Biology Reference
In-Depth Information
only the techniques that have been applied to pattern VNPs are discussed
here. For further reading, the following topic is suggested:
Nanolithography:
A Borderland between STM, EB, IB, and X-ray Lithographies
(Gentili
et al
.,
2008).
To pattern VNPs,
(SPN) has been
utilized. SPN is a technique using an atomic force microscope (AFM). One
differentiates between
scanning probe nanolithography
dip-pen nanolithography
and
nanografting
(Figs
7.12 and 7.14)
the AFM tip is used as a “pen”
that is coated with chemical linkers, the “ink”. The tip (or ”pen”) is brought
into contact with the substrate that can be regarded as the “paper”. The
molecules (that is the “ink”) are transferred onto the surface (the “paper”)
using solvent meniscus effects (Fig. 7.12). In nanografting,
.
In dip-pen nanolithography,
the AFM tip is
used to remove molecules from a coated surface. First, a surface is coated
with a chemical (compound A), and then the AFM tip is used in contact mode
to draw lines or other structures on the surface by removing compound A
from the surface. A different functional chemical compound (compound B)
can then be introduced onto the surface (Fig. 7.14).
Figure 7.12
(a, b) Schematic of the dip-pen nanolithography process and CPMV
binding strategies. (c) Tapping-mode atomic force microscopic (AFM) image, zoom-
in image, and height profile of the CPMV wild-type nanoarray (see dotted line).
(d) Tapping-mode image, zoom-in image, and height profile (see dotted line) of a CPMV
Cys-mutant nanoarray. Reproduced with permission from Smith, J. C., Lee, K., Wang,
Q., Finn, M. G., Johnson, J. E., Mrksich, M., and Mirkin, C. A. (2003) Nanopatterning
the chemospecific immobilization of cowpea mosaic virus capsid,
Nano Lett.
,
3
,
883-886.
Dip-pen nanolithography has been used to specifically pattern CPMV
particles. Gold substrates were patterned with either mercaptohexanoic
acid (MHA) or maleimide-terminated polyethylene glycol (PEG) chains.
Circular features were “written” on the substrate. The surrounding areas
were
with PEG chains. PEG is a hydrophilic polymer that prevents
non-specific adsorption or interaction; hence, the surface area coated with
PEG is referred to as
passivated
passivated
. VNPs do not bind to the passivated areas.
 
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