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The Nano-particles (NPs) for Cancer Diagnosis and Photo-thermal Therapy (PTT)

The Nano-particles (NPs) for Cancer Diagnosis and Photo-thermal Therapy (PTT). See p.35. 2011/11/23 Reporter: Kuang-Yu Chen Advisor : Hsien-Chang Chang. Int. J. Cancer, 2007, 120:2527-2537. Outline. The different between normal tissue and cancer The nanotechnology applications in cancer

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The Nano-particles (NPs) for Cancer Diagnosis and Photo-thermal Therapy (PTT)

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  1. The Nano-particles (NPs) for Cancer Diagnosis and Photo-thermal Therapy (PTT) See p.35 2011/11/23 Reporter: Kuang-Yu Chen Advisor : Hsien-Chang Chang Int. J. Cancer, 2007, 120:2527-2537

  2. Outline • The different between normal tissue and cancer • The nanotechnology applications in cancer • The nanoparticles used for photothermal therapy (PTT) • The biological window in near infrared ray (NIR) region • Some In vitro and In vivo examples of PTT • Photodynamic therapy (PDT) • Conclusion

  3. Nanotechnology Applications in Cancer • Schematic diagrams showing enhanced permeability and retention of nanoparticles in tumors. • Normal tissue vasculatures are lined by tight endothelial cells, thereby preventing nanoparticle drugs from escaping or extravasation, whereas tumor tissue vasculatures are leaking and hyperpermeable allowing preferential accumulation of nanoparticles in the tumor interstitial space. Annu. Rev. Biomed. Eng., 9(2007)257–288

  4. Nanotechnology Applications in Cancer • Nanoparticle drug delivery and targeting using receptor-mediated endocytosis. • The nanoparticle drug is internalized by tumor cells through ligand-receptor interaction. • Depending on the design of the cleavable bond, the drug will be released intracellularly on exposure to lysosomal enzymes or lower pH. Annu. Rev. Biomed. Eng., 9(2007)257–288

  5. Nanotechnology Applications in Cancer • Self-assembled polymeric nanoparticles with dual tumor-targeting and therapeutic functions. • Delivery of the nanoparticle drugs by receptor-mediated endocytosis and controlled drug release inside the cytoplasm. Annu. Rev. Biomed. Eng., 9(2007)257–288

  6. Nanotechnology Applications in Cancer • Multifunctional nanoparticles for integrated cancer imaging and therapy. • A truly exciting feature of cancer nanotechnology is that drug delivery, treatment efficacy, and toxicity could be monitored by using embedded imaging agents. Annu. Rev. Biomed. Eng., 9(2007)257–288

  7. Summary:Nanotechnology Applications in Cancer • Nanometer-sized particles have novel optical, electronic, magnetic, or structural properties and are currently under intense development for applications in cancer, cardiovascular diseases, and degenerative neurological disorderssuch as Alzheimer’s disease. • Targeted nanoparticle drugs offer significant advantages in improving cancer therapeutic efficacy and simultaneously reducing drug toxicity. • Future work needs to address the potential long-term toxicity, degradation, and metabolism of nanoparticle agents, to identify and develop new biomarker-probe systems, and to develop multifunctional nanoscale platforms for integrated imaging, detection, and therapy. Annu. Rev. Biomed. Eng., 9(2007)257–288

  8. A Clearer Vision for in vivo Imaging • Hemoglobin (Hb) and water, the major absorbers of visible and infrared light, respectively, have their lowest absorption coefficient in the NIR region around 670-900 nm. Nat. Biotechnol., 19(2001)316-317

  9. Gold Nanocages Nanospheres Nanorods Nanoshells Nanocubes The nanomaterials used for cancer photothermal therapy Lasers Med. Sci., 2008, 23:217-228 ACS Nano., 2010, 4(1):113-20 Small, 2010, 6(7) 811-817

  10. Gold Nanoparticles: Interesting Optical Properties and Recent Applications in Cancer Diagnostics and Therapy • Important optical processes resulting from the interaction of light with a gold nanoparticle, viz. light absorption, Mie scattering, surface-enhanced luminescence and surface-enhanced Raman scattering (SERS) from adsorbed molecules. Nanomedicine, 2007, 2(5):681–693

