Venous thromboemboli constitute an increasing problem in children with complex medical problems. The treatment of thromboemboli in children is challenging because unlike in adults, the use of thrombolytics is not well studied and is often associated with bleeding. These risks can be minimized by delivering the thrombolytic agent specifically and directly to the clot. Our objective is to use novel dendritic nanodevices loaded with streptokinase (SK) to achieve enhanced clot lysis. We hypothesize that these nanodevices enhance clot lysis by improving the stability of streptokinase, decreasing its immunogenicity and allowing more effective diffusion of the nanodevice into the clot to deliver the drug.
Three different nanodevices were designed: Hydroxyl terminated nanopolymers that were (1)complexed with SK and (2)conjugated with SK and (3)polylactic acid-glycolic acid nanoparticles loaded with SK. Drug loading was determined by Lowry protein estimation, and streptokinase activity evaluated using a chromogenic assay kit. A rabbit model of jugular venous thrombus using time, extent of reperfusion (measured by doppler flowmetry) and decrease in clot weight as therapeutic end points was established for in vivo testing of nanodevices.
In vitro studies showed that streptokinase was present in the nanodevices. Streptokinase activity was measured using a chromogenic assay and it was found to be active. From kinetic analysis, it was found that the streptokinase nanodevices took a longer time than free streptokinase to hydrolyse the peptide substrate nanoparticle>conjugate>complex>free SK. In vivo studies, showed that treatment with saline did not produce any significant reperfusion. Upon treatment with free streptokinase 30% of baseline blood flow was restored in 60 minutes. The clot weight with streptokinase treatment was 60% of control.
These results indicate that novel streptokinase loaded nanodevices can be successfully prepared and that they achieve sustained and controlled delivery of streptokinase. The in vivo model has been established and the nanodevices will be tested.
Nanodevices can non-invasively enhance clot lysis and minimize side effects by achieving controlled delivery of thrombolytics.
S. Kannan, None.