New method for creating biological sensors on silicon chips
30 October 2014
Scientists from Chile and Germany have developed a novel process to layer two readily available
chemicals on a silicon
substrate to mimic a cell membrane and give the ability to link
biological processes to electronics.
Artificial membranes mimicking those found in living organisms
have many potential applications because they offer the possibility
of containing membrane proteins, which could be used for detecting
toxins, diseases and many other biosensing applications.
The importance of this type of dual-layer membrane to life is
hard to overstate. It is a principal component of all living cells,
separating distinct spaces within cells and defining the 'walls'
around cells. It serves many physiological processes, protecting
genetic material, regulating what comes in and out of cells, and
maintaining the function of separate organs.
Described in The Journal of Chemical Physics, this is the first
time anyone has ever made an artificial membrane without mixing
liquid solvents together. And because the new process creates
membranes on silicon surfaces, it is a significant step toward
creating bio-silicon interfaces, where biological "sensor" molecules
can be printed onto cheap silicon chips holding integrated
"Our idea is to create a biosensor that can transmit electrical
signals through the membrane," said María José Retamal, a PhD
student at Pontificia Universidad Católica de Chile and first author
of the paper.
Retamal and her colleagues chose silicon because of its low cost,
wide availability and because its 'hydrophobicity' (how much it
repels water) can be controlled chemically, allowing them to build
membranes on top.
They evaporated the chemical chitosan onto the silicon. Chitosan
is derived from chitin, a sugar found in the shells of certain
crustaceans, such as lobsters or shrimp. They chose this ingredient
for its ability to form a moisturizing matrix. It is insoluble in
water, but is porous, so it is capable of retaining water. Next they
evaporated a phospholipid known as dipalmitoylphosphatidylcholine
(DPPC) onto the chitosan-covered silicon substrate.
Layers of chitosan and DPPC deposited on
silicon mimic cell membranes and add the ability to interface with
computer chips. Credit: S.E.Gutierrez-Maldonado/FCV
The researchers then showed that these chemicals formed a stable
bilayer, the classic form of a membrane. Spectroscopy showed that
these artificial membranes were stable over a wide range of
More work is needed to standardize the process by which proteins
are inserted in the membranes, to define the mechanism by which an
electrical signal would be transmitted when a protein binds its
target and to calibrate how that signal is detected by the
underlying circuitry, Retamal said.
MJ Retamal, et al. Towards bio-silicon interfaces: Formation of
an ultra-thin self-hydrated artificial membrane composed of
dipalmitoylphosphatidylcholine (DPPC) and Chitosan deposited in high
vacuum from the gas-phase. The Journal of Chemical Physics DOI: