Magnetically Reusable and Well-dispersed Nanoparticles for Oxygen Detection in Water.

In this study, we aimed to synthesize magnetically well-dispersed nanosensors for detecting dissolved oxygen (DO) in water, and explore their biological applications. Firstly, we synthesized two kinds of magnetic nanoparticle with average sizes of approximately 82 nm by one-step emulsion polymerization: polystyrene magnetic nanoparticles (Fe3O4@Os1-PS) and polymethylmethacrylate magnetic nanoparticles (Fe3O4@Os1-PMMA). Both types of nanoparticle present good dispersibility and fluorescence stability. The nanoparticles could be used as oxygen sensors that exhibited a high DO-sensitivity response in the range 0-39.30 mg/L, with a strong linear relationship. The nanoparticles have good magnetic properties, and so they could be recycled by magnet for further use. Recovered Fe3O4@Os1-PS still presented high stability after continued use in oxygen sensing for one month. Furthermore, Fe3O4@Os1-PS was employed for detecting the bacterial oxygen consumption of Escherichia coli (E-coli) to monitor the metabolism of bacteria. The results show that Fe3O4@Os1-PS provide high biocompatibility and non-toxicity. Polystyrene magnetic nanoparticles therefore present significant potential for application in biological oxygen sensing.

A Dual pH/O2 Sensing Film Based on Functionalized Electrospun Nanofibers for Real-Time Monitoring of Cellular Metabolism.

Real-time monitoring of dissolved oxygen (DO) and pH is of great significance for understanding cellular metabolism. Herein, a dual optical pH/O2 sensing membrane was prepared by the electrospinning method. Cellulose acetate (CA) and poly(ε-caprolactone) (PCL) nanofiber membrane blended with platinum (II)-5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorophenyl)-porphyrin (PtTFPP) was used as the DO sensing matrix, upon which electrospun nanofiber membrane of chitosan (CS) coupled with fluorescein 5-isothiocyanate (FITC) was used as the pH sensing matrix. The electrospun sensing film prepared from biocompatible biomaterials presented good response to a wide range of DO concentrations and physiological pH. We used it to monitor the exracellular acidification and oxygen consumption levels of cells and bacteria. This sensing film can provide a luminescence signal change as the DO and pH change in the growth microenvironment. Due to its advantages of good biocompatibility and high stability, we believe that the dual functional film has a high value in the field of biotechnology research.