a comparative study for interpenetrating polymeric
TRANSCRIPT
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AfricanJournalofPharmacyandPharmacology,Vol.4(2)pp.035-054,February2010
Availableonlinehttp://www.academicjournals.org/ajpp ISSN1996-08162010AcademicJournals
FullLengthResearchPaper
Acomparativestudyforinterpenetratingpolymeric
network
(IPN)
of
chitosan-amino
acid
beads
forcontrolleddrugrelease
Manjusha
Rani1,
Anuja
Agarwal1,
Tungabidya
Maharana2
and
Yuvraj
Singh
Negi2*
1Department
of
Chemistry,
J.
V.
Jain
College,
Saharanpur
(U.
P.)
India.2PolymerScienceandTechnologyProgram,DepartmentofPaperTechnology,
Saharanpur
Campus,
Indian
Institute
of
Technology,
Roorkee,
Saharanpur
(U.
P.)
India.
Accepted
13
January,
2010
ThepaperaddressesdevelopmentofnovelpHsensitiveinterpenetratingpolymericnetwork(IPN)
beads
composed
of
chitosan-glycine-glutamic
acid
cross
linked
with
glutaraldehyde
and
their
use
for
controlled
drug
release.A
comparative
study
hasbeen
carried
out
on
these
IPN
beads
with
the
beadsthatofchitosan,chitosan-glycineandchitosan-glutamicacidcrosslinkedwithglutaraldehyde.ThebeadswerecharacterizedbyFTIR toconfirm thecross linkingreactionanddrug interactionwithcrosslinkedpolymer
inbeads,scanningelectronmicroscopy(SEM)
tounderstandthe
surface
morphologyand
internalstructureand
DSCto
find
out
thethermalstabilityof
beads.Theswelling
behaviorof
thebeadsatdifferenttimeintervalswasmonitoredinsolutionsofpH2.0andpH7.4.Thereleaseexperimentswereperformed insolutionsofpH2.0andpH7.4at37Cusingchlorpheniraminemaleate(CPM)asamodeldrug.TheswellingbehaviorandreleaseofdrugwereobservedtobedependentonpH,degreeofcrosslinkingandtheircomposition.TheresultsindicatethatthenewlyconstructedcrosslinkedIPNbeadsofchitosan-glycine-glutamicacidmightbeusefulasavehicleforcontrolledreleaseofdrug.Thekineticsofdrugrelease frombeadswasbest fittedbyHiguchismodel inwhichrelease rateislargelygovernedbyrateofdiffusionthroughthematrix.
Key
words:
Cross-linked
beads,
chitosan,
chlorpheniramine
maleate,
glycine,
glutamic
acid,
controlled
drug
release.
INTRODUCTION
Polymersfrom
naturalresourceshavebeenstudiedintherecentpastastheimportant
materialforbiotech-nologicalandbiomedicalapplicationowingtotheiruniquecharacteristicssuchasbiologicalcompatibilitywithnaturalenvironment,non-toxicityandbiodegradability. Deacetylatedproductofchitinprovidesapolysaccharide
(1
4)
2
amino-2
deoxy
-
D
glucan
which
is
known
as
the
chitosan
and
is
one
of
the
wellknown
biodegradable
polymersmetabolizedbyhumanenzymes.Chitosancanbepreparedashydrogelbeads,havingapositivechargeatmetabolicandphysiologicalpH,bioadhesivityandwaterholdingcapacityenhancedintissuesofhumanbodyforextendedperiodoftime.Threedimensionalhydro-
*Correspondingauthor.E-mail:[email protected].
Tel:+91-132-2714328.
philic
polymer
networkofhydrogel
beads
are
capableofretaininglargeamountof
water
or
biofluids.Hydrogelsarethermodynamicallycompatiblewithwaterandexhibitswellinginaqueousmedia.Hydrogelshasresemblancewithnaturallivingtissuesduetotheirhighwaterretentioncapacity.Crosslinkedhydrogelnetworkcanbeobtained
by
cross
linking
chitosan
by
using
a
cross
linker
likeglutaraldehyde.
