Bright Photoluminescent Gd-MXene Quantum Dots for Cell Imaging with Synergistic MRI/CT Capability

Theranostic agents, which integrate diagnostic and therapeutic capabilities into a single nanoscale architecture, offer substantial advantages over conventional approaches. In this study, the potential of functionalized two-dimensional Titanium Carbide (Ti₃C₂) MXene Quantum Dots (MQDs) was explored as multifunctional agents capable of Magnetic Resonance Imaging (MRI), Computed Tomography (CT), and Photothermal Therapy (PTT). MQDs inherently possess efficient photothermal properties, making them suitable for therapeutic applications. To enhance diagnostic performance, MQDs were functionalized with Gadolinium (Gd) using two different methods, imparting magnetic properties and a high effective atomic number (Z-number), which significantly improved MRI and CT contrast capabilities. The MQDs, synthesized via a facile one-step hydrothermal method, exhibited an average size of 3.4 ± 1 nm and demonstrated intrinsic photoluminescent properties, enabling an additional Photoluminescence Imaging (PLI) modality. Surface modification with Polyethylene Glycol (PEG) was employed to effectively mitigate Gd-associated cytotoxicity while concurrently enhancing cellular internalization of the MQDs confirmed with RD cell line. Subsequent red (630 nm) laser irradiation studies were done at max power of 550mW for 10 min maximum, results of which confirmed that Gd-functionalization did not compromised the intrinsic photothermal efficiency of MQDs; remarkably, it enhanced the photoluminescence emission intensity by approximately 85% compared to the unmodified MQDs. Finally, this study successfully demonstrates the feasibility and possibility of Gd-functionalized MQDs as robust single-component multimodal theranostic agents capable of simultaneous MRI, CT, and photoluminescent imaging, along with potent photothermal therapeutic efficacy.