Label-free and sensitive impedimetric nanosensor for the detection of cocaine based on a supramolecular complexation with β-cyclodextrin, immobilized on a nanostructured polymer film

Cocaine in Different Matrices: Recent Updates on Pretreatment and Detection Techniques

Cocaine abuse has attracted increased attention in the recent past since it can cause addiction and great harm to the normal human body. Due to cocaine exists in various complex matrices, the detection of it in different matrices is helpful to prevent abuse. It is thus imperative to establish efficient and accurate methods for pretreatment and detection of cocaine in different samples. The present study provides a summary of the research progress of cocaine pretreatment methods (such as different microextraction methods, QuEChERS, and solid phase extraction based on novel extraction materials) and detection approaches (such as liquid chromatography coupled with different detectors, gas chromatography and related techniques, capillary electrophoresis and sensors). A comparison of the pros and cons of different pretreatment and detection methods is presented. The findings of this study will provide a reference for selection of the most suitable cocaine pretreatment and detection techniques.

Overoxidation of Intrinsically Conducting Polymers

Intrinsically conducting polymers may undergo significant changes of molecular structure and material properties when exposed to highly oxidizing conditions or very positive electrode potentials, commonly called overoxidation. The type and extent of the changes depend on the experimental conditions and chemical environment. They may proceed already at much lower rates at lower electrode potentials because some of the processes associated with overoxidation are closely related to more or less reversible redox processes employed in electrochemical energy conversion and electrochromism. These changes may be welcome for some applications of these polymers in sensors, extraction, and surface functionalization, but in many cases, the change of properties affects the performance of the material negatively, contributing to material and device degradation. This report presents published examples, experimental observations, and their interpretations in terms of both structural and of material property changes. Options to limit and suppress overoxidation are presented, and useful applications are described extensively.

A simple label-free electrochemical sensor for sensitive detection of alpha-fetoprotein based on specific aptamer immobilized platinum nanoparticles/carboxylated-graphene oxide

A label-free electrochemical aptamer-based sensor has been fabricated for alpha-fetoprotein (AFP) detection. Platinum nanoparticles on carboxylated-graphene oxide (PtNPs/GO-COOH) modified screen-printed graphene-carbon paste electrode (SPGE) was utilized as an immobilization platform, and the AFP aptamer was employed as a bio-recognition element. The synthesized GO-COOH helps to increase the surface area and amounts of the immobilized aptamer. Subsequently, PtNPs are decorated on GO-COOH to enhance electrical conductivity and an oxidation current of the hydroquinone electrochemical probe. The aptamer selectively interacts with AFP, causing a decrease in the peak current of the hydroquinone because the binding biomolecules on the electrode surface hinder the electron transfer of the redox probe. Effects of aptamer concentration and AFP incubation time were studied, and the current changes of the redox probe before and after AFP binding were investigated by square wave voltammetry. The developed aptasensor provides a linear range from 3.0–30 ng mL⁻¹ with a detection limit of 1.22 ng mL⁻¹. Moreover, the aptamer immobilized electrode offers high selectivity to AFP molecules, good stability, and sensitive determination of AFP in human serum samples with high recoveries.

Electrified Soft Interface as a Selective Sensor for Cocaine Detection in Street Samples

A straightforward, direct, and selective method is presented for electrochemical cocaine identification in street samples. The sensing mechanism is based on a simple ion transfer reaction across the polarized liquid–liquid interface. The interfacial behavior of a number of cutting agents is also reported. Interfacial miniaturization has led to improved electroanalytical properties of the liquid–liquid interface based sensor as compared with the macroscopic analogue. The reported method holds great potential to replace colorimetric tests with poor selectivity for on-site street sample analysis.

Mobile Phone Sensing of Cocaine in a Lateral Flow Assay Combined with a Biomimetic Material

Lateral flow assays (LFAs) are an ideal choice for drug abuse testing favored by their practicability, portability, and rapidity. LFA based on-site rapid screening devices provide positive/negative judgment in a short response time. The conventionally applied competitive assay format used for small molecule analysis such as abused drugs restricts the quantitation ability of LFA strips. We report herein, for the first time, a new strategy using the noncompetitive assay format via a biomimetic material, namely, poly(p-phenylene) β-cyclodextrin poly(ethylene glycol) (PPP-CD-g-PEG) combined with gold nanoparticle (AuNP) conjugates as the labeling agent to recognize the target cocaine molecule in the test zone. The intensities of the visualized red color in the test line indicate that the cocaine concentrations were analyzed via a smartphone application. Significantly, a combination of this platform with a smartphone application provides quantitative data on the cocaine amount, making it a very inventive and attractive approach especially for on-site applications at critical points such as traffic stops and the workplace.

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.