Browsing School, Graduate by Subject "Nanoparticles"
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Development of Novel Nanostructured Therapeutic Root Canal Dental Sealers with Strong Antibacterial and Remineralization CapabilitiesRoot canal therapy aims to remove microorganism or at least reduce them to subcritical levels that permit the host’s immunity to eliminate infection and regenerate damaged tissues. However, due to the complex and variable root canal anatomy and the resistant nature of root canal biofilm, complete elimination of root canal microorganisms is rarely accomplished. In addition, it has been frequently reported that some of the most commonly used irrigating solutions, such as, sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) can adversely alter the chemical and mechanical properties of dentin, resulting in a brittle dentin structure that is more susceptible to root fracture. This dissertation aims to develop a therapeutic root canal sealing material with potent antibacterial properties and remineralizaition capabilities through the incorporation of dimethylaminohexadecyl methacrylate (DMAHDM) to provide bacterial contact killing in case of micro leakage, nanoparticles of silver ions (NAg) to eliminate bacteria in the more complex root canal anatomy through release of silver ions, and nanoparticles of amorphous calcium and phosphate (NACP) to reverse the action of NaOCl and EDTA on root dentin and strengthen the root structure through the release of Ca and P ions. In this dissertation projects, the effects of incorporating DMAHDM, NAg, and NACP on the physical and sealing properties were evaluated. The antibiofilm properties were assessed by polysaccharide production, live/dead, and colony-forming units (CFU) assays. The antibiofilm properties of the developed sealer were assessed on cured sealer disks and utilizing a human dentin model. In addition, the effects of NACP on the Ca and P ion release, pH-alkalizing properties, and influence on dentin hardness were all measured. The triple incorporation of DMAHDM, NAg, and NACP did not compromise the physical properties of the root canal sealer and demonstrated sealing properties that were similar to that of a commercial control material. The incorporation of DMAHDM and NAg alone into the root canal sealer demonstrated great reductions in bacterial viability and quantity. However, when both agents were combined the antibiofilm effects were maximized, resulting in CFU reductions of 6 orders of magnitude. The DMAHDM NAg containing root canal sealer was able to kill bacteria not only on the surface of resin disks but also bacteria impregnated inside human dentin. The incorporation of NACP into the respective sealer allowed for the release of high levels of Ca and P ions, neutralized the acid and increased the solution pH, and increased the dentin hardness to match that of sound dentin. This bioactive antibacterial and remineralizing root canal sealer is promising to prevent endodontic treatment failure and secondary endodontic infections while releasing high levels of Ca and P ions that could remineralize and strengthen the tooth structures and potentially prevent future root fractures and teeth extractions.
Fn14-targeted, Tissue-penetrating Nanoparticles for Treatment of Primary and Metastatic TumorsNanotherapeutics is a burgeoning field in cancer therapy that may address some of the issues associated with systemically administered chemotherapeutics, including a non-specific mechanism of action and a poor biodistribution profile, which results in dose-limiting toxicities. However, many of the nanoparticle (NP) formulations approved for clinical use in solid tumor therapy provide only modest improvements in patient survival. This is in part due to rapid clearance from the circulation, inability to efficiently target tumor cell drug uptake, and NP tumor penetration barriers, including a dense and complex extracellular matrix (ECM) and an elevated interstitial fluid pressure. These barriers hinder the penetration of drugs and NPs into and within tumors limiting therapeutic efficacy. Fibroblast growth factor-inducible 14 (Fn14), a member of the tumor necrosis factor receptor (TNFR) superfamily, is expressed at low levels in normal tissues but highly expressed in over 20 solid cancer types. Thus, Fn14 has the potential to be an ideal candidate for the development of targeted therapy and its down-regulation may contribute to positive disease outcomes. However, while targeting therapeutics to specific disease components may decrease some of the limitations mentioned, in order to fully capitalize on the potential benefits of targeting, low levels of non-specific adhesivity and off-target binding must be maintained in setting off an effective level of target-specific binding. My thesis project tests the hypothesis that biodegradable, polyethylene glycol (PEG)- and anti-Fn14 antibody-coated, drug-loaded NPs will exhibit high efficacy against Fn14-positive tumors due to their ability to penetrate tissue and effectively target Fn14-positive cancer cells. We tested this hypothesis in the following Specific Aims: 1) Determine the thresholds for NP size and PEG density for effective tumor penetration and examine the potential penetrative capacity of FDA-approved NPs used for breast cancer patients, 2) Determine if Fn14-targeted and/or non-targeted tissue-penetrating, paclitaxel (PTX)-loaded biodegradable NPs are more effective than the FDA-approved NP formulation Abraxane in reducing primary and metastatic breast cancer growth, and 3) Evaluate the potential use of our biodegradable NP formulation against glioblastoma (GBM), the most common and deadly form of adult brain cancer, by examining NP dispersion, cellular uptake, and tumor retention in a murine model of GBM. These findings will generate new knowledge related to the value of tumor-specific targeting for NP therapeutics.
