Hydrogels have gained recent attention for biomedical applications because of their large water content, which imparts biocompatibility. However, their mechanical properties can be limiting. There has been significant recent interest in the strength and fracture toughness of hydrogel materials in addition to their stiffness and time-dependent behavior. Hydrogels can fail in a brittle manner, although they are extremely compliant. In this work, the failure and fracture of hydrogels are examined using a compression test of spherical hydrogel particles. Spheres of commercially available polyacrylamide–potassium polyacrylate were hydrated and tested to failure in compression as a function of loading rate. The spheres exhibited little relaxation when compressed to small fixed displacements. The distributions of strength values obtained were examined in a particle fracture framework previously used for brittle ceramics. There was loading rate dependence apparent in the measured peak force and calculated peak strength values, but the data fell on a single empirical distribution function of strength for the hydrogels regardless of loading rate. Strength values for these hydrogels were mostly in the range of 0.05–0.3 MPa, illustrating the challenges using hydrogels for mechanically demanding applications such as tissue engineering.

The purpose of this study was to construct a glycyrrhetinic acid (GA)-mediated, breakable, intracellular, nanoscale drug-delivery carrier via amide and esterification reactions. The structures were identified by Fourier-transformed infrared (FTIR) and 1H-nuclear magnetic resonance (1H-NMR) spectrophotometry. The compatibility and safety of the carrier were evaluated using hemolysis and cytotoxicity tests. The GA-copolymer micelle was prepared using the solvent evaporation method. FTIR and 1H-NMR detection demonstrated the successful construction of the polymer. No hemolysis occurred in any concentration of polymer within 3 h, and the hemolysis rate was less than 5%. 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) experimental results showed that the novel polymer reduced the cell survival rate and had significant cytotoxic effects. The blank nanoparticles were liquid with light blue opalescence. Transmission electron microscopy revealed that the empty micelles were uniform spheres, with an average size of 62 nm and a zeta potential of −13 mV. The novel GA-mediated polymeric carrier material developed here has the potential to effectively kill human SMMC-7721 cancer cells within 3 days when the dose is above 500 ug/mL.

Microencapsulation of functioning cells for transplantation therapies is particularly promising, but the cells must retain their proper physiology and viability after being encapsulated. K-562 cells are multipotential and exhibit erythroid, megakaryocytic, or granulocytic properties that can be exploited by using an array of physiologically differentiating factors. The potential for cell differentiation makes it attractive the use of K-562 cells as functional model to the assessment of the effects of encapsulation on cell viability and physiology. Thus, alginate and hybrid alginate matrices were produced by extrusion technique for K-562 cell encapsulation. The produced systems were composed of bare alginate (1–3 wt%) and alginate in combination with chitosan or silica. The resulting materials were characterized by dynamic laser scattering, zeta potential measurements, small-angle X-ray scattering, and Fourier transform infrared spectroscopy. To assess viability, the encapsulated cells were subjected to the Trypan blue exclusion technique and NAD(P)H-dependent oxidoreductase (MTT) assays; hemin-induced erythroid differentiation capacity was also evaluated. The encapsulated alginate-based systems were shown to be monomodal and bimodal, depending on the nature of the capsule, with mean sizes in the range between 414 and 4.129 nm. Encapsulated cells exhibited viability ratios compatible with their use for prolonged cell cultures. Erythroid differentiation occurred in the range between 39 and 44%. The present results allow the consideration of the viability of therapeutic cells encapsulated in both bare alginate and in hybrid matrices.

Some interesting properties such as superelasticity, shape memory effect, kink resistance, good biocompatibility, biomechanical properties, and corrosion resistance made nitinol a popular biomaterial as stent and orthopedic implants. But surface modification is needed to control nickel leaching from its surface, making safe for human body. The aim of this study was to modify the nitinol surface by the silanization technique and electrophoretically deposited hydroxyapatite coating, and to conduct a detailed in vitro and in vivo investigation. Detailed in vitro investigation involved MTT assay with the human osteoblastic cells (MG63 cell) over a period of 5 days and confocal image study. In case of in vivo study, histological study, fluorochrome labeling study, and Micro-Ct study were conducted. The overall in vitro and in vivo results indicate that silanized nitinol samples are showing slightly better level of performance, but both the surface-modified samples are suitable as the potential bio-implant for orthopedic purpose.

