The biomedical application of electrospun fibers is mainly in four aspects: drug-controlled release, biological dressing, tissue repair and enzyme immobilization.
Composite materials with multiple functions are the hotspots in the field of biomedicine .
Combination of 3D printing and traditional electrospinning techniques could bring a breakthrough for fabrication of considerably complex nanofiber-based 3D scaffolds/tissue constructs with appropriate chemical, mechanical, and biological cues in a spatially controlled manner .
Electrospinning has gained considerable attention in many fields due to its ability to produce continuous fibers from a variety of polymers and composites in a simple way. Electrospun nano fibers have many merits such as diverse chemical composition, easily adjustable structure, adjustable diameter, high surface area, high porosity, and good pore connectivity, which give them broad application prospects in the biomedical field.
Biological and medical applications
Many human tissues have limited regenerative capacity, thus, the injury and degeneration usually cause significant disability. In an attempt to improve the clinical outcome, drug delivery, tissue engineering, regenerative medicine, and regenerative engineering concepts have emerged aiming to regenerate damaged tissues and restore their functions in the past decades. Owing to the advances in material sciences, engineering, and life sciences, enormous progress has been made for tissue regeneration with better recapitulation of anatomical structures and functional recovery.
Great potencial for drug delivery applications
In drug delivery and regenerative medicine, scaffolds/substrates play a crucial role in controlling drug release rate, regulating cell behavior, and regenerating injured tissues. Scaffolds composed of electrospun fibers with diameters ranging from several nanometers to tens of micrometers are ideal owing to the biomimicry of extracellular matrix (ECM). In addition, electrospun fiber scaffolds offer distinct features including large surface area-to-volume ratio, high porosity, uniformity in fiber size, diversity in composition, flexibility in assembled structure, and ease of functionalization with bioactive molecules, making them promising candidates as carriers for drug delivery and scaffolds for regenerative medicine.
The drug delivery systems made of electrospun nanofibers have been new horizons in drug delivery. Up to date, a number of therapeutic agents including small molecular drugs and biological substances such as antibiotics, proteins, DNA, RNA, growth factors, and living cells have been incorporated to electrospun fibers through either encapsulation during electrospinning such as blended electrospinning, emulsion electrospinning, and coaxial electrospinning or surface modification post-electrospinning.The electrospun nanofiber scaffolds are suitable for topical drug delivery, transdermal drug delivery, and oral drug delivery, while short nanofibers/fragments are feasible for local injection to diseased sites in a minimal invasive way. In addition, electrospun nanofibers afford remarkable advantages in controlling drug release rate by varying the composition (e.g. hydrophobic and hydrophilic materials), microstructure (e.g. homogenous structure, core-sheath structure and multilayered structure), or macrostructure (e.g. stacked meshes). Recently, the emergence of stimuli-responsive nanofibers provided a novel strategy of controlled drug delivery and release temporally and spatially. 
Tissue regeneration and other applications
The biomimetic nanofiber scaffolds capable of imitating fiber morphology, ECM architecture, and biochemical cues may be ideal for tissue regeneration. Therefore, the use of electrospun nanofibers as scaffold in regenerative medicine has drawn a great deal of attention. The introduction of 3D printing technology holds tremendous promise for development of shape-specific fiber scaffolds to repair damaged tissues. In addition, the breakthroughs in stem cell biology, in particular for human induced pluripotent stem cells, and genome editing may facilitate tissue regeneration. 
Electrospun nanofibers have good application prospects in tissue repair, biological dressing, drug-controlled release and enzyme immobilization. Tissue repair is the main research direction in the field of biomedical applications, and electrospun fiber materials were first applied to vascular repair tissue engineering in 1978. They were then used for bone tissue, nerve tissue, tendon tissue, heart valves, urethral stents, skin, and cartilage. In recent years, electrospun nano-fibers have been widely used in the pharmaceutical field. A variety of drugs including antibiotics, proteins, DNA, RNA, growth factors and anticancer drugs have been loaded into electrospun nanofibers for disease treatment. In recent years, many kinds of enzyme have also been successfully immobilized in fibers by electrospinning. 
