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Stability Testing > Stability of Nanoformulations > Flashcards

Stability of Nanoformulations Flashcards

1
Q

Why are nanoparticles thermodynamically instable?

A

Due to their large surface area, without a stabilization ist will leads to formation of agglomearates.lossing the advantges of the larger surface area

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2
Q

what are the two ways to stabilizier nanoparticles?

A

steric and electrostatic stabilization

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3
Q

Which polymer are used for steric and electrostatic stabilization

A

non-ionic surfactants, pr unchardged water soluble polymers for steric and ionic surfactants for electrostatic stabilization

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4
Q

Production of Nanoparticles

A

Top down and Bottow up processes

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5
Q

What kind of particle size do used in both porcessess

A

TDP: API microparticles
BUP: API molecules

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6
Q

what do you have to create in the TDP:

A

one has to creat a microsuspension, using high pressure homogenisation to prodcued the nanoparticles

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7
Q

Process in the BUP

A
  1. the API solvent mixed with an anisolvent (low solubility of the API). this will lead to precipitation–>nucleation–>growth.
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8
Q

What happend to the crystals in the BUP if there are not stabilisied

A

it will leads to aggregation

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9
Q

Which guidelines targted the nano-medicine

A 
ICH guideline Q5C for cancer targeting
Nontargeted Q1A(R2) and Q1C
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10
Q

Where are the general storage conditions mentioned

A

ICH Q1A(R2)

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11
Q

What are some application for nanoformulation

A

oral and perenteral administrations

emerging application: ocular drug delivery

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12
Q

What other instabilities exist during storage or Nanosuspensions

A

Ostwald ripening

sedimentation/creaming and cakeing

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13
Q

What is ostwald ripening?

A

It is define as the growth of larger particle at the loss of samll partciles, due to diffusion of the API molecules from the small particles (higherconcentrated areas) to surfacelayer of the big particles (lower concentrated areas)

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14
Q

Was is the results of ostwald ripening?

A

Precipitation of the API in low concentrated areas

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15
Q

How can ostwald ripening be avoid or slowdown?

A

having a narrow particle size distribution
low storage temperatures
solidification of suspensions

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16
Q

Why can ostwald ripening be avioded with NPSD?

A

Small devaition between PSD of particles in system cause low concentration gradients and therefore lower flux

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17
Q

what’s the aim of the top/down bottom-up process?

A

Lower polydispersity index (PDI) or PSD

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18
Q

What does PDI 1 or 0 means?

A

PDI 1 means more polydisperse is the sample and 0 menas that just one particle size is present

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19
Q

Effect of the low storage temperatures?

A

Due to the fact that diffusion is temperature dependent, the low temperatures, the diffusion process is low down and therefore ostwald ripening

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20
Q

Process of solidification of suspensions

A

Spray drying and Freeze drying

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21
Q

what are reversible agglomeration?

A

rapid sedimentation/creaming

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22
Q

What’s the consequence of agglomeration?

A

inconsistent dosing, prevention is very important

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23
Q

How does the electrostatic stabilization works

A

Around the particle there is a electric doble layer, which is the surface potential of the particles.

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24
Q

Stern layer?

A

the particles in the stern layer abdsorbed strongly ounter ions, leading to
linear decrease of the potential

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25
Q

Diffuse layer?

A

wakly bound ions on the particles, leading to an expoentail decrease of the potential

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26
Q

When can the potential of shear plan be measured?

A

during the particle movement, thus causeing the shearing off of the diffuse layer

27
Q

What is the name of the measured potential?

A

Zeta-potential

28
Q

On what does the diffusion layer depends on?

A

it depends on the ionic strength, higher ionic strength results to no diffsuion layer

29
Q

Why is the DLVO-theory relevant?

A

For eletrostatic stabilization

30
Q

What the born repulsion?

A

Occur due to small distance between the partciles(higher movemnt of the particles going above the energy barrier). it results to formation of aggregates

31
Q

On what does the shape of curve depends on?

A

Depends stronly on the ionic strength

32
Q

what happen at high ionic strength to the electrical double layer around the particles?

A

it causes compression of electrical double layer

33
Q

What’s the advantage of the small particle size of Nanoparticles

A

Particles smove according to Brownian motion there negligible affected by gravity

34
Q

What’s Cakeing?

A

no redisoersible of the sedimented particles–> inconsistent dosing

35
Q

How can caking be prevented?

A

High viscosity of suspension, reasonable selection of stabilizer or solidification of suspension

36
Q

When can the stok’es law be applied?

A

Just for laminar flow in cases of sedimentation

37
Q

Light scattering methods for Nanoparticles?

A

the fraunhofer is not used, because the refractive and absorption index is needed. better Mie-theory

38
Q

Dynamic light scattering measuremnet for the movement of the nanoparticles

A

speed of the brownian molecular movement dpending on size and vicosity

39
Q

What is the attenautor?

A

it’s regulates the particles, more light into the curvet, less particles into the sytstem

40
Q

What does high attenuator means?

A

higher attenuator means, less particles, desidmentation of the particle

41
Q

How does the structure of a crystalline and amorphous looks like in a XRPD

A

crystalline shape peaks

amorphous hallo structur

42
Q

How should be stability testing be perfomered?

A

Under trasportation and storage conditions

43
Q

storage conditions

A

Long term, intermediate and accelerated studies

44
Q

Why it is important to stabilizier nanosuspensions

A

because the formation of agglomeration especially for parenteral application could cuase vessel bockage and therefore embolia

45
Q

What are the four scattering phenoema in light interactions with matters?

A

Fefraction, Reflection, Diffraction and Adsorption

46
Q

which phenomenon happend with larger particles

A

Diffraction

47
Q

Describe the diffraction phenomenon

A

Scattering pattern occur which is correlated with particle size

48
Q

What is the angle of bigger and small particle

A

the smaller the particles the bigger the scattering angle

49
Q

What is important if one has small particles ?

A

refraction and absorption become more dominating

50
Q

What is then necessary using small particles

A

Refractive index and absorption

51
Q

When can Fraunhofer theory be used

A

larger particles, correlation between scattering angle and particle size

52
Q

Which method can be used for smaller particles

A

Mie-theory is used

53
Q

What is Mie-theory

A

Modelling of scattering which results of diffraction, refraction, absorption and reflection

54
Q

Which particle size can be used in laser diffraction

A

limited to ~ 70 nm

55
Q

what can be used instead of laser diffraction

A

Dynamic light scattering

56
Q

Dynamic light scattering

particle size

A

particle size measuremnets of < 1µm

57
Q

XRPD

A

Sample is exposed to x-rays,

detector detects diffracted x-rays

58
Q

Crystalline state in XRPD

A

Angle dependent high X-ray intensities (Bragg peaks)

59
Q

Amorphous state in XRPD

A

No Bragg peaks detected

60
Q

What is the procedure of the Dynamic light scattering

A

Measurement of the time-dependent fluctuations of the scattered light intensity and determine of the difusion coefficient

61
Q

XRPD for which state of the molecule

A

Solid state

62
Q

What is a power compensating DSC

A

Differential power signal is recorded as function of actual sample temperature

63
Q

Which stability study have to be carried out for nanosupsension

A 
Long term stability and accelarted stability 
Thermal stability (storage at high temperatures)

Stability Testing (5 decks)

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