Design and Assessment of Mucoadhesive Insitu Gel Forming Spray for Oral Delivery of Ibuprofen

The buccal drug delivery system offers several benefits compared to traditional and systemic drug formulations. It enhances bioavailability by bypassing the first-pass metabolism and promotes better absorption through the mucosal surface, along with a prolonged residence time. [1] Among the various transmucosal drug delivery routes, the buccal mucosa stands out as one of the most accessible and practical sites for administering therapeutic agents, catering to both local and systemic effects. Oral sprays are often considered an optimal option due to their ability to improve patient compliance. Furthermore, these sprays can quickly release the drug in the form of micro-sized droplets, which are absorbed through the buccal mucosa. This enables a rapid and direct dispersion of the active ingredient across a large surface area of the oral cavity, facilitating more efficient absorption through the mucosal lining. [2] In situ gel systems are typically liquid at room temperature but undergo gelation when they come into contact with body fluids or when there is a shift in pH. Unlike rigid gels, these systems are easy to administer in liquid form and can transform into bioadhesive gels at the site of absorption. Upon application, they swell and form a gel that enhances the residence time of the drug, thereby supporting sustained drug release. A wide range of natural and synthetic polymers are suitable for the formulation of in situ gels, which can gel in response to various stimuli such as changes in pH, temperature fluctuations, or ionic interactions. These gels can be delivered through multiple routes, including oral, ocular, rectal, vaginal, injectable, and intraperitoneal pathways. Among these, in situ spray gels represent a novel delivery system where gelation is triggered solely by pH changes, serving as the physiological stimulus. Typically, anionic pH-sensitive polymers like polyacrylic acid (Carbopol®, carbomer) and its derivatives are used. These are usually in solution form at acidic pH and convert to a viscous gel as the pH increases. Compared to conventional topical gels, in situ gel-forming sprays provide distinct advantages. Topical gels often spread beyond the intended application site and show reduced retention in the plaque area, potentially leading to side effects such as numbness in the lips, tongue, and cheeks, and increasing the risk of accidental ingestion. [3]

MATERIALS AND METHODS

MATERIAL:  

In this work, two grades of Carbopol were used (Carbopol 934 and Carbopol 940) as in situ gelling polymers. Other materials like xanthan gum, propylparaben All other chemicals and solvents were of analytical reagent grade, and deionized water was used in this study. [4]

Method of Prepration:

Make four different formulations, which you can see in Table 1. These formulations used different concentrations of Carbopol 934 and 940 (0.1%, 0.3%, w/v) along with 0.2% (w/v) xanthan gum. Then started by dispersing Carbopol and xanthan gum in purified water and letting it hydrate overnight in the fridge at 4°C.After that dissolve the Ibuprofen, which is a drug that doesn't dissolve easily which is soluble in ethanol and then in phosphate buffer pH 6.8. Add propyl paraben to the drug solution and then mixed it with the polymer solution until it became a uniform solution. Finally, add enough deionized water to bring the volume up to 100 ml. [5]

Formula

Table no 1: Formulation composition of Ibuprofen oral in situ gel spray(%w/v)

Preformulation characterization of drug

Melting point: Ibuprofen melting point was ascertained using micro-controlled melting point apparatus (Chemi line CL 726). A capillary tube was used to contain the substance, with one end maintained closed. The capillary was then immersed in a bath of silicone oil that had been carefully heated with an electrical heating coil.

λmax determination: In methanol, the UV-spectrum of pure ibuprofen was measured. The medication (10 mg) was diluted in 100 ml methanol to form a stock solution with a concentration of 100 g/ml. One ml. of the stock solution was collected and diluted to ten ml. The absorbance was measured using a UV spectrophotometer. It should create a peak matching to its maximum wavelength of 264 nm. [6]

Calibration curve of ibuprofen

Calibration curve of ibuprofen in methanol:

Preparation of Stock Solution Weigh 100 mg of ibuprofen accurately and transfer it into a 100 mL volumetric flask. Dissolve completely in methanol and make up the volume to 100 mL to obtain a 1000 µg/mL stock solution. Preparation of Working Standard Solutions From the stock solution (1000 µg/mL), take 2 mL, 4 mL, 6 mL, 8 mL, and 10 mL into separate 10 mL volumetric flasks. Dilute each to 10 mL with methanol to get final concentrations of 20, 40, 60, 80, and 100 µg/mL. UV Spectrophotometric Analysis Set the spectrophotometer to 264 nm (as determined from the λ max study). Measure the absorbance of each concentration using methanol as the blank.

