Label free MUC1 aptasensors based on electrodeposition of gold nanoparticles on screen printed electrodes

Beyond traditional biosensors: Recent advances in gold nanoparticles modified electrodes for biosensing applications

Gold nanoparticles (AuNPs) have emerged as powerful tools in the construction of highly sensitive electrochemical biosensors. Their unique properties, such as the ability to serve as an effective platform for biomolecule immobilization and to facilitate electron transfer between the electrode surface and the immobilized molecules, make them a promising choice for biosensor applications. Utilizing AuNPs modified electrodes can lead to improved sensitivity and lower limits of detection compared to unmodified electrodes. This review provides a comprehensive overview of the recent advancements and applications of AuNPs-based electrochemical biosensors in the biomedical field. The synthesis methods of AuNPs, their key properties, and various strategies employed for electrode modification are discussed. Furthermore, this review highlights the remarkable applications of these nanostructure-integrated electrodes, including immunosensors, enzyme biosensors, and DNA biosensors.

Straightforward fabrication of electrochemical aptasensors with outstanding antifouling performance

Self-assembled monolayers (SAMs) are popular tools for many different applications - SAMs of commercially available chemicals that convincingly inhibit unspecific binding for electrochemical sensors, however, have yet to be developed. While adsorption of foulants prohibits the reliable analysis of biological samples, unspecific binding of the analyte similarly impedes the investigation of binding characteristics from buffer solutions. In this communication, diglycolamine is introduced for the modification of electrodes with outstanding antifouling performance. The presented sensor design, solely consisting of diglycolamine and an aptamer of choice, convinces with its ease of preparation, low cost, and, most importantly, an exceptional specificity. The latter was found to rely on a gentle but potent cleaning of the electrodes, as only our optimized cleaning procedure granted the diglycolamine layer its excellent fouling minimization performance, while literature standard protocols failed to do so. Each step of the sensor fabrication protocol was optimized by electrochemical impedance spectroscopy, while square-wave voltammetry, surface-enhanced Raman spectroscopy, and zeta potential measurement were performed for further characterization. The presented approach of surface modification with diglycolamine is a versatile method applicable not just to electrochemical measurements, but to a variety of other detection techniques, too, and has the potential to change the way we investigate binding characteristics and fabricate sensors for the analysis of complex biological samples.

Printed Electrochemical Strip for the Detection of miRNA-29a: A Possible Biomarker Related to Alzheimer’s Disease

The development of electrochemical strips, as extremely powerful diagnostic tools, has received much attention in the field of sensor analysis and, in particular, the detection of nucleic acids in complex matrixes is a hot topic in the electroanalytical area, especially when directed toward the development of emerging technologies, for the purpose of facilitating personal healthcare. One of the major diseases for which early diagnosis is crucial is represented by Alzheimer’s disease (AD). AD is a progressive neurodegenerative disease, and it is the most common cause of dementia worldwide. In this context microRNAs (miRNAs), which are small noncoding RNAs, have recently been highlighted for their promising role as biomarkers for early diagnosis. In particular, miRNA-29 represents a class of miRNAs known to regulate pathogenesis of AD. In this work we developed an electrochemical printed strip for the detection of miRNA-29a at low levels. The architecture was characterized by the presence of gold nanoparticles (AuNPs) and an anti-miRNA-29a probe labeled with a redox mediator. The novel analytical tool has been characterized with microscale thermophoresis and electrochemical methods, and it has been optimized by selection of the most appropriate probe density to detect low target concentration. The present tool was capable to detect miRNA-29a both in standard solution and in serum, respectively, down to 0.15 and 0.2 nM. The platform highlighted good repeatability (calculated as the relative standard deviation) of ca. 10% and satisfactory selectivity in the presence of interfering species. This work has the objective to open a way for the study and possible early diagnosis of a physically and socially devastating disease such as Alzheimer’s. The results demonstrate the suitability of this approach in terms of ease of use, time of production, sensitivity, and applicability.

Recent progress in the early detection of cancer based on CD44 biomarker; nano-biosensing approaches

CD44 is a cell matrix adhesion molecule overexpressed on the cell surfaces of the major cancers. CD44 as a cancer-related biomarker has an essential role in the invasion and metastasis of cancer. The detection and quantification of CD44 can provide essential information useful for clinical cancer diagnosis. In this regard, biosensors with sensitive and specific properties, give prominence to the development of CD44 detection platforms. To date, various aptamer-based sensitive-enhancers together with nanoparticles (NPs) have been combined into the biosensors systems to provide an innovative biosensing method (aptasensors/nano-aptasensors) with substantially improved detection limit. This review article discusses the recent advances in the field of biosensors, nanobiosensors, and aptasensors for the quantitative determination of CD44 and the detection of CD44-expressing cancer cells.

A Broad-Range Disposable Electrochemical Biosensor Based on Screen-Printed Carbon Electrodes for Detection of Human Noroviruses

Human noroviruses (HuNoVs) are the major non-bacterial pathogens causing acute gastroenteritis in people of all ages worldwide. No stable culture system in vitro is available for routing the detection of multiple strains of HuNoVs. A simple and rapid method for detection of HuNoVs is of great significance for preventing and controlling this pathogen. In this work, an electrochemical biosensor for sensitive and fast detection of HuNoVs was constructed based on a screen-printed carbon electrode (SPCE). Gold nanoparticles and protein-A were applied on the SPCE surface for enhancement of the electrical signals and the linkage of antibodies with a fixed orientation, respectively. A monoclonal antibody (MAb) against the S domain protein of the viral capsid (VP1) was further immobilized on the SPCE to bind HuNoVs specifically. The binding of VP1 to the coated MAbs resulted in the reduction of conductivity (current) measured by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The reduction in the current was correlated to the concentration of VP1/HuNoVs. The detection limitation of Genogroup I.1 (GI.1) VP1 and Genogroup II.4 (GII.4) VP1 was 0.37 ng/ml (≈1.93×10⁷ HuNoVs/mL) and 0.22 ng/ml (≈1.15×10⁷ HuNoVs/mL), respectively. The detection limitation of both GI and GII HuNoVs in clinical fecal samples was 10⁴ genomic copies/mL. The results could be obtained in 1 h. We demonstrated that this disposable electrochemical biosensor was a good candidate for rapid detection of different genogroup and genotype HuNoVs.

Ultrasensitive early detection of insulin antibody employing novel electrochemical nano-biosensor based on controllable electro-fabrication process

An ultrasensitive novel electrochemical nano-biosensor for rapid detection of insulin antibodies against diabetes antigens was developed in this research. The presence of insulin antibodies has been demonstrated to be a strong predictor for the development of type 1 diabetes in individuals who do not have diabetes but are genetically predisposed. The proposed nano-biosensor fabrication process was based on the optimized sequential electropolymerization of polyaniline and electrodeposition of gold nanoparticles on the surface of the functionalized gold electrode. The morphological and chemical characterization of the modified electrode was studied by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), and micro Raman spectroscopy. Moreover, the role of each component in the modification of the electrode was studied by electrochemical methods systematically. After immobilizing insulin antigen and blocking with bovine serum albumin, the nano-biosensor was used for determining different concentrations of insulin antibody under the optimal conditions. This nano-biosensor could respond to insulin antibody with a linear calibration range from 0.001 ng ml^-1 to 1000 ng ml^-1 with the detection limit of 0.017 pg ml^-1 and 0.034 pg ml^-1 and selectivity of 18.544 μA ng^-1 ml.cm^-2 and 31.808 μA ng^-1 ml.cm^-2 via differential pulse voltammetry and square wave voltammetry, respectively. This novel nano-biosensor exhibited a short response time, high sensitivity, and good reproducibility. It was successfully used in determining the insulin antibody in human samples with a standard error of less than 0.178. Therefore, the nano-biosensor has the potential for the application of early detection of type 1 diabetes. To our best knowledge, label-free electrochemical detection of insulin antibody based on immunosensor is developed for the first time.

