Dendrimer-functionalized electrospun nanofibres as dual-action water treatment membranes

Ionic conductive nanocomposite based on poly(l-lactic acid)/poly(amidoamine) dendrimerelectrospun nanofibrous for biomedical application

The modification of poly (l-lactic acid) (PLLA) electrospun nanofibrous scaffolds was carried out by blending with second-generation poly amidoamine (PAMAM) for enhancement of their ionic conductivity. The samples containing PLLA and various amounts of PAMAM (1%, 3%, 5%, and 7% by wt.) were fabricated by electrospinning techniques. The electrospun fibers were characterized using scanning electron microscopy (SEM), porosity, Fourier-transform infrared (FTIR) spectroscopy, differential scanning calorimetry, contact angle measurement, water uptake measurement, mechanical properties, and electrical properties. Furthermore,in vitrodegradation study and cell viability assay were investigated in biomaterial applications. Creating amide groups through aminolysis reaction was confirmed by FTIR analysis successfully. The results reveal that adding PAMAM caused an increase in fiber diameter, crystallinity percentage, hydrophilicity, water absorption, elongation-at-break, and OE-mesenchymal stem cell viability. It is worth mentioning that this is the first report investigating the conductivity of PLLA/PAMAM nanofiber. The results revealed that by increasing the amount of PAMAM, the ionic conductivity of scaffolds was enhanced by about nine times. Moreover, the outcomes indicated that the presence of PAMAM could improve the limitations of PLLA like hydrophobicity, lack of active group, and poor cell adhesion.

Lead and cadmium adsorption by electrospun PVA/PAA nanofibers: Batch, spectroscopic, and modeling study

Water-stable PVA/PAA nanofibers were fabricated through electrospinning and evaluated for their performance in lead (Pb(II)) and cadmium (Cd(II)) removal from water in a batch experiment. The adsorption mechanism of Pb(II) was explored using the extended X-ray absorption fine structure (EXAFS) spectroscopic analysis. The PVA/PAA nanofibers showed a pH-dependent behavior for heavy metal removal, and its adsorption capacities for Pb(II) and Cd(II) could reach as high as 159 and 102 mg/g, respectively. The calcium ion (Ca(II)) had no effect on Pb(II) removal at pH 5.0 whereas it significantly reduced Cd(II) removal at pH 7.0. The adsorption of Pb(II) and Cd(II) was spontaneous and exothermic in nature with a decrease in randomness. The saturated PVA/PAA nanofibers could be regenerated using acidic solutions for reuse. The Fourier-transform infrared (FTIR) spectroscopic analysis indicated the formation of surface complexes between adsorbed Pb(II) and Cd(II) and carboxyl groups on PVA/PAA nanofibers. Moreover, EXAFS analysis suggested that a Pb(II) cation was chelated with three carboxyl groups on the nanofibers. This molecular-level adsorption structure was successfully implemented into a surface complexation model for the prediction of the macroscopic Pb(II) and Cd(II) adsorption behaviors. The results gained from this study provided complementary information on heavy metal removal by a new generation of adsorbents and improved the fundamental understanding for the removal process.

An Exfoliated Graphite-Based Electrochemical Immunosensor on a Dendrimer/Carbon Nanodot Platform for the Detection of Carcinoembryonic Antigen Cancer Biomarker

An electrochemical immunosensor for the quantification of carcinoembryonic antigen (CEA) using a nanocomposite of polypropylene imine dendrimer (PPI) and carbon nanodots (CNDTs) on an exfoliated graphite electrode (EG) is reported. The carbon nanodots were prepared by pyrolysis of oats. The nanocomposites (PPI and CNDTs) were characterized using X-ray powder diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). The proposed immunosensor was prepared on an exfoliated graphite electrode sequentially by drop coating CNDTs, the electrodeposition of G2-PPI (generation 2 poly (propylene imine) dendrimer), the immobilization of anti-CEA on the modified electrode for 80 min at 35 °C, and dropping of bovine serum albumin (BSA) to minimize non-specific binding sites. Cyclic voltammetry was used to characterize each stage of the fabrication of the immunosensor. The proposed immunosensor detected CEA within a concentration range of 0.005 to 300 ng/mL with a detection limit of 0.00145 ng/mL by using differential pulse voltammetry (DPV). The immunosensor displayed good stability and was also selective in the presence of some interference species such as ascorbic acid, glucose, alpha-fetoprotein, prostate-specific antigen and human immunoglobulin. Furthermore, the fabricated immunosensor was applied in the quantification of CEA in a human serum sample, indicating its potential for real sample analysis.

Polyamidoamine dendrimer decorated nanoparticles as an adsorbent for magnetic solid-phase extraction of tetrabromobisphenol A and 4-nonylphenol from environmental water samples

Polyamidoamine dendrimer decorated Fe₃O₄ magnetic nanoparticles were successfully synthesized by Michael addition with methyl acrylate and amidation with ethylenediamine. The decorated magnetic particles were utilized as an effective adsorbent for magnetic solid-phase extraction of tetrabromobisphenol A and 4-nonylphenol at trace levels from environmental water samples. A number of parameters such as generation number, ionic strength, adsorbent dosage, eluent, adsorption time, elution volume, elution time, pH, humic acid and sample volume were optimized. Under the optimal conditions, a wide linearity was achieved in the range of 0.1-500 μg L^-1 of the analytes with the correlation coefficients (R²) of 0.9985-0.9995. The limits of detection were approximately 0.011 μg L^-1 of tetrabromobisphenol A and 0.017 μg L^-1 of 4-nonylphenol. Satisfactory average recoveries of the analytes ranged from 93.2% to 101.1%. The results indicated that the decorated magnetic nanoparticles can be suitable for extraction of phenols from environmental water samples. The proposed method was sensitive, effective, practical and robust for the determination of tetrabromobisphenol A and 4-nonylphenol in environmental water samples.

High Performance of Covalently Grafting onto Collagen in The Presence of Graphene Oxide

A collagen-based copolymer, ASC-g-Poly(methyl methacrylate-co-Ethyl Acrylate), was synthesized in the presence of Graphene Oxide (GO) via an in-situ polymerization. The presence of GO that increased the accessible surface area for initiated collagen chains allowed for an accelerated polymerization with highly improved grafting performance and efficiency. This was conducted from two polymerization systems with varied comonomer feed ratios, in which two distinguished GO loadings were used. The processability of the achieved nanocomposite was then evaluated through casting and electrospinning processing methods. Fourier Transform Infrared Spectroscopy (FT-IR), UV-Vis spectroscopy, Differential Scanning Calorimeter (DSC), Thermogravimetric analysis (TGA), Scanning Electron Microscope (SEM), Transmission electron microscopy (TEM), and tensile analysis were conducted to characterize the GO-ASC-g-P(MMA-co-EA). The nanocomposite films showed a unique morphology, multilayer nanostructure of the grafted GO monolayers that deposited simultaneously one on top of another. The morphology of the electrospun fibers was affected by the addition of GO loadings in which the increase in fiber diameter was observed while the surface of the nanofibers was decorated by the GO nanolayers. To modify the collagen, this research highlights the importance of introducing functional groups of GO and the substitution of GO loadings as an active nanostructure filler to highly monomer feed ratios improving the physiochemical properties of collagen. This easy-to-apply approach is suggested for applications intending the mechanical properties and deterred degradation of Collagen-based materials.