Surface Modification of Nanoparticles for Biomedical Applications


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Surface ligands on nanoparticles control their properties and interactions, which can be harnessed for biomedical imaging, cell targeting, and therapeutic applications.

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Surface Modification of Nanoparticles for Biomedical Applications

  1. 1. Surface Modification of Nanoparticles for Biomedical Applications Cristina Resetco Polymer and Materials Science University of Toronto 1
  2. 2. Functions of Surface Ligands on Nanoparticles 2
  3. 3. Biomedical Applications of NanoparticlesGold Optical Thiol Biomolecular absorption, disulfide recognition stability amine sensingCdSe Luminescence Thiol Imagingquantum photo-stability phosphine sensingdots pyridineFe2O3 Magnetic Diol MR imaging,nanoparticles amine biomolecule purification 3
  4. 4. Phase Transfer of Nanoparticles(1) Ligand exchange (2) Additional ligand layer (3) Amphiphilic polymer 4
  5. 5. PEG-Modified NanoparticlesSolubility in organic solvents andwater where PEG is heavily hydrated,forming random coilsLess non-specific binding in cells byPEG-modified nanoparticlesIntroduction of new functionalgroups on nanoparticles by bifunctionalPEGSeparation by gel electrophoresis of Nanoparticles modified with NH2-PEG-nanoparticles with a defined number of NH2 yield nanoparticles with exactly one orchemical groups with PEG with two amino groups, separated by gelmolecular weight above 5000 g/mol, electrophoresis (Sperling et al. 2006).which forms discrete bands 5
  6. 6. Requirements for Solubilizationand Bioconjugation of Nanoparticles 6
  7. 7. Quantum Dot PropertiesHigh quantum yield compared to common fluorescent dyesBroadband absorption: light that has a shorter wavelength thanthe emission maximum wavelength can be absorbed, peakemission wavelength is independent of excitation sourceTunable and narrow emission, dependent on composition andsizeHigh resistance to photo bleaching: inorganic particles are morephotostable than organic molecules and can survive longerirradiation timesLong fluorescence lifetime: fluorescent of quantum dots are 15to 20 ns, which is higher than typical organic dye lifetimes.Improved detection sensitivity: inorganic semiconductornanoparticles can be characterized with electron microscopes 7
  8. 8. Quantum dots conjugated with folate–PEG– PMAM for targeting tumor cellsFolate–poly(ethylene glycol)–polyamidoamine ligands encapsulate and solubilizeCdSe/ZnS quantum dots and target folate receptors in tumor cells.Dendrimer ligands with multivalent amino groups can react with Zn2+ on the surfaceof CdSe/ZnS QDs based on direct ligand-exchange reactions with ODA ligands Y. Zhao et al. Journal of Colloid and Interface Science 350 (2010) 44–50. 8
  9. 9. Poly(amidoamine) (PAMAM) Dendrimer LigandsMore dense than linear ligands, which improves stabilityMore anchoring groups, which generate strong interactions between QDs and PAMAMTerminal groups (amine, carboxyl, and hydroxyl) of polyamidoamine (PAMAM)dendrimers can be modified with different functionalities to link with various biomolecules 9 Y. Zhao et al. Journal of Colloid and Interface Science 350 (2010) 44–50
  10. 10. Quantum Dots for Imaging of Tumor Cells Figure 2. Phase contrast images (top row) and fluorescence image NIH-3T3 cells incubated with QDs2; (c) SKOV3 cells were incubated with QDs2FPP-QDs specifically bind to tumor cells via themembrane expression of FA receptors on cell surface Y. Zhao et al. Journal of Colloid and Interface Science 350 (2010) 44–50.10
  11. 11. Surface Density of Ligands on Nanoparticles 11
  12. 12. Monofunctionalized Nanoparticles by a Solid Phase Exchange Reaction Bifunctional alkanethiol ligands with a carboxylic acid group are immobilized on a solid support such as polymeric Wang resin at a low density. Exchange reaction of resin-bound thiol ligands with gold nanoparticles results in one resin-bound thiol ligand on each nanoparticle. Cleavage from the resin yields nanoparticles with a single carboxylic acid functional group. 12 Schaffer, et al. Langmuir, Vol. 20, No. 19, 2004.
  13. 13. Monofunctionalized Gold NanoparticlesFor solid phase exchange product there is Figure 1. TEM image of gold nanoparticleminimal hydrogen bonding since C=O dimers formed by coupling reaction ofstretching vibration band appears at higher carboxylic group modified goldwavenumbers. nanoparticles with bifunctional 1,2- ethylenediamine. 13 Schaffer, et al. Langmuir, Vol. 20, No. 19, 2004.
