Differential conjugation of tat peptide to superparamagnetic nanoparticles and its effect on cellular uptake.
Surface modification of superparamagnetic contrast agents with HIV-1 tat peptide has emerged as a promising means for intracellular magnetic labeling and noninvasive tracking of a large number of cell types with MRI. To achieve efficient intracellular delivery of the nanoparticles, we investigated the effect on cellular uptake of superparamagnetic iron oxide particles by varying the number of attached tat peptides. First, we report here a modified P2T method in measuring the numbers of surface attachments per particle through disulfide linkage. The method was shown to have desirable simplicity and reproducibility. With the P2T method as a tool, conjugates with progressively higher ratios of peptide-to-particle were synthesized. We were able to demonstrate that higher numbers of tat peptide facilitate the cellular uptake of iron oxide nanoparticles in a nonlinear fashion. Cells labeled with these optimized preparations were readily detectable by MR imaging. The increase in sensitivity could allow in vivo tracking of 100-fold lower cell concentration than currently described.
Center for Molecular Imaging Research, Harvard Medical School, Room 5404, Building 149, 13th Street, Charlestown, Massachusetts 02169, USA. mingzhao@helix.mgh.harvard.edu
Ming
M
Zhao
Moritz F
MF
Kircher
Lee
L
Josephson
Ralph
R
Weissleder
D000818:Animals; D003287:Contrast Media / Q000138:chemical synthesis* / Q000493:pharmacokinetics / Q000592:standards; D016503:Drug Delivery Systems; D005290:Ferric Compounds; D015696:Gene Products, tat / Q000737:chemistry* / Q000493:pharmacokinetics; D008214:Lymphocytes / Q000378:metabolism; D008279:Magnetic Resonance Imaging / Q000379:methods; D008280:Magnetics; D051379:Mice; D008810:Mice, Inbred C57BL; D036103:Nanotechnology; D010316:Particle Size; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000493:pharmacokinetics; D012680:Sensitivity and Specificity
D003287:Contrast Media; D005290:Ferric Compounds; D015696:Gene Products, tat; D010446:Peptide Fragments; C000499:ferric oxide