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Biotechnology > Biosensors > Flashcards

Biosensors Flashcards

1
Q

Bio sensor Definition

A

Chemical signalling device in which a biologically derived recognition entity is coupled to a transducer, allowing quantitative or qualitative analysis in complex biochemical matrix

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2
Q

Couple biorecognition element to transducer (4)

A

Membrane entrapment
Physial Adsorption
Porous entrapment
Covalent Bonding

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3
Q

Membrane Entrapment

A

semi-permeable membrane separates analyte and bioelement

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4
Q

Physical Adsorption

A

Dependent on combination of van der Waals forces, hydrophobic, hydrogen and ionic forces to attach biomaterial/analyte to the surface of the sensor

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5
Q

Porous Entrapment

A

Form porous encapsulation matrix around biological material - helping it bind to sensor, e.g. carbon paste

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6
Q

Covalent Binding (most common)

A

sensor surface treated as reactive group to which biological material binds

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7
Q

Biosensors must exhibit

A

repeatability - intra-assay
reproducibility - inter-assay
specificity/selectivity
sensitivity - linear range, detection limit, response time

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8
Q

Resonance Biosensors 2 steps included

A

light-wave transducer coupled with antibody/bioelement

  • analyte binds - increases mass membrane - distort sensor
  • changes resonant frequency and angle of deflection
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9
Q

Thermal Detection Biosensor 3 steps and example

A
  • analyte comes into contact with enzyme
  • energy change measured and calibrated against conc
  • total heat produced or absorbed proportional no. molecules
    detection pesticides/pathogenic bacteria
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10
Q

Ion-selective field effect transistor

A

semi-conductive FET
ion selective surface - gate between source (+ve) + drain (-ve)
- surface electrical potential changes when ions and semi-conductor interact
- measure change in potential
e.g. pH measurement

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11
Q

Conductometric/Chemisresistor definition

A 
measure conductance (opposite resistance)
how easy electrons flow
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12
Q

Potentiometric definition

A

measure change in potential difference (voltage)

charge +ve - hydrogen production

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13
Q

Amperometric definition

A

measure change in current

flow of electrons

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14
Q

Ohms Law

A

V=IR

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15
Q

Conductometric types (2)

A
  • material clamped between 2 contact electrodes (gas sensing CO)
  • active layer immersed in electrolyte solution
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16
Q

Potentiometric

A

ion-selective electrodes
immobilised enzyme membrane surrounding pH meter
difference in pH between two areas

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17
Q

Amperometric

A

high sensitivity and selective
detect electroactive species
may require redox enzymes to produce electroactive species - oxidative = active
electrode reduced rate proportional to concentration

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18
Q

Commercial (2)

A

Blood glucose - diabetes

Pregnancy test - clear blue

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19
Q

Technical Issues (3)

A

Fragile
many different materials needed
issues - bonding, connection, reading

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20
Q

Blood Glucose biosensor required

A 
diabetes -->
increased heart disease 2-4x
lead to blindness
40% increase serious kidney
60% increase ampuations
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21
Q

Blood glucose chemistry

A

redox enzymes
glucose oxidase - oxidise substrate and become reduced
transfer electron to oxygen –> hydrogen peroxide
glucose dehydrogenase - “
reduces NAD+ to NADH in order to regen

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22
Q

Glucose Oxidase pros and cons

A

+ cheap

-require oxygen and performance reduces throughout

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23
Q

Glucose Hydrogenase

A

+ independent of oxygen

-NAD+ expensive and unstable

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24
Q

Redox mediators (electron shuttles)

A

independent of local oxygen conc
allowing operation at lower potentials
–> minimise detection inteferents

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25
Q

Ferrocene states and features (2) -

A

oxidated - ferricyanide
reduced - ferrocyanide
range of redox potentials - independent of pH
easy manufacture

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26
Q

Clear Blue Pregnancy Test

A

Antibody plotted on nitrocellulase (result strip)

Antibody adsorbed latex sprayed onto wick material (reservoir/test strip)

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27
Q

Pregnancy test substrate/hormone and mechansim

A

human chorionic gonadotrophin (hcG)
both antibodies complimentary to hcG
urine resuspends latex and carried through nitrocellulase
hormone bound by capture and form blue latex line

28
Q

Redox enzyme - intrinsic example and description

A

e.g. cytochrome c oxidase
electron-transfer outside confines of enzyme
electron-transfer between prosthetic group and substrate in vicinity of active site
not require ET path from active site to protein (directly)

29
Q

Extrinsic enzyme - most biosensors

A

glucose oxidase
ET within confines of enzyme
difficult to achieve ET between active site and electrode
electron donating/receiving species required - bind at separate site
ET pathway with co-substrate, bind site and active centre
expensive

30
Q

Difficult to make direct communication between extrinsic and electrode

A

deeply buried active centre
ET rates low due to distance
denaturation at electrode (Hg electrode)

31
Q

Extrinsic solution

A

electrode mimic intermolecular recognition

32
Q

cytochrome c peroxidase

A

water soluble, haeme-containing
reduced by cytochrome c
reduces water to Hydrogen peroxide

33
Q

Bind cytochrome c to electrode to

A

achieve direct interaction with electrode

using DTSSP - dimer - binds 2 cytochrome c

34
Q

Inappropriate production of radicals creates (4)

A

cardiovascular dysfunction
arteriosclerosis
ischameia
neurodegenerative diseases

35
Q

Free radicals features (2)

A

hard to detect as unstable and high interactivity
try to detect end point/products
mopped up by antioxidants

36
Q

Possible detect radicals details (3)

A

by cytochrome c on electrode
using xanthine oxidase or cells
superoxide reduces cytochrome c

37
Q

Human glioblastoma cells (3)

A

destroy pathogen with O2- by NAPDH oxidase
leak some - collateral damage
first produce NO. then O2-, NO. react with O2-

38
Q

Third gen glucose sensor

A

direct electronn transport between enzyme active site and electrode surface

39
Q

Glucose Oxidase structure

A

dimer - active site buried
co-factor FAD/FADH2 1 (per subunit)
electrostatic site at entrance active site -> +ve

40
Q

Lysine residues in Glucose oxidase react

A

with DTSSP

so bind active site of GoX to electrode surface

41
Q

Horse radish peroxide use with electrode (3)

A

re-reduced by carbon electrodes
electrodes fabricated using screen printing tech
HRP mixed into carbon ink - printed directly on electrode

42
Q

HRP reduced by

A

by electrode
oxidised by hydrogen peroxide
immunosensor using antigen bound to GOD

43
Q

PEBBLE sensors meaning and definiton (4)

A

Probes encapsulated by Biologically Localised Embedding
(polyacrylamide porous shell with fluorophore inside)
nano-scale spherical devices with sensor molecules in chemically inert matrix

44
Q

PEBBLE structure (2)

A

protective coating eliminates interferences - protein binding/membrane or organelle sequestration
–> which alter dye response
matrix protects cell contents - dye would be toxic otherwise

45
Q

PEBBLEs able to measure

A

calcium, potassium, nitric oxide, oxygen, chloride, sodium and glucose

46
Q

Fibre-optic probe

A

fluorophore on the tip - measure pH, glucose, oxygen

47
Q

Fibre-optic negatives

A

punch hole in cell

measure very small area

48
Q

PEBBLE extras

A

reference dye

enzyme create product that reacts with dye

49
Q

Characterisitics of PEBBLE (3)

A

non-invasive in cell - not seen as threat
cell viability 97%
Response time <1ms

50
Q

Sol-gel also used as matrix

A

not as rigid

not change shape of enzymes within

51
Q

Ratiometric Device

A

e.g. oxygen sensor
silica glass
ruthenium dye - orange, decreases with higher oxygen
oregon dye - green, not sensitive to oxygen

52
Q

Free dye problem

A

Bind other proteins such as Bovine Serum Albumin

53
Q

Nanosensor not able to enter

A

Nuclear membrane - very selective

54
Q

Gene Gun

A

deliver DNA and PEBBLEs
helium shoots dried PEBBLEs off a disk
embed in cells
able to penetrate nuclear membrane

55
Q

Gene Gun -ve

A

shoot right through cell

multiple ruptures

56
Q

Phagocytic Nanosensor Internalisation

A

Sensors ingested
remain encapsulated
However not free in membrane

57
Q

Lipid Transfection

A

Nanosensors internalised into liposome

free in cytoplasm

58
Q

PEBBLEs +ve

and synthesis

A

cheap,easy, fast

water in oil microemulsions - then concentratedm washed nad vacuum filtered

59
Q

PEBBLE modification

A

attach molecules to outside of matrix - specific attachment to specific cellular membrane

60
Q

Amine groups on surface of nanosensor

A

bind ester groups on biotin
then bind avidin and biotin
then bind antibody

61
Q

SeLCA (future)

A

Sensing living cell arrays
combine optical nanoprobes delivered to cell interior
and electrochem sensing arrays to measure extracell

62
Q

Microtitre-plate cell retainers

A

Insert Micro-ring electrodes of gold and platinum into wells (electrodes)
monitor different analytes
sharp borders stop cells sticking together

63
Q

Myalgic Encephalomyelitis/Chronic Fatigue

A

Decreased function of pyruvatedehydrogenase complex

  • -> increased conversion pyruvate to lactate via lactate dehydrogenase pathway
  • -> intracellular acidosis
64
Q

ME sensors

A

pH nanosensors

65
Q

Dichloroacetate

A

up-regulates function of pyruvate dehyrdogenase
–> inhibition of inhibitory kinase
neurological SE

Biotechnology (7 decks)

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