Facile synthesis of monodisperse chromogenic amylose-iodine nanoparticles as an efficient broad-spectrum antibacterial agent.

The famous chromogenic reaction between starch and iodine has been widely used for chemical analysis since its first discovery in the year of 1814 while it is seldom utilized in biomedical applications. Inspired by their high iodine content and strong optical absorbance in the near infrared (NIR) region, monodisperse amylose-iodine nanoparticles (AM-I NPs), synthesized by simple mixing of amylose NPs and KI-I2 solutions, were explored as a new class of high-performance antibacterial agent. Benefiting from the broad-spectrum antibacterial property of iodine and photothermal effect of the amylose-iodine complex, the obtained AM-I NPs exhibited an excellent photothermal-enhanced sterilization effect for both Gram-negative Escherichia coli (E. coli) and Gram-positive methicillin-resistant Staphylococcus aureus (MRSA). For instance, upon incubation with AM-I NP suspensions (30 µg mL-1) plus NIR laser irradiation (808 nm, 1.33 W cm-2, 5 min), the relative survival rates of E. coli and MRSA were only 1.2% and 1.7%, respectively. In addition, the AM-I NPs depicted better biocompatibility in vitro than that of KI-I2 solution, indicating their safety for potential biomedical applications in vivo. This proof-of-concept study revealed the antibacterial applications of a traditional starch-iodine complex and is expected to provide insights into the design and development of efficient broad-spectrum antibacterial agents.

Liquid Exfoliation of Atomically Thin Antimony Selenide as an Efficient Two-Dimensional Antibacterial Nanoagent.

The ever-growing global crisis of multidrug-resistant bacteria has triggered a tumult of activity in the design and development of antibacterial formulations. Here, atomically thin antimony selenide nanosheets (Sb2Se3 NSs), a minimal-toxic and low-cost semiconductor material, were explored as a high-performance two-dimensional (2D) antibacterial nanoagent via a liquid exfoliation strategy integrating cryo-pretreatment and polyvinyl pyrrolidone (PVP)-assisted exfoliation. When cultured with bacteria, the obtained PVP-capped Sb2Se3 NSs exhibited intrinsic long-term antibacterial capability, probably due to the reactive oxygen species generation and sharp edge-induced membrane cutting during physical contact between bacteria and nanosheets. Upon near-infrared laser irradiation, Sb2Se3 NSs achieved short-time hyperthermia sterilization because of strong optical absorption and high photothermal conversion efficiency. By virtue of the synergistic effects of these two broad-spectrum antibacterial mechanisms, Sb2Se3 NSs exhibited high-efficiency inhibition of conventional Gram-negative Escherichia coli, Gram-positive methicillin-resistant Staphylococcus aureus, and wild bacteria from a natural water pool. Particularly, these three categories of bacteria were completely eradicated after being treated with Sb2Se3 NSs (300 µM) plus laser irradiation for only 5 min. In vivo wound healing experiment further demonstrated the high-performance antibacterial effect. In addition, Sb2Se3 NSs depicted excellent biocompatibility due to the biocompatible element constitute and bioinert PVP modification. This work enlightened that atomically thin Sb2Se3 NSs hold great promise as a broad-spectrum 2D antibacterial nanoagent for various pathogenic bacterial infections.

[Predicting soil salinity based on spectral symmetry under wet soil condition].

There has been a growing interest in using spectral reflectance as a rapid and inexpensive tool for soil salinity monitoring in recent years. However, since soil moisture often exerts a tremendous influence on soil reflectance, the monitoring accuracy under various moisture conditions cannot fully satisfy the requirements of agricultural practice. In the present paper, a linear model was built to relate the spectral symmetry in the band of 1 370 - 1 610 nm with the salt content and moisture content of the saline soil based on regularly measured data of reflectance, soil moisture and salt content of the surface of 5 soil columns during the simulated evaporation process in laboratory. The results showed that the model was good with r greater than 0.8. By inversing the model, soil salt content then was predicted after moisture content was determined. The results showed that the prediction accuracy was acceptable with a root mean square error (RMSE) of 2.059 g x kg(-1) and an r of 0.656. The results demonstrated the feasibility of using spectral symmetry to predict soil salt content under various moisture conditions.