an elastin derived self assembling polypeptide

Elastin is an extracellular matrix protein responsible for the elastic properties of organs and tissues, the elastic properties being conferred to the protein by the presence of elastic fibers. In the perspective of producing tailor-made biomaterials of potential interest in nanotechnology and biotechnology fields, we report a study on an elastin-derived polypeptide. The choice of the polypeptide sequence encoded by exon 6 of Human Tropoelastin Gene is dictated by the peculiar sequence of the polypeptide. As a matter of fact, analogously to elastin, it is constituted of a hydrophobic region (GLGAFPAVTFPGALVPGG) and of a more hydrophilic region rich of lysine and alanine residues (VADAAAAYKAAKA). The role played by the two different regions in triggering the adoption of beta-turn and beta-sheet conformations is herein discussed and demonstrated to be crucial for the self-aggregation properties of the polypeptide

DInSAR deformation time series for monitoring urban areas: The impact of the second generation SAR systems

We investigate the capability improvement of the DInSAR techniques to map deformation phenomena affecting urban areas, by performing a comparative analysis of the deformation time series retrieved by applying the full resolution Small BAseline Subset (SBAS) DInSAR technique to selected sequences of SAR data acquired by the ENVISAT, RADARSAT-1 and COSMO-SkyMed (CSK) SAR data. The presented study, focused on the city of Napoli (Italy), allows us to quantify the dramatic increase of the DInSAR coherent pixel density achieved by exploiting the high resolution X-Band CSK SAR images with respect to the RADARSAT-1 and ENVISAT products, respectively; this permits us to analyze nearly all the structures located within the investigated urbanized area and, in many cases, also portions of a same building. © 2012 IEEE

Statistical shape analysis in neuroimaging : methods, challenges, validation : applications to the study of brain asymmetries in schizophrenia

The study of brain shape and its patterns of variations can provide insights into the understanding of normal and pathological brain development and brain degenerative processes. This thesis focuses on the in vivo analysis of human brain shape as extracted from three-dimensional magnetic resonance images. Major automatic methods for the analysis of brain shape are discussed particularly focusing on the computation of shape metrics, the subsequent inference procedures, and their applications to the study of brain asymmetries in schizophrenia. Methodological challenges as well as possible biological factors that complicate the analysis of brain shape, and its validation, are also discussed. The contributions of this research work are as it follows. First, a novel automatic method for the statistical shape analysis of local interhemispheric asymmetries is presented and applied to the study of cerebral structural asymmetries in schizophrenia. The method extracts and analyzes smooth surface representations approximating the gross shape of the outlines of cerebral hemispheres. Second, a novel and fully automatic image processing framework for the validation of measures of brain asymmetry is proposed. The framework is based on the synthesis of realistic three-dimensional magnetic resonance images with a known asymmetry pattern. It employs a parametric model emulating the normal interhemispheric bending of the human brain while retaining other subject-specific features of brain anatomy. The framework is applied for the quantitative validation of measures of asymmetry in brain tissues' composition as computed by voxel-based morphometry. Particularly, the framework is used to investigate the dependence of voxel-based measures of brain asymmetry on the spatial normalization scheme, template space, and amount of spatial smoothing applied. The developed automatic framework is made available as open-source software. Third, a novel Simplified Reeb Graph based descriptor of the human striatum is proposed. The effectiveness of such a descriptor is demonstrated for the purposes of automatic registration, decomposition, and comparison of striatal shapes in schizophrenia patients and matched normal controls. In conclusion, this thesis proposes novel methods for shape representation and analysis within three-dimensional magnetic resonance brain images, an original way for validating these methods, and applies the methods for the study of brain asymmetries in schizophrenia. The impact of this research lies in its potential implications for the development of biomarkers aiming to a better understanding of the brain in normal and pathological conditions, early diagnosis of a number of brain diseases, and development of novel therapeutic strategies for improving the quality of life of affected individuals. In addition, the distribution of simulated data and automatic tools for validation of morphometric measures of brain asymmetry is expected to have a great impact in enabling systematic validation of novel and existing methods for the analysis of brain asymmetries, quantitatively comparing them, and possibly clarifying contradicting findings in the neuroimaging literature of brain lateralizations