Their
properties
depend
mainly
on
thecrosslinkeddensity(theratioofmolesofcrosslinkingagenttothemolesofpolymerrepeatingunits).Formationofhydrogelnetworkrequiresacriticalnumberofcrosslinksperchainand it formsporousstruc-turewhoseporesizedependsuponswellingofbeadswhichinturndependsonexternalenvironment.Currently,chitosanisthepreferred
materialforcon-trolled
drug
delivery
devices
(Machida
et
al.,
1989;
CheinandYie,1983;Yaoetal.,1994;Yujietal.,1996;ChandyandSharma,1992;Chandyand
Sharma,
1993;Houetal.,
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036Afr.J.Pharm.Pharmacol.
Table1.CompositionofIPNbeadsandalignmentofthecolumn(Glutaraldehyde%)
Beadtype Chitosan(g) Glycine(g) Glutamicacid(g) 2%aceticacid(ml) Glutaraldehyde(%)
A1
A2
A3
A4A5
A6
A7
1.0
1.0
1.0
1.01.0
1.0
1.2
-
-
1.0
0.50.5
0.6
0.5
-
1.0
-
0.50.5
0.4
0.5
40
40
40
4040
40
40
12.5
12.5
12.5
12.525.0
12.5
12.5
1985;Miyazakietal.,1981;Leeetal.,1997).Theuse inthedevelopmentoforalsustainedreleasepreparationisbasedontheintragastricfloatingtabletsofchitosan(ShethandTossounian,1984;Inouyeetal.,1988).Moreover,theantacidandantiulcercharac-teristicsofchitosanpreventsorweakendrugirritationinthe
stomach
(Hou
et
al.,
1985).
Therefore,
chitosan
has
greatpotentialfor itsuseasasuitablecarrier incontrolleddrug
deliverysystems.However,therehavebeensomereportsonchitosanbasedbeadscrosslinkedwithglutaraldehyde
asoral
drug
deliverysystemcom-posedofchitosanandoneofthe
aminoacidslike
glycine(GuptaandRaviKumar,2000),glycine,glutamic
acid(KumariandKundu,
2008)andalanine(KumariandKundu,2007)toobtainbeadsfororaldrugdelivery.Ourpresentstudyisanattempttodevelopcrosslinkedbeadscomposedofchitosanandtwoaminoacidsasspacergroupscrosslinkedwithglutaraldehyde
forsustainedreleaseof
chlorpheniraminemaleateasamodeldrug
and
to
compare
it
with
cross
linked
beads
of
chitosan
and
chitosan-amino
acid.
We
have
prepared
four
types
of
beadscrosslinkedwithglutaraldehyde(a)chitosan(b)chitosan-glutamicacid(c)chitosan-glycine(d)chitosan-glycine-glutamicacidhavingdifferentcompositiontoinvestigate the comparative swelling behavior andmodelingdrugreleaseproperties.
MATERIALSANDMETHODS
Chitosan
was
purchased
by
India
Sea
Food,
Kerala
and
was
used
asreceived.Itspercentage
ofdeacetylation
afterdrying
was89%.Chlorpheniraminemaleate(CPM),C16H19ClN2C4H4O4wasobtainedas
agift
sample
fromSarthak
BiotechPvt.
Ltd.,
HSIDC,
Haryana,
India.
Glutaraldehyde,
glycine
and
monosodium
glutamate
wereprocured
from
SD
Fine
Chemicals
Ltd.,
Mumbai,
India,
SiscoResearchLaboratoriesPvt.Ltd.,IndiaandReidalChemicals, India
respectively.Allotherchemicalsusedwereofanalyticalgrade.Doubledistilledwaterwasusedinthroughoutthestudies.
Preparationofsemi-interpenetratingpolymernetwork(IPN)
beads
DifferentIPNbeads(A1-A7)varyingincompositionwereprepared
separately.Theircomposition
isdescribed
in
Table1.
