Fungal keratitis is estimated to have at least 1 million incidences and causes 100,000 eye removal globally annually. Hourly eye drop administration remains the standard of care, and however, its low bioavailability and low patient compliance often lead to poor patient outcomes. My work is a response to the call for the urgent unmet need for an alternative drug delivery platform to combat ocular infection. In my dissertation, I utilized two composite systems for the antifungal contact lens: mesoporous silica nanoparticle (MSN) embedded chitosan and poly(lactic-co-glycolic acid) (PLGA) embedded poly(2-hydroxyethyl methacrylate) (pHEMA). For the MSN-chitosan system, I explored the loading methods and conditions to incorporate antifungal drugs into MSNs, characterized drug release profile and materials properties, verified fungal killing efficacy against Fusarium and Aspergillus to evaluate its potential as an antifungal contact lens material. For the PLGA-pHEMA system, I converted a planar structure prototype into a convex lens. I described the adjustment of lens fabrication process for precise geometry control, lens design iteration for improvement of drug release, and verification of the antifungal performance of the convex lens. This work provides insights of drug loading and delivery of highly insoluble drug and examples on contact lens fabrication process design with precise control on the laboratory scale.

Corneal disease is the second most prevalent cause of blindness in the world. Keratoplasty or corneal transplant is available as the last treatment resort and extended drug delivery following the procedure are preferred to be delivered by a drug eluting contact lens. Patients using either device in the wounded eye are prone to microbial infection that could complicate the outcome of the sight recovery. Thus, nanotopography, a physical surface modification studied to have potential antimicrobial effect and wound healing promotion, is considered to be integrated in novel design of both devices. Due to the spherical nature of the eye, conventional nanotechnology could not produce such surface, or requires heavy cost and resources.

In this thesis, I : 1) improve a nanopatterning technique for spherical surface and apply it on a novel cornea device, 2) validate its biological responses in vivo, 3) apply the patterning technique for a contact lens design with a new class of material, 4) analyze the economic and commercial benefits of both device in current ophthalmic market. This thesis consists universal protocol for adaptive patterning methods on various material platform and outline validation method for future regulatory works. This thesis shall set the foundation for a medical device startups that could restore sights for millions around the world.

Pathogenic microbes, such as bacteria and fungi, often contaminate medical systems resulting in 1.7 million annual cases of hospital acquired infections, 99,000 annual deaths, and $16.6 billion spent in healthcare costs in US alone. Current solutions declining in efficacy are drug therapies, which have led to the rise of antimicrobial resistance and created an urgent need for alternative strategies. Here, the fabrication and physical antimicrobial effects of polymeric nanoimprinted surfaces based on bactericidal nanotopography inspired by nature are explored. A materials science and engineering approach is combined with microbiology and mechanobiology to further probe the cell-surface interface for the the ability of the bioinspired nanotopography to (1) hinder surface-attached Pseudomonas aeruginosa bacterial growth and virulence, (2) disrupt P. aeruginosa bacterial mechanoresponsive upstream motility in fluid flow, and (3) inhibit Aspergillus fumigatus and Fusarium oxysporum filamentous fungal growth demonstrating antimicrobial effects in a eukaryotic cell type system. This work promises broad applications for synergistic antimicrobial solutions in medically relevant systems and heralds’ new platforms to study mechanobiology.

Approximately 2 million cases of microbial keratitis occur in the world every year. Microbial keratitis can develop into vision loss and other severe complications. The current treatment is the use of antibiotic eye drops, which have diminished effect due to the increasing development of antimicrobial resistance. Instead of using drugs to control microbe growth, we engineered an antimicrobial nanopillared topography onto a hydrogel material to physically inhibit microbe growth and reduce the risk of contact lens-related microbial keratitis. The challenges, thus objective of this research, is to develop a method to integrate the nanotopography onto curved lens surfaces and to stabilize the nanostructures by crosslinking the hydrogel polymer. The hydrogel chitosan has antimicrobial and mucoadhesive properties that can promote wound healing. The dimensions and curvatures of the lens need to be controllable after the material is saturated with solvent. Chitosan hydrogels are stabilized by co-crosslinking with a covalent crosslinker, genipin (GP), and ionic crosslinker, tripolyphosphorous (TPP), or single crosslinking with only TPP. The material properties are modulated and characterized to suit the contact lens application. The antifungal properties of the engineered contact lens are also characterized with in vitro tests. The result shows that the resulting ophthalmic device is able to stabilize the nanotopography and hinder Fusarium oxysporum growth on the device surface for 24 hours.

