In the last two years, the COVID-19 pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has impacted the entire world. SARS-CoV-2 detection methods include Polymerase Chain Reaction (PCR), which is expensive, and Rapid Antigen Test, which is not highly sensitive. Therefore, this study aimed for a viral diagnostic tool that is cost-effective and highly sensitive, a biomimetic biosensor.   The aim was to build a biomimetic biosensor using Surface Plasmon Resonance (SPR) based equipment. Three epitopes named here alpha 1, alpha 2, and alpha 3 from the angiotensin converting enzyme-2 (ACE-2), the target receptor for cell entry for SARS-CoV-2 and SARS-CoV in the body, were immobilized on a surface. Then, samples containing WT SARS-CoV-2 RBD, WT SARS-CoV-2 Spike, Delta SARS-CoV-2 RBD, and SARS-CoV RBD were injected over the surface. SPR allowed the detection of any binding that occurred.   The results revealed that the WT SARS-CoV-2 spike protein and the Delta SARS-CoV-2 RBD binding to alpha 2 showed the best results with high signals and high binding affinities. Alpha 1 interestingly showed good binding only two out of six times but the exact reason for that remains unknown. Alpha 3 did not seem to be promising as it either did not bind the analytes at all or was bound with very low signals.   These findings indicate that it is possible to build a biomimetic biosensor using peptides from ACE-2 to detect SARS-CoV-2, but further investigations are needed to optimize it. Future perspectives can include focusing on optimizing alpha 1 efficiency and finding the reason why it is not so stable.     Keywords: SARS-CoV-2, biosensor, SPR, ACE-2, spike, RBD / Adaptable host-cell mimetic receptors for antibody-free sensing of SARS-CoV-2 variants

Silicone hydrogels haves been widely utilized in many in ophthalmic and other biomedical applications due to the its comfort of hydrogels, their excellent biocompatibility, high oxygen permeability and transparency. For use as a contact lens, the silicone hydrogel with interacts with the tear film, cornea, and eyelid;, thus surface properties of the gel are crucial to be considered. The highly oxygen permeabilitye performance of the silicone hydrogel contact lens materials mainly relies on the incorporationng of the siloxane functional groups., Hhowever these groups are extremely mobile and surface active, which can result in an increase in the of lens surface hydrophobicity, as well as protein and lipid deposition. Therefore, there is a need for surface modification of silicone hydrogel contact lenses. Otherwise users may might have to choose to decrease the frequency and length of wearing duration of silicone contact lenses due to dryness or bio-fouling related issues. A novel biomimetic methacrylate monomer which contains a phosphorylcholine group, 2-mMethacryloyloxyethyl pPhosphorycholine (MPC) is was grafted onto the surface of novel silicone hydrogel materials surface to create a thick hydration layer in order to enhance the protein resistance and surface wettability. Low temperature air plasma has beenwas chosen to initiate grafting polymerization of MPC monomers onto silicone hydrogel substrates. Hydrogels were treated with plasma and exposed to air flow to yield hydroperoxides on the surface; the, and peroxides group acted as a photo-initiators for further thermal MPC grafting polymerization. After surface modification, the silicone hydrogels were characterized by XPS and ATR-FTIR to confirm the structure and elemental composition. A significant amount of phosphorus element was found shown on the XPS spectra of the modified materialsum,, demonstrating that so the MPC monomers were successfully grafted onto the gel surface. According to water contact measurement results, the modified samples possessed very hydrophilic surfaces, with advancing angles of about 27°, while compared the unmodified samples at around 110°. After surface grafting, between a around 20% and to 50%’s reduction in protein deposition was also observed, which aligned with water contact angle results. Other properties such as oxygen permeability, transparency, water equilibrium, and elastic modulus remained unchanged after the air plasma exposure and thermal MPC polymerization. / Thesis / Master of Applied Science (MASc)

