Maloplatin-B, a
cisplatin-based complex, namely [Pt(A-BOD)(NH3)2](NO3) (Pt-A-BOD) with a pendant
boron-dipyrromethene (
BODIPY) moiety, where HA-BOD is a methyl malonyl
chloride derived monostyryl
BODIPY ligand, was designed and developed as near-IR light (600-720 nm) organelle-targeting
photodynamic therapy agent. The complex [Pt(acac)(NH3)2](NO3) (Pt-Ac) was used as a control. Pt-A-BOD displayed an absorption band at 616 nm (ε = 2.9 × 104 M-1 cm-1) in 10%
dimethyl sulfoxide/Dulbecco's Modified Eagle's Medium (
DMSO/DMEM, pH 7.2). This complex displayed a broad emission band within 650-850 nm with a λem value of 720 nm in 10%
DMSO-DMEM (pH 7.2) upon excitation (λex) at 615 nm with a large Stokes shift. The fluorescence quantum yield (ΦF) value for Pt-A-BOD is 0.032 and for the
ligand HA-BOD is 0.24. The
BODIPY complex and
ligand showed the formation of
singlet oxygen as the ROS (
reactive oxygen species) on irradiation with near-IR red light of 660 nm, as evidenced from a
1,3-diphenylisobenzofuran (DPBF) assay. The complex displayed remarkable apoptotic NIR light-induced
PDT activity with half-maximum inhibitory concentration values (IC50) of 1.6-2.4 μM in A549 lung and HeLa
cervical cancer cells, while it was less active in the dark. The cellular ROS generation by the complex in red light was ascertained by a
DCFDA (2',7'-dichlorofluorescein diacetate) assay. Cellular imaging showed its localization primarily in the mitochondria of A549
cancer cells. The JC1 and
Annexin-V FITC/PI assays carried out for A549
cancer cells treated with the
BODIPY complex showed the alteration of mitochondrial membrane potential and apoptotic cell death on near-IR red light (600-720 nm) irradiation, respectively.