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Year : 2022  |  Volume : 25  |  Issue : 2  |  Page : 128-134
Formulation and evaluation of oral disintegrating films using a natural ingredient against Streptococcus mutans

1 Centre for Food Technology, Anna University, Chennai, Tamil Nadu, India
2 Department of Conservative Dentistry and Endodontics, SRM Dental College, SRM Institute of Science and Technology, Ramapram, Chennai, Tamil Nadu, India
3 Department of Conservative Dentistry and Endodontics, Mamata Institute of Dental Sciences, Bachupally, Hyderabad, Telangana, India

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Date of Submission16-Mar-2021
Date of Decision14-Jul-2021
Date of Acceptance06-Oct-2021
Date of Web Publication04-May-2022


Background: Oral disintegrating films (ODFs) are one of the forms of drug delivery system with better patient compliance. The advantage is that it disintegrates quickly when placed on the tongue and has better bioavailability.
Aim: The aim of this study is to develop an ODF using Vaccinium oxycoccos and Plectranthus amboinicus targeting Streptococcus mutans.
Setting and Design: This in vitro study was conducted at an institutional laboratory
Materials and Methods: The chemical composition of aqueous extracts of Vaccinium oxycoccos and Plectranthus amboinicus was examined using gas chromatography (GC)-mass spectrometry (MS). Extracts were added at its minimal inhibitory concentration (MIC) into the hydroxy propylmethyl cellulose (HPMC) polymer matrix solution to develop active ODF. The study concentrated on assessing the physical properties such as thickness of film, PH of the film, folding endurance, swelling test, disintegration, and dissolution test. Color analysis, Fourier transform infrared (FTIR), spectroscopy, and scanning electron microscope (SEM) were the mechanical properties of the film assessed.
Statistical Analysis: Data were analyzed statistically, one-way analysis of variance followed by post hoc analysis for the assessment of MIC. Descriptive statistics were performed for the analysis of film properties.
Results: MIC was 25 μg/ml for Vaccinium oxycoccos and 50 μg/ml for Plectranthus amboinicus. Three percentage HPMC with 1% citric acid and 1% aspartame was used to develop a polymer matrix. Films pH was between 6 and 7. FTIR and SEM analysis were done to confirm the attachment of active compound in a polymer matrix.
Conclusion: Vaccinium oxycoccos and Plectranthus amboinicus showed good antibacterial activity, therefore could be a potent source to minimize the incidence of S. mutans

Keywords: Oral disintegrating film, Plectranthus amboinicus, Streptococcus mutans, Vaccinium oxycoccos

How to cite this article:
Harini K, Janani K, Teja KV, Mohan C, Sukumar M. Formulation and evaluation of oral disintegrating films using a natural ingredient against Streptococcus mutans. J Conserv Dent 2022;25:128-34

How to cite this URL:
Harini K, Janani K, Teja KV, Mohan C, Sukumar M. Formulation and evaluation of oral disintegrating films using a natural ingredient against Streptococcus mutans. J Conserv Dent [serial online] 2022 [cited 2022 Jul 3];25:128-34. Available from:

   Introduction Top

The oral disintegrating films (ODFs) are becoming a popular form of drug delivery system due to their excellent patient convenience and compliance.[1] When placed on the tongue or the cheeks, these films rapidly start dissolving by soaking saliva, even without water administration, thereby releasing the active pharmaceutical ingredient (API) of the film. This film is made using hydrophilic polymers, which can be rapidly dissolved in the tongue or cheek, delivering the drug through dissolution when contact liquid is made.[2]

Our work has planned to incorporate a natural bioactive component as an API with antibacterial activity against Streptococcus mutans. The bioactive ingredients derived from Vaccinium oxycoccos[3] (Cranberry) and Plectranthus amboinicus[4] (Karpuravalli) have many beneficial properties.

Researches have shown Vaccinium oxycoccos to exhibit antibacterial properties against streptococcus species.[5] Regarding Plectranthus amboinicus, researchers have proven to exhibit antimicrobial efficiency against Gram-positive organisms.[6] Studies have also proven to show antineoplastic activity,[7] analgesic effect,[8] and anxiolytic activity.[9]

According to our knowledge, this is the first and foremost study on developing combined natural bioactive agents as an ODF. Therefore, this study aims to develop an ODF using Vaccinium oxycoccos and Plectranthus amboinicus as a source of API targeting the S. Mutans. The objective of the study was to formulate an ODF and to characterize its properties.

   Materials and Methods Top

Compound extraction

We collected the fresh leaves of Plectranthus amboinicus and dried Vaccinium oxycoccos for analysis. Twenty gram of leaves of Plectranthus amboinicus and Vaccinium oxycoccos were taken and dried in a hot air oven for 24 h. The dried leaves were suspended in deionized distilled water and incubated at 40°C for extraction (24 h).

Gas chromatography-mass spectrometry (GC-MS), minimum inhibition concentration (MIC), and antibacterial activity of the extract were assessed.

GC-MS was done to identify the individual compounds.[10],[4] MTCC strain of S. mutans (IMTECH, Chandigarh, India) was selected, and the MIC was determined by broth microdilution method[11] with concentration (25–100 μg/ml) according to the clinical laboratory standards institute (CLSI) 2012 protocol.[12] Thereafter, the cultures were incubated and serially diluted until it attained a density of 2 × 104 cells per ml. A hemocytometer was used to count the cells. One hundred liters of cell culture were inoculated in two milliliters of Mueller Hinton Agar (MHA) broth broth dispensed in tubes. Then, in each tube, 100 mL of varied oil concentrations (25.0, 50.0, 75.0, and 100 g/ml) were added. A positive control for bacteria was amoxicillin (10 g/ml), while a negative control was disc without extract. Every experiment was done in conjunction with a growth control. For 48 h, all of the experimental tubes were cultured in anaerobic jars. The optical density of broth was measured at 600 nm after the completion of the incubation period.

Bacterial inhibition was calculated using the following formula:

Antibacterial activity was assessed using the agar well-diffusion method.[11] The experiment was repeated in a triplicate set.

Formulation of oral disintegrating films

ODF was formulated by solvent casting method,[13] and the aqueous extract incorporated into the film solution with gentle stirring. The following trials were performed.

  • Trail 1: Two percentage (w/v) hydroxy propylmethyl cellulose (HPMC) in hot water and chloroform
  • Trail 2: i) Two percentage, 3% and 4% (w/v) HPMC with hot water

    ii) One percentage and 2% (w/v) HPMC with methanol
  • Trail 3: Three percentage (w/v) HPMC film with 1% (w/v) methanol
  • Trail 4: Three percentage (w/v) HPMC solution with hot water and polyethylene glycol (PEG) and glycerol at 1, 2, and 3% (w/v)
  • Trail 5: HPMC with citric acid 3% and aspartame 3%
  • Trail 6: Optimization of citric acid and aspartame to 1%.

Characterization of developed films

Physical properties

Thickness of film

The thickness of the film was measured using a calibrated digital micrometer at a different randomly chosen area of the film. The average thickness is noted.

pH of the film

The pH of the film was evaluated by dissolving them in a phosphate buffer of pH 6.95.

Folding endurance

The folding endurance was determined by folding the film several times at the same point until it breaks. Therefore, higher folding endurance indicates the higher mechanical strength of the film.

Swelling test

The film was dipped in 50 ml of buffer solution. The increase in the weight of the film was noted at an interval of 30 s.[14]

Disintegration time

It is the time required for the dosage form to break down into granules of a specified size. Therefore, the film was suspended into 30 mL of buffer solution and left undisturbed and noted for disintegration time.

Dissolution test

The film was suspended in a 30 mL buffer solution and stirred at (50 rpm). The time required by the film to completely dissolve was noted.[15]

Mechanical Properties

Strength analysis

The tensile strength and extensibility of the film were determined at a load of 50 kg by fixing a film of size 7 cm × 2 cm on the tensile grip probe of the TAXT texture analyzer (Stable microsystems PVT Ltd, United Kingdom).

Color analysis

Ultrascan VIS color spectrophotometer (Hunter Associates Laboratory Inc., Reston, VA, USA) was used to assess the color of film samples. Illuminant A (light source) was used to acquire CIE L* (lightness), a* (redness), and b* (yellowness) values. The observer angle was 10°, and the area view and port size (diameter) were 0.64 cm2 and 1.02 cm, respectively.

Fourier transform infrared of film

Perkin Elmer Fourier transform infrared (FTIR) spectrometer was used to record FTIR spectra of plain HPMC films and aqueous extracts infused films (Perkin-Elmer Co., USA).

0.3–0.5 mg of sample was combined with around 0.5 g of potassium bromide and pressed to form pellets with a diameter of 13 mm. Spectrum analysis was performed on each sample in the wavelength range of 4000–400 cm‒1 with a resolution of 4 cm‒1.[16]

Surface morphology

The microstructure was observed by scanning electron microscope (SEM) (HITACHI-S3400N, Japan). Each sample was positioned horizontally with a 90° angle on a stub using double-sided adhesive tape. An accelerating potential of 20.0 kV was used to evaluate all samples.[16]

Statistical analysis

Data were analyzed using the SPSS software version 11 (IBM SPSS Predictive Analytics Community, Bangalore, Karnataka, India). One-way analysis of variance followed by post hoc analysis for the assessment of MIC. Descriptive statistics were performed for the analysis of film properties.

   Results Top

The active compound extraction yield of Plectranthus amboinicus and Vaccinium oxycoccos was estimated to be 16.87 ± 0.82% and 26.52 ± 0.47%, respectively. The GCMS profile of both the extracts was tabulated [Table 1]. A MIC of 25 μg/ml was observed for Vaccinium oxycoccos extract and 50 μg/ml for Plectranthus amboinicus. The results showed a statistically significant difference as compared with negative control (disc without test solution) (P < 0.001). The zone of inhibition against S. mutans with a film of Plectranthus amboinicus was 35 ± 0.03 (Mean ± standard deviation [SD]) (n = 3), a film with Vaccinium oxycoccos was 32 ± 0.02 (mean ± SD) (n = 3), a combination of both the extracts was 36 ± 0.04 (Mean ± SD) (n = 3).
Table 1: Chemical composition of Plectranthus amboinicus leaf aqueous extract and Vaccinium oxycoccos aqueous extract

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Film formulation

3% (w/v) HPMC film with hot water as solvent had even thickness with integrity and smooth surface. Trails have been made to fix the plasticizer and its concentration for the development of ODF. The response from each trial has been illustrated [Table 2]. 1% Glycerol (w/v) is chosen over PEG because of its smooth surface and even solute distribution. One percentage citric acid (w/v) acts as a saliva-stimulating agent by not affecting the film-forming properties, and 1% aspartame (w/v) provides less bitter taste, thereby not affecting the organoleptic property.
Table 2: Film formulation and properties of film

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Physical properties of films

The developed films were evaluated for weight, thickness, pH, folding endurance, swelling index, disintegration time, and dissolution time. The results are depicted in [Table 2].

Mechanical property of films

[Table 2] shows combined film extracts to possess suitable mechanical property. Results showed that the final film has optimal integral stability to withstand mechanical damage.

Colour analysis

Plain HPMC does not possess any color [Table 2]. A film with Plectranthus amboinicus extract showed increased b * value, exhibiting yellowness. Similarly, an increase in a * and b * value with Vaccinium oxycoccos extract. Combined film extracts infused exhibited high redness and yellowness.

Fourier Transform Infrared of film

[Figure 1]a,[Figure 1]b,[Figure 1]c,[Figure 1]d,[Figure 1]e shows the FTIR spectra of ODF, except control HPMC film; all other sample films showed a similar IR absorption pattern. Peak around ~3200–3600 cm‒1 represents a characteristic polymeric OH stretch. Peaks around ~2900, 1680, and 1190 cm‒1 denoted CH Asym./Sym. Stretch, CH2 binding stretch, and CH skeletal vibrations, respectively. HPMC characteristic peaks of–C-O-C-stretch and CH3 binding stretch were around ~1068 and 1378 cm‒1, respectively.
Figure 1: Fourier Transform infrared analysis shows (a) Raw HPMC film, (b) HPMC+Citric acid film, (c) Vaccinium Oxycoccos extract infused film, (d) Plectranthus Amboinicus extract infused film, (e) Vaccinium Oxycoccos and Plectranthus Amboinicus extract combination film

