We present a rapid synthetic method for the development of hyperbranched PEIs decorated with different oligosaccharide architectures as carrier systems (CS) for drugs and bioactive molecules for in vitro and in vivo experiments. Reductive amination of hyperbranched PEI with readily available oligosaccharides results in sugar functionalized PEI cores with oligosaccharide shells of different densities. These core-shell architectures were characterized by NMR spectroscopy, elemental analysis, SLS, DLS, IR, and polyelectrolyte titration experiments. ATP complexation of theses polycations was examined by isothermal titration calorimetry to evaluate the binding energy and ATP/CS complexation ratios under physiological conditions. In vitro experiments showed an enhanced cellular uptake of ATP/CS complexes compared to those of the free ATP molecules. The results arise to initiate further noncovalent complexation studies of pharmacologically relevant molecules that may lead to the development of therapeutics based on this polymeric delivery platform.

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An artificial anion receptor is presented, in which two cyclohexapeptide subunits containing l-proline and 6-aminopicolinic acid subunits in an alternating sequence are connected via an adipinic acid spacer. This compound was devised to stabilize the 2:1 sandwich-type anion complexes that are observed when the two cyclopeptide moieties are not covalently connected and to obtain a 1:1 stoichiometry for these aggregates. Electrospray ionization mass spectrometry and NMR spectroscopic investigations showed that the bridged bis(cyclopeptide) does indeed form defined 1:1 complexes with halides, sulfate, and nitrate. ROESY NMR spectroscopy and molecular modeling allowed a structural assignment of the sulfate complex in solution. The stabilities of various anion complexes were determined by means of NMR titrations and isothermal titration microcalorimetry in 50% water/methanol. Both methods gave essentially the same quantitative results, namely stability constants that varied in the range 105-102 M-1 and decreased in the order SO42- > I- > Br- > Cl- > NO3-. This order was rationalized in terms of the size of the anions with the larger anions forming the more stable complexes because they better fit into the cavity of the host. The ability of sulfate to form stronger hydrogen bonds to the NH groups of the receptor, in addition to its slightly larger ionic radius with respect to iodide, causes the higher stability of the sulfate complex. No significant effect of the countercation on complex stability was observed. Furthermore, complex stability is enthalpically as well as entropically favored. A comparison of the iodide and sulfate complex stabilities of the ditopic receptor with those of a cyclopeptide that forms 1:1 anion complexes in solution showed that the presence of a second binding site increases complex stability by a factor of 100-350.

Aqueous colloidal poly (N-isopropylacrylamide-co-4-vinylpyridine) [poly(NIPAM-co-4-VP)] copolymer microgels have been synthesized using different percentages of 4-vinylpyridine (4-VP). A surfactant-free emulsion polymerization reaction using N-isopropylacrylamide (NIPAM) and 4-vinylpyridine comonomers cross-linked with N,N′-methylenebisacrylamide was utilized. The reaction was initiated using the cationic initiator 2,2′-azobis(2-amidinopropane) dihydrochloride. Transmission electron micrograph data show the copolymer microgels to be monodisperse spheres. The pH and electrolyte sensitivity of the copolymer microgels have been studied, as well as temperature sensitivity, since microgels undergo a reversible volume phase transition in response to heating and cooling. Changes in the hydrodynamic diameters in the system were monitored as a function of temperature (25-60°C), pH (3-8), and ionic strength (10 -3 -10 -1 mol dm -3 NaCl or NaClO4) using photon correlation spectroscopy. The hydrodynamic diameter of poly-(NIPAM-co-4-VP) microgels increases with decreasing pH, as the vinylpyridine units become more protonated. However, the hydrodynamic diameter decreases with increasing ionic strength (over the pH range 3-8) and with increasing temperature (at pH 3 and pH 6). UV-visible spectrophotometry measurements showed a good correlation between the molar absorption and the percentage of vinylpyridine incorporated. Potentiometric titrations were used to determine the pKa values of the copolymer microgels.

A neutral receptor that binds anions by hydrogen bonds even in water is the cyclopeptide reported in this article. This property results from the particular structure of the complex in which the anions are effectively shielded from the surrounding solvent, as can be seen in the iodide complex shown.

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Recently developed MOF surface-coating techniques, the controlled SBU approach (CSA) for the generation of MOF-5, and the use of self-assembled monolayers have been combined to generate a wall-bonded, crosslinked stationary phase for gas chromatographic capillary columns displaying excellent performance in the separation of natural gas components. The chromatographic performance of this new type of column has been compared to the state-of-the-art solution for this separation problem, namely a coated silica column of the porous layer open tubular (PLOT) type. Chromatographic parameters such as separation, resolution, and tailing factors, as well as plate numbers and heights in the case of isothermal operation, have been determined. Kinetic and thermodynamic parameters characterizing the analyte-stationary phase interaction have been determined for various C1-C4 analytes.