Effects of Mangosteen Peel Phenolic Compounds on Tilapia Skin Collagen-Based Mineralized Scaffold Properties.

A proper valorization of biological waste sources for an effective conversion into composites for tissue engineering is discussed in this study. Hence, the collagen and the phenolic compound applied in this investigation were extracted from waste sources, respectively, fish industry rejects and the peels of the mangosteen fruit. Porous scaffolds were prepared by combining both components at different compositions and mineralized at different temperatures to evaluate the modifications in the biomimetic formation of apatite. The inclusion of mangosteen extract showed the advantage of increasing the collagen denaturation temperature, improving the stability of its triple helix. Moreover, the extract provided antioxidant activity due to its phenolic composition, as confirmed by 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant assays. Mineralization was successfully achieved as indicated by thermogravimetry and scanning electron microscopy. A higher temperature and a lower extract concentration reduced the calcium phosphate deposits. The extract also affected the pore size, particularly at a lower concentration. The X-ray diffraction pattern identified a low degree of crystallization. A high mineralization temperature induced the formation of smaller crystallites ranging from 18.9 to 25.4 nm. Although the deposited hydroxyapatite showed low crystallinity, the scaffolds are suitable for bone tissue applications and may be effective in controlling the resorbability rate in tissue regeneration.

Reversible Photo-Induced Reshaping of Imprinted Microstructures Using a Low Molecular Azo Dye.

A blend of low molecular azo glass (AZOPD) and polystyrene (PS) were used for the systematic investigation of photo-induced stretching and recovery of nanoimprinted structures. For this purpose, light and heat was used as recovery stimuli. The AZOPD/PS microstructures, fabricated with thermal nanoimprint lithography (tNIL), comprises three different shapes (circles, crosses and squares) and various concentrations of AZOPD fractions. The results show a concentration-dependent reshaping. Particularly the sample with 43 w-% of the AZOPD fraction have shown the best controllable recovery for the used parameters. A possible explanation for shape recovery might be the stabilizing effect of the PS-matrix.

Polarization Dependent Photoinduced Supramolecular Chirality in High-Performance Azo Materials.

Here, we will show photo-induced supramolecular chirality in thin films of achiral amorphous polymers with azo groups in their side-chain. A matter of particular interest is the effect of various film thicknesses on azimuthal rotation and ellipticity of incident/transmitted polarized light. Furthermore, we investigated the temporal stability of inscribed chirality. By polarimetric measurements, we found out that the azimuthal rotation gets higher with layer thickness. In this scope, we were able to measure a very high azimuthal rotation of Δψ/d=112.5∘/µm. The inscribed chirality was stable for several days. Furthermore, we investigated the time-resolved behavior of incident and transmitted polarization ellipticities for various thicknesses. The time dependency may be explained by a two-step process: (1) fast trans-cis-isomerization resulting in photo-orientation and (2) slow photo-induced mass flow.

Mineralization of Phosphorylated Fish Skin Collagen/Mangosteen Scaffolds as Potential Materials for Bone Tissue Regeneration.

In this study, a potential hard tissue substitute was mimicked using collagen/mangosteen porous scaffolds. Collagen was extracted from Tilapia fish skin and mangosteen from the waste peel of the respective fruit. Sodium trimetaphosphate was used for the phosphorylation of these scaffolds to improve the nucleation sites for the mineralization process. Phosphate groups were incorporated in the collagen structure as confirmed by their attenuated total reflection Fourier transform infrared (ATR-FTIR) bands. The phosphorylation and mangosteen addition increased the thermal stability of the collagen triple helix structure, as demonstrated by differential scanning calorimetry (DSC) and thermogravimetry (TGA) characterizations. Mineralization was successfully achieved, and the presence of calcium phosphate was visualized by scanning electron microscopy (SEM). Nevertheless, the porous structure was maintained, which is an essential characteristic for the desired application. The deposited mineral was amorphous calcium phosphate, as confirmed by energy dispersive X-ray spectroscopy (EDX) results.

Is the diatom sex clock a clock?

The unique life cycle of diatoms with continuous decreasing and restoration of the cell size leads to periodic fluctuations in cell size distribution and has been regarded as a multi-annual clock. To understand the long-term behaviour of a population analytically, generic mathematical models are investigated algebraically and numerically for their capability to describe periodic oscillations. Whereas the generally accepted simple concepts for the proliferation dynamics do not sustain oscillating behaviour owing to broadening of the size distribution, simulations show that a proposed limited lifetime of a newly synthesized cell wall slows down the relaxation towards a time-invariant equilibrium state to the order of a hundred thousand generations. In combination with seasonal perturbation events, the proliferation scheme with limited lifetime is able to explain long-lasting rhythms that are characteristic for diatom population dynamics. The life cycle thus resembles a pendulum clock that has to be wound up from time to time by seasonal perturbations rather than an oscillator represented by a limit cycle.

Phase Separation and Nanostructure Formation in Binary and Ternary Blends of Spiro-Linked Molecular Glasses.

