Iron-based contrast agents have recently garnered attention as positive (T1) magnetic resonance imaging (MRI) contrast agents providing an alternative to gadolinium-based contrast agents mired with the nephrogenic systemic fibrosis downsides. Whereas the magnetic cores of iron enable T1 MRI contrast enhancement, the non-magnetic materials (e.g., polymers) usually deployed to stabilize the metal cores affect bulk water diffusion to the iron centers. We present an innovative approach in designing biocompatible complex of asphaltene-derived carbon dots (ACDs) with iron (ACD-Fe), where the ACDs enhanced hydrophilicity improves accessibility of Fe3+ centers to water molecules to achieve effective tumor MRI. The ACD-Fe design strategy involves synthesizing ACDs at a lower temperature (80 °C) with high mass yield, followed by iron doping via easy complexation with FeCl3 at room temperature. The ACD-Fe complex thus serves as tissue-tolerant T1 MRI contrast agent (r1 = 1.33 mM−1s−1) for tumor imaging. This report pioneers the use of asphaltene-derived materials in MRI and tumor imaging, presenting a low-cost, scalable synthesis protocol for the ACD-Fe complex as an effective T1 MRI contrast agent.
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