DOI: 10.14457/tu.the.2022.790
title: Encapsulation of lavender essential oil into polyurethane nanoparticles for wound healing application

description: Polyurethane (PU) nanoparticles (NPs) are potential drug carriers due to their biodegradability and biocompatibility. This work aims to fabricate the PU NPs loaded with lavender essential oil (LO) for use in wound healing application. The work was divided into 2 parts: part I involved the utilization of commercial PU colloidal as a template for simple swelling-diffusion of LO and part II involved synthesis of PU from alcoholyzed polylactic acid (PLA) and use as protective shell to encapsulate LO via nanoemulsion method. Part I, the oil phase of LO dissolved in EtOH/water mixture, was gently mixed with the aqueous phase of commercial preformed PU NPs. Based on swelling-diffusion, LO diffused into the PU NPs’ cavity through a nanochannel that exists naturally on their surface. The effect of EtOH/water mixture ratios on the stability, and encapsulation efficiency of the obtained LO-loaded PU (LO@PU) NPs were studied. Moreover, the quantitative results of encapsulation efficiency (EE) and loading capacity (LC) including the release behaviors of the LO from the PU NPs and their antibacterial properties were investigated. With the proper ratio of EtOH/water at 0/100, the stable, monodispersed, and spherical LO@PU NPs (101±0.3 nm) with high %EE and %LC of 59.67% and 27.98%, respectively, were obtained. The release behavior of LO from the NPs under dialysis technique showed that 61.48% within 192 h. The cytotoxicity assay in the fibroblasts cell line showed the decreasing CC50 of the LO@PU NPs compared with free LO, which confirm the non-cytotoxic profile of PU NPs. Furthermore, the encapsulated NPs showed good antibacterial activity against Staphylococcus aureus and Escherichia coli, resulting biocompatible materials and suitable use in wound healing applications. Part II involved the using of synthesized PU (named PUD) as a polymer matrix to encapsulate LO. The PUD NPs loaded with LO (LO@PUD) was prepared via nanoemulsion method. Firstly, PUD was synthesized from alcoholyzed PLA and 1,6-Diisocyanatohexane (HDI) in a chloroform solvent. Then, the dispersion of LO and PUD in chloroform was mixed with the aqueous phase containing 0.001M NaOH. The mixture was then emulsified under Ultra-Turrax homogenizer at 10,000 rpm for 10 min without using any surfactants. The effect of weight ratios of PUD:LO (e.g., 1.25:1, 2.50:1, 3.75:1, 5.00:1, 6.25:1) on the physicochemical properties of NPs e.g., chemical composition, physiochemical stability, size, shape and crystal structure of NPs was studied. With the ratios of PUD:LO at 3.75:1, the stable NPs with high %EE and %LC of 88.4 and 23.6, respectively, were obtained. The negative charge formation on polymer chain promoting the stability of NPs in the emulsion due to the deprotonation of carboxylic acid end-chain group of polyurethane backbone in the alkaline solution. The different releasing rate of LO occurred by the different diffusion of LO to the medium through the free volume of the crystalline polymer. Within 192 h, a total of 41.4% release of LO was observed in alkaline solution at pH of 8.5. The NPs' sustained drug release provides long-term protection and treatment for skin wounds. In addition, the cytotoxicity assay of LO@PUD NPs in the HaCaT cell line showed a non-toxic effect to the cell line HaCaT. These results suggested that the prepared LO@PUD NPs have high potential for use in wound healing applications.