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BIEN 210 > Quiz 2 > Flashcards

Quiz 2 Flashcards

1
Q

M(O)EMS

A

micro-(opto)-electromechanical systems in the size range between 1 micron and 1 millimeter

Manufactured mostly on semiconductor materials

Used to make sensors, actuators (E-> mech F), accelerometers (piezo -> elec), light manipulation

The MOEMS devices are used in all industries, as well as in biology and medicine

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2
Q

Pumps that can be used in moems

A

Electrophoresis : Particle induced to move in presence of elctric field relative to stationary or moving liquid

Streaming potential: Aqueous ion containing solution forced through a capillary/microchannel under applied hydrostatic pressure, creating a electroviscous effect

Dielectrophoresis: mvm dielectric particles in nonuniform el field

Electro-osmosis: fluid mvm relative to a stationary charged or conducting surface through application of an electric field

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3
Q

Types of optofluidics

A

Optofluidics combine microfluidics with optics
Dye laser, lens, modulator, sensor, water purification

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4
Q

What geometries are better for mixing

A

serpentine, faster when smaller device, uniform flow allows uniform mixing, smaller distance diffusion = better mixing

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5
Q

Passive vs active mixers

A

Passive mixers rely on diffusion and geometry of the device

Active mixers enhance mixing by increasing the interfacial areas between the fluids. It can be achieved by piezoelectric, ultrasonic, or other mechanisms

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6
Q

Biomimetic examples

A

Velcro, Displays and detectors (compound eye), gecko feet, optoelectric network, camo, antibac,

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7
Q

What are pathologists looking for to diagnose

A
  • Levels of disease biomarkers (cancer, neurodegeneration)
  • Presence of antibodies
  • Pathogens
  • Individual’s genes and chromosomes
  • Morphology of cells and organelles
    • Distribution of cells
    • Number of cells
    • Types of cells
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8
Q

Types of anatomical pathologies

A

Surgical pathology
Cytopathology
Molecular pathology
Forensics pathology
Gross examination
Histopathology
Immunohistochemistry
Electron Microscopy
Genomics
Proteomics

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9
Q

Types of diagnostic imaging techniques

A

Nuclear (PET)
X-rays (CT)
Acoustic (US, elastography) Optical (endoscopy, photography, DOS, in vivo optical imaging) Acousto-optical (PA) Electrical (ECG, EEG) Magnetic (MRI) Thermography Ophtalmology

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10
Q

Staining types

A

Eosin (cytoplasm)
Hematoxylin (nuclei)

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11
Q

Components of LFA

A
  1. Sample pad accepts the sample solution.
  2. Conjugate Pad contains antibodies for the analyte the test is looking to
    detect.
  3. Test line contains secondary antibodies that will bind only to a complex of the conjugate pad antibodies and the analyte.
  4. Control line contains antibodies that bind only to free conjugate pad antibodies. It acts as a way of ensuring the proper functioning of the
    test.
  5. Absorbent pad will absorb the fluid at the end of the device.
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12
Q

Transducers

A

converts stimulus to electrical signal (converts E)

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13
Q

Biosensors def

A

analytical devices that measure analytes of interest (atoms, molecules, particles, cells, etc.) via a biorecognition element (biological component such as antibody, enzyme, nucleic acid sequence, that binds specifically to the analyte)

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14
Q

Applications of biosensors

A

Medicine, biomedical research, drug discovery
plant pathogens
environment monitoring
security and defense
food quality and safety
process industries

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15
Q

Components of biosensors

A
  1. Bioreceptor (biorecognition element which is designed to specifically detect a stimulus) (Enzyme, cell, aptamer, DNA, nanoparticles)
  2. Transducer stimulus -> electrical signal (photodiode, Thermistor, pH electrode, Quartz electrode)
  3. Electronics (anolog to digital conversion, conditioning, amplifier)

(amplifier which boosts the voltage of the signal)
(signal converter which transforms the signal from analog to digital such that it can be processed by a computer)

  1. Display (light, number, signal, yes no)
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16
Q

Catalytic biosensors

A

Use enzymes as recognition element in biosensor

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17
Q

immunosensors

A

use antibodies as recognition element in biosensor

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18
Q

Genosensors

A

Use nucleic acids as recognition element in biosensor

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19
Q

Aptasensors

A

use aptamers (short nucleic acid sequences) as recognition element in biosensor

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20
Q

Specifications/qualities of biosensors

A

High specificity of detection (analyte binding)
High sensitivity of detection (how well small changes detected)
High linear range of detection
Multiplexing ability
Label-free
Easy to use
Portable
Inexpensive

21
Q

Classification of transducers based on physiochemical changes induced by binding events

A

Electric and magnetic (dielectric properties, permeability properties, voltage or current)

Electrochemical (potentiometric, amperometric)

Optical (reflection, absorption, fluorescence, scattering, interference)

Mechanical (mass-based, using cantilevers, piezoelectric effect, SAW)

Temperature

22
Q

Transducers electric methods

A

Conductiviity (Capture analyte and detect changes in electrical parameters (conductivity) of sample)

Capacitance (detect permeability diff bc binding on the plates)

23
Q

Nonlinear phenomena

A

wavelength of light emitted is significantly different from wavelength of excitation light (nonlinear wavelength mixing)

24
Q

Rayleigh resolution criteria for spatial resolution

A

Minimum of center of diffraction overlaps with the maximum of the next diffraction ring

25
Q

Advantages of two-photon excitation

A

Less phototoxicity
Improved spacial resolution
Larger depth (less mie scatter)

26
Q

Dielectric

A

material that can be polarized in an external electric field, but charges do not flow through it

