Date of Award

Winter 3-2-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical Engineering

First Advisor

David Mills

Abstract

With the development of technology and engineering, nanotechnology has been a multidisciplinary scientific field applied in nearly all science areas, including medicine, genetics, food industry, robotics. In this respect, nanomedicine has gained increasing attention and been a useful, effective therapy for cancer diagnosis, gene transfer, and drug delivery. To design an ideal nano drug delivery system with controlled drug releasing and improved encapsulated drug’s pharmacokinetic and pharmacodynamic profiles, hydrogels and polymer composites have witnessed increased research interest during the last decades. Recently, numerous polymers have been studied to fabricate the ideal wound dressing with biocompatibility, biodegradability, porous structural, and suitable mechanical properties. This research was divided into three projects and aims to fabricate a biocompatible, bioactive, and antimicrobial dressing with appropriate mechanical properties using poly-caprolactone (PCL) and polyethylene oxide (PEO) polymers incorporated with halloysite nanotubes (HNT) and strontium coated halloysite (SrHNT) by solution blow spinning. The first project involves the fabrication and characterization of PCL/PEO composite airbrushed films with different compositions. SEM and digital microscopy were used to observe the morphological characters and study the surface roughness of the polymer composites films. The mechanical properties of the airbrushed nanocomposite fibers were assessed via tensile testing. Additional characterization tests carried out in this project include porosity, degradation, and contact angle testing. The results showed that different mass ratios between PCL and PEO (3:7, 4:6, 5:5, 6:4, and 7:3 wt./wt.) and various solvent concentrations (2.5, 5.0, and 7.5 wt./v%) impact the structure of fibers, which affects the mechanical stress and strain, the degradation and biodegradation rate, and hydrophilicity. The second project involves the characterization of PCL/PEO composite solution spun fibers incorporated with HNTs and strontium coated HNTs. Fourier transform infrared (FTIR spectroscopy, X-ray Diffraction (XRD), and SEM were used to observe the presence of strontium on halloysite and in the fibers. Tensile test and Differential Scanning Calorimetry (DSC) showed the addition of uncoated or strontium-coated halloysites could adjust the mechanical stress and strain and the thermodynamic characteristics of the airbrushed nanocomposite fibers. The results of the antimicrobial activity showed a pronounced inhibition of bacterial growth against both gram-positive and gram-negative bacteria in all fabricated nanocomposites with uncoated or strontiumcoated halloysites, in which the groups with uncoated halloysites have better antibacterial property than the groups with strontium-coated halloysites. The third project involves in vitro assessment of the solution spun PEO/PCL composite fibers for wound healing. Biocompatibility was evaluated by live/dead assay for cytotoxicity, cell proliferation, scratch assay, migration assay, and Picrosirius Red staining. The results suggested that the composite airbrushed fibers were non-toxic and improved cell proliferation and migration on skin dermal fibroblasts. The histological staining showed an increase in collagens. These results suggest that the airbrushed PEO/PCL composite fibers incorporated with halloysites, and strontium coated halloysites could serve as a novel and convenient candidate of wound dressing.

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