A novel fluorescent aptasensor based on mesoporous silica nanoparticles for the selective detection of sulfadiazine in edible tissue

Highly Sensitive Dual-Probe Fluorescence Assay Based on an Aptamer for the Detection of Sulfasalazine

Sulfadiazine (SD) is extensively utilized in agriculture, aquaculture, poultry, medical, and other industries. Its residues pose a threat to human health by entering the food chain and can also be released into the environment through animal feces and urine, leading to ecotoxicological pollution. Consequently, there is an urgent need to establish an efficient method for detecting SD residues in the environment. In this study, a novel two-probe fluorescence assay for determining SD in the environment, based on magnetic separation and real-time quantitative PCR-TaqMan probe technology, was successfully developed. In the experiment, SD served as the target substance, and an aptamer (Apt) with high affinity for SD was synthesized. Additionally, a non-fully complementary chain (Cdna) with favorable hybridization properties with the aptamer was designed and synthesized to create a magnetic probe of magnetic beads@Apt@Cdna. When SD was introduced, Apt specifically bound to SD with a hairpin structure and was released from the magnetic probe, allowing SD detection via the PCR-TaqMan method. Factors affecting the determination accuracy of this assay system, such as Apt concentration, SD standard solution pH, and incubation time, were optimized. Under the optimized conditions, the assay demonstrated high sensitivity for SD, with a detection limit of 2.34 × 10-5 ng/mL. Finally, the method was applied to detect SD in water samples from the Jialu River Basin in Zhengzhou City, yielding spiked recoveries of 88.82-117.05%. The results indicated that the detection system is a highly sensitive and specific method for determining SD residues in environmental water samples, showcasing its potential application in SD detection.

A highly sensitive and selective colorimetric aptasensor for detecting sulfadiazine in river waters based on gold nanoparticles synthesized from discarded Longan seed extract

Gold nanoparticles (AuNPs) were extensively employed for in-situ detection sulfadiazine (SDZ) residues, yet current synthesis methods suffer from complex procedures, reagent pollution of the environment, and low particle quality. This study presents a novel synthesis method using discarded longan seed extract as a reducing agent to synthesized high-quality AuNPs, and then can be used for in-situ SDZ detection. Response surface methodology (RSM) was employed to optimize synthesis parameters, which resulted in five optimal combinations that enhanced the flexibility of synthesis. These AuNPs, ranging in size from 18.26 nm to 33.8 nm with zeta potentials from - 29.5 mV to - 14.3 mV, were successfully loaded with functional groups from longan seed extract. In the detection of SDZ, the colorimetric aptasensor demonstrated excellent sensitivity and selectivity over other antibiotics with a limit of detection and quantification at 70.98 ng·mL-1 and 236.59 ng·mL-1 in the concentration range of 200-800 ng·mL-1. Recoveries of spiked SDZ samples ranged from 97.90% to 106.7%, with RSD values below 9.25%. Meanwhile, the aptasensor exhibited exceptional diagnostic efficacy (AUC: 0.976) compared to UV absorption methods in the ROC evaluation. In conclusion, this study highlights the potential of using AuNPs synthesized from longan seed extract coupled with aptamer technology as a straightforward detection method for SDZ in river water, offering promising applications in environmental monitoring.

Multiplexed SELEX for Sulfonamide Antibiotics Yielding a Group-Specific DNA Aptamer for Biosensors

The widespread use of sulfonamide (SA) antibiotics in animal husbandry has led to residues of SAs in the environment, causing adverse effects to the ecosystem and a risk of bacterial resistance, which is a potential threat to public health. Therefore, it is highly desirable to develop simple, high-throughput methods that can detect multiple SAs simultaneously. In this study, we isolated aptamers with different specificities based on a multi-SA systematic evolution of ligands by the exponential enrichment (SELEX) strategy using a mixture of sulfadimethoxine (SDM), sulfaquinoxaline (SQX), and sulfamethoxazole (SMZ). Three aptamers were obtained, and one of them showed a similar binding to all tested SAs, with dissociation constant (Kd) ranging from 0.22 to 0.63 μM. For the other two aptamers, one is specific for SQX, and the other is specific for SDM and sulfaclozine. A label-free detection method based on the broad-specificity aptamer was developed for the simultaneous detection of six SAs, with detection of limits ranging from 0.14 to 0.71 μM in a lake water sample. The aptasensor has no binding for other broad-spectrum antibiotics such as β-lactam antibiotics, quinolones, tetracyclines, and chloramphenicol. This work provides a promising biosensor for rapid, multiresidue, and high-throughput detection of SAs, as well as a shortcut for the preparation of different specific recognition elements required for the detection of broad-spectrum antibiotics.

