Sensitive imprinted optical sensor based on mesoporous structure and green nanoparticles for the detection of methamphetamine in plasma and urine

Aptamer-controlled gold nanozyme sensor for fluorescent and colorimetric dual-channel detection of methamphetamine

Methamphetamine (METH) is the second abused drug which affects abusers' health and induces social crimes, developing novel methods with high sensitivity and selectivity for METH detecting is still challenging. In this paper, a colorimetric and fluorescent dual-channel sensor for METH has been constructed. We combine the enzyme-mimic catalytic activity of gold nanoparticles (GNPs) with high target specificity of METH aptamer to create a nanosensor (Apt-GNP), in the presence of METH, the absorption of 3,3',5,5'-tetramethylbenzidine (OxTMB) at 650 nm enhanced with METH concentration increasing, while the absorption characteristic peak of GNPs at 530 nm remained almost unchanged. The ratio of A650nm/A530nm and METH concentration had a good linear relationship when METH concentration was in the range of 5-50 μM, and the corresponding linear equation is A650nm/A530nm = 0.00727CMETH (μM) + 0.783 with R2 = 0.997 and LOD = 0.40 μM (LOD = 3σ/s, n = 11). Interestingly, the fluorescence emission of Rhodamine B (RB) overlaps with the absorption spectrum of OxTMB which represents the content of METH and the fluorescence signal of RB can be quenched through internal filtering effect (IEF). Hence, when RB was doped to the detection system, the decay of RB fluorescence can reflect the concentrations change of METH. Accordingly, the linear equation is F/FR = -0.00751CMETH (μM) + 0.895 with R2 = 0.993 and LOD = 0.40 μM, where F was the fluorescence of the analytical solution at 580 nm with METH and FR was fluorescence of RB control solution. The dual-channel sensor can measure METH in serum and artificial urine successfully which is potential to be applied in drug-using crime sites and provide direct evidence to law enforcement officials.

Carboxyl hybrid monolithic column in-tube solid-phase microextraction coupled with UPLC-QTRAP MS/MS for the determination of amphetamine-type stimulants

A carboxyl functionalized organic-inorganic hybrid monolithic column (TMOS-co-CES) was applied as in-tube solid-phase microextraction (SPME) sorbent combining with ultra-performance liquid chromatography-triple quadrupole/linear ion trap mass spectrometer for separation and analyzation of seven typical amphetamine-type stimulants (ATSs), including amphetamine (AM), methamphetamine (MAM), cathinone, methcathinone, 3,4-methylenedioxyamphetamine, 3,4-methylenedioxymethamphetamine and 3,4-methylenedioxyethylamphetamine. The application potential of TMOS-co-CES material to ATSs was preliminarily confirmed by computational simulation by using cathinone as a representative. The influences of various SPME parameters and analytical performance were investigated systematically. As matched with the results of computational simulation, TMOS-co-CES column could capture ATSs under milder near neutral pH condition with high extraction efficiency basing on the adsorption mechanism explained as a mixed mode of electrostatic and hydrophobic interactions. Seven target trace ATSs in spiked sewage, pond water and urine could be rapidly and conveniently separated and enriched by the proposed TMOS-co-CES in-tube SPME method under the optimized conditions with good accuracy, repeatability and resistance to matrix interference. Moreover, AM and MAM had been successfully detected in real urines of suspected drug abusers by TMOS-co-CES in-tube SPME method, which indicated that the proposed method had good application feasibility for drug monitoring. The mild extraction condition and ideal method performance further made the TMOS-co-CES in-tube SPME method more potential in applications for forensic analysis and drug abuse.

Quantitative determination of amphetamine-type stimulants in sewage and urine by hybrid monolithic column solid-phase microextraction coupled with UPLC-QTRAP MS/MS

A needle-solid-phase microextraction (SPME) method based on hybrid monolithic column (HMC) was proposed for simultaneous separation and extraction of seven amphetamine-type stimulants (ATSs) (amphetamine, methamphetamine, cathinone, methcathinone, 3,4-methylenedioxyamphetamine, 3,4-methylenedioxymethamphetamine, and 3,4-methylenedioxyethylamphetamine), combining with ultra-performance liquid chromatography-triple quadrupole/linear ion trap mass spectrometer (UPLC-QTRAP MS/MS). Thiol functionalized HMC (T-HMC) showed high extraction efficiency and excellent elution results towards target analytes, among three kinds of single/bi-functionalized HMCs. Various parameters of SPME operation and analytical performance were investigated systematically. The adsorption mechanism of T-HMC to ATSs was also discussed and explained as a mixed mode of electrostatic and hydrophobic interactions. Under the optimum experimental conditions, the proposed T-HMC needle-SPME-UPLC-QTRAP MS/MS method was rapid and convenient with good accuracy, low sample consumption, high sensitivity and strong anti-interference ability. This method was successfully applied to quantitative determination of seven trace ATSs in complex sewage and urine samples. In view of abundant types of HMCs, the needle-SPME based on functional HMC also had the potential to selectively separating and enriching other tract new psychoactive substances in complex matrices, and could provide a reliable tool for drug monitoring, especially in applications for forensic analysis and drug abuse.

