title: Targeted silver nanoparticles for ratiometric cell phenotyping.
abstract: Affinity targeting is used to deliver nanoparticles to cells and tissues. For efficient targeting, it is critical to consider the expression and accessibility of the relevant receptors in the target cells. Here, we describe isotopically barcoded silver nanoparticles (AgNPs) as a tool for auditing affinity ligand receptors in cells. Tumor penetrating peptide RPARPAR (receptor: NRP-1) and tumor homing peptide GKRK (receptor: p32) were used as affinity ligands on the AgNPs. The binding and uptake of the peptide-functionalized AgNPs by cultured PPC-1 prostate cancer and M21 melanoma cells was dependent on the cell surface expression of the cognate peptide receptors. Barcoded peptide-functionalized AgNPs were synthesized from silver and palladium isotopes. The cells were incubated with a cocktail of the barcoded nanoparticles [RPARPAR (R), GKRK (K), and control], and cellular binding and internalization of each type of nanoparticle was assessed by inductively coupled plasma mass spectrometry. The results of isotopic analysis were in agreement with data obtained using optical methods. Using ratiometric measurements, we were able to classify the PPC-1 cell line as mainly NRP-1-positive, with 75 ± 5% R-AgNP uptake, and the M21 cell line as only p32-positive, with 89 ± 9% K-AgNP uptake. The isotopically barcoded multiplexed AgNPs are useful as an in vitro ratiometric phenotyping tool and have potential uses in functional evaluation of the expression of accessible homing peptide receptors in vivo.
authors.affiliation: Laboratory of Cancer Biology, Institute of Biomedicine and Translational Medicine, University of Tartu, Ravila 14B, Tartu, 50411, Estonia. tambet.teesalu@ut.ee.
authors.forename: Anne-Mari A
authors.initials: AM
authors.lastname: Willmore
authors.affiliation: Laboratory of Cancer Biology, Institute of Biomedicine and Translational Medicine, University of Tartu, Ravila 14B, Tartu, 50411, Estonia. tambet.teesalu@ut.ee.
authors.forename: Lorena
authors.initials: L
authors.lastname: Simón-Gracia
authors.affiliation: Laboratory of Cancer Biology, Institute of Biomedicine and Translational Medicine, University of Tartu, Ravila 14B, Tartu, 50411, Estonia. tambet.teesalu@ut.ee.
authors.forename: Kadri
authors.initials: K
authors.lastname: Toome
authors.affiliation: Department of Geology, University of Tartu, Ravila 14A, Tartu, 50411, Estonia.
authors.forename: Päärn
authors.initials: P
authors.lastname: Paiste
authors.affiliation: Sanford Burnham Prebys Medical Discovery Institute, Cancer Research Center, 10901 N. Torrey Pines Road, La Jolla, CA, 92037 USA. gbraun@sbpdiscovery.org.
authors.forename: Venkata Ramana
authors.initials: VR
authors.lastname: Kotamraju
authors.affiliation: Laboratory of Cancer Biology, Institute of Biomedicine and Translational Medicine, University of Tartu, Ravila 14B, Tartu, 50411, Estonia. tambet.teesalu@ut.ee.
authors.forename: Tarmo
authors.initials: T
authors.lastname: Mölder
authors.affiliation: Sanford Burnham Prebys Medical Discovery Institute, Cancer Research Center, 10901 N. Torrey Pines Road, La Jolla, CA, 92037 USA. gbraun@sbpdiscovery.org.
authors.forename: Kazuki N
authors.initials: KN
authors.lastname: Sugahara
authors.affiliation: Sanford Burnham Prebys Medical Discovery Institute, Cancer Research Center, 10901 N. Torrey Pines Road, La Jolla, CA, 92037 USA. gbraun@sbpdiscovery.org and Center for Nanomedicine, and Department of Molecular Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, USA.
authors.forename: Erkki
authors.initials: E
authors.lastname: Ruoslahti
authors.affiliation: Sanford Burnham Prebys Medical Discovery Institute, Cancer Research Center, 10901 N. Torrey Pines Road, La Jolla, CA, 92037 USA. gbraun@sbpdiscovery.org.
authors.forename: Gary B
authors.initials: GB
authors.lastname: Braun
authors.affiliation: Laboratory of Cancer Biology, Institute of Biomedicine and Translational Medicine, University of Tartu, Ravila 14B, Tartu, 50411, Estonia. tambet.teesalu@ut.ee and Sanford Burnham Prebys Medical Discovery Institute, Cancer Research Center, 10901 N. Torrey Pines Road, La Jolla, CA, 92037 USA. gbraun@sbpdiscovery.org and Center for Nanomedicine, and Department of Molecular Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, USA.
authors.forename: Tambet
authors.initials: T
authors.lastname: Teesalu
mesh_terms: D045744:Cell Line, Tumor; D003584:Cytological Techniques; D006801:Humans; D007554:Isotopes; D008297:Male; D053768:Metal Nanoparticles; D010455:Peptides; D010641:Phenotype; D012834:Silver
chemical_list: D007554:Isotopes; D010455:Peptides; D012834:Silver