible Co-MOF/CC sensing interface, effectively increasing the specific area and catalytic sites than the traditional plane electrode. Based on the button-sensor, rapid quantitative detection of glucose was achieved in multiple complex bio-matrixes, such as serum, urine, and saliva, with desired selectivity, stability, and durability. With the advantages of low cost, high environment tolerance, ease of production, our nanozyme-based electrochemical analytical chip achieved reliable nonenzymatic electrocatalysis, has great potential for the application of rapid on-site analysis in personalized diagnostic and disease prevention.

An Electrochemical Aptasensor for Pb2+ Detection Based on Metal-Organic-Framework-Derived Hybrid Carbon

A new double-shelled carbon nanocages material was synthesized and developed an aptasensor for determining Pb²⁺ in aqueous solution. Herein, nanoporous carbon materials derived from core–shell zeolitic imidazolate frameworks (ZIFs) demonstrated excellent electrochemical activity, stability, and high specificity surface area, consequently resulting in the strong binding with aptamers. The aptamer strands would be induced to form G-quadruplex structure when Pb²⁺ was introduced. Under optimal conditions, the aptasensor exhibited a good linear relationship of Pb²⁺ concentration ranging from 0.1 to 10 μg L⁻¹ with the detection limits of 0.096 μg L⁻¹. The feasibility was proved by detecting Pb²⁺ in spiked water samples and polluted soil digestion solution. The proposed aptasensor showed excellent selectivity and reproducibility, indicating promising applications in environmental monitoring.

Graphene Oxide-Coated Gold Nanorods: Synthesis and Applications

The application of gold nanorods (AuNRs) and graphene oxide (GO) has been widely studied due to their unique properties. Although each material has its own challenges, their combination produces an exceptional material for many applications such as sensor, therapeutics, and many others. This review covers the progress made so far in the synthesis and application of GO-coated AuNRs (GO-AuNRs). Initially, it highlights different methods of synthesizing AuNRs and GO followed by two approaches (ex situ and in situ approaches) of coating AuNRs with GO. In addition, the properties of GO-AuNRs composite such as biocompatibility, photothermal profiling, and their various applications, which include photothermal therapy, theranostic, sensor, and other applications of GO-AuNRs are also discussed. The review concludes with challenges associated with GO-AuNRs and future perspectives.

An electrochemical aptasensor-based CoxP-decorated porous carbon microspheres and AuNRs labelled methylene blue as signal labels for the sensitive detection of PCB77

In this work, a simple, specific and ultra-sensitive electrochemical aptasensor was successfully developed based on a novel signal reduction strategy for the detection of polychlorinated biphenyls (PCB77). This aptasensor was prepared by the electrodeposition of gold nanoparticles (AuNPs) on an Au electrode (AuE) modified with cobalt phosphide (Co_xP, a mixture of CoP and Co₂P) decorated porous carbon microspheres. In this study, the thiolated single-complementary DNA (cDNA) was immobilized on the surface of the modified electrode via the Au-S bond. Subsequently, the gold nanorod@methylene blue connection aptamer (AuNRs@MB-Apt) signal labels were immobilized onto the modified electrode through the principle of complementary base pairing. Further, the aptamer preferentially binds to PCB77, decreasing the amount of AuNR@MB-Apt. The DPV current response was related to the PCB77 concentration. Under the optimized experimental conditions, a low detection limit of 5.9 × 10^-2 ng L^-1 and a wide linear range of 1 × 10^-11 mg mL^-1 to 1 × 10^-4 mg mL^-1 (S/N = 3) for PCB77 were achieved. Moreover, the proposed aptasensor offered high selectivity, stability and reproducibility, indicating the broad potential application in environmental monitoring.

