A photoactivatable dopamine-conjugated platinum(IV) anticancer complex (Pt-DA) has been incorporated into G-quadruplex G(4)K(+) borate hydrogels by using borate ester linkages (Pt-G(4)K(+)B hydrogel). These were characterized by B-11 NMR, attenuated total reflection Fourier transform infrared spectroscopy, circular dichroism, scanning electron microscopy and transmission electron microscopy. Microscopy investigations revealed the transformation of an extended fiber assembly into discrete flakes after incorporation of Pt-DA. Pt-DA showed photocytotoxicity against cisplatin-resistant A2780Cis human ovarian-cancer cells (IC50 74 mu M, blue light) with a photocytotoxic index <2, whereas Pt-G(4)K(+)B hydrogels exhibited more potent photocytotoxicity (IC50 3 mu M, blue light) with a photocytotoxic index >5. Most notably, Pt-DA and Pt-G(4)K(+)B hydrogels show selective phototoxicity for cancer cells versus normal fibroblast cells (MRC5).