Hydroxyapatite (HAp) scaffolds with uniform pore size and interconnected pore network were constructed based on the inverted colloidal crystal (ICC) geometry and a simple sol-gel formulation. Monodisperse polystyrene microspheres were self-assembled and annealed into a hexagonal close packed structure. HAp sol-gel was infiltrated in this template followed by thermal treatment for simultaneous HAp matrix sintering and polymeric colloidal crystal calcination. The resultant ICC scaffolds exhibit an ordered architecture that was able to offer a favorable environment for human osteoblasts adhesion and proliferation, an essential feature for bone ingrowth in tissue engineering applications.

Electrospun fibers of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-bithiophene] (F8T2) with exceptional electro-optical performance are obtained. The I/T characteristics measured in fibers with 7–15 µm diameter and 1 mm length show a semiconductor behavior; their thermal activation energy is 0.5 eV and the dark conductivity at RT is 5 × 10−9 (Ω cm)−1. Besides exhibiting a photosensitivity of about 60 under white light illumination with a light power intensity of 25 mW · cm−2, the fibers also attain RT photoluminescence in the cyan, yellow, and red wavelength range under ultraviolet, blue, and green light excitation, respectively. Optical microscope images of F8T2 reveal homogeneous electrospun fibers, which are in good agreement with the uniformly radial fluorescence observed.

Truncated sialylated O-glycans, such as cell-surface carbohydrate antigen sialyl-Tn (STn) are overexpressed by several cancer types, but not by the respective normal tissues. STn expression is associated with oncogenesis and metastatic ability of cancer cells, with reduced overall survival and lack of response to chemotherapy. Advances in nanomedicine have resulted in rapid development of biocompatible superparamagnetic iron oxide nanoparticles (SPIONs) with considerable potential in cancer treatment. Therefore, in this study SPIONs coated with oleic acid (OA) or dimercaptosuccinic acid (DMSA) were developed and characterized for internalization in two breast cancer cell lines: cell line expressing the STn antigen and the corresponding control. SPIONs with an average diameter of 8 nm showed superparamagnetic behavior and high potential to be used as magnetic hyperthermia agents. OA and DMSA coating provided high stability of SPIONs in physiological conditions while not changing their main properties. NPs internalization studies showed a higher accumulation of DMSA coated NPs in the breast cancer MDA-MB-231 WT cell line. In MDA-MB-231 cell line expressing STn both coated NPs showed a similar accumulation. Therefore, STn antigen can act as a receptor capable of detecting and covalently bind to the molecules present on NPs surface and induce their cellular uptake by endocytosis.

In this work, eco-friendly magnesium-silicide (Mg2Si) semiconducting (n-type) thermoelectric pastes for building components concerning energy-harvesting devices through 3D printing, spray and electrospinning were synthetized and tested for the first time. The Mg2Si fine powders were obtained through the combination of ball milling and thermal annealing under Ar atmosphere. While the latter process was crucial for obtaining the desired Mg2Si phase, the ball milling was indispensable for homogenizing and reducing the grain size of the powders. The synthetized Mg2Si powders exhibited a large Seebeck coefficient of ~ 487 µV/K and were blended with a polymeric solution in different mass ratios to adjust the paste viscosity to the different requirements of 3D printing, electrospinning and low-pressure spray. The materials produced in every single stage of the paste synthesis were characterized by a variety of techniques that unequivocally prove their viability for producing thermoelectric parts and components. These can certainly trigger further research and development in green thermoelectric generators (TEGs) capable of adopting any form or shape with enhanced thermoelectric properties. These green TEGs are meant to compete with common toxic materials such as Bi2Te3, PbTe and CoSb that have Seebeck coefficients in the range of ~ 290–700 μV/K, similar to that of the produced Mg2Si powders and lower than that of 3D printed bulk Mg2Si pieces, measured to be ~ 4866 μV/K. Also, their measured thermal conductivities proved to be significantly lower (~ 0.2 W/mK) than that reported for Mg2Si (≥ 4 W/mK). However, it is herein demonstrated that such thermoelectric properties are not stable over time. Pressureless sintering proved to be indispensable, but difficultly achievable by long thermal annealing (even above 32 h) in inert atmosphere at 400 °C, at least for bulk Mg2Si pieces constituted by a mean grain size of 2–3 μm. Hence, for overcoming this sintering challenge and become the silicide’s extrusion viable in the production of bulk thermoelectric parts, alternative pressureless sintering methods will have to be further explored.

