Formulation and Characterization of Ofloxacin Microspheres Prepared By Ionotropic Gelation Technique

M. Purushothaman¹*, Sowjanya Battu², K. Jyothshna Devi³, C. Madhusudhana Chetty², M. Alagusundaram² and K. Mallikarjuna Rao²

¹Dept. of Pharmaceutics, Vasavi Institute of Pharmaceutical Sciences, Bakarapeta, Kadapa Dist., A.P, India. ²Dept. of Pharmaceutics, Annamacharya College of Pharmacy, Rajampet - 516 126, Kadapa Dist., (A. P.) India. ³Department of Pharmaceutics, S.V University, Tirupathi, A.P, India

*Corresponding Author E-mail: Dazlingdude.s@gmail.com

ABSTRACT:

The main aim of the present study was to formulate ofloxacin microspheres by Ionotropic gelation technique using various polymers such as carbopol grades 934 and 940, sodium carboxy methyl cellulose (SCMC) and sodium alginate. Where 10 % calcium chloride is used as a cross linking agent to form a discrete microspheres with sodium alginate. The prepared ofloxacin microspheres were evaluated for its Particle size and shape analysis, flow properties, micromeritic properties, drug entrapment efficiency, drug content, in vitro drug release studies. The prepared microsphere were bulky, free flowing, spherical and showed an drug entrapment ranging between 60 – 80 % and had a mean particle size ranging from 120 – 380 µm as determined by the optical microscopy and SEM analysis. The in vitro release of the drug from the polymer coated microspheres had shown controlled and sustained drug delivery more than 12 h. The in vitro release data were fit to different equations and kinetic models to explain release profiles. The kinetic models used were zero order, higuchi’s and peppa’s. The correlation coefficient value (r) indicates that the kinetic of drug release was zero to first order and the mechanism of drug release follows super case II transport. Based upon the evaluation parameters results the formulation F3 showed the best controlled release than the other formulations.

KEYWORDS: Ofloxacin, Ionic gelation technique, Carbopol 940, Sodium alginate zero order.

INTRODUCTION:

Microencapsulation is a technique by which solid, liquid or gaseous active ingredients are packaged within a second material for the purpose of shielding the active ingredient from the surrounding environment¹. Thus the active ingredient is designated as the core material whereas the surrounding material forms the shell. Microspheres are mono or multinuclear materials embedded in spherical coating matrix. Currently, oral sustained release formulationscontinue to be the most popular ones among all the drug delivery systems as it offers several advantages over conventional systems like better plasma level profile, prolonged and sustained action, lower dosing etc. The major advantage of sustained release formulation is their ability to increase the residence time of the dosage form in the stomach which remain at the absorption site for a long time, unlike controlled release systems^2,3.

The criteria for choosing microspheres in the present study is, lower the surface area of the particle, greater is the absorption, thus quicker onset of action. The sustained and controlled release action of these microspheres can be attained by using the suitable polymers such as carbopol 934 and 940, SCMC, along with sodium alginate and calcium chloride^4,5.

Ofloxacin is a fluoroquinolone antibiotic act as a DNA gyrase inhibitor. It is used for the treatment of acute exacerbations of chronic bronchitis, community acquired pneumonia, skin and skin structure infections, urethral and cervical gonorrhea, cystitis, UTI’s, prostatitis, pelvic inflammatory diseases etc. Ofloxacin is available as both tablets and ophthalmic solutions. The problems/toxicity due to over dosage of ofloxacin such as renal failure, seizures, nausea and vomiting may be avoided by sustained release microspheres. In the present study multiparticulate (microspheres) system was preferred as a formulation over conventional forms as it has several advantages like, it increases the surface area exposed to the absorption site and increases the absorption of drug and thus decreases the dosing of the drug⁶.

