Amorphous DNA layers

Atomic Force Microscopy Studies of Amorphous DNA Layers. 145... 

These conditions are met in most practical situations, in micro- and even nanobiodevice applications. For instance, the high density of DNA molecules is required to increase the sensitivity of the device long DNA molecules are commonly (but not exclusively) used as target molecules in e.g., biosensors, microarrays and microPCR devices single DNA species used as targets translate in lack of complementarity and most substrates, (e.g., glass, polymers) for micro/nanobiodevices are amorphous. The critical difference between the self-assembled and amorphous DNA layers, which leads to the polymerlike character of the latter, is the lack of complementarity between adjacent strands. Still, as with polymers, the DNA chains have to have a consider-... 

Silicon wafers can act as substrates in the fabrication of DNA arrays. Chemical functionalization of silicon surfaces is compUcated by the fact that silicon spontaneously oxidizes in air to produce an amorphous sihca layer. 

The amorphous character of DNA layers emerges when several conditions are met, namely ... 

An enormous amount of work, part of which has been recently reviewed [28,29], has been reported regarding the immobilisation of DNA molecules in high concentration layers, mostly referring to hard surfaces (e.g., glass or mica) and mainly for practical devices and AFM experiments. However, the rapid development of, and increasing demand for, DNA-based microdevices both push for lower cost, easily processable materials, and towards disposable devices. As polymers seem to be the logical choice, the resulting DNA layers will almost certainly be amorphous. 

In principle, there are two methods for the AFM probing of amorphous layers, namely (i) an active probing, which probes the surface chemistry, and (ii) a passive probing, which probes the surface physics. The active AFM probing, which is essentially an extension of the AFM-based single molecule studies, relies on the measurement of LF by an AFM tip that is fimctionahsed with molecular recognition-active molecules (e.g., a potentially complementary DNA). 

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