Sensitive Biomarker Detection Research Articles

Bio-functionalized carbon dots for signaling immuno-reaction of carcinoembryonic antigen in an electrochemical biosensor for cancer biomarker detection

Early diagnosis of cancer demands sensitive and accurate detection of cancer biomarkers in blood. Carbon dots (CDs) bio-functionalization with antibodies, peptides or aptamers have played significant role in cancer diagnosis and targeted cancer therapy. Herein, a biosensor for detection of cancer biomarker carcinoembryonic antigen (CEA) in blood serum has been designed using CDs bio-functionalized with HRP-conjugated CEA antibody (CUCDs@CEAAb2) as detection probe. CDs were synthesized by upscaling of cow urine, a nitrogen rich biomass waste, by hydrothermal method. Detection probe based on CDs resulted in 3.5 times higher sensitivity as compared to conventional electrochemical sandwich immunoassay. To further improve the sensor performance, hyper-branched polyethylenimine grafted poly amino aniline (PEI-g-PAANI) was used as the sensing interface, which enabled immobilization of higher amount of capture antibody. Detection of CEA in human blood serum coupled with wide linear range (0.5–50 ng/ml), good specificity, stability, reproducibility and low detection limit (10 pg/ml) signified the excellence of CUCDs based CEA immunosensor. CUCDs exhibited excitation wavelength dependent fluorescence property and showed strong blue emission under UV irradiation. MTT assay indicated that the material is not toxic towards human dental pulp stem cells (hDPSCs) and MG63 osteosarcoma cells (cell viability > 90%). The present study demonstrates a methodology for valorization of animal waste to a cost-effective carbon based functional nanomaterial for clinical detection of cancer biomarkers.

Development of Shark Single Domain Antibodies Specific for Human α-Fetoprotein and the Multimerization Strategy in Serum Detection.

Sensitive detection of cancer biomarkers can contribute to the timely diagnosis and treatment of diseases. In this study, the whitespotted bamboo sharks were immunized with human α-fetoprotein (AFP), and a phage-displayed variable new antigen receptor (VNAR) single domain antibody library was constructed. Then four unique VNARs (VNAR1, VNAR11, VNAR21, and VNAR25) against AFP were isolated from the library by biopanning for the first time. All of the sequences belong to type II of VNAR, and the VNAR11 was much different from the rest of the three sequences. Then VNAR1 and VNAR11 were selected to fuse with the C4-binding protein α chain (C4bpα) sequence and efficiently expressed in the Escherichia coli system. Furthermore, a VNAR-C4bpα-mediated sandwich chemiluminescence immunoassay (VSCLIA) was developed for the detection of AFP in human serum samples. After optimization, the VSCLIA showed a limit of detection of 0.74 ng/mL with good selectivity and accuracy. Moreover, the results of clinical serum samples detected by the VSCLIA were confirmed by an automatic immunoanalyzer in the hospital, indicating its practical application in actual samples. In conclusion, the novel antibody element VNAR exhibits great potential for immunodiagnosis, and this study also provides a new direction and experimental basis for AFP detection.

Label-Free Electrochemical Immunosensor Based on Conjugated Polymer Film Coated Disposable Electrode for Ultrasensitive Determination of Resistin Potential Obesity Biomarker.

A new label-free immunosensor was designed for sensitive detection of resistin obesity biomarker in human biological fluids. To construct a sensing interface, the monomer of double epoxy groups-substituted thiophene (TdiEpx) was synthesized for the fabrication of the biosensing system. A disposable indium tin oxide sheet was first modified by electrochemical polymerization of the TdiEpx monomer, and this robust and novel surface was characterized using different spectroscopic and electrochemical analyses. The double epoxy ends were linked to the amino ends of anti-resistin, and they served as binding points for the covalent binding of biomolecules. The double epoxy ends present in each TdiEpx monomer ensured an extensive surface area, which improved the quantity of attached anti-resistin. The determination of resistin antigen was based on the specific coupling of resistin with anti-resistin, and this interaction hindered the electron transfer reaction. The immunosensor introduced a wide linear range of 0.0125-15 pg/mL, a low detection limit of 4.17 fg/mL, and an excellent sensitivity of 1.38 kohm pg mL-1 cm2. In this study, a sandwich enzyme-linked immunosorbent assay spectrophotometric method was utilized as a reference technique for the quantitative analysis of resistin in human serum and saliva samples. Both measurements in clinical samples displayed correlations and high-correlation coefficients. In addition, this immunosensor had good storage stability, acceptable repeatability and reproducibility, high specificity, and good accuracy. The proposed immunosensor provided a simple and versatile impedimetric immunosensing platform and a promisingly sensitive way for clinical applications.

