AVS 53rd International Symposium
    Biomaterial Interfaces Tuesday Sessions
       Session BI-TuP

Paper BI-TuP20
Preparation of Biodegradable Double-layered Microshells using Surfactant-free Emulsion Method

Tuesday, November 14, 2006, 6:00 pm, Room 3rd Floor Lobby

Session: Biomaterial Interfaces Poster Session
Presenter: F. Nagata, National Institute of Advanced Industrial Science and Technology (AIST), Japan
Authors: F. Nagata, National Institute of Advanced Industrial Science and Technology (AIST), Japan
T. Miyajima, National Institute of Advanced Industrial Science and Technology (AIST), Japan
Correspondent: Click to Email
Double-layered microshells comprised of poly(lactic acid) (PLA) internal wall and calcium phosphate external wall were synthesized by a improvement surfactant-free emulsion method. PLA is one of the most commonly used hydrophobic and biodegradable polyesters which can encapsulate various poorly water-soluble drugs. PLA-based microcapsules have been investigated for biomedical applications such as drug carriers for targeted delivery. In this study, we demonstrate a method for direct synthesis of double layered microshells composed of PLA and calcium phosphate using organic/inorganic interaction on the interface between oil and water phases. The microshells were prepared as follows. The organic phase composed of PLA (Mw = 20,000) and dichloromethane was poured in calcium acetate aqueous solution. The mixture was stirred at 300 rpm to yield emulsion at room temperature, then the beaker filled with the emulsion was set in an ice bath and was allowed to cool down for 30 min with stirring. Diammonium hydrogenphosphate aqueous solution was slowly added into the emulsion to precipitate calcium phosphate. After adding diammonium hydrogenphosphate aqueous solution, the beaker was taken out from an ice bath and allowed to return room temperature. The obetained microshells had a wide distribution ranging from 50 to 300µm and their wall thickness was 1 to 10µm. The internal wall of the microshells was smooth, contrary to this, the external wall have rough morphology, which indicate that the wall would have multiple layers. The external wall was identified as Dicalcium Phosphate Dihydrate (DCPD) by XRD. On the interface of the oil-in-water emulsion, DCPD would be precipitated on the nucleation sites of dissolved PLA in the oil droplets, which formed calcium phosphate microshell structure. After the precipitated DCPD stabilized the oil droplets, dichloromethane was volatilized and PLA would be deposited on the internal wall of DCPD microshells.