Targeted Imaging Agent to HSP70 Induced In Vivo

Abstract

Heat shock protein expression can be induced by heat shock making it possible to artificially modulate their levels noninvasively in vivo in a spatially and temporally controlled manner. Here, we report the use of the major heat shock protein 70 (HSP70) as an inducible target by using the small molecule deoxyspergualin (DSG) conjugated to the near-infrared fluorophore (Cy5.5). We demonstrate that heat induction in the form of localized hyperthermia of normal tissue in living mice results in sufficient HSP70 overexpression for detection with DSG-Cy5.5 conjugate. This effect is dependent on total energy delivered and reaches maximum fluorescence signal in 6 to 8 hours post heat induction and declines over a period of up to 24 hours. These results suggest that DSG-Cy5.5 agent accumulates in tissue with elevated HSP70 by heat.