Targeting somatostatin receptors using in situ-bioconjugated fluorescent nanoparticles.
OBJECTIVE
The author's group report, for the first time, on the development of a quantum dot (QD)-based fluorescent somatostatin (somatotropin release-inhibiting factor [SRIF]) probe that enables specific targeting of somatostatin receptors. Receptor-mediated endocytosis of SRIF was imaged using this probe.


METHODS
Biotinylated SRIF-analog (SRIF-B) and streptavidin (Sav)-coated QDs were used for the probe synthesis. A dye-labeled streptavidin complex was used to evaluate the effect of Sav binding on the activity of SRIF-B.


RESULTS
A preconjugated probe of the form SRIF-B:Sav-QD, was inactive and unable to undergo receptor-mediated endocytosis. An alternative in situ bioconjugation strategy, where SRIF-B and Sav-QD were added in two consecutive steps, enabled visualization of the receptor-mediated endocytosis. The process of Sav binding appeared to be responsible for the inactivity in the first case.


CONCLUSIONS
The in situ two-step bioconjugation strategy allowed QDs to be targeted to somatostatin receptors. This strategy should enable flexible fluorescent tagging of SRIF for the investigation of molecular trafficking in cells and targeted delivery in live animals.
Macquarie University, NSW 2109, Australia.
Varun K A
VK
Sreenivasan
Eun J
EJ
Kim
Ann K
AK
Goodchild
Mark
M
Connor
Andrei V
AV
Zvyagin
D000818:Animals; D045744:Cell Line, Tumor; D004705:Endocytosis; D005456:Fluorescent Dyes; D008564:Membrane Potentials; D053758:Nanoparticles; D045663:Quantum Dots; D051381:Rats; D017481:Receptors, Somatostatin / Q000187:drug effects* / Q000378:metabolism
D005456:Fluorescent Dyes; D017481:Receptors, Somatostatin