Surface modification of a biodegradable composite by UV laser ablation:<i>in vitro</i>biological performance

Melt blends of chitosan and biodegradable aliphatic polyester have been physically and biologically studied, presenting great potential for biomedical applications. Structurally, poly(butylene succinate)-chitosan (PBS/Cht) composite scaffolds are covered by a thin PBS layer, preventing the desired interaction of cells/tissues with the chitosan particules. In the present work, a selective and controlled ablation of this skin layer was induced by UV laser processing. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) data demonstrated an increment of chitosan components and others resulting from the laser ablation process. The biological activity (i.e. cell viability and proliferation) on the inner regions of the composite scaffolds is not significantly different from those of the external layer, despite the observed differences in surface roughness (determined by interferometric optical profilometry) and wettability (water contact angle). However, the morphology of human osteoblastic cells was found to be considerably different in the case of laser-processed samples, since the cells tend to aggregate in multilayer columnar structures, preferring the PBS surface and avoiding the chitosan-rich areas. Thus, UV laser ablation can be considered a model technique for the physical surface modification of biomaterials without detrimental effects on cellular activity.