The catalytic activity of many metals can be increased when the catalyst exists as tiny nanoclusters as opposed to large bulk-like metal particles. Thus materials, or supports, that facilitate the growth of nanoparticle catalysts are highly desired. Of these supports, the most widely used are metal-oxides. The growth of catalysts on these supports can be better understood by studying the chemical bonding at the metal-oxide interface. The Mallouk group has found a calcium niobate nanosheet, HCa₂Nb₃O₁₀, that when used as a support both resists and reverses the coalescence of metal-oxide or hydroxide nanoparticles on the surface. These nanosheets are of additional interest because they are smooth on the atomic scale, similar to single crystal surfaces, with a large ratio of terrace sites to edge sites. Here, calorimetric measurements of the adsorption energies of silver and copper vapor on oxide thin films composed of four layers of these nanosheets are directly measured using adsorption calorimetry in ultrahigh vacuum. The initial heat of adsorption of silver atoms was found to be ~112 kJ/mol which closely resembles the predicted density functional theory (DFT) values for silver monomers. The growth mode of silver was determined using a surface sensitive spectroscopy technique, low-energy He+ ion scattering spectroscopy (LEIS). The number density of silver particles, as estimated from the LEIS data, was found to be ~2.2x10¹⁰ particles/cm² at 1.7 monolayer silver coverage. This is much lower than the particle densities on other metal-oxide supports and is attributed to the lower density of step/nanosheet edges on this support. The evolution of the LEIS signal indicates that silver grew as 3D nanoparticles. This data encourages further investigations of the adsorption calorimetry of different metals on this interesting support.

 Polyethylenimine (PEI) is considered as the most promising alternative gene carrier to viral vectors. PEI-based carriers minimize unwanted immunogenicity and promote loading capacity. However, PEIs’ nondegradable nature determines their high cytotoxicity. To minimize the toxicity and improve gene transfection efficacy, biodegradable cross-linking agents have been screened to synthesize biocompatible PEIs. Various cross-linkers have been linked to low molecular weight PEI (MW = 800) and tested across multiple cell lines (xPEI). N,N'-Methylenebis(acrylamide) (NDA) showed the lowest toxicity and highest transfection rate among all cross-linkers. To further optimize gene transfection efficacy, xPEIs were modified with increasing amount of fluorocarbon (xPEI-FC). DNA that expresses red fluorescence protein are bound to xPEI and xPEI-FC and then incubated with cells for 48 hours. Green florescence light is later used to examine the presence of RFP. xPEI-FC has demonstrated higher biocompatibility as well as higher transfection rate in vitro with higher level of RFP. The best-performing candidates for xPEI, PEI-FC and xPEI-FC based on toxicity and transfection efficiency will be selected for nanoparticle (NP) modification. Selected candidates will be conjugated with Chitosan-poly(ethylene glycol) (PEG)-catechol copolymer (CCP) and then grafted onto iron oxide nanoparticle (IOCCP-PEI). The resulting nano-vector delivery system will be tested in vitro. Ultimately, in vivo test will be performed to evaluate its transfection efficacy in living organisms.

This research aims to examine the effects of nanoparticle-mediated inhibition of the phospholipid glutathione peroxidase (GPX4) pathway in mesenchymal state cells on radio-resistance in glioblastoma (GBM) therapy. GBM is a particularly deadly cancer with poor survival rates and relatively low treatment success, despite aggressive surgery and radiotherapy. Recent research has shown that biocompatible, tumor-targeted iron oxide nanoparticles (NPs) can serve to enhance radiotherapy through production of secondary electrons and subsequent reactive oxygen species (ROS) within the tumor volume. The presence of these NPs in the tumor during radiotherapy has shown to decrease damage to the healthy surrounding cells and prolong survival in mice with GBM tumors. This approach however, has not demonstrated the ability to eliminate the cancer completely, in part due to the presence of mesenchymal state cancer stem cells. The GPX4 pathway has shown to effectively kill mesenchymal state cells in sarcomas by inducing ferroptosis, an iron-dependent form of cell death. Here we plan to evaluate the efficacy of a range of GPX4 inhibitors on silencing of the GPX4 pathway and the ability to induce ferroptosis in primary human GBM cells. Inhibitors identified as effective silencers of the GPX4 pathway will be combined with a NP delivery vector to provide targeted delivery to GBM. The radioenhancement capabilities of iron oxide NPs in conjunction with targeted therapy against mesenchymal state cancer stem cells may provide a means to overcome radioresistance in GBM therapy.

