Yasser Ahmed

Date of Award

January 2025

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biomedical Engineering

First Advisor

Ali S. Alshami

Second Advisor

Ryan Striker

Abstract

This thesis introduces a new cost-effective method for fabricating bone scaffolds from triply periodic minimal surface (TPMS) geometries—namely Gyroid and Diamond structure—using a poly(lactic-co-glycolic acid)-nanohydroxyapatite (PLGA-nHA) composite and 3D-printed polyvinyl alcohol (PVA) molds. Current TPMS scaffold fabrication techniques depend on costly laser-based techniques like selective laser sintering and thus remain inaccessible. Herein, we reveal a cost-effective and repeatable indirect approach via fused deposition modeling (FDM) for printing water-soluble PVA molds, which are then iteratively cast filled with a PLGA-nHA solution. The protocol was optimized through concentration modulation and controlled evaporation of the solvent for optimum infiltration and uniformity in the scaffolds. Two main goals motivated this work: first, automate and optimize scaffolding through bioprinting and second, design and test TPMS scaffolds versus conventional lattice geometries. The automated casting approach decreased variability and material loss and doubled the scaffolding's thickness and decreased processing time by over fivefold as compared to manual casting. Integrity of the structure and composition were confirmed through Fourier-transform infrared spectroscopy (FTIR), light microscopy and compression testing and were found to be superior in Diamond scaffolds (1.0 MPa compressive strength and 0.25 MPa modulus) when compared with lattices. Cell adhesion and viability in vitro assays showed good adhesion and viability of cells through all scaffolds and TPMS scaffolding showing better cell spreading and integration because of their better surface area and interconnected porosity. This study proves TPMS scaffolding fabricated through the presented method possesses better mechanical strength, high porosity and biocompatibility and very low cost of production. This sets the stage for accessibility of advanced scaffolding designs in the application of bone tissue engineering and future directions also could be extended to in vivo and long-duration degradation tests.

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