Wax-printed paper-based device for direct electrochemical detection of 3-nitrotyrosine

Simple graphite/PVC ink-designed paper-based electrodes integrated with a 3D-printed electrochemical device for affordable analyses

A simple and cost-effective methodology for manufacturing a portable electroanalytical device is reported. The device is based on a graphite/polyvinyl chloride (PVC) paper-based electrode coupled to a miniaturized 3D-printed electrochemical cell (3DEC). The 3DEC was designed to ensure the reproducibility of the system by delimitating the paper-based graphite electrode (PGE) area. The disposable PGE was fabricated by paint-brushing a conductive ink based on graphite powder and toluene-free PVC glue, onto a kraft paper. Different weight proportions (wt%) of graphite/PVC were evaluated regarding mechanical stability and electrochemical behavior. Cyclic voltammetric (CV) analysis in the presence of the [Fe(CN)6]3-/4- redox probe has shown that as the wt% of graphite in the ink increased from 50 to 90%, a clear decrease in peak potential separation (ΔEp) and increase in current are observed, indicating an improvement in charge transfer kinetics. However, 90 wt% graphite electrodes have shown poor adhesion to the substrate and easy leaching due to the small amount of PVC (binder). Therefore, the best PGE was achieved using 80:20 wt% graphite/PVC ink (PGE8020). Moreover, scanning electron microscopy (SEM) images and energy dispersive spectroscopy (EDS) mapping revealed a rugous and more uniform deposition of the conductive ink containing 80 wt% graphite. As a proof of concept, the graphite/PVC ink-based disposable electrodes were employed for the detection of 3-nitro-L-tyrosine (3-NLT) in synthetic urine samples, showing a detection limit of 2.85 μmol L-1, and %recovery in synthetic urine between 97 and 109%, highlighting the reliability and applicability of the proposed approach.

Advances in human papillomavirus detection for cervical cancer screening and diagnosis: challenges of conventional methods and opportunities for emergent tools

Human papillomavirus (HPV) infection is the main cause of cervical cancer and other cancers such as anogenital and oropharyngeal cancers. The prevention screening and treatment of cervical cancer has remained one of the top priorities of the World Health Organization (WHO). In 2020, the WHO came up with the 90-70-90 strategy aimed at eliminating cervical cancers as a public health problem by the year 2030. One of the key priorities of this strategy is the recommendation for countries to ensure that 70% of their women are screened using a high-performance test by the age of 35, and again by the age of 45. Over the years, several traditional methods (notably, Pap smear and nucleic acid-based techniques) have been used for the detection of cervical cancer. While these methods have significantly reduced the incidence of cervical cancer and death, they still come short of excellence for the total eradication of HPV infection. The challenges include low sensitivity, low specificity, poor reproducibility, the need for high-level specialists, and the high cost of access to the facilities, to mention a few. Interestingly, however, several efforts are being made today to mitigate these challenges. In this review, we discussed the pros and cons of the traditional screening and testing of HPV infections, the efforts being made to improve their performances, and the emergent tools (especially, the electrochemical methods) that promise to revolutionize the screening and testing of HPV infections. The main aim of the review is to provide some novel clues to researchers that would allow for the development of high-performance, affordable, and triage-suitable electrochemical-based diagnostic tools for HPV and cervical cancer.

Development of a selective electrochemical microsensor based on molecularly imprinted polydopamine/ZIF-67/laser-induced graphene for point-of-care determination of 3-nitrotyrosine