  11. Cancer-cell Diagnostics Using Dark-field Light-scattering Imaging of Gold Nanoparticles HOC: Human osteocalcin HSC: Hematopoietic stem cells EGFR: epidermal growth factor receptor • without nanoparticles • (B) with anti-EGFR antibody-conjugated gold nanospheres • (C) with anti-EGFR antibody conjugated gold nanorods • The anti-EGFR-conjugated gold nanoparticles are bound to the cancer cells assembled in an organized fashion, whereas they are distributed randomly around normal cells, thus enabling the optical differentiation and detection of the cancer cells. Nanomedicine, 2(2007)681–693 J. Am. Chem. Soc., 2006, 128 (6): 2115-2120

  12. Selective Photothermal Therapy of Cancer Cells with Anti-EGFR/Au Nanorods Incubated • At 80 mW (10 W/cm2), the HSC and HOC malignant cells are obviously injured while the HaCat normal cells are not affected. • The HaCat normal cells start to be injured at 120 mW (15 W/cm2) and are obviously injured at 160 mW (20 W/cm2). Nanomedicine, 2(2007)681–693 J. Am. Chem. Soc., 2006, 128 (6): 2115-2120

  13. Near-Infrared Resonant Nanoshells for Combined Optical Imaging and Photothermal Cancer Therapy • Extinction spectra of nanoshells used in this study by UV-Vis spectrophotometer. • Nanoshells are 143 nm in diameter with a core of 119 ±11 nm (silica)and a shell thickness of 12 nm (gold). Nano Letters, 2007, 7(7):1929-1934

  14. Histological Examination of Tumors Using Silver Staining Confirmed The Presence of Nanoshells throughout The Tumors 12.5 ppm 0 ppm • The silver staining of representative areas of tumors from mice treated with nanoshells (A) or with PBS (B). • The neutron activation analysis (NAA) verified nanoshells present in the tumor shown in figure A at 12.5 ppm (equivalent to approximately 3x106 nanoshells/gram of tumor tissue). Nano Letters, 2007, 7(7):1929-1934

  15. The Survival Data for The Treatment Groups Post Irradiation Nanoshell + NIR Laser Irradiation Tumor Size Before Irradiation and 12 Days Post-rradiation of Mice nanoshell + NIR sham + NIR untreated control nanoshell + NIR sham + NIR untreated control The long-term survival rate of nanoshell + NIR group: 83% Nano Letters, 2007, 7(7):1929-1934

  16. A New Photothermal Therapeutic Agent: Core-Free Nanostructured AuxAg1-x Dendrites • The SEM image of core-free Au0.3Ag0.7 dendrites. • The arrows show the voids on the tips of the stems of the dendrites. • UV/Vis absorption spectra of various AuxAg1-x composites as a function of the amount of added HAuCl4. • The inset shows a linear relationship between the atomic ratio of Au and the amount of added HAuCl4. Chem. Eur. J., 14(2008)2956-2964

  17. The Photothermal Effect of Au0.3Ag0.7 Dendrites Conjugating anti-EGFR Monoclonal Ab by NIR Au0.3Ag0.7 dendrites 150 mg mL-1 Au nanorod 500 mg mL-1 20 W cm-2 30 W cm-2 15 W cm-2 25 W cm-2 10 W cm-2 20 W cm-2 Anti-EGFR conjugated with Au0.3Ag0.7 dendrites treated A549 cancer cells were irradiated by different laser dosages (unit: W cm-2) for 4 min. Green  calcein AM  living cells Red  EthD-1  dead cells Chem. Eur. J., 14(2008)2956-2964

  18. Laser Confocal Microscopy of HeLa Cells Exposed to FITC Loaded Porous Iron Oxide Nanorods • Aggregations of nanorods presented as dark spots could be observed by DIC microscopy observation. • The FITC images showing accumulation of FITC fluorescence signal in the HeLa cells were observed in a time-dependent manner. • The merged images show the location of nuclei and FITC. The reconstructed saggital sections of the cancer cells in the area across the red lines are shown in the bottom two rows. • Time-dependent accumulation of FITC was observed (Z-FITC). The Z-merge showed that FITC also diffuses through the nucleus (scale bar: 10 mm). • b) FITC image of quantified accumulation of the FITC fluorescent signal. Chem. Eur. J., 13(2007)3878-3885

