(548f) A Biocompatible Heparin-Binding Polycation as a Potential Growth Factor Delivery Vehicle

Problem: Growth factors hold enormous therapeutic potential [1, 2]. However, they have short half-life in plasma making the design of appropriate delivery vehicle critical. The delivery vehicle should be biocompatible and should enable the control of release rate and duration of the delivery of growth factors. Most growth factors are bound to heparan sulfates in the human body. Heparan sulfates like heparin are known to stabilize many growth factors. We reasoned that to maximize the therapeutic efficacy of growth factors, they should be delivered in the heparin-sulfate-bound sate and the complexation of growth factor with the delivery vehicle should be performed in aqueous buffer to minimize denaturation. To materialize this design principle, we set out to create biocompatible polycations capable of binding heparins which can further complex heparin-binding growth factors in an aqueous media.

Methods: Arginine-based poly(ethylene argininylaspartate diglyceride) (PEAD) was synthesized by polycondensation of aspartic acid and ethylene glycol diglycidyl ether (EGDE) followed by the conjugation of arginine. The in vitro cytotoxicity was tested by culture with baboon smooth muscle cells (BaSMC). The ability of PEAD to interact with heparin was examined by zeta potential measurement, SEM and dimethylmethylene blue (DMB) binding assay.

Results: PEAD showed no cytotoxicity up to 2 mg/ml, higher than many existing polycations in biocompatibility including well known poly-l-lysine (PLL) and polyethyleneimine (PEI). Under physiological conditions, PEAD bearing +2 charges per monomer interacts strongly with heparin trough columbic attraction. The SEM images revealed the morphology of PEAD:heparin as fiber-like structures. Zeta potential measurement determined that the complex is neutral at the mass ratio of PEAD to heparin between 4 and 5. Besides, DMB binding assay showed, PEAD precipitated over 99 % of heparin in the solution at the ratios of 3 and 4. PEAD:heparin successfully incorporated FGF-2 which is one of the growth factors binding to heparin. The releasing file suggests the release of FGF-2 was nearly linear and lasted for three weeks.

Conclusions: Highly biocompatible PEAD has a great potential for growth factor delivery in combination with heparin.

References: 1) Davis, M.E., et al. Circ. Res. 2005;97:8-15

2) Piccirillo, S.G.M., et al. Nature 2006;444:761-5

Acknowledgements: The authors would like to acknowledge Dr. Nils Kröger for the zeta potential instrument and Mr. Ming-Yen Liu for SEM assistance.

Disclosures: None of the authors have financial interests related to the topic of the abstract.