Int J App Pharm, Vol 10, Issue 5, 2018, 261269Original Article
RIZATRIPTAN BENZOATE LOADED NATURAL POLYSACCHARIDE BASED MICROSPHERES FOR NASAL DRUG DELIVERY SYSTEM
MEENAKSHI SHARMA^{*}, NITIN SHARMA, ANJANA SHARMA
Department of Pharmacy, Meerut Institute of Engineering and Technology, NH58, Baghpat Crossing, Partapur Bypass Road, Meerut, 250005, India
Email: meenakshisharma500@gmail.com
Received: 10 Jun 2018, Revised and Accepted: 14 Aug 2018
ABSTRACT
Objective: The objective of this research was to formulate and evaluate the different grades of rizatriptan benzoate loaded polysaccharide based microspheres for the nasal drug delivery system.
Methods: The polysaccharide was extracted from the seed of Trigonella foenumgraecum and microspheres were prepared by emulsification, followed by crosslinking using epichlorohydrin. A 3^{2} full factorial design was employed in formulating the microspheres with polymer concentration (X_{1}), and stirring rate (X_{2}) as independent variables and particle size (Y_{1}) and entrapment efficiency (Y_{2}) were dependent variables.
Results: The microspheres were discrete and freeflowing. The mean particle size (Y_{1}) of microspheres ranged from 40.82+12 µm to 62.48+0.41 µm and the encapsulation efficiency (Y_{2}) was found to be increased from 60.7+0.2% to 79.22+0.2% as the drug polysaccharide ratio increased. A 3^{2} full factorial design confirmed that the X_{1} and X_{2} both effect on particle size whereas X_{1} alone effect on entrapment efficiency. SEM revealed the smooth spherical surface of microspheres whereas kinetic model revealed that drug release followed the case II transport. FTIR indicated good compatibility of the excipients with rizatriptan benzoate. Stability studies were carried out for formulation F7 at 4°C ambient, 25+2°C/60+5%, 40+2°C/75+5% relative humidity revealed that the physical drug appearance, entrapment efficiency were within the permissible limits.
Conclusion: The result obtained in this research work indicate a promising potential of control release rizatriptan benzoate loaded microspheres whereas the Trigonella foenumgraecum polysaccharide used as rate controlling polymer for the effective treatment of migraine patients.
Keywords: Rizatriptan benzoate, Polysaccharide, Microspheres, Nasal drug delivery.
© 2018 The Authors. Published by Innovare Academic Sciences Pvt Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
DOI: http://dx.doi.org/10.22159/ijap.2018v10i5.27877
INTRODUCTION
In a novel drug delivery system, various route of administration may be used to achieve the controlled and targeted drug delivery [1]. A nasal cavity, as a site of drug delivery, have many advantages such as avoid firstpass metabolism, applicability for longterm treatment and because of the large surface area for absorption it may provide ease of administration. In a novel drug delivery system, microspheres are used to improve the bioavailability and stability of a drug. Intranasal drug administration is receiving increased attention as a delivery method for bypassing the bloodbrain barrier (BBB) and rapidly targeting therapeutics to the central nervous system (CNS) [2]. There are two classes of nasal delivered therapeutics are in the market. The first one comprises with low molecular weight and hydrophobic drugs mostly useful in the treatment of the nasal mucosa and sinus. Whereas the second class of drugs having poor absorption properties, instability in a gastrointestinal tract (GIT) and have a sufficient nasal absorption to display systemic effects [3]. Single emulsion technique is a wellestablished process for microspheres preparation. The microparticulate carriers of natural polysaccharides i.e., those of proteins and carbohydrates are prepared by a single emulsion technique. The natural polymers are dissolved or dispersed in aqueous medium followed by dispersion in a nonaqueous medium like oil. In the next step, the crosslinking of the dispersed globule is carried out. The crosslinking can be achieved either by heat or by using the chemical crosslinkers [4].
Rizatriptan benzoate is a selective serotonin (5hydroxytryptamine; 5HT) type 1B and 1D receptor agonist (“triptan”) commonly used for the treatment of a migraine and completely absorbed from GIT, but absolute bioavailability (as conventional tablet) is 45%, indicating the firstpass metabolism, which is due to the metabolism of the drug by monoamine oxidase A isoenzyme (MAOA) to an inactive indole acetic acid metabolite. Rizatriptan benzoate has also relatively short elimination halflife (about 3 h) and the prolonged drug release is needed [5, 6].
