Flashcards in L7-9 Deck (25):
How does a biosensor(generic) work?
Biomolecule mediates interaction with surface
Measures chemical entity
List four ways of signal generation and transduction in biosensors.
Electron- redox- current
Ion- conduct- potential measures
Photon- fluorescence, scattering- optical
Mass change- mechanical measure of electrical change
Give an example of using electron signal generation in biosensors.
BLOOD GLUCOSE SENSOR FOR DIABETICS
glucose oxidase needed for glucose oxidation
Current made when a pair of e- pulled from reduced H2O2
Blood glucose changes: flow of O2 changes- current change
How does nano-cantilevers work?
Cantilevers are thin silicone sheets
We have receptors on them
Ligand binds to cause stress in lever causing it to deflect
How can we use nano cantilevers clinically?
How does nanowire work? What is an advantage of using nanowire?
Nanowire has current flowing through. It is sensitive to molecular presence on its surface.
Place receptor that can bind to thrombin;
- no thrombin: current flowing
-yes thrombin: current drops or changes
In nanopore sequencing, membrane with the nanopore has current flowing. Which ion causes this current?
PEBBLES are optical biosensors that can interact with intracellular environment. How can we use this to measure glucose conc?
Fluorescent if glucose present because
Enzyme attached to PEBBLES lead to oxidation of glucose because conc of O2 drops (used)
This leads to fluorescence
Why is nanomaterials for biosensing fantastic?
Immobilization of bioreceptor units
High specific surface
Thick polymer would be degraded faster or thin polymer? Why?
Thick polymer degrades faster.
As a product of polymer hydrolysis acid is made
Accelerates degradation rapidly
How can you make polylactides more amorphous?
Use a mix of its isoforms
Cannot form crystalline structure
What is Tg?
Below Tg polymer becomes tighter or looser?
Temp below Tg will pack chains tighter
Outline the degradation of polymers
Water diffusion into polymer
Attack amorphous areas
Units fall off but no mechanical property changes
At some point chains fall apart
Oligomers (shorter) formed
PH decrease and when critical Mw reached,
Oligomers leave the structure
More water can diffuse etc etc
What does rate of hydrolysis depend on?
Water absorption which depends on
Degree of crystallisation
Compare PolyGlycolides (PGA) and Polylactides (PLLA).
High Mw, hard and crystalline. Tg 37degree so we can use it in our body because it can be degraded.
Low water uptake
Takes way longer in PLLA to degrade
What is WHOOSH effect?
Hydrolysis is accelerated under acidic conditions
What is PDLLA and how does it differ from PLLA?
Its an enantiomer of PLLA
Amorphous polymer with random mix of both lactic acid isoforms
So no crystalline structure
Low tensile strength
Rapid degradation than PLLA
FAB FOR DRUG DELIVERY
MIX the PGA AND PLLA?
More than 50% PLLA will slow down degradation
High PGA WILL Give AMORPHOUS PROPERTY
What is monocryl made of?
What external factors affect rate of degradation of polymers?
Why is it difficult to use dry heat sterilization on biodegradable polymers?
Temperature must be below Tg.
How would you sterilize polymers?
Electron beam radiation
What requirements are there for bone graft replacements?
Easy and cheaply reproducible
What are the requirements for regenerative grafts?
Should be a good 3D tissue growth template ( interconnected macroporous network allowing vascularisation and tissue growth)
Mechanically similar to host