Octadecyltrichlorosilane Incorporated Alginate Micro-granules as Sustained-Release Carriers for Small Hydrophilic Molecules

Hydrogels are excellent drug carriers, but their inability to retain hydrophilic drugs for a prolonged period of time has greatly limited their usage. Research has mostly focused on intricate designs and manipulations of hydrogels to expand their applications in drug delivery. In this study, a simple approach by incorporating a hydrophobic agent, octadecyltrichlorosilane (OTS), to alginate hydrogel micro-granules (Alg-Ms), was investigated as an effective technique to prolong the release of small hydrophilic drugs. Sodium benzoate (SB), a highly water-soluble antimicrobial and anti-inflammatory compound, was used as a model drug. The presence of hydrophobic OTS impeded swelling of these OTS incorporated Alg-Ms (OTS-Alg-Ms), hence sustaining the release of SB. The release data was fitted with Ritger-Peppas and Peppas-Sahlin models and the results showed that SB released from OTS-Alg-Ms with a higher OTS content was mainly controlled by Fickian diffusion; with a lower OTS content, OTS-Alg-Ms swelled more easily, the combined diffusion and swelling led to a faster SB release. Thus, by simply tuning the OTS concentration in the solution where Alg-Ms were briefly submerged in, a predefined release period, from hours to a few days, of small hydrophilic drugs from these OTS-Alg-Ms could be successfully achieved.