I use two-photon polymerization to crosslink bovine serum albumin (BSA) and gelatin into hydrogels on the scale of 100 microns. These are printed on glass coverslips and submerged in buffer or bacterial growth media. I'd like to get bacteria to attach to the surface of these hydrogels.

I thought of adding poly-l-lysine, a cationic polymer, to promote attachment since bacteria are negatively charged. I also thought of adding a nutrient source to the hydrogel precursor solution and trapping this in the hydrogel matrix during fabrication. Something like bacto agar might work, but it would need to have a lower melting point.

Do you have any suggestions for substances I might add to the hydrogel precursor solution or to fabricated structures to promote attachment?