Phage Display and Targeted Delivery (Finished)

• 3 Noble Prize winners in 2018


  • Frances Arnold
  • George Smith (from MU woooo)
  • Sir Gregory Winter
• Humira (anti-TNF-a monoclonal antibody drug) was discovered by phage display technology

  • Treats rheumatoid arthritis, psoriasis, inflammatory bowel disease
• Phage is a virus that only infects and replicates in bacterial cells
• Modified viruses can be used as gene therapy to human patients


  Viruses can be used to deliver a healthy gene that can correct mutated or diseased genes in a patient
• (T/F) Phages can infect humans


  False. They only infect bacteria
• Phage library


  Library of phages that express a wide diversity of peptides or proteins
• Phage Display


  Technology to select ligands for a specific molecule/cell/tissue using a phage library
• Phage Composition

  • Protein coating - protection, to recognize different bacteria
  • Capsid - holds genome (gene 3)
• Gene 3 can be genetically changed/expressed to express different peptides, proteins, or antibodies (like monoclonal antibodies) on their surface -> creation of phage library


  Phage library contains ~15 billion candidates
• Phage Display Biopanning Steps:

  1. Build a phage library
  2. Identify peptide that can bind to target (can be proteins, cells, tissues) on a solid surface
  3. Phages binds. Any phages that don't bind are washed away
  4. Use buffer to elude phages
  5. Amplify previously-bound phages
  6. Repeat cycle
• Applications of Peptides:

  • Ligands for targeted drug delivery
  • Diagnostic agents & tumor imaging
  • Therapeutic agents
• The most popular way to administer drugs is orally because it is more convenient
• Injections are the most effective way to administer medications because it makes direct contact with the blood
• Local delivery: delivery of drugs directly to a specific diseased site in the body

  • Most specific
  • Usually goes to target tissues
  • Less toxic, less side effects
  • Limited applications
• Systemic delivery: the delivery of drugs to the bloodstream to reach the diseased organs or cells of the body

  • Can be used for most disease states
  • More toxic
  • Small fraction can be delivered into the target organ
  • Can cause more side effects on non-targeted organs
• System Drug Administration: injections, transdermal, oral

  Local Drug Administration: otic, ocular, nasal, topical, rectal

  Both: inhalation
• Chemotherapy side effects:

  • Hair loss
  • Nausea & vomiting
  • Weakened immune system
  • Neuropathy
  • Trouble breathing
  • Bruising & bleeding more easily
• Passive targeted drug delivery: drug is encapsulated in a nanoparticle system (100-200 nm) that can accumulate in tumors due to leaky vasculature ofr tumors
• Active targeted drug delivery: system contains targeting ligands that recognize specific markers on target tissues or cells
• Targeting ligands are molecules that can specifically bind to markers on cells

  • Ex.: peptide, antibody, carbohydrate, aptamer, small molecules
• Drug-ligand conjugate: drug is conjugated to a targeting ligand via a linker
• Ligand-modified nanoparticles: drug is encapsulated in nanoparticles that are modified with targeting ligands

  • Can spontaneously accumulate in tumors
  • Targeted ligands allow it to bind a very specific marter on tumor cells
• Active targeted drug delivery systems are more specific than passive drug delivery
• Antibody drug conjugate (ADC) is a drug that is attached to an antibody that can target and destroy cancer cells
• Parts of antibody drug conjugates (ADC):

  • Antibody: highly specific with high affinity for tumor-associated antigens
  • Cytotoxic Agent: designed to kill tumor cells when internalized and released
  • Linker: attaches cytotoxic agent to antibodies
• Immunoliposome conjugated with scFv targeting HER-2 on the surface of breast tumor cells

  • Drug is encapsulated in liposome vesicle
  • Has high specificity for HER-2
  • Reduced toxicity to normal cells
• By blocking PD-L1 in tumor cells and inhibiting binding between tumor cell and T cells, the immune system is able to recognize and destroy tumor cells

  • Inhibited by checkpoint inhibitors
• Monoclonal antibodies can't cross the barrier of the stomach - so they can't be absorbed orally
• Peptides can be absorbed via the stomach and GI tract because it is smaller in size
• Active targeted drug delivery always uses ligands to define a target