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| Author(s): |
Carla Pazzini
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Faculdade de Ciências Médicas |
| Defense date: | 2010-12-03 |
| Examining board members: |
Joyce Maria Annichino Bizzacchi;
Sara Teresinha Olalla Saad;
Patricia da Silva Melo
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| Advisor: | Joyce Maria Annichino Bizzacchi |
| Abstract | |
Heparin is an anticoagulant widely used in the treatment and prophylaxis of deep vein thrombosis (DVT). Some limitations of its use is the cost and route of administration, intravenous or subcutaneous, sometimes in repeated doses in 24 hours. Thus, the development of a product that can be administered subcutaneously in a smaller number of applications or orally becomes a major challenge, with interesting clinical applications. The use of a system for sustained release of drugs can come to meeting that goal, because it allows the agent to be protected and released gradually. This project consisted of the preparation and characterization of biodegradable nanoparticles of poly (e-caprolactone) (PCL) as a carrier of heparin of low molecular weight, and its evaluation of anticoagulant and antithrombotic activity in vivo. The nanoparticles were prepared by the method of double emulsion w/o/w and evaporation of solvent. The characterization of nanoparticles was performed by scanning electron microscopy (SEM), which showed homogeneous spherical nanoparticles. The average diameter of nanoparticles was 269±36 nm and zeta potential was -1.20±1.93 mV, indicating negative charge. The encapsulation efficiency, assayed by Azure II, was 80±2.3%. The release of heparin in vitro, at the 24-hour period was 4±1.8%. After the addition of esterase the release of heparin was increased to 10±1.9%, probably by accelerating the degradation of particles by the enzyme. The in vivo release of encapsulated heparin after subcutaneous administration in rats, was assessed by anti-Xa plasma activity and the results were compared with free heparin. The dose of heparin encapsulated had to be 5 times the dose of heparin free. Heparin-encapsulated nanoparticles showed a sustained release for up to 12 hours for a period significantly longer (P<0.01), but with lower anti-Xa activity. These data suggest that nanoparticles may allow heparin to be released in a more gradual, but with lower activity. When comparing the anti-Xa activity obtained by subcutaneous injection of nanoparticles with different doses of heparin, 800 IU/kg and 1000 IU/kg, demonstrated that the effect and duration of action depends on the dose applied. To evaluate the antithrombotic action of nanoparticles with heparin a model of DVT by stasis in rats was used. The doses of nanoparticles used for the evaluation of antithrombotic action were calculated by anti-Xa activity similar to that obtained with free heparin, 0.3 to 0.7 IU/mL. Heparin free or encapsulated in nanoparticles was applied in a single dose subcutaneously. The results showed a significant decrease of thrombus formed with the use of free heparin, compared with the control group (P=0.004). There were virtually no formation of venous thrombosis in any of the rats that received heparin encapsulated in nanoparticles, with a significant difference both in the control group (P<0.001) and the group with free heparin (P<0.001). In summary, the method of double emulsion w/o/w proved an efficient method for the encapsulation of heparin, providing spherical homogeneous nanoparticles with high encapsulation efficiency. For in vivo studies, heparin encapsulated showed a sustained release for a period greater than that of free heparin, and with excellent antithrombotic action. If these results are confirmed by the continuity of this study, the use of heparin encapsulated in nanoparticles in clinical practice can be of great benefits for the patient. (AU) | |