Coated Interpenetrating Blend Microparticles of Chitosan and Guar

Article pubs.acs.org/IECR

Coated Interpenetrating Blend Microparticles of Chitosan and Guar Gum for Controlled Release of Isoniazid Sudha C. Angadi, Lata S. Manjeshwar,* and Tejraj M. Aminabhavi† Department of Chemistry, Karnatak University, Dharwad 580 003, India ABSTRACT: This work reports on the novel development of IPN microparticles of chitosan (CS) and guar gum (GG) that are enteric coated with NaAlg and magnesium aluminum silicate (MAS) for controlled release of isoniazid. The matrices have been characterized by X-ray diffraction (XRD) to understand drug distribution, DSC for thermal stability, and Fourier transform infrared spectroscopy (FTIR) for investigating the chemical interactions of drug with the matrices. Surface morphology was investigated by scanning electron microscopy. These microparticles exhibited encapsulation efficiencies from 47 to 58%. Equilibrium swelling as well as in vitro release trends of the formulations studied in pH 1.2 and 7.4 buffer media showed the dependence of drug release on cross-linking, blend ratio of the matrix and coating, all of which affected the release time of drug from 1 to 4 h up to 50 h. The coated microparticles have reduced the burst release in gastric media to enhance in intestinal media. well documented.20−22 In situ cross-linking of NaAlg with Ca2+ in a fluidized bed could form a coating film onto the pellets, thus facilitating its sustained-release characteristics for drugs to overcome the burst release problem.23−26 MAS is a biologically accepted natural material that has the potential to reinforce NaAlg coated films to modify the drug release from the microparticles. In the present investigation, CS and GG blends have been used to prepare IPNs in the form of microparticles and coated by dispersing with NaAlg and MAS in order to reduce the burst effect of INH in acidic stomach pH of 1.2 to facilitate the controlled release (CR) of isoniazid (INH), which is a widely used antituberculosis drug in the market. The overdosages of INH with its short half-life of 1 to 4 h, depending on the rate of metabolism, produce the signs and symptoms within 30 min to 3 h after ingestion. Nausea, vomiting, dizziness, slurring of speech, blurring of vision and visual hallucinations (including bright colors and strange designs) are among the early manifestations after the intake of the drug. Severe metabolic acidosis, acetonuria, and hyperglycemia are the typical laboratory findings, but the drug has a pronounced absorption rate from all the three sections of small intestine.24,27 Earlier,25−31 we developed several different types of devices for the CR of INH. In continuation of these studies, we report here the development of a novel type of IPN blend microparticles from CS and GG polymers by the conventional w/o emulsion method using glutaraldehyde (GA) as a crosslinking agent. These microparticles after coating with 1% of NaAlg and MAS mixture extended the release time of isoniazid to effectively reach the intestinal region by reducing its burst effect in the gastric media. The formulations of this study were fully characterized by the physicochemical techniques,

1. INTRODUCTION Among the many biopolymers available in the nature, chitosan (CS), a cationic poly-β(1→4)-D-glucopyranosamine, composed of glucosamine and a N-acetyl glucosamine units, is the second most abundant natural material that possesses mucoadhesive properties, biocompatibility, and nontoxicity.1,2 In particular, CS has the special quality of gelling in contact with anions, forming beads under very mild conditions, and is a weak base3 having a pKa value of 6.5. The functional groups of CS can be modified by combining with other hydrocolloids,4 and this has prompted active research in developing a novel type of drug delivery devices by blending CS with other biopolymers. Natural gums are other types of biodegradable and nontoxic materials that can be hydrated and swollen upon contact with aqueous media and are widely used in the preparation of dosage forms.5,6 Particularly, guar gum (GG), a galactomannan obtained from the Indian cluster bean Cyamopsis tetragonoloba (L.), is a water-soluble polysaccharide, having a linear backbone of β-1,4-linked mannose residues to which galactose residues are linked at every second mannose, forming the short sidebranches.7 Featuring different physicochemical properties, GG is a versatile biomaterial used in many biomedical applications8−10 including pharmaceutical, biomedical, cosmetic, and food industries.11,12 Interpenetrating networks (IPNs) based on carbohydrate polymers have been extensively studied in the earlier literature for drug delivery applications.13−15 Sodium alginate (NaAlg) is one such a polymer that is the sodium salt of alginic acid, which is a nontoxic polysaccharide found in brown algae. Similarly, magnesium aluminum silicate (MAS) is a mixture of natural montmorillonites and saponites having a layered structure. Each layer is constructed from the tetrahedrally coordinated silica atoms fused into an edge-shared octahedral plane of either aluminum hydroxide or magnesium hydroxide.16,17 The charges on the layers of MAS interact with anionic polymers like xanthan gum,18 carbomer,19 and NaAlg, resulting in a viscosity synergism. NaAlg is also a good film forming material by crosslinking with divalent ions, whose physical properties have been © 2013 American Chemical Society

