Downloaded from joumal.pda.org on February
`
`2017
`
`PDA Joutnal
`of Pharmaceutical Science and Technology
`
`___
`
`Rheological Characterization of Cellulosic and Alginate
`Polymers
`
`Srinivas Duggirala and Patrick
`
`Deluca
`
`PDA
`
`Pharm Sd and Tech 1996 50290-296
`
`flITOSJ
`wit nccLtcbct
`DATEL1l
`
`ALKERMES Exh. 2031
`Luye v. Alkermes
`IPR2016-1096
`
`

`

`RESEARCH ARTICLE
`
`Downloaded from Joumal.pda.org on February 15 2017
`
`Rheological Characterization of Cellulosic and Alginate Polymers
`
`SRINIVAS DUGGIRALA and PATRICK
`
`College of Pharmacy University of Kentucky Lexington Kentucky
`
`respectively
`
`water at
`
`the
`
`ABSTRACT The purpose of this study was to assess the properties of aqueous solutions of various polymeric
`sustained release device for various proteins Polymers that were
`materials intended for use as components of
`studied included Sodium Carbrnymethylcellulose CMC Methylcellulose MC Hydroxypropylmethylcellulose
`HPMC and Sodium Alginate ALG The effects of polymer concentration
`temperature and autoclaving on
`solution viscosity were determined With all the polymers viscosity/concentration
`relationships were linearized by
`Ca
`and
`using an equation of the type
`referred to solution viscosity and concentration
`f37ç where
`and
`were constants related to polymer type and molecular weight whereas /3 reflected viscosity of
`temperature of measurement
`which reflects the sensitivity of the
`viscosity/concentration
`relationship was determined to be 4for both low and high molecular weight CMC and ALG and 8for MC and
`HPMC
`on the other hand was directly proportional
`to polymer molecular weight The same equation could
`for each polymer For both CMC and ALG
`also adequately describe viscosity/temperature
`relationships
`increasing solution concentration had
`greater effect on the reduction of viscosity upon increasing temperature
`thermal gelation phenomena was observed with MC solutions Autoclaving
`concentration
`dependent
`in ALG solutions as compared to CMC samples in the 0.5 to 3.0% w/v concentration
`were more pronounced
`long term effects on solution viscosity were observed with MC and HPMC however
`range No significant
`
`effects
`
`Introduction
`
`The sustained release of proteins can be affected by
`combining them with substances with gel-like properties
`and unique viscosity/concentration behavior The cellu
`losics namely Sodium Carboxymethylcellulose CMC
`Methylcellulose MC Hydroxypropylmethylcellulose
`HPMC and Sodium Aiginate ALO have such prop
`erties These materials have widely been used in con
`CMC for example
`trolled release applications
`used as
`in various
`thickening agent
`formulations due to its effects on vehicle
`parenteral
`viscosity Additionally solutions of such substances
`when freeze dried form matrices which can be used as
`implants For parenteral applications
`the materials
`must be sterilizable either by filtration or autoclaving
`these sub
`of the rheological behavior of
`Knowledge
`stances would be beneficial
`in the design of protein
`formulations
`for sustained
`
`is
`
`routinely
`
`delivery as gels or solid
`
`matrices
`Research in our laboratory has focused on the devel
`novel
`opment of
`lyophilized polymeric delivery system
`month delivery of bone growth
`for sustained
`factors The working hypothesis
`has been that such
`factors can be incorporated into high molecular weight
`
`1995 Accepted
`
`for publication January
`
`Received September
`1996
`to whom correspondence should be addressed Rose Street
`Author
`Lexington KY 40536
`of requirements for Ph.D degree
`Submitted as partial
`Grand St
`1001
`Present address Whitehall-Robins Healthcare
`Hammonton NJ 08037
`
`fulfillment
`
`hydrophiic polymer solutions and lyophilization of such
`solutions would result in unitary devices that could be
`defect site with little pretreat
`directly implanted at
`ment
`if any Furthermore the preparation procedure
`and composition of
`the unitary devices can provide
`integrity and growth
`desired characteristics of physical
`factor release rates
`In this study we report on the rheological character
`ization of the various candidate polymers referred to as
`sequestering agents henceforth reflecting their ability
`of
`to sequester or separate the various components
`controlled release matrix formulation under investiga
`tion CMC MC HPMC and ALG The objectives were
`relationships which ad
`obtain mathematical
`and viscosity/
`equately described viscosity/concentration
`temperature behavior enabling prediction at
`particu
`lar operating condition when data are not inmiediately
`available and
`on
`the effects of autoclaving
`assess
`
`to
`
`solution viscosity
`
`Materials and Methods
`
`Materials
`
`Sodium Carboxymethylcellulose CMC was supplied by
`Aqualon Chemical Company Delaware in high and low
`molecular weights designated respectively as CMC
`7HF and CMC 7LF the number
`referring to the
`degree of substitution of the basic cellulosic unit Methyl-
`cellulose MC was supplied by Dow Chemical Company
`Midland Michigan in four different molecular weights
`designated as MC A15LV MC A4CP MC A15CP and
`MC A4MP Listed in increasing
`order of molecular
`
`290
`
`POLk Journal of Pharmaceutical Science
`
`Technology
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`