Antibody-Protein-Aptamer Electrochemical Biosensor based on Highly Efficient Proximity-Induced DNA Hybridization on Tetrahedral DNA Nanostructure for Sensitive Detection of Insulin-like Growth Factor-1.

Herein, an antibody-protein-aptamer electrochemical biosensor was designed by highly efficient proximity-induced DNA hybridization on a tetrahedral DNA nanostructure (TDN) for ultrasensitive detection of human insulin-like growth factor-1 (IGF-1). Impressively, the IGF-1 antibody immobilized on the top vertex of the TDN could effectively capture the target protein with less steric effect, and the ferrocene-labeled signal probe (SP) bound on the bottom vertex of the TDN was close to the electrode surface for generating a strong initial signal. In the presence of target protein IGF-1 and an aptamer strand, an antibody-protein-aptamer sandwich could be formed on the top vertex of TDN, which would trigger proximity-induced DNA hybridization to release the SP on the bottom vertex of TDN; therefore, the signal response would decrease dramatically, enhancing the sensitivity of the biosensor. As a result, the linear range of the proposed biosensor for target IGF-1 was 1 fM to 1 nM with the limit of detection down to 0.47 fM, which was much lower than that of the traditional TDN designs on electrochemical biosensors. Surprisingly, the use of this approach offered an innovative approach for the sensitive detection of biomarkers and illness diagnosis.

An ImmunoFET Coupled with an Immunomagnetic Preconcentration Technique for the Sensitive EIS Detection of HF Biomarkers.

We propose a new strategy using a sandwich approach for the detection of two HF biomarkers: tumor necrosis factor-α (TNF-α) and interleukin-10 (IL-10). For this purpose, magnetic nanoparticles (MNPs) (MNPs@aminodextran) were biofunctionalized with monoclonal antibodies (mAbs) using bis (sulfosuccinimidyl) suberate (BS3) as a cross-linker for the pre-concentration of two biomarkers (TNF-α and IL-10). In addition, our ISFETs were biofunctionalized with polyclonal antibodies (pAbs) (TNF-α and IL-10). The biorecognition between pAbs immobilized on the ISFET and the pre-concentrate antigen (Ag) on MNPs was monitored using electrochemical impedance spectroscopy (EIS). Our developed ImmunoFET showed a low detection limit (0.03 pg/mL) toward our target analyte when compared to previously published electrochemical immunosensors. It showed a higher sensitivity than for other HF biomarkers. Finally, the standard addition method was used to determine the unknown concentration in artificial saliva. The results matched with the expected values well.

The nature of PDMS affects the results of the immunoassays carried out in microfluidic channels

Due to various physical or biochemical processes, the nature of polydimethylsiloxane (PDMS) could affect the sensitivity and accuracy of immunoassays performed in microfluidic channels. An appropriate PDMS membrane with high adsorption properties and low background noise allows more sensitive detection of biomarkers. Here, we explored the unusual correlation between membrane surface properties and the signal-to-noise ratio (SNR) of immunoassay, developed a microfluidic-based versatile point-of-care (MVP) detection system on PDMS membrane to simultaneously detect multiple vitamins from multiple human serums. Compared with conventional enzyme-linked immunosorbent assay (ELISA) and Roche electroluminescence method, the MVP detection system exhibits a lower consumption of sample and reagents (10 µL per test), a lower limit of detection (LOD: 6.15 ng/mL), a higher SNR (33.49 dB) and multiplexed ability (seven samples and two targets in one assay). Our MVP detection system can quantitatively detect folic acid (FA) and vitamin D3 (VD3) from human serums and shows good consistency with ELISA and Roche electroluminescence methods. The R square values of FA and VD3 detections are 0.94 and 0.91, respectively. The MVP system is more cost-effective than utilizing conventional methods for a single detection (about 0.04 USD for each target) because of the straightforward design of our detection instruments, their superior anti-interference capabilities, and the low cost of routine instrument maintenance.

