Abstract:
The aims of this study were to prepare nisin loaded solid lipid nanoparticles by high pressure homogenization method and to study the effect of difference in pH and salt concentration on nisin releasing profile for sustained antimicrobial activity. An optimized condition for particle preparation was studied by characterization of unloaded nanoparticles. Using IMWITOR 900 as solid matrix at pressure of 1500 bar of high pressure homogenizer with 3 cycles, small size and narrow polydispersity were observed when 5% poloxamer 188 and 0.125% sodium deoxyglycholate were used as surfactant and co-surfactant, respectively. For 0.5%-3.0% nisin loaded, result from Photon correlation spectroscopy (PCS) showed that particle size was in range of 159-167 nm which increased from unloaded nanoparticle. Zeta-potential was in range of -28.3 to -29.2 mV. During 28 days at room temperature, size and zeta-potential were increased to range of 214-245 nm and -21.6 to -25.9 mV, respectively. In vitro release studies showed that nisin was released throughout 25 days exccept incubation with 0.5 M sodium chloride. However, the release was lower as the salt concentration and pH of the buffer increased. In vitro nisin biological activity was investigated by incubation in liquid medium containing either Listeria monocytogenes DMST 2871 or Lactobacillus plantarum TISTR 850 and showed that antimicrobial activity was maintained up to 20 days and 10 days of incubation, respectively. Scanning electron microscopy demonstrated that particle size was slightly changed during experiment.