Weighedquantityofchitosanandaminoacidweredissolvedin40mlof2%
acetic
acidbyweight
andstirredfor
three
hours
usingmagnetic
stirreratroomtemperature.Thehomogeneousmixturewasextru-dedintheformofdropletsusingasyringeintoNaOH-methanosolution
(1:20
w/w)understirring
condition
at400
rpm.The
beadswerewashedwithhotandcoldwaterrespectively.TheresultantbeadswereallowedtoreactwithglutaraldehydesolutionasgiveninTable1at50Cforabout10min.Finally,thecrosslinkedIPN
beads
were
successively
washed
with
hot
and
cold
water
followedbyairdrying.
Drug
loaded
beads
of
same
composition
were
also
preparedseparatelybyadding
aknown
amount
of
CPM(150mg,
200
mg)respectivelytothechitosan,aminoacidmixturebeforeextrudingintotheNaOH-methanolsolution.
Swellingstudies
Swellingbehaviorofchitosan
beads(A1-A7)werestudiedin
differentpH(2.0and7.4)solutions.Thepercentageofswellingforeachsampleattimetwascalculatedusingthefollowingformula.
Percentageofswelling={(Wt-Wo)/Wo}x100
Where;
Wt
=
weight
of
the
beads
at
time
t
after
emersion
in
thesolution.Wo=weightofthedriedbeads.
Drugloadingassay
Accuratelyweighed(0.1g)drug loadedsamplewaskept in100m
of2%aceticacidfor48h.AftercentrifugationtheCPMinthesupernatant
wasassayedbySpectrophotometerat193.5nm.
Drugreleasestudies
The
drug
release
experimentswere
performed
at37C
under
unstirredconditioninacidic(pH2.0)
andbasic(pH7.4)solution
Beads
(0.1
g)
containing
known
amount
of
the
drug
were
added
tothe
release
medium
(30
ml).
At
pre
decided
intervals,
samples
of
2mlaliquotswerewithdrawn, filteredandassessedby recording theabsorbanceat
193.5nm.
ThecumulativeCPMreleasewasmeasuredasafunctionoftime.
Kineticanalysisofdrugrelease
A fairamountofworkhasbeenincluded in literatureonkineticsof
drug
release
(Agnihotrietal.,2004;Laszlo
etal.,2006).A
largenumber
of
modified
release
dosage
forms
contain
some
sort
ofmatrixsystemandthedrugdissolvesfromthismatrix.Thediffusion
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Ranietal. 037
Figure1(a).Swellingbehaviorofcross linkedA1-A4beadsasa functionoftimeinsolutionpH2.0andpH7.4at37C.
patternofthedrugisdictectedbywaterpenetrationrate(diffusioncontrolled)
andthustheHiguchisequation(Higuchi,
1963)relationshipapplies
Mt/M=kt1/2
Where;Mt/Misthefractionaldrugreleaseattimetandkisa
constantrelated
to
the
structuraland
geometricpropertiesof
thedrug releasesystem.According toHiguchismodel,aninertmatrixshouldprovideasustaineddrugreleaseover
areasonableperiodoftimeandyieldareproduciblestraightlinewhenthepercentageof
drugreleasedisplottedversusthesquarerootoftime.
Characterization
of
IPN
beads
FTIRspectra ofIPNbeads
FTIRspectraofIPNbeadswererecordedusingathermoNicolet
Avatar370FT-IRspectrometersystemusingKBrpellets.
Scanningelectronmicroscopy (SEM)
The
shapeand
surfacemorphology
of
the
beads
were
examined
using
FESEM
QUANTA200
FEG
model
(FEI,
the
Netherlandsmake)withoperatingvoltagerangingfrom200Vto30kV.FESEMmicrographsweretakenaftercoatingthesurfacesofbeadsampleswithathinlayerofgoldbyusingBAL-TEC-SCD-005SputterCoater
(BAL-TECAG,Balzers,Liechtensteincompany,Germany)under
argon
atmosphere.
SEM
was
used
to
perform
textural
charac-terizationoffullandcrosssectionedIPNbeads,magnificationwere
applied
to
each
sample
in
orderto
estimate
the
morphologyand
interiorofthebead.
