Evaluation of aptamer and molecularly imprinted polymers as a first hybrid sensor for leptin detection at femtogram levels

NanoMIP beacons with a co-operative binding mechanism for the all-in-one detection of methamphetamine aptamer complexes

Methamphetamine is a highly addictive stimulant with significant public health implications, necessitating the development of rapid, sensitive, and reliable detection methods. Traditional analytical techniques, though accurate, often involve complex sample preparation, expensive equipment, and lengthy analysis times. This study presents the design, synthesis, and application of nanoMIP beacons with a unique co-operative binding mechanism for the detection of methamphetamine. NanoMIP beacons selective for methamphetamine/aptamer complexes were synthesized using a solid-phase synthesis method that involved the bio-conjugation of an aptamer on the stationary phase and the incubation of methamphetamine to form a methamphetamine-aptamer complex. The resultant nanoMIP beacons were eluted off the affinity column and characterised using transmission electron microscopy. The co-operative binding mechanism, which relies on the structure-switching capability of the aptamer upon analyte binding was demonstrated through comparison of the fluorescence quenching signal of a scrambled sequence and nanoNIP controls. The fluorescence quenching assay was established using a fixed optimal concentration of aptamer and varying amounts of methamphetamine. The nanoMIP beacons showed enhanced the sensitivity (LOD = 23 ± 3.5 nM) and excellent selectivity, with a 40-fold increase in quenching for methamphetamine compared to other illicit drugs. The nanoMIP beacons demonstrated acceptable sample recoveries in both urine diluent and 50% human serum. This work provides a new strategy for the development of hybrid nanoMIP/aptamer-based sensors and provides a robust analytical tool for combating methamphetamine abuse.

Engineering of dual recognition functional aptamer-molecularly imprinted polymeric solid-phase microextraction for detecting of 17β-estradiol in meat samples

In this study, an enhanced selective recognition strategy was employed to construct a novel solid-phase microextraction fiber coating for the detection of 17β-estradiol, characterized by the combination of aptamer biorecognition and molecularly imprinted polymer recognition. Benefiting from the combination of molecularly imprinted and aptamer, aptamer-molecularly imprinted (Apt-MIP) fiber coating had synergistic recognition effect. The effects of pH, ion concentration, extraction time, desorption time and desorption solvent on the adsorption capacity of Apt-MIP were investigated. The adsorption of 17β-estradiol on Apt-MIP followed pseudo-second order kinetic model, and the Freundlich isotherm. The process was exothermic and thermodynamically spontaneous. Compared with polymers that only rely on imprinted recognition, non-imprinted recognition or aptamer affinity, Apt-MIP had the best recognition performance, which was 1.30-2.20 times that of these three materials. Furthermore, the adsorption capacity of Apt-MIP for 17β-estradiol was 885.36-1487.52 times than that of polyacrylate and polydimethylsiloxane/divinylbenzone commercial fiber coatings. Apt-MIP fiber coating had good stability and could be reused for more than 15 times. Apt-MIP solid-phase microextraction coupled with high-performance liquid chromatography was successfully applied to the determination of 17β-estradiol in pork, chicken, fish and shrimp samples, with satisfactory recoveries of 79.61 %-105.70 % and low limits of detection (0.03 μg/kg). This work provides new perspectives and strategies for sample pretreatment techniques based on molecular imprinting technology and improves analytical performance.

Selective extraction of maleic hydrazide in foods using magnetic molecularly imprinted polymers and colorimetric detection via smartphone

Maleic hydrazide (MH) is a plant growth regulator, herbicide, and sprout inhibitor used to improve the growth and quality of certain vegetables and fruits, unfortunately, MH has genotoxic and carcinogenic effects; thus, MH residues in food need to be analyzed. Herein, magnetic molecularly imprinted polymers (MagMIP) were synthesized by radical polymerization in just 30 min using a microwave for rapid and selective extraction of MH. The colorimetric detection of MH using the immobilized Folin Ciocalteau's reagent (FCR) on 96-well microplate via smartphone sensor exhibits useful sensitivity for MH with a limit of detection (LOD = 0.6 ppm) which is far lower than the maximum residue limits (higher than 5 ppm). The immobilized FCR was stored dry at two different storage conditions at +4 °C and room temperature without losing its performance over six months. The coupling MagMIP-extraction/clean-up and smartphone determination were tested towards food samples (i.e., potatoes, and carrots), obtaining good recovery (79-96 %), high repeatability (RSD 4.5 %; n = 10), and high selectivity for MH determination.

Research progress on preparation methods and sensing applications of molecularly imprinted polymer-aptamer dual recognition elements

The aptamer (Apt) and the molecularly imprinted polymer (MIP), as effective substitutes for antibodies, have received widespread attention from researchers because of their creation. However, the low stability of Apt in harsh detection environment and the poor specificity of MIP have hindered their development. Therefore, some researchers have attempted to combine MIP with Apt to explore whether the effect of "1 + 1 > 2" can be achieved. Since its first report in 2013, MIP-Apt dual recognition elements have become a highly focused research direction in the fields of biology and chemistry. MIP-Apt dual recognition elements not only possess the high specificity of Apt and the high stability of MIP in harsh detection environment, but also have high sensitivity and affinity. They have been successfully applied in medical diagnosis, food safety, and environmental monitoring fields. This article provides a systematic overview of three preparation methods for MIP-Apt dual recognition elements and their application in eight different types of sensors. It also provides effective insights into the problems and development directions faced by MIP-Apt dual recognition elements.