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Melatonin, a pineal secretory product, and its precursors, tryptophan and serotonin, were examined for their metal binding affinities for both essential and toxic metals: aluminium, cadmium, copper, iron, lead, and zinc. An electrochemical technique, adsorptive stripping voltammetry, showed the varying abilities of melatonin and its precursors to bind the metals in situ. The results show that the following metal complexes were formed: aluminium with melatonin, tryptophan, and serotonin; cadmium with melatonin and tryptophan; copper with melatonin and serotonin; iron(III) with melatonin and serotonin; lead with melatonin, tryptophan, and serotonin; and zinc with melatonin and tryptophan. Iron(II) showed the formation of an in situ complex with tryptophan only. These studies suggest a further role for melatonin in the reduction of free radical generation and metal detoxification, and they may explain the accumulation of aluminium in Alzheimer's disease.

Research demonstrates that antioxidants and metal chelators may be of beneficial use in the treatment of neurodegenerative diseases, such as Alzheimer's disease (AD). This study investigated the antioxidant and metal-binding properties of curcumin, capsaicin, and S-allylcysteine, which are major components found in commonly used dietary spice ingredients turmeric, chilli, and garlic, respectively. The DPPH assay demonstrates that these compounds readily scavenge free radicals. These compounds significantly curtail iron- (Fe2+) and quinolinic acid (QA)-induced lipid peroxidation and potently scavenge the superoxide anion generated by 1 mM cyanide in rat brain homogenate. The ferrozine assay was used to measure the extent of Fe2+ chelation, and electrochemistry was employed to measure the Fe3+ binding activity of curcumin, capsaicin, and S-allylcysteine. Both assays demonstrate that these compounds bind Fe2+ and Fe3+ and prevent the redox cycling of iron, suggesting that this may be an additional method through which these agents reduce Fe2+-induced lipid peroxidation. This study demonstrates the antioxidant and metal-binding properties of these spice ingredients, and it is hereby postulate that these compounds have important implications in the prevention or treatment of neurodegenerative diseases such as AD.

This study investigated the neuroprotective effects of the curcuminoids against lead-induced neurotoxicity. The results show that lead significantly increases lipid peroxidation and reduces the viability of primary hippocampal neurons in culture. This lead-induced toxicity was significantly curtailed by the co-incubation of the neurons with the curcuminoids. In a whole animal experiment, rats were trained in a water maze and thereafter dosed with lead and/or curcumin (CURC), demethoxycurcumin (DMC), or bisdemethoxycurcumin (BDMC) for 5 days. Animals treated with curcumin and demethoxycurcumin but not bisdemethoxycurcumin had more glutathione and less oxidized proteins in the hippocampus than those treated with lead alone. These animals also had faster escape latencies when compared to the Pb-treated animals indicating that CURC- and DMC-treated animals retain the spatial reference memory. The findings of this study indicate that curcumin, a well-established dietary antioxidant, is capable of playing a major role against heavy metal-induced neurotoxicity and has neuroprotective properties.

Copper is an essential trace element which forms an integral component of many enzymes. While trace amounts of copper are needed to sustain life, excess copper is extremely toxic. Copper has been implicated in various neurodegenerative disorders, such as Wilson's and Alzheimer's diseases. Previous studies showed that melatonin, the principle secretory product of the pineal gland, binds Cupric chloride (Cu2+) and that this may have implications in copper-induