Nano-mechanical transduction of polymer micro-cantilevers to detect bio-molecular interactions

Using variothermal polymer micro-injection molding, disposable arrays of eight polymer micro-cantilevers each 500 μm long, 100 μm wide and 25 μm thick were fabricated. The present study took advantage of an easy flow grade polypropylene. After gold coating for optical read-out and asymmetrical sensitization, the arrays were introduced into the Cantisens(®) Research system to perform mechanical and functional testing. We demonstrate that polypropylene cantilevers can be used as biosensors for medical purposes in the same manner as the established silicon ones to detect single-stranded DNA sequences and metal ions in real-time. A differential signal of 7 nm was detected for the hybridization of 1 μM complementary DNA sequences. For 100 nM copper ions the differential signal was found to be (36 ± 5) nm. Nano-mechanical sensing of medically relevant, nanometer-size species is essential for fast and efficient diagnosis.

The role of the interplay between polymer architecture and bacterial surface properties on the microbial adhesion to polyoxazoline-based ultrathin films

Surface platforms were engineered from poly(L-lysine)-graft-poly(2-methyl-2-oxazoline) (PLL-g-PMOXA) copolymers to study the mechanisms involved in the non-specific adhesion of Escherichia coli (E. coli) bacteria. Copolymers with three different grafting densities (PMOXA chains/Lysine residue of 0.09, 0.33 and 0.56) were synthesized and assembled on niobia (Nb O ) surfaces. PLL-modified and bare niobia surfaces served as controls. To evaluate the impact of fimbriae expression on the bacterial adhesion, the surfaces were exposed to genetically engineered E. coli strains either lacking, or constitutively expressing type 1 fimbriae. The bacterial adhesion was strongly influenced by the presence of bacterial fimbriae. Non-fimbriated bacteria behaved like hard, charged particles whose adhesion was dependent on surface charge and ionic strength of the media. In contrast, bacteria expressing type 1 fimbriae adhered to the substrates independent of surface charge and ionic strength, and adhesion was mediated by non-specific van der Waals and hydrophobic interactions of the proteins at the fimbrial tip. Adsorbed polymer mass, average surface density of the PMOXA chains, and thickness of the copolymer films were quantified by optical waveguide lightmode spectroscopy (OWLS) and variable-angle spectroscopic ellipsometry (VASE), whereas the lateral homogeneity was probed by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Streaming current measurements provided information on the charge formation of the polymer-coated and the bare niobia surfaces. The adhesion of both bacterial strains could be efficiently inhibited by the copolymer film only with a grafting density of 0.33 characterized by the highest PMOXA chain surface density and a surface potential close to zero.

Two-Dimensional Manganese(II) Coordination Polymer Based on Phthalate and Pyrazine Bridges Exhibiting Antiferromagnetic Porperties

Benzodifuran-functionalised pyrene and anthracene fluorophores 1 and 2 were obtained in reasonable yields. Their single crystal structures, electrochemical, optical absorption, and fluorescence characteristics have been described. They show strong luminescence with high quantum yields of 0.53 for 1 and 0.48 for 2. Magnetic measurements for the 2D coordination polymer [Mn(Pht(Pyz(H2O)2]n (1), in which metal centres are linked together by pyrazine (Pyz) and 1,6-bridging o-phthalate ligand (Pht2-), revealed antiferromagnetic interactions between Mn(II) ions.

Polymer stent coating for prevention of neointimal hyperplasia

AIMS: Restenosis has been the principal limitation of bare metal stents. Based upon the presumption that platelet and inflammatory cell recruitment initiate neointimal proliferation, we explored a novel polymer coating that reduces cell-stent interactions. The purpose of the present study was to investigate the effect of poly(L-lysine)-graft-poly(ethyleneglycol) (PLL-g-PEG) adsorbed to stent surfaces to reduce neointimal hyperplasia in the porcine restenosis model. METHODS AND RESULTS: Seven animals were instrumented each with 2 stainless steel stents (15 mm length, 2.5-3.5 mm diameter), randomly implanted in 1 major epicardial coronary artery. One stent was dip-coated with PLL-g-PEG, whereas the other stent served as the uncoated control stent. All animals were sacrificed after 6 weeks for histological examination. Neointimal hyperplasia was significantly less (-51%) in the PLL-g-PEG-coated stents (1.15 +/- 0.59 mm2) than in the uncoated control stents (2.33 +/- 1.01 mm2; p < 0.001). Conversely, lumen size was larger in the PLL-g-PEG-coated stents (2.91 +/- 1.17 mm2) than in the uncoated stents (2.04 +/- 0.64 mm2; p < 0.001). High magnification histomorphologic examination revealed no signs of inflammation or thrombus formation in either stent group. CONCLUSIONS: Polymeric steric stabilization of stents with PLL-g-PEG significantly reduces neointimal hyperplasia in the porcine restenosis model. Reduction of cell-stent interactions mediated by PLL-g-PEG appear to improve biocompatibility of stainless steel stents without evidence of adverse inflammatory or prothrombotic effects.

Surface charge of polymer coated SPIONs influences the serum protein adsorption, colloidal stability and subsequent cell interaction in vitro

It is known that the nanoparticle-cell interaction strongly depends on the physicochemical properties of the investigated particles. In addition, medium density and viscosity influence the colloidal behaviour of nanoparticles. Here, we show how nanoparticle-protein interactions are related to the particular physicochemical characteristics of the particles, such as their colloidal stability, and how this significantly influences the subsequent nanoparticle-cell interaction in vitro. Therefore, different surface charged superparamagnetic iron oxide nanoparticles were synthesized and characterized. Similar adsorbed protein profiles were identified following incubation in supplemented cell culture media, although cellular uptake varied significantly between the different particles. However, positively charged nanoparticles displayed a significantly lower colloidal stability than neutral and negatively charged particles while showing higher non-sedimentation driven cell-internalization in vitro without any significant cytotoxic effects. The results of this study strongly indicate therefore that an understanding of the aggregation state of NPs in biological fluids is crucial in regards to their biological interaction(s).

Interactions of Polyvinylpyrrolidone with Chlorin e6-Based Photosensitizers Studied by NMR and Electronic Absorption Spectroscopy

Polyvinylpyrrolidone (PVP) can act as potential drug delivery vehicle for porphyrin-based photosensitizers in photodynamic therapy (PDT) to enhance their stability and prevent porphyrin self-association. In the present study the interactions of PVP (MW 10 kDa) were probed with five different derivatives of chlorin e6 (CE6) bearing either one of the amino acids serine, lysine, tyrosine or arginine, or monoamino-hexanoic acid as substituent. All derivatives of CE6 (xCE) formed aggregates of a similar structure in aqueous buffer in the millimolar range. In the presence of PVP monomerization of all xCE aggregates could be proved by 1H NMR spectroscopy. xCE-PVP complex formation was confirmed by 1H NMR T2 relaxation and diffusion ordered spectroscopy (DOSY). 1H1H-NOESY data suggested that the xCE uptake into the PVP polymer matrix is governed by hydrophobic interactions. UV–vis absorption and fluorescence emission bands of xCE in the micromolar range revealed characteristic PVP-induced bathochromic shifts. The presented data point out the potential of PVP as carrier system for amphiphilic derivatives of chlorin e6. The capacity of PVP to monomerize xCE aggregates may enhance their efficiency as possible photosensitizers in PDT.