Atenolol-releasing buccal patches made of Dillenia indica L. fruit gum: preparation and ex vivo evaluations
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The objective of present research deals with the utility of extracted dillenia fruit gum (DG) as pharmaceutical excipient in the formulation of buccal patches containing atenolol (for the use in the treatment of hypertension). The atenolol-releasing buccal patches having a mucoadhesive polymeric layer of extracted DG-hydroxypropyl methylcellulose (HPMC K4M) and a drug-free backing layer of ethyl cellulose (1%) were prepared through the solvent-casting process. Various physicochemical parameters such as drug content, average weight, thickness, folding endurance and moisture content of all these buccal patches were found satisfactory. Ex vivo buccoadhesion was also found satisfactory. Ex vivo drug permeation across the excised porcine buccal mucosal membrane demonstrated the atenolol permeation over 12 h, which obeyed the first-order model (R2 = 0.9858–0.9967) with non-Fickian (anomalous) diffusion mechanism (n = 0.72–0.75). These buccal patches were also characterized by SEM and FTIR spectroscopy. These atenolol-releasing buccal patches can be used in the treatment of hypertension and angina pectoris bypassing the extensive hepatic first-pass metabolism.
KeywordsGum Buccal patches Buccoadhesion Atenolol
List of symbols
The drug quantity permeated across buccal mucosal membrane per unit time function at the steady-state condition (μg/h)
Area (cm2) of buccal mucosal membrane exposed to Franz diffusion cell
Permeation flux (μg/cm2/h)
Zero-order rate constant
First-order rate constant
Higuchi rate constant
Korsmeyer–Peppas rate constant
Amount of atenolol permeation at time, t
Amount of atenolol permeation at time 0
Dillenia fruit gum
- DG-HPMC K4M
Dillenia fruit gum-hydroxypropyl methylcellulose
- HPMC K4M
Scanning electron microscopy
The delivery of different drugs by means of buccal mucosa to the systemic blood circulation is identified as buccal drug delivery [1, 2]. The buccal mucosa is recognized as one of the well-vascularised areas, and the drugs are believed to be speedily absorbed into the systemic blood circulation beneath the buccal mucosal surface [3, 4]. The buccal mucosa possesses a larger, smoother and relatively immobile surface facilitating a larger contact surface for the drug absorption by the buccal drug delivery systems, which confers to the rapid and wide-ranging absorptions of drugs . Recent researches on the buccal drug delivery systems have already been proven as useful means of effective drug delivery through facilitating a number of benefits: circumventing of the gastro-intestinal tract as well as hepatic-portal systems, enhancement of the bioavailability for various drugs for oral administrations (eliminating the chances of hepatic first-pass metabolisms), facilitating drug administration to the unconscious patients, simplest way of drug administration (eliminating chances of invasive painful medications), improvement in the patient compliances, controlled and sustained drug releasing facilities, and easy termination of the drug delivery through detaching the dosage forms from the application site [6, 7].
Since the past few decades, a considerable amount of research endeavours towards the formulation and development of buccal patches have already been reported [8, 9, 10]. Buccal patches are the dosage forms in the form of films/membranes, where a thinner matrix is composed of matrix film/membrane forming polymers, mucoadhesive agents/polymers, other excipients and drugs. In the previously reported literature, several researches have already been carried out to prepare various buccal films/patches using plant-derived natural mucoadhesive polymers [10, 11]. Shiledar et al.  prepared and evaluated buccoadhesive bilayered patches of zolmitriptan employing xanthan gum. In another research, Avachat et al.  prepared and evaluated mucoadhesive films made of tamarind seed xyloglucan for buccoadhesive delivery of rizatriptan benzoate. However, no research is reported for the preparation of buccal films/patches using dillenia fruit gum (DG) as mucoadhesive polymer. DG is extracted from ripe dellinia (Dillenia indica L., family: Dilleniaceae) fruits . It is water soluble and biocompatible . It is reported as mucoadhesive gelling agents [12, 14]. In the recent years, DG is being exploited as pharmaceutical excipients in the formulation of various drug delivery dosage systems such as sustained drug releasing tablets, microbeads and mucoadhesive nasal gels [12, 13, 14, 15, 16]. Considering some useful properties of DG such as hydrophilicity, biocompatibility, biomucoadhesive potential, economic production and easy availability from the plant resources in the nature, in the current research, we made an endeavour to prepare and evaluate atenolol-containing buccal patches made of DG and hydroxypropyl methylcellulose (HPMC K4M) in the different amounts and combinations to make sure of the slower sustained releasing of atenolol over a longer period by means of reasonable biomucoadhesivity.
