Guy Standen

The rapid and specific real-time detection of Legionella pneumophila in water samples using Optical Waveguide Lightmode Spectroscopy

The detection of Legionella pneumophila in water samples using standard microbiological culture techniques is both prolonged and problematic. The bacterium is slow-growing and nutritionally fastidious, such that other indigenous species can out-compete the Legionella even when using antibiotic supplemented media. Optical Waveguide Lightmode Spectroscopy (OWLS) is a real-time analytical system whereby a change to a higher coupling angle where the refractive index of a bacterial cell is higher than that of the covering medium. In this study an aqueous suspension of L. pneumophila was passed across the surface of waveguides functionalised with a specific anti-Legionella antibody. The binding between the bacterial cells and the antibody specific for that cell resulted in an increase in the refraction indices of the transverse electric and transverse magnetic photoelectric currents. We report the optimisation of a rapid and sensitive (1.3 x 10(4) CFU mL-1) detection method for L. pneumophila contamination in a water sample in less than 25 min. This is a significant reduction in the time taken to determine the presence of the bacterium which with conventional techniques normally takes up to fourteen days. In addition, the specificity of the technique to L. pneumophila was demonstrated. The OWLS results were validated by conventional microbiology screening and atomic force microscopy of the surface of the waveguide, showing its species specificity and potential applications in environmental and clinical analysis.

Escherichia coli Nissle 1917 enhances bioavailability of serotonin in gut tissues through modulation of synthesis and clearance

Accumulating evidence shows indigenous gut microbes can interact with the human host through modulation of serotonin (5-HT) signaling. Here we investigate the impact of the probiotic Escherichia coli Nissle 1917 (EcN) on 5-HT signalling in gut tissues. Ex-vivo mouse ileal tissue sections were treated with either EcN or the human gut commensal MG1655, and effects on levels of 5-HT, precursors, and metabolites, were evaluated using amperometry and high performance liquid chromatography with electrochemical detection (HPLC-EC). Exposure of tissue to EcN cells, but not MG1655 cells, was found to increase levels of extra-cellular 5-HT. These effects were not observed when tissues were treated with cell-free supernatant from bacterial cultures. In contrast, when supernatant recovered from untreated ileal tissue was pre-incubated with EcN, the derivative cell-free supernatant was able to elevate 5-HT overflow when used to treat fresh ileal tissue. Measurement of 5-HT precursors and metabolites indicated EcN also increases intracellular 5-HTP and reduces 5-HIAA. The former pointed to modulation of tryptophan hydroxylase-1 to enhance 5-HT synthesis, while the latter indicates an impact on clearance into enterocytes through SERT. Taken together, these findings show EcN is able to enhance 5-HT bioavailability in ileal tissues through interaction with compounds secreted from host tissues.

Metal chelation by a plant lignan, secoisolariciresinol diglucoside

Abstract Secoisolariciresinol diglucoside (SDG) is a polyphenolic phytoestrogen which is particularly abundant in flaxseed. As a diphenolic compound, SDG is expected to function as a metal chelating ligand. The affinity of SDG for metal cations was determined using a mass spectrometric approach. Experiments yielded equilibrium constants in aqueous solution for SDG·Ca2+, SDG·Cu2+, SDG·Pb2+, SDG·Ni2+, SDG·Fe2+ and SDG·Ag+ of 20.34, 5.99, 4.26, 2.77, 2.46 and 1.90, respectively. These values are consistent with those determined for plant phenolics. Semiempirical calculations for the SDG metal complexes yield an insight into their likely structures.Graphical Abstract.

Nanostructured DPA‐MPC‐DPA triblock copolymer gel for controlled drug release of ketoprofen and spironolactone

Uncontrolled rapid release of drugs can reduce their therapeutic efficacy and cause undesirable toxicity; however, controlled release from reservoir materials helps overcome this issue. The aims of this study were to determine the release profiles of ketoprofen and spironolactone from a pH‐responsive self‐assembling DPA‐MPC‐DPA triblock copolymer gel and elucidate underlying physiochemical properties.

Development of MPC-DPA polymeric nanoparticle systems for inhalation drug delivery applications

Abstract Inhalation of nanoparticles for pulmonary drug delivery offers the potential to harness nanomedicine formulations of emerging therapeutics, such as curcumin, for treatment of lung cancer. Biocompatible nanoparticles composed of poly(2‐methacryloyloxyethyl phosphorylcholine)‐b‐poly(2‐(diisopropylamino)ethyl methacrylate) (MPC‐DPA) have been shown to be suitable nanocarriers for drugs, whilst N‐trimethyl chitosan chloride (TMC) coating of nanoparticles has been reported to further enhance their cellular delivery efficacy; the combination of the two has not been previously investigated. Development of effective systems requires the predictable, controllable, and reproducible ability to prepare nanosystems possessing particle sizes, and drug loading capacities, appropriate for successful airway travel, lung tissue penetration, and tumor suppression. Although a number of MPC‐DPA based nanosystems have been described, a complete understanding of parameters controlling nanoparticle formation, size, and morphology has not been reported; in particular the effects of differing solvents phases remains unclear. In this current study a matrix of 31 solvent combinations were examined to provide novel data pertaining to the formation of MPC‐DPA nanoparticles, and in doing so afforded the selection of systems with particle sizes appropriate for pulmonary delivery applications to be loaded with curcumin, and coated with TMC. This paper presents the first report of novel data detailing the successful preparation, characterisation, and optimisation of MPC‐DPA nanoparticles of circa 150–180 nm diameter, with low polydispersity, and a curcumin loading range of circa 2.5–115 &mgr;M, tunable by preparation parameters, with and without TMC coating, and thus considered suitable candidates for inhalation drug delivery applications. Graphical Abstract Figure. No Caption available.