Encapsulation and release of a bacterial carotenoid from hydrogel matrix: Characterization, kinetics and antioxidant study

Abstract

Various natural polymers with hydrophilic properties have been used to form hydrogels for the encapsulation and delivery of nutrients and drugs in food and pharmaceutical industries. Among them, chitosan (ChiHG)- and alginate (AlgHG)- based hydrogels have been extensively explored for delivery of several nutraceuticals in recent years. Release of natural canthaxanthin (CX) obtained from Dietzia maris NITD (accession number: HM151403) has been investigated with emphasis on biomedical applications. Significant changes (P < 0.05) in degree of swelling $(\%)$ and moisture content (% dry basis) were found after encapsulation of bacterial canthaxanthin (BCX), but the gel content remained unchanged. BCX encapsulation efficiency was calculated to be 55.92% and 60.45% in ChiHG and AlgHG, respectively. A noticeable change in heat of fusion $\left(\Delta H_m\right)$ d melting point $\left(T_m\right)$ was recorded in ChiHG and AlgHG after BCX encapsulation. Swelling and BCX release from gel matrix was performed under two different pH (1.2 and 7.4). The results showed that swelling of hydrogel and BCX release was facilitated at higher pH (7.4) than acidic pH (1.2). With regard to the release kinetics data, it was found that BCX is released from both $\mathrm{ChiHG}$ and AlgHG in a $\mathrm{non}-\mathrm{Fickian}$ diffusion transport method. In addition, antioxidant activity of BCX encapsulated hydrogels was found significantly higher (P < 0.001) in terms of DPPH, ABTS, nitrite, hydroxyl radical scavenging and reducing power assay. These results indicated that BCX can be successfully encapsulated into a polymeric hydrogel to obtain a dynamic biomaterial that may be used in drug delivery applications in future.

Keywords: Antioxidant activity; Canthaxanthin; Hydrogel; Pharmaceuticals; Release kinetics.