Bifunctional Mo2N Nanoparticles with Nanozyme and SERS Activity: A Versatile Platform for Sensitive Detection of Biomarkers in Serum Samples

Bifunctional Mo₂N Nanoparticles with Nanozyme and SERS Activity: A Versatile Platform for Sensitive Detection of Biomarkers in Serum Samples

Smartphone-assisted self-powered dual-mode biosensor designed on binary 3D DNA Walkers mediated CRISPR/Cas12a system

Malignant tumors are significant diseases that pose a threat to human life and health. The advancement of highly sensitive and specific methods is of excellent significance. This study proposes a novel detection platform that employs a smartphone-assisted self-powered sensing system with binary 3D DNA Walkers mediated CRISPR/Cas12a system and ultra-thin 2D graphdiyne for ultrasensitive dual-mode detection of breast cancer biomarker microRNA-let-7a. The binary 3D DNA Walkers possess high efficiency in movement and multifunctional characteristics. When combined with the CRISPR/Cas12a system, they can retain the advantages of 3D DNA Walker while releasing a large of trigger strands complementary to CRISPR RNA, thereby greatly enhancing the sensitivity of the sensor. In addition, capacitors are also integrated into the sensing system to further amplify the detection signal, resulting in a 20.7-fold increase in sensitivity of the method. Additionally, the adoption of an electrochemical/colorimetric dual-mode detection strategy significantly enhances the accuracy of the new approach. The newly developed detection method exhibits a linear range of 0.0001–10000 pM with a detection limit of 8.11 aM (S/N = 3). This work offers a reliable portable sensor for sensitive and accurate detection of tumor biomarkers, enabling remote disease sensing and on-site monitoring applications.

Gold nanomaterials: important vectors in biosensing of breast cancer biomarkers.

Breast cancer (BC) is one of the most common malignant tumors in women worldwide, and its incidence is increasing every year. Early diagnosis and treatment are critical to improve the curability and prognosis of patients. However, existing detection methods often suffer from insufficient sensitivity and specificity, which limits their clinical application. Fortunately, the rapid development of nanotechnology offers new possibilities for diagnosing BC. For example, the unique physicochemical properties of gold nanomaterials (Au NMs), such as fascinating optical properties and quantum size effect, along with excellent biocompatibility and modifiability, enable them to manifest great potential in the field of biosensing, especially in the detection of BC biomarkers. Through fine surface modification and functionalization, Au NMs can accurately bind to specific antibodies, nucleic acids, and other biomolecules, thus achieving sensitive and precise detection of specific biomarkers. Here, we focus on the research progress of Au NMs as a key biosensing vector in BC biomarker detection. From four major perspectives of early diagnosis, prognostic evaluation, risk prediction,and bioimaging applications, we have thoroughly analyzed the broad application of Au NMs in BC biomarker detection and prospectively addressed its possible future trends. We hope this review will provide more comprehensive ideas for future researchers and promote the further development of this field.

Droplet-Based Preparation of ZnO-nanostructure Array for Microfluidic Fluorescence Biodetection.