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`
`the viscosity of 2.0% aqueous solutions at 20C
`weight
`of the individual polymers are 15 400 1500 and 4000
`cPoise respectively These polymers are Generally Rec
`ognized As Safe GRAS by the US F.D.A Hydroxypro
`pylmethylcellulose HPMC was supplied by Dow Chemi
`cal Company Midland Michigan as pharmaceutical
`is also GRAS Sodium
`grade HPMC E4MP which
`Alginate ALG was obtained from Protan Biopolymers
`Drammen Norway as Ultrapure grade Alginate UP
`MVG
`
`Solubilization Techniques
`
`agents were prepared in
`Solutions of the sequestering
`accordance with the manufacturers directions and stored
`at room temperature for 24 hours prior to characteriza
`tion
`
`Viscosity Measurement
`
`Increasing concentration and/or molecular weight
`especially for polymeric materials results in large in
`to flow primarily due to
`in the resistance
`creases
`polymer chain entanglement The fundamental math
`relationship used to define viscosity
`ematical
`can be
`written as
`
`I.LJ
`
`In the above relationship
`represents the shear stress
`applied to the solution and d/d the velocity gradient
`caused due to the applied stress Viscosity
`.t
`between the shear stress and
`constant
`proportionality
`velocity gradient with units of cPoise gm/cm
`sec
`Viscosity determinations in this study were performed
`the basic mathemati
`capillary tube viscometer
`using
`cal form being as follows
`
`is
`
`kt
`
`In Eq
`represents kinematic viscosity of the sample
`solution with units of mm2/sec and
`the time in seconds
`specific capillary tube viscom
`required to flow through
`eter the diameter of which is directly proportional
`to
`is derived from the
`Equation
`the tube constant
`Poiseuille equation for fluid flow through
`cylindrical
`tube
`with the weight of
`the fluid being the sole
`driving force for flow
`Capillary tube viscometers used in this study were
`manufactured by Schott Gerate GMBH Germany
`values for the tubes ranged between 0.003 to 10 valid for
`between
`0.1 and
`measurement of sample viscosities
`10000 cP and were supplied by the manufacturer The
`Lauda constant
`viscosity measurement setup included
`temperature water bath with attached heating circula
`variable pressure pump and capillary viscometer
`tor
`stand all from Brinkmann Instruments Inc Westbury
`NY Computer control of the measurement process was
`Epsom HX-20 notebook
`calculator Epsom Corp
`Torrance CA Mineral oil standards ranging in viscos
`Inc Warring-
`ity from 0.8 to 10000 cP Polysciences
`ton PA were used to verify the
`values for each of the
`
`via
`
`viscometers
`
`maintained at
`
`Initial
`
`test
`
`During actual measurement runs the capillary tube
`viscometers were filled with approximately 18 ml of test
`solution and clamped onto the viscometer stand The
`stand was then placed
`viscometer
`in the water bath
`Samples ware
`desired temperature
`allowed to equilibrate for 15 minutes to attain the preset
`runs with temperature
`bath temperature
`probes held within the sample validated that
`period of
`15 minutes was sufficient for samples of highest viscosity
`to attain bath temperature The following parameters
`were set for automatic sample viscosity measurement
`equilibration time 15 minutes number of runs
`time
`interval between runs minutes and maximal allowable
`0.2% of predicted
`standard
`deviationapproximately
`solution viscosity Equilibration of the sample was fol
`lowed
`by automatic viscosity measurement with the
`from the system yielding kinematic
`final output
`values with units of mm2jsecond
`Sample densities were obtained by transferring ml
`and obtaining the
`aliquots to specific gravity bottles
`weights of the empty and sample filled bottles Triplicate
`values were determined for each density measurement
`Sample viscosity ji was then obtained using the follow
`ing equation
`
`viscosity
`
`Viscosity/concentration curves for aqueous solutions
`of the various sequestering agents described above were
`determined at 30C The viscosities of selected sequester
`ing agent solutions were also determined over
`30 to
`70C temperature range To study the effects of autoclav
`ing 121C 15 p.s.i
`12 minute cycle on solution
`viscosity the following procedure was utilized
`40 ml of previously prepared samples were trans
`ferred to 50 cc glass vials stoppered and crimped The
`vials were loaded into Getinge autoclave steam steril
`izer Getinge Co Lakewood NJ maintained at 121C
`and
`rapid cooldown
`preprogrammed liquid cycle with
`was utilized Following autoclaving the vials were with
`drawn from the sterilizer and refrigerated at 4C for 24
`hours prior to sample viscosity measurement
`
`Results and Discussion
`
`Viscosity/Concentration
`
`Figure
`
`depicts the viscosity/concentration relation
`ship for CMC 7LF low molecular weight at 30C An
`apparent non-linear
`increase in viscosity upon increas
`ing the solution concentration was evident
`this trend is
`widely seen in polymer solutions wherein physical en
`tanglements of individual polymer chains result in syner
`gistic increases in solution viscosity upon increasing the
`concentration
`convenient way to represent data as shown in
`is to utilize linearized viscosity/concentration
`Figure
`relationships such as plotting the data on
`logarithmic
`scale etc One such relationship originally described for
`has been written as
`Methylcellulose polymers
`
`In the above relationship
`
`represents
`
`the viscosity of
`
`Vol 50 No
`
`SeptemberOctober 1996
`
`291
`
`

