Studies of P(L/D)LA 96/4 non-woven scaffolds and fibres; properties, wettability and cell spreading before and after intrusive treatment methods

Poly(L/D)lactide 96/4 fibres with diameters of 50 and 80 μm were produced. The smaller diameter fibres were carded and needle punched to form a non-woven mat. Fibres and non-woven mats were hydrolysed for a period of 20 weeks. Fibres and pressed non-woven discs were treated with low-temperature oxygen plasma and alkaline KOH hydrolysis and ethanol washing was used as a reference treatment. The non-wovens lost 50% of their tear strength after 8 weeks in vitro while the fibres still retained 65% tensile strength after 20 weeks. Hydrolysation time in KOH, treatment time and power settings of the oxygen plasma were all directly proportional to the mechanical properties of the fibres. Increasing time (and power) resulted in lower tensile properties. Rapid wetting of the scaffolds was achieved by oxygen plasma, KOH hydrolysation and ethanol washing. Cell culturing using fibroblast cell line was carried out for the treated and non-treated non-woven scaffolds. In terms of adhesion and the spreading of the cells into the scaffold, best results after 3-day culturing were obtained for the oxygen plasma treated scaffolds.     

Comparison of absolute spectral irradiance responsivity measurement techniques using wavelength-tunable lasers

Independent methods for measuring the absolute spectral irradiance responsivity of detectors have been compared between the calibration facilities at two national metrology institutes, the Helsinki University of Technology (TKK), Finland, and the National Institute of Standards and Technology (NIST). The emphasis is on the comparison of two different techniques for generating a uniform irradiance at a reference plane using wavelength-tunable lasers. At TKK's Laser Scanning Facility (LSF) the irradiance is generated by raster scanning a single collimated laser beam, while at the NIST facility for Spectral Irradiance and Radiance Responsivity Calibrations with Uniform Sources (SIRCUS), lasers are introduced into integrating spheres to generate a uniform irradiance at a reference plane. The laser-based irradiance responsivity results are compared to a traditional lamp-monochromator-based irradiance responsivity calibration obtained at the NIST Spectral Comparator Facility (SCF). A narrowband filter radiometer with a 24 nm bandwidth and an effective band-center wavelength of 801 nm was used as the artifact. The results of the comparison between the different facilities, reported for the first time in the near-infrared wavelength range, demonstrate agreement at the uncertainty level of less than 0.1%. This result has significant implications in radiation thermometry and in photometry as well as in radiometry.     

Finite frequency f-sum rule for assessment of number density of gold nanoparticles (AuNPs) and Kramers-Kronig relation for refractive index of colloidal gold

Absorption spectra from colloids containing different concentrations of spherical gold nanoparticles in water were measured with a spectrophotometer. The absorption spectra were used to calculate the number density of nanoparticles (NPs) with the aid of an unconventional finite spectral band f-sum rule applied for gold colloid. Good correlation between the number density of dispersion electrons, obtained from the f-sum rule, and the number density of nanoparticles was found. The effective absolute refractive index of the gold colloid was obtained with the aid of a singly subtractive Kramers-Kronig relation, and in addition the refractive index change due to the nanoparticles was obtained with the aid of a conventional Kramers-Kronig relation. Such optical properties are valuable in studies of light interaction with nanoparticles.     

Lithography-free fabrication of carbon nanotube network transistors

A novel non-lithographic technique for the fabrication of carbon nanotube thin film transistors is presented. The whole transistor fabrication process requires only one mask which is used both to pattern transistor channels based on aerosol synthesized carbon nanotubes and to deposit electrodes by metal evaporation at different angles. An important effect of electrodynamic focusing was utilized for the directed assembly of transistor channels with feature sizes smaller than the mask openings. This dry non-lithographic method opens up new avenues for device fabrication especially for low cost flexible and transparent electronics.     

Preparation and characterization of collagen/PLA,chitosan/PLA,and collagen/chitosan/PLA hybrid scaffolds for cartilage tissue engineering

