Forming PCL-gelatin electrospun multiaxial fibers with tunable release of therapeutic agents

摘要

Introduction: Novel developments in electrospinning allow formation of nano and micro size fibers with controllable functions such as altered surface (hydrophobic and hydrophilic) structures, and multi-layered structures. Structures with desirable properties can be developed by layering synthetic polymer to provide mechanical properties while natural polymer to promote cellular regulation. Primary caveat is limitation in suitable solvents that offer compatibility and high production rates. There is also a limited understanding of the influence of the compartment in which a drug is loaded. In this regard, we explored the formation of polycaprolactone (PCL) and gelatin multiaxial fibers either in combination using a common solvent along with various configurations of individual components. Doxycycline (Dox) an antibiotic and inhibitor of matrix degrading enzymes with short serum half-life was used as a model drug. We evaluated the fabrication of PCL/gelatin electrospun fibers to provide controlled release of Dox. Experimental Methods: We used a custom-built multi-axial electrospinning setup as described previously. PCL and gelatin were dissolved separately in TFE and solutions were mixed together when needed. We tested the effect of ⅰ) PCL/Gelatin ratio, ⅱ) flow rate and ⅲ) spinning distance. Fibers were characterized using SEM, TEM, DSC and FTIR were performed to determine the presence of components. Using the optimized setting, we formed multi-axial fibers with PCL-gelatin as the ⅰ) inner core and ⅱ) outer sheath. We tested forming fibers with gelatin, PCL and PCL/Gelatin as various configurations. Distribution and stability of gelatin was evaluated. Dox was loaded in various locations and release profiles were compared over five days. Alterations in fiber morphologies were evaluated by SEM. Cell culture studies were performed and inhibition of matrix metalloprotease-2/9 was evaluated. Results and Discussion: We successfully formed single/coaxial and triaxial fibers loaded Doxy. SEM images showed uniform fiber size distribution. Gelatin distribution in PC/Gelatin blend single and coaxial fibers was uniform. When fiber diameters were determined, PCL/Gelatin fibers formed at 1 ml/hr had 5.36 (±2.12) μm diameter (Figure 1 A), nearly double that formed at 0.5 ml/hr (Figure 1.B). Increasing the polymer concentration increased the fiber sizes. Loading Doxy in the spinning solution increased the fiber diameter. FT-IR and DSC revealed the presence of each component. TEM results showed presence of multiple layers but co-axial to have more uniform distribution (Figure 1.C). Presence of PCL/gelatin as the outer sheath produced more uniform fibers consistently than when it was present as the inner sheath. Also, Dox release studies were performed in fibers with PCL/gelatin combination as the outer sheath. Dox release studies showed differences based on the compartment in which they were loaded. Compared to single fibers where quick release was observed, co-axial fibers produced better release profiles. There were differences in release profiles when Dox was loaded in the inner PCL alone, gelatin alone or combination of PCI/gelatin. Also, triaxial fibers had large deviations, probably due to non-uniform distribution of fibers. Conclusion: We show that multilayered fibers with PCL and gelatin can be formed. They can be used for altering the release profile of therapeutic agents.