Developing nanotechnology for biofuel and plant science applications

This dissertation presents the research on the development of mesoporous silica based nanotechnology for applications in biofuels and plant science. Mesoporous silica nanoparticles (MSNs) have been the subject of great interest in the last two decades due to their unique properties of high surface area, tunable pore size and particle morphology. The robust nature of the silica framework is easily functionalized to make the MSNs a promising option for selective separations. Also, the independent channels that form the pores of MSN have been exploited in the use of particles as platforms for molecular delivery. Pore size and organic functionality are varied to identify the ideal adsorbent material for free fatty acids (FFAs). The resulting material is able to sequester FFAs with a high degree of selectivity from a simulated solution and microalgal oil. The recyclability and industrial implications are also explored. A continuation of the previous material, further tuning of MSN pore size was investigated. Particles with a smaller diameter selectively sequester polyunsaturated free fatty acids (PUFAs) over monounsaturated FFAs and saturated FFAs. The experimental results were verified with molecular modeling. Mesoporous silica nanoparticle materials with a pore diameter of 10 nm (MSN-10) were decorated with small gold nanoparticles. The resulting materials were shown to deliver proteins and DNA into plant cells using the biolistic method

Developing nanotechnology for biofuel and plant science applications

This dissertation presents the research on the development of mesoporous silica based nanotechnology for applications in biofuels and plant science. Mesoporous silica nanoparticles (MSNs) have been the subject of great interest in the last two decades due to their unique properties of high surface area, tunable pore size and particle morphology. The robust nature of the silica framework is easily functionalized to make the MSNs a promising option for selective separations. Also, the independent channels that form the pores of MSN have been exploited in the use of particles as platforms for molecular delivery. Pore size and organic functionality are varied to identify the ideal adsorbent material for free fatty acids (FFAs). The resulting material is able to sequester FFAs with a high degree of selectivity from a simulated solution and microalgal oil. The recyclability and industrial implications are also explored. A continuation of the previous material, further tuning of MSN pore size was investigated. Particles with a smaller diameter selectively sequester polyunsaturated free fatty acids (PUFAs) over monounsaturated FFAs and saturated FFAs. The experimental results were verified with molecular modeling. Mesoporous silica nanoparticle materials with a pore diameter of 10 nm (MSN-10) were decorated with small gold nanoparticles. The resulting materials were shown to deliver proteins and DNA into plant cells using the biolistic method.</p

Functional Mesoporous Silica Nanoparticles for the Selective Sequestration of Free Fatty Acids from Microalgal Oil

A series of 2d-hexagonally packed mesoporous silica nanoparticle material with 10 nm pore diameter (MSN-10) covalently functionalized with organic surface modifiers have been synthesized via a post-synthesis grafting method. The material structure has been characterized by powder X-ray diffraction, electron microscopy, and nitrogen sorption analyses, and the free fatty acid (FFA) sequestration capacity and selectivity was investigated and quantified by thermogravimetric and GC/MS analysis. We discovered that aminopropyl functionalized 10 nm pore mesoporous silica nanoparticle material (AP-MSN-10) sequestered all available FFAs and left nearly all other molecules in solution from a simulated microalgal extract containing FFAs, sterols, terpenes, and triacylglycerides. We also demonstrated selective FFA sequestration from commercially available microalgal oil.Reprinted (adapted) with permission from ACS Applied Materials & Interfaces 4 (2012): 1003, doi:10.1021/am201647t. Copyright 2012 American Chemical Society.</p

Evaluation of AISI Type 304 stainless steel as a suitable surface material for evaluating the efficacy of peracetic acid-based disinfectants against Clostridium difficile spores.

Disinfectants play an important role in controlling microbial contamination on hard surfaces in hospitals. The effectiveness of disinfectants in real life can be predicted by laboratory tests that measure killing of microbes on carriers. The modified Quantitative Disk Carrier Test (QCT-2) is a standard laboratory method that employs American Iron and Steel Institute (AISI) Type 430 stainless steel carriers to measure hospital disinfectant efficacy against Clostridium difficile spores. The formation of a rust-colored precipitate was observed on Type 430 carriers when testing a peracetic acid (PAA)-based disinfectant with the QCT-2 method. It was hypothesized that the precipitate was indicative of corrosion of the Type 430 carrier, and that corrosion could impact efficacy results. The objective of this study was to compare the suitability of AISI Type 430 to Type 304 stainless steel carriers for evaluating PAA-based disinfectants using the QCT-2 method. Type 304 is more corrosion-resistant than Type 430, is ubiquitous in healthcare environments, and is used in other standard methods. Suitability of the carriers was evaluated by comparing their impacts on efficacy results and PAA degradation rates. In efficacy tests with 1376 ppm PAA, reductions of C. difficile spores after 5, 7 and 10 minutes on Type 430 carriers were at least about 1.5 log10 lower than reductions on Type 304 carriers. In conditions simulating a QCT-2 test, PAA concentration with Type 430 carriers was reduced by approximately 80% in 10 minutes, whereas PAA concentration in the presence of Type 304 carriers remained stable. Elemental analyses of residues on each carrier type after efficacy testing were indicative of corrosion on the Type 430 carrier. Use of Type 430 stainless steel carriers for measuring the efficacy of PAA-based disinfectants should be avoided as it can lead to an underestimation of real life sporicidal efficacy. Type 304 stainless steel carriers are recommended as a suitable alternative

