Browsing by Author "Kipper, Matt J., committee member"
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Item Open Access A drug eluting, osseointegrative phospholipid coating for orthopedic implants(Colorado State University. Libraries, 2011) Prawel, David A., author; James, Susan P., advisor; Popat, Ketul C., advisor; Kipper, Matt J., committee member; Ryan, Stewart D., committee memberMillions of implant surgeries are performed each year. Titanium is commonly used for implantable metallic devices, especially total hip and knee replacements. However, titanium implants are far from perfect. Although the absolute failure rate is not particularly high, the case-by-case direct and human cost of each device implant failure is tremendous. Cementless titanium implant devices, although preferred by surgeons, frequently fail due to loosening of the device, often as a result of poor integration of naturally forming bone with the metallic implant, and by infection. Phospholipids are naturally occurring substances that are shown to enhance integration of new bone with implants, and to help reduce inflammation, a common precursor to infection. In addition, numerous studies have shown phospholipids to be effective drug delivery agents. To date, dip and drip coating techniques for applying phospholipid coatings have been used on titanium. Both coating techniques are easy to perform, but result in coatings too thick and non-conformal for in vivo use. Electro-spraying (E-spray) is a method of atomizing a liquid by means of electrical forces. E-spraying provides the advantage of being able to create coatings with relatively high efficiencies because the electrical charge difference "carries" the liquid source material, which also provides good control of coating morphology, especially on rough and intricately shaped surfaces. Other advantages of this technique are low cost and easy setup. In our work, the E-spraying technique was successfully adapted to apply thin, conformal, consistent coatings of 1,2-dioleoyl-sn-glycero-3-phospho-L-serine (DOPS) to small, flat, commercially pure titanium plates. DOPS coatings were E-sprayed, then loaded with gentamicin sulfate (GS), a popular antibiotic used in treatment of osteomyelitis. An elution study was completed to assess drug delivery capabilities of the coatings. This work demonstrated that elution profile could be modified by changing E-spray parameters. Rat marrow stromal cells were harvested, and seeded onto the test coatings. Mesenchymal stem cells (MSCs) were selected from the general cell population, successfully cultured and differentiated into osteoblasts. Cytotoxicity of the coatings, along with cell viability, cell differentiation, biomineralization activity, cell morphology and early osseogenesis markers were evaluated at multiple time points in dual multi-week studies. DOPS coatings were found to be non-cytotoxic, and cell viability and biomineralization were higher on DOPS-coated surfaces and gentamicin-loaded coatings than on plain titanium samples. At the two week time point, excessive delamination of the coatings occurred in the cell growth environment. Research was undertaken to identify and test techniques to enhance coating retention. Surface chemistry was modified by passivation and pretreatment with calcium-chloride, and cholesterol was added to the DOPS E-spray. A repeated elution study demonstrated that elution profile could be modified as a result of changes in coating chemistry. An additional MSC cell study was completed to reconfirm the effects of enhanced coating chemistry on the cytotoxicity, cell viability and biomineralization. Cell morphology was re-evaluated at all time points via SEM imaging. Hydroxyapatite formation was confirmed. Preliminary osseogenesis biomarkers were also measured, showing deposition of osteocalcin and osteopontin, important protein precursors to normal bone growth, on enhanced coatings. This work demonstrates the viability of electro-sprayed DOPS coatings on titanium orthopedic implant material, and the enhanced osseogenic characteristics of these coatings. We also demonstrated that DOPS coatings can carry and release an antibiotic over time at clinically relevant dosages, and that this release profile can be engineered by modifications to E-spray process parameters, surface chemistry and E-sprayed material formulation.Item Embargo Development of low-cost capillary driven immunoassays for improved medical diagnostics(Colorado State University. Libraries, 2023) Link, Jeremy S., author; Henry, Charles S., advisor; Van Orden, Alan, committee member; Ackerson, Christopher J., committee member; Kipper, Matt J., committee memberRapid medical diagnostics are a crucial part of an effective healthcare system. While traditional laboratory diagnostic methods are well established and