3-nitrotyrosine (3-NT) is a biomarker closely associated with the early diagnosis of oxidative stress-related disorders. The development of an accurate, cost-effective, point-of-care 3-NT sensor holds significant importance for self-monitoring and clinical treatment. In this study, a selective, sensitive, and portable molecularly imprinted electrochemical sensor was developed. ZIF-67 with strong adsorption capacity was facilely modified on an electrochemically active laser-induced graphene (LIG) substrate (formed ZIF-67/LIG). Subsequently, biocompatible dopamine was chosen as the functional monomer, and interference-free ʟ-tyrosine was used as the dummy template to create molecularly imprinted polydopamine (MIPDA) on the ZIF-67/LIG, endowing the sensor with selectivity. The morphologies, electrochemical properties, and detection performance of the sensor were comprehensively investigated using scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry. To achieve the best performance, several parameters were optimized, including the number of polymerization cycles (15), elution time (60 min), incubation time (7 min), and pH of the buffer solution (6). The turnaround time for this sensor is 10 min. Benefiting from the alliance of MIPDA, ZIF-67, and LIG, the sensor exhibited excellent sensitivity with a detection limit of 6.71 nM, and distinguished selectivity against 11 interfering substances. To enable convenient clinical diagnosis, a customized electrochemical microsensor with MIPDA/ZIF-67/LIG was designed, showcasing excellent reliability and convenience in detecting biological samples without pretreatment. The proposed microsensor will not only facilitate clinical diagnosis and improve patient care, but also provide inspiration for the development of other portable and accurate electrochemical biosensors.

Trends in Paper-Based Sensing Devices for Clinical and Environmental Monitoring

Environmental toxic pollutants and pathogens that enter the ecosystem are major global issues. Detection of these toxic chemicals/pollutants and the diagnosis of a disease is a first step in efficiently controlling their contamination and spread, respectively. Various analytical techniques are available to detect and determine toxic chemicals/pathogens, including liquid chromatography, HPLC, mass spectroscopy, and enzyme-linked immunosorbent assays. However, these sensing strategies have some drawbacks such as tedious sample pretreatment and preparation, the requirement for skilled technicians, and dependence on large laboratory-based instruments. Alternatively, biosensors, especially paper-based sensors, could be used extensively and are a cost-effective alternative to conventional laboratory testing. They can improve accessibility to testing to identify chemicals and pollutants, especially in developing countries. Due to its low cost, abundance, easy disposal (by incineration, for example) and biocompatible nature, paper is considered a versatile material for the development of environmentally friendly electrochemical/optical (bio) sensor devices. This review presents an overview of sensing platforms constructed from paper, pointing out the main merits and demerits of paper-based sensing systems, their fabrication techniques, and the different optical/electrochemical detection techniques that they exploit.

Capillary Flow-Driven Microfluidics Combined with a Paper Device for Fast User-Friendly Detection of Heavy Metals in Water

Human exposure to heavy metals is a concerning global problem because of its detrimental effect on our health and ecosystem. Assessing the levels of these metals is cost- and labor-intensive and nonuser friendly because current analysis approaches typically rely on heavy instrumentations like inductively coupled plasma-mass spectrometry, which is only possible in centralized labs. Hence, simple economical detection methods are in high demand in developing countries and areas with insufficient infrastructure, professional experts, and appropriate environmental treatment. Several microfluidic paper-based analytical devices have been reported as promising alternatives to conventional testing methods for on-site heavy metal detection. Paper-based microfluidics are advantageous because of their simple fabrication, biodegradability, low cost, and ability to operate without pumps. However, typical assay times for current platforms are slow, and they typically rely on pipetting a fixed volume into the assay cards. This adds complexity in actual field scenarios. Here, we report a novel, inexpensive, and straightforward capillary-driven microfluidic device combined with paper for rapid and user-friendly detection of Ni(II), Cu(II), and Fe(III) in water. A colorimetric approach was adopted to quantify these metals. The device was able to produce a homogeneous color signal within 8 s of sample insertion. The limit of detection and limit of quantification were calculated to be 2 and 6.67 ppm for nickel, 0.3 and 1 ppm for Cu, and 1.1 and 3.67 ppm for Fe, respectively. The majority (>90%) of the collected samples showed recovery in the 80-110% range with acceptable accuracy and precision (<15% RSD) for a colorimetric device. This technique can be beneficial for rapidly assessing heavy metal exposure in drinking and surface water at drastically reduced assay time and is the first example of capillary flow-driven microfluidic devices as a transport medium for heavy metal detection.

