Shih-Hsun Cheng

Surface charge-mediated rapid hepatobiliary excretion of mesoporous silica nanoparticles.

Nanoparticle-assisted drug delivery has been emerging as an active research area in recent years. The in vivo biodistribution of nanoparticle and its following mechanisms of biodegradation and/or excretion determine the feasibility and applicability of such a nano-delivery platform in the practical clinical translation. In this work we report the synthesis of the highly positive charge, near-infrared fluorescent mesoporous silica nanoparticles (MSNs) that demonstrate rapid hepatobiliary excretion, for use as traceable drug delivery platforms of high capacity. MSNs were incorporated with near-infrared fluorescent dye indocyanine green (ICG) via covalent or ionic bonding, to derive comparable constructs of significantly different net surface charge. In vivo fluorescence imaging and subsequent inductively coupled plasma-mass spectroscopy of harvested tissues, urine, and feces revealed markedly different uptake and elimination behaviors between the two conjugations; with more highly charged moieties (+34.4 mV at pH 7.4) being quickly excreted from the liver into the gastrointestinal tract, while less charged moieties (-17.6 mV at pH 7.4) remained sequestered within the liver. Taken together, these findings suggest that charge-dependent adsorption of serum proteins greatly facilitates the hepatobiliary excretion of silica nanoparticles, and that nanoparticle residence time in vivo can be regulated by manipulation of surface charge.

Tri-functionalization of mesoporous silica nanoparticles for comprehensive cancer theranostics—the trio of imaging, targeting and therapy

In this work we report the development of the tri-functionalized mesoporous silica nanoparticles (MSNs) for use as theranostic compounds that orchestrate the trio of imaging, target and therapy in a single particle. The MSNs are functionalized in sequence with (1) contrast agents that enable traceable imaging of particle targeting, (2) drug payloads for therapeutic intervention and, (3) biomolecular ligands for highly-targeted particle delivery. Traceable imaging of nanoparticles was accomplished by directly incorporating a near-infrared (NIR) fluorescent contrast agent, ATTO647N, into the silica framework of MSNs, to exploit the relative transparency of most tissues at NIR wavelengths and maximize MSN surface area available for the subsequent conjugating drugs and targeting ligands. An oxygen-sensing, palladium-porphyrin based photosensitizer (Pd-porphyrin; PdTPP) was incorporated into the MSNs nanochannels, to enable photodynamic therapy (PDT). cRGDyK peptides, tiling the outermost surfaces of MSNs, were used for targeting the overexpressed αvβ3 integrins of cancer cells, and to ensure the internalization of the photosensitizer PdTPP. In vitro cell evaluation of the theranostic platform demonstrated not only excellent targeting specificity and minimal collateral damage, but highly potent therapeutic effect as well.

Mesoporous silica nanoparticles functionalized with an oxygen-sensing probe for cell photodynamic therapy: potential cancer theranostics

Functionalization of mesoporous silica nanoparticles (MSNs) with Pd-porphyrins for cancer cell photodynamic therapy is reported. The composite platform, MSN–PdTPP, expands the role of Pd-porphyrins from their routine use as phosphorescence probes for oxygen sensing/imaging (diagnostics) to that of novel nano-photosensitizers for cancer cell phototherapy (therapeutics). The utility of MSN–PdTPP in the phototherapeutic treatment of MDA-MB-231 breast cancer cells is also evaluated, suggesting it is a promising cancer theranostic platform.

Enhanced Chemotherapy of Cancer Using pH-Sensitive Mesoporous Silica Nanoparticles to Antagonize P-Glycoprotein-Mediated Drug Resistance