Atenolol is a selective β-1 blocker candidate and mainly given in the management of hypertension as well as angina pectoris . The chemical name of atenolol is (RS) 4-(2-hydroxy-3-isopropyl amino propoxy) phenyl acetamide. Its molecular formula is C14H22N2O3 with low molecular weight (i.e. 266.336) and low dosing (i.e. 25–50 mg) . Atenolol has lower gastro-intestinal membrane permeability because of its hydrophilic properties as it is sparingly soluble in the aqueous medium, and also the partition coefficient value is low (i.e. 0.23). Moreover, atenolol is a drug candidate showing very extensive first-pass metabolism in the liver possessing poor bioavailability (i.e. 40%, approximately). The lower dose, low molecular weight, very extensive first-pass metabolism as well as short half-life make atenolol as an appropriate drug for the buccal administration [19, 20]. In the literature, a number of atenolol-releasing buccal drug delivery systems have been already reported by various research groups [19, 20, 21, 22, 23, 24, 25, 26]. The goal of the current research was to prepare and assess the atenolol-releasing buccal patches having a mucoadhesive polymeric layer of isolated DG-HPMC K4 M and drug-free backing layer of ethyl cellulose (1%). These buccal patches were investigated for various physicochemical parameters (such as average weight, thickness, drug content, folding endurance and moisture contents) and ex vivo tests (such as ex vivo buccoadhesion and ex vivo drug permeation across excised porcine buccal mucosal membrane), which could be beneficial for providing sustained buccoadhesive delivery of atenolol over a prolonged period in the treatment of hypertension and angina pectoris bypassing the extensive hepatic first-pass metabolism.
2 Materials and methods
Atenolol (M/S. P.D.I.L, India), HPMC K4 M (Matrix Laboratories, India), ethyl cellulose (Matrix Laboratories, India), anhydrous calcium chloride (SD Fine Chemicals, India), glycerine (Loba Chemie Pvt. Ltd., India), sodium saccharin (Reidel India Chemicals, India) and acetone (Merck Ltd., India) were utilized. DG is extracted from ripe dellinia fruits (Dillenia indica L., family: Dilleniaceae) fruits purchased from Baripada market (Dist: Mayurbhanj, Odisha) in the month of September 2015. All other reagents and chemicals were commercially available and of analytical grade.
2.2 Extraction of DG
DG was extracted from ripe dillenia fruits according to the previously reported method by Ketousetuo and Bandyopadhyay  with little modifications. Collected dillenia fruits were washed with demineralised water and reduced into small pieces with a knife. Small pieces of dillenia fruits (1 kg) were soaked in the demineralised water and then boiled at 45 ± 1 °C under occasional agitation using an electrical water bath until thick slurry was formed. The thick slurry was then cooled and kept in the refrigerator for 24 h to settle down the undissolved part. The clear solution at the upper part was transferred and then centrifuged for 20 min at a speed of 500 rpm. The supernatant of the prepared solution was separated. Afterwards, the separated solution was concentrated at 50 ± 2 °C using an electric water bath until the volume reduction to one-fourth of the original volume, and cooled down to the room temperature. The concentrated solution was then poured into one-third of the volume of acetone with constant stirring by using a magnetic stirrer (Remi Motors, India). The formed precipitate was washed repeatedly with acetone and subsequently with demineralised water. The washed precipitate was collected and then dried at 45 ± 1 °C in an oven for 12 h. The dried DG was crushed to fine powder, passed through the 80-mesh screen and stored in an airtight desiccator for further use.
