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<p>Magnetic quantum dots (MQDs) combining optical fluorescence with magnetic responsiveness are of growing interest for magnetic resonance-based applications; however, their relaxation behavior in complex biological environments is not fully understood. In this work, MQDs were synthesized via a green, plant-mediated hydrothermal route using <i>Punica granatum</i> peel extract as a natural reducing and stabilizing agent, followed by controlled incorporation of Fe<sup>3</sup>⁺ ions to impart magnetic functionality. The resulting MQDs are quasi-spherical, nanoscale particles exhibiting good colloidal stability and preserved surface functionalization. High-field <sup>1</sup>H NMR studies in human serum revealed concentration-dependent modulation of spectral features and relaxation behavior induced by MQDs, arising from localized magnetic field inhomogeneities. Comparative analysis with carbon quantum dots and free Fe<sup>3</sup>⁺ ions demonstrated that MQDs exhibit controlled transverse relaxation effects in a biological environment. NMR relaxation measurements and MRI phantom experiments further confirmed the ability of MQDs to enhance T₂-weighted contrast, with a non-monotonic T₂ response reflecting the interplay between interfacial shielding at low concentrations and susceptibility-driven dephasing at higher concentrations. Overall, this study provides a systematic assessment of the magnetic relaxation behavior of green-synthesized MQDs in a biologically relevant medium and highlights their potential utility as magnetically responsive nanomaterials for magnetic resonance-based imaging and sensing applications.</p> Graphic abstract <p></p>

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NMR and MRI Relaxation Effects Induced by Bio-Synthesized Magnetic Quantum Dots in Serum: Comparative Analysis with Carbon Quantum Dots

  • 期刊论文

  • 发表日期：

    2026年3月19日

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  • Ayush Shukla,
  • Gurvinder Singh,
  • Mayur Mohan Ghate,
  • Krishna Mohan Poluri,
  • Poonam Tandon,
  • Dinesh Kumar

摘要

Magnetic quantum dots (MQDs) combining optical fluorescence with magnetic responsiveness are of growing interest for magnetic resonance-based applications; however, their relaxation behavior in complex biological environments is not fully understood. In this work, MQDs were synthesized via a green, plant-mediated hydrothermal route using Punica granatum peel extract as a natural reducing and stabilizing agent, followed by controlled incorporation of Fe3⁺ ions to impart magnetic functionality. The resulting MQDs are quasi-spherical, nanoscale particles exhibiting good colloidal stability and preserved surface functionalization. High-field 1H NMR studies in human serum revealed concentration-dependent modulation of spectral features and relaxation behavior induced by MQDs, arising from localized magnetic field inhomogeneities. Comparative analysis with carbon quantum dots and free Fe3⁺ ions demonstrated that MQDs exhibit controlled transverse relaxation effects in a biological environment. NMR relaxation measurements and MRI phantom experiments further confirmed the ability of MQDs to enhance T₂-weighted contrast, with a non-monotonic T₂ response reflecting the interplay between interfacial shielding at low concentrations and susceptibility-driven dephasing at higher concentrations. Overall, this study provides a systematic assessment of the magnetic relaxation behavior of green-synthesized MQDs in a biologically relevant medium and highlights their potential utility as magnetically responsive nanomaterials for magnetic resonance-based imaging and sensing applications.

Graphic abstract