27
Q

Resolution limit

A

is due to loss of high- frequency spatial information in optical microscopy resulting from the diffraction of light when it propagates through a distance larger then the wavelength of light (far field)

28
Q

Point spread function

A

3D distribution of the image of a point object

29
Q

Four types of interferometers

A

Michelson
Fabry-perot
Sagnac
Mach Zenhder

30
Q

Near field scanning optical microscopy

A

Traditional superresolution method
Distance between aperture and sample is smaller than wavelength of light

31
Q

Tip-enhanced microscopy

A

Cantilever is used on metal. beam which enhances sample signal

32
Q

How do thermal inkjet printers work

A

● In regular printers, droplets cannot be deposited in small amounts on paper
due to surface tension
● High-resolution printing can be achieved by packing the nozzles very densely
● Printing of organic materials, including DNA, is possible

33
Q

How does atomic force microscopy work

A

Cantilever tip is scanned over
sample surface
● Laser reflects off of the cantilever
tip; this allows for sub-nm resolution
to be achieved
● Provides information about local
stiffness and topography of a
sample

34
Q

Clinical pathology

A

the field that searches for certain markers within a biological medium.

35
Q

Diagnostic methods by target

A

Protein: ELISA, Gel electrophoresis, Microarray

Nucleic acids: PCR, gel electrophoresis, Microarrays, fish

Cell: microarrays, flow cytometry, microscopy

36
Q

Steps of sandwich ELISA

A
  1. The capture antibody is fixed to the wells of well plate
  2. The sample containing the antigen is placed in the well
  3. Primary antibodies are added to the wells, to form a complex with the target the antigen
  4. Secondary antibodies are labelled with enzyme; bind to the primary antibody
  5. A substrate is added to the well; this will react with the enzyme to produce a colour in the solution.
  6. The intensity of the colour measured in a well is then proportional to the amount of antigen present in that
    well.
37
Q

Direct vs indirect ELISA

A

Direct:
● The primary conjugate antibody is labelled with the enzyme, this
antibody binds to the fixed antigen, and reacts with the substrate
to produce colour

Indirect:
● A primary antibody binds to the antigen
● The secondary conjugate antibody is labelled with the enzyme
● Used to amplify the signal - the primary antibody has multiple
binding sites, for multiple labelled secondary antibodies to bind

38
Q

PCR

A

● Process that amplifies nucleic acid sequences through thermal cycling.
● It leads to the exponential growth of chains assuming a sufficient
number of polymerase enzymes.
● Variants of this technique exist such as qPCR (quantitative PCR),
isothermal qPCR, and rtPCR (reverse transcriptase PCR).

39
Q

Gel electrophoresis

A

Involves the separation of nucleic acid
fragments by molecular weight in a gel
by generating an electric field that acts
on the innate negative charge of
nucleic acids.
● Shorter molecules move faster and
migrate further through the pores of
the gel
● By staining the gel after the
experiment, bands allow for the
identification of the fragment sizes.
● This is particularly useful in forensic
analysis, as well as in sequencing.

40
Q

FISH

A

● FISH is a technique that allows for specific DNA sequences to be identified on particular chromosomes.
● This can be used to track a target DNA strand in space and time throughout an experiment, and to quantify specific gene expression.
● It can be particularly useful for identifying pathogenic DNA sequences within a sample

41
Q

How is cell staining done

A
  1. Permeabilization: cells are treated with a mild surfactant to dissolve the cell membrane. The dye molecules can therefore be introduced into the cell. Note that electroporation is a valid alternative to this step.
  2. Fixation: cell morphology is “frozen” in place. A chemical fixative is used to solidify bonds in proteins, increasing overall cell rigidity.
  3. Mounting: cells are placed on a microscope slide.
  4. Staining: cells are bathed in dyes and then rinsed. The cells can then be imaged under a microscope.
42
Q

SPR functioning

A

Light from the laser is reflected off the metallic plate and into a detector.
● At a certain angle (i.e., SPR angle), light is absorbed by the plate’s electrons, making them resonate. These electrons are called surface plasmons.
● Since a component of the light’s energy is absorbed by the electrons, the intensity drops, leading to a darker band on the detector.
● When a binding event occurs, the refractive index changes, and the dark band shifts
● This allows for the binding event to be identified. Analyte detection occurs due to this change in reflectivity.

43
Q

Biosensors characteristics

A

Linearity: the accuracy of measured responses fall on a straight line. For a high substrate concentration, linearity should be quite high.

Sensitivity: the minimum concentration of analyte that can be detected. The probability of a positive test result given that the condition is truly positive
(the true positive rate, or TPR). It measures how a signal changes in response to a varying analyte concentration.

Specificity: ability to distinguish the analyte from other components in the sample. The probability of a negative test result given that the condition is
truly negative (the true negative rate, or TNR).

Response time: the time necessary for the biosensor to achieve 95% of the total response.

44
Q

Photodiode

A

Converts light to electrical signal (transducer)
Reverse current in photodiode when light passes, proportional to incident light, sensitivity prop to the wavelength

45
Q

Types of moems transducers

A

Electrical (dielectric voltage or current), mech (cantilevers, mass, piezo), temp, electrochem (potential/current), optical (reflection, absorption, scattering, interference)

46
Q

Enzyme-linked assay

A

detects the presence of a ligand protein in a liquid sample using an antibody directed against the target protein

47
Q

Biosensor

A

Analytic device that analyses an analyte using a biorecognition element.

48
Q

Applications of biosensors

A

medicine, research, plant pathogens, environmental monitoring, security, food safety, process industries

BIEN 210 (2 decks)

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