Recent trends in nanomaterial-based signal amplification in electrochemical aptasensors

Ultrasensitive biosensors have become a necessity in the world of scientific research, and several signal enhancement strategies have been employed to attain exceptionally low detection limits. Nanotechnology turns out to be a strong contender for signal amplification, as they can be employed as platform modifiers, catalysts, carriers or labels. Here, we have described the most recent advancements in the utilization of nanomaterials as signal amplification components in aptamer-based electrochemical biosensors. We have briefly reviewed the methods that utilized nanomaterials, namely gold and carbon, as well as nanocomposites such as: graphene, carbon nanotubes, quantum dots, and metal-organic frameworks.

A Comprehensive Study on Aptasensors For Cancer Diagnosis

Cancer is the most devastating disease in the present scenario, killing millions of people every year. Early detection, accurate diagnosis, and timely treatment are considered to be the most effective ways to control this disease. Rapid and efficient detection of cancer at their earliest stage is one of the most significant challenges in cancer detection and cure. Numerous diagnostic modules have been developed to detect cancer cells early. As nucleic acid equivalent to antibodies, aptamers emerge as a new class of molecular probes that can identify cancer-related biomarkers or circulating rare cancer/ tumor cells with very high specificity and sensitivity. The amalgamation of aptamers with the biosensing platforms gave birth to "Aptasensors." The advent of highly sensitive aptasensors has opened up many new promising point-of-care diagnostics for cancer. This comprehensive review focuses on the newly developed aptasensors for cancer diagnostics.

Aptamer-based sensing of breast cancer biomarkers: a comprehensive review of analytical figures of merit

INTRODUCTION

Accurate determination of the aberrantly expressed biomarkers such as human epidermal growth factor receptor 2 (HER2), carcinoembryonic antigen (CEA), platelet-derived growth factor (PDGF), mucin 1 (MUC1), and vascular endothelial growth factor VEGF₁₆₅ have played an essential role in the clinical management of the breast cancer. Assessment of these cancer-specific biomarkers has conventionally relied on time-taking methods like the enzyme-linked immunosorbent assay and immunohistochemistry. However, recent development in the aptamer-based diagnostics has allowed developing tools that may substitute the conventional means of biomarker assessment in breast cancer. Adopting the aptamer-based diagnostic tools (aptasensors) to clinical practices will depend on their analytical performance on clinical samples.

AREAS COVERED

In this review, we provide an overview of the analytical merits of HER2, CEA, PDGF, MUC1, and VEGF₁₆₅ aptasensors. Scopus and Pubmed databases were searched for studies reporting aptasensor development for the listed breast cancer biomarkers in the past one decade. Linearity, detection limit, and response time are emphasized.

EXPERT OPINION

In our opinion, aptasensors have proven to be on a par with the antibody-based methods for detection of various breast cancer biomarkers. Though robust validation of the aptasensors on significant sample size is required, their ability to detect pathophysiological range of biomarkers suggest the possibility of future clinical adoption.

Critical role of biosensing on the efficient monitoring of cancer proteins/biomarkers using label-free aptamer based bioassay

Cancer is the second most extended disease during the world with an improved death rate over the past several time. Due to the restrictions of cancer analysis methods, the patient's real survival rate is unknown. Therefore early stage diagnosis of cancer is crucial for its strong detection. Bio-analysis based on biomarkers may help to overcome this problem. Aptamers can be employed as high-affinity tools for cancer detection. The utilization of aptamer-based strategy in cancer investigation and strategy shows new opportunities in biotechnology. The label-free system is an important method to study biomolecules in different sizes, such as biomarkers in real-time because of their greatest sensitivity, selectivity, and multi examination. In this review (with 75 references), excellent features of the label-free aptasensors on the sensitive and accurate monitoring of cancer biomarkers were discussed. Also, the role of advanced of nanomaterials on the construction of label-free aptasensors were investigated. In addition, application of different detection methods such as electrochemical, optical, electronic, and photoelectrochemical (PEC), electrochemiluminescence (ECL) were surveyed. Finally, advantages and limitation of different strategies on the early stage diagnosis of cancer biomarkers were discussed. This article has been updated until July 2020.