1. Tissue repair
Electrospinning enables the preparation of continuous ultrafine fibers with diameters similar to those of natural extracellular matrices (ECMs). Electrospun nanofiber scaffolds can thus mimic the structure of ECMs in humans to a great extent. Electrospun fiber membranes or fiber mats have high porosity, good pore connectivity, a large specific surface area and biocompatibility, which provide a good microenvironment for cell survival to help cells adhere, differentiate, and proliferate. The thickness, the three-dimensional structure, and mechanical properties of the electrospun nanofiber scaffold can be regulated by adjusting the electrospinning parameters. Moreover, bioactive molecules (such as growth factors, cell regulators, and even living cells) and inorganic particles (such as hydroxyapatite) could be added into to nano-scaffolds in electrospinning, which give electrospun fiber scaffolds a variety of functions. Electrospun nanofiber materials are widely used in the field of tissue repair such as trachea, nerves, skin, cartilage, bones, blood vessels, tendons, and ligaments.
Electrospun fibers have been used to repair a variety of tissues as shown above and summarized in Table 5. Current studies have shown that electrospun fibers mainly repair tissue by directly interfering with cell orientation and proliferation, affecting cell mobility, changing cell morphology, interfering with cell differentiation. However, these studies are far from enough. As a substitute for functional tissue, it is necessary to further deepen its action mechanism. 
2. Drug delivery
Electrospun nanofibers have many advantages as drug delivery systems, and have been studied for many years as transdermal, oral, injection dosage forms. Examples of electrospun fibers used to deliver multiple types of drugs are also given above and summarized in the Table 1. However, the study of drugs release mechanism and pharmacokinetics of drug-loaded electrospun nanofibers is still very few, which would limit the practical application. 
3. Biological dressings
Electrospun fibers have good gas permeability and can provide a biomimetic environment for skin cell regeneration during wound healing. The small pore size distribution of the fiber membrane can also effectively block the invasion of bacteria, which is suitable for skin dressings and artificial imitation skin (Fig. 8). In addition, the electrospun fiber membrane has a large specific surface area and can be loaded with drugs to promote the rapid recovery of damaged skin.
Electrospun fibers have made great progress in wound dressings, but there are still many areas need to be improved. For example, the fabrication of new structure nanofibers for wound healing, and the combination of electrospinning and 3D printing technology. The electrospun fibers can also be combined with electrical stimulation, pressure, magnetic force and other external forces to play a better role. 
4. Enzyme immobilization
The high specific surface area and porosity of the electrospun fibers can effectively alleviate the diffusion resistance of the matrix and greatly improve the catalytic ability of the loaded enzyme. The method of enzyme immobilization in electrospun fibers is mainly the surface loading method (such as the active functional group loading method, chemical crosslinking, and surface modification).
At present, the enzyme immobilization in electrospun fibers is mainly by surface loading method. Different loading modes lead to different binding capacities between enzymes and fibers. Considering new loading modes will be of great help to explore the applications of enzymes. 
5. Conclusions and Future Perspectives
Electrospinning offers a versatile and robust method for producing 1D nanofiber fragments, 1D nanofiber bundles/yarns, 2D nanofiber membranes with patterned structure, and 3D fiber scaffolds with highly porous structures. Owing to the biomimicry, these electrospun nanofiber materials have opened up numerous opportunities for the biomedical applications including drug delivery, control of cell behavior, and regenerative medicine.
Combination of 3D printing and traditional electrospinning techniques could bring a breakthrough for fabrication of considerably complex nanofiber-based 3D scaffolds/tissue constructs with appropriate chemical, mechanical, and biological cues in a spatially controlled manner.
Regarding to regenerative medicine, the innovation in electrospun fiber-based scaffolds has provided better mimicry of the structure and effective drug/growth factor/cell delivery, resulting in robust tissue regeneration. However, full repair and regeneration has not been achieved. In the future, introduction of programmed delivery system into nanofiber-based tissue engineering scaffolds would create exciting opportunities for tissue regeneration. In recent years, the stem cell-based therapy holds great potential in regenerative medicine. The success of the stem cell transplantation strategy still needs long-term preclinical studies. Use of nanofiber scaffolds to optimize the microenvironment of stem cells is promising to favor stem cell therapy. 
 Y. Sun, S. Cheng, W. Lu, Y. Wang, P. Zhang, and Q. Yao, “Electrospun fibers and their application in drug controlled release, biological dressings, tissue repair, and enzyme immobilization,” RSC Advances. 2019, doi: 10.1039/c9ra05012d.
 S. Hinderer et al., “Engineering of fibrillar decorin matrices for a tissue-engineered trachea,” Biomaterials, 2012, doi: 10.1016/j.biomaterials.2012.03.075.
 K. E. Kador et al., “Tissue engineering the retinal ganglion cell nerve fiber layer,” Biomaterials, 2013, doi: 10.1016/j.biomaterials.2013.02.027.
