Nanomaterials for use in immunosensing of carcinoembryonic antigen (CEA): Recent advances

Recent Advances in Electrochemiluminescence Biosensors for MicroRNA Detection

Electrochemiluminescence (ECL) as an analytical technology with a perfect combination of electrochemistry and spectroscopy has received considerable attention in bioanalysis due to its high sensitivity and broad dynamic range. Given the selectivity of bio-recognition elements and the high sensitivity of the ECL analysis technique, ECL biosensors are powerful platforms for the sensitive detection of biomarkers, achieving the accurate prognosis and diagnosis of diseases. MicroRNAs (miRNAs) are crucial biomarkers involved in a variety of physiological and pathological processes, whose aberrant expression is often related to serious diseases, especially cancers. ECL biosensors can fulfill the highly sensitive and selective requirements for accurate miRNA detection, prompting this review. The ECL mechanisms are initially introduced and subsequently categorize the ECL biosensors for miRNA detection in terms of the quenching agents. Furthermore, the work highlights the signal amplification strategies for enhancing ECL signal to improve the sensitivity of miRNA detection and finally concludes by looking at the challenges and opportunities in ECL biosensors for miRNA detection.

Advancing CEA quantification: Designing a sensitive electrochemical immunosenor using MWCNT/Ni(OH)2 nanocomposite

An ultra-sensitive immunosensor was designed for the accurate determination of Carcinoembryonic Antigen (CEA). To enhance the performance of immunosensor, an MWCNT/Ni(OH)2 nanocomposite was utilized as the electrochemical interface and modifier of the electrode surface. The simple preparation procedures for MWCNT/Ni(OH)2 composite were provided. Its characteristics and properties were investigated by HRTEM, FESEM, XRD, and FTIR techniques. Leveraging the unique electrochemical characteristics shown by the MWCNT/Ni(OH)2 nanocomposite and its correlation with CEA, high accuracy in CEA detection was achieved. Experimental findings provide evidence that the proposed immunosensor has the ability to detect CEA in laboratory samples. This research contributes towards achieving precise and rapid CEA detection in cancer diagnosis and prognosis. Across a wide concentration range of CEA, the designed immunosensor demonstrated a linear response from 0.0001 ng/mL to 2 ng/mL, and its limit of detection (LOD) was just 0.076 pg/mL. To evaluate the practical applicability of the electrochemical immunosensor, blood serum samples were examined, revealing the immunosensor's remarkable specificity and longevity. Its high accuracy and stability make it a valuable tool in clinical settings and biomedical research, paving the way for improved cancer management and patient outcomes.

Realizing the label-free sensitive detection of carcinoembryogenic antigen (CEA) in blood serum via a MNC-decorated flexible immunosensor

A label-free electrochemical immunosensor utilising nitrogen-rich mesoporous carbon (MNC) as the substrate material was developed for the sensitive quantification of carcinoembryonic antigen (CEA). The synergic interactions between MNC and AbCEA also eliminated the need for coupling agents such as EDC/NHS. The novel immunosensor demonstrated a wide detection range from 500 fM (9.04 pg mL-1) to 50 nM (1 μg mL-1) and a low detection limit (LOD) of 500 fM. Moreover, the immunosensor showed sensitivities of 12.27 mA nM-1 cm-2 and 0.066 mA nM-1 cm-2 for detecting CEA in the linear ranges 10 pM to 1 nM and 2 nM to 50 nM, respectively, while maintaining long-term storage stability of 6 weeks. Analysis of real serum sample analysis yielded highly accurate results with recovery rates ranging from 99.3% to 103.7%. Furthermore, the developed paper-based screen-printed electrode exhibited a similar detection range, suggesting its potential for use in point-of-care detection devices in future applications.

Highly bright and stable CsPbBr3 perovskite nanocrystals with amphiphilic polymer binding based dual-readout lateral flow immunoassay for detection of carcinoembryonic antigen

Rapid and highly sensitive detection of tumor marker (TM) is critical for the early diagnosis and treatment of cancers. Herein, utilizing highly bright and water-stable CsPbBr3 perovskite nanocrystals (NCs) capped with amphiphilic polymer ligand of octylamine-modified polyacrylic acid (OPA) and gold nanoparticles (AuNPs) as reporters, a lateral flow immunoassay (LFIA) strip is developed for fluorescence and colorimetric dual-mode detection of carcinoembryonic antigen (CEA). The prepared CsPbBr3 NCs capped by an amphiphilic polymeric of OPA ligand showed high stability and bright fluorescence. Moreover, the AuNPs immunoprobes were captured with CEA antigen and quench the green fluorescence of CsPbBr3/OPA NCs on the T line due to the inner filter effect (IFE). Therefore, CEA could be quantitative analyzed by the dual-readout of fluorescence and colorimetric signal. The detection limits of CEA can reach as low as 0.023 ng/mL and 0.027 ng/mL for the fluorescence and colorimetric mode, respectively. Good specificity and reproducibility were also demonstrated for this method. Finally, the CsPbBr3/OPA NCs-based LFIA showed good accuracy in detection of CEA level from clinical serum samples. This work firstly enables the application of CsPbBr3 perovskite NCs in a LFIA, displaying great potential in point-of-care clinical diagnosis.

