A nanoporous gold-based electrochemical aptasensor for sensitive detection of cocaine

Aptasensors: employing molecular probes for precise medical diagnostics and drug monitoring

Accurate detection and monitoring of therapeutic drug levels are vital for effective patient care and treatment management. Aptamers, composed of single-stranded DNA or RNA molecules, are integral components of biosensors designed for both qualitative and quantitative detection of biological samples. Aptasensors play crucial roles in target identification, validation, detection of drug-target interactions and screening potential of drug candidates. This review focuses on the pivotal role of aptasensors in early disease detection, particularly in identifying biomarkers associated with various diseases such as cancer, infectious diseases and cardiovascular disorders. Aptasensors have demonstrated exceptional potential in enhancing disease diagnostics and monitoring therapeutic drug levels. Aptamer-based biosensors represent a transformative technology in the field of healthcare, enabling precise diagnostics, drug monitoring and disease detection.

A fluorescent aptasensor for quantification of cocaine mediated by signal amplification characteristics of UiO-66/AuNPs nanocomposite

Due to the detrimental effects of cocaine on the human body such as organ damage, paranoia, immunodeficiency, cardiovascular disease, blood pressure, and stress, it is highly required to develop sensing approaches for its rapid and facile determination. Based on the signal enhancement capability of the UiO-66/AuNPs nanocomposite and acting as a capture agent, we designed a cost-effective fluorescent aptasensor for cocaine detection. The cocaine presence in the sample would cause a considerable escalation in the quenching of the fluorescence signal. The aptasensor achieved the linear response range over 0.5 μM-20 μM with a low detection limit of 0.178 μM. The selectivity of the designed aptasensing assay was successfully confirmed by examining several analgesic drugs. The aptasensor was employed for cocaine determination in human serum as the real samples. This method has a substantial benefit the for development of a low-cost and facile tool in medicine and forensic science.

Real-Time Intracellular Analysis of Kanamycin Using Microaptasensors

With the emergence of multidrug-resistant bacteria, infection-related death toll is on the rise. Overuse of antibiotics and their leakage into waterways have transformed the environment into a sink, resulting in bacterial resistance permeating through all tiers of the food cycle. As one of the primary sources of food, fish and fish products such as fish eggs must be studied for their ability to accumulate relevant antibiotics. While the accumulation of these pharmaceuticals has previously been studied, there remains a need to analyze these processes in real time. Electrochemical aptamer-based sensor technology allows for selective, real-time monitoring of small molecules. Herein, we report the first use of miniaturized electrochemical aptamer-based sensors for the analysis of the passive uptake of the aminoglycoside antibiotic, kanamycin, in single salmon eggs. We use pulled platinum microelectrodes and increase the surface area at the electrode tip through dendritic gold deposition. These electrodes showed a 100-fold increase in DNA immobilization on the electrode surface as compared to bare microelectrodes. Additionally, the sensors showed improved stability in complex biological media over an extended period of time when compared to the more widely used macrosensors (r = 1 mm). The sensor range was determined to extend from nanomolar to micromolar concentrations of kanamycin in fish egg lysate and when used in a single salmon egg the μ-aptasensors were able to monitor the passive uptake of kanamycin over time. The accumulation kinetics were simulated using COMSOL Multiphysics software. This research presents the first reported record of passive uptake of a small molecule in a single cell in real-time using electrochemistry.

Use of a nano-porous gold film electrode modified with chitosan / polypyrrole for electrochemical determination of metronidazole in the Presence of Acetaminophen

This study, it was aimed to provide a sensitive, easy and selective method for designing Nano-porous gold film electrode (NPGF) electrode for simultaneous measurement of metronidazole (MT) and acetaminophen (AC). For this purpose, the NPGF electrode surface was modified with chitosan (CS) and poly pyrrole (PPY) by electrochemical method, and then CS and PPY modified NPGF (PPY-CS-NPGF) electrode were used to measure these drugs. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) are employed for the characterization of the attained PPY-CS-NPGF electrode. Using cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS) and chronoamperometry, the electrochemical behavior of MT was investigated with the modified electrode. By differential pulse voltammetry, linear ranges of concentration 0.005-100 μM with linear coefficients of 0.9898 and a detection limit of 0.0009 μM were obtained for MT. Finally, an electrochemical sensor was used to measure MT in a real sample, which yielded acceptable results. PPY-CS-NPGF electrodes have a wide linear range, high selectivity, sensitivity and stability and can be used successfully to determine these drugs.