The aim of this research was, to formulate and evaluated rizatriptan benzoate loaded polysaccharide based microspheres for the delivery via the nasal route with aim to avoid hepatic firstpass metabolism, and enhance residence time. The natural polysaccharide was extracted from the seeds of Trigonella foenumgraecum L. (Fenugreek seeds, Family: Fabaceae) as mucoadhesive excipient [7]. In traditional Chinese medicine, it is also used for kidney problems and conditions affecting the male reproductive tract. The recent researches have proved it beneficial for atherosclerosis, constipation, diabetes, high cholesterol and hypertriglyceridemia [8].
MATERIALS AND METHODS
Materials
Rizatriptan benzoate was obtained as a generous gift from Cipla (Raighar, India). Castor oil, epichlorohydrin, Isopropyl alcohol and acetone were purchased from the CDH, (New Delhi, India). All other reagents used were of analytical grade.
Extraction of fenugreek polysaccharide
Extraction of polysaccharide was done using a reported method [9, 10] with minored modification. The plant materials of Trigonella foenumgraecum (fenugreek seeds, NHCP/NBPGR/201416) were collected from the local market in Meerut (India), and were washed with water to remove dirt, dried and crushed them to convert into powdered form. The powder was soaked in water for 56 h, boiled for 30 min. and allowed to stand for 1hr so that all the mucilage was released into the water. Then the materials were squeezed from muslin bag to remove the marc from the solution. After that 1500 ml of acetone was added to the filtrate to precipitate the mucilage. The mucilage was separated, dried in an oven at a temperature less than 50 °C, and the dried powder was passed through a sieve no. 80 and retained on sieve no. 100. It was stored in desiccators.
Preparation of microspheres by emulsion technique
Microspheres of Trigonella foenumgraecum polysaccharides were prepared using an emulsification technique. Aqueous solutions containing different drug and polysaccharide ratios (1:1 to 1:3) were prepared by dissolving required amount of rizatriptan benzoate and polysaccharide in distilled water. The final volume was adjusted in such a way such a way that the concentration of the polysaccharide in the final solution was 2% w/v. The mixture was kept for 4 h under magnetic stirring at 100 rpm (round per minute) for completed hydration of polysaccharide. An aqueous phase was emulsified into castor oil using span 80 (1% v/v) as an emulsifying agent. The phase: volume ratio of the oil and aqueous phase was maintained at 10:1. The emulsion was homogenized for 5 min. with the addition of 0.2 ml H_{2}SO_{4} using high speed a mechanical stirrer (Yamato, LT400, Tokyo, Japan) at different rotation rate (2000 to 3000 rpm). Epichlorohydrin (4% v/v) was added for covalent crosslinking of droplets. Stirring was continued for 18 h at 40^{ο}C. The formed microspheres were separated by sedimentation and centrifugation at 1500 rpm for 5 min. Microspheres were washed thrice using isopropyl alcohol [11].
Experimental design
The design of the experiment is an approach for effectively and efficient exploring the cause and effect relationship between process variables and output. A 2factor 3level factorial central composite experimental design technique was employed to investigate the variables. This technique was applied to quantify the influence of operating parameters on the particle size and entrapment efficiency of microspheres. The dependent variables were polymer concentration and stirring rate. The factorial design parameters and experimental condition are shown in table 1. Various batches of rizatriptan benzoate loaded microspheres were prepared based on the 3^{2} factorial designs. The independent variables were polymer concentration 1 to 3% (X_{1}) and stirring rate 2000 to 3000 rpm (X_{2}) and their levels were shown in table 1.
Table 1: Factorial design parameters and experimental condition
S. No.  Coded value  Actual value  
Drugpolysaccharide ratio (X_{1})  Stirring rate in rpm (X_{2})  
1  1  1:1  2000 
2  0  1:2  2500 
3  +1  1:3  3000 
Optimization data analysis and model validation
A nonlinear quadratic polynomial model was generated to more precisely evaluated effect of independent variables on dependent variables using Design Expert v10 software (StatEase, Inc. Minneapolis, MN).
