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Biotechnology > Biosensors > Flashcards

Biosensors Flashcards

(65 cards)

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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
Ferrocene states and features (2) -
oxidated - ferricyanide reduced - ferrocyanide range of redox potentials - independent of pH easy manufacture
26
Clear Blue Pregnancy Test
Antibody plotted on nitrocellulase (result strip) | Antibody adsorbed latex sprayed onto wick material (reservoir/test strip)
27
Pregnancy test substrate/hormone and mechansim
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
Redox enzyme - intrinsic example and description
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
Extrinsic enzyme - most biosensors
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
Difficult to make direct communication between extrinsic and electrode
deeply buried active centre ET rates low due to distance denaturation at electrode (Hg electrode)
31
Extrinsic solution
electrode mimic intermolecular recognition
32
cytochrome c peroxidase
water soluble, haeme-containing reduced by cytochrome c reduces water to Hydrogen peroxide
33
Bind cytochrome c to electrode to
achieve direct interaction with electrode | using DTSSP - dimer - binds 2 cytochrome c
34
Inappropriate production of radicals creates (4)
cardiovascular dysfunction arteriosclerosis ischameia neurodegenerative diseases
35
Free radicals features (2)
hard to detect as unstable and high interactivity try to detect end point/products mopped up by antioxidants
36
Possible detect radicals details (3)
by cytochrome c on electrode using xanthine oxidase or cells superoxide reduces cytochrome c
37
Human glioblastoma cells (3)
destroy pathogen with O2- by NAPDH oxidase leak some - collateral damage first produce NO. then O2-, NO. react with O2-
38
Third gen glucose sensor
direct electronn transport between enzyme active site and electrode surface
39
Glucose Oxidase structure
dimer - active site buried co-factor FAD/FADH2 1 (per subunit) electrostatic site at entrance active site -> +ve
40
Lysine residues in Glucose oxidase react
with DTSSP | so bind active site of GoX to electrode surface
41
Horse radish peroxide use with electrode (3)
re-reduced by carbon electrodes electrodes fabricated using screen printing tech HRP mixed into carbon ink - printed directly on electrode
42
HRP reduced by
by electrode oxidised by hydrogen peroxide immunosensor using antigen bound to GOD
43
PEBBLE sensors meaning and definiton (4)
Probes encapsulated by Biologically Localised Embedding (polyacrylamide porous shell with fluorophore inside) nano-scale spherical devices with sensor molecules in chemically inert matrix
44
PEBBLE structure (2)
protective coating eliminates interferences - protein binding/membrane or organelle sequestration --> which alter dye response matrix protects cell contents - dye would be toxic otherwise
45
PEBBLEs able to measure
calcium, potassium, nitric oxide, oxygen, chloride, sodium and glucose
46
Fibre-optic probe
fluorophore on the tip - measure pH, glucose, oxygen
47
Fibre-optic negatives
punch hole in cell | measure very small area
48
PEBBLE extras
reference dye | enzyme create product that reacts with dye
49
Characterisitics of PEBBLE (3)
non-invasive in cell - not seen as threat cell viability 97% Response time <1ms
50
Sol-gel also used as matrix
not as rigid | not change shape of enzymes within
51
Ratiometric Device
e.g. oxygen sensor silica glass ruthenium dye - orange, decreases with higher oxygen oregon dye - green, not sensitive to oxygen
52
Free dye problem
Bind other proteins such as Bovine Serum Albumin
53
Nanosensor not able to enter
Nuclear membrane - very selective
54
Gene Gun
deliver DNA and PEBBLEs helium shoots dried PEBBLEs off a disk embed in cells able to penetrate nuclear membrane
55
Gene Gun -ve
shoot right through cell | multiple ruptures
56
Phagocytic Nanosensor Internalisation
Sensors ingested remain encapsulated However not free in membrane
57
Lipid Transfection
Nanosensors internalised into liposome | free in cytoplasm
58
PEBBLEs +ve | and synthesis
cheap,easy, fast | water in oil microemulsions - then concentratedm washed nad vacuum filtered
59
PEBBLE modification
attach molecules to outside of matrix - specific attachment to specific cellular membrane
60
Amine groups on surface of nanosensor
bind ester groups on biotin then bind avidin and biotin then bind antibody
61
SeLCA (future)
Sensing living cell arrays combine optical nanoprobes delivered to cell interior and electrochem sensing arrays to measure extracell
62
Microtitre-plate cell retainers
Insert Micro-ring electrodes of gold and platinum into wells (electrodes) monitor different analytes sharp borders stop cells sticking together
63
Myalgic Encephalomyelitis/Chronic Fatigue
Decreased function of pyruvatedehydrogenase complex - -> increased conversion pyruvate to lactate via lactate dehydrogenase pathway - -> intracellular acidosis
64
ME sensors
pH nanosensors
65
Dichloroacetate
up-regulates function of pyruvate dehyrdogenase --> inhibition of inhibitory kinase neurological SE

Biotechnology (7 decks)

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