sensitive, they are also time consuming and expensive. Point of care (POC) diagnostics offer an attractive alternative to traditional testing for more affordable, fast results. Their simplicity allows for POC devices to be run quickly by untrained personnel, but the simplicity often limits their detection range and sensitivity. In this dissertation I discuss affordable, capillary-driven immunoassay devices that are capable of passively delivering reagents associated with a traditional well-plate enzyme linked immunosorbent assay (ELISA) to test strips. These devices are made of patterned and laser cut double-sided adhesive. When stacked and laminated together, the patterns cut from the layers form hollow microfluidic channels that can passively transport fluids through capillary action. The devices in this dissertation require only a single end-user step to perform a sandwich immunoassay, and signal from the enzyme/substrate reaction is detectable in under 30 min. Chapter 2 discusses the first application for visual detection of SARS-CoV-2 in these affordable capillary-driven immunoassay devices. The device in this chapter uses the enzyme horseradish peroxidase (HRP) and the substrate 3,3',5,5'-tetramethylbenzydine (TMB) to produce signal at the test line. Upon sample addition, the device channels fill, rehydrating the detection antibody and substrate dried on conjugate release pads that are stored in the channels of the device. Within 20 min, target, reagents, and washing steps are passively delivered to a nitrocellulose test strip containing a capture antibody test line. The device performance was compared to a well-plate ELISA, and the detection limits for inactivated SASR-CoV-2 were 86 PFU/mL and 8 PFU/mL for the device and ELISA respectively. A dose response curve was also generated for spiked nasal swab samples with a detection limit of 222 PFU/mL, demonstrating the device's use with complex biological samples. Chapter 3 expands on the work in Chapter 2 by demonstrating an alternative detection method. Chemiluminescent immunoassays are highly sensitive assays that rely on the energy provided by a chemical reaction to excite electrons. When the electrons move back to the ground state, they produce light that can be detected with an imager. In Chapter 3, I demonstrate the first example of a one-step, capillary driven immunoassay for chemiluminescent detection. The device is similar to that in Chapter 2, but the detection system relies on the reaction between HRP and a luminol based substrate to detect SARS-CoV-2 antigen. This work was done in collaboration with Burst Diagnostics Inc. and will be published when the appropriate patents and protections are in place. Chapter 4 introduces the first capillary driven enzyme-linked immunoassay for the simultaneous detection of multiple biomarkers. This multiplexed device is made of the same inexpensive materials as the previous chapters, but the microfluidic channels are designed in such a way that reagents are delivered to two, spatially separated test strips. This separation allows for simultaneous detection of two targets without cross-reactivity between reagents, reducing the chance of false positives. To demonstrate the purpose of this device, they were used to detect SARS-CoV-2 antigen on one test strip, and influenza antigen on the other. The illnesses caused by these two viruses lead to very similar symptoms, so distinguishing between the two illnesses from a single device would be beneficial. Dose response curves were gathered for both antigens, and the device was able to detect both diseases visually without false positives on the other test strip. Another form of multiplexed detection is simultaneous detection of two targets. To demonstrate this, SARS-CoV-2 and influenza antigen were detected simultaneously. Additionally, SARS-CoV-2 virus and c-reactive protein (CRP), a biomarker that can be used to determine the severity of COVID-19 cases, were detected simultaneously. This multiplexed assay has the potential to tell a healthcare provider 1) if an infection is or is not SARS-CoV-2, and 2) what level of care might be needed. This dissertation introduces three capillary driven immunoassay devices primarily for the use of detecting communicable diseases. The devices all run from a single end-user step, and fully automate the steps required for a more time consuming and expensive ELISA. Although the focus of this dissertation was on detecting communicable diseases, these devices can (and are) being further developed for chronic illnesses. In the future, by swapping the antibodies used in the immunoassay, the applications of these devices are innumerable. Additionally, different detection methods, such as fluorescent, electrochemical, and further chemiluminescent work could continue to push the detection limit