Hossein Mohammad Khanlou

Chitosan (PEO)/bioactive glass hybrid nanofibers for bone tissue engineering

A novel hybrid nanofibrous scaffold prepared with chitosan [containing 1.2 wt% polyethylene oxide (PEO)] and bioactive glass (BG) was fabricated by an electrospinning technique. The morphological and physicochemical properties of scaffolds were studied by scanning electron microscopy (SEM) and spectroscopy. The measurements of tensile strength and water-contact angles suggested that the incorporation of BG into the nanofibers improves the mechanical properties and hydrophilicity of the scaffolds. Biomineralization of the nanofibers was evaluated by soaking them in simulated body fluid (SBF), and the formation of hydroxycarbonate apatite (HCA) layer was determined by EDX and FE-SEM. The results showed that BG-containing nanofibers could induce the formation of HCA on the surface of the composite after 14 days of immersion in SBF. In vitro-cell viability of human mesenchymal stromal cells (hMSCs) on nanofibers was assessed by using the MTT assay. The cell-adhesion results showed that hMSCs were viable at variable time points on the chitosan/PEO/BG nanofiber scaffolds. In addition, the presence of BG enhanced the alkaline phosphatase (ALP) activity of hMSCs cultured on composite scaffolds at day 14 compared to that on pure chitosan/PEO scaffolds. Our results suggest that a chitosan/PEO/BG nanofibrous composite could be a potential candidate for application in tissue engineering.

Electrospinning of polymethyl methacrylate nanofibers: optimization of processing parameters using the Taguchi design of experiments

The effects of polymer concentration and electrospinning parameters on the diameter of electrospun polymethyl methacrylate (PMMA) fibers were experimentally investigated. It was also studied how the controlled factors would affect the output with the intention of finding the optimal electrospinning settings in order to obtain the smallest PMMA fiber diameter. Subsequently the solution feed rate, needle gauge diameter, supply voltage, polymer concentration and tip-to-collector distance were considered as the control factors. To achieve these aims, Taguchi’s mixed-level parameter design (L18) was employed for the experimental design. Optimal electrospinning conditions were determined using the signal-to-noise (S/N) ratio that was calculated from the electrospun PMMA fiber diameter according to “the-smaller-the-better” approach. Accordingly, the smallest fiber diameter observed was 228 (±76) nm and it was yielded at 15 wt% polymer concentration, 20 kV of supply voltage, 1 ml/h feed rate, 15 cm tip-to-distance and 19 needle gauge. Moreover, the S/N ratio response showed that the polymer concentration was the most effective parameter on determination of fiber diameter followed by feed rate, tip-to distance, needle gauge and voltage, respectively. The Taguchi design of experiments method has been found to be an effective approach to statistically optimize the critical parameters used in electrospinning so as to effectively tailor the resulting electrospun fiber diameters and morphology.

Fabrication and characterisation of chitosan/ poly vinyl alcohol nanofibres via electrospinning

Abstract In this study, chitosan nanofibres were fabricated using electrospinning process. Initially, chitosan powders were further deacetylated with sodium hydroxide to deprotonate the polymer chains and decrease the molecular weight. Subsequently, the treated chitosan (5 wt-% in 90:10 acetic acid/water ratio) were mixed with poly vinyl alcohol (8 wt-% in water) at different ratios in order to facilitate the electrospinning through cross-links formation. Field-emission scanning electron microscopic images showed that 60:40 (chitosan/poly vinyl alcohol) ratio was the threshold for formation of beads (chitosan/poly vinyl alcohol >50:50 contains imperfections) and that increasing chitosan/poly vinyl alcohol ratio from 20:80 to 60:40 decreased the average diameter of fibres from 80 to 40 nm. Fourier transform infrared spectra proved the formation of chitosan/poly vinyl alcohol cross-linked nanofibres.

Preparation and characterisation of electrospun silica nanofibres

Abstract In this study, the silica electrospun nanofibres were fabricated using silica sol containing tetraethylorthosilicate, polyvinylpyrrolidone and butanol (solvent). The perfect concentration for silica sol to undergo the electrospinning was found to be 0·095 gr(pvp)/mL (butanol, tetraethyl orthosilicate), where the tetraethyl orthosilicate/butanol volume ratio was 3:2. Later with the intention of achieving the silica nanofibres, the electrospun samples afterwards were put in a furnace at 700°C for 3 hours. After that the morphological studies on the fibres before and after the thermal treatment were done employing the scanning electron microscopy. The results showed that fibre diameter before thermal treatment fits the micrometre scale, while it decreases dramatically to the 260–360 nm range when it goes through the thermal stage. Furthermore, Fourier transform infrared spectroscopy and energy-dispersive X-ray spectroscopy spectrums proved that polyvinylpyrrolidone and butanol were removed from the fibres after calcination and that the silica nanofibres were fabricated.

Prediction, modeling and characterization of surface texturing by sulfuric etchant on non-toxic titanium bio-material using artificial neural networks and fuzzy logic systems

Abstract Multilayer feed forward network, radial biased function network, generalized regression neural network and adaptive network-based fuzzy inference system (ANFIS) were used to predict the surface roughness of Ti-13Zr-13Nb alloy in etching sulfuric acid. Subsequent processes – polishing, sandblasting and acid etching or SLA – were employed to modify the surface. Alumina particles for surface blasting and concentrated sulfuric acid for acid etching were utilized in this experiment. This was performed for three different periods of time (10, 20 and 30 s) and temperature (25, 45 and 60°C). Correspondingly, the Ti-13Zr-13Nb surfaces were evaluated using a field emission scanning electron microscope for roughening and a contact mode profilometer for the average surface roughness (Ra) (nm). Different configurations of neural networks and ANFIS approaches are examined in order to minimize the root mean square error. Consequently, the ANFIS model is selected by dividing the time and temperature into one and three spaces, respectively, using the Gaussian-shaped membership function. A mathematical model is attained from the best approach in terms of root mean square error to realize the relation of the surface roughness of Ti-13Zr-13Nb alloy in etching sulfuric acid and time and temperature as the effective parameters.

Correction: Chitosan (PEO)/bioactive glass hybrid nanofibers for bone tissue engineering

Correction for ‘Chitosan (PEO)/bioactive glass hybrid nanofibers for bone tissue engineering’ by Sepehr Talebian et al., RSC Adv., 2014, 4, 49144–49152.