  14. 14. Bioconjugation of Nanoparticles Covalent Non-Covalent Binding InteractionsBifunctional linkers Hydrophobic forcesmercaptoacetic acid used to link modifiedis used to link acrylic acid polymerquantum dots with to TOPO cappedbiomolecules quantum dotsSilanization Electrostaticalkosiloxane interactionsmolecules form high affinity ofcovalent Si-O-Si cationicbonds biomolecules for negatively charged backbone of DNA 14
  15. 15. Gold Nanocages Precise tuning of LSPR Potential to trap drug molecules or enzymes in pores and release them through an externally controlled mechanism Photothermal effect for cancer therapeutics(1) PEG with N-hydroxysuccinimide (NHS) group at one end and an orthopyridyl disulfide (OPSS) group at the other is attached to the surface of the nanocages by breaking the disulfide bond of the OPSS group and forming a gold-thiolate bond(2) Primary amine on antibody reacts with the NHS group of PEG molecule 15
  16. 16. Gold nanocages covered by smart polymers for controlled release with NIR light Au nanocages are synthesized by galvanic replacement reaction between Ag nanocubes and HAuCl4 in water. Figure 1. Drug release from gold nanocages Temperature-sensitive polymer based on poly(N-isopropylacrylamide) (pNIPAAm) changes conformation due to variations in temperature. Photothermal effect induced by laser beam with a wavelength matching the absorption peak of Au nanocage, causes light to be absorbed and converted into heat Drug release due to temperature increase that causes polymer chains to Figure 2. TEM images of Au nanocages covered collapse exposing nanocage pores by a pNIPAAm-co-pAAm copolymer 16Yavuz, et al. Nature Materials. Vol 8, December 2009.
  17. 17. Polymer Synthesis by ATRPAtom-transfer radical polymerization of N-isopropylacrylamide (NIPAAm)and acrylamide (Aam) initiated by a disulphide initiator forming polymerwith tunable low critical solution temperature (LCST) between 32-50 C. 17
  18. 18. Controlled Drug Release from NanocagesFigure 1. Controlled release of alizarin dye Figure 2. Cell viability for samples (C-1) cellsfrom the Au nanocages covered by a irradiated with a pulsed near-infrared laser for 2 mincopolymer with an LCST at 39 C Absorption without Au nanocages (C-2) cells irradiated with thespectra of alizarin-PEG released from the laser for 2 min in the presence of Au nanocages; andcopolymer-covered Au nanocages (2/5 min) cells irradiated with the laser for 2 and 5 min in the presence of doxorubicin (Dox)-loaded Au nanocages. 18
  19. 19. Multifunctional NanoparticlesNanoparticles for imaging: quantum dotsTargeting agent: antibody or peptideCell-penetrating agent: peptideStimulus-sensitive element for drug release 19Stabilising polymer to ensure biocompatibility: polyethylene glycol
  20. 20. Multifunctional Magnetic Nanoparticles• Magnetic nanocrystals as ultrasensitive MR contrast agents: MnFe2O4• Anticancer drugs as chemotherapeutic agents: doxorubicin, DOX• Amphiphilic block copolymers as stabilizers: PLGA-PEG• Antibodies to target cancer cells: anti-HER antibody (HER, herceptin) conjugated by carboxyl group on the surface of the MMPNs 20 Yang, etal. Angew. Chem. 2007, 119, 8992 –8995.
  21. 21. Targeted Drug Delivery and Inhibition of Tumor Growth Figure 1. Multifunctional magneto- polymeric nanohybrids (MMPNs) containing manganese ferrite (MnFe2O4) nanocrystals prepared by Figure 2. MR signal intensity and colour maps of NIH3T6.7 nanoemulsion with anticancer drug and MDA-MB-231 cells treated with IRR-MMPNs; black, (doxorubicin, DOX) and PLGA-PEG HER-MMPNs; white.Human epidermal growth factor receptor (HER2) -- tumor-targeting marker for breastcancerFibroblast NIH3T6.7 cells -- highly express the HER2/neu cancer markersMDA-MB-231 cells -- express low levels of the cancer markers 21 Yang, etal. Angew. Chem. 2007, 119, 8992 –8995.
  22. 22. Inhibition of Tumor Growth by Magnetic Nanoparticles HER-MMPNs had the greatest tumor growth inhibition than since HER-MMPNs were target- delivered to HER2/neu receptors of NIH3T6.7 cells and DOX was released 22
  23. 23. Nanoparticle ToxicityNanoparticles affect biological behaviour at cellular, subcellular, protein,and gene levels by formation reactive oxygen species (ROS). 23
  24. 24. Characterization of Nanoparticles and Surface Ligands 1H NMR spectroscopy Fourier Transform Infrared Sectroscopy (FTIR) UV/VIS Spectrophotometry transmission electron microscopy (TEM) dynamic light scattering gel electrophoresis size exclusion chromatography analytical ultracentrifugation fluorescence correlation spectroscopy 24
  25. 25. AcknowledgementsProfessor Eugenia Kumacheva Siyon (Lucy) Chung Dr. Jemma Vickery Dr. Kun Liu Ariella Lukash Anna Lee Dan Voicu Ethan Tumarkin Dr. Jesse Greener Jai Il Park Dr. Ziliang Wu Dr. Dinesh Jagadeesan 25