The repair of damaged or diseased bone tissue often requires the use of metallic implants which form an interface with the surrounding bone tissue. Understanding this interface is important for improving the outcomes of implant placement and overall health of patients. Bone is a composite material of organic collagen fibrils and inorganic mineral phases that have structural variations across multiple length scales. This heterogeneous and hierarchical nature poses characterization challenges for (i) understanding bone, (ii) creating biomaterial structures that mimic it, and (iii) approaches for evaluating biomaterials. These challenges formed the basis for the three papers presented in this thesis. In Chapter 3, leporine bone was examined using atom probe tomography (APT) to visualize in vivo mineralized collagen fibrils, their chemical composition, and spatial arrangement in 3D with sub-nanometer accuracy. This provided new insight into the location of biomineral with respect to collagen and demonstrated the power of APT for understanding collagen-mineral arrangement. In Chapter 4, commercially pure titanium was laser ablated to generate periodic surface structures inspired by the periodicity of collagen. Three different periodicities were generated with submicron-scale roughness and a high degree of reproducibility. All the surfaces were non-cytotoxic and encouraged cells to adhere perpendicular to the orientation of the surface structures. In Chapter 5, a simple five-minute room temperature ionic liquid treatment was developed to investigate the same laser-ablated titanium periodic structures with osteoblast-like cells adhered. The development of this technique fulfills an important niche in biological imaging by allowing for simultaneous and repeated visualization of submicron surface features and wet cells. Therefore, the combined impact of this thesis is novel imaging and biomaterials evaluation strategies to (i) improve understanding of bone structure; (ii) leading to bioinspired biomaterials design; and (iii) new methods for simultaneous biological and biomaterials evaluation. / Thesis / Doctor of Philosophy (PhD) / Bone implant devices are required to treat, augment, or replace bone tissue in dental and orthopaedic applications. These, often metallic, implanted devices have success when a structural and functional connection with natural bone tissue is created, a phenomenon known as osseointegration. Good osseointegration is required to ensure stability of the implant without compromising the quality of life of the patient. In order to improve osseointegration of biomaterials, both sides of the interface, i.e. the bone and implant surface, must be better understood. This thesis focuses on exploring methods to improve the evaluation and understanding of both bone structure at the nanoscale and structured metallic implant surfaces for the design of bone-interfacing biomaterials.

Soft tissue engineering has become increasingly relevant in efforts to create complex, functional tissues for tissue replacement in tissue engineering applications or for the development of more complex tissue models for drug screening or fundamental research. Tissue engineering of micro- and nano-scale structures has been explored through a number of biofabrication techniques but most successfully on the nano-scale through electrospinning. Electrospun nanofibers represent one of the most similar structures to natural extracellular matrix (ECM), while electrospinning of hydrogel nanofibers is particularly relevant given that such nanofibers support the high water content environment required by cells to survive. Herein, a reactive cell electrospinning process is demonstrated based on dynamic hydrazone-crosslinked poly(oligoethylene glycol methacrylate (POEGMA) hydrogel nanofibers that can be electrospun from an aqueous solution, allowing for the generation of cell-loaded hydrogel nanofibers in a single fabrication/cell-seeding step. Using the proper collectors, the fabrication of aligned and/or multi-layered scaffolds is demonstrated without the risk of layer delamination due to the dynamic crosslinking of POEGMA hydrogels. Co-electrospun NIH 3T3 fibroblasts and Psi2 12S6 epithelial cells were found to proliferate over 14 days within the networks, while electrospun C2C12 myoblasts were found to align along the direction of aligned fibers. POEGMA hydrogels provide a suitable environment for cells and can be expanded to multi-layer, multi-cellular networks with tunable micro-architectures to better mimic more complex aligned (e.g. muscle) and/or multi-layer (e.g. smooth muscle vasculature, esophageal) tissues. / Thesis / Master of Applied Science (MASc) / Successful regeneration of diseased tissues relies first on understanding the healthy tissue structures and functions that currently exist within the body, and second, how to synthetically replicate those structures using biomaterials. Re-creating the natural networks that cells use to attach and grow has many challenges, including the challenge of creating nano-scale structures, controlling any immune response to the biomaterial(s) used, and ensuring the correct response of cells to the fabricated structures. One method of generating suitable nano-scale structures is through a process called electrospinning, specifically when it is used to produce hydrogel-based nanofibers which can bind large amounts of water. When implanted, hydrogels swell to form a hydrated environment suitable for cells. These nanofibers are generated on a scale that is smaller than the encapsulated cells to allow for guided cell responses to the material. Furthermore, the use of cell-friendly polymer solutions allows for cells to be in contact with the biomaterial without resulting in high cell death. In this thesis, aligned and/or multi-layered nanofiber structures are generated to replicate the naturally existing support structures seen in the body. These fibers are also loaded with cells to create semi-functional body tissues that in the future can serve to replace non-functional tissues or used to better understand cell interactions with their environment.

