To extend the retention time of aerosol-delivered growth factors in the lung for stem cell homing/ activation purposes, we examined a formulation of vascular endothelial growth factor (VEGF) complexed to dextran sulfate (DS) and chitosan (CS) polyelectrolytes. Optimal incorporation of VEGF was found at a VEGF:DS:CS ratio of 0.12:1:0.33, which resulted in nanoparticle complexes with diameters of 612±79 nm and zeta potentials of -31±1 mV. The complexes collapsed in physiological solution, and released VEGF in a biphasic time course in vitro. In rat lungs, however, VEGF delivered in the complex was cleared at a constant exponential decay rate, 8-fold slower than that delivered in free form. The extended VEGF retention was likely due to equilibrium binding of VEGF to DS and to endogenous glycosaminoglycans. A similar retention effect is expected with other glycosaminoglycans-binding proteins (including many growth factors) when complexed with these glycans. Owing to its unique application, this type of complex is, perhaps, better described as a nanoglycan complex.

The potential applications for nanomaterials continue to grow as new materials are developed and environmental and safety concerns are more adequately addressed. In particular, virus-like particles (VLPs) have myriad applications in medicine and biology, exploiting both the reliable, symmetric self-assembly mechanism and the ability to take advantage of surface functionalities that may be appropriately modified through mutation or bioconjugation. Herein we describe the design and application of hybrid VLPs for use as potent heparin antagonists, providing an alternative to the toxic heparin antidote protamine. A two-plasmid system was utilized to generate VLPs that contain both the wild-type coat protein and a second coat protein with either a C- or N-terminal cationic peptide extension (4-28 amino acids). Incorporation of the modified coat proteins varied from 8 to 31%, while activated partial thromboplastin time (APTT) assays revealed a range of the heparin antagonist activity. Notably, when examined on the basis of the quantity of peptide delivered due to the varied incorporation rates, it appeared that the VLPs largely followed a similar trend, with the quantity of peptide delivered more closely correlating with heparin antagonist activity. The particle with the highest incorporation rate and best antiheparin activity displayed the C-terminal peptide ARKAKA, which corresponds to the Cardin-Weintraub consensus sequence for binding to glycosaminoglycans. Analysis of this particle using heparin affinity chromatography with fraction collection revealed that particles eluting at higher salt concentration had a greater proportion of peptide incorporation. Preliminary dual polarization interferometry experiments further support a strong interaction between this particle and heparin.