|Year : 2013 | Volume
| Issue : 2 | Page : 90-94
Controlled ocular drug delivery of ofloxacin using temperature modulated in situ gelling system
Upendra Nagaich, Nidhi Jain, Divya Kumar, Neha Gulati
Department of Pharmaceutics, School of Pharmacy, Bharat Institute of Technology, Meerut, Uttar Pradesh, India
|Date of Web Publication||23-Jul-2013|
Department of Pharmaceutics, School of Pharmacy, Bharat Institute of Technology, Meerut, Uttar Pradesh - 250 103
Source of Support: None, Conflict of Interest: None
Background: The designing of ocular dosage form off ers complicated issues. Numerous protective mechanisms are present in the eye to prevent the absorption of drug candidate from the corneal membrane. The poor bioavailability and therapeutic response exhibited by conventional ophthalmic solutions due to rapid precorneal elimination of the drug may be overcome by the use of in situ gel forming systems, which are instilled as drops into the eye and then undergo a sol-gel transition in the cul-de-sac. In situ forming polymeric formulations drug delivery systems is in sol form before administration in the body, but once administered, undergoes gelation in situ to form a gel. The formulation of gel depends upon factors like temperature modulation, pH changes, presence of ions, and ultraviolet irradiation, from which drug gets released in sustained and controlled manner. Objective: The present investigation deals with formulation and evaluation of Pluronic; based in situ gel of ofloxacin. Material and Method: Pluronic as gelling agent, HPMC as viscosity modifying agent was used. Ofloxacin was used as Active Pharmaceutical Ingredient. Results: In vitro drug release studies indicated that the formulated in situ gel retained the drug better than the conventional dosage forms. The formulations were therapeutically efficacious, sterile, stable, and provided controlled release of the drug over a period of time. Conclusion: The results demonstrate that the developed system is an alternative to conventional ophthalmic drops, patient compliance, industrially-oriented, and economical.
Keywords: Controlled opthalmic delivery, novel in situ gel, ocular drug delivery, ofloxacin, temperature modulated in situ gel
|How to cite this article:|
Nagaich U, Jain N, Kumar D, Gulati N. Controlled ocular drug delivery of ofloxacin using temperature modulated in situ gelling system. J Sci Soc 2013;40:90-4
|How to cite this URL:|
Nagaich U, Jain N, Kumar D, Gulati N. Controlled ocular drug delivery of ofloxacin using temperature modulated in situ gelling system. J Sci Soc [serial online] 2013 [cited 2019 Jul 19];40:90-4. Available from: http://www.jscisociety.com/text.asp?2013/40/2/90/115477
| Introduction|| |
Conventional ophthalmic delivery systems like eye drops result in poor ocular drug bioavailability due to ocular anatomical and physiological constraints, which include the relative impermeability of the corneal epithelial membrane, tear dynamics, and nasolacrimal drainage. In situ gel forming systems are liquid aqueous solutions before administration but transformed to gel under physiological conditions. These are the delivery systems, which can be instilled as eye drops and undergo an immediate gelation when in contact with the eye. ,
In situ drug delivery system offers advantages such as reduced frequency of administration, improved patient compliance, and comfort . An in situ gel formulation provides an interesting alternative for achieving effective plasma drug concentration, an advantage over conventional delivery systems. In situ gelling system delivers accurate dose as well as prolongs residence time of drug in contact with mucosal membrane, thus overcomes the problems generally encountered in semisolid dosage forms. 
There are several possible mechanisms that lead to in situ gel formation like ionic cross linking, pH change, and temperature modulation. Several polymers have been developed for in situ gel forming systems to prolong the precorneal residence time of a drug and improve ocular bioavailability.  The use of biopolymers whose transition from sol-to-gel is triggered by an increase in the temperature is an attractive way to approach in situ gel formation. Temperature modulated hydrogels are liquid at room temperature (20-25°C) and forms gel when comes in contact with body fluids (35-37°C), due to an increase in temperature. Temperature sensitive polymers have a lower critical solvent temperature (LCST). These polymers contract when heated above LCST. LCST is a temperature below which the components of the mixture are miscible in all proportions. The ideal critical temperature for this system is ambient and physiologic temperature so that phase transition does not require any external source of heat other than the body heat. ,
The aim of the present work is to study the temperature modulated in situ gelling system of ofloxacin, a second generation fluoroquinolone derivative, used in the infection of the eye such as acute conjunctivitis.
| Materials and Methods|| |
Ofloxacin was received as a gift sample from Cotec Healthcare, Roorkee, India. Pluronic and Hydroxy propyl methyl cellulose (HPMC) were purchased from Central Drug House, New Delhi, India. All other chemicals used were of analytical grade.
