Introducing dip pen nanolithography as a tool for controlling stem cell behaviour: unlocking the potential of the next generation of smart materials in regenerative medicine.

Reproducible control of stem cell populations, regardless of their original source, is required for the true potential of these cells to be realised as medical therapies, cell biology research tools and in vitro assays. To date there is a lack of consistency in successful output when these cells are used in clinical trials and even simple in vitro experiments, due to cell and material variability. The successful combination of single chemistries in nanoarray format to control stem cell, or any cellular behaviour has not been previously reported. Here we report how homogenously nanopatterned chemically modified surfaces can be used to initiate a directed cellular response, particularly mesenchymal stem cell (MSC) differentiation, in a highly reproducible manner without the need for exogenous biological factors and heavily supplemented cell media. Successful acquisition of these data should lead to the optimisation of cell selective properties of materials, further enhancing the role of nanopatterned substrates in cell biology and regenerative medicine. The successful design and comparison of homogenously molecularly nanopatterned surfaces and their direct effect on human MSC adhesion and differentiation are reported in this paper. Planar gold surfaces were patterned by dip pen nanolithography (DPN) to produce arrays of nanodots with optimised fixed diameter of 70 nanometres separated by defined spacings, ranging from 140 to 1000 nm with terminal functionalities of simple chemistries including carboxyl, amino, methyl and hydroxyl. These nanopatterned surfaces exhibited unprecedented control of initial cell interactions and subsequent control of cell phenotype and offer significant potential for the future.