Date of Award

Summer 2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical Engineering

First Advisor

David Mills

Abstract

Orthopedic and oro-maxillofacial implants have revolutionized treatment of bone diseases and fractures. Currently available metallic implants have been in clinical use for more than 40 years and have proved medically efficacious. However, several drawbacks remain, such as excessive stiffness, accumulation of metal ions in surrounding tissue, growth restriction, required removal/revision surgery, inability to carry drugs, and susceptibility to infection. The need for additional revision surgery increases financial costs and prolongs recovery time for patients. These metallic implants are bulk manufactured and often do not meet patient's requirements. A surgeon must machine (cut, weld, trim or drill holes) them in order to best suit the patient specifications.

Over the past few decades, attempts have been made to replace these metallic implants with suitable biodegradable materials to prevent secondary/revision surgery. Recent advances in biomaterials have shown multiple uses for lactic acid polymers in bone implant technology. However, a targeted/localized drug delivery system needs to be incorporated in these polymers, and they need to be customized to treat orthopedic implant-related infections and other bone diseases such as osteomyelitis, osteosarcoma and osteoporosis. Rapid Prototyping (RP) using additive manufacturing (AM) or 3D printing could allow customization of constructs for personalized medicine. The goal of this study was to engineer customizable and biodegradable implant materials that can elute bioactive compounds for personalized medicine and targeted drug delivery.

Post-operative infections are the most common complications following dental, orthopedic and bone implant surgeries. Preventing post-surgical infections is therefore a critical need that current polymethylmethacrylate (PMMA) bone cements fail to address. Calcium Phosphate Cements (CPCs) are unique in their ability to crystallize calcium and phosphate salts into hydroxyapatite (HA) and hence is naturally osteoconductive. Due to its low mechanical strength, its use in implant fixation and bone repair is limited to nonload-bearing applications. Novel CPCs were formulated and were doped with drug loaded Halloysite Nanotubes (HNTs) to enhance their mechanical and anti-infective properties.

In this study we also explored the use of customized biopolymer filaments and 3D printing technology to treat bone diseases such as osteomyelitis, osteosarcoma, and osteoporosis. Biopolymer filaments were successfully loaded with antibiotics, chemotherapeutics and hormones (female sex hormones). Using a Fused Deposition Modeling (FDM)-based 3D printer, these customized filaments were fabricating into 3D scaffolds. Constructs with variable mechanical strengths and porosities were successfully designed and 3D printed. Scanning electron microscopy was used to study the surface architecture of the scaffolds. Compression and flexural testing was conducted for testing the mechanical strength of the constructs. Bacterial and suitable cell culture studies were applied to test bioactivity of the constructs. From above experiments, this study showed that 3D printing technology can be used to fabricate bioactive biopolymers for personalized medicine and localized drug delivery.

Download

Share

COinS