"The morphology of ordered mesoporous silica materials might also play an important role in the drug adsorption and release. Zhao and co-workers   found that rod-like SBA-15 (about 1–2 μm in length) had a faster adsorption rate and immobilized larger amount of enzymes than rope-like SBA-15 (20 μm in length). They proposed that pore-mouth amounts on the external surface increased with the decrease of particle size of mesoporous silica, which led to the different adsorption behavior of mesoporous materials. "
[Show abstract][Hide abstract] ABSTRACT: Mesoporous silica spheres with controllable particle size were synthesized in mixed ethanol–water solvent. These materials possessed same pore size distribution and pore channel geometry. The amount of ibuprofen (IBU) adsorbed in mesoporous channels increased with the surface area of mesoporous silica spheres. Three kinds of release fluids, simulated intestinal fluid (SIF, pH=7.4), simulated body fluid (SBF, pH=7.4), and simulated gastric fluid (SGF, HCl aqueous solution, pH=1.2) were used to investigate drug release. The effects of particle size and dispersancy of mesoporous spheres on drug release rate were discussed in detail. It was found that larger or agglomerate mesoporous silica spheres could delay the drug release process, which could be attributed to pore-mouth amount and mesopore channel length of mesoporous spheres. Furthermore, to obtain a well controlled drug release system, hydrophobic trimethylsilyl (TMS) groups were functionalized on the surface of mesoporous silica spheres. The release of IBU from TMS-functionalized mesoporous spheres was obviously delayed with the increase of TMS content.
"Up to now, little report has employed this rigorously shaking condition for the stability test. Most of the researchers just incubated the samples in a static non-shaking condition for the evaluation of the stability of immobilized enzymes in mesoporous silica (Díaz and Balkus, 1996; Fan et al., 2003a, 2003b; Han et al., 1999, 2002; Takahashi et al., 2000 "
[Show abstract][Hide abstract] ABSTRACT: alpha-chymotrypsin (CT) and lipase (LP) were immobilized in hierarchically-ordered mesocellular mesoporous silica (HMMS) in a simple but effective way for the enzyme stabilization, which was achieved by the enzyme adsorption followed by glutaraldehyde (GA) crosslinking. This resulted in the formation of nanometer scale crosslinked enzyme aggregates (CLEAs) entrapped in the mesocellular pores of HMMS (37 nm), which did not leach out of HMMS through narrow mesoporous channels (13 nm). CLEA of alpha-chymotrypsin (CLEA-CT) in HMMS showed a high enzyme loading capacity and significantly increased enzyme stability. No activity decrease of CLEA-CT was observed for 2 weeks under even rigorously shaking condition, while adsorbed CT in HMMS and free CT showed a rapid inactivation due to the enzyme leaching and presumably autolysis, respectively. With the CLEA-CT in HMMS, however, there was no tryptic digestion observed suggesting that the CLEA-CT is not susceptible to autolysis. Moreover, CLEA of lipase (CLEA-LP) in HMMS retained 30% specific activity of free lipase with greatly enhanced stability. This work demonstrates that HMMS can be efficiently employed as host materials for enzyme immobilization leading to highly enhanced stability of the immobilized enzymes with high enzyme loading and activity.
Biotechnology and Bioengineering 02/2007; 96(2):210-8. DOI:10.1002/bit.21107 · 4.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: With their hollow morphology and large openings, the as-synthesized porous silica nano-tubes (NTPS), prepared through a sol-gel routine by using nano-sized needle-shaped CaCO3 particles as templates, were used as host for enzyme immobilization. Bioimmobilization study showed that enzyme molecules could not only be adsorbed on the external surface of NTPS but also entrapped in their inner hollow cores, leading to higher enzyme loading capacities of NTPS (more than 350 mg/g silica) in a shorter time, as compared to common porous silica (less than 50 mg/g) and most conventional mesoporous silica materials (less than 100 mg/g).
China Particuology 12/2004; 2(6):270-273. DOI:10.1016/S1672-2515(07)60073-6 · 1.10 Impact Factor
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