In this study, we investigate the antibacterial activity of ZnO nanoparticles with various particle sizes. ZnO was prepared by the base hydrolysis of zinc acetate in a 2-propanol medium and also by a precipitation method using Zn(NO) and NaOH. The products were characterized by x-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. Bacteriological tests such as minimum inhibitory concentration (MIC) and disk diffusion were performed in Luria-Bertani and nutrient agar media on solid agar plates and in liquid broth systems using different concentrations of ZnO by a standard microbial method for the first time. Our bacteriological study showed the enhanced biocidal activity of ZnO nanoparticles compared with bulk ZnO in repeated experiments. This demonstrated that the bactericidal efficacy of ZnO nanoparticles increases with decreasing particle size. It is proposed that both the abrasiveness and the surface oxygen species of ZnO nanoparticles promote the biocidal properties of ZnO nanoparticles.

Storage solutions: DNA is shown to be soluble in a variety of choline‐based, hydrated ionic liquids (ILs; see picture). The IL‐stored DNA molecules have exceptional long‐term stability, in excess of one year.

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A systematic and complete antibacterial study on well-designed and well-characterized microparticle (micro), nanoparticle (nano), and capped nano ZnO has been carried out in both dark and light conditions with the objective of arriving at the mechanism of the antibacterial activity of ZnO, particularly in the dark. The present systematic study has conclusively proved that reactive oxygen species (ROS) such as (•)OH, (•)O2(-), and H2O2 are significantly produced from aqueous suspension of ZnO even in the dark and are mainly responsible for the activity in the dark up to 17%, rather than Zn(2+) ion leaching as proposed earlier. This work further confirms that surface defects play a major role in the production of ROS both in the presence and absence of light. In the dark, superoxide ((•)O2(-)) radical mediated ROS generation through singly ionized oxygen vacancy is proposed for the first time, and it is confirmed by EPR and scavenger studies. ROS such as (•)O2(-), H2O2, and (•)OH have been estimated by UV-visible spectroscopy using nitro blue tetrazolium (NBT), KMnO4 titrations, and fluorescence spectroscopy, respectively. These are correlated to the antibacterial activity of ZnO in the dark and light. The activity is found to be highest for nano ZnO and least for micro ZnO, with capped ZnO between the two, highlighting the important role of surface defects in generation of ROS. The surface charge density of ZnO in dark and light has been estimated for the first time to the best of our knowledge, and it can influence antibacterial activity. Our work proposes a new mechanism mediated by superoxide species, for antibacterial activity of ZnO especially in the dark.

Keratin from various livestock industries is currently a waste material that has potential as a source of polyamide polymers that could replace fossil fuel derived materials if processing methods can be developed. In this work we have investigated methods for the dissolution and regeneration of keratin. Dissolution of keratin (from turkey feather) in ionic liquids was conducted under nitrogen at 130 °C for 10 hours. It was found that [BMIM]Cl, [AMIM]Cl and [choline][thioglycolate] could dissolve turkey feather keratin without addition of solvent or other chemicals. A significant percentage of solubility was obtained, up to 45% by weight. A water insoluble fraction was recovered by addition of water to the solution (∼50%). The structure and properties of this regenerated, water insoluble fraction were investigated. Compared to the starting material, the regenerated keratin shows structural changes rather than chemical changes within the polypeptide chains. The remaining fraction, consisting of water soluble fragments, was characterised by gel electrophoresis.

Transient implantable medical bionics offer great promise in the field of smart controlled release and tissue regeneration. On-board energy storage is the ideal power system to drive them. In this work, a critical component of such a device, a biodegradable polymer electrolyte (silk fibroin-choline nitrate) has been developed. The efficiency of this electrolyte is demonstrated when deployed in a biodegradable thin-film magnesium battery. The battery, encapsulated in silk, offers a specific capacity of 0.06 mAh cm-2. The enzymatic degradation of the whole device occurs over 45 days in the buffered protease XIV solution. A programmed battery lifetime can be achieved using silk protection layers. This battery system provides a new avenue for an on-board biodegradable power source for next-generation transient medical bionics.

Substantial dissolution of wool was obtained in [AMIM][dca] and [choline][thioglycolate] ionic liquids as well as in deep eutectic solvent mixtures, under a variety of conditions including the use of a reducing agent.

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