Study of Influence of Formulation and process variables on entrapment efficiency and particle size of Floating microballoons of Clopidogrel bisulphate by DoE

Seelam Ramya Krishna¹*, Dr. A. Ramu², Dr. S. Vidyadhara³

¹Research Scholar, Chebrolu Hanumaiah Institute of Pharmaceutical Sciences, Chowdavaram, Guntur, A.P., India.

²Guide, Chebrolu Hanumaiah Institute of Pharmaceutical Sciences, Chowdavaram, Guntur, A.P., India.

³Principal, Chebrolu Hanumaiah Institute of Pharmaceutical Sciences, Chowdavaram, Guntur, A.P., India.

*Corresponding Author E-mail: ramya.krishna.seelam@gmail.com

ABSTRACT:

Microparticulate drug delivery is a prominent method of oral delivery of drugs which is more beneficial than the single unit dosage forms. A prior approach to increase the gastric retention time of the drug through multiparticulate drug delivery is by formulating floating microballoons. They result in more reproducible drug absorption and reduced risk of local irritation, thereby improving the bioavailability of the drug. In the current research work, clopidogrel, a BCS class – II drug was formulated as controlled release microballoons using ethyl cellulose as polymer and span 80 as the surfactant to improve the gastric retention of the drug. Box – Benhken design was selected to design the experiment and the study of effect of various formulation and process parameters like concentration of surfactant, volume of solvent, volume of internal phase, concentration of polymer, speed of rotation on the drug entrapment efficiency and particle size of the microballoons were carried out. The highest drug entrapment efficiency was found to be 93.1% in the F14 formulation. The smallest particle size of the microballoons was found to be 183.9µm in the F32 formulation. Buoyancy studies showed all the formulations have good floating characteristics. The maximum yield of microballoons was found in the F7 formulation with 93.1% yield. The final results were statistically treated using ANOVA and were found to be significant. (p – value < 0.05).

KEYWORDS: Box – Benhken design, Clopidogrel, Gastric transit time, Gastric emptying, Microballoons.

INTRODUCTION:

The ease of administration of the oral dosage forms has immensely achieved most of the attention among different dosage forms but the variability of the gastric transit time and the gastric tract physiology leads to unpredictable bioavailability and non-reproducible therapeutic effects. Most of the drugs are well absorbed throughout the GIT but some drugs are poorly absorbed in the large intestine and have a site of absorption only in the stomach. Such drugs are influenced by the gastric emptying process when formulated as conventional dosage forms. These drugs are to be formulated considering to improve their GI residence time¹.

One such approach for improving gastric residence time is to incorporate the drug into a floating² device that is less dense than the gastric fluid. The uniform distribution of the multi particulate dosage in the gastric content could result in more reproducible absorption and a reduced risk of local irritation than single-unit dosage forms. Such a prolonged gastric retention not only controls the time but also the space in the stomach by maintaining the delivery system positioned at a steady site and thereby properly delivering the drug.

Clopidogrel bisulfate belongs to the class thienopyridine of antiplatelets. It is used to reduce the formation of clots in patients with risk of heart disease and stroke. It belongs to BCS class – II drugs with low solubility and high permeability. Hence a controlled release formulation^3-6 of clopidogrel helps in improving its bioavailability. Clopidogrel bisulfate being a moderate acidic pKa drug, its absorption is pH dependent and has a better absorption in the stomach as it is an acidic drug and a poor absorption in the intestine. When formulated into a normal controlled release dosage form, it crosses both the stomach and intestine due to gastric emptying thereby the plasma concentration cannot be maintained as the absorption decreases in the intestine. Hence formulating the clopidogrel into microballoons helps in increasing the gastric retention⁷ time thereby maintaining constant plasma concentration. In the current research work, clopidogrel bisulfate was formulated as floating microballoons to improve its gastric residence time thereby enhancing its bioavailability.

MATERIALS:

Clopidogrelbisulfate pure drug was received as a gift sample from Mankind Pharma, Hyderabad. Ethyl cellulose, span 80, methanol, diethyl ether and liquid paraffin were purchased from SD Fine Chemicals Ltd, Mumbai.

