Understanding how gold nanoparticles interact with liposomes is important for biotechnology and drug delivery. The characterization of liposome structure and composition using gold nanoparticles by surface-enhanced Raman scattering (SERS) has show that the composition of the lipid bilayers influences the interaction of the gold nanoparticles with the lipid structures. Here, vesicles composed of phosphatidylcholine, sphingomyelin, and cholesterol in different proportions reveal that very small changes in the lipid composition can alter the contact between liposomes and gold nanostructures. The SERS spectra of phosphatidylcholine and phosphatidylcholine / cholesterol liposomes indicate that cholesterol has strong effects on the contacts of the vesicles with the nanoparticles. Moreover, the interaction of citrate-stabilized gold nanoparticles varies depending on the preparation protocol, and the presence of organic solvent during preparation of the gold nanoparticle-liposome composites. In a model system where the charge of the lipid bilayers is varied, the influence of negative charge of the lipids on liposome structure and their contact with the nanoparticles is discussed. The results have implications for the development of new gold nanoparticle and gold nanoparticle-liposome-based drug delivery systems.
Increasing the information content from bioassays which requires robust and efficient strategies for the detection of
multiple analytes or targets in a single measurement is an important field of research, especially in the context of meeting
current security and health concerns.
An attractive alternative to spectral multiplexing, which relies on fluorescent labels excitable at the same wavelength, yet
sufficiently differing in their emission spectra or color presents lifetime multiplexing. For this purpose, we recently
introduced a new strategy based on "pattern-matching" in the lifetime domain, which was exemplary exploited for the
discrimination between organic dyes and quantum dot labels revealing multi-exponential decay kinetics and allowed
quantification of these labels. Meanwhile, we have succeeded in extending this lifetime multiplexing approach to
nanometer-sized particle labels and probes absorbing and emitting in the visible (vis) and near-infrared (NIR) spectral
region. Here, we present a first proof-of-principle of this approach for a pair of NIR-fluorescent particles. Each particle
is loaded with a single organic dye chosen to display very similar absorption and emission spectra, yet different
fluorescence decay kinetics. Examples for the lifetime-based distinction between pairs of these fluorescent nanoparticles
in solution and in cells are presented. The results underline the potential of fluorescenc lifetime multiplexing in life
science and bioanalysis.
Syrian hamster nervous tissue was investigated by FTIR microspectroscopy with conventional and synchrotron infrared light sources. Various tissue structures from the cerebellum and medulla oblongata of scrapie-infected and control hamsters were investigated at a spatial resolution of 50 μm. Single neurons in dorsal root ganglia of scrapie-infected hamsters were analyzed by raster scan mapping at 6 μm spatial resolution. These measurements enabled us to (i) scrutinize structural differences between infected and non-infected tissue and (ii) analyze for the first time the distribution of different protein structures in situ within single nerve cells. Single nerve cells exhibited areas of increased β-sheet content, which co-localized consistently with accumulations of the pathological prion protein (PrPSc). Spectral data were also obtained from purified, partly proteinase K digested PrPSc isolated from scrapie-infected nervous tissue of hamsters to elucidate similarities/dissimilarities between prion structure in situ and ex vivo. A further comparison is drawn to the recombinant Syrian hamster prion protein SHaPrP90-232, whose in vitro transition from the predominantly a-helical isoform to β-sheet rich oligomeric structures was also investigated by FTIR spectroscopy.
Transmissible spongiform encephalopathies (TSE), such as BSE in cattle, scrapie in sheep and goats, and Creutzfeldt-Jakob disease in man are a group of fatal infectious diseases of the central nervous system that are far from being fully understood. Presuming the pathological changes to originate from small disease-specific compositional and structural modifications at the molecular level, Fourier-transform infrared (FTIR) spectroscopy can be used to achieve insight into biochemical parameters underlying pathogenesis. We have developed an FTIR microspectroscopy-based strategy which, as a combination of image reconstruction and multivariate pattern recognition methods, permitted the comparison of identical substructures in the cerebellum of healthy and TSE-infected Syrian hamsters in the terminal stage of the disease. Here we present FTIR data about the pathological changes of scrapie-infected and normal tissue of the gray matter structures stratum granulosum and stratum moleculare. IR spectroscopy was also applied to tissue pieces of the medulla oblongata of infected and control Syrian hamsters. Mapping data were analyzed with cluster analysis and imaging methods. We found variations in the spectra of the infected tissue, which are due to changes in carbohydrates, nucleic acids, phospholipids, and proteins.
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