`

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`
`on February 15 2017
`
`Effect of concentration on solution viscosity CMC 7LF
`
`Data at 30
`
`3000
`
`2500
`
`2000
`
`1500
`
`1000
`
`500
`
`Concentration
`Figure Effect of concentration on solution viscosity CMC 7LF
`
`the concentration in
`
`is
`
`the
`
`is
`
`is
`
`the solution in cPoise units
`wv and
`gmdL
`the viscosity of water at
`temperature of measurement
`constant
`that
`related to polymer molecular weight with increasing
`values of ci signifying increasing molecular weight of the
`polymer
`constant specific for each polymer type
`indicating how significantly the viscosity changes with
`given value of
`higher value of
`concentration for
`more sensitive
`denotes
`the exponent
`viscosity
`concentration relationship This mathematical relation
`to be physically similar to the commonly
`ship appears
`kM
`used Mark-Howink
`which
`ji
`to molecular
`intrinsic polymer viscosity
`and constants
`reflecting the polymer chain
`and
`conformation in solution solvent characteristics
`temperature Mathematical manipulation of Eq
`to yield the following linearized form
`be carried out
`
`equation
`
`relates
`
`weight
`
`can
`
`Ca
`
`Subtracting f3 from both left and right hand sides of Eq
`the following form is obtained
`
`p.Ih
`
`f3
`
`Ca
`
`slope
`
`versus
`
`then results in plots having
`
`slopes representing higher
`
`Plotting p.Wv
`with increasing
`polymer molecular weights -y for both CMC 7LF and
`trial and error linear
`71-IF was determined to be
`by
`regression model Figure
`depicts an example of such
`for both molecular weight CMC poly
`linearized plot
`mers by utilizing Eq
`An overall summary of
`the
`which lists values
`linearized data is presented in Table
`
`is
`
`of
`
`until
`
`and -y for each polymer alongwith
`the regression
`coefficient R2 for each linearized viscosityconcentra
`tion plot
`the weight average molecular weight
`also included
`As expected
`clear correlation between
`and
`was discerned from the data and possibly reflects the
`physical similarity between Eq
`and the Mark-Howink
`relationship briefly described earlier
`The effect of cross-linking on ALG solution viscosity is
`Control viscosities refer to values
`depicted in Figure
`that took dilution effects into account when progres
`50 mM CaCI2
`sively larger amounts
`of an aqueous
`2.0% ALG solution The
`solution were added to
`starting viscosity of the 2.0% ALG solution was
`1150
`cP No significant increases in viscosity were observed
`threshold value of Ca2 concentration was
`reached on
`volumevolume basis calcium salt solu
`tionALG this represented
`ratio of 0.16 Drastic
`increases in solution viscosity were observed upon fur
`in Ca2 concentration
`volume
`ther
`increases
`at
`volume ratio of 0.20 viscosity of the cross-linked gel was
`approximately 120 times that of the control solution
`
`II Viscosity Temperature
`
`The variation of solution viscosity with temperature
`for CMC 7HF is shown in Figure
`Two clear trends
`were discerned
`progressive decrease in viscosity
`occurred with increasing temperature and
`the reduc
`upon increasing the concen
`tion was more pronounced
`tration The plot indicates that at higher concentrations
`
`292
`
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`
`Technology
`
`