Multidrug resistance (MDR) is the major clinical obstacle in the management of cancer by chemotherapy. Overexpression of ATP-dependent efflux transporter P-glycoprotein (PGP) is a key factor contributing to multidrug resistance of cancer cells. The purpose of the present study was to use the endosomal pH-sensitive MSN (mesoporous silica nanoparticles; MSN-Hydrazone-Dox) for controlled release of doxorubicin (Dox) in an attempt to overcome the PGP-mediated MDR. In vitro cell culture studies indicate that uptake of MSN-Hydrazone-Dox by the human uterine sarcoma MES-SA/Dox-resistant tumor (MES-SA/Dx-5) cell occurs through endocytosis, thus bypassing the efflux pump resistance. This improves the efficacy of the drug and leads to significant cytotoxicity and DNA fragmentation evidenced by terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling and DNA laddering assays. In vivo studies show that the intratumor injection of MSN-Hydrazone-Dox induces significant apoptosis of MES-SA/Dox-resistant cancer cells. This is validated by active caspase-3 immunohistochemical analysis. However, MSN-Hydrazone, without doxorubicin conjugation, cannot induce apoptosis in vitro and in vivo. In conclusion, both in vitro and in vivo studies show that MSN could serve as an efficient nanocarrier entering cell avidly via endocytosis, thus bypassing the PGP efflux pump to compromise the PGP-mediated MDR. MSN-Hydrazone-Dox could further respond to endosomal acidic pH to release doxorubicin in a sustained manner. Besides the cell study, this is the first report that successfully shows the therapeutic efficacy of using MSN against MDR cancer in vivo. Mol Cancer Ther; 10(5); 761–9. ©2011 AACR.

Recent Advances in Nanoparticle-Based Förster Resonance Energy Transfer for Biosensing, Molecular Imaging and Drug Release Profiling

Förster resonance energy transfer (FRET) may be regarded as a “smart” technology in the design of fluorescence probes for biological sensing and imaging. Recently, a variety of nanoparticles that include quantum dots, gold nanoparticles, polymer, mesoporous silica nanoparticles and upconversion nanoparticles have been employed to modulate FRET. Researchers have developed a number of “visible” and “activatable” FRET probes sensitive to specific changes in the biological environment that are especially attractive from the biomedical point of view. This article reviews recent progress in bringing these nanoparticle-modulated energy transfer schemes to fruition for applications in biosensing, molecular imaging and drug delivery.

Enhanced photoacoustic stability of gold nanorods by silica matrix confinement

Photoacoustic tomography (PAT) has garnered much attention for its high contrast and excellent spatial resolution of perfused tissues. Gold nanorods (GNRs) have been employed to further enhance the imaging contrast of PAT. However, the photon fluences typically needed for PA wave induction often also result in GNR shape changes that significantly reduce the efficiency of acoustic wave generation. In this work, we propose, synthesize, and evaluate amorphous silica-coated gold nanorods (GNR-Si) in an effort to improve contrast agent stability and ameliorate efficiency loss during photoacoustic (PA) wave induction. TEM and optical absorption spectra measurements of GNR and GNR-Si show that encasing GNRs within amorphous silica provides substantial protection of nanorod conformation from thermal deformation. PA signals generated by GNR-Si demonstrate considerably greater resistance to degradation of signal intensity with repetitive pulsing than do uncoated GNRs, thereby enabling much longer, high-contrast imaging sessions than previously possible. The prolongation of high-contrast imaging, and biocompatibility and easy surface functionalization for targeting ligands afforded by amorphous silica, suggest GNR-Si to be potentially significant for the clinical translation of PAT.

pH-controllable release using functionalized mesoporous silica nanoparticles as an oral drug delivery system

We designed a novel oral colon-specific drug delivery system (OCDDS) using a modification of mesoporous silica nanoparticle (MSN) surfaces with pH-sensitive trimethylammonium (TA) groups through a pH-sensitive hydrazone bond. The pH-sensitive TA groups can efficiently increase the loading amounts of anionic drugs by a strong electrostatic attraction. After oral administration, the acidic pH of gastric juice can fully hydrolyze the TA–hydrazone bonds and further eliminate the positive charges of TA groups from MSN surfaces. When the hydrolyzed complexes were further delivered to the colons pH of 7–8, a rapid and complete release of adsorbed drugs was observed. From the studies of spectroscopic characterizations, we demonstrated that the combination of pH-sensitive hydrazone–TA groups and nano-sized particles of the MSN carriers took the advantages of increasing the accessible surface areas of drug molecules and varying the charges of MSN surfaces, which can increase dissolution and release rate of hydrophobic drug molecules. In addition, a cell viability assay also indicated that no cytotoxicity of MSN–hydrazone–TA complexes was observed even with treatment in an extremely high nanoparticle concentration. Consequently, our new formulation is highly biocompatible for the OCDDS, and we can completely solve the low stability, low solubility, and low drug bioavailability in the free form of drug molecules for the design of OCDDS.

