Fig. 4. Loading and release behaviors of eTuSp1 spheres. (A) Loading and loading efficiency of eTuSp1 spheres. (B) Zeta-potential of eTuSp1-Dox spheres with regard to different w/w-ratios. (C) Cytotoxicity of free Dox and eTuSp1-Dox spheres. The Dox concentration of eTuSp1-Dox spheres is equivalent to that of the free Dox. (D) Cumulative release of eTuSp1-Dox spheres at different pH media.