down, widening the application of these devices even further.Item Open Access Development of tethered micelle hydrogel networks through sphere-forming AB/ABA block copolymer melts(Colorado State University. Libraries, 2013) Guo, Chen, author; Bailey, Travis S., advisor; Kipper, Matt J., committee member; Chen, Eugene, committee member; Wickramasinghe, S. Ranil, committee memberThe overriding theme of the work contained in this thesis is concerned with the preparation of tethered micelle hydrogel networks through the melt-state self-assembly of sphere-forming AB diblock and ABA triblock copolymer blends. The first chapter of this dissertation introduces the various projects pursued and provides background information for the reader. The second chapter of this thesis contains the initial demonstration of this novel strategy using polystyrene-poly(ethylene oxide) (PS-PEO, SO) diblock and PS-PEO-PS (SOS) triblock copolymers. Included in this chapter is a discussion of the synthetic polymerization techniques used to produce the SO and SOS block copolymers, the basic melt-state fabrication and characterization strategies used to pre-structure the tethered micelle networks, and the impact of changing both the SOS concentration and temperature on the resultant properties of the hydrogels produced. In these initial studies, the SOS triblock copolymer was constructed to be exactly double the SO diblock copolymer molecular weight, such that the preferred lattice dimensions during self-assembly were "matched". These "matched" hydrogels produced equilibrium swelling ratios (3.8-36.9 g water/g polymer) and dynamic elastic moduli (G' = 1.7-160 kPa) tunable across an impressive range of values using only temperature (10-50 °C) and SOS concentration (3.3-72.0 mol%). The third chapter of this thesis describes our efforts to influence the swelling and mechanical properties exhibited by simply modifying the PEO midblock molecular weight in the SOS tethering molecules. In doing so, we were able to show that the degree of coronal layer overlap between adjacent micelles was the primary contributing factor determining the dynamic mechanical response of the hydrogel. That is, the changes in mechanical properties produced due to altering tether concentration, tether length, or temperature, could all be understood in terms of their impact on the degree of coronal layer overlap in the system. In addition to these findings, we also discovered an interesting relationship between swelling and tether length. Increases in tether length by a factor of 1.6 compared to that of the matched system, resulted in higher swelling ratios and smaller elastic moduli (due to reduced coronal layer overlap). However, increases in tether length by a factor of 2.3 produced swelling behavior and mechanical properties nearly identical to that of the matched system. We concluded that the increase in tether length by a factor of 2.3 was sufficient to allow bridging into the second shell of the nearest neighbor micelles, negating the swelling advantage anticipated for the system. The fourth chapter of this thesis concerns our efforts to demonstrate the modification potential of the swollen hydrogel systems of Chapters 2 and 3. In this study, the terminal hydroxyl functionality present in the aforementioned SO diblock copolymers was substituted with either an azide or alkyne functionality. Cu(I) catalyzed coupling of the azide/alkyne functional diblock copolymer was then performed in the swollen state, producing a secondary network of tethers in the system. Installation of the secondary network produced dramatic improvements in the hydrogel tensile modulus, strain at break, stress at break, and toughness, while permitting swelling ratios, small strain rheological properties, and response in unconfined compression to remain largely unchanged. The fifth and final chapter of this thesis concerns a discussion of preliminary data supporting several promising directions for future work involving the further development of these tethered micelle networks.Item Open Access Enantioselective β-functionalization of enals via N-heterocyclic carbene catalysis(Colorado State University. Libraries, 2015) White, Nicholas Andrew, author; Rovis, Tomislav, advisor; Kennan, Alan J., committee member; Chen, Eugene Y.