.
Angewandte
Communications
DOI: 10.1002/anie.201204836
Surface Patterning
Immobilization of Liposomes and Vesicles on Patterned Surfaces by
a Peptide Coiled-Coil Binding Motif**
Jens Voskuhl, Christian Wendeln, Frank Versluis, Eva-Corinna Fritz, Oliver Roling,
Harshal Zope, Christian Schulz, Stefan Rinnen, Heinrich F. Arlinghaus, Bart Jan Ravoo,* and
Alexander Kros*
Coiled-coil motifs are abundant in proteins where they
exhibit an array of functions like gene regulation,[1] cell
signaling,[2] transport of small molecules,[3] and membrane
fusion.[4] Native SNARE proteins control fusion processes
between and within cells (for example, exocytosis). The
common feature of all these coiled-coils is that at least two a-
helical peptide strands bind, thereby acting as molecular
Velcro. The specific molecular recognition between helices
has enabled scientists to develop self-assembled, highly
structured materials based on the coiled-coil motif.[5–7]
Herein we describe a completely new function for the
coiled-coil peptide binding units, namely their application in
materials science and surface modification. We report that an
a-helical coiled-coil pair exclusively forms parallel hetero-
dimers, denoted “peptide E” (EIAALEK)3 and “peptide K”
(KIAALKE)3 and acts as selective recognition unit through
which liposomes and cyclodextrin (CD) vesicles can be
selectively immobilized in surface patterns obtained using
microcontact printing.
tigate reactions in immobilized liposomes,[16–19] including
single-molecule reactions.[20]
In this study we used microcontact printing to produce
well-defined patterns of peptide E (1) by the formation of
a covalent bond (i.e. a triazole unit) between an azide self-
assembled monolayer (SAM) and the alkyne-terminated
peptide E in the presence of CuI. Surface patterning by
microcontact chemistry has been widely studied by several
groups during the last years, and it was successfully applied for
the preparation of various functional surfaces, including
carbohydrate,[21,22] DNA,[23] and peptide microarrays.[24] Pep-
tide E is able to bind to the complementary peptide K by
forming a coiled-coil binding motif, which has previously been
used to induce liposomal fusion processes in buffered aqueous
media.[25–27] The main benefits of this complementary peptide
binding motif include its simplicity, selectivity, pH and
temperature stability, and low cost.
Figure 1 describes the process of liposome and vesicles
immobilization on patterned surfaces, and Scheme 1 shows
the molecular structures of the key components. After
functionalization of a glass or silicon slide with an azide
SAM (see the Supporting Information), patterns of the
alkyne-terminated peptide E (1) were prepared by inducing
the CuI-catalyzed azide–alkyne cycloaddition (CuAAC) with
a structured polydimethylsiloxane (PDMS) stamp. The inter-
space was passivated with the alkyne–tetraethylene glycol
derivative 2. After incubation with either liposomes deco-
rated with peptide K 4 or CD vesicles[28] functionalized by
host–guest complexation with peptide K 5, patterns of
liposomes/CD vesicles were obtained. The noncovalent,
reversible nature of liposome immobilization was checked
by washing the liposome surface with ethanol, or with an
excess of a buffered b-CD solution for the immobilized CD
vesicles.
The immobilization of vesicles and liposomes by recog-
nition units, such as complementary DNA strands,[8] electro-
static interactions[9] and protein–ligand pairs,[10] has attracted
increasing attention in recent years. By using these recog-
nition units, it is possible to attach liposomes and vesicles to
a variety of substrates, to prepare microarrays of lipo-
somes,[11,12] to construct sensing platforms,[13–15] and to inves-
[*] Dr. J. Voskuhl, M. Sc. F. Versluis, M. Sc. H. Zope, Dr. A. Kros
Soft Matter Chemistry, Leiden Institute of Chemistry
P.O. Box 9502, 2300 RA Leiden (The Netherlands)
E-mail: a.kros@chem.leidenuniv.nl
Dr. C. Wendeln, M. Sc. E.-C. Fritz, M. Sc. O. Roling, Dr. C. Schulz,
Prof. Dr. B. J. Ravoo
The immobilization of peptide E (1) results in a significant
increase in the wettability of the surface, which is consistent
with the hydrophilic nature of peptide E. This behavior was
observed by water condensation on the printed surface, which
shows clear dot patterns of water at the hydrophilic islands
(Supporting Information, Figure S1). After CuAAC using flat
PDMS stamps, the static water contact angle decreased from
around 838 for the azide SAM to around 508 for the surface
immobilized peptide E (Supporting Information, Figure S1).
Furthermore, the presence of carbonyl carbon atoms and
amide groups was verified by X-ray photoelectron spectros-
copy (XPS). After printing by using a flat PDMS stamp, an
additional band (288.5 eV) in the C1s region belonging to the
Organic Chemistry Institute and CeNTech, Westfꢀlische Wilhelms-
Universitꢀt Mꢁnster, Corrensstrasse 40, 48149 Mꢁnster (Germany)
E-mail: b.j.ravoo@uni-muenster.de
Dipl.-Phys. S. Rinnen, Prof. Dr. H. F. Arlinghaus
Physikalisches Institut, Westfꢀlische Wilhelms-Universitꢀt Mꢁnster,
Wilhelm-Klemm-Strasse 10, 48149 Mꢁnster (Germany)
[**] A.K. acknowledges the support of the European Research Council by
an ERC starting grant. B.J.R. acknowledges DFG for financial
support (grant Ra 1732/1). Silicon wafers were kindly donated by
Siltronic AG. Patrick Seelheim and Prof. Dr. H. J. Galla are
acknowledged for access to and discussion of QCM-D measure-
ments.
Supporting information for this article is available on the WWW
12616
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2012, 51, 12616 –12620