Lab-on-Membrane Platform Coupled with Paper Spray Ionization for Analysis of Prostate-Specific Antigen in Clinical Settings

The analysis of protein antigens as biomarkers in clinical samples is particularly helpful for the early diagnosis of diseases. However, this is difficult to accomplish owing to the presence of the antigens in trace amounts as well as the complexity of the matrixes in clinical samples. In this study, a lab-on-membrane platform that can be combined with paper spray ionization mass spectrometry was developed for the in situ high-throughput sensitive detection of the prostate-specific antigen (PSA). The sensitivity of the proposed platform was enhanced via two strategies: (1) the synthesis of a biotin-streptavidin scaffold caused an increase in the capturing efficiency of PSA by a factor of 5 and (2) the immobilization of a large number of mass tag molecules on the gold nanoparticles allowed for the amplification of the mass spectrometry signals. The limit of detection was approximately 3.0 pg mL^-1. The selectivity to PSA was guaranteed by using an antibody-aptamer pairing sandwich immunoassay, and PSA detection was unaffected even when other protein antigens (carcinoembryonic antigen and carbohydrate antigen 125) were present. The modified membranes maintained their performance for at least 30 days when stored at 4 °C. Finally, analysis of human serum samples confirmed that the PSA concentration as determined using the proposed platform was consistent with that determined with a conventional chemiluminescent immunoassay. Thus, this PSA analyzing platform is suitable for prostate cancer diagnosis in clinical settings.

Recent advances in optical aptasensor technology for amplification strategies in cancer diagnostics

Aptamers are chemically synthetic single-stranded DNA or RNA molecules selected by molecular evolution. They have been widely used as attractive tools in biosensing and bioimaging because they can bind to a large variety of targets with high sensitivity and high affinity and specificity. As recognition elements, aptamers contribute in particular to cancer diagnostics by recognizing different cancer biomarkers, while they can also facilitate ultrasensitive detection by further employing signal amplification elements. Optical techniques have been widely used for direct and real-time monitoring of cancer-related biomolecules and bioprocesses due to the high sensitivity, quick response, and simple operation, which has greatly benefited cancer diagnostics. In this review, we highlight recent advances in optical platform-based sensing strategies for cancer diagnostics aided by aptamers. Limitations and current challenges are also discussed.

Precision medicine, bioanalytics and nanomaterials: toward a new generation of personalized portable diagnostics

The customization of disease treatment focused on genetic, environmental and lifestyle factors of individual patients, including tailored medical decisions and treatments, is identified as precision medicine. This approach involves the combination of various aspects such as the collection and processing of a large amount of data, the selection of optimized and personalized drug dosage for each patient and the development of selective and reliable analytical tools for the monitoring of clinical, genetic and environmental parameters. In this context, miniaturized, compact and ultrasensitive bioanalytical devices play a crucial role for achieving the goals of personalized medicine. In this review, the latest analytical technologies suitable for providing portable and easy-to-use diagnostic tools in clinical settings will be discussed, highlighting new opportunities arising from nanotechnologies, offering peculiar perspectives and opportunities for precision medicine.

Advances in prostate specific antigen biosensors-impact of nanotechnology

Prostate cancer is one of the most dangerous and deadly cancers in elderly men. Early diagnosis using prostate-specific antigen (PSA) facilitates disease detection, management and treatment. Biosensors have recently been used as sensitive, selective, inexpensive and rapid diagnostic tools for PSA detection. In this review, a variety of PSA biosensors such as aptasensors, peptisensors and immunesensors are highlighted. These use aptamers, peptides and antibodies in the biorecognition element, respectively, and can detect PSA with very high sensitivity via electrochemical, electrochemiluminescence, fluorescence and surface-enhanced Raman spectroscopy. To improve the sensitivity of most of these PSA biosensors, different nanostructured materials have played a critical role.

A novel fluorescent assay based on DNAzyme-assisted detection of prostate specific antigen for signal amplification

Prostate specific antigen (PSA) is one of the most common biomarkers for the management of prostate cancer. However, it still remains urgent to develop highly sensitive, cost-effective and selective strategies for PSA assay. In this paper, we developed a low-cost, highly sensitive and specific analytical strategy for the detection of PSA by using a fluorescence sensor based on Pb²⁺-dependent DNAzyme. We designed a DNA sequence called cmMB with a hairpin structure, containing PSA-specific aptamers and Pb²⁺-dependent DNAzyme chains. Also, a fluorophore-labelled DNA sequence called Sub-FAM, which contains a cleavage site of Pb²⁺-dependent DNAzyme and serves as substrate, is also designed for the signal generation. In the presence of PSA, interaction between aptamer and PSA blocks the hairpin structure of cmMB, resulting in the formation of Pb²⁺-dependent DNAzyme with Pb²⁺. Then, Pb²⁺-dependent DNAzyme can cleavage Sub-FAM and produce a high fluorescence. In the absence of PSA, since Sub-FAM remains to be ssDNA and can be absorbed by GO, only low fluorescence can be detected. Under optimal experimental conditions, a good linear relationship in the range of 1-100 pg mL^-1 was exhibited, with a limit of detection (LOD) of 0.76 pg mL^-1. In addition, the proposed method has potential value in the diagnosis and monitoring of prostate cancer because of its good selectivity and practical application in biological samples.

