SEM images of cell-free printed alginate/gelatin hydrogels.

<p>(<b>A</b>) Appearance of the basic alginate/gelatin hydrogel cylinders, containing neither silica nor biosilica nor polyP·Ca²⁺-complex. (<b>B</b>) Hydrogel containing 10 µg/ml of silicatein. (<b>C</b> and <b>D</b>) Printed basic alginate/gelatin hydrogel containing 50 µmoles/L ortho-silicate (>si<). (<b>E</b> and <b>F</b>) Cylinders of hydrogel supplemented with 50 µmoles/L biosilica (>bs<). (<b>G</b> and <b>H</b>) Alginate/gelatin hydrogel cylinders containing 100 µmoles/L polyP·Ca²⁺-complex (>polyP<). (<b>I</b> and <b>J</b>) Hydrogel containing both 50 µmoles/L biosilica (>bs<) and 100 µmoles/L polyP·Ca²⁺-complex.