Thrombus-Targeted Nanocarrier Attenuates Bleeding Complications Associated with Conventional Thrombolytic Therapy
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To test the hypothesis that thrombus-specific tissue plasminogen activator (tPA)-loaded nanocarriers enhance thrombolytic efficacy and attenuate hemorrhagic complications.
A series of pegylated and non-pegylated tPA-loaded liposomes were prepared and their surfaces were decorated with the peptide sequence (CQQHHLGGAKQAGDV) of fibrinogen gamma-chain that binds with GPIIb/IIIa expressed on activated platelets. All formulations were characterized for physical properties, stability and in vitro release profile. The thrombolytic activities of tPA-loaded liposomes were tested by visual end-point detection, fibrin agar-plate and human blood clot-lysis assays. The thrombus-specificity of the peptide-modified-liposomes was evaluated by studying the binding of fluorescent peptide-liposomes with activated platelets. The pharmacokinetic profile and thrombolytic efficacy were evaluated in healthy rats and an inferior vena-cava rat model of thrombosis, respectively.
Both pegylated and non-pegylated peptide-modified-liposomes showed favorable physical characteristics and colloidal stability. Formulations exhibited an initial burst release (40–50% in 30 min) followed by a continuous release of tPA (80–90% in 24 h) in vitro. Encapsulated tPA retained >90% fibrinolytic activity as compared to that of native tPA. Peptide-grafted-liposomes containing tPA demonstrated an affinity to bind with activated platelets. The half-life of tPA was extended from 7 to 103 and 141 min for non-pegylated and pegylated liposomes, respectively. Compared to native tPA, liposomal-tPA caused a 35% increase in clot-lysis, but produced a 4.3-fold less depletion of circulating fibrinogen.
tPA-loaded homing-peptide-grafted-liposomes demonstrate enhanced thrombolytic activity with reduced hemorrhagic risk.
KEY WORDSlocalized fibrinolysis peptide-modified-liposomes protein delivery targeted delivery tissue plasminogen activator
Acute myocardial infarction
Analysis of variance
Area under the curve
Bovine serum albumin
Inferior vena cava
Plasminogen activator inhibitor-1
Phosphate buffered saline
Percutaneous coronary intervention
Platelet rich plasma
Tissue plasminogen activator
ACKNOWLEDGMENTS AND DISCLOSURES
The authors would like thank Dr. Imam Shaik and Kowser Miah for their technical assistance in developing the thrombosis model. We also thank Mr. George Littlejohn at the Coffee Memorial Blood Center (Amarillo, TX) for providing us with human plasma sample. The work was supported by the internal fund of TTUHSC.
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