Synthesis of poly(methyl methacrylate)-block-poly(L-histidine) and its use as a hybrid silver nanoparticle conjugate

Poly[(methyl methacrylate)-block-poly(L-histidine)] (PMMA-b-PHIS) was synthesized by combining atom transfer radical polymerization and living ring-opening polymerization of alpha-amino acid-N-carboxyanhydride. The resulting hybrid block copolymer forms reverse micelles in the mixture solution of water and N,N-dimethylformamide (DMF) and self-assembles into PHIS/PMMA core/shell spheres with controllable size in the range of 80 to 250 nm depending on the micellization temperature. The self-assembly of PMMA-b-PHIS was carried out in H2O/DMF (3/7) mixture in the presence of AgNO3. Reduction of the resulting Ag ions encapsulated inside of the reverse micelles yielded an attractive Ag nanoparticle core/polymer shell conjugate system.     

Chitosan–poly(aminopropyl/phenylsilsesquioxane) hybrid nanocomposite membranes for antibacterial and drug delivery applications

We fabricated hybrid (CSSQ) membranes from chitosan and poly(aminopropyl/phenylsilsesquioxane) (PAPSQ) blends via a sol–gel reaction and solution casting followed by crosslinking with glutaraldehyde. The CSSQ membranes were then used for loading of 5‐fluorouracil (5‐FU) as an anticancer drug as well as templates for the production of silver nanoparticles (AgNPs). The physicochemical properties of the CSSQ membranes were examined using UV‐visible spectroscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis and scanning electron microscopy (SEM). SEM results showed the controllable formation of AgNPs around PAPSQ. CSSQ–Ag nanocomposite membranes exhibited good antibacterial activity towards both Escherichia coli and Bacillus subtilis, while the CSSQ membranes worked as good carriers for controlled release of 5‐FU as model drug. The results suggest that both CSSQ and CSSQ–Ag nanocomposite membranes can be potentially applied for biomedical applications such as controlled release carriers as well as antibacterial wound dressing materials. © 2014 Society of Chemical Industry     

Fabrication of organic shell-covered gold nanospheres with near-infrared absorption

A simple protocol is developed for the fabrication of stable organic shell-covered gold nanospheres with near-infrared absorption characteristics. The designed strategy mainly concentrates on two steps: (i) the polymerization of gold nanoparticles (AuNPs) induced by 1,2-ethanedithiol in water/ethanol; (ii) conjugation of the polymerized AuNPs with marocyclic compound for the formation of the organic shell. In the first step, the 1,2-ethanedithiol containing two thiols towards both ends of the chain enables the successful polymerization of AuNPs due to the forceful appetency of thiols to AuNPs. In the second step, the polymerized AuNPs are covered by the marocyclic compound attributing to the hydrogel-bonding effect between NH and SH. Because of the organic shell, the stability and dispersibility of the obtained nanospheres are improved. The optical properties of the fabricated gold nanospheres (400 nm average diameter) are well investigated by the UV-vis absorption spectroscopy which exhibit intense near-infrared absorption at 972 nm in acetone. The strategy developed in this study is promising in that excellent stability and dispersibility of gold nanospheres can be achieved in a facile and economic way.     

Secondary standard of unit of length: state and development

The state and alternative paths for further improvements in the secondary standard of the unit of length are considered. Problems that may be solved with the use of this standard along with a method of dissemination of the unit of length in the range 1–24 m using laser coordinate-measurement systems are described. Translated from Izmeritel’naya Tekhnika, No. 12, pp. 10–12, December, 2008.