Lack of a small animal model of the human hepatitis C virus (HCV) has impeded development of antiviral therapies against this epidemic infection. By transplanting normal human hepatocytes into SCID mice carrying a plasminogen activator transgene (Alb-uPA), we generated mice with chimeric human livers. Homozygosity of Alb-uPA was associated with significantly higher levels of human hepatocyte engraftment, and these mice developed prolonged HCV infections with high viral titers after inoculation with infected human serum. Initial increases in total viral load were up to 1950-fold, with replication confirmed by detection of negative-strand viral RNA in transplanted livers. HCV viral proteins were localized to human hepatocyte nodules, and infection was serially passaged through three generations of mice confirming both synthesis and release of infectious viral particles. These chimeric mice represent the first murine model suitable for studying the human hepatitis C virus in vivo.

We report herein thermally responsive elastin-like polypeptides (ELPs) in a linear AB diblock architecture with an N-terminal peptide ligand that self-assemble into spherical micelles when heated slightly above body temperature. A series of 10 ELP block copolymers (ELP BC s) with different molecular weights and hydrophilic-to-hydrophobic block ratios were genetically synthesized by recursive directional ligation. The self-assembly of these polymers from unimers into micelles was investigated by light scattering, fluorescence spectroscopy and cryo-TEM. These ELP BC s undergo two phase transitions as a function of solution temperature: a unimer to spherical micelle transition at an intermediate temperature, and a micelle to bulk aggregate transition at a higher temperature when the hydrophilic-to-hydrophobic block ratio is between 1:2 and 2:1. The critical micelle temperature is controlled by the length of the hydrophobic block and the size of the micelle is controlled by both the total ELP BC length and hydrophilic-to-hydrophobic block ratio. These polypeptide micelles display a critical micelle concentration in the range of 4-8 μM demonstrating high stability of these structures. These studies have also identified a subset of ELP BC s bearing terminal peptide ligands that are capable of forming multivalent spherical micelles that present multiple copies of the ligand on their corona in the clinically relevant temperature range of 37-42 °C and target cancer cells. These ELP BC s may be useful for drug targeting by thermally triggered multivalency. More broadly, the design rules uncovered by this study should be applicable to the design of other thermally reversible nanoparticles for diverse applications in medicine and biology.

Polymacromonomers consisting of oligostyrene side chains (700 ≤ M n ≤ 5000 g/mol) and of a high molar mass polymethacrylate main chain are shown to exhibit a bottlebrush structure in that the PMA main chain adopts an extremely stiff conformation (i.e., a Kuhn statistical segment length of up to l k = 2000 Å) which is surrounded by the expanded but still flexible polystyrene side chains.

The conformation of cylindrical brush polymers with a polymethacrylate main and polystyrene side chains (6 e P n sc e 33, with P n sc the number-average degree of polymerization of the side chains) were studied by combined light and small-angle neutron scattering experiments. The results reveal that the main chain stiffness expressed in terms of the Kuhn statistical segment length, l k , increases with side chain length but does not follow scaling predictions which most probably is due to the limited length of the side chains investigated experimentally. In this respect the present work addresses the transition regime from flexible coils to stiff cylindrical brushes as a function of side chain length. In detail, the increase of l k is stronger in toluene, a very good solvent for the side chains, than in the poor solvent cyclohexane and does not level off for the longest side chains investigated (P n sc ) 33). In contrast to earlier work, the cylinder length per main chain monomer is found to be independent of side chain length but to depend slightly on the solvent quality, i.e., l m ) 0.241 nm in toluene and l m ) 0.207 nm in cyclohexane. The value determined in toluene is close to the maximum value of l m ) 0.25 nm expected for a fully stretched vinylic main chain, whereas the smaller value for l m in cyclohexane suggests a local coiling of the main chain, most probably caused by less repulsive interactions between the side chains. The discrepancy to some earlier scattering experiments could be resolved, but the origin of frequently reported much smaller cylinder lengths derived by atomic force microscopy remains unclear.

High molar mass polymacromonomers based on methacryloyl end-functionalized oligo methacrylates (Mn ) 2410 g/mol) adopt the conformation of wormlike cylindrical brushes. Comparison of the absolute molar mass, Mw, determined by static light scattering and the contour length, Lw, of the molecules measured by SFM in the dry state revealed the length per vinylic main chain monomer of the cylindrical structure to be less than 0.1 nm, thus being much shorter than the maximum value of 0.25 nm. In solution this shrinkage could be quantified to 0.071 nm per monomer by Holtzer analysis of the scattering curves which in addition yielded the Kuhn statistical segment length lk ) 120 nm. GPC MALLS investigations of such samples showed an anomalous elution effect: After a regular elution at small elution volumes the molar mass of the eluting molecules increased drastically with increasing elution volume. Fractionation by GPC showed that this effect is caused by a fraction of extremely high molar mass molecules which elute by an unknown mechanism rather than by size exclusion.