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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
Diffuse layer?
wakly bound ions on the particles, leading to an expoentail decrease of the potential
26
When can the potential of shear plan be measured?
during the particle movement, thus causeing the shearing off of the diffuse layer
27
What is the name of the measured potential?
Zeta-potential
28
On what does the diffusion layer depends on?
it depends on the ionic strength, higher ionic strength results to no diffsuion layer
29
Why is the DLVO-theory relevant?
For eletrostatic stabilization
30
What the born repulsion?
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
On what does the shape of curve depends on?
Depends stronly on the ionic strength
32
what happen at high ionic strength to the electrical double layer around the particles?
it causes compression of electrical double layer
33
What's the advantage of the small particle size of Nanoparticles
Particles smove according to Brownian motion there negligible affected by gravity
34
What's Cakeing?
no redisoersible of the sedimented particles--> inconsistent dosing
35
How can caking be prevented?
High viscosity of suspension, reasonable selection of stabilizer or solidification of suspension
36
When can the stok'es law be applied?
Just for laminar flow in cases of sedimentation
37
Light scattering methods for Nanoparticles?
the fraunhofer is not used, because the refractive and absorption index is needed. better Mie-theory
38
Dynamic light scattering measuremnet for the movement of the nanoparticles
speed of the brownian molecular movement dpending on size and vicosity
39
What is the attenautor?
it's regulates the particles, more light into the curvet, less particles into the sytstem
40
What does high attenuator means?
higher attenuator means, less particles, desidmentation of the particle
41
How does the structure of a crystalline and amorphous looks like in a XRPD
crystalline shape peaks | amorphous hallo structur
42
How should be stability testing be perfomered?
Under trasportation and storage conditions
43
storage conditions
Long term, intermediate and accelerated studies
44
Why it is important to stabilizier nanosuspensions
because the formation of agglomeration especially for parenteral application could cuase vessel bockage and therefore embolia
45
What are the four scattering phenoema in light interactions with matters?
Fefraction, Reflection, Diffraction and Adsorption
46
which phenomenon happend with larger particles
Diffraction
47
Describe the diffraction phenomenon
Scattering pattern occur which is correlated with particle size
48
What is the angle of bigger and small particle
the smaller the particles the bigger the scattering angle
49
What is important if one has small particles ?
refraction and absorption become more dominating
50
What is then necessary using small particles
Refractive index and absorption
51
When can Fraunhofer theory be used
larger particles, correlation between scattering angle and particle size
52
Which method can be used for smaller particles
Mie-theory is used
53
What is Mie-theory
Modelling of scattering which results of diffraction, refraction, absorption and reflection
54
Which particle size can be used in laser diffraction
limited to ~ 70 nm
55
what can be used instead of laser diffraction
Dynamic light scattering
56
Dynamic light scattering | particle size
particle size measuremnets of < 1µm
57
XRPD
Sample is exposed to x-rays, | detector detects diffracted x-rays
58
Crystalline state in XRPD
Angle dependent high X-ray intensities (Bragg peaks)
59
Amorphous state in XRPD
No Bragg peaks detected
60
What is the procedure of the Dynamic light scattering
Measurement of the time-dependent fluctuations of the scattered light intensity and determine of the difusion coefficient
61
XRPD for which state of the molecule
Solid state
62
What is a power compensating DSC
Differential power signal is recorded as function of actual sample temperature
63
Which stability study have to be carried out for nanosupsension
``` Long term stability and accelarted stability Thermal stability (storage at high temperatures) ```

Stability Testing (5 decks)

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