alginic acid sodium salt ( al ) ( viscosity : 20.0 - 40.0 cp in 1% water , mw : 7334 ) , diclofenac sodium salt and cellulose acetate dialysis tube ( mw : 7014 ) was procure from sigma louis , usa . calcium chloride , hydrochloric acid , potassium chloride , potassium dihydrogen orthophosphate , sodium chloride and sodium hydroxide were purchased from s. d. fine chemicals , mumbai , india . mmt rich bentonite clay was collected from akli mines , barmer district , rajasthan , india . de - ionized water was obtained from milli - q gradient a10 water purification system . to obtain mmt in na - form , the raw bentonite ( 300 g ) was dispersed in 3 l solution of 0.1 m nacl and stirred for 12 h. finally , the slurry was centrifuged and washed with de - ionized water until the supernatant is free from chloride ion as tested by agno3 solution . the raw bentonite was purified by sedimentation technique as described earlier . according to the stoke 's law of sedimentation , the purified clay was obtained by dispersing 150 g of raw bentonite in 10 l of de - ionized water and clay particles of < 2 m size were collected from 15 cm height after 10 h at 30. the desired particles thus obtained was dried at 90 - 100 , ground and sieved through 200 mesh sieve ( astm ) . the cation exchange capacity ( cec ) of clay was measured by the standard ammonium acetate method at ph 7 and was found to be 91 meq/100 g of mmt on dry basis ( dried at 110 ) . the suitable amount of al dissolved in 25 ml of milli - q water with stirred till complete homogeneous solution was obtained . the desired quantity of ds was added into al and solution was kept at 35 into shaking water bath ( 100 rpm ) for 3 h. to this mmt ( 200 mesh size ) powder was added and the emulsion was stirred overnight at 40. this emulsion was dropped using a peristaltic pump ( master flex l / s 7518 - 00 , cole - parmer , usa ) with helps of a 20-guage hypodermic needle fitted with a rubber tubing ( falling distance 2 cm , pumping rate 1.5 ml / min ) into 200 ml of 100 mm calcium chloride solution , gently agitated with a magnetic stirrer . the formed beads were allowed to stand in solution for 20 min for curing , then collected by filtration and were washed thrice with milli - q water . the mean diameter of the beads was determined by measuring 50 beads , using micrometer screw ( mitutoyo , japan ) . the formulation code , content for the formulation , encapsulation efficiency and bead diameter are given in table 1 . formulation codes and different characteristic of ds - mmt - al composites the ds content in beads was determined by a digestion method . the ds - loaded beads ( 900 mg ) were smashed and incubated in 50 ml of phosphate buffer ( ph 7.4 ) . the resulting suspension was stirred to promote swelling and break - up of the cross linked structure to facilitate liberation of ds from ds - mmt - al composite into buffer media . the ds was quantified by centrifuging the suspension at 10,000 rpm for 30 min ( kubota-6500 , kubota corporation , japan ) and ds was determined from the clear supernatant by uv - spectrophotometer at max = 276 nm . these studies were performed in triplicate for each sample and the average values were used in data analysis . the ds encapsulation efficiency , ee ( % ) was determined by using equation ; ee = ( aq / tq)100 , where aq is the actual quantity of ds present in ds - mmt - al composite beads and tq is 100 % theoretical quantity of ds present in ds - mmt - al composite beads . the intercalation of ds and al into interlayer of mmt was examined by powder x - ray diffraction ( p - xrd ) analysis . p - xrd was carried out on a phillips powder diffractometer x pert mpd using pw3123/00 curved cu - filtered cu - ka ( =1.54056  ) radiation with slow scan of 0.3 deg / s in 2 range of 2 - 10. fourier transform infrared spectra ( ft - ir ) were measured with perkin - elmer , gx - ftir as kbr pellet over the wavelength range 4000400 cm . thermogravimetric analysis was carried out within 30 - 800 at the rate 10/min in the nitrogen flow of 60 ml / min using mettler - toledo , tga / sdta 851e . uv / vis absorbance of ds solutions was measured at a characteristic max = 276 nm by uv / vis spectrophotometer ( cary 500 , varian ) equipped with a quartz cell having a path length of 1 cm . the surface morphology of composite was observed under scanning electron microscope ( sem ) , leo-1430vp , uk . buffer solution of ph 7.4 ( simulated intestinal fluid ) was prepared by mixing 500 ml of 0.1 m kh2po4 and 391 ml of 0.1 m naoh . in vitro release studies were performed using usp six stage dissolution rate test apparatus ( thermonik , campbell electronics , mumbai , india ) by using dialysis bag technique . the dialysis sac was equilibrated with the dissolution medium for few hours prior to experiments . three hundred milligrams of ds loaded composite beads suspended in 5 ml of dissolution medium was taken in a dialysis bag and sealed at both ends . dialysis bag was dipped into 500 ml of dissolution medium , stirred at 100 rpm at 371. at time intervals of 30 minutes , 5 ml of the dissolution medium was taken and the ds concentration was determined by uv / vis spectrophotometer at max = 276 nm . to obtain mmt in na - form , mmt slurry was treated with nacl solution . the raw bentonite ( 300 g ) was dispersed in 3 l solution of 0.1 m nacl and stirred for 12 h. finally , the slurry was centrifuged and washed with de - ionized water until the supernatant is free from chloride ion as tested by agno3 solution . the raw bentonite was purified by sedimentation technique as described earlier . according to the stoke 's law of sedimentation , the purified clay was obtained by dispersing 150 g of raw bentonite in 10 l of de - ionized water and clay particles of < 2 m size were collected from 15 cm height after 10 h at 30. the desired particles thus obtained was dried at 90 - 100 , ground and sieved through 200 mesh sieve ( astm ) . the cation exchange capacity ( cec ) of clay was measured by the standard ammonium acetate method at ph 7 and was found to be 91 meq/100 g of mmt on dry basis ( dried at 110 ) . the suitable amount of al dissolved in 25 ml of milli - q water with stirred till complete homogeneous solution was obtained . the desired quantity of ds was added into al and solution was kept at 35 into shaking water bath ( 100 rpm ) for 3 h. to this mmt ( 200 mesh size ) powder was added and the emulsion was stirred overnight at 40. this emulsion was dropped using a peristaltic pump ( master flex l / s 7518 - 00 , cole - parmer , usa ) with helps of a 20-guage hypodermic needle fitted with a rubber tubing ( falling distance 2 cm , pumping rate 1.5 ml / min ) into 200 ml of 100 mm calcium chloride solution , gently agitated with a magnetic stirrer . the formed beads were allowed to stand in solution for 20 min for curing , then collected by filtration and were washed thrice with milli - q water . the mean diameter of the beads was determined by measuring 50 beads , using micrometer screw ( mitutoyo , japan ) . the formulation code , content for the formulation , encapsulation efficiency and bead diameter are given in table 1 . the ds content in beads was determined by a digestion method . the ds - loaded beads ( 900 mg ) the resulting suspension was stirred to promote swelling and break - up of the cross linked structure to facilitate liberation of ds from ds - mmt - al composite into buffer media . the ds was quantified by centrifuging the suspension at 10,000 rpm for 30 min ( kubota-6500 , kubota corporation , japan ) and ds was determined from the clear supernatant by uv - spectrophotometer at max = 276 nm . these studies were performed in triplicate for each sample and the average values were used in data analysis . the ds encapsulation efficiency , ee ( % ) was determined by using equation ; ee = ( aq / tq)100 , where aq is the actual quantity of ds present in ds - mmt - al composite beads and tq is 100 % theoretical quantity of ds present in ds - mmt - al composite beads . the intercalation of ds and al into interlayer of mmt was examined by powder x - ray diffraction ( p - xrd ) analysis . p - xrd was carried out on a phillips powder diffractometer x pert mpd using pw3123/00 curved cu - filtered cu - ka ( =1.54056  ) radiation with slow scan of 0.3 deg / s in 2 range of 2 - 10. fourier transform infrared spectra ( ft - ir ) were measured with perkin - elmer , gx - ftir as kbr pellet over the wavelength range 4000400 cm . thermogravimetric analysis was carried out within 30 - 800 at the rate 10/min in the nitrogen flow of 60 ml / min using mettler - toledo , tga / sdta 851e . uv / vis absorbance of ds solutions was measured at a characteristic max = 276 nm by uv / vis spectrophotometer ( cary 500 , varian ) equipped with a quartz cell having a path