Observations & Considerations: The calibration curve follows a linear trend, but the absorbance value for 80 µg/mL (0.11) and 100 µg/mL (0.158) appear lower than expected based on the trend. This could be due to instrumental error, sample preparation errors, or possible precipitation of ibuprofen at higher concentrations. For better accuracy, repeat the measurements or verify solution homogeneity. [7]

Calibration curve of ibuprofen in phosphate buffer pH 6.8:  Preparation of Stock Solution Weigh 100 mg of ibuprofen accurately and transfer it into a 100 mL volumetric flask. Dissolve completely in methanol and make up the volume to 100 mL to obtain a 1000 µg/mL stock solution. Preparation of Working Standard Solutions From the stock solution (1000 µg/mL), take 2 mL, 4 mL, 6 mL, 8 mL, and 10 mL into separate 10 mL volumetric flasks. Dilute each to 10 mL with methanol to get final concentrations of 20, 40, 60, 80, and 100 µg/mL. UV Spectrophotometric Analysis Set the spectrophotometer to 264 nm (as determined from the λ max study). Measure the absorbance of each concentration using methanol as the blank

Observations & Considerations: The calibration curve shows a linear relationship, suggesting that ibuprofen follows Beer- Lambert’s law in phosphate buffer pH 6.8. The absorbance values are relatively low, indicating that ibuprofen has lower solubility in phosphate buffer compared to methanol. Ensure that the buffer is properly prepared and that all solutions are homogeneous before measurement. [8]

Evaluation parameter

Visual appearance and clarity: The visual clarity and overall appearance of the prepared formulations were examined by observing them against contrasting white and black backgrounds.

pH of the formulation: The pH of the formulations was measured using a digital pH meter. The pH probe was immersed in the formulation for 5 minutes and readings were recorded.

Content Uniformity: To assess the drug content of the insitu spray gel, 1 mL of formulation liquid was placed in a 100 mL volumetric flask. To increase the volume to 100 ml, phosphate buffer pH 6.8 was added to the flask. Transfer 4ml of the diluted solution to a 10ml volumetric flask and adjust with pH 6.8 phosphate buffer. Absorbance was measured at 264 nm with a double-beam UV spectrophotometer. The drug content was determined by using calibration curve. [9]

Gelling capacity (in vitro/sol-to-gel transition): To determine which composition would be best suited for use as an in-situ gelling system, the gelling capacity of each created formulation was assessed. To conduct the gelling capacity test, a drop of each formula was added to a 10-ml beaker that had been equilibrated at 37°C with 5-ml of phosphate buffer. During this test, the gel's visual assessment during its formation, gelation time, and dissolution time were all recorded. [10]

Syringeability: The produced formulations were put into a 5-ml syringe with a 20-gauge needle at a constant volume of 1 ml. Solutions that easily passed through the syringe were referred to as pass, while those that were difficult to pass were referred to as fail.

Spray angle: In situ gel sprays were directed horizontally onto a white paper mounted 1 cm from the nozzle. The radius of the minimum and maximum diameters of a circle drawn on paper were measured.

Equation 1 was used to calculate spray angle (θ) = tan?¹ l/r …. (1)

In this equation,

θ = spray angle in degrees = distance between the paper and the nozzle, and

r = average radius of the circle.

Rheological studies: Rheological properties of the prepared in situ gelling system were determined at non-physiological (pH 4.5–5.8 and 25°C) and physiological (pH 6.8 and 37°C) conditions, respectively, using digital viscometer with spindle number 3. The viscosity of the samples was recorded before and after gelation. [11]

Drug release study: Franz Diffusion Cell with Dialysis Membrane [12]

Introduction: The Franz diffusion cell is a widely used experimental apparatus to study drug permeation and release kinetics across biological or synthetic membranes. In this study, a dialysis membrane is used to evaluate the diffusion of ibuprofen from an in-situ gel formulation.

Components of Franz Diffusion Cell: Donor Compartment - Contains the ibuprofen in-situ gel formulation. Receiver Compartment - Holds the dissolution medium (phosphate buffer, simulated saliva).

Dialysis Membrane - Semi-permeable barrier allowing controlled drug diffusion.

METHODOLOGY

1. Preparation of the Dialysis Membrane: Soak in distilled water for 12 hours before use. Equilibrate with buffer solution to mimic experimental conditions.
2. Setup of Franz Diffusion Cell: Fill the receiver compartment with phosphate buffer (pH 6.8). Secure the dialysis membrane between the donor and receiver compartments. Maintain temperature at 37 ± 0.5°C and stir continuously at 200-300 rpm.
3. Loading of the Formulation: Add 1 mL of ibuprofen in-situ gel spray into the donor compartment. Cover the compartment to prevent evaporation.
4. Sampling and Analysis: Withdraw 1 mL of sample at 0, 15, 30, 60, 120, 180, and 240 minutes. Replace with fresh buffer after each withdrawal. Measure ibuprofen concentration using UV-Vis Spectrophotometry (lambda max = 264nm).
5. Data Interpretation: Plot cumulative drug release (%) vs. time (minutes). Apply kinetic models to understand Release

MECHANISMS:

Advantages of Franz Diffusion Cell with Dialysis Membrane- Mimics biological membranes while ensuring controlled drug diffusion. Cost-effective and reproducible method for permeability studies. Useful for preclinical screening before in vivo test.

