Multifunctional Mesoporous Silica Nanocomposite Nanoparticles for Theranostic Applications

• Main Authors: Nai-Tzu Chen, 陳乃慈
• Other Authors: Chung-Yuan Mou
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/92s794

博士 === 國立臺灣大學 === 化學研究所 === 101 === During the last decade, mesoporous silica nanoparticles (MSNs) have garnered great interest for potential use as nanocarriers of anticancer drugs. Their unique chemical and structural properties – their tunable size and pore diameter, excellent biocompatibility, intrinsically large surface area, and topologically distinct domains that can be easily and individually functionalized – make MSNs especially well-suited to efficient conveyance of a wide variety of therapeutic payloads. When combined with other organic/inorganic nanomaterials, the resultant MSN composites demonstrate novel synergies and even greater versatility than those of their constituents. In this dissertation we examine, in depth, the design, synthesis, and evaluation of MSNs and MSN composites as cancer nanotheranostics: nanomaterials that simultaneously serve as both diagnostic and therapeutic agents. To accomplish this task we focus on three very different nanotheranostic constructs with three very different mechanisms of action: (1) Mesoporous silica-encased gold nanorods, for two-photon activated photodynamic therapy (TPA-PDT) via plasmonic resonance energy transfer; (2) Lectin-functionalized fluorescent MSNs, for in situ diagnostic imaging of nascent colorectal cancers using confocal fluorescence endoscopy; and (3) pH-sensitive controlled-release MSNs, for real-time fluorescence lifetime imaging microscopy (FLIM) of doxorubicin-DNA intercalation dynamics during the initial activation of apoptosis. We begin with a description of the design, synthesis, and evaluation of mesoporous silica-coated gold nanorods (MS-GNRs) that incorporate photosensitizers for TPA-PDT. Enveloping gold nanorods with mesoporous silica confers a number of advantages on bare GNRs that include: (i) stabilization of the gold nanorods’ shape against thermal deformation following repeated laser pulse irradiation; (ii) enhanced two-photon luminescence intensity and nanoplatform longevity, and (iii) increased surface area for conjugation of additional photosensitizers. Using a 2-step sequential intra-particle plasmonic energy transfer post two-photon excitation, we observe substantial cytotoxicity both in vitro and in vivo, using human breast carcinoma cells and a murine model of human breast cancer. Next we discuss our development and evaluation of MSNs that target dysplastic adenomas and whose silica frameworks contain the fluorophore fluorescein isothiocyanate (FITC), for potential use as endoscopic contrast agents of nascent colon cancer. The exteriors of these fluorescent MSNs were labeled with the lectin Ulex europaeus agglutinin 1 (UEA-1), to target the α-L-fucose that is expressed on the luminal surfaces of glycoproteins of colorectal dysplastic adenomas and nascent cancers. In vitro affinity assays, as well as in vivo endoscopy and ex vivo histopathological analyses of tissues harvested from murine models of human colorectal cancer, demonstrate significant binding specificity to α-L-fucose of these UEA-1-FITC-MSN constructs. Lastly, we describe our use of (a) pH-sensitive MSNs, to target and controllably release the chemotherapeutic drug doxorubicin, and (b) FLIM, to dynamically monitor drug release, migration, and DNA intercalation during the early apoptosis – as a prototypical analysis of nanotheranostic function. In these studies we discovered that monitoring the rate of change of doxorubicin fluorescence lifetime within cell nuclei enables the detection of very subtle changes in chromatin structure, well in advance of the commencement of DNA fragmentation. Taken together, these studies, and the endless permutations of form/function such nanocomposites afford, provide a compelling argument for the clinical translation of multifunctional MSNs and MSN composites as cancer nanotheranostic compounds.