Date of Completion

6-1-2016

Embargo Period

5-31-2017

Keywords

biomaterial, sequential delivery, mulitfactor, bone regeneration

Major Advisor

Liisa T. Kuhn

Associate Advisor

Gloria Gronowicz

Associate Advisor

Marja Hurley

Associate Advisor

A. Jon Goldberg

Associate Advisor

Caroline Dealy

Field of Study

Biomedical Engineering

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Many of the most promising strategies for tissue engineering and regeneration aim to replicate natural cellular microenvironments including matrix components, growth factors, and cellular proteins as a means to guide the migration, proliferation, and differentiation of progenitor cells. Combinations of growth factors synergistically enhance tissue regeneration, but typically require sequential, rather than co-delivery from biomaterials for maximum efficacy. Polyelectrolyte multilayer (PEM) coatings can deliver multiple factors without loss of activity; however, sequential delivery has been limited due to interlayer diffusion of multiple factors that results in co-delivery.

This dissertation examined the incorporation of a biomimetic calcium phosphate (bCaP) layer into a poly-L-Lysine/poly-L-Glutamic acid PEM film (bCaP-PEM) to provide sequential delivery of two different factors. The bCaP-PEM was uniformly deposited onto two-dimensional (2-D), and three-dimensional (3-D) porous substrates. Measurements of MC3T3-E1 osteoprogenitor cell proliferation and viability over time were used to evaluate kinetics of active biomolecule delivery and demonstrate that bCaP-PEM enables sequential delivery of a proliferative factor (fibroblast growth factor -2 (FGF-2) followed by a cytotoxic factor (antimycin A, AntiA) a few days later. Alterations to the PEM composition via increasing the number of bilayers or using the D- enantiomer polyelectrolytes hindered delivery of the proliferative factor. Increasing the bCaP layer thickness resulted in sustained delivery of the embedded factor as compared to burst delivery. Accelerated cell-mediated delivery kinetics from the bCaP-PEM coating was demonstrated in vitro using a murine macrophage cell line. Scanning electron microscopy revealed the bCaP-PEM coating could be uniformly applied to the 3-D, commercially available bone graft substitute Healos®, (DePuy Synthes Spine, Raynham, MA). Effects of sequential delivery of FGF-2, then bone morphogenetic protein 2 (BMP-2), from a bCaP-PEM coated Healos® scaffold was evaluated in vivo in a mouse calvarial defect model. This work resulted in the development of a novel, biomimetic coating capable of sequential delivery of two factors. This technology has potential to be applied in multiple research applications where a sequential delivery profile activated by cell degradation of the biomaterial is desired.

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