RESULTS AND DISCUSSION

Preformulation characterization of drug

Melting point: Melting point of Ibuprofen determined by using the capillary method, and It was discovered to be within the range of 75-78ºC.

λmax determination: λmax is an essential parameter used to compare the spectral properties of various substances. It provides maximum sensitivity while minimizing deviations from Beer’s Law. The UV spectrum of pure Ibuprofen was determined, showing a λmax at 264 nm. At a low concentration (100 µg/mL), a peak was observed at 264 nm, with an absorbance value of approximately 0.7. However, at higher concentrations, when the absorbance exceeds 1, a shift in λmax may occur due to molecular interactions or solvent effects.

Fig no. 1 Ultraviolet absorption spectra of ibuprofen

Calibration curve of ibuprofen

Table no. 2 Data for calibration curve of ibuprofen in methanol λ max determination the optimal absorbance was found at 264 nm. Thus, λ max of Ibuprofen was found to be at 264 nm in Methanol. Calibration curve of ibuprofen in methanol shown in fig no 2.

Table no. 2

Table no. 3 Data for calibration curve of ibuprofen in phosphate buffer pH 6.8. λ max determination the optimal absorbance was found at 264 nm. Thus, max of Ibuprofen was found to be at 264 nm in Phosphate buffer 6.8. curve show in fig no 3.

Table no.3

Fig no. 2 

Fig no. 3 

Evaluation Parameter:

Visual Appearance and pH: The created in situ spray gelling systems were assessed for visual appearance, clarity, and pH. As Carbopol concentration increases, the formulation's pH decreases due to the polymer's acidic nature.

Fig no.4 clarity and appearance 

Fig no.5 pH of the solution

Table 4: pH values and Appearance of the insitu gel forming spray

Content uniformity:

The drug content of the buccal formulations of Ibuprofen in situ gel forming spray was found to be satisfactory ranging between 98.20%±0.04 and 95.10%±0.03, indicating uniform distribution of the drug throughout the formula. Gelling capacity (sol-to-gel transition/in vitro):

Formulations with 0.1%-0.3% (w/v) Carbopol appear to have free-flowing qualities at non- physiological pH levels. A 0.3% (w/v) Carbopol concentration (F2, F4) resulted in a harder gel with better gelation capacity at physiological pH compared to 0.1% (w/v) Carbopol formulations.

Fig no.6 clarity and appearance

Fig no.7 pH of the solution

Syringeability:

The formulations' Syringeability was measured based on their substance and concentration. The mixtures flowed smoothly through the syringe needle.

Fig no.8 clarity and appearance

Fig no.9 pH of the solution

Table 5. Syringeability of gel forming spray.

The results of spray angle are shown in Table 4. The spray angle was found to be significantly increased in the range of 25.7°±0.3 – 42°±0.1 as the volume per each actuation increased and the viscosity decreased for either polymer grade.

Fig no 10. Spray angle of gel forming spray

Table 6. Spray angle of gel forming spray

Rheological studies:

Viscosity of formulations was measured under non-physiological and physiological conditions to investigate the rheology of these formulations. To apply easily at the affected site, the formulation must possess optimum viscosity. Furthermore, the formulation should undergo rapid sol-to-gel transition on contact with the affected site. The formulations were in a liquid state are exhibited low viscosity. An increase in the pH to 6.8 caused the solutions to transform into gels with high viscosity. The viscosity of the formulations was found to be influenced by the concentration of polymers used; hence, a significant increase in viscosity was observed with increasing polymer concentrations. This may be due to higher degree of cross-linking at higher concentrations of polymers.

Table 7. Viscosity of gel forming spray of Ibuprofen

Drug Release: Graphical representations of release profile for in situ gelling spray regarding the effect of polymer concentration are shown in Fig no 11 using Carbopol 934 and 940. The results indicated that, as the concentration of Carbopol increases, the release of drug decreases. F3 and F4 Carbopol 940 have slowest release profile.

Table no 8. drug release rate

Fig 11. Drug release study by Franz cell diffusion apparatus.

The following graphs represents time vs CADD/ Unit area as follows: