Combined nanomanipulation by atomic force microscopy and UV-laser ablation for chromosomal dissection

Nanomanipulation and nanoextraction on a scale close to and beyond the resolution limit of light microscopy is needed for many modern applications in biological research. For the manipulation of biological specimens a combined microscope allowing for ultraviolet (UV) microbeam laser manipulation together with manipulation by an atomic force microscope (AFM) was used. In a one-step procedure, human metaphase chromosomes were dissected optically by the UV-laser ablation and mechanically by AFM manipulation. With both methods, sub-400-nm cuts could be achieved routinely. Thus, the AFM is an indispensable tool for in situ quality control of nanomanipulation. However, already on this scale the dilation of the topographic AFM image due to the tip geometry can become significant. Therefore the AFM images were restored using a tip geometry obtained by a blind tip-reconstruction algorithm. Cross-sectional analysis of the restored image reveals a 380-nm-wide UV-laser cut and AFM cuts between 70 nm and 280 nm.