In the USA, yearly, over 1.7 million patients acquire infection during their hospital stay; about 99,000 of them died. The only cure and prevention currently in use are antibiotics; however, more severe infections have been seen in the past decade because of the development of microbial resistance to antibiotics. We have discovered that it is possible to engineer a nanopatterned surface that can kill and/or prevent the growth of microbes by mimicking nature’s antibacterial surfaces. Others have explored top-down approaches, such as lithography and anodization to fabricate an array of nanopatterned surfaces. Limitations for such an approach are the size of the template and types of surfaces. Here, I describe the use of a self-assembled microstructured polymeric surface coating that is inherently biocompatible and designed to overcome the problems described above. The desired surface is coated with LPEI (linear polyethylenimine), a hydrogel that undergoes water-induced crystallization. By controlling the solution pH and concentration, the simple dip-coating method can be used to fabricate coatings with nanostructure possessing well-defined morphology and tunable geometry on any arbitrary surface. Using material characterization techniques and rheometer, an insight to LPEI macromolecules behavior in the solution to promote pillar-like morphology formation can be described. Specifically, I focused on gaining an understanding of the effect of the cohesive behavior of LPEI macromolecules and the interaction of the polymer with water in controlling such morphology. Our grand vision is to be able to engineer an effective, long-lasting, and biocompatible coating layer to prevent device-associated infection around the world.

Cell-to-substrate interactions are known to regulate important cellular processes such as migration, proliferation, and intercellular signaling. Cancer cells remodel the surrounding collagen matrix and promote collagen fibrillogenesis for invasion. This increases substrate density and activates the mechanosensing pathway for events such as adhesion and migration. Recent studies indicate that metabolism is able to affect cancer invasion and that mitochondria are recruited towards the invading edges of the cell. There seems to be a link between the mechanosensing and metabolism pathway in promoting invasion; however, it is unclear how these are regulated and affects mitochondria trafficking towards the protruding edges. In this thesis, focal adhesion (FA) dynamics within NIH3T3 cells were studied using the Number and Molecular Brightness analysis and were found to adapt to the underlying nanotopography by modulating their adhesion size and turnover dynamics leading to a change in cell speed. This laid the foundational studies within cancer cells. In MDA-MB231 breast cancer cells, raster imaging correlation spectroscopy (RICS) was used to study focal adhesion dynamics in response to substrate topography and collagen density. The increase of substrate density and addition of nanolines showed a decrease in FA protein dynamics and increased tension, respectively. In addition, Fluorescent lifetime imaging microscopy (FLIM) was used to measure metabolic signatures within MDA-MB231 cells. A shift from oxidative phosphorylation (OXPHOS) to glycolysis (GLY) with increasing collagen density was observed. Since the increase of substrate density is known to upregulate focal adhesion formation, actin polymerization, migration, and invasion, a large amount of ATP is consumed. Rac1 activation was stimulated to promote membrane formation and actin polymerization to observe mitochondria recruitment. Mitochondria transport speed increased when Rac1 was activated compared to when it was inactivated, specifically in breast tumor cells. This shows that mitochondria are transported to regions of high energy consumption and sustain processes needed for invasion. In addition, metabolism of the invading protrusions was found to shift towards a GLY metabolic signature. Results indicate that collagen density, metabolism and mitochondria trafficking all play an important role in regulating cancer cell invasion. When developing therapies, these parameters should be considered in order to effectively prevent metastasis.

The ability to control cell adhesion on material surfaces is critical to the performance and compatibility of medical implants in the body. One such application that would benefit from controlled adhesion is an artificial cornea, an implant for replacing the anterior portion of the eye. For a successful implant, we need to simultaneously promote cell adhesion on the periphery of the implant to improve integration, while limiting adhesion in the central region to provide clear vision.

To address this challenge, we used nanoimprint lithography to create arrays of precisely defined nanopatterns on the scale of 100-500 nm on surfaces of polymer films. We postulated that nanoline patterns resembling the natural collagen fibers in the cornea would encourage adhesion, and that the transparent nanopillars would discourage cell adhesion on polymer films. We designed experiments to evaluate the degree of adhesion on the nanopatterned polymer surfaces, which confirmed our postulates. Using fluorescence correlation spectroscopy, we found that nanotopography influenced cell motility by inducing protein reorganization in cell adhesions. Studies under conditions of fluid flow induced shear confirmed that nanoline patterns were better than flat surfaces at encouraging cell adhesion, as significantly more cells remained on nanolines at the highest shear rate applied.

Results described in this thesis demonstrate the feasibility of using nanotopography to control the degree of cell adhesion. As for the artificial cornea, future in vitro studies with corneal keratocytes are suggested to evaluate corneal wound healing before ultimately conducing in vivo studies to evaluate the efficacy of our proposed device. This thesis shows that implementing nanotopography could lead to improved implantable medical devices and scaffolds for tissue-engineered constructs by providing greater spatial control of cell adhesion even under kinematic conditions without the need to chemically modify material surfaces.

Contact lenses contaminated by pathogenic fungi and bacteria cause eye infections, resulting in ~1 million doctor’s office visits every year, at a cost of $175 million annually in the USA alone. The most severe of these infections are plagued by protective biofilm, which make the microbes more tolerant to current drug therapies, and creates an urgent need for alternative strategies. In my thesis research, material and topographical solutions inspired by nature are explored. I investigated the use of the biopolymer chitosan, which is antimicrobial, biocompatible, plentiful, and inexpensive. The anti-biofouling surface structures found on cicada wings, shark skin, and fish scales are used as inspiration for nanopillars imprinted on chitosan. The fabricated surfaces can prevent biofouling and influence the mechanical performance of the material.The specific goals of this dissertation are to: 1) Fabricate, characterize, and optimize the design of a chitosan hydrogel film with nanopillars which remain stabilize even after immersion in liquid; 2) Evaluate the antimicrobial efficacy of the chitosan hydrogels with nanopillars against Fusarium oxysporum and Pseudomonas aeruginosa; and 3) Investigate the link between the mechanical performance and nanopillar surface on the chitosan hydrogels. I demonstrated in this thesis a scalable process to fabricate bioinspired nanopillar surface structures. The bioinspired surface generally enhances the antimicrobial efficacy and mechanical performance of several types of hydrogel films. The generalization of this technique has important implications and commercial potential.

Corneal afflictions are the second leading cause of blindness worldwide. When a corneal transplant is unavailable or contraindicated, an artificial cornea device is the only chance to save sight. Bacterial or fungal biofilm build up on artificial cornea devices can lead to serious complications including the need for systemic antibiotic treatment and even explantation. As a result, much emphasis has been placed on anti-adhesion chemical coatings and antibiotic leeching coatings. These methods are not long-lasting, and microorganisms can eventually circumvent these measures. Thus, I have developed a surface topographical antimicrobial coating. Various surface structures including rough surfaces, superhydrophobic surfaces, and the natural surfaces of insects’ wings and sharks’ skin are promising anti-biofilm candidates, however none meet the criteria necessary for implementation on the surface of an artificial cornea device.

In this thesis I: 1) developed scalable fabrication protocols for a library of biomimetic nanostructure polymer surfaces 2) assessed the potential these for poly(methyl methacrylate) nanopillars to kill or prevent formation of biofilm by E. coli bacteria and species of Pseudomonas and Staphylococcus bacteria and improved upon a proposed mechanism for the rupture of Gram-negative bacterial cell walls 3) developed a scalable, commercially viable method for producing antibacterial nanopillars on a curved, PMMA artificial cornea device and 4) developed scalable fabrication protocols for implantation of antibacterial nanopatterned surfaces on the surfaces of thermoplastic polyurethane materials, commonly used in catheter tubings. This project constitutes a first step towards fabrication of the first entirely PMMA artificial cornea device.

The major finding of this work is that by precisely controlling the topography of a polymer surface at the nano-scale, we can kill adherent bacteria and prevent biofilm formation of certain pathogenic bacteria, without the use of any chemical antibiotic agents. Such nanotopographic coatings can be applied to implantable polymer medical devices with scalable, commercializable processes, and may deter or delay biofilm formation, potentially improving patient outcomes. This thesis also opens the door for adaptation of antibacterial, nanopillared surfaces for other applications including other medical devices, marine applications and environmental surfaces.