Aptamer-enhanced fluorescence determination of bisphenol A after magnetic solid-phase extraction using Fe3O4@SiO2@aptamer

Potential application of 2D nano-layered MXene in analysing and remediating endocrine disruptor compounds and heavy metals in water

With the advancement of technologies and growth of the economy, it is inevitable that more complex processes are deployed, producing more heterogeneous wastewater that comes from biomedical, biochemical and various biotechnological industries. While the conventional way of wastewater treatment could effectively reduce the chemical oxygen demand, pH and turbidity of wastewater, trace pollutants, specifically the endocrine disruptor compounds (EDCs) that exist in µg L-1 or ng L-1 have further hardened the detection and removal of these biochemical pollutants. Even in small amounts, EDC could interfere human's hormone, causing severe implications on human body. Hence, this review elucidates the recent insights regarding the effectiveness of an advanced 2D material based on titanium carbide (Ti3C2Tx), also known as MXene, in detecting and removing EDCs. MXene's highly tunable feature also allows its surface chemistry to be adjusted by adding chemicals with different functional groups to adsorb different kinds of EDCs for biochemical pollution mitigation. At the same time, the incorporation of MXene into sample matrices also further eases the analysis of trace pollutants down to ng L-1 levels, thereby making way for a more cleaner and comprehensive wastewater treatment. In that sense, this review also highlights the progress in synthesizing MXene from the conventional method to the more modern approaches, together with their respective key parameters. To further understand and attest to the efficacy of MXene, the limitations and current gaps of this potential agent are also accentuated, targeting to seek resolutions for a more sustainable application.

Synthesis and characterization of pH-responsive deep eutectic solvent followed by HPLC for trace determination of bisphenol A in water samples

A microextraction based on pH-responsive deep eutectic solvent combined with high-performance liquid chromatography was developed for the separation, preconcentration, and determination of bisphenol A in water samples. Five deep eutectic solvents were prepared using thymol (hydrogen bond acceptor) and 6-, 8-, 9-, 10-, and 12-carbon carboxylic acids (hydrogen bond donor), and were used as extraction solvent. Herein, by alkalinizing the environment, phase transition takes place, and by adding acid, phase separation and extraction of analytes occur simultaneously. Some important parameters on the extraction such as deep eutectic solvent type, molar ratio of deep eutectic solvent components, deep eutectic solvent volume, potassium hydroxide concentration, hydrochloric acid volume, extraction time, and salt addition were optimized. Under the optimum conditions, intra- and interday precisions of the method based on seven replicate measurements of 10 μg L-1 of bisphenol A in water samples were 2.2% and 4.3%, respectively. The analytical performance of the method showed linearity over the concentration of 0.05-50 μg L-1 with the detection limit of 0.02 μg L-1 . The accuracy of the method was confirmed by spiking different concentrations of bisphenol A in real water samples and obtaining relative recoveries in the range of 92.5%-105.2%.

An Overview of Aptamer-Based Sensor Platforms for the Detection of Bisphenol-A

Endocrine disruptive compounds are natural or anthropogenic environmental micropollutants that alter the function of the endocrine system ultimately damaging the metabolism. Bisphenol A (BPA) is the most common of these pollutants and it is often used in epoxy coatings and polycarbonates as a plasticizer. Therefore, monitoring BPA levels in different environments is very important and challenging. In recent years, an increasing number of BPA detection methods have been proposed. This article presents a critical review of aptamer-based electrochemical, fluorescence-based, colorimetric, and several other BPA detection platforms published in the last decade. Furthermore, a statistical evaluation has been made using principle component analysis showing analytical performance parameters do not create very different clusters. Comparisons to other BPA detection methods are also presented so that the reader has an overall literature overview.

Aptamer-Based Biosensors for the Analytical Determination of Bisphenol A in Foodstuffs

Bisphenol A (BPA) is a synthetic compound utilized to manufacture plastics for Food Contact Materials (FCMs) or resins for the inside of food containers. Since it was recognized as an Endocrine-Disrupting Chemical (EDC), its implications in pathologies, such as cancer, obesity, diabetes, immune system alterations, and developmental and mental disorders, have been widely documented. Diet is considered the main source of exposure for humans to BPA. Consequently, continuous monitoring of the levels of BPA in foods is necessary to assess the risk associated with its consumption in one’s diet. So far, many reviews have been published on biosensors and aptamer-based biosensors, but none of them focus on their applications in their analyses of bisphenols in food matrices. With this review, the authors aim to fill this gap and to take a snapshot of the current state-of-the-art research on aptasensors designed to detect BPA in food matrices. Given that a new TDI value has recently been proposed by the EFSA (0.04 ng/kg), the search for new sensitive tools for the quantitative analysis of BPA is more topical and urgent than ever. From this perspective, aptasensors prove to be a good alternative to traditional analytical techniques for determining BPA levels in food.

