The Influence of Cyanine 5.5 and Doxorubicin on Cell Cycle Arrest, Magnetic Resonance, and Near‐Infrared Fluorescence Optical Imaging for Fe₃O₄‐Encapsulated PLA‐TPGS Nanoparticles

The combination of magnetic resonance imaging (MRI)/near-infrared (NIR) fluorescence signals and chemotherapy agents has been developed for cancer diagnosis and treatment. In this work, we investigated the impacts of Cyanine 5.5 and Doxorubicin on cell cycle arrest, magnetic resonance, and NIR fluorescence optical imaging for Fe₃O₄-encapsulated nanosystems based on poly(lactide)-tocopheryl polyethylene glycol succinate (PLA-TPGS) copolymer. Although Cyanine 5.5 and Fe₃O₄ nanoparticles (NPs) are less cytotoxic than Doxorubicin, they present a cytostatic effect, inducing cell cycle arrest at the G2/M phase in human brain adenocarcinoma (CCF-STTG1) cells. For MRI applications, the permeability of the PLA-TPGS copolymer coating layer to water molecules might lengthen the translational diffusion time ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>τ</mml:mi> <mml:mi>D</mml:mi></mml:msub> <mml:annotation>${{{{\bf\tau}}}_{{\bf D}}}$</mml:annotation> </mml:semantics> </mml:math> ), causing the higher relaxivity ratio (r₂/r₁) compared to bare Fe₃O₄ NPs under an applied magnetic field (7 Tesla). Notably, the chemical structures of Cyanine 5.5 and Doxorubicin significantly contribute to the enhancement of the T₂ relaxivities of Fe₃O₄ NPs through π-π and ρ-π conjugation. Furthermore, the radiance ratio and signal-to-noise ratio enhancement and a slight blue shift in the optimal excitation and emission wavelengths were recorded. These findings show the potential for in vivo MRI and NIR bioimaging experiments of the nanoparticles.