Manganese-Templated Nontrivial Structures for MRI and Therapy

Area of Science:

• Nanotechnology
• Materials Science
• Oncology

Background:

• Metal-organic architectures offer platforms for integrated medical applications.
• Manganese (Mn)-based structures are explored for combined diagnostic and therapeutic capabilities.
• Developing targeted cancer therapies with advanced imaging modalities is crucial.

Purpose of the Study:

• To design and synthesize novel Mn-based metal-organic architectures for combined MRI and cancer therapy.
• To evaluate the relaxivity, tumor-selective cytotoxicity, and in vivo efficacy of these structures.
• To elucidate the mechanisms of cellular uptake, Mn2+ release, and therapeutic action.

Main Methods:

• Synthesis of three distinct Mn-templated structures: Mn-[2]Catenate (Mn-[2]C), Mn-Trefoil Knot (Mn-TK), and Mn-Borromean Rings (Mn-BR).
• Assessment of longitudinal relaxivity (r1) and T1-weighted MRI contrast.
• In vitro cytotoxicity assays on glioblastoma cells (U251-MG) and normal cells.
• In vivo studies in subcutaneous and orthotopic glioblastoma models.
• Mechanistic studies involving cellular uptake pathways, pH-triggered Mn2+ release, ROS generation, and apoptosis induction.

Main Results:

• Mn-BR and Mn-TK demonstrated high longitudinal relaxivities (10.1 and 6.8 mM-1.s-1 at 3 T), outperforming Gd-DTPA and Mn-DPDP.
• In vitro, Mn-BR and Mn-TK exhibited potent and selective glioblastoma cell killing (IC50 values of 3.0 ± 0.9 μM and 5.6 ± 1.9 μM, respectively), surpassing cisplatin.
• Cellular uptake occurred via energy-dependent endocytosis, leading to pH-triggered Mn2+ release, ROS accumulation, and apoptosis.
• In vivo, Mn-TK and Mn-BR showed tumor-specific accumulation, enhanced MRI contrast, and significant tumor growth inhibition.
• Both Mn-TK and Mn-BR demonstrated blood-brain barrier permeability and persistent tumor-specific MRI enhancement in orthotopic models.

Conclusions:

• Mn-BR and Mn-TK represent a new class of Mn-based metal-organic architectures with significant potential for integrated MRI and cancer therapy.
• These structures offer superior tumor selectivity and therapeutic efficacy compared to existing agents.
• Their ability to provide precise MRI-guided tumor visualization and treatment opens new avenues for precision medicine and advanced cancer care.