Hydroxypropyl methylcellulose (HPMC), maltodextrin, and PEG 400 were purchased from Labimex Ltd. (Sofia, Bulgaria). Galantamine hydrobromide (Gal) was supplied from Sopharma AD (Sofia, Bulgaria). Chitosan and tripolyphosphate pentasodium (TPP) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Glacial acetic acid was supplied by Labimex Ltd. (Sofia, Bulgaria).

Galantamine-loaded chitosan nanoparticles were prepared according to a previously optimized procedure (Georgieva et al. 2023): chitosan (1.25 mg/mL) and gal (0.35 mg/mL) were dissolved in a 1% (v/v) acetic acid solution under vigorous stirring for a period of 24 h. Afterwards, a solution of TPP (0.75 mg/mL) was added dropwise with stirring for 30 min. The resulting solution was left overnight at room temperature until the formation of the particles, then stored in a refrigerator.

The loading efficiency (LE%) was determined by centrifugation. The Gal-loaded nanoparticles were separated from the solution by ultracentrifugation (Beckman OptimaTM LE-80 K Ultracentrifuge, GMI, Ramsey, MN, USA) at 14 000 rpm for 40 min. The amount of non-incorporated Gal in the supernatant was determined at 288 nm using a Hewlett-Packard 8452 A Diode Array spectrophotometer (Walldorf, Germany). The LE (%) was calculated using the following equation:

$\text{LE (\%)}=\frac{\text{total amount of Gal (g) - non incorporated Gal (g)}}{\text{total amount of Gal (g)}}\times 100$

The nanoparticles were characterized by dynamic light scattering (DLS) in order to study their size and by measuring the Z-potential to investigate their stability. The nanoparticle solution was subjected to DLS analysis with a Zetasizer Nano ZS apparatus (Malvern Instruments, Worcestershire, UK). The device consists of a 632-nm HeNe gas laser and an optical detector. Three measurements were made at a temperature of 25 °C.

The films consisted of a film-forming polymer (HPMC), a film modifier (maltodextrin), and a plasticizer (PEG 400), and were prepared by the solvent casting method (Bala et al. 2013). HPMC was dispersed in hot, distilled water in a beaker and allowed to swell. Maltodextrin and PEG 400 were then added to the swollen polymer, and the solution was left in the refrigerator until the HPMC was completely dissolved (for a period of 12 h to 24 h), with the system being stirred at given time intervals to accelerate the dissolution. Four solutions were prepared with different concentrations of the compounds. Then, each of these four solutions was mixed with the solution containing the nanoparticles. The resulting polymer solutions (F1, F2, F3, and F4) were poured into clean and dry silicone molds with an area of 10 cm2. The films were dried in a dryer (Aeromatic, Germany) at 40 °C for 24 h. After drying, the films were carefully removed from the molds and stored in a desiccator at room temperature. The composition of the different formulations is presented in Table 1.

The quality of the prepared films was evaluated based on the following criteria: flexibility, spreading ability, adhesiveness, non-sticky and easily peeled, and appearance. The appearance of the films was checked by visual inspection, determining the homogeneity and texture by touching.

Thickness was measured at five different locations on each film using a micrometer. The test was performed in triplicate (Bhyan et al. 2011).

To determine the folding endurance, a strip is cut from the film and is repeatedly folded in the same place until it breaks. The number of times the film is folded in the same place without breaking represents the folding endurance value.

Disintegration time is the time (in seconds) required for the film to break on contact with water or saliva. The determination is carried out by placing the film in a Petri dish and dropping 2 mL of distilled water onto it. The time when the film breaks or disintegrates into small fragments is noted.

The study was conducted using a shaking water bath (IKASH-B20, Staufen, Germany). The tests were carried out at a shaking speed of 50 rpm and a temperature maintained at 37 ± 0.5 °C in 100 mL of distilled water. At certain time intervals, 2 mL of samples were taken for analysis. After each sampling, the volume was restored with 2 mL of distilled water. The amount of released galantamine was determined by UV spectroscopy (absorbance at 288 nm) using a Hewlett-Packard 8452 A Diode Array spectrophotometer. The percentage of galantamine released was calculated using the data obtained from the study.

Gal-loaded chitosan NPs were prepared using the ionotropic gelation method. TPP was used as a cross-linking agent. Chitosan interacts with the oppositely charged TPP, thus leading to the formation of the particles. An advantage of the method is that it does not use any harmful organic solvents and is carried out at room temperature, which helps effectively preserve the bioactivity of the drug during incorporation into the particles.

The results obtained from the study showed high values for the LE (%), namely 69%. This indicates that the method used is suitable for incorporating water-soluble drugs into chitosan particles.

DLS was used to evaluate the particle size and the Z-potential. It was found that the average size of the obtained particles was 260 nm, and the Z-potential values were 58 mV. These results showed that the particles obtained were nanosized and stable.

Since the use of orally dispersible films relies on their disintegration in the saliva in order to achieve the desired effect, the final film must necessarily be water-soluble. This requires the use of a water-soluble polymer with a low molecular weight and excellent film-forming capacity (Kulkarni et al. 2010). The polymer used in this study was HPMC, and PEG 400 was used as a plasticizer. Maltodextrin was included in the composition in order to improve the flexibility and reduce the cracking of the films (Chapdelaine et al. 2002).

The quality of the prepared films was evaluated based on the following criteria: flexibility, spreading ability, adhesiveness, non-sticky and easily peeled, and appearance. The visual inspection confirmed successfully obtaining good-quality films. They were elastic, did not stick to the molds, and were easily peeled without cracking. The films were characterized by different homogeneity, as can be seen from Fig. 1. It was established that increasing the concentration of HPMC led to a decrease in the homogeneity of the prepared films.

Figure 1. 

Image of the different films.

From the data presented in Fig. 2, it is evident that increasing the concentration of HPMC led to an increase in the film thickness, which varied from 0.30 to 0.47 mm.

Figure 2. 

Thickness of the different formulations.

The folding endurance value takes into account the film’s ability to withstand tearing; the higher the folding endurance value, the less likely the film is to crack easily. The folding endurance of the films was determined by repeatedly folding a small strip of each film in the same place until it broke. The folding endurance of films ranged from 22 ± 0.24 to 50 ± 1.21, as given in Fig. 3. As can be seen from the results presented, formulation F1 was characterized by the highest value of folding endurance, although it had the lowest concentration of HPMC and the lowest thickness. This was probably due to the fact that this formulation had the highest ratio of chitosan to HPMC, which granted flexibility to the film, which in turn led to an increase in folding endurance. This fact has also been established by other scientific groups that used chitosan as a component in the composition of orally dispersible films, which led to an increase in flexibility and tensile strength (Cardelle-Cobas et al. 2015; AnjiReddy and Karpagam 2017). Formulations F2, F3, and F4 showed a lowering of the folding endurance from 40 to 22.

Figure 3. 

Folding endurance of the prepared films.

This was due to two factors, namely: a decrease in the ratio chitosan/HPMC, which led to a decrease in the flexibility of the films; and, on the other hand, an increase in the concentration of HPMC led to an increase in the thickness of the films, which negatively affected their flexibility.

Disintegration time is a critical parameter that plays an important role in the release and subsequent absorption of the drug across biological membranes. The rapid disintegration of orally dispersible films is important to ensure the rapid obtaining of smaller fragments, resulting in the largest possible surface area (Elkordy et al. 2013). The prepared formulations showed variation in disintegration times; the results are presented in Fig. 4. It is evident from the data that all the formulations showed fast disintegration times ranging from 15 to 60 sec. The research conducted showed that the concentration of HPMC had a major effect on the disintegration time. Increasing the polymer concentration resulted in a significant increase in the disintegration time.

Figure 4. 

Disintegration time of the different formulations.

The results obtained from the in vitro dissolution studies are presented in Fig. 5. From the data obtained from the study, it can be seen that the different films released a different amount of the incorporated galantamine within 9 minutes. When comparing the different formulations, it is evident that the fastest release of the loaded galantamine was observed from the film with the lowest concentration of HPMC (F1), and the drug release rate decreased as the concentration of HPMC increased. These results are expected given the disintegration times of the different films.

Figure 5. 

In vitro galantamine release from the different films in distilled water at 37 °C.

Based on the research conducted, it can be concluded that F1 has potential as a drug delivery system in cases where a rapid effect is desired.