Thermalanalysis
Thermalgravimetricanalysis(TGA),Differentialthermalgravimetric
(DTG)and
Derivative
thermalanalysis(DTA)were
carried
outsimultaneouslybyusinga(PYRISDiamond).TG/DTAthermalanalyzermodelDSC-7,suppliedbyPerkinElmerand thedatawasprocessedandanalyzedbyPYRISmusemeasureandstandardanalysis
software
(V.3.3U;#.
2002Seiko
instruments
Inc.).
The
sample
was
kept
in
alumina
pan,
the
reference
material
wasaluminapowderandstudywascarriedoutatheatingrateo10C/minunder200ml/min flow rateofairornitrogenatmosphere.Indium
and
gallium
were
usedas
standards
for
temperaturecalibration.
RESULTSANDDISCUSSION
Swellingstudies
The
percentage
swellingofchitosanbeads(A1
-A4)
cross linkedwithglutaraldehyde insolutionofpH2.0and7.4isshowninFigure1(a).Itwasobservedthatswellingrate
followed
order
as
follows
AtpH-2.0 A2
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038Afr.J.Pharm.Pharmacol.
Figure
1(b).
Swelling
behavior
of
cross
linked
A4-A7
beads
as
a
function
of
time
in
solutionpH2.0andpH7.4at370C.
inacidicsolution
whichmaybeduetothepresenceoffreecarboxylicendsofthechitosan-glutamicacidIPNandthefreecarboxylicendsaremorelikelytobeattackedbybasicsolution.Incaseofchitosan-glycine-glutamicacidbeads,their
rateofswellingwasalsofoundtobehigheratpH2.0thanchitosan-glutamicacidandchitosan-glycinebeadsandatpH7.4,theirrateofswellingisintermediatebetweenchitosan-glutamicacidandchitosan-glycine
beads.
Thus
it
was
concluded
that
over
all
rate
of
swellingwasaffectedbyglycinewhenchitosan-glycine-glutamicacidbeadsweresubjectedtoswellingstudies.Theswelling
behavior
ofthe
cross
linkedchitosan-glycine-glutamicacid
beads(A4
-A7)asa
functionoftimeinsolution
pH
2.0
andpH
7.4has
beenshown
inFigure1(b).
Itwasobserved
that
the
swelling
ratewasdecreasedon
increasingconcentrationofcrosslinkerglutaraldehyde.Theobservedswellingrates
ofA4crosslinkedbeadswerefoundtobehigherthantheswellingratesofA5bead,becauseinA5beadsthehigherconcentrationofglutaraldehydeincreasedthedegreeofcrosslinking,whichdecreasedthedegradationofcross
linked
polymer.
Further,
the
percentage
of
swelling
wasfound
to
be
higher
in
acidic
solution
than
in
basicsolution.Thechangeinaminoacidscomposition,(thatis,
decreaseinglutamicacidconcentrationandincreaseinglycineconcentration)ofcrosslinkedbead(A6)havingsame
concentrationofglutaraldehydeas
compare
toA4bead
hasalso
been
studied
and
observed
thattheincrease
in
concentration
ofglycine
decreased
the
swel-lingpercentageof
chitosan-glycine-glutamic
acidbeadsinbasicsolutionwhileincreasedinacidicsolution.Thepercentageofswellingof
thecrosslinkedbeads
havingthesameconcentrationofcrosslinkerdecreased(A7A4).ItcanbeexplainedasthepercentageofaminoacidsactingasaspacerincreasedinA4beads(25%)ascomparedtoA7beads(22.7%)andalsochitosanpercentagedecreasedinA4beads(50%)ascomparedtoA7beads(54.5%),theporesizeofA7beadsalsodecreasedand thepenetrationofsolutioninto thebeadsbecomedifficult,whichresult in lesserdegreeofswelling
(Kumari
and
Kundu,
2008).
