Electrospinning Equipment: Long Lasting Fragrance Coaxial Essential Oil Nanofiber Membrane with Antibacterial Properties

In modern life, people's pursuit of the quality of life is constantly increasing, and long-lasting fragrance products have received more and more attention. Such products can continuously release fragrance, improve the environmental atmosphere, and mask unpleasant odors. Nanofiber (NF) membranes have been widely applied in the field of long-lasting fragrance products due to their unique microstructure and high specific surface area. They are prepared through the electrospinning machine, which can encapsulate aromatic compounds and control their release. Moreover, the slow-release effect can be optimized through surface functionalization and multi-layer coaxial structure design.

Cinnamon essential oil (CEo) has multiple functions, such as broad-spectrum anti-infection, antibacterial properties, and mood improvement. Combining it with nanofiber membranes to construct coaxial essential oil-releasing nanofiber membranes has become a research hotspot. This research aims to enhance the sustained release performance of essential oils, control the release rate, and improve their stability, which is of great significance for expanding the application range of essential oils and enhancing their practicality.

To this end, the research team led by Professor Hongbin Zhao from the University of Science and Technology Liaoning successfully prepared long-lasting fragrance coaxial essential oil nanofiber membranes using an electrospinning device through coaxial electrospinning technology, with polyvinylpyrrolidone (PVP) as the core layer and polyimide (PI) as the shell layer. This membrane fully utilizes the advantages of the coaxial structure to encapsulate the essential oil in the core layer and use the shell layer to protect and control the release of the essential oil, achieving continuous fragrance release for up to 14 days. Experimental data show that it has a high release efficiency in the first 48 hours, followed by a stable slow release, and it also has good antibacterial properties against various bacteria and molds. The relevant results were published in the journal Applied Polymer under the title "Long Lasting Fragrance Coaxial Essential Oil Nanofiber Membrane: Fabrication, Characterization and Antibacterial Properties".

This study successfully prepared long-lasting fragrance-releasing PI/PVP nanofiber membranes using an electrospinning device through coaxial electrospinning technology. The synthesis process of the PI/PVP CEo-loaded NFs membrane is shown in Figure 1. This technology uses PVP as the core layer and PI as the shell layer to achieve the loading and release of essential oils. The morphology of the nanofibers was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) (as shown in Figure 2C and 1I), clearly demonstrating its microstructure. As can be directly seen from Figure 2I, the coaxial nanofibers have a distinct core-shell boundary, and this structure ensures the efficient encapsulation and slow release of essential oils.

Figure 1：The synthesis process of PI/PVP CEo loaded NFs membranes.

Figure 2: (A) FTIR spectra of PI/PVP NF mats, Photo of PI/PVP NF mats, (B) XRD of PI/PVP NF mats, (C) SEM/TEM images of NF membranes, (D) PI/PVP (0 wv% CEo) NFs SEM image, (E) PI/PVP (3 wv% CEo) NFs SEM image, (F) PI/PVP (5 wv% CEo) NFs SEM image, (G) PI/PVP (7 wv% CEo) NFs SEM image, (H) PI/PVP (10 wv% CEo) NFs SEM image, (I) TEM image of PI/PVP coaxial NFs.

The prepared nanofiber membranes can continuously release essential oils for up to 14 days. The release rate shows a trend of being fast at first and then slow. The release efficiency is relatively high in the first 48 hours and then gradually slows down. The results of thermogravimetric analysis (TGA) (as shown in Figure 3B) show that when the temperature of the nanofiber membrane reaches about 300°C, the membrane begins to decompose because PVP starts to decompose at around this temperature. When the temperature reaches about 380°C, the mass loss is approximately 40%, and the remaining PI material continues to decompose. PI/PVP - 5wv%, PI/PVP - 10wv%, and pure PI nanofibers all start to decompose at around 500°C. This indicates that the nanofiber membranes containing essential oils have a certain degree of high-temperature resistance and can maintain structural stability within a certain temperature range.

Figure 3：(A) The CEo release profile from PI/PVP coaxial NFs, (B) TG - DTG analysis of CEo loaded PI/PVP coaxial NFs. 

It can be known from the antibacterial zone experiment that CEo has a certain antibacterial effect on different types of bacteria and molds, and it has the best antibacterial effect on Pseudomonas aeruginosa (PA) (as shown in Figure 4A). Figure 4A shows the diameters of multiple antibacterial circles. Among them, the diameter of the bacteriostatic ring of PA reaches 56.47 ± 0.14mm, which is significantly larger than that of other strains. Cinnamaldehyde, the main component of CEo, accounts for about 90%. It has broad-spectrum antibacterial activity and can destroy the bacterial cell membrane, interfere with its energy metabolism and protein synthesis, thereby inhibiting bacterial growth.

Figure 4：(A) The diameter of multi-type antibacterial circles, (B) the combination diagram of CEo.

This study successfully achieved the innovative preparation of long-lasting fragrance-releasing PI/PVP NF membranes using an electrospinning machine through coaxial electrospinning technology. The NF morphology was visually displayed through SEM and TEM, and the efficient encapsulation and slow release of essential oils were achieved through the adjustment of the core-shell structure. The prepared NF membranes can release essential oils continuously for 14 days. TGA analysis shows that the prepared NF membranes containing essential oils decompose at around 500°C, demonstrating high-temperature resistance. According to the results of the bacteriostatic rings, it can be observed that CEo has a certain antibacterial effect on different types of bacteria and molds, and the antibacterial effect on Pseudomonas aeruginosa (PA) is the best. This study provides a new method for the sustainable improvement of long-lasting fragrance release. The prepared coaxial NF samples are confirmed to have excellent core-shell microstructure, crystal structure, chemical composition, and thermal stability, as well as the ability to release fragrance for a long time.

Article source: https://doi.org/10.1002/app.57234