Nanobiosensors for detection of opioids: A review of latest advancements

Opioids are generally used as analgesics in pain treatment. Like many drugs, they have side effects when overdosing and causeaddiction problems.Illegal drug use and misuse are becoming a major concern for authorities worldwide; thus, it is critical to have precise procedures for detecting them in confiscated samples, biological fluids, and wastewaters. Routine blood and urine tests are insufficient for highly selective determinations and can cause cross-reactivities. For this purpose, nanomaterial-based biosensors are great tools to determine opioid intakes, continuously monitoring the drugs with high sensitivity and selectivity even at very low sample volumes.Nanobiosensors generally comprise a signal transducer nanostructure in which a biological recognition molecule is immobilized onto its surface. Lately, nanobiosensors have been extensively utilized for the molecular detection of opioids. The usage of novel nanomaterials in biosensing has impressed biosensing studies. Nanomaterials with a large surface area have been used to develop nanobiosensors with shorter reaction times and higher sensitivity than conventional biosensors. Colorimetric and fluorescence sensing methods are two kinds of optical sensor systems based on nanomaterials. Noble metal nanoparticles (NPs), such as silver and gold, are the most frequently applied nanomaterials in colorimetric techniques, owing to their unique optical feature of surface plasmon resonance. Despite the progress of an extensive spectrum of nanobiosensors over the last two decades, the future purpose of low-cost, high-throughput, multiplexed clinical diagnostic lab-on-a-chip instruments has yet to be fulfilled. In this review, a concise overview of opioids (such as tramadol and buprenorphine, oxycodone and fentanyl, methadone and morphine) is provided as well as information on their classification, mechanism of action, routine tests, and new opioid sensing technologies based on various NPs. In order to highlight the trend of nanostructure development in biosensor applications for opioids, recent literature examples with the nanomaterial type, target molecules, and limits of detection are discussed.

Nanoarchitectonics for Abused-Drug Biosensors

Rapid, accessible, and highly accurate biosensors for the detection of addictive and abused drugs are needed to reduce the adverse personal and societal impacts of addiction. Modern sensors that utilize next-generation technologies, e.g., nanobiotechnology and nanoarchitectonics, have triggered revolutionary progress in the field as they allow accurate detection and tracking of trace levels of major classes of drugs. This paper reviews advances in the field of biosensors for the detection of commonly abused drugs, both prescribed such as codeine and morphine, and illegal narcotics like cocaine.

Advances in Medical Wearable Biosensors: Design, Fabrication and Materials Strategies in Healthcare Monitoring

In the past decade, wearable biosensors have radically changed our outlook on contemporary medical healthcare monitoring systems. These smart, multiplexed devices allow us to quantify dynamic biological signals in real time through highly sensitive, miniaturized sensing platforms, thereby decentralizing the concept of regular clinical check-ups and diagnosis towards more versatile, remote, and personalized healthcare monitoring. This paradigm shift in healthcare delivery can be attributed to the development of nanomaterials and improvements made to non-invasive biosignal detection systems alongside integrated approaches for multifaceted data acquisition and interpretation. The discovery of new biomarkers and the use of bioaffinity recognition elements like aptamers and peptide arrays combined with the use of newly developed, flexible, and conductive materials that interact with skin surfaces has led to the widespread application of biosensors in the biomedical field. This review focuses on the recent advances made in wearable technology for remote healthcare monitoring. It classifies their development and application in terms of electrochemical, mechanical, and optical modes of transduction and type of material used and discusses the shortcomings accompanying their large-scale fabrication and commercialization. A brief note on the most widely used materials and their improvements in wearable sensor development is outlined along with instructions for the future of medical wearables.