Electrochemical approaches based on micro- and nanomaterials for diagnosing oxidative stress

This review article comprehensively discusses the various electrochemical approaches for measuring and detecting oxidative stress biomarkers and enzymes, particularly reactive oxygen/nitrogen species, highly reactive chemical molecules, which are the byproducts of normal aerobic metabolism and can oxidize cellular components such as DNA, lipids, and proteins. First, we address the latest research on the electrochemical determination of reactive oxygen species generating enzymes, followed by detection of oxidative stress biomarkers, and final determination of total antioxidant activity (endogenous and exogenous). Most electrochemical sensing platforms exploited the unique properties of micro- and nanomaterials such as carbon nanomaterials, metal or metal oxide nanoparticles (NPs), conductive polymers and metal-nano compounds, which have been mainly used for enhancing the electrocatalytic response of sensors/biosensors. The performance of the electroanalytical devices commonly measured by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in terms of detection limit, sensitivity, and linear range of detection is also discussed. This article provides a comprehensive review of electrode fabrication, characterization and evaluation of their performances, which are assisting to design and manufacture an appropriate electrochemical (bio)sensor for medical and clinical applications. The key points such as accessibility, affordability, rapidity, low cost, and high sensitivity of the electrochemical sensing devices are also highlighted for the diagnosis of oxidative stress. Overall, this review brings a timely discussion on past and current approaches for developing electrochemical sensors and biosensors mainly based on micro and nanomaterials for the diagnosis of oxidative stress.

The Road to Unconventional Detections: Paper-Based Microfluidic Chips

Conventional detectors are mostly made up of complicated structures that are hard to use. A paper-based microfluidic chip, however, combines the advantages of being small, efficient, easy to process, and environmentally friendly. The paper-based microfluidic chips for biomedical applications focus on efficiency, accuracy, integration, and innovation. Therefore, continuous progress is observed in the transition from single-channel detection to multi-channel detection and in the shift from qualitative detection to quantitative detection. These developments improved the efficiency and accuracy of single-cell substance detection. Paper-based microfluidic chips can provide insight into a variety of fields, including biomedicine and other related fields. This review looks at how paper-based microfluidic chips are prepared, analyzed, and used to help with both biomedical development and functional integration, ideally at the same time.

Photochemical synthesis of pink silver and its use for monitoring peptide nitration via surface enhanced Raman spectroscopy (SERS)

Oxidative stress may cause extended tyrosine posttranslational modifications of peptides and proteins. The 3-nitro-L-tyrosine (Nit), which is typically formed, affects protein behavior during neurodegenerative processes, such as Alzheimer's and Parkinson's diseases. Such metabolic products may be conveniently detected at very low concentrations by surface enhanced Raman spectroscopy (SERS). Previously, we have explored the SERS detection of the Nit NO₂ bending vibrational bands in a presence of hydrogen chloride (Niederhafner et al., Amino Acids 53:517-532, 2021, ibid). In this article, we describe performance of a new SERS substrate, "pink silver", synthesized photochemically. It provides SERS even without the HCl induction, and the acid further decreases the detection limit about 9 times. Strong SERS bands were observed in the asymmetric (1550-1475 cm^-1) and symmetric (1360-1290 cm^-1) NO stretching in the NO₂ group. The bending vibration was relatively weak, but appeared stronger when HCl was added. The band assignments were supported by density functional theory modeling.

Smart sensor for assessment of oxidative/nitrative stress biomarkers using a dual-imprinted electrochemical paper-based analytical device

