Preparation and Characterization of Silica Xerogels as Carriers for Drugs

Figures & data

TABLE 1  Composition of the precursors used in the experiments^a

Formulation	Sample notation	TEOS (ml)	Ethanol (ml)	Drug (ml)	water (ml)	HCl (ml)	Ammonia (ml)
acid-catalyzed SiO2+ DD	DD1	9.7	20	2.5	3.6	0.1	0
base-catalyzed SiO2+ DD	DD2	9.7	20	2.5	3.6	0	0.1
acid/base-catalyzed SiO2+ DD	DD3	9.7	20	2.5	3.6	0.1	0.25
acid-catalyzed SiO2+ IB	IB1	9.7	20	2.5	3.63	0.1	0
base-catalyzed SiO2+ IB	IB2	9.7	20	2.5	3.6	0.1	0.1
acid/base-catalyzed SiO2+ IB	IB3	9.7	20	2.5	3.6	0.1	0.25

^aThe concentration of drug in ethanol was 0.01 mM.

TABLE 2  Gelation time, specific surface area, and average pore size of prepared xerogels^a

Sample	Gelation time	Pore size (nm)	Specific surface area (m^2/g)
acid-catalyzed SiO2	9 days	ND	ND
base-catalyzed SiO2	6 days	3.85	670
acid/base-catalyzed SiO2	0.5 hr	2.31	549

^aND, not determined.

FIG. 1  SiO₂ xerogels made by the sol-gel method: (A) acid-catalyzed xerogel, (B) base-catalyzed xerogel, (c) two-step prepared xerogel.

FIG. 2  X-ray diffractograms of the prepared xerogels.

FIG. 3  FTIR spectra of silica xerogel.

FIG. 4  SEM micrographs for (A) acid-catalyzed xerogel, (B) base-catalyzed xerogel, (C) acid/base-catalyzed xerogel.

FIG. 5  Release of Diclofenac and Ibuprofen from silica xerogels obtained in the basic catalysis conditions.

FIG. 6  Release of Diclofenac and Ibuprofen from silica xerogels obtained in the acid/base catalysis conditions.

TABLE 3  Release kinetics parameters

Sample notation	Correlation coefficient	Diffusional coefficient (n)^a
DD2	0.96	0.58
DD3	0.97	0.64
IB2	0.99	0.40
IB3	0.96	0.61

^aSlope of the log M_t/M vs. log t plot.

FIG. 7  Degradation of silica xerogels obtained in the different catalysis conditions.