Designing Molecular Probes To Prolong Intracellular Retention: Application to Nitroxide Spin Probes

Abstract

Targeted delivery of molecular probes into cells enables cellular imaging through optical and magnetic modalities. Probe molecules that are well retained by cells can accumulate to higher intracellular concentrations, and thus increase the signal-to-noise ratio of, and widen the temporal window for, imaging. Here we synthesize a paramagnetic spin probe bearing six ionic functional groups and show that it has long intracellular half-life (> 12 hours) and exceptional biostability in living cells. We demonstrate that judicious incorporation of ionic substituents on probe molecules systematically increases intracellular retention time, and should therefore be beneficial to imaging experiments.

A Simple Method of Synthesis of 3-Carboxy-2,2,5,5-Tetraethylpyrrolidine-1-oxyl and Preparation of Reduction-Resistant Spin Labels and Probes of Pyrrolidine Series

“…For these applications, both decay of nitroxides and their physical clearance from the tissue into the blood stream play an important role. Intracellular targeting is one of the efficient methods to increase retention in tissues [ 35 , 36 ]. If this technique is used, reduction-resistant nitroxides, which showed high lifetimes in cytosol extracts [ 9 ], may have an important advantage over conventional tetramethyl-substituted spin probes, which are known to undergo rapid reduction inside cells.…”