Parkinson’s Disease (PD), a neurodegenerative disorder, features accumulation and transmission of toxic species of the protein a-synuclein in specific brain regions. Because examination of such proteins in the brain is invasive and expensive, a robust diagnostic or predictive blood biomarker for PD is strongly required. Previous studies have observed that oligomeric a-synuclein was present in the red blood cells (RBCs) of PD patients, but it did not work well as a biomarker. Because toxic forms of proteins are secreted from cells to the extracellular space in membrane-bounded vesicles called exosomes, therefore we believe that the RBC derived exosomes could be an potential biomarker for PD diagnosis. Also, isolation of specific type of exosome could be equivalent for testing the originated cells. However, there are all types of exosomes in blood released not only by the RBC but also by most cell types, particularly large fenestrated organs such as liver and kidney. To test these vesicles, we have developed the technique of immunoprecipitation to purify distinct kinds of exosomes by targeting its novel unique markers, such as the RBC-specific membrane protein CD235a, and quantifying the amount and size by nanoparticle tracking analysis. My preliminary data have shown that the antibody of CD235a can successfully target the membrane proteins on RBC membrane and its derived exosomes and can collect pure extract of exosomes by immunoprecipitation. In sum, we think the RBC derived exosomes is a promising candidate for PD diagnosis that is worth further investigation. However, the ratio of CD235a positive exosome in whole plasma is still unknown and further tests need to be done on the amount and size distribution of RBC derived exosome in a PD cohort.

Fluorescent nanocrystal quantum dots (QDs) show promise for biomedical application, but are often negatively associated with cellular toxicity. To investigate the potential of QDs as a biomarker in the brain, a systematic evaluation of potential toxicity is necessary. In this study, we evaluated QDs with various surface functionalities and assessed toxicity as a function of concentration and exposure time. We utilized organotypic brain slices obtained from healthy postnatal day 14 (P14) rat pups. Four cadmium selenide (CdSe)-core QD conjugates were evaluated: mercaptopropionic acid (MPA), hydroxyl-polyethylene glycol (PEG-OH), amine-PEG (PEG-NH2), and methoxy-PEG (PEG-MeO) at 0.01, 0.1, and 1.0 μM concentration. Cell toxicity was primarily quantified by measuring lactate-dehydrogenase (LDH) production, which is an indicator of cell death, over a five-day period. Results were supplemented with confocal microscopy analysis of two imaging-based assays: propidium iodide, a stain of the nuclei of dying cells, and fluoro-jade C, a stain of degenerating neurons. QD-MPA treated slices had 7-8% greater toxicity than the non-treated (NT) control. All other functionalities were comparable to the NT control except QD-PEG-OMe, which had 3% lower cytotoxicity suggesting a possible neuroprotective effect. Alternatively, certain functionalities (MPA, NH2) may show lower than expected toxicity due to aggregation before cellular uptake. Compared to 0.1 μM concentrations, 0.01 μM QD treated groups had around 4% lower toxicity. Similarly, 1-3% greater toxicity was observed in extended QD exposure conditions (24h) versus shorter exposures (1h). Results show that toxicity is dependent on surface chemistry, concentration, and exposure time. This is useful in identifying QD conjugates with low cytotoxicity in the developing brain. Understanding QD toxicity can lead to rational design of QDs for site and cell-specific uptake in the brain as a biomarker of neurological disease severity, improving the selectivity of current imaging techniques and providing a powerful diagnostic with regards to diseased cell fate.

Quantum dots (QDs), fluorescent semiconductor nanocrystals, can be used as a biomarker and diagnostic tool for central nervous system (CNS) diseases because of their unique physical properties. To serve as an effective diagnostic platform, QDs must diffuse from the point of access to a desired target within the brain. To maximize diffusion within the CNS, QDs need to remain monodisperse, and avoid any adhesive interactions or steric limitations imposed by the brain microenvironment. Therefore, characterization of physicochemical properties and overall colloidal stability in physiologically relevant solvents is required to understand QDs diffusivity within the CNS. A methodology based on dynamic light scattering (DLS) was employed to assay QD hydrodynamic diameter, where increase in particle size served as an indicator of QD aggregation and instability. Time dependent stability was investigated by incubating QDs in 1xPBS, a low concentration salt solution, and artificial cerebrospinal fluid (aCSF), a more complex medium that mimics in vivo interstitial fluid. Measurements were recorded for 24 h at both room and physiological temperatures. Compared to 1xPBS, QDs without poly(ethylene glycol) (PEG) ligands showed more rapid and significant aggregation in aCSF while PEGylated QDs remains relatively stable in both mediums. To explore the rate at which QDs initially aggregate, particle size was measured for the first 200 seconds post-incubation in solutions of varying concentrations of calcium ion, an ion which plays an important role in many neuronal processes and is often found in abnormal amounts in the brain in diseased states. The results showed that the rate of initial aggregation is concentration dependent and is diminished by PEGylation. With further analysis of QD stability in CNS relevant mediums, this methodology will aid in establishing key properties that govern QD behavior in the brain microenvironment, which can be used to employ QDs as an effective biomarker for brain diseases.