Date of Award

Summer 2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical Engineering

First Advisor

David Mills

Abstract

Major medical needs may be achieved through regenerative medicine. Nanotechnology has triggered a research revolution in many important areas such as the biomedical sciences and bioengineering at the molecular level which has grown significantly due to the availability of new analytical applications and tools based on nanotechnology. Clinical conditions and diseases being targeted by nanotechnology research include burns, Alzheimer's and Parkinson's disease, implant failure, improved wound healing, birth defects, osteoporosis and congestive heart defects. Therapeutic use of growth factors and drugs to stimulate the production and/or function of endogenous cells represents a key area of regenerative medicine. The development of methods to expand ex vivo and drug delivery through advances in cell culture and scaffold technology have led to successful new treatment modalities for bone and wound repair.

The studies in this dissertation focused on several regenerative medicine approaches, with a future goal of an implantable scaffold material that can efficiently act as a repair material for wound healing and repair or as a replacement material for bones, teeth and other tissues. In this study, two different materials were nanoengineered for regenerative medicine applications. Anodization was used to produce nanoporous titanium scaffolds. Electrospinning was used to form Poly (ϵ-caprolactone) (PCL) scaffolds, halloysite-PCL composite scaffolds and drug loaded halloysite-PCL scaffolds. Cellular response was assessed in each study through cell-based assays, including the PicoGreen DNA assay, the Coomassie Plus total protein assay, and the Alizarin Red mineralization assay. Cell characterization methods were used to measure the potential of these nanoengineered materials to enhance cell proliferation, functionality, tissue formation and mineralization.

The results from the cell characterization assays suggest nanoporous titanium and the type I collagen coated halloysite-PCL scaffold both hold promise for bone tissue engineering and aiding in wound repair. Nanoporous titanium surfaces supported cell growth, cell differentiation and mineralization and are more biologically supportive compared to smooth titanium. The incorporation of HNTs up to 7wt%, within the PCL-scaffold did not extensively change the morphology of the PCL scaffold. Scanning electron microscopy and fluorescein isothiocyanate (FITC) labeling of halloysites indicated the nanotubes were not incorporated into PCL fibers but clustered together to form a ball-like structure that also linked adjacent fibers producing a complex, mesh-like (and extracellular matrix-like) composite scaffold. Type I collagen coated halloysite-PCL scaffold produced higher cell proliferation rates, increased protein synthesis and enhanced mineralization in comparison with halloysite-PCL and PCL only scaffolds.

In a companion study, hallyosite-loaded scaffolds containing more than one drug were created. Sustained release of Brilliant Green was achieved from both drug loaded PCL scaffolds and the drug loaded halloysite-PCL scaffold. This data supports the conclusion that drug loaded halloysite-PCL scaffolds may be a novel, biodegradable material for wound healing, producing anti-bacterial materials, or enhanced tissue bandages.

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