Development and validation of a label-free colorimetric aptasensor based on the HCR and hemin/G-quadruplex DNAzyme for the determination of patulin in fruits and fruit-based products from Xinjiang (China)

Visualization detection of mycotoxin patulin in fruit juices by a small-molecule fluorescent probe

The mycotoxin patulin is a common contaminant in rotten fruits, posing severe food safety risks and threats to human health. Developing a convenient, sensitive and reliable method for patulin detection is of utmost importance but remains challenging. In this study, we have successfully designed and synthesized a small-molecule fluorescent probe, FITC-Lys, which demonstrates good sensitivity in detecting patulin. Upon contact with patulin, the terminal Lys group of the FITC-Lys probe reacts with patulin, resulting in the formation of the fluorescein dimer that subsequently quenches fluorescence. This variation of fluorescence enables the visualization and sensitive detection of patulin. The probe exhibits good sensitivity with a low LOD of 8 ng mL-1 for the fluorescence spectrum method and a LOD of 12 ng mL-1 for the fluorescence imaging method. Moreover, we have validated the probe's capability for patulin detection in apple and pear juices, achieving good recoveries ranging from 98.60% to 103.80%. Notably, the probe FITC-Lys is the first small-molecule fluorescent probe that has proven successful in visualizing patulin in juices derived from decayed apples and pears. Consequently, this probe holds great potential as a practical tool for monitoring patulin in foodstuffs, thereby contributing to enhanced food safety standards.

Rational design of a ratiometric fluorescent aptasensor for patulin in traditional Chinese medicine through the studies of the interaction mechanism between its DNA aptamer and the target molecule

Patulin (PAT) is a kind of mycotoxin which must be monitored for the sake of quality and safety in traditional Chinese medicine (TCM) owing to its harm to human health. On this account, a rationally designed ratiometric fluorescent aptasensor was developed based on the studies of the interaction mechanism between PAT and its aptamer (PAT-APT). First, CD spectroscopy, molecular docking, and molecular dynamic simulation were applied to investigate the details on how PAT-APT binds with its target molecule. The results indicated that the structure of PAT-APT changed to a certain extent and was stabilized after binding with PAT. C-11, C-37 and C-38 were the key sites for the recognition and interaction between PAT-APT and its target. Second, based on these results, a ratiometric aptasensor was designed using fluorescence resonance energy transfer (FRET) and synchronous fluorescence spectroscopy. A complementary sequence (cDNA) to the aptamer with an appropriate length and hybridization position was obtained through rational design and optimization. Both PAT-APT and cDNA were labeled using a pair of fluorophores, which could generate FRET when the two single-stranded oligonucleotides hybridized. The accurate detection of PAT could be realized according to the change ratio of the fluorescence intensity at the corresponding wavelengths of the two fluorophores before and after the assay. The aptasensor achieved an ultralow limit of detection of 0.16 nM, perfect selectivity, and satisfactory practicability in complex TCM samples. To our knowledge, this is the first aptasensor for PAT designed through the interaction mechanism between its aptamer and the target molecule. Moreover, the assay for PAT is cost-effective, does not need complicated pretreatment and only takes less than an hour. In summary, this study makes a contribution to the safety control of TCM and provides a thinking mode from mechanism to rational design to conquer the problem of sensitive aptasensing of one component in a complex system.

An ultrasensitive ratiometric aptasensor based on the dual-potential electrochemiluminescence of Ru(bpy)32+ in a novel ternary system for detection of Patulin in fruit products

To sensitively monitor trace-level of toxic patulin (PAT), an ultrasensitive PAT ratiometric aptasensor based on the dual-potential electrochemiluminescence (ECL) of Ru(bpy)₃²⁺ was first proposed. Noteworthily, Ru(bpy)₃²⁺-doped trimetallic nanocube (Ru@Tri) innovatively integrated the luminophore and cathode coreaction accelerator (CCA), which could generate strong cathodic ECL in the existence of low concentration of K₂S₂O₈. Simultaneously, anthocyanin-derived carbon quantum dots (anth-CQDs) prepared from purple potato skins was first served as a green anodic coreactant. And SiO₂-coated anth-CQDs (anth-CQDs@SiO₂) exhibited excellent performance for enhancing anodic ECL of Ru@Tri. Based on this, a novel ternary ECL system was established. In the presence of PAT, the ECL intensity ratio of anode to cathode (I_ECL-A/I_ECL-C) was significantly increased, and a low detection limit of 0.05 pg mL^-1 was obtained. Moreover, when proposed method and high performance liquid chromatography (HPLC) were simultaneously applied to series of fruit products, the obtained results were completely consistent, reflecting its practicability.

A Dual-Signaling Electrochemical Aptasensor Based on an In-Plane Gold Nanoparticles-Black Phosphorus Heterostructure for the Sensitive Detection of Patulin

Patulin (PAT), a type of mycotoxin existing in foodstuffs, is harmful to food safety and human health. Thus, it is necessary to develop sensitive, selective and reliable analytical methods for PAT detection. In this study, a sensitive aptasensor based on a dual-signaling strategy was fabricated, in which a methylene-blue-labeled aptamer and ferrocene monocarboxylic acid in the electrolyte acted as a dual signal, for monitoring PAT. To improve the sensitivity of the aptasensor, an in-plane gold nanoparticles-black phosphorus heterostructure (AuNPs-BPNS) was synthesized for signal amplification. Due to the combination of AuNPs-BPNS nanocomposites and the dual-signaling strategy, the proposed aptasensor has a good analytical performance for PAT detection with the broad linear range of 0.1 nM-100.0 μM and the low detection limit of 0.043 nM. Moreover, the aptasensor was successfully employed for real sample detection, such as apple, pear and tomato. It is expected that BPNS-based nanomaterials hold great promise for developing novel aptasensors and may provide a sensing platform for food safety monitoring.