METHODS:

Preparation of Floating Microballoons:

Experimental design⁸:

Response surface model was selected to optimize the influence of various formulation and process variables (independent variables) on the responses of microballoons. The microballoons were prepared by emulsion solvent evaporation method. Five different independent variables were taken viz. polymer concentration, concentration of methanol in the internal phase, volume of internal phase, concentration of surfactant in the external phase and speed of rotation. The selected responseswere entrapment efficiency and particle size of microballoons. All the five variables were taken at three levels each and so the Box-Behnken design was selected and performed by employing Stat Ease Design Expert software.

Table 1: Formulation codes with combinations of various factors according to Box – Behnken design

Standard order	Run order	Formulation code	Factor A (%w/w)	Factor B (%v/v)	Factor C (mL)	Factor D (%v/v)	Factor E (rpm)
1	24	F1	50.00	20.00	7.50	0.25	550.00
2	25	F2	75.00	20.00	7.50	0.25	550.00
3	21	F3	50.00	60.00	7.50	0.25	550.00
4	40	F4	75.00	60.00	7.50	0.25	550.00
5	31	F5	62.50	40.00	5.00	0.00	550.00
6	36	F6	62.50	40.00	10.00	0.00	550.00
7	7	F7	62.50	40.00	5.00	0.50	550.00
8	16	F8	62.50	40.00	10.00	0.50	550.00
9	15	F9	62.50	20.00	7.50	0.25	400.00
10	20	F10	62.50	60.00	7.50	0.25	400.00
11	5	F11	62.50	20.00	7.50	0.25	700.00
12	3	F12	62.50	60.00	7.50	0.25	700.00
13	18	F13	50.00	40.00	5.00	0.25	550.00
14	6	F14	75.00	40.00	5.00	0.25	550.00
15	26	F15	50.00	40.00	10.00	0.25	550.00
16	19	F16	75.00	40.00	10.00	0.25	550.00
17	28	F17	62.50	40.00	7.50	0.00	/400.00
18	23	F18	62.50	40.00	7.50	0.50	400.00
19	34	F19	62.50	40.00	7.50	0.00	700.00
20	2	F20	62.50	40.00	7.50	0.50	700.00
21	17	F21	62.50	20.00	5.00	0.25	550.00
22	14	F22	62.50	60.00	5.00	0.25	550.00
23	38	F23	62.50	20.00	10.00	0.25	550.00
24	11	F24	62.50	60.00	10.00	0.25	550.00
25	33	F25	50.00	40.00	7.50	0.00	550.00
26	41	F26	75.00	40.00	7.50	0.00	550.00
27	32	F27	50.00	40.00	7.50	0.50	550.00
28	10	F28	75.00	40.00	7.50	0.50	550.00
29	13	F29	62.50	40.00	5.00	0.25	400.00
30	1	F30	62.50	40.00	10.00	0.25	400.00
31	4	F31	62.50	40.00	5.00	0.25	700.00
32	22	F32	62.50	40.00	10.00	0.25	700.00
33	9	F33	50.00	40.00	7.50	0.25	400.00
34	37	F34	75.00	40.00	7.50	0.25	400.00
35	30	F35	50.00	40.00	7.50	0.25	700.00
36	12	F36	75.00	40.00	7.50	0.25	700.00
37	8	F37	62.50	20.00	7.50	0.00	550.00
38	35	F38	62.50	60.00	7.50	0.00	550.00
39	27	F39	62.50	20.00	7.50	0.50	550.00
40	39	F40	62.50	60.00	7.50	0.50	550.00
41	29	F41	62.50	40.00	7.50	0.25	550.00

Method of preparation of floating microballoons⁹:

The polymer was dissolved in the mixture of methanol and diethyl ether, to which drug was added and dissolved by placing on vertex mixture for 2 minutes to get the organic phase. Liquid paraffin was taken in another beaker and 0.0% or 0.25% or 0.5% v/v of span 80 was added to it to get the oily phase. The oil phase was placed under the mechanical stirrer and set 400/550/700rpm. The organic phase was added drop by drop to the oil phase under stirring. Stirring was continued for 4-5 hrs until the organic solvents were evaporated completely to yield hollow microspheres. The obtained hollow microspheres were washed with petroleum ether to remove paraffin and then dried. The compositions of various formulations were shown in the table – 1 where Factor A represents the polymer concentration in the total weight of microspheres, Factor B represents the concentration of methanol in internal phase, Factor C indicates the total volume of the internal phase, Factor D indicates concentration of Span 80 (surfactant)¹⁰ and Factor E represents the speed in rpm.

