Delivery of Plasmid DNA Encoding Bone Morphogenetic Protein-2 with a Biodegradable Branched Polycationic Polymer in a Critical-Size Rat Cranial Defect Model

Abstract

This study investigated the delivery of plasmid DNA (pDNA) encoding bone morphogenetic protein-2 in the form of polyplexes with a biodegradable branched triacrylate/amine polycationic polymer (TAPP) that were complexed with gelatin microparticles (GMPs) loaded within a porous tissue engineering scaffold. More specifically, the study investigated the interplay between TAPP degradation, gelatin degradation, pDNA release, and bone formation in a critical-size rat cranial defect model. The pDNA release kinetics in vitro were not affected by the crosslinking density of the GMPs but depended, rather, on the degradation rates of the TAPPs. Besides the initial release of polyplexes not bound to the GMPs and the minimal release of polyplexes through diffusion or dissociation from the GMPs, the pDNA was likely released as naked pDNA or as part of an incomplete polyplex, after the degradation of fragments of the polycationic polymer. After 30 days, significantly higher amounts of pDNA were released (93%-98%) from composite scaffolds containing naked pDNA or pDNA complexed with P-AEPZ (synthesized with 1-[2-aminoethyl]piperazine, a faster degrading TAPP) compared with those containing pDNA complexed with P-DED (synthesized with N,N-dimethylethylenediamine, a slower degrading TAPP) (74%-82%). Composite scaffolds containing GMPs complexed with TAPP/pDNA polyplexes did not result in enhanced bone formation, as analyzed by microcomputed tomography and histology, in a critical-size rat cranial defect at 12 weeks postimplantation compared with those loaded with naked pDNA. The results demonstrate that polycationic polymers with a slow degradation rate can prolong the release of pDNA from the composite scaffolds and suggest that a gene delivery system comprising biodegradable polycationic polymers should be designed to release the pDNA in an intact polyplex form.

Restoration of rat calvarial defects by poly(lactide-co-glycolide)/hydroxyapatite scaffolds loaded with bone mesenchymal stem cells and DNA complexes

“…This is in accordance with previous studies, in which scaffolds containing plasmid DNA did not result in enhanced bone formation [32,33]. The incorporation of TMC/pDNA-hBMP-2 complexes into PLGA/HA scaffolds also resulted in decreased bone formation compared with the delivery of recombinant BMP-2 protein with this system in our previous study (unpublished work).…”

Restoration of Critical-Size Defects in the Rabbit Mandible Using Porous Nanohydroxyapatite-Polyamide Scaffolds

“…[23][24][25][26][27] Meng et al have reported that bone tissue engineering requires endogenous bone cells, extracellular matrix, and scaffold materials to be addressed holistically as a three-component system. 28 Endogenous bone cells, which mainly differentiate from BMSCs, play an important role in bone formation.…”

Characterization of an injectable, degradable polymer for mechanical stabilization of mandibular fractures

“…Poly(propylene fumarate) (PPF), is a biodegradable fumarate-based synthetic polymer that has shown promise in craniofacial bone applications. [6][7][8][9][10] A PPF construct typically incorporates PPF, a crosslinking agent (N-vinyl pyrrolidone, NVP), a radical initiator (benzoyl peroxide, BP), and an accelerator (N,N-dimethyl-p-toluidine, DMT). PPF can crosslink in situ, thus providing the possibility of injecting the material directly into a fracture or bony defect.…”