Defense Date

7-6-2004

Graduation Date

Summer 2004

Availability

Immediate Access

Submission Type

thesis

Degree Name

MS

Department

Biological Sciences

Committee Chair

John S. Doctor

Committee Member

Mark Miller

Committee Member

Mary Alleman

Committee Member

Phil G. Campbell

Keywords

attachment, CMOS sensor, differentiation, human adult mesenchymal stem cells, proliferation, surface topography, titanium

Abstract

Osteoblasts and osteoblast precursor cells (mesenchymal stem cells) respond to the surface topography of metal implants by aligning along surface features in order to minimize shear stress. While several previous studies have investigated the morphology, attachment and proliferation of both osteoblasts and mesenchymal stem cells along grooved surfaces, the current study investigates the cellular response to depressions and peaks in surface topography, as well as surfaces that contain alternating combinations of depressions and peaks. The Complementary Metal Oxide Semiconductor (CMOS) sensor is a transducer fabricated from silicon and sputter coated with titanium. The CMOS sensor is designed to utilize piezoresistive strain gauges in the detection of stress on bone. To the left and right of the piezoresistive strain gauges are surfaces that contain either depression (dimple) or peak (pimple) topographies. The CMOS sensor topographies were prepared using photolithographic processing, a technique that creates surface topographies in a precisely controlled manner. This study assessed the attachment, proliferation, and differentiation of human adult mesenchymal stem cells (hAMSC) on the depressions and peaks of CMOS sensors as a preliminary means of selecting surface topographies that might promote the greatest bone in-growth in vivo and therefore display the greatest osteoconductive properties. The distance above and below the nominal surface plane (etch depth) for surface topographies examined was either 15, 37, or 60um. LIVE/DEAD viability staining and electron microscopy revealed that cells attach on all CMOS sensor topographies. LIVE/DEAD viability staining was also used to determine that once attached, cells proliferate on all topographies after 3 days of incubation. Regardless of differences in initial cell attachment, after 14 days in medium containing an osteogenic supplement that promotes hAMSC differentiation into osteoblasts, comparable amounts of calcium were detected on all topographies. Although the specific topography (depressions, peaks, or the combination topography with both depressions and peaks) had no impact on the amount of calcium deposited on CMOS sensors, there was a significantly greater amount of calcium deposited on topographies with an etch depth of 15um when compared to the same topography with an etch depth of 60um.

Format

PDF

Language

English

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