 Y. Gustafsson et al., “Viability and proliferation of rat MSCs on adhesion protein-modified PET and PU scaffolds,” Biomaterials, 2012, doi: 10.1016/j.biomaterials.2012.07.060.
 C. Vaquette, W. Fan, Y. Xiao, S. Hamlet, D. W. Hutmacher, and S. Ivanovski, “A biphasic scaffold design combined with cell sheet technology for simultaneous regeneration of alveolar bone/periodontal ligament complex,” Biomaterials, 2012, doi: 10.1016/j.biomaterials.2012.04.038.
 Y. Xi, J. Ge, Y. Guo, B. Lei, and P. X. Ma, “Biomimetic Elastomeric Polypeptide-Based Nanofibrous Matrix for Overcoming Multidrug-Resistant Bacteria and Enhancing Full-Thickness Wound Healing/Skin Regeneration,” ACS Nano, 2018, doi: 10.1021/acsnano.8b01152.
 B. Luo, L. Tian, N. Chen, S. Ramakrishna, N. Thakor, and I. H. Yang, “Electrospun nanofibers facilitate better alignment, differentiation, and long-term culture in an: In vitro model of the neuromuscular junction (NMJ),” Biomater. Sci., 2018, doi: 10.1039/c8bm00720a.
 Y. Wang, W. Cui, J. Chou, S. Wen, Y. Sun, and H. Zhang, “Electrospun nanosilicates-based organic/inorganic nanofibers for potential bone tissue engineering,” Colloids Surfaces B Biointerfaces, 2018, doi: 10.1016/j.colsurfb.2018.08.032.
 X. Jing, H. Y. Mi, X. C. Wang, X. F. Peng, and L. S. Turng, “Shish-Kebab-structured poly(ε-caprolactone) nanofibers hierarchically decorated with chitosan-poly(ε-caprolactone) copolymers for bone tissue engineering,” ACS Appl. Mater. Interfaces, 2015, doi: 10.1021/acsami.5b00900.
 S. Mirzaei, A. Karkhaneh, M. Soleimani, A. Ardeshirylajimi, H. Seyyed Zonouzi, and H. Hanaee-Ahvaz, “Enhanced chondrogenic differentiation of stem cells using an optimized electrospun nanofibrous PLLA/PEG scaffolds loaded with glucosamine,” J. Biomed. Mater. Res. – Part A, 2017, doi: 10.1002/jbm.a.36104.
 J. F. Piai et al., “Chondroitin sulfate immobilization at the surface of electrospun nanofiber meshes for cartilage tissue regeneration approaches,” Appl. Surf. Sci., 2017, doi: 10.1016/j.apsusc.2016.12.135.
 D. Liu, S. Liu, X. Jing, X. Li, W. Li, and Y. Huang, “Necrosis of cervical carcinoma by dichloroacetate released from electrospun polylactide mats,” Biomaterials, 2012, doi: 10.1016/j.biomaterials.2012.02.062.
 R. Ramírez-Agudelo et al., “Hybrid nanofibers based on poly-caprolactone/gelatin/hydroxyapatite nanoparticles-loaded Doxycycline: Effective anti-tumoral and antibacterial activity,” Mater. Sci. Eng. C, 2018, doi: 10.1016/j.msec.2017.08.012.
 J. Li et al., “Locally Deployable Nanofiber Patch for Sequential Drug Delivery in Treatment of Primary and Advanced Orthotopic Hepatomas,” ACS Nano, 2018, doi: 10.1021/acsnano.8b01729.
 H. L. Che et al., “Simultaneous drug and gene delivery from the biodegradable poly(ε-caprolactone) nanofibers for the treatment of liver cancer,” J. Nanosci. Nanotechnol., 2015, doi: 10.1166/jnn.2015.11233.
 Y. Yuan, K. Choi, S. O. Choi, and J. Kim, “Early stage release control of an anticancer drug by drug-polymer miscibility in a hydrophobic fiber-based drug delivery system,” RSC Adv., 2018, doi: 10.1039/c8ra01467a.
 I. Bonadies et al., “Electrospun core/shell nanofibers as designed devices for efficient Artemisinin delivery,” Eur. Polym. J., 2017, doi: 10.1016/j.eurpolymj.2017.02.015.
 B. Wang et al., “Local in vitro delivery of rapamycin from electrospun PEO/PDLLA nanofibers for glioblastoma treatment,” Biomed. Pharmacother., 2016, doi: 10.1016/j.biopha.2016.08.033.
 L. Ma et al., “Trap effect of three-dimensional fibers network for high efficient cancer-cell capture,” Adv. Healthc. Mater., 2015, doi: 10.1002/adhm.201400650.
 T. Potrč et al., “Electrospun polycaprolactone nanofibers as a potential oromucosal delivery system for poorly water-soluble drugs,” Eur. J. Pharm. Sci., 2015, doi: 10.1016/j.ejps.2015.04.004.
 M. F. Canbolat, A. Celebioglu, and T. Uyar, “Drug delivery system based on cyclodextrin-naproxen inclusion complex incorporated in electrospun polycaprolactone nanofibers,” Colloids Surfaces B Biointerfaces, 2014, doi: 10.1016/j.colsurfb.2013.11.021.
 H. Lu, Q. Wang, G. Li, Y. Qiu, and Q. Wei, “Electrospun water-stable zein/ethyl cellulose composite nanofiber and its drug release properties,” Mater. Sci. Eng. C, 2017, doi: 10.1016/j.msec.2017.02.004.
 A. O. Basar, S. Castro, S. Torres-Giner, J. M. Lagaron, and H. Turkoglu Sasmazel, “Novel poly(ε-caprolactone)/gelatin wound dressings prepared by emulsion electrospinning with controlled release capacity of Ketoprofen anti-inflammatory drug,” Mater. Sci. Eng. C, 2017, doi: 10.1016/j.msec.2017.08.025.
 M. M. Castillo-Ortega, A. G. Montaño-Figueroa, D. E. Rodríguez-Félix, G. T. Munive, and P. J. Herrera-Franco, “Amoxicillin embedded in cellulose acetate-poly (vinyl pyrrolidone) fibers prepared by coaxial electrospinning: Preparation and characterization,” Mater. Lett., 2012, doi: 10.1016/j.matlet.2012.02.093.
 G. Yang, J. Wang, L. Li, S. Ding, and S. Zhou, “Electrospun micelles/drug-loaded nanofibers for time-programmed multi-agent release,” Macromol. Biosci., 2014, doi: 10.1002/mabi.201300575.
 Š. Zupančič et al., “Impact of PCL nanofiber mat structural properties on hydrophilic drug release and antibacterial activity on periodontal pathogens,” Eur. J. Pharm. Sci., 2018, doi: 10.1016/j.ejps.2018.07.024.
 S. Chen et al., “Twisting electrospun nanofiber fine strips into functional sutures for sustained co-delivery of gentamicin and silver,” Nanomedicine Nanotechnology, Biol. Med., 2017, doi: 10.1016/j.nano.2017.01.016.
 D. de Cassan et al., “Attachment of nanoparticulate drug-release systems on poly(ε-caprolactone) nanofibers via a graftpolymer as interlayer,” Colloids Surfaces B Biointerfaces, 2018, doi: 10.1016/j.colsurfb.2017.12.050.
 D. Han, S. Sherman, S. Filocamo, and A. J. Steckl, “Long-term antimicrobial effect of nisin released from electrospun triaxial fiber membranes,” Acta Biomater., 2017, doi: 10.1016/j.actbio.2017.02.029.
 M. E. Wright, I. C. Parrag, M. Yang, and J. P. Santerre, “Electrospun polyurethane nanofiber scaffolds with ciprofloxacin oligomer versus free ciprofloxacin: Effect on drug release and cell attachment,” J. Control. Release, 2017, doi: 10.1016/j.jconrel.2017.02.008.
 J. Xue et al., “Electrospun microfiber membranes embedded with drug-loaded clay nanotubes for sustained antimicrobial protection,” ACS Nano, 2015, doi: 10.1021/nn506255e.
 L. Martínez-Ortega, A. Mira, A. Fernandez-Carvajal, C. Reyes Mateo, R. Mallavia, and A. Falco, “Development of a new delivery system based on drug-loadable electrospun nanofibers for psoriasis treatment,” Pharmaceutics, 2019, doi: 10.3390/pharmaceutics11010014.
 A. Haider, K. C. Gupta, and I. K. Kang, “Morphological effects of HA on the cell compatibility of electrospun HA/PLGA composite nanofiber scaffolds,” Biomed Res. Int., 2014, doi: 10.1155/2014/308306.
 M. G. Lancina, R. K. Shankar, and H. Yang, “Chitosan nanofibers for transbuccal insulin delivery,” J. Biomed. Mater. Res. – Part A, 2017, doi: 10.1002/jbm.a.35984.
 Y. Zhu, M. Pyda, and P. Cebe, “Electrospun fibers of poly(l-lactic acid) containing lovastatin with potential applications in drug delivery,” J. Appl. Polym. Sci., 2017, doi: 10.1002/app.45287.