length of 1 cm . the surface morphology of composite was observed under scanning electron microscope ( sem ) , leo-1430vp , uk . buffer solution of ph 7.4 ( simulated intestinal fluid ) was prepared by mixing 500 ml of 0.1 m kh2po4 and 391 ml of 0.1 m naoh . in vitro release studies were performed using usp six stage dissolution rate test apparatus ( thermonik , campbell electronics , mumbai , india ) by using dialysis bag technique . the dialysis sac was equilibrated with the dissolution medium for few hours prior to experiments . three hundred milligrams of ds loaded composite beads suspended in 5 ml of dissolution medium was taken in a dialysis bag and sealed at both ends . dialysis bag was dipped into 500 ml of dissolution medium , stirred at 100 rpm at 371. at time intervals of 30 minutes , 5 ml of the dissolution medium was taken and the ds concentration was determined by uv / vis spectrophotometer at max = 276 nm . basal spacing   of mmt and ds - mmt - al was found to be 1.18 nm ( 2=7.4 ) and 1.5 nm ( 2=5.9 ) , respectively ( fig . the peak shifting from higher diffraction angle to lower diffraction angle can be attributed to the increase in the basal spacing during the formation of clay - alginate hybrid , indicating successful intercalation of ds and al into the interlayer of mmt . p - xrd pattern p - xrd pattern of mmt and ds - mmt - al ft - ir spectra of ds , mmt , al and ds - mmt - al composite beads are shown in fig . the virgin alginate showed asymmetric and symmetric stretching vibrations at 1617 and 1417 cm due to carboxyl anions , and at 1030 cm due to cyclic ether bridge . mmt shows a broad band centered near 3400 cm due to -oh stretching band for interlayer adsorbed water . the bands at 3620 and 3698 cm are due to -oh band stretch for al oh and si  oh . the shoulders and broadness of the structural oh band are mainly due to contributions from several structural oh groups present in mmt . the overlaid absorption peaks in the region of 1640 cm is attributed to oh bending mode of adsorbed water . ( out - of - plane ) and the peak at 1035 cm is attributed to si - o stretching ( in - plane ) vibration for mmt . the ir peaks at 915 , 875 and 836 cm are attributed to alaloh , alfeoh and almgoh bending vibrations , respectively . ft - ir spectra of ds showed n - h , c = o , c - cl stretching vibration at 3398 , 1675 and 1335 cm , respectively . in the ftir spectra of ds - al beads , the asymmetrical band of carboxylate ion was shifted from 1617 cm to 1635 cm whereas carboxyl group of ds was shifted from 1575 cm to 1454 cm . the hydroxyl band of sodium al was shifted from 3493 cm to 3438 cm due the interaction between ds and al . ft - ir spectra ft - ir spectra of ( a ) ds ( b ) al ( c ) ds - al ( d ) mmt ( e ) ds - mmt - al composites and ( f ) mmt - al pongjanyakul and puttipipatkhachorn explained the shift in the ir band of coo while al interacted with mmt . incorporation of mmt into al caused a shift to a higher wave number and decreased the intensity of coo stretching peaks of al . the oh stretching peak of the silanol group ( sioh ) at 3698 cm disappeared in the spectra of mmt - al composites , and the oh stretching peak of al shifted to a higher wave number . this may be due to the intermolecular hydrogen bonding between silanol groups on the surface of mmt and the hydroxyl or carboxyl groups of al . with these results , the bond formation of al and mmt in the dry state intermolecular hydrogen bonding and electrostatic forces between al and mmt were confirmed by ftir studies . the possible structural model of the mmt - al composites the al molecules possessed a negative charge due to ionization of the carboxyl groups and could form intermolecular hydrogen bonding ( fig . it can be seen that al and mmt formed electrostatic and intermolecular hydrogen bonds , which brought about numerous points of contact to create a three dimensional network . al chains could also serve as a bridge between neighboring silicate layers when a higher content of mmt was incorporated . possible structure model possible structure model of ( a ) al gel ( b ) mmt dispersion and ( c ) mmt - al composites the thermogravimetric analysis ( fig . 