(W1030-09-52) Development of L-dopa-Loaded Nanofiber for Transbuccal Drug Delivery

Purpose: L-dopa is the most effective pharmacologic agent in Parkinson’s disease. However, in long-term treatments, as the effects of L-dopa, which has a short duration of action, wear off, a phenomenon known as "wearing off" occurs, where there are periods of time when the drug is effective and periods of time when it is not. Transbuccal drug delivery has the following characteristics: they can avoid the first-pass effect, they are expected to have a more immediate effect than oral administration, and they are easy to administer¹. In this study, we thought that delivering L-dopa through buccal mucosa could quickly replenish dopamine when "wearing off" occurs, and developed L-dopa-loaded nanofiber formulations to deliver L-dopa through the buccal mucosa. The nanofiber was formulated using nanofiber technology based on electrospinning.

Methods: Perform electrospinning using L-dopa polymer solutions: As a polymer solution in which L-dopa was soluble, the following solutions were prepared.
F1: 0.10 g L-dopa + 0.90 g PVA + 0.91 g EtOH + 8.19 g 0.1M HCl
F2: 0.13 g L-dopa + 1.20 g PVA + 8.80 g 30wt% formic acid
F3: 0.13 g L-dopa + 1.20 g PVA + 0.88 g EtOH + 7.92 g 30wt% formic acid. The polymer solutions were processed using an electrospinning system NS1. Characterization of L-dopa-loaded nanofiber: The nanofiber after electrospinning were observed using SEM. The crystallinity of the drug in the nanofiber was evaluated by differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). Drug release properties from L-dopa-loaded nanofiber: Artificial saliva (pH7.4) was used as the dissolution media. The dissolution media (20 mL) was placed in a glass container, and L-dopa (1 mg) or L-dopa-loaded nanofiber (10 mg) was immersed in the dissolution media warmed to 37°C and stirred at 100 rpm. Over time, the test sample was collected, filtered through a membrane filter (0.45 μm). The filtrate was analyzed by HPLC².

Results: Characteristics of L-dopa-loaded nanofiber: As a result of electrospinning, L-dopa-loaded nanofibers were prepared. From SEM images (Fig. 1), the formulation F1 appeared a cylindrical structure fiber with a smooth surface and the fiber diameter 282 nm (mean, n=30). In the formulation F2 prepared using 30wt% formic acid, fusion of the fibers was observed, and more rapid evaporation of the solvent was required. The formulation F3 prepared using EtOH + 30wt% formic acid showed reduced fiber fusion and the fiber diameter was 165 nm (mean, n=30). DSC measurement results are presented in Fig. 2(a). An endothermic peak was produced due to the melting of L-dopa crystals at around 290°C. An endothermic peak derived from L-dopa crystals was not present in the formulations F1 and F3, indicating that L-dopa was amorphous in the nanofibers. PVA revealed glass transition at 49.7°C and the onset of melting at 172.1°C (enclosed in a square). The peak near 242°C was presumably due to the decomposition of PVA. In the formulations, the peak due to the melting of PVA was small or disappeared. Fig. 2(b) presents PXRD patterns of L-dopa, PVA, the formulations F1 and F3. L-dopa showed sharp crystalline peaks. The diffraction patterns of the formulations F1 and F3 showed the disappearance of L-dopa crystal peaks, indicating that L-dopa was amorphous in the formulations. PVA showed broad peaks at 19.5 and 40.5. The diffraction patterns of the formulations F1 and F3 showed a broader peak at 21.0 and 21.3 than that of PVA. Thus, DSC and PXRD suggest that the crystallinity of PVA was also reduced in the nanofiber formulations. Drug release properties of L-dopa-loaded nanofiber: The release profiles of L-dopa are shown in Fig. 3. Approximately 80.5% and 88.5% of L-dopa was released from the formulations F1 and F3 in 15 min. Both formulations released L-dopa rapidly, but the drug release was faster in the formulation F3 than in the formulation F1. Furthermore, the drug release was more controlled than that of the L-dopa crude.

Conclusion: L-dopa-loaded nanofibers were successfully prepared by electrospinning using the polymer solutions containing HCl or formic acid. The fiber diameter of the formulation F3 prepared using formic acid was slightly smaller than that of the formulation F1 prepared using HCl. The drug in the nanofibers existed in an amorphous state, and the formulation of a solid dispersion of L-dopa was suggested. The rapid drug release from the L-dopa-loaded nanofibers was observed. These findings suggest the usefulness of L-dopa-loaded nanofibers as a formulation to deliver L-dopa through the buccal mucosa.

References: 1. Morales JO, et al., Challenges and Future Prospects for the Delivery of Biologics: Oral Mucosal, Pulmonary, and Transdermal Routes, AAPS J, 19(3), 652-668 (2017).
2. Allegritti E, et al., Novel liposomal formulations for protection and delivery of levodopa: Structure-properties correlation, Int J Pharm, 643, 123230 (2023).

Acknowledgements: We would like to thank Physio Mckina Co., Ltd. (Saitama, Japan) for providing an electrospinning system NS1. This work was partially supported by JSPS KAKENHI Grant Number JP22K06705 (Yuri Ikeuchi-Takahashi).

Fig.1 SEM images of L-dopa-loaded nanofibers prepared using different solvents. (Left) the formulation F1 prepared using EtOH + 0.1M HCl, (Middle) the formulation F2 prepared using 30wt% formic acid, (Right) the formulation F3 prepared using EtOH + 30wt% formic acid.


Fig. 2 (a) DSC thermogram and (b) PXRD patterns of L-dopa crude, PVA, the formulation F1 and the formulation F3


Fig. 3 Drug release profiles from the L-dopa crude, the formulation F1 and the formulation F3
Each data point represents the mean±S.D. (n=3).