From Small Molecules Toward Whole Cells Detection: Application of Electrochemical Aptasensors in Modern Medical Diagnostics

This paper focuses on the current state of art as well as on future trends in electrochemical aptasensors application in medical diagnostics. The origin of aptamers is presented along with the description of the process known as SELEX. This is followed by the description of the broad spectrum of aptamer-based sensors for the electrochemical detection of various diagnostically relevant analytes, including metal cations, abused drugs, neurotransmitters, cancer, cardiac and coagulation biomarkers, circulating tumor cells, and viruses. We described also possible future perspectives of aptasensors development. This concerns (i) the approaches to lowering the detection limit and improvement of the electrochemical aptasensors selectivity by application of the hybrid aptamer-antibody receptor layers and/or nanomaterials; and (ii) electrochemical aptasensors integration with more advanced microfluidic devices as user-friendly medical instruments for medical diagnostic of the future.

Electrochemical analysis of speedball-like polydrug samples

Increasing global production, trafficking and consumption of drugs of abuse is an emerging threat to people's health and safety. Electrochemical approaches have been proved to be useful for on-site analysis of drugs of abuse. However, less attention has been focused on the analysis of polydrug samples, even though these samples pose severe health concerns, especially when stimulants and depressants are combined, as is the case of speedball, a mixture of cocaine and heroin. In this work, we provide solutions for the selective detection of cocaine (stimulant) in polydrug samples adulterated with heroin and codeine (depressants). The presence of either one of these compounds in cocaine street samples leads to an overlap with the cocaine signal in square-wave voltammetry measurements at unmodified carbon screen-printed electrodes, leading to inconclusive screening results in the field. The provided solutions to this problem consist of two parallel approaches: (i) cathodic pretreatment of the carbon screen-printed electrode surface prior to measurement under both alkaline and neutral conditions and (ii) electropolymerization of orthophenylenediamine on graphene modified carbon screen-printed electrodes prior to measurement under neutral conditions. Both strategies allow simultaneous detection of cocaine and heroin in speedball samples as well as simultaneous detection of cocaine and codeine. Implementing these strategies in portable devices holds great potential for significantly improved accuracy of on-site cocaine screening in polydrug samples.

Recent developments in electrochemical detection of illicit drugs in diverse matrices

Drug abuse is a global problem, requiring an interdisciplinary approach. Discovery, production, trafficking, and consumption of illicit drugs have been constantly growing, leading to heavy consequences for environment, human health, and society in general. Therefore, an urgent need for rapid, sensitive, portable and easy-to-operate detection methods for numerous drugs of interest in diverse matrices, from police samples, biological fluids and hair to sewage water has risen. Electrochemical sensors are promising alternatives to chromatography and spectrometry. Last decades, electrochemical sensing of illegal drugs has experienced a very significant growth, driven by improved transducers and signal amplifiers helping to improve the sensitivity and selectivity. The present review summarizes recent advances (last 10 years) in electrochemical detection of the most prevailing illicit drugs (such as cocaine, heroin, and (meth)amphetamine), their precursors and derivatives in different matrices. Various electrochemical sensors making use of different transducers with their (dis)advantages were discussed, and their sensitivity and applicability were critically compared. In those cases where natural or synthetic recognition elements were included in the sensing system to increase specificity, selected recognition elements, their immobilization, working conditions, and analytical performance were discussed. Finally, an outlook is presented with suggestions and recommendations for future developments.

Aptasensors for Point-of-Care Detection of Small Molecules

Aptamers, a group of nucleic acids which can specifically bind to a target molecule, have drawn extensive interest over the past few decades. For analytics, aptamers represent a viable alternative to gold-standard antibodies due to their oligonucleic nature combined with advantageous properties, including higher stability in harsh environments and longer shelf-life. Indeed, over the last decade, aptamers have been used in numerous bioanalytical assays and in various point-of-care testing (POCT) platforms. The latter allows for rapid on-site testing and can be performed outside a laboratory by unskilled labor. Aptamer technology for POCT is not limited just to medical diagnostics; it can be used for a range of applications, including environmental monitoring and quality control. In this review, we critically examine the use of aptamers in POCT with an emphasis on their advantages and limitations. We also examine the recent success of aptasensor technology and how these findings pave the way for the analysis of small molecules in POCT and other health-related applications. Finally, the current major limitations of aptamers are discussed, and possible approaches for overcoming these challenges are presented.

