Three‐Dimensional Bioactive and Biodegradable Scaffolds Fabricated by Surface‐Selective Laser Sintering

Abstract

A new method of surface-selective laser sintering (SSLS) leads to the fabrication of three-dimensional (3D) composite scaffolds (spatial resolution ∼200 μm) that are both bioactive and biodegradable. Moreover, the scaffolds can have very precise dimensions and intricate structure. Conventionally, in selective laser sintering (SLS), the polymer absorbs infrared (λ=10.6 μm) radiation and this leads to a volumetric absorption by the whole polymer particle. In other words, each particle of polymer is completely melted and fuses to the next in order to form the desired morphology. In our experiments we have used near-infrared (λ=0.97 μm) laser radiation, which polymer particles do not absorb at all. To initiate the sintering process a small quantity (< 0.1 wt.-%) of carbon microparticles were homogeneously distributed on the surfaces of the polymer particles. Thus, the melting process was limited to only the surfaces of each particle. The carbon microparticles are strong absorbers of laser radiation, and this opens up the technique to a range of polymers that up till now could not be processed by laser sintering. More importantly, since the laser melts only the surfaces of the particles, delicate bioactive species trapped within each particle retain their activity throughout the processing. We have demonstrated the application of this technique by the incorporation of the enzyme ribonuclease A into particles of poly(d,l-lactic) acid (PLA) and the assembly of 3D matrices at three different laser intensities, using a 0.97 μm wavelength continuous wave (CW) diode laser.