A Novel Method for the Treatment of Dentinal Hypersensitivity: Penetration of Magnetic Nanoparticles into Dentinal TubulesDentinal hypersensitivity (DH) is characterized by temporary, sharp-shooting pain arising from exposed dentin in response to different types of stimuli, such as thermal, mechanical, osmotic or chemical elements This study looked the treatment of dentinal hypersensitivity (DH) by utilizing magnetic nanoparticles (MNPs). DH was simulated by creating a class V preparation on an extracted human tooth. 72 samples were divided into two groups. Three different MNPs (100nm, 300nm, 500nm) were applied to the class V preparation. A magnet was placed on the opposing side of the class V preparation for the experimental group. No magnet was used for the control group. All samples were decalcified, sectioned and mounted for visualization of MNPs through light and fluorescent microscopes. The percentage of dentinal tubule penetration of the three different MNP groups was calculated by measuring the total depth of the dentinal tubule from the inner surface of the preparation to the pulp. The second measurement was from the inner surface of the preparation to the depth that the MNPs travelled. Data were analyzed using ANOVA and Tukey's Honestly Significant Difference test. Overall, Smaller magnetic nanoparticles have a significantly higher percentage of dentinal tubule penetration than the larger magnetic nanoparticles with or without an external magnetic field (p≤.0005). There was no significant difference between the percentage of dentinal tubule penetration of 300nm and 500nm in control group. A significantly higher percentage of dentinal tubule penetration was found with application of the external magnetic field (p≤.0005). In conclusion, MNPs could potentially be utilized for DH treatment.
Repurposing Oxaliplatin for the Treatment of GlioblastomaGlioblastoma (GBM) is the most common and deadly primary brain tumor in adults, accounting for approximately 40% of primary brain tumors. Even with the most aggressive therapy, the mean survival for patients with GBM is still less than 18 months, highlighting the critical need for new therapeutic strategies for this deadly cancer. Among the strategies under consideration is a repurposing of platinum-based chemotherapeutics. Traditionally considered DNA damaging cytotoxic agents, recent findings suggest that platinum-based chemotherapeutics, especially oxaliplatin (OXA), can induce multi-faceted anti-tumor effects, including modulation of cytokines, transcription factors, and tumor immunosuppressive mechanisms, even at lower concentrations that are not directly cytotoxic. Data suggests that a major alternative effect of OXA is the inhibition of signal transducer and activator of transcription 3 (STAT3), a transcription factor at the core of GBM pathobiology. STAT3 signaling is constitutively active in many gliomas and dictates diverse aspects of glioma biology including angiogenesis, invasion, chemotherapeutic resistance, and immunosuppression. STAT3 also controls and co-opts the primary gliomainfiltrating immune cell, the macrophage, which composes up to 40% of the tumor mass. OXA treatment may overcome the pleiotropic glioma-supporting functions of STAT3. It is likely that OXA therapeutic formulations designed to maximize the multi-faceted effects of OXA, including STAT3 inhibition, will have potent anti-GBM effects, including reprogramming of the tumor microenvironment. Although high-dose platinum-based chemotherapeutics have been investigated for CNS tumors, systemic and direct neuronal toxicity at high doses has thus far limited their use. However, new therapeutic delivery strategies including polymeric nanoparticle formulations capable of improving drug delivery to tumor cells, providing a sustained release of chemotherapeutic at the target site, and significantly reducing toxicity are facilitating the adaptation of these compounds in the CNS. We sought to investigate the multi-faceted anti-tumor effects of low-dose OXA in glioma cells and macrophages, with a particular focus on STAT3 modulation. We hypothesized that OXA will reduce STAT3 activity in glioma cells as well as macrophages and that OXA nanoparticle formulations will sustain STAT3 inhibition in vivo, thereby enabling the use of OXA as a biomaterial inhibitor of STAT3 for the treatment of glioma.