Received: Revised: Accepted: Published: 6399

September 21, 2012 April 4, 2013 April 19, 2013 April 19, 2013 dx.doi.org/10.1021/ie302581m | Ind. Eng. Chem. Res. 2013, 52, 6399−6409

Industrial & Engineering Chemistry Research

Article

encapsulation efficiency (EE), in vitro drug release, and equilibrium swelling.

blend microparticles of CS and GG prepared as above were poured and stirred at 50 °C to allow evaporation of the solvent until the formation of a coating film of NaAlg and MAS on the surface of microparticles.31,34 2.4. Drug Content. Estimation of drug concentration from the IPN microparticles was done as per the method described elsewhere.32,35 Beads of known weight (10 mg) were ground to get the powder using an agate mortar, extracted with 50 mL of distilled water, stirred for 24 h and sonicated up to 60 min (UP 400s, Dr. Hielscher, GmBH, Germany). The solution was centrifuged (Jouan, MR23i, France) to remove polymeric debris and washed twice to extract the drug completely. The clear solution was analyzed by UV spectrophotometer (Secomam, Anthelie, France) at the fixed λmax of 263 nm. The percent drug loading and percent encapsulation efficiency (EE) were calculated as

2. EXPERIMENTAL SECTION 2.1. Materials. INH was purchased from Loba Chemicals, Mumbai, India. NaAlg (viscosity of 2000 cs) and GG were purchased from s.d. fine Chemicals, Mumbai, India. Chitosan (medium molecular weight with 75−85% deacetylation) having a viscosity (Brookfield, 15 solution in 1% acetic acid) of 200− 800 cps was purchased from Sigma Aldrich, Mumbai, India. Magnesium aluminum silicate (MAS) was purchased from Himedia Laboratory Pvt. Ltd. Mumbai, India. Analytical reagent grade glutaraldehyde (GA) aqueous solution 25% (v/v), petroleum ether, and liquid paraffin oil were all purchased from s.d. fine Chemicals, Mumbai, India. Span-80 was purchased from Loba Chemicals, Mumbai, India. The water used was of high-purity deionized and double-distilled. 2.2. Preparation of Microparticles. The IPN blend microparticles were prepared using different ratios of CS and GG by varying the INH concentration as well as the GA as the cross-linking agent by an emulsion cross-linking method (Table 1).29,32 In this protocol, 2% (w/v) of CS solution was prepared

%Drug loading =

weight of drug in microparticles 100 weight of microparticles

%Encapsulation efficiency =

(1)

actual drug loading 100 theoretical drug loading (2)

Table 1. Formulation Parameters of IPN Blend Microparticles formulation codesa

CS (% w/w)

GG (% w/w)

F1 F2 F3 F4 F5 F6 F7 F8

100 90 80 70 80 80 80 80

10 20 30 20 20 20 20

INH (% w/w)

GA (% w/w)

5 5 5 5 5 10

5 5 5 5 10 5 5 5

5

2.5. Swelling Experiments. Equilibrium swelling of IPN microparticles was determined gravimetrically by measuring the extent of swelling in double distilled water. To ensure attainment of complete equilibrium, the samples were allowed to swell for 24 h and excess surface-adhered liquid droplets were removed by blotting with a soft tissue paper. The swollen particles were weighed to an accuracy of ±0.01 mg on an electronic microbalance (Mettler, model AT120, Greifensee, Switzerland). The microparticles were then dried in an oven at 60 °C for 5 h until no further weight gain of the dried samples was observed and percent equilibrium swelling was calculated as

a

In these formulations, F8 formulaion is uncoated and all other formulations are coated with 1% dispersion of NaAlg and MAS.