MATERIALS AND METHODS:

Ofloxacin was a gift sample by caplin point laboratory Ltd, Pondichery. Sodium alginate was obtained from Sd. Fine. Chem. Ltd as a gift sample. Carbopol (934 and 940) and SCMC were gifted by Himedia Labs, Pvt., Ltd. All other reagents used were of analytical grade. The microspheres were prepared by ionic gelation technique and the concentrations of ofloxacin were measured with UV-VIS Spectrophotometer Labomed, Inc, USA No: 2602.

Preparation of ofloxacin Microspheres by ionotropic gelation technique:^7-10

Weighed quantities of sodium alginate and polymers (carbopol 934/940 or SCMC) as per the ratios mentioned in the Table 1 were dissolved in purified water (30 ml) to form a homogenous polymer solution. The drug ofloxacin was added to the polymer solution and mixed homogenously to get a smooth viscous dispersion. The resulting dispersion was then added in a thin stream to about 500 ml of liquid paraffin containing 400 ml of light liquid paraffin and 100 ml of heavy liquid paraffin in a 1000 ml volumetric flask, stirring with 400 rpm for 5 mins to emulsify. Therefore 30 ml of calcium chloride (10% W/V) solution was added slowly by stirring. The microspheres were separated and washed with petroleum ether followed by a stream of water. These were then dried at 45˚c for 8 hrs and kept in desiccators.

EVALUATION OF PREPARED MICROSPHERES: (Table-2)

Assessment of Flow Property:^{11, 12}

Angle of Repose:

Flow property of granules was assessed by determining the angle of repose. The angle of repose was measured by allowing the granules to fall on a graph paper placed on a horizontal surface through a funnel kept at a certain convenient height about 6 cm. The height of the heap was measured and then the circumference of the base of the heap was drawn on the paper with the help of a pencil. The radius of the circle obtained was measured. Angle of repose between 35 & 45 indicates that the microspheres do not have satisfactory flow property the angle of repose is given as:

Tan θ = h / r

Where, θ =Angle of Repose.

h= Height of the heap.

R = Radius of the base of the heap.

The results were tabulated.

Bulk density:

Bulk density was determined by pouring the microspheres into a graduated cylinder. The bulk volume (V) and weight of the powder (M) was determined. The bulk density was calculated by using the below mentioned formula,

Mass of microspheres

Bulk density = -------------------------------

Volume microspheres

Tapped density:

The measuring cylinder containing a known mass of microspheres was tapped for a fixed time. The minimum volume (Vt) occupied in the cylinder and the weight (M) of the microspheres was measured. The tapped density was calculated using the following formula,

Weight of the microspheres

Tapped density = -----------------------------------------

Volume occupied in the cylinder (Vt)

Compressibility index:

The simplest way for measurement of free flow of microspheres is compressibility, a indication of the ease with which a material can be induced to flow is given by compressibility index (I) which is calculated as follows,

Vt - Vo

I = ------------ X 100

Vbx

Here, Vo is bulk volume and Vt is tapped volume. The value below 15% indicates a powder with usually give rise to good flow characteristics, whereas above 25% indicate poor flow ability.

Scanning electron microscopy:

Morphological details of the specimens were determined by using a scanning electron microscope (SEM), model ISM 35 CF, JEOL, Japan.

Drug Content determination^{13, 14}

A 100 mg equivalent of ofloxacin microspheres were triturated in a glass mortar and pestle dissolved in methanol, it was then filtered to remove debris and the volume was made up to 100ml with ph 7.4 phosphate buffer. Then prepare a suitable dilution and the absorbance of the resulting solution was measured at 225 nm using U.V Visible Spectrophotometer and the amount of Ofloxacin in 100 mg of microspheres was calculated.

Encapsulation of efficiency^{15, 16}

The drug encapsulated efficiency was determined using the formula

E = _________ x 100

Where, E = Percentage encapsulation of microspheres

QP = Quantity of drug encapsulated in microspheres

Qt = Quantity of drug added for encapsulation

The results are tabulated.

