High sensitive electrochemical methamphetamine detection in serum and urine via atom transfer radical polymerization signal amplification

A handheld fluorescent lateral flow immunoassay platform for highly sensitive point-of-care detection of methamphetamine and tramadol

The escalating issue of drug abuse poses a significant threat to public health and societal stability worldwide. An on-site drug detection platform is vital for combating drug abuse and trafficking, as it eliminates the need for additional tools, extensive processes, or specialized training. Therefore, it is imperative to develop a fast, sensitive, non-invasive, and reliable multiplex drug testing platform. In this study, we have presented a silica core@dual quantum dot-shell nanocomposite (SI/DQD)-based fluorescent lateral flow immunoassay (LFIA) platform for the highly sensitive and simultaneous point-of-care (POC) detection of methamphetamine (MET) and tramadol (TR). A 3D-printed attachment was designed to integrate optical and electrical components, facilitating the miniaturization of the instrument and reducing both cost and complexity. The device's advanced hardware and effective fluorescence extraction algorithm with waveform reconstruction enable swift, automatic noise reduction and data analysis. SI/DQD nanocomposites were utilized as fluorescent nanotags in the LFIA strips due to their outstanding luminous efficiency and robustness. This LFIA platform achieves impressive detection limits (LODs) of 0.11 ng mL-1 for MET and 0.017 ng mL-1 for TR. The method has also successfully detected MET and TR in complex biological samples, demonstrating its practical application capabilities. The proposed fluorescent LFIA platform, based on SI/DQD technology, holds significant promise for the swift and accurate POC detection of these substances. Its affordability, compact size, and excellent analytical performance make it suitable for on-site drug testing, including at borders and roadside checks, and open up new possibilities for the design and implementation of drug testing methods.

Point-of-care testing of methamphetamine and cocaine utilizing wearable sensors

The imperative for the point-of-care testing of methamphetamine and cocaine in drug abuse prevention necessitates innovative solutions. To address this need, we have introduced a multi-channel wearable sensor harnessing CRISPR/Cas12a system. A CRISPR/Cas12a based system, integrated with aptamers specific to methamphetamine and cocaine, has been engineered. These aptamers function as signal-mediated intermediaries, converting methamphetamine and cocaine into nucleic acid signals, subsequently generating single-stranded DNA to activate the Cas12 protein. Additionally, we have integrated a microfluidic system and magnetic separation technology into the CRISPR system, enabling rapid and precise detection of cocaine and methamphetamine. The proposed sensing platform demonstrated exceptional sensitivity, achieving a detection limit as low as 0.1 ng/mL. This sensor is expected to be used for on-site drug detection in the future.

A facile electrochemical immunosensor based on EDTA-Pb2+ complexation reaction

The sensitivity of electrochemical (EC) sensors has been improved through the development of multiple approaches. However, the majority of EC sensors were limited in their practical application by high costs or tedious procedures. Herein, based on ethylenediaminetetraacetic acid (EDTA)-Pb2+ complexation reaction, a facile and affordable immunosensor was designed. Pb2+-magnesium silicate hydrate was served as the sensing substrate. The immunorecognition process was carried out in the Eppendorf tube, and antibody-functionalized Pb2+-polydopamine was utilized as immunoprobe. In the tube, the quantitative and appropriate excess of EDTA was introduced to complex with Pb2+ on the immunoprobes. The remaining EDTA was added to the sensing substrate surface to coordinate with some Pb2+ in it. This leaded to the reduction of the EC signal of Pb2+, which was related to the antigen concentration. Using prostate-specific antigen as the model analyte, the sensitive detection was realized with a low limit of detection (30.49 fg mL-1). Remarkably, the assay results were available within 24 min, sensibly faster than the most existing EC sensors.

