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Elastic fibers are a fundamental requirement for tissue-engineered equivalents of physiologically elastic native tissues. Here, a simple one-step electrospinning approach is developed, combining i) catalyst-free click chemistry, ii) coaxial electrospinning, and iii) recombinant elastin-like polymers as a relevant class of biomaterials. Water-stable elastin-like fibers are obtained without the use of cross-linking agents, catalysts, or harmful organic solvents. The fibers can be directly exposed to an aqueous environment at physiological temperature and their morphology maintained for at least 3 months. The bioactivity of the fibers is demonstrated with human vascular cells and the potential of the process for vascular tissue engineering is shown by fabricating small-diameter tubular fibrous scaffolds. Moreover, highly porous fluffy 3D constructs are obtained without the use of specially designed collectors or sacrificial materials, further supporting their applicability in the biomedical field. Ultimately, the strategy that is developed here may be applied to other click systems, contributing to expanding their potential in medical technology., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Herein we present a system to obtain fibers from clickable elastin-like recombinamers (ELRs) that crosslink in situ during the electrospinning process itself, with no need for any further treatment to stabilize them. These ELR-click fibers are completely stable under in vitro conditions. A wrinkled fiber morphology is obtained. In addition to a random fiber orientation, oriented fibers with a high degree of alignment and coherence can also be obtained by using a rotational electrode. The production of multicomponent fibers means that different functionalities, such as cell-adhesion domains (RGD peptides), can be incorporated into them. In a subsequent study, two main cell lines present in the dermis and epidermis, namely keratinocytes and fibroblasts, were cultured on top of the ELR-click fibers. Adhesion, proliferation, fluorescence, immunostaining and histology studies showed the cytocompatibility of these scaffolds, thus suggesting their possible use for wound dressings in skin tissue engineering applications., Statement of Significance: For the first time stable electrospun bioactive fibers are obtained by the in situ mixing of two "clickable" ELR components previously described by Gonzalez et al (Acta Biomaterialia 2014). This work describes an efficient system to prepare fibrous scaffolds based on peptidic polymers by electrospinning without the need of crosslinking agents that could be harmful for cells or living tissues. These bioactive fibers support cell growth due to the inclusion of RGD motifs (Staubli et al. Biomaterials 2017). Finally, the in vitro biocompatibility of the two main cell types found in the outer layers of skin, fibroblasts and keratinocytes, indicates that this system is of great interest to prepare elastic artificial skin substitutes for wound healing applications., (Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

The study involves design and synthesis of three different elastin like polypeptide (ELP) gene monomers namely ELP1, ELP2 and ELP3 that encode for ELP proteins. The formed ELPs were assessed as an ideal nerve conduit for peripheral nerve regeneration. ELP1 was constructed with a small elongated pentapeptide carrying VPGVG sequence to mimic the natural polypeptide ELP. The ELP2 was designed by the incorporation of 4-penta peptide chains to improve the biocompatibility and mechanical strength. Thus, the third position in unique VPGVG was replaced with alanine to VPAVG and in a similar way modified to VPGKG, VPGEG and VPGIG with the substitution of lysine, glutamic acid and isoleucine. In ELP3, fibronectin C5 domain endowed with REDV sequence was introduced to improve the cell attachment. The ELP1, ELP2 and ELP3 proteins expressed by Escherichia coli were purified by inverse transition cycling (ITC). The purified ELPs were confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and western blotting. The Schwann cell (SC) morphology and cell adhesion were assessed by fabrication of ELP membrane cross-linked with glutaraledhyde. The Schwann cell proliferation was measured by WST-1 assay. Immunofluorostaining of Schwann cells was accomplished with SC specific phenotypic marker, S100., (Copyright © 2014 Elsevier B.V. All rights reserved.)