In this study, three-dimensional (3D) porous scaffolds were developed for the repair of articular cartilage defects. Novel collagen/polylactide (PLA), chitosan/PLA, and collagen/chitosan/PLA hybrid scaffolds were fabricated by combining freeze-dried natural components and synthetic PLA mesh, where the 3D PLA mesh gives mechanical strength, and the natural polymers, collagen and/or chitosan, mimic the natural cartilage tissue environment of chondrocytes. In total, eight scaffold types were studied: four hybrid structures containing collagen and/or chitosan with PLA, and four parallel plain scaffolds with only collagen and/or chitosan. The potential of these types of scaffolds for cartilage tissue engineering applications were determined by the analysis of the microstructure, water uptake, mechanical strength, and the viability and attachment of adult bovine chondrocytes to the scaffolds. The manufacturing method used was found to be applicable for the manufacturing of hybrid scaffolds with highly porous 3D structures. All the hybrid scaffolds showed a highly porous structure with open pores throughout the scaffold. Collagen was found to bind water inside the structure in all collagen-containing scaffolds better than the chitosan-containing scaffolds, and the plain collagen scaffolds had the highest water absorption. The stiffness of the scaffold was improved by the hybrid structure compared to plain scaffolds. The cell viability and attachment was good in all scaffolds, however, the collagen hybrid scaffolds showed the best penetration of cells into the scaffold. Our results show that from the studied scaffolds the collagen/PLA hybrids are the most promising scaffolds from this group for cartilage tissue engineering.     

Elaboration and relationships between structure and rheological properties of microtalc or nanotalc/polyamide composites

This study focuses on the elaboration of nanocomposites processed by melt mixing of a polyamide 12 matrix and a hydrogel filled with synthetic talc particles. The systems are obtained by simultaneous mixing using either an internal mixer or a lab twin‐screw extruder. The structure and rheological properties of synthetic talc/polyamide composites are compared with those of natural talc/polyamide microcomposites and modified montmorillonite/polyamide nanocomposites. A multiscale structure, composed of numerous nanometric particles but also few micrometric aggregates, is obtained for synthetic talc/polyamide composites. In terms of processability, the lab twin‐screw extruder is more adequate than the internal mixer for the elaboration of synthetic talc/polyamide composites with relatively high filler volume fractions. For composites elaborated with the extruder, the percolation threshold, estimated from linear viscoelastic measurements, is close to 1, 6, and 11%, respectively, with modified montmorillonite, synthetic talc, and natural talc particles, in agreement with structural results. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42299.     

Hierarchically Ordered Supramolecular Protein-Polymer Composites with Thermoresponsive Properties

Synthetic macromolecules that can bind and co-assemble with proteins are important for the future development of biohybrid materials. Active systems are further required to create materials that can respond and change their behavior in response to external stimuli. Here we report that stimuli-responsive linear-branched diblock copolymers consisting of a cationic multivalent dendron with a linear thermoresponsive polymer tail at the focal point, can bind and complex Pyrococcus furiosus ferritin protein cages into crystalline arrays. The multivalent dendron structure utilizes cationic spermine units to bind electrostatically on the surface of the negatively charged ferritin cage and the in situ polymerized poly(di(ethylene glycol) methyl ether methacrylate) linear block enables control with temperature. Cloud point of the final product was determined with dynamic light scattering (DLS), and it was shown to be approximately 31 °C at a concentration of 150 mg/L. Complexation of the polymer binder and apoferritin was studied with DLS, small-angle X-ray scattering, and transmission electron microscopy, which showed the presence of crystalline arrays of ferritin cages with a face-centered cubic (fcc Fm3¯m) Bravais lattice where lattice parameter a = 18.6 nm. The complexation process was not temperature dependent but the final complexes had thermoresponsive characteristics with negative thermal expansion.     

Intact free prostate-specific antigen and free and total human glandular kallikrein 2. Elimination of assay interference by enzymatic digestion of antibodies to F(ab')2 fragments

Various blood constituents can interfere with immunoassays, usually by binding the Fc portion of antibodies. Our previously developed assays for intact free prostate-specific antigen (PSA), free human kallikrein 2 (hK2), and total hK2 frequently yielded falsely high results despite including an excess of scavenger antibodies. We investigated whether this interference could be eliminated by replacing monoclonal capture or tracer antibodies with F(ab')2 or recombinant Fab fragments. Female heparin plasma samples (n = 1092), which should have negligible PSA and hK2, and male samples (n = 957) were analyzed to identify samples manifesting interference, which then were used to optimize protocols for the immunoassays. We compared original assays (monoclonal antibodies) versus optimized assays (F(ab')2 fragments: denatured mouse IgG added as scavenger) using another set of EDTA plasma (n = 113), heparin plasma (n = 160), and serum samples (n = 171). With the original assays, the frequency of falsely elevated hK2 and intact free PSA was 15 and 13%, respectively. The optimized assays eliminated 70-85% of these falsely elevated results and importantly reduced the magnitude in the remainder. F(ab')2 fragmentation was the most important factor in reducing interference. The optimized intact free PSA, free hK2, and total hK2 assays manifested high accuracy close to the lower limit of detection.