Nanobiosensors for detection of opioids: A review of latest advancements

Portable Near-Infrared to Near-Infrared Platform for Homogeneous Quantification of Biomarkers in Complex Biological Samples

Förster resonance energy transfer (FRET)-based homogeneous immunoassay obviates tedious washing steps and thus is a promising approach for immunoassays. However, a conventional FRET-based homogeneous immunoassay operating in the visible region is not able to overcome the interference of complex biological samples, thus resulting in insufficient detection sensitivity and poor accuracy. Here, we develop a near-infrared (NIR)-to-NIR FRET platform (Ex = 808 nm, Em = 980 nm) that enables background-free high-throughput homogeneous quantification of various biomarkers in complex biological samples. This NIR-to-NIR FRET platform is portable and easy to operate and is mainly composed of a high-performance NIR-to-NIR FRET pair based on lanthanide-doped nanoparticles (LnNPs) and a custom-made microplate reader for readout of NIR luminescence signals. We demonstrate that this NIR-to-NIR FRET platform is versatile and robust, capable of realizing highly sensitive and accurate detection of various critical biomarkers, including small molecules (morphine and 1,25-dihydroxyvitamin D), proteins (human chorionic gonadotropin), and viral particles (adenovirus) in unprocessed complex biological samples (urine, whole blood, and feces) within 5-10 min. We expect this NIR-to-NIR FRET platform to provide low-cost healthcare for populations living in resource-limited areas and be widely used in many other fields, such as food safety and environmental monitoring.

A near-infrared plasmonic biosensor for detection of morphine and codeine in biological samples based on the end-to-end assembly of modified gold nanorods

The analytical determination of opiates in biological samples is a critical mission and remains a challenge for almost all judicial and clinical drug testing panels due to their high abuse potential. Based on the high sensitivity of the longitudinal surface plasmon resonance (LSPR) peak of gold nanorods (AuNRs), we successfully developed a novel and simple refractive index sensing platform for detection of morphine (MOR) and codeine (COD) by means of 2-amino-5-mercapto-1,3,4-thiadiazole functionalized gold nanorods (AMTD-AuNRs) in aqueous solution, which is, to the best of our knowledge, the first report on the assay of MOR and COD using AuNRs. AMTD molecules strongly anchor onto the tips of AuNRs via the mercapto group and subsequent hydrogen-bonding interactions between AMTD and the analytes induced end-to-end chain assembly of AuNRs and a consequent decrease of the LSPR absorption band at 850 nm along with a bathochromic shift and emergence of a new hybridized plasmon mode at 1050 nm which was characterized using a Vis-NIR spectrophotometer. After systematic optimization, the absorbance ratio (A1050/A850) was proportional to the concentration of MOR in the ranges of 0.08-5 μM and 0.2-8 μM for COD without any significant effect from possible interferents. Furthermore, detection limits of 40 and 62 nM were achieved for MOR and COD, respectively, which are much lower than the cut-off level of 2000 ng mL-1 for opiates in urine samples set by the Substance and Abuse Mental Health Services Administration (SAMHSA). Eventually, as proof-of-applicability, human urine and blood serum samples spiked with MOR and COD were analyzed and excellent recoveries ranging from 94.4 to 108.9% were obtained, demonstrating the successful applicability of the designed refractive index probe in real biological specimens.

Functionalized Gold Nanoparticles and Halogen Bonding Interactions Involving Fentanyl and Fentanyl Derivatives

Fentanyl (FTN) and synthetic analogs of FTN continue to ravage populations across the globe, including in the United States where opioids are increasingly being used and abused and are causing a staggering and growing number of overdose deaths each year. This growing pandemic is worsened by the ease with which FTN can be derivatized into numerous derivatives. Understanding the chemical properties/behaviors of the FTN class of compounds is critical for developing effective chemical detection schemes using nanoparticles (NPs) to optimize important chemical interactions. Halogen bonding (XB) is an intermolecular interaction between a polarized halogen atom on a molecule and e--rich sites on another molecule, the latter of which is present at two or more sites on most fentanyl-type structures. Density functional theory (DFT) is used to identify these XB acceptor sites on different FTN derivatives. The high toxicity of these compounds necessitated a "fragmentation" strategy where smaller, non-toxic molecules resembling parts of the opioids acted as mimics of XB acceptor sites present on intact FTN and its derivatives. DFT of the fragments' interactions informed solution measurements of XB using 19F NMR titrations as well as electrochemical measurements of XB at self-assembled monolayer (SAM)-modified electrodes featuring XB donor ligands. Gold NPs, known as monolayer-protected clusters (MPCs), were also functionalized with strong XB donor ligands and assembled into films, and their interactions with FTN "fragments" were studied using voltammetry. Ultimately, spectroscopy and TEM analysis were combined to study whole-molecule FTN interactions with the functionalized MPCs in solution. The results suggested that the strongest XB interaction site on FTN, while common to most of the drug's derivatives, is not strong enough to induce NP-aggregation detection but may be better exploited in sensing schemes involving films.