High-Performance Voltammetric Aptasensing Platform for Ultrasensitive Detection of Bisphenol A as an Environmental Pollutant

Bisphenol A (BPA) as a pervasive endocrine-disrupting compound (EDC) has been shown to cause multiple detrimental effects including cardiovascular disorders, pregnancy complications, obesity, glucose metabolism disorders, and reproductive toxicity even at a concentration as low as tolerable daily intake (TDI) (4 μg/kg/day). In the present study, a novel ultra-sensitive, electrochemical aptasensor was designed using a screen-printed carbon electrode (SPCE) modified by gold nanoparticles (Au NPs) conjugated to thiolated aptamers for accurate determination of BPA in biological, industrial and environmental samples. To characterize the electrochemical properties of the aptasensor, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were implemented. Detection of BPA was also performed through differential pulse voltammetry (DPV) in [Fe(CN)₆]^3–/4– electrolyte solution. Under optimum condition, the present electrochemical aptasensor demonstrated an outstanding linear response in the concentration range of 1 pM to 10 nM with a remarkably low limit of detection of 0.113 pM. Due to the superb affinity between anti-BPA aptamers and BPA molecules, the designed aptasensor did not show any significant interaction with other analytes in real samples. Also, fabricated biosensor remained perfectly stable in long-term storage. The analytical results of the fabricated aptasensor are well compatible with those obtained by the ELISA method, indicating the trustworthiness and reasonable accuracy of the application of aptasensor in real samples. Overall, the proposed aptasensor would be a credible and economical method of precise, reproducible, and highly selective detection of minimum levels of BPA in food containers and clinical samples. This would be a promising strategy to enhance the safety of food products and reduce the risk of BPA daily exposure.

Recent advances in aptamer-based sensors for breast cancer diagnosis: special cases for nanomaterial-based VEGF, HER2, and MUC1 aptasensors

Cancer is one of the most common and important diseases with a high mortality rate. Breast cancer is among the three most common types of cancer in women, and the mortality rate has reached 0.024% in some countries. For early-stage preclinical diagnosis of breast cancer, sensitive and reliable tools are needed. Today, there are many types of biomarkers that have been identified for cancer diagnosis. A wide variety of detection strategies have also been developed for the detection of these biomarkers from serum or other body fluids at physiological concentrations. Aptamers are single-stranded DNA or RNA oligonucleotides and promising in the production of more sensitive and reliable biosensor platforms in combination with a wide range of nanomaterials. Conformational changes triggered by the target analyte have been successfully applied in fluorometric, colorimetric, plasmonic, and electrochemical-based detection strategies. This review article presents aptasensor approaches used in the detection of vascular endothelial growth factor (VEGF), human epidermal growth factor receptor 2 (HER2), and mucin-1 glycoprotein (MUC1) biomarkers, which are frequently studied in the diagnosis of breast cancer. The focus of this review article is on developments of the last decade for detecting these biomarkers using various sensitivity enhancement techniques and nanomaterials.

Electrochemical mixed aptamer-antibody sandwich assay for mucin protein 16 detection through hybridization chain reaction amplification

A mixed aptamer-antibody sandwich assay for the determination of mucin protein 16 (MUC16) was developed based on hybridization chain reaction (HCR) with methylene blue (MB) as an electrochemical indicator. First, MUC16 antibody was adsorbed onto the surface of the Au nanoparticle (AuNP)-modified indium tin oxide (ITO) electrode to effectively capture the target MUC16. After MUC16 was captured by the MUC16 aptamer, an antibody/MUC16/aptamer sandwich structure formed for the highly selective detection of MUC16. The 3' end of the aptamer was then subjected to HCR with the assistance of auxiliary probes to obtain DNA concatemers. Numerous MB molecules bonded with G bases in the DNA concatemers by immersing the modified ITO electrode into a stirred solution containing MB with KCl. Stepwise changes in the microscopic features of the electrode surface were studied by scanning electron microscopy (SEM). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the electrochemical behavior of the different modified electrodes. The oxidation current of MB was detected by differential pulse voltammetry (DPV). Under the optimum conditions, the proposed mixed aptamer-antibody sandwich assay showed wide dynamic range from 0.39 to 200 unit mL^-1 with a low detection limit of 0.02 unit mL^-1 (S/N ratio = 3). The proposed method showed good accuracy, selectivity, and acceptable reproducibility. Graphical abstract An electrochemical mixed aptamer-antibody sandwich assay based on the aptamer-induced HCR amplification strategy was fabricated for the highly sensitive detection of MUC16. The mixed aptamer-antibody sandwich assay showed acceptable performance of detection range, detection limit, reproducibility, and selectivity.

