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.