-X., committee member; Williams, Robert M., committee member; Kipper, Matt J., committee memberA series of δ-nitroesters were synthesized through the N-heterocyclic carbene catalyzed coupling of enals and nitroalkenes. The asymmetric coupling of these substrates via the homoenolate pathway afford δ-nitroesters in good yield, diastereoselectivity, and enantioselectivity. This methodology allows for the rapid synthesis of δ-lactams. Using this approach, we synthesized the pharmaceutically relevant piperidines paroxetine and femoxetine. A novel single-electron oxidation pathway for the N-heterocyclic carbene generated Breslow intermediate has been developed. Nitroarenes have been shown to transfer an oxygen from the nitro group to the β-position of an enal in an asymmetric fashion to generate β-hydroxy esters. This reaction affords desired β-hydroxy ester products in good yield and enantioselectivity and tolerates a wide range of enal substrates. A dimerization of aromatic enals to form 3,4-disubstituted cyclopentanones has been investigated. Using a single-electron oxidant, aromatic enals couple to form cyclopenanone products in good yield, good enantioselectivity, and excellent diastereoselectivity. A cross coupling has also been developed to afford non-symmetrical cyclopentanone products.Item Open Access Fabrication of omniphobic and superomniphobic surfaces(Colorado State University. Libraries, 2017) Pendurthi, Anudeep, author; Kota, Arun K., advisor; Yalin, Azer P., advisor; Kipper, Matt J., committee memberSuperomniphobic surfaces (i.e., surfaces that are extremely repellent to both high surface tension liquids like water and low surface tension liquid like oils and alcohols) can be fabricated through a combination of surface chemistry that imparts low solid surface energy and a re-entrant surface texture. Recently, surface texturing with lasers has received significant attention because laser texturing is scalable, solvent-free, and can produce a monolithic texture (i.e., a texture that is an integral part of the surface unlike a coating that is deposited on the underlying substrate) on virtually any material. In this work, we fabricated nanostructured omniphobic and superomniphobic surfaces with stainless steel 430, stainless steel 316, stainless steel 304, titanium, aluminum and glass surfaces using a simple, inexpensive and commercially available CO2 laser engraver. Further, we demonstrated that the nanostructured omniphobic and superomniphobic surfaces fabricated using our laser texturing technique can be used to design patterned surfaces, surfaces with discrete domains of the desired wettability and on-surface microfluidic devices. Systematic experiments were conducted to evaluate the importance of various laser parameters to fabricate these omniphobic and superomniphobic surfaces. Also, the performance of these surfaces under adverse acidic and basic conditions was evaluated systematically. In addition to surface texturing with lasers, in this work, we also report a simple and versatile method to fabricate superomniphobic glass microfiber paper by growing silicone nanofilaments using trichloromethylsilane (TCMS).Item Open Access Interaction between membrane and protein properties on flux decline during sterile microfiltration(Colorado State University. Libraries, 2010) Cutler, Hailey, author; Wickramasinghe, Sumith Ranil, advisor; Kipper, Matt J., committee member; Venayayamoorthy, S. Karan, committee memberMicrofiltration is widely used in industry to filter out particulate matter that contaminates or slows down the performance of the membrane. In the biopharmaceutical industry in particular, bacteria, microorganisms and viruses are filtered out using sterile microfiltration. Numerous studies have been conducted to further the understanding of flux decline due to protein fouling. Many times the operating conditions, the type of membrane and type of protein all interact to have an effect on protein fouling and flux decline. Normal-flow microfiltration experiments were conducted using uncoated polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) membranes, and PTFE and PVDF membranes coated with polyvinyl alcohol (PVA). Feed streams consisted of lysozyme, β-lactoglobulin and ovalbumin. The pH values of the solution were set at the isoelectric point of each of the proteins (11.0, 5.8, and 4.7 respectively). The experiments were operated with a feed pressure of 2 or 10 psi. Each of the proteins was tested at 0.1 and 2 g/L with uncoated PTFE. No flux decline was seen using 0.1 g/L, so 2 g/L was focused on for PVA coated PTFE, PVA coated PVDF and uncoated PVDF membranes. Protein fouling of the membrane was investigated by determining the variation of permeate flux versus filtrate volume and by analysis of Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectra and Field Emission Scanning Electron Microscopy (FESEM) images of unfouled membranes and membranes after microfiltration. Results indicate that the greatest amount of fouling occurs with ovalbumin. The order of most to least fouling was found to be ovalbumin> β-lactoglobulin>lysozyme. Fouling was more severe at the higher protein concentration (2 g/L) and feed pressure (10 psi) and seen only when filtering the solution through uncoated and PVA coated PTFE. Flux decline under these conditions was analyzed using classical