Tissue engineering holds great promise to develop functional constructs resembling the structural organization of native tissues to improve or replace biological functions, with the ultimate goal of avoiding organ transplantation. In tissue engineering, cells are often seeded into artificial structures capable of supporting three-dimensional (3D) tissue formation. An optimal scaffold for tissue-engineering applications should mimic the mechanical and functional properties of the extracellular matrix (ECM) of those tissues to be regenerated. Amongst the various scaffolding techniques, electrospinning is an outstanding one which is capable of producing non-woven fibrous structures with dimensional constituents similar to those of ECM fibres. In recent years, electrospinning has gained widespread interest as a potential tissue-engineering scaffolding technique and has been discussed in detail in many studies. So why this review? Apart from their clear advantages and extensive use, electrospun scaffolds encounter some practical limitations, such as scarce cell infiltration and inadequate mechanical strength for load-bearing applications. A number of solutions have been offered by different research groups to overcome the above-mentioned limitations. In this review, we provide an overview of the limitations of electrospinning as a tissue-engineered scaffolding technique, with emphasis on possible resolutions of those issues. Copyright © 2015 John Wiley & Sons, Ltd.

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Osteochondral tissue regeneration is a complicated field due to the distinct properties and healing potential of osseous and chondral phases. In a natural osteochondral region, the composition, mechanics, and structure vary smoothly from bony to cartilaginous phase. Therefore, a homogeneous scaffold cannot satisfy the complexity of the osteochondral matrix. In essence, a natural extracellular matrix is composed of fibrous proteins elongated into a gelatinous background. A hydrogel/fiber scaffold possessing gradient in both phases would be of the utmost interest to imitate tissue arrangement of a native osteochondral interface. However, there are limited research works that exploit hydrogel/fiber scaffolds for osteochondral restoration. In the present review, currently used fibrous or gelatinous scaffolds for osteochondral damages are discussed. Moreover, superiority of using gradient hydrogel/fiber composites for osteochondral regeneration and practical approaches to develop those scaffolds is debated.

Hydrogel/fiber composites have emerged as compelling scaffolds for regeneration purposes. Any biorelated modification or feature may endow more regenerative functionality to these composites. In the present study, a hydrogel/fiber scaffold possessing electrical conductivity in both phases, hydrogel and fiber, has been prepared and evaluated. Fiber component possessed electrical conductivity due to the presence of polyaniline (PANi) and hydrogel fraction thanks to the presence of graphene nanoparticles. PANi based fibers were processed through electrospinning and transformed into a three-dimensional structure through ultrasonication. The hydrogel precursor solution composed of oxidized polysaccharides, gelatin and graphene with predesigned ratio was added to fibers and left to gel. The results of assessments on pristine hydrogel and hydrogel/fiber denoted that inclusion of conducting fibers into hydrogel increased elastic modulus, roughness and electrical conductivity, whereas decreased hydrophilicity. Moreover, the results showed that hydrogel/fiber composite better supported human osteoblast-like cell adhesion, proliferation, and morphology comparing hydrogel alone. In a nutshell, the presence of gel/fiber architecture along with electrical conductivity may lead the scaffold to be very promising for bone regeneration. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 718-724, 2018.

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Oxygen is an important signaling molecule which affects many behaviors of bone progenitor cells. Oxygen releasing biomaterials depend on their material and design are able to provide and modulate the desired oxygen for cells. To date, many oxygen releasing vehicles have been developed by incorporating microsized calcium peroxide (CPO) into polymeric matrixes. However, an oxygen releasing system based on nano CPO is still lacking. Not only can nanosized CPO provide more controllable oxygen release, but also can be loaded in vehicles of different shapes and sizes. Current research was conducted to take the advantages of nanomaterials as oxygen releasing components. To this end, CPO nanoparticles were synthesized using a hydrolysisprecipitation procedure and then loaded into the poly (lactide-co-glycolide) (PLGA) matrix via an electrospray process. The surface of PLGA/CaO 2 particles was decorated with amine functionalities to render them more bioactive through a controlled aminolysis reaction. The studies on PLGA/CaO 2 microparticles revealed that biconcave disk-like morphology with a mean diameter of 5.3 μm was formed. The particles persistently provide oxygen content of 35-67.5 mmHg up to 14 days which lies within the acceptable range for bone tissue engineering applications. PLGA/CaO 2 microparticles induced 208 and 76% increase in number of viable mesenchymal cells on 6th and 14th days of cell seeding comparing PLGA counterparts. Furthermore, the expression of two bone biomarkers, that is, alkaline phosphatase and osteocalcin, at protein level as well as the extent of calcium deposition was increased in the presence of PLGA/CaO 2 microparticles compared to PLGA ones. K E Y W O R D Sbone tissue engineering, calcium peroxide, microparticle, oxygen

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