Uniform tricalcium phosphate beads with an open porous structure for tissue engineering

Uniform tricalcium phosphate (TCP) porous beads with micro and macro pore sizes were fabricated using a simple fluidic device. For micro-porous TCP beads, an aqueous gelatin mixture containing TCP powder was introduced as the discontinuous phase into the fluidic device, where a toluene phase served as the continuous phase. The resulting aqueous TCP droplets were instantly frozen at -20°C and freeze-dried, followed by calcination at 1200°C. An oil-in-water-in-oil (O/W/O) emulsion templating method was employed to fabricate macro-porous TCP beads. An oil-in-water (O/W) emulsion was introduced into the fluidic device as the discontinuous phase with all other experimental conditions the same as for the micro-porous TCP beads. Uniform macro-porous TCP beads with a highly porous structure were finally obtained after freeze-drying and calcination. Large pore size and good interconnectivity of the macro-porous TCP beads were confirmed by scanning electron microscopy and porosimetry. In addition, penetration of host tissue into the macro-pores of the TCP beads was demonstrated by subcutaneously implanting the two types of porous TCP beads into mice and histologically analyzing stained sections at 1-4 weeks post implantation. The macro-porous TCP beads with a highly open porous structure could potentially be used as an injectable material for bone tissue engineering.