Manipulating formation and drug-release behavior of new sol-gel silica matrix by hydroxypropyl guar gum

To develop biocompatible sol-gel silica matrix for the encapsulation of biomolecules or drugs, a novel watersoluble silica precursor, tetrakis(2-hydroxyethyl) ortho silicates (THEOS), was used in combination with a water-soluble polysaccharide derivative, hydroxypropyl guar gum (HPGG). We found that the introduction of HPGG could trigger and accelerate the sol-gel transition of THEOS in water and induce rapid formation of homogeneous gel matrix without the addition of any organic 'solvents or catalysts. Moreover, added HPGG macromolecules had a great influence on the network structure and particle dimension in the silica gel matrix, as confirmed by scanning electron microscope (SEM) observation. From the time sweep theological measurements, it was found that a higher HPGG amount could lead to shorter gelation time for the sol-gel transition. From the strain and frequency sweep theological experiments, it was found that the resultant silica matrix containing a higher amount of HPGG exhibited a narrower linear viscoelastic region, a higher dynamic muduli, and greater complex viscosity. In particular, the gel strength of the silica matrix could be modulated by the amount of HPGG. By investigating the controlled release of vitamin B-12 from the sol-gel silica matrixes, a strong dependence of the release profile on the amount of introduced HPGG was observed. In this case, a higher HPGG amount resulted in lower release rate.