Nanotechnology Flashcards
Name 3 advantages of micro needles
1) Painless and easy to use
2) Safe needle disposal
3) Eliminate spread of pathogens
Name 2 reasons why drugs can’t always be oral
1) Poor absorption
2) Drug degradation in GI tract and Liver
Where do micro needles penetrate the skin
Stratum corner into viable epidermis avoiding contact with nerve fibres and blood belles that reside in german layer
Describe the process of photolithography
1) Silicon Wafer
2) Layer of oxide and nitrate
3) Layer of photo resist
4) UV shine
5) Photoresist developed to remove area exposed to UV
6) Reactive ion etching with KOH removes oxide and nitrate
Describe the process of sacrificial micromolding and selective electrodeposition
1) Fabrication of master structure with laser ablated cavity
2) Micromold created featuring protruding pillow that will become lumen exit hole
3) Creation of replica
4) Sputting a gold seed layer onto replica
5) Electrodeposition of metal everywhere except cavity - dissolving sacrificial base material to release metal hollow microneedle
Describe how solid micro needles work
Skin pretreatment
Insert and remove micro needles to form micro scale pores in surface
Drug formulation applied to skin for slow diffusion of drug through pores into body
Drug coated micro needles - expectations
Dipping or spray
Controlled wetting/spreading
Should be water soluble for coating and dissolution
Adhesion between dried drug coating and micro needle
Coating excipient and solvent safe and compatible
Explain and describe Drug Encapsulated microneedles
Rapid dissolving - water soluble sugars and polymers, photopolymerisable liquid monomers. - PLGA
Thermo -sensitive - moderate conditions
Speed of dissolution decides time of insertion
Hollow Microneedles
What are they
Advantages
Requirements
Infusion of liquid formulations or diffusion through needle
Great control over amount/timing
Separation of micro needles during manufacturing
Already existing drug liquid formulations
Requires drug reservoir, pump, microfluidic networks
A small molecule is how big
~1nm
Basic structure of insulin
Six insulin molecules assembled in a hexameter ~6kda
Size of trastuzumab
Herceptin (breast cancer) ~160kda with 10nm radius
Advantage and disadvantage of proteins
Highly specific and potent, low permeability across biological barriers so injection route
Structure of nucleic acids
Negatively charged due to phosphate group in backbone and hydrophilic due to sugar-phosphate backbone
Disadvantages of antibodies
Low cell uptake, short blood circulation time, rapid degradation and lack of cell specificity
What are the four viral vector types
1 - Adenovirus (non-enveloped, without outer layer)
2 - Adeno-associated virus
3 - Retrovirus
4 - Lentivirus
Advantages and disadvantages of viral vectors
Efficient cell uptake, endosomal escape
Immunogenicity, low cell specificity, limited packaging ability and difficult to produce
Advantages of non-viral vectors
Lower immunogenicity, no pre-existing immunity, larger pay load and easier to synthesise
Advantages of degradable (PGLA)
Long term delivery, can affect pharmacokinetics by enabling sustained release
Nanoparticles role in cancer
Usually larger than 10nm impedes diffusion through small vascular pores, leaky in tumours so up to 700nm can penetrate through endothelium
How can we increase serum 1/2 life
Fc fusion proteins fuse with drug.
DNA recombinant technologies can endow proteins with IG like property by utilising neonatal Fc receptor recycling pathway
Major Components of liposome
DOTMA
Phosphatidylcholine and phosphatidylserine
Ampiphillic molecule for making liposome
Define ampiphillic
Both hydrophilic and lipophilic
Hydrophobic tails face inwards away from aqueous solution while hydrophilic heads are in contact with solution
How do polymerosomes work
Polymeric versions of liposome (nitrogen = hydrophilic) self assemble into vesicle
How do cationic polymers work
PE1 (Polyethyenimine) for delivering nucleic acids, positively charged so can condense negatively charged nucleic acids to form polyplexes.
Also helps binding to negative cell membrane
Describe cell-penetrating peptides
Transactivator of transcription (TAT) protein from HIV virus could directly enter cells
Describe pegylation
1) Highly hydrated which increase hydrodynamic radius of conjugate, reduce renal filtration
2) Prevents uptake and clearance by mononuclear phagocyte system
3) Decreases formation of neutralising antibodies against a protein drug by masking antigenic sites
4) Protection from proteolytic enzymes and proteases
Three types of endocytosis
1) Phagocytosis
2) Pinocytosis
3) Receptor-mediated endocytosis
Drug loading efficiency =
Loading capacity =
DLE = (drug added-free)/drug added LC = (encapsulated drug/ nanoparticle mass) X 100
Principle of 3D printing
Complex structures difficult to make using subtractive, additive can make within limited timeframe
Problems with bioprinting
1) High temp - fuse deposition and selective laser sintering
2) Long UV exposure time - stereolithography
3) 3D printing - toxic binders
Describe process of selective laser sintering
1) Lay an even layer of powders using roller
2) Laser beam scanned at pre-decided positions to fuse/melt powders together
3) Stage lowered and second layer laid
METAL, POLYMER, CERAMIC
Describe process of 3D printing
1) Lay even layer of powder using roller
2) Binder jetted onto positions to fuse powders - adhesive
3) repeated then put in oven to make mechanically strong
METAL, POLYMER, CERAMIC
Describe Inkjet printing
1) Piezoelectric actuator generates picoliter drop
2) Drop ejects and reaches substrate
3) Solidification - UV
PHOTOPOLYMERISABLE MONOMERS or cell suspension
Describe the process of Stereolithography
1) UV laser scanned across layer of photopolymerisable monomers (reservoir of liquid monomers)
2) monomers polymerise and solidify
PHOTOPOLYMERISABLE MONOMERS
Describe process of Fused Deposition Modelling
1) feed polymer into heater
2) Melt polymer
3) Extrude polymer through nozzle whilst stage moved in x,y,z direction
4) Cools and solidified
THERMOPLASTIC MONOMERS - Polyetherether ketone
Describe Laser assisted printing
1) Laser beam shines upon energy absorbing layer
2) Shockwave generated resulting in ejection of drop which reaches substrate
3) Energy absorbing layer expands when UB light shone, expelling drop
Describe Microextrusion bioprinting
1) Hydrogel with suitable viscosity range loaded into cartridge
2) Material extruded through nozzle by pressure
3) Hydrogel strand forms 3D structure
What is a hydrogel
Non-fluidic colloidal network/polymer networks that ar physically or chemically cross-linked and contain a large amount of water. (shear thinning)
