Exogenous interference and autofluorescence-free ratiometric aptasensor for detection of OTA based on dual-colored persistent luminescence nanoparticles

A controllable Y-shaped DNA structure assisted aptasensor for the simultaneous detection of AFB1 and OTA based on ARGET ATRP

The development of a simple, rapid, and sensitive technology for the simultaneous detection of mycotoxins is of great significance in ensuring the safety of foods and drugs. Herein, a fluorescence aptasensor with high sensitivity and reproducibility for the simultaneous detection of aflatoxin B1 (AFB1) and ochratoxin A (OTA) was developed. In this sensing system, AFB1 and OTA aptamers were co-immobilized on the surface of magnetic beads (MBs) to form a Y-shaped structure through the principle of complementary base pairing, and were used as recognition probes to specifically capture the target. Activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) was used as a signal amplification strategy to improve the sensitivity. The initiator modified at the end of an antibody initiates the ARGET ATRP reaction. Different fluorescence signals were designed to achieve the simultaneous detection of OTA and AFB1 with limits of 426.18 and 79.55 fg mL-1 for AFB1 and OTA, respectively. In addition, experiments were conducted on three types of samples, and the recoveries of the two mycotoxins ranged from 87.30% to 109.50%, with relative standard deviations ranging from 0.50% to 4.92% under reproducible conditions. The results suggest that the developed aptasensor is sufficient to meet the different regulatory requirements of the two mycotoxins in food and drug safety and shows great potential.

Self-evolving persistent luminescence nanoprobes for autofluorescence-free ratiometric imaging and on-demand enhanced chemodynamic therapy of pulmonary metastatic tumors

Precise imaging-guided therapy of a pulmonary metastasis tumor is of great significance for tumor management and prognosis. Persistent luminescence nanoparticles (PLNPs) are promising probes due to their in situ excitation-free and low-background imaging characteristics. However, most of the PLNP-based probes cannot intelligently distinguish between normal and tumor tissues or balance the needs of targeted accumulation and rapid metabolism, resulting in false positive signals and potential side effects. Besides, the luminescence intensity of single-emissive PLNPs is affected by external factors. Herein, we report a self-evolving double-emissive PLNP-based nanoprobe ZGMC@ZGC-TAT for pulmonary metastatic tumor imaging and therapy. Acid-degradable green-emitting PLNPs (ZGMC) with good afterglow performance and therapeutic potential are synthesized by systematic optimization of dopants. Ultra-small red-emitting PLNPs (ZGC) are then prepared as imaging and reference probes. The two PLNPs are finally covalently coupled and further modified with a cell-penetrating peptide (TAT) to obtain ZGMC@ZGC-TAT. Dual emission ensures a stable luminescence ratio (I700/I537) independent of probe concentration, test voltage and time gate. ZGMC degrades and phosphorescence disappears in a tumor microenvironment (TME), resulting in an increase in I700/I537, thus enabling tumor-specific ratiometric imaging. Cu2+ and Mn2+ released by ZGMC degradation achieve GSH depletion and enhance CDT, effectively inhibiting tumor cell proliferation. Meanwhile, the size of ZGMC@ZGC-TAT decreases sharply, and the resulting ZGC-TAT further causes nuclear pyknosis and quickly clear metabolism. The developed ZGMC@ZGC-TAT turns non-targeted lung aggregation of nanomaterials into a unique advantage, and integrates TME-triggered phosphorescence and size self-evolution, and on-demand therapeutic functions, showing outstanding prospects in precise imaging and efficient treatment of pulmonary metastatic tumors.

A DNA tetrahedral scaffolds-based electrochemical biosensor for simultaneous detection of AFB1 and OTA

Herein, a bifunctional electrochemical biosensor based on the DNA tetrahedral scaffolds (TDNs) was proposed, OTA@TDNs and AFB1@TDNs were adopted for electrochemical signal output in response to OTA and AFB1 concentration, simultaneously. In order to increase the conductivity of the biosensor, highly porous gold (HPG) was loaded on electrode surface by pulse electrodeposition. Under optimal conditions, the PFc displayed a linear range with AFB1 concentration between 0.05 ∼ 360 ng·mL-1 with the LOD of 3.5 pg·mL-1. And the PMB selective and sensitive responses to OTA are achieved with a linear range of 0.05 ∼ 420 ng·mL-1 and a LOD of 2.4 pg·mL-1. This biosensor has high sensitivity, selectivity and stability for OTA and AFB1 detection in peanut samples. The approach streamlines the experimental procedure, leading to significantly improve the detection efficiency of mycotoxins. Collectively, this method suggest a novel approach for the detection and monitoring of OTA and AFB1 in food sample.

Coordinating Etching Inspired Synthesis of Fe(OH)3 Nanocages as Mimetic Peroxidase for Fluorescent and Colorimetric Self-Tuning Detection of Ochratoxin A

The development of multifunctional biomimetic nanozymes with high catalytic activity and sensitive response is rapidly advancing. The hollow nanostructures, including metal hydroxides, metal-organic frameworks, and metallic oxides, possess excellent loading capacity and a high surface area-to-mass ratio. This characteristic allows for the exposure of more active sites and reaction channels, resulting in enhanced catalytic activity of nanozymes. In this work, based on the coordinating etching principle, a facile template-assisted strategy for synthesizing Fe(OH)₃ nanocages by using Cu₂O nanocubes as the precursors was proposed. The unique three-dimensional structure of Fe(OH)₃ nanocages endows it with excellent catalytic activity. Herein, in the light of Fe(OH)₃-induced biomimetic nanozyme catalyzed reactions, a self-tuning dual-mode fluorescence and colorimetric immunoassay was successfully constructed for ochratoxin A (OTA) detection. For the colorimetric signal, 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) can be oxidized by Fe(OH)₃ nanocages to form a color response that can be preliminarily identified by the human eye. For the fluorescence signal, the fluorescence intensity of 4-chloro-1-naphthol (4-CN) can be quantitatively quenched by the valence transition of Ferric ion in Fe(OH)₃ nanocages. Due to the significant self-calibration, the performance of the self-tuning strategy for OTA detection was substantially enhanced. Under the optimized conditions, the developed dual-mode platform accomplishes a wide range of 1 ng/L to 5 μg/L with a detection limit of 0.68 ng/L (S/N = 3). This work not only develops a facile strategy for the synthesis of highly active peroxidase-like nanozyme but also achieves promising sensing platform for OTA detection in actual samples.

Development of a Novel Magnetic-Bead-Based Automated Strategy for Efficient and Low-Cost Sample Preparation for Ochratoxin A Detection Using Mycotoxin–Albumin Interaction

The mycotoxin ochratoxin A (OTA) is toxic to humans and frequently contaminates wine and beer. Antibodies are essential recognition probes for the detection of OTA. However, they have several drawbacks, such as high costs and difficulty in preparation. In this study, a novel magnetic-bead-based automated strategy for efficient and low-cost OTA sample preparation was developed. Human serum albumin, which is an economical and stable receptor based on the mycotoxin–albumin interaction, was adapted and validated to replace conventional antibodies to capture OTA in the sample. Ultra-performance liquid chromatography–fluorescence detection was used in combination with this preparation method for efficient detection. The effects of different conditions on this method were investigated. The recovery of OTA samples spiked at three different concentrations ranged from 91.2% to 102.1%, and the relative standard deviations (RSDs) were 1.2%–8.2% in wine and beer. For red wine and beer samples, the LODs were 0.37 and 0.15 µg/L, respectively. This reliable method overcomes the drawbacks of conventional methods and offers significant application prospects.