When dispersed in biological fluids, engineered nanoparticles are selectively coated with proteins, resulting in the formation of a protein corona. It is suggested that the protein corona is critical in regulating the conditions of entry into the cytoplasm of living cells. Recent reports describe this phenomenon as ubiquitous and independent of the nature of the particle. For nanomedicine applications, however, there is a need to design advanced and cost-effective coatings that are resistant to protein adsorption and that increase the biodistribution in vivo. In this study, phosphonic acid poly(ethylene glycol) copolymers were synthesized and used to coat iron oxide particles. The copolymer composition was optimized to provide simple and scalable protocols as well as long-term stability in culture media. It is shown that polymers with multiple phosphonic acid functionalities and PEG chains outperform other types of coating, including ligands, polyelectrolytes, and carboxylic acid functionalized PEG. PEGylated particles exhibit moreover exceptional low cellular uptake, of the order of 100 femtograms of iron per cell. The present approach demonstrates that the surface chemistry of engineered particles is a key parameter in the interactions with cells. It also opens up new avenues for the efficient functionalization of inorganic surfaces.

Disruption of the integrity of the plasma membrane by amyloidogenic proteins is linked to the pathogenesis of a number of common age-related diseases. Although accumulating evidence suggests that adverse environmental stressors such as unbalanced levels of metal ions may trigger amyloid-mediated membrane damage, many features of the molecular mechanisms underlying these events are unknown. Using human islet amyloid polypeptide (hIAPP, aka amylin), an amyloidogenic peptide associated with β-cell death in type 2 diabetes, we demonstrate that the presence of Ca(2+) ions inhibits membrane damage occurring immediately after the interaction of freshly dissolved hIAPP with the membrane, but significantly enhances fiber-dependent membrane disruption. In particular, dye leakage, quartz crystal microbalance, atomic force microscopy, and NMR experiments show that Ca(2+) ions promote a shallow membrane insertion of hIAPP, which leads to the removal of lipids from the bilayer through a detergent-like mechanism triggered by fiber growth. Because both types of membrane-damage mechanisms are common to amyloid toxicity by most amyloidogenic proteins, it is likely that unregulated ion homeostasis, amyloid aggregation, and membrane disruption are all parts of a self-perpetuating cycle that fuels amyloid cytotoxicity.

Protein-inspired biomaterials have gained great interest as an alternative to synthetic polymers, in particular, for their potential use as biomedical devices. The potential inspiring models are mainly proteins able to confer mechanical properties to tissues and organs, such as elasticity (elastin, resilin, spider silk) and strength (collagen, silk). The proper combination of repetitive sequences, each of them derived from different proteins, represents a useful tool for obtaining biomaterials with tailored mechanical properties and biological functions. In this report we describe the design, the production, and the preliminary characterization of a chimeric polypeptide, based on sequences derived from the highly resilient proteins resilin and elastin and from collagen-like sequences. The results show that the obtained chimeric recombinant material exhibits promising self-assembling properties. Young's modulus of the fibers was determined by AFM image analysis and lies in the range of 0.1-3 MPa in agreement with the expectations for elastin-like and resilin-like materials.

Protein adsorption plays a key role in the biological response to implants. We report how nanoscale topography, chemistry, crystallinity, and molecular chain anisotropy of ultrahigh molecular weight polyethylene (UHMWPE) surfaces affect the protein assembly and induce lateral orientational order. We applied ultraflat, melt drawn UHMWPE films to show that highly oriented nanocrystalline lamellae influence the conformation and aggregation into network structures of human plasma fibrinogen by atomic force microscopy with unprecedented clarity and molecular resolution. We observed a transition from random protein orientation at low concentrations to an assembly guided by the UHMWPE surface nanotopography at a close to full surface coverage on hydrophobic melt drawn UHMWPE. This assembly differs from the arrangement at a hydrophobic, on the nanoscale smooth UHMWPE reference. On plasma-modified, hydrophilic melt drawn UHMWPE surfaces that retained their original nanotopography, the influence of the nanoscale surface pattern on the protein adsorption is lost. A model based on protein-surface and protein-protein interactions is proposed. We suggest these nanostructured polymer films to be versatile model surfaces to provide unique information on protein interactions with nanoscale building blocks of implants, such as nanocrystalline UHMWPE lamellae. The current study contributes to the understanding of molecular processes at polymer biointerfaces and may support their future design and molecular scale tailoring.

Solution processability endows polymer semiconductors with several intriguing prospects, from low-cost processing, such as inkjet printing, to the possibility of creating new materials by simply mixing solutions. Polymer blends have already been exploited in light-emitting diodes (LEDs) [1] and photovoltaic diodes, [2,3] as well as light-emitting electrochemical cells (LECs), [4] although the factors controlling their supramolecular structures [5] and properties are not fully understood. Most polymer blends undergo phase segregation. [6] This has been used to generate large-area heterojunctions, [2] but it can be detrimental where solid solutions are sought to increase photoluminescence (PL) efficiency, and where rough surface morphology is a problem. Here we use three supramolecular strategies to prepare a complex material that has none of these drawbacks and benefits from enhanced electroluminescence properties: firstly, ionic interactions favor mixing of a conjugated polyelectrolyte with poly(ethylene oxide), PEO, preventing phase segregation and boosting the PL efficiency; secondly, the PEO facilitates ion transport and allows fabrication of LEC-like devices which display a two orders-of-magnitude increase in the electroluminescence (EL) efficiency; thirdly, threading the conjugated polymer through cyclodextrins gives higher PL efficiencies at small PEO loadings, and increases the EL efficiency over the full range of PEO concentrations. Insulated molecular wires, IMWs, consisting of conjugated polymers threaded through cyclodextrin rings (b-CD-poly(paraphenylene) (b-CD-PPP), b-CD-poly(fluorene) (b-CD-PF), a-CD-poly(4,4′-diphenylene vinylene) (a-CD-PDV), and b-CD-poly(4,4′-diphenylene vinylene) (b-CD-PDV); Fig. 1) are versatile supramolecular architectures [7] that display a reduced degree of interchain interactions reflected in higher electroluminescence efficiency, blue-shifted absorption/emission, and reduced luminescence quenching and packing density, when compared to their uninsulated analogues (PPP, PDV, and PF). [8] In this paper we exploit their polyelectrolytic nature, and use the presence of lithium carboxylate and sulfonate substituents to drive the formation of supramolecular complexes with polymers featuring ion-coordination properties. This supramolecular assembly enables us to reduce the tendency of the different components to phase separate, to promote smooth surface morphologies, and to boost the PL and EL efficiency. The interaction of PEO with polyrotaxanes in aqueous solution was tested by fluorescence titration, using b-CD-PDV and PDV. This experiment revealed that both conjugated polymers bind PEO strongly even under extremely dilute conditions (1 ppm PEO by weight, ca. 1 × 10 -8 mol dm -3 of both components). The fluorescence spectra of PDV at a range of PEO concentrations are shown in Figure 2a, and the corresponding titration curve is plotted in Figure 2b (see Fig. S1 in the Supporting Information for analogous data for b-CD-PDV). The titration curves for b-CD-PDV and PDV fit remark...