  19. Gold Nanocages as Photothermal Transducers for Cancer Treatment PVP-coated nanocages in PBS at pH 7.4 (solid line) PEGylated nanocages in PBS at pH 7.4 (dashed line) PEGylated nanocages in fetal bovine serum (dotted line) UV–vis–NIR spectra showing the local surface plasma resonance (LSPR) peaks of Au nanocages in different media. The inset shows a typical TEM image of the Au nanocages with an edge length of 48 ± 3.5 nm. Small, 2010, 6(7) 811-817

  20. Plots of Temperature Increase for Suspensions of Au Nanocages at Various Concentrations (for 10 min) 1W/cm2 0.5W/cm2 Temperature Increase (ΔT) for Aqueous Suspensions of Au Nanocages upon Irradiation by Laser for 10 min Small, 2010, 6(7) 811-817

  21. The Photothermal Effect of the Au Nanocages for Selective Destruction of the Neoplastic Tissue using A Bilateral Tumor Model nanocage saline 1 min 3 min 5 min 10 min The mice were intravenously administrated with 100 mL of 10 mg/mL (15 nM or 9 x 1012 particle/ml) PEGylated Au nanocages in PBS. 72 h post injection, 0.7W/cm2 for 10 min Small, 2010, 6(7) 811-817

  22. 18F-FDG PET/CT Co-registered Images of Mice Intravenously Administrated with either Saline or Au Nanocages, Followed by Laser Treatment • Saline, B) Nanocage, • C) Saline, after irradiation, • D) Nanocage, after irradiation. E) A plot showing the ratios of laser-treated tumor (Rt tumor) to non-treated tumor (Lt tumor) 18F-FDG standardized uptake values (SUV, p < 0.001). The white arrows indicated the tumors that were exposed to the diode laser at a power density of 0.7 W/cm2 for 10 min. Small, 2010, 6(7) 811-817

  23. saline, w/o irradiation C) nanocage w/o irradiation • B) saline, w/ irradiation D) nanocage, w/ irradiation • (0.7W/cm2 for 10 min) Representative Histology Images of Tumor Tissues from the Two Mice Intravenously Administrated with Saline and Au Nanocages, Respectively Tumors from mice treated with nanocages and laser irradiation showed distinctive characteristics of cellular damage, such as abundant pyknosis (arrow), karyorhexis (open arrow), karyolysis (arrowhead), and interstitial edema (asterisk). Small, 2010, 6(7) 811-817

  24. http://en.wikipedia.org/wiki/File:Nuclear_changes.jpg

  25. (A) Tissue Distribution of PEGylated Au Nanocages in Mice (B) Distribution of the PEGylated Au Nanocages in Tumor (A) Tissue distribution of PEGylated Au nanocages intravenously administrated (100 ml, 9 x 1012 particles/ml) into tumor-bearing mice (analyze by ICP-MS, 96 h post. i.v.) (B) E, C and EC represent the edge, center, and region between edge and center. Small, 2010, 6(7) 811-817

  26. Bifunctional Gd2O3/C Nanoshells for MR Imaging and NIR Therapeutic Applications a) Raman spectrum of Gd2O3/C nanoshells prepared after annealing at 600℃ under N2, showing G and D bands due to the presence of carbon. b) UV/Vis spectra of Gd2O3/C@PSMA, Gd2O3 nanoshells at 800℃ and PSMA polymer in aqueous solution. • The inset in figure a) : Gd2O3/C@PSMA nanoshells suspension. • PSMA: poly(styrene-alt-maleic acid) (PSMA) polymer can improve water dispersion for further antibody conjugation Adv. Funct. Mater., 19(2009)249-258

  27. The anti-EGFR Conjugated with Nanoshells Combined NIR Irradiation Treated with Cancer Cells fix: 500 mg mL-1 fix: 20 W cm-2 20 W cm-2 500 mg mL-1 15 W cm-2 400 mg mL-1 300 mg mL-1 10 W cm-2 a) Anti-EGFR conjugated with Gd2O3/C@PSMA nanoshells (500 mg mL-1) treated with A549 cancer cells were irradiated by different laser dosages for 7 min. b) Anti-EGFR conjugated with Gd2O3/C@PSMA nanoshells irradiated by the laser dosages of 20 W cm-2 as a function of nanoshell dosages. Green  calcein AM  living cells Red  EthD-1  dead cells Adv. Funct. Mater., 19(2009)249-258