Application of Ag nanoparticles decorated on graphene nanosheets for electrochemical sensing of CEA as an important cancer biomarker

In this research, a novel biosensing platform is described based on graphene nano-sheets decorated with Ag nano-particles (GNSs@Ag NPs). The designed electrochemical aptasensor was employed to determine carcinoembryonic antigen (CEA), an important cancer biomarker. Inherently, aptasensing interfaces provide high sensitivity for CEA tumor marker because of the high specific surface area and excellent conductivity of the prepared GNSs@Ag NPs composite. The established assay demonstrated a wide linear range from 0.001 pg/mL to 10 pg/mL with a correlation coefficient of 0.9958 and low detection limit (DL) of 0.5 fg/mL based on S/N = 3 protocol. The derived biosensor illustrated acceptable selectivity towards common interfering species including HER2, VEGF, IgG, MUC1 and CFP10. In addition, the aptsensor showed good reproducibility and fast response time. The applicability of the suggested strategy in human serum samples was also examined and compared to the commercial enzyme-linked immunosorbent assay (ELISA). Based on the experimental data, it was found that the discussed sensing platform can be exerted in the monitoring of CEA in different cancers for early diagnosis.

Immobilization-free electrochemical homogeneous aptasensor for highly sensitive detection of carcinoembryonic antigen by dual amplification strategy

Electrochemical aptasensor has been widely studied, while its practical application is limited by the unavoidable variations of aptamer loading densities and low signal amplification efficiency. To overcome these restrictions, an immobilization-free and label-free electrochemical homogeneous aptasensor was constructed for carcinoembryonic antigen (CEA) assay by combining RecJ_f exonuclease-mediated target cycling strategy and rolling circle amplification technology. In this system, the pre-immobilization of aptamers or other relevant signal elements on the electrode substrate is no longer necessary, thus the electrochemical homogeneous aptasensor shows good versatility on different transducers. Moreover, the whole recognition and signal amplification process are activated instantaneously by a non-professional operation of the solution mixture. This strategy can not only increase the stability (95.1% after 30 days of storage) and reproducibility (2.12% among five independent electrodes), but also further improve the sensitivity (detection limit of fg mL^-1 level) due to the free target recognition and dual signal amplification in the homogeneous solution phase. The proposed immobilization-free electrochemical homogeneous aptasensors on different electrode substrates both achieve satisfactory results in actual sample tests, which has the potential for commercial applications and the establishment of other target platforms in the future.

A simple, sensitive, label-free electrochemical immunosensor based on the chitosan-coated silver/cerium oxide (CS@Ag/CeO2) nanocomposites for the detection of alpha-fetoprotein (AFP)

Metal oxide-based sensors have the benefit of inexpensive, quick response, and high sensitivity in detecting specific biological species. In this article, a simple electrochemical immunosensor was fabricated using antibody-chitosan coated silver/cerium oxide (Ab-CS@Ag/CeO₂) nanocomposites on a gold electrode for sensitive alpha-fetoprotein (AFP) diagnosis in human serum samples. Successfully synthesis of AFP antibody-CS@Ag/CeO₂conjugates was confirmed through Fourier transform infrared spectra of the prototype. The amine coupling bond chemistry was then used to immobilize the resultant conjugate on a gold electrode surface. It was observed that the interaction of the synthesized Ab-CS@Ag/CeO₂nanocomposites with AFP prevented an electron transfer and reduced the voltammetric Fe(CN)₆^3-/4-peak current, which was proportional to the amount of AFP. The linear ranges of AFP concentration were found from 10^-12-10^-6g.ml^-1. The limit of detection was calculated using the calibration curve and came out to be 0.57 pg.ml^-1. The designed label-free immunosensor successfully detected AFP in human serum samples. As a result, the resulting immunosensor is a promising sensor plate form for AFP detection and could be used in clinical bioanalysis.