An electrochemical aptasensor for methylamphetamine rapid detection by single-on mode based on competition with complementary DNA

A simple and rapid electrochemical sensing method with high sensitivity and specificity of aptamers was developed for the detection of methylamphetamine (MAMP). A short anti-MAMP thiolated aptamer (Apt) with a methylene blue (MB) probe at 3'-end was immobilized on the surface of a gold electrode (MB-Apt-S/GE). The electrochemical signal appeared when MAMP presenting in the sample solution competed with cDNA for binding with MB-Apt-S. Under optimized conditions, the liner range of this signal-on electrochemical aptasensor for the detection of MAMP achieved from 1.0 to 10.0 nmol/L and 10.0-400 nmol/L. LOD 0.88 nmol/L were obtained. Satisfactory spiked recoveries of saliva and urine were also obtained. In this method, only 5 min were needed to incubate before the square wave voltammetry (SWV) analysis, which was much more rapid than other electrochemical sensors, leading to a bright and broad prospect for the detection of MAMP in biological sample. This method can be used for on-site rapid detection on special occasions, such as drug driving scenes, entertainment venues suspected of drug use, etc.

Vitamin B12-catalyzed electro-polymerization for ultrasensitive RNA detection

Vitamin B12 being a natural catalyst in atom transfer radical polymerization (ATRP), has the advantages of mild reaction conditions, good biocompatibility and high catalytic efficiency. In this report, an electrochemical biosensor of the lung cancer biomarker microRNA-21 (miRNA-21) is designed for early screening of lung cancer with high sensitivity at the femtomolar level. In this approach, hairpin DNA with N3 end group was first attached to the electrode surface. When miRNA-21 was present and paired with hairpin DNA, the N3 group released and attached to the ATRP initiator through "click reaction". Through eATRP, a large number of FerrocenylMethyl Methacrylate (FcMMA) monomers polymerized into long chains for signal amplification. These long chains had a distinct electrical signal in the square wave voltammetry (SWV), which can detect RNA with high sensitivity. The limit of detection (LOD) goes down to 1.010 fM after ATRP polymerization, which is lower than that of the majority of other ultra-sensitive RNA electrochemical assays. Results also show that the vitamin B12-based electrochemical biosensor is highly selective and suitable for RNA detection in complex biological samples.

Hybridization chain reaction-enhanced electrochemically mediated ATRP coupling high-efficient magnetic separation for electrochemical aptasensing of cardiac troponin I

The sensitive and accurate detection of cardiac troponin I (cTnI) as a gold biomarker for cardiovascular diseases at an early stage is crucial but has long been a challenge. In this study, we presented such an electrochemical (EC) aptasensor by combining hybridization chain reaction (HCR)-enhanced electrochemically mediated atom transfer radical polymerization (eATRP) amplification with high-efficient separation of magnetic beads (MBs). Aptamer-modified MBs empowered effective recognition and separation of cTnI from complex samples with high specificity. The specific binding of cTnI and aptamer could release triggered DNA (T-DNA) into solution to drive an HCR process, which produced plentiful active sites for eATRP initiators labeling followed by initiating eATRP process. With the development of eATRP, a great many of electroactive polymer probes were continually in situ formed to generate amplified current output for signal enhancement. Compared to no amplification, HCR-enhanced eATRP promoted the signals by ∼10-fold, greatly improving detection sensitivity for low-abundant cTnI analysis. Integrating MBs as capture carriers with HCR-enhanced eATRP as amplification strategy, this EC aptasensor achieved a low detection limit of 10.9 fg/mL for cTnI detection. Furthermore, the reliable detectability and anti-interference were confirmed in serum samples, indicating its promising application toward early diagnosis of cardiovascular diseases.

Investigating the electrochemical profile of methamphetamine to enable fast on-site detection in forensic analysis

Methamphetamine (MA) is a synthetic psychoactive drug which is consumed both licitly and illicitly. In some countries it is prescribed for attention-deficit and hyperactivity disorder, and short-term treatment of obesity. More often though, it is abused for its psychostimulant properties. Unfortunately, the spread and abuse of this synthetic drug have increased globally, being reported as the most widely consumed synthetic psychoactive drug in the world in 2019. Attempting to overcome the shortcomings of the currently used on-site methods for MA detection in suspected cargos, the present study explores the potential of electrochemical identification of MA by means of square wave voltammetry on disposable graphite screen-printed electrodes. Hence, the analytical characterization of the method was evaluated under optimal conditions exhibiting a linear range between 50 μM and 2.5 mM MA, a LOD of 16.7 μM, a LOQ of 50.0 μM and a sensitivity of 5.3 μA mM^-1. Interestingly, two zones in the potential window were identified for the detection of MA, depending on its concentration in solution. Furthermore, the oxidative pathway of MA was elucidated employing liquid chromatography - mass spectrometry to understand the change in the electrochemical profile. Thereafter, the selectivity of the method towards MA in mixtures with other drugs of abuse as well as common adulterants/cutting agents was evaluated. Finally, the described method was employed for the analysis of MA in confiscated samples and compared with forensic methods, displaying its potential as a fast and easy-to-use method for on-site analysis.