Machine learning-enhanced drug testing for simultaneous morphine and methadone detection in urinary biofluids

The simultaneous identification of drugs has considerable difficulties due to the intricate interplay of analytes and the interference present in biological matrices. In this study, we introduce an innovative electrochemical sensor that overcomes these hurdles, enabling the precise and simultaneous determination of morphine (MOR), methadone (MET), and uric acid (UA) in urine samples. The sensor harnesses the strategically adapted carbon nanotubes (CNT) modified with graphitic carbon nitride (g-C3N4) nanosheets to ensure exceptional precision and sensitivity for the targeted analytes. Through systematic optimization of pivotal parameters, we attained accurate and quantitative measurements of the analytes within intricate matrices employing the fast Fourier transform (FFT) voltammetry technique. The sensor's performance was validated using 17 training and 12 test solutions, employing the widely acclaimed machine learning method, partial least squares (PLS), for predictive modeling. The root mean square error of cross-validation (RMSECV) values for morphine, methadone, and uric acid were significantly low, measuring 0.1827 µM, 0.1951 µM, and 0.1584 µM, respectively, with corresponding root mean square error of prediction (RMSEP) values of 0.1925 µM, 0.2035 µM, and 0.1659 µM. These results showcased the robust resiliency and reliability of our predictive model. Our sensor's efficacy in real urine samples was demonstrated by the narrow range of relative standard deviation (RSD) values, ranging from 3.71 to 5.26%, and recovery percentages from 96 to 106%. This performance underscores the potential of the sensor for practical and clinical applications, offering precise measurements even in complex and variable biological matrices. The successful integration of g-C3N4-CNT nanocomposites and the robust PLS method has driven the evolution of sophisticated electrochemical sensors, initiating a transformative era in drug analysis.

How new nanotechnologies are changing the opioid analysis scenery? A comparison with classical analytical methods

Opioids such as heroin, fentanyl, raw opium, and morphine have become a serious threat to the world population in the recent past, due to their increasing use and abuse. The detection of these drugs in biological samples is usually carried out by spectroscopic and/or chromatographic techniques, but the need for quick, sensitive, selective, and low-cost new analytical tools has pushed the development of new methods based on selective nanosensors, able to meet these requirements. Modern sensors, which utilize "next-generation" technologies like nanotechnology, have revolutionized drug detection methods, due to easiness of use, their low cost, and their high sensitivity and reliability, allowing the detection of opioids at trace levels in raw, pharmaceutical, and biological samples (e.g. blood, urine, saliva, and other biological fluids). The peculiar characteristics of these sensors not only have allowed on-site analyses (in the field, at the crime scene, etc.) but also they are nowadays replacing the gold standard analytical methods in the laboratory, even if a proper method validation is still required. This paper reviews advances in the field of nanotechnology and nanosensors for the detection of commonly abused opioids both prescribed (i.e. codeine and morphine) and illegal narcotics (i.e. heroin and fentanyl analogues).

Sensors in the Detection of Abused Substances in Forensic Contexts: A Comprehensive Review

Forensic toxicology plays a pivotal role in elucidating the presence of drugs of abuse in both biological and solid samples, thereby aiding criminal investigations and public health initiatives. This review article explores the significance of sensor technologies in this field, focusing on diverse applications and their impact on the determination of drug abuse markers. This manuscript intends to review the transformative role of portable sensor technologies in detecting drugs of abuse in various samples. They offer precise, efficient, and real-time detection capabilities in both biological samples and solid substances. These sensors have become indispensable tools, with particular applications in various scenarios, including traffic stops, crime scenes, and workplace drug testing. The integration of portable sensor technologies in forensic toxicology is a remarkable advancement in the field. It has not only improved the speed and accuracy of drug abuse detection but has also extended the reach of forensic toxicology, making it more accessible and versatile. These advancements continue to shape forensic toxicology, ensuring swift, precise, and reliable results in criminal investigations and public health endeavours.

