Surface roughness in action - Cells in opposition.

Aim of this work is to study the interaction of krypton fluoride (KrF) excimer laser beam with a biopolymer and creation of new nanostructures with great potential for cell growth guidance. As a substrate we used biocompatible and biodegradable polymer polyhydroxybutyrate, which is frequently used in medicine and drug delivery system. Modification was carried out by KrF laser and method was also supplemented by treatment with Ar+ plasma. The changes in physico-chemical properties of surface layer were determined by goniometry, gravimetry and X-ray photoelectron spectroscopy (XPS). Morphological changes and roughness were observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Effect of laser treatment on the bulk material was studied by differential scanning calorimetry (DSC). Finally, the tests of mouse embryonic fibroblast (NIH 3T3) and human bone osteosarcoma (U-2 OS) cells' response was carried out on the selected samples. Modification of surface by laser with high number of pulses and fluence led to creation of surface layers with huge valleys and very high roughness. These structures were caused by extreme effect of ablation in combination with mass transfer. The results of the surface characterization will be useful for further research in the field of biopolymers structuring and modification, and may find a strong application in tissue engineering for single cell assays.