Electrochemical Immunosensor Using Electroactive Carbon Nanohorns for Signal Amplification for the Rapid Detection of Carcinoembryonic Antigen

In this work, a novel sandwich-type electrochemical immunosensor was developed for the quantitative detection of the carcinoembryonic antigen, an important tumor marker in clinical tests. The capture antibodies were immobilized on the surface of a gold disk electrode, while detection antibodies were attached to redox-tagged single-walled carbon nanohorns/thionine/AuNPs. Both types of antibody immobilization were carried out through Au-S bonds using the novel photochemical immobilization technique that ensures control over the orientation of the antibodies. The electroactive SWCNH/Thi/AuNPs nanocomposite worked as a signal tag to carry out both the detection of carcinoembryonic antigen and the amplification of the detection signal. The current response was monitored by differential pulse voltammetry. A clear dependence of the thionine redox peak was observed as a function of the carcinoembryonic antigen concentration. A linear detection range from 0.001-200 ng/mL and a low detection limit of 0.1385 pg/mL were obtained for this immunoassay. The results showed that carbon nanohorns represent a promising matrix for signal amplification in sandwich-type electrochemical immune assays working as a conductive and binding matrix with easy and versatile modification routes to antibody and redox tag immobilization, which possesses great potential for clinical diagnostics of CEA and other biomarkers.

Impedimetric aptasensor based on zirconium-cobalt metal-organic framework for detection of carcinoembryonic antigen

A zirconium-cobalt metal-organic framework (ZrCo-MOF) was prepared and used as sensing material to fabricate an aptasensor for trace detection of carcinoembryonic antigen (CEA). The ZrCo-MOF integrates the 3D porous structure and abundant defects of the MOF framework, the catalytic activity and inherent redox behavior of Co, and high stability of Zr-MOF, providing abundant active sites to effectively anchor aptamers. As a result, the ZrCo-MOF-based aptasensor shows high sensitivity to detect CEA via specific recognition between aptamer and CEA, as well as the formation of aptamer-CEA complex. A detection limit of 0.35 fg·mL^-1 was deduced from the electrochemical impedance spectroscopy within a wide linear range of 0.001-100 pg·mL^-1 for CEA, which was substantially lower than those of most reported CEA biosensors. The ZrCo-MOF-based aptasensor also shows good selectivity, reproducibility, regenerability, stability, and applicability for human serum sample. Therefore, the developed ZrCo-MOF-based aptasensor will be promising for ultrasensitive detection of biomarkers and the early diagnosis of cancer. This work presents a novel electrochemical aptasensor for the trace detection of carcinoembryonic antigen (CEA) based on a zirconium-cobalt metal-organic framework (ZrCo-MOF), which shows low detection limit of 0.35 fg·mL^-1, high selectivity as well as good reproducibility, regenerability, stability, and applicability. The result provides a promising approach to detect the cancer biomarkers in an early age.

Applications of Smartphone-Based Aptasensor for Diverse Targets Detection

Aptamers are a particular class of functional recognition ligands with high specificity and affinity to their targets. As the candidate recognition layer of biosensors, aptamers can be used to sense biomolecules. Aptasensors, aptamer-based biosensors, have been demonstrated to be specific, sensitive, and cost-effective. Furthermore, smartphone-based devices have shown their advantages in binding to aptasensors for point-of-care testing (POCT), which offers an immediate or spontaneous responding time for biological testing. This review describes smartphone-based aptasensors to detect various targets such as metal ions, nucleic acids, proteins, and cells. Additionally, the focus is also on aptasensors-related technologies and configurations.

An innovative electrochemical immuno-platform towards ultra-sensitive monitoring of 2-arachidonoyl glycerol in samples from rats with sleep deprivation: bioanalysis of endogenous cannabinoids using biosensor technology

The endocannabinoid system (ECS) is a complex of neurotransmitters in the central nervous system and plays a key role in regulating cognitive and physiological processes. 2-Arachidonoylglycerol (2-AG) is one of the imperative endocannabinoids that play key roles in the central nervous system. It acts as a signaling lipid and activates the cannabinoid CB1 receptor. In addition, 2-AG is involved in a variety of physiological functions such as energy balance, emotion, pain sensation, cognition, and neuroinflammation. So, rapid and specific diagnosis of 2-AG is of great importance in medical neuroscience. The development of new methods in this area has been one of the most important research areas in recent years. Herein, an innovative immunosensor is developed for quantification of 2-AG. For this means, gold nanostars (GNS) were synthesized and conjugated with a specific biotinylated antibody against 2-AG. The resultant bioconjugate, a bioreceptor with GNS, was immobilized on the surface of a gold electrode and used for the detection of the antigen based on the immunocomplex formation followed by analysis using different electrochemical techniques. For the first time, 2-AG protein was measured with an excellent linear range of 0.48–1 ng mL⁻¹ and lower limit of quantification of 0.48 ng L⁻¹ by the electroanalysis method. The engineered immunosensor showed high sensitivity and specificity in the presence of interfering antigens, proving its utility in neurological disorder detection. This immunosensor is the first sandwich type immunoassay for the detection of 2-AG in real samples and the first innovation of designing a novel sandwich type immunosensor for this analyte. Also, excellent analytical results are other advantages of this biosensor for the detection of 2-AG in human plasma samples and serum samples of rats under sleep deprivation. So, this is the first report of an immunosensor of 2-AG using a sandwich type immunosensor.

