Respiration of patients suffering from severe lung diseases e.g. cystic fibrosis or chronic obstructive pulmonary disease (COPD) can be supported by so-called "extracorporeal membrane oxygenation" (ECMO). Such an ECMO-system ensures CO2 elimination and O2 support by a membrane based on hollow fibers. Due to unspecific protein adsorption, resulting in a decrease of gas transfer and because of other side effects, the application is limited to short-term. However, as a bridge-to-decision or a bridge-to-transplant a system applicable for weeks to months is needed. The aim of the presented project is therefore the creation of a biocompatible device with a physiological gas-exchange surface made of an endothelialised flat membrane. The cell seeding requires an all new membrane and device concept. In order to develop a biohybrid lung assist device, clinicians, natural scientist, engineers, medical and material scientists work closely together. First cell seeding results on modified PMP membrane are presented.