Boron nitride decorated poly(vinyl alcohol)/poly(acrylic acid) composite nanofibers: A promising material for biomedical applications.

In this study, polyvinyl alcohol (PVA) and polyacrylic acid (PAA) nanofibers loaded with boron nitride nanoparticles (mBN) were fabricated by using electrospinning and crosslinked by heat treatment. The physical, chemical, and mechanical properties, hydrophilic behavior, and degradability of composite nanofibers were evaluated. The mechanical properties such as elastic modulus, elongation percentage at the break, and mechanical strength of PVA/PAA nanofibers improved with mBN loading. The thermal conductivity of composite nanofibers reached 0.12 W/m·K at mBN content of 1.0 wt% due to the continuous heat conduction pathways of mBN. In the meantime, while there was no cytotoxicity recorded for both L929 and HUVEC cell lines for all composite nanofibers, the antimicrobial efficiency improved with the incorporation of mBN compared with PVA/PAA and recorded as 68.8% and 75.1% for Escherichia coli and Staphylococcus aureus, respectively. On this basis, the present work proposes a promising biomaterial for biomedical applications such as dual drug delivery, particularly including both hydrophobic and hydrophilic drugs or wound dressing.

Evolution of dynamics of physico-chemical and mechanical properties of hydroxyapatite with fluorine addition and degradation stability of new matrices.

This multidisciplinary study examined sensitively the change in the dynamics of main mechanical performance, stability of crystal structure, crystallinity quality, strength, corrosion resistance, biocompatibility, resistance to structural degradation/separations and mechanical durability features of hydroxyapatite (HAp) biomedical materials based on the fluorine addition and degradation process to guide future medical and dental treatment studies. In the study, the fluorine ions were used to be the dental coating, filling and supporting material for biologically or synthetically produced bone minerals. The general characteristic properties were investigated by means of standard spectroscopic, structural and mechanical analysis methods including RAMAN, SEM-EDS, TEM, Vickers micro-indentation hardness and density measurements. A time dependent release test was performed to evaluate possible fluorine ion release after the degradation process. It was found that the fundamental characteristic properties of HAp biomedical materials are noted to improve with the increase in the fluoride level up to 2% due much more stabilization of HAp crystal system. The combination of RAMAN spectra and powder XRD analyzes indicates that 2% addition level affects positively the formation velocity of characteristic HAP phase. Besides, fluorine doped HAp materials all exhibited the main characteristic peaks after degradation process. This is attributed to the fact that the fluorine ions enabled the hydroxyapatite to enhance the structural quality and stability towards the corrosion environment. However, in case of excess dopant level of 3% the degradation rates were obtained to increase due to higher contribution rate and especially electrostatic interactions. As for the surface morphology examinations, 2% fluorine added HAp with the highest density of 3.0879 g/cm3 was determined to present the superior crystallinity quality (smallest grain size, best smooth surface, honeycomb pattern, regular shaped particles and densest particle distributions through the specimen surface). Conversely, the excess fluorine triggered to increase seriously degree of micro/macro porosity in the surface morphology and microscopic structural problems in the crystal system. Thus, the HAp doped with 3% was the most affected material from the degradation process. Additionally, the fluorine ion values read after the release process were quite far from the value that could cause toxic effects. Lastly, the optimum fluorine addition provides the positive effects on the highest durability, stiffness and mechanical fracture strength properties as a consequence of differentiation in the surface residual compressive stress regions (lattice strain fields), amplification sites and active operable slip systems in the matrix. Hence, the crack propagations prefer to proceed in the transcrystalline regions rather than the intergranular parts. Similarly, it was found that Vickers micro-indentation hardness tests showed that the microhardness parameters increased after the degradation process. All in all, the fluorine addition level of 2% was noted to be good choice to improve the fundamental characteristic properties of hydroxyapatite biomedical materials for heavy-duty musculoskeletal, orthopedic implant, biological and therapeutic applications in medicine and dentistry application fields.

Methylene blue adsorption on magnetic alginate/rice husk bio-composite.

Magnetic alginate/rice husk (m-ALG/RH) bio-composite beads prepared with ionotropic gelation method and used for methylene blue (MB) removal. Structural analysis of magnetic alginate/rice husk composite beads was performed using FTIR, SEM-EDS and TGA techniques. The accomplishment of magnetic alginate/rice husk composite beads as an adsorbent for the removal methylene blue was investigated from aqueous solution. Maximum experimental adsorption capacity of the bio-composite beads was calculated as 274.9 mg/g. The various process parameters such as pH, temperature and initial MB concentration optimized. It was determined that pH no significant effect on dye removal efficiency of beads while temperature and ionic strength caused a decrease on removal efficiency. The various isotherm models were applied for determine the adsorption mechanism and Freundlich isotherm model is more compatible with the experimental data. The kinetic studies showed that the adsorption of methylene blue can be well described by the fractal Brouers-Sotolongo kinetic model. The thermodynamic calculations indicated that methylene blue adsorption was a spontaneous and exothermic nature. The results showed that the magnetic alginate/rice husk bio-composite as low-cost and eco-friendly adsorbent can be effectively used for cationic dye removal steps in the environmental engineering applications.