Visualizing dynamics of sub-hepatic distribution of nanoparticles using intravital multiphoton fluorescence microscopy.

Nanoparticles that do not undergo renal excretion or in vivo degradation into biocompatible debris often accumulate in the reticuloendothelial system, also know as the mononuclear phagocyte system, with undesired consequences that limit their clinical utility. In this work, we report the first application of intravital multiphoton fluorescence microscopy to dynamically track the hepatic metabolism of nanoparticles with subcellular resolution in real time. Using fluorescently labeled mesoporous silica nanoparticles (MSNs) in mice as a prototypical model, we observed significant hepatocyte uptake of positively charged, but not negatively charged, moieties. Conversely, in vivo imaging of negatively charged, but not positively charged, MSNs reveals an overwhelming propensity for the formers rapid uptake by Kupffer cells in liver sinusoids. Since the only prerequisite for these studies was that nanoparticles are fluorescently labeled and not of a specific composition or structure, the techniques we present can readily be extended to a wide variety of nanoparticle structures and surface modifications (e.g., shape, charge, hydrophobicity, PEGylation) in the preclinical assessment and tailoring of their hepatotoxicities and clearances.

Mesoporous silica nanoparticles for the improved anticancer efficacy of cis-platin

We designed a novel cis-platin (CP) delivery system by modification of mesoporous silica nanoparticle (MSN) surfaces with a carboxylate group through a hydrazone bond. The further immobilization of CP can be achieved through the coordination of the carboxylate-modified MSN surfaces with the hydroxo-substituted CP. This new formulation can efficiently increase efficiency of both the cellular uptake and the drug release under endosomal or lysosomal pHs; therefore, the anti-proliferative effect of this new formulation on the colon cancer cell line (HT-29) was twenty times more than the free CP molecules. In addition, the encapsulation of CP complexes in the confined spaces of MSNs can decrease non-specific release from enzymatic hydrolysis because most hydrolytic enzymes have diameters considerably greater than the pore size of MSNs. The DNA fragmentation and caspase-3 activity assay showed that the apoptosis was induced by DNA damages and then an increase in caspase-3 activity. Thus, the TA-MSN-carboxylate-CP samples were induced cell apoptosis through the caspase-3 dependent pathway. Moreover, the hemolysis assay also indicated that the exposure of the carboxylate-modified MSNs in red blood cells (RBCs) did not observe the release of red hemoglobin from the cell lysis, and the further exposure of the TA-MSN-carboxylate-CP complexes to RBCs also did not observe notably the lysis of RBCs under the effectively therapeutic dosage. Therefore, our design of MSN with controllable release of CP has highly therapeutic effects and is highly biocompatible; however, a low cytotoxicity and site effect were observed.

Enhanced plasmonic resonance energy transfer in mesoporous silica-encased gold nanorod for two-photon-activated photodynamic therapy.

The unique optical properties of gold nanorods (GNRs) have recently drawn considerable interest from those working in in vivo biomolecular sensing and bioimaging. Especially appealing in these applications is the plasmon-enhanced photoluminescence of GNRs induced by two-photon excitation at infrared wavelengths, owing to the significant penetration depth of infrared light in tissue. Unfortunately, many studies have also shown that often the intensity of pulsed coherent irradiation of GNRs needed results in irreversible deformation of GNRs, greatly reducing their two-photon luminescence (TPL) emission intensity. In this work we report the design, synthesis, and evaluation of mesoporous silica-encased gold nanorods (MS-GNRs) that incorporate photosensitizers (PSs) for two-photon-activated photodynamic therapy (TPA-PDT). The PSs, doped into the nano-channels of the mesoporous silica shell, can be efficiently excited via intra-particle plasmonic resonance energy transfer from the encased two-photon excited gold nanorod and further generates cytotoxic singlet oxygen for cancer eradication. In addition, due to the mechanical support provided by encapsulating mesoporous silica matrix against thermal deformation, the two-photon luminescence stability of GNRs was significantly improved; after 100 seconds of 800 nm repetitive laser pulse with the 30 times higher than average power for imaging acquisition, MS-GNR luminescence intensity exhibited ~260% better resistance to deformation than that of the uncoated gold nanorods. These results strongly suggest that MS-GNRs with embedded PSs might provide a promising photodynamic therapy for the treatment of deeply situated cancers via plasmonic resonance energy transfer.