**2.3 Preparation of CPX1 and CPX2**

PolyGC-DOX intercalation was obtained by mixing 2 mg/ml DOX with DNA solutions with different concentrations to find the DOX/DNA ratio at which free DOX can insert into DNA chain completely. The fluorescence (exciting: 480 nm; emission: 590nm) of DOX quenched when inserting in the DNA. By detecting the fluorescence of DOX, the formation of the intercalation could be determined. CPX1 was formed by mixing PolyGC-DOX intercalation with cationic gelatin solution at different DNA/Gelatin weight ratio. CPX2 was obtained by mixing CPX1 solution with the some volume of 2mg/ml PEG-His-alginate solution by gently agitation for 1 hour. The physical stability of each complex was studied by agarose gel electrophoresis (0.8% agarose in TAE buffer). The diameters and zeta potential of the complex were analyzed by photon correlation spectroscopy by using 90 Plus Particle Sizer (Brookhaven Instruments, Holtsville, NY). The DOX fluorescence of CPX1 was also examined to investigate whether the combination between the intercalation and cationic gelatin release the DOX from DNA chain.
