1. Rapid Precipitation of Drug
Nanoparticles using Ultrasound
By
PATIL CHETAN CHANDRAKANT
Dissertation submitted to the Faculty of the
Indian Institute of Technology Gandhinagar,
in partial fulfillment of requirements for the degree of
Bachelor of Technology, Chemical Engineering
2014
Advisor:
Dr. Sameer V. Dalvi
Department of Chemical Engineering
Indian Institute of Technology, Gandhinagar
3. 1
Abstract
Title of Document:
RAPID PRECIPITATION OF DRUG
NANOPARTICLES USING ULTRASOUND
Patil Chetan Chandrakant,
Bachelor of Technology, Department of
Chemical Engineering, 2014
Directed By: Dr. Sameer V. Dalvi,
Department of chemical engineering
The Liquid Antisolvent (LAS) precipitation process for production of
ultra-fine particles has been widely researched for a last few decades.
In LAS process, precipitation of solute is achieved by decreasing the
solvent power for the solute dissolved in a solution. This is done by
addition of a non-solvent for solute called as Antisolvent. The method
is applicable for a wide range of materials such as pharmaceutical
ingredients, inorganic compounds, polymers and proteins. Particle
formation by the Liquid Antisolvent (LAS) method involves two steps:
mixing of Solution-Antisolvet stream to generate superasturation and
precipitation (which involves nucleation and growth by coagulation
and condensation).
4. 2
The objective of this work is to develop a better understanding of the
use of LAS for precipitation and stabilization of ultrafine particles of
Curcumin. The process of precipitation of drug nanoparticles through
addition of LAS can be controlled by either controlling the mixing of
the Solution and Antisolvent or by controlling the precipitation i.e.
controlling the nucleation and the growth.
5. 3
Acknowledgements
First I would like to express my deep sense of gratitude to my project
guide Dr. Sameer V. Dalvi to give me the opportunity to work on this
project under his guidance. His Guidance, advices and support to my
work were very helpful.
I would also like to thank Ms. Alpana Thorat for helping me throughout
the project providing innovative ideas for the experiments.
6. 4
Table of Contents
Abstract 2
Acknowledgements 3
Table of Contents 4
List of Figures 6
List of Tables 7
Chapter 1: Introduction 8
Chapter 2: Theoretical 9-12
2.1 Nucleation 9-10
2.1.1 Primary Nucleation 9
2.1.2 Secondary Nucleation 10
2.2 Growth 10
2.3 Mixing 11
2.4 Induction Time 12
Chapter 3: Experiment 13-14
3.1 Material 133
3.2 Apparatus and Experimental Procedure 133
Chapter 4: Reults and Conclusion 15-18
4.1 Experiment1 155
4.2 Experiment 2 16
4.3 Conclusion 17
References 19
7. 5
.
Nomenclature
Symbol Description Units
Qm mixing time ratio Qm
K Boltzmann's constant (1.381×10−23 J/K) K
τmeso mesoscale mixing time (ms) τmeso
Vm molecular volume Vm
k kinetic energy (J) k
Dt turbulent diffusivity constant Dt
Greek Alphabet
Symbol Description Units
γ solution activity coefficient γ
ε energy dissipation rate (W/kg) ε
σ interfacial energy (J/m2 ) σ
ηB viscosity of aqueous solution (cP) ηB
8. 6
List of Figures
Figure 1: Shematic of Particle precipitation process
Figure 2: Experimental setup for LAS precipitation method
Figure 3: SEM image for sample 1 for 0 min
Figure 4: SEM image for sample 1 for 24 hrs
Figure 5: SEM image for sample 2 for 0 min
Figure 6: SEM image for sample 2 for 24 hrs
9. 7
List of Tables
Table 1: Particle size distribution for sample1 for 0-4 hrs
Table 2: Particle size distribution for sample2 for 0-4 hrs
10. 8
Chapter 1: Introduction
Crystallization is one of the important unit operations, which
involves chemical solid liquid separation. It has many
application in pharmaceutical and chemical industries such as
purification and separation of pure active pharmaceutical
ingredients (API) etc. the process of making of solid crystal
from a solution involves such as nucleation, growth and
agglomeration as shown in Fig.1 . The extent o these steps
determines the size of crystal and their distribution.
Since the properties of material affect the other process and
other characteristics of the material itself. Particle size is one
such property, which has huge impact on the reaction
involving the material. So monitoring and controlling the size
of the solid particles through crystallization is very essential.
Pharmaceutical and chemical grade crystalline products
require a narrow range of particle size distribution.
Figure 1: Schematic of particle precipitation process.
11. 9
Chapter 2: Theoretical
2.1 Nucleation
Nucleation is the process of formation of initial crystals from a
given solution, in which a small number of ions, atoms or
molecules become arranged in a pattern, characteristics of a
crystalline solid. Hence it forms sites on which additional
particles can be deposited
2.1.1 Primary Nucleation
Primary nucleation is the formation of crystals in the initial
stage when no other crystal are present and if present then
are in so small amount that they don’t influence the formation
of new nuclei.
These are further classified as homogeneous and
heterogeneous nucleation. In homogeneous nucleation;
nucleation is not influenced by wall of crystallizer and any
foreign substance. Heterogeneous nucleation includes the
enhanced nucleation because of presence of foreign particles.
For primary nucleation
Where
B = no. of nuclei formed per unit volume per unit time
Kn = rate constant
C= solute concentration
C*= solute equilibrium concentration
N= empirical exponent
12. 10
2.1.2 Secondary Nucleation
Secondary nucleation includes nucleation formation in the influence of
microscopic crystals. It occurs because of the fluid shear and other
collisions between the already existing nuclei and newly formed nuclei.
For secondary nucleation
MT
j
=Suspension density
K1 = rate constant
2.2 Growth
The solute molecules present near the nuclei formed get attached to
the nuclei and hence increases the size of the nuclei resulting into its
growth. This happens mainly because nuclei formed are unstable due
to super-saturation. The rate of increase of size of the nuclei is known
as growth rate. It is influenced by several factors, such as surface
tension of solution, pressure, temperature, relative crystal velocity in
the solution etc. The Relation between mixing time, induction time
and crystal growth time is calculated using
Damkohler number:
for nucleation
for growth
Low Da suggests that mixing will have minimal effect, while increasing
Da increases criticality of mixing. For growth, at low value of Da mixing
would have minimal effect on the particle size distribution. For high
values of Da, slow mixing and fast nucleation or crystal growth, mixing
would impact the particle size distribution since localized
concentrations would lead to variable nuclei generation or crystal
growth rate throughout the solution
13. 11
2.3 Mixing
In LAS precipitation process, mixing generates superasturation which is
followed by, nucleation and growth. Accordingly, there are two main
time scales associated with the process of particle formation, namely
mixing time (τmix) and the precipitation or induction time (τprecipitation)
τ m i x =τ m e s o +τ m i c r o
Qm can also be predicted as follows:
Dt=the turbulent diffusivity (Baldyga et al., 1995),
U= solution velocity,
qo = volumetric flow rate, ν the kinematic viscosity,
ε = energy dissipation rate ( Torbacke and Rasmuson,
2001 and Baldyga et al., 1995).
Qm= relative degree of exchange of material between eddies in a
suspension (Vicum et al., 2004),
contributions of mesomixing and micromixing to the redistribution of
material can be evaluated using Qm
When
In cases where Qm is large and greater than 1, mesomixing controls
and if Qm is small and lower than 1, micromixing controls.
Consequently, if mesoscale mixing controls the mixing rate, shear
forces (viscous) are the main components controlling the process.
14. 12
2.4 Induction Time
Induction time is defined as the time difference between reaching
super-saturation and formation of first nuclei in the solution. But
because of measurement difficulties in detecting first few nuclei,
another modified definition of induction time is developed, as the time
needed for the number density (Nm/V) of nuclei to reach a fixed value.
This fixed value depends upon the method of detection of nuclei. If the
instrument that is used to detect the nuclei is more sensitive the
number density taken will be small, however for less sensitive device it
would be a greater value.
Factors affecting induction time:
Degree of super-saturation: For high super-saturated solution
induction time will be less in comparison to solution with less
super-saturation. Since in case of high superasturation, there
will be more driving force for precipitation because of a bigger
change in free energy of solution.
Degree of mixing: For more degree of mixing induction time
will be less in comparison to lower degree of mixing.
Antisolvent Solvent ratio: For more Antisolvent degree of
precipitation will be higher hence lower will be the induction
time.
Temperature of the solution: For higher temperature the
degree of superasturation will decrease resulting into higher
induction time of precipitation.
Stabilizer: Presence of stabilizer will increase the induction
time by reducing the instability of solution. The change in the
value of induction time also depends upon the amount of
stabilizer added to the solution. For higher amount of stabilizer
added, the value of induction time will also increase.
15. 13
Chapter 3: Experiment
3.1 Materials
Curcumin,Ethanol (99.8 % pure) were purchased from Sigma-Aldrich
Inc. India. All these chemicals were used without further purification.
Deionized Millipore water was used as an Antisolvent
3.2 Apparatus and experimental procedure
Figure 2. Experimental Setup for LAS precipitation method
The diagram represent Flowcell having a jacket around its boundary,
through which hot or cold liquid can be passed in order to maintain
the desired temperature. There are two peristaltic pumps to maintain
the continuous flow of Solvent and Antisolvent stream in the Flowcell.