Y_{i} = β_{0}+β_{1}X_{1}+β_{2}X_{2}+β_{3}X_{3}+β_{3}X_{1}X_{2}+β_{4}X_{1}^{2}+β_{5}X_{2}^{2}………………… (1)
Where Y_{i} is the level of response variable, β_{i} (β_{1}, β_{2}, β_{3}, β_{4} and β_{5}) is the regression coefficient; X_{1}, X_{2} stands for the main effect; X_{1}X_{2} is the interactions between the main effects, and X_{1}, X_{2} are quadratic terms of the independent variables that are used to simulate the curvature of the designed sample space. The X_{1} and X_{2} were termed as codes for the concentration of polysaccharide and stirring rate.
The polynomial equation was used to draw conclusions after considering the magnitude of coefficients, and the mathematical sign it carries, i.e., positive or negative. A positive sign signifies a synergistic effect, whereas a negative sign stands for an antagonistic effect. In the model analysis, the responses: the particle size of the microsphere and entrapment efficiency of all model formulations were treated by Design Expert® software. The best fitting mathematical model was selected based on the comparisons of several statistical parameters including the coefficient of variation (CV), the multiple correlation coefficient (R^{2}), adjusted multiple correlation coefficient (adjusted R^{2}), and the predicted residual sum of square (PRESS), provided by Design Expert® software. Level of significance was considered at p<0.05. Threedimensional response surface plots resulting from equations were obtained by the Design Expert® software [12].
Characterization of microspheres
Production Yield
The production yield of microspheres of various batches were calculated using the weight of final product after drying with respect to the initial total weight of the drug and polymer used for the preparation of microspheres [13].
Particle size analysis
The geometric particle size of microspheres was measured using a phase contrast microscope (Radical Instruments, India). Suspension of microspheres was prepared in paraffin oil. Two or three drops of the suspension were transferred onto a glass slide and covered with a coverslip. The geometrical diameter of 300 microspheres of each batch was separately measured, and the average diameter was calculated [14].
Entrapment efficiency
For the estimation of encapsulation efficiency and drug content, accurately weighed a sample of microspheres (20 mg) was dispersed in 20 ml phosphate buffer (pH 6.8). The dispersion was sonicated for 30 min and kept overnight for the complete erosion of microspheres. Then the sample was centrifuged (Remi), filtered and analyzed using a UVvisible spectrometer (Shimadzu 1700, Japan) at 225 nm. After that encapsulation efficiency and drug content of microsphere were calculated by the following equation (3).
Fourier transforms infrared spectroscopy (FTIR) studies
To determine any possible changes in the chemical nature of the drug during the preparation of microspheres, FTIR spectra of drug, polysaccharide, and the microspheres were recorded by using the FTIR spectrophotometer (Shimadzu, Kyoto, Japan) following the potassium bromide disc method.
Scanning electron microscopy (SEM)
The surface morphology of the microspheres was studied using SEM (Leo, 435 VP, Milpitas, CA). Microspheres were placed on an aluminum stub with doublesided adhesive tape and were subjected to gold sputtering before SEM analysis.
In vitro drug release
The in vitro release of the drug from the microspheres was studied using the modified dissolution method [15]. An accurately weighed amount of microspheres equivalent to 10 mg of drug was suspended into 10 ml of phosphate buffer (pH 6.8) in a beaker containing 0.1% v/v of Tween 80. The microspheres were packed into a small pouch of filter paper, which was kept immersed in the dissolution medium.
The medium was maintained at 37+1^{ο}C and continuously stirred at 50 rpm using a magnetic stirrer. Samples (200 ml) were withdrawn at the time interval of 5 min., diluted, filtered and centrifuged at 4000 rpm for 15 min. The supernatant was collected and estimated for the drug content using UV spectrophotometer at 225 nm. Quantitative estimation of released drug was done using a calibration curve of the drug in a phosphate buffer of pH 6.8 in the concentration range of 1–10 µg/ml.
