Electrospinning has been employed extensively in tissue engineering to generate nanofibrous scaffolds from either natural or synthetic biodegradable polymers to simulate the cellular microenvironment. Electrospinning rapidly produces fibers of the nanolength scale and the process offers many opportunities to tailor the physical, chemical, and biological properties of a material for specific applications and cellular environments. There is growing evidence that nanofibers amplify certain biological responses such as contact guidance and differentiation, however this has not been fully exploited in tissue engineering. This review addresses the cellular interactions with electrospun scaffolds, with particular focus on neural, bone, cartilage, and vascular tissue regeneration. Some aspects of scaffold design, including architectural properties, surface functionalization and materials selection are also addressed.

Current therapies have limited capacity to curtail disease progression or damage of the central nervous system (CNS) of adult mammals and successful regeneration following injury or disease does not occur. Regeneration of the CNS is limited by physical and chemical inhibitory barriers within the injured environment and the absence of positive cues that elicit and guide repair. Neural tissue engineering strategies focus on developing scaffolds that artificially generate favourable cellular microenvironments that attempt to tip the balance in favour of regeneration. Some recent advances using scaffolds to promote regeneration within the CNS, particularly in conjunction with stem cells, has generated promising results. This review focuses on hydrogel scaffolds which have been used extensively in neural tissue engineering applications and addresses the physical and chemical modifications of these materials to promote nerve regeneration.

In nature, durable self-cleaning surfaces such as the Lotus leaf rely on the multiscale architecture and cohesive regenerative properties of organic tissue. Real-world impact of synthetic replicas has been limited by the poor mechanical and chemical stability of the ultrafine hierarchical textures required for attaining a highly dewetting superhydrophobic state. Here, we present the low-cost synthesis of large-scale ultradurable superhydrophobic coatings by rapid template-free micronano texturing of interpenetrated polymer networks (IPNs). A highly transparent texture of soft yielding marshmallow-like pillars with an ultralow surface energy is obtained by sequential spraying of a novel polyurethane-acrylic colloidal suspension and a superhydrophobic nanoparticle solution. The resulting coatings demonstrate outstanding antiabrasion resistance, maintaining superhydrophobic water contact angles and a pristine lotus effect with sliding angles of below 10° for up to 120 continuous abrasion cycles. Furthermore, they also have excellent chemical- and photostability, preserving the initial performance upon more than 50 h exposure to intense UVC light (254 nm, 3.3 mW cm(-2)), 24 h of oil contamination, and highly acidic conditions (1 M HCl). This sprayable polyurethane-acrylic colloidal suspension and surface texture provide a rapid and low-cost approach for the substrate-independent fabrication of ultradurable transparent self-cleaning surfaces with superior abrasion, chemical, and UV-resistance.

Attempts to repair the central nervous system damaged as a result of trauma or disease will depend on the ability to restore the appropriate neuronal connectivity. This will rely on establishing appropriate chemical and physical environments for supporting neural cells and their processes and in this regard, engineering of biomaterials is of increasing interest. It will be important to understand how cells behave on these biomaterials in vitro, prior to future in vivo application. We reveal that modification of 3-dimensional (3D) electrospun poly-epsilon-caprolactone (PCL) nanofiber scaffolds by fiber alignment and aminolysation is superior to classical 2-dimensional (2D) culture-ware in promoting in vitro proliferation and differentiation of cortical cells. Many studies have examined the importance of exogenous soluble factors to promote cell fate specification. Here, we demonstrate that tethering the neurotrophin, brain-derived neurotrophic factor (BDNF), onto modified nanofibers is superior to culturing in the presence of soluble BDNF. Functional immobilization of BDNF to polymer nanofibers enhances neural stem cell (NSC) proliferation and directs cell fate toward neuronal and oligodendrocyte specification, essential for neural tissue repair. These findings indicate that modified PCL nanofibrous 3D scaffolds are capable of supporting NSCs and their derivatives and may present a new avenue for encouraging neural repair in the future.

No abstract

Nanofibrous materials yielded by the self-assembly of peptides are rich in potential; particularly for the formation of scaffolds that mimic the landscape of the host environment of the cell. Here, we report a novel methodology to direct the formation of supramolecular structures presenting desirable amino acid sequences by the selfassembly of minimalist peptides which cannot otherwise yield the desired scaffold structures under biologically relevant conditions. Through the rational modification of the pK a , we were able to optimise ordered charge neutralised assembly towards in vivo conditions.

Stem cell transplants offer significant hope for brain repair following ischemic damage. Pre-clinical work suggests that therapeutic mechanisms may be multi-faceted, incorporating bone-fide circuit reconstruction by transplanted neurons, but also protection/regeneration of host circuitry. Here, we engineered hydrogel scaffolds to form "bio-bridges" within the necrotic lesion cavity, providing physical and trophic support to transplanted human embryonic stem cell-derived cortical progenitors, as well as residual host neurons. Scaffolds were fabricated by the self-assembly of peptides for a laminin-derived epitope (IKVAV), thereby mimicking the brain's major extracellular protein. Following focal ischemia in rats, scaffold-supported cell transplants induced progressive motor improvements over 9 months, compared to cell- or scaffold-only implants. These grafts were larger, exhibited greater neuronal differentiation, and showed enhanced electrophysiological properties reflective of mature, integrated neurons. Varying graft timing post-injury enabled us to attribute repair to both neuroprotection and circuit replacement. These findings highlight strategies to improve the efficiency of stem cell grafts for brain repair.

No abstract