Biodegradable polyurethanes have been studied as scaffolds for tissue engineering due to their adjustable physico-chemical properties. In this work, we synthesized a biodegradable gelatin-based poly(urethane urea) using polycaprolactone-diol, as soft segment, and isophorone diisocyanate and gelatin from cold water fish skin as hard segment. The synthesis was confirmed by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance and the influence of the amount of gelatin introduced in the polymer backbone was analyzed by thermal analysis. Gelatin-based poly(urethane urea) electrospun fibrous mats and solvent cast films were then produced and their physico-chemical and biological properties studied. They present an amorphous structure, elastomeric behavior and water contact angles typical of hydrophobic surfaces. Hydrolytic degradation was analyzed in phosphate buffer saline (PBS), lipase and trypsin solutions. No mass changes were detected during 37 days in PBS and trypsin while significant degradation by lipase was observed. Human foetal foreskin fibroblasts were seeded on the fibrous mats and films. Populations were evaluated by colorimetric cell viability assays and morphology by fluorescence imaging. The substrates supported cell adhesion and proliferation. The novel gelatin-based poly(urethane urea) fibrous mats offer attractive physico-chemical and biological properties for soft tissue engineering applications.

We assembled a new electrospinning apparatus and used poly(ethylene oxide) as a model polymer to perform a systematic study on the influence of solution and processing parameters on the morphology of electrospun nanofibers. Solution parameters studied were polymer concentration and molecular mass. The solvent used, 60 wt% water,40 wt% ethanol, was the same throughout the study. Processing parameters analyzed were: solution feed rate, needle tip-collector distance and electrostatic potential difference between the needle and collector. Solution viscosity increased both with polymer concentration and molecular mass. Polymer concentration plays a decisive role on the outcome of the electrospinning process: a low concentration led to the formation of beaded fibers; an intermediate concentration yielded good quality fibers; a high concentration resulted in a bimodal size distribution and at even higher concentration a distributed deposition. Fiber diameter increased with polymer molecular mass and higher molecular masses are associated with a higher frequency of splaying events. Fiber diameter increased linearly with solution feed rate. While an increase in needle-collector distance represents a weaker electric field, a greater distance to be covered by the fibers and a longer flight time, presumably favoring the formation of thinner fibers, as solvent evaporation leads to a local increase of concentration and viscosity, viscoelastic forces opposing stretching caused an increase of fiber diameter with needle-collector distance. A higher voltage applied at the needle is associated with a higher charging of the polymer and a higher electrical current through it ultimately leading to incomplete solvent evaporation and merged fibers being produced. Controlling the charging of the polymer independently of the electric field strength was achieved by applying a voltage to the collector while distance and potential difference were kept constant. The increased electrostatic repulsion associated with an increase of the high voltage applied to the needle led to the disappearance of merged fibers.

The tensile properties of cross-linked and uncross-linked composite films (thickness ∼20–35 μm) prepared from Hydroxypropylcellulose (HPC) with incorporation of microcrystalline cellulose fibers (Avicel) were studied. The concentration of fibers in the composites ranged from 0 to 30 w/w% and cross-linked composites were obtained by the reaction of HPC-Avicel mixtures with 1,4-butyldiisocyanate. It was demonstrated that the inclusion of fibers in a HPC matrix produces composites with enhanced mechanical properties that are improved by cross-linking. Mechanical results seem to indicate that the elastic deformation of the cross-linked composites is predominantly dominated by the fiber content while the cross-linking affects mainly the plastic deformation. Maximum values of the Young's Modulus, yield stress and tensile stress were observed at 10 w/w% for the cross-linked and 20 w/w% for the uncross-linked composites. Furthermore cross-linked films with 10 w/w% of fibers present values of yield stress and tensile stress that are in average 15 to 20% higher than those obtained for uncross-linked composites with 20 w/w% of fibers. Studies in Polarizing Optical Microscopy and Atomic Force Microscopy (AFM) seem to indicate that tensile properties of these composites are correlated to the packing of fibers. For the concentration of the utilized cross-linking agent, and for a fiber content of 10 w/w%, an optimal packing of fibers throughout the matrix has been correlated to the minimal difference between the roughness parameters obtained by AFM analysis of the top and bottom surfaces of the films.

Chitosan is a biopolymer widely used for biomedical applications such as drug delivery systems, wound healing, and tissue engineering. Chitosan can be used as coating for other types of materials such as iron oxide nanoparticles, improving its biocompatibility while extending its range of applications.
In this work iron oxide nanoparticles (Fe3O4 NPs) produced by chemical precipitation and thermal decomposition and coated with chitosan with different molecular weights were studied. Basic characterization on bare and chitosan-Fe3O4 NPs was performed demonstrating that chitosan does not affect the crystallinity, chemical composition, and superparamagnetic properties of the Fe3O4 NPs, and also the incorporation of Fe3O4 NPs into chitosan nanoparticles increases the later hydrodynamic diameter without compromising its physical and chemical properties. The nano-composite was tested for magnetic hyperthermia by applying an alternating current magnetic field to the samples demonstrating that the heating ability of the Fe3O4 NPs was not significantly affected by chitosan.