Rose bengal-mediated photoinduced atom transfer radical polymerization for high sensitivity detection of target DNA

Convenient and sensitive detection of biomolecules is of utmost importance in the field of early disease screening. In this study, a Rose Bengal-Mediated photoinduced atom transfer radical polymerization (photoATRP) method was used to achieve highly sensitive detection of target DNA (tDNA). The tDNA was specifically recognized using PNA with terminal modified sulfhydryl groups, and the initiator α-bromophenylacetic acid (BPAA) was attached to the electrode surface via a phosphate-Zr⁴⁺-carboxylate acid structure. Under the excitation of blue light, rose bengal (RB) acts as a photocatalyst, β-nicotinamide adenine dinucleotide (NADH) as an electron donor, and ferrocenylmethyl methacrylate (FMMA) as a monomer to activate the photoATRP reaction and generate a large number of electroactive polymer chains on the electrode surface. Under optimal conditions, the method can be used for the quantitative analysis of tDNA in the concentration range of 1-10⁵ fM (R² = 0.994) with a limit of detection (LOD) of 0.115 fM. This metal-free mediated photoATRP biosensor, with low cost and environmental friendliness, has great potential in the field of highly sensitive biomolecule detection.

Carboxyl porphyrin as signal molecule for sensitive fluorescent detection of aflatoxin B1 via ARGET-ATRP

In this work, a novel fluorescent biosensor for sensitive detecting of aflatoxin B₁ (AFB₁) was constructed through activators regenerated by electron transfer for atom transfer radical polymerization (ARGET-ATRP) for the first time. The AFB₁ antigen was immobilized on the carboxy magnetic beads (MBs) by forming a sandwich-type "aptamer-antigen-antibody" immune system. Then, acrylamid (AM) was introduced through ARGET-ATRP to provide binding sites for the signaling molecules. Finally, carboxy porphyrins (TPP*) were connected with monomers through an amide bond and fixed on the MBs. Under the optimal experimental conditions, the fluorescence intensity and the logarithm of the concentration of AFB₁ showed a good relationship from 100 fg mL^-1 to 100 ng mL^-1, with the limit of detection (LOD) as low as 8.38 fg mL^-1. In addition, the method shows good selectivity and excellent reproducibility. More importantly, the biosensor has applied to the quantitative analysis of AFB₁ in four Chinese medicines, and this strategy could potentially serve as a novel means for sensitive detecting of AFB₁ in complex matrices.

Highly sensitive electrochemical aptasensor for SARS-CoV-2 antigen detection based on aptamer-binding induced multiple hairpin assembly signal amplification

In this work, a brief electrochemical aptasensor was developed for highly sensitive detection of SARS-CoV-2 antigen utilizing an aptamer-binding induced multiple hairpin assembly strategy for signal amplification. In the presence of SARS-CoV-2, a pair of aptamers was brought in a close proximity according to the aptamer-protein antigen binding, which initiated strand displacement reaction thereby triggering a multiple hairpin assembly to obtain long linear DNA concatemers on the electrode surface. As the fabricated hairpin probes were labeled with biotin, massive streptavidin-alkaline phosphatases (ST-ALP) could be further introduced on the electrode interface via biotin-streptavidin interaction thus generating strong electrochemical signal in electrolyte solution containing 1-naphthol phosphate. Benefiting from the non-enzymatic multiple hairpin assembly signal amplification strategy, the designed aptasensor for SARS-CoV-2 spike protein detection exhibited the wide linear range from 50 fg·mL⁻¹ to 50 ng·mL⁻¹ and low detection limit of 9.79 fg·mL⁻¹. Meaningfully, this proposed electrochemical assay provided a potential application for the point of care analysis of viral diseases under ambient temperature.