An aptamer folding-based sensory platform decorated with nanoparticles for simple cocaine testing

The LOD paradox: When lower isn't always better in biosensor research and development

Biosensor research has long focused on achieving the lowest possible Limits of Detection (LOD), driving significant advances in sensitivity and opening up new possibilities in analysis. However, this intense focus on low LODs may not always meet the practical needs or suit the actual uses of these devices. While technological improvements are impressive, they can sometimes overlook important factors such as detection range, ease of use, and market readiness, which are vital for biosensors to be effective in real-world applications. This review advocates for a balanced approach to biosensor development, emphasizing the need to align technological advancements with practical utility. We delve into various applications, including the detection of cancer biomarkers, pathology-related biomarkers, and illicit drugs, illustrating the critical role of LOD within these contexts. By considering clinical needs and broader design aspects like cost-effectiveness, sustainability, and regulatory compliance, we argue that integrating technical progress with practicality will enhance the impact of biosensors. Such an approach ensures that biosensors are not only technically sound but also widely useable and beneficial in real-world applications. Addressing the diverse analytical parameters alongside user expectations and market demands will likely maximize the real-world impact of biosensors.

Aptamer-Based Point-of-Care Devices: Emerging Technologies and Integration of Computational Methods

Recent innovations in point-of-care (POC) diagnostic technologies have paved a critical road for the improved application of biomedicine through the deployment of accurate and affordable programs into resource-scarce settings. The utilization of antibodies as a bio-recognition element in POC devices is currently limited due to obstacles associated with cost and production, impeding its widespread adoption. One promising alternative, on the other hand, is aptamer integration, i.e., short sequences of single-stranded DNA and RNA structures. The advantageous properties of these molecules are as follows: small molecular size, amenability to chemical modification, low- or nonimmunogenic characteristics, and their reproducibility within a short generation time. The utilization of these aforementioned features is critical in developing sensitive and portable POC systems. Furthermore, the deficiencies related to past experimental efforts to improve biosensor schematics, including the design of biorecognition elements, can be tackled with the integration of computational tools. These complementary tools enable the prediction of the reliability and functionality of the molecular structure of aptamers. In this review, we have overviewed the usage of aptamers in the development of novel and portable POC devices, in addition to highlighting the insights that simulations and other computational methods can provide into the use of aptamer modeling for POC integration.

Luminescence-based detection and identification of illicit drugs

Luminescence-based sensing is capable of being used for the sensitive, rapid, and in some cases selective detection of chemicals. Furthermore, the method is amenable to incorporation into handheld low-power portable detectors that can be used in the field. Luminescence-based detectors are now commercially available for explosive detection with the technology built on a strong foundation of science. In contrast, there are fewer examples of luminescence-based detection of illicit drugs, despite the pervasive and global challenge of combating their manufacture, distribution and consumption and the need for handheld detection systems. This perspective describes the relatively nascent steps that have been reported in the use of luminescent materials for the detection of illicit drugs. Much of the published work has focused on detection of illicit drugs in solution with less work on vapour detection using thin luminescent sensing films. The latter are better suited for handheld sensing devices and detection in the field. Illicit drug detection has been achieved via different mechanisms, all of which change the luminescence of the sensing material. These include photoinduced hole transfer (PHT) leading to quenching of the luminescence, disruption of Förster energy transfer between different chromophores by a drug, and chemical reaction between the sensing material and a drug. The most promising of these is PHT, which can be used for rapid and reversible detection of illicit drugs in solution and film-based sensing of drugs in the vapour phase. However, there are still significant knowledge gaps, for example, how vapours of illicit drugs interact with the sensing films, and how to achieve selectivity for specific drugs.

