Available at: https://digitalcommons.calpoly.edu/theses/2705
Date of Award
12-2023
Degree Name
MS in Biomedical Engineering
Department/Program
Biomedical Engineering
College
College of Engineering
Advisor
Kristen Cardinal
Advisor Department
Biomedical Engineering
Advisor College
College of Engineering
Abstract
Electrospinning has provided the opportunity to create extracellular matrix (ECM) mimicking scaffolds for the development of tissue-engineered constructs. Within Professor Kristen Cardinal’s Blood Vessel Mimic (BVM) Lab, at Cal Poly, there exists a constant demand for innovation and the expansion of polymer types and electrospinning capabilities for its BVM model. Along these lines, the BVM Lab has recently acquired two new electrospinning systems: the Spinbox, a commercially graded electrospinning system, and the Learn-By-Doing system, which was part of a recently completed thesis conducted by Jason Provol. Additionally, recently published literature has demonstrated polyvinyl alcohol (PVA) as a viable option for creating electrospun scaffolds in the nanometer range. These findings prompt interest in investigating this polymer type due to its potential for producing extremely thin fiber diameters. Therefore, the overall objective of this thesis was to enhance the electrospinning capabilities of the BVM Lab through the utilization of the water-soluble polymer, PVA and to comprehensively compare the three available electrospinning systems within the BVM Lab, for novel tissue engineering or classroom applications.
The work performed in this thesis was structured around three main Aims. The first Aim of this thesis was to demonstrate the feasibility of using PVA to create flatsheet scaffolds using the Spinbox system. To achieve this, different PVA types with varying degrees of hydrolysis (DH) and molecular weight (MW) were spun to determine the most suitable PVA formulation. These experiments revealed that PVA with low DH and ultra-high MW was the most suitable for electrospinning. Subsequently, a formal Design of Experiments (DOE) was conducted to determine an effective parameter combination for Spinbox flatsheets. The DOE yielded a parameter combination with a voltage of 27 kV, a flow rate of 0.50 ml/hr, a gap distance of 17 cm, and a weight percentage of 10%. The selection of a PVA formulation with appropriate parameters in Aim 1 established the groundwork for accomplishing the objectives of Aim 2. Aim 2 sought to extend PVA’s electrospinning utility to other collector geometries across all three of the BVM lab’s electrospinning systems, while also comparing the usability, safety, and adjustability of each system relative to one another. This was the first time all 3 systems were directly compared. The results from Aim 2 demonstrated the reproducibility of tubular scaffolds on both the Custom and Spinbox systems, featuring nanoscale fibrous scaffolds, as well as on the LBD system with flatsheets. Furthermore, a qualitative comparison of the systems indicated that the Spinbox exhibited the highest degree of adjustability and safety among the electrospinners, albeit with the lowest relative degree of usability. Conversely, the LBD system demonstrated the highest usability or intuitiveness, while also being the most hazardous and least adjustable of the systems. The Custom system ranked in the middle for all three metrics.
Finally, the successful creation of tubular PVA scaffolds led to Aim 3 of this thesis, which focused on evaluating the potential of PVA scaffolds in a bioreactor environment for research applications and devising an accessible classroom PVA protocol for teaching applications. To accomplish this final aim, the scaffolds produced in Aim 2 were characterized and evaluated based on their solubility in cell-media. Additionally, methods for enhancing water-resistance through methanol cross-linking were explored and assessed. The results indicated that cross-linking PVA with methanol could enhance water resistance, but additional treatment would be necessary for PVA to serve as a standalone vascular scaffold in BVMs. However, a PVA Lab protocol was successfully developed to facilitate classroom education, providing a tangible and immediately impactful outcome of this thesis.