Papers by Author: Wen You Zhou

Abstract: The aim of this study was to investigate the feasibility of utilizing selective laser sintering (SLS) to build 3D porous tissue engineering scaffolds from small quantities of poly(L-lactide) (PLLA). PLLA microspheres with suitable particle sizes for the SLS process were produced by the oil-in-water emulsion solvent evaporation technique. A miniature build platform was designed, fabricated and incorporated in an existing Sinterstation® 2000 system to enable small quantities of polymer powder to be used for the production of 3D porous scaffolds. Trial runs were first performed using the DuraForm™ polyamide powder and interfacing problems between the miniature build platform and the existing machine were solved. Then 3D porous scaffolds were successfully built from the PLLA microspheres using the modified SLS machine. This study paved the way for further comprehensive studies on selective laser sintering of tissue engineering scaffolds using expensive biopolymers and their composites.

Abstract: This paper reports a study on the modification of a commercial selective laser sintering (SLS) machine for the fabrication of tissue engineering scaffolds from small quantities of poly(L-lactide) (PLLA) microspheres. A miniature build platform was designed, fabricated and installed in the build cylinder of a Sinterstation 2000 system. Porous scaffolds in the form of rectangular prism, 12.7×12.7×25.4 mm3, with interconnected square and round channels were designed using SolidWorks. For initial trials, DuraFormTM polyamide powder was used to build scaffolds with a designed porosity of ~70%. The actual porosity was found to be ~83%, which indicated that the sintered regions were not fully dense. PLLA microspheres in the size range of 5-30 μm were made using an oil-in-water emulsion solvent evaporation procedure and they were suitable for the SLS process. A porous scaffold was sintered from the PLLA microspheres with a laser power of 15W and a part bed temperature of 60oC. SEM examination showed that the PLLA microspheres were partially melted to form the scaffold. This study has demonstrated that it is feasible to build tissue engineering scaffolds from small amounts of biomaterials using a commercial SLS machine with suitable modifications.

Abstract: Nano-sized carbonated hydroxyapatite (CHAp) particles were firstly synthesized using a nanoemulsion method. TEM analyses revealed that as-synthesized nanoparticles were calcium-deficient and spherical in shape (diameter: 16.8±2.6nm). Biocomposite microspheres comprising CHAp nanoparticles and poly(L-lactide) (PLLA) were fabricated using the single emulsion solvent evaporation technique. SEM images showed that composite microspheres were mainly 5-30 μm in size despite the change of CHAp nanoparticle content. When the CHAp nanoparticle content in composite microspheres was below 10 wt%, all nanoparticles were encapsulated within the microspheres which possessed a nanocomposite structure. DSC results showed that the crystallinity of the PLLA matrix of microspheres increased from 38 to 42% when the CHAp nanoparticle content was increased from 0 to 20 wt%. The biocomposite microspheres should be a suitable material for constructing bone tissue engineering scaffolds.