In-Vitro Drug Release Studies:^17-19

Invitro release study of ofloxacin microspheres was carried out using U.S.P dissolution apparatus type 1 and using 0.1 N HCl and 7.4 pH buffer solution as a medium. 100 mg equivalent of ofloxacin microspheres were weighed and placed in a rotating basket, 900 ml of 0.1 N HCl is taken as medium and temperature was maintained at 37°C and fluid was agitated properly. For every 1 hour interval the medium was withdrawn and replaced with the same amount of fluid for maintaining proper sink conditions. The samples were filtered; 3 ml of filtrate was taken and diluted by using suitable dilution. These were analyzed spectrophotometrically at 225 nm.

TABLE NO 01: COMPOSITION OF THE PREPARED CONTROLLED RELEASE OFLOXACIN MICROSPHERES

Formulation code	Drug /polymer ratio	Drug (gm)	Sodium alginate (gm)	Carbopol 940 (g)	Carbopol 934 (g)	SCMC (g)	10 % calcium chloride (ml)
F1	1:1	2	1	1	_	_	30
F2	1:1.5	2	1.5	1.5	_	_	30
F3	1:2	2	2	2	_	_	30
F4	1:1	2	1	_	1	_	30
F5	1:1.5	2	1.5	_	1.5	_	30
F6	1:2	2	2	_	2	_	30
F7	1:1	2	1	_	_	1	30
F8	1:1.5	2	1.5	_	_	1.5	30
F9	1:2	2	2	_	_	2	30

TABLE NO. 02: MICROMERITIC PROPERTIES OF PREPARED MICROSPHERES

Formulation Code	Bulk density (gm/ml)	Tapped density (gm/ml)	Angle of repose (θ)	Compressibility Index	Drug content (gm)	Percentage Encapsulation efficiency
F – 1	0.55 ± 0.015	0.65 ± 0.026	27^•48″ ± 15	14.71 ± 0.115	1.738 ± 0.49	86.6 ± 0.5
F – 2	0.54 ± 0.02	0.67 ± 0.005	27^•36″±0.17	16.35 ± 0.1	1.734 ± 0.52	86.7 ± 0.37
F – 3	0.56 ± 0.005	0.68 ± 0.011	27^•24″± .12	14.5 ± 0.057	1.812 ± 0.11	90.6 ± 0.14
F – 4	0.58 ± 0.018	0.66 ± 0.01	27^•34″± .05	15.4 ± 0.152	1.697 ± 0.26	84.85 ± 0.28
F – 5	0.58 ± 0.01	0.65 ± 0.005	27^•12″± .26	14.68 ± 0.12	1.762 ± 0.15	88.1 ± 0.132
F – 6	0.60 ± 0.02	0.67 ± 0.005	26^•56″±0.15	13.24 ± -.05	1.613 ± 0.2	80.65 ± 0.15
F – 7	0.55 ± 0.011	0.66 ± 0.015	30^•24″±0.11	14.65 ± 0.11	1.203 ± 0.25	60.16 ± 0.45
F – 8	0.42 ± 0.015	0.68 ± 0.01	29^•43″±0.24	14.6 ± 0.027	1.269 ± 0.15	63.46 ± 0.2
F – 9	0.414±0.005	0.69 ± 0.015	28^•58″±0.15	17.8 ± 0.012	1.365 ± 0.37	68.27 ± 0.26

After 2 hrs, replace the Medium with 900 ml of 7.4 pH phosphate buffer. The above procedure was repeated for every 1 hour, process was continued for 12 hrs. The amount of drug released was calculated from the calibration curve. The results were tabulated and represented graphically (Fig.-1).

FIGURE NO. 01: IN-VITRO DRUG RELEASE PROFILE FOR PREPARED OFLOXACIN SUSTAINED RELEASE MICROSPHERES

RESULTS AND DISCUSSION:

