David H. Bremner

Stimulation of bioprocesses by ultrasound

Ultrasound (US) has become a ubiquitous technological process in a large variety of scientific disciplines. However, little information exists on the use of ultrasound to enhance biological processes and/or processing and consequently this paper provides an overview of work reported to date on this topic. This review provides a brief introduction to ultrasound and the history of ultrasound as applied to bioprocesses. This is followed by a discussion of the influence of US on discrete enzyme systems, enzymes used in bioremediation, microbial fermentations and enzymatic hydrolysis of biopolymers. Augmentation of anaerobic digestion by US is then considered along with enhancement of enzymes in food science and technology. The use of ultrasonically stimulated enzymes in synthesis is then considered and other relevant miscellaneous topics are described. It is concluded that the precise mechanism of action of US in bio-processing remains to be elucidated though a variety of plausible suggestions are made.

Carboxymethyl chitosan-mediated synthesis of hyaluronic acid-targeted graphene oxide for cancer drug delivery

In order to enhance the efficiency and specificity of anticancer drug delivery and realize intelligently controlled release, a new drug carrier was developed. Graphene oxide (GO) was first modified with carboxymethyl chitosan (CMC), followed by conjugation of hyaluronic acid (HA) and fluorescein isothiocyanate (FI). The resulting GO-CMC-FI-HA conjugate was characterized and used as a carrier to encapsulate the anticancer drug doxorubicin (DOX) to study in vitro release behavior. The drug loading capacity is as high as 95% and the drug release rate under tumor cell microenvironment of pH 5.8 is significantly higher than that under physiological conditions of pH 7.4. Cell uptake studies show that the GO-CMC-FI-HA/DOX complex can specifically target cancer cells, which are over-expressing CD44 receptors and effectively inhibit their growth. The above results suggest that the functionalized graphene-based material has potential applications for targeted delivery and controlled release of anticancer drugs.

Removal of blue-green algae using the hybrid method of hydrodynamic cavitation and ozonation.

A suspension of Microcystis aeruginosa (30 μg L(-1)chlorophyll a) was circulated in a hydrodynamic cavitation device and ozone was introduced at the suction side of the pump. The removal of algae over 10 min using hydrodynamic cavitation alone and ozone alone is less than 15% and 35%, respectively. The destruction of algae rises significantly from 24% in the absence of the orifice to 91% with the optimized orifice on 5 min of processing using hydrodynamic cavitation along with ozone (HC/O(3)) and the utilization of ozone increases from 32% to 61%. Interestingly, the suction process is more effective than the extrusion method (positive pressure) and the optimal bulk temperature for algal elimination was found to be 20 °C. Increasing the input concentration of ozone is favorable for the removal of algae but leads to a greater loss of ozone and a decrease in the utilization of ozone. Under the optimal conditions, the algal cells and chlorophyll a are completely destroyed in 10 min by use of the hybrid method.

Malondialdehyde and 4-hydroxy-2-nonenal in plant tissue cultures : LC-MS determination of 2, 4-dinitrophenylhydrazone derivatives

The cytologically active secondary lipid peroxidation products, malondialdehyde (MDA) and 4-hydroxy-2-nonenal (HNE) have been detected as their 2,4-dinitrophenylhydrazone (DNP) derivatives in plant tissue cultures using LC-MS. This paper reports, for the first time, the use of LC-MS methodology to definitively identify 4-hydroxy-2-nonenal in plants. Limits of detection for the two derivatives are approximately 5 pmol (1.2 x 10(-9) g; 1 microM) and 0.1 pmol (3 x 10(-11) g; 20 nM) respectively. Mass spectrometer response was linear in the range from 2-200 microM DNP-MDA and 0.02-10 microM DNP-HNE. This methodology has been used to assess the formation of aldehydic secondary lipid peroxidation products in dedifferentiated callus cultures of Daucus carota. The finding that profiles of MDA and HNE can be correlated with embryogenic competence is of considerable interest as oxidative status has already been implicated as a regulatory factor in animal development.

Coupling of chemical, electrochemical and ultrasonic energies for controlled generation of hydroxyl radicals: Direct synthesis of phenol by benzene hydroxylation

Hydroxyl radicals HO are generated under Fenton-like (Fe2++H2O2→HO+OH−+Fe3+) catalytic conditions using chemical, electrochemical and ultrasonic energies in combination. The resulting hydroxyl radicals are utilised in a model reaction in which benzene is hydroxylated directly to produce phenol. Chemical energy alone using a FeCl2 catalyst supported on silica gel gives synthetic yields of ca. 2% (calculated on benzene initially present), which are increased to 13–15% when irradiated with ultrasound. Coupled chemical and electrochemical synthesis in which the Fe2+ catalyst is generated in situ through controlled dissolution of an iron electrode produces yields of 10–13%. Higher yields (15–20%) are obtained when ultrasonic energy is coupled with the chemical–electrochemical method. The merits and limitations of these different methods and the significance of the yields of the model reaction in terms of the efficiency of radical generation are discussed. It is concluded that the combined chemical–electrochemical–ultrasonic approach offers more effective control of energy input for hydroxyl radical generation appropriate to various synthetic reactions. The direct synthesis of phenol approaches a limiting yield of ca. 20% when competing side reactions, such as further oxidation, occur.