  28. The Cell Viability Versus NIR Laser Power for A549 Cells Treated with anti-EGFR Conjugated with Different Nanorods and Nanoshells • The cell viability versus NIR laser power for A549 cells treated with anti-EGFR conjugated with Gd2O3/C@PSMA nanoshells, Au nanorods, and silica@Au nanoshells (dosage: 500 mg mL-1). Adv. Funct. Mater., 19(2009)249-258

  29. Gd2O3/C @PSMA Gd2O3/C The Biodistribution of Gd2O3/C and Gd2O3/C @PSMA Nanoshells in Mouse Organs by ICP-AES Analysis • Inductively coupled plasma atomic emission spectrometer (ICP-AES) analysis of biodistribution of a) Gd2O3/C and b) Gd2O3/C @PSMA nanoshells in mouse organs that were surgically removed at each time point. Adv. Funct. Mater., 19(2009)249-258

  30. In vivo Magnetic Resonance Imaging afterGd2O3/C nanoshells Injection from Jugular Vein a) In vivo progressive MRI events. T1-weighted images of male BALB/c mice administrated with Gd2O3/C nanoshells at the indicated temporal points (The white and black arrows indicate the kidneys and liver, respectively). b) The signal intensities of liver and kidney in T1-weighted imaging at the indicated temporal points. Adv. Funct. Mater., 19(2009)249-258

  31. Targeted Photothermal Ablation (PTA) of Murine Melanomas with Melanocyte-Stimulating Hormone (MSH) Analog Conjugated Hollow Gold Nanospheres (HGN) The basic idea of PTA HGNs are actively linked to target cancer cells though Ab-Ag or ligand (e.g., hormone)-receptor interaction. Heat (Δ) generated from light illumination of the HGNs is used for thermal imaging and/or destroying of the cancer cells. J. Phys. Chem. Lett., 1(2010)686-695 • HGN were stabilized with PEG coating and attached with a MSH analog, [Nle4,D-Phe7]a-MSH (NDP-MSH), which is a potent agonist of melanocortin type-1 receptor over expressed in melanoma.

  32. Synthesis, Characterization, and Tunable Optical Properties of Hollow Gold Nanospheres Image showing the color range of HGN solutions. The vial on the far left contains solid gold nanoparticles, the rest are HNGs with varying diameters and wall thicknesses. UV-visible absorption spectra of nine HGN samples with varying diameters and wall thicknesses J. Phys. Chem. B, 110(2006)19935-19944

  33. Conjugation of NDP-MSH peptide to HAuNS through PEG linker outer diameter: 43.5 ± 2.3 nm, shell thickness: 3-4 nm A: schematic of nanoshell synthesis and bioconjugation. B: TEM image of NDP-MSH-PEG-HAuNS. Bar, 50 nm. C:absorbance of HAuNS in water before and after bioconjugation. D: TEM images of NDP-MSH-PEG-HAuNS and PEG-HAuNS subjected to immunogold staining. Only NDP-MSH-PEG-HAuNS were stained with 5-nm gold nanoparticles (arrow). Bar, 20 nm. Clin. Cancer Res., 2009, 15(3):876-886

  34. Temperature-time profile of aqueous PEG-HAuNS solution exposed to NIR light (808 nm) at 8 W/cm2 Colloidal stability of uncoated HAuNS, NDP-MSH-PEG-HAuNS, and PEG-HAuNS The nanoparticles were incubated in different solutions at 37oC for 24 h. Clin. Cancer Res., 2009, 15(3):876-886

  35. Specific Uptake of NDP-MSH-PEG-HAuNS in B16/F10 Cells B A A: uptake of FITC-tagged HAuNS in B16/F10 cells. (Cell nuclei: DAPI. Bar: 20 mm.) B: distribution of b-arrestin expression in relation to FITC-tagged HAuNS in B16/F10 cells. In cells incubated with NDP-MSH-PEG-HAuNS, the HAuNS colocalized with b-arrestin in polarized fashion (yellow, arrows), whereas in cells incubated with PEG-HAuNS, b-arrestin was evenly distributed in the cytoplasm and did not co-localize with the HAuNS. (Cell nuclei: DAPI. Bar: 20 mm.) Clin. Cancer Res., 2009, 15(3):876-886

  36. Specific Uptake of NDP-MSH-PEG-HAuNS in B16/F10 Cells Clin. Cancer Res., 15(2009)876-886 C: TEM images of B16/F10 cells incubated with NDP-MSH-PEG-HAuNS or PEG-HAuNS. The electron-dense NDP-MSH-PEG-HAuNS were seen in coated pits (arrowheads), early endosomes (arrow), and cytoplasm. PEG-HAuNS were found only outside the cell membrane.