Characterization of Microballoons^11-13:

Determination of percentage yield of microballoons:

Percentage yield of floating micro balloons was calculated by dividing actual weight of product to total amount of all non-volatile components that are used in the preparation of floating micro balloons and is represented by following formula.

Drug entrapment efficiency and loading efficiency:

The amount of drug entrapped was estimated by crushing the microballoons taken of 100mg drug equivalent microballoons in 100ml beaker contain 50ml of 0.1N HCL. The beaker was placed on magnetic stirrer and set suitable rpm. After 3hrs sample was withdrawn and the absorbance was measured at 240nm against 0.1N HCL as blank by thermo UV spectrophotometer. The percentage drug entrapment and the percentage loading efficiency were calculated as follows:

Floating characterization:

100 floating microballoons from each formulation were taken in a 100ml beaker containing 70ml of water and allowed to stand for 24hrs. After 24hrs,the number of microballoons floating on the surface was observed.

Particle size and surface morphology:

The particle size and the surface morphology of microballoons of F14 formulation having the highest entrapment efficiency was examined by scanning electron microscopy.

Drug release studies¹⁴ and kinetic studies:

In vitro dissolution studies were performed for F14, F21, F28, F34 microballoons which have high entrapment efficiency, in USP II paddle type dissolution test apparatus using 900ml of 0.1M HCl as the dissolution medium and the rpm was maintained at 100. The samples were withdrawn at 30mins, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 hrs and the samples were analyzed after suitable dilutions by using UV-Visible spectrophotometer at the maximum wavelength of 240nm. The obtained data was fitted to various kinetic models viz. zero-order, first-order, Higuchi’s and Korsemeyer-Peppas models to find out the kinetics and mechanism of drug release.

Experimental design validation¹⁵ and ANOVA:

Several formulation and process parameters influence the different characteristics of microballoons. The optimization of these parameters can be achieved effectively only by the application of different statistical techniques. The various experimental designs that can be applied in the optimization of the parameters include empirical models, factorial designs¹⁶, fractional factorial designs, simplex optimization, and response surface methodology¹⁷. All the combinations of factors were taken in a single block with one center point per block to attain a total of 41 runs as given by the Box-Behnken design of response surface method. The response parameter was evaluated by 2 factorial interaction (2FI) model. The observed and predicted values of the response were compared and graphs were also plotted. Linear model of ANOVA was performed to identify whether the selected factors were significant or not¹⁸.

RESULTS AND DISCUSSION:

Determination of percentage yield of microballoons:

The results of percentage yield of clopidogrel microballoons were shown in table 2. All the formulations of microballoons were prepared by solvent evaporation technique and from the results, more than 74.3% yield was observed in any case, which indicated that the solvent evaporation technique along with the selected experimental conditions was highly effective for the preparation of floating microspheres.

Drug entrapment efficiency and Percentage loading efficiency:

The drug entrapment efficiency of all the formulations was found to be above 72% inferring a considerably better entrapment of the drug in the polymer matrix occurred as shown in table 3. The maximum drug entrapment efficiency was found to be in the formulations F14, F21, F28 and F34 having drug entrapment efficiency above 92%.  The percent loading efficiency of the drug in different formulated microballoons were shown in table 2and the loading efficiency for all the microballoons were found to be within a range of 20% to 42%.