A novel electrochemical immunosensor based gold nanoparticles for the sensitive recognition of 2-AG was introduced.

An ultrasensitive carcinoembryonic antigen electrochemical aptasensor based on 3D DNA nanoprobe and Exo III

In this study, a highly ordered three dimensional (3D) DNA nanostructure was self-assembled by label-free DNA nanotweezers, which was used as recognized probe to interact with target. Once the target was recognized by the 3D DNA nanoprobe (3D DNT), DNA nanotweezers opened to release target analog (T1). This recognition process was proceeded in homogeneous solution, which can avoid complex electrode modification and improve reaction efficiency. Then these target analogs were captured by the signal DNA probes (E1) modified on the electrode. In the assistance of Exo III, E1 was digested and the T1 was released to participate in the next cycle to realize signal amplification. Finally, an ultrasensitive carcinoembryonic antigen (CEA) electrochemical biosensing with a detection limit of 4.88 fg mL^-1 was developed.

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.

Novel dual-sensitization electrochemiluminescence immunosensor using photopermeable Ru(bpy)3 2+ -doped chitosan/SiO2 nanoparticles as labels and chitosan-decorated Nafion/MWNTs composites as enhancer

A novel dual-sensitization electrochemiluminescence (ECL) immunosensor for the detection of tumour protein prostate specific antigen (PSA) at trace level using Ru(bpy)₃ ²⁺ -doped chitosan/SiO₂ nanoparticles (Ru(bpy)₃ ²⁺ /chitosan/SiO₂ NPs) as the first signal enhancers was fabricated. Due to chitosan with excellent pore forming capacity, these nanoparticles possess porous structures and better photopermeability, and therefore have higher luminescence efficiencies compared with Ru(bpy)₃ ²⁺ /SiO₂ NPs reported in previous publications. Conversely, chitosan with good biocompatibility and high hydrophilicity was electrochemically decorated onto a Nafion/multiwall carbon nanotubes (Nafion/MWNTs) modified electrode surface and used as the second sensitizing matrix to seize large amounts of prostate specific capture antibody (Ab₁ ). The chitosan-decorated Nafion/MWNTs composites exhibited a 5.5-times higher ECL intensity than the unadorned Nafion/MWNTs films. Also, without additional reagents, such as (3-aminopropyl)triethoxysilane (APTS), the one-step functionalized Ru(bpy)₃ ²⁺ /chitosan/SiO₂ NPs provided a large number of active arms to connect with PSA-detected antibodies (Ab₂ ) through the amino groups in chitosan. After a sandwich immunoreaction, the PSA antigen and Ru(bpy)₃ ²⁺ /chitosan/SiO₂ NPs-labelled Ab₂ were sequentially captured onto the Ab₁ /chitosan/Nafion/MWNTs-modified electrode surface. The ECL signal increases were linearly related to the PSA antigen concentrations and ranged from 0.01 pg·mLl^-1 to 10.0 pg·mLl^-1 . Under the optimized experimental conditions, the immunosensor displayed excellent sensitivity and selectivity. The detection limit was as low as 3.4 fg·mLl^-1 , equivalent to, or better than, those of the reported ECL immunosensors for PSA.

4-Nitrophenol-Loaded Magnetic Mesoporous Silica Hybrid Materials for Spectrometric Aptasensing of Carcinoembryonic Antigen