Formulation of gel
Aqueous solutions of Pluronic F127 and HPMC were prepared by dispersing them in distilled water with constant stirring. Ofloxacin was dissolved in glacial acetic acid and added to HPMC solution. HPMC drug solution was then poured into Pluronic solution with constant agitation and was allowed to stand at 4°C for 24 h to make a clear solution [Table 1].
| Characterization of Formulated In Situ Gel|| |
Visual appearance and clarity
The appearance of the prepared in situ gel systems was determined visually. Clarity of the in situ gel was observed against a white and black background for presence of any particulate matter. 
Viscosity and pH
The viscosity was measured using a Brookfield viscometer (LV-DVE model, Brookfield, USA). pH of the formulation was measured using a digital pH meter (Equiptronics Mumbai, India). 
In situ gel forming systems were also characterized for the drug content. 1 mL of the preparation was left for 24 h in simulated artificial tear fluid (Ph: 7.4) and the sample was analyzed in ultraviolet spectrophotometer (UV 1601, Shimadzu, Japan) at 288 nm. 
The gelling capacity was determined by placing one drop of the formulation in a vial containing 2 mL of freshly prepared artificial tear fluid and visually assessing time for gelation and the time taken for the gel to redissolve. The composition of artificial tear fluid used was NaCl: 0.670 gm, sodium bicarbonate: 0.200 gm, calcium chloride: 2H 2 O 0.008 gm, in 100.0 gm of purified water. 
Isotonicity is an important characteristic of ophthalmic preparation and has to maintain to prevent tissue damage or irritation of eye. Formulations were mixed with few drops of blood and observed under microscope at ×45 magnification. 
In vitro diffusion studies
In vitro drug release studies were carried out in Franz-Diffusion (F-D) cell using cellophane membrane and artificial tear fluid (pH: 7.4) as diffusion membrane and medium, respectively. The cellophane membrane (previously soaked overnight in the receptor medium) was tied at one end of the F-D cell. Accurately weighed, 1 mL of gel was spread uniformly on a cellophane membrane, which was in contact with receptor medium. The receptor medium was stirred continuously at 20 rpm to simulate blinking action of eyelids. The whole assembly was adjusted on magnetic stirrer and maintained at 36 ± 1°C to mimic physiological condition at which Pluronic remains in gel form. Aliquots of medium were withdrawn at appropriate time intervals and equal volumes of fresh media were added to replace the withdrawn samples. Withdrawn samples were filtered, diluted, and estimated by ultraviolet double beam spectrophotometer (UV 1601, Shimadzu, Japan) at 288 nm. 
Antimicrobial efficiency studies were carried out to ascertain the biological activity of sol-to-gel systems against microorganisms. This was determined by "disc diffusion method". Sterile solution of marketed ofloxacin eye drops was used as a standard. The standard solution and the developed formulations (test solution) between the ranges of 50 and 150 μg/mL were poured into separate cups bored into sterile agar solution previously seeded with organism Staphylococcus aureus. After allowing diffusion of solutions for 2 h, the plates were incubated for 24 h. The zone of inhibition measured around each cup was compared with that of the standard. 
Ocular irritancy test
Draize irritancy test was performed on male albino rabbit in order to demonstrate the safety potential of prepared formulation in animal model. A total of 100 μL of the optimized batch F3 was placed in the lower cul-de-sac and was observed at various time intervals. Rabbits were visually examined for any redness, swelling or excessive tear production. 
