Construction of ultrasmall gold nanoparticles based contrast agent via Host-Guest interaction for Tumor-targeted magnetic resonance imaging

•To achieve the goal of precision diagnosis, ultrasmall AuNPs based contrast agent were fabricated through host–guest interaction for tumor-targeted magnetic resonance imaging.•β-cyclodextrin-modified ultrasmall gold nanoparticle (AuNP@CD) was prepared as a functional core, and then reacted with AD-PEG2000-PLL(Gd-DTPA) through host–guest interaction followed by conjugation of tumor targeting ligand.•AuNP@CD-AD-PEG2000-PLL(DTPA-Gd)-FA nanocomposite could effectively permeate through tumor and accumulate in the tumor region, thus acquiring MR images with high resolution.