Abstract: Chitosan microspheres encapsulating cytoderm peptidoglycan derived from Lactobacillus plantarum were prepared by emulsion-crosslinking method. The sustained-release effect of peptidoglycan was evaluated in experimental mice orally administered with naked peptidoglycan or peptidoglycan microspheres for a consecutive week at low, medium and high dosages. Blood was collected from mouse tails within 15 d at an interval of 3 d. Enzyme-linked immunosorbent assay (ELISA) was used to measure lysozyme content in mouse serum. The results showed that the average drug loading capacity (LC) and encapsulation efficiency (EE) of microspheres varied with different ratios between peptidoglycan and chitosan. At the ratio of 1:1, the LC and EE were( 37.00 ± 3.24) g/ 100 g and (92.00 ± 2.38)%, respectively. The highest lysozyme content in serum was achieved at the 9th day post-administration of peptidoglycan microspheres, which was significantly higher than that in the control group. Meanwhile, high lysozyme content could last to the 15th day post-vaccination. Therefore, chitosan microspheres revealed an obvious sustained-release effect, which can effectively extend the action time of peptidoglycan.

Key words: peptidoglycan, chitosan, microsphere, sustained release