Abstract:

Objective Curcumin (Cur) has widely used in food and medical field by virtue of its proven antioxidant and anti-inflammatory action. Because of its hydrophobicity, low bioavailability, and instability, reasonable drug delivery systems are gaining growing attention. The biocompatible or biodegradable materials used to prepare drug delivery systems are recognized to be the safe and sustainable choice. In order to improve the utilization of Cur and achieve sustained release, the Cur-loaded nanofibrous membranes was developed via coaxial electrospinning technology, with Cur/starch (St) as a core layer and the polyvinyl alcohol (PVA) as the shell layer.
Method The coaxial electrospinning technology was adopted to develop Cur-loaded nanofibrous membranes with core-shell structure. The natural antioxidants Cur was added to the biopolymer St solution to form a core layer spinning solution, and the degradable PVA was used as the shell layer spinning solution. The nanofibrous morphological structure, fiber diameter, shell thickness and sustained-release performance were regulated by the shell flow rate. The structures and properties of nanofibrous membranes were characterized by means of scanning electron microscope, transmission electron microscopy, infrared spectrometer, X-ray diffractor and UV spectrophotometer.
Results The flow rate of shell solution during the coaxial electrospinning was adjusted to 0.4, 0.6, 0.8, 1.0 mL/h, and the corresponding average nanofiber diameter was 235.34, 266.18, 315.38, 293.63 nm, respectively. When the shell flow rate was 0.8 mL/h, the shell thickness was 108.42 nm, which was larger than that of the other groups. Therefore, the shell flow rate had an obvious effect on the morphological structure of the nanofibers from SEM and TEM, and all nanofibers were featured with core-shell structure and a smooth fiber surface. From the FT-IR and XRD, it was depicted that Cur-loaded core-shell nanofiber membranes were successfully prepared, Cur in the core layer was amorphous, and hydrogen bonding existed between the components of core and shell, which provided a structural basis for sustained release. With the increase of shell flow rate, the content of PVA in the fibers gradually increased, and the relative content of Cur and St in the core layer decreased. Therefore, the loading capacity decreased with the increase of shell flow rate. However, the encapsulation efficiency first increased and then decreased when the shell flow rate increased. When the shell flow rate increased to 0.8 mL/h, the encapsulation efficiency increased to 71.11%. When the shell flow rate further increased to 1.0 mL/h, the encapsulation efficiency showed a slight decreasing to 68.26%, because a negative effect on the Taylor cone shape and the formation of fiber occurred when the shell flow velocity exceeded a certain value, which in turn affected the encapsulation effect of the nanofibers. The Cur release rate was high in the initial stage, and the release curve flattened after 24 h, entering the sustained release stage. With the increase of shell flow rate, the cumulative sustained release rate within 24 h and 96 h increased accordingly, realizing the regulation of Cur content and sustained-release effect. And the release mode exhibited the Fickian diffusion behavior.
Conclusion The Cur-loaded nanofibrous membranes with core-shell structure were developed by the coaxial electrospinning technology. The Cur-loaded nanofiber had an obvious core-shell structure and a smooth fiber surface. The shell flow rate directly affected Cur content and morphological structure of nanofibers. With the increase of the shell flow rate, the fiber diameter and shell thickness first increased and then decreased. Cur in the core layer was amorphous, and hydrogen bonding existed between the components of corer and shell layer. With the increase of shell flow rate, the loading capacity decreased, and the encapsulation efficiency first increased and then decreased, which did not affect the efficient release of Cur. The shell flow rate influenced Cur content and cumulative release rate, and the release behaviors followed the Fickian diffusion law, which indicated the shell flow rate could regulate Cur content and sustained release effect. The Cur-loaded nanofiber membrane prepared in this paper has a broad application prospect in the food and medical fields.

Key words: curcumin, coaxial electrospinning, nanofiber, core-shelll structure, sustained-release, polyvinyl alcohol