In the field of biomaterials, naturally-derived and synthetic polymers are utilized individually or in combination with each other, to create bio-inspired or biomimetic materials for various bioengineering applications, including drug delivery and tissue engineering. Natural polymers, such as proteins and polysaccharides, are advantageous due to low or non-toxicity, sustainable resources, innocuous byproducts, and cell-instructive properties. Synthetic polymers offer a variety of controlled chemical and physical characteristics, with enhanced mechanical properties. Together, natural and synthetic polymers provide an almost endless supply of possibilities for the development of novel, smart materials to resolve limitations of current materials, such as limited resources, toxic components and/or harsh chemical reactions. Herein is discussed the synthetic-biological material formation for cell-instructive tissue engineering and controlled drug delivery. We hypothesized that the combination of hydrogel-based scaffold and engineered nanomaterials would assist in the development or regeneration of tissue and disease treatment. Chemically-modified alginate was formed into alginate-based nanoparticles (ABNs) to direct the intracellular delivery of proteins (e.g., growth factors) and small molecular drugs (e.g., chemotherapeutics). The ABN surface was modified with cell-targeting ligands to control drug delivery to specific cells. The ABN approach to controlled drug delivery provides a platform for studying and implementing non-traditional biological pathways for disease (e.g., osteoporosis, multiple sclerosis) and cancer treatment. Through traditional organic and polymer chemistry techniques, and materials engineering approaches, a stimuli-responsive alginate-based smart hydrogel (ASH) was developed. Physical crosslinks formed based on supramolecular networks consisting of β-cyclodextrin-alginate and a tri-block amphiphilic polymer, which also provided a reversible thermo-responsiveness to the hydrogel. The hydrogel was shear-thinning, and recovered physical crosslinks, i.e., self-healed, after un-loading. The ASH biomaterials provide a platform for injectable, therapeutics for tissue regeneration and disease treatment. Indeed, various hydrogel constituents and tunable mechanical properties created cell-instructive hydrogels which promoted tissue formation.

Philosophiae Doctor - PhD / Polyamic acid (PAA) nanostructured materials were successfully produced by electrochemical deposition and electrospinning using polyvinlypyrrolidone (PVP) as supporting polymer. Polyamic acid thin film and nanofibers were deposited directly at the surface of a screen-printed carbon electrode (SPCE) as electro-catalysts for reliable analytical reporting of sulphonamide as contaminants of emerging concern by electrochemical techniques. Fourier transform infrared (FTIR) spectroscopy was used to confirm the structural integrity of the PAA electrospun nanofibers compared to the chemical synthesized PAA. Brunauer-Emmett-Teller (BET) was used to determine the surface area of the nanofibers. The surface morphology and surface thickness of the polyamic acid (PAA) nanofibers on the screen-printed electrodes was studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Cyclic voltammetry (CV) was used to study redox behavior of the nanostructured PAA modified screen-printed carbon electrodes. Electrochemical parameters surface concentration, diffusion coefficient, formal potential and peak separation were determined. Three sulphonamides were selected based on the United States of protection agency (US EPA) and World Health Organization (WHO) list of emerging contaminants and detected sulphonamides in environmental waters in South Africa and other African regions. The selected sulfonamides were evaluated at the unmodified and modified screen-printed carbon electrodes. The sulphonamides were evaluated in three different supporting electrolytes at pH < 7 and >7 to enhance electrochemical signal reporting. Sulfadiazine (SDZ), sulfamethoxazole (SMX) and sulfamethazine (SMZ) displayed peaks at 0.80 V vs Ag/AgCl in 0.1 M tris-HCl using square wave voltammetry at the unmodified transducer. At the PAA thin film transducer, SDZ, SMX and SMZ displayed well-defined analytical oxidative peaks at 0.77 V 0.82 V and 0.83 V vs Ag/AgCl respectively. The LOD (n=3) for SDZ was found to be 12.14 ųM with a correlation coefficient of 0.9950. The LOD (n=3) for SMX and SMZ was found to 14.59 ųM (R2 =0.9928) and 10.41 ųM (R2 =0.9963). These sulphonamides were also electro-analytical evaluated at the screen-printed carbon PAA nanofiber modified transducer. SDZ, SMX and SMZ produced well-defined analytical signals at 0.79 V, 0.81 V and 0.78 V vs Ag/AgCl respectively. The determined LOD (n=3) for the individual sulphonamides was 8.26 ųM, 16.59 ųM and 8.81 ųM SDZ, SMX and SMZ respectively. The linearity correlation coefficient (R2) was determined to be 0.9977, 0.9956 and 0.9974 respectively. The efficacy of the proposed nanostructured PAA thin film modified screen-printed carbon sensor was evaluated by performing recovery studies for the selected sulphonamides using square wave voltammetry. Tap water was used to simulate environmental matrix. The recoveries of SDZ with respect to each concentration were 98.84% (RSD 4.98%) to 40.58% (RSD 6.74%). For SMX the recoveries were 154.17% (RSD 11.00%) to 111.03% (RSD 16.80%). The recoveries for SMZ with respect to each concentration were 184% (RSD 8.19%) to 90.26 (RSD 18.26%) indicating the reliability of the analytical results. / 2021-09-01

