Dual Delivery of EPO and BMP2 from a Novel Modular Poly-ɛ-Caprolactone Construct to Increase the Bone Formation in Prefabricated Bone Flaps

Abstract

Poly-e-caprolactone (PCL) is a biocompatible polymer that has mechanical properties suitable for bone tissue engineering; however, it must be integrated with biologics to stimulate bone formation. Bone morphogenetic protein-2 (BMP2) delivered from PCL produces bone when implanted subcutaneously, and erythropoietin (EPO) works synergistically with BMP2. In this study, EPO and BMP2 are adsorbed separately on two 3D-printed PCL scaffold modules that are assembled for codelivery on a single scaffold structure. This assembled modular PCL scaffold with dual BMP2 and EPO delivery was shown to increase bone growth in an ectopic location when compared with BMP2 delivery along a replicate scaffold structure. EPO (200 IU/mL) and BMP2 (65 mg/mL) were adsorbed onto the outer and inner portions of a modular scaffold, respectively. Protein binding and release studies were first quantified. Subsequently, EPO + BMP2 and BMP2 scaffolds were implanted subcutaneously in mice for 4 and 8 weeks, and the regenerated bone was analyzed with microcomputed tomography and histology; 8.6 -1.4 mg BMP2 (22%) and 140 -29 IU EPO (69.8%) bound to the scaffold and < 1% BMP2 and 83% EPO was released in 7 days. Increased endothelial cell proliferation on EPO-adsorbed PCL discs indicated protein bioactivity. At 4 and 8 weeks, dual BMP2 and EPO delivery regenerated more bone (5.1 -1.1 and 5.5 -1.6 mm 3 ) than BMP2 alone (3.8 -1.1 and 4.3 -1.7 mm 3 ). BMP2 and EPO scaffolds had more ingrowth (1.4% -0.6%) in the outer module when compared with BMP2 (0.8% -0.3%) at 4 weeks. Dual delivery produced more dense cellular marrow, while BMP2 had more fatty marrow. Dual EPO and BMP2 delivery is a potential method to regenerate bone faster for prefabricated flaps.

Evaluation of multi-scale mineralized collagen–polycaprolactone composites for bone tissue engineering

“…Early work by Wagoner Johnson et al, demonstrated the use of 3D-printed hydroxyapatite ceramic scaffolds able to enhance bone ingrowth and healing in vivo (Woodard et al, 2007). Ongoing efforts by Hollister et al have demonstrated the use of polycaprolactone (PCL) constructs as well as additional control over incorporation of bioactive agents to enhancing biomolecule absorption and release (Patel et al, 2015a;Suarez-Gonzalez et al, 2012), gene transfer (Hu et al, 2009), and resultant in vivo treatment of both cartilage and bone defects (Jeong et al, 2011;Patel et al, 2015b). The nature of the PCL construct allows rapid patient customization.…”

Multigrowth Factor Delivery via Immobilization of Gene Therapy Vectors

“…CVD Polymerization : PCL, PLGA, and titanium discs were coated with a layer of amine‐reactive polymer using a custom‐built CVD system previously reported . During the coating process, discs were fixed inside the deposition chamber at 15 °C.…”

“…During the coating process, discs were fixed inside the deposition chamber at 15 °C. The starting material (synthesis is described elsewhere) was sublimated at 120 °C, which was then pyrolyzed at 540 °C to form into a stream of reactive di‐radical vapor. The stream of reactive di‐radicals then entered the deposition chamber where they deposited and polymerized simultaneously on the discs.…”

“…Biodegradable and biocompatible scaffold materials, such as PCL and PLGA, are approved by the FDA for several clinical applications and promote tissue regeneration in numerous biomedical studies . Several methods for attachment of biomolecules to material surfaces depend on physical adsorption, which lacks the ability to target and immobilize biomolecules or release them in a controlled manner .…”

3D-Printed Poly(ɛ-caprolactone)/Graphene Scaffolds Activated with P1-Latex Protein for Bone Regeneration

“…The scaffolds were then adsorbed with P1-latex protein using a procedure described by Patel et al to coat PCL substrates. 27 In brief, lyophilized P1-latex protein was prepared in 1 mL Dulbecco's phosphate-buffered saline (DPBS) to obtain 1% (w/v) stock, with a concentration of 0.01 g/mL.…”