Table 2: Results of some physical characterization studies of floating microspheres

S. No.	Formulation	Entrapment efficiency (%)	Loading efficiency (%)	Particle size (µm)	Buoyancy (%)	Yield (%)
1	F1	81.0	40.5	251.3	94.67±1.15	83.5
2	F2	90.3	22.58	205.6	90.00±2.0	81.9
3	F3	75.1	37.55	273.1	93.33±2.31	86.2
4	F4	89.5	22.38	422.8	91.33±2.31	88.7
5	F5	82.2	30.83	437.6	92.00±2.0	80.7
6	F6	74.3	27.87	348.2	86.00±2.0	85.5
7	F7	90.2	33.83	341.9	94.67±1.15	93.2
8	F8	74.9	28.09	214.5	95.33±3.06	81.6
9	F9	90.6	33.98	462.3	92.00±3.46	78.3
10	F10	87.9	32.97	405.8	90.67±4.16	82.6
11	F11	83.2	31.21	245.1	90.00±3.46	83.1
12	F12	80.8	30.31	302.6	94.67±3.06	90.2
13	F13	81.8	40.9	324.7	90.67±1.15	89.5
14	F14	93.1	23.28	468.3	88.00±2.0	74.5
15	F15	74.6	37.3	212.9	90.67±1.15	81.5
16	F16	77.5	19.38	311.8	92.67±1.15	86.3
17	F17	83.3	31.24	427.3	86.67±2.31	76.5
18	F18	90.5	33.95	362.0	93.33±1.15	83.2
19	F19	76.2	28.58	316.8	92.67±1.15	81.6
20	F20	82.8	31.06	219.3	95.33±1.15	88.3
21	F21	92.7	34.77	393.2	96.00±3.46	79.6
22	F22	88.2	33.08	412.5	94.00±3.46	81.7
23	F23	82.5	30.94	292.3	89.33±1.15	78.4
24	F24	80.5	30.19	284.7	87.33±5.03	90.2
25	F25	74.0	37.0	306.5	90.67±1.15	84.5
26	F26	83.4	20.85	451.3	92.67±2.31	87.2
27	F27	80.8	40.4	206.9	88.67±3.06	84.3
28	F28	92.8	23.2	414.6	90.67±1.15	86.4
29	F29	90.6	33.98	589.4	92.67±1.15	75.8
30	F30	75.9	28.47	338.1	95.33±3.06	84.5
31	F31	75.8	28.43	352.7	93.33±1.15	88.9
32	F32	74.2	27.83	183.9	96.67±1.15	81.6
33	F33	83.5	41.75	350.6	93.33±2.31	84.9
34	F34	92.1	23.02	620.3	87.33±3.06	74.3
35	F35	72.3	36.15	196.7	93.33±3.06	86.4
36	F36	83.9	20.98	368.2	88.67±1.15	81.5
37	F37	84.5	31.70	381.6	91.33±1.15	84.9
38	F38	82.9	31.10	423.8	95.33±2.31	87.1
39	F39	91.8	34.43	281.3	87.33±1.15	91.2
40	F40	86.4	32.41	311.6	92.00±3.46	84.7
41	F41	80.7	30.27	351.7	92.67±3.06	86.4

The contour plots signifying the influence of different formulation and process parameters on the drug entrapment efficiency were plotted using Design Expert software shown in Fig 1. It was inferred from the Fig 1(a) that upon increase in the concentration of polymer there was an increase in the drug entrapment efficiency. This might be attributed to the stronger polymer matrix at higher amounts of polymer which might hold the drug tightly and hinder the leakage of the drug, thus finally resulted in increased entrapment efficiency. As the concentration of the methanol was increased, the entrapment efficiency decreased. Upon increase in the concentration of methanol in the internal phase, the rate of evaporation might be decreased because of higher melting point of methanol than that of diethyl ether. During slow evaporation for longer time, more amount of drug might be diffused out of the microspheres thus resulted in decreased entrapment efficiency.

Fig. 1 (b) infers that as the volume of the internal phase increased, the entrapment efficiency decreased. This might be because of the high diffusion rate of the solvent due to higher evaporation rate at lower viscosities upon increasing volume of internal phase. Fig. 1 (c) infers that as the concentration of the surfactant was increased, the drug entrapment efficiency of the microballoons increased which might be due to the fact that as the surfactant concentration increases, the stability of the emulsion increases which helps in the deposition of polymer efficiently on the globule thereby increasing the drug entrapment efficiency. As the speed of rotation of mixing was increased, the entrapment efficiency decreased because at high rpm, there might be a rapid solvent evaporation which might lead to more amount of drug out of the globulesalong with the solvent. The experimental results of entrapment efficiency were statistically treated using analysis of variance and it was inferred from table 3 that the statistical difference was significant for all the factors affecting the drug entrapment efficiency as the p - value  was found to be < 0.05.

Fig 1: Contour plot showing the effect of factors on entrapment efficiency (a) polymer concentration and concentration of methanol (b) polymer concentration and volume of internal phase (c) Concentration of surfactant and stirring speed

Table 3: ANOVA for entrapment efficiency and particle size of clopidogrel microballoons

Response	Source	SS	Df	MSS	F – value	p – value	Inference
Entrapment efficiency	Model	1255.24	5	251.05	26.22	< 0.0001	Significant
	A	395.02	1	395.02	41.26	< 0.0001	Significant
	B	40.01	1	40.02	4.18	0.0485	Significant
	C	402.00	1	402.00	41.99	<0.0001	Significant
	D	152.52	1	152.52	15.93	0.0003	Significant
	E	265.69	1	265.69	27.79	<0.0001	Significant
	Residual	335.09	35	9.57
Particle size	Model	3.199x10^5	5	63978.03	28.35	<0.0001	Significant
	A	81253.50	1	81253.5	41.26	<0.0001	Significant
	B	6569.10	1	6569.10	4.18	0.0968	Not Significant
	C	80358.08	1	80358.08	41.99	<0.0001	Significant
	D	34317.56	1	34317.56	15.93	0.0004	Significant
	E	1.174x10^5	1	1.174x10^5	27.79	<0.0001	Significant
	Residual	78977.36	35	2256.5

Floating characterization:

The buoyancy of all the formulated microballoons was observed after a period of 24hrs and the percent buoyancy of all the microballoons was found to be 86% and above as shown in table 2 indicating that the selected formulation and experimental conditions were suitable to develop floating microballoons. This was further evidenced by the results of SEM studies (shown in Fig 2) that the microparticles had surface dents which indicated hollowness inside the particles.

Particle size and size distribution:

The SEM analysis conducted for the formulation F14 is depicted in the picture fig 2. The SEM analysis pictures of figure 2 indicate the presence of a smooth surface of the microballoons with the presence of surface dents inferring the presence of hollowness inside the microballoons. It was inferred from fig 3(a) that upon increase in polymer concentration, the particle size was found to be increased which might be because of the increased viscosity of the dispersion at high amount of polymer that might inversely affect the fine globule formation in the emulsion. Upon increase in volume of internal phase, the particle size was found to be decreased which might be attributed to decrease in the viscosity of the internal phase at higher volume of solvent that might result in the fine globule formation in the emulsion.

Fig 3(b) indicated that upon increase in concentration of surfactant, aggregation of globules in the emulsion might be reduced and thus resulted in microspheres with smaller particle size. Upon increase in the speed of rotation, the particle size was found to be reduced. This might be due to more energy input into the emulsion at higher speed that lead to the formation of smaller globules in the emulsion which finally lead to the formation of microspheres of smaller size upon evaporation of the solvent. From the results of ANOVA (shown in table 3), the effect of concentration of methanol in the internal phase on particle size was found to be insignificant as the p – value is more than 0.05.

Fig 2: SEM images of floating microspheres of formulation F14 indicating a) Surface morphology and b) Surface dents that indicate inside of the microspheres is hollow

Fig 3: Contour plot showing the effect of factors on particle size (a) polymer concentration and volume of internal phase on particle size (b) concentration of surfactant and speed

Drug release and release kinetic studies:

The results of drug release studies and release kinetic studies were shown in table 4. Among all the formulations, F34 showed maximum control of drug release with a release rate constant of 0.11hr^-1 and F15 showed least control with a release rate constant of 0.274hr^-1. Drug release from all the formulations followed first – order kinetics and release mechanism was found to be non-fickian diffusion.

Experimental design validation and ANOVA:

Box – Behnken design was used for the development of the clopidogrel microballoons is advantageous over the full factorial designs because in the full factorial design the number of runs will increase when the number of factors and levels taken are increased where as in the box – Behnken design, the same conclusion of results can be obtained for a less number of trials. It can be inferred from table 4 that the model was found to be significant through statistical analysis by ANOVA as the p – value was found to be < 0.05.

