Polydiacetylene liposomes

A further partihon system based on the use of liposomes, and commercialized under the name Transil [110, 111], has shown its utiUty as a UpophiUcity measure in PBPK modeling [112]. Fluorescent-labeled liposomes, called fluorosomes, are another means of measuring the rate of penetration of small molecules into membrane bilayers [113, 120]. Similarly, a colorimetric assay amenable to HTS for evaluating membrane interactions and penetrahon has been presented [116]. The platform comprises vesicles of phospholipids and the chromahc Upid-mimehc polydiacetylene. The polymer undergoes visible concentrahon-dependent red-blue transformahons induced through interactions of the vesicles with the studied molecules. 

Reppy MA, Pindzola BA (2006) Polydiacetylene liposomes attached to glass fibers for bioassays. Mater Res Soc Symp Proc 942(0942) W13-10... 

The sensors discussed so far are based on ligands covalently bound to the polymer backbone. Other methods of detection - often referred to as mix and detect methods - work by simple noncovalent incorporation of the polymer with the ligand of interest. Reichert et al. generated liposomes of polydiacetylene with sialic acid for the same purpose of detection as Charych s surface-bound polymers, but realized that covalent functionalization of the polymer was not necessary [17]. Through simple mixing of the lipid-bound sialic acid with the polymer before sonication and liposome formation, they were able to form a functional colorimetric recognition system (Fig. 8). 

Fig. 8 (top) Liposome with polydiacetylene linked monolayer mixed with ligand for receptor detection. (bottom) Colorimetric detection of influenza virus using polymerized liposomes to which have been added increasing amounts of influenza virus from left to right. [18]... 

Reichert A, Nagy JO, Spevak W, Charych D (1995) Polydiacetylene liposomes functionalized with sialic-acid bind and colorimetrically detect influenza-virus. J Am Chem Soc 117 829-830... 

Cheng Q, Stevens RC. Charge-induced chromatic transition of amino acid-derivatized polydiacetylene liposomes. Langmuir 1998 14 1974-1976. 

Rangin M, Basu A. Lipopolysaccharide identification with functionalized polydiacetylene liposome sensors. J Am Chem Soc 2004 126 5038-5039. 

Jung, K., Kim, T.W., Park, H.G., and Sob, H.T. 2010. Specific clorimetric detection of proteins using bidentate aptamer-conjugated polydiacetylene (PDA) liposomes. Adv. Funct. Mater. 20 3092-3097. 

Polydiacetylene liposomes have been used for detection and analyses of metal ions, " ° cyclodextrins, nucleic acids, proteins,bacteria, " viruses, " and so on (Figure 10.1). Some of these applications are discussed... 

Reichert, A., J.O. Nagy, W. Spevak, and D. Charych. 1995. Polydiacetylene liposomes functionalized with sialic-acid bind and colorimetrically detect influenza-vims. J Am Chem Soc 117 (2) 829-830. Charych, D., Q. Cheng, A. Reichert, G. Kuziemko, M. Stroh, J.O. Nagy, W. Spevak, and R.C. Stevens. 1996. A Htmus test for molecular recognition using artificial membranes. Chem Biol 3 (2) 113-120. 

Clickable , polymerized liposomes as a general liposomal platform for rapid attachment of functional moieties to their peripheries via click chemistry. The platform was based on polydiacetylene lipids terminated with alkynyl groups... 

Studies on the biological activity of polydiacetylene veacles were repotted by Wagner et al. F j-F,-ATPase from Rhodospirilium rubrum could easily be incorporated into polymerized liposomes under retention of the protein activity. While monomeric liposomes showed a lower activity than corresponding natural phospholipids, it increased upon polymerization to the value determined for natural liposomes. Different from the natural ones the ATPase containing polymers are stable over long time periods. 

Figure 27 Photopolymerization of the precursor with an embedded butadyine moiety leads to a blue-colored polydiacetylene material (a) analyte binding to the receptor or affinity moiety (red pentagon) results in a change in the polydiacetylene conjugated backbone and shift of absorption spectra from blue to red and (b) photographs of wells comprising solution Zn(dipicolylamine)2 containing liposome (0.25 mM) and various sodium salts anions (0.25 mM) in HEPES buffer, pH = 7. (Adapted from Ref. 126. Wiley-VCH, 2011.)...

Other bio-responsive hydrogels have been developed to give an optical output that use different actuation methods. These include sensors for a-cyclodextrin, in which a reaction with polydiacetylene liposomes embedded in poly(ethylene glycol) diacrylate (PEGDA) leads to a visible colour change of the hydrogel from blue to red [17]. 

Synthesis of peptide nucleic acid-functionalized polydiacetylene liposomes Potential novel colorimetric nucleic acid biosensors... 

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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