At the start of the experiment desired flow rates for the solvent and
Antisolvent streams were set on the pumps. Using a chiller temp of the
Flowcell was maintained at 1°C, the Flowcell was connected to the
Ultrasound probe for ultra-sonication with power of 115 W. for various
16. 14
concentrations of Curcumin in the solvent and for various Solvent-
Antisolvent ratio experiments were performed using the same set up.
Then those sample were tested in LSI3 Beckman Coulter Laser
Diffraction machine to check for the Particle size distribution over a
period of time.
17. 15
Chapter 4: Results and Conclusions
4.1 Experiment 1
5 mg/ml of curcumin was dissolved in EtOH (Solvent)+ Deionized water
(Antisolvent) maintaining the Solvent to Antisolvent flow rate at 1:10
resp.
Table.1 : Particle size distribution for sample1 for 0-4 hrs
0 min 15 min 30 min 45 min 1 hr 4 hr
mean 0.715 1.073357 20.21273 18.13803 19.8064 19.7912
median 0.500 1.306547 18.63263 17.34808 18.40393 18.10837
d10 0.176 0.134934 5.118763 4.7083 4.90727 4.706263
d50 0.500 1.306547 18.63263 17.34808 18.40393 18.10837
d90 1.659 1.925503 37.35407 32.33.403 36.5329 36.99333
Figure 3. SEM image of sample1 for 0 min reading
18. 16
Figure 4. SEM image of sample1 for 24 hrs reading
By the images and the Table we can see that at the beginning when
the nucleation just takes place the molecules are very small and the
process of nucleation and agglomeration is taking place, but the
growth of the particle is not specific as there is no control on the
growth of the particles. We can see that that the particles are not
stable and they keep on growing till they reach till 30 microns (± 10
microns)
4.2 Experiment 2
5 mg/ml of curcumin was dissolved in EtOH (Solvent)+ Deionized water
maintaining the Solvent to Antisolvent flow rate at 1:3 resp.
Table2. Particle Sixe Distribution for smaple 2 for 0-4 hrs
0 min 15 min 30 min 45 min 1 hr 4 hr
mean 3.82359 3.223427 5.504133 5.500883 5.753948 6.007013
median 3.315547 2.734123 4.707977 4.90877 5.056284 5.203797
d10 0.706049 0.62808 0.701396 0.652097 0.667331 0.682564
d50 3.315547 2.734123 4.707977 4.90877 5.056284 5.203797
d90 8.00452 6.681507 11.75647 11.47133 12.0.832 12.6653
19. 17
Figure 5. SEM image of sample2 for 0 min reading
Figure 6. SEM image2 of sample for 2 hrs reading
The same thing that we observed for the sample one is repeated here
but here the particles grew from 3microns to 6 microns even after 4
hrs. Which means for lower flow rate ratio of Solvent-Antisolvent
there was better mixing and the particles were well sonicated and
growth of the particle was very less as compared to the sample
20. 18
4.3 Conclusion
In this work, a Flowcell in combination with ultrasound, has been
demonstrated for precipitation of ultra-fine particle APIs by LAS. It has
been shown that the use of ultrasound in a Flowcell induces uniform
mixing conditions. In the absence of ultrasound, micromixing controls
the mixing process and hence it becomes difficult to achieve better
control over particle size. However, use of ultrasound improves
micromixing and drastically reduces values of Da below 1, which
indicates that the process of particle formation is precipitation
controlled and a greater control over particle size can be obtained
through manipulation of physicochemical properties of the constituent
materials.
21. 19
References
Liquid antisolvent precipitation and stabilization of
nanoparticles of poorly water soluble drugs in aqueous
suspensions: Recent developments and future perspective
Alpana A. Thorat, Sameer V. Dalvi
Binay K. Dutta N.d. Principles of Mass Transfer andSeparation
Processes. PHI learning Private Limited, Eastern Econommy
G.L. Amidon, H. Lennernas, V.P. Shah, J.R. Crison A theoretical
basis for a biopharmaceutical drug classification: the
correlation of in vitro drug product dissolution and in vivo
bioavailability
Controlling Particle Size of a Poorly Water-Soluble Drug Using
Ultrasound and Stabilizers in Antisolvent Precipitation
Sameer V. Dalvi and Rajesh N. Dave*
Controlling particle size of a poorly water-soluble drug using
ultrasound and stabilizers in antisolvent precipitation Ind.
Eng. Chem. Res., 48 (16) (2009), pp. 7581–7593
J. Dodds, F. Espitalier, O. Louisnard, R. Grossier, R. David, M.
Hassoun, F. Baillon, C. Gatumel, N. Lyczko
The effect of ultrasound on crystallization–precipitation
processes: some examples and a new segregation model
Part. Syst. Charact., 24 (2007), pp. 18–28
