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The formation of ultrathin chitosan-based nanocoating on HL-60 model cells and their protective function in hypothermic storage are presented. HL-60 cells are encapsulated in ultrathin shells by adsorbing cationic and anionic chitosan derivatives in a stepwise, layer-by-layer, procedure carried out in an aqueous medium under mild conditions. The chitosan-based films are also deposited on model lipid bilayer and the interactions are studied using ellipsometry and atomic force microscopy. The cells covered with the chitosan-based films and stored at 4 °C for 24 h express viability comparable to that of the control sample incubated at 37 °C, while the unprotected cells stored under the same conditions do not show viability. It is shown that the chitosan-based shell protects HL-60 cells against damaging effect of hypothermic storage. Such nanocoatings provide protection, mechanical stability, and support the cell membrane, while ensuring penetration of small molecules such as nutrients/gases what is essential for cell viability.

This report presents simple and reliable approach developed to study the specific recognition events between chlorinated ovalbumin (OVA) and macrophages using atomic force microscopy (AFM). Thanks to the elimination of nonspecific adhesion, the interactions of the native and chlorinated OVA with a membrane of macrophages could be quantified using exclusively the so-called adhesion frequency (AF). The proposed system not only enabled the application of AFM-based force measurements for such poorly defined ligand-receptor pairs but also significantly improved both the acquisition and the processing of the data. The proteins were immobilized on the gold-coated AFM tips from the aqueous solutions containing charged thiol adsorbates. Such surface dilution of the proteins ensured the presence of single or just a few macromolecules at the tip-surface contact. The formation of negatively charged monolayer on the tip dramatically limited its nonspecific interactions with the macrophage surface. In such systems, AF was used as a measure of the recognition events even if the interaction forces varied significantly for sets of measurements. The system with the native OVA, a weak immunogen, showed only negligible AF compared with 85% measured for the immunogenic chlorinated OVA. The AF values varied with the tip-macrophage contact time and loading velocity. Blocking of the receptors by the chlorinated OVA was also confirmed. The developed approach can be also used to study other ligand-receptor interactions in poorly defined biological systems with intrinsically broad distribution of the rupture forces, thus opening new fields for AFM-based recognition on molecular level.

Summary: Block amphiphilic copolymer, poly(sodium styrenesulfonate-block-5-(4-acryloyloxyphenyl)-10,15,20-tritolylporphyrin) (PSSS-block-Po) was synthesized by nitroxide-mediated controlled radical polymerization. The polymer is soluble in water and can absorb light in the visible region. The absorbed energy migrates between the porphyrin chromophores. The polymer chains form nanospheres in aqueous solution. Their interiors are highly hydrophobic and can effectively solubilize the large hydrophobic molecules of the various organic compounds (pyrene, azulene, rubrene). The polymer photosensitizes oxidation of organic compounds via photoinduced electron transfer and/or via formation of singlet oxygen. The effect of the architecture, chain properties and Po content on the photochemical properties of the porphyrin-containing photosensitizers was also discussed.

Novel thermosensitive, cationic polyelectrolyte was obtained by grafting N-vinylformamide onto hydroxypropylcellulose followed by the hydrolysis of the formamide groups to the amine groups. The effect of the ionic strength on the lower critical solution temperature of the polymers was studied. The interactions of the polymers with sodium dodecyl sulfate (SDS) as a model anionic surfactant were studied. It was found by the measurements of the light scattering and fluorescence spectroscopy that the graft copolymers obtained strongly interact with SDS with the formation of polymer-surfactant complexes. The values of critical association concentration (cac) of these polymer-surfactant systems were found to be of the order of 10−5 mol/dm3 at pH = 6.5 and of the order of 10−6 mol/dm3 at pH = 2.5. The polymer was shown to be potentially useful for the purification of water from anionic surfactants. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

A copolymer of poly(vinyl naphthalene) grafted onto poly(vinyl alcohol) has been synthesized with nitroxide-mediated controlled radical polymerization. By separating the processes of the generation of grafting sites and polymerization, we can avoid the formation of the homopolymer. Because of its architecture, the polymer is soluble in water, despite the high content of hydrophobic groups. The naphthalene chromophores tend to aggregate, forming hydrophobic microdomains in an aqueous solution. Those aggregates exist in a very constrained environment that leads to extraordinarily large redshifts of both the absorption and emission of the polymer. The polymer acts as an efficient photosensitizer in photoinduced electron transfer. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2675–2683, 2006