Accessible and Generalizable in Vitro Luminescence Assay for Detecting GPCR Activation

G protein-coupled receptors (GPCRs) serve critical physiological roles as the most abundant family of receptors. Here, we describe the design of a generalizable and cell lysate-based method that leverages the interaction between an agonist-activated GPCR and a conformation-specific binder to reconstitute split nanoluciferase (NanoLuc) in vitro. This tool, In vitro GPCR split NanoLuc ligand Triggered Reporter (IGNiTR), has broad applications. We have demonstrated IGNiTR's use with three Gs-coupled GPCRs, two Gi-coupled GPCRs and three classes of conformation-specific binders: nanobodies, miniG proteins, and G protein peptidomimetics. As an in vitro method, IGNiTR enables the use of synthetic G protein peptidomimetics and provides easily scalable and portable reagents for characterizing GPCRs and ligands. We tested three diverse applications of IGNiTR: (1) proof-of-concept GPCR ligand screening using dopamine receptor D1 IGNiTR; (2) detection of opioids for point-of-care testing; and (3) characterizing GPCR functionality during Nanodisc-based reconstitution processes. Due to IGNiTR's unique advantages and the convenience of its cell lysate-based format, this tool will find extensive applications in GPCR ligand detection, screening, and GPCR characterization.

Nanomaterials-based biosensor and their applications: A review

A sensor can be called ideal or perfect if it is enriched with certain characteristics viz., superior detections range, high sensitivity, selectivity, resolution, reproducibility, repeatability, and response time with good flow. Recently, biosensors made of nanoparticles (NPs) have gained very high popularity due to their excellent applications in nearly all the fields of science and technology. The use of NPs in the biosensor is usually done to fill the gap between the converter and the bioreceptor, which is at the nanoscale. Simultaneously the uses of NPs and electrochemical techniques have led to the emergence of biosensors with high sensitivity and decomposition power. This review summarizes the development of biosensors made of NPssuch as noble metal NPs and metal oxide NPs, nanowires (NWs), nanorods (NRs), carbon nanotubes (CNTs), quantum dots (QDs), and dendrimers and their recent advancement in biosensing technology with the expansion of nanotechnology.

An Ultrasensitive Norfentanyl Sensor Based on a Carbon Nanotube-Based Field-Effect Transistor for the Detection of Fentanyl Exposure

The opioid crisis is a worldwide public health crisis that has affected millions of people. In recent years, synthetic opioids, primarily illicit fentanyl, have become the primary driver of overdose deaths. There is a great need for a highly sensitive, portable, and inexpensive analytical tool that can quickly indicate the presence and relative threat of fentanyl. In this work, we develop a semiconductor enriched (sc-) single-walled carbon nanotube (SWCNT)-based field-effect transistor (FET) biosensor functionalized with norfentanyl antibodies for the sensitive detection of norfentanyl, the primary inactive metabolite of fentanyl, in urine samples. Different sensor configurations were explored in order to obtain the most optimized sensing results. Moreover, by employing the "reduced" antibody, we achieved orientated immobilization of the norfentanyl antibody and thus brought the antigen-antibody interaction closer to the sensor surface, further improving the sensitivity. The reported norfentanyl biosensors have a limit of detection in the fg/mL region in both calibration samples and synthetic urine samples, showing ultrasensitivity and high reliability.