%Swelling =

Ws − Wd 100 Wd

(3)

where Ws and Wd are, respectively, the weights of swollen and dry microparticles. Experiments performed in triplicate were reproducible within ±3% standard errors, and the average values were considered in data analysis and graphical display. The percent swelling results are included in Table 2. 2.6. In Vitro Drug Release Experiments. Drug release from the coated IPN microparticles containing different IPN

by dissolving the CS in 2% (w/v) acetic acid in double-distilled deionized water and stirring the solution continuously until a homogeneous solution was attained. GG was then dispersed in this CS solution and stirred overnight to obtain a homogeneous solution. INH was then dissolved in the above polymer blend solution, to which a light liquid paraffin (100 g, w/w) containing 2% (w/w) Span-80 was added slowly under constant stirring at 400 rpm speed for about 15 min. To this w/o emulsion, GA in 0.5 mL of 1 N HCl was added under continuous stirring for 4 h. The hardened microparticles were separated by filtration and washed repeatedly with n-hexane to remove light liquid paraffin oil followed by washing with 0.1 M glycine solution and water to remove the unreacted GA. The Brady’s test was found to be negative,30,33 suggesting the absence of unreacted GA and safe usage of these formulations for in vivo applications. 2.3. Coating of Microparticles. NaAlg (1%) was dispersed in distilled water using a homogenizer for 5 min, whereas MAS was prehydrated with hot water for 15 min. The MAS dispersion was mixed (in the ratio of 4:1 of NaAlg:MAS) into a NaAlg solution using the homogenizer for 5 min, which was then adjusted to the volume by adding 50 mL of distilled water. NaAlg−MAS dispersion was kept for full hydration at the ambient temperature (25 °C) for overnight. To this dispersion,

Table 2. Results of % Swelling, % Encapsulation Efficiency (EE), n and k Parameters of eq 4, along with the Correlation Coefficients (r2) swelling (%)

equation 4

formulation codesa

pH 1.2

pH 7.4

EE (%)

n

k

r2

F1 F2 F3 F4 F5 F6 F8

321 280 275 500 210 301 560

720 582 545 950 450 700 645

58 54 51 49 55 47 53

0.56 0.614 0.65 0.64 0.637 0.571 0.349

0.108 0.0944 0.08 0.094 0.075 0.095 0.258

0.93 0.95 0.95 0.95 0.95 0.94 0.97

a

In the formulations, F8 formulation is uncoated and all other formulations are coated with 1% dispersion of NaAlg and MAS.

6400

dx.doi.org/10.1021/ie302581m | Ind. Eng. Chem. Res. 2013, 52, 6399−6409


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Figure 1. FTIR of (A) chitosan, (B) guar gum, and (C) placebo microparticles.

matrix. FTIR spectra of CS, GG, placebo IPN microparticles, drug-loaded microparticles, and pristine INH were all taken by grinding each sample separately with KBr and making pellets under a hydraulic pressure of 600 kg/cm2. Spectral scanning was done in the range 4000−500 cm−1. 3.2. Differential Scanning Calorimetry (DSC). Differential scanning calorimetry (DSC-Q20, TA InstrumentsWaters, USA) was performed on placebo IPN microparticles, pristine INH, and INH-loaded microparticles by heating the samples from 25° to 400 °C at the heating rate of 10 °C/min in a nitrogen atmosphere. 3.3. X-ray Diffraction (XRD). The crystallinity of INH after encapsulation was evaluated by XRD recorded for IPN microparticles with INH and without INH as well as pristine INH using the X-ray diffractometer (x-Pert, Philips, UK). Scanning was done up to 2θ of 80°. 3.4. Scanning Electron Microscopy (SEM). SEM images were taken using a JEOL model JSM-840A, Japan, instrument

blend composition, extent of cross-linking, and enteric coating were investigated in pH 1.2 for the initial 2 h, followed by the release in phosphate buffer of pH 7.4 until completion of the dissolution process. These experiments were performed in triplicate in a tablet dissolution tester (Lab India, Disotest, Mumbai, India) equipped with eight baskets (glass jars) at the stirring speed of 100 rpm. A weighed quantity of each sample was placed in 500 mL of dissolution medium maintained at 37 °C. At regular intervals of time, sample aliquots were withdrawn and analyzed using a UV spectrophotometer (Secomam, Anthelie, France) at the fixed λmax of 263 nm.

