Preparation and stabilization of x-ray amorphous solid state structure of salbutamol sulfate adsorbed on mesoporous silica

Abstract

The main objective of this study was to focus on the preparation of X-ray amorphous salbutamol sulfate (SS) with mesoporous silica (S244 silica) carrier by using incipient wetness impregnation approach and further investigated on the utilization of poly (vinylpyrrolidone) (PVP) K12 for the stabilization of amorphous produced. Initially, SS was prepared in solution state and later loaded on S244 silica. The output product showed the non-ordered arrangement of SS with the longer interconversion time to crystalline when comparing with ground amorphous SS. It should be explained that SS was located on the silica surface randomly with no molecular packing according to hydrogen-bonding and weak attractive forces. The molecular mobility was then slower than non-ordered amorphous ground SS. Therefore, the more stable X-ray amorphous SS was gained. PVP K12, short chain vinyl polymer, was utilized as a model polymer for amorphous stabilization. It provided an adverse effect for X-ray amorphous SS adsorbed on S244 silica. The PVP K12 concentration 5 to 30% w/w of drug obviously accelerated the crystalline form formation on the S244 silica surface. Meanwhile, the lower concentration 0.1-1% w/w showed comparable result on the amorphous interconversion rate to that of the control (product not contain PVP K12). This finding contradicted to several previous reported that showed the positive effect of higher concentration of polymer on the retardation of amorphous interconversion. It might be due to the degree of competitiveness on the surface adsorption of silica surface and PVP K12 or SS molecule.