(A) SRB cytotoxicity assay of blank CS-NPs and CS-LZ-NPs at different concentrations ranged from 50 to 450 µg/ml. (B) Encapsulation efficiency percent of CS-LZ-NPs at pH 4 with different concentration of lysozyme (0.5, 1, 1.5, 2 and 2.5 mg/ml). (C) In vitro release study of CS-LZ-NPs with lysozyme concentration of 2.5 mg/ml prepared at pH 4.