Effects of Ambient Relative Humidity and Solvent Properties on the Electrospinning of Pure Hyaluronic Acid Nanofibers

Abstract

Nanofibers exist ubiquitously in natural extracellular matrix (ECM) of all kinds of human tissues forming hydrated interwoven network. Electrospinning nanotechnology has been proven to be a powerful technique to fabricate controllable nanofibers mimicking the natural ECM structures. Hyaluronic acid (HA), as a critical component of natural ECM, has been widely used in tissue engineering and regenerative medicine. In this study, pure HA nanofibers with average diameter of 33 +/- 5 nm, 59 +/- 12 nm, 79 +/- 12 nm and 113 +/- 19 nm were successfully prepared using different electrospinning parameters. The effect of the ambient relative humidity on HA electrospinnability was investigated for the first time in detail, which was proven to be one of the most important factors to control the morphology of HA nanofibers beside the solution properties. A critical value of humidity for a defined HA solution was observed, only below which HA nanofibers with similar diameters and morphologies could be successfully obtained. When the ambient relative humidity was higher than the critical value, the HA nanofibers started dissolving at the cross points and even fused together forming a spreading layer. Moreover, only a small amount of N, N-Dimethylformamide (DMF) was found to be required to promote the electrospinnability of HA solution by mixing with water as solvents. With the increase in the DMF content, the surface tension of the solution decreased significantly, which was thought to be benefit for the stable Taylor cone and fluid jet formation in electrospinning. At the same time, it should be noted that the conductivity of the solution also decreased with the increase of DMF content in the solution, which was believed to be responsible for the increasing diameters of HA nanofibers corresponding to higher DMF content. Controllable HA nanofibers with diameter below 100 nm have great promising for developing novel nanobiomaterials applied in tissue engineering and regenerative medicine.

Hyaluronan-Based Nanofibers: Fabrication, Characterization and Application

“…For example, Jou [36] presented multilayer fiber based on polyethylene terephthalate. Polyethylene terephthalate fibers were treated with 60 Co-γ-ray and grafted with acrylic acid, and then were grafted with chitosan via esterification. At last, hyaluronic acid was immobilized onto chitosan-grafting fibers.…”

“…Yao Shenglian et al [60], apart from solvents properties, highlighted an influence of ambient relative humidity on the electrospinnability of the hyaluronan solutions. A critical value of humidity allowing them to successfully obtain uniform hyaluronan fibers with similar diameters and morphologies was equal to 8%.…”

“…It is worth noting that the results obtained from research are difficult to compare each other because of different analysis methods utilized. Several studies [57,[59][60][61]74] included only physical and rheological parameters of polymer solutions, and physicomechanical, physicochemical, and morphological characteristics of the fibers obtained. By contrast, some studies, for instance, [67,70], investigated the morphology, physicochemistry, and the biological effectiveness of each fiber.…”

Electrospinning of Nanofibers and Their Applications for Energy Devices

“…The characteristics of electrospun nanofibers depend on a number of parameters. These parameters are commonly divided into three categories: solution parameters (such as solution concentration and/or viscosity, solution surface tension, and solution conductivity), process parameters (such as feed rate, applied voltage, and tip to collector distance), and ambient conditions (like ambient temperature and humidity) [34][35][36]. The following will discuss the influential parameters on morphology and diameter of fibers in the process of electrospinning.…”

Effect of humidity on melt electrospun polycaprolactone scaffolds

“…As RH increased further, droplets started to form with poly(vinyl alcohol), poly(ethylene oxide), poly(vinyl alcohol)/hyaluronic acid, poly(ethylene oxide)/chitosan and polystyrene as evaporation rates lowered [7,9,10]. Yao et al [16] reported that by electrospinning a hyaluronic acid solution above a critical RH value, which is Figure 1: Schematic of the direct-write melt-electrospinning apparatus. The water bath is used to melt a PCL polymer which is extruded onto a moving collector plate via the syringe pump.…”