Biosensors liposome preparation

One of the primary applications of entrapment immobilization has been to prepare enzyme-electrode-based biosensors [27], and one of the first functional enzyme electrodes utilized urease entrapped in an acrylamide film to detect urea using an ammonium ion selective electrode [28]. Highly hydrophobic bilayer lipid membranes and liposomes have also been used to entrap highly labile biomolecules (see chapter 9). Such films and layers are, however, inherently unstable themselves and are useful primarily as research tools. 

In principle, several different systems can serve as a basis for the mentioned platforms. As shown in Fig. 1, we will discuss in this contribution a variety of complementary 2D and quasi-3D architectures. SAMs of organothiols, disulfides or sulfides on gold [29,59] and SAMs of organosilicon compounds on hydroxylated silicon surfaces [60-62] are probably among the best known model systems due to their ease of preparation and the high level of structural and chemical control. Vesicles (liposomes) [63] and substrate-supported lipid bilayers [64-67] are related well-established model systems for biological membranes that allow one to study membrane constituents in a controlled environment, and they can serve as a platform for biosensors based on naturally existing biomolecules present in a milieu that approximates a ceU mem-... 

The ability to identify particular sequences of DNA, both quickly and precisely has become of increasing importance in recent years. Current DNA detection methods are limited by their need for the DNA in the sample to be chemically labelled before analysis. In this poster, the biosensor described does not. In fact, the detector is the DNA mimic, peptide nucleic acid (PNA) whilst the sensor is based on polydiacetylene (PDA) liposomes. It is envisaged that when the PNA detector binds to its target gene, the PDA sensor will be induced to change colour from blue to red. It is anticipated that this response will be detected visually and quantified through UVA/is spectroscopy. In order to improve the hydrophilic character of the liposomes, a hydrophilic spacer has been included. Here, we report our progress to date on the preparation and evaluation of PNA-functionalised PDA liposomes as potential, novel colorimetric nucleic acid biosensors. 

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