Preparation and characterisation of hyaluronan microspheres by electrostatic field system and ultrasound atomisation system

Two simple in situ methods, involving the injection of a hyaluronan (HA) solution through a pair of hollow-centred parallel disc electrodes of an electrostatic field system and a micronozzle transducer of an ultrasound atomisation system, were developed and used to prepare HA microspheres in watery phase. The HA microspheres were treated by FeCl₃ and 1-ethyl-3-(3-dimethyl aminopropyl) carbodimide (EDC) to secure the spherical structure shape. Depending on certain treatment conditions, the resulting series of HA microspheres exhibited good sphericity in the range of 317±22 to 579±49±±m in diameter by the electrostatic field system. Stricter conditions were needed to produce HA microspheres by the ultrasound atomisation system because of a viscosity restriction of micronozzle transducer. However, the HA microspheres could be produced and exhibited good sphericity in a smaller size under certain HA concentrations conditions. These prepared HA microspheres had various mechanical durability and could maintain their particulate shape after intra-articular administration of HA microspheres into a rabbit articular cavity for an 11-day period.