Sustained Release of Risedronate from PLGA Microparticles Embedded in Alginate Hydrogel for Treatment of Bony Lesions

Inflammatory bone resorption in periodontitis can lead to tooth loss. Systemic administration of bisphosphonates such as risedronate for preventing bone resorption can cause adverse effects. Alginate hydrogel (ALG) and poly (lactic acid-co-glycolic acid) (PLGA) microparticles have been studied as drug delivery systems for sustained release of drugs. Therefore, the release pattern of risedronate from PLGA microparticles embedded with ALG was studied as a drug delivery system for sustained release of the drug, which can be used in local administrations.

Risedronate-containing PLGA microparticles were fabricated using double emulsion solvent evaporation technique. Ionic cross-linking method was used to fabricate risedronate-loaded ALG. Risedronate-containing PLGA microparticles were then coated with ALG. The calibration curve of risedronate was traced to measure encapsulation efficiency (EE) and study the release pattern. Scanning electron microscope (SEM) imaging was carried out, and cell toxicity was examined using MTT assay. Statistical analysis of data was carried out using SPSS ver. 20 software, via one-way ANOVA and Tukey’s tests.  

SEM imaging showed open porosities on ALGs. The mean EE of PLGA microparticles for risedronate was 57.14 ± 3.70%. Risedronate released completely after 72 h from ALG, and the cumulative release was significantly higher (p = 0.000) compared to PLGA microspheres coated with ALG, which demonstrated sustained released of risedronate until day 28. Risedronate-loaded ALG showed a significant decrease in gingival fibroblasts cell viability (p < 0.05).

Alginate-coated PLGA microspheres could release risedronate in a sustained and controlled way and also did not show cell toxicity. Therefore, they seem to be an appropriate system for risedronate delivery in local applications