Enzyme-free sandwich-type electrochemical immunosensor for highly sensitive prostate specific antigen based on conjugation of quantum dots and antibody on surface of modified glassy carbon electrode with core–shell magnetic metal-organic frameworks

Rapid, flexible fabrication of a microfluidic electrochemical chip nucleic acid target for selective, label-free detection of influenza virus DNA using catalytic redox-recycling

H5N1 flu is a highly virulent and variable subtype of influenza with significant epidemic and pandemic potential. In this study, we introduce a novel, maskless, and rapid manufacturing process for a microfluidic chip integrated with electrodes for the quantitative detection of H5N1-DNA sequences. This detection leverages a catalytic redox-recycling signal via a novel Fe₃O₄@TMU-8 nanocomposite, which facilitates the turnover of the oxidation state of [Ru(NH₃)₆]³⁺, thereby amplifying the electrochemical signal output. The positively charged [Ru(NH₃)₆]³⁺ molecule associates with the phosphate backbone of the nucleic acids in H5N1-DNA. Changes in the aptasensor's redox-recycling signal, due to the hybridization of DNA sequences with [Ru(NH₃)₆]³⁺, were used as the electrochemical sensing response. Under optimal conditions, the signal exhibited a linear relationship with H5N1-DNA concentration, ranging from 1 fM to 1 nM, with a detection limit of 0.16 fM. This report details the fabrication of the microfluidic device using Poly(methyl methacrylate) (PMMA) sheet substrates. A laser system was employed to generate microfluidic patterns directly on the PMMA sheet. This biosensing device demonstrated long-term stability and good reproducibility, making it suitable for the quantitative assay of H5N1-DNA sequences. The results from food sample analyses further confirmed the applicability and effectiveness of the resulting biosensor.

Integration of Carboxylate Carbon Dot-Supported Gold Nanoparticles with Boron Nitride Nanosheets for Electrochemical Sensing of Prostate-Specific Antigen via Sandwich Immunoassays

An electrochemical sandwich immunoassay was fabricated to measure the prostate-specific antigen (PSA) biomarker. The PSA immunosensor was developed by altering the surface of a glassy carbon electrode (GCE) with a nanocomposite comprising carboxyl-functionalized carbon dots that support gold nanoparticles (AuNPs), which were then combined with hydroxylated boron nitride nanosheets (HO-BN). This construction possesses distinctive signal enhancement characteristics and was prepared via a facile method. Considering the high biological affinity of AuNPs for biomolecules, carbon dots (CDs) with carboxyl (COOH) groups make a suitable substrate for electrode modification. This alteration allows for the PSA antibody (Ab1) attachment, resulting in a sandwich-like configuration. Additionally, carbon dot-stabilized AuNPs integrated into HO-BN nanosheet nanocomposites considerably boost the electron transfer rate, leading to remarkable potential in sensor applications. By utilizing horseradish peroxidase (HRP)-conjugated antifree PSA antibody (Ab2), a reduction in hydrogen peroxide (H2O2) was achieved within the electrochemical cell. This reduction led to increased current, attributed to the increased PSA concentration, which is required for the biosensor analysis to perform properly. The developed immunosensor revealed a linear correlation with PSA concentrations ranging from 1.0 to 3500 pg mL-1, achieving a low detection limit of 0.136 pg mL-1. Furthermore, the PSA aptasensor demonstrates excellent selectivity, remarkable stability, and commendable reproducibility, indicating its significant potential for clinical research and diagnostic applications.

Scientific Insights into the Quantum Dots (QDs)-Based Electrochemical Sensors for State-of-the-Art Applications

Size-dependent optical and electronic properties are unique characteristics of quantum dots (QDs). A significant advantage is the quantum confinement effect that allows their precise tuning to achieve required characteristics and behavior for the targeted applications. Regarding the aforementioned factors, QDs-based sensors have exhibited dramatic potential for the diverse and advanced applications. For example, QDs-based devices have been potentially utilized for bioimaging, drug delivery, cancer therapy, and environmental remediation. In recent years, use of QDs-based electrochemical sensors have been further extended in other areas like gas sensing, metal ion detection, monitoring of organic pollutants, and detection of radioactive isotopes. Objective of this study is to rationalize the QDs-based electrochemical sensors for state-of-the-art applications. This review article comprehensively illustrates the importance of aforementioned devices along with sources from which QDs devices have been formulated and fabricated. Other distinct features of QDs devices are associated with their extremely high active surfaces, inherent ability of reproducibility, sensitivity, and selectivity for the targeted analyte detection. In this review, major categories of QD materials along with justification of their key roles in electrochemical devices have been demonstrated and discussed. All categories have been evaluated with special emphasis on the advantages and drawbacks/challenges associated with QD materials. However, in the interests of readers and researchers, recent improvements also have been included and discussed. On the evaluation, it has been concluded that despite significant challenges, QDs-based electrochemical sensors exhibit excellent performances for state-of-the-art and targeted applications.

An electrochemical/SERS dual-mode immunosensor using TMB/Au nanotag and Au@2D-MoS2 modified screen-printed electrode for sensitive detection of prostate cancer biomarker

This study describes a novel dual-mode immunosensor that combines electrochemical (EC) and surface-enhanced Raman scattering (SERS) techniques for the detection of prostate-specific antigen (PSA), a biomarker associated with prostate cancer. The sensor consists of a nanocomposite of gold nanoparticles (AuNPs) deposited on two-dimensional (2D) molybdenum disulfide (Au@MoS2) modified on a working carbon electrode of a screen-printed electrode (SPE). Subsequently, the primary antibody (Ab1) is immobilized on the modified electrode, creating Ab1/Au@MoS2/SPE for specific recognition of the target PSA. In parallel, AuNPs are conjugated with a secondary antibody (Ab2) and a probe molecule, 3,3',5,5'-tetramethylbenzidine (TMB), leading nanotags (TMB/Ab2/AuNPs) formation exhibiting strong SERS and EC responses. Upon the presence of the target, sandwich immunocomplexes can be formed through antigen-antibody interactions (Ab1-PSA-Ab2). The differential pulse voltammetry (DPV) technique is employed for EC detection mode, while a handheld Raman spectrometer with a 785 nm excitation laser is utilized to collect SERS signals. The developed system demonstrates excellent selectivity and sensitivity, with low limits of detection (LODs) of 3.58 pg mL-1 and 4.83 pg mL-1 for EC and SERS sensing, respectively. Importantly, the dual-mode immunosensor proves effective quantifying PSA protein in human serum samples with good recovery. Given its high sensitivity and proficiency in analyzing biological samples, this proposed immunosensor holds promise as an alternative tool for the early diagnosis of cancers.