Ex vivo diffusion study
Ex vivo permeation study was carried out using goat corneal membrane. The eyeballs of goat were procured from a slaughter house. Washed corneal membranes were kept in freshly prepared tear fluid (pH: 7.4). The study was carried out by using F-D cell in such a w ay that corneum side is continuously remained in an intimate contact with formulation in the donor compartment. The receptor compartment was filled with TF (Simulated Tear Fluid) (pH: 7.4) at 34°C ± 0.5°C. The receptor medium was stirred on a magnetic stirred. The samples were withdrawn at different time intervals and analyzed for drug content. Receptor phase were replenished with an equal volume of STF (pH: 7.4) at each time interval. 
| Results and Discussion|| |
The formulations were light yellow in color and the clarity was found to be satisfactory. Clear sol-to-gel system is desired as it does not cause blurred vision.
The formulation should have an optimum viscosity that will allow easy instillation into the eye as a liquid (drops) that would undergo a rapid sol-to-gel transition. Viscosity of the instilled formulation is an important factor in determining residence time of drug in the eye. The prepared solutions were allowed to gel in the simulated tear fluid, and then the viscosity determination was carried out by using Brookfield viscometer (DV-E LV model) with spindle LV-3 with angular velocity run from 10 to 100 rpm. Viscosity of the prepared system was found in range of 22 to 48 cps.
The pH of all the formulations was within the acceptable range which indicates no possible irritation up on instillation of the formulation in the eyes. The pH of the formulation was found to be in range from 5.2 to 5.9 and the pH of artificial tear fluid was found to be 7.4.
Gelling capacity was determined by placing 100 μL of formulation in 2 mL freshly prepared artificial tear fluid. Formulation F4 and F5 showed an immediate gelling capacity and retained as gel for extended period of time. Formulation F1 and F2 were not having desired gelling capacity. This may be attributed to the concentration of Pluronic (gelling agent). For determination of gelation temperature, the temperature of the formulation was gradually raised by heating the container in a water bath. The change in viscosity at each temperature was recorded. Gelation temperature was found to be from 35 ± 0.5°C to 37 ± 0.5°C.
Drug content was analyzed with ultraviolet spectrophotometer at 288 nm and was found to be from 98.97% to 100.04%. Antimicrobial activity of the prepared ofloxacin in situ gelling system was found to be satisfactory.
Antimicrobial assay was performed using cup-plate method. The study indicated that the ofloxacin retained its antimicrobial efficacy even after formulated as an in situ gelling system [Figure 1].
|Figure 1: Data illustrating zone of inhibition of several ofloxacin loaded in situ gelling system|
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Formulation was subjected to isotonicity study and exhibited no change in the shape of blood cells (bulging or shrinkage), which reveals the isotonic nature of the formulation and compared with that of standard marketed ophthalmic eye drop of ofloxacin. The in vitro drug diffusion from the formulation was depicted in [Figure 2]. As dictated by in vitro diffusion data, the increase in amount of Pluronic (from F1-F5) progressively retarded the drug diffusion rate. The lowest polymer concentration (F1) showed faster diffusion 92.8% in 24 h and the highest polymer concentration (F5) diffused only 69% drug after 24 h. The diffusion of drug was prolonged with increased concentration of polymer in the formulation [Table 2].
|Figure 2: In vitro diffusion profiles of ofloxacin loaded in situ gelling system|
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Ocular irritancy studies showed no potential threat to the corneal surface. Optimized formulation (F3) was instilled in the lower cul-de-sac and the rabbit was observed for a week at regular intervals. There was no indication of any damage to the corneal tissues [Table 3].
|Table 3: Draize test for ocular irritancy of the optimized ofloxacin loaded in situ gel|
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Ex vivo permeation study using goat corneal tissue supported the in vitro diffusion pattern data. Formulation F1 has the fastest permeation rate, while the formulation with maximum polymeric concentration has shown slowest permeation through the corneal surface [Figure 3].
|Figure 3: Ex vivo diffusion profiles of ofloxacin loaded in situ gelling system|
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| Conclusion|| |
Novel temperature modulated ofloxacin loaded ophthalmic in situ gel was successfully formulated using Pluronic F127 and HPMC as gelling agent and viscosity modifying agent, respectively. The developed formulation was characterized for all parameters and had shown a viable alternative to conventional eye drops by virtue of its ability to enhance the antibacterial effect through its longer percorneal residence time and ability to sustain the drug release. The ease of administration coupled with its ability to provide sustained release for 24 h could probably result in less dosing frequency, which may contribute in enhancing the patient's compliance.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]