The drug chosen for this study is ofloxacin which is a flouroquinalone derivative used as antibiotic over the years has shown several dose related toxicities associated with multiple dosing during its therapeutic usage. But, present study is an endeavor to produce a novel system, which eliminates the need for repeated dosing and hence less chances for overdose. Microspheres were prepared by using the Ionotropic Gelation Technique with different ratios of drug to polymer. The encapsulation efficiency ranged from 60.16 to 80.64 %. The drug release rates varied from 11.25 to 98.66 %. From the above results, it is clear that formulations 7, 8 and 9 shows faster drug release profile (i.e., 8 hrs) where as formulations 1 to 6 shows better drug release properties. Among these first 6 formulations, formulations 1 to 3 shows better release than 4 to 6. From 1 to 3, formulation 3 shows slow drug release rates i.e., good sustained release properties, because F3 shows of about 79.80 % release even after 12 hrs (Fig.-1). Ofloxacin is an ideal drug for formulating as sustained release product. Sustained release products are most useful in long term therapy. Likewise this product can be used to extend the release rate of drug. For this purpose we have used polymer which is available as cheap retarded material to make concept of sustained release drug delivery system.

The obtained results in these formulations were plotted in various model treatment are as follows. i.e. Cumulative percentage release of drug Vs Square root of time (Higuchi’s) and Log cumulative percentage release Vs Log time (Peppas). The formulations F1 to F9 comparative plotted graphs of Higuchi’s and Peppas were shown in the Fig. 2 and 3 respectively. To find out the mechanism of drug release from hydrophilic matrices, the invitro dissolution data of each formulation with different kinetic drug release equations (Table-3).

TABLE NO. 03: DIFFUSION CHARACTERISTICS OF OFLOXACIN MICROSPHERES

FORMULATION CODE	CORRELATION COEFFICIENT VALUES (R)		DIFFUSION EXPONENT VALUE (n)
FORMULATION CODE	ZERO ORDER	PEPPAS MODEL	DIFFUSION EXPONENT VALUE (n)
F1	0.9973	0.9711	0.9977
F2	0.9973	0.9983	0.9984
F3	0.9939	0.8977	0.9942
F4	0.9904	0.9883	0.9984
F5	0.9903	1.036	0.998
F6	0.9968	1.122	0.997
F7	0.996	0.9406	0.9905
F8	0.9965	0.9655	0.9952
F9	0.9937	0.9633	0.97

FIGURE NO. 02: HIGUCHI’S PLOT

FIGURE NO. 03: PEPPA’S PLOT

Namely Zero order: Q=K0t; Higuchi’s square rate at time: Q=KHt1/2 and Peppas: F=Kmtn, where Q is amount of drug release at time t, F is Fraction of drug release at time t, K0 is zero order kinetic drug release constant, KH is Higuchi’s square root of time kinetic drug release constant, Km is constant incorporating geometric and structural characteristic of the films and n is the diffusion exponent indicative of the release mechanism. The correlation coefficient values (R) indicate that the kinetics of drug release was zero order and the mechanism of drug release by peppas model indicates the super case II transport evidenced with diffusion exponent values (n)

FIGURE NO. 04: SEM ANALYSIS FOR PREPARED BEST SUSTAINED RELEASE OFLOXACIN MICROSPHERES

CONCLUSION:

Microspheres were prepared using Ionotropic gelation technique and evaluated different parameters such as physico chemical properties, micromeritic properties, drug content, percentage encapsulation efficiency, In-vitro drug release studies. Good results were obtained for all the evaluated parameters and it was found that from the 9 different formulations, F3 was a better one when compared to all other formulations, because F3(C-940, 1:2) shows for about 79.80 % release after 12 hours and ensuring the sustained and controlled release property. Hence, the above results showed that Ofloxacin, a fluoroquinolone antibiotic is a right choice to formulate as microspheres.

ACKNOWLEDGEMENT:

The authors are thankful to caplin point laboratory Ltd, Pondichery for providing the gift sample of ofloxacin. The authors also thankful to Sd. Fine. Chem. Ltd. for providing the polymers and solvent systems and also thankful to management of, Sree Vidyanikethan College of Pharmacy, Rangampet, Tirupathi, Chittoor Dist for providing the all facilities for carried out this research work.

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Received on 04.05.2010 Modified on 20.05.2010

Research J. Pharm. and Tech.3 (4): Oct.-Dec.2010; Page 1265-1269