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A Custom-Engineered Water-Soluble Peptide-Based Macrocyclic Polynuclear Gd3+-Chelated Paramagnetic Multimodal
Samiran Kar1, Rabi Sankar Das1, Tapas Bera1
1Department of Chemistry, Organic Chemistry Section, Jadavpur University, Kolkata 700032, India.
Abstract:
The strategic development of cellular organelle-targeted multimodal imaging probes, which integrate fluorescent biomarkers with magnetic resonance (MR) contrast agents to harvest synergistic imaging information, holds transformative potential in biomedical diagnostics. In this pursuit, a custom-engineered peptide-based multimodal contrast agent, featuring the integration of an orange-red emissive synthetic hemicyanine (HCy) fluorescent dye with a preorganized macrocyclic polynuclear tri-Lys(DOTA-Gd3+) chelated MRI contrast agent, HCy-Lys(DOTA-Gd3+)-Lys(DOTA-Gd3+)-Lys(DOTA-Gd3+)-Gly, has been meticulously synthesized via the Fmoc-solid phase peptide synthesis methodology on Wang resin. This rational design paradigm harnesses synergistic advantages to transcend the inherent boundaries of traditional single-modality imaging methods. This paramagnetic peptide-based multimodal contrast agent, HCy-Lys(DOTA-Gd3+)-Lys(DOTA-Gd3+)-Lys(DOTA-Gd3+)-Gly, exhibits a substantial magnetic moment (7.54 μB per Gd3+) alongside pronounced magnetic susceptibility. The peptide-multimodal contrast agent HCy-Lys(DOTA-Gd3+)-Lys(DOTA-Gd3+)-Lys(DOTA-Gd3+)-Gly has been successfully employed for living cell mitochondrial-targeted confocal laser scanning microscopy, three-dimensional imaging, real-time dynamic monitoring, and multicolor imaging, in conjunction with T1-weighted MRI, demonstrating a notably high longitudinal relaxivity (r1) of 7.65 mM-1 s-1. The Lys amino acid-based preorganized macrocyclic scaffold confers exceptional kinetic stability to Gd3+ chelation, while the polynuclear architecture enhances MRI contrast. The water-soluble, biocompatible, noncytotoxic, bright orange-red emissive, paramagnetic, preorganized macrocyclic polynuclear tri-Lys(DOTA-Gd3+) chelates embodied in HCy-Lys(DOTA-Gd3+)-Lys(DOTA-Gd3+)-Lys(DOTA-Gd3+)-Gly represent a promising multifunctional contrast agent for live-cell mitochondria-targeted multimodal imaging techniques.
