*Article* **Formulation of Fast Dissolving** β**-Glucan/Bilberry Juice Films for Packaging Dry Powdered Pharmaceuticals for Diabetes**

**Ionut Avramia \* and Sonia Amariei**

Faculty of Food Engineering, Stefan cel Mare University of Suceava, 720229 Suceava, Romania

**\*** Correspondence: ionut.avramia@usm.ro

**Abstract:** The aim of this study was to develop fast dissolving films based on β-glucan and bilberry juice due to the bioactive potential of β-glucan and antidiabetic effect of bilberry juice. The benefit of incorporation of bioactive compounds into the films is due to the removal of unnecessary excipients and to confer protection as well as increase stability and shelf life to the packaged product. Due to the fast dissolving requirements of the European Pharmacopeia, which reduced the dissolution time from 180 to 60 s, indicating less than a minute, hygroscopic materials, such as sodium alginate and a suitable plasticizer, such as glycerin were incorporated. Moreover, the influence of ingredients and surfactants, such as soybean oil was studied in the design of fast dissolving films. Additionally, the steady state rate water vapor transmission rate (WVTR), water vapor permeability (WVP), and FT-IR spectroscopy tests were performed at high resolution to ensure the reliability of the films and composition as well as to validate the results. Our data suggest that the addition of surfactants contributed to the development of fast dissolving films without influencing the diffusion of water vapor. Low levels of WVTR and short dissolution time made from β-glucan and bilberry juice are a convenient candidate for packaging dry powdered pharmaceuticals for diabetes.

**Keywords:** fast dissolving films; yeast β-glucan; bilberry juice; diabetes

### **1. Introduction**

Films based on different bioactive compounds are defined as a new generation of edible films due to the active agents, which act as antimicrobials, anti-inflammatory, antioxidants, immunostimulants, anti-cancer, etc. [1–3]. There are plenty of natural compounds that can be incorporated into the film-forming solution for film making, depending on their role in therapeutics and the related medical condition. Films with strong antioxidant properties were successfully developed using natural compounds, such as plants from *Moringaceae* family [4], chitosan/ellagic acid films were found to have strong antimicrobial activity against *S. aureus* and *P. aeruoginosa* [5], while β-glucan/pomegranate juice films had potential in the management of diabetes through the variety of tannins and bioactivities [6].

Diabetes is the most common noncontagious disease in the world [7]. A study conducted in 2019 estimates that this serious, long-term condition with a major impact on the lives and well-being of individuals around the world affects about 463 million people. It was estimated that, by 2030 this number will increase to 578 million people and in 2045 it will increase to 700 million people (equivalent to 10.9% of the population), with over 200 million more than 2019 [8].

Functional ingredients, such as bilberry (*Vaccinium myrtillus* L.) are recognized since centuries to have antidiabetic potential and have been used to control blood sugar levels [9]. A comprehensive review in 2022 of the phytochemical and pharmacological antidiabetic properties of bilberries by Chehri et al. (2022) highlighted the beneficial properties of the most significant components from the fruit. In addition to the antidiabetic effects, the authors analyzed the cardioprotective effects, anti-obesity, anti-inflammatory or ocular disorder effects, with all of these found in diabetes-related complications [10].

**Citation:** Avramia, I.; Amariei, S. Formulation of Fast Dissolving β-Glucan/Bilberry Juice Films for Packaging Dry Powdered Pharmaceuticals for Diabetes. *Plants* **2022**, *11*, 2040. https://doi.org/ 10.3390/plants11152040

Academic Editors: Juei-Tang Cheng, I-Min Liu and Szu-Chuan Shen

Received: 12 July 2022 Accepted: 3 August 2022 Published: 4 August 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Yeast β-glucan is a complex polysaccharide of β-1,3, which is linked with β-1,6 glucose polymers that are found in the cell wall of yeast [11]. The biological effects of the β-glucans are related to the immunity, anti-cancer, and anti-inflammatory properties of the body with a mechanism of action not yet fully understood [12]. It is known to act by binding to Pattern Recognition Receptors, such as Dectin-1, LacCer, CR3, and SR3 [13]. By stimulating the Dectin-1 signaling pathway, β-glucans might confer protection of β pancreatic cells against the T cells in T1D [14]. Several authors have studied the oral dispersible polysaccharides film with pullulan (a linear structure of glucan) as a drug delivery system for treatment of diabetes [15], while other researchers used immediate-release layers of coatings to prepare fixed-dose combination tablets for diabetes [16].

Taken together, a fast dissolving film that allows the incorporation of these bioactive compounds is the aim of this study. The composition of film-forming solution (FFS) has been chosen to examine the rapid dissolving forms of films. Therefore, the addition of hygroscopic materials, plasticizers, and surfactants was evaluated to observe significant changes between samples. Moreover, for an adequate packaging film, additional tests including thickness, WVTR, WVP, film opacity, water activity, moisture content, and color profile were performed. Finally, further statistical correlation between dependent and independent variables, such as chemical film composition was determined.

### **2. Results**

### *2.1. Optimization of the Film Composition Considering Dietary Intake and Total Solids*

In order to find an optimal composition for a fast dissolving film with a high content of bioactive compounds, seven samples with different amounts of β-glucan and bilberry juice were cast onto a plastic petri dish with or without soybean oil as surfactant. This allows for the identification of any changes in the surface tension reduction as well as improvements on wettability and adhesion of the film. While the bilberry juice rich in anthocyanins, quercetin derivatives, proanthocyanidins or chlorogenic acid phytochemicals has no dietary intake recommendation, β-glucans are limited by the European Food Safety Authority up to 1.275 g/day of dietary use for the general adult population [17].

From the data presented in Table 1, it can be seen that an equal amount of sodium alginate was introduced in all seven samples, which in relation to the total volume has a concentration of 0.53 % (*w*/*v*). This falls within the limits of 0.125–1.5% and exhibits a pseudoplastic shear flow behavior [18]. Additionally, film sizing was performed to a corresponding area density between 7.82 and 12.19 mg <sup>×</sup> cm−<sup>2</sup> . The plasticizer (glycerin) with the best compatibility related to β-glucan and most popular for anthocyanin-based films [19,20] was added to the all polymer samples, while the soybean oil was included in three different samples as 2% (*w*/*w*) of the total solids (β-glucan, sodium alginate, and bilberry juice).

**Table 1.** Composition of β-glucan/bilberry juice blends.


### *2.2. Film Thickness*

The film thickness expressed in µm is an important characteristic in packaging materials. Different thicknesses are essential to the other properties, such as water barrier, transparency or color attributes [21,22]. The film thickness of β-glucan/bilberry juice films ranges between 66.43 and 119.7 µm and was significant (*p* < 0.001) depending on the total solids in the film-forming solution (2.95 and 4.6 g, respectively). This behavior is in accordance with the observations of Arham et al. (2016) who observed an interaction between film thickness and based materials [23]. Similar results have been obtained by Peltzer et al. (2018) and Zhao et al. (2022), in which thicknesses up to 200 µm contributed to the stability and uniformity of the film making suitable for packaging applications [24,25].

### *2.3. Water Vapor Transmission Rate (WVTR)*

WVTR of the β-glucan/bilberry juice films generally has low values between 3.2562 and 7.1111 g × h <sup>−</sup><sup>1</sup> <sup>×</sup> <sup>m</sup>−<sup>2</sup> (Table 2). It was observed that the increasing trend of WVTR was determined by the increase in the total content of substances introduced in the filmforming solution. Additionally, studies conducted by Rahmawati et al. (2020) showed that the amount of plasticizer strongly influenced the water absorption rates [26]. Due to the hydrophilic nature of glycerin, which has three hydroxyl groups, the influence of the plasticizer on the water vapor that permeates the film was investigated. The results are shown in Table 3.


**Table 2.** Physicochemical characteristics of β-glucan/bilberry juice film.

Apart from thickness which is determined in 10 data points (*n* = 10), each value is the mean of three replicates ± standard deviation (*n* = 3). \*\*\* Statistically significant at *p* < 0.001. a–f Different letters in the same rows indicate significant differences between samples. WVTR: Water Vapor Transmission Rate; WVP: Water Vapor Permeability; L, a\*, b\*: Color profile; aw: Water activity; MC: Moisture content.

**Table 3.** The effect of glycerin content on WVTR values.


\*\*\* Statistically significant at *p* < 0.001. a,b Different letters in the same column indicate significant differences.

Indeed, WVTR has a tendency to increase with the glycerin content. The maximum value of 7.1111 g × h <sup>−</sup><sup>1</sup> <sup>×</sup> <sup>m</sup>−<sup>2</sup> (Table 2) has the highest value of glycerin content of 1.15 g in the film-forming solution. Interestingly, Sample 7 with the same amount of glycerin has a low value of WVTR of 5.9036 g × h <sup>−</sup><sup>1</sup> <sup>×</sup> <sup>m</sup>−<sup>2</sup> . One of the reasons for the difference is due to the fact that in the sample with the highest WVTR value the film does not contain

soybean oil, which is known to have hydrophobic nature. Therefore, by decreasing the intermolecular interaction, the mobility of the molecule promotes the migration of water vapor through membranes. Compared with other bilberry-based films, which have values between 52.91 and 61.87 g × h <sup>−</sup><sup>1</sup> <sup>×</sup> <sup>m</sup>−<sup>2</sup> depending on the bilberry concentration [27], WVTR showed low values with a minimum of 3.2562 g × h <sup>−</sup><sup>1</sup> <sup>×</sup> <sup>m</sup>−<sup>2</sup> . The addition of β-glucan or pullulan to the films has also been shown to increase moisture barrier properties [28]. Ultimately, of course, our data are 32 higher than the value of pure low density polyethylene (LDPE) film values of 0.1012 g × h <sup>−</sup><sup>1</sup> <sup>×</sup> <sup>m</sup>−<sup>2</sup> found by Reesha et al. (2015) [29]. To date, a bioactive film with potential packaging product applications showed the best barrier properties.

### *2.4. Water Vapor Permeability (WVP)*

The results of the water vapor flux through the film (WVP) determined by dividing WVTR value to the differential water vapor partial pressure across the film and multiplied by the thickness of the film (in mm) are presented in Table 2. It was observed that WVP values ranged between 0.1057 and 0.3568 g <sup>×</sup> mm <sup>×</sup> kPa−<sup>1</sup> <sup>×</sup> <sup>h</sup> <sup>−</sup><sup>1</sup> <sup>×</sup> <sup>m</sup>−<sup>2</sup> , particularly with the increase in bilberry juice and β-glucan content. An increased value of the WVP parameter indicates that the film is more susceptible to water vapor flux penetration [24]. With an investigation of the physicochemical properties of films, and with the knowledge that high polar polymers and the addition of plasticizers resulted in an increased WVP values, Henrique et al. (2007) concluded that vapor permeability can be related to the quantity of –OH groups in the molecule [30]. On the other hand, Garcia et al. (1999) mentioned that coatings without plasticizing agents led to significantly (*p* < 0.05) higher values of WVP than those with plasticizer due to the formation of pores and cracks [31]. Undoubtedly, we can conclude that our data are lower than those found in films made only from β-glucan without the addition of plasticizer. This is the case of research conducted by Sarossy et al. (2013), which reported WVP values of 0.4625 g <sup>×</sup> mm <sup>×</sup> kPa−<sup>1</sup> <sup>×</sup> <sup>h</sup> <sup>−</sup><sup>1</sup> <sup>×</sup> <sup>m</sup>−<sup>2</sup> (or 11.1 g <sup>×</sup> mm <sup>×</sup> kPa−<sup>1</sup> <sup>×</sup> <sup>m</sup>−<sup>2</sup> <sup>×</sup> <sup>d</sup> −1 ) [32] or by those determined by Peltzer et al. (2018) with an amount of 2.8 <sup>×</sup> <sup>10</sup>−<sup>10</sup> <sup>g</sup> <sup>×</sup> <sup>s</sup> <sup>−</sup><sup>1</sup> <sup>×</sup> <sup>m</sup>−<sup>1</sup> <sup>×</sup> Pa−<sup>1</sup> [24].

### *2.5. Dissolution Time*

One of the most important aspects in developing a fast dissolving film is the time that should not exceed 1 min [33]. Significant differences between samples (*p* < 0.001) are observed in Table 2 with a higher variation between sample means relative to the variation within the samples (an F-value of 674.08). The values of the dissolution time range from 22.33 to 105.66 s. This is mainly due to the composition of the film-forming solution. While soybean oil behaves as a good surfactant [34], Rodriguez et al. (2006) investigated the combined effect of plasticizers and surfactants on the physical properties of films. The authors concluded that surfactants improved the wettability properties of the film solutions by decreasing the surface tension and in combination with glycerin allowed a higher molecular mobility [35]. To verify whether the composition significantly influenced the dissolution time, Table 4 investigated the film composition and the addition of surfactant on dissolution time.

In Table 4, we can observe that the incorporation of β-glucan between 1 and 1.5 g in films does not have a significant influence on dissolution time (*p* > 0.05; *p* = 0.3). On the other hand, data analysis showed that soybean oil and bilberry juice content have significant influence on the dissolution time of the films (*p* < 0.05 and *p* < 0.001, respectively). The obtained F-value of 20.06, which is significant at 0.1%, indicates that there is a significant influence of bilberry juice on dissolution time. High content in the amount of bilberry juice had a negative effect in terms of dissolution time of the films with an average of 74.08 s at 20 g compared with 31.44 s at 10 g of added bilberry juice. At the same time, the addition of 2% soybean oil to the film-forming solution showed a significant decrease (5% level of significance) in the dissolution time.


**Table 4.** The influence of β-glucan, soybean oil, and bilberry juice on dissolution time.

ns: Not significant; \* *p* < 0.05; \*\*\* *p* < 0.001. a,b Different letters in the same rows indicate significant differences.

By correlation, for example, we can observe that in Table 1 the composition of Sample 7 differs from Sample 6 only by the addition of soybean oil, with other compounds remaining in the same proportion. On the other hand, in Table 2, we can observe a major difference in the dissolution time of 50.33 s in the sample with the addition of surfactant and 105.66 s without the soybean oil. Finally, we can summarize that the addition of surfactant positively influences the dissolution time and acts as a solubilizing agent.