Recent advances in organic synthesis utilizing ultrasound

Abstract This review describes the recent applications of ultrasound in organic synthesis. Oxidation processes, N-C and C-C bond formation (encompassing the Wittig, Ullman and acyloin reactions), cycloaddition reactions (including the first example of an ultrasonically promoted Diels-Alder reaction), bond cleavage reactions and biological examples are discussed. The important area of sonochemical switching is reviewed and comments are made on the relationship between ionic and radical sonochemical reactions.

Visualisation of fingermarks and grab impressions on fabrics. Part 1: gold/zinc vacuum metal deposition.

Vacuum metal deposition (VMD) is a highly sensitive technique originally introduced for detecting latent fingermarks on smooth non-porous surfaces such as carrier bags, plastics and glass. The current study explores whether VMD can be used in the examination of clothing from physical and sexual assault cases in order to visualise identifiable fingermark ridge detail and/or palmar flexion crease detail, thus allowing potential areas to be indicated for DNA swabbing and/or to determine the sequence of events. Four different fabrics were utilised during this study - nylon, polyester, polycotton and cotton, along with 15 donors who ranged in their age and propensity to leave fingermarks, from good to medium to poor as determined by results obtained from test runs using paper and plastic carrier bags processed with VMD. Once samples were collected they were kept for a determined time (1, 2, 3, 4, 5, 6, 7, 14, 21 or 28 days) and then treated using the gold/zinc metal VMD process. From the results, it appears that greater ridge detail is visible on the smoother non-porous fabrics, such as nylon whereas on rougher porous fabrics, such as cotton, only empty prints and impressions, rather than any ridge details, were visible. All fabrics did however allow the development of touch marks that could be targeted for DNA taping thus potentially leading to a DNA profile and possible identification of a suspect.

The chemistry of ultrasonic degradation of organic compounds

The destruction of toxic organic molecules using a dvanced oxidation processes (AOPs) is a potent tool for pollution con trol and environmental protection. Ultrasound is a convenient and effective method of generating hydroxyl radicals which is the key oxidant in AOPs. This review desc ribes the use of ultrasound and associated chemical reactions, with and without add itives, as a powerful means of remediating water contaminated with organic pollutants. After a brief introduction to ultrasound and sonochemistry, their application for the oxidation of polycyclic aromatic hydrocarbons, phenol and substituted pheno ls is considered. Next is the decomposition of chlorinated phenols, and other chl orinated organics, then removal of recalcitrant smaller organic molecules. A discussi on follows of recent work that has investigated the effects of initial concentration o f substrates; the use of different ultrasonic frequencies; the inclusion of oxidising species, inorganic particles, or salts and their contribution to enhanced degradation. Fi ally, brief comments are made on the status of ultrasound as an AOP treatment.

Effects of the Lipid Peroxidation Products 4-Hydroxy-2-Nonenal and Malondialdehyde on the Proliferation and Morphogenetic Development of in vitro Plant Cells

Summary The purpose of this study was to evaluate the toxicological effects of 4-hydroxy-2-nonenal (HNE) and malondialdehyde (MDA) on in vitro plant cells using the model morphogenetic system of Daucus carota L. for the production of somatic embryos. It was found that both HNE and MDA inhibited proliferative growth and embryogenesis in D. carota cultures. However, embryogenic capacity was restored when callus cultures were transferred to embryo induction medium without FINE or MDA and the recovery of morphogenetic competence was more pronounced in cultures which had been exposed to MDA as compared to those which had been treated with HNE. Also, differential responses between embryogenic and nonembryogenic cultures were observed in relation to the delivery of aldehydes in different culture media. This paper reports, for the first time, the toxicological effects of HNE and MDA on in vitro plant cells. The significance of these findings in relation to the control of in vitro development in plant tissue cultures which are used in biotechnology programmes is discussed.

Effect of ultrasound on the extraction of total anthocyanins from Purple Majesty potato

This study examined anthocyanin extraction using the application of ultrasound to raw freeze dried, microwaved and raw sliced Purple Majesty potato, a new pigmented potato variety rich in anthocyanins. A 20 kHz probe was used for the sonication at 3 different amplitudes (30%, 50% and 70%) and ethanol in water at different ratios (50:50 and 70:30 v/v) was used for the extraction. Anthocyanin extraction from raw freeze dried purple potato was optimal at an ethanol:water ratio (70:30; v/v) after 5 min of ultrasonication, while the least amount of anthocyanins was extracted from raw sliced potatoes. The application of microwaves (as a pre-treatment) before the UAE resulted in an increase in the amount of anthocyanins extracted and a decrease in the amount of solvent used. Analysis of variance showed that potato form, ultrasonication time, ultrasonication amplitude and solvent ratio as well as two and three way interactions between some of these factors had a very significant effect (p<0.000) on the amount of anthocyanins extracted.