In this paper, we report the preparation by the sol-gel technique of organic-inorganic hybrid composites containing the biopolymer chitosan incorporated in a siloxane-based inorganic network. The hybrid xerogels were transformed into porous silica particles by elimination of the organic phase. Surface characteristics of the silica samples can be easily tailored. In this way Brunauer-Emmett-Teller areas, pore volume, and pore diameter of the prepared silica can be predetermined within a wide range. Morphology of the particles at longer length scales can be designed to obtain either irregularly shaped particles with layered morphology or spherical particles. The results are explained on the basis of the cationic polyelectrolytic properties of chitosan, which allows easy association with siloxane oligomers, the precursors of silica in forming hybrid nanocomposites.

Mesoporous titania with a large surface area has been prepared by calcination of hybrid composites. The composites were obtained by the incorporation of the biopolymer chitosan in titania networks produced from titanium isopropoxide by a sol-gel process. The resultant titania is of the pure anatase form. The effect of the experimental variables on the product's characteristics are studied.

Conclusions Female newborn infants have higher total and subcutaneous AT, but similar internal abdominal AT compared to males. Longitudinal study is required to assess gender specific alterations in AT distribution during infancy and childhood, and may identify possible influences of internal abdominal AT development in males.