`

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`
`Linearized Viscosity/Concentration CMC 7LF
`
`7HF
`
`10
`
`Concentration9
`Figure 2Unearized viscosity/concentration
`
`CMC 7LF
`
`7HF
`
`Figure
`
`CMC solutions were more sensitive
`to temperature
`trend that was confirmed during autoclaving
`changes
`studies Statistically the slopes of the individual viscosity
`individual concentrations were
`temperature curves at
`0.01
`significantly different
`depicts linearized viscosity/temperature data
`obtained for ALO As with CMC progressive reductions
`in viscosity upon increasing temperature were observed
`Also temperature effects were more pronounced
`at
`higher solution concentrations These differences were
`0.03
`statistically significant
`Methylcellulose solutions exhibited unique viscosity
`temperature relationships
`as depicted
`in Figure
`Representative data are shown for various concentra
`tion of high molecular weight MC A4MP At all
`the
`concentrations studied
`progressive decrease in viscos
`ity upon increasing temperature was observed until
`certain point Further increases in temperature resulted
`in an increase in viscosity this specific inflection tempera
`
`Values
`
`and
`
`-y
`
`TABLE
`for Sequestering Agents Studied
`
`Seq Agent
`CMC 7LF
`CMC 7HF
`ALG
`MCA15LV
`MC A4CP
`MCA15CP
`MC A4MP
`HPMC E4MP
`
`R2
`
`0.98
`
`0.99
`
`0.99
`
`1.00
`
`0.98
`
`0.99
`
`0.99
`
`0.98
`
`0.87
`
`5.88
`
`2.53
`
`0.18
`
`0.56
`
`0.75
`
`0.90
`
`0.93
`
`g/ mole
`
`90000
`700000
`NA
`57000
`320000
`
`530000
`900000
`
`900000
`
`ture is called the gelation temperature Physically
`the gelation temperature signifies the temperature at
`which individual polymer chain interactions are suffi
`ciently strong to overcome
`the polymer chain-water
`interactions resulting in the precipitation of
`viscous gel-like Methylcellulose matrix
`
`highly
`
`III Effect ofAutoclaving on Solution Viscosity
`
`shows
`on the
`the effect
`of autoclaving
`Figure
`viscosity of 0.5 1.0 2.0 and 3.0% aqueous solutions of
`CMC 7HF ALO MC A4MP and HPMC E4MP respec
`re
`tively The
`abscissa represents percent
`viscosity
`tained or the ratio of the solution viscosity after autoclav
`ing to that before it As stated in the experimental
`rapid cooldown cycle followed by refrigeration
`section
`of the samples at 4C was utilized after autoclaving This
`procedure minimized excessive exposure of sample solu
`tions to high temperatures
`reduction in viscosity
`concentration dependent
`occurred with CMC 7HF and ALG polymers For CMC
`3.0% solution caused an approximate
`autoclaving
`33% Alginate samples on
`reduction in viscosity by
`the other hand lost approximately 70% of their original
`Interest
`greater autoclaving effect
`viscosity signifing
`ing observations were made with respect
`to autoclaved
`MC and HPMC solutions Upon completion of the cycle
`two distinct phases were observed at each concentration
`rigid gel phase and an aqueous one Refrigeration of
`the samples at 4C for 24 hours and brief stirring at 2000
`period of 10 minutes resulted in homogenous
`r.p.m for
`
`of
`
`Vol 50 No.5
`
`SeptemberOctober 1996
`
`293
`
`

`

`120
`
`.100
`
`80
`
`60
`
`40
`
`20
`
`10
`
`-3
`h4
`4-
`
`CM
`
`IA
`
`CM
`
`CI
`
`Ct
`
`Downloaded from Journal pda.org on February 15 2017
`
`Effect of cross-linking on viscosityALG
`
`cross-linking of 50 ml of
`
`2.0
`
`ALG solution with
`
`viscosity of 1150 cP
`
`Data at 30
`
`Volume of CaCl2 added ml
`Figure 3Effect of cross-linking on viscosity ALO
`
`10
`
`Linearized Viscosity/Temperature CMC 7111
`
`2.00%
`
`1.50%
`
`0.10%
`
`30
`
`40
`
`50
`
`60
`
`70
`
`Temperature
`
`Figure 4Linearized viscosity/temperature
`
`CMC 7HF
`
`294
`
`PDA Journal of Pharmaceutical Science
`
`Technology
`
`