3. CHARACTERIZATION 3.1. Fourier Transform Infrared (FTIR) Spectral Measurements. FTIR spectra were obtained using Nicolet (model Impact 410, Milwaukee, WI, USA) instrument to confirm the formation of full IPN structure as well as to confirm any chemical interactions of INH with the polymer 6401



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Scheme 1. Formation of IPN by CS and GG in the Presence of GA as the Crosslinking Agent

bending in GG is assigned to the absorption at 1436 cm−1 and the one appearing at 1384 cm−1 is attributed to CH bending, but the bending vibration of the OH group is observed at 1280 cm−1. In case of the placebo microspheres, all the characteristic bands of both CS and GG are observed in addition to a new band appearing at 1650 cm−1 due to C−N stretching vibration of the imine group of Schiff base formed due to the reaction of the aldehydic functional group of GA and the amino group of CS. The band at 1015 cm−1 is due to the presence of an acetal group due to the reaction of GA with hydroxyl groups of GG. Thus, FTIR data confirm the successful cross-linking of both CS and GG to form a full IPN network structure in the presence of GA and the proposed reaction is displayed in Scheme 1. Figure 2 shows the FTIR spectra of the INH drug, placebo IPN microparticles, and drug-loaded microparticles. For pristine INH, a band at 3300 cm−1 is due to N−H stretching vibrations, while that at 3180 cm−1 is for NH2 stretching vibrations. The bands at 3061, 3013, 2949, and 2854 cm−1 are

(STIC, Cochin University, Kochi, India). The microparticles were sputtered with gold to make them conducting and placed on a copper stub. The thickness of the gold layer accomplished by gold sputtering was about 10 nm.

4. RESULTS AND DISCUSSION 4.1. Fourier Transform Infrared Spectral Study. FTIR spectra (see Figure 1A) of CS, GG, and placebo blend IPN microparticles were taken to confirm the formation of the full IPN blend structure. In the case of CS, a broad band at 3427 cm−1 is attributed to O−H stretching vibrations, while the bands at 2922 and 2810 cm−1 represent the presence of C−H aliphatic stretching vibrations. Three bands appearing at 1651, 1590, and 1379 cm−1 are assigned to amide-I, amide-II, and amide-III, respectively. Chitosan is characterized by its saccharide structure for which the bands appear at 899 cm−1 and 1154 cm−1. In the case of GG, the presence of a very strong and broad absorption band at 3407 cm−1 is assigned to OH stretching while a reasonably sharp absorption band at 2926 cm−1 is assigned to −CH stretching vibrations. The −CH2 6402



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Figure 2. FTIR of (A) INH drug, (B) placebo microparticles, and (C) drug-loaded microparticles.

observed at 172 °C, indicating that the melting point of INH disappeared in the INH-loaded microparticles because of the change in its physical state from its original crystalline state to the amorphous state.26,28,29,31 4.3. X-ray Diffraction (XRD). X-ray diffractograms of INHloaded microparticles, placebo microparticles and pristine INH drug presented in Figure 4 have been used for investigating drug’s polymorphism after its encapsulation. The XRD curves of INH show intense peaks at 2θ of 14◦, 16◦ and 20◦ that are characteristics of its crystalline nature, but these peaks have disappeared in the INH-loaded microspheres, but only the peaks observed in placebo matrix are seen. Typically, the peak depends on crystal size, but in the present study, for the INHloaded formulations, the characteristic peaks of INH have merged with the polymer blend matrix, thereby suggesting that INH is in the amorphous state in IPN matrix, though it is difficult to investigate drug’s crystallinity at the detection limit of the crystal size in case of drug-loaded microparticles. XRD results further suggest that drug is molecularly dispersed in the IPN blend matrix.28,31 4.4. Scanning Electron Microscopy (SEM). SEM images of the group of IPN microparticles and single microparticles taken at 500× and 2000× magnifications indicate spherical

