3D printing of hydroxyapatite scaffolds with good mechanical and biocompatible properties by digital light processing

Hydroxyapatite is a scaffold material widely used in clinical repair of bone defects, but it is difficult for traditional methods to make customized artificial bone implants with complicated shapes. 3D printing biomaterials used as personalized tissue substitutes have the ability to promote and enhance regeneration in areas of defected tissue. The present study aimed at demonstrating the capacity of one 3D printing technique, digital light processing (DLP), to produce HA scaffold. Using HA powder and photopolymer as raw materials, a mixture of HA mass ratio of 30 wt% was prepared by viscosity test. It was used for forming ceramic sample by DLP technology. According to differential scanning calorimetry and thermal gravity analysis, it was revealed that the main temperature range for the decomposition of photopolymer was from 300 to 500 °C. Thus, the two-step sintering process parameters were determined, including sintering temperature range and heating rate. XRD analysis showed that the phase of HA did not change after sintering. SEM results showed that the grain of the sintered ceramic was compact. The compression model was designed by finite element analysis. The mechanical test results showed that the sample had good compression performance. The biological properties of the scaffold were determined by cell culture in vitro. According to the proliferation of cells, it was concluded that the HA scaffold was biocompatible and suitable for cell growth and proliferation. The experimental results show that the DLP technology can be used to form the ceramic scaffold, and the photopolymer in the as-printed sample can be removed by proper high-temperature sintering. The ceramic parts with good compression performance and biocompatibility could be obtained.