Tissue engineering uses a combination of cell biology, chemistry, and biomaterials to fabricate three dimensional (3D) tissues that mimic the architecture of extracellular matrix (ECM) comprising diverse interwoven nanofibrous structure. Among several methods for producing nanofibrous scaffolds, electrospinning has gained intense interest because it can make nanofibers with a porous structure and high specific surface area. The processing and solution parameters of electrospinning can considerably affect the assembly and structural morphology of the fabricated nanofibers. Electrospun nanofibers can be made from natural or synthetic polymers and blending them is a straightforward way to tune the functionality of the nanofibers. Furthermore, the electrospun nanofibers can be functionalized with various surface modification strategies. In this review, we highlight the latest achievements in fabricating electrospun nanofibers and describe various ways to modify the surface and structure of scaffolds to promote their functionality. We also summarize the application of advanced polymeric nanofibrous scaffolds in the regeneration of human bone, cartilage, vascular tissues, and tendons/ligaments.

Current advances in biomaterial fabrication techniques have broadened their application in different realms of biomedical engineering, spanning from drug delivery to tissue engineering. The success of biomaterials depends highly on the ability to modulate cell and tissue responses, including cell adhesion, as well as induction of repair and immune processes. Thus, most recent approaches in the field have concentrated on functionalizing biomaterials with different biomolecules intended to evoke cell- and tissue-specific reactions. Marine mussels produce mussel adhesive proteins (MAPs), which help them strongly attach to different surfaces, even under wet conditions in the ocean. Inspired by mussel adhesiveness, scientists discovered that dopamine undergoes self-polymerization at alkaline conditions. This reaction provides a universal coating for metals, polymers, and ceramics, regardless of their chemical and physical properties. Furthermore, this polymerized layer is enriched with catechol groups that enable immobilization of primary amine or thiol-based biomolecules via a simple dipping process. Herein, this review explores the versatile surface modification techniques that have recently been exploited in tissue engineering and summarizes polydopamine polymerization mechanisms, coating process parameters, and effects on substrate properties. A brief discussion of polydopamine-based reactions in the context of engineering various tissue types, including bone, blood vessels, cartilage, nerves, and muscle, is also provided.

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Over the past decades, hydrogels have been widely studied as biomaterials for various biomedical applications like implants, drugs and cell delivery carriers because of their high biocompatibility, high water contents and excellent permeability for nutrients and metabolites. Especially, in situ forming hydrogel systems have received much attention because of their easy application based on minimal invasive techniques. Chemical cross-linking systems fabricated using enzymatic reactions have various advantages, such as high biocompatibility and easy control of reaction rates under mild condition. In this study, we report enzyme-triggered injectable and biodegradable hydrogels composed of Tetronic-tyramine conjugates. The Tetronic-tyramine conjugates were synthesized by first reacting Tetronic with succinic anhydride and subsequent conjugation with tyramine using DCC/NHS as coupling reagents. The chemical structure of Tetronic-succinic anhydride-tyramine (Tet-SA-TA) copolymer was characterized by (1)H NMR and FTIR. The hydrogels were prepared from a Tet-SA-TA solution above 3 wt % in the presence of horseradish peroxidase (HRP) and H(2)O(2) under physiological conditions. Their mechanical property, gelation time, swelling ratio and degradation time were evaluated at different polymer, HRP, and H(2)O(2) concentrations. In addition, a cyto-compatibility study was performed using the MC3T3-E1 cell line. In the cytotoxicity test, it was clear that the Tet-SA-TA hydrogel had no apparent cytotoxicity except for the hydrogel formed with 0.25 wt % H(2)O(2) due to the cytotoxicity of residual H(2)O(2). In conclusion, the obtained results demonstrated that the Tet-SA-TA hydrogel has great potential for use as an injectable scaffold for tissue engineering and as a drug carrier for controlled drug delivery systems.

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Most polymeric vascular prosthetic materials have low patency rate for replacement of small diameter vessels (<5 mm), mainly due to failure to generate healthy endothelium. In this study, we present polydopamine-mediated immobilization of growth factors on the surface of polymeric materials as a versatile tool to modify surface characteristics of vascular grafts potentially for accelerated endothelialization. Polydopamine was deposited on the surface of biocompatible poly(L-lactide-co-ε-caprolactone) (PLCL) elastomer, on which vascular endothelial growth factor (VEGF) was subsequently immobilized by simple dipping. Surface characteristics and composition were investigated by using scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Immobilization of VEGF on the polydopamine-deposited PLCL films was effective (19.8 ± 0.4 and 197.4 ± 19.7 ng/cm(2) for DPv20 and DPv200 films, respectively), and biotin-mediated labeling of immobilized VEGF revealed that the fluorescence intensity increased as a function of the concentration of VEGF solution. The effect of VEGF on adhesion of HUVECs was marginal, which may have been masked by polydopamine layer that also enhanced cell adhesion. However, VEGF-immobilized substrate significantly enhanced proliferation of HUVECs for over 7 days of in vitro culture and also improved their migration. In addition, immobilized VEGF supported robust cell to cell interactions with strong expression of CD 31 marker. The same process was effective for immobilization of basic fibroblast growth factor, demonstrating the robustness of polydopamine layer for secondary ligation of growth factors as a simple and novel surface modification strategy for vascular graft materials.

Composite nanofibers of poly(caprolactone) (PCL) and gelatin crosslinked with genipin are prepared. The contact angles and mechanical properties of crosslinked PCL-gelatin nanofibers decrease as the gelatin content increases. The proliferation of myoblasts is higher in the crosslinked PCL-gelatin nanofibers than in the PCL nanofibers, and the formation of myotubes is only observed on the crosslinked PCL-gelatin nanofibers. The expression level of myogenin, myosin heavy chain, and troponin T genes is increased as the gelatin content is increased. The results suggest that PCL-gelatin nanofibers crosslinked with genipin can be used as a substrate to modulate proliferation and differentiation of myoblasts, presenting potential applications in muscle tissue engineering.

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