Screen-Printed Electrodes (SPE) for In Vitro Diagnostic Purpose

Due to rapidly spreading infectious diseases and the high incidence of other diseases such as cancer or metabolic syndrome, there is a continuous need for the development of rapid and accurate diagnosis methods. Screen-printed electrodes-based biosensors have been reported to offer reliable results, with high sensitivity and selectivity and, in some cases, low detection limits. There are a series of materials (carbon, gold, platinum, etc.) used for the manufacturing of working electrodes. Each version comes with advantages, as well as challenges for their functionalization. Thus, the aim is to review the most promising biosensors developed using screen-printed electrodes for the detection/quantification of proteins, biomarkers, or pathogenic microorganisms.

An Electrochemical Aptasensor Platform Based on Flower-Like Gold Microstructure-Modified Screen-Printed Carbon Electrode for Detection of Serpin A12 as a Type 2 Diabetes Biomarker

Purpose

In the present study, a highly sensitive and simple electrochemical (EC) aptasensor for the detection of serpin A12 as a novel biomarker of diabetes was developed on a platform where flower-like gold microstructures (FLGMs) are electrodeposited onto a disposable screen-printed carbon electrode. Meanwhile, serpin A12-specific thiolated aptamer was covalently immobilized on the FLGMs.

Methods

The electrochemical activity of a fabricated aptasensor under various conditions were examined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Aptamer concentration, deposition time, self-assembly time, and incubation time were optimized for assay of serpin A12. The differential pulse voltammetry (DPV) was implemented for quantitative detection of serpin A12 in K₃ [Fe (CN) ₆]/K₄ [Fe (CN) ₆] solution (redox probe).

Results

The label-free aptasensor revealed a linear range of serpin A12 concentration (0.039–10 ng/mL), detection limit of 0.020 ng/mL (S/N=3), and 0.031 ng/mL in solution buffer and plasma, respectively.

Conclusion

The results indicate that this aptasensor has a high sensitivity, selectivity, stability, and acceptable reproducibility for detection of serpin A12 in diabetic patients.

Advances in aptasensor technology

Aptasensors form a class of biosensors that function on the basis of a biological recognition. An aptasensor is advantageous because it incorporates a unique biologic recognition element, i.e., an aptamer, coupled to a transducer to convert a biological interaction to readable signals that can be easily processed and reported. In such biosensors, the specificity of aptamers is comparable to and sometimes even better than that of antibodies. Using the SELEX technique, aptamers with high specificity and affinity to various targets can be isolated from large pools of different oligonucleotides. Nowadays, new modifications of the SELEX technique and, as a result, easy generation and synthesis of aptamers have led to the wide application of these materials as biological receptors in biosensors. In this regard, aptamers promise a bright future. In the present research a brief account is initially provided of the recent developments in aptasensors for various targets. Then, immobilization methods, design strategies, current limitations and future directions are discussed for aptasensors.