Aptamer- or antibody-based sensing protocols have been reported for detecting carcinoembryonic antigen (CEA), but most exhibit complicated procedures or multiple reactions. In this work, we developed a one-step aptasensing protocol for the spectrometric determination of CEA based on 4-nitrophenol (4-NP)-loaded magnetic mesoporous silica nanohybrids (MMSNs) for bioresponsive controlled-release applications. To fabricate such a responsive–controlled sensing system, single-stranded complementary oligonucleotides relative to the CEA-specific aptamer were first modified on the aminated MMSN. Thereafter, 4-NP molecules blocked the pores with the assistance of the aptamers via a hybridization reaction. The introduced target CEA specifically reacted with the hybridized aptamer, thus detaching from the MMSN to open the gate. The loaded 4-NP molecules were released from the pores, as determined using ultraviolet–visible (UV–vis) absorption spectroscopy after magnetic separation. Under optimum conditions, the absorbance increased with an increase in the target CEA in the sample and exhibited a good linear relationship within the dynamic range of 0.1–100 ng mL⁻¹, with a detection limit of 46 pg mL⁻¹. Moreover, this system also displayed high specificity, good reproducibility, and acceptable accuracy for analyzing human serum specimens, in comparison with a commercialized human CEA-enzyme-linked immunosorbent assay (ELISA) kit.

Graphene-Assisted Electrochemical Sensor for Detection of Pancreatic Cancer Markers

Pancreatic cancer is a highly lethal gastrointestinal malignancy. Most patients are already in the middle to advanced stages of pancreatic cancer at the time of diagnosis and cannot be treated completely. As a single-atom planar two-dimensional crystal, graphene's unusual electronic structure, specific electronic properties and excellent electron transport capacity make it uniquely advantageous in the field of electrochemical sensing. In this mini-review, we summarize the potential application of graphene in pancreatic cancer detection. K-Ras gene, CEA and MicroRNA are important in the early diagnosis of pancreatic cancer.

Environmental risk of nanomaterials and nanoparticles and EPR technique as an effective tool to study them-a review

Nanotechnologies and different types of nanomaterials belong in present day to intensively studied materials due to their unique properties and diverse potential applications in, e.g., electronics, medicine, or display technologies. Together with the investigation of their desired beneficial properties, a need to investigate and evaluate their influence on the environment and possible harmful effects towards living organisms is growing. This review summarizes possible toxic effects of nanomaterials on environment and living organisms, focusing on the possible bioaccumulation in organisms, toxicity, and its mechanisms. The main goal of this review is to refer to potential environmental risks rising from the use of nanomaterials and the necessity to deal with the possible toxic effects considering the growing interest in the wide-scale utilization of these materials. Electron paramagnetic resonance spectroscopy as the only analytical technique capable of detecting radical species enables detection, quantification, and monitoring of the generation of short-lived radicals often coupled with toxic effects of nanomaterials, which makes it an important method in the process of nanotoxicity mechanism determination.

Chemical binding of molecular-imprinted polymer to biotinilated antibody: Utilization of molecular imprinting polymer as intelligent synthetic biomaterials toward recognition of carcinoma embryonic antigen in human plasma sample

In this study, a novel biosensor based on molecular imprinting polymer (MIP) methodology was fabricated toward recognition of carcinoembryonic antigen (CEA). For this purpose, poly (toluidine blue) (PTB) was electropolymerized on the surface of gold electrode in the absence and presence of CEA. So, the target molecules were entrapped into the imprinted specific cavities of MIP. Obtained results show that, the binding affinity of the MIP system was significantly higher than that of revealed for the nonimprinted polymer (NIP) system, MIP-based biosensor revealed linear response from (0.005 to 75 μg/L) and low limit of quantification of (0.005 μg/L) by using chronoamperometry technique, leading to CEA monitoring in real and clinical samples. Thus, a novel technique for rapid, simple, sensitive and affordable monitoring of CEA (LLOQ = 0.005 μg/L) has provided through developed biosensor. From a future perspective, moreover, this method can be considered as an applicable candidate in biomedical and clinical analysis for point-of-care usages.

Novel fluorescent biosensor for carcinoembryonic antigen determination via atom transfer radical polymerization with a macroinitiator

A novel fluorescence method for CEA via β-CD and BIBB-initiated atom transfer radical polymerization (ATRP) was reported.

GPI-AP: Unraveling a New Class of Malignancy Mediators and Potential Immunotherapy Targets

With millions of cases diagnosed annually and high economic burden to cover expensive costs, cancer is one of the most difficult diseases to treat due to late diagnosis and severe adverse effects from conventional therapy. This creates an urgent need to find new targets for early diagnosis and therapy. Progress in research revealed the key steps of carcinogenesis. They are called cancer hallmarks. Zooming in, cancer hallmarks are characterized by ligands binding to their cognate receptor and so triggering signaling cascade within cell to make response for stimulus. Accordingly, understanding membrane topology is vital. In this review, we shall discuss one type of transmembrane proteins: Glycosylphosphatidylinositol-Anchored Proteins (GPI-APs), with specific emphasis on those involved in tumor cells by evading immune surveillance and future applications for diagnosis and immune targeted therapy.