attributed to aromatic and aliphatic C−H stretching vibrations, while the one appearing at 1666 cm−1 is assigned to carbonyl of amide group stretching vibrations. Another band at 1221 cm−1 is due to C−N stretching vibrations, while a band at 1556 cm−1 is attributed to N−H bending vibrations. Characteristic peaks of INH are also present in the FTIR spectrum of drug-loaded IPN microparticles with some broadening and reduction in intensity, indicating the absence of chemical interactions between INH, the polymer matrix, and counterions after the formation of the IPN structure. 4.2. Differential Scanning Calorimetry (DSC). DSC was used to study the thermal transitions during the heating cycles of the samples under inert atmosphere. DSC thermograms of placebo IPN microparticles, pristine INH, and INH-loaded microparticles displayed in Figure 3, show a sharp peak at 172 °C for pure INH at its melting temperature.33,36 For the placebo beads, the peak observed at 105 °C is due to the endothermic transition as a result of loss of moisture from the CS/GG blend IPN matrix. The two peaks appearing at 252 and 281 °C are due to the exothermic transition of IPN blend matrix as a result of the decomposition of GG and CS polymers. The IPN-blend microparticles have also shown similar patterns as that of the placebo, but no peaks are 6403



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Figure 3. DSC thermograms of placebo microparticles, INH drug, and drug-loaded microparticles.

4.6. Equilibrium Swelling. Drug release from the IPN matrix is influenced by swelling of the cross-linked microparticles in buffer media of pH 1.2 and 7.4. The coated microparticles were swollen to a lesser extent in pH 1.2 than the uncoated microparticles because of intact coating onto their surfaces as a result of the formation of a thin film of NaAlg and MAS (not assessable by the SEM experiments). The NaAlg forms insoluble alginic acid in acidic media, but the uncoated microparticles (F8) are highly swollen in acidic pH of 1.2, as CS has a net positive charge in acidic pH, which results in higher swelling. In phosphate buffer solution of pH 7.4, the coated microparticles are more swollen than the uncoated microparticles (F8), since in alkaline media, NaAlg of the coating mixture ionizes, thereby allowing the penetration of more drug particles into the IPN blend matrix compared to uncoated microparticles. The percent equilibrium swelling results of the cross-linked microparticles presented in Table 2 indicate that as the amount of GA in the coated and uncoated matrices is increased from 5 to 10 mL, equilibrium swelling decreased significantly due to a reduction in matrix swelling at higher cross-link density. Thus, formulation F2 containing 10 wt % GG exhibits a lower swelling than F1 due to the rigid nature of the blend IPN; a

shapes (see Figure 5A−D). However, both the coated and uncoated microparticles have the spherical shapes, and the coated microparticles have more rough surfaces than the uncoated ones. Compared to Figure 5B and 5D, the surface of the single microparticle of F8 (uncoated) formulation is smooth, whereas that of F2 (coated) formulation has the wrinkled rough surfaces, due to the presence of hydrophilic NaAlg containing MAS particles as the coating material.28,31 From the SEM images, one can visualize that the approximate size of the microparticles is around 50 μm without considering the thickness of the coating layer, which we could not assess within the limits of the experimental observations to acquire cross sectional images of the microparticles. 4.5. Encapsulation Efficiency. The percent encapsulation efficiency (EE) of INH in the microparticles ranged between 47 and 58%, depending upon the percentage of components of the blend in the matrix. By increasing the GG concentration, EE values slightly decreased. For instance, the F4 (30% w/w GG) formulation has a smaller EE value of 49 than do F3 (20% w/w GG) and F2 (10% w/w GG) formulations, which exhibited % EE of 51 and 54, respectively; this could be due to the rigid nature of the IPN matrix at a higher concentration of GG. 6404



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Figure 4. XRD spectra of drug-loaded microparticles, placebo microparticles and pristine INH drug.

