Controlling the Hydrophilicity and Cohesion During Deposition of Highly Oriented Type I Collagen Films: an approach for biomedical applications

Using the Langmuir-Blodgett (LB) technology we have pioneered a straightforward and low-cost approach to fabricate highly oriented collagen in thin film format (thickness: ~20 nm, surface areas: 2.5 x ~6.0 cm). An important factor for the use of these films is their cohesion under various conditions. Film formation was studied by coating hydrophilic or hydrophobic glass substrates. The fresh or aged (2 ½ years, -18°C.) collagen solutions used for this purpose either contained collagen network-stabilizing agents (n-propanol or phosphate ions) or were prepared without these stabilizers. Film formation on the air/water interface was analyzed by pressure-area isotherms. Maximum surface pressures were ~ 4-7 mN/m and ~ 10-18 mN/m for isotherms using n-propanol or phosphate buffer saline (PBS), respectively, versus ~ 0.4-0.8 mN/m without using a stabilizer; with higher surface pressures for the combination fresh solution/n-propanol or aged solution/PBS. Deposited films were studied by optical and electron microscopy and fast Fourier transform analysis. Coatings (to both substrate types) exhibit a defined orientation of collagen aggregates within a matrix of oriented collagen when freshly made or aged collagen solutions were used and n-propanol was present during film formation. The higher degree of hydrophilicity of the aged solution does not adversely affect the cohesion and collagen orientation during film formation. Using physiological phosphate ions shows that deposition of defect-free and oriented collagen (on both substrate types) is only possible using fresh collagen solutions. Unlike n-propanol-containing solutions, films were most stable using hydrophilic glass substrates. Film formation failed in the absence of network stabilizers. Controlling the cohesion via (a) the water accessibility of collagen structures, (b) specific network stabilizers and (c) substrate properties enables tunable film characteristics for future biomedical approaches

Zr-doped TiO2 as a Thermostabilizer in Plasmon-Enhanced Dye-Sensitized Solar Cells

Harvesting solar energy is a promising solution toward meeting the world’s evergrowing energy demand. Dye-sensitized solar cells (DSSCs) are hybrid organic–inorganic solar cells with tremendous potential for commercial application, but they are plagued by in efficiency due to their poor sunlight absorption. Plasmonic silver nanoparticles (AgNPs) have been shown to enhance the absorptive properties of DSSCs, but their plasmonic resonance can cause thermal damage resulting in cell deterioration. Hence, the influence of Zr-doped TiO2 on the efficiency of plasmon-enhanced DSSCs was studied, showing that 5 mol.% Zr-doping of the photoactive TiO2 material can improve the photovoltaic performance of DSSCs by 44%. By examining three different DSSC designs, it became clear that the efficiency enhancing effect of Zr strongly depends on the proximity of the Zr-doped material to the plasmonic AgNPs

Orientation Distribution of Highly Oriented Type I Collagen Deposited on Flat Samples with Different Geometries

The structural arrangement of type I collagen in vivo is critical for the normal functioning of tissues, such as bone, cornea, tendons and blood vessels. At present, there are no established low-cost techniques for fabricating aligned collagen structures for applications in regenerative medicine. Here, we report on a straightforward approach to fabricate collagen films, with defined orientation distributions of collagen fibrillar aggregates within a matrix of oriented collagen molecules on flat sample surfaces. Langmuir Blodgett (LB) technology was used to deposit thin films of oriented type I collagen onto flat substrates exhibiting various shapes. By varying the shapes of the substrates (e.g. rectangles, squares, circles, parallelograms, and various shaped triangles) as well as their sizes, a systematic study on collagen alignment patterns was conducted. It was found that the orientation and the orientation distribution of collagen along these various shaped substrates is directly depending on the geometry of the substrate and the dipping direction of that sample with respect to the collagen/water subphase. An important factor in tissue engineering is the stability, durability and endurance of the constructed artificial tissue, and thus its functioning in regenerative medicine applications. By testing these criteria we found that the coated films and their alignments were stable for at least three months under different conditions and, moreover, that these films can withstand temperatures of up to 60°C for a short time. Therefore, these constructs may have widespread applicability in the engineering of collagen-rich tissues

Kidney stones in primary hyperoxaluria: new lessons learnt.

To investigate potential differences in stone composition with regard to the type of Primary Hyperoxaluria (PH), and in relation to the patient's medical therapy (treatment naïve patients versus those on preventive medication) we examined twelve kidney stones from ten PH I and six stones from four PH III patients. Unfortunately, no PH II stones were available for analysis. The study on this set of stones indicates a more diverse composition of PH stones than previously reported and a potential dynamic response of morphology and composition of calculi to treatment with crystallization inhibitors (citrate, magnesium) in PH I. Stones formed by PH I patients under treatment are more compact and consist predominantly of calcium-oxalate monohydrate (COM, whewellite), while calcium-oxalate dihydrate (COD, weddellite) is only rarely present. In contrast, the single stone available from a treatment naïve PH I patient as well as stones from PH III patients prior to and under treatment with alkali citrate contained a wide size range of aggregated COD crystals. No significant effects of the treatment were noted in PH III stones. In disagreement with findings from previous studies, stones from patients with primary hyperoxaluria did not exclusively consist of COM. Progressive replacement of COD by small COM crystals could be caused by prolonged stone growth and residence times in the urinary tract, eventually resulting in complete replacement of calcium-oxalate dihydrate by the monohydrate form. The noted difference to the naïve PH I stone may reflect a reduced growth rate in response to treatment. This pilot study highlights the importance of detailed stone diagnostics and could be of therapeutic relevance in calcium-oxalates urolithiasis, provided that the effects of treatment can be reproduced in subsequent larger studies

SEM micrographs of PHIII stone fragments.

<p>Panels A–D show a complete stone (A), surface characteristics (B, C) and internal structures (D). Panel C reveals a section of B showing small COD crystals (bipyramidal shapes) grown on a large uneven COD surface. The unevenness possibly originates from organic compounds coating the crystal surface. Panel D shows doughnut-shaped COM crystals in the interstitial spaces between large COD crystals. Scale bars (sample ID) A: 400 µm (H11); B: 100 µm (H13); C: 4 µm (H13); D: 14 µm (H7).</p

Light microscopy photographs of typical calculi from patients diagnosed with primary hyperoxaluria.

<p>Panels A and B show stones from patients diagnosed with PH I before receiving treatment (A, sample H18) and stones formed under treatment with citrate and vitamin B6 (B, sample H9). Panels C and D depict stones from an untreated PH III patient (C, sample H28) and from a patient treated with citrate (D, sample H4). Note in 1C the large very fine-grained COM region and smaller crystalline region (arrow) with bipyramidal COD crystals. The inset shows the back of this stone. Panels E and F depict typical idiopathic Ca-Ox stones for comparison consisting of COM only. Note the dark pigmentation and the characteristic core and mantle structure in the cut and polished cross-section. Scale bars A = 2 mm, B = 500 µm, C = 200 µm, D = 250 µm, E = 500 µm, F = 250 µm.</p

Synopsis of stones used in this study with details of preventive treatment and genotype.

<p>Asterisk denotes stones from newly-diagnosed and at the time untreated patients.</p>1<p>stone composition determined by multiple spot analyses on one polished surface. UL = Urolithiasis, NC = Nephrocalcinosis, HCT = Hydrochlorothiazide, GFR = Glomerular Filtration Rate, p.resp. = partly responsive to vit. B6 treatment.</p