Chemical modification of graphene with grape seed extract: Its structural, optical and antimicrobial properties

Natural Extracts for Antibacterial Applications

Bacteria-induced epidemics and infectious diseases are seriously threatening the health of people around the world. In addition, antibiotic therapy has been inducing increasingly more serious bacterial resistance, which makes it urgent to develop new treatment strategies to combat bacteria, including multidrug-resistant bacteria. Natural extracts displaying antibacterial activity and good biocompatibility have attracted much attention due to greater concerns about the safety of synthetic chemicals and emerging drug resistance. These antibacterial components can be isolated and utilized as antimicrobials, as well as transformed, combined, or wrapped with other substances by using modern assistive technologies to fight bacteria synergistically. This review summarizes recent advances in natural extracts from three kinds of sources-plants, animals, and microorganisms-for antibacterial applications. This work discusses the corresponding antibacterial mechanisms and the future development of natural extracts in antibacterial fields.

A Review on Graphene Based Materials and Their Antimicrobial Properties

Graphene-based materials are found as excellent resources and employed as efficient anti-microbial agents, and they have been receiving significant attention from scientists and researchers in this regard. By giving special attention to recent applications of graphene-based materials, the current review is dedicated to unveiling the antimicrobial properties of graphene and its hybrid composites and their preparation methods. Different factors like the number of layers, concentration, size, and shape of the antibacterial activity are thoroughly discussed. Graphene-based materials could damage the bacteria physically by directly contacting the cell membrane or wrapping the bacterial cell. It can also chemically react to bacteria through oxidative stress and charge transfer mechanisms. This review explains such mechanisms thoroughly and summarizes the antibacterial applications (wound bandages, coatings, food packaging, etc.) of graphene and its hybrid materials.

Comprehensive Enhancement in Thermomechanical Performance of Melt-Extruded PEEK Filaments by Graphene Incorporation

A simple and scalable fabrication process of graphene nanoplatelets (GnPs)-reinforced polyether ether ketone (PEEK) filaments with enhanced mechanical and thermal performance was successfully demonstrated in this work. The developed PEEK-GnP nanocomposite filaments by a melt-extrusion process showed excellent improvement in storage modulus at 30 °C (61%), and significant enhancement in tensile strength (34%), Young's modulus (25%), and elongation at break (37%) when GnP content of 1.0 wt.% was used for the neat PEEK. Moreover, the GnPs addition to the PEEK enhanced the thermal stability of the polymer matrix. Improvement in mechanical and thermal properties was attributed to the improved dispersion of GnP inside PEEK, which could form a stronger/robust interface through hydrogen bonding and π-π* interactions. The obtained mechanical properties were also correlated to the mechanical reinforcement models of Guth and Halpin-Tsai. The GnP layers could form agglomerates as the GnP content increases (>1 wt.%), which would decline neat PEEK's crystallinity and serve as stress concentration sites inside the composite, leading to a deterioration of the mechanical performance. The results demonstrate that the developed PEEK-GnP nanocomposites can be used in highly demanding engineering sectors like 3D printing of aerospace and automotive parts and structural components of humanoid robots and biomedical devices.

Effect of graphene oxide with different morphological characteristics on properties of immobilized enzyme in the covalent method

Although graphene oxide (GO) has great potential in the field of immobilized enzyme catalysts, the detailed effects of GO with different morphological structures on immobilized enzyme are not well understood. GOs were prepared from 8000 mesh and nanoscale graphite at different reaction temperatures, and used as carriers to immobilize alpha-amylase by cross-linking method. The properties of GOs were characterized through Atomic force microscope, Fourier-transformed infrared, X-ray photoelectron spectroscopy, Raman and UV-Vis. Furthermore, the dosage of cross-linking agent, cross-linking time, optimum temperature/pH, thermal/pH/storage stability, reusability and kinetic parameters of immobilized enzymes were investigated. The results showed that the loading of alpha-amylase on GOs was 162.3-274.2 mg g^-1. The reusability experiments revealed high activity maintenance of immobilized alpha-amylase even after seven reaction cycles. Moreover, the storage stability of immobilized enzyme improved via immobilization in comparison with free one and it maintained over 70% of their initial activity after 20 days storage at 4 °C.