Sandwich-Type Electrochemical Aptasensor with Supramolecular Architecture for Prostate-Specific Antigen

A novel sandwich-type electrochemical aptasensor based on supramolecularly immobilized affinity bioreceptor was prepared via host-guest interactions. This method utilizes an adamantane-modified, target-responsive hairpin DNA aptamer as a capture molecular receptor, along with a perthiolated β-cyclodextrin (CD) covalently attached to a gold-modified electrode surface as the transduction element. The proposed sensing strategy employed an enzyme-modified aptamer as the signalling element to develop a sandwich-type aptasensor for detecting prostate-specific antigen (PSA). To achieve this, screen-printed carbon electrodes (SPCEs) with electrodeposited reduced graphene oxide (RGO) and gold nanoferns (AuNFs) were modified with the CD derivative to subsequently anchor the adamantane-modified anti-PSA aptamer via supramolecular associations. The sensing mechanism involves the affinity recognition of PSA molecules on the aptamer-enriched electrode surface, followed by the binding of an anti-PSA aptamer-horseradish peroxidase complex as a labelling element. This sandwich-type arrangement produces an analytical signal upon the addition of H2O2 and hydroquinone as enzyme substrates. The aptasensor successfully detected the biomarker within a concentration range of 0.5 ng/mL to 50 ng/mL, exhibiting high selectivity and a detection limit of 0.11 ng/mL in PBS.

A facile electrochemical immunosensor based on EDTA-Pb2+ complexation reaction

The sensitivity of electrochemical (EC) sensors has been improved through the development of multiple approaches. However, the majority of EC sensors were limited in their practical application by high costs or tedious procedures. Herein, based on ethylenediaminetetraacetic acid (EDTA)-Pb2+ complexation reaction, a facile and affordable immunosensor was designed. Pb2+-magnesium silicate hydrate was served as the sensing substrate. The immunorecognition process was carried out in the Eppendorf tube, and antibody-functionalized Pb2+-polydopamine was utilized as immunoprobe. In the tube, the quantitative and appropriate excess of EDTA was introduced to complex with Pb2+ on the immunoprobes. The remaining EDTA was added to the sensing substrate surface to coordinate with some Pb2+ in it. This leaded to the reduction of the EC signal of Pb2+, which was related to the antigen concentration. Using prostate-specific antigen as the model analyte, the sensitive detection was realized with a low limit of detection (30.49 fg mL-1). Remarkably, the assay results were available within 24 min, sensibly faster than the most existing EC sensors.

Nanotherapeutics for prostate cancer treatment: A comprehensive review

Prostate cancer (PCa) is the most prevalent solid organ malignancy and seriously affects male health. The adverse effects of prostate cancer therapeutics can cause secondary damage to patients. Nanotherapeutics, which have special targeting abilities and controlled therapeutic release profiles, may serve as alternative agents for PCa treatment. At present, many nanotherapeutics have been developed to treat PCa and have shown better treatment effects in animals than traditional therapeutics. Although PCa nanotherapeutics are highly attractive, few successful cases have been reported in clinical practice. To help researchers design valuable nanotherapeutics for PCa treatment and avoid useless efforts, herein, we first reviewed the strategies and challenges involved in prostate cancer treatment. Subsequently, we presented a comprehensive review of nanotherapeutics for PCa treatment, including their targeting methods, controlled release strategies, therapeutic approaches and mechanisms. Finally, we proposed the future prospects of nanotherapeutics for PCa treatment.

Advancements in biosensors for cancer detection: revolutionizing diagnostics

Cancer stands as the reigning champion of life-threatening diseases, casting a shadow with the highest global mortality rate. Unleashing the power of early cancer treatment is a vital weapon in the battle for efficient and positive outcomes. Yet, conventional screening procedures wield limitations of exorbitant costs, time-consuming endeavors, and impracticality for repeated testing. Enter bio-marker-based cancer diagnostics, which emerge as a formidable force in the realm of early detection, disease progression assessment, and ultimate cancer therapy. These remarkable devices boast a reputation for their exceptional sensitivity, streamlined setup requirements, and lightning fast response times. In this study, we embark on a captivating exploration of the most recent advancements and enhancements in the field of electrochemical marvels, targeting the detection of numerous cancer biomarkers. With each breakthrough, we inch closer to a future where cancer's grip on humanity weakens, guided by the promise of personalized treatment and improved patient outcomes. Together, we unravel the mysteries that cancer conceals and illuminate a path toward triumph against this daunting adversary. This study celebrates the relentless pursuit of progress, where electrochemical innovations take center stage in the quest for a world free from the clutches of carcinoma.

Electrochemical bio- and chemosensors for cancer biomarkers: Natural (with antibodies) versus biomimicking artificial (with aptamers and molecularly imprinted polymers) recognition

Electrochemical (EC) bio- and chemosensors are highly promising for on-chip and point-of-care testing (POST) devices. They can make a breakthrough in early cancer diagnosis. Most current EC sensors for cancer biomarkers' detection and determination use natural antibodies as recognition units. However, those quickly lose their biorecognition ability upon exposure to harsh environments, comprising extreme pH, humidity, temperature, etc. So-called "plastic antibodies," including aptamers and molecularly imprinted polymers (MIPs), are hypothesized to be a smart alternative to antibodies. They have attracted the interest of the sensor research community, offering a low cost-to-performance ratio with high stability, an essential advantage toward their commercialization. Herein, we critically review recent technological advances in devising and fabricating EC bio- and chemosensors for cancer biomarkers, classifying them according to the type of recognition unit used into three categories, i.e., antibody-, aptamer-, and MIP-based EC sensors for cancer biomarkers. Each sensor fabrication strategy has been discussed, from the devising concept to cancer sensing applications, including using different innovative nanomaterials and signal transduction strategies. Moreover, employing each recognition unit in the EC sensing of cancer biomarkers has been critically compared in detail to enlighten each recognition unit's advantages, effectiveness, and limitations.