Implication of Magnetic Nanoparticles in Cancer Detection, Screening and Treatment

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

TiO2 nanotubes/reduced GO nanoparticles for sensitive detection of breast cancer cells and photothermal performance

In this study, we developed a simple and cost effective aptasensor based on TiO₂ nanotubes-reduced graphene oxide (TiO₂ nanotube-rGO) linked to MUC1 aptamers for ultrasensitive electrochemical detection of breast cancer cell (MCF-7). Moreover, the photothermal performance of nanohybrid TiO₂-rGO was investigated for cancer treatment. In this regard, after synthesize of TiO₂ nanotubes via anodization process, TiO₂ nanotubes-rGO hybrid was synthesized by UV assisted reduction of GO and subsequent TiO₂ nanotubes attachment to rGO sheets. The resultant hybrid could provide an excellent large surface area leading to improvement of suitable sites for MUC1 aptamer immobilization. Our results revealed that TiO₂-rGO aptasensor exhibited superior analytical performance for MCF-7 cell detection with the detection limit of 40 cells.ml^-1 within the detection range of 10³-10⁷ cells. ml^-1. In addition, the designed aptasensor was effectively applied to detect MUC1 marker in a real sample. Moreover, the TiO₂ nanotube-rGO hybrid nanoparticles revealed great photothermal performance exposed to NIR laser. It could be concluded that nanohybrid TiO₂-rGO would be a useful and beneficial platform for detection and treatment of breast cancer.

An exonuclease-assisted triple-amplified electrochemical aptasensor for mucin 1 detection based on strand displacement reaction and enzyme catalytic strategy

The development of some sensitive methods for MUC1 is critical for preclinical diagnosis of tumors. In this experiment, we built a triple-amplified electrochemical aptasensor to achieve sensitive detection of MUC1, which was based on exonuclease III (Exo III)-assisted with strand displacement reaction and enzyme catalytic strategy. Firstly, with the help of Exo III, MUC1 and aptamer could be recycled during the cycle I, the single stranded DNA-1 (S-1) was produced during the process and was introduced to the hybride reaction on the electrode. Secondly, during the cycle II, strand displacement reaction was triggered on the electrode with the adding of hairpin DNA-2 (H-2). Thirdly, after the gold nanoparticles (AuNPs)-DNA-enzyme conjugates hybrided with the H-2 on the electrode, the AuNPs-DNA-enzyme conjugates could act as signal probe to produce electrochemical catalytic signal. We used the fabricated triple-amplified electrochemical aptasensor that could detect MUC1 from 0.1 pg mL^-1 to 10 ng mL^-1 with the detection limit of 0.04 pg mL^-1 under the optimized experimental conditions. The constructed triple-amplified electrochemical aptasensor could be applied in real samples determination. Besides, the strategy can be applied to detect other proteins for health monitoring.

Aptasensors as a new sensing technology developed for the detection of MUC1 mucin: A review

Mucin 1 protein (MUC1) is a membrane-associated glycoprotein overexpressed in the majority of human malignancies and considered as a predominant protein biomarker in cancers. Owing to the crucial role of MUC1 in cancer dissemination and metastasis, detection and quantification of this biomarker is of great importance in clinical diagnostics. Today, there exist a wide variety of strategies for the determination of various types of disease biomarkers, especially MUC1. In this regard, aptamers, as artificial single-stranded DNA or RNA oligonucleotides with catalytic and receptor properties, have drawn lots of attention for the development of biosensing platforms. So far, various sensitivity-enhancement techniques in combination with a broad range of smart nanomaterials have integrated into the design of novel aptamer-based biosensors (aptasensors) to improve detection limit and sensitivity of analyte determination. This review article provides a brief classification and description of the research progresses of aptamer-based biosensors and nanobiosensors for the detection and quantitative determination of MUC1 based on optical and electrochemical platforms.

Aptasensor Based on Hierarchical Core-Shell Nanocomposites of Zirconium Hexacyanoferrate Nanoparticles and Mesoporous mFe3O4@mC: Electrochemical Quantitation of Epithelial Tumor Marker Mucin-1

