| Summary: | In order to overcome the shortcomings of small-molecule contrast agents (CAs) in clinic, gadolinium-based CAs have attracted increasingly interesting in tumor diagnosis. Herein, β-cyclodextrin-modified ultrasmall gold nanoparticle (AuNP@CD) was prepared as a functional core, which provided a large number of binding sites through host–guest interaction. Afterward, AD-PEG2000-PLL(Gd-DTPA) was anchored on the surface of AuNP@CD followed by the conjugation of folic acid through bioorthogonal chemistry, which endowed the AuNP with the capability to targeting tumor cells. Compared to Magnevist (Gd-DTPA, r1 = 4.25 mM−1 s−1) used in clinic, the AuNP nanocomposite exhibited higher longitudinal relaxivity (r1 = 19.47 mM−1 s−1), and presented excellent biocompatibility. Furthermore, in vivo studies indicated that AuNP@CD-AD-PEG2000-PLL (DTPA-Gd) nanocomposite could effectively permeate through tumor and accumulate in the tumor region, thus acquiring MR images with high resolution. These results suggest that this AuNP nanocomposite could be a potential candidate as MRI CA for tumor-targeted diagnosis.
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