Control of swelling and release rate of electrospray fabricated calcium alginate microparticles by freeze-thaw cycles

To improve structure of the electrospray fabricated calcium alginate microhydrogels in order to control the swelling and release properties, Poly (vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) PVP were used and structure of the microhydrogels were reinforced by two freezing and thawing cycles. The particles did not show any swelling in HCl (pH=1.2). Swelling in the phosphate buffer (pH=7.4) showed amending effect of PVA and PVP and freeze-thaw cycles on the particles. In phosphate buffer media the freeze dried calcium alginate particles (ALG), the particles which improved by PVA and PVP (FD) and particles reinforced by freeze-thaw cycles (FT) showed swelling of 244.65, 152.15 and 126.34% respectively after 8 hours. On the other hand release rate of caffeine as a hydrophilic compound delayed in the FD and FT particles. According to the FTIR spectra, caffeine was entrapped physically in the particles. Results showed that calcium alginate particles reinforced with PVA and PVP especially those were undergone on freeze-thaw cycles could be applied for more efficient encapsulating of bioactive compounds without any chemical cross-linkers.