Drug release kinetics
To study the release kinetics of rizatriptan benzoate from Trigonella foenumgraecum microspheres, dissolution data were fit according to Zeroorder, Firstorder, Higuchi, and Korsmeyer–Peppas equations. Value of kinetic rate constant (k), mucoadhesive microspheres of Trigonella foenumgraecum correlation coefficient (r^{2}) and release exponent (n) were calculated to find out the best fit model. To investigate the drug release mechanism, the release data were fitted to model representation: Zero order (see equation 4) as cumulative amount of drug released vs. time, First order (see equation 5) as log cumulative percentage of drug remaining vs. time and Higuchi's model (see equation 6) as cumulative percentage of drug released vs. square root of time [12].
Zeroorder
…….. (4)
Where K_{0} is the zeroorder rate constant expressed in units of concentration/time and t is the time in minutes. A graph of concentration vs. time would yield a straight line with a slope equal to K_{0} and intercept the origin of the axes.
First order
…….. (5)
Where C_{0} is the initial concentration of d the rug, K is the first order constant and t is the time.
Higuchi model
……….. (6)
Where Q_{t} is the amount of drug release in time t, K is the kinetic constant and t is the time in minutes.
Korsmeyerpeppas model
A more stringent test was used to distinguish between the mechanisms of drug release. The release data were fitted to the Peppas exponential model as a cumulative log percentage of drug released vs. log time (equation 7). The release exponent n and K value were calculated through the slope of the straight line.
M_{t}/M_{∞} = K_{t}^{n} ………. (7)
Where M_{t} represents an amount of the released drug at time t, M_{∞} is the total amount of drug released after an infinite time, K is the diffusion characteristic of drug polysaccharide system constant and n is an exponent that characterizes the mechanism of drug release. The value of n indicates the drug release mechanism from the delivery system. If the exponent n=0.43 then the drug release mechanism is Fickian diffusion, if 0.43<n<0.85 then it is nonFickian or anomalous diffusion, if n=0.85 mechanism is nonFickian case II diffusion [16, 17].
Stability studies
Stability study was carried out for rizatriptan benzoate loaded microspheres as per ICH guidelines. The best batch of microspheres was sealed in an ambered coloured bottle and stored at 25+2°C/60+5%, 40+2°C/75+5% relative humidity (RH) for 90 d. The sample was evaluated for physical appearance and entrapment efficiency [22].
RESULTS AND DISCUSSION
Formulation of microspheres
Nine formulations of rizatriptan benzoate loaded mucoadhesive microspheres were prepared by emulsion technique using factorial design, in which the independent variables of drug polysaccharide ratio 1 to 3% (X_{1}) and stirring rate (X_{2}) 2000 to 3000 rpm and particle size (Y_{1}) and % entrapment efficiency (Y_{2}) were taken a response parameters as the dependent variables as shown in table 2.
Table 2: Formulation of microspheres using 3^{2} factorial designs
Batch code  Drug polysaccharide ratio (X_{1}) 
Stirring rate in rpm (X_{2}) 
Particle size (µm+SD)^{a} (Y_{1}) 
Entrapment efficiency (%+SD)^{a} (Y_{2}) 
F_{1}  1  1  40.82+0.12  60.70+0.20 
F_{2}  1  0  55.82+0.50  62.60+0.10 
F_{3}  1  +1  62.48+0.41  65.07+1.30 
F_{4}  0  1  49.15+1.02  67.46+0.50 
F_{5}  0  0  49.15+0.70  68.66+0.41 
F_{6}  0  +1  49.98+1.20  69.64+0.8 
F_{7}  +1  1  60.81+0.50  70.84+1.2 
F_{8}  +1  0  57.48+0.80  76.83+0.3 
F_{9}  +1  +1  46.65+0.20  79.22+0.2 
^{a}mean+SD, (n= 3),n= number of observation, F = formulation code of microspheres
Optimization data analysis and modelvalidation
Fitting of data to the model
The two factors with lower, middle and upper design points in coded and encoded values are shown in table 1. The ranges of responses Y_{1} and Y_{2} were 40.82+0.1262.48+0.41μm and 60.70+0.279.22+0.2%, respectively. Response observed for all the prepared batches were fitted to various models using DesignExpert® software. It was observed that the bestfitted models were F1 for particle size and linear for entrapment efficiency. The values of R^{2}, adjusted R^{2}, predicted R^{2}, SD and % CV are given in table 3.
The result of ANOVA in table 4 for the dependent variables demonstrates that the model was significant for both the response variables. It was observed that independent variables drug polysaccharide ratio (X_{1}) and stirring rate (X_{2}) had a positive effect on particle size (Y_{1}) and entrapment efficiency (Y_{2}).
