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Nano-Vehicular Targeted Drug Delivery

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Nano-Vehicular Targeted Drug Delivery

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Nano-Vehicular Targeted Drug Delivery

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  2. 2. <ul><li>Drug Delivery</li></ul>In vast majority cases, drugs are delivered throughout the body via circulatory system<br />Example : Intravascular injection or oral ingestion<br />
  3. 3. <ul><li>Targeted Drug Delivery</li></ul>Method of delivering medication preferentially <br />– To the right place in a body <br />– At the right time, the right dose <br />– For the right time period<br />– Not to the other places where drug side-effects may arise<br />
  4. 4. Surgery<br />• Surgical excision of cancer tissues <br />• Accompany pain, risk of infection, poor wound healing<br />Radiation<br />• Method of completely killing cancer cells or shrinking tumors <br /> or relieving symptoms using high-energy radiation <br />• Harm health tissues and damage nearby normal cells <br />• Accompany pain, nausea, hair loss, damage to normal cells<br />Chemotherapy<br />• Chemical method of killing cells that divide rapidly (cancer cells) <br />• Kills normal cells that divide rapidly under normal conditions <br />• Accompany pain, nausea, memory loss, malnutrition<br />
  5. 5. Target to <br />tumor cell<br />Signaling<br />Agent<br />Targeting<br />Agent<br />Monitor <br />targeting<br />Drug<br />Smuggle attached drug into tumor cell<br />Released inside tumor cell<br />Targeted Drug Delivery Systems<br />• Nano-particle that carries attached drug to the site of action, with its path monitored by attached fluorescent detecting agent <br />Tumor<br />Cell<br />Blood stream<br />Technical Advantages<br />• Higher efficacy resulting from selectively targeting <br /> and killing cancer cells<br />• Reduced toxicity and lower side-effects<br />• Potentially more cost-effective<br />• Prospect for shorter treatments times<br />
  6. 6. Dendrimers : Ideal Building Block <br />for Creating a Biologically Active Nano-material<br />Dendrimers : Repeatedly Branched Molecules<br />• Consist of a series of chemical shells built on a small core molecule<br />• Each shell (generation) consists of monomer layers, made by repeating chemical-linking <br />• Beyond G5 : Begin to become spherical and 3-D structure <br />
  7. 7. Surface Groups <br />• Can be variously functionalized<br />• Cationic / Anionic / Neutral<br />• Targeting groups<br />• Dyes & Biomarkers <br />Similarity to Protein<br />• Size / Weight <br />• Very well-defined chemical structure<br />• Ease of cellular uptake <br />
  8. 8. Targets : Folic Acid (FA)<br />• FAR (high affinity receptor for FA) : over-expressed in several human cancers, even up to a 100-fold<br />• Easily available and inexpensive / small molecular size<br />Therapeutic Agent : Methotrexate (MTX)<br />• Widely used chemotherapeutic drug for the treatment of a variety of malignancies<br />• Inhibits cytosolic enzyme dihydrofolatereductase (DHFR)<br />• Results in depletion of reduced FA required for nucleotide synthesis <br />• Thus leading to the inhibition of DNA replicationand subsequent cell death<br />Fluorescence Tag<br />• Various chemicals : Fluorescein, AlexaFluor<br />• Used for monitoring and tracking<br />
  9. 9. Fluorescent tagged nanodevice are taken up through<br />the receptors then spread into cytosolic area<br />To Target Specifically to Cancer Cells <br />• Cells have on their surfaces receptors for specific molecules <br />• Specific receptors for specific molecules are targeted<br />• Specificity can be precisely controlled by targeting active receptor<br />• Taken up into the cell through specific receptor on cancer cell<br />
  10. 10. Difficult to Assemble Multiple Functions onto One Dendrimer <br />• Complex chemistry needed for self-assembly of core and shell dendrimers<br />• No specificity between the coupling of dendrimers<br />Self-Assembly using DNA <br />• Each of two dendrimers carries single-stranded DNA with the same length<br />• DNA strands are complementary<br />• Self-assembly with forming double-stranded DNA<br />• Barbell-shaped, two-dendrimer complexes<br />• Fluorescence can be separated to the other<br />
  11. 11. Preparation of Each DNA-Dendrimer Conjugate<br />1. Control surface charge density of amines <br /> - By substituting with acetyl groups to prevent infinite network formation due to electrostatic interaction<br /> - Acetylation limited to 90% of amines due to densely packed structure<br /> - G5 : 12 amine groups / G7 : 108 amine groups<br />2. Prepare DNA strand <br /> - 16-32 nucleotides for spacer from dendrimer / 34 for complementary base pairing <br />3. EDC/imidazole (0.1M) chemistry used : to activate DNAs for 10mins<br />4. Slowly mix with LiCl (0.5M) used to weaken electrostatic interactions<br />5. Allow to react overnight at RT<br />6. Remove small molecules with membrane filter <br />7. Purify non-conjugated DNA from using gel electrophoresis<br />8. Extract purified DNA-dendrimer conjugate from gel<br />9. Each dendrimer is functionalized : Target, drug and Fluorescence <br />
  12. 12. G5<br />G5<br />G7<br />G7<br />Annealing<br />Self-assembly <br />1. Mix two DNA-conjugated G7 and G5 dendrimers in equimolar ratio<br /> - to prevent crosslinking and formation of very large complexes<br />2. Annealing : Heated at 90°C for 10 mins with hybridization buffer<br />3. Cool at RT for 3 hours<br />

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