Magnetite nanoparticles (Fe₃O₄ NPs) are a well proven biocompatible nanomaterial, which hold great promise in various biomedical applications. Interestingly, unlike conventional biocompatible materials (e.g., polyethylene glycol (PEG)) that are chemically and biologically inert in nature, Fe₃O₄ NPs are known to be catalytically active and exhibit prominent physiological effects. Herein, we report an "active", dynamic equilibrium mechanism for maintaining the cellular amenity of Fe₃O₄ NPs. We examined the effects of two types of iron oxide (magnetite and hematite) NPs in rat pheochromocytoma (PC12) cells and found that both induced stress responses. However, only Fe₂O₃ NPs caused significant programmed cell death; whereas Fe₃O₄ NPs are amenable to cells. We found that intrinsic catalase-like activity of Fe₃O₄ NPs antagonized the accumulation of toxic reactive oxygen species (ROS) induced by themselves, and thereby modulated the extent of cellular oxidative stress, autophagic activity, and programmed cell death. In line with this observation, we effectively reversed severe autophagy and cell death caused by Fe₂O₃ NPs via co-treatment with natural catalase. This study not only deciphers the distinct intrinsic antagonism of Fe₃O₄ NPs, but opens new routes to designing biocompatible theranostic nanoparticles with novel mechanisms.

We report a novel nanotechnology-based approach for the highly efficient catalytic oxidation of phenols and their removal from wastewater. We use a nanocomplex made of multi-walled carbon nanotubes (MWNTs) and magnetic nanoparticles (MNPs). This nanocomplex retains the magnetic properties of individual MNPs and can be effectively separated under an external magnetic field. More importantly, the formation of the nanocomplex enhances the intrinsic peroxidase-like activity of the MNPs that can catalyze the reduction of hydrogen peroxide (H₂O₂). Significantly, in the presence of H₂O₂, this nanocomplex catalyzes the oxidation of phenols with high efficiency, generating insoluble polyaromatic products that can be readily separated from water.

A novel nano- and micro-integrated protein chip (NMIPC) that can detect proteins with ultrahigh sensitivity has been fabricated. A microfluidic network (μFN) was used to construct the protein chips, which allowed facile patterning of proteins and subsequent biomolecular recognition. Aqueous phase-synthesized, water-soluble fluorescent CdTe/CdS core-shell quantum dots (aqQDs), having high quantum yield and high photostability, were used as the signaling probe. Importantly, it was found that aqQDs were compatible with microfluidic format assays, which afforded highly sensitive protein chips for cancer biomarker assays.