Abstract: Proteins are natural amphoteric polyelectrolyte. We studied the encapsulation and release of lysozyme as a model protein-drug using natural biomacromolecules. We prepared non-toxic β-casein-g-dextran copolymer through Maillard reaction and fabricated β-casein-g-dextran/lysozyme micelles through electrostatic attractive force between β-casein and lysozyme. The micelles with β-casein/lysozyme core and dextran shell are stable against dilution. The micelles dissociate in acidic, alkaline or salt solution where the electrostatic attraction disappears. The lysozyme released from the micelles shows the same activity as the nature lysozyme. Addition of Ca²⁺ ion can improve the stability of the micelles in acidic solution but cannot do so in alkaline or salt solution. Replacing β-casein-g-dextran with more hydrophobic casein-g-dextran and crosslinking the micelles with Ca²⁺ ion lead to the resultant micelles much more stable in acidic solution; the stability in alkaline or salt solution can also be improved.

Key words: Casein-g-dextran copolymer, Lysozyme, Self-assembly