A flexible surface-enhanced Raman scattering (SERS) substrate was prepared by vacuum evaporation of silver on the surface of woven nylon fabrics. SERS properties of the Ag-coated nylon fabrics varied as the thickness of silver coatings changed, relative to the morphologies and distribution of silver nanoparticles (NPs) on fiber. The SERS enhancement performance of Ag-coated nylon fabrics was evaluated by collecting Raman signals of different concentrations of p-aminothiophenol (PATP). The results suggested that the nylon fabrics coated with 10 nm thickness Ag NPs coatings possessed high SERS activity and its detection concentration for PATP is as low as 10−9 M. Furthermore, sensitive SERS signals with excellent reproducibility (Relative standard deviation = 8.25%) and stability (30 days) have been demonstrated. In addition, the SERS nylon fabrics have been applied to rapidly detect thiram pesticides on cucumber, which indicated a great potential for trace analysis.

Iron oxide nanoparticles presenting colloidal stability in water were prepared through precipitation and then surface-functionalized with varying citric acid (CA) concentrations (0.10, 0.25, 0.50, and 0.70 g/mL). CA introduced functionality and minimized agglomeration. Iron oxide nanoparticles with colloidal stability in water at physiological pH were obtained after functionalization with 0.25–0.70 g/mL CA, whereas iron oxide nanoparticles without stability in water were obtained after functionalization with 0.10 g/mL CA. An electrode for glucose detection was fabricated by self-assembling colloidal-stable γ-Fe2O3 NP–CA in water on indium tin oxide (ITO) glass, followed by a glucose oxidase (GOx) and Nafion layer. The optimal functionalization of the γ-Fe2O3 NPs was obtained at a CA concentration of 0.25 g/mL. The electrochemical properties and electrocatalytic behavior of the modified electrode designated as Nafion/GOx/γ-Fe2O3 NP–0.25 CA/ITO were then evaluated. The electrode showed high sensitivity for glucose detection of 995.57 and 5.81 µA/(mM cm2) within the linear ranges of 0.1–5.0 µM and 5.0 µM–20.0 mM, respectively. The modified electrode also demonstrated a low limit of detection, good repeatability of 2.5% (n = 10), and sufficient reproducibility of 3.2% (n = 5).

Surface modification of titanium and titanium alloys is a common method to improve anchoring of bone tissue and implants in hard tissue engineering applications. In the current work, a combination of chemical and physical methods (anodization and physical vapor deposition) was used to roughen the titanium surface and deposit iron (Fe) on the surface of titanium at different thicknesses. The optimized thickness of 100 Å was selected for mechanical and biological characterization. We found that anodization increases the surface roughness of Ti from 21 ± 0 to 229 ± 9 nm, whereas Fe deposition does not change it significantly. Our results also showed that surface modification of Ti by anodization increases the proliferation of osteosarcoma cells at both time points, whereas Fe-deposited samples showed the lowest cellular activity. These results suggest that Fe-deposited Ti implants may be suitable candidates for patients with osteosarcoma, as the proliferation of malignant cells decreases in the presence of Fe.

Biomagnetic field sensors based on AlN/FeCoSiB magnetoelectric (ME) composites desire a resonant frequency that can be precisely tuned to match the biomagnetic signal of interest. A tunable mechanical resonant frequency is achieved when ME composites are integrated onto shape memory alloy (SMA) thin films. Here, high-quality c-axis growth of AlN is obtained on (111) Pt seed layers on both amorphous and crystallized TiNiCu SMA thin films on Si substrates. These composites show large piezoelectric coefficients as high as d33,f= 6.4 pm/V ± 0.2 pm/V. Annealing the AlN/Pt/Ta/amorphous TiNiCu/Si composites to 700 °C to crystallize TiNiCu promoted interdiffusion of Ti into the Ta/Pt layers, leading to an enhanced conductivity in AlN. Depositing AlN onto already crystalline TiNiCu films with low surface roughness resulted in the best piezoelectric films and hence is found to be a more desirable processing route for ME composite applications.

