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Nephelium lappaceum is a tropical fruit whose peel possesses antioxidant properties. Experiments on the isolation and identification of the active constituents were conducted, and on their antioxidant activity using a lipid peroxidation inhibition assay. The methanolic extract of N. lappaceum peels exhibited strong antioxidant properties. Sephadex LH-20 chromatography was utilized in the isolation of each constituent and the antioxidant properties of each was studied. The isolated compounds were identified as ellagic acid (EA) (1), corilagin (2) and geraniin (3). These compounds accounted for 69.3% of methanolic extract, with geraniin (56.8%) as the major component, and exhibited much greater antioxidant activities than BHT in both lipid peroxidation (77-186 fold) and DPPH• (42-87 fold) assays. The results suggest that the isolated ellagitannins, as the principal components of rambutan peels, could be further utilized as both a medicine and in the food industry.

A series of acyclic thiourea derivatives, designed to create a cleft with four hydrogen bond donors suitable for carboxylate recognition, have been prepared, and their ability to bind to N-protected amino acid carboxylate salts has been investigated. The crystal structure of one of the thioureas has been determined showing that it forms a hydrogen bonded centrosymmetric dimer in the solid-state, in a conformation appropriate for the desired binding of carboxylates. The thioureas show good discrimination between different amino acids and those thioureas incorporating chiral moieties show moderate enantioselectivity for a range of amino acid derivatives.

Organic linkers such as (N-Boc-aminomethyl)phenyl (BocNHCH2C6H4) and N-Boc-ethylenediamine (Boc-EDA) have been covalently tethered onto a glassy carbon surface by employing electrochemical reduction of BocNHCH2C6H4 diazonium salt or oxidation of Boc-EDA. After removal of the Boc group, anthraquinone as a redox model was attached to the linker by a solid-phase coupling reaction. Grafting of anthraquinone to electrodes bearing a second spacer such as 4-(N-Boc-aminomethyl)benzoic acid or N-Boc-beta-alanine was also performed by following this methodology. The surface coverage, stability and electron transfer to/from the tethered anthraquinone redox group through the linkers were investigated by cyclic voltammetry. The effects of pH and scan rate were studied, and the electron-transfer coefficient and rate constant were determined by using Laviron's equation for the different types of linker. The combination of electrochemical attachment of protected linkers and subsequent modifications under the conditions of solid-phase synthesis provides a very versatile methodology for tailoring a wide range of organic functional arrangements on a glassy carbon surface.

Various mono-Boc-protected diamines have been covalently grafted to glassy carbon electrodes by electrochemical oxidation of the free amine. After deprotection of the Boc group, anthraquinone and nitrobenzene probes were coupled to the linkers using solid-phase coupling reactions. X-Ray photoelectron spectroscopy and cyclic voltammetry were used to monitor the coupling efficiency, effect of linker length on the surface coverage and electron transfer between the attached redox probes and electrode. The anthraquinone surface coverage was found to decrease as the chain length of alkyl diamine linker increased and the electron transfer kinetics were found to be faster for the lower coverages and the longer, more flexible linkers. In the case of nitrobenzene, there was only a slightly change in coverage with increasing linker length. This electrochemical attachment of protected diamine linkers followed by solid-phase coupling provides a very versatile methodology for attaching a wide range of molecular architectures onto glassy carbon surfaces.

Surface modification techniques are essential to the construction of enzyme based elements of biofuel cells and biosensors. In this article we report on the preparation and characterisation of modified carbon electrodes which were used as supports for the immobilisation of laccase from Trametes hirsuta. The electrodes were electrochemically modified with diamine or diazonium linkers followed by attachment of either anthracene or anthraquinone head groups using solid phase chemical methodology. These well defined surfaces were found to effectively bind laccase and to provide direct electrical contact to the enzyme active site, as evidenced by XPS, EIS and voltammetry, respectively. The influence of the type of linker and head group on enzyme binding and bioelectrocatalytic activity are evaluated.

Here for the first time, we detail self-contained (wireless and self-powered) biodevices with wireless signal transmission. Specifically, we demonstrate the operation of self-sustained carbohydrate and oxygen sensitive biodevices, consisting of a wireless electronic unit, radio transmitter and separate sensing bioelectrodes, supplied with electrical energy from a combined multi-enzyme fuel cell generating sufficient current at required voltage to power the electronics. A carbohydrate/oxygen enzymatic fuel cell was assembled by comparing the performance of a range of different bioelectrodes followed by selection of the most suitable, stable combination. Carbohydrates (viz. lactose for the demonstration) and oxygen were also chosen as bioanalytes, being important biomarkers, to demonstrate the operation of the self-contained biosensing device, employing enzyme-modified bioelectrodes to enable the actual sensing. A wireless electronic unit, consisting of a micropotentiostat, an energy harvesting module (voltage amplifier together with a capacitor), and a radio microchip, were designed to enable the biofuel cell to be used as a power supply for managing the sensing devices and for wireless data transmission. The electronic system used required current and voltages greater than 44 µA and 0.57 V, respectively to operate; which the biofuel cell was capable of providing, when placed in a carbohydrate and oxygen containing buffer. In addition, a USB based receiver and computer software were employed for proof-of concept tests of the developed biodevices. Operation of bench-top prototypes was demonstrated in buffers containing different concentrations of the analytes, showcasing that the variation in response of both carbohydrate and oxygen biosensors could be monitored wirelessly in real-time as analyte concentrations in buffers were changed, using only an enzymatic fuel cell as a power supply.