3D bioprinting allows for the manufacturing of tissue-like structures that could be used for culturing and studying cells in a microenvironment representative of the cell’s natural environment. In recent years, hydrogel bioinks from different biomaterials have been in development and utilized in tissue engineering applications. The most common biomaterial is collagen, the main component of the ECM, due to its high biocompatibility. However, collagen bioinks have poor mechanical properties, limiting their use for bioprinting without addition of chemical crosslinks. Efforts have been made in attempts to overcome these issues. In this project collagen hydrogels of high concentration derived from decellularized ECM of rat tail tendons were developed and examined for future use as bioink. After decellularization, the dECM was translated into pre-gels of varying concentrations and exposure to pepsin, to see how this would affect the gelation kinetics and rheological properties. The biochemical profile of the pre-gel consisted of collagen type 1 and various glycosaminoglycans. The pre-gels displayed promising rheological properties for direct printing. Regardless of concentration and pepsin exposure, the pre-gel displayed shear thinning behavior and gelation below 10 min. Increasing the concentration of the hydrogels, increased the storage modulus from 1 kPa to 10 kPA. Increasing the concentration, also affected the gelation temperature to below 37 °C. However, cells could not be cultured within the hydrogels. Further research would need to be done in order to evaluate the cell compatibility of the pre-gels and suitable printing approaches

Thesis (Ph. D.)--University of Michigan. / eContent provider-neutral record in process. Description based on print version record.

Thesis (Ph. D.)--University of Michigan.

Spider silks are incredible natural materials that possess desirable combinations of strength, elasticity, weight, and robustness. Other properties such as biocompatibility and biodegradability further increase the worth of these materials. The possibility of farming spiders is impractical due to spiders’ natural behaviors. Modern biotechnologies have allowed for recombinant spider silk proteins (rSSps) to be produced without the use of spiders. However, the features responsible for spider silks impressive properties can cause difficulties with producing silk materials. A recently developed water-based and biomimetic solvation method has provided a solution to such difficulties and has also led to novel silk biomaterials. Most notable among these materials are; coatings, fibers, adhesives, films, foams, hydrogels, aerogels, capsules, and sponges. Many of these material possess specific properties that may be suitable for many commercial, industrial, and biomedical uses. This study has developed numerous spider silk biomaterials, identified their essential properties and features, provided preliminary evidence for various applications, and identified directions for future studies and uses.

<p>Multi-stimuli-responsive materials with dual sensitivities to both temperature and light were designed and investigated for their responsive properties in aqueous media.</p> <p>Amphiphilic polymers were synthesized by copolymerizing monomers of thermoresponsive N-isopropylacrylamide (NIPAM) with vinyl cinnamate (VC), using different chain transfer agents to both control the molecular weight and impart functionality of an amine-terminal or carboxylic acid- terminal end groups. Linear polymers based on pNIPAM-VC were characterized and their thermo- and photo-responsive properties confirmed by ¹H NMR, GPC, and UV-visible spectroscopy.</p> <p>To obtain desired solubility and phase transition properties for the copolymer, latent variable methods were applied to past polymer data to identify the correlated reaction variables. Using model inversion, the ability to predict polymer properties was possible. The outcomes helped to determine ideal reaction reagents and conditions for future designs, facilitating the synthesis of both amine-capped and carboxylic acid-capped poly(NIPAM-co-VC) polymers with high solubility and phase transition onset below physiological temperature (<37°C)</p> <p>The designed poly(NIPAM-co-VC) polymers were subsequently grafted to a polysaccharide, hyaluronic acid (HA) or carboxymethyl cellulose (CMC), via carbodiimide chemistry. The graft material’s mechanical strength was compromised by both the linear polymer size and the architecture (end-group-grafting) which lead to unsuitable materials.</p> <p>Microgels with multi-responsive properties were synthesized by copolymerizing NIPAM with either acrylic acid (AA) or methacrylic acid (MAA) by conventional precipitation-emulsion methods. These microgels were aminated and subsequently grafted with a cinnamate pendant group. As an alternative, microgels were fabricated by microfluidics using linear polymers precursors. Both types of microgels exhibited significant deswelling upon changes in temperature, light, and pH, suggesting their potential utility as smart, photo-responsive drug delivery vehicles.</p> / Master of Applied Science (MASc)