Mixed-mode cationic exchange sorptive tapes combined with direct infusion mass spectrometry for determining opioids in saliva samples

This article describes the synthesis of mixed-mode cationic exchange (MCX) tapes as sorptive phases in bioanalysis, and it faces the determination of methadone and tramadol in saliva as the model analytical problem. The tapes are synthesized using aluminum foil as substrate, which is subsequently covered with double-sided adhesive tape where the MCX particles (ca. 1.4 ± 0.2 mg) finally adhere. MCX particles allow the extraction of the analytes at the physiological pH, where both drugs are positively charged, minimizing the potential co-extraction of endogenous matrix compounds. The extraction conditions were studied considering the main variables (e.g. ionic strength, extraction time, sample dilution). Under the optimum conditions and using direct infusion mass spectrometry as the instrumental technique, detection limits as low as 3.3 μg·L^-1 were obtained. The precision calculated at three different levels, and expressed as relative standard deviation, was better than 3.8%. The accuracy, expressed as relative recoveries, ranged from 83 to 113%. The method was finally applied to determine tramadol in saliva samples from patients under medical treatment. This approach opens the door to easily preparing sorptive tapes based on commercial (or ad-hoc synthesized) sorbent particles.

A follow-up study on "A sensitive determination of morphine in plasma using AuNPs@UiO-66/PVA hydrogel as an advanced optical scaffold"

A double solvent-assisted approach was developed for the preparation of AuNPs@UiO-66 based polyvinyl alcohol hydrogel nanocomposite and evaluated its potential as a nanoprobe for the determination of morphine. The characterization and morphology of the synthesized platform were studied and performance comparison for morphine determination was done between the synthesized scaffold and the reported one in our previous work and discussed in detail. Due to the encapsulation of AuNPs inside UiO-66 in a double solvent-assisted approach, no energy transfer was performed with UiO-66 and finally, morphine could not bind with AuNPs. Given these values, such a hydrogel-based matrix prepared with different methodologies with the same thermal stability demonstrates dissimilar potential toward morphine determination in biological samples.

Recent Advances in the Development of Portable Electrochemical Sensors for Controlled Substances

This review article summarizes recent achievements in developing portable electrochemical sensing systems for the detection and/or quantification of controlled substances with potential on-site applications at the crime scene or other venues and in wastewater-based epidemiology. Electrochemical sensors employing carbon screen-printed electrodes (SPEs), including a wearable glove-based one, and aptamer-based devices, including a miniaturized aptamer-based graphene field effect transistor platform, are some exciting examples. Quite straightforward electrochemical sensing systems and methods for controlled substances have been developed using commercially available carbon SPEs and commercially available miniaturized potentiostats. They offer simplicity, ready availability, and affordability. With further development, they might become ready for deployment in forensic field investigation, especially when fast and informed decisions are to be made. Slightly modified carbon SPEs or SPE-like devices might be able to offer higher specificity and sensitivity while they can still be used on commercially available miniaturized potentiostats or lab-fabricated portable or even wearable devices. Affinity-based portable devices employing aptamers, antibodies, and molecularly imprinted polymers have been developed for more specific and sensitive detection and quantification. With further development of both hardware and software, the future of electrochemical sensors for controlled substances is bright.

Key differences in regulation of opioid receptors localized to presynaptic terminals compared to somas: Relevance for novel therapeutics

Opioid receptors are G protein-coupled receptors (GPCRs) that regulate activity within peripheral, subcortical and cortical circuits involved in pain, reward, and aversion processing. Opioid receptors are expressed in both presynaptic terminals where they inhibit neurotransmitter release and postsynaptic locations where they act to hyperpolarize neurons and reduce activity. Agonist activation of postsynaptic receptors at the plasma membrane signal via ion channels or cytoplasmic second messengers. Agonist binding initiates regulatory processes that include phosphorylation by G protein receptor kinases (GRKs) and recruitment of beta-arrestins that desensitize and internalize the receptors. Opioid receptors also couple to effectors from endosomes activating intracellular enzymes and kinases. In contrast to postsynaptic opioid receptors, receptors localized to presynaptic terminals are resistant to desensitization such that there is no loss of signaling in the continuous presence of opioids over the same time scale. Thus, the balance of opioid signaling in circuits expressing pre- and postsynaptic opioid receptors is shifted toward inhibition of presynaptic neurotransmitter release during continuous opioid exposure. The functional implication of this shift is not often acknowledged in behavioral studies. This review covers what is currently understood about regulation of opioid/nociceptin receptors, with an emphasis on opioid receptor signaling in pain and reward circuits. Importantly, the review covers regulation of presynaptic receptors and the critical gaps in understanding this area, as well as the opportunities to further understand opioid signaling in brain circuits. This article is part of the Special Issue on "Opioid-induced changes in addiction and pain circuits".