  37. Cell Viability after NIR Region Laser Irradiation B16/F10 cells, NIR 808 nm(32 W/cm2; 3 mins) Viable cells dead cells After different treatment , cells retained normal morphology, and few dead cells were observed. In contrast, after treatment with NDP-MSH-PEG-HAuNS plus NIR region laser, most cells were dead. Viable cells were stained green with calcein AM; dead cells were stained red with EthD-1. Circled area labeled with asterisk, laser-irradiated area; bar: 100 mm Clin. Cancer Res., 15(2009)876-886

  38. Biodistribution and Intratumoral Distribution of FITC-tagged HAuNS Tissue and tumors were removed 4 h after i.v. injection of HAuNS. A: representative fluorescence micrographs of cryosectioned B16/F10melanoma. Microvessels were stained with rat anti-mouse CD31 monoclonal antibody. Cell nuclei: DAPI . Significantly more HAuNS were found in the tumors of mice injected with NDP-MSH-PEG-HAuNS than in the tumors of mice injected with PEG-HAuNS. NDP-MSH-PEG-HAuNS were distributed throughout the tumor matrix in the interstitial space, whereas PEG-HAuNS were distributed around tumor vessels (arrows). Bar, 100 mm. B: biodistribution of FITC-tagged HAuNS in different tissues. Data were calculated as the number of particle aggregates per mm2 visual area at X200, and values are presented as mean FSD (n = 5). Clin. Cancer Res., 2009, 15(3):876-886

  39. Biodistribution and Intratumoral Distribution of FITC-tagged HAuNS C: biodistributionof NDP-MSH-PEG-HAuNS and PEG-HAuNS. Data were plottedas %ID/g).Mean FSD(n =5).*,P < 0.01. D: Z-stack images of tumor sections at higher magnification. Melanocortin type-1 receptor was stained with rabbit anti-mouse melanocortin type-1 receptor polyclonal antibody (pseudo colored red). Blood vessels were stained with rat anti-mouse CD31monoclonal antibody (pseudo colored blue). FITC-tagged HAuNS were green. NDP-MSH-PEG-HAuNS but not PEG-HAuNS co-localized with melanocortin type-1receptor (yellow and orange, arrowheads), indicating melanocortin type-1receptor mediated endocytosis of NDP-MSH-PEG-HAuNS in vivo. Asterisks, the lumens of tumor vasculature with discontinuous CD31 staining; bar,10 mm Clin. Cancer Res., 15(2009)876-886

  40. In vivo PTA with Targeted NDP-MSH-PEG-HAuNS Induced Selective Destruction of B16/F10 Melanoma in Nude Mice [18F] fluorodeoxyglucose PET imaging shows significantly reduced metabolic activity in tumors after PTA in mice pretreated with NDP-MSH-PEG-HAuNS but not in mice pretreated with PEG-HAuNS or saline. PET was conducted before 0 h and 24 h after NIR region laser irradiation (0.5 W/cm2 at 808 nm for 1 min), which was commenced 4 h after i .v. injection of HAuNS or saline. T, tumor. Arrowheads, tumors irradiated with NIR region light. Clin. Cancer Res., 15(2009)876-886

  41. Histologic Assessment of Tumor Necrosis The necrotic area as a percentage of the tumor. (n = 5). The whole tumors stained with H&E 24 h after NIR region laser irradiation. (Bar: 500 mm.) The microphotographs show tumor cells characterized by extensive pyknosis (arrows), karyolysis (arrowheads), cytoplasmic acidophilia, and degradation of the ECM of the tumor (asterisks) in mice treated with NDP-MSH-PEG-HAuNS plus laser. In mice treated with PEG-HAuNS plus laser, such features were observed mostly in areas close to the surface. (Bar: 50 mm. ) Clin. Cancer Res., 2009, 15(3):876-886

