Luminescent Heteroatom doped Carbon Quantum Dots for Sensing and Drug Delivery Applications

The present dissertation entitled, “Luminescent Heteroatom doped Carbon Quantum Dots for Sensing and Drug Delivery Applications” is an embodiment of the investigations aimed at developing simple inexpensive synthetic methodologies for producing heteroatom doped carbon quantum dots pertinent for sensing and biomedical application. The diagnostic and therapeutic applications of these multifunctional nanomaterials have been studied in vitro. The thesis has been divided into seven chapters. Hydrophilic boronic acid modified nitrogen sulphur doped carbon quantum dots (BNSCQD) have been prepared following a cost effective hydrothermal approach. The co-doping is aimed to improve the luminescence as well as targeting affinity of the CQD. Due to intense fluorescence property, appreciable photostability, boronic acid functionality and low cytotoxicity the carbon quantum dots (CQD) have been utilised in sensing glucosamine and cancer cell receptor Sialyl Lewisa (SLa). This method is highly sensitive and selective for visual detection of glucosamine sensing using a paper based sensor strip. Furthermore, integration of dopamine with BNSCQD (BNSCQD-Dopa) sets a platform for development of a fluorescence turn-on nanoprobe for fluoride detection in real samples. Due to boron’s affinity towards fluorine, the system was very selective towards fluoride when compared with other anions with a detection limit 0.7 pM. The practical ultrasensitive utility of the sensor is well demonstrated in human serum samples and also extended for fluoride detection in cellular environment. Further, the BNSCQD has been integrated with gadolinium iron oxide and mesoporous silica to construct a theranostic nanoparticle where BNSCQD imparts multiple functions such as simultaneous pH-sensitive gate opening, leading to control drug release, optical imaging, and receptor targeted internalization of the theranostic particle. The drug release experiment under variable pH and in the presence of competitive binding ligand SLa clearly shows the excellent responsiveness of the BNSCQD capped MSN hybrid system toward dual stimuli. Because of reasonably good r1 r2 relaxivities of the magnetic core and excellent fluorescence property of the doped carbon quantum dot, the hybrid can be utilized to monitor the therapeutic response through MRI and/or fluorescence imaging. Nitrogen doped mesoporous hollow carbon nanospheres (NCQD-HCS) have been prepared by inert calcination of polymer synthesized using pyrrole, aniline and Triton X-100 as molecular precursors. Here a direct synthetic approach is followed to yield high surface area carbon spheres with fluorescence property. An optimization of both surface area and photoluminescence is achieved by tuning temperature of calcination. The highest PL quantum yield of 14.6% is recorded, which is suitable for confocal imaging of cells. The fluorescence property of these spheres is attributed to the embedded nitrogen doped carbon quantum dots (NCQD) in carbon matrix. The photothermal property of NCQD-HCS has been investigated under 980 nm NIR irradiation. Cell killing efficacy of hollow spheres by photothermal ablation effect is evaluated in FaDu cells (oral cancer) as a modal cell line. Similarly, the upconversion property of carbon spheres is explored for light responsive drug release of gemcitabine. A highly biocompatible click chemistry based gating system is designed to restrict the premature release of drug molecules from porous nanospheres. The utilization of upconverted radiation by substituted nitrobenzyl linker, initiating its cleavage followed by drug release under periodic irradiation (980 nm laser) intervals has been tested in vitro. These fluorescent multifunctional nanoparticles provide a platform for combinatorial therapy of oral cancer

The Roles of the Drosophila Protein Tribbles in Oogenesis and Insulin Signaling Pathway

Title from PDF of title page, viewed on October 19, 2015Dissertation advisor: Leonard DobensVitaIncludes bibliographic references (pages 111-127)Thesis (Ph.D.) -- School of Biological Sciences. University of Missouri--Kansas City, 2015In this dissertation, I examined the molecular mechanism of function of the Drosophila melanogaster protein Tribbles (Trbl) during oogenesis and larval development. Trbl is the founding member of an evolutionarily conserved family of kinase proteins that play diverse roles in cell signaling and energy homeostasis. In addition to the central Serine/Threonine kinase domain, members of the Tribbles gene family (Trib) shares C terminal mitogen activated protein kinase kinase MEK1 and E3 ubiquitin ligase COP1 binding motifs, the latter required for the degradation of target proteins via proteasome. During oogenesis, Trbl controls border cell (BC) cluster migration by mediating degradation of C/EBP transcription factor Slbo. I first investigated Trbl’s role during oogenesis using a Trbl specific antisera. Trbl localizes to the nucleus of main body follicle cells (MBFC) up to stage 10 of oogenesis. In the case of BC, Trbl expresses in a complementary pattern to Slbo expression. The Trbl level decreases gradually as the BC cluster delaminates from the epithelium and starts migrating when Slbo protein level increases. Moreover, Slbo was found to be essential but not sufficient to decrease the Trbl level required for BC migration. In a wing misexpression screen for Trbl interacting proteins, I identified the Serine/Threonine protein kinase Akt, a major mediator of insulin signaling. In recent years, mammalian Trib3 and Trib2 proteins have been implicated in the regulation of Insulin signaling by inhibiting the activating phosphorylation of Akt, Given the central role of Akt in insulin signaling, I tested whether the function of Trib family in insulin signaling is evolutionarily conserved. Using Drosophila larval development as a model system, I found that Trbl has a conserved role in binding and inhibiting Akt phosphorylation-activation, implicating Trib proteins as novel sites of signaling pathway integration that link nutrient availability with cell growth and proliferation. Finally, I have identified a previously unknown motif (R141) in Trib proteins essential for their function to regulate insulin signaling mediated growth and metabolism.Background and significance -- The kinase domain of drosophila tribbles is required for turnover of fly c/ebp during cell migration -- Drosophila tribbles antagonized insulin signaling mediated growth and metabolism via interactions with akt kinase -- Evolutionarily conserved arginine 141 of drosophila tribbles plays crucial roles in the regulation of the insulin-signaling pathway -- Appendix -- Future direciton