(584i) Chitosan/Poly L Lysine (PLL)-Alginate Microspheres for Growth Factor Delivery in Electrospun Scaffolds

Chitosan/poly L lysine (PLL)-alginate microspheres for growth factor delivery in electrospun scaffolds

Introduction:

     Electrospinning has been widely used to create scaffolds for musculoskeletal, vascular and skin tissue engineering. While electrospun scaffolds are known to provide topographical cues, incorporation of growth factors (GF) in electrospun scaffolds will provide additional biological cues to modulate tissue regeneration. However, electrospinning GF is limited due to instability of GF during electrospinning and influence of fiber degradation on GF release kinetics. We hypothesize that these limitations can be addressed by adopting a two step process. The first step involves fabrication of microspheres (MS) to load and protect the GF; while the second step involves co-axially electrospinning GF loaded MS in outer sacrificial fiber, followed by solvent extraction of sacrificial phase to yield GF loaded MS entrapped on surface of core phase fibers.

Materials and Methods:

     Towards the first step, GF loaded chitosan/PLL-alginate MS were manufactured via ionic gelation. Briefly, fluorescein labeled bovine serum albumin (FITC-BSA, model GF) was mixed with alginate solution followed by addition of CaCl₂ to form pre-gel. Chitosan/PLL was added to the pre-gel to create MS. The viscosity (mol wt) of alginate, concentration of CaCl₂ and ratio of chitosan/PLL to alginate was varied to study the effect of changing processing parameters on MS sizes. Concentration of CaCl₂was varied to study its effect on release kinetics of FITC-BSA. Cytotoxicity studies of MS were performed using C3H10T1/2 cells.

     With regards to the second step, DiI was added to PLGA and DiO was added to PEO and the fibers were co-axially electrospun with PEO as sheath and PLGA as core phase.

Results and Discussions:

     The size of MS increased with increasing viscosity of alginate. For both the ratio of chitosan/PLL to alginate and concentration of CaCl₂ the MS size decreased with increase in the processing parameter, reached a minimum and then increased. The release study revealed that different concentrations of CaCl₂ released different amounts of FITC-BSA with highest release recorded at highest CaCl₂concentration and vice versa. Fluorescent images confirmed the presence of both dyes alluding to fibers being co-axially electrospun.

Conclusions:

     Chitosan/PLL-alginate MS were successfully created via ionic gelation and loaded with FITC-BSA. MS sizes can be tuned by tuning the processing parameters such as viscosity of alginates, ratio of chitosan/PLL to alginate and concentration of CaCl₂. Release kinetics of FITC-BSA can be tuned by varying the ratio of CaCl₂. Polymer fibers were co-axially electrospun with PLGA as core and PEO as sheath phase.