Shape-memory collagen scaffold for enhanced cartilage regeneration: native collagen versus denatured collagen.

OBJECTIVE: Nowadays, it is still questionable whether denatured collagen (DCol) can replace the native collagen (Col) as a bioactive protein in cartilage engineering. We sought to study the advantages of Col with a triple-helical structure in the collagen-based composite materials for cartilage engineering. METHODS: We presented new three-dimensional (3D) Col and DCol scaffolds with shape memory properties. The effects of Col and DCol scaffolds on rabbit chondrocytes' proliferation, adhesion, differentiation and interaction with matrix were investigated. Tissue compatibility was performed in a subcutaneous Sprague Dawley (SD) rat model. The repair ability of different scaffolds with chondrocytes for full-thickness articular cartilage defects in knee joints of New Zealand white rabbits were investigated. RESULTS: The results indicated that the Col scaffolds (with concentration 1.6wt% and 0.8wt%, respectively) promoted the proliferation, adhesion and redifferentiation of chondrocytes, as well as chondrocyte-matrix interaction, to a greater degree than the DCol scaffolds. In the animal experiment, the Col scaffolds filled in the defect hole significantly maintained chondrocytes function, promoted cartilage and subchondral bone regeneration, compared with the DCol scaffolds, and the scaffolds loaded with chondrocytes were better than the cell-free scaffolds, especially in the case of the Col scaffolds (1.6 wt%). CONCLUSIONS: Taken together, these insights suggest that the better proliferation, adhesion and redifferentiation of chondrocytes in Col scaffolds with the triple-helical structure may contribute to the greater cartilage repair ability. Col scaffolds may be more appropriate for repairing cartilage defects than DCol scaffolds, and DCol cannot as an alternative when using collagen-based materials for cartilage engineering applications.

Creating artificial Rhino Horns from Horse Hair.

Demand for rhino horn is driving poaching with devastating effect for the few individuals left of the few species surviving from this once numerous, widespread and cosmopolitan clade of pachyderms. We bundled together tail hairs of the rhino's ubiquitous near relative, the horse, to be glued together with a bespoke matrix of regenerated silk mimicking the collagenous component of the real horn. This approach allowed us to fabricate composite structures that were confusingly similar to real rhino horn in look, feel and properties. Spectral and thermal FT-IR, DSC and TGA analysis demonstrated the similar chemical composition and thermo-mechanical properties between the natural and the faux horns.

Systemic absorption of L- and D-phenylalanine across the rat nasal mucosa.

Nasal absorption of L-phenylalanine (L-Phe) and D-phenylalanine (D-Phe) have been investigated in rats using an in vivo absorption technique. L-Phe was effectively absorbed into systemic circulation with peak plasma level at 45 min after nasal administration. The absolute nasal bioavailability was calculated to be 96.3% when 5 mg/kg dose was given to fasted rats. The absolute bioavailability declined to 66.8% when 12.5 mg/kg of L-Phe was given intranasally while the time to reach peak concentration remained at 45 min. The results substantiated previous in situ data that, despite its high polarity, L-Phe was transported across the rat nasal mucosa into blood stream by the large neutral amino acid (LNAA) carrier. The carrier showed partial saturation at higher doses. On the other hand, when 5 mg/kg of D-Phe was given intranasally, slow and incomplete absorption was observed resulting in a peak time of 60 min and an absolute bioavailability of only 35.2%, suggesting specificity of the carrier for natural L-amino acids.

Variability in the mechanical properties of spider silks on three levels: interspecific, intraspecific and intraindividual.

The mechanical characteristics of dragline silks collected from a range of spiders drawn from the Argiopidae, Tetragnathidae, Theridiidae and Pisauridae displayed significant inter- and intraspecific differences. Dragline silks of the same species could show considerable variability probably dependent upon spider condition: starvation, for example, lead to decreased breaking elongation in Nephila edulis. Environmental conditions such as reeling speed affected silk properties such that (i) breaking elongation decreased, (ii) breaking stress increased and (iii) Young's modulus increased with increasing reeling speed. However, N. edulis and Araneus diadematus responded differently to the reeling speed treatments suggesting differences in basic silk properties.