Despite being known for decades (since 1934), electrospinning has emerged recently as a very widespread technology to produce synthetic nanofibrous structures. These structures have morphologies and fiber diameters in a range comparable with those found in the extracellular matrix of human tissues. Therefore, nanofibrous scaffolds are intended to provide improved environments for cell attachment, migration, proliferation and differentiation when compared with traditional scaffolds. In addition, the process versatility and the highly specific surface area of nanofiber meshes may facilitate their use as local drug-release systems. Common electrospun nanofiber meshes are characterized by a random orientation. However, in some special cases, aligned distributions of the fibers can be obtained, with an interconnected microporous structure. The characteristic pore sizes and the inherent planar structure of the meshes can be detrimental for the desired cell infiltration into the inner regions, and eventually compromise tissue regeneration. Several strategies can be followed to overcome these limitations, and are discussed in detail here.

The aim of this work was to develop novel electrospun nanofiber meshes coated with a biomimetic calcium phosphate (BCP) layer that mimics the extracellular microenvironment found in the human bone structure. Poly (epsilon-caprolactone) (PCL) was selected because of its well-known medical applications, its biodegradability, biocompatibility and its susceptibility to partial hydrolysis by a straightforward alkaline treatment. The deposition of a calcium phosphate layer, similar to the inorganic phase of bone, on PCL nanofiber meshes was achieved by means of a surface modification. This initial surface modification was followed by treatment with solutions containing calcium and phosphate ions. The process was finished by a posterior immersion in a simulated body fluid (SBF) with nearly 1.5 x the inorganic concentration of the human blood plasma ions. After some optimization work, the best conditions were chosen to perform the biological assays. The influence of the bone-like BCP layer on the viability and adhesion, as well as on the proliferation of human osteoblast-like cells, was assessed. It was shown that PCL nanofiber meshes coated with a BCP layer support and enhance the proliferation of osteoblasts for long culture periods. The attractive properties of the coated structures produced in the present work demonstrated that those materials have potential to be used for applications in bone tissue engineering. This is the first time that nanofiber meshes could be coated with a biomimetic bone-like calcium phosphate layer produced in a way that the original mesh architecture can be fully maintained.

As the current global trend towards more stringent environmental standards, technical applicability and cost-effectiveness became key factors in the selection of adsorbents for water and wastewater treatment. Recently, various low-cost adsorbents derived from agricultural waste, industrial by-products or natural materials, have been intensively investigated. In this respect, the eggshells from egg-breaking operations constitute significant waste disposal problems for the food industry, so the development of value-added by-products from this waste is to be welcomed. The egg processing industry is very competitive, with low profit margins due to global competition and cheap imports. Additionally, the costs associated with the egg shell disposal (mainly on landfill sites) are significant, and expected to continue increasing as landfill taxes increase. The aim of the present review is to provide an overview on the development of low-cost adsorbents derived from eggshell by-products.