Magnetic mesoporous silica nanoparticles: fabrication and their laccase immobilization performance.

Newly large-pore magnetic mesoporous silica nanoparticles (MMSNPs) with wormhole framework structures were synthesized for the first time by using tetraethyl orthosilicate as the silica source and amine-terminated Jeffamine surfactants as template. Iminodiacerate was attached on these MMSNPs through a silane-coupling agent and chelated with Cu(2+). The Cu(2+)-chelated MMSNPs (MMSNPs-CPTS-IDA-Cu(2+)) showed higher adsorption capacity of 98.1 mg g(-1)-particles and activity recovery of 92.5% for laccase via metal affinity adsorption in comparison with MMSNPs via physical adsorption. The Michaelis constant (K(m)) and catalytic constant (k(cat)) of laccase immobilized on the MMSNPs-CPTS-IDA-Cu(2+) were 3.28 mM and 155.4 min(-1), respectively. Storage stability and temperature endurance of the immobilized laccase on MMSNPs-CPTS-IDA-Cu(2+) increased significantly, and the immobilized laccase retained 86.6% of its initial activity after 10 successive batch reactions operated with magnetic separation.

Spontaneous vesicle formation of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer.

A novel method has been developed to prepare vesicles from aqueous solutions of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer, by adding anionic surfactant sodium dodecyl sulfate (SDS) and inorganic salt NaF. As determined by TEM and dynamic light scattering (DLS) measurements, the average diameter of vesicles is about 800 nm having 50 nm outer shell thickness. Identifying hydrophobic interactions between the block copolymers and the microenvironments around the vesicles using FTIR, 1H NMR, and fluorescence spectroscopy techniques revealed the vesicle formation mechanism. The spontaneously formed vesicles were further cross-linked by converting the terminal hydroxyl groups of block copolymers into aldehydes, and then chemically bridging the polymer chains by the reaction between aldehydes and diamine compounds. The cross-linked vesicles are proved much more stable than free vesicles even at higher dilutions. The obtained vesicles with good stability and biocompatibility are promising candidates for widespread applications.

Temperature-responsive magnetite/PEO-PPO-PEO block copolymer nanoparticles for controlled drug targeting delivery.

In this study, temperature-responsive magnetite/polymer nanoparticles were developed from iron oxide nanoparticles and poly(ethyleneimine)-modified poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymer. The particles were characterized by TEM, XRD, DLS, VSM, FTIR, and TGA. A typical product has an approximately 20 nm magnetite core and an approximately 40 nm hydrodynamic diameter with a narrow size distribution and is superparamagnetic with large saturation magnetization (51.34 emu/g) at room temperature. The most attractive feature of the nanoparticles is their temperature-responsive volume-transition property. DLS results indicated that their average hydrodynamic diameter underwent a sharp decrease from 45 to 25 nm while evaluating the temperature from 20 to 35 degrees C. The temperature-dependent evolution of the C-O stretching band in the FTIR spectra of the aqueous nanoparticles solution revealed that thermo-induced self-assembly of the immobilized block copolymers occurred on the magnetite solid surfaces, which is accompanied by a conformational change from a fully extended state to a highly coiled state of the copolymer. Consequently, the copolymer shell could act as a temperature-controlled "gate" for the transit of guest substance. The uptake and release of both hydrophobic and hydrophilic model drugs were well controlled by switching the transient opening and closing of the polymer shell at different temperatures. A sustained release of about 3 days was achieved in simulated human body conditions. In primary mouse experiments, drug-entrapped magnetic nanoparticles showed good biocompatibility and effective therapy for spinal cord damage. Such intelligent magnetic nanoparticles are attractive candidates for widespread biomedical applications, particularly in controlled drug-targeting delivery.