A sandwich amperometric immunosensor for the detection of fowl adenovirus group I based on bimetallic Pt/Ag nanoparticle-functionalized multiwalled carbon nanotubes

An enzyme-free sandwich amperometric immunosensor based on bimetallic Pt/Ag nanoparticle (Pt/AgNPs)-functionalized chitosan (Chi)-modified multiwalled carbon nanotubes (MWCNTs) as dual signal amplifiers and Chi-modified MWCNTs (MWCNTs-Chi) as substrate materials was developed for ultrasensitive detection of fowl adenovirus group I (FAdV-I). MWCNTs have a large specific surface area, and many accessible active sites were formed after modification with Chi. Hence, MWCNTs-Chi, as a substrate material for modifying glassy carbon electrodes (GCEs), could immobilize more antibodies (fowl adenovirus group I-monoclonal antibody, FAdV-I/MAb). Multiple Pt/AgNPs were attached to the surface of MWCNTs-Chi to generate MWCNTs-Chi-Pt/AgNPs with high catalytic ability for the reaction of H2O2 and modified active sites for fowl adenovirus group I-polyclonal antibody (FAdV-I/PAb) binding. Amperometric i-t measurements were employed to characterize the recognizability of FAdV-I. Under optimal conditions, and the developed immunosensor exhibited a wide linear range (100.93 EID50 mL-1 to 103.43 EID50 mL-1), a low detection limit (100.67 EID50 mL-1) and good selectivity, reproducibility and stability. This immunosensor can be used in clinical sample detection.

A multispectroscopic approach for ultra-trace sensing of prostate specific antigen (PSA) by iron nanocomposite fabricated on graphene nanoplatelet

Herein we report an easy, rapid and cost-effective method for spectroscopic sensing of a prostate cancer biomarker prostate specific antigen (PSA) using a novel nanocomposite. The material is a synthetic quinoxaline derivative-based iron nanocomposite fabricated on graphene nanoplatelet surface (1d-Fe-Gr). Presence of graphene enhanced the efficacy of synthesized 1d-Fe-Gr to sense PSA in serum medium with an impressive limit of detection (LOD) value of 0.878 pg/mL compared to 1d-Fe alone (LOD 17.619 pg/mL) using UV-visible absorption spectroscopy. LOD of PSA by 1d-Fe-Gr using Raman spectroscopy is even more impressive (0.410 pg/mL). Moreover, presence of interfering biomolecules like glucose, cholesterol, bilirubin and insulin in serum improves the detection threshold significantly in presence of 1d-Fe-Gr which otherwise cause LOD values of PSA to elevate in control sets. In presence of these biomolecules, the LOD values improve significantly as compared to healthy conditions in the range 0.623-3.499 pg/mL. Thus, this proposed detection method could also be applied efficiently to the patients suffering from different pathophysiological disorders. These biomolecules may also be added externally during analyses to improve the sensing ability. Fluorescence, Raman and circular dichroism spectroscopy were used to study the underlying mechanism of PSA sensing by 1d-Fe-Gr. Molecular docking studies confirm the selective interaction of 1d-Fe-Gr with PSA over other cancer biomarkers.

Microfluidic Platform Integrated with Carbon Nanofibers-Decorated Gold Nanoporous Sensing Device for Serum PSA Quantification

Prostate cancer is a disease with a high incidence and mortality rate in men worldwide. Serum prostate-specific antigens (PSA) are the main circulating biomarker for this disease in clinical practices. In this work, we present a portable and reusable microfluidic device for PSA quantification. This device comprises a polymethyl methacrylate microfluidic platform coupled with electrochemical detection. The platinum working microelectrode was positioned in the outflow region of the microchannel and was modified with carbon nanofibers (CNF)-decorated gold nanoporous (GNP) structures by the dynamic hydrogen bubble template method, through the simultaneous electrodeposition of metal precursors in the presence of CNF. CNF/GNP structures exhibit attractive properties, such as a large surface to volume ratio, which increases the antibody's immobilization capacity and the electroactive area. CNFs/GNP structures were characterized by scanning electron microscopy, energy dispersive spectrometry, and cyclic voltammetry. Anti-PSA antibodies and HRP were employed for the immune-electrochemical reaction. The detection limit for the device was 5 pg mL^-1, with a linear range from 0.01 to 50 ng mL^-1. The coefficients of variation within and between assays were lower than 4.40%, and 6.15%, respectively. Additionally, its clinical performance was tested in serum from 30 prostate cancer patients. This novel device was a sensitive, selective, portable, and reusable tool for the serological diagnosis and monitoring of prostate cancer.

A New Electrochemical Sensor for the Detection of Ketoconazole Using Carbon Paste Electrode Modified with Sheaf-like Ce-BTC MOF Nanostructure and Ionic Liquid

An ultrasensitive and selective voltammetric sensor with an ultratrace-level detection limit is introduced for ketoconazole (KTC) determination in real samples using a modified carbon paste electrode with a sheaf-like Ce-BTC MOF nanostructure and ionic liquid. The as-synthesized nanostructure was characterized by several techniques, including energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). The electrocatalytic performance of the developed electrode was observed by cyclic voltammetry (CV), differential pulse voltammetry (DPV), linear sweep voltammetry (LSV), and chronoamperometry. The limit of detection (LOD) of the developed sensor for KTC is 0.04 μM, and the response was found to be in the dynamic concentration range of 0.1-110.0 μM in a phosphate buffer solution. The proposed electrode exhibits acceptable electrocatalytic activity for KTC oxidation with a high sensitivity of 0.1342 μA·μM^-1. The ability of the fabricated sensor to monitor KTC in real aqueous samples is demonstrated using standard addition data.