SEMstudies
SEMmicrographsofdriedbeads(A1-A7)andtheir
surfacemorphologyareshown inFigures2aandbwhile,thecrosssectioneddriedbeadsandtheirinternastructureareshowninFigures3aandb.ItwasconcludedfromFigures2aandbthatthebeadswerenearlysphericalorsomewhatovalinshapeandtheirapproximatesizevariedfrom1.2to1.8mm.Cross linked
chitosan
amino
acid
beads
(A2
-
A7)
had
rough,
rubbery,fibrous
and
folded
surfaces
as
com-pared
to
chitosanbeads(A1)whichhadrelativelysmooth
surfaces
withfewwrinkles.
Withthe
higherconcentrationof
crosslinker,incaseofA5thechainscomecloser toeachotherandexhibitaregular,fibrousstructureascomparedtoA4having
lower
concentrationof
glutaraldehyde.A7beadsconstituting
higherconcentration
ofchitosan
showedmoreregularfibroussurfacesascomparedtoA4due
tothesmallerconcentrationofspaceraminoacid.Duetothisreasonthechaincameclosertoeachotherdespiteofhavingthesamedegreeofcrosslinker.Theinternal
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Ranietal. 039
Figure2a.SEMphotographsofchitosan-aminoacidcrosslinkedbeads(A1A4)andtheirmorphology
(A1*-A4*).
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Figure2b.SEMphotographs ofchitosan-aminoacidcrosslinkedbeads(A5-A7)andtheirMorphology(A5*-A7*).
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Ranietal. 041
Figure3a.SEMphotographsofcrosssectionedchitosan-aminoacidcross linkedbeads (A1A4)andtheirinternalstructure(A1*-A4*).
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peak
at1384cm wasassignedtoCH3symmetricalde-
deacetylationofchitosan.Peakobservedat2924cm is
NH-stretchingvibrationsin-NH-COCH3 at1639cm o
at1567cm ofthenewlyformedstructurebetweenamino
042Afr.J.Pharm.Pharmacol.
Figure3b.SEMphotographsofcrosssectionedchitosan-aminoacidcrosslinkedbeads(A5A7)andtheirinternalstructure(A5*-A7*).
structureofbeadsappearedtohavemicroporesaswere
seeninSEM(Figures3aandb).
FTIRstudies
Figure4(a)showstheFTIRspectraofchitosanpowder,
glutamicacid,glycineandA1-A7drugunloadedbeads.An
FTIR
spectrum
of
chitosan
powder
curve
(A)
has
showntwopeaksaround894and1171cm-1corres-
pondingtosaccharidestructure(Yoshiokaetal.,1990).Theobservedpeakat1613cm
-1canbeassignedas
aminoabsorptionpeak.Theabsorptionpeakforamidewereobservedat1639and1319cm
-1andobserved
-1
formationmode(Pengetal.,1994;Sannanetal.,1978).
Abroadbandappearingaround1083cm-1indicated
the>CO-CH3stretchingvibrationofchitosan.Another
broad
band
at
3450
cm-1
wasdue
to
the
amine
N-H
symmetricstretchingvibrationwhichmightbedueto-1
typicalofC-Hstretchingvibration.simultaneouslythe
peakassignedforaminoabsorptionat1613cm-1in
originalchitosanbroadenedordisappearedincrosslinkedbeadsandanewpeakappearingatabout1567cm
-1
due
to
imine
bond
(-C=N-)
which
was
formed
as
aresultofcrosslinkingreactionbetweenaminogroupinchitosanandaldehydicgroup inglutaraldehyde(Bellamy,1980;Leeetal.,1999)incurveA5-A7.Howeverthiswas
due
tothe
overlapping
ofpeaks
correspondingto
-1
theoriginalchitosanwiththatofimino(-C=N-)stretching-1
groupofchitosanandaldehydegroupofglutaraldehyde
inA2-A4.Areactiontakingplaceintheformationof
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correspondingto1567cm was sharpened and distinct
Ranietal. 043
Figure
4(a).
FTIR
spectra
of
glutamic
acid
(A),
glycine
(B),
chitosan
powder
(C)
and
drug
unloaded
cross
linkedbeads(A1-A7).
cross-linkisasfollows
-NH2 + O=HC- -N=CH-
Amino aldehyde imino(Chitosan) (Glutaraldehyde) (Crosslink)On increasingtheglutaraldehydeconcentration, thepeak
-1
inA5.AllthecurvesA1toA7showedadditionalpeaksofaminoacid.