Plasmonic tweezers for optical manipulation and biomedical applications

This comprehensive minireview highlights the recent research on the subtypes, optical manipulation, and biomedical applications of plasmonic tweezers.

Reduced graphene oxide-gold nanoparticles-catalase-based dual signal amplification strategy in a spatial-resolved ratiometric electrochemiluminescence immunoassay

A novel spatial-resolved electrochemiluminescent (ECL) ratiometry for cardiac troponin I (cTnI) analysis was developed using resonance energy transfer (RET) and a coreactant consumption strategy for signal amplification.

A nanocomposite prepared from bifunctionalized ionic liquid, chitosan, graphene oxide and magnetic nanoparticles for aptamer-based assay of tetracycline by chemiluminescence

A nanocomposite was prepared from a bifunctionalized ionic liquid, chitosan on magnetic nanoparticle-modified graphene oxide (IL/Chit@MGO). It was used in a chemiluminescencc (CL) assay for tetracycline. The materials were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray powder diffraction, nitrogen adsorption-desorption isotherm, vibrating sample magnetometry and zeta potentials. Subsequently, a tetracycline-binding aptamer (TC-Apt) acting as a recognition element, and G-quadruplex DNAzyme (G-DNAzyme) acting as a signal amplification component were modified on IL/Chit@MGO. So, the bifunctional G-DNAzyme/TC-Apt/IL/Chit@MGO was prepared. The IL/Chit@MGO is found to possess excellent loading capability for TC-Apt. This is attributed to the large specific surface and abundant charge on the surface of IL/Chit@MGO. The composite was used to construct a CL assay for tetracycline. Tetracycline binds to TC-Apt and causes the release of the G-DNAzyme. The latter catalyzes the CL of luminol-H₂O₂ CL system at pH 7.4. Under optimized conditions, the blue CL at the emission wavelength of 425 nm increases linearly in the 0.16 pM to 2.0 nM concentration range, and the detection limit is 21 fM (at 3σ). The assay is selective, reproducible and stable. The assay was applied to tetracycline detection in practical samples. The apparent recoveries are 98.0% to 101.3% for the milk sample and 97.0% to 102.2% for the water sample. Graphical abstractG-quadruplex DNAzyme (G-DNAzyme) and tetracycline aptamer (TC-Apt) bifunctionalized ionic liquid/chitosan@magnetic graphene oxide (IL/Chit@MGO) was prepared. The nanocomposite was used to construct a chemiluminescence (CL) assay for tetracycline.

Functionalized Hybridization of 2D Nanomaterials

The discovery of graphene and subsequent verification of its unique properties have aroused great research interest to exploit diversified graphene-analogous 2D nanomaterials with fascinating physicochemical properties. Through either physical or chemical doping, linkage, adsorption, and hybridization with other functional species into or onto them, more novel/improved properties are readily created to extend/expand their functionalities and further achieve great performance. Here, various functionalized hybridizations by using different types of 2D nanomaterials are overviewed systematically with emphasis on their interaction formats (e.g., in-plane or inter plane), synergistic properties, and enhanced applications. As the most intensely investigated 2D materials in the post-graphene era, transition metal dichalcogenide nanosheets are comprehensively investigated through their element doping, physical/chemical functionalization, and nanohybridization. Meanwhile, representative hybrids with more types of nanosheets are also presented to understand their unique surface structures and address the special requirements for better applications. More excitingly, the van der Waals heterostructures of diverse 2D materials are specifically summarized to add more functionality or flexibility into 2D material systems. Finally, the current research status and faced challenges are discussed properly and several perspectives are elaborately given to accelerate the rational fabrication of varied and talented 2D hybrids.