Nanostructure-enhanced biodetection is widely used for early diagnosis and treatment, which plays an essential role in improving the cure rates of cancer patients. ZnO nanostructure-based fluorescence immunoassay has been demonstrated to enable effective and sensitive detection of cancer biomarkers for their excellent biocompatibility, high electrical point, and unique fluorescence enhancement properties. Further optimization of such fluorescence detection technology is still in demand to meet the requirements of highly sensitive, multiplex detection, and user-friendly devices. Droplet microfluidics is a promising platform for high-throughput analysis of biological assays, and they have been intensively used in analytical chemistry and synthesis of nanoparticles. Here, we propose a simple droplet chip, where a static droplet array was successfully obtained for in situ growth of ZnO nanostructures with varied diameters by changing the entire growth time and replenishment interval. This device provides a novel and alternative approach for patterned growth of ZnO nanostructures and understanding the growth condition of ZnO nanostructures in static droplet, which offers some guidance toward the design of multiple fluorescence amplification platforms potentially for biosensing. As a demonstration, we used the patterned grown ZnO nanostructures for multiple detection of cancer biomarkers, achieving a low limit of detection as low as 138 fg/mL in the human α-fetoprotein assay and 218 fg/mL in the carcinoembryonic antigen assay with a large dynamic range of 8 orders. These results suggest that such multifunctional microfluidic devices may be useful tools for efficient fluorescence diagnostic assays.

Enzyme-Free Dynamic DNA Reaction Networks for On-Demand Bioanalysis and Bioimaging.

ConspectusThe pursuit of in-depth studying the nature and law of life activity has been dominating current research fields, ranging from fundamental biological studies to applications that concern synthetic biology, bioanalysis, and clinical diagnosis. Motivated by this intention, the spatiotemporally controlled and in situ analysis of living cells has been a prospective branch by virtue of high-sensitivity imaging of key biomolecules, such as biomarkers. The past decades have attested that deoxyribonucleic acid (DNA), with biocompatibility, programmability, and customizable features, is a competitive biomaterial for constructing high-performance molecular sensing tools. To conquer the complexity of the wide extracellular-intracellular distribution of biomarkers, it is a meaningful breakthrough to explore high-efficiently amplified DNA circuits, which excel at operating complex yet captivating dynamic reaction networks for various bioapplications. In parallel, the multidimensional performance improvements of nucleic acid circuits, including the availability, detection sensitivity, and reliability, are critical parameters for realizing accurate imaging and cell regulation in bioanalysis.In this Account, we summarize our recent work on enzyme-free dynamic DNA reaction networks for bioanalysis from three main aspects: DNA circuitry functional extension of molecular recognition for epigenetic analysis and regulation, DNA circuitry amplification ability improvement for sensitive biomarker detection, and site-specific activation of DNA circuitry systems for reliable and accurate cell imaging. In the first part, we have designed an epigenetically responsive deoxyribozyme (DNAzyme) circuitry system for intracellular imaging and gene regulation, which enriches the possible analyzed species by chemically modifying conventional DNAzyme. For example, an exquisite N6-methyladenine (m6A)-caged DNAzyme was built for achieving the precise FTO (fat mass and obesity-associated protein)-directed gene regulation. In addition, varieties of DNAzyme-based nanoplatforms with self-sufficient cofactor suppliers were assembled, which subdued the speed-limiting hardness of DNAzyme cofactors in live-cell applications. In the second part, we have developed a series of hierarchically assembled DNA circuitry systems to improve the signal transduction ability of traditional DNA circuits. First, the amplification ability of the DNAzyme circuit has been significantly enhanced via several heterogeneously or homogeneously concatenated circuitry models. Furthermore, a feedback reaction pathway was integrated into these concatenated circuits, thus dramatically increasing the amplification efficiency. Second, considering the complex cellular environment, we have simplified the redundancy of multicomponents or reaction procedures of traditional cascaded circuits, relying on the minimal component complexity and merely one modular catalytic reaction, which guaranteed high cell-delivering uniformity while fostering reaction kinetics and analysis reliability. In the third part, we have constructed in-cell-selective endogenous-stimulated DNA circuitry systems via the multiply guaranteed molecular recognitions, which could not only eliminate the signal leakage, but could also retain its on-site and multiplex signal amplification. Based on the site-specific activation strategy, more circuitry availability in cellular scenarios has been acquired for reliable and precise biological sensing and regulation. These enzyme-free dynamic DNA reaction networks demonstrate the purpose-to-concreteness engineering for tailored multimolecule recognition and multiple signal amplification, achieving high-gain signal transduction and high-reliability targeted imaging in bioanalysis. We envision that the enzyme-free dynamic DNA reaction network can contribute to more bioanalytical layouts, which will facilitate the progression of clinical diagnosis and prognosis.

Photonic Crystal Surface Mode Real-Time Imaging of RAD51 DNA Repair Protein Interaction with the ssDNA Substrate.

Photonic crystals (PCs) are promising tools for label-free sensing in drug discovery screening, diagnostics, and analysis of ligand-receptor interactions. Imaging of PC surface modes has emerged as a novel approach to the detection of multiple binding events at the sensor surface. PC surface modification and decoration with recognition units yield an interface providing the highly sensitive detection of cancer biomarkers, antibodies, and oligonucleotides. The RAD51 protein plays a central role in DNA repair via the homologous recombination pathway. This recombinase is essential for the genome stability and its overexpression is often correlated with aggressive cancer. RAD51 is therefore a potential target in the therapeutic strategy for cancer. Here, we report the designing of a PC-based array sensor for real-time monitoring of oligonucleotide-RAD51 recruitment by means of surface mode imaging and validation of the concept of this approach. Our data demonstrate that the designed biosensor ensures the highly sensitive multiplexed analysis of association-dissociation events and detection of the biomarker of DNA damage using a microfluidic PC array. The obtained results highlight the potential of the developed technique for testing the functionality of candidate drugs, discovering new molecular targets and drug entities. This paves the way to further adaption and bioanalytical use of the biosensor for high-content screening to identify new DNA repair inhibitor drugs targeting the RAD51 nucleoprotein filament or to discover new molecular targets.

Dual-emissive europium doped UiO-66-based ratiometric light-up biosensor for highly sensitive detection of histidinemia biomarker

BackgroundLanthanide metal-organic frameworks (Ln-MOFs) are a kind of emerging crystalline porous materials with high fluorescence and easy-to-tunable properties, making them ideal for sensing applications. However, current Ln-MOFs based fluorescent probes are primarily single-emissive or fluorescence-quenched, which greatly limited the detection performances such as sensitivity, accuracy and repeatability, thereby hindering their applications in efficient target monitoring and related disease diagnosis. To address these issues, the reasonable design of Ln-MOFs equipped with dual fluorescence emissions and light-up mode is urgently needed for a high-performance biosensor. ResultsA dual-emissive europium doped UiO-66 (Eu@UiO-66-NH2-PMA)-based ratiometric fluorescent biosensing platform was constructed for highly sensitive and selective detection of the histidinemia biomarker-histidine (His). Eu@UiO-66-NH2-PMA (pyromellitic acid abbreviated as PMA) was synthesized utilizing a post-synthetic modification method via coordination interactions between the free –COOH of UiO-66-NH2-PMA and Eu3+, which exhibited characteristic peaks of broad ligand emission and sharp Eu3+ emissions simultaneously. Considering that Cu2+ had the excellent fluorescence quenching ability toward Eu3+ and superior affinity with His, it was deliberately introduced into the Eu@UiO-66-NH2-PMA, acting as active sites for target His responsiveness. The Eu@UiO-66-NH2-PMA/Cu2+/His ternary competition system demonstrated a low detection limit of 74 nM, excellent selectivity and good anti-interference capability that allowed for sensitive analysis of His levels in milk and human serum samples. SignificanceAttributing to the superior luminescent properties, good stability and self-calibration capability of Eu@UiO-66-NH2-PMA, the developed ratiometric light-up sensing platform enabled sensitive, selective and credible analysis of His in complex practical samples, which might provide an available tool for food nutrition guideline and diagnostic applications of His related diseases.