AIE-doped Poly(Ionic Liquid) Photonic Spheres for the Discrimination of Psychoactive Substances

Drugs of abuse has drawn intense attention due to increasing concerns to public health and safety. The construction of a sensing platform with the capability to identify them remains a big challenge because of the limitations of synthetic complexity, sensing scope and receptor extendibility. Here a kind of poly(ionic liquid) (PIL) photonic crystal spheres doped with aggregation-induced emission (AIE) luminogens was developed. As diverse noncovalent interactions involve in PIL moieties, the single sphere shows different binding affinity to a broad range of psychoactive substances. Furthermore, the dual-channel signals arising from photonic crystal structures and sensitive AIE-luminogens provide high-dimensional information for discriminative detection of targets, even for molecules with slight structural differences. More importantly, such single sphere sensing platform could be flexibly customized through ion-exchange, showing great extendibility to fabricate high-efficiency/high-throughput sensing arrays without tedious synthesis.

Competitive fluorescence immunoassay for the rapid qualitative screening and accurate quantitative analysis of ketamine

In this paper, a sensitive and specific competitive fluorescence immunoassay (CFIA) method was developed for the qualitative and quantitative analysis of ketamine (KET). A novel competitive model in which ketamine hapten (KET-BSA), coated on microporous plates, competed with ketamine antigen (KET-Ag) in actual samples to bind fluorescein isothiocyanate-labeled antibody (KET-Ab) could be used for rapid and indirect quantitative analysis of KET in human urine, blood, or sewage. In the CFIA method, KET concentration in the sample negatively correlated with the detected fluorescence intensity. The linear correlation coefficient of the competitive quantitative equation was 0.992, the linear range was 0.01-0.5 μg mL^-1, and the limit of detection (LOD) was 0.1 pg mL^-1. The specificity results showed that the cross-reaction rate of norketamine was less than 10%. Recoveries of spiked samples at low, medium, and high concentrations ranged from 96% to 117%. The CFIA method and classical gas chromatography-tandem mass spectrometry (GC-MS/MS) were used to detect the actual samples simultaneously. The relative deviation of the quantitative results was less than 10%. The LOD value of KET by CFIA was four orders of magnitude lower than that by GC-MS/MS. Additionally, CFIA had great advantages over GC-MS/MS in terms of sample pretreatment and economic investment. In conclusion, this study provided a targeting detection platform for KET, which achieved a rapid, portable, and sensitive analysis of trace KET in various materials.

Emerging trends in point-of-care sensors for illicit drugs analysis

Consumption of illicit narcotic drugs and fatal or criminal activities under their influence has become an utmost concern worldwide. These drugs influence an individual's feelings, perceptions, and emotions by altering the state of consciousness and thus can result in serious safety breaches at critical workplaces. Point-of-care drug-testing devices have become the need-of-the-hour for many sections such as the law enforcement agencies, the workplaces, etc. for safety and security. This review focuses on the recent progress on various electrochemical and optical nanosensors developed for the analysis of the most common illicit drugs (or their metabolites) such as tetrahydrocannabinol (THC), cocaine (COC), opioids (OPs), amphetamines & methamphetamine, and benzodiazepine (BZDs). The paper also highlights the sensitivity and selectivity of various sensing modalities along with evolving parameters such as real-time monitoring and measurement via a smart user interface. An overall outlook of recent technological advances in point of care (POC) devices and guided insights and directions for future research is presented.

Visible-light and near-infrared fluorescence and surface-enhanced Raman scattering point-of-care sensing and bio-imaging: a review

This review article deals with the concepts, principles and applications of visible-light and near-infrared (NIR) fluorescence and surface-enhanced Raman scattering (SERS) in in vitro point-of-care testing (POCT) and in vivo bio-imaging. It has discussed how to utilize the biological transparency windows to improve the penetration depth and signal-to-noise ratio, and how to use surface plasmon resonance (SPR) to amplify fluorescence and SERS signals. This article has highlighted some plasmonic fluorescence and SERS probes. It has also reviewed the design strategies of fluorescent and SERS sensors in the detection of metal ions, small molecules, proteins and nucleic acids. Particularly, it has provided perspectives on the integration of fluorescent and SERS sensors into microfluidic chips as lab-on-chips to realize point-of-care testing. It has also discussed the design of active microfluidic devices and non-paper- or paper-based lateral flow assays for in vitro diagnostics. In addition, this article has discussed the strategies to design in vivo NIR fluorescence and SERS bio-imaging platforms for monitoring physiological processes and disease progression in live cells and tissues. Moreover, it has highlighted the applications of POCT and bio-imaging in testing toxins, heavy metals, illicit drugs, cancers, traumatic brain injuries, and infectious diseases such as COVID-19, influenza, HIV and sepsis.