Enhancing Cytochrome C Recognition and Adsorption through Epitope-Imprinted Mesoporous Silica with a Tailored Pore Size

We have reported the synthesis of epitope-imprinted mesoporous silica (EIMS) with an average pore size of 6.2 nm, which is similar to the geometrical size of the target protein, cytochrome C (Cyt c, 2.6 × 3.2 × 3.3 nm3), showing great recognition and large-scale adsorption performance. The characteristic fragment of Cyt c was used as a template and docked onto the surface of C16MIMCl micelles via multiple interactions. Nitrogen adsorption-desorption and transmission electron microscopy confirmed the successful preparation of EIMS. Due to the ordered pore structure, larger pore size, and high specific surface area, the prepared EIMS show superior specificity (IF = 3.8), excellent selectivity toward Cyt c, high adsorption capacity (249.6 mg g-1), and fast adsorption equilibrium (10 min). This study demonstrates the potential application of EIMS with a controllable pore size for high-effective and large-scale separation of Cyt c, providing a new approach for effective biomacromolecular recognition.

A Review of Sensing Applications of Molecularly Imprinted Fluorescent Carbon Dots for Food and Biological Sample Analysis

Molecularly imprinted fluorescent carbon dots (MI-FCDs) find numerous applications in analytical chemistry due to their outstanding photoluminescent properties and having specific pockets for the recognition of target molecules. Despite significant advances, practical applications of MI-FCDs-based fluorescent sensors are still in their initial stages. Therefore, the topical developments in the synthesis, working, and application of MI-FCDs for sensing various target species (e.g., pharmaceuticals, biomolecules, pesticides, food additives, and miscellaneous species) in food and biological media have been highlighted. Moreover, a careful evaluation has been made to select the best methods based on their performance in terms of analytical parameters. To expand the horizons of this field, important challenges and future directions for developing MI-FCDs for practical use are also presented. This review will highlight important aspects of MI-FCDs-based fluorescent sensors for their applicability in food science, material science, environmental science, nanoscience, and biotechnology.

Antibody-Conjugated Electrospun Nanofibers for Electrochemical Detection of Methamphetamine

Multifunctional electrospun nanofibers (ENs) with improved properties have increased attention nowadays. Their insoluble forms in water with decreased hydrophobicity are desired for the immobilization of biological molecules. Also, the addition of functional groups on the backbone provides the conjugation of biomolecules onto the surface of ENs via covalent bonds to increase their stability. Here, poly(vinylidene fluoride) (PVDF) was chosen to prepare a platform, which is insoluble in water, and polyethylenimine (PEI) was used to add amine groups on the surface of ENs to bind biological molecules via covalent conjugation. So, PVDF-PEI nanofibers were prepared on a glassy carbon electrode to immobilize an antimethamphetamine antibody (Anti-METH) as a model biomolecule. The obtained PVDF-PEI/Anti-METH was used for the bioelectrochemical detection of methamphetamine (METH), a common illicit drug. Bioelectrochemical detection of METH on PVDF-PEI/Anti-METH-coated electrodes was carried out by voltammetry in the range of 2.0-50 ng/mL METH. Moreover, the effect of dansyl chloride (DNC) derivatization of METH on the sensitivity of PVDF-PEI/Anti-METH was tested. Finally, METH analysis was carried out in synthetic body fluids. The obtained results showed that PVDF-PEI ENs can be adopted as an immobilization matrix for the biorecognition elements of biobased detection systems, and the derivative of METH (METH-DNC) increased the sensitivity of PVDF-PEI/Anti-METH.

