Enhancement of Scaffold In Vivo Biodegradability for Bone Regeneration Using P28 Peptide Formulations.

The field of bone tissue engineering has shown a great variety of bone graft substitute materials under development to date, with the aim to reconstruct new bone tissue while maintaining characteristics close to the native bone. Currently, insufficient scaffold degradation remains the critical limitation for the success of tailoring the bone formation turnover rate. This study examines novel scaffold formulations to improve the degradation rate in vivo, utilising chitosan (CS), hydroxyapatite (HAp) and fluorapatite (FAp) at different ratios. Previously, the P28 peptide was reported to present similar, if not better performance in new bone production to its native protein, bone morphogenetic protein-2 (BMP-2), in promoting osteogenesis in vivo. Therefore, various P28 concentrations were incorporated into the CS/HAp/FAp scaffolds for implantation in vivo. H&E staining shows minimal scaffold traces in most of the defects induced after eight weeks, showing the enhanced biodegradability of the scaffolds in vivo. The HE stain highlighted the thickened periosteum indicating a new bone formation in the scaffolds, where CS/HAp/FAp/P28 75 µg and CS/HAp/FAp/P28 150 µg showed the cortical and trabecular thickening. CS/HAp/FAp 1:1 P28 150 µg scaffolds showed a higher intensity of calcein green label with the absence of xylenol orange label, which indicates that mineralisation and remodelling was not ongoing four days prior to sacrifice. Conversely, double labelling was observed in the CS/HAp/FAp 1:1 P28 25 µg and CS/HAp/FAp/P28 75 µg, which indicates continued mineralisation at days ten and four prior to sacrifice. Based on the HE and fluorochrome label, CS/HAp/FAp 1:1 with P28 peptides presented a consistent positive osteoinduction following the implantation in the femoral condyle defects. These results show the ability of this tailored formulation to improve the scaffold degradation for bone regeneration and present a cost-effective alternative to BMP-2.

Detection of fibronectin conformational changes in the extracellular matrix of live cells using plasmonic nanoplates.

Protein conformational changes are detected both in vitro and for the first time in the presence of living cells using versatile plasmonic nanoplates. Au-edge-coated triangular silver nanoplates (AuTSNP) exhibit some of the highest refractive index sensitivity values recorded to date and exhibit a strong spectral response to surface biomolecular interactions. Large spectral shifts of over 30 nm distinguish between pH induced compact and extended conformations of the ubiquitous extracellular matrix protein fibronectin (Fn). Conformational transition of Fn from compact to extended is accompanied by a red spectral shift of 27 nm while a corresponding blue spectral shift of 25 nm accompanies the reverse conformational transition. Cleavage of Fn by cathepsin B, which plays an important role in cellular functions and in cancer metastasis is characterised by a blue spectral shift with detection in serum using a straightforward no-wash assay demonstrated. Spectral monitoring of nanoplates decorated with Fn and incubated with MDCK II cells shows extensive shifts of 156 nm and cellular morphological re-arrangement as Fn uncoils from a compact format to from fibrils within the extracellular matrix.

Effect of nanoparticle stabilization and physicochemical properties on exposure outcome: acute toxicity of silver nanoparticle preparations in zebrafish (Danio rerio).

Nanotechnology has vast potential for expanded development and novel application in numerous sectors of society. With growing use and applications, substantial production volumes and associated environmental release can be anticipated. Exposure effect of nanoparticles (NP) on biological systems may be intrinsic to their physicochemical properties introducing unknown associated risk. Herein, we expand the knowledge of health and environmental impact of silver nanoparticles (AgNPs), testing the acute toxicity of 14 AgNP preparations on developing zebrafish embryos (Danio rerio). Toxicological end points, including mortality, hatching rate, and heart rate were recorded. Concentration, stabilization agent and physicochemical properties were monitored as contributing outcome factors. Our findings indicate wide ranging LC50 24 h postfertilization values (0.487 ppm (0.315, 0.744 95% CI) to 47.89 ppm (18.45, 203.49 95% CI)), and indicate surface charge and ionic dissolution as key contributory factors in AgNP exposure outcome.

Versatile solution phase triangular silver nanoplates for highly sensitive plasmon resonance sensing.

Solution phase triangular silver nanoplates (TSNP) with versatile tunability throughout the visible-NIR wavelengths are presented as highly sensitive localized surface plasmon refractive index sensors. A range of 20 TSNP solutions with edge lengths ranging from 11 to 200 nm and aspect ratios from 2 to 13 have been studied comprehensively using AFM, TEM, and UV-vis-NIR spectroscopy. Studies of the localized surface plasmon resonance (LSPR) peak's sensitivity to refractive index changes are performed using a simple sucrose concentration method whereby the surrounding refractive index can solely be changed without variation in any other parameter. The dependence of the TSNP localized surface plasmon resonance (LSPR) peak wavelength lambda(max) and its bulk refractive index sensitivity on the nanoplate's structure is determined. LSPR sensitivities are observed to increase linearly with lambda(max) up to 800 nm, with the values lying within the upper limit theoretically predicted for optimal sensitivity, notwithstanding any diminution due to ensemble averaging. A nonlinear increase in sensitivity is apparent at wavelengths within the NIR region with values reaching 1096 nm.RIU(-1) at lambda(max) 1093 nm. Theoretical studies performed using a simple aspect ratio dependent approximation method and discrete dipole approximation methods confirm the dependence of the LSPR bulk refractive index sensitivity upon the TSNP aspect ratio measured experimentally. These studies highlight the importance of this key parameter in acquiring such high sensitivities and promote these TSNP sols for sensing applications at appropriate wavelengths for biological samples.

Etching-resistant silver nanoprisms by epitaxial deposition of a protecting layer of gold at the edges.

The protection of silver nanoprisms against etching by the epitaxial deposition of a thin layer of gold in solution has been investigated. It has been found that at low Au/Ag ratios (approximately 0.08 to 0.17) a thin layer of gold is deposited on the edges of the nanoprisms as expected, but without the structural damage typically associated with galvanic replacement. Furthermore, this layer of gold provides robust protection against etching of the nanoprisms by chloride and is strong evidence that etching by chloride is face-selective and does not take place at the flat {111} faces of the nanoprisms. Additionally, the deposition of a protecting layer of gold results in only a small red shift in the position of the main plasmon resonance. We have investigated the sensitivity of the localized surface plasmon resonance (LSPR) to changes in the bulk refractive index of the solution and find that the gold-protected silver nanoprisms are promising candidates for the development of new refractive index-based biosensors.