The choice of material for tissue engineering applications depends upon the type of scaffold required. The correct material to fulfill the requirement of specific mechanical properties and degradation times required for the particular application [5]. Polymer are the main source materials of electrospun nanofibers. Certain of the synthetic and natural polymers have been introduced widely to electrospinning technique for regenerative medicine. Aliphatic polyesters, such as PCL, poly(lactide) (PLA), and their copolymers and blends, are some of the many biodegradable synthetic polymers that have been electrospun. By adjusting electrospinning parameters such as voltage, distance between the electrodes, and flow rate of the solution during electrospinning, and polymer solution properties, such as viscosity and conductivity, most of the biocompatible polymers can be electrospun (e.g. Poly(L-lactic acid) (PLLA), PLGA).

Compared with synthetic polymers, natural biopolymers have good biocompatibility and provide many of the instructive cues required by the cells for attachment and proliferation; however, they tend to display poor processability, which needs to be modified for better electrospinnability. For instance, Zhang et al. have tried to improve the electrospun processability of gelatin by modifying the solubility of gelatin at elevated temperature and the degree of cross-linking of the resultant gelatin fibers [6].

Besides polymer nanofibers, ceramic nanofibers were also fabricated using electrospinning. For example, Zhang et al. developed woven-bone-like β-TCP fibers by sol–gel electrospinning [7]. Optimization studies were conducted in terms of sol–gel synthesis and the electrospinning process, to fabricate electrospun nanofibrous scaffolds with pure β-TCP fibers that mimic the mineralized collagen fibrils in woven bone in size [7].

The formation of core/shell nanofibers by coaxial electrospinning was first reported by [20]. This technique proved to be very versatile not only for the encapsulation of biorelevant molecules and nanocomposites but also for modifying the surfaces of electrospun fibers. The effect of nanofiber surface coatings on the cell-proliferation behavior was studied by Zhang et al. studied the effect of nanofiber surface coatings on cell-proliferation behavior the coaxial electrospinning technique [21]. They produced collagen coated PCL nanofibers. Coatings of collagen on PCL were shown to favor proliferation of human dermal fibroblasts and also encouraged cell migration inside the scaffolds. Using a similar approach, biodegradable fibrous scaffolds composed of gelatin coated PCL were prepared by Zhao et al. by coaxial electrospinning [22]. More recently, Sun et al. developed core–shell PAN–PMMA nanofibers by coaxial electrospinning [23].

Bioactive factors-loaded microparticles can generally be achieved by two different electrospray approaches: coaxial or emulsion electrospray. Coaxial electrospray was first reported by Loscertales et al. [24]. Two immiscible solutions are coaxially and simultaneously electrosprayed through two separate feeding channels into one nozzle. The eventual jet, by which the outer polymeric solution encapsulates the inner proteinaceous liquid, breaks into droplets to generate microparticles with core–shell structure. This technique is preferred for preparing protein-loaded microcapsules, because it totally eliminates the emulsion step that is basically unsuitable for sensitive biomacromolecules [25, 26]. Coaxial electrospray is envisioned a promising approach to prepare biomacromolecule-loaded microcapsules for controlled drug delivery applications.

Emulsion electrospray involves mixing of an aqueous solution containing proteins with immiscible polymeric solution by ultrasonication [27, 28]. Compared with other conventional manufacture methods, the second emulsion or high temperature is omitted in emulsion electrospray. It increases the drug-loading efficiency and is suited for encapsulation of thermosensitive bioactive compounds.

Low-temperature plasma treatment has been shown to be a convenient and effective way to modify surfaces to improve the hydrophilicity of biomaterials, thus increasing their biocompatibility and facilitate cell attachment [31, 32]. Wan et al. reported that ammonia plasma treatment significantly increased the hydrophilicity of PLA scaffolds and resulted in enhanced cell adhesion and proliferation of mouse 3T3 fibroblasts [33]. D’Sa et al. reported that improved hydrophilicity of PMMA surfaces by plasma treatment increased adsorption of proteins and promoted actin stress fiber formation [34]. Moreover, plasma technique was found to modify levels of chemical groups, such as –COOH, –OH, or –NH₂ on scaffold surfaces, thereby influencing the cell–substrate interactions. For example, human umbilical vein endothelial cell (HUVEC) adhesion was improved by plasma treatment of PLA through the control of carbon and oxygen concentration [35], and human embryonic palatal mesenchyme (HEPM) cell proliferation was increased by plasma-treated poly(ether ether ketone) (PEEK) through assembling amino groups on the surface [36]. Amino-rich PLA surfaces created by plasma treatment were also reported to promote osteogenic differentiation of MC3T3-E1 cells [32]. More recently, Liu et al. investigated the effects of plasma treatment on the surface of PLLA nanofibrous membranes, and the subsequent dose-dependent cellular response and osteogenesis of MSCs were clarified preliminary [37]. These results support the feasibility of plasma technology to regulate the biological functions of biomaterials.

In addition to encapsulation of inorganic materials to improve the properties of fibrous materials, depositing inorganic phase materials i.e. biomineralization on the surface of polymeric nanofibers to form uniform coatings is an alternative methods. Biomineralization on the nanofiber surface can not only enhance its mechanical properties, but also provide a favorable substrate for cell proliferation and osteogenic differentiation. Ramakrishna and co-workers mineralized electrospun PLGA/collagen fibrous scaffolds, and the presence of the functional groups of collagen significantly hastened n-HA deposition in comparison with pure PLGA fibrous scaffolds [38]. The use of simulated body fluid (SBF), a kind of solution with ionic concentration closely resembling human blood plasma to biomimetically coat the composite fibers with apatite layers should be a good choice.

In principle, the morphology and grain size of minerals deposited on the nanofibers can be tailored by controlling the composition of the mineralized solution, the surface charge of substrate and the surface chemical properties. Recently, Cai et al. reported biomineralization of electrospun poly(l-lactic acid)/gelatin composite fibrous scaffold by using a supersaturated simulated body fluid with continuous CO₂ bubbling [39]. They found that the mineralites could be formed heterogeneously in the 5× SBF with CO₂ bubbling.

Nature is a source of inspiration for scientists and engineers to design advanced functional materials. Very weak local magnetic fields exist in living organisms and various organs in humans. Earlier clinical research showed that the magnetic field might be beneficial for enhancing bone tissue regeneration though mechanisms that have not yet been clarified.

In recent years, interest in magnetic biomimetic scaffolds for tissue engineering has increased considerably. Magnetic nanoparticles are of great interest owing to their potential biomedical applications [40, 41], such as cell expansion, cell sheets construction, magnetic cell seeding, as drug delivery vehicles and for hyperthermia treatment. For bone regenerative research, electrospinning technique has been used successfully to fabricate magnetic fibrous scaffolds, including Fe₃O₄/PVA nanofibers [42], Fe₃O₄/CNF, and FePt/PCL nanofibers. More recently, Wei et al. fabricated magnetic biodegradable Fe₃O₄/CS/PVA nanofibrous membranes, which promoted MG63 cells adhesion and proliferation on these membranes [43]. These results support the feasibility of incorporating magnetic nanoparticles into polymer nanofibers to regulate the biological functions of biomaterials.