2.3 Characterization of extracted DG
2.3.1 Determination of yield
2.3.2 Physicochemical characterization
Various physicochemical properties such as colour, odour, taste, solubility in water, pH (1% solution at 37 °C) and viscosity (1% solution at 37 °C) of the extracted gum were measured. pH of the 1% solution of extracting gum was measured using a digital pH meter (Systronics Instruments, India) by placing the glass electrode completely into the gel system. The viscosity of 1% solution of isolated gum was determined by using a Brookfield DV III ultra V6.0 RV cone and plate viscometer (Brookfield Engineering Laboratories, Middle-boro, MA) at 100 rpm spindle rotation using Rheocalc V2.6. Software.
2.3.3 1H nuclear magnetic resonance (1H NMR) spectroscopy analysis
1H NMR (600 MHz, 25 °C) spectra of extracted gum sample in dimethyl sulfoxide (DMSO) were recorded on a BrukerAvance™ III 500 spectrometer (Bruker Biospin Gmbh, Germany) operating at 500.13 MHz using a 4-mm CP-MAS probe head.
2.4 Preparation of atenolol-containing buccal patches
Composition formula of atenolol-containing buccal patches made of DG
HPMC K4M (mg)
Extracted DG (mg)
Glycerine (% w/w)
Sodium saccharin (% w/v)
Distilled water (ml)
Ethyl cellulose (% w/v) (for backing membrane)
2.5 Measurement of average weight and thickness
Buccal patches of 56 cm2 area size from all formulation batches were weighed separately by using a digital electronic weighing balance (Mettler Toledo) to calculate the average weights of buccal patches of each formulation batch. By using thickness gauze (Mitutoyo, Japan), the thickness of these prepared buccal patches was measured at different points. Three buccal patches were picked randomly for every formulation batch, and then measured .
2.6 Determination of drug content
Drug (here atenolol) contents within each prepared atenolol-containing buccal patch were measured via dissolving 1 cm2 of buccal patches in the 100 ml of phosphate buffer (pH 6.8) using a magnetic stirrer set (Remi Motors, India) at a speed of 600 rpm for 24 h at the room temperature. The solutions obtained after dissolving prepared atenolol-containing buccal patches were filtered through the Whatman® filter paper (No. 42). Atenolol contents in the solutions were measured spectrophotometrically by UV–VIS spectrophotometer (Shimadzu, Japan) at 275 nm wavelength (λmax) against the blank sample.
2.7 Measurement of folding endurance
The folding endurances of prepared atenolol-containing buccal patches were measured manually by the procedure of repetitively folding at the same position until the breakages of the tested patches. The number of folding times for tested buccal patches folded up the same position without breakages of the patches was taken as the measure of folding endurance .
2.8 Determination of moisture content
2.9 Ex vivo studies
2.9.1 Preparation of porcine buccal mucosal membrane
The porcine buccal mucosa was excised from the cheek pouch of pork, which was collected from the local slaughtering shop. The porcine cheek pouch was collected within 1 h after sacrificing the animal in slaughtering shop and then brought to the laboratory within the phosphate buffer (pH 6.8), instantly. The mucosal membrane was disconnected from the full thickness of the buccal mucosa layer and then immersed in the phosphate buffer (pH 6.8) for 1 min at 37 ± 0.5 °C. By using a scalpel, the fat layers present onto the buccal mucosal membrane were eliminated, and the buccal mucosal membrane was then separated. Finally, the collected excised buccal mucosal membrane was rinsed using phosphate buffer (pH 6.8) .