and these also extended the release time of INH up to 30 h. In that study, the coating of IPN blend microspheres with stearic acid helped to reduce the burst effect in gastric media and the drug was released in intestinal media. In another study,30 Sullad et al. developed a novel pH-sensitive hydrogel blend of poly(vinyl alcohol) with acrylic acid-grafted-GG via a water-inoil (w/o) emulsification method for investigating the CR of INH, which increased the release time of INH up to only 8 h. The paper by Angadi et al.31 addressed the GA cross-linked IPN microspheres prepared from the blends of CS and hydroxyethyl cellulose, which extended the release time of INH up to 16 h by releasing 75% of the drug. In continuation of this work, the present study was aimed to develop a novel type of CS/GG full IPN blend microparticles by the w/o emulsion method using GA as a cross-linking agent.

similar trend is observed for F3 (20 wt % of GG). In the case of F3 (20 wt % of GG), lower swelling is observed than in F2 (10 wt % GG), since the IPN matrix absorbs a lesser amount of aqueous media. Conversely, F4 (contains 30 wt % GG) exhibits higher swelling due to the highly hydrophilic nature of GG compared to CS. Even though there are many cross-linking points in the IPN matrix in the case of F4, the hydrophilicity of GG dominates, thereby leading to a higher swelling. 4.7. In Vitro Release Study. In the earlier literature,28 sodium alginate microspheres were prepared by a modified emulsification method to investigate the CR of INH in pH 7.4 media, which was extended up to 30 h. In our own published report,29 pH-sensitive stearic acid-coated IPN blend microspheres of CS and gelatin were prepared by an emulsion crosslinking method in the presence of GA as a cross-linking agent, 6405



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Figure 5. SEM figures of (A) group of microparticles of F8 i.e., uncoated formulation, (B) single microparticle of F8 formulation, (C) group of microparticles of F2 i.e., coated formulation, and (D) single microparticle of F2 formulation.

of INH is higher in pH 7.4 than in pH 1.2 media for all the formulations, and, hence, the present formulations can be conveniently used through the peroral route in tuberculosis patients. 4.7.2. Effect of Extent of Cross-Linking. As displayed in Figure 6B, formulation F5 has a lower release of INH than that of F3, but F5, which contains 10 mL of GA is highly crosslinked and hence, is more rigid compared to F3, which contains only 5 mL of GA. The F5 released nearly 29% of INH in about 46 h, whereas F3 released 35% in 50 h. 4.7.3. Effect of Coating. The 1% coating mixture (NaAlg and MAS in the ratio of 4:1) was used to coat the microparticles in all the formulations. Figure 6C shows higher INH release in the case of F8 compared to F2. About 35% of INH was released in 50 h from the 1% coated F2 formulation, whereas nearly 60% of INH was released from the uncoated F8 formulation in 30 h. This is due to the effect of F8, which is a covalently cross-linked blend IPN. F8 has shown the CR of INH up to 30 h, as the INH are not coated with the film of NaAlg and MAS which might typically act as a barrier for diffusion and could control the release of INH up to 30 h and later declining. The burst release in gastric media in pH 1.2 from the uncoated F8 formulation was reduced by the coating and thereby its release was controlled in pH 7.4 media. Since it is necessary to develop the CR formulations of INH for delivering in the small intestine by reducing its burst effect in gastric medium, the present formulations may be suitable as oral dosage formulations.