Explore how immobilization strategies affected immunosensor performance by comparing four methods for antibody immobilization on electrode surfaces

Among the common methods used for antibody immobilization on electrode surfaces, which is the best available option for immunosensor fabrication? To answer this question, we first used graphene-chitosan-Au/Pt nanoparticle (G-Chi-Au/PtNP) nanocomposites to modify a gold electrode (GE). Second, avian reovirus monoclonal antibody (ARV/MAb) was immobilized on the GE surface by using four common methods, which included glutaraldehyde (Glu), 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide/N-hydroxysuccinimide (EDC/NHS), direct incubation or cysteamine hydrochloride (CH). Third, the electrodes were incubated with bovine serum albumin, four different avian reovirus (ARV) immunosensors were obtained. Last, the four ARV immunosensors were used to detect ARV. The results showed that the ARV immunosensors immobilized via Glu, EDC/NHS, direct incubation or CH showed detection limits of 10^0.63 EID₅₀ mL^-1, 10^0.48 EID₅₀ mL^-1, 10^0.37 EID₅₀ mL^-1 and 10^0.46 EID₅₀ mL^-1 ARV (S/N = 3) and quantification limits of 10^1.15 EID₅₀ mL^-1, and 10^1.00 EID₅₀ mL^-1, 10^0.89 EID₅₀ mL^-1 and 10^0.98 EID₅₀ mL^-1 ARV (S/N = 10), respectively, while the linear range of the immunosensor immobilized via CH (0-10^5.82 EID₅₀ mL^-1 ARV) was 10 times broader than that of the immunosensor immobilized via direct incubation (0-10^4.82 EID₅₀ mL^-1 ARV) and 100 times broader than those of the immunosensors immobilized via Glu (0-10^3.82 EID₅₀ mL^-1 ARV) or EDC/NHS (0-10^3.82 EID₅₀ mL^-1 ARV). And the four immunosensors showed excellent selectivity, reproducibility and stability.

Prostate-Specific Antigen Monitoring Using Nano Zinc(II) Metal-Organic Framework-Based Optical Biosensor

BACKGROUND

The prostate-specific antigen (PSA) is an important cancer biomarker that is commonly utilized in the diagnosis of prostate cancer. The development of a PSA determination technique that is rapid, simple, and inexpensive, in addition to highly accurate, sensitive, and selective, remains a formidable obstacle.

METHODS

In this study, we developed a practical biosensor based on Zn(II) metal-organic framework nanoparticles (Zn-MOFs-NPs). Many spectroscopic and microanalytical tools are used to determine the structure, morphology, and physicochemical properties of the prepared MOF.

RESULTS

According to the results, Zn-MOFs-NPs are sensitive to PSA, selective to an extremely greater extent, and stable in terms of chemical composition. Furthermore, the Zn-MOFs-NPs did not exhibit any interferences from other common analytes that might cause interference. The detection limit for PSA was calculated and was 0.145 fg/mL throughout a wide linear concentration range (0.1 fg/mL-20 pg/mL).

CONCLUSIONS

Zn-MOFs-NPs were successfully used as a growing biosensor for the monitoring and measurement of PSA in biological real samples.

A Novel, Quick, and Reliable Smartphone-Based Method for Serum PSA Quantification: Original Design of a Portable Microfluidic Immunosensor-Based System

Simple Summary

Prostate cancer (PCa) is the most frequently diagnosed malignancy and second most common cause of cancer-related death in males. An early diagnosis is crucial to improve the prognosis. Prostate-Specific Antigen (PSA) is the most widely used biomarker for PCa, but this type of biomarker analysis is performed in centralized laboratories, delaying the diagnosis and initiation of treatment. Our team has developed a miniaturized platform for portable PSA quantification to overcome this shortcoming. It includes a microfluidic chip, immune capture of PSA by magnetic microbeads, and electrochemical quantification. The utilization of a micro-potentiostat allows PSA levels to be read on a smartphone in less than 30 min. This technique was found to offer a fast, easy, specific, sensitive, and reproducible method for PSA quantification. Further research is warranted to verify these findings and explore its potential application at all health care levels.

Abstract

We describe a versatile, portable, and simple platform that includes a microfluidic electrochemical immunosensor for prostate-specific antigen (PSA) detection. It is based on the covalent immobilization of the anti-PSA monoclonal antibody on magnetic microbeads retained in the central channel of a microfluidic device. Image flow cytometry and scanning electron microscopy were used to characterize the magnetic microbeads. A direct sandwich immunoassay (with horseradish peroxidase-conjugated PSA antibody) served to quantify the cancer biomarker in serum samples. The enzymatic product was detected at −100 mV by amperometry on sputtered thin-film electrodes. Electrochemical reaction produced a current proportional to the PSA level, with a linear range from 10 pg mL⁻¹ to 1500 pg mL⁻¹. The sensitivity was demonstrated by a detection limit of 2 pg mL⁻¹ and the reproducibility by a coefficient of variation of 6.16%. The clinical performance of this platform was tested in serum samples from patients with prostate cancer (PCa), observing high specificity and full correlation with gold standard determinations. In conclusion, this analytical platform is a promising tool for measuring PSA levels in patients with PCa, offering a high sensitivity and reduced variability. The small platform size and low cost of this quantitative methodology support its suitability for the fast and sensitive analysis of PSA and other circulating biomarkers in patients. Further research is warranted to verify these findings and explore its potential application at all healthcare levels.

Nanomaterials in bioelectrochemical devices: on applications enhancing their positive effect

Electrochemical biosensors and biofuel cells are finding an ever-increasing practical application due to several advantages. Biosensors are miniature measuring devices, which can be used for on-the-spot analyses, with small assay times and sample volumes. Biofuel cells have dual benefits of environmental cleanup and electric energy generation. Application of nanomaterials in biosensor and biofuel-cell devices increases their functioning efficiency and expands spheres of use. This review discusses the potential of nanomaterials in improving the basic parameters of bioelectrochemical systems, including the sensitivity increase, detection lower-limit decrease, detection-range change, lifetime increase, substrate-specificity control. In most cases, the consideration of the role of nanomaterials links a certain type of nanomaterial with its effect on the bioelectrochemical device upon the whole. The review aims at assessing the effects of nanomaterials on particular analytical parameters of a biosensor/biofuel-cell bioelectrochemical device.

