Polyelectrolyte Complexes Stabilize and Controllably Release Vascular Endothelial Growth Factor

Abstract

Angiogenesis has long been a desired therapeutic approach to improve clinical outcomes of conditions typified by ischemia. Vascular endothelial growth factor (VEGF) has demonstrated the ability to generate new blood vessels in vivo, but trials using intravenous delivery have not yet produced clinical success. Localized, sustained delivery of VEGF has been proven necessary to generate blood vessels as demonstrated by implantable, controlled release devices. Ultimately, nanoparticles delivered by intravenous injection may be designed to accumulate in target tissues and sustain the local VEGF concentration; however, injectable nanosuspensions that control the release of stabilized VEGF must first be developed. In this study, we utilize the heparin binding domain of VEGF to bind the polyanion dextran sulfate, resulting in an enhanced thermal stability of VEGF. Coacervation of the VEGF-bound dextran sulfate with selected polycations (chitosan, polyethylenimine, or poly-L-lysine) produced nanoparticles approximately 250 nm in diameter with high VEGF encapsulation efficiency (50-85%). Release of VEGF from these formulations persisted for >10 days and maintained high VEGF activity as determined by ELISA and a mitogenic bioassay. Chitosan-dextran sulfate complexes were preferred because of their biodegradability, desirable particle size ( approximately 250 nm), entrapment efficiency ( approximately 85%), controlled release (near linear for 10 days), and mitogenic activity.

Incorporation of heparin-binding proteins into preformed dextran sulfate-chitosan nanoparticles

“…SDF-1α was diluted in 0.6 mL of migration medium [RPMI-1640 medium containing 0.5% BSA (Sigma # A9576)] and added to wells in a 24-well plate ("bottom wells"). Transwell inserts ("top wells") were placed into the bottom wells and loaded with 5×10 5 Jurkat cells suspended in 100 µL migration medium. After 2 h incubation at 37°C, cells that transmigrated into the bottom well were mixed and counted with a BD Accuri C6 flow cytometer (BD Biosciences).…”

“…The incorporation efficiency was 96%-100% at all tested VEGF loading amounts (0.25-2 nmol/100 nmol charged saccharide units) (Figure 5B), which is greater than that achieved by an entrapment method, which were ~40% or 50%-80% from two separate studies. 5,9 Albumin and globulins are the most abundant proteins in blood. As proteins can adsorb to the surfaces of various inorganic/organic materials, the authors examined the adsorption of these proteins to preformed DSCS NPs.…”

“…This result is consistent with previous studies using a differential scanning calorimetry method to determine the thermal stability of VEGF. 5,39 The studies found that VEGF has an unusually high melting temperature of 107°C or 108°C, 5,39 indicating a very high thermal stability. VEGF NP further increases the melting temperature to over 115°C, 5 indicating that the thermal stability of VEGF was further enhanced by incorporation into DSCS NPs.…”

Controlled release of chitosan/heparin nanoparticle-delivered VEGF enhances regeneration of decellularized tissue-engineered scaffolds

“…This is usually accomplished by the administration of high doses of VEGF, which can induce severe side effects, such as undesired vascularization at nontarget sites, tumor growth at locations away from the scaffold, hypotension, and edema. 9,10 In contrast, sustained local concentration of growth factors is necessary for the development of mature blood vessels. Therefore, it is particularly important to localize VEGF to the scaffold and control its release at the site of implantation.…”

In vitro osteoclastogenesis on textile chitosan scaffold

“…With respect to its chemical nature chitosan is reminiscent of glycosaminoglycans, components of the extracellular matrix with great importance for bone formation. Similarly, chitosan is able to bind different components of the extracellular matrix as growth factors and cytokines (Huang et al, 2007;Park et al, 2006;Zisch et al, 2003). For tissue engineering that is an interesting feature, because chitosan is able to concentrate added factors in the close vicinity of the scaffold material right on the growth site.…”