We present a novel dual-imprinted electrochemical paper-based analytical device (Di-ePAD) to simultaneously determine 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 3-nitrotyrosine (3-NT) and assess oxidative and nitrative biomarkers in urine and plasma samples. The Di-ePAD was designed with hydrophobic barrier layers formed on filter paper to provide three-dimensional circular reservoirs and assembled electrodes. The molecularly imprinted polymer (MIP) was synthesized using a silica nanosphere decorated with silver nanoparticles (SiO₂@AgNPs) as a core covered with dual-analyte imprinted sites on the polymer to recognize selectively and bind the target biomarkers. This strategy drives monodispersity and enhances the conductivity of the resulting MIP core-shell products. 3-NT-MIP and 8-OHdG-MIP were synthesized by successively coating the surface of SiO₂@AgNPs with l-Cysteine via the thiol group, then terminating with MIP shells. The dual imprinted core-shell composites possess attractive properties for the target biomarkers' sensing, including catalytic activity, selectivity, and good conductivity. The Di-ePAD revealed excellent linear dynamic ranges of 0.01-500 μM for 3-NT and 0.05-500 μM for 8-OHdG, with detection limits of 0.0027 μM for 3-NT and 0.0138 μM for 8-OHdG. This newly developed method based on the synergistic effects of SiO₂@AgNPs combined with promising properties of MIP offers outstanding selectivity, sensitivity, reproducibility, simplicity, and low cost for quantitative analysis of 3-NT and 8-OHdG. The proposed Di-ePAD showed good accuracy and precision when applied to actual samples, including urine and serum samples validated by a conventional HPLC method.

Recent Advances and Applications in Paper-Based Devices for Point-of-Care Testing

Point-of-care testing (POCT), as a portable and user-friendly technology, can obtain accurate test results immediately at the sampling point. Nowadays, microfluidic paper-based analysis devices (μPads) have attracted the eye of the public and accelerated the development of POCT. A variety of detection methods are combined with μPads to realize precise, rapid and sensitive POCT. This article mainly introduced the development of electrochemistry and optical detection methods on μPads for POCT and their applications on disease analysis, environmental monitoring and food control in the past 5 years. Finally, the challenges and future development prospects of μPads for POCT were discussed.

Paper-Based Biosensors for COVID-19: A Review of Innovative Tools for Controlling the Pandemic

The appearance and quick spread of the new severe acute respiratory syndrome coronavirus disease, COVID-19, brought major societal challenges. Importantly, suitable medical diagnosis procedures and smooth clinical management of the disease are an emergent need, which must be anchored on novel diagnostic methods and devices. Novel molecular diagnostic tools relying on nucleic acid amplification testing have emerged globally and are the current gold standard in COVID-19 diagnosis. However, the need for widespread testing methodologies for fast, effective testing in multiple epidemiological scenarios remains a crucial step in the fight against the COVID-19 pandemic. Biosensors have previously shown the potential for cost-effective and accessible diagnostics, finding applications in settings where conventional, laboratorial techniques may not be readily employed. Paper- and cellulose-based biosensors can be particularly relevant in pandemic times, for the renewability, possibility of mass production with sustainable methodologies, and safe environmental disposal. In this review, paper-based devices and platforms targeting SARS-CoV-2 are showcased and discussed, as a means to achieve quick and low-cost PoC diagnosis, including detection methodologies for viral genomic material, viral antigen detection, and serological antibody testing. Devices targeting inflammatory markers relevant for COVID-19 are also discussed, as fast, reliable bedside diagnostic tools for patient treatment and follow-up.

Molecular Imprinting on Nanozymes for Sensing Applications

As part of the biomimetic enzyme field, nanomaterial-based artificial enzymes, or nanozymes, have been recognized as highly stable and low-cost alternatives to their natural counterparts. The discovery of enzyme-like activities in nanomaterials triggered a broad range of designs with various composition, size, and shape. An overview of the properties of nanozymes is given, including some examples of enzyme mimics for multiple biosensing approaches. The limitations of nanozymes regarding lack of selectivity and low catalytic efficiency may be surpassed by their easy surface modification, and it is possible to tune specific properties. From this perspective, molecularly imprinted polymers have been successfully combined with nanozymes as biomimetic receptors conferring selectivity and improving catalytic performance. Compelling works on constructing imprinted polymer layers on nanozymes to achieve enhanced catalytic efficiency and selective recognition, requisites for broad implementation in biosensing devices, are reviewed. Multimodal biomimetic enzyme-like biosensing platforms can offer additional advantages concerning responsiveness to different microenvironments and external stimuli. Ultimately, progress in biomimetic imprinted nanozymes may open new horizons in a wide range of biosensing applications.