Development and Validation of Aptasensor Based on MnO2 for the Detection of Sulfadiazine Residues

The monitoring of sulfadiazine (SDZ) is of great significance for food safety, environmental protection, and human health. In this study, a fluorescent aptasensor based on MnO₂ and FAM-labeled SDZ aptamer (FAM-SDZ30-1) was developed for the sensitive and selective detection of SDZ in food and environmental samples. MnO₂ nanosheets adsorbed rapidly to the aptamer through its electrostatic interaction with the base, providing the basis for an ultrasensitive SDZ detection. Molecular dynamics was used to explain the combination of SMZ1S and SMZ. This fluorescent aptasensor exhibited high sensitivity and selectivity with a limit of detection of 3.25 ng/mL and a linear range of 5-40 ng/mL. The recoveries ranged from 87.19% to 109.26% and the coefficients of variation ranged from 3.13% to 13.14%. In addition, the results of the aptasensor showed an excellent correlation with high-performance liquid chromatography (HPLC). Therefore, this aptasensor based on MnO₂ is a potentially useful methodology for highly sensitive and selective detection of SDZ in foods and environments.

High-Sensitive FAM Labeled Aptasensor Based on Fe3O4/Au/g-C3N4 for the Detection of Sulfamethazine in Food Matrix

In this study, we developed a fluorescent aptasensor based on Fe₃O₄/Au/g-C₃N₄ and a FAM-labeled aptamer (FAM-SMZ1S) against sulfamethazine (SMZ) for the specific and sensitive detection of SMZ in food matrix. The FAM-SMZ1S was adsorbed by the Fe₃O₄/Au/g-C₃N₄ via π–π stacking and electrostatic adsorption, serving as a basis for the ultrasensitive detection of SMZ. Molecular dynamics was used to explain the reasons why SMZ1S and SMZ were combined. This aptasensor presented sensitive recognition performance, with a limit of detection of 0.16 ng/mL and a linear range of 1–100 ng/mL. The recovery rate ranged from 91.6% to 106.8%, and the coefficient of variation (CV) ranged from 2.8% to 13.4%. In addition, we tested the aptasensor for the monitoring of SMZ in various matrix samples, and the results were well-correlated (R² ≥ 0.9153) with those obtained for HPLC detection. According to these results, the aptasensor was sensitive and accurate, representing a potentially useful tool for the detection of SMZ in food matrix.

A label-free dual-modal aptasensor for colorimetric and fluorescent detection of sulfadiazine

Sulfadiazine (SDZ) residues in food products and the environment pose a serious threat to human health and ecological balance, thereby warranting the development of new methods for simple, rapid and accurate detection of these compounds. To this end, we developed a novel label-free dual-modal aptasensor for SDZ detection based on distance-dependent color change of gold nanoparticles (AuNPs) and fluorescence resonance energy transfer between AuNPs and rhodamine B (RhoB). In this aptasensor, the binding of the aptamer to SDZ causes unprotected AuNPs to aggregate in NaCl solution, which alters the color of the solution and restores the fluorescence of RhoB. Under optimal conditions, the aptasensor exhibited a linear colorimetric response in the SDZ concentration range of 50-1000 ng mL^-1, and a linear fluorescence response in the SDZ concentration range of 4-256 ng mL^-1. The limits of detection for colorimetric and fluorescent readings were 28 ng mL^-1 and 2 ng mL^-1 respectively. The recoveries of SDZ in the spiked real samples were 88.28-108.44% by colorimetry and 90.27-106.04% by fluorometry. Furthermore, the results of this aptasensor showed excellent correlation (R² ≥ 0.9858) with HPLC findings. Taken together, these experimental results demonstrate that the proposed label-free dual-modal aptasensor can be employed to screen for SDZ contamination in food and environmental samples.