  42. Conclusion To development of an ideal photo thermal therapy nano-particles • Increase the photothermal ablation efficiency • Decrease the energy dose of the laser light • Need to minimize the potential damage to surrounding normal tissues • Size effect- 10 nm, 50 nm, 100 nm • Shape effect- rod, tube, cage, cube, capsule, sphere • Materials effect- Au, Ag, Si or Fe2O3 • Cytotoxicity effect • Biodistribution in body or clearance of organ • Specificity (targeting) • Cost

  43. What is the PDT? • PDT is based on photosensitizers (PSs) generating singlet oxygen (1O2), and subsequently reactive oxygen species (ROS) upon localized exposure to light in the presence of ground state oxygen (O2). • After excitation of the PS from its ground singlet state to an excited singlet state, the PS undergoes intersystem crossing to a longer-lived excited triplet state. • Energy transfer from the PS’s excited triplet state to a nearby oxygen molecule (which posses a ground triplet state) results in the relaxation of the PS to its ground singlet state and the formation of an excited singlet state oxygen molecule. • The intrinsic cytotoxity of singlet oxygen leads to selective and irreversible destruction of diseased tissues in the vicinity of 1O2.

  44. Mechanism of action of photodynamic therapy (PDT) • PDT requires 3 elements: light, a photosensitizer and oxygen. • When the PS is exposed to specific wavelengths of light, it becomes activated from a ground to an excited state. • As it returns to the ground state, it releases energy, which is transferred to oxygen to generate reactive oxygen species (ROS), such as singlet oxygen and free radicals. • These ROS mediate cellular toxicity. Nature Reviews Cancer, 3(2003)380-387

  45. How does the PDT successful? • In order to minimize systemic toxicity, the PS should be highly targeted. • The adequate oxygen permeability/perfusion in the region of disease is critical, it directly correlates to oxidative damage to neighboring cells. • The adequate local concentration of PS in diseased tissue and quantum yield of singlet oxygen are needed to minimize collateral thermal damage from photoirradiation.

  46. Mesoporous Silica Nanoparticles (MSNs) Functionalized with an Oxygen-sensing Probe for Cell Photodynamic Therapy (PDT): Potential Cancer Theranostics Theranostics = Therapeutics + Diagnostics MSNs serve as a matrix in which high densities of transportable molecules reside, shielded fromtheir local environment. J. Mater. Chem., 19(2009)1252–1257

  47. The Photosensitizer- Pd-meso-tetra(4-carboxyphenyl) porphyrin (PdTPP) • Pd-porphyrin is a synthetic metallo-porphyrin with long phosphorescence lifetime and is well known in use for quantitative in vivo oxygen sensing and imaging which are conventional PSs for PDT: both in vitro and in vivo. • The phosphorescent Pd-meso-tetra(4-carboxyphenyl) porphyrin (PdTPP) is a metallo-porphyrin and frequently used to measure oxygen distributions in tissues via oxygen-dependent quenching of phosphorescence. • The long-lived triplet state of PdTPP is produced with unity quantum yield, while the concentration of singlet oxygen generated in PDT depends on the accessibility of the excited PdTPP to oxygen. J. Mater. Chem., 19(2009)1252–1257

  48. A photodynamic model of MSNs and the covalent modification of PdTPP onto the nanochannel surface of MSNs The conjugation of Pd-porphyrin to MSNs, they extend the functionality of Pd-porphyrins from their original ‘‘diagnostics’’ role in oxygen sensing and imaging to ‘‘therapeutics’’ in PDT. J. Mater. Chem., 19(2009)1252–1257

  49. FTIR spectra was used to evaluate the covalent bonding of MSN and PdTPP Two strong absorption bands: amide I (1650 cm-1, carbonyl stretch), amide II (1540 cm-1, CN stretch and NH bend) J. Mater. Chem., 19(2009)1252–1257 • The spectra shows the characteristic peak of amide bond which was self-assembled with PdTPP and MSNs. • The spectra provide strong support for the assertion that PdTPP attachment to MSNs was by means of amide bonds.

  50. A TEM image of MSN–PdTPP uniform tertiary structure of MSN–PdTPP (average particle size ~100 nm). After PdTPP modification, the surface area and mean pore diameter of MSNs decreased from 1026 m2/g and 3 nm to 540 m2/g and 2.3 nm, respectively (by N2 adsorption–desorption isotherm measurement, BET), which implied the majority of PdTPP conjugation took place within the MSN’s nanochannels. J. Mater. Chem., 19(2009)1252–1257

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