Cocaine Detection by a Laser-Induced Immunofluorometric Biosensor

The trafficking of illegal drugs by criminal networks at borders, harbors, or airports is an increasing issue for public health as these routes ensure the main supply of illegal drugs. The prevention of drug smuggling, including the installation of scanners and other analytical devices to detect small traces of drugs within a reasonable time frame, remains a challenge. The presented immunosensor is based on a monolithic affinity column with a large excess of immobilized hapten, which traps fluorescently labeled antibodies as long as the analyte cocaine is absent. In the presence of the drug, some binding sites of the antibody will be blocked, which leads to an immediate breakthrough of the labeled protein, detectable by highly sensitive laser-induced fluorescence with the help of a Peltier-cooled complementary metal-oxide-semiconductor (CMOS) camera. Liquid handling is performed with high-precision syringe pumps and microfluidic chip-based mixing devices and flow cells. The biosensor achieved limits of detection of 7 ppt (23 pM) of cocaine with a response time of 90 s and a total assay time below 3 min. With surface wipe sampling, the biosensor was able to detect 300 pg of cocaine. This immunosensor belongs to the most sensitive and fastest detectors for cocaine and offers near-continuous analyte measurement.

Monoclonal Antibodies Application in Lateral Flow Immunochromatographic Assays for Drugs of Abuse Detection

Lateral flow assays (lateral flow immunoassays and nucleic acid lateral flow assays) have experienced a great boom in a wide variety of early diagnostic and screening applications. As opposed to conventional examinations (High Performance Liquid Chromatography, Polymerase Chain Reaction, Gas chromatography-Mass Spectrometry, etc.), they obtain the results of a sample's analysis within a short period. In resource-limited areas, these tests must be simple, reliable, and inexpensive. In this review, we outline the production process of antibodies against drugs of abuse (such as heroin, amphetamine, benzodiazepines, cannabis, etc.), used in lateral flow immunoassays as revelation or detection molecules, with a focus on the components, the principles, the formats, and the mechanisms of reaction of these assays. Further, we report the monoclonal antibody advantages over the polyclonal ones used against drugs of abuse. The perspective on aptamer use for lateral flow assay development was also discussed as a possible alternative to antibodies in view of improving the limit of detection, sensitivity, and specificity of lateral flow assays.

Analysis of the role played by ligand-induced folding of the cocaine-binding aptamer in the photochrome aptamer switch assay

The Photochrome Aptamer Switch Assay (PHASA) relies on ligand binding by an aptamer to alter the local environment of a stilbene compound covalently attached to the 5' end of the aptamer. We used the PHASA with both structure switching and non-structure switching versions of the cocaine-binding aptamer. We show that the largest change in fluorescence intensity and the lowest concentration limit of detection (C_Loo_D) is obtained using the structure-switching cocaine-binding aptamer. Fluorescence anisotropy measurements were used to quantify the affinity of the conjugated aptamer to cocaine. We also used thermal melt analysis and Nuclear Magnetic Resonance (NMR) spectroscopy to show that the addition of the stilbene to the aptamer increases the melt temperature of the cocaine-bound structure-switching aptamer by (6.4 ± 0.3) °C compared to the unconjugated aptamer while the free form of the structure-switching aptamer-stilbene conjugate remains unfolded.

