Sorption behaviour of tebuconazole on microplastics: kinetics, isotherms and influencing factors.

Microplastics (MPs) and pesticides are two classes of environmental pollutants and have become global challenges. MPs could adsorb substantial environmental pollutants, which may affect their transportation, distribution and cause combination toxicity. Therefore, the study of sorption properties and mechanisms is the basis of the ecological risk assessment of co-exposure of pesticides and MPs. In this research, typical triazole fungicide tebuconazole (TEB) is selected as a model pollutant, and its sorption behaviour was investigated by kinetic and isotherm models. Meanwhile, a series of environmental influencing factors, like pH, salinity, and metals were conducted. Results showed that the sorption of TEB on MPs could reach equilibrium at 24 h, and the sorption capacity followed the order of PA (polyamide) > PS (polystyrene) > PP (polypropylene). The pseudo-second-order model was the most appropriate model to describe kinetic data, and the Freundlich model was well fit for PA sorption isotherms, in contrast the Langmuir model is better for PP and PS. Additionally, the pH of the solution, salinity, and metals have an important effect on sorption. Combined with Fourier Transform Infrared Spectroscopy and environmental influencing factors, the sorption mechanisms were mainly electrostatic interaction and hydrogen bond for PA and PP, and hydrophobic force, intermolecular force, and electrostatic force for PS, respectively.

A smartphone-based fluorospectrophotometer and ratiometric fluorescence nanoprobe for on-site quantitation of pesticide residue.

Cost-effective and user-friendly quantitation at points-of-need plays an important role in food safety inspection, environmental monitoring, and biomedical analysis. This study reports a stand-alone smartphone-based fluorospectrophotometer (the SBS) installed with a custom-designed application (the SBS-App) for on-site quantitation of pesticide using a ratiometric sensing scheme. The SBS can collect fluorescence emission spectra in the wavelength range of 380-760 nm within 5 s. A ratiometric fluorescence probe is facilely prepared by directly mixing the blue-emissive carbon nanodots (the Fe3+-specific fluorometric indicator) and red-emissive quantum dots (the internal standard) at a ratio of 11.6 (w/w). Based on the acetylcholinesterase/choline oxidase dual enzyme-mediated cascade catalytic reactions of Fe2+/Fe3+ transformation, a ratiometric fluorescence sensing scheme is developed. The practicability of the SBS is validated by on-site quantitation of chlorpyrifos in apple and cabbage with a comparable accuracy to the GC-MS method, offering a scalable solution to establish a cost-effective surveillance system for pesticide pollution.

Preparation of Injectable Composite Hydrogels by Blending Poloxamers with Calcium Carbonate-Crosslinked Sodium Alginate.

The effects of calcium carbonate-crosslinked sodium alginate on poloxamer hydrogels have been investigated. The mechanical strength, degradability, and thermal stability of hydrogels were characterized. The chemical and physical crosslinking in the composite hydrogels has resulted in an improvement of the compressive strength and elasticity of the hydrogels. These mixed hydrogels showed improved mechanical properties, elasticity, and stability as well as environmental responsiveness and injectability.

A Smartphone-Based Sensing System for On-Site Quantitation of Multiple Heavy Metal Ions Using Fluorescent Carbon Nanodots-Based Microarrays.

The development of cost-effective and versatile sensing system for simultaneous and rapid quantitation of multiple targets is highly demanded for environmental surveillance, food safety inspection, home healthcare, etc. This work reports on (1) paper-based microarrays relying on fluorescence turn-off of carbon nanodots (CDs) for analyte recognition and (2) a stand-alone smartphone-based portable reader (SBR) installed with a custom-designed APP (SBR-App), which can accurately and reproducibly acquire fluorescence change from the microarray chip, automatically report the results, generate and share the reports via wireless network. Simultaneous detection of Hg2+, Pb2+, and Cu2+ in the Pearl River water samples was achieved with the reported sensing system. End-user operation is limited to pipet samples to the microarray chip, insert the chip to the SBR, and open the SBR-App to acquire an image 5 min after sample introduction. There is no requirement for complicated sample pre-treatment and expensive equipment except for a smartphone. This versatile and cost-effective smartphone-based sensing system featured with reliability and simplicity is ideally suited for user- and eco-friendly point-of-need detection in resource-constrained environments.

Fabrication of Konjac glucomannan-based composite hydrogel crosslinked by calcium hydroxide for promising lacrimal plugging purpose.

Swelling, mechanical strength, flexibility, and toughness are important parameters in hydrogel preparation for application in the human body. Herein, composite hydrogels were prepared using a mix of Konjac glucomannan (KGM), sodium alginate (SA), and polyvinyl alcohol (PVA) cross-linked by calcium hydroxide. The PVA/KGM/SA composite hydrogel showed a suitable swelling ratio and rate, as well as elasticity and flexibility. In addition, the elongation at break was 660.3%, with a breaking strength of 87.25 kPa and a compression modulus of 1.660 MPa. Rheological studies showed that the composite hydrogel was composed of a multiply cross-linked network involving chemical and physical interactions, thereby affecting the elasticity and flexibility of the gel. Interestingly, the composite gel network was reformed when the temperature decreased. In rabbit models of dry eye, the hydrogel effectively maintained the normal tear meniscus height and increased the low tear meniscus area. The results therefore showed that the PVA/KGM/SA gels not only provide a simple, effective, and safe method for the preparation of hydrogels, but also have potential applications in the treatment of dry eye syndrome.

Enhancement of membrane stability on magnetic responsive hydrogel microcapsules for potential on-demand cell separation.

It is of high interest to obtain hydrogel membranes with optimum mechanical stability, which is a prerequisite to the successful fabrication of hydrogel microcapsules for cell separation. In this work, we developed magnetic responsive alginate/chitosan (MAC) hydrogel microcapsules by co-encapsulation of microbial cells and superparamagnetic iron oxide nanoparticles (SPIONs) reacting under a high voltage electrostatic field. We investigated the influence of the molecular weight of chitosan, microcapsules size, and membrane crosslinking time on the swelling behavior of microcapsules as an indicator of stability of the membranes. The results demonstrated that the suitable membrane stability conditions were obtained by a crosslinking of the microspheres with a chitosan presenting a molecular weight of 70kDa for 15-30min resulting in a membrane thickness of approximately 30mm. Considering the need of maintaining the cells inside the microcapsules, fermentation at 37°C and at neutral pH was favorable. Moreover, the MAC microcapsules sizing between 300 and 380µm were suitable for immobilizing Bacillus licheniformis in a 286h multiple fed-bath operation with no leakage of the SPIONs and cells. Overall, the results of this study provided strategies for the rational design of magnetic microcapsules exhibiting suitable mechanical stable membranes.