Electrochemical aptasensors based on the gold nanostructures

Electrochemical aptasensors as novel diagnostic tools have attracted sufficient research interest in biomedical sciences. In this review, recent leading trends about gold (Au) nanostructures based electrochemical aptasensors have been collected, reviewed, and compared. Here, the considered electrochemical aptasensors were categorized based on the analytes and diagnostic techniques. Pharmaceutical analytes and biomolecules were reviewed in a separate section consisting of a variety of antibiotics, analgesics, and other biomolecules. Various aptasensors have also measured toxins, ions, and hazardous chemicals, and the findings of them have also been reviewed. Many aptasensors have been designed to detect different disease biomarkers that will play an essential role in the future of early diagnosis of diseases. Pathogen microorganisms have been considered as the analyte in several designed electrochemical aptasensors in recent researches, and their results have been reviewed and discussed as another section. Important aspects considered in the review of the mentioned aptasensors were the type of analyte, features of the aptamer as the biorecognition element, type of Au nanostructures, diagnostic technique, diagnostic mechanism, detection range and the limit of detection (LOD). In the last section, an in-depth analysis has been provided based on the crucial features of all included aptasensors.

A Bottom-Up Approach for Developing Aptasensors for Abused Drugs: Biosensors in Forensics

Aptamer-based point-of-care (POC) diagnostics platforms may be of substantial benefit in forensic analysis as they provide rapid, sensitive, user-friendly, and selective analysis tools for detection. Aptasensors have not yet been adapted commercially. However, the significance of the applications of aptasensors in the literature exceeded their potential. Herein, in this review, a bottom-up approach is followed to describe the aptasensor development and application procedure, starting from the synthesis of the corresponding aptamer sequence for the selected analyte to creating a smart surface for the sensitive detection of the molecule of interest. Optical and electrochemical biosensing platforms, which are designed with aptamers as recognition molecules, detecting abused drugs are critically reviewed, and existing and possible applications of different designs are discussed. Several potential disciplines in which aptamer-based biosensing technology can be of greatest value, including forensic drug analysis and biological evidence, are then highlighted to encourage researchers to focus on developing aptasensors in these specific areas.

Amplified oxygen reduction signal at a Pt-Sn-modified TiO2 nanocomposite on an electrochemical aptasensor

In this work, a metallic composite with strong electrocatalytic property was designed by uniformly decorating Pt and Sn nanoparticles on the surface of TiO₂ nanorods (Pt-Sn@TiO₂). A detection scheme was then developed based on a dual signal amplification strategy involving the Pt-Sn@TiO₂ composite and exonuclease assisted target recycling. The Pt-Sn@TiO₂ composite exhibited an enhanced oxygen reduction current owing to the synergistic effect between Pt and Sn, as well as high exposure of Pt (111) crystal face. Initially, a Pt-Sn@TiO₂ modified glassy carbon electrode produced an amplified electrochemical signal for the reduction of dissolved oxygen in the analyte solution. Next, a DNA with a complementary sequence to a streptomycin aptamer (cDNA) was immobilised on the Pt-Sn@TiO₂ modified electrode, followed by the streptomycin aptamer that hybridised with cDNA. The corresponding oxygen reduction current was diminished by 51% attributable to the hindrance from the biomolecules. After a mixture of streptomycin and RecJ_f exonuclease was introduced, both the streptomycin-aptamer complex and the cDNA were cleaved from the electrode, making the Pt-Sn and Pt (111) surface available for oxygen reduction. RecJ_f would also release streptomycin from the streptomycin-aptamer complex, allowing it to complex again with aptamers on the electrode. This has then promoted a cyclic amplification of the oxygen reduction current by 85%, which is quantitatively related to streptomycin. Under optimal conditions, the aptasensor exhibited a linear range of 0.05-1500 nM and a limit of detection of 0.02±0.0045 nM streptomycin. The sensor was then used in the real-life sample detection of streptomycin to demonstrate its potential applications to bioanalysis.