Colorimetric immunosensor for determination of prostate specific antigen using surface plasmon resonance band of colloidal triangular shape gold nanoparticles

In this work, we demonstrated the development of a colorimetric immunosensor using surface plasmon resonance band of gold nanoparticles for the detection of prostate specific antigen (PSA). To develop this biosensing tool, triangular gold nanoparticles (AuNPs) were synthesized using Tween-20 as a nonionic surfactant and then, conjugated with PSA capture antibody (Ab₁-AuNPs). When exposed to Ab₁-AuNPs, PSA antigens were found to be successfully captured by nanosystem (PSA)-Ab₁-AuNPs. Next, (PSA)-Ab₁-AuNPs were incubated with second PSA antibody (2)-decorated magnetite (Fe₃O₄-Ab₂) and separated by an external magnetic force to leave Ab₁-AuNPs in the supernatant solution to be directly analyzed using UV-Vis spectroscopy. It was found that the absorption intensity was directly proportional to the PSA concentration. As a result, the linear range for PSA detection was found to be 0.01-20 ng mL^-1 with a detection limit of 0.009 ng mL^-1. Because of significant stability of the prepared Ab₁-AuNPs and excellent selectivity to the PSA antigen, this simple and sensitive sensing system is proposed to be potentially effective in the fast and real-time analysis of clinical samples from prostate cancer patients. We believe that the simple platform of this immunosensor to be useful in the development of future point-of-care sensing tools, working on the quantification of biomarkers in a drop of blood.

Novel Amino-pillar[5]arene as a Fluorescent Probe for Highly Selective Detection of Au3+ Ions

A novel fluorescent probe, amino-pillar[5]arene (APA), was prepared via a green, effective, and convenient synthetic method, which was characterized by nuclear magnetic resonance (NMR), infrared (IR), and high-resolution mass spectrometry. The fluorescence sensing behavior of the APA probe toward 22 metal ions in aqueous solutions were studied by fluorescence spectroscopy. The results showed that APA could be used as a selective fluorescent probe for the specificity detection of Au3+ ions. Moreover, the detection characteristics were investigated by fluorescence spectral titration, pH effect, fluorescence competitive experiments, Job's plot analysis, 1H NMR, and IR. The results indicated that detection of Au3+ ions by the APA probe could be achieved in the range of pH 1-13.5 and that other coexisting metal ions did not cause any marked interference. The titration analysis results indicated that the fluorescence intensity decreased as the concentration of Au3+ ions increased, with an excellent correlation (R 2 = 0.9942). The detection limit was as low as 7.59 × 10-8 mol·L-1, and the binding ratio of the APA probe with Au3+ ions was 2:1. Therefore, the APA probe has potential applications for detecting Au3+ ions in the environment and in living organisms.

Electrochemiluminescence Double Quenching System Based on Novel Emitter GdPO4:Eu with Low-Excited Positive Potential for Ultrasensitive Procalcitonin Detection

Nowadays, the electrochemiluminescence (ECL) immunosensor with the unique superiority of tunable luminescence and ultrahigh sensitivity has become one of the most promising immunoassay techniques, especially for low-abundance biomarkers analysis. However, the use of signal probes with high excited potential and applied emitters which owned good intensity but biotoxicity limited its application. Herein, an ECL resonance energy transfer strategy was developed based on protein bioactivity protection utilizing europium-doped phosphoric acid gadolinium (GdPO₄:Eu) as novel low-potential luminophor (donor) and Pd@Cu₂O as the quenching probe (acceptor). Specifically, GdPO₄:Eu was first prepared by using the hydrothermal synthesis method to apply in ECL, and when it coexisted with K₂S₂O₈, cathode, a strong ECL signal would be generated at a low potential of -1.15 V (vs Ag/AgCl), where the immunocompetence of antigens and antibodies can be maintained well. Electrical pair Eu³⁺/Eu²⁺, as the coreactant promoter, produced by potential excitation could produce more SO₄^•- to accelerate the oxidation process of GdPO₄:Eu. Meanwhile, Cu₂O coated onto Pd (Pd@Cu₂O), as a dual-quencher, enhanced the quenching effect of Pd alone and controlled the ECL intensity of the "signal on" state within a reasonable range. As a result, the proposed biosensor for detection of trace procalcitonin, a biomarker of systemic inflammatory response syndrome, exhibited a far low detection limit, 0.402 fg/mL (S/N = 3). Importantly, this work not only utilized a promising ECL emitter for biosensing platform construction but also had momentous potential in biomarker detection of disease diagnosis and clinical analysis.