Table 3: Summary of results of regression analysis for response Y_{1} and Y_{2}
Models  R^{2}  Adjusted R^{2}  Predicted R^{2}  SD  %CV 
Response (Y_{1}) F1 model 
0.8368  0.7388  0.6801  3.63  6.92 
Response (Y_{2}) Linear model 
0.9567  0.9422  0.8884  1.47  2.12 
Table 4: Results of analysis of variance for a measured response
Parameters  SS  DF  MS  F  Significance p 
Particle size Model Residual Total 
337.98 65.94 403.92 
3 5 8 
112.66 13.19  
8.54   
0.0206 significant   
E. E. Model Residual Total 
284.45 12.89 297.33 
2 6 8 
142.22 2.15  
66.23   
<0.0001 significant   
Regression equation
Particle size (Y_{1}) = 11.94+18.88X_{1}+19.29X_{2}8.95X_{1}X_{2} ………. (8)
Entrapment efficiency (Y_{2}) = 51.18+6.42X_{1}+2.48X_{2 …………..………} (9)
From the above equation 8 it was confirmed that the major factor which is influencing the particle size of the film is stirring rate (X_{2}). The interaction factor between both the independent variables is very less. The concentration of Trigonella foenumgraecum (X_{1}) also has an effect on particle size of Trigonella foenumgraecum microsphere. In case of entrapment efficiency, the concentration of Trigonella foenumgraecum (X_{1}) also has an effect on entrapment efficiency of microsphere because the higher the amount of polysaccharide, the more will be entrapment efficiency because of the more availability of polysaccharide to encapsulate the drug.
Polynomial quadratic models were generated for each response parameter, and the regression coefficients for each term regression model were summarized in table 5 together with r^{2}, F values (with pvalues) of the regression model. In the present study, the model was significant in all the cases because for all the dependent variables, the p value for the generated model was less than 0.05. Effects of formulation variables on different dependent variables were assessed by this generated regression coefficient and r^{2} values. The high values of correlation coefficients for all the response variables indicate a good fit (i.e., good agreement between the dependent and independent variables).
Table 5: Regression coefficient and r^{2}values for Trigonellafoenumgraecum microspheres containing rizatriptan benzoate
Regression coefficient  β_{0}  β_{1}  β_{2}  β_{3}  r^{2}  Fvalues for the model (pvalue) 
Independent variables  X_{1}  X_{2}  X_{1}X_{2}  
Dependent variables  
Particle size  11.94  18.88  19.29  8.95  0.8368  8.54 (0.0206) 
Entrapment efficiency  51.18  6.42  2.48  0  0.9567  66.23 (<0.0001) 
Response surface plot analysis
Threedimensional response surface plots generated by the Design Expert® software are presented (in fig. 1 and 2) for the studied responses, i.e., particle size and entrapment efficiency. The (fig. 1) depicts response surface plot of drug polysaccharide ratio (X_{1}) and stirring rate (X_{2}) on particle size, which indicate that X_{1} and X_{2} show linear effect i.e., when increased polysaccharide concentration and stirring rate from 2000 to 3000 the value of particle size was decreased. The (fig. 2) represent response surface plot of the effect of drug polysaccharide ratio (X_{1}) and stirring rate (X_{2}) on entrapment efficiency which indicate a linear effect. This explains that the higher the amount of polysaccharide, the more will be entrapment efficiency because of the more availability of polysaccharide to encapsulate the drug.
Optimization and validation
The result in table 6 illustrates the comparison between the observed values of both the response Y_{1} and Y_{2} for all the batches were presented. It can be seen that in all cases there was a reasonable agreement between the experimental values. The equations describe the influence of the selected independent variables on the responses under study adequately. This indicates that the optimization technique was appropriated for optimizing the rizatriptan benzoate loaded Trigonella foenumgraecum microsphere. The low magnitudes of error in the present investigation prove the high prognostic ability of the optimization technique by factorial design.
