Engineering Hydrophobic and Hydrophilic Carbon Quantum Dots from Curcumin for Spatially Controlled Liposome Integration

Carbon quantum dots (CQDs) are widely explored for bioimaging, drug delivery, and theranostic applications due to their tunable fluorescence, biocompatibility, and adaptable surface chemistry. Nevertheless, precise hydrophobic-hydrophilic tuning from a single precursor remains underdeveloped, as most approaches depend on postsynthetic modification or multiple carbon sources, which can introduce additional processing steps and variability in surface composition. A single-precursor strategy may help simplify the synthesis and provide more consistent control over surface functionalities, offering a more direct route to polarity-tuned CQDs. Herein, we report a single-precursor-directed strategy to generate CQDs with distinct surface polarities, enabling controlled spatial organization within liposomal nanostructures. Curcumin was utilized as the carbon source in a solvothermal process conducted in the absence and presence of 3-aminopropyltrimethoxysilane, producing hydrophobic (Hb-CQD) and hydrophilic (Hp-CQD) carbon dots, respectively. The engineered polarity contrast dictated their interfacial behavior: Hb-CQDs preferentially embedded within the hydrophobic lipid bilayer (L-Hb-CQD), Hp-CQDs localized in the aqueous core of liposomes (L-Hp-CQD), and liposome-in-liposome (L-Hb-CQD-in-L-Hb-CQD) system. Encapsulation conditions were optimized to ensure homogeneous dispersion, improved colloidal stability, and enhanced intrinsic fluorescence of both CQD systems. Encapsulation efficiency, structural integrity, and spatial localization were systematically verified using fluorescence spectroscopy, TEM, and confocal laser scanning microscopy. The polarity control from a unified precursor platform demonstrates a rational route for directing nanoscale positioning of carbon dots within biomimetic architectures. The approach provides a versatile framework for designing multifunctional nanohybrids with potential applications in advanced bioimaging, controlled drug delivery, integrated theranostics, and mechanistic studies of nanoparticle-membrane interactions.