TPA Immobilization on Iron Oxide Nanocubes and Localized Magnetic Hyperthermia Accelerate Blood Clot Lysis

The low specificity and high risk of intracranial hemorrhage associated with currently approved thrombolytic therapies limit their efficacy in recanalizing occluded vessels. Here, a nanoscale thrombolytic agent is demonstrated by immobilizing tissue plasminogen activator molecules (tPA) over 20 nm clustered iron oxide nanocubes (NCs). The resulting nanoconstructs (tPA-NCs) are capable of dissolving clots via both direct interaction of tPA with the fibrin network (chemical lysis) and localized hyperthermia upon stimulation of superparamagnetic NCs with alternating magnetic fields (AMFs) (mechanical lysis). In vitro, as compared to free tPA, the proposed nanoconstructs demonstrate a approximate to 100-fold increase in dissolution rate, possibly because of a more intimate interaction of tPA with the fibrin network. The clot dissolution rate is further enhanced (approximate to 10-fold) by mild, localized heating resulting from the exposure of tPA-NCs to AMF. Intravital microscopy experiments demonstrate blood vessel reperfusion within a few minutes post tail vein injection of tPA-NCs. The proposed nanoconstructs also exhibit high transverse relaxivity (>400 x 10(-3) M-1 s(-1)) for magnetic resonance imaging. The multifunctional properties and the 3 orders of magnitude enhancement in clot dissolution make tPA-NCs a promising nano-theranosis agent in thrombotic disease.