Background: Sensitive and selective molecular recognition is important
throughout biology. Certain organisms and toxins use specific binding
at the cell surface as a first step towards invasion. A new series of
biomolecular materials, with novel optical and interfacial properties
, have been designed to sense molecular recognition events. These poly
mers, the diacetylenic lipids, have previously been shown to undergo c
hromatic transitions in response to virus binding to the surface of th
e material. Results: Gangliosides that specifically bind cholera toxin
, heat-labile Escherichia coli enterotoxin and botulinum neurotoxin we
re incorporated into a matrix oi diacetylenic lipids, 5-10% of which w
ere derivatized with sialic acid. The lipids were self-assembled into
Langmuir-Blodgett layers and polymerized with ultraviolet irradiation,
yielding a polydiacetylene membrane with a characteristic blue color
into which the ganglioside is non-covalently incorporated. When toxin
is added, the polymerized membrane turns red. The response is specific
and selective, and can be quantified by visible absorption spectropho
tometry. Conclusions: Polydiacetylenic Lipid membranes offer a general
'litmus test' for molecular recognition at the surface of a membrane.
A concentration of 20 ppm of protein could be detected using polymeri
zed thin films. The speed, sensitivity and simplicity of the design of
fers a new and general approach towards the direct colorimetric detect
ion of a variety of different molecules.