This research investigates the interfacial interactions between biological entities and synthetic materials at two length scales: bulk and nanometer size. At the bulk scale, biomolecule adhesion is key for synthetic material incorporation in the body. Quantifying the adhesion strength becomes necessary. For the nanometer scale, the nanoparticles are generally delivered through the blood stream and their effect on the blood flow must be studied. An experimental approach was taken to study interaction at both material length scales. The cell/protein adhesion strength to bulk-sized materials was studied. The goal was to identify the most influential factor affecting adhesion: chemistry or surface roughness. The effects of nanoparticles on the viscosity of protein and amino acid solutions were measured. A statistical thermodynamic analysis was focused on the entropy change induced by the addition of gold nanoparticles to protein/amino acid solutions. Rheological studies were applied. A rheometer with a parallel plate was used to quantify the adhesion strength of cells and proteins to synthetic surfaces at the bulk scale. The adhesion strength depends on the applied shear stress and the radius of cells or proteins that remained attached to the surface after testing. At the nanometer scale, the viscosity of the nanoparticle enhanced protein or amino acid solutions were measured with a cone and plate. The adhesion studies were conducted with the following biological entities: fibroblasts, egg-white protein, and neurons. The fibroblast adhesion to poly(carbonate) and poly(methyl methacrylate) demonstrate fibroblasts are strongly attached to highly polar materials. Protein adhesion to titanium and chromium nitride coatings showed that chemical composition is the most influential factor. The neuron adhesion to poly-D-lysine coated glass demonstrated that neuron strengthening was due to an increase in adhesion molecules at the neuron/material interface. For nanoparticulates, it was found that the charged nanoparticles affect the protein and amino acid conformation and the potential energy of the solutions. Quantifying biomolecule adhesion to surfaces and predicting the behavior of nanoparticles inside a biological system are crucial for material selection and application. The major impact of this research lies in observing the interaction mechanisms at the interfaces of material-biological entities.

The aim of this study was to investigate the reaction behaviors of nanoscale Fe3O4 and H1/10-[Fe3O4]MgO slurry injection coupled with the electrokinectic (EK) process for remediation of NO3− and Cr6+ in saturated soil. To assure the above-mentioned nanomaterials were capable of reductively adsorbing inorganic pollutants (e.g., NO3− and Cr6+) in the acidic environment in the anode reservoir of the ek remediation system, an investigation on transformation of the concerned nanomaterials in different aqueous solutions (de-ionized water and simulated groundwater ) of different initial pHs (2 and 3.5) was conducted. Due to a high dose of nanoscale Fe3O4 and a resulting serious agglomeration while adsorbing NO3− and Cr6+, the characteristic peaks of the X-ray diffraction (XRD) analysis for nanoscale Fe3O4 remained the same after adsorption experiments. But the situations were quite different in the case of nanoscale H1/10-[Fe3O4]MgO, the characteristic peaks of £\-Fe2O3 in the XRD pattern were detected, confirming that this nanomaterial could reductively adsorb NO3− and Cr6+ in the acidic environment. The effectiveness of using polyacrylic acid (PAA) and soluble starch (SS) to stabilize nanoscale Fe3O4 and H1/10-[Fe3O4]MgO in different aqueous solutions containing humic acid was compared. It was found the former yielded a better stability. Therefore, PAA was chosen to prepare the slurries of target nanomaterials. Then slurry injection coupled with the EK process was tested for remediation of NO3- and Cr6+ in saturated soil. The results showed that the removal efficiency of NO3− was more than 90%, and the NO3− concentration in the anode reservoir was below Taiwan¡¦s Pollution Control Standards of type¢¹Groundwater for NO3−-N. Under the same test conditions, however, the removal efficiency of Cr6+ was unsatisfactory. This might be ascribed to acidification of soil near the anode resulting in high adsorption of Cr2O72− by soil. Thus, a solution to solve this problem has to seeked. The solution lies in how to enhance the contact of the above-mentioned nanomaterials with Cr6+ in the anode reservoir. One possibility is to use the nature of SS would hydrolyze in the acidic environment. Therefore, SS-stabilized nanomaterials in the acidic environment would hydrolyze resulting in the exposure of the soil nanomaterials therein. To this end, SS was used to replace PAA for nanomaterial slurry preparation for remediation of Cr6+. In addition, polarity reversal was practiced in the EK system to maintain a neutral ph of soil and increase the mobility of Cr6+ in soil. Finally, the result showed that nanoscale Fe3O4 and H1/10-[Fe3O4]MgO slurry injection coupled with the polarity reversal electrokinetic system could really enhance the removal efficiency of Cr6+ in the saturated soil. In summary, nanoscale Fe3O4 and H1/10-[Fe3O4]MgO slurry injection coupled with the EK process has been proven to be capable of remedying NO3− and Cr6+ in saturated soil. Meanwhile, the concept of reductive adsorption was realized in this work as well.

When nanoparticles are small in size compared to the wavelength of incident light, a localized surface plasmon resonance occurs. For certain noble metals, such as gold and silver, this frequency occurs in the visible or near IR range, and therefore it can be utilized for many important applications. Only silver and gold nanoparticles were utilized in this thesis work, and they were used in application for three separate files: environment, catalysis, and energy.

Fullerenes have been the focus of significant research effort and curiosity for their unique physicochemical and photochemical properties since their discovery almost 30 years ago. C60 fullerene in particular has received tremendous attention, due to its prevalence in fullerene production and chemical stability. While ambitious prospective applications for C60 have been ubiquitous, the extremely hydrophobic nature of fullerenes and consequent aggregation at the nano scale has hampered many endeavors. Researchers, therefore, have turned their attention to the functionalization of fullerenes to add hydrophilic moieties for applications in aqueous media. It is known that functionalizing the C60 cage alters its innate physicochemical and photochemical properties, but how these changes translate to the properties of C60 aggregates, often termed nC60, is not well understood. Functionalized fullerenes present an intriguing environmental dichotomy. On the one hand C60 has excellent potential as a novel singlet oxygen producing disinfection tool, and on the other the potential toxicological effects of functionalized C60 are largely unknown. With thousands of possible functionalities, a mechanistic understanding of the effects of functionalization is essential. To explore the effects of functionalization on fullerene photochemistry in relevant systems, three types of functional groups were selected and obtained each in series of mono-, bis-, and tris-functionalized forms. Two functionalities contrasted the presence or lack of a quaternary ammonium group and the third was the sterically bulkier phenyl-C61 butyic acid methylester, which is commonly used in polymer photovoltaics. The fullerenes were characterized for innate photochemical properties in organic solvents using UV/Vis, laser flash photolysis, and photochemical degradation experiments. Aqueous aggregates of each derivative were additionally characterized for their physical and chemical properties by dynamic light scattering, transmission electron microscopy, energy dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. All derivatives were photoactive when dispersed molecularly in organic solvents, but only the cationic fullerenes showed significant photoactivity as aqueous aggregates. Differences in aggregate size or crystallinity were unable to explain the differential photoactivity between derivatives, contrary to two established hypotheses. Antimicrobial properties were probed using innate toxicity tests and photoinactivation experiments. Again, only the cationic fullerenes were found to exert photochemical action towards Escherichia coli or MS2 bacteriophages. The cationic fullerenes were also innately toxic to E. coli due to the presence of quaternary ammonium moieties. In order to establish a mechanistic understanding of the photochemistry of functionalized C60 aggregates, simulations of the molecular dynamics (MD) were employed and compared with empirical evidences. Simulations provided theoretical values for C60-O2, C60-C60, and C60-H2O interactions for each derivative. Trends observed in the MD results were compared to photochemical characterizations as described above and Raman spectroscopic measurements of C60’s effect on localized water structure. High resolution transmission electron microscopy was used to provide empirical evidence of the C60-C60 interactions. Overall, fullerene aggregate photochemistry is likely driven by aggregate morphology and by intermolecular interactions between fullerenes, water, and O2.

The objectives of this thesis were to optimize the synthesis and surface coating of metallic and semiconductor nanoparticles, to understand how these materials interact with cells and physiological systems and to investigate how they can be used to deliver thermal therapy for medical applications. Reproducible high-yield synthesis of gold nanorods and surface coating with a variety of polymers and silica was optimized. Using gold nanorods as a model system, the relationship between particle surface chemistry, surface charge and cellular uptake was studied, as well as the toxicity of nanoparticles of different surface chemistry. Low toxicity in vitro was encouraging and was confirmed in vivo by intravenously injecting Sprague-Dawley rats with semiconductor quantum dots of various surface coatings. Low toxicity was found during biochemical, haematological and pathological assessment, and these results indicate that applications of nanoparticles should be further investigated. One such application is the use of near infrared absorbing gold nanorods in remotely activated hyperthermia. It was shown that gold nanorods act synergistically with the chemotherapeutic cisplatin to improve cytotoxicity, and reduce the required cytotoxic drug dose to 33% of the unheated amount. Due to the success of hyperthermia treatment in vitro, continuing and future work involves the use of gold nanorods ex vivo on excised human corneas in a novel application to weld corneal tissue for improved wound closure following cataract surgery.

abstract: In the nano-regime many materials exhibit properties that are quite different from their bulk counterparts. These nano-properties have been shown to be useful in a wide range of applications with nanomaterials being used for catalysts, in energy production, as protective coatings, and in medical treatment. While there is no shortage of exciting and novel applications, the world of nanomaterials suffers from a lack of large scale manufacturing techniques. The current methods and equipment used for manufacturing nanomaterials are generally slow, expensive, potentially dangerous, and material specific. The research and widespread use of nanomaterials has undoubtedly been hindered by this lack of appropriate tooling. This work details the effort to create a novel nanomaterial synthesis and deposition platform capable of operating at industrial level rates and reliability. The tool, referred to as Deppy, deposits material via hypersonic impaction, a two chamber process that takes advantage of compressible fluids operating in the choked flow regime to accelerate particles to up several thousand meters per second before they impact and stick to the substrate. This allows for the energetic separation of the synthesis and deposition processes while still behaving as a continuous flow reactor giving Deppy the unique ability to independently control the particle properties and the deposited film properties. While the ultimate goal is to design a tool capable of producing a broad range of nanomaterial films, this work will showcase Deppy's ability to produce silicon nano-particle films as a proof of concept. By adjusting parameters in the upstream chamber the particle composition was varied from completely amorphous to highly crystalline as confirmed by Raman spectroscopy. By adjusting parameters in the downstream chamber significant variation of the film's density was achieved. Further it was shown that the system is capable of making these adjustments in each chamber without affecting the operation of the other. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2015

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The rational combination of dielectric and metallic nano particles brings novel optical properties to conventional subwavelength structures. This thesis introduces the optoplasmonic geometries demonstrating versatile ability in both far and near field modification within nano scale. Template-assisted self-assembly approaches are applied creating nano entities with titanium dioxide and gold nano spheres. A top-bottom mono hybrid unit and interdigitated array are developed. With the examination of the elastic and inelastic response of these hybrid materials, physical models are simulated to depict the scenario of varied geometry and combination of nano particles. In contrast to solely metal or dielectric particle arrays, this type of artificial material not only enhances the near electric field intensity within the metal nano cluster hot spots, but also expands the overall volume of enhanced electric field. Further study reveals that the additional enhancement and redistribution of near field are derived from the coupling between the nano gold cluster plasmon resonance and the in-plane diffractive mode of the dielectric array. The redirected emission profile of the fluorescent dyes within the hybrid array is explored.