Priming cells for their final destination: microenvironment controlled cell culture by a modular ECM-mimicking feeder filmElectronic supplementary information (ESI) available: CLSM observation of gelatin film, metabolic activity of HUVEC cells and F-actin and PECAM labeling of HUVEC cells on various gelatin substrates, observation of labelled HUVEC cells on gelatin films first loaded with growth factors and then crosslinked, effectiveness of the gel-feeder substrate loaded with growth factors after storage under frozen conditions, 3T3 fibroblast labelled cells seeded on various gelatin films, effect of nanoparticle loading on the gelatin film on spreading of HGF, 3T3 and HUVEC labelled cells, AFM nanoindentation experiments to determine the Young modulus of gelatin films loaded with various concentrations of nanoparticles, Capillary electrophoresis (CE) coupled with electrospray ionization mass spectrometry (ESI-MS) measurements used to monitor the loading and release of proteins from

Mammalian cell culture is the starting point in many research studies focusing on biomedical applications. However, researchers have little control over the standardized cell microenvironment parameters. Here a modular ECM-mimicking surface coating for cell culture environment is designed. This substrate is a new and versatile thin film obtained by spin-coating of concentrated gelatin crosslinked by transglutaminase. It can be modified with respect to the biochemical and biophysical needs of the final cell destination, i.e.it delivers loaded multi-growth factors and serum components and allows for cell culture in a serum-free culture medium. Also, a well-known cell behavior modulator, the substrate stiffness, is controlled exogenously by addition of nanoparticles. In addition to growth factors, antimicrobial agents such as natural peptides are added to the substrate for limiting the repeated addition of antimicrobial agents to the culture medium and to prevent the increase of resistant bacterial strains in the culture environment. Finally, this substrate contains simultaneously ECM components, growth factors, stiffening elements and antimicrobial agents. It provides a favorable microenvironment and sterile conditions. It is a free-of-maintenance system, as cells will grow without addition of serum or antimicrobial cocktails. This low cost and easy-to-use substrate could emerge as a new standard for cell culture.