Hydroxyl Group-Targeted Conjugate and Its Self-Assembled Nanoparticle of Peptide Drug: Effect of Degree of Saturation of Fatty Acids and Modification of Physicochemical Properties

Abstract

Purpose

To conjugate different degree of saturation of C18 fatty acids (stearic acid, oleic acid, and linoleic acid) with the hydroxyl groups of leuprolide acetate (LEU acetate) and to investigate the controlled release and enhanced permeability through self-assembled nanoparticles (L18FNs).

Methods

Yamaguchi esterification with benzoyl chloride and DMAP (4-Dimethylaminopyridine) allowed the conjugation of the fatty acid to the hydroxyl group of LEU. The three conjugates were then designated as stearic acid-conjugated LEU, LSC, oleic acid-conjugated LEU, LOC, and linoleic acid-conjugated LEU, LLC, respectively. The conjugates (L18FCs) were purified using preparative HPLC (Prep-HPLC) and identified through various instrumental analyses.

Results

The zeta potential, particle size, and morphology of each L18FNs were evaluated. In the case of LSNs, the zeta potential value was relatively low and the particle size was larger than LONs and LLNs owing to the higher hydrophobicity of saturated fatty chain, while the LLNs showed a higher zeta potential and smaller particle size. In human plasma, LLC showed the fastest degradation rate with the highest accumulative drug release. The permeability of L18FNs was analyzed through the Franz diffusion cell experiment, confirming that the degree of saturation of fatty acids affects the permeability of LFNs. While the permeability of LSNs was not significantly enhanced due to higher particle size after nanonization, LONs and LLNs increased 1.56 and 1.85 times in permeation, respectively, compared to LEU.

Conclusion

Utilization of different degree of saturation of fatty acids to conjugate a peptide drug could provide pharmaceutical versatility via self-assembly and modification of physicochemical properties.

Keywords:

• leuprolide acetate
• hydroxyl targeted conjugation
• different degree of saturation of C18 fatty acids
• fatty acid-conjugated leuprolide
• self-assembled nanoparticles
• controlled release
• enhanced permeability

Abbreviations

LEU, leuprolide; LEU acetate, leuprolide acetate; L18FCs, leuprolide-C18 fatty acid conjugates; LSC, leuprolide-stearic acid conjugate; LOC, leuprolide-oleic acid conjugate; LLC, leuprolide-linoleic acid conjugate; L18FNs, leuprolide-C18 fatty acid nanoparticles; LSN, leuprolide-stearic acid nanoparticle; LON, leuprolide-oleic acid nanoparticle; LLN, leuprolide-linoleic acid nanoparticle; NMR, nuclear magnetic resonance; MALDI-TOF, matrix-assisted laser desorption/ionization-time of flight; FT-IR, Fourier transform infrared spectroscopy; DSC, differential scanning calorimetry; DLS, dynamic light scattering; FE-SEM, field emission scanning electron microscope; FE-TEM, field emission transmission electron microscope; HPLC, high-performance liquid chromatography; Prep-HPLC, preparative-high-performance liquid chromatography; DW, deionized water; DMAP, 4-dimethylaminopyridine.

Data Sharing Statement

The data presented in this study are available upon request.

Acknowledgments

This work was primarily supported by a grant from the Korea Evaluation Institute of Industrial Technology (KEIT) funded by the Ministry of Trade, Industry and Energy, Republic of Korea (20008840) in 2020. We would like to thank the staff of the Ajou Central Laboratory for allowing us to use the FE-SEM, FE-TEM, DSC, and FT-IR facilities.

Disclosure

Kye Wan Lee reports grants from Ministry of Trade, Industry & Energy (MOTIE, Korea), during the conduct of the study, and is an employee of Dongkook Pharmaceutical Co., Ltd, Seoul, Republic of Korea. The authors report no other potential conflicts of interest in relation to this work and declare that they have no known competing financial interests or personal relationships that could have influenced the work reported in this paper.