Fig. 1: Response surface plots for the X_{1} and X_{2} on particle size (Y_{1}), where X_{1} = drug polysaccharide ratio, X_{2} = stirring rate
Fig. 2: Response surface plots for the X_{1} and X_{2} on entrapment efficiency (Y_{2}), where X_{1}= drug polysaccharide ratio and X_{2} = stirring rate
Table 6: The predicted and observed response variables of the rizatriptan benzoate loaded microspheres
Formulation code  Actual and predicted values for  
Particle size (Y_{1})  Entrapment efficiency (Y_{2})  
Actual value  Predicted value  Residual  Actual value  Predicted value  Residual  
F1  40.82  41.16  0.34  60.70  60.08  0.62 
F2  55.82  51.50  4.32  62.60  62.56  0.04 
F3  62.48  61.84  0.64  65.07  65.04  0.03 
F4  49.15  51.09  1.94  67.46  66.50  0.96 
F5  49.15  52.48  3.33  68.66  68.98  0.32 
F6  49.98  53.87  3.89  69.64  71.46  1.82 
F7  60.81  61.02  0.21  70.84  72.92  2.08 
F8  57.48  53.46  4.02  76.83  75.40  1.43 
F9  46.65  45.90  0.75  79.22  77.88  1.34 
F= formulation code of microspheres
Characterization of microspheres
Percentage yield
The percentage yield of production was found in the range 64.5+0.2% to77.60+0.6% (table 7). These respectively low values could be attributed mainly to the loss of fines particles during the washing of microspheres with Isopropyl alcohol.
Particle size
The mean particle size of microspheres ranged from 40.82+10 µm to 62.48+6.56 µm (table 7), indicating a narrow size distribution (fig. 1). Such a particle size distributions were considered favorable for intranasal administration. The particle size of microsphere was to increase with an increase in the drug polysaccharide ratio. The formation of larger droplets during emulsification due to the higher viscosity of polysaccharide solution at higher concentration. Increase stirring rate also contributed to decreasing the particle size but not much significantly and this may be due to the narrower range being selected to focus this parameter [20].
Encapsulation efficiency result
The percentage encapsulation efficiency was found to increase as the drug polysaccharide ratio increased (table 7). It was 60.7+0.2% in a batch F1 (1:1 drug polysaccharide ratio) and increased subsequently, to 79.22+0.22% in a batch F9 (1:3 drug polysaccharide ratio). The reason behind the increased value of percent encapsulation efficiency is the more availability of Trigonella foenumgraecum polysaccharide as a carrier for the encapsulation of drug. At high concentration of polysaccharide, highly viscous aqueous droplets are formed during emulsification, which makes a complex network of polysaccharide and prevents the migration of drug into surrounding media [21]. In a batch F1 with drug polysaccharide ratio 1:1, drug loading was less because most of the drug remained unentrapped due to an insufficient amount of carrier polysaccharide.
Table 7: Mean value of percentage yield, particle size and entrapment efficiency of microspheres
Batch code  Percentage yield^{a} (%+SD)  Particle size^{a} (µm+SD)  Entrapment efficiency^{a} (%+SD) 
F1  64.5+0.2  40.82+0.12  60.70+0.20 
F2  70.4+0.5  55.82+0.50  62.60+0.10 
F3  76.2+0.1  62.48+0.41  65.07+1.30 
F4  74.5+0.2  49.15+1.02  67.46+0.50 
F5  69.7+1.3  49.15+0.70  68.66+0.41 
F6  72.3+0.1  49.98+1.20  69.64+0.8 
F7  77.6+0.6  60.81+0.50  70.84+1.2 
F8  71.4+1.4  57.48+0.80  76.83+0.3 
F9  73.1+0.2  46.65+0.20  79.22+0.2 
^{a}mean+SD (n= 3), n = no of observation, F=formulation code of microspheres
FTIR spectroscopy
Interpretation of FTIR spectrum of Trigonella foenumgraecum polysaccharide (fig. 3(a)) was:OH stretch (3656.78),CH (3150.50),C=C (2313.46),CH bend (1636.49),CH rock (1617.20),CH bend out of plane (1029.45) and FTIR spectrum of rizatriptan benzoate (fig. 3(b)) wasNH stretching (3446),CH_{3} stretching (2947),CH_{2} stretching (2893),C=C stretching (1608), C=N stretching (1506),NH bending (1570),CH_{2} bending (1458),CH_{3} bending (1375),CN (1016, 1140,1296).