A novel nanostructured hierarchical core-shell nanocomposite of zirconium hexacyanoferrate (ZrHCF) and a mesoporous nanomaterial composed of Fe₃O₄ and carbon nanospheres (denoted as ZrHCF@mFe₃O₄@mC) was prepared and used as a novel platform for an aptasensor to detect the epithelial tumor marker mucin-1 (MUC1) sensitively and selectively. The prepared ZrHCF@mFe₃O₄@mC nanocomposite exhibited good chemical functionality, water stability, and high specific surface area. Therefore, large amounts of aptamer molecules resulted in high sensitivity of the developed electrochemical aptasensor toward traces of MUC1. The constructed sensor also showed a good linear relationship with the logarithm of MUC1 concentration in the broad range of 0.01 ng·mL^-1 to 1.0 μg·mL^-1, with a low detection limit of 0.90 pg·mL^-1. The fabricated ZrHCF@mFe₃O₄@mC-based aptasensor exhibited not only high selectivity because of the formation of aptamer-MUC1 complex but also good stability, acceptable reproducibility, and applicability. The proposed novel strategy based on a newly prepared hierarchical core-shell nanocomposite demonstrated outstanding biosensing performance and presents potential applications in biomedical fields.

Biosensors for breast cancer diagnosis: A review of bioreceptors, biotransducers and signal amplification strategies

Breast cancer is highly prevalent in females and accounts for second highest number of deaths, worldwide. Cumbersome, expensive and time consuming detection techniques presently available for detection of breast cancer potentiates the need for development of novel, specific and ultrasensitive devices. Biosensors are the promising and selective detection devices which hold immense potential as point of care (POC) tools. Present review comprehensively scrutinizes various breast cancer biosensors developed so far and their technical evaluation with respect to efficiency and potency of selected bioreceptors and biotransducers. Use of glycoproteins, DNA biomarkers, micro-RNA, circulatory tumor cells (CTC) and some potential biomarkers are introduced briefly. The review also discusses various strategies used in signal amplification such as nanomaterials, redox mediators, p19 protein, duplex specific nucleases (DSN) and redox cycling.

An electrochemical DNA sensor based on polyaniline/graphene: high sensitivity to DNA sequences in a wide range

In the platform constructed by a polyaniline/graphene composite, double-stranded DNA, resulting from hybridization of a DNA probe, was escaping from or remaining on the sensor surface.

Current Trends in Nanomaterial-Based Amperometric Biosensors

The last decade has witnessed an intensive research effort in the field of electrochemical sensors, with a particular focus on the design of amperometric biosensors for diverse analytical applications. In this context, nanomaterial integration in the construction of amperometric biosensors may constitute one of the most exciting approaches. The attractive properties of nanomaterials have paved the way for the design of a wide variety of biosensors based on various electrochemical detection methods to enhance the analytical characteristics. However, most of these nanostructured materials are not explored in the design of amperometric biosensors. This review aims to provide insight into the diverse properties of nanomaterials that can be possibly explored in the construction of amperometric biosensors.

Immunosensor based on electrodeposition of gold-nanoparticles and ionic liquid composite for detection of Salmonella pullorum

In order to increase the reproducibility and stability of electrochemical immunosensor, which is a key issue for its application and popularization, an accurate and stable immunosensor for rapid detection of Salmonella pullorum (S. pullorum) was proposed in this study. The immunosensor was fabricated by modifying Screen-printed Carbon Electrode (SPCE) with electrodeposited gold nanoparticles (AuNPs), HRP-labeled anti-S. pullorum and ionic liquids (ILs) (AuNP/HRP/IL). AuNPs are electrodeposited on the working electrode surface to increase the amount of antibodies that bind to the electrode and then modified with ILs to protect the antibodies from being inactivated in the test environment and maintain their biological activity and the stability of the detection electrode. The electrochemical characteristics of the stepwise modified electrodes and the detection of S. pullorum were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). As shown in the results of the experiments, AuNPs with unique electrochemical properties as well as biocompatibility characteristics have been proven to be able to strengthen the antibody combination effectively and to increase the electrochemical response signal. In addition, a crucial assessment regarding implementation of stability and reproducibility analysis of a range of immunosensors is provided. We found that application of AuNPs/ILs in the immune modified electrodes showed obvious improvement when compared with other groups. Given their high levels of reproducibility, stability, target specificity and sensitivity, AuNPs and ILs were considered to be excellent elements for electrode modification.