Elastin-Hyaluronan Bioconjugate as Bioactive Component in Electrospun Scaffolds

Hyaluronic acid or hyaluronan (HA) and elastin‐inspired peptides (EL) have been widely recognized as bioinspired materials useful in biomedical applications. The aim of the present work is the production of electrospun scaffolds as wound dressing materials which would benefit from synergic action of the bioactivity of elastin peptides and the regenerative properties of hyaluronic acid. Taking advantage of thiol‐ene chemistry, a bioactive elastin peptide was successfully conjugated to methacrylated hyaluronic acid (MAHA) and electrospun together with poly‐d,l‐lactide (PDLLA). To the best of our knowledge, limited reports on peptide‐conjugated hyaluronic acid were described in literature, and none of these was employed for the production of electrospun scaffolds. The conformational studies carried out by Circular Dichroism (CD) on the bioconjugated compound confirmed the preservation of secondary structure of the peptide after conjugation while Scanning Electron Microscopy (SEM) revealed the supramolecular structure of the electrospun scaffolds. Overall, the study demonstrates that the bioconjugation of hyaluronic acid with the elastin peptide improved the electrospinning processability with improved characteristics in terms of morphology of the final scaffolds

The Inhibitory Effect of Resveratrol on Elastin Amyloidogenesis

The role of polyphenols in the prevention of degenerative diseases is emerging in the last years. In this report, we will investigatein vitrothe inhibitory effect of resveratrol on elastin amyloidogenesis. The effect of resveratrol on molecular structure was investigated by circular dichroism spectroscopy, while the inhibitory effect on self-assembly was evaluated by turbidimetry as a function of temperature and by atomic force microscopy

Phase behavior and chain dynamics of elastin-like peptides versus amino acid sequences

Elastin fibrillogenesis is conditioned by multiple self-assembly processes. Previous studies have evidenced the crucial influence of amino acid specificities on molecular organization of glycine-rich elastin-like peptides, but also the important role of environment on the self-assembly processes. For the first time, we combined a differential scanning calorimetry (DSC) study on aqueous solutions of three elastin-like peptides with thermally stimulated currents (TSC) experiments in the condensed state. We have studied three pentadecapeptides having the XGGZG motif threefold repeated with X and Z residues constituted of valine and leucine, known to form fiber structures. Valine and leucine moieties differ only by the presence of –CH2– spacer occupying in the pattern the first or the fourth position. Both of the residues are among the most abundant in elastin. Via DSC, we showed that the simple substitution of one amino acid strongly influences the surrounding hydration of the pentadecapeptides. During the self-assembly process, a slow exchange between bound water and bulk water is highlighted for (VGGLG)3, whereas a fast exchange of water molecules is found for(VGGVG)3 and (LGGVG)3. In the pre-fibrillar condensed state, TSC analysis reveals localized and delocalized motions and gives a fingerprint of the dynamics via activation parameters. At the localized level, a profound difference in the carbonyl environment is observed between(VGGLG)3 and the other peptides. The delocalized chain dynamics of the three peptides can be connected to the different conformations. The dominant unordered conformation of (VGGLG)3 leads to a softer system, while the large amount of b sheets and b turns in (VGGVG)3 and (LGGVG)3 leads to stiffer systems. Around the physiological temperature occurs a structural, isochronal phasetransition, sequence specific, suggested to be associated with the ferroelectricity of such elastin-like peptides

Electrospun poly-L-lactide scaffold for the controlled and targeted delivery of a synthetically obtained Diclofenac prodrug to treat actinic keratosis

