ELECTROSPUN NANOFIBERS FOR DRUG DELIVERY

With the accumulative evidence on the unique physical, chemical, and biological properties of materials that occur exclusively at the nanoscale, there is great interest in identifying, controlling, and manipulating various parameters to engineer the next generation of materials. In the biomedical regime, especially in tissue regeneration, the primary motive for using nanostructured materials comes from the premise that the native extracellular matrix (ECM) imparts instructive physical and biological cues to cells at a similar scale (Discher et al., 2009). Thus, the creation of an in vitro microenvironment that can capture the key physicochemical features of native ECM would lead to predictable cell responses in vivo. It has been shown that cells can respond to stimuli at different length scales, from nanometer to millimeter (Lutolf and Hubbell, 2005). Scaffold fabrications, likewise, have involved the incorporation of physical or chemical cues at different scales. Sophisticated micro- and nanopatterning techniques, originally intended for the semiconductor industry, have been adopted for generating 3D structures with controlled topology to modulate cellular functions without any biological input (Fu et al., 2014; Chen et al., 2013; Huang et al., 2012). The distinct cell behaviors on isotropic and nonisotropic substrates imply that cells can sense the topography of their immediate microenvironment and respond accordingly. However, the morphological deviation of such 3D structures from the native ECM would cause different cell responses. As recognized, fifibrous matrices with submicrometer dimensions would be benefificial. In addition to morphology and dimension, fifibrous matrices possess other distinct properties, such as high surface-to-mass ratio, low density, high porosity, and interconnected pores, desirable for tissue formation. Meanwhile, in the native ECM, a plethora of biomolecules are stored via physical adsorption or chemical immobilization with spatiotemporal release to instruct the development of residing cells. To this end, it would be highly desirable to fabricate ECM-like matrices with the capability of releasing various drugs.

By now, several approaches are available to fabricate fifibrous matrices (Barnes et al., 2007), including phase separation (Jiang and Hasan, 2014), self-assembly (Gelain et al., 2006), and elec trospinning (Matthews et al., 2002; Telemeco et al., 2005; Pham et al., 2006). Among these, elec trospinning has received great attention due to its easy operation, low cost, high production rate, and good reproducibility. Moreover, a variety of materials, including synthetic polymers (e.g., polycaprolactone [PCL], polylactide [PLA]), natural polymers (e.g., collagen, gelatin), or hybrids (e.g., PCL blended with collagen), can be electrospun into submicrometer fifibers with various fifiber spatial arrangements (e.g., aligned, random, or cross aligned), indicating the capability to capture the major features of native ECM, from composition and morphology to spatial organization. As a result, extensive efforts have been made to explore the potential utilization of electrospun nanofifibers for biomimetic engineering of various tissues (Ashammakhi et al., 2006). Our laboratory has extensive experience in different aspects of electrospinning, but we limit the current discussion to the utility of electrospun fifibrous matrices for drug delivery. We have structured this chapter by comprehensively reviewing all the available approaches to incorporate drugs onto or within electrospun fifibrous matrices, discussing the possible release mechanisms of various drugs and highlighting the utility of such drugeluting fifibrous matrices for regeneration of various tissues, such as neural, vascular, cardiac, skin, and bone.

Paper link：https://www.sciencedirect.com/book/9780323512701/electrospinning-nanofabrication-and-applications