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The functionalization of nanoparticles is important to improve their oxidation resistance, prevent agglomeration and improve stability of colloids. However, capping magnetic nanoparticles with a stable ultrathin layer of organic or inorganic materials, without compromising magnetic properties, is still a challenge. In this paper, we report for the first time a novel approach to prepare magnetite (Fe 3 O 4) nanoparticles with superior thermal stability by capping them with a thin shell of silicon carbide (SiC), using sonochemical degradation of dimethyldichloro silane (DMDCSi). The synthesized silicon carbide capped Fe 3 O 4 nanoparticles are characterized using Fourier transform infrared (FT-IR) spectroscopy, and thermogravimetric analyzer. FTIR analysis confirms the hydrophilic SiC capping over the Fe 3 O 4 nanoparticles. The influence of silicon carbide capping over magnetic property and crystal structure was analyzed by vibrating sample magnetometer (VSM) and X-ray diffractometer (XRD) measurements, respectively. The possible mechanism of SiC capping over the particles is explained. SiC capped particles are hydrophilic in nature, where water molecules dissociate spontaneously on the surface of the SiC layer and form Si–OH and electropositive Si atom stabilizes the surface dangling bonds and reduces surface energy. The SiC-capped particles showed better thermal stability with an increased magnetic γ-Fe 2 O 3 to the non-magnetic α-Fe 2 O 3 phase transition temperature of >167 °C as compared to bare particles. The enhancement of phase transition temperature in SiC capped Fe 3 O 4 is due to the increased activation energy by effective binding of SiC with the surface oxidized γ-Fe 2 O 3 layer and the formation of an oxidized passive layer that acts as a thermal barrier. The results suggest that the surface oxidized maghemite (γ-Fe 2 O 3) content over the Fe 3 O 4 particles surface can improve SiC adsorption and enhance their phase stability significantly. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Polylactide (PLA) polymer particles entrapping tetanus toxoid (TT) were evaluated in terms of particle size, antigen load, dose and additional adjuvant for achieving high and sustained anti-TT antibody titer from single point intramuscular immunization. Admixture of polymer entrapped TT and alum improved the immune response in comparison to particle-based immunization. High and long lasting antibody titer was achieved upon immunization with 2–8μm size particles. Microparticles within the size range 50–150μm elicited very low serum antibody response. Immunization with very small particles (<2μm) and with intermediate size range particles (10–70μm) elicited comparable antibody response from single point immunization but lower in comparison to that achieved while immunizing with 2–8μm size particles. Potentiation of antibody response on immunization of admixture of microparticles and alum was also dependent on particle size. These results indicate the need of optimal particle sizes in micron ranges for improved humoral response from single point immunization. Increasing antigen load on polymer particles was found to have positive influence on generation of antibody titers from particle based immunization. Maximum peak antibody titer of ∼300μg/mL was achieved on day 50 upon immunization with particles having highest load of antigen (94μg/mg of polymer). Increase in dose of polymer entrapped antigen resulted in concomitant increase in peak antibody titers indicating the importance of antigen stability, particle size and load on generating reproducible immune response. Optimization of particle size, antigen load, dose and use of additional adjuvant resulted in high and sustained anti-TT antibody titers over a period of more than 250 days from single point immunization. Serum anti-TT antibody titers from single point immunization of admixrure of PLA particles and alum was comparable with immunization from two divided doses of alum adsorbed TT. [Copyright &y& Elsevier]

Abstract: Enzymatic synthesis of α-32P and α-33P labelled deoxyribonucleotides involves the transfer of radiolabelled phosphorus from either γ-32P adenosine triphosphate (γ-ATP) or γ-32P guanosine triphosphate (γ-GTP). Subsequent removal of these ribonucleotides is essential for the preparation of chemically pure deoxyribonucleotides. Agarose-phenyl boronate columns, which bind specifically to cis-diol moieties, have been used for the removal of ribonucleotide contaminants. However, this involves column losses and additional radiation exposure. In the present work we describe a chemical method for the improvement of the chemical purity, based on the preferential oxidation of ribose sugars by periodate. The cis-diol moiety of ribose is specifically oxidised to the dialdehyde. The excess periodate ions were destroyed using ethylene glycol. The phosphate group was then cleaved by β-elimination using alkali. The product was purified using anion exchange chromatography. The efficiency of the process was validated using tracer γ-32P ATP and α-32P dATP. Samples at various steps were analysed by TLC, autoradiography and HPLC. During the process ATP is oxidised whereas 2′-deoxyadenosine triphosphate (dATP) remains intact. The α-32P dATP synthesized by this process was assayed for its incorporation in λ-DNA by the random priming method and was found to be effectively incorporated. The process developed is an efficient and convenient method for the preparation of chemically pure deoxyribonucleotides. [Copyright &y& Elsevier]