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Flashcards in L7-9 Deck (25):
1

How does a biosensor(generic) work?

Biomolecule mediates interaction with surface

Measures chemical entity
Generates signal

2

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

3

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

4

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

5

How can we use nano cantilevers clinically?

Detecting antibodies

6

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

FAST detection

7

In nanopore sequencing, membrane with the nanopore has current flowing. Which ion causes this current?

Cl-

8

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

INDIRECT MEASURING

9

Why is nanomaterials for biosensing fantastic?

Increase sensitivity
Immobilization of bioreceptor units

High specific surface

10

Thick polymer would be degraded faster or thin polymer? Why?

Thick polymer degrades faster.

As a product of polymer hydrolysis acid is made

Ph decreases
Accelerates degradation rapidly

11

How can you make polylactides more amorphous?

Use a mix of its isoforms

Cannot form crystalline structure
More amorphpus

12

What is Tg?

Below Tg polymer becomes tighter or looser?

Glass temperature

Temp below Tg will pack chains tighter

13

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
COOH made
PH decrease and when critical Mw reached,
Oligomers leave the structure

Space made
More water can diffuse etc etc

14

What does rate of hydrolysis depend on?

Water absorption which depends on

Tg

Mw

Hydrophilicity

Degree of crystallisation

15

Compare PolyGlycolides (PGA) and Polylactides (PLLA).

PGA
High Mw, hard and crystalline. Tg 37degree so we can use it in our body because it can be degraded.

PLLA
more hydrophobic
Low water uptake
Slower hydrolysis
Tg 60degree

Takes way longer in PLLA to degrade

16

What is WHOOSH effect?

Hydrolysis is accelerated under acidic conditions

17

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

Tg-55
Low tensile strength
High strain
Rapid degradation than PLLA

FAB FOR DRUG DELIVERY

18

MIX the PGA AND PLLA?

PGA-PLLA copolymer!!!!!

More than 50% PLLA will slow down degradation

High PGA WILL Give AMORPHOUS PROPERTY

19

What is monocryl made of?

75% glycolide
25% e-caprolactone

20

What external factors affect rate of degradation of polymers?

pH
Temperature
Enzyme
Sterilisation technique
External stress
Shape

21

Why is it difficult to use dry heat sterilization on biodegradable polymers?

Temperature must be below Tg.

22

How would you sterilize polymers?

Electron beam radiation
Y-radiation
Ethylene oxide

23

What requirements are there for bone graft replacements?

Biocompatible
Easy and cheaply reproducible
Mechanically appropriate

24

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

25

What is Osteoconductivity and what is Osteoinducibility!

Osteoconductivity: after the implant the bone grows along the interface of surface of material

Osteoinducibility: as well as osteoconduction, new bone grows on implant away from bone/material interface