Boronate ester bond-based potentiometric aptasensor for screening carcinoembryonic antigen-glycoprotein using nanometer-sized CaCO3 with ion-selective electrode

Phenylboronic acid-functionalized nanometer-sized CaCO₃ particles (PBA-CaCO₃) were designed to determine the carcinoembryonic antigen (CEA) glycoprotein with a portable Ca²⁺ ion-selective electrode (Ca-ISE) through a typical boronate ester bond. CaCO₃ nanospheres were conjugated to 3-aminophenylboronic acid by amine-epoxy reaction, whereas target CEA was captured into the aptasensing interface by the immobilized thiolated aptamer on gold substrate. Upon PBA-CaCO₃ introduction, 3-aminophenylboronic acid labeled to CaCO₃ microsphere specifically recognized with CEA glycoprotein based on sugar-boronic acid interaction to form a sandwiched complex. The carried CaCO₃ was dissolved under acidic conditions to release Ca²⁺ ion with a portable Ca-ISE readout. Thanks to the specific boronate ester bond between PBA and 1,2-diols, the synthesized PBA-CaCO₃ exhibited good conjugation properties for CEA glycoprotein. Under optimum conditions, Ca-ISE-based aptasensing platform exhibited good electrode potential response for evaluation of target CEA, and allowed detection of CEA at a concentration as low as 7.3 pg mL^-1. Importantly, Ca-ISE-based aptasensing system is readily extended to detect other disease-related glycoproteins by controlling the corresponding aptamer.

Biosensors: A novel approach to and recent discovery in detection of cytokines

Cytokines in tissues and physiological fluids can function as potentially suitable biomarkers. Cytokines are involved in stimulating different body responses including inflammatory response to external pathogens, regulating cell-to-cell communication, and maintaining tissue homeostasis. Consequently, cytokines are extensively used to monitor and predict disease progression and to track the outcome of patient treatment. The critical diagnosis of cytokine and chemokine biomarkers has been the focus of attention and it has been continuously directing the trajectory of related research to developing a novel sensing platform. Given the major challenges and constraints of the older identification methods including their high costs, low sensitivity, and high specificity, the development of biosensor technology as a simple and inexpensive tool with high sensitivity is quite attractive and interesting. The fundamental aim of this study is to present the state-of-the-art biosensor systems in order to detect different types of cytokines and to emphasize the role of these systems in the prevention, monitoring, and treatment of various cytokine-associated diseases.

Recent Trends in Electrochemical Sensors for Vital Biomedical Markers Using Hybrid Nanostructured Materials

This work provides a succinct insight into the recent developments in electrochemical quantification of vital biomedical markers using hybrid metallic composite nanostructures. After a brief introduction to the biomarkers, five types of crucial biomarkers, which require timely and periodical monitoring, are shortlisted, namely, cancer, cardiac, inflammatory, diabetic and renal biomarkers. This review emphasizes the usage and advantages of hybrid nanostructured materials as the recognition matrices toward the detection of vital biomarkers. Different transduction methods (fluorescence, electrophoresis, chemiluminescence, electrochemiluminescence, surface plasmon resonance, surface-enhanced Raman spectroscopy) reported for the biomarkers are discussed comprehensively to present an overview of the current research works. Recent advancements in the electrochemical (amperometric, voltammetric, and impedimetric) sensor systems constructed with metal nanoparticle-derived hybrid composite nanostructures toward the selective detection of chosen vital biomarkers are specifically analyzed. It describes the challenges involved and the strategies reported for the development of selective, sensitive, and disposable electrochemical biosensors with the details of fabrication, functionalization, and applications of hybrid metallic composite nanostructures.

Detection of carcinoembryonic antigen using a magnetoelastic nano-biosensor amplified with DNA-templated silver nanoclusters

Here we develop a magnetoelastic (ME) nano-biosensor based on the competitive strategy for the detection of a carcinoembryonic antigen (CEA). Specifically, the gold-coated ME material provided a platform and the thiolated single-stranded DNA (HS-DNA) containing a half-complementary sequence towards the CEA aptamer was modified on the surface via Au-S bonding. DNA-templated silver nanoclusters (DNA-AgNCs) containing another half-complementary sequence towards the aptamer were used to amplify the signals by about 2.1 times, compared to those obtained using just the aptamer. CEA aptamers as a bio-recognition element were employed to link HS-DNA and DNA-AgNCs through DNA hybridization. The CEA aptamer preferentially combined with CEA rather than hybridized with DNA. Due to the magnetostrictive nature of the ME materials, the resonant frequency of the nano-biosensor would increase along with the release of DNA-AgNCs and CEA aptamers. The modification process was demonstrated by UV-vis spectra, x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, transmission electron microscope (TEM) and an atomic force microscope (AFM). The nano-biosensor has a linear response to the logarithmic CEA concentrations ranging from 2 pg ml^-1 to 6.25 ng ml^-1, with a limit of detection (LOD) of 1 pg ml^-1 and a sensitivity of 105.05 Hz/ng · ml^-1. This study provides a low-cost, highly sensitive and wireless method for selective detection of CEA.