2.9.2 Ex vivo mucoadhesion study
2.9.3 Ex vivo drug permeation study
Ex vivo drug (here atenolol) permeation study of these prepared atenolol-containing buccal patches across excised porcine buccal mucosal membrane was carried out by using the Franz diffusion cell. The effectual diffusion area of the Franz diffusion cell used was determined as 1.67 cm2. The receptor compartment (50 ml) of Franz diffusion cell filled up by phosphate buffer (pH 6.8) and 37 ± 0.5 °C of temperature was controlled throughout the experiment. Applying a magnetic stirrer, 50 rpm speed of stirring was employed to simulate the buccal setting within the Franz diffusion cell. A prepared atenolol-containing buccal patch was fixed under the occlusion on excised porcine buccal mucosal membrane surface fitted between receptor and donor compartments of the Franz diffusion cell used in the experiment. At regular intervals, 5 ml of samples from receptor compartment was withdrawn. After each collection of samples from the Franz diffusion cell, 5 ml of fresh phosphate buffer (pH 6.8) was replaced immediately. Collected samples were filtered through the Whatman® filter paper (No. 42), and atenolol contents within the samples were measured spectrophotometrically using UV–VIS spectrophotometer (Shimadzu, Japan) at 274 nm wavelength (λmax) against the blank sample.
2.9.4 Ex vivo permeation data analysis
220.127.116.11 Permeation flux
18.104.22.168 Ex vivo permeation kinetics
2.10 Scanning electron microscopy (SEM)
The surface morphology of these atenolol-containing buccal patches was examined by SEM. The dried buccal patches were coated with the gold ion-sputter and then inspected under a scanning electron microscope (JEOL, Japan) functioning at the working distance of 6 mm and the accelerating voltage of 15 kV and × 5000 magnification.
2.11 Fourier-transform infrared (FTIR) spectroscopy
Drug–polymer compatibility of the prepared atenolol-containing buccal patches was examined by FTIR spectroscopy by potassium bromide pellet method. Pure atenolol and atenolol-containing buccal patches were scanned by a FTIR spectrophotometer (BRUKER, UK) within the frequency range of 3600–600 cm−1 of the transmission mode.
2.12 Statistical analysis
Data were examined by the simple statistical analyses. Simple statistical analysis was performed by MedCalc software version 22.214.171.124.
3 Results and discussion
3.1 Extraction, identification and characterization of extracted DG
DG was extracted from ripe Dellinia indica L. fruits using the previously reported method by Ketousetuo and Bandyopadhyay  with little modifications. The yield (%) of extracted DG was found to be 14.73%.
3.2 Physical characteristics of extracted DG
Physicochemical properties of extracted DG
Solubility in water
Soluble in water at room temperature; also soluble in cold and hot water
pH (1% solution at 37 °C)
6.18 ± 0.17 (mean ± S.D.; n = 6)
Viscosity (1% solution at 37 °C)
14.27 ± 1.22 cps (mean ± S.D.; n = 6)
3.3 1H NMR spectroscopy of extracted DG
3.4 Preparation of atenolol-containing buccal patches
During the past few years, various buccal drug releasing dosage forms were developed using plant-derived natural mucoadhesive polymers [10, 11]. However, development of buccal drug releasing dosage forms using DG as mucoadhesive composition material is not reported till date. In the current research, novel buccal patches containing atenolol (an anti-hypertensive drug) comprising a drug containing mucoadhesive polymeric layer of isolated DG-HPMC K4M and drug-free backing membrane of ethyl cellulose (1%) were formulated by the solvent-casting process (Table 1). Backing layer was formed to avoid backside releasing occurrence of the drug from the buccal patches after application.
3.5 Average weight and thickness
Average weight, thickness, drug content, folding endurance and moisture content of atenolol-containing buccal patches
Average weight (g)a
2.15 ± 0.07
2.22 ± 0.11
2.18 ± 0.09
2.16 ± 0.10
0.60 ± 0.07
0.62 ± 0.08
0.63 ± 0.08
0.65 ± 0.09
Drug content (%)b
98.18 ± 2.63
98.94 ± 2.88
99.05 ± 2.57
99.12 ± 2.05
Moisture content (%)b
1.18 ± 0.07
1.29 ± 0.12
1.43 ± 0.14
1.73 ± 0.27
3.6 Drug content
The drug contents present in each 1 cm2 buccal patch were measured separately. The drug contents in all these newly prepared atenolol-containing buccal patches were in-between the range of 98.18 ± 2.63–99.12 ± 2.05% (Table 3). This result designates that the drug (here atenolol) was consistently dispersed throughout the drug containing a polymeric layer of the buccal patches.
