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PNA Microcontact Printing
surface 19 . The immobilization on glass or silicon can be done by activating the surface
through reactive monolayers such as isothiocyanate 20 , N-hydroxysuccinimidyl 21,22 or
aldehydic 23 groups used to link the amino-end; click chemistry has been exploited, as well, in
a reaction between an acetylene-modified surface and an azido-coumarin modified-PNA 24 .
Moreover coupling of PNAs to nanoparticles has been studied as well; these systems have
been developed by coupling the PNA directly through its amino group to the nanoparticle by
EDC mediated coupling 25 , or by click chemistry 26 and their aggregation has been studied with
complementary DNA sequences.
Although the combination of PNA probes with the microarray technology can show good
performances, the fabrication methods are still time consuming and good performances can
usually be achieved only under strictly controlled moisture and temperature conditions which
are not always reproducible 24 . One way to improve the fabrication of these devices on surface,
is to derivatize the surface by microcontact printing (µCP).
Figure 5-1: Schematic representation of microcontact printing (A. Bernard, J. P.
Renault et al., Adv. Mater., 2000, 12, 14, 1069)
Microcontact printing is a well-known powerful tool to functionalize substrates with spatially
patterned molecular monolayers 27 . The technique is based on the use of a stamp made of a
cross-linked elastomer bearing the desired features on the surface exploited for the printing.
The stamps are obtained using a silicon master containing the pattern to be printed and
silanized to make it hydrophobic. The elastomer (usually polydimethtylsiloxane, PDMS) is
poured on the master and the crosslinking reaction is carried out at 60°C for at least 4 hours.
The solid stamp is then removed from the master and inked with a solution of the molecule to
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