Simultaneous determination of BoNT/A and /E using an electrochemical sandwich immunoassay based on the nanomagnetic immunosensing platform

Developing new ultrasensitive assays for the detection of the presence, and determination of the serotype of the most poisonous material known i.e. botulinum neurotoxin (BoNT) is vital to human health and the wellbeing of the surrounding environment. Here, an electrochemical sandwich immunoassay with high sensitivity is adopted to achieve simultaneous determination of BoNT serotypes A and E based on polystyrene@polydopamine/Cd²⁺ and Ag nanoparticles acting as monoclonal antibody labels. Two well-separated peaks with strong electrochemical signals are generated by the labels, allowing for the simultaneous detection of two analytes existing on the electrode. To obtain well-oriented polyclonal antibodies immobilization, boronic acid is directly attached to the magnetic core/metal-organic framework (MOF) shell nanoagent surfaces without the requirement of a long and flexible spacer. Accordingly, it is possible to directly detect the metal ion labels through square wave voltammetry without the metal pre-concentration step. This results in distinct and well-defined voltammetric peaks, pertaining to each sandwich-type immunocomplexes. The limits of detection of BoNT/A and BoNT/E analyses were found to be 0.04 and 0.16 pg mL^-1 with the linear dynamic ranges of 0.1-1000 and 0.5-1000 pg mL^-1, respectively. Based on the obtained results, this immunosensor has the wide linear ranges, while also exhibiting low limits of detection along with good stability and reproducibility.

A Sandwich-Type Electrochemical Immunosensor Using Antibody-Conjugated Pt-Doped CdTe QDs as Enzyme-Free Labels for Sensitive HER2 Detection Based on a Magnetic Framework

Tumor markers are highly sensitive and play an important role in the early diagnosis of cancer. We developed an electrochemical sandwich-type immunosensor that detects human epidermal growth factor receptor 2 (HER2). Magnetic framework (Fe₃O₄@ TMU-24) and AuNPs (Fe₃O₄@ TMU-24 -AuNPs) are utilized in this sensing platform. In addition to their high specific surface area and excellent biocompatibility, Fe₃O₄@ TMU-24-AuNPs nanocomposites exhibited excellent electrocatalytic properties. The primary antibody of HER2 (Ab₁) was immobilized on the surface of the Fe₃O₄@ TMU-24-AuNPs. In this sensing method, palatine doped to CdTe QDs (Pt: CdTe QDs) is utilized as a novel labeling signal biomolecule (secondary antibodies). Pt: CdTe QDs own good biocompatibility and excellent catalytic performance. The amperometric technique was used to achieve the quantitative determination of HER2 by using a sandwich-type electrochemical immunosensor. Under the optimum conditions, the dependency of the current signal and HER2 concentration showed a linear region from 1 pg ml⁻¹–100 ng ml⁻¹ with 0.175 pg ml⁻¹ as the limit of detection. This biosensing device also showed long stability and good reproducibility, which can be used for the quantitative assay of HER2.

Rapid electrochemical quantification of trace Hg2+ using a hairpin DNA probe and quantum dot modified screen-printed gold electrodes

Rapid, simple, sensitive and specific approaches for mercury(ii) (Hg²⁺) detection are essential for toxicology assessment, environmental protection, food analysis and human health. In this study, a ratiometric hairpin DNA probe based electrochemical biosensor, which relies on hairpin DNA probes conjugated with water-soluble and carboxyl functionalized quaternary Zn–Ag–In–S quantum dot (QD) on screen-printed gold electrodes (SPGE), referred to as the HP-QDs-SPGE electrochemical biosensor in this study, was developed for Hg²⁺ detection. Based on the “turn-off” reaction of a hairpin DNA probe binding with a mismatched target and Hg²⁺ through the formation of T–Hg²⁺–T coordination, the HP-QDs-SPGE electrochemical biosensor can rapidly quantify trace Hg²⁺ with high ultrasensitivity, specificity, repeatability and reproducibility. The conformational change of the hairpin DNA probe caused a significant decrease in electrochemical intensity, which could be used for the quantification of Hg²⁺. The linear dynamic range and high sensitivity of the HP-QDs-SPGE electrochemical biosensor for the detection of Hg²⁺ was studied in vitro, with a broad linear dynamic range of 10 pM to 1 μM and detection limits of 0.11 pM. In particular, this HP-QDs-SPGE electrochemical biosensor showed excellent selectivity toward Hg²⁺ ions in the presence of other metal ions. More importantly, this biosensor has been successfully used to detect Hg²⁺ in deionized water, tap water, groundwater and urine samples with good recovery rate and small relative standard deviations. In summary, the developed HP-QDs-SPGE electrochemical biosensor exhibited promising potential for further applications in on-site analysis.

A ratiometric hairpin DNA probe based electrochemical biosensor, which relies on hairpin DNA probes conjugated with water-soluble and carboxyl functionalized quantum dot on screen-printed gold electrodes, was developed for Hg²⁺ detection.

Nanotechnology-based approaches for effective detection of tumor markers: A comprehensive state-of-the-art review

As well-appreciated biomarkers, tumor markers have been spotlighted as reliable tools for predicting the behavior of different tumors and helping clinicians ascertain the type of molecular mechanism of tumorigenesis. The sensitivity and specificity of these markers have made them an object of even broader interest for sensitive detection and staging of various cancers. Enzyme-linked immunosorbent assay (ELISA), fluorescence-based, mass-based, and electrochemical-based detections are current techniques for sensing tumor markers. Although some of these techniques provide good selectivity, certain obstacles, including a low sample concentration or difficulty carrying out the measurement, limit their application. With the advent of nanotechnology, many studies have been carried out to synthesize and employ nanomaterials (NMs) in sensing techniques to determine these tumor markers at low concentrations. The fabrication, sensitivity, design, and multiplexing of sensing techniques have been uplifted due to the attractive features of NMs. Various NMs, such as magnetic and metal nanoparticles, up-conversion NPs, carbon nanotubes (CNTs), carbon-based NMs, quantum dots (QDs), and graphene-based nanosensors, hyperbranched polymers, optical nanosensors, piezoelectric biosensors, paper-based biosensors, microfluidic-based lab-on-chip sensors, and hybrid NMs have proven effective in detecting tumor markers with great sensitivity and selectivity. This review summarizes various categories of NMs for detecting these valuable markers, such as prostate-specific antigen (PSA), human carcinoembryonic antigen (CEA), alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), human epidermal growth factor receptor-2 (HER2), cancer antigen 125 (CA125), cancer antigen 15-3 (CA15-3, MUC1), and cancer antigen 19-9 (CA19-9), and highlights recent nanotechnology-based advancements in detection of these prognostic biomarkers.

Biosensing strategies for diagnosis of prostate specific antigen

Almost from the time of its discovery, the prostate specific antigen (PSA) has been one of the most accurate and most extensively studied indicators of prostate cancer (PC). Because of advancements in biosensing systems and technology, PSA analysis methods have been substantially updated and enhanced as compared to their first instances. With the development of techniques in biosensor technology, the number of PSA biosensors that can be used in the biomedical sector is increasing year by year. Many different recognition elements and transducers have been used in the development of biosensor systems that exhibit high sensitivity, selectivity, and specificity. Here in this review, we provide a current overview of the different approaches to PSA detection.

Metal-Organic Frameworks (MOFs) for Cancer Therapy

MOFs exhibit inherent extraordinary features for diverse applications ranging from catalysis, storage, and optics to chemosensory and biomedical science and technology. Several procedures including solvothermal, hydrothermal, mechanochemical, electrochemical, and ultrasound techniques have been used to synthesize MOFs with tailored features. A continued attempt has also been directed towards functionalizing MOFs via "post-synthetic modification" mainly by changing linkers (by altering the type, length, functionality, and charge of the linkers) or node components within the MOF framework. Additionally, efforts are aimed towards manipulating the size and morphology of crystallite domains in the MOFs, which are aimed at enlarging their applications window. Today's knowledge of artificial intelligence and machine learning has opened new pathways to elaborate multiple nanoporous complex MOFs and nano-MOFs (NMOFs) for advanced theranostic, clinical, imaging, and diagnostic purposes. Successful accumulation of a photosensitizer in cancerous cells was a significant step in cancer therapy. The application of MOFs as advanced materials and systems for cancer therapy is the main scope beyond this perspective. Some challenging aspects and promising features in MOF-based cancer diagnosis and cancer therapy have also been discussed.

Au@Zr-based metal-organic framework composite as an immunosensing platform for determination of hepatitis B virus surface antigen

An ultrasensitive electrochemical immunosensor has been prepared using an immunofunctionalized zirconium (Zr)-based metal-organic framework (MOF) with gold (Au) decoration Au@UiO-66(NH2) composite-coated glassy carbon electrode (GCE) for the determination of infectious hepatitis B surface antigen (HBsAg). We fabricated GCE with specific composite via immune-functionalization using anti-HBsAg with Au nanoparticles embedded in UiO-66(NH2). The electrochemical sensing performance of the immunofunctionalized Au@UiO-66(NH2)/GCE with HBsAg was characterized by cyclic voltammetry and differential pulse voltammetry. Under optimized conditions, there was a linear dynamic relationship in the buffer system between the electrical signal and HBsAg levels over the range 1.13 fg mL-1-100 ng mL-1 (R2 = 0.999) with a detection limit of 1.13 fg mL-1. The total analysis time was 15 min per sample. Further validations were performed with HBsAg-spiked human serum samples, and similar detection limits as in the buffer system were observed with reduced signal intensities at lower concentrations of HBsAg (1, 10, and 100 fg mL-1) and minimal interference. The HBsAg electrochemical immunosensing assay had good selectivity and excellent reproducibility, thereby indicating its significant potential in the super-fast diagnosis of hepatitis B.

Enzyme-free sandwich-type electrochemical immunosensor for CEA detection based on the cooperation of an Ag/g-C3N4-modified electrode and Au@SiO2/Cu2O with core-shell structure

Effective signal amplification is a prerequisite for electrochemical immunosensors to achieve ultra-sensitive detection. In this work, we prepared a sandwich-type electrochemical immunosensor for the quantitative detection of carcinoembryonic antigen (CEA). As a base platform, Ag NPs modified aminated two-dimensional nitrogen carbide nanosheets (Ag/g-C₃N₄) have good biocompatibility and conductivity. In addition, with the layered structure of Au@SiO₂/Cu₂O as the signal label, the response current value of H₂O₂ was monitored by the Amperometric i-t Curve (i-t), so as to realize the accurate measurement of CEA. The presence of SiO₂ nanoframes not only reduces the agglomeration of Au NPs and Cu₂O but also provides good biocompatibility to facilitate the connection of secondary antibodies. Finally, we also verified the signal amplification mechanism of the immunosensor through XPS and other means, and calculated the kinetic parameters of the signal tag, which proved the good peroxidase-like activity of Au@SiO₂/Cu₂O. Under the best test conditions, the prepared immunosensor has a detection range from 0.01 pg/mL to 80 ng/mL, and the detection limit is as low as 0.0038 pg/mL. The results show that the immunosensor has good analytical performance and it can provide a new method for the clinical diagnosis of CEA.

A label-free photoelectrochemical immunosensor for prostate specific antigen detection based on Ag2S sensitized Ag/AgBr/BiOBr heterojunction by in-situ growth method

Prostate cancer is one of the most common cancers in the world, and its early detection is vital to saving the lives of patients. In this research, a novel label-free photoelectrochemical immunosensor was designed for sensitive detection of prostate specific antigen (PSA). Ag₂S sensitized on Ag/AgBr/BiOBr heterojunction could effectively inhibit photogenic holes recombination and improve photocurrent response and sensitivity. Ascorbic acid was an effective electron donor, which can effectively eliminate photo-generated holes. The photocurrent reduced linearly with the logarithm of PSA concentration ranged from 0.001 to 50 ng·mL^-1 and the limit of detection was 0.25 pg·mL^-1. The designed sensor had the advantages of wide linear range, good stability, high reproducibility, and good selectivity. This study not only provided a method for efficient and sensitive detection of PSA, but also provided valuable reference ideas for the detection of other tumor markers.

Design of metal-organic framework composites in anti-cancer therapies

Metal-organic frameworks are a class of new and promising anti-cancer materials. MOFs with adjustable pore size, large specific surface area, diverse structure, and excellent chemical and physical properties make them a class of effective protection carriers for anti-cancer substances. This review is centered on the core point of "anti-cancer" and discusses MOFs' research progress in anti-cancer therapies. Firstly, we provided readers with the different types of MOFs, their preparation strategies and the resulting structures. Then, different MOF composites and their biological applications were systematically presented. The specificity of biomolecules endows MOFs with broader anti-cancer applications, while MOFs can protect the drugs and biomolecules to make the best of a challenging situation. Finally, we elucidated a comprehensive overview of the biological applications of MOFs, including research hotspots as drug delivery and biomolecule carriers. Besides, we looked forward to the future developments of MOFs in the field of anti-cancer therapies. As a class of novel materials, the anti-cancer applications of MOFs are extended through the combination of different materials and different methods to improve their efficacy.

Penicillin biosensor based on rhombus-shaped porous carbon/hematoxylin/penicillinase

In this experiment, we designed an electrochemical sensor using penicillinase (Pen X)-rhombus porous carbon (RPC) as the detection element and hematoxylin as the indicator to detect low concentrations of penicillin sodium (Pen G). A differential pulse voltammetry (DPV) method was used to detect Pen G in the concentration range of 10^-8 -10^-5 mg·mL^-1 under optimal experimental conditions. The results showed that the peak current value and the logarithm of Pen G concentration showed a good linear relationship (R² = 0.9915), and the LOD was 2.68 × 10^-7 mg·mL^-1 (S/N = 3). The actual milk samples were detected by the addition method and compared with the high-performance liquid phase method; no significant difference was found in the detection results. The working electrode prepared by cross-linking method not only extends the service life of the sensor, but also improves the sensitivity and reproducibility of the sensor. It can also be used to detect the Pen G residue in the actual milk samples repeatedly. PRACTICAL APPLICATION: In this study, an electrochemical sensor for the rapid detection of penicillin sodium in milk was prepared, which has good sensitivity and fast detection speed.

Metal Nanoparticle and Quantum Dot Tags for Signal Amplification in Electrochemical Immunosensors for Biomarker Detection

With the increasing importance of healthcare and clinical diagnosis, as well as the growing demand for highly sensitive analytical instruments, immunosensors have received considerable attention. In this review, electrochemical immunosensor signal amplification strategies using metal nanoparticles (MNPs) and quantum dots (Qdots) as tags are overviewed, focusing on recent developments in the ultrasensitive detection of biomarkers. MNPs and Qdots can be used separately or in combination with other nanostructures, while performing the function of nanocarriers, electroactive labels, or catalysts. Thus, different functions of MNPs and Qdots as well as recent advances in electrochemical signal amplification are discussed. Additionally, the methods most often used for antibody immobilization on nanoparticles, immunoassay formats, and electrochemical methods for indirect biomarker detection are overviewed.

Magnetic nanoparticles in developing electrochemical sensors for pharmaceutical and biomedical applications

A revolutionary impact on the pharmaceutical and biomedical applications has been arisen in the few years to come as a result of the advances made in magnetic nanoparticles (MNPs) research. The use of MNPs opens wide opportunities in diagnostics, drug and gene delivery, in vivo imaging, magnetic separation, and hyperthermia therapy, etc. Besides, their possible integration in sensors makes them an ideal essential element of innovative pharmaceutical and biomedical applications. Nowadays, MNPs-based electrochemical sensors have attracted great attention to pharmaceutical and biomedical applications owing to their high sensitivity, stability. Selectivity towards the target as well as their simplicity of manufacture. Therefore, this review focus on recent advances with cutting-edge approaches dealing with the synthesis, design, and advantageous analytical performance of MNPs in the electrochemical sensors utilized for pharmaceutical and biomedical applications between 2015 and 2020. The challenges existing in this research area and some potential strategies/future perspectives for the rational design of electrochemical sensors are also outlined.

A novel electrochemical immunosensor for hepatitis B surface antigen based on Fe3O4 nanoflowers and heterogeneous chain reaction signal amplification strategy

Herein, a novel sandwich-type electrochemical immunosensor was fabricated based on Fe₃O₄ nanoflowers (Fe₃O₄ NFs) and heterogeneous chain reaction (HCR) signal amplification strategy for the sensitive detection of hepatitis B surface antigen (HBsAg). The aldehyde-functionalized Fe₃O₄ NFs are used as a supporting matrix to immobilize the hepatitis B surface antibody 1 (HBsAb1). The biotin-modified single-strand DNA (biotin-S0) was connected onto the biotin-HBsAb2 via linkage of streptavidin (SA), followed by addition of methylene blue (MB) modified single strand DNA1 (MB-S1) and DNA2 (MB-S2) for HCR signal amplification. The designed immunosensor exhibited a detection linear range of 0.5 pg mL^-1-0.25 ng mL^-1 and a low detection limit of 0.16 pg mL^-1, with excellent stability, selectivity and reproducibility. Furthermore, HBsAg is detected in the serum samples with a stable and fast response, indicating that the proposed immunosensor has a promising potential application in clinical analysis.