3.7 Folding endurance
The folding endurances of these newly prepared atenolol-containing buccal patches were manually assessed. The highest folding endurance value was noticed for the buccal patch F 1 (28), whereas the lowest endurance value was measured for the buccal patch F 4 (20) (Table 3). From the overall results of the folding endurance, it was noticed that the folding endurances of the prepared buccal patches were lessened with the decreasing incorporation of isolated DG in the buccal patch formula. The results of the folding endurance study ensured the flexibility of these newly prepared atenolol-containing buccal patches.
3.8 Moisture content
The moisture content (%) of all these newly prepared atenolol-containing buccal patches was calculated, and this ranged in between 1.18 ± 0.07 and 1.73 ± 0.27 (Table 3). The lower moisture content within the buccal patches is well appreciable to avoid the chances of microbial contaminations. In addition, it can help to preserve the stability enough from being dried and brittle .
3.9 Ex vivo mucoadhesion
Ex vivo mucoadhesive parameters (mucoadhesive strength, force of adhesion and bonding strength) of atenolol-containing buccal patches
Mucoadhesive strength (g)a
22.27 ± 1.44
25.38 ± 1.38
28.44 ± 1.63
32.70 ± 2.37
Force of adhesion (N)a
21.85 × 10−2
24.89 × 10−2
27.90 × 10−2
32.08 × 10−2
Bonding strength (N/m2)a
3.10 Ex vivo drug permeation
Permeation flux (J, μg/cm2/h) results for various atenolol-containing buccal patches
Permeation flux (J, µg/cm2/h)
Results of curve fitting of the ex vivo permeation of different atenolol-containing buccal patches
n (diffusion exponent)
3.11 SEM analysis
3.12 FTIR spectroscopy analyses
Atenolol-releasing buccal patches containing mucoadhesive polymeric layer of isolated DG-HPMC K4 M and drug-free backing layer of ethyl cellulose (1%) were prepared through the solvent-casting process. Drug content, average weight, thickness, folding endurance and moisture content of all these buccal patches were found satisfactory. Ex vivo mucoadhesive properties were found satisfactory for the buccoadhesion with buccal mucosal membrane. Amongst all, buccal patch F-4 exhibited the highest mucoadhesive strength (32.70 ± 2.37 g), force of adhesion (32.08 × 10−2 N) and bonding strength (1920.90 N/m2). The ex vivo drug permeation results of various buccal patches across the excised porcine buccal mucosal membrane demonstrated ex vivo atenolol permeation over 12 h. The highest permeation flux (32.27 μg/cm2/h) was measured for the buccal patch F-4. The ex vivo atenolol permeations from these buccal patches followed the first-order model (R2 = 0.9858–0.9967) and non-Fickian (anomalous) diffusion mechanism (n = 0.72–0.75) over 12 h across the excised porcine buccal mucosal membrane. The SEM observation suggested a fine lamination of the excipient polymers within the prepared buccal patch tested (F-4), where the drug particles were homogeneously dispersed throughout the patch matrix. The FTIR analyses suggested no chemical interaction had taken place between atenolol and biopolymer excipients utilized in the buccal patch formula. These atenolol-releasing buccal patches were found suitable for providing sustained buccoadhesive delivery of atenolol over a prolonged period in the treatment of hypertension and angina pectoris bypassing the extensive hepatic first-pass metabolism.
The first author would like to acknowledge the University Grant Commission, New Delhi, India, for providing the Maulana Azad National Fellowship for minority students.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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