An enhanced microstamping technique for controlled deposition of proteins

It has been demonstrated that protein adsorbed onto poly-dimethyl-siloxane (PDMS) stamps is transferred to substrates in the process of microstamping, and it has been assumed that this amount is sufficient for supporting cellular growth on activated glass substrates. Currently, there exists no characterization of the microstamping process and no method to control the amount of protein deposited onto substrate surfaces. In this report, we demonstrate a new technique to vary the protein loaded onto the stamp and hence the amount transferred onto substrates. Using fluorescence, we characterized this new microstamping process with regard to the amount of time needed for complete transfer of protein and the variation of protein transfer with pressure and stamp age. Furthermore, we compared growth of cells on protein film (poly-D-lysine, 70 to 150 kDa) transferred with this new process and that of the traditional process and concluded: 1) a minimum of 7 μg of PDL/cm² (20 minute loading time) is necessary for bare minimum growth of neurons and 2) good cellular growth can be obtained with 10-12 μg of PDL/cm² (60 minute loading time)