Scheme of NalGYOrn(PEG4SH)R peptide conjugation to IONPs; Step 1: succinimide iodoacetate, amine functionalized IONPs, HEPES buffer (pH 8.5), room temperature, 1 hour; Step 2: NalGYOrn(PEG4SH)R, SIA-functionalized IONPs, HEPES buffer (pH 7), room temperature, 21 hours; Purification by dialysis.