Public-Health-Driven Microfluidic Technologies: From Separation to Detection

Separation and detection are ubiquitous in our daily life and they are two of the most important steps toward practical biomedical diagnostics and industrial applications. A deep understanding of working principles and examples of separation and detection enables a plethora of applications from blood test and air/water quality monitoring to food safety and biosecurity; none of which are irrelevant to public health. Microfluidics can separate and detect various particles/aerosols as well as cells/viruses in a cost-effective and easy-to-operate manner. There are a number of papers reviewing microfluidic separation and detection, but to the best of our knowledge, the two topics are normally reviewed separately. In fact, these two themes are closely related with each other from the perspectives of public health: understanding separation or sorting technique will lead to the development of new detection methods, thereby providing new paths to guide the separation routes. Therefore, the purpose of this review paper is two-fold: reporting the latest developments in the application of microfluidics for separation and outlining the emerging research in microfluidic detection. The dominating microfluidics-based passive separation methods and detection methods are discussed, along with the future perspectives and challenges being discussed. Our work inspires novel development of separation and detection methods for the benefits of public health.

Point-of-care diagnostics for infectious diseases: From methods to devices

The current widespread of COVID-19 all over the world, which is caused by SARS-CoV-2 virus, has again emphasized the importance of development of point-of-care (POC) diagnostics for timely prevention and control of the pandemic. Compared with labor- and time-consuming traditional diagnostic methods, POC diagnostics exhibit several advantages such as faster diagnostic speed, better sensitivity and specificity, lower cost, higher efficiency and ability of on-site detection. To achieve POC diagnostics, developing POC detection methods and correlated POC devices is the key and should be given top priority. The fast development of microfluidics, micro electro-mechanical systems (MEMS) technology, nanotechnology and materials science, have benefited the production of a series of portable, miniaturized, low cost and highly integrated POC devices for POC diagnostics of various infectious diseases. In this review, various POC detection methods for the diagnosis of infectious diseases, including electrochemical biosensors, fluorescence biosensors, surface-enhanced Raman scattering (SERS)-based biosensors, colorimetric biosensors, chemiluminiscence biosensors, surface plasmon resonance (SPR)-based biosensors, and magnetic biosensors, were first summarized. Then, recent progresses in the development of POC devices including lab-on-a-chip (LOC) devices, lab-on-a-disc (LOAD) devices, microfluidic paper-based analytical devices (μPADs), lateral flow devices, miniaturized PCR devices, and isothermal nucleic acid amplification (INAA) devices, were systematically discussed. Finally, the challenges and future perspectives for the design and development of POC detection methods and correlated devices were presented. The ultimate goal of this review is to provide new insights and directions for the future development of POC diagnostics for the management of infectious diseases and contribute to the prevention and control of infectious pandemics like COVID-19.

Paper-Based Screen-Printed Electrodes: A New Generation of Low-Cost Electroanalytical Platforms

Screen-printed technology has helped considerably to the development of portable electrochemical sensors since it provides miniaturized but robust and user-friendly electrodes. Moreover, this technology allows to obtain very versatile transducers, not only regarding their design, but also their ease of modification. Therefore, in the last decades, the use of screen-printed electrodes (SPEs) has exponentially increased, with ceramic as the main substrate. However, with the growing interest in the use of cheap and widely available materials as the basis of analytical devices, paper or other low-cost flat materials have become common substrates for SPEs. Thus, in this revision, a comprehensive overview on paper-based SPEs used for analytical proposes is provided. A great variety of designs is reported, together with several examples to illustrate the main applications.

Transduction Mechanisms, Micro-Structuring Techniques, and Applications of Electronic Skin Pressure Sensors: A Review of Recent Advances

Electronic skin (e-skin), which is an electronic surrogate of human skin, aims to recreate the multifunctionality of skin by using sensing units to detect multiple stimuli, while keeping key features of skin such as low thickness, stretchability, flexibility, and conformability. One of the most important stimuli to be detected is pressure due to its relevance in a plethora of applications, from health monitoring to functional prosthesis, robotics, and human-machine-interfaces (HMI). The performance of these e-skin pressure sensors is tailored, typically through micro-structuring techniques (such as photolithography, unconventional molds, incorporation of naturally micro-structured materials, laser engraving, amongst others) to achieve high sensitivities (commonly above 1 kPa⁻¹), which is mostly relevant for health monitoring applications, or to extend the linearity of the behavior over a larger pressure range (from few Pa to 100 kPa), an important feature for functional prosthesis. Hence, this review intends to give a generalized view over the most relevant highlights in the development and micro-structuring of e-skin pressure sensors, while contributing to update the field with the most recent research. A special emphasis is devoted to the most employed pressure transduction mechanisms, namely capacitance, piezoelectricity, piezoresistivity, and triboelectricity, as well as to materials and novel techniques more recently explored to innovate the field and bring it a step closer to general adoption by society.