`

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`
`Linearized Viscosity/TemperatureALG
`
`In
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`70
`
`Temperature
`
`Figure 5Linearized viscosity/temperature
`
`ALG
`
`Linearized Viscosity/Temperature MC
`
`2.0
`
`__
`
`1.6
`
`2.29%
`
`Gelation
`
`1.2
`
`0.8
`
`0.4
`
`0.0
`
`25
`
`107%
`
`a-
`
`0.49%
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`Temperature
`Figure 6Linearized viscosity/temperature MC
`
`Vol 50 No.5
`
`SeptemberOctober 1996
`
`295
`
`

`

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`
`Effect of Autoclaving 121
`15 p.s.i 12 minutes on Sequestering Agent
`Solution Viscosity at 30
`
`CMC 7HF
`ALG
`MC A4MP
`
`120
`
`100
`
`80
`
`60
`
`40
`
`20
`
`Ct
`
`Concentration
`Figure 7Effect of autoclaving 12100 15 psi 12 minutes on sequestering agent solution viscosity at 30C
`
`solutions with viscosity values similar to those of
`controls These results suggest
`that
`for each polymer
`unique temperature at which physical
`type there exists
`of the polymer molecules commences con
`breakdown
`lowering of the molecular weight Mw for
`sistent with
`MC and HPMC 121C appears to be below this thresh
`old value
`
`the
`
`agent solutions are to be presented 10 The effects of
`type and concentration on the buffer
`sequestering
`agent
`and erosion properties of blank and Poly dl
`uptake
`Lactide-co-Glycolide PLGA microspheres containing
`devices will be described with reference to the potential
`of such devices as long term delivery systems for various
`bone growth factors
`
`Conclusions
`
`rela
`
`The polymeric materials CMC MC HPMC and
`ALG showed non-I inear viscosity/concentration
`tionships Mathematical manipulation of the data yielded
`linearized forms of such
`the slopes of
`relationships
`which were directly related to polymer molecular weights
`CMC and ALG solutions exhibited continuous
`de
`creases in viscosity with increasing temperature percent
`at higher concentra
`decreases were more pronounced
`tions MC solutions on the other hand exhibited unique
`properties of thermal gelation resulting in physical
`flow beyond
`characteristic
`structures that did not
`temperature Gelation temperatures were inversely pro
`to solution concentration Autoclaving effects
`portional
`in ALG solutions as compared
`were more pronounced
`to CMC samples in the 0.5 to 3.0% concentration range
`No significant
`long term effects on solution viscosity
`were observed with MC and HPMC however
`subsequent publication the in-vitro behavior of
`prepared from the sequestering
`freeze dried devices
`
`In
`
`References
`
`Ford Propranolol hydrochloride and aminophylline release
`from matrix tablets containing hydroxymethylcellulose inc
`Phann it 131148 1985
`Bun and
`Doelker Formulation of extended
`II hydrophilic matrices Pharin Ada lieu 55 189197 1980
`KIug Some properties of water-soluble hydroalkyl cellu
`36 491498
`Polym Sci Pan
`loses and their derivatives
`1971
`1-liementa Principles of Colloid and Surface Chemistry Marcel
`Dekker New York 1977
`BeMifler Industrial Gwns Polysaceharides
`Whistler and
`3rd Edition Academic Press San Diego
`and Their Derivatives
`1993
`
`release tablets
`
`Cellulose and
`Bikales and
`Segal High Polymers Vol
`Cellulose Derivatives Wiley-lnterscience New York 1971
`METHOCEL
`The Dow
`Technical Handbook
`Cellulose Ethers
`Chemical Company Midland MI 1988
`Vollmert Polymer Chemnistmy Springer-Verlag New York 1972
`2nd Edi
`Brandrup and
`lmmergrut Polymer Handbook
`New York 1975
`tion Wiley-Intcrscience
`DeLuca Buffer uptake
`and mass loss
`Duggirala and
`characteristics of freeze-dried cellulosic and alginate devices
`Phann Sci Tech 505 000000 1996
`
`10
`
`296
`
`PDA Journal of Pharmaceutical Science
`
`Technology
`
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`

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