Ultrasensitive electrochemical immunoassay for melanoma cells using mesoporous polyaniline

Biosensors for melanoma skin cancer diagnostics

Skin cancer is a critical global public health concern, with melanoma being the deadliest variant, correlated to 80% of skin cancer-related deaths and a remarkable propensity to metastasize. Despite notable progress in skin cancer prevention and diagnosis, the limitations of existing methods accentuate the demand for precise diagnostic tools. Biosensors have emerged as valuable clinical tools, enabling rapid and reliable point-of-care (POC) testing of skin cancer. This review offers insights into skin cancer development, highlights essential cutaneous melanoma biomarkers, and assesses the current landscape of biosensing technologies for diagnosis. The comprehensive analysis in this review underscores the transformative potential of biosensors in revolutionizing melanoma skin cancer diagnosis, emphasizing their critical role in advancing patient outcomes and healthcare efficiency. The increasing availability of these approaches supports direct diagnosis and aims to reduce the reliance on biopsies, enhancing POC diagnosis. Recent advancements in biosensors for skin cancer diagnosis hold great promise, with their integration into healthcare expected to enhance early detection accuracy and reliability, thereby mitigating socioeconomic disparities.

A polyaniline functionalized NiFeP nanosheet array-based electrochemical immunosensor using Au/Cu2O nanocubes as a signal amplifier for the detection of SARS-CoV-2 nucleocapsid protein

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which emerged as a novel pathogen in 2019. The virus is responsible for a severe acute respiratory syndrome outbreak, affecting the respiratory system of infected individuals. COVID-19 is a super amplifier of basic diseases, and the disease with basic diseases is often more serious. Controlling the spread of the COVID-19 pandemic relies heavily on the timely and accurate detection of the virus. To resolve the problem, a polyaniline functionalized NiFeP nanosheet array-based electrochemical immunosensor using Au/Cu₂O nanocubes as a signal amplifier is fabricated for the detection of SARS-CoV-2 nucleocapsid protein (SARS-CoV-2 NP). Polyaniline (PANI) functionalized NiFeP nanosheet arrays are synthesized as an ideal sensing platform for the first time. PANI is coated on the surface of NiFeP by electropolymerization to enhance biocompatibility, beneficial for the efficient loading of the capture antibody (Ab₁). Significantly, Au/Cu₂O nanocubes possess excellent peroxidase-like activity and exhibit outstanding catalytic activity for the reduction of H₂O₂. Therefore, Au/Cu₂O nanocubes combine with a labeled antibody (Ab₂) through the Au-N bond to form labeled probes, which can effectively amplify current signals. Under optimal conditions, the immunosensor for the detection of SARS-CoV-2 NP shows a wide linear range of 10 fg mL^-1-20 ng mL^-1 and a low detection limit of 1.12 fg mL^-1 (S/N = 3). It also exhibits desirable selectivity, repeatability, and stability. Meanwhile, the excellent analytical performance in human serum samples confirms the practicality of the PANI functionalized NiFeP nanosheet array-based immunosensor. The electrochemical immunosensor based on the Au/Cu₂O nanocubes as a signal amplifier demonstrates great potential for application in the personalized point-of-care (POC) clinical diagnosis.

Advancements in Nanofiber-Based Electrochemical Biosensors for Diagnostic Applications

Biosensors are analytical tools that can be used as simple, real-time, and effective devices in clinical diagnosis, food analysis, and environmental monitoring. Nanoscale functional materials possess unique properties such as a large surface-to-volume ratio, making them useful for biomedical diagnostic purposes. Nanoengineering has resulted in the increased use of nanoscale functional materials in biosensors. Various types of nanostructures i.e., 0D, 1D, 2D, and 3D, have been intensively employed to enhance biosensor selectivity, limit of detection, sensitivity, and speed of response time to display results. In particular, carbon nanotubes and nanofibers have been extensively employed in electrochemical biosensors, which have become an interdisciplinary frontier between material science and viral disease detection. This review provides an overview of the current research activities in nanofiber-based electrochemical biosensors for diagnostic purposes. The clinical applications of these nanobiosensors are also highlighted, along with a discussion of the future directions for these materials in diagnostics. The aim of this review is to stimulate a broader interest in developing nanofiber-based electrochemical biosensors and improving their applications in disease diagnosis. In this review, we summarize some of the most recent advances achieved in point of care (PoC) electrochemical biosensor applications, focusing on new materials and modifiers enabling biorecognition that have led to improved sensitivity, specificity, stability, and response time.

Biomimetic Nanoscale Materials for Skin Cancer Therapy and Detection

Skin cancer has developed as one of the most common types of cancer in the world, with a significant impact on public health impact and the economy. Nanotechnology methods for cancer treatment are appealing since they allow for the effective transport of medicines and other biologically active substances to specific tissues while minimizing harmful consequences. It is one of the most significant fields of research for treating skin cancer. Various nanomaterials have been employed in skin cancer therapy. The current review will summarize numerous methods of treating and diagnosing skin cancer in the earliest stages. There are numerous skin cancer indicators available for the prompt diagnosis of this type of disease. Traditional approaches to skin cancer diagnosis are explored, as are their shortcomings. Electrochemical and optical biosensors for skin cancer diagnosis and management were also discussed. Finally, various difficulties concerning the cost and ease of use of innovative methods should be addressed and overcome.

