2D MOF-enhanced SPR sensing platform: Facile and ultrasensitive detection of Sulfamethazine via supramolecular probe.

Sulfamethazine (SMZ) is widely present in the environment and can cause severe allergic reactions and cancer in humans. Accurate and facile monitoring of SMZ is crucial for maintaining environmental safety, ecological balance, and human health. In this work, a real-time and label-free surface plasmon resonance (SPR) sensor was devised using a two-dimensional metal-organic framework with superior photoelectric performance as an SPR sensitizer. The supramolecular probe was incorporated at the sensing interface, allowing for the specific capture of SMZ from other analogous antibiotics through host-guest recognition. The intrinsic mechanism of the specific interaction of the supramolecular probe-SMZ was elucidated through the SPR selectivity test in combination with analysis by density functional theory, including p-π conjugation, size effect, electrostatic interaction, π-π stacking, and hydrophobic interaction. This method facilitates a facile and ultrasensitive detection of SMZ with a limit of detection of 75.54 pM. The accurate detection of SMZ in six environmental samples demonstrates the potential practical application of the sensor. Leveraging the specific recognition of supramolecular probes, this direct and simple approach offers a novel pathway for the development of novel SPR biosensors with outstanding sensitivity.

Immobilization for Lipase: Enhanced Activity and Stability by Flexible Combination and Solid Support.

In this study, an enhanced activity and stability method for immobilizing porcine pancreatic lipase (PPL) was developed based on ZIF-8 encapsulated supramolecular-modified gold nanoparticle complexes (pSC4-AuNPs@ZIF-8). Supramolecular calix[4]arene (pSC4) can recognize the amino group of PPL through non-covalent force, and this flexible binding method protected the structure of PPL during the immobilization process. Due to the hydrophilic of pSC4-AuNPs and hydrophobic of ZIF-8, PPL can maintain a "lid open" conformation, which can enhance the stability of PPL structure and reduce PPL activity loss. ZIF-8 was used to immobilize PPL to avoid the difficult recovery of free PPL. Compared with the native form of PPL, it exhibited 70.6% maintained activity with terrific pH and temperature stability, and had good performance in thermal stability, time stability, and reusability. In addition, three immobilized PPL methods were designed to further clarify the influence of synthetic methods and additives on the activity and stability of PPL. Importantly, the loading rate of pSC4-AuNPs@ZIF-8@PPL was up to 51.2% among these immobilized PPL systems. Therefore, pSC4-AuNPs@ZIF-8 may serve as a versatile and promising immobilization system for enzymes.

Electrochemical sensor for ultrasensitive detection of paraquat based on metal-organic frameworks and para-sulfonatocalix[4]arene-AuNPs composite.

The widespread occurrence of pesticides in surface water, groundwater, soil, and food has received increasing attention towards environmental safety. Paraquat (PQ) is world widely used as a rapid sterilant herbicide and is highly toxic to humans. A simple, rapid, sensitive, and on-site detection method for the water environment to detection of PQ is urgently required. Here, we prepared a zeolite imidazole skeleton-8 (ZIF-8) and para-sulfonylcalix[4]arene (pSC4) coated gold nanoparticles composite (pSC4-AuNPs@ZIF-8) by one-step method. An electrochemical biosensor assay for PQ was established based on pSC4-AuNPs@ZIF-8 modified glassy carbon electrode through host-guest recognition of PQ and pSC4. Under the optimal conditions, recoveries of targets determination results were 92.7%-103% (n = 3), respectively. The quantity PQ detection limit was found to be 0.49 pM. Therefore, the signal amplification strategy based on pSC4-AuNPs@ZIF-8 has potential value in detecting trace pollutants in the water environment.

Colorimetric detection of sulfamethazine based on target resolved calixarene derivative stabilized gold nanoparticles aggregation.

Sulfamethazine (SMZ) is one of the most used broad-spectrum antibiotics owing to its low cost and high efficacy towards bacterial diseases. This workreports a novel label-free SMZ sensor based on para-sulfonatocalix[4]arene (pSC4) capped gold nanoparticles (pSC4-AuNPs) for colorimetric detection through the host-guest interaction. The existence of SMZ resulted in the aggregation of pSC4-AuNPs and can be observed through colorimetric assay. A good linear relationship in the range 2.5 ~ 20 nM was obtained with a correlation coefficient of 0.9908. The limit of detection for SMZ was 1.39 nM. High recoveries (90.18-107.06%) were obtained, and RSD ranged from 1.21 to 2.05%. The color changes can be observed from red to gray within 10 min. Combining the supermolecule's recognition and AuNP's optical performance, the method paves a new, easy, and rapid way for small target sensing.