4 ) of mmt shows two distinct steps , the first one is due to the loss of free water at < 150 and the second weight loss at 550700 due to the loss of structural oh group from mmt . al , mmt - al and the degradation of ds from ds - mmt - al was observed over a range of 200 - 500 while al moiety was degraded 550700. the degradation of alginate in mmt - al was not prominent , may be due to the reinforcement of cross linked ca - alginate by mmt , and therein increases the thermal stability of mmt - al composite . thermogravometric analysis thermogravometric analysis of ( a ) mmt ( b ) mmt - al ( c ) ds - mmtal and ( d ) al the surface and cross - sectional morphology of ds - al beads and ds - mmt - al composite beads are depicted in sem images ( fig . ds - al beads displayed an unstable structure while ds - mmt - al composite beads are stable . ds - mmt - al composite beads demonstrated a more rigid and flat surface as compared to ds - al beads , whose surface was convoluted . the rigidity imparted in ds - mmt - al composite beads may be due to the reinforcement effect of mmt in the al matrix . the sem image of ds - al and ds - mmt - al composite beads revealed their porous structure ( fig 5 b d ) . sem images sem images of ( a ) ds - al , scale : 100 m and ( b ) cross - section of ds - al , scale : 30 m ; ( c ) ds - mmt - al composite bead , scale 100 m and ( d ) cross - section of ds - mmt - al composite bead , scale 30 m in vitro release profiles of ds from ds - alginate ( formulation ads - al ) and ds - mmt - alginate composite beads ( ds - mmt - al - i to iv ) in simulated gastric fluid and simulated intestinal fluid was done at 371. only 1 - 2% ds release was observer in simulated gastric fluid ( ph 1.2 ) after 8 h. the release profile in simulated intestinal fluid showed ( fig . 6 ) 9.8% and 17.7% ds released from ds - al composite in 1 h , and 4 h , respectively , thereafter the release of ds remained constant up to 8 h. while , in the case of ds - mmt - al - i to ds - mmt - al - iv formulation , the average release of ds was ~63% within 5 - 8 h depending upon the content of mmt in different formulations . the study reveals that the plateau for the release of ds was reached more rapidly in ds - al as compared to the ds - mmt - al - i to ds - mmt - al - iv . there was an increase in the release rate of ds from ds - mmt - al composite beads with an increase in the mmt loading . it may be due to the weak interaction between the ds and mmt as both ds and mmt are negatively charged . the ds encapsulation efficiency was lower in the case of virgin al beads as compare to ds - mmt - al composite beads . the ds encapsulation efficiency increases with the increase in the mmt content in ds - mmt - al composite beads ( table 1 ) . a possible explanation to this behavior is the presence of more hydroxyl groups on the surface of mmt facilitating hydrogen bonding with ds . a release of ds from ds - al and ds - mmt - al beads in 8 h was found to be 17.7% ( ds - al ) and 48.80% , 55.52% , 59.41% and 62.49% from ds - mmt - al - i to ds - mmt - al - iv , respectively . in vitrorelease profile in vitrorelease of ds from ( a ) ds - al ( b ) ds - mmt - al - i ( c ) dsmmt - al - ii ( d ) ds - mmt - al - iii ( e ) ds - mmt - al - iv composite beads ds - mmt - al composite beads were successfully synthesized by gelation methodology . the amount of ds released from ds - al and ds - mmt - al composite bead is 17.7% and 62.49% , respectively in simulated intestinal fluid . mmt content in ds - mmt - al composite beads regulate the release rate of ds . this approach can be effectively use for the oral administration of ds to enhance its therapeutic efficacy .
diclofenac sodium and alginate was intercalated into montmorillonite to form uniform sized beads by gelation method . 
 the structure and surface morphology of the synthesized composite beads were characterized by powdered x - ray diffraction , fourier transform infrared spectroscopy , thermo gravimetric analysis and scanning electron microscopy . 
 diclofenac release kinetics of the composite in simulated intestinal fluid medium ( ph 7.4 ) and effect of montmorillonite content on the in vitro release of diclofenac from diclofenac - montmorillonite - alginate composites bead was investigated by uv / vis spectrophotometer . 
 diclofenac encapsulation efficiency in the montmorillonite - alginate composites bead increases with an increase in the montmorillonite content . 
 the control release of diclofenac from diclofenac - montmorillonite - alginate composites beads was observed to be better as compared to diclofenac - alginate beads .