Choice of Better Laboratory Technique for the
Preparation of Microspheres Applying
Analytical Hierarchy Process: A Case Study
OTECH - 8
P.Venkatesan
Lecturer , Annamalai university
Annamalainagar 608002
Tamilnadu, India
Choice of Better Laboratory Technique for the
Preparation of Microspheres Applying Analytical
Hierarchy Process: A Case Study
P.Venkatesan1*, C.Muralitharan2, R.Manavalan1 and K.Valliappan1
Annamalai university, Annamalainagar, Tamilnadu, India.
OBJECTIVE
The objective of the case study is to select an
appropriate technique that would deliver the quality
product with reproducibility of release profile and
consistency with good entrapment efficiency
applying
technique.
Analytical
Hierarchy
Process
by
(AHP)
INTRODUCTION
Microencapsulation
Microencapsulation is a process by which relatively thin
coatings are applied to small particles of solids or droplets
of liquids and dispersions.
They usually have particle size ranging from several tenths
of a micron to 5000 micron
APPLICATIONS
•This technology has been used widely in the design of
controlled release and sustained release dosage forms.
•To mask the bitter taste of drugs like Paracetamol,
Nitrofurantoin etc.
•To reduce gastric and other G.I. tract irritations.
•A liquid can be converted to a pseudo-solid
handling and storage. eg.Eprazinone.
for easy
•To provide protection to the core materials against
atmospheric effects, e.g. Vit.A.Palmitate.
METHODS OF MICROENCAPSULATION











Air Suspension Coating
Thermal Change
Incompatible Polymer Addition
Non-Solvent Addition
Salt Addition
Polymer-Polymer Interaction
Multi orifice - Centrifugal Process
Solvent Evaporation
Spray Drying and Spray Congealing
Pan Coatings
Coacervation Phase Separation.
ANALYTIC HIERARCHY PROCESS (AHP)
Analytical Hierarchy Process developed by Thomas
L.Saaty is one of the very effective Multi criteria
decision making (MCDM) Model. This has been
employed very successfully in many situations where a
decision situation is characterized by a multitude of
complementary and conflicting factors.
Saaty’s nine-point comparison scale
Intensity of
importance
Definition
Explanation
1
Equal importance
Two activities constitute equally to the
objective
3.
Moderate importance
Experience and judgment of one over another
slightly favour one activity over another
5.
Essential or strong importance Experience and judgment strongly favour one
over another
Very strongly demonstrated
An activity is favoured very strongly over
importance
another; its dominance demonstrated in practice
7.
9.
2,4,6,8
Absolute importance
Intermediate values between
adjacent scale values
The evidence favouring one activity over
another is of highest possible order of
affirmation
When compromise is needed
Reciprocals of If activity i has one of the above non zero numbers assigned to it when
above non zero compared with activity j, then j has the reciprocal value when compared with i
METHODOLOGY AND EXPERIMENTAL WORK
The case study was conducted with an objective to choose
the better technique between four alternatives, namely
Solvent Evaporation (SET),
Coacervation Phase Separation (CAP)
Pan Coatings (PAN)
Spray Drying and Spray Congealing (SPR)
for carrying out microencapsulation.
Overall objective
Identify relevant criteria
Identify alternatives to be rated
Develop matrix of pair wise comparison of
Calculate normalized weights of criteria
Calculate consistency ratio (CR) of pairwise comparison matrix
IS CR  0.10
NO
yes
Develop matrix of pairwise alternatives with respect to each
Calculate normalised weights of alternatives
consistency ratio of pair wise comparison of alternatives
Choose a the next
IS CR  0.10
NO
yes
Have alternatives been compared
yes
Calculate the overall weight of each alternative
Choose the best alternative
NO
yes
NO
1. Process Information [PI]
Production scale
[PS]
Lab scale, Pilot scale, Industrial scale
Process condition
[PC]
Temperature, Stirring speed, Ph
2. Operation Skill [OS]
Technique
Microencapsulation is a process where by small discrete
[MET] solid particles or liquid droplets are surrounded and
enclosed by an intact shall
Knowledge
[KN]
Refers to Microencapsulation theoretical background
Training
[TR]
Hands on training on instrument
Availability
[AV]
How easily the machine can be procured.
Experience
[EX]
Reputation of the Supplier
Service
[SE]
Serving and maintenance facilities
Spares
[SP]
Availability of spare parts
Monopoly
[MO]
Vendor status single/Multi Vendor
3. Supplier [SUP]
4. Technical information [TEI]
Literature
[LT]
Scientific Journal, News,
updating current trends
magazines
Manual
[MA]
Operational and service manual.
Establish Technique
[ET]
Standing of the technique in the global
level research
Growth
[GH]
Growth in the field of encapsulation
technique
Versatility
[VE]
Operational Flexibility, RPM,
Encapsulation
Complexity
[CO]
Complexity of the machine how easily one
can handle the instrument
5. Technical Status [TES]
6. Machine [MAC]

