Surface functionalized magnetic iron oxide nanoparticles (NPs) are a kind of novel functional materials, which have been widely used in the biotechnology and catalysis. This review focuses on the recent development and various strategies in preparation, structure, and magnetic properties of naked and surface functionalized iron oxide NPs and their corresponding application briefly. In order to implement the practical application, the particles must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of iron oxide NPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The problems and major challenges, along with the directions for the synthesis and surface functionalization of iron oxide NPs, are considered. Finally, some future trends and prospective in these research areas are also discussed.

The blood–brain barrier (BBB) is a critical biological structure that prevents damage to the brain and maintains its bathing microenvironment. However, this barrier is also the obstacle to deliver beneficial drugs to treat CNS (central nervous system) diseases. Many efforts have been made for improvement of delivering drugs across the BBB in recent years to treat CNS diseases. In this review, the anatomical and functional structure of the BBB is comprehensively discussed. The mechanisms of BBB penetration are summarized, and the methods and effects on increasing BBB permeability are investigated in detail. It also elaborates on the physical, chemical, biological and nanocarrier aspects to improve drug delivery penetration to the brain and introduces some specific drug delivery effects on BBB permeability.

No abstract

Nitrite (NO 2 − ) has been extensively applied in agricultural and industrial products and is often found in various foodstuff, tap water, biological samples and environmental systems. However, NO 2 − as a toxic contaminant probably threaten the human health by producing highly carcinogenic N-nitrosamines. Compared with the traditional analytical techniques, electroanalytical method has considerable advantages such as cost-effective, rapidness, facile operation, and easy miniaturization. Graphene nanocomposites have significant synergistic electrocatalytic effect toward the nitrite redox, which could eventually amplify the electrochemical response signals, and improve the selectivity, sensitivity, and practicability for the nitrite detection in various real samples. The recent developments on graphene-based nitrite electrochemical sensors are reviewed from the view of sensing materials, including graphene, metal nanoparticle/graphene composites, nanostructured metal compound/graphene composites, polymer/graphene composites, MOF/graphene composites, enzyme/graphene composites, MWCNT/graphene composites, and electron mediator/graphene composites. Moreover, the sensing performances including detection ranges, limit of detection (LOD) and sensitivity are tabulated. Finally, the major drawbacks, opportunities and challenges of graphene-based nitrite electrochemical sensors are also discussed.

Air-stable nanoparticles of Fe3O4/Au were prepared via sonolysis of a solution mixture of hydrogen tetrachloroaureate(III) trihydrate (HAuCl4) and (3-aminopropyl)triethoxysilane (APTES)-coated Fe3O4 nanoparticles with further drop-addition of sodium citrate. The Fe3O4/Au nanoparticles were characterized by x-ray powder diffraction (XRD), ultraviolet–visible spectroscopy (UV–vis), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS) and superconducting quantum interference device (SQUID) magnetometry. Nanoparticles of Fe3O4/Au obtained under appropriate conditions possess a very high saturation magnetization of about 63 emu g−1 and their average diameter is about 30 nm.