BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Lecture 14: Nano- and micro-particle carriers Last time: molecular switches Proteins as motors in nanodevices Today: nano- and micro-particle drug carriers Reading: D.A. Hammer and D.E. Discher, ‘Synthetic cells- Self-assembling polymer membranes and bioadhesive colloids,’ Annu. Rev. Mater. Res., 31, 387-404 (2001) Nano- and Micro-scale Drug Carriers and Detection Reagents Nano- to Micro-particle polymer-protein conjugates vesicles Polymer-drug conjugates micelles nanoparticles microparticles Packed chromosomes organelles Actin fibers proteins Protein complexes cellular structures carriers liposomes polymerosomes Thickness of lipid bilayer QuickTime? and a Graphics decompressor are needed to see this picture. QuickTime? and a Graphics decompressor are needed to see this picture. 1 nm 10 nm 100 nm 1000 nm ? Image sources: o Plama membrane EM: http://cellbio.utmb.edu/cellbio/membrane_intro.htm o Ribonuclease space-filling model: http://www.blc.arizona.edu/courses/181gh/rick/biomolecules/protein.html o Hepatitis B virus nucleocapsid: http://www.cryst.bbk.ac.uk/PPS2/course/section11/assembli.html Lecture 14 – nano- and micro-particles 1 of 6 BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Applications of tiny drug carriers and cellular markers Applications ? Delivery to tissues from circulation o Therapeutic drugs ? Anti-cancer drugs 1 o Markers for analysis/detection ? Detect tumors ? Infected cells ? Anti-pathogen lymphocytes ? Intracellular delivery o Vaccines ? class I MHC loading – priming CD8 + T cells o Gene delivery ? Delivery of plasmid DNA o Anti-sense therapy ? Shutting off production of certain proteins by delivery of anti-sense oligonucleotides to bind ribosomal mRNA o Intracellular toxins for cancer therapy o Ribozyme delivery ? ? o drug delivery to organelles 2 ? drug delivery to mitochondria Objectives ? protection of cargos from degradation o e.g. DNA protection from DNAses o protein protection from proteases, phosphatases ? avoid opsonization and production of antibodies against drug molecule o opsonization: coating foreign protein, small molecule, or particle with antibodies or complement proteins ? leads to macrophage binding and destruction ? source of opsonization animation: http://medtech.cls.msu.edu/ISL/immunology/opsonize.htm Lecture 14 – nano- and micro-particles 2 of 6 BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Opsonization: QuickTime? and a GIF decompressor are needed to see this picture. B cells binding to a foreign protein, drug, or particle can be triggered to produce antibodies against the drug or carrier: ? targeted delivery to select tissues, cells Molecular Carriers Role of polymeric carriers 1. Multivalency ? High avidity binding to low-affinity receptors for detection/delivery x CD40-dextran conjugate example ? Potent delivery on per-molecule basis x 1 carrier delivered = 10-50 drug molecules delivered 2. penetration of tissues 3. ‘stealth’ functions Chemistry and physical chemistry of conjugation ? non-covalent linkages o Ni-histadine linkages ? Molecular size considerations 3 Micelle Carriers ? Amphiphilic block copolymer structures form micelles in water o Monodisperse copolymers can form relatively monodisperse micelle spheres o Compartmentalization/association of cargo within the micelle 3 ? Electrostatic interactions 4 ? Localization driven by hydrophilic/hydrophobic balance x Hydrophobic core-hydrophobic drug x Hydrophilic drugs – only associate with corona x Amphiphilic drugs – localized at core-corona interface Lecture 14 – nano- and micro-particles 3 of 6 BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 (Kakizawa and Kataoka, 2002) o Composition range for core-shell structure? Vesicle carriers ? Liposomes o Mechanisms of cargo delivery ? Membrane fusion ? Receptor-mediated endocytosis (internalization by cell) o Functionalizing liposomes o ‘stealth’ functions o limitations ? difficulty in storage/stability ? rapid drug leakage (T.M. Allen, Drugs 54 suppl. 4, 8-14 (1997)) x unstable drug entrapment x hydrophobic drugs interact with bilayer and destabilize structure ? drug instability within liposomes x proteins interact with bilayer and become denatured ? unmodified liposomes activate complement 5 x causes pseudo-allergic reactions that damate heart and liver cells ? polymerosomes o larger amphiphilic molecules than lipids ? larger hydrophobic blocks increase membrane stability and mechanical strength ? can be polymerized to make membrane associations covalent Lecture 14 – nano- and micro-particles 4 of 6 BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Nano- and Microparticle carriers Approaches ? Electrostatic Complexation of cargo with carrier o E.g. DNA delivery by polycationic polymers ? Plasmid DNA + comb with cationic backbone hydrophilic side chains -> nano- to micro-particles x Reduce adsorption of proteins to particle surface that could trigger phagocytosis x Hydrophilic, steric barrier to block uptake by RES Nanoparticle DNA packaging + Plasmid DNA Polycation backbone* Hydrophilic side chains** ** side chain components * Backbone components PEI -(CH 2 -CH 2 -O) n - PEO PLL dextran (Park and Healy, 2003) Protection from DNAses ? Encapsulation ? Surface immobilization o Conjugation of cargos/targeting agents to surface of microparticles -OH -COOH -(CO)(NH)- 0.1M NaOH 15 min Lecture 14 – nano- and micro-particles 5 of 6 6 BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 References 1. Torchilin, V. P. PEG-based micelles as carriers of contrast agents for different imaging modalities. Advanced Drug Delivery Reviews 54, 235-252 (2002). 2. Weissig, V. & Torchilin, V. P. Drug and DNA delivery to mitochondria. Adv Drug Deliv Rev 49, 1-2 (2001). 3. Kakizawa, Y. & Kataoka, K. Block copolymer micelles for delivery of gene and related compounds. Adv Drug Deliv Rev 54, 203-22 (2002). 4. Torchilin, V. P. PEG-based micelles as carriers of contrast agents for different imaging modalities. Adv Drug Deliv Rev 54, 235-52 (2002). 5. Harris, J. M. & Chess, R. B. Effect of pegylation on pharmaceuticals. Nat Rev Drug Discov 2, 214-21 (2003). 6. Park, S. & Healy, K. E. Nanoparticulate DNA packaging using terpolymers of poly(lysine-g-(lactide-b-ethylene glycol)). Bioconjug Chem 14, 311-9 (2003). 7. Moghimi, S. M., Hunter, A. C. & Murray, J. C. Long-circulating and target-specific nanoparticles: theory to practice. Pharmacol Rev 53, 283-318 (2001). 8. Li, Y. et al. PEGylated PLGA nanoparticles as protein carriers: synthesis, preparation and biodistribution in rats. J Control Release 71, 203-11 (2001). 9. Stolnik, S., Illum, L. & Davis, S. S. Long Circulating Microparticulate Drug Carriers. Advanced Drug Delivery Reviews 16, 195-214 (1995). 10. Kozlowski, A. & Harris, J. M. Improvements in protein PEGylation: pegylated interferons for treatment of hepatitis C. J Control Release 72, 217-24 (2001). 11. Efremova, N. V., Bondurant, B., O'Brien, D. F. & Leckband, D. E. Measurements of interbilayer forces and protein adsorption on uncharged lipid bilayers displaying poly(ethylene glycol) chains. Biochemistry 39, 3441-51 (2000). 12. Halperin, A. Polymer brushes that resist adsorption of model proteins: Design parameters. Langmuir 15, 2525- 2533 (1999). Lecture 14 – nano- and micro-particles 6 of 6