Multimodal/Multifunctional Nanomaterials in (Bio)electrochemistry: Now and in the Coming Decade

Multifunctional nanomaterials, defined as those able to achieve a combined effect or more than one function through their multiple functionalization or combination with other materials, are gaining increasing attention in the last years in many relevant fields, including cargo targeted delivery, tissue engineering, in vitro and/or in vivo diseases imaging and therapy, as well as in the development of electrochemical (bio)sensors and (bio)sensing strategies with improved performance. This review article aims to provide an updated overview of the important advances and future opportunities exhibited by electrochemical biosensing in connection to multifunctional nanomaterials. Accordingly, representative aspects of recent approaches involving metal, carbon, and silica-based multifunctional nanomaterials are selected and critically discussed, as they are the most widely used multifunctional nanomaterials imparting unique capabilities in (bio)electroanalysis. A brief overview of the main remaining challenges and future perspectives in the field is also provided.

Application of magnetic nanomaterials in electroanalytical methods: A review

Magnetic nanomaterials (MNMs) have gained high attention in different fields of studies due to their ferromagnetic/superparamagnetic properties and their low toxicity and high biocompatibility. MNMs contain magnetic elements such as iron and nickel in metallic, bimetallic, metal oxide, and mixed metal oxide. In electroanalytical methods, MNMs have been applied as sorbents for sample preparation before the electrochemical detection (sorbent role), as the electrode modifier (catalytic role), and the integration of the above two roles (as both sorbent and catalytic agent). In this paper, the application of MNMs in electroanalytical methods have been classified based on the main role of the nanomaterial and discussed separately. Furthermore, catalytic activities of MNMs in electroanalytical methods such as redox electrocatalytic, nanozymes catalytic (peroxidase, catalase activity, oxidase activity, superoxide dismutase activity), catalyst gate, and nanocontainer have been discussed.

Metal Nanoparticles for Electrochemical Sensing: Progress and Challenges in the Clinical Transition of Point-of-Care Testing

With the rise in public health awareness, research on point-of-care testing (POCT) has significantly advanced. Electrochemical biosensors (ECBs) are one of the most promising candidates for the future of POCT due to their quick and accurate response, ease of operation, and cost effectiveness. This review focuses on the use of metal nanoparticles (MNPs) for fabricating ECBs that has a potential to be used for POCT. The field has expanded remarkably from its initial enzymatic and immunosensor-based setups. This review provides a concise categorization of the ECBs to allow for a better understanding of the development process. The influence of structural aspects of MNPs in biocompatibility and effective sensor design has been explored. The advances in MNP-based ECBs for the detection of some of the most prominent cancer biomarkers (carcinoembryonic antigen (CEA), cancer antigen 125 (CA125), Herceptin-2 (HER2), etc.) and small biomolecules (glucose, dopamine, hydrogen peroxide, etc.) have been discussed in detail. Additionally, the novel coronavirus (2019-nCoV) ECBs have been briefly discussed. Beyond that, the limitations and challenges that ECBs face in clinical applications are examined and possible pathways for overcoming these limitations are discussed.

A critical review on quantum dots: From synthesis toward applications in electrochemical biosensors for determination of disease-related biomolecules

Fluorescent quantum dots (QDs), defined by a diameter size of <10 nm, have been the core concept of nanoscience and nanotechnology since their inception. QDs possess many unique structural, electrochemical and photochemical properties that render them a promising platform for sensing applications. These nanomaterials can greatly enhance the analytical performances of biosensors, namely detection limit, sensitivity and selectivity. QDs are being developed not only because of their ability for signal enhancement but also because of their high capacity for fuctionalization with bioreceptors. In this review, we summarize a basic knowledge of QDs before focusing on their application to sensing thus far followed by a discussion of future directions for research into the sensing field. Due to the nature of QDs, especially their ability to combine nanotechnology and biotechnology, they possess the potential to open a novel paradigm on early diagnosis of diseases using the electrochemical biosensors. Therefore, we try to give a comprehensive view of the role of these zero-dimensional (0D) nanomaterials in the designing electrochemical sensors for determination of disease-related biomolecules, including tumor markers, inflammatory biomarkers, depression markers and archetypal biomarker in diabetes diagnosis. Considering the high potential of QDs for the electrochemistry-based biosensing strategies, the authors suggest that more research is needed on understanding their electronic properties and why synthesis and surface modification methods can affect these properties.

Advances in immunosensor technology

In recent years, advances in immunosensor device fabrication have significantly expanded the use of this technology in a broad range of applications including clinical diagnosis, food analysis, quality control, environmental studies and industrial monitoring. The most important aspect in fabrication is to obtain a design that provides a low detection limit. The utilization of nanomaterials as a label, catalyst and biosensing transducer is, perhaps, the most popular approach in ultrasensitive devices. This chapter reviews recent advances in immunosensor fabrication and summarizes the most recent studies. Strategies employed to significantly improve sensitivity and specificity of immunosensor technology and the advantages and limitations thereof are explored.

Nanotreatment and Nanodiagnosis of Prostate Cancer: Recent Updates

The fabrication and development of nanomaterials for the treatment of prostate cancer have gained significant appraisal in recent years. Advancements in synthesis of organic and inorganic nanomaterials with charge, particle size, specified geometry, ligand attachment etc have resulted in greater biocompatibility and active targeting at cancer site. Despite all of the advances made over the years in discovering drugs, methods, and new biomarkers for cancer of the prostate (PCa), PCa remains one of the most troubling cancers among people. Early on, effective diagnosis is an essential part of treating prostate cancer. Prostate-specific antigen (PSA) or serum prostate-specific antigen is the best serum marker widely accessible for diagnosis of PCa. Numerous efforts have been made over the past decade to design new biosensor-based strategies for biomolecules detection and PSA miniaturization biomarkers. The growing nanotechnology is expected to have a significant effect in the immediate future on scientific research and healthcare. Nanotechnology is thus predicted to find a way to solve one of the most and long-standing problem, "early cancer detection". For early diagnosis of PCa biomarkers, different nanoparticles with different approaches have been used. In this review, we provide a brief description of the latest achievements and advances in the use of nanoparticles for PCa biomarker diagnosis.