Atomically dispersed single-atom catalysts (SACs) and enzymes (SAzymes): synthesis and application in Alzheimer's disease detection.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline and memory loss. Conventional diagnostic methods, such as neuroimaging and cerebrospinal fluid analysis, typically detect AD at advanced stages, limiting the efficacy of therapeutic interventions. Early detection is crucial for improving patient condition by enabling timely administration of treatments that may decelerate disease progression. In this context, single-atom catalysts (SACs) and single-atom nanozymes (SAzymes) have emerged as promising tools offering highly sensitive and selective detection of Alzheimer's biomarkers. SACs, consisting of isolated metal atoms on a support surface, deliver unparalleled atomic efficiency, increased reactivity, and reduced operational costs, although certain challenges in terms of stability, aggregation, and other factors persist. The advent of SAzymes, which integrate SACs with natural metalloprotease catalysts, has further advanced this field by enabling controlled electronic exchange, synergistic productivity, and enhanced biosafety. Particularly, M-N-C SACs with M-Nx active sites mimic the selectivity and sensitivity of natural metalloenzymes, providing a robust platform for early detection of AD. This review encompasses the advancements in SACs and SAzymes, highlighting their pivotal role in bridging the gap between conventional enzymes and nanozyme and offering enhanced catalytic efficiency, controlled electron transfer, and improved biosafety for Alzheimer's detection.

A terbium-functionalized ZIF-8 nanosensor for rapid and sensitive detection of an anthrax spore biomarker

Because anthrax spores are highly lethal to humans and animals as well as potential biological warfare agents, there is a great need for rapid, sensitive, and selective quantification of dipicolinic acid (DPA) as a biomarker for anthrax spores.

SERS-based immunoassay on a plasmonic syringe filter for improved sampling and labeling efficiency of biomarkers.

Rapid, sensitive, and quantitative detection of biomarkers is needed for early diagnosis of disease and surveillance of infectious outbreaks. Here, we exploit a plasmonic syringe filter and surface-enhanced Raman spectroscopy (SERS) in the development of a rapid detection system, using human IgG as a model diagnostic biomarker. The novel assay design facilitates multiple passages of the sample and labeling solution through the detection zone enabling us to investigate and maximize sampling efficiency to the capture substrate. The vertical flow immunoassay process in this study involves the utilization of filter paper embedded with gold nanoparticles (AuNPs) to form a plasmonic substrate. Capture antibody (anti-human IgG) is then immobilized onto the prepared plasmonic paper and inserted into a vertical flow device (syringe filter holder). Sample solution is passed through the filter paper and the target antigen (human IgG) is selectively captured by the immobilized antibody to form an antibody-antigen complex. Next, functionalized AuNPs as extrinsic Raman labels (ERLs) are passed through the filter paper to label the captured biomarker molecules forming a layered structure. This sandwiched geometry enhances plasmonic coupling and SERS signal to provide highly sensitive detection of biomolecules. Systematic studies to investigate the impact of multiple infuse/withdraw cycles of the sample and labeling solutions reveal that antigen and ERL binding are maximized with 10 and 20 cycles, respectively. The optimized assay achieves a detection limit of ∼0.2 ng mL-1 for human IgG with a total assay time of less than 5 minutes, meeting the demands for rapid point of care diagnostics. Additionally, the optimized platform was implemented in the quantitative analysis of the SARS-CoV-2 nucleocapsid protein, the typical target in commercial, FDA-approved rapid antigen tests for COVID-19.

Integrated magneto-plasmonic nanostructures-based immunoassay for galectin-3 detection.