Table 4: Drug release kinetics of clopidogrel microballoons

S. No.	Formulation	Regression values			Peppas ‘n’ value	Drug release rate constant (k hr^-1)
		Zero - order	First - order	Higuchi
1	F1	0.67	0.991	0.986	0.613	0.219
2	F2	0.885	0.989	0.943	0.873	0.121
3	F3	0.539	0.961	0.977	0.557	0.195
4	F4	0.886	0.997	0.964	0.762	0.132
5	F5	0.956	0.99	0.923	0.986	0.129
6	F6	0.734	0.994	0.995	0.619	0.205
7	F7	0.915	0.998	0.945	0.797	0.138
8	F8	0.566	0.984	0.964	0.619	0.255
9	F9	0.567	0.933	0.972	0.585	0.168
10	F10	0.858	0.989	0.964	0.764	0.13
11	F11	0.456	0.984	0.966	0.503	0.26
12	F12	0.722	0.994	0.984	0.659	0.209
13	F13	0.662	0.973	0.988	0.564	0.178
14	F14	0.896	0.992	0.946	0.86	0.12
15	F15	0.182	0.97	0.919	0.397	0.274
16	F16	0.762	0.967	0.946	0.767	0.184
17	F17	0.888	0.997	0.968	0.715	0.15
18	F18	0.763	0.984	0.99	0.697	0.163
19	F19	0.706	0.991	0.997	0.578	0.215
20	F20	0.761	0.989	0.98	0.71	0.192
21	F21	0.636	0.948	0.981	0.628	0.163
22	F22	0.814	0.983	0.977	0.699	0.137
23	F23	0.417	0.963	0.958	0.513	0.238
24	F24	0.722	0.994	0.989	0.621	0.193
25	F25	0.717	0.994	0.993	0.617	0.211
26	F26	0.954	0.99	0.918	0.916	0.125
27	F27	0.69	0.997	0.985	0.637	0.233
28	F28	0.882	0.998	0.951	0.89	0.158
29	F29	0.814	0.991	0.987	0.634	0.145
30	F30	0.649	0.979	0.988	0.59	0.189
31	F31	0.56	0.984	0.98	0.56	0.226
32	F32	0.412	0.987	0.961	0.481	0.269
33	F33	0.725	0.991	0.988	0.648	0.183
34	F34	0.889	0.992	0.963	0.801	0.11
35	F35	0.282	0.977	0.941	0.398	0.261
36	F36	0.72	0.987	0.98	0.682	0.189
37	F37	0.798	0.992	0.99	0.63	0.202
38	F38	0.912	0.998	0.957	0.824	0.131
39	F39	0.567	0.988	0.985	0.54	0.225
40	F40	0.824	0.992	0.971	0.764	0.157
41	F41	0.566	0.981	0.983	0.556	0.215

CONCLUSION:

Entrapment efficiency is one of the most important characteristic of particulate drug delivery systems and it decides the weight of the formulation to be taken in order to have the required dose. In this work, influence of various formulation and process parameters on entrapment efficiency and particle size was aimed to explore so as to develop microballoons with high entrapment efficiency. The experiment was designed according to Box – Behnken design under response surface methodology and performed. The obtained results suitably analyzed by ANOVA and found that all the selected factors were found to have significant influence on entrapment efficiency and hence the major objective of the work was achieved.

REFERENCES:

1. Gannu Praveen Kumar, Jannu Anand. Porous floating microspheres: A new dimension in controlled drug delivery. Research J. Pharm. and Tech. 2011; 4(9): 1340 – 1357.

2. MR Shivalingam, KSG Anil Kumara, YV Kishore Reddy, et.al. Formulation and evaluation of floating microballoons of ibuprofen for the enhanced enteric bioavailability. Research J. Pharm. and Tech. 2010; 3(2): 583 – 585.

3. UK Patil, Ravish Sahu, SK Yadav. Formulation and Evaluation of Controlled Release Microspheres Containing Metformin Hydrochloride. Research J. Pharm. and Tech. 2009; 2(1): 176 – 179.