Using the AHP model the priority weights,
[PR_WT], to the attributes and sub-attributes
are calculated by
pair wise comparison matrix
Evaluation
criteria
C1
C2
C3...
C1
1
Reciprocal of
entries below the
diagonal
C2
Degree of
preferences of C2
versus C1
1
C3
C3 versus C1
C3 versus C2
1
Cm
C3 versus C1
Cm versus C2
Cm versus C3...
Cm
1
RESULTS AND DISCUSSION

In the case study, AHP technique was applied to make
choice amongst alternative microencapsulation techniques
(SET/CAP/PAN/SPR) and thereby opt the best technique.

The composite score is used for the final ranking of the
alternatives. The solution of the problem involves finding
the composite score that reflects the relative priorities of all
the alternatives at the lowest level of the hierarchy.
Attributes
Process
Information
Operation
skill
Supplier
Notation
PI
OS
SUP
PR_WT
PR_WT
Subattributes
PR_WT
PS
SET
CAP
PAN
SPR
0.25
0.591
0.247
0.049
PS
PC
0.75
0.559
0.323
0.058
PC
MET
0.455
0.558
0.263
0.056
MET
KN
0.455
0.558
0.263
0.056
KN
TR
0.090
0.469
0.469
0.063
TR
AV
0.334
0.530
0.311
0.096
AV
EX
0.333
0.450
0.450
0.049
EX
SE
0.111
0.450
0.450
0.049
SE
SP
0.111
0.450
0.450
0.049
SP
MO
0.111
0.438
0.438
0.081
MO
0.421
0.261
0.153
PR_WT
Attributes
Notation
Technical
information
Technical
status
Machine
TEI
TES
MAC
Composite score
PR_WT
Subattributes
PR_WT
LT
SET
CAP
PAN
SPR
0.250
0.520
0.297
0.124
LT
MA
0.750
0.520
0.297
0.124
MA
ET
0.833
0.638
0.230
0.055
0.073
GR
0.167
0.638
0.230
0.055
0.073
VE
0.750
0.535
0.327
0.091
0.044
CO
0.250
0.535
0.327
0.091
0.044
0.521
0.305
0.064
0.076
0.094
0.046
0.025

It is seen here that, PI is most important (priority = 0.421)
followed by OS (priority = 0.261) and so on.

In the next level of comparison, sub-attributes are compared
with each other with respect to an attribute at a higher level.
For instance, within PI the sub-attributes PS, PC are
compared . Similarly in all the other sub-attributes are
compared .

The composite score favored the selection of SET
(score=0.5216)
over
CAP
(score=0.3059),
PAN
(score=0.0645),
SPR
(score=0.0769)
for
microencapsulation technique
CONCLUSION

In today competitive scenario, an effective framework for
selecting a technique for the preparation of microspheres
using AHP as MCDM tool is presented in this case study
here.

This approach is a systematic one and it includes both
quantitative and qualitative factors. Software for computing
priority weights can be easily developed else commercial
software (expert choice) is available.

The factors considered here are illustrative only and these
may vary from case to case .

The proposed approach can be extended to other situations
like selection of alternatives such as tablets formulation
machines, characterization technique like pharmacokinetic
studies, release behavior, drug content, etc.
References

Mine Qrlu, Erdal Cevher, Ahmet Araman(2006). Design
and evaluation of colon specific drug delivery system
containing flurbiprofen microspheres. International
Journal of pharmaceutics. Doi:10.1016/J.ijpharm.
2006.03.025.

Frederic Lagarcea,b et al(2004).Baclofen loded
microspheres:Preparation and efficacy testing in a
rabbit model. European journal of pharmaceutics and
Biopharmaceutics 59:449-459.

microspheres containing Zedoary turmeric oil by the
emulsion– solvent-diffusion method and evaluation of the
self-emulsification and bioavailability of the oil.colloides
and surfaces B:Biointerfaces 48:35-41.

Khawla Abu-Izza et al (1996).Preparation and evaluation of
Zidovudine- Loded sustained release
microspheres:
Optimization of multiple response Variables. Journal of
Pharmaceutical sciences85:572-575.

Yan Gao. et.al(2006).Preparation of roxithromycinpolymeric microspheres by the emulsion solvent diffusion
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