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Surface morphology of films

[Figure 2]a,[Figure 2]b,[Figure 2]c,[Figure 2]d shows the surface morphology of HPMC film. Control HPMC film showed a smooth surface. Films infused with extract showed a microfibrous structure on the surface with the observed diameter below 1000 nm. The microfibrous patterns observed in combination film could be due to active extracts in the film matrix.
Figure 2: Image shows Surface morphology (a)control HPMC film, (b) Vaccinium oxycoccos infused HPMC film (c) Plectranthus amboinicus infused HPMC film (d) Vaccinium oxycoccos and Plectranthus amboinicus extract combination HPMC film

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   Discussion Top

With the concern of antimicrobial resistance of the chemical agents, the recent trends have shifted their focus to the use of natural products with almost least to nil cytotoxic effects.[17],[18] Plectranthus amboinicus and Vaccinium oxycoccos were used in the current study for developing the ODF after assessing its MIC. Plectranthus amboinicus (family Lamiaceae) had proven to exhibit antibacterial property.[11] This study stated that the MIC of aqueous extract Plectranthus amboinicus possesses results similar to previous research.[4] Vaccinium oxycoccos was used to treat uroepithelial infection caused predominantly by Gram-positive microorganisms.[19] Therefore, Vaccinium oxycoccos was incorporated in this study. The MIC of Vaccinium oxycoccos in this study was not in corroboration with the previous research. The variation in the result can be due to various influencing factors such as type of extract (ethanolic extract),[20] molecular size of compounds, different isomers, growth medium, and incubation conditions.[21]

The agar disk-diffusion method cannot be appropriate to determine MIC as it is not possible to evaluate the amount of antibacterial agent diffused into the agar medium. Nevertheless, it' is a simple test to assess numerous microorganisms with better result interpretation.[22] However, according to the standard provided by CLSI appropriate method of determining the MIC, the broth dilution method aid in quantitatively measuring the antibacterial efficiency against the tested bacteria. Although the prolonged incubation time, size of the inoculum, and pH of the medium can lead to false-positive result,[23],[24] both the extracts used in our study had neutral pH, at a range of 7.2, to avoid false-positive results. Furthermore, the concept of killing the bacteria using antimicrobial agents and antibiotics can lead to antibacterial-resistant bacterial overgrowth. Therefore, appropriate treatment should selectively inhibit cariogenic pathogens by maintaining the intact ecosystem.[25]

When film properties have to be assessed, evaluating the film's thickness and uniformity is directly proportional to accuracy in the agents' concentration. It is mandatory to maintain the pH of the film close to neutral pH to avoid irritation to oral mucosa and other adverse effects. A swelling test is carried to assess the expansion of the film. A previous study has reported that the use of carboxy methylcellulose has shown to produce extensive expansion of the film, leading to discomfort.[16] The plasticizer plays a significant role in developing the matrix, as it is correlated with folding endurance. In the present study, glycerol is used as a plasticizer to impart strength and flexibility to the film. For better efficiency, the film inside the oral cavity should disintegrate slowly. The incorporation of hydrophobic oil extracts can hinder and change films' mechanical and physical properties.[26] Thus, hydrophilic extract of active compounds was selected for incorporation with HPMC film to improve its active effect. In the present study, an HPMC-based polymer matrix was used due to its good mechanical property and dissolution character.[14],[13]

FTIR and SEM analysis were performed as a confirmatory test to assess compound integration into a film. The FTIR analysis of ODF proved the inert nature of HPMC molecules with active compounds of both aqueous extracts; this will facilitate the release of active compounds in the mouth without any chemical interactions with the matrix. The surface morphology of the extracts infused HPMC films showed a microfibrous structure, which may hold the active compounds inside them and facilitate active compounds within the film. Therefore, greater antimicrobial efficiency was reported in the current research suggesting the film's utilization in clinical practice.

Future direction

Release kinetics of active compounds from ODF need to be determined in future studies as this was the preliminary study that focused on formulation, development, and characterization of film.

   Conclusion Top

Aqueous extract of Vaccinium oxycoccos and Plectranthus amboinicus showed antimicrobial activity against S. mutans. The physical and mechanical characterization showed the integrity of the developed ODF. Therefore, the produced ODF could be a potent source to minimize the incidence of S. mutans.

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Conflicts of interest

There are no conflicts of interest.

   References Top

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Correspondence Address:
Dr. Chandra Mohan
Centre of Food Technology, Anna University, Chennai, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jcd.jcd_143_21

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