Abstract:

Objective The nanofiber membrane structure with high specific surface area and high porosity can be applied in the detection field in response to external stimuli. Recently, the preparation of colorimetric sensors with nanofiber membrane as a carrier has attracted increasing attention. In order to develop nanofiber materials for monitoring wound infection, a colorimetric sensing nanofiber membrane for wound monitoring was prepared from chitosan/fish gum protein as raw material and plant dye hematoxylin as indicator by electrospinning technology.

Method Colorimetric sensing nanofiber membrane was prepared by electrospinning technology after the spinning solution containing hematoxylin was well mixed by the original solution coloring method with optimized parameters of electrospinning. Scanning electron microscope, differential scanning calorimetry and X-ray diffraction (XRD) were dopted to characterize the microscopic morphology of the nanometer fiber membrane and analysis, and the color change situation under different pH values was also studied. In addition, the hydrophilicity of the nanofiber membrane was proved by the hydrophobic angle test.

Results In the prepared nanofiber membrane without beading, the fibers with an average diameter of 346.1 nm were found thin and straight when the mass ratio of chitosan (CS) to collagen (Col) is 1:1 (Fig.1). When the voltage was set to 12 kV, the propulsion speed was 1.5 mL/L, and the receiving distance was 20 cm, the fibers without adhesion phenomenon showed straight and smooth, in which the average fiber diameter was about 264 nm, and the diameter CV value was 14.51% (Tab.2 and Fig.3). Based on the optimal parameters of electrospinning, the colorimetric sensing nanofiber membrane was prepared with hematoxylin (Fig.4). The thickness of the nanofiber membrane was 0.01 mm, in which the average diameter of the fiber was 246.2 nm. The colorimetric sensing nanofiber membrane had a peak of 93.8 ℃, which is lower than CS and Col (Fig.5). This believed to be precise because the melting temperature of polyethylene oxide (PEO) in the nanofiber membrane is lower than that of CS and Col. Therefore, the introduction of PEO reduced the melting temperature of the nanofiber membrane, indicating that the three materials successfully integrated into the nanofiber membrane. Furthermore, the stucture test results showed that the nanofiber membrane reveals a peak near 10°, meanwhile, the peak strength is lower than that of chitosan and collagen (Fig.6). It may be because CS and Col were successfully mixed, which destroys the helical structure of collagen and affects the crystal structure of nanofiber membrane. The contact angle test results showed that the contact angle of the prepared nanofiber membrane changed from 80° to 46° within 4 s, which showed good hydrophilicity and suitability for medical applications (Fig.7). Most importantly, the color changes of colorimetric sensing nanofiber membranes at different pH values (Fig.8). With the increase of pH value, colorimetric sensing nanofiber membranes exhibited different colors. When pH value increased from 5 to 7, the color change was more obvious, the fiber membrane changed from yellow to purple, the color difference from 0 to 10.59, and the color change of nanofiber membrane could be observed by naked eye, which was in line with the need of wound monitoring.

Conclusion When the mass ratio of the CS to Col of 1:1, the spinning voltage is 12 kV, the pushing speed is 1.5 mL/h, and the receiving distance is 20 cm, the nanofiber membrane obtained possess good hydrophilicity. The average fiber diameter is 246.2 nm, and the diameter CV value is 29.54%. More importantly, the color of the colorimetric sensing nanofiber membrane changes from yellow to purple, when the pH value changes from 5 to 7. Moreover, the color change range of the nanofiber membrane is consistent with the pH value of the exudate when the skin is inflamed, which meets the requirements of wound monitoring.

Key words: wound monitoring, nanofiber membrane, colorimetric sensor, electrospinning, hematoxylin, chitosan, fish collagen