Graphene-Based Electrochemical Sensors for Psychoactive Drugs

Sensors developed from nanomaterials are increasingly used in a variety of fields, from simple wearable or medical sensors to be used at home to monitor health, to more complicated sensors being used by border customs or aviation industries. In recent times, nanoparticle-based sensors have begun to revolutionize drug-detection techniques, mainly due to their affordability, ease of use and portability, compared to conventional chromatography techniques. Thin graphene layers provide a significantly high surface to weight ratio compared to other nanomaterials, a characteristic that has led to the design of more sensitive and reliable sensors. The exceptional properties of graphene coupled with its potential to be tuned to target specific molecules have made graphene-based sensors one of the most popular and well-researched sensing materials of the past two decades with applications in environmental monitoring, medical diagnostics, and industries. Here, we present a review of developments in the applications of graphene-based sensors in sensing drugs such as cocaine, morphine, methamphetamine, ketamine, tramadol and so forth in the past decade. We compare graphene sensors with other sensors developed from ultrathin two-dimensional materials, such as transition-metal dichalcogenides, hexagonal boron nitrate, and MXenes, to measure drugs directly and indirectly, in various samples.

Rapid nanomolar detection of methamphetamine in biofluids via a reagentless electrochemical aptamer-based biosensor

The availability of sensing platforms able to rapidly measure abused drugs directly in biological fluids in a single step would allow performing drugged driving screening on the site. The achievement of this goal is extremely important for preventing and controlling drug abuse and crime incidence. Motived by this, we constructed a simple, cost-effective and reagentless electrochemical aptamer-based (EAB) sensor with methamphetamine (MAMP) as the target molecule. This EAB sensor produced a nanomolar level of detection accuracy in unprocessed or minimally processed bio-samples. Specifically, circular dichroic spectrum was used to confirm that the truncated aptamer from the original sequence would undergo large binding-induced conformational changes. We then engineered the aptamer to work in the EAB platform and the resulting sensor enabled sensitive and specific detection of MAMP with the detection limit of 30 nM in undiluted serum, 50 nM in undiluted urine and 20 nM in 50% saliva. The sensor has good recovery rate, implying this method has good reliability and repeatability. The detection limit is far below the clinical detection threshold, it would be hopefully used for preliminary screening of drugged driving in real world.

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.

Recent advances in developing optical and electrochemical sensors for analysis of methamphetamine: A review

Recognition of misused stimulant drugs has always been a hot topic from a medical and judicial perspective. Methamphetamine (MAMP) is an addictive and illegal drug that profoundly affects the central nervous system. Like other illicit drugs, the detection of MAMP in biological and street samples is vital for several organizations such as forensic medicine, anti-drug headquarters and diagnostic clinics. By emerging nanotechnology and exploiting nanomaterials in sensing applications, a great deal of attention has been given to the design of analytical sensors in MAMP tracing. For the first time, this study has briefly reviewed all the optical and electrochemical sensors in MAMP detection from earlier so far. How various receptors with engineering nanomaterials allow developing novel approaches to measure MAMP have been studied. Fundamental concepts related to optical and electrochemical recognition assays in which nanomaterials have been used and relevant MAMP sensing applications have been comprehensively covered. Challenges, opportunities and future outlooks of this field have also been discussed at the end.

A review of the incorporation of QDs and imprinting technology in optical sensors – imprinting methods and sensing responses

This review aims to cover the simultaneous method of using molecularly imprinted technology and quantum dots (QDs) as well as its application in the field of optical sensors.

Point-of-Care Diagnostics: Molecularly Imprinted Polymers and Nanomaterials for Enhanced Biosensor Selectivity and Transduction

Significant healthcare disparities resulting from personal wealth, circumstances of birth, education level, and more are internationally prevalent. As such, advances in biomedical science overwhelmingly benefit a minority of the global population. Point-of-Care Testing (POCT) can contribute to societal equilibrium by making medical diagnostics affordable, convenient, and fast. Unfortunately, conventional POCT appears stagnant in terms of achieving significant advances. This is attributed to the high cost and instability associated with conventional biorecognition: primarily antibodies, but nucleic acids, cells, enzymes, and aptamers have also been used. Instead, state-of-the-art biosensor researchers are increasingly leveraging molecularly imprinted polymers (MIPs) for their high selectivity, excellent stability, and amenability to a variety of physical and chemical manipulations. Besides the elimination of conventional bioreceptors, the incorporation of nanomaterials has further improved the sensitivity of biosensors. Herein, modern nanobiosensors employing MIPs for selectivity and nanomaterials for improved transduction are systematically reviewed. First, a brief synopsis of fabrication and wide-spread challenges with selectivity demonstration are presented. Afterward, the discussion turns to an analysis of relevant case studies published in the last five years. The analysis is given through two lenses: MIP-based biosensors employing specific nanomaterials and those adopting particular transduction strategies. Finally, conclusions are presented along with a look to the future through recommendations for advancing the field. It is hoped that this work will accelerate successful efforts in the field, orient new researchers, and contribute to equitable health care for all.