FTIRspectral
dataof
drug
loadedbeads
inFigure4b
were
usedtoconfirmthechemicalstabilityofCPM inchitosanaminoacidbeads.FTIRspectraofpureCPMdrug(curveD)andCPM loadedcross-linkedbeads(A1-A7) inFigure4bwerecomparedwithdrugunloadedcross-linkedbeads(A1-
A7)
inFigure4a.
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bandataround864cm duetoaromaticC-Clstretching.
044Afr.J.Pharm.Pharmacol.
Figure
4(b).
FTIR
spectra
of
pure
CPM
drug
(D)
and
drug
loaded
cross
linked
beads
(A1
-
A7).
CPMhasshowncharacteristicbandat2966and2917cm
-1
due
to
aliphaticC-Hstretching.
The
band
at
1619and1588cm
-1duetoC=Nstretchingvibration.While
thoseof1476and1432cm-1areduetoaromaticC=C
stretchingvibration.CPMhasalsoshowncharacteristic-1
Whendrugwasincorporatedintothe crosslinked
chitosan-aminoacidbeads,alongwithallthecharacteris-
ticband
ofthe
crosslinked
chitosan
and
amino
acidsadditionalbandhave
appearedduetothepresenceofCPMinthematrix.ItindicatesthatCPMhasnotundergoneanychemicalchangewithinthebeads.
THERMALANALYSIS
TGAexperimentswerecarriedoutonchitosan,glutamic
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by
chitosan
powder
(curve
A)
below
100C
due
to
loss
of
Ranietal. 045
Figure5(a).TGcurvesforchitosanpowder(A),glutamic acid(B),glycine(C)anddrugunloadedcrosslinkedbeads(A1-A7).
acid,glycineandcrosslinkeddrugunloadedbeadsA1-
A7
and
the
curve
obtained
are
presented
in
Figure5awhichclearlyshowsthatapproximately10%
weight
loss
o
freewater.Afterthis,weightlossremainsconstantupto
249C.Asuddenweightlossisobservedafter249Cand
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046Afr.J.Pharm.Pharmacol.
Figure
5(b).
TG
curves
for
pure
CPM
drug
(D)
and
drug
loaded
cross
linked
beads
(A1-A7).
thetotalweightlossat400Cisabout60%,whereaspurechitosancross linkedbeads (A1)showsweight lossafter200Candweightlossat400Cisapproximately46%,
lesser
than
chitosan
powder
thisshows
thatcrosslinkingofchitosanwithglutaraldehydeincreases
itsthermalstability.Similarly,chitosan-glutamicacid,
chitosan-glycineand
chitosan-glycine-glutamicacidbeadsshowweight lossat400Cabout50,43,and45%respectivelywhichclearlyindicatethatchitosanaminoacidspecially,
chitosan-glycine-glutamicacidbeadsareasthermallystableaschitosanbeads(A1)andthermalstabilityofchitosan-glycine-glutamicacidbeadsisgreaterthanchitosan-glutamic
acid
beads
and
slightly
lesser
than
thatofchitosan-glycinebeads.TG
curvesfor
CPMmodel
drug
(curve
D)and
drugloaded
crosslinked
beads
(A1
-
A7)
are
shown
in
Figure5b.CPMdruglostabout67%weightbetween208and274C(curveD)whichwasduetothedecompositionof
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Ranietal. 047
Figure6(a).DTGcurves forchitosanpowder(A),glutamicacid(B),glycine(C)anddrugunloaded
cross
linked
beads
(A1
-
A7).
ofdrug
above
itsmeltingpoint.