Sandwich-type electrochemical immunosensor constructed using three-dimensional lamellar stacked CoS2@C hollow nanotubes prepared by template-free method to detect carcinoembryonic antigen

Effective treatment of cancer depends on early detection of tumor markers. In this paper, an effective template-free method was used to prepare CoS₂@C three-dimensional hollow sheet nanotubes as the matrix of the immunosensor. The unique three-dimensional hybrid hollow tubular nanostructure provides greater contact area and enhanced detection limit. The CoS₂@C-NH₂-HRP nanomaterial was synthesized as a marker and had a high specific surface area, which can effectively improve the electrocatalytic ability of hydrogen peroxide (H₂O₂) reduction while increasing the amount of capture-fixed carcinoembryonic antigen antibody (anti-CEA). In addition, the co-bonded horseradish peroxidase (HRP) can further promote the redox of H₂O₂ and amplify the electrical signal. Carcinoembryonic antigen (CEA) was quantified by immediate current response (i-t), and the prepared immunosensor had good analytical performance under optimized conditions. The current signal and the concentration of CEA were linear in the range of 0.001-80 ng/mL, and the detection limit was 0.33 pg/mL (S/N = 3). The designed immunosensor has good selectivity, repeatability and stability, and the detection of human serum samples shows good performance. Furthermore, electrochemical immunosensor has broad application prospects in the clinical diagnosis of CEA.

Paper based immunosensing of ovarian cancer tumor protein CA 125 using novel nano-ink: A new platform for efficient diagnosis of cancer and biomedical analysis using microfluidic paper-based analytical devices (μPAD)

Ovarian cancer is the first and most important cause of malignancy death in women. Mucin 16 or MUC16 protein also known as carcinoma antigen 125 (CA 125) is the most commonly used glycoprotein for early stage diagnosis of ovarian cancer. In this work, a novel paper-based bio-device through hand writing of Ag/RGO (silver nanoparticles/reduced graphene oxide) nano-ink on the flexible paper substrate using pen-on-paper technology was developed. The prepared interface was used to the recognition of CA 125 protein in human biofluid. For this purpose, Ag/rGO nano-ink was synthesized by deposition of Ag nanoparticles onto graphene oxide sheets and the reduction of graphene oxide to rGO simultaneously. Conductivity and resistance of conductive lines were studied after drawing on photographic paper. Subsequently, to prepare a new and unique immuno-device, paper electrode modified by cysteamine caped gold nanoparticles (CysA/Au NPs) using electrochemical techniques. CysA is bonded by sulfur atoms with Au (CysA/Au NPs), and from the amine group with hydroxyl and carboxyl groups of Ag/RGO nano-ink deposited on the surface of paper-based electrodes (CysA/Au NPs/Ag-rGO). Then, anti-CA 125 antibody was immobilized on the electrode surface through Au NPs and CA 125 positively charged amine groups interaction. Atomic force microscopy, Transmission electron microscopy, Field emission scanning electron microscopy, and dynamic light scattering, were performed to identify the engineered immunosensor. Using chronoamperometry technique and under the optimized conditions, the low limit of quantitation (LLOQ) for the proposed immunoassay was recorded as 0.78 U/ml, which this evaluation was performed at highly linear range of 0.78-400 U/ml. The high sensitivity of the electrochemical immunosensor device is indicative of the ability of this immuno-device to detect early stages ovarian cancer.

