Continuous phase matrix (CPM)

Pre-polymer PEG-DA (MW 575) was mixed with prepared DEP medium (described for each cell type below) at 15% PEG-DA. The photo-initiator 2,2-dimethoxy-2- phenylacetophenone (DMPA) was dissolved in catalyst 1-vinyl-2-pyrrolidone (NVP) at 100 mg/ml. Once cells were resuspended in the pre-polymer DEP solution, DMPA was added to 1 ml of cell suspensions at 0.01% v/v.

We initially investigated the most commonly used blue-light photo-initiators found in the literature; camphorquinone (CQ), eosin-y (E-Y) and triethanolamine (TEA)⁴⁴ (Sigma-Aldrich). Following protocols for optimal cell viability^37,45 initial investigation of these initiators in the DOT electrode system revealed E-Y and TEA cured PEG in approximately 6 min, CQ and TEA cured in approximately 10 min, and CQ alone did not cure within 10 min. Thus the E-Y and TEA combination was used for all further testing. These were prepared in 15% PEG at 0.1 mM and 0.2% respectively.

Powdered gelatin (from porcine skin, type A, 300 bloom) was dissolved in a prepared buffer solution at 6.75%w/v. Conductivities of these were about 875 mS/m at 40 °C. Cell suspensions in the gelatin were kept in a water bath at 40 °C and periodically sonicated to prevent temperature dependent gelation. PuraMatrix™ was investigated at 25% concentration of the precursor solution in the prepared buffer solution with conductivity of 100 mSm^-1.