In vitro assessment of cell penetration into porous hydroxyapatite scaffolds with a central aligned channel

There is a clinical need for synthetic scaffolds that promote bone regeneration. A common problem encountered when using scaffolds in tissue engineering is the rapid formation of tissue on the outer edge of the scaffold whilst the tissue in the centre becomes necrotic. To address this, the scaffold design should improve nutrient and cell transfer to the scaffold centre. In this study, hydroxyapatite scaffolds with random, open porosity (average pore size of 282±11 μm, average interconnecting window size of 72±4 μm) were manufactured using a modified slip-casting methodology with a single aligned channel inserted into the centre. By varying the aligned channel diameter, a series of scaffolds with channel diameters ranging from 170 to 421 μm were produced. These scaffolds were seeded with human osteosarcoma (HOS TE85) cells and cultured for 8 days. Analysis of cell penetration into the aligned channels revealed that cell coverage increased with increasing channel diameter; from 22±3% in the 170 μm diameter channel to 38±6% coverage in the 421 μm channel. Cell penetration into the middle section of the 421 μm diameter channel (average cell area coverage 121×103±32×103 μm2) was significantly greater than that observed within the 170 μm channel (average cell area coverage 26×103±6×103 μm2). In addition, the data presented demonstrates that the minimum channel (or pore) diameter required for cell penetration into such scaffolds is approximately 80 μm. These results will direct the development of scaffolds with aligned macroarchitecture for tissue engineering bone.