Cardiovascular diseases remain a leading cause of global mortality, highlighting the need for accurate diagnostic tools and the detection of specific cardiac biomarkers. Surface-enhanced Raman scattering (SERS) spectroscopy has proved to be a promising alternative diagnostic tool to detect relevant biomarkers compared to traditional methods. To our knowledge, SERS methodology has never been used to detect galectin-3 (Gal-3), a crucial biomarker for cardiovascular conditions. Our study aimed to develop plasmonic and magneto-plasmonic nanoplatforms for the sensitive immunodetection of Gal-3 using SERS. Spherical gold nanoparticles (AuNPs) were synthesized and functionalized with 11-mercaptoundecanoic acid (MUDA) to enable antibody binding and 4-mercaptobenzoic acid (4MBA) that served as a Raman reporter due to its intense Raman signal. Following bioconjugation with Gal-3 antibody, the AuNPs were employed in the immunodetection of Gal-3 in phosphate-buffer saline (PBS) solution, offering a limit of detection (LOD) of 12.2 ng mL-1 and a working range up to 120 ng mL-1. Furthermore, our SERS-based immunosystem demonstrated selectivity for Gal-3 (40 ng mL-1) in the presence of other biomolecules such as α-amylase, bovine serum albumin and human C-reactive protein. As a proof of concept, we developed magneto-plasmonic nanoparticles composed of silica-coated magnetite decorated with the bioconjugated AuNPs aimed at enhancing the uptake and detection of Gal-3 via SERS coupled with Raman imaging. Our findings underscore the potential of SERS-based techniques for the sensitive and specific detection of biomarkers, holding significant implications for improved diagnosis and surveillance of cardiovascular diseases. Future research will focus on further optimizing these nanoplatforms and their translation into clinical settings.

Portable microfluidic immunoassay platform for the detection of inflammatory protein biomarkers

A portable microfluidic platform uses a novel programmable magnetic actuation mechanism to process samples for sensitive detection of inflammatory biomarkers.

Cu2+-doped zeolitic imidazolate frameworks and gold nanoparticle (AuNPs@ZIF-8/Cu) nanocomposites enable label-free and highly sensitive electrochemical detection of oral cancer-related biomarkers.

It is of great significance to accurately and sensitively detect oral cancer-related biomarkers (ORAOV 1) for the early diagnosis of oral cancer. Present here is a novel electrochemical biosensor based on Cu2+-doped zeolitic imidazolate frameworks and gold nanoparticle (AuNPs@ZIF-8/Cu) nanocomposites and a one-step strand displacement reaction for label-free, simple and sensitive detection of ORAOV 1 in saliva. It is worth noting that AuNPs@ZIF-8/Cu nanocomposites show large electrochemically effective surface area, good electrical conductivity and electrocatalytic activity due to the synergistic effect of metal nanoparticles (MNPs) and ZIF-8. Consequently, the newly developed electrochemical sensor displays a wide linear range of 0.1-104 pM and a low limit of detection (LOD) of 63 fM. Meanwhile, the electrochemical biosensor can distinguish single base mismatch. The relative standard deviation (RSD) of intra-assays and inter-assays is 1.46% and 1.76%, respectively, and the peak current values decline by 9.20% with a RSD value of 1.35% after being stored at 4 °C for 7 days, suggesting that the newly designed electrochemical sensor exhibits good selectivity, reproducibility and stability to detect ORAOV 1. More importantly, this novel electrochemical sensor is found to be applicable for detecting ORAOV 1 in human saliva samples with a satisfactory result. The RSD values range from 1.15% to 1.77%, and the recoveries range from 95.46% to 112.98%.

Microfluidic devices integrated with plasmonic nanostructures for sensitive fluorescent immunoassays.

The robust identification and quantification of various biomarkers is of utmost significance in clinical diagnostics and precision medicine. Fluorescent immunoassays are widely used and considered as a gold standard for biomarker detection due to their high specificity and accuracy. However, current commercial immunoassay tests suffer from limited detection sensitivity and complicated, labor-intensive operation procedures, making them impractical for point-of-care diagnosis, particularly in resource-limited regions. Recently, microfluidic immunoassay devices integrated with plasmonic nanostructures have emerged as a powerful tool for sensitive detection of biomarkers, addressing specific issues, such as integration schemes, easy operation, multiplexed detection, and sensitivity enhancement. In this paper, we provide a discussion on the recent advances in the plasmonic nanostructures integrated with microfluidic devices for fluorescent immunoassays. We shed light on the nanofabrication strategies and various fluidic designs for rapid, sensitive, and highly efficient sensing of antigens. Finally, we share our perspectives on the potential directions of these integrated devices for practical applications.