The spectrum of physical mixture indicates that there was no evidence of any possible interaction between the drug and the polysaccharide and characteristic peaks of the pure drug were found present in the spectrum of mixture (fig. 3 (c)), which confirmed the absence of interaction between a drug and the polysaccharide [10, 1819].
(a)
(b)
(c)
Fig. 3: IR spectra of Trigonella foenumgraecum polysaccharide (a), Rizatriptan benzoate (b) and Physical mixture (Rizatriptan benzoate and Trigonella foenumgraecum polysaccharide) (c)
Surface morphology
The morphology of all the batches was examined by a Scanning Electron Microscopy (SEM) shown in fig. 4. Microspheres are spherical and possessed a smooth surface also they had no rupture on the surface; such morphology would result in slow clearance and good deposition pattern in a nasal cavity [16].
F1
F2
F3
F4
F5
F6
F7
F8
F9
Fig. 4: SEM image all batches at 100×
Result of in vitro drug release
The release profiles of the drug from different batches of Trigonella foenumgraecum microspheres are shown in fig. 5. Batches of microspheres were found to release 50% drug within 15 min., and the whole drug content within 60 min. time except batch F7, which might due to high concentration of Trigonella foenumgraecum polysaccharide retarded the drug release from the microspheres, because of the viscous threedimensional network at higher concentration of polysaccharide, which reduced the diffusion of drug.
Result of release kinetics
The release constant was calculated from the slope of the zero order, first order, Higuchi plots and determined the regression coefficient (R^{2}) in the range of 0.700.98. It was found that the in vitro drug release of all the nine batches was best explained by zero order kinetic, as plot show the highest linearity, R^{2}(see table 8), indicating diffusion controlled drug release. The corresponding plot log of cumulative percentage drug release vs. log time of the KorsmeyerPeppas equation indicated good linearity of regression coefficient (R^{2}); 0.270.97. The release exponent (n) values for all the nine batches were found to be>0.45, indicating that all batches followed the case II transport, which was the drug transport mechanism associated with stress in hydrophilic polysaccharides which swells in water and biological fluids.
Fig. 5: In vitro release of microspheres. Each reading is an average of six determinants (mean+SD) (n=6) n= no. of observation
Table 8: Model fitting of the release profile using four different models
Formulations  Kinetic models(R^{2})  
Zeroorder  First order  Higuchi  Best fit model  Korsmeyer peppa’s equation  
K value  
F1  0.987  0.659  0.940  Zero order  0.627 
F2  0.970  0.667  0.570  Zero order  0.9099 
F3  0.701  0.995  0.977  Zero order  0.9713 
F4  0.928  0.521  0.860  Zero order  0.2796 
F5  0.956  0.985  0.893  Zero order  0.5426 
F6  0.982  0.642  0.931  Zero order  0.6186 
F7  0.962  0.802  0.916  Zero order  0.5138 
F8  0.903  0.750  0.834  Zero order  0.2528 
F9  0.916  0.558  0.85  Zero order  0.2728 
Stability studies
Stability studies for the optimized batch (F7) were carried out at a different temperature for 90 d. The formulation was evaluated for physical appearance and entrapment efficiency. There was no significant change in physical appearance and entrapment efficiency even after exposing to stress conditions at a different temperature. Hence, it was concluded that the F7 batch of microspheres has good stability during their shelf life.
CONCLUSION
The rizatriptan benzoate loaded polysaccharide based microspheres can be successfully prepared by double emulsion techniques. A full 3^{2} factorial design was applied taking drug polysaccharide ratio (X_{1}) and stirring rate (X_{2}) as two independent variables than the dependent variables were evaluated. The prepared batches of microspheres were spherical and freeflowing. The entrapment efficiencies ranged from 60.7+0.2% to 79.22+0.2% and mean size was in the range of 40.82+0.12 µm to 62.48+0.41 µm. The concentration of polysaccharide ratio influences the entrapment efficiency. Thus, the investigation indicates a promising potential of control release rizatriptan benzoate loaded microspheres whereas the Trigonella foenumgraecum polysaccharide used as rate controlling polymer for the effective treatment of migraine patients.
AUTHORS CONTRIBUTIONS
All the authors have contributed equally
CONFLICT OF INTERESTS
Declare none
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