Screen-Printed Electrodes: Promising Paper and Wearable Transducers for (Bio)Sensing

Screen-printing technology has revolutionized many fields, including that of electrochemical biosensing. Due to their current relevance, this review, unlike other papers, discusses the relevant aspects of electrochemical biosensors manufactured using this technology in connection to both paper substrates and wearable formats. The main trends, advances, and opportunities provided by these types of devices, with particular attention to the environmental and biomedical fields, are addressed along with illustrative fundamentals and applications of selected representative approaches from the recent literature. The main challenges and future directions to tackle in this research area are also pointed out.

Electrochemistry at Bimetallic Pd/Au Thin Film Surfaces for Selective Detection of Reactive Oxygen Species and Reactive Nitrogen Species

In this work, we designed and fabricated Pd/Au bimetallic thin film electrodes with isolated Pd nanoparticles via underpotential deposition of copper on a gold substrate followed by in situ redox replace reaction in a Pd salt solution. The Pd/Au electrode was characterized by AFM and XPS as well as multiple electrochemical techniques including CV and electrochemical quartz crystal microbalance (EQCM) in sulfuric acid and phosphate buffer electrolytes. Results show that the reduction reactions of the analytes (i.e., H₂O₂ and 3-nitrotyrosine (3-NT)) at the Pd/Au thin film surfaces affect the nature and reactivity of Pd/Au surface electrochemistry including the adsorbed/absorbed hydrogen and/or the premonolayer palladium oxide redox processes at Pd. The EQCM experiment supports the arrangement of small size Pd nanoparticles in the Pd thin film in the presence of gold exhibits unusual properties, acting as a new physicochemical dimension between the electrode and target H₂O₂ and 3-NT molecules. The Pd/Au thin film was demonstrated as an extremely sensitive and selective probe for detection of common ROS and RNS (i.e., H₂O₂ and 3-NT). The integration of two different metallic species, Pd and Au, into a surface structure on nanoscale by exploiting their unique surface electrochemistry establishes an innovative analytical method for highly sensitive and selective detection of H₂O₂ and 3-NT simultaneously. This method has a general scope for detecting a broad range of redox active and nonredox active species simultaneously, which opens up new opportunities to develop new electrocatalytic materials and innovative sensing approaches.

Electrochemical Paper-Based Biosensor Devices for Rapid Detection of Biomarkers

In healthcare, new diagnostic tools that help in the diagnosis, prognosis, and monitoring of diseases rapidly and accurately are in high demand. For in-situ measurement of disease or infection biomarkers, point-of-care devices provide a dramatic speed advantage over conventional techniques, thus aiding clinicians in decision-making. During the last decade, paper-based analytical devices, combining paper substrates and electrochemical detection components, have emerged as important point-of-need diagnostic tools. This review highlights significant works on this topic over the last five years, from 2015 to 2019. The most relevant articles published in 2018 and 2019 are examined in detail, focusing on device fabrication techniques and materials applied to the production of paper fluidic and electrochemical cell architectures as well as on the final device assembly. Two main approaches were identified, that are, on one hand, those ones where the fabrication of the electrochemical cell is done on the paper substrate, where the fluidic structures are also defined, and, on the other hand, the fabrication of those ones where the electrochemical cell and liquid-driving paper component are defined on different substrates and then heterogeneously assembled. The main limitations of the current technologies are outlined and an outlook on the current technology status and future prospects is given.