Reduced graphene oxide supported titanium dioxide (GO/TiO2) heterojunction composites as highly active photocatalysts were synthesized via simple ultrasonic mixing and hydrothermal reaction using TiCl3 and GO as precursors. Their structure and morphology were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectra, UV-vis spectroscopy, and thermogravimetic analysis. The GO/TiO2 heterojunction composites were used to degrade methyl orange (MO). The adsorption and photocatalytic degradation rate of the prepared GO/TiO2 composites increased by nearly three times compared with that of pristine TiO2 or GO, which reached up 90%, to degrade MO after 4 h, which provides a simple method to obtain photocatalytic materials.

This work demonstrates a double-step method, a simple chemical bath deposition and an in situ polymerization process, to synthesize the stable structure of a composite of Polyaniline/BiVO4/cellulose aerogel (PBC) in wastewater treatment. The poor stability of the carrier catalyst was improved significantly by forming a dense film of polyaniline (PANI) through polymerization on BiVO4/cellulose aerogel (BC). The developed three-dimensional porous structure enhanced photocatalytic stability. For instance, photocatalytic degradation of a dye, methylene blue, reached to 91.67% under the eight times successive irradiation of the visible light. The resulted fine performance could be owed to the strong adsorption of cellulose aerogel, uniform spreading of BiVO4, and the speedy electron separation efficiency of PBC. Moreover, the photocatalytic mechanisms including the role of the free radicals (•OH and •O2−) of the developed PBC were also discussed. The novel structure may present a new insight into the development of the carrier catalyst.

Zn1−xGax/2Fex/2O (x= 0, 0.0156, 0.0312) represents the polycrystalline hexagonal (wurtzite) phase with a space group P63mc synthesized using the sol–gel technique. A comparative study and investigation of structural, optical, and photo-sensing properties of these samples were performed. Structural and vibrational studies show enhancement in the crystallinity of the codoped samples. Optical band gap increases from ∼3.21 to 3.24 eV with substitution because of the improved crystallinity. The photoluminescence properties show modification from yellowish green for x= 0 to a more distinct green for x= 0.0156. The intensity of the luminescence decreases with doping, indicating an overall reduction of defects in the band gap helping the material to become more transparent to visible light. Photocurrent and photosensitivity are modified with the illumination wavelength (290, 450, 540 and 640 nm) with codoping. Sensitivity toward visible lights reduced with codoping. On the other hand, it is more sensitive to ultraviolet light. It indicates the material becomes more transparent for visible light and may be used as photostable device.

The structural, vibrational, and optoelectronic properties of sol–gel synthesized Zn1−x(Al0.5Si0.5)xO nanoparticles were investigated. The X-ray diffraction studies of the samples confirmed the hexagonal wurtzite phase with the space group P63mc. No significant changes were observed in the lattice parameters. The increase in the intensity of $E_{{\rm{high}}}^2$ Raman mode observed at 438 cm−1 indicates a decrease in the crystallite size. The reduction in the deep-level emission band with the introduction of Al/Si indicates a decrease in intrinsic defects for the codoped sample. A unique electron paramagnetic resonance signal at g= 1.96 follows the same trend as the green luminescence, and its evolution was shown to probe the oxygen vacancy concentrations. I–V characteristics curve confirm the increase in the conductivity for the codoped samples. To evaluate the role of surface defects, ultraviolet photoresponse behavior as a function of time was also studied, and an increase in the photocurrent was observed. The slow decay and rise in the photocurrent are because of multiple trapping by interstitial defects. A relatively faster response time was observed with the substitution of Al/Si. It has been observed that prepared nanomaterials are suitable for optoelectronic devices.