Date of Award

Spring 5-2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Molecular Science and Nanotechnology

First Advisor

David K. Mills

Abstract

Metals such as titanium have been used in implants, but there are often cases of infection and rejection of the implant from the body. In the past decade, the use of metal nanoparticles has seen increasing demand as an alternative treatment for reducing microbial infections, leading to progress in orthopedic surgery and wound healing. Recent investigations have developed new biomaterial bone substitutes with novel structural, biological, and mechanical properties. Advanced ceramic materials, such as Si3N4, may fulfill all the requirements above and represent a promising alternative to metals or polymers. However, the above mentioned materials have limitations because they are not biodegradable, not biocompatible, and do not contain inherent antimicrobial properties. This research is subdivided into three projects. First, it aims to introduce antibacterial properties into fabricated 3D implants by combining antimicrobial and base polymer powders before processing, which will make the material biocompatible and biodegradable. Second, it aims to fabricate multifunctional antimicrobial blow-spun nanocomposite fiber to facilitate wound healing and reduce microbial infection. Third, it aims to fabricate a biodegradable nanocomposite hydrogel patch for the development of chronic wound healing treatment.

A patented electrodeposition process was used to coat magnesium (Mg) on the HNT outer surfaces to add additional antimicrobial properties. Gentamicin sulfate was vacuum loaded into the lumen of the HNTs, which had already been coated with Mg. Si3N4 was added to the gentamicin-loaded MgHNT to promote cell adhesion and differentiation, and the resulting composite was then 3D printed/blow-spun into the required shapes according to the testing protocol.

FTIR, XRD, and SEM images showed the presence of magnesium on halloysite. cytotoxicity tests show that the fabricated nanocomposites were not toxic to mammalian cells. The results of the antimicrobial activity showed a pronounced inhibition of bacterial growth in all fabricated nanocomposites. Cell proliferation assays showed that Si3N4 enhanced proliferation in all nanocomposites. The porosity test showed that the addition of Si3N4 does not affect the porosity and the cell attachment. The histological staining showed an increase in both calcium and mucopolysaccharides. The nanocomposite shows excellent mechanical properties and a lower contact angle after surface coating with protein. Nanocomposites degraded slowly during the biodegradation test, enabling the growth of new bone cells. Si3N4 gives the cellular surface roughness structure, hydrophilicity, and protein adsorption capability.

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