Cranberry Proanthocyanidins-PANI Nanocomposite for the Detection of Bacteria Associated with Urinary Tract Infections

Consumption of cranberries is associated with the putative effects of preventing urinary tract infections (UTIs). Cranberry proanthocyanidins (PAC) contain unusual double A-type linkages, which are associated with strong interactions with surface virulence factors found on UTI-causing bacteria such as extra-intestinal pathogenic Escherichia coli (ExPEC), depicting in bacterial agglutination processes. In this work, we demonstrated the efficacy of cranberry PAC (200 μg/mL) to agglutinate ExPEC (5.0 × 108 CFU/mL) in vitro as a selective interaction for the design of functionalized biosensors for potential detection of UTIs. We fabricated functionalized screen-printed electrodes (SPEs) by modifying with PAC-polyaniline (PANI) nanocomposites and tested the effectiveness of the PAC-PANI/SPE biosensor for detecting the presence of ExPEC in aqueous suspensions. Results indicated that the PAC-PANI/SPE was highly sensitive (limit of quantification of 1 CFU/mL of ExPEC), and its response was linear over the concentration range of 1-70,000 CFU/mL, suggesting cranberry PAC-functionalized biosensors are an innovative alternative for the detection and diagnosis of ExPEC-associated UTIs. The biosensor was also highly selective, reproducible, and stable.

Electrochemical sensing technology for liquid biopsy of circulating tumor cells-a review

In recent years, a lot of new detection techniques for circulating tumor cells (CTCs) have been developed. Among them, electrochemical sensing technology has gradually developed because of its advantages of good selectivity, high sensitivity, low cost and rapid detection. Especially in the latest decade, the field of electrochemical biosensing has witnessed great progress, thanks to the merging of biosensing research area with nanotechnology, immunotechnology, nucleic acid technology, and microfluidic technology. In this review, the recent progress for the detection of CTCs according to the principle of detection was summarized and how they can contribute to the enhanced performance of such biosensors was explained. The latest electrode construction strategies such as rolling circle amplification reaction, DNA walker and microfluidic technology and their advantages were also introduced emphatically. Moreover, the main reasonswhy the existing biosensors have not been widely used clinically and the next research points were clearly put forward.

Increase of tyrosinase activity at the wound site in zebrafish imaged by a new fluorescent probe

Tyrosinase plays a pivotal role in the hyperpigmentation of wounds. Here, we develop a new fluorescent probe and with it, we reveal an increase of tyrosinase activity at the wound site in zebrafish.

Novel Cells-Based Electrochemical Sensor for Investigating the Interactions of Cancer Cells with Molecules and Screening Multitarget Anticancer Drugs

A novel, effective, and label-free electrochemical sensor was constructed for investigating the interactions between cancer cells and molecules, based on targeted cancer cells immobilized on a bilayer architecture of N-doped graphene-Pt nanoparticles-chitosan (NGR-Pt-CS) and polyaniline (PANI). The interactions between folic acid (FA, positive control) and dimethyl sulfoxide (DMSO, negative control) and the choice of targeted cells, HepG2 and A549 cells, were investigated by measuring the current change of the sensor to [Fe(CN)₆]^3-/4- before and after interactions, and the binding constants were calculated to be 1.37 × 10⁵ and 1.92 × 10⁵ M^-1 by sensing kinetics. Furthermore, 18 main components from Aidi injection (ADI) were studied to screen compounds that have interactions with different targeted cancer cells including HepG2 and A549 cells. The potential target groups of the interactions between screened active compounds and targeted cancer cells were analyzed through computer-aided molecular docking. In this sensing system, molecules did not require electrochemical activity, and different targeted cancer cells could be immobilized on the modified electrode surface, truly reflecting the categories and numbers of targets. Additionally, the proposed sensor specifically circumvented the current paradigm in most cells-based electrochemical sensors for screening drugs, in which the changes in cell behavior induced by drugs are monitored. This study provided a novel, simple, and generally applicable method for exploring the interaction of molecules with cancer cells and screening multitarget drugs.

Ultrathin quasi-hexagonal gold nanostructures for sensing arsenic in tap water

Monodispersed colloidal gold nanoparticles (AuNPs) were synthesized by an easy, cost-effective, and eco-friendly method. The AuNPs were mostly quasi-hexagonal in shape with sizes ranging from 15 to 18 nm. A screen-printed electrode modified with AuNPs (AuNPs/SPE) was used as an electrochemical sensor for the detection of As(iii) in water samples. The mechanistic details for the detection of As(iii) were investigated and an electrochemical reaction mechanism was proposed. Under the optimal experimental conditions, the sensor was highly sensitive to As(iii), with a limit of detection of 0.11 μg L⁻¹ (1.51 nM), which is well below the regulatory limit of 10 μg L⁻¹ established by the United States Environmental Protection Agency and the World Health Organization. The sensor responses were highly stable, reproducible, and linear over the As(iii) concentration range of 0.075 to 30 μg L⁻¹. The presence of co-existing heavy metal cations such as lead, copper, and mercury did not interfere with the sensor response to As(iii). Furthermore, the voltammogram peaks for As(iii), lead, copper, and mercury were sufficiently separate for their potential simultaneous measurement, and at very harsh acidic pH it may be possible to detect As(v). The AuNPs/SPE could detect As(iii) in tap water samples at near-neutral pH, presenting potential possibilities for real-time, practical applications.

Monodispersed colloidal gold nanoparticles (AuNPs) were synthesized by an easy, cost-effective, and eco-friendly method for electrochemical detection of As(iii).

Sensitive electrochemical sensing platform for selective determination of dopamine based on amorphous cobalt hydroxide/polyaniline nanofibers composites

In this study, amorphous cobalt hydroxide/polyaniline nanofibers (Co(OH)₂/PANINF) composites were successfully prepared. The formation of amorphous Co(OH)₂ with irregular surface structure was confirmed by x-ray diffraction, scanning electron microscopy, and selected-area electron diffraction. The non-enzymatic electrochemical sensor for the selective and sensitive determination of dopamine (DA) has been constructed by using Co(OH)₂/PANINF composites modified glassy carbon electrode (Co(OH)₂/PANINF/GCE), which exhibited excellent electrocatalytic activity toward DA, in a large part owing to the advantages of large surface area of amorphous Co(OH)₂ and the synergetic effect between Co(OH)₂ and PANINF. The electrochemical kinetics reveal that the DA oxidation involves two electrons and two protons in a quasi-reversible electrode reaction. Differential pulse voltammetry (DPV) studies show remarkable sensing performance for the determination of DA, with a low detection limit of 0.03 μM, and a wide linear range from 0.1 to 200 μM. From a broader perspective, the present study demonstrates that Co(OH)₂/PANINF composites would be promising supporting materials for novel sensing platforms.

Sensitive and specific detection of tumour cells based on a multivalent DNA nanocreeper and a multiplexed fluorescence supersandwich

A self-assembled DNA nanostructure based on a DNA nanocreeper and multiplexed fluorescence supersandwich was designed for the sensitive and specific detection of tumour cells. This nanostructure could improve the binding affinity of current aptamers and trigger signal amplification, which provide potential for the discrimination of low abundant target cells in liquid biopsy.

Single-molecule biosensors: Recent advances and applications

Single-molecule biosensors serve the unmet need for real time detection of individual biological molecules in the molecular crowd with high specificity and accuracy, uncovering unique properties of individual molecules which are hidden when measured using ensemble averaging methods. Measuring a signal generated by an individual molecule or its interaction with biological partners is not only crucial for early diagnosis of various diseases such as cancer and to follow medical treatments but also offers a great potential for future point-of-care devices and personalized medicine. This review summarizes and discusses recent advances in nanosensors for both in vitro and in vivo detection of biological molecules offering single-molecule sensitivity. In the first part, we focus on label-free platforms, including electrochemical, plasmonic, SERS-based and spectroelectrochemical biosensors. We review fluorescent single-molecule biosensors in the second part, highlighting nanoparticle-amplified assays, digital platforms and the utilization of CRISPR technology. We finally discuss recent advances in the emerging nanosensor technology of important biological species as well as future perspectives of these sensors.

A flow-through microfluidic system for the detection of circulating melanoma cells

We report the fabrication of polyaniline nanofiber (PANI)-modified screen-printed electrode (PANI/SPE) incorporated in a poly-dimethylsiloxane (PDMS) microfluidic channel for the detection of circulating tumor cells. We employed this device to detect melanoma skin cancer cells through specific immunogenic binding of cell surface biomarker melanocortin 1 receptor (MC1R) to anti-MC1R antibody. The antibody-functionalized PANI/SPE was used in batch-continuous flow-through fashion. An aqueous cell suspension of ferri/ferrocyanide at a flow rate of 1.5 mL/min was passed over the immunosensor, which allowed for continuous electrochemical measurements. The sensor performed exceptionally well affording an ultralow limit of quantification of 1 melanoma cell/mL, both in buffer and when mixed with peripheral blood mononuclear cells, and the response was log-linear over the range of 10-9000 melanoma cells/10 mL.

A novel hydrosoluble near-infrared fluorescent probe for specifically monitoring tyrosinase and application in a mouse model

A novel hydrosoluble near-infrared fluorescent probe is applied to imaging and detection of endogenous tyrosinase in living cells, zebrafish and a mouse model.

A new enzyme immunoassay for alpha-fetoprotein in a separate setup coupling an aluminium/Prussian blue-based self-powered electrochromic display with a digital multimeter readout

A new immunoassay was designed for the detection of disease-related biomarkers (alpha-fetoprotein, AFP, as a model), coupling an aluminium (Al)/Prussian blue-based electrochromic display with a digital multimeter readout.