Electrospinning Equipment: Curcumin-Loaded PCLBSA Composite Fibers via Surfactant-Free Electrospinning for Biomedical Use

Emulsion electrospinning with electrospinning machine is a green technique for preparing multifunctional nanofibers and can be used in fields such as drug delivery. However, traditional methods require the use of surfactants or nanoparticles to stabilize emulsions, and it is difficult to completely remove them from fiber products, which affects the biocompatibility and functionality of fibers. Therefore, the research on surfactant - free emulsion systems has attracted much attention. To this end, a team led by Professor Shu - Hua Teng and Professor Peng Wang from the School of Materials Science and Physics, China University of Mining and Technology, published the latest research findings titled "Surfactant - free emulsion electrospinning of curcumin - loaded poly(ε - caprolactone)/bovine serum albumin composite fibers for biomedical applications" in the journal Frontiers of Materials Science. This research successfully prepared super - hydrophilic curcumin - loaded PCL/bovine serum albumin composite fibers by using surfactant - free emulsion electrospinning technology and ethyl acetate/water as a benign solvent. This achievement provides a new method for improving the hydrophilicity and biological functions of PCL and expands its application potential in the biomedical field.

The team innovatively adopted a novel and environmentally friendly ethyl acetate/water solvent system. When preparing stable water - in - oil (W/O) emulsions of curcumin (Cur) - loaded poly(ε - caprolactone) (PCL)/bovine serum albumin (BSA), no surfactants were added at all. This measure not only simplifies the preparation process but also avoids the potential adverse effects of surfactant residues on fiber properties in traditional methods.

The change rules of emulsion characteristics can be directly observed from Figure 1. When the BSA concentration gradually increases, the interaction between emulsion droplets inside changes, resulting in a significant decreasing trend in droplet size. This is because BSA molecules can form a closer and more stable adsorption layer at the oil - water interface, effectively inhibiting the aggregation and growth of droplets. On the contrary, when the oil - to - water (OTW) ratio decreases, it means that the relative content of the oil phase in the system decreases and the water phase increases. The overall stability of the emulsion system changes, and the collision probability between droplets changes, ultimately leading to an increase in emulsion droplet size.

Figure 1. Micrographs of emulsion droplets obtained with different concentrations of BSA: (a) 0% (w/v); (b) 5% (w/v); (c) 10% (w/v)

During the electrospinning device -assisted electrospinning process, as the BSA concentration gradually increases from 0% (w/v) to 10% (w/v), a significant transformation in the morphology of the Cur - loaded PCL/BSA composite can be clearly observed from Figure 2. At low BSA concentrations, the fibers show a bead - like structure. This is because factors such as the viscosity and surface tension of the solution at this time are not conducive to the formation of continuous fibers. The jet is unstable in the electric field and is likely to break and form beads. As the BSA concentration increases, the properties of the solution change, and the stability of the jet is enhanced, eventually forming a uniform fiber structure. At the same time, when the OTW volume ratio increases, that is, the proportion of the oil phase increases, the diameter of the composite fibers significantly increases and the morphology becomes more uniform. This is because the increase in the oil - phase content changes the rheological properties of the spinning solution, making the stretching process of the jet in the electric field more stable and uniform, thus forming fibers with a larger diameter and regular morphology.

Figure 2. SEM images of Cur - loaded PCL/BSA composite fibers obtained with different concentrations of BSA: (a) 0% (w/v); (b) 5% (w/v); (c) 10% (w/v)

As the oil - to - water ratio gradually decreases from 10:0 to 7:3, significant changes occur in the morphology and diameter of the fibers, as shown in Figure 3. When the oil - to - water ratio is 10:0, the fibers show an irregular bead - like structure. As the oil - to - water ratio decreases, the fiber morphology gradually improves, and the bead - like structure decreases. Finally, at an oil - to - water ratio of 7:3, uniform fibers with the largest diameter are formed. This indicates that the increase in the oil - to - water ratio improves the rheological properties of the spinning solution, making the stretching process of the jet in the electric field more stable, thus forming regular and uniform fibers. This discovery provides an important reference for optimizing the preparation process of composite fibers.

Figure 3. SEM images of Cur - loaded PCL/BSA composite fibers obtained at different oil - to - water ratios: (a) 10:0; (b) 9:1; (c) 8:2; (d) 7:3

The team also studied the mechanical properties of the composite fibers. As can be seen from Figure 4, when the OTW volume ratio is 7:3, the fibers exhibit the highest elastic modulus, reaching 0.198 MPa, and the elongation at break also reaches a maximum of 199%. This indicates that at this ratio, the molecular arrangement and interaction mode inside the fibers endow the fibers with good flexibility and anti - deformation ability. When the OTW volume ratio is 8:2, the fibers achieve the maximum tensile strength, with a value of 3.83 MPa, indicating that when the fiber structure withstands tensile force, the internal components work together in the best state and can effectively resist external force damage.

Figure 4. Stress - strain curves of Cur - loaded PCL/BSA fibrous membranes obtained at different oil - to - water ratios

In addition, the presence of BSA greatly changes the wettability of the composite fibers, endowing them with super - hydrophilicity, as shown in Figure 5a. This is because BSA, as a hydrophilic protein, has hydrophilic groups in its molecular structure that accumulate on the fiber surface, reducing the surface tension between the fiber and water, allowing water to spread rapidly on the fiber surface, thus exhibiting super - hydrophilicity. This property is of great significance in biomedical applications, for example, it is conducive to cell adhesion and growth. In terms of drug release, all composite fibers exhibit a sustained drug - release behavior, as shown in Figure 5b. Among them, the release behavior of the composite fibers with an OTW volume ratio of 7:3 is the most consistent with the first - order model. This means that for the composite fibers at this ratio, the drug - release rate is related to the drug concentration inside the fiber and the concentration difference in the external environment. The drug is continuously and stably released from the fibers through mechanisms such as diffusion, and can maintain a certain drug concentration for a long time, providing a stable drug supply for biomedical treatment.

Figure 5. (a) Contact angles and (b) drug release profiles of composite membranes obtained at different oil - to - water ratios

This research successfully prepared curcumin - loaded PCL/BSA composite fibers through surfactant - free ethyl acetate/water emulsion electrospinning machine -assisted electrospinning technology. By adjusting the BSA concentration and oil - to - water ratio, the morphology, mechanical properties, hydrophilicity, and drug - release behavior of the fibers were optimized. This achievement provides a new method for improving the biological functions of hydrophobic PCL and expanding its applications in the biomedical field.

Article source: https://doi.org/10.1007/s11706-025-0717-0