The microparticles were coated with 1% of NaAlg and MAS mixture for extending the release time of INH in the intestinal region up to 50 h by reducing its burst effect in the gastric media. The in vitro release data are discussed in terms of the effect of polymer blend composition, extent of cross-linking as well as enteric coating in pH 1.2 for the initial 2 h, followed by release in phosphate buffer of pH 7.4 until the completion of the dissolution process. The percent average cumulative release versus time plots of the triplicate data for all the formulations are displayed in Figure 6A−C to examine the effect of polymer blend composition, extent of cross-linking, and enteric coating. The error bars indicate the maximum of ±3% standard deviations from the average values that were used to construct smoothened release curves. 4.7.1. Effect of Polymer Blend Composition. As displayed in Figure 6A, the F3 has a lesser release rate than F2, and F2 has a smaller release rate than F1. Since F3 has a higher content of GG (20% w/w) and higher number of cross-linking points, it aquires a more denser matrix than F2 or F1 that contained 10% and 0% w/w of GG, respectively. On the other hand, F4 releases a higher amount of drug compared to F3 and F2 even though it contains 30% w/w of GG. The reason may be that F4 contains 30% w/w of GG, which is more hydrophilic than CS and hence, its swelling capacity is also higher than F2 and F3, thereby releasing a large amount of drug compared to F2 and F3. In all the formulations, in vitro release profiles follow identical patterns and the release of INH is extended up to 50 h, suggesting its utility in developing oral dosage formulations of INH to control tuberculosis. Notice that the percent release 6406



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Figure 6. (A) Effect of polymer blend composition, (B) effect of cross-linking agent, and (C) effect of enteric coating on the in vitro release of INH for the IPN blend microparticles.

5. EMPIRICAL CORRELATION To understand the molecular transport of INH through the polymeric IPN matrix, cumulative release data have been fitted to the empirical equation:34,37 M t /M∞ = kt n

the INH release mechanism. Using the least-squares procedure at the 95% confidence limit, we have estimated the values of n and k for all the eight formulations, and these data along with estimated correlation coefficients are included in Table 2. For the values of n = 0.5, drug diffuses and releases out of the polymer matrix following a Fickian diffusion. For n > 0.5, anomalous or non-Fickian transport operates, but if n = 1, nonFickian or more commonly called Case II transport is operative. For n > 1, non-Fickian Super Case II is operative. If the values

(4)

where Mt/M∞ represents the fractional release of INH at time, t; k is a characteristic interaction parameter of the INH− polymer system, and n is an empirical parameter characterizing 6407



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of n vary between 0.5 and 1.0, then transport is classified as an anomalous type.35,38 The values of n and k are also dependent on polymer blend composition, concentration of cross-linking agent (GA) and enteric coating. The values of k decrease with increasing concentration of GG initially up to 20% wt of GG, but when the concentration of GG reached 30% wt as in F4, the k value increased. The n values for coated IPN microparticles are higher than those found for the uncoated formulation (F8) due to the formation of an outer barrier layer, thereby leading to the CR of INH. The values of n are higher for IPN microparticles due to the formation of a rigid network matrix, and are also higher for those that contain higher concentration of GG. In the present work, n values for all the coated IPN microparticles range from 0.57 to 0.65, indicating the release of INH was of an anomalous transport mechanism.

6. CONCLUSIONS In this study, a novel type of IPN blend systems of chitosan and guar gum that are enteric coated with sodium alginate and magnesium aluminum silicate have been prepared by a w/o emulsion method. The blend systems have been cross-linked with GA to overcome the burst release of INH in gastric media and thereby release INH in small intestine. Although the method of preparation of microparticles may be difficult for scale up, as indicated before, several authors have been using this process to achieve the CR patterns. The IPN microparticles of this study have been successfully used to extend the release time of INH to nearly 50 h from its original plasma half-life of 1−4 h. The coating was effective to reduce the burst effect in gastric medium for achieving the release in intestinal media. The release of water-soluble INH was described by an empirical equation, the analysis of which suggested the anomalous release of INH through IPN microparticles.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel.: +91 836 2215286. Fax: +91 836 2771275. Notes

The authors declare no competing financial interest. † Emeritus Fellow, All India Council for Technical Education, New Delhi, India. SET’s College of Pharmacy, Dharwad 580 002, India.

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ACKNOWLEDGMENTS

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REFERENCES

Mrs Sudha C. Angadi and Prof. L. S. Manjeshwar thank the University Grants Commission (UGC), New Delhi, India (KU/SCH/UGC/RFSMS/2008-09) for a fellowship to Mrs. S. C. Angadi. Professor T. M. Aminabhavi thanks the All India Council for Technical Education [F. No. 1-51/RIFD/ EF4(13)], New Delhi, India, for an Emeritus Fellowship.

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Coated Interpenetrating Blend Microparticles of Chitosan and Guar

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