Abstract Actinic Keratosis' (AKs) are small skin lesions that are related to a prolonged sun-damage, which can develop into invasive squamous cell carcinoma (SCC) when left untreated. Effective, specific and well tolerable therapies to cure AKs are still of great interest. Diclofenac (DCF) is the current gold standard for the local treatment of AKs in terms of costs, effectiveness, side effects and tolerability. In this work, an electrospun polylactic acid (PLA) scaffold loaded with a synthetic DCF prodrug was developed and characterized. Specifically, the prodrug was successfully synthetized by binding DCF to a glycine residue via solid phase peptide synthesis (SPPS) and then incorporated in an electrospun PLA scaffold. The drug encapsulation was verified using multiphoton microscopy (MPM) and its scaffold release was spectrophotometrically monitored and confirmed with MPM. The scaffold was further characterized with scanning electron microscopy (SEM), tensile testing and contact angle measurements. Its biocompatibility was verified by performing a cell proliferation assay and compared to PLA scaffolds containing the same amount of DCF sodium salt (DCFONa). Finally, the effect of the electrospun scaffolds on human dermal fibroblasts (HDFs) morphology and metabolism was investigated by combining MPM with fluorescence lifetime imaging microscopy (FLIM). The obtained results suggest that the obtained scaffold could be suitable for the controlled and targeted delivery of the synthesized prodrug for the treatment of AKs. Statement of Significance Electrospun scaffolds are of growing interest as materials for a controlled drug delivery. In this work, an electrospun polylactic acid scaffold containing a synthetically obtained Diclofenac prodrug is proposed as a novel substrate for the topical treatment of actinic keratosis. A controlled drug delivery targeted to the area of interest could enhance the efficacy of the therapy and favor the healing process. The prodrug was synthesized via solid phase, employing a clean and versatile approach to obtain Diclofenac derivatives. Here, we used multiphoton microscopy to image drug encapsulation within the fibrous scaffold and fluorescence lifetime imaging microscopy to investigate Diclofenac effects and potential mechanisms of action

Amyloidogenesis of proteolytic fragments of human elastin

Some polypeptides encoded by the C-terminal region of human tropoelastin gene have been demonstrated to be amyloidogenic in vitro. The biological relevance of this finding is still under investigation given that only limited evidence concerning the involvement of elastin in amyloidosis exists. Recent studies identified, by mass spectrometry, several elastin fragments produced from the cleavages made by some elastases in human elastin substrate. Some of these fragments are contained into the same polypeptide sequences previously demonstrated to be amyloidogenic. Our hypothesis is that the upregulation of elastases in inflammatory processes triggered, for example, by aging induces the release of elastin fragments potentially amyloidogenic. Therefore our aim in this study is to demonstrate if any of these fragments is amyloidogenic in vitro. At molecular level, CD, NMR, FTIR spectroscopies and MD simulations were used, while, at supramolecular level, Congo red binding assay and ThT fluorescence spectroscopy complemented with AFM microscopy were carried out. Our results show that the longest peptide, among those synthesized and mimicking the elastin fragments produced by elastases on human elastin, constituted of 22 residues, is able to aggregate into amyloid-like fibres. These findings support the hypothesis of amyloidogenesis of proteolytic fragments of elastin

Influence of the architecture on the molecular mobility of synthetic fragments inspired from human tropoelastin

This work deals with the vibrational, thermal and dielectric characterization of a synthetic peptide (S4) released during the proteolysis of human tropoelastin. This peptide was shown to form amyloid-like fibers implied in neurodegenerative pathologies. The comparison between the linear peptides and the associated amyloidlike fibers evidences the strong influence of the secondary structures on the physical structure and chain dynamics of these polypeptides

Heparan sulfates facilitate harmless amyloidogenic fibril formation interacting with elastin-like peptides

Heparan sulfates (HSs) modulate tissue elasticity in physiopathological conditions by interacting with various matrix constituents as tropoelastin and elastin-derived peptides. HSs bind also to protein moieties accelerating amyloid formation and influencing cytotoxic properties of insoluble fibrils. Interestingly, amyloidogenic polypeptides, despite their supposed pathogenic role, have been recently explored as promising bio-nanomaterials due to their unique and interesting properties. Therefore, we investigated the interactions of HSs, obtained from different sources and exhibiting various degree of sulfation, with synthetic amyloidogenic elastin-like peptides (ELPs), also looking at the effects of these interactions on cell viability and cell behavior using in vitro cultured fibroblasts, as a prototype of mesenchymal cells known to modulate the soft connective tissue environment. Results demonstrate, for the first time, that HSs, with differences depending on their sulfation pattern and chain length, interact with ELPs accelerating aggregation kinetics and amyloid-like fibril formation as well as self-association. Furthermore, these fibrils do not negatively affect fibroblasts' cell growth and parameters of redox balance, and influence cellular adhesion properties. Data provide information for a better understanding of the interactions altering the elastic component in aging and in pathologic conditions and may pave the way for the development of composite matrix-based biomaterials