Melting
point
ofCPM
is134Candsuchahuge loss inweightwasnotshownbydrug loadedbeadsA1-A7.Thisconcluded that thedrugisquitestablewithinthebeads.DTGthermogramsofpurechitosan,glutamicacid,glycineandcrosslinkedbeadsA1-A7arepresentedinFigure6a.Theseindicated
the
rate
of
weight
loss
for
chitosan
powder
washighest
at
290C
and
cross
linked
chitosan
beadsshowed
lesserrateofweightlossat244C.Oncomparing
A1 -A4
beads
it
can
be
concluded
that
chitosan-glutamicacid-glycinebeadswerefoundtobemoststableasthelossweightathighesttemperature(271C)ascomparedtochitosanbeadsat244C,chitosan-glutamicacidbeadsat249Candchitosan-glycinebeadsat268C.DTGcurves
for
CPMdrugand
drugloadedcrosslinkedbeadsareshown
inFigure6b.CurveDforpure
CPM
drug
have
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Figure6(b).DTGcurvesforCPMdrug(D)anddrugloadedcrosslinkedbeads(A1-A7).
peaksforweightlossat134,207and256C.
ThecomparisonofdrugunloadedbeadsA1-A7in
Figure
6a
and
drug
loaded
beads
A1
-
A7
in
Figure
6b
showed
almost
similar
peaks
with
same
rate
of
weight
lostalsoproveddrugstability
inthepolymericmatrix.DTA
thermograms
forpure
chitosan,
glutamicacid,glycineand
cross
linked
drug
unloadedbeads
(A1-A7)arepresentedinFigure7a.Thermogramsforchitosanpowdershowedoneendothermicpeakat65Cduetolossoffreewaterandoneexothermicpeakat296Cduetochemicaltransformation.Glutamicacidgivestwoandglycinegivesoneendothermicpeakintheirthermograms.While incaseof(A1-A4)beadsonlyoneexothermicpeakisobserved.Itwasconcludedthatchitosan-
glycine-glutamicacidbeadsarethemoststableasinthermograms forA1-A4beadsexothermicpeakmoves
towards
higher
temperature
(240
to
274C).
DTA
thermograms
for
pure
CPM
drug
and
drug
loaded
beads
A1-A7are
represented
in
Figure7(b).
Incase
ofCPMdrug(curve
D)one
endothermicpeakand
one
exothermicpeakwereobserved.Oneat134Cwhichcorrespondstomelting
processand
otherat254C
to
chemicatransformation.Drugloadedbeads(A1-A7)showedalmostsimilar
thermogramsinwhichnopeakswereobservedat134and254Cindicatingtheamorphousdispersionofdruginto thebeads(AgnihotriandAminabhavi,2006;Kulkarnietal.,2007).
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Ranietal. 049
Figure
7(a).DTAcurvesfor
chitosanpowder(A),glutamicacid(B),glycine(C)anddrugunloadedcrosslinkedbeads(A1-A7).
Drugloadingassay
When(1g)drugloadedsamplewaskeptin100ml
2%
aceticacid,thetotaldrugreleasedafter48hwasfoundtobe78gand142gforthebeadsincorporatedwith
150and200mgofCPMrespectively.
Drugreleasestudy
Figures8aand
bshowsthereleaseprofileof
CPM
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050Afr.J.Pharm.Pharmacol.
Figure7b.DTAcurvesforCPMdrug(D)anddrugloadedcrosslinkedbeads(A1-A7).
fromchitosanbeads(78gofdrugloadedbead)atvarioustime
intervalsin
acidic(pH2.0)and
basic(pH7.4)
at
37C.
There
wasa
burstrelease
initiallyfor
thefirsthourinbothacidicandbasicmediafollowedbyamoderatereleasefornextfourhoursandfinallyanalmost
constant
releaseofCPM
fromthe
matrixforthestudiedperiodof48h.Theamountandpercentage
ofdrug
releasedfollowedtheorderofswellingofbeads.Itisbecause
the
release
rate
depends
on
swelling
of
thebeads.
It
was
noticed
that
drugrelease
waspHdependentandfollowedthefollowingorderinacidicandbasicmedium
AtpH2.0 A2
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Figure8(a).ReleaseofCPMforA1-A4beads(78gCPM
loadedbeads)vstimeinsolutionpH2.0andpH7.4at37C
Figure8(b).ReleaseofCPM forA4 -A7beads(78gCPM
loadedbeads)vstimeinsolutionpH2.0andpH7.4at37C.
AtpH7.4 A3
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%drugrelease
052Afr.J.Pharm.Pharmacol.
Figure9a.ReleaseofCPMforA1-A4beads(142gCPMloadedbead)vs.timeinsolutionpH2.0andpH7.4at37C.
Figure9b.ReleaseofCPMforA4-A7beads(142gCPM loaded
bead)vs.timeinsolutionpH2.0andpH7.4at37C.
thekineticdataofdrugrelease.Linearplotsofpercent
cumulativeamountreleaseversussquarerootoftimeisshowninFigure10demonstratingthatthereleasefromthecrosslinkedpolymericmicrospherematrixisdiffusioncontrolled
and
obeys
the
Higuchis
model
(Jameela
et
al.,
1998).Theconstantk,presentedinTable2wascalculated
fromtheslopeof
the
linear
portion
of
plotof
percentageof
cumulative
drug
released
versusthesquarerootoftime.Thevalueof
k
forthereleaseprocess
has
beenfound tobe lower insolutionofpH7.4 than insolutionofpH2.0exceptforA2beads.However,thevaluesweresmallerwhichindicatemildinteractionbetweenthedrugandpolymericmatrices(Orientietal.,1996;Ganza-Gonzalezetal.,1999).
Figure10a.PlotsshowingdrugreleaseprofilefromA1-A4beads
(78gCPM
loaded)
in
solutionpH2.0
andpH
7.4
by
fitting
the
Higuchis
equation.
A4pH2 A5pH2 A6pH2 A7pH2
A4pH7.4
A5pH7.4
A6pH7.4 A7pH7.4
60
50
40
30
20
10
0
0
1 2
3
t1/2
Figure10b.Plotsshowingdrugreleaseprofile fromA4-A7beads
(78
g
CPM
loaded)in
solution
pH
2.0
and
pH
7.4
by
fitting
theHiguchisequation.
Conclusion
Theobservationsofthepresentstudyhaveshownthat
chitosan-glycine-glutamic
acid
beads
posses
a
pHdependentswellingbehavior. Itcanbeusedsuccessfullyfortheformulationofcontrolleddrugdeliverydevices.Theyhaveoptimumentrappingcapacityforthestudieddrugsandprovideasustainedreleaseofdrugsforextendedperiodswhichmakethemappropriatefordelivery
of
drug
at
a
controlled
rate.
ACKNOWLEDGEMENT
Authorsaregrateful
to
Prof.B.Gupta,
Bioengineering
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Ranietal. 053
Table2.ResultsofdrugreleasemechanismbyfittingdatainHiguchismodelforCPMloadedbeads.
pH2.0 pH7.4
Beads
type
CPMloadedbeadswith
78g 142g 78g 142g
K S.D. R K S.D. R K S.D. R k S.D R
A1
A2
A3
A4
A5
A6
A7
.15
.12
.19
.26
.22
.28
.21
.013
.011
.019
.030
.025
.031
.024
.99
.99
.99
.99
.99
.99
.99
.13
.10
.19
.20
.195
.20
.19
.015
012
.021
015
015
.011
.015
.99
.99
.99
.99
.99
.99
.99
.074
.24
.058
.10
.078
.061
.085
.055
.027
.048
.089
.081
.048
.052
.98
.99
.97
.99
.95
.98
.99
.081
.198
.064
.083
.078
.061
.085
.01
.021
.074
.083
.086
.083
.087
.99
.99
.99
.99
.99
.98
.99
Figure
10c.
Plots
showing
drug
release
profile
from
A1-
A4
beads(142
g
CPM
loaded)in
solution
pH
2.0
andpH7.4byfittingtheHiguchisequation.
Figure10d.Plotsshowingdrugreleaseprofile fromA4-A7
beads(142gCPM loaded)insolutionpH2.0andpH7.4
byfittingtheHiguchisequation.
Laboratory,TextileDepartment,
IIT,
Delhi
forgiftingchitosansampleandtechnicalhelp.
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