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Investigating ligand-receptor interactions at bilayer surface using electronic absorption spectroscopy and fluorescence resonance energy transfer.

ABSTRACT: We investigate interactions between receptors and ligands at bilayer surface of polydiacetylene (PDA) liposomal nanoparticles using changes in electronic absorption spectroscopy and fluorescence resonance energy transfer (FRET). We study the effect of mode of linkage (covalent versus noncovalent) between the receptor and liposome bilayer. We also examine the effect of size-dependent interactions between liposome and analyte through electronic absorption and FRET responses. Glucose (receptor) molecules were either covalently or noncovalently attached at the bilayer of nanoparticles, and they provided selectivity for molecular interactions between glucose and glycoprotein ligands of E. coli. These interactions induced stress on conjugated PDA chain which resulted in changes (blue to red) in the absorption spectrum of PDA. The changes in electronic absorbance also led to changes in FRET efficiency between conjugated PDA chains (acceptor) and fluorophores (Sulphorhodamine-101) (donor) attached to the bilayer surface. Interestingly, we did not find significant differences in UV-vis and FRET responses for covalently and noncovalently bound glucose to liposomes following their interactions with E. coli. We attributed these results to close proximity of glucose receptor molecules to the liposome bilayer surface such that induced stress were similar in both the cases. We also found that PDA emission from direct excitation mechanism was ~2-10 times larger than that of the FRET-based response. These differences in emission signals were attributed to three major reasons: nonspecific interactions between E. coli and liposomes, size differences between analyte and liposomes, and a much higher PDA concentration with respect to sulforhodamine (SR-101). We have proposed a model to explain our experimental observations. Our fundamental studies reported here will help in enhancing our knowledge regarding interactions involved between soft particles at molecular levels.

SUBMITTER: Dogra N

PROVIDER: S-EPMC3439585 | biostudies-literature | 2012 Sep

REPOSITORIES: biostudies-literature

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Investigating ligand-receptor interactions at bilayer surface using electronic absorption spectroscopy and fluorescence resonance energy transfer.

Dogra Navneet N Li Xuelian X Kohli Punit P

Langmuir : the ACS journal of surfaces and colloids 20120716 36

We investigate interactions between receptors and ligands at bilayer surface of polydiacetylene (PDA) liposomal nanoparticles using changes in electronic absorption spectroscopy and fluorescence resonance energy transfer (FRET). We study the effect of mode of linkage (covalent versus noncovalent) between the receptor and liposome bilayer. We also examine the effect of size-dependent interactions between liposome and analyte through electronic absorption and FRET responses. Glucose (receptor) mol ...[more]

PMID: 22734511

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Project description:Conjugated polydiacetylene (PDA) possessing stimuli-responsive properties has been intensively investigated for developing efficient sensors. We report here fluorescence resonance energy transfer (FRET) in liposomes synthesized using different molar ratios of dansyl-tagged diacetylene and diacetylene-carboxylic acid monomers. Photopolymerization of diacetylene resulted in cross-linked PDA liposomes. We used steady-state electronic absorption, emission, and fluorescence anisotropy (FA) analysis to characterize the thermal-induced FRET between dansyl fluorophores (donor) and PDA (acceptor). We found that the monomer ratio of acceptor to donor ( R ad) and length of linkers (functional part that connects dansyl fluorophores to the diacetylene group in the monomer) strongly affected FRET. For R ad = 10 000, the acceptor emission intensity was amplified by more than 18 times when the liposome solution was heated from 298 to 338 K. A decrease in R ad resulted in diminished acceptor emission amplification. This was primarily attributed to lower FRET efficiency between donors and acceptors and a higher background signal. We also found that the FRET amplification of PDA emissions after heating the solution was much higher when dansyl was linked to diacetylene through longer and flexible linkers than through shorter linkers. We attributed this to insertion of dansyl in the bilayer of the liposomes, which led to an increased dansyl quantum yield and a higher interaction of multiple acceptors with limited available donors. This was not the case for shorter and more rigid linkers where PDA amplification was much smaller. The present studies aim at enhancing our understanding of FRET between fluorophores and PDA-based conjugated liposomes. Furthermore, receptor tagged onto PDA liposomes can interact with ligands present on proteins, enzymes, and cells, which will produce emission sensing signal. Therefore, using the present approach, there exist opportunities for designing FRET-based highly sensitive and selective chemical and biochemical sensors.

Dataset Information

Investigating ligand-receptor interactions at bilayer surface using electronic absorption spectroscopy and fluorescence resonance energy transfer.

Publications

Investigating ligand-receptor interactions at bilayer surface using electronic absorption spectroscopy and fluorescence resonance energy transfer.

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