Preparation and characterization of hyaluronan/collagen II microspheres under an electrostatic field system with disc electrodes

Collagen II and hyaluronan are the two major components of the native extracellular matrix (ECM). Both biopolymers are responsible for providing the associated tissues with tensile strength, and also serve as a structural scaffold for cell adhesion and growth. Over the years, many researchers have focused on the preparation and evaluation of man-made ECM comprising the two polymers in the form of a membrane for chondrocyte culture applications. Here, a simple and in situ method, involving the injection of the hyaluronan/collagen II (HA/Col II) mixture solution through a pair of hollow-centered parallel disc electrodes (HCPDEs) of a high-voltage electrostatic field system, was developed and employed to prepare HA/Col II microspheres in watery phase. The HA/Col II microspheres were firmed up by a two-step cross-linking treatment (first by FeCl3 and then by 1-ethyl-3-(3-dimethyl aminopropyl) carbodimide, EDC) to secure the spherical structure shape. Then, at 37 °C, reconstitution treatment of the Col II molecules was conducted to further strengthen the microspheres. Depending on treatment conditions, the resulting series of HA/Col II microspheres all exhibited good sphericity in the range of 486 ± 43 to 679 ± 24 μm in diameter. Furthermore, the ratio and amount of HA/Col II in the mixture solutions would affect the morphological structure and basic characteristics, including mechanical strength, thermal properties and water content. In the preliminary study, the HA/Col II microspheres have shown to provide favorable ECM characteristics, with appropriate mechanical strength, and exhibited a 3D inclination.