Understanding phase separation phenomena in blends of organic electron acceptor and donor materials is of special interest in the context of organic optoelectronic applications. In this study, we focus on the phase behavior of a special class of spiro-linked compounds, which serve as model systems for morphological control in phase-separated small-molecule electron donor-acceptor blends. Thermal analysis and quantitative image analysis were the key techniques for developing a suitable approach for modeling the phase diagram with minimal material consumption. We report an uncommon miscibility gap in the liquid and glassy phase and show that the phase diagram can be modified by addition of a third, ambipolar compound in analogy to ternary A/B/AB polymeric blends. For an exemplary ternary system, a bicontinuous morphology with a pattern length scale of a few tens of nanometers was realized in the bulk that verifies the applicability of this approach to morphology control.

Two-dimensional Wrinkle Resonators for Random Lasing in Organic Glasses.

Random lasers consisting of slab waveguides with two-dimensional disordered wrinkling patterns that act as scattering resonators are reported. As active material 2,2',7,7'-tetraphenyl-9,9'-spirobifluorene is used which is sandwiched between an oxidized silicon wafer and a cladding with higher glass transition temperature. Wrinkles with tailorable periodicity have been induced by thermal annealing. Photopumping experiments show the transition from amplified spontaneous emission to a multiple peak laser spectrum with linewidths as low as 0.1 nm, demonstrating the applicability of this approach for random laser design.

Simultaneous uptake of a Förster transfer dye pair by diatoms: Application in determination of staining density.

The simultaneous uptake of PDMPO and Rhodamine B as two fluorescent dyes forming a Förster transfer pair by the diatom Cyclotella meneghiniana is demonstrated by in vivo-fluorochromation. The incorporation density in the cell walls was high enough for achieving resonant energy transfer between the two dyes as detected by fluorescence and excitation spectroscopy. The mean fluorescence lifetime of the donor is shortened in the presence of the acceptor by a factor of 0.75. By determining the mean lifetime from the fluorescence decay fitted by three eponentials, the efficiency of the energy transfer and the acceptor concentration is calculated assuming a homogenous distribution. For an initial concentration of both dyes of 5µM in the culture medium which is at the saturation limit of incorporation, an acceptor incorporation density of 0.6mM is obtained. In addition to such quantitative determinations, efficient emitting systems based on resonant energy transfer between two laser dyes may be useful in photonic applications of the hybrid biomineral. By achieving stimulated emission, the presence of optical modes in diatom frustules, which may act as photonic resonators due to the refractive index contrast to the environment in combination with the more or less regular pore pattern, may be characterized further.

Photoinduced sign change of the magnetoresistance in field-effect transistors based on a bipolar molecular glass.

The application of a novel bipolar molecular glass in field-effect transistors leads to devices with photoinduced magnetoresistance (MR) sign change. In darkness a low external magnetic field increases the resistance (positive MR up to +0.1%), while a magnetic-field induced resistance decrease (negative MR up to -6.5%) can be achieved under illumination.

Surface wrinkling induced by photofluidization of low molecular azo glasses.

Photoinduced surface wrinkling is demonstrated for a low molecular azo compound confined between a substrate and a thin inorganic elastic layer. The wrinkling process is investigated by time-resolved light scattering as well as by two-dimensional autocorrelation analysis of microscopic images. It is shown that the temporal evolution of the wrinkling pattern is directly controlled by the amount of photons absorbed by the sample and that there is no significant dependence of the equilibrium wavelength on irradiation intensity. Finally, the comparison of thermal and photoinduced wrinkling revealed that photoinduced wrinkles are characterized by a narrower mode distribution and less coarsening.

Staining diatoms with rhodamine dyes: control of emission colour in photonic biocomposites.

The incorporation of rhodamine dyes in the cell wall of diatoms Coscinodiscus granii and Coscinodiscus wailesii for the production of luminescent hybrid nanostructures is investigated. By systematic variation of the substitution pattern of the rhodamine core, we found that carbonic acids are considerably better suited than esters because of their physiological compatibility. The amino substitution pattern that controls the optical properties of the chromophore has no critical influence on dye uptake and incorporation, thus a variety of biocomposites with different emission maxima can be prepared. Applications in biomineralization studies as well as in materials science are envisioned.

Bipolar redox behaviour, field-effect mobility and transistor switching of the low-molecular azo glass AZOPD.

We present electrochemical and spectroelectrochemical data for the bipolar azo compound N,N'-diphenyl-N,N'-bis[4-(phenylazo)phenyl]-4,4'diaminobiphenyl (AZOPD) demonstrating reversible bipolar redox behaviour with a bandgap of 2.1 eV. The reduced species formed upon two-electron transfer can be described as bis(radical anion) as was confirmed by comparison with a reference compound with only one azo chromophore. Hole and electron transport behaviour in amorphous films was demonstrated by the fabrication of organic field-effect transistors using gold and magnesium contacts, respectively. The transistors are sensitive to light due to E-Z photoisomerization.