Electrochemical paper-based devices: sensing approaches and progress toward practical applications

Paper-based sensors offer an affordable yet powerful platform for field and point-of-care (POC) testing due to their self-pumping ability and utility for many different analytical measurements. When combined with electrochemical detection using small and portable electronics, sensitivity and selectivity of the paper devices can be improved over naked eye detection without sacrificing portability. Herein, we review how the field of electrochemical paper-based analytical devices (ePADs) has grown since it was introduced a decade ago. We start by reviewing fabrication methods relevant to ePADs with more focus given to the electrode fabrication, which is fundamental for electrochemical sensing. Multiple sensing approaches applicable to ePADs are then discussed and evaluated to present applicability, advantages and challenges associated with each approach. Recent applications of ePADs in the fields of clinical diagnostics, environmental testing, and food analysis are also presented. Finally, we discuss how the current ePAD technologies have progressed to meet the analytical and practical specifications required for field and/or POC applications, as well as challenges and outlook.

A Review: New Trends in Electrode Systems for Sensitive Drug and Biomolecule Analysis

Drug and biomolecule analysis with high precision, fast response, not expensive, and user-friendly methods have been very important for developing technology and clinical applications. Electrochemical methods are highly capable for assaying the concentration of electroactive drug or biomolecule and supply excellent knowledge concerning its physical and chemical properties such as electron transfer rates, diffusion coefficients, electron transfer number, and oxidation potential. Electrochemical methods have been widely applied because of their accuracy, sensitivity, cheapness, and can applied on-site determinations of various substances. The progress on electronics has allowed developing reliable, more sensitive and less expensive instrumentations, which have significant contribution in the area of drug development, drug and biomolecule analysis. The developing new sensors for electrochemical analysis of these compounds have growing interest in recent years. Screen-printed based electrodes have a great interest in electrochemical analysis of various drugs and biomolecules due to their easy manufacturing procedure of the electrode allow the transfer of electrochemical laboratory experiments for disposable on-site analysis of some compounds. Paper based electrodes are also fabricated by new technology. They can be preferred due to their easy, cheap, portable, disposable, and offering high sensitivity properties for many application field such as environmental monitoring, food quality control, clinical diagnosis, drug, and biomolecules analysis. In this review, the recent electrochemical drug and biomolecule (DNA, RNA, µRNA, Biomarkers, etc.) studies will be presented that involve new trend disposable electrodes.

Carbon quantum dots encapsulated in super small platinum nanocrystals core-shell architecture/nitrogen doped graphene hybrid nanocomposite for electrochemical biosensing of DNA damage biomarker-8-hydroxy-2'-deoxyguanosine

In this work, carbon quantum dots (CQD) encapsulated in super small platinum nanocrystals core-shell architecture/nitrogen doped graphene hybrid nanocomposite (CQD@PDA@PtNCs-NGR) was design synthesized. Without using any capping reagent, stabilizer and surfactant, very small CQD was served as template and anchoring point for the synthesis of Pt NCs with a super small size (2.25 nm) and a uniform distribution. Meanwhile, dopamine (DA) was used as bridging agent, positioning agent and weak reducing agent to make Pt²⁺ grow on the CQD. Combine the high dispersed Pt NCs with high specific surface area and high conductivity of NGR, the CQD@PDA@PtNCs-NGR shows excellent electrocatalytic performance towards the biosensing of DNA damage biomarker- 8-Hydroxy-2'-deoxyguanosine (8-OH-dG). A very low detection limit of 0.45 nM and 0.85 nM (S/N = 3), a wide linear range of 0.013 μM-109.78 μM and a high sensitivity of 7.912 μA μM^-1cm^-2 and 4.190 μA μM^-1cm^-2 were obtained. The fabricated CQD@PDA@PtNCs-NGR realized the detection of 8-OH-dG in human urine practical sample. Furthermore, CQD@PDA@PtNCs-NGR was applied for the determination of 8-OH-dG generated from damaged DNA and damaged guanine (G), respectively. This work effectively combines the electrochemical signal of 8-OH-dG with DNA damage, confirms the mechanism of DNA damage, which might pave a new way to establish the associations between degree of DNA damage and 8-OH-dG.