Investigation on phenol degradation capability of Scenedesmus regularis: influence of process parameters.

Phenol removal from environmental solutions has attracted much attention due to phenol's high toxicity, even at low concentrations. This study aims to reveal the phenol biodegradation capacity of Scenedesmus regularis. Batch system parameters (pH, amount of algal cell, phenol concentration) on biodegradation were examined. After 24 h of treatment, 92.16, 94.50, 96.20, 80.53, 65.32, 52 and 40% of phenol were removed by Scenedesmus regularis in aqueous solutions containing 5, 10, 15, 20, 30, 40 and 50 mg/L of phenol, respectively. To describe the correlation between degradation rate and phenol concentration, the Michaelis-Menten kinetic equation was used where Vmax and Km are 0.82 mg phenol g algea-1 h-1 and 24.97 ppm, respectively. Phenol remediation ability of S.regularis can enable the usage of the spent biomass as biofuel feedstock and animal feed makes it a 'green' environmental sustainable process.

Poly (methyl vinyl ether-co-maleic acid) - Pectin based hydrogel-forming systems: Gel, film, and microneedles.

Cross-linking of natural and synthetic polymers is widely explored to achieve the desired material properties (mechanical strength, drug loading capacity, swelling and erosion rates). However, the potential of polymers produced by crosslinking poly (methyl vinyl ether-co-maleic acid) (PMVE/MA) and pectin (PE) in pharmaceutics is mainly unexplored so far. We have investigated the effect of various esterification conditions and pectin content on the physicochemical properties. Materials have been characterized by fourier transform infrared, differential scanning calorimetry and scanning electron microscopy. In addition, swelling and bioadhesive features of PMVE/MA-PE hydrogel systems were investigated. A band shift for the carbonyl group from 1706 to 1776cm-1, and glass transition (Tg) increased from 55.4±0.9°C to 119.5±0.3°C confirmed the formation of esterification reaction within the cross-linked films. Cross-linked PMVE/MA:PE films with a ratio of 5 demonstrated a superior mass increase when compared to 2.5, 3.125, 3.75, 6.25, and 7.5 ratios of the same hydrogel film. Formulations containing PMVE/MA and pectin with a ratio of 3.75 showed superior bioadhesive features. For the first time, we engineered three-dimensional printing based swell-able microneedle arrays made out of cross-linked PMVE/MA-PE. Microneedle arrays height and aspect ratio were ranged from 702.5±11.9µm to 726±23.3µm and 3.12±0.20 to 3.29±0.21, respectively. Cross-linked PMVE/MA-PE Microneedle arrays (10-2, 24h) indicated the least height loss, 22.33±4.15%, during axial compression test; whilst, transverse failure of cross-linked PMVE/MA-PE Microneedle arrays was varied from 0.15±0.05 to 0.25±0.04N/needle. In conclusion, we obtained a novel cross-linked polymer system with promising features of drug delivery and bio-analytical applications.

One step effective removal of Congo Red in chitosan nanoparticles by encapsulation.

Chitosan nanoparticles (CNPs) were prepared with ionotropic gelation between chitosan and tripolyphosphate for the removal of Congo Red. The production of chitosan nanoparticles and the dye removal process was carried out in one-step. The removal efficiency of Congo Red by encapsulation within chitosan from the aqueous solution and its storage stability are examined at different pH values. The influence of some parameters such as the initial dye concentration, pH value of the dye solution, electrolyte concentration, tripolyphosphate concentration, mixing time and speed on the encapsulation is examined. Congo Red removal efficiency and encapsulation capacity of chitosan nanoparticles were determined as above 98% and 5107mg Congo Red/g chitosan, respectively.

Fibrous polymer-grafted chitosan/clay composite beads as a carrier for immobilization of papain and its usability for mercury elimination.

Papain, which is an industrially important enzyme, has been immobilized on fibrous polymer-modified composite beads, namely poly(methacrylic acid)-grafted chitosan/clay. Characterization studies have been done using FTIR and SEM analysis. Operating parameters such as pH and initial concentration of papain have been varied to obtain the finest papain immobilized polymer-modified composite beads. The immobilization capacity of composite beads has been determined as 34.47 ± 1.18 (n = 3) mg/g. The proteolytic activity of immobilized papain was operated using bovine serum albumin (BSA) and maximum velocity (V max) and Michaelis-Menten constant (Km) values of the free and immobilized enzymes were determined using Lineweaver-Burk and Eadie-Hofstee equations. Usability of papain immobilized polymer-modified composite beads as adsorbents for the elimination of mercury was investigated. The maximum removal capacity of PIPMC beads has been found to be 4.88 ± 0.21 mg Hg/g when the initial metal concentration and weight of polymer-modified composite beads were 50 mg/L and 0.04 g at pH 7, respectively. Mercury removal performance of the papain immobilized polymer-modified composite beads was investigated in conjunction with Cu (II), Zn (II) and Cd (II) ions. The mercury adsorption capacity of papain immobilized polymer-modified composite beads was a slight reduction from 1.15 to 0.89 mg/g in presence of multiple metal salts.