Year of Publication

2005

Document Type

Thesis

College

Graduate School

Department

Biomedical Engineering

First Advisor

Ahmed El-Ghannam

Abstract

The objective of the present study was to synthesize porous, biodegradable poly (D, l- lactide-co-glycolide) PLGA-B-HA (Bovine hydroxyapatite) composite and evaluate the effect of ceramic content on bone marrow cell differentiation in vitro. A macroporous biodegradable PLGA-B-HA composite with the pore size varying from 0.1 to 1000?? and a highly interconnected structure was fabricated using the freeze-drying/lyophilization technique. A pilot study was done to determine the effects of B-HA on to the osteoblast function. The main study was done to determine the effect of the increase in B-HA concentration on to the mesenchymal stem cell differentiation. Morphological characteristics of the composites were analyzed using FTIR and SEM/EDX analysis. The composites were seeded with neonatal rat calvarial osteoblasts (NRCO). The polymer: ceramic ratio in this study was 35%:65%. For comparison parallel experiments involving pure HA-200 discs were performed. SEM results indicated a higher proliferation and mineralization on PLGA-B-HA composites than pure HA discs. In addition, we evaluated the in vitro characteristics of PLGA-B-HA composites with varying ratios, i.e., 1:1, 1:2 and 1:3, seeded with rat marrow cells. FTIR indicated an increase in the area under the ceramic peak as ceramic concentration was increased. In addition, the average roughness values increased in the order of 1:3 andgt; 1:2 andgt; 1:1. Both compressive strength and modulus of 1:1 were significantly higher than 1:2 and 1:3 PLGA-B-HA composites. No significant difference in compressive modulli and strengths could be observed for 1:2 and 1:3 PLGA-B-HA composites. Cellular activity was determined by measuring AP activity, total protein analysis and osteocalcin concentration. Evaluation of alkaline phosphatase activity showed bone cells attached to 1:3 (PLGA-B-HA) expressed significantly higher alkaline phosphatase as compared to 1:1 and 1:2 PLGA-B-HA composites. In addition, cells seeded on to 1:3 composites secreted significantly higher osteocalcin and at a relatively short time period as compared to the other samples. Corrosion studies (ICP) and pH values indicate minimal difference in the concentration of Ca and P and pH in tissue culture media for all the samples at the end of all time periods. Hence we conclude that an increase in the ceramic concentration stimulated mesenchymal stem cell differentiation thereby promoting osteogenesis.

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