A replacement-type electrochemiluminescent aptasensor for lysozyme based on full-electric modification electrode coupled to silica-coated Ru(bpy)32+/silver nanospheres

This research proposed a replacement-type electrochemiluminescent (ECL) aptasensor for lysozyme (LYZ) detection at trace levels based on a full-electric modification electrode (FEMG) coupled to silica-coated Ru(bpy)₃²⁺/silver nanospheres (Ru/SNs@SiO₂). The multi-walled carbon nanotubes-doped-thionine (MWCNTs/PTn) electropolymerized modified electrode was decorated with electrodeposited gold nanoparticles (GNs) to form the FEMG. Then, the FEMG was utilized as sensing substrates for the immobilization of the anti-lysozyme aptamer (LA); the stability and number of LA attaching onto the FEMG were dramatically increased. The ECL measurement was used to evaluate the hybridization reaction of LA and the Ru/SNs@SiO₂ marked DNA probe, and it was noted as I_a. After the combination of the LA with the LYZ, the target-triggered replacement of the DNA probe was actualized and the ECL measurement descended to I_b. The ECL difference (ΔI_ECL = I_a - I_b) before and after the replacement event was utilized for quantitation of LYZ. As a result, the fabricated aptasensor with great sensitivity and specificity achieved a wide linear range (10 fM-10 pM) and a low limit of detection (5 fM). It obtained satisfactory recovery for the detection of LYZ in human serum, and the results were identified with the LYZ ELISA kit. Therefore, the proposed ECL sensor is expected to become a promising approach in the field of biomolecule detection.

A fluorescent aptasensor based on berberine for ultrasensitive detection of bisphenol A in tap water

The residues of bisphenol A (BPA) in food packaging and water systems have a potential impact on human health; therefore, its analysis and detection have drawn scientists' attention. In this work, based on the change in fluorescence intensity resulting from the conformational switch of a berberine/BPA-aptamer system in the presence and absence of BPA, an ultra-sensitive fluorescence aptasensing system is proposed, in which BPA-aptamer is employed as the identification unit and berberine as the fluorescent probe. Various factors affecting the detection of BPA, including the concentration of the fluorescent probe, BPA-aptamer, BPA, pH, system stability time and other experimental conditions, were investigated in detail. Under the optimal experimental conditions, the fluorescence intensity of the sensing system of berberine/BPA-aptamer exhibited a good linear correlation with the BPA concentration in the range of 0-1300 μM with a LOD of 32 nM. The proposed fluorescent sensing system also exhibited excellent recoveries of 92.4-102.3% in tap water samples and showed good application prospects for the analysis and detection of BPA.

Rapid and highly sensitive detection of Salmonella typhimurium in lettuce by using magnetic fluorescent nanoparticles

The highly efficient detection of Salmonella typhimurium (S. typhimurium), a common foodborne bacterial, is important for the safety assurance of leafy vegetables. In this study, a fluorescent sensor (FMNCs-Apt), based on Fe3O4 magnetic nanoparticles and aptamer-modified carbon quantum dots, was developed for the rapid and highly sensitive detection of S. typhimurium in lettuce. First, carbon quantum dots were covalently bonded to the surface of prepared Fe3O4@chitosan to form magnetic fluorescence composite nanoparticles (FMNCs). Then, the aptamers of S. typhimurium were covalently linked to the surface (and named FMNCs-Apt). Fluorescence intensity of the FMNCs-Apt probes decreased as they aggregated on the surface of the bacteria, and the aggregation was separated using a magnet. Under the optimal conditions, the fluorescence change values of the solution showed a good linear relationship with the concentration of Salmonella (103-106 CFU mL-1). The detection limit of the method is 100 CFU mL-1 and 138 CFU mL-1 in fresh-cut vegetable washing solution and lettuce sample, respectively. Accordingly, this developed fluorescent probe became a highly sensitive and efficient sensor for the rapid detection of S. typhimurium in lettuce.