Iron oxide nanoparticles (NPs) have been extensively studied in the last few decades for several biomedical applications such as magnetic resonance imaging, magnetic drug delivery and hyperthermia. Hyperthermia is a technique used for cancer treatment which consists in inducing a temperature of about 41–45 °C in cancerous cells through magnetic NPs and an external magnetic field. Chemical precipitation was used to produce iron oxide NPs 9 nm in size coated with oleic acid and trisodium citrate. The influence of both stabilizers on the heating ability and in vitro cytotoxicity of the produced iron oxide NPs was assessed. Physicochemical characterization of the samples confirmed that the used surfactants do not change the particles' average size and that the presence of the surfactants has a strong effect on both the magnetic properties and the heating ability. The heating ability of Fe3O4 NPs shows a proportional increase with the increase of iron concentration, although when coated with trisodium citrate or oleic acid the heating ability decreases. Cytotoxicity assays demonstrated that both pristine and trisodium citrate Fe3O4 samples do not reduce cell viability. However, oleic acid Fe3O4 strongly reduces cell viability, more drastically in the SaOs-2 cell line. The produced iron oxide NPs are suitable for cancer hyperthermia treatment and the use of a surfactant brings great advantages concerning the dispersion of NPs, also allowing better control of the hyperthermia temperature.

In the present work composite nanoparticles with a magnetic core and a chitosan-based shell were produced as drug delivery systems for doxorubicin (DOX). The results show that composite nanoparticles with a hydrodynamic diameter within the nanometric range are able to encapsulate more DOX than polymeric nanoparticles alone corresponding also to a higher drug release. Moreover the synthesis method of the iron oxide nanoparticles influences the total amount of DOX released and a high content of iron oxide nanoparticles inhibits DOX release. The modelling of the experimental results revealed a release mechanism dominated by Fickian diffusion.

The incorporation of thermosensitive microgels that can act as active sites into polymeric fibers through colloidal electrospinning originates multifunctional, highly porous, and biocompatible membranes suitable for biomedical applications. The use of polyvinylpyrrolidone (PVP), a biocompatible, water-soluble polymer as a fiber template, not only allows the use of a simple set-up to produce composite membranes, but also avoids the use of organic solvents to prepare such systems. Further crosslinking with ultraviolet (UV) radiation avoids membrane dissolution in physiological conditions. Highly porous, UV crosslinked composite membranes with monodisperse mean fiber diameters around 530 nm were successfully produced. These composite membranes showed a Young Modulus of 22 MPa, and an ultimate tensile strength of 3 MPa, accessed in the mechanical tests. Furthermore, the same composite membranes were able to swell about 30 times their weight after 1 hour in aqueous medium. In this work composite multifunctional membranes were designed and extensively studied. PVP, a biocompatible water-soluble polymer, was used as a fiber template to incorporate thermoresponsive poly-(N-isopropylacrylamide) (PNIPAAm)-based microgels into the composite membrane using colloidal electrospinning. The design of multifunctional membranes can be further tailored to several biomedical applications such as temperature-controlled drug delivery systems.

Control of the properties of electrospun polycaprolactone can be achieved by adjusting the acetic acid:water ratio used to dissolve and electrospin the polymer. In this work, we studied the effect of using up to 15 wt% water in the solvent mixture. Solution conductivity and viscosity and fibre morphology vary dramatically with water content and solution age. Two days after initial solution preparation, electrospinning yields regular fibres for a water content of 0 wt% and 5 wt%, irregular fibres for a 10 wt% water content and irregular and fused fibres for a 15 wt% water content. Fibres with the highest crystallinity (60%) were obtained from solutions containing 5 wt% water while the highest elastic modulus (8.6 ± 1.4 MPa) and tensile stress (4.3 ± 0.3 MPa) pertain to fibres obtained from solutions containing 10 wt% water. Enzymatic fibre degradation is faster the higher the water content in the precursor solution. Adhesion ratio of human foetal fibroblasts was highest on scaffolds obtained from precursor solutions containing 0 wt% water. Cell population increases for all scaffolds and populations quickly become equivalent, with no statistically significant differences between them. Cells exhibit a more extended morphology on the 5 wt% scaffold and a more compact morphology on the 0 wt% scaffold. In summary, a small water content in the solvent allows a significant control over fibre diameter, scaffold properties and the production of scaffolds that support cell adhesion and proliferation. This strategy can be used in soft tissue engineering to influence cell behaviour and the degradation rate of the scaffolds.