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In order to trace the origin and evolution of avian infectious bronchitis virus (IBV) isolates in China and Southeast Asia, genomic sequencing was used for molecular characterization of 24 IBV isolates and two reference strains in comparison with the published sequences. The 5' region of the S1 genes, containing hypervariable regions I and II, and 3' region of the nucleocapsid genes, containing cytotoxic T lymphocyte epitopes, were used to construct phylogenetic trees for analysis. The results showed that the 24 isolates could be divided into three distinct groups, that is, American, Asian, and European. Some isolates formed a distinct Asian phylogenetic group, suggesting that IBV has existed for some time in Asia. Our results also showed that in vivo recombination of IBV may have occurred at a rather high frequency, contributing to the diversity of these IBV isolates. Importantly, recombination events have probably occurred between vaccine strains and field strains in the natural condition.

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Tannin grafted on mesoporous silica nanoparticles (tannin-MSNs) was synthesized by the amidation reaction of carboxyl benzyl borate with amino group modified MSN. Tannin-MSNs were an MCM-41 type of mesoporous material with a uniform diameter of about 150 nm. The XRD and N 2 adsorption/ desorption isotherm results demonstrated that the rhodamine was effectively loaded and the pores of MSN were blocked by tannin. Rhodamine as a model cargo was used to evaluate the loading and releasing behaviors of tannin-MSNs. The drug release rate of tannin-MSNs was pH dependent. An in vitro cellular cytotoxicity test indicated that tannin-MSNs were highly biocompatible and suitable to be used as drug carriers. The cellular uptake was investigated by confocal laser scan microscopy. The results showed that tannin-MSNs are promising platforms to construct a pH-responsive controlled drug delivery system for cancer and stomach therapy.