pore blockage models. In general, flux decline was found to be caused by complete pore blocking. In the case of ovalbumin filtered through PVA coated PTFE, the flux decline was first caused by pore blockage and then later transitioned to cake filtration. The proteins which showed significant fouling conditions were looked at more closely by pre-filtering the protein solution. The goal of pre-filtration was to decrease any protein aggregates present in solution. This pre-filtration step was conducted with 0.2, 0.45 and 1 μm diameter pore sizes. The flux decline when pre-filtering the feed solution with 1 μm pores was equivalent to the filtration experiments without pre-filtration. The only significant decrease in flux was present when pre-filtering with the 1μm pores. Additional experiments were conducted using hemoglobin (Hb) at 2 g/L and 10 psi operating conditions. Previous literature had shown that using 1 μm pre-filtration, there was severe flux decline for uncoated and PVA coated PTFE. To follow up on these experiments, Hb was pre-filtered using 0.2 and 0.45 μm pre-filtration membranes and then filtered through uncoated and PVA coated PTFE. These experiments resulted in no flux decline. The Hb experiments verified the results from the ovalbumin and β-lactoglobulin experiments. All together, these results indicate that there is an interaction among membrane properties, protein properties, operating conditions and pre-filtration characteristics that determine whether fouling occurs and to what extent.Item Open Access Part I - Access to UV photocured nanostructures via selective morphological trapping of block copolymer melts. Part II - Morphological phase behavior of poly(RTIL) containing block copolymer melts(Colorado State University. Libraries, 2012) Scalfani, Vincent F., author; Bailey, Travis S., advisor; Finke, Richard G., committee member; Henry, Charles S., committee member; Kipper, Matt J., committee member; Prieto, Amy L., committee memberA thermally stable photocuring system was developed for high fidelity translation of block copolymer based melt-state morphologies into their equivalent solid analogs. Cationic photoacids were combined with partially epoxidized polyisoprene-b-poly(ethylene oxide) (PI-PEO) block copolymers, forming composite blends that allow for extended thermal processing prior to cure, in addition to precise trapping of selected morphologies, a consequence of the temperature independent UV curing mechanism. The parent PI-PEO block copolymer exhibited multiple melt-state morphologies including crystalline lamellae (Lc), hexagonally packed cylinders (C), bicontinuous gyroid (G), and an isotropic disordered state (Dis). Modification of the PI-PEO backbone with epoxy groups and addition of a UV cationic photoacid acted only to shift transition temperatures quantitatively, leaving the overall morphological behavior completely unmodified. UV irradiation exposure of the composite blends directly in the melt-phase at selected temperatures resulted in permanent trapping of both the cylinder and gyroid morphologies from a single block copolymer sample. The studied photocuring chemistry was extended to produce spherical nanostructured hydrogel networks. Fabricated hydrogel networks are built from a pre-structured lattice of body-centered cubic spheres (SBCC), produced via melt-state self-assembly of blended AB diblock and ABA triblock copolymers. Added ABA triblock serves to produce active tethered junction points between the AB diblock spherical micelles. The integrated thermally stable photocuring chemistry allows for in situ trapping of these spherical domains directly in the melt phase, independent from the required thermal processing necessary to achieve the tethered BCC lattice. Specifically, the hydrogel networks were fabricated from partially epoxidized blends of polybutadiene-b-poly(ethylene oxide) diblock (PB-PEO) and PB-PEO-PB triblock copolymers. UV cured samples of composite copolymer disks containing an added amount of UV activated cationic photoinitiator samples retained the SBCC structure with high fidelity, which serves to pre-structure the hydrogel network prior to swelling. Photocured disks preserved their original shape when swollen in water or organic media, were highly elastic and had excellent mechanical properties. Control experiments with uncured samples immediately dissolved or dispersed when swollen. Simple photopatterning of the cross-linked hydrogel system is also explored. The developed pre-structured hydrogel network was then adapted to incorporate light sensitive anthracene groups into the spherical forming AB diblock copolymer for in situ generation of tethering ABA triblock. Pressed disks of anthracene terminated poly(styrene)-b-poly(ethylene oxide) diblock (PS-PEO-An) were photocoupled with UV 365 nm filtered light directly in the melt-phase, post the necessary thermal self-assembly process. Photocoupled disks swelled in water, were highly elastic, had tunable mechanical properties (based on UV irradiation time), and showed complete preservation of initial shape. Swollen photocoupled disks were found to exhibit similar properties to pre-blended PS-PEO/PS-PEO-PS hydrogels with slight differences likely resulting from an asymmetric distribution of triblock in the photocoupled gels. The PS-PEO-An based hydrogels are proposed to be possible future candidates for the development of new asymmetric hydrogels because of their simple fabrication and excellent mechanical properties. In part II of this dissertation, a new poly(room temperature ionic liquid) (RTIL) BCP platform was developed based on the sequential, living ring-opening metathesis polymerization (ROMP) of a hydrophobic non-charged dodecyl ester norbornene monomer followed by a cationic imidazolium norbornene ionic liquid (RTIL) monomer. The synthesized BCPs were found to exhibit surfactant behavior in solution and form highly periodic nanoscale melt morphologies. Extensive control experiments with homopolymer blends do not show any surfactant behavior in solution nor microphase separation in the neat melt phase. After an initial study optimizing the synthesis and verifying the block architecture, a series of 16 poly(RTIL)-based BCP samples were synthesized with varying compositions of 0.42-0.96 vol% poly(norbornene dodecyl ester). A phase diagram was developed through a combination of small-angle X-ray scattering and dynamic rheology. Morphologies identified and assigned within the phase space studied include lamellae (Lam), hexagonally packed cylinders (Hex), a coexistence of Hex and Lam domains in place of the gyroid region, spheres on a body-centered cubic lattice (SBCC), and a "liquid like" packing of spheres (LLP). Annealing samples containing a coexistence of Lam and Hex domains suggest extremely slow ordering kinetics disposing one of the morphologies. The studied poly(RTIL)-based BCPs containing highly charges species are very strongly segregated (large Chi parameter), resulting in limited if any access to the disordered and gyroid regime. Finally, in Appendix I a supramolecular polymer system comprised of benzene-1,3,5-tricarboxamide (BTA) and 2-ureido-4[1H]-pyrimidinone (UPy) functional hydrogenated polybutadiene was developed that forms two unique and independent nanorods motif assemblies. When the two supramolecular motifs are end-capped to different homopolymers, the motifs self-assemble independent of each other into separate nanorod stacked structures. However, when a telechelic polymer is introduced into the system containing both supramolecular motifs (one on each end), a network is formed between the nanorod assemblies. Without the telechelic polymer, the supramolecular material is a viscous liquid with little mechanical integrity. In contrast, addition of the telechelic polymer acts as a cross-linker and results in a networked material that is highly elastic with excellent mechanical properties.Item Open Access Superhydrophobic coatings for electrical insulators(Colorado State University. Libraries, 2018) Vallabhuneni, Sravanthi, author; Kota, Arun K., advisor; Popat, Ketul, committee member; Kipper, Matt J., committee memberDielectric breakdown in electrical insulators is a frequently encountered phenomenon leading to surface damage, material loss and eventually a complete breakdown of electrical insulators. Dielectric breakdown is accelerated under severe conditions such as humidity and rain. As a result, the service life of the electrical insulators is affected. In our work, we employed superhydrophobic coatings, which are extremely repellent towards water, in an attempt to retain the dielectric strength of electric insulators in the presence of water. In addition, we studied the influence of surface roughness on the dielectric breakdown of electrical insulators. In this work, hydrophobic PDMS sheets (as a mimic to silicone bushings/insulators) with different surface roughness were fabricated and superhydrophobicity was imparted to these sheets via surface modification. The dielectric breakdown of these PDMS sheets was studied under both dry and wet conditions. The influence of surface roughness on the dielectric breakdown was also investigated by using PDMS sheets with different surface roughness. We noticed an increase in surface roughness leads to lower dielectric breakdown. Further, we demonstrated that superhydrophobic coatings on the surface of electrical insulators allow the retention of dielectric strength under wet conditions. Consequently, we envision that superhydrophobic coatings on electrical insulators will lead to enhanced performance and prolonged service life of insulators.