Tailoring the dimensionality of carbon nanostructures as highly electrochemical supports for detection of carcinoembryonic antigens

Partially- and fully-unzipped nitrogen-doped carbon nanotubes (NCNTs) were prepared by unzipping pristine NCNTs and three carbon nanostructures were applied to support Au nanoparticles (AuNPs) to form nanocomposites (Au/NCNTs, Au/PU-NCNTs, and Au/FU-NCNTs). The electrochemical behavior and the electrocatalytic activities of the nanocomposite-modified electrodes were examined. The oxygen functional groups, doped N content, and AuNP loaded concentrations are dependent on the unzipping-degree and then affect the electrochemical response and electrocatalytic performance of the electrodes. Besides, the three nanocomposites were also used for the immobilization of carcinoembryonic antigen (CEA) aptamer strands and applied for the detection of CEA. The Au/FU-NCNTs possess the optimal electrocatalytic activity and biosensing performance for the biomolecules and CEA, which is attributed to the maximum loaded AuNPs, the largest specific surface areas and the most active sites. The Au/FU-NCNT-based electrochemical aptasensor exhibits high sensitivity with a low detection limit of 6.84 pg mL-1 within a broad linear range of CEA concentration from 0.01 to 10 ng mL-1. All of these results indicate that the Au/FU-NCNTs may be a potential support for construction of aptasensors with high electrochemical effect and can be employed in the fields of biosensing or biomedical diagnosis.

A chemiresistive thin-film translating biological recognition into electrical signals: an innovative signaling mode for contactless biosensing

An innovative signaling mode in which a chemiresistive thin-film electrode monitors the specific gaseous component that results from a biological recognition event to indirectly detect targets in the liquid phase is developed for highly-efficient contactless biosensing. This signaling mode may open a new horizon in designing robust biosensing devices for bioanalysis.

Enhanced immunofluorescence detection of a protein marker using a PAA modified ZnO nanorod array-based microfluidic device

Zinc oxide (ZnO) often serves as protein microarray substrates owing to its outstanding fluorescence enhancement effect. However, the integration of functional substrates with microfluidic technology to detect cancer biomarkers still needs to be optimized and promoted, for example, the optimization of micro/nanostructure and hydrophilic modification strategies for fluorescence immunoassays. Here, ZnO nanorod arrays were constructed on the inner wall of glass capillaries through a microfluidic chemical method, and the electrostatic layer by layer self-assembly was applied to modify the nanorod array with hydrophilic polyelectrolyte-polyacrylic acid (PAA). The effects of the flow rate and the reagent concentration on the morphology of the ZnO nanorod array were investigated. The ZnO nanorod array-based glass capillary, prepared at 25 μL min-1 for 4 min with 50 mM Zn2+ in solution, showed a remarkable enhancement in fluorescence performance. In addition, the introduction of PAA suppressed the interference of nonspecific protein and improved the antibody loading capacity effectively. In the detection of carcinoembryonic antigen, the limit of detection reached 100 fg mL-1, which indicated that the ZnO@PAA nanorod array-based microfluidic device exhibits remarkable fluorescence detection performance towards protein markers and possesses potential to be applied to point-of-care diagnostics and high throughput cancer biomarker detection.

Ultrasensitive immunoassay of carcinoma antigen 125 in untreated human plasma samples using gold nanoparticles with flower like morphology: A new platform in early stage diagnosis of ovarian cancer and efficient management

Ovarian cancer, as one of the most life-threatening malignancies among women worldwide, is usually diagnosed at the late stage despite up regulation of molecular markers such as carcinoma antigen 125 (CA 125) at the early stages of the malignancy. CA 125 is the only tumor marker recommended for clinical use in the diagnosis and management of ovarian cancer. The potential role of CA-125 for the early detection of ovarian cancer is controversial and has not yet been adopted for widespread screening efforts in asymptomatic women. Therefore, early detection of CA 125 in human biofluids is highly demanded. In the present study, a novel method was proposed for the fabrication of electrochemical immunosensor based reduced graphene oxide (RGO). Cysteamine capped gold nanoparticle (Cys-AuNPs) were deposited over the surface of ERGO probe using electrophoretic deposition method. These Cys-AuNPs/ERGO probes provide the favorable sites to attach the monoclonal antibody specific to CA 125 antigen. Cyclic voltammetry (CV), and square wave voltammetry (SWV) were applied for the electrochemical recognition of the biolayer. The represented signals demonstrates excellent figure of merits and good capability of the engineered immunosensor towards sensitive detection of CA 125. Quantitative measurements of CA 125 in human plasma samples have been demonstrated, showing the potential of the practical application of this novel immunosensor for the analysis of this biomarker in blood serum samples. This immunosensor has the ability of direct electron transfer as compared to earlier reported electrochemical immunosensors based electrochemical methods. Further, this immunosensor provides a very suitable and convenient alternative to replace the expensive commercially available methods such as immunohistochemistry. The following regression equation between the electrochemical current response and the CA 125 concentration range from 0.1 to 400 U/mL was found. The low limit of quantification for this immunosensor was 0.1 U/mL. To the best of our knowledge, this is the first reported on the direct immobilization of antibody on the surface of Cys-AuNPs/ERGO for fabrication of immunosensors.