Magnetic and fluorescent graphene for dual modal imaging and single light induced photothermal and photodynamic therapy of cancer cells

Developing a simple and cost-effective strategy to diagnose and treat cancer with single and minimal dosage through noninvasive strategies are highly challenging. To make the theranostic strategy effective, single light induced photothermal and photodynamic reagent with dual modal imaging capability is highly desired. Herein, a simple non-covalent approach was adopted to immobilize hydrophobic silicon napthalocyanine bis (trihexylsilyloxide) (SiNc₄) photosensitizer onto water dispersible magnetic and fluorescent graphene (MFG) via π–π stacking to yield MFG–SiNc₄ functioned as a theranostic nanocarrier. Taking the advantage of broad near infra-red absorption (600–1200 nm) by graphene, photosensitizer of any wavelength within this range will facilitate the single light induced phototherapy. Phosphorescence spectra, singlet oxygen sensor green (SOSG) experiments, and 1,3-diphenyl isobenzofuran quenching studies confirm the generation of singlet ¹O₂ upon photoirradiation. Confocal microscopic images reveal successful internalization of MFG–SiNc₄ in HeLa cells; whereas T₂-weighted magnetic resonance images of MFG reveal a significant concentration dependent darkening effect. In vitro photodynamic/photothermal therapeutic studies on HeLa cells have demonstrated that the killing efficacy of MFG–SiNc₄ using a single light source is ∼97.9%, presumably owing to the combined effects of generating reactive oxygen species, local heating, and induction of apoptosis. The developed MFG–SiNc₄ may thus be utilized as a potential theranostic nanocarrier for dual modal imaging and phototherapy of cancer cells with single light source for time and cost effective treatments with a minimal therapy dose.