 J. Chen et al., “Self-assembled liposome from multi-layered fibrous mucoadhesive membrane for buccal delivery of drugs having high first-pass metabolism,” Int. J. Pharm., 2018, doi: 10.1016/j.ijpharm.2018.05.062.
 G. Z. Yang, J. J. Li, D. G. Yu, M. F. He, J. H. Yang, and G. R. Williams, “Nanosized sustained-release drug depots fabricated using modified tri-axial electrospinning,” Acta Biomater., 2017, doi: 10.1016/j.actbio.2017.01.069.
 S. Chen, R. Li, X. Li, and J. Xie, “Electrospinning: An enabling nanotechnology platform for drug delivery and regenerative medicine,” Adv. Drug Deliv. Rev., 2018, doi: 10.1016/j.addr.2018.05.001.
(2014) Electrospinning for regenerative medicine: A review of the main topics, Drug Discovery Today, doi:10.1016/j.drudis.2014.03.024
(2015) Biodegradable polymers for electrospinning: Towards biomedical applications, Materials Science and Engineering C, doi:10.1016/j.msec.2014.04.051
(2015) Preparation of animal polysaccharides nanofibers by electrospinning and their potential biomedical applications, Journal of Biomedical Materials Research – Part A, doi:10.1002/jbm.a.35187
(2016) In pursuit of functional electrospun materials for clinical applications in humans, Therapeutic Delivery, doi:10.4155/tde-2016-0017
(2016) Biomedical applications of electrospun polycaprolactone fiber mats, Polymers for Advanced Technologies, doi:10.1002/pat.3876
(2016) Electrospinning applications from diagnosis to treatment of diabetes, RSC Advances, doi:10.1039/c6ra15252j
(2017) Robot-aided electrospinning toward intelligent biomedical engineering, Robotics and Biomimetics, doi:10.1186/s40638-017-0075-1
(2017) Medical applications of functional electrospun nanofibers -A review, Key Engineering Materials, doi:10.4028/www.scientific.net/KEM.752.132
(2017) Electrospinning based functional nanofibers for biomedical applications, Journal of Biomaterials and Tissue Engineering, doi:10.1166/jbt.2017.1605
(2018) Biomedical applications of polyurethane materials and coatings, Transactions of the Institute of Metal Finishing, doi:10.1080/00202967.2018.1450209
(2018) Comprehensive review on electrospinning of starch polymer for biomedical applications, International Journal of Biological Macromolecules, doi:10.1016/j.ijbiomac.2017.08.079
(2018) A comprehensive review summarizing the effect of electrospinning parameters and potential applications of nanofibers in biomedical and biotechnology, Arabian Journal of Chemistry, doi:10.1016/j.arabjc.2015.11.015
(2018) From nano to micro to macro: Electrospun hierarchically structured polymeric fibers for biomedical applications, Progress in Polymer Science, doi:10.1016/j.progpolymsci.2017.12.003
(2018) Trends in polymeric electrospun fibers and their use as oral biomaterials, Experimental Biology and Medicine, doi:10.1177/1535370218770404
(2018) A comprehensive review summarizing the effect of electrospinning parameters and potential applications of nanofibers in biomedical and biotechnology, Arabian Journal of Chemistry
(2018) Electrospinning of plant oil-based, non-isocyanate polyurethanes for biomedical applications, Journal of Applied Polymer Science, doi:10.1002/app.46464
(2019) Biomedical applications of chitosan electrospun nanofibers as a green polymer – Review, Carbohydrate Polymers, doi:10.1016/j.carbpol.2018.12.011
(2019) ELECTROSPUN BIOMATERIALS AND RELATED TECHNOLOGIES, Jurnal Teknosains, doi:10.22146/teknosains.46652
(2019) Magnesium-based composites and alloys for medical applications: A review of mechanical and corrosion properties, Journal of Alloys and Compounds, doi:10.1016/j.jallcom.2019.04.080
(2019) Electrospun fibers and their application in drug controlled release, biological dressings, tissue repair, and enzyme immobilization, RSC Advances, doi:10.1039/c9ra05012d
(2019) Fabrication of porous fibers via electrospinning: strategies and applications, Polymer Reviews, doi:10.1080/15583724.2019.1688830
(2019) Electrospun polymer biomaterials, Progress in Polymer Science, doi:10.1016/j.progpolymsci.2019.01.002
(2020) Development of highly porous, Electrostatic force assisted nanofiber fabrication for biological applications, International Journal of Polymeric Materials and Polymeric Biomaterials, doi:10.1080/00914037.2019.1581197