Nanomaterial-based aptamer sensors for analysis of illicit drugs and evaluation of drugs consumption for wastewater-based epidemiology

The abuse of illicit drugs usually associated with dramatic crimes may cause significant problems for the whole society. Wastewater-based epidemiology (WBE) has been demonstrated to be a novel and cost-effective way to evaluate the abuse of illicit drugs at the community level, and has been used as a routine method for monitoring and played a significant role for combating the crimes in some countries, e.g. China. The method can also provide temporal and spatial variation of drugs of abuse. The detection methods mainly remain on the conventional liquid chromatography coupled with mass spectrometry, which is extremely sensitive and selective, however needs advanced facility and well-trained personals, thus limit it in the lab. As an alternative, sensors have emerged to be a powerful analytical tool for a wide spectrum of analytes, in particular aptamer sensors (aptasensors) have attracted increasing attention and could act as an efficient tool in this field due to the excellent characteristics of selectivity, sensitivity, low cost, miniaturization, easy-to-use, and automation. In this review, we will briefly introduce the context, specific assessment process and applications of WBE and the recent progress of illicit drug aptasensors, in particular focusing on optical and electrochemical sensors. We then highlight several recent aptasensors for illicit drugs in new technology integration and discuss the feasibility of these aptasensor for WBE. We will summarize the challenges and propose our insights and opportunity on aptasensor for WBE to evaluate community-wide drug use trends and public health.

Ultrasensitive covalently-linked Aptasensor for cocaine detection based on electrolytes-induced repulsion/attraction of colloids

A quick and easy colorimetric sensor based on gold nanoparticles (GNPs) and aptamers for the detection of cocaine was developed. The sensor was named as 'GAPTA' and showed extremely interesting results regarding cocaine detection with a sensitivity to doses of 0.2 nM. The experimental approach consisted of creating a conjugate between GNPs (10 nm size) and aptamers as a sensing base with the addition of an electrolyte (NaCl) that plays the role of aggregation inducer. In the absence of the aptamer, the electrolyte was able to induce aggregation of the GNPs turning the color of the solution from red to blue while the presence of the aptamer is able to hinder the charges attraction and protects the GNPs from aggregating. The optimization of the aptamer and electrolyte concentration was determined to be 118 nM and 55 mM, respectively, and the resultant GAPTA sensor had a detection limit of 0.97 nM. Furthermore, the selectivity of the platform was tested in the presence of different interferents and showed a specific response towards cocaine while interference ranged between 20 and 40%. The applicability of the GAPTA biosensor was tested on synthetic saliva and demonstrated a sensitivity range between 0.2 and 25 nM. These results suggest the potential of the current colorimetric sensor in abuse drugs screening and creates a stable base for new routine platforms for biomedical and toxicology applications. Graphical abstract.

Interpol review of controlled substances 2016-2019

This review paper covers the forensic-relevant literature in controlled substances from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20Papers%202019.pdf.

Molecularly imprinted polymer containing fluorescent graphene quantum dots as a new fluorescent nanosensor for detection of methamphetamine

A novel fluorescent nanosensor based on graphene quantum dots embedded within molecularly imprinted polymer (GQDs@MIP) was developed for detection and determination of methamphetamine (METH). The resulting GQDs@MIP nanocomposite exhibited higher methamphetamine selectivity in comparison with corresponding non-imprinted polymer (GQDs@NIP). Characterization of the GQDs@MIP nanocomposite was done by nitrogen adsorption and desorption analysis (BET method), transmission electron microscopy (TEM), photoluminescence (PL), ultraviolet-visible (UV-Vis), and Fourier transform infrared (FT-IR) spectroscopies. The fluorescence intensity of GQDs@MIP was efficiently quenched in the presence of methamphetamine template molecules while no quenching was observed in the presence of other analytes such as amphetamine, ibuprofen, codeine, and morphine. Using this method, the detection limit of 1.7 μg/L was obtained for methamphetamine determination.

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.