4. Mohanraj Palanisamy, Jasmina Khanam, N Arun Kumar, C Rani. Chitosan Microspheres Encapsulated With Metoprolol Succinate: Formulation and In - Vitro Evaluation. Research J. Pharm. and Tech. 2009; 2(2): 349 – 352.

5. V. Swathi, G. Velrajan, Balasubramaniam. Formulation and Evaluation of Albumin Microspheres containing Stavudine. 2013; 6(2): 174 – 177.

6. Chinna Gangadhar B, Shyam Sunder R, Vimal Kumar Varma. M, Sleeva Raju M, Sai Kiran M. Formulation and Evaluation of Indomethacin Microspheres using Natural and Synthetic Polymers as Controlled Release Dosage Forms. International Journal of Drug Discovery. 2010; 2(1): 08-16.

7. Rajamanickam Deveswaran, Rajappan Manavalan, Vardharajan Madhavan, Srinivasan Bharath. Formulation and Evaluation Of Albumin Microspheres Containing Aceclofenac. International Journal of Pharmaceutical Sciences Review and Research. 2010; 4(1): 112-117.

8. Srikar G, Avula P, Annapurna P, Boola M. Development of extended release matrix tablets of felodipine through solid dispersions for better drug release profile by a 3² factorial design. Ind J Pharm Edu Res. 2016; 50(2S): S89-99.

9. Zhenqiu Yang, Baozhen Song, Qiaoxia Li, Honglei Fan, Fan Ouyang. Preparation of Microspheres with Microballoons Inside for Floating Drug-Delivery Systems, Journal of Applied Polymer Science, 2004; 94, 197–202.

10. Vimal Kumar Yadav, Awani Kumar Rai, A.K. Ghosh. Encapsulation of Repaglinidine into Eudragit RS Microspheres and modulation of their release characters by use of surfactants. International Journal of Pharmaceutical Sciences and Research. 2017; 8(9): 3936- 3947.

11. Prashant Malik, Upendra Nagaich, Raj Kaur Malik, and Neha Gulati. Pentoxifylline Loaded Floating Microballoons: Design, Development and Characterization, Journal of Pharmaceutics, Volume 2013: 1-5.

12. Kumar S, Nagpal K, Singh SK, Mishra DN. Improved bioavailability through floating microspheres of lamivudine. DJPS. 2011, 19, 57-64.

13. Jagtap Yogesh Mukund, Bhujbal Rohan Kantilal, Ranpise Nisharani Sudhakar. Floating microspheres: A Review. Brazilian Journal of Pharmaceutical Sciences. 2012, 48, 17-30.

14. Jain SK, Agrawal GP, Jain NK. Evaluation of porous carrier-based floating orlistat microspheres for gastric delivery. AAPS Pharm. Sci. Tech. 2006; 7:E54-62.

15. Jain D, Panda AK, Majumdar DK. Eudragit s100 entrapped Insulin Microspheres for Oral Delivery. AAPS Pharm. Sci. Tech.2005; 6:e100-7.

16. Gidwani B, Vyas A, Ahirwar K, Shukla S. Factorial design and a practical approach for gastro – retentive drug delivery system. Research J. Pharm. and Tech. 2016; 9(4): 641-9.

17. Grandhi Srikar, Avula Prameela Rani. Study on infuence of polymer and surfactant on in vitro performance of biodegradable aqueous-core nanocapsules of tenofovirdisoproxil fumarate by response surface methodology. Brazilian Journal of Pharmaceutical Sceinces. 2019; 55; e18736.

18. Srikar Grandhi, A. Prameela Rani, Raghuveer Pathuri. Voriconazole Solid Lipid Nanoparticles: Optimization of Formulation and Process Parameters. Research Journal of Pharmacy and Technology. 2018 Jul 31;11(7):2829-35.

Received on 10.10.2019                 Modified on 17.12.2019

Accepted on 20.02.2020                 © RJPT All right reserved

Research J. Pharm. and Tech 2020; 13(9):4373-4380.

DOI: 10.5958/0974-360X.2020.00773.8