The preparation of bilayer lipid membranes (BLMs) on solid surfaces is important for many studies probing various
important biological phenomena including the cell barrier properties, ion-channels, biosensing, drug discovery and
protein/ligand interactions. In this work we present new membrane platforms based on suspended BLMs on nanoporous
anodic aluminium oxide (AAO) membranes. AAO membranes were prepared by electrochemical anodisation of
aluminium foil in 0.3 M oxalic acid using a custom-built etching cell and applying voltage of 40 V, at 1oC. AAO
membranes with controlled diameter of pores from 30 - 40 nm (top of membrane) and 60 -70 nm (bottom of membrane)
were fabricated. Pore dimensions have been confirmed by scanning electron microscopy (SEM) and atomic force
microscopy (AFM). AAO membranes were chemically functionalised with 3-aminopropyltriethoxysilane (APTES).
Confirmation of the APTES attachment to the AAO membrane was achieved by means of infrared spectroscopy, X-ray
photoelectron spectroscopy and contact angle measurements. The Fourier transform infrared (FTIR) spectra of
functionalised membranes show several peaks from 2800 to 3000 cm-1 which were assigned to symmetric and
antisymmetric CH2 bands. XPS data of the membrane showed a distinct increase in C1s (285 eV), N1s (402 eV) and
Si2p (102 eV) peaks after silanisation. The water contact angle of the functionalised membrane was 80o as compared to
20o for the untreated membrane. The formation of BLMs comprising dioleoyl-phosphatidylserine (DOPS) on APTESmodified
AAO membranes was carried using the vesicle spreading technique. AFM imaging and force spectroscopy was
used to characterise the structural and nanomechanical properties of the suspended membrane. This technique also
confirmed the stability of bilayers on the nanoporous alumina support for several days. Fabricated suspended BLMs on
nanoporous AAO hold promise for the construction of biomimetic membrane architectures with embedded
transmembrane proteins.
Poly(dimethylsiloxane) (PDMS) is a popular material for microfluidic devices due to its relatively low cost, ease of
fabrication, oxygen permeability and optical transmission characteristics. However, its highly hydrophobic surface is still
the main factor limiting its wide application, in particular as a material for biointerfaces. A simple and rapid method to
form a relatively stable hydrophilised PDMS surface is reported in this paper. The PDMS surface was treated with pure
undecylenic acid (UDA) for 10 min, 1 h and 1 day at 80 °C in a sealed container. The effects of the surface modification
were investigated using water contact angle (WCA) measurements, Fourier transform infrared spectroscopy in attenuated
total reflection mode (FTIR-ATR), and streaming zeta-potential analysis. The water contact angle of 1 day UDAmodified
PDMS was found to decrease from that of native PDMS (110 °) to 75 °, demonstrating an increase in
wettability of the surface. A distinctive peak at 1715 cm-1 in the FTIR-ATR spectra after UDA treatment was
representative of carboxylation of the PDMS surface. The measured zeta-potential (ζ) at pH 4 changed from -27 mV for
pure PDMS to -19 mV after UDA treatment. In order to confirm carboxylation of the surface visually, Lucifer Yellow
CH fluorescence dye was reacted via a condensation reaction to the 1 day UDA modified PDMS surface. Fluorescent
microscopy showed Lucifer Yellow CH fluorescence on the carboxylated surface, but not on the pure PDMS surface.
Stability experiments were also performed showing that 1 day modified UDA samples were stable in both MilliQ water
at 50 °C for 17 h, and in a desiccator at room temperature for 19.5 h.
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