<p>Surface-induced thrombosis is a continuing issue in the development of biomaterials for blood contacting applications. Protein adsorption is a key factor in thrombosis since it occurs rapidly upon contact of a material with blood, initiating coagulation and other adverse reactions including platelet adhesion. The research presented in this thesis explores the use of a unique antithrombin-heparin covalent complex (ATH) for surface modification to provide antithrombogenicity. ATH was tethered to surfaces by various methods. Polyethylene oxide (PEO) was investigated as a linker-spacer molecule for surface attachment of ATH as well as for its antifouling properties.</p> <p>In the first phase of the work gold was used as a model substrate. ATH was attached by three different methods: direct attachment, attachment via a short chain linker, and attachment via PEO. Analogous heparin-modified surfaces were prepared for comparison. Surfaces were characterized using contact angle measurements, x-ray photoelectron spectroscopy (XPS), ellipsometry and quartz-crystal microbalance (QCM). The data suggested that the heparin moiety of ATH was directed away from the surface, in an orientation allowing ready interaction with blood components. The ATH-modified surfaces showed greater antithrombin binding than the heparin-modified surfaces as measured by radioactive labelling and Western blotting analysis. Antithrombin binding was found to occur predominantly through the active pentasaccharide sequence of the heparin moiety of ATH, demonstrating the potential of the ATH for catalytic anticoagulant function. From measurements of the ratio of total heparin to active heparin (anti-factor Xa assay), ATH-modified surfaces were shown to have greater bioactivity than heparin-modified surfaces. The adhesion of platelets to gold and modified gold surfaces was measured from flowing whole blood <em>in vitro</em> using a cone-and-plate device and was lower on all of the modified surfaces compared to bare gold. PEO-ATH surfaces were also shown to prolong plasma clotting times compared to control and heparinized surfaces.</p> <p>In subsequent work, surface modification methods were developed for polyurethane (PU) substrates. Isocyanate groups were introduced into the PU surface for attachment of PEO and ATH was attached to the “distal” end of the PEO. Surfaces using PEO of varying molecular weight and end group were investigated to determine conditions for maximum anticoagulant activity and minimum non-specific protein adsorption. Surfaces were characterized using contact angle measurements and XPS, and protein interactions were studied using radiolabelling. The optimum balance of bioactivity and protein resistance was found to occur with PEO of low to mid range MW (ie. MW 300-600). These PU-PEO-ATH surfaces showed low fibrinogen adsorption and high selectivity for antithrombin. Consistent with results using gold substrates, platelet adhesion remained low when ATH was attached to polyurethane surfaces grafted with PEO. A hetero-bifunctional amino-carboxy-PEO (PEO-COOH surface) was compared with a “conventional” homo-bifunctional dihydroxy-PEO (PEO-OH surface) with respect to their effectiveness as linkers for attachment of ATH. The PEO-COOH-ATH surface was shown to bind slightly greater amounts of antithrombin, indicating higher catalytic anticoagulant activity. Thrombin binding was measured to determine whether the surfaces could provide direct anticoagulant activity. The PEO-OH-ATH surface bound high amounts of thrombin, indicating potential for direct thrombin inhibition. It is hypothesized that the PEO properties (MW and functional end group) may have an effect on the orientation of ATH on the surface thus influencing its "preference" for catalytic vs. direct anticoagulant function.</p> <p>This thesis provides new information regarding the interactions of proteins and platelets with ATH immobilized on biomaterials. ATH-modified surfaces were superior to analogous heparin-modified surfaces with respect to antithrombin binding and catalytic anticoagulant ability. Immobilized ATH was also shown to bind thrombin, suggesting potential for direct anticoagulant activity. It can thus be seen as a unique surface modifier with dual functioning anticoagulant activity. The modification of polyurethane with ATH using PEO as a protein resistant linker-spacer, may provide a material of improved antithrombogenicity for the construction of blood contacting devices.</p> / Doctor of Philosophy (PhD)