Effect of carrier materials on the properties of the andrographolide solid dispersion

Abstract In the work the andrographolide (AG)-solid dispersions (SDs) were prepared by the spray-drying method, using polyethylene glycol 8000 (PEG8000), Poloxamer188, polyvinylpyrrolidone K30 (PVPK30), Soluplus® as carrier materials. The effect of different polymers as carrier materials on the properties of the AG-SDs were studied. The results showed obvious differences in intermolecular interaction, thermal stability, drug state, powder properties, dissolution behavior, and so on of AG-SDs prepared using different polymers as carrier materials. AG-PEG8000-SD was a partial-crystalline and partial-amorphous powder with smaller surface area and pore volume, but it was easy to wetting and did not swell in contact with dissolved medium. AG-Soluplus®-SD was completely amorphous powder with larger specific surface area and pore volume, but it swelled in contact with water. Therefore, the dissolution profile of AG in AG-PEG8000-SD was similar to that in AG-Soluplus®-SD. Soluplus® and PEG8000 were suitable polymers to design AG-SDs, considering both physicochemical properties and dissolution behaviors. The results of this reseach showed that when selecting carrier materials for SD, we should not only consider the state of drugs in SD and the powder properties of SD, but also consider whether there is swelling when the carrier materials are in contact with the dissolution medium.

Cloning of the Bacillus thuringiensis serovar sotto chitinase (Schi) gene and characterization of its protein

Chitinase plays a positive role in the pathogenicity of Bacillus thuringiensis to insect pests. We used touchdown PCR to clone the chitinase (Schi) gene from Bacillus thuringiensis serovar sotto (Bt sotto) chromosomal DNA. Our DNA sequencing analysis revealed that the Bt sotto Schi gene consists of an open reading frame (ORF) of 2067 nucleotides with codes for the chitinase precursor. We also found that the putative promoter consensus sequences (the -35 and -10 regions) of the Bt soto Schi gene are identical to those of the chiA71 gene from Bt Pakistani, the chiA74 gene from Bt kenyae and the ichi gene from Bt israelensis. The Schi chitinase precursor is 688 amino acids long with an estimated molecular mass of 75.75 kDa and a theoretical isoelectric point of 5.74, and contains four domains, which are, in sequence, a signal peptide, an N-terminal catalytic domain, a fibronectin type III like domain and a C-terminal chitin-binding domain. Sequence comparison and the evolutionary relationship of the Bt sotto Schi chitinase to other chitinase and chitinase-like proteins are also discussed