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Advances in Medicine > Magnetic Nanoparticles > Flashcards

Magnetic Nanoparticles Flashcards

1
Q

What techniques are used to make NP’s?

A

Chemical based techniques (synthesis in solutions)
Physical vapour approach (atom by atom)
Electron Beam Lithography (electron carving)
Exploiting nature (bacteria)

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2
Q

Outline the life cycle of a magnetic nanoparticle

A
  1. Synthesis of particle and characterisation
  2. Surface modification
  3. Magnetic guiding to the target
  4. Binding at target location
  5. Apply alternating magnetic field (therapeutics)
  6. Delivery of drug/gene
  7. Phagocytosis
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3
Q

What is the formulae for magnetic susceptibility?

A 
x= M/H
M= magnetisation
H= an applied magnetic field
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4
Q

Explain paramagnetism in terms of spin moments

A

No magnetic field- spin moments are randomised
Magnetic field- small net magnetism develops through aligning of spin moments resulting in positive magnetic susceptibility

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5
Q

Explain ferromagnetism in terms of spin moments

A

Spin moments coupled together and act over large distance. Retain permanent magnetisation and have large positive magnetic susceptibility.

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6
Q

Explain diamagnetisation in terms of spin moments

A

Magnetic field- small opposing magnetisation in the material (repelled). Small negative magnetic susceptibility

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7
Q

Explain magnetic domains

A

Separated areas of parallel magnetic skin moments.

If particles smaller than a critical diameter, Dc, only a single domain can form. Dc is material dependent.

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8
Q

Define remnance

A

Residual magnetisation

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9
Q

What terms is relaxation time given in?

A

Material constant (the anisotropy constant) K, the particle volume, v, and the temperature, T.

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10
Q

Explain the blocked magnetic state

A

The relaxation time for a given particle is much longer than our measurement time

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11
Q

Explain the superparamagnetic state

A

The relaxation time for a given particle is much shorter than our measurement time

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12
Q

Why do superparamagnets have a higher magnetic susceptibility than paramagnets?

A

The magnetic field aligns whole particle moments

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13
Q

What are the properties of a useful magnet?

A

Strong magnetic susceptibility
Zero remanence
Well matched relaxation times

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14
Q

What are the functions of thermotherapy?

A

Raise local temperature in tumours
Deactivation of normal cellular processes
Increase therapeutic effect of other treatment
Can be modified to target a specific tissue

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15
Q

Properties of nanoscale superpara particles

A

Small enough for admin
Must reside in vivo long enough to reach target
Avoid immunological reactions
Longer plasma half life
No residual magnetism when magnet removed
Do not agglomerate

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16
Q

Name some polymers that modify the surface of nanoparticles

A 
Polyethyleneglycol
Dextran, PVP
Polypeptides
Chitosan
Gelatin
17
Q

Name some targeting ligands used for functionalising nanoparticles

A

Transferrin
Insulin
Elastin
Tat-peptide

18
Q

How does MRI enable measurements of signal variation?

A

The receiver coil measures transverse magnetisation but is not stable
Longitudinal relaxation and transverse relaxation
Altering time at which signal is measured by utilizing variations in relaxation processes

19
Q

How do ferromagnet contrast agents work?

A

They change the contrast by distorting the magnetic field around ferromagnetic material in the contrast agent. Typically FeO NP’s attached to organic substrate

20
Q

How do paramagnetic contrast agents work?

A

Create time varying magnetic fields which promote spin-lattice and spin-spin relaxation of water molecules

21
Q

What are the difficulties with mechanical conditioning in bioreactors?

A

Interruption of nutrient flow to apply force
Invasive processes can comprise sterility
Scaffolds must be strong
Forces must be transmitted to cells rather than applied directly
Limitations on size of constructs

22
Q

What are the advantages of the MICA system?

A

Application of mechanical stress
Removes requirement for fixed dimension
Allows the use of mechanically weak scaffold materials
Reduced infection potential
Control of physical stress parameters
Allows for multiple load profile to be assigned across complex tissue

23
Q

What are the stages if ex vivo transgene delivery?

A
  1. target cells removed form patient
  2. cells grown in culture
  3. cultured cells are transfected
  4. cells reintroduced into the body
  5. Inside the body, the cells produce the desired proteins
24
Q

What are the stages if in vivo transgene delivery?

A
  1. copies of therapeutic gene are insrted into viral DNA, liopsome or in form of plasmid DNA
  2. genetically-altered DNA is inserted into patient body by cell-specific direct tissue injection
  3. DNA incorporated into cells of specific tissue it was injected into.
25
Q

What are the goals for delivering material into cells?

A

Don’t kill the cell outright
Don’t damage the cell so that it can’t recover
Don’t adversely change the cell
Controllably deliver the material to the cell
Delivery vector can’t be toxic
Safe and efficient

26
Q

What are the advantages and disadvantages of non-viral transfection?

A

Advantages:
Eliminates safety concerns
Variety of techniques to choose from
Can be used for large groups of cells or individual cells

Disadvantages:
Less efficient than viral transfection
Technically demanding
No best method for all applications

27
Q

Explain the Luciferase assay

A
  1. Luciferase first extracted from transfected cells via cell lysis
  2. Buffer and additional components added to lysate to increase sensitivity and maintain pH
  3. The luminescent reaction is then triggered by an injection of luciferin
  4. Emitted light is recorded
28
Q

What does magnetofection rely on?

A

Selection of appropriate type, size and surface coating of the magnetic nanoparticles for binding with genetic materials. Attach to surface by cleavable linkers and utilising electrostatic interactions.

29
Q

How do magnetic materials generate heat inside the body?

A

Alternating magnetic field
Movement of magnetic domain walls
Phase lag between the magnetisation vector and field
Eddy currents: negligible effect at frequencies of interest

30
Q

How is heat generated in larger particles?

A

Due to losses in magnetic energy during hysteresis cycling

31
Q

How is heat generated in smaller particles?

A

Due to a phase lag between the applied frequency and the particle magnetization vector

32
Q

What are the two types of relaxation that produce heat?

A 
Brownian relaxation (rotation of particles) which is dependent on particle size 
Neel relaxation (internal fluctuations) which is dependent on particle size and magnetic material properties
33
Q

What is dynamic light scattering (DLS) used for?

A

Measuring particle sizes and their distributions in solution based on the fact that smaller particles will diffuse faster than larger particles

34
Q

Why is hyperthermia effective?

A

It is possible to kills cells at temps between 39-42
Tumour tissue more thermally sensitive than normal tissue due to its vasculature
Can reverse chemosresistance
increases tumour oxygenation

35
Q

What are the basic principles of MRI?

A
  1. A strong magnetic field is used to align proton spins
  2. A radio frequency pulse briefly rotates the alignment by 90 degrees into the xy plane
  3. The magnetisation in this plane is detected as a signal in receiving coils
36
Q

What is T1 and T2?

A 
T1= Longitudinal Relaxation
T2= Transverse relaxation

Advances in Medicine (7 decks)

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