Microfluidic electrochemical immunosensor for the trace analysis of cocaine in water and body fluids

Quick but accurate testing and on-the-spot monitoring of cocaine in oral fluids and urine continues to be an important toxicological issue. In terms of drug testing, a number of devices have been introduced into the market in recent decades, notably for workplace inspection or roadside testing. However, these systems do not always fulfill the requirements in terms of reliability, especially when low cut-off levels are required. With respect to surface water, the presence of anthropogenic small organic molecules such as prescription and over-the-counter pharmaceuticals as well as illicit drugs like cannabinoids, heroin, or cocaine, has become a challenge for scientists to develop new analytical tools for screening and on-site analysis because many of them serve as markers for anthropogenic input and consumer behavior. Here, a modular approach for the detection of cocaine is presented, integrating an electrochemical enzyme-linked immunosorbent assay (ELISA) performed on antibody-grafted magnetic beads in a hybrid microfluidic sensor utilizing flexible tubing, static chip and screen-printed electrode (SPE) elements for incubation, recognition, and cyclic voltammetry measurements. A linear response of the sensor vs. the logarithm of cocaine concentration was obtained with a limit of detection of 0.15 ng/L. Within an overall assay time of 25 minutes, concentrations down to 1 ng/L could be reliably determined in water, oral fluids, and urine, the system possessing a dynamic working range up to 1 mg/L.

Novel technologies in detection, treatment and prevention of substance use disorders

Substance use disorders are a widely recognized problem, which affects various levels of communities and influenced the world socioeconomically. Its source is deeply embedded in the global population. In order to fight against such an adversary, governments have spared no efforts in implementing substance abuse treatment centers and funding research to develop treatments and prevention procedures. In this review, we will discuss the use of immunological-based treatments and detection kit technologies. We will be detailing the steps followed to produce performant antibodies (antigens, carriers, and adjuvants) focusing on cocaine and methamphetamine as examples. Furthermore, part of this review is dedicated to substance use detection. Owing to novel technologies such as bio-functional polymeric surfaces and biosensors manufacturing, detection has become a more convenient method with the fast and on-site developed devices. Commercially available devices are able to test substance use disorders in urine, saliva, hair, and sweat. This improvement has had a tremendous impact on the prevention of driving under influence and other illicit behaviors. Lastly, substance abuse became a major issue involving the cooperation of experts on all levels to devise better treatment programs and prevent abuse-based accidents, injury and death.

Chromogenic and Fluorogenic Probes for the Detection of Illicit Drugs

The consumption of illicit drugs has increased exponentially in recent years and has become a problem that worries both governments and international institutions. The rapid emergence of new compounds, their easy access, the low levels at which these substances are able to produce an effect, and their short time of permanence in the organism make it necessary to develop highly rapid, easy, sensitive, and selective methods for their detection. Currently, the most widely used methods for drug detection are based on techniques that require large measurement times, the use of sophisticated equipment, and qualified personnel. Chromo- and fluorogenic methods are an alternative to those classical procedures.

Development of a thermal-stable structure-switching cocaine-binding aptamer

We have developed a new cocaine-binding aptamer variant that has a significantly higher melt temperature when bound to a ligand than the currently used sequence. Retained in this new construct is the ligand-induced structure-switching binding mechanism that is important in biosensing applications of the cocaine-binding aptamer. Isothermal titration calorimetry methods show that the binding affinity of this new sequence is slightly tighter than the existing cocaine-binding aptamer. The improved thermal performance, a T_m increase of 4 °C for the cocaine-bound aptamer and 9 °C for the quinine-bound aptamer, was achieved by optimizing the DNA sequence in stem 2 of the aptamer to have the highest stability based on the nearest neighbor thermodynamic parameters and confirmed by UV and fluorescence spectroscopy. The sequences in stem 1 and stem 3 were unchanged in order to retain the structure switching and ligand binding functions. The more favorable thermal stability characteristics of the OR3 aptamer should make it a useful construct for sensing applications employing the cocaine-binding aptamer system.

Double fluorescence assay via a β-cyclodextrin containing conjugated polymer as a biomimetic material for cocaine sensing

A double fluorescence based μ-well assay was designed by using a novel biomimetic material (PPP-CD-g-PEG) for cocaine detection.

Synthesis and application of a novel poly-l-phenylalanine electroactive macromonomer as matrix for the biosensing of ‘Abused Drug’ model

The synthesis and biosensing application of a novel poly-l-phenylalanine-bearing electroactive macromonomer has been carried out.