Synthesis,properties and self‐assembly of intelligent core‐shell nanoparticles based on chitosan with different molecular weight and N‐isopropylacrylamide

In this study, a series of chitosan‐graft‐poly(N‐isopropylacrylamide) (CTS‐g‐PNIPAAm) copolymers based on different molecular weight (Mw) of CTS and NIPAAm were synthesized through the polymerization of NIPAAm in an acid aqueous solution. The structures were verified by Fourier transform infrared and nuclear magnetic resonance. The influence of the CTS Mw on the properties of the resulting copolymers and self‐assembled nanoparticles was fully examined. The grafting ratio and grafting efficiency of the copolymers increased with the CTS Mw. All the copolymers have a similar low critical solution temperature of 33.5°C, which was independent of the CTS Mw. Furthermore, the copolymers were less temperature sensitive, when CTS Mw increased to 200 kDa. Besides, once the CTS Mw increased to 700 kDa, the copolymers were less pH sensitive near the tumor site (from pH 7.4 to 6.8). The copolymers could form uniform nanoparticles once the temperature increased to 34°C, which was reversible. After crosslinking by N,N‐methylenebisacrylamide (MBA), structurally stable nanoparticles could be obtained. The results from Transmission electron microscope (TEM) and Atomic force microscopy (AFM) showed that the MBA crosslinked nanoparticles were uniformly spherical with a loose structure. Surface tension method indicated that the critical aggregate concentrations were 0.045, 0.042, 0.037, and 0.036 mg mL^?1 prepared from CTS 50, 100, 200, and 700 kDa, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Health effects of exposure to nano-TiO2: a meta-analysis of experimental studies

The paper is aimed to investigate the toxicity of nano-TiO₂ and its potential harmful impact on human health using meta-analysis of in vitro and short-time animal studies. Data were retrieved according to included and excluded criteria from 1994 to 2011. The combined toxic effects of nano-TiO₂ were calculated by the different endpoints by cell and animal models. From analysis of the experimental studies, more than 50% showed positive statistical significance except the apoptosis group, and the cytotoxicity was in a dose-dependent but was not clear in size-dependent manner. Nano-TiO₂ was detained in several important organs including the liver, spleen, kidney, and brain after entering the blood through different exposure routes, but the coefficient of the target organs was altered slightly from animal models. It is possible that nano-TiO₂ can induce cell damage related to exposure size and dose. Further studies will be needed to demonstrate that nanoparticles have toxic effects on human body, especially in epidemiological studies.     

Iron-Based Nanozymes in Disease Diagnosis and Treatment

Iron-based nanozymes are currently one of the few clinical inorganic nanoparticles for disease diagnosis and treatment. Overcoming the shortcomings of natural enzymes, such as easy inactivation and low yield, combined with their special nanometer properties and magnetic functions, iron-based nanozymes have broad prospects in biomedicine. This minireview summarizes their preparation, biological activity, catalytic mechanism, and applications in diagnosis and treatment of diseases. Finally, challenges to their future development and the trends of iron-based nanozymes are discussed. The purpose of this minireview is to better understand and reasonably speculate on the rational design of iron-based nanozymes as an increasingly important new paradigm for diagnostics.     

Ultra-small particles of iron oxide as peroxidase for immunohistochemical detection

Dimercaptosuccinic acid (DMSA) modified ultra-small particles of iron oxide (USPIO) were synthesized through a two-step process. The first step: oleic acid (OA) capped Fe(3)O(4) (OA-USPIO) were synthesized by a novel oxidation coprecipitation method in H(2)O/DMSO mixing system, where DMSO acts as an oxidant simultaneously. The second step: OA was replaced by DMSA to obtain water-soluble nanoparticles. The as-synthesized nanoparticles were characterized by TEM, FTIR, TGA, VSM, DLS, EDS and UV-vis. Hydrodynamic sizes and Peroxidase-like catalytic activity of the nanoparticles were investigated. The hydrodynamic sizes of the nanoparticles (around 24.4 nm) were well suited to developing stable nanoprobes for bio-detection. The kinetic studies were performed to quantitatively evaluate the catalytic ability of the peroxidase-like nanoparticles. The calculated kinetic parameters indicated that the DMSA-USPIO possesses high catalytic activity. Based on the high activity, immunohistochemical experiments were established: using low-cost nanoparticles as the enzyme instead of expensive HRP, Nimotuzumab was conjugated onto the surface of the nanoparticles to construct a kind of ultra-small nanoprobe which was employed to detect epidermal growth factor receptor (EGFR) over-expressed on the membrane of esophageal cancer cell. The proper sizes of the probes and the result of membranous immunohistochemical staining suggest that the probes can be served as a useful diagnostic reagent for bio-detection.     

Effective PEGylation of Iron Oxide Nanoparticles for High Performance In Vivo Cancer Imaging

A practical and effective strategy for synthesizing PEGylated superparamagnetic iron oxide nanoparticles (SPIONs) is established. In this strategy, poly(acrylic acid) (PAA) is combined with SPIONs via multiple coordination between the carboxylic groups of PAA and SPIONs, which introduces abundant carboxylic groups, then, α,ω‐diamino PEG is linked to SPIONs via the amidation of the carboxylic groups. The synthesized PEGylated SPIONs exhibit no cytotoxicity and high resistance to phagocytosis by macrophages in vitro as well as low uptake by the liver and spleen in vivo, which makes the SPIONs highly efficient in tumor imaging by magnetic resonance imaging (MRI) at a relatively low dose of SPIONs. These outstanding properties are largely due to the significant shielding effect of the dense PEG coating as well as the net neutral surface of the PEGylated SPIONs in physiological conditions. In summary, the PEGylated SPIONs prepared by this strategy exhibit great application potential in tumor imaging as MRI contrast agents targeting through enhanced permeability and retention (EPR) effect.     

Synthesis,characterization, and application of composite alginate microspheres with magnetic and fluorescent functionalities

Composite alginate microspheres were synthesized via a modified emulsification technique and characterized by inverted optical microscope, transmission electron microscope, ζ‐potential analyzer, UV–vis spectrophotometer, luminescence spectrometer, and vibrating sample magnetometer. The results show that the synthetic parameters including the weight ratio of maghemite nanoparticles to alginate, hydrophile‐lipophile balance (HLB) value, stirring speed, and CaCl₂ dripping rate play important roles in the synthesis of microspheres. Furthermore, the composite alginate microspheres exhibit good superparamagnetism and fluorescence, which can serve both as magnetic resonance contrast agents and optical probes for biological imaging. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Surface properties of encapsulating hydrophobic nanoparticles regulate the main phase transition temperature of lipid bilayers: A simulation study

The main phase transition temperature of a lipid membrane, which is vital for its biomedical applications such as controllable drug release, can be regulated by encapsulating hydrophobic nanoparticles into the membrane. However, the exact relationship between surface properties of the encapsulating nanoparticles and the main phase transition temperature of a lipid membrane is far from clear. In the present work we performed coarse-grained molecular dynamics simulations to meet this end. The results show the surface roughness of nanoparticles and the density of surface-modifying molecules on the nanoparticles are responsible for the regulation. Increasing the surface roughness of the nanoparticles increases the main phase transition temperature of the lipid membrane, whereas it can be decreased in a nonlinear way via increasing the density of surface-modifying molecules on the nanoparticles. The results may provide insights for understanding recent experimental studies and promote the applications of nanoparticles in controllable drug release by regulating the main phase transition temperature of lipid vesicles.