Mimicking Red Blood Cell Lipid Membrane To Enhance the Hemocompatibility of Large-Pore Mesoporous Silica

Mesoporous silica nanoparticles (MSNs) have been repeatedly demonstrated as potential drug-delivery devices. The study of biocompatibility and interaction of these materials with the various cell types is of great interest with regard to the development of viable pharmaceutical products. By mimicking the cholesterol, phosphatidylcholine, and phosphatidylethanolamine composition of the outer leaflet of a human red blood cell (RBC), lipid-bilayer-coated mesoporous silica particles show considerably improved hemocompatibility over phosphatidylcholine-coated and uncoated large-pore MSN (<i>l</i>-MSN). These inorganic/organic composite nanomaterials are shown to be capable of interfacing with RBCs without damaging the cells even at relatively high concentrations, as observed through electron microscopy, UV–vis spectroscopy, and flow cytometry analyses. Interestingly, the absence of cholesterol in the outer bilayer composition is shown to produce toxic effects without resulting in hemolysis. By maintaining the ζ potential of lipid-bilayer-functionalized MSNs similar to that of the hemolytic <i>l</i>-MSNs, we demonstrate that the bilayer composition, and not the surface charge, plays a significant role in determining the hemocompatibility of MSN-based materials

Prevalence of probable mental disorders and help-seeking behaviors among veteran and non-veteran community college students.

ObjectiveMillions of disadvantaged youth and returning veterans are enrolled in community colleges. Our objective was to determine the prevalence of mental disorders and help-seeking behaviors among community college students.MethodsVeterans (n=211) and non-veterans (n=554) were recruited from 11 community colleges and administered screeners for depression (PHQ-9), generalized anxiety (GAD-7), posttraumatic stress disorder (PC-PTSD), non-lethal self-injury, suicide ideation and suicide intent. The survey also asked about the perceived need for, barriers to and utilization of services. Regression analysis was used to compare prevalence between non-veterans and veterans adjusting for non-modifiable factors (age, gender and race/ethnicity).ResultsA large proportion of student veterans and non-veterans screened positive and unadjusted bivariate comparisons indicated that student veterans had a significantly higher prevalence of positive depression screens (33.1% versus 19.5%, P&lt;.01), positive PTSD screens (25.7% versus 12.6%, P&lt;.01) and suicide ideation (19.2% versus 10.6%, P=.01). Adjusting for age, gender and race/ethnicity, veterans were significantly more likely than non-veterans to screen positive for depression (OR=2.10, P=.01) and suicide ideation (OR=2.31, P=.03). Student veterans had significantly higher odds of perceiving a need for treatment than non-veterans (OR=1.93, P=.02) but were more likely to perceive stigma (beta=0.28, P=.02). Despite greater need among veterans, there were no significant differences between veterans and non-veterans in use of psychotropic medications, although veterans were more likely to receive psychotherapy (OR=2.35, P=.046).ConclusionsFindings highlight the substantial gap between the prevalence of probable mental health disorders and treatment seeking among community college students. Interventions are needed to link community college students to services, especially for student veterans

Universal and Versatile Route for Selective Covalent Tethering of Single-Site Catalysts and Functional Groups on the Surface of Ordered Mesoporous Carbons

A universal and benign strategy for the surface functionalization of OMCs through lithium-mediated chemistry has been reported. For this purpose, a hard templating method for the facile synthesis of monodispersed ordered mesoporous carbons (OMCs) with well-defined morphology templated from large pore mesoporous silica nanoparticles (<i>l-</i>MSN) has been used. These OMCs have high surface areas (800–1000 m²g^–1) and large pore sizes (4–6 nm) suitable for anchoring bulky inorganic complexes. It has been demonstrated that the numerous defect sites present in the graphitic structure of OMCs can be effectively utilized for selective and covalent tethering of functional groups and single-site catalysts through lithiation of OMCs. Accordingly, for the first time a copper-based single-site oxidation catalyst has been covalently anchored onto the surface of OMCs. This novel system has been thoroughly characterized with advanced techniques such as electron microscopy, Raman spectroscopy, thermogravimetric analysis, X-ray diffraction, and acid–base titrations along with structural insights regarding the tethered copper catalyst by X-ray photoelectron spectroscopy. As a proof-of-principle, this active catalytic system has been used to demonstrate environmentally benign, room temperature selective oxidation of benzyl alcohol. We envision that this strategy for surface functionalization would be universal and can be applied for tethering a variety of different single-site catalysts onto OMCs with high surface areas. We also believe that it would have a direct impact on the currently available limited syntheses and surface functionalization techniques of mesoporous carbons for catalytic, electrocatalytic, and biological applications

Energy dispersive X-ray spectroscopy: elements in the residue on an AISI Type 304 carrier after efficacy testing with the QCT-2 method.

<p>Energy dispersive X-ray spectroscopy: elements in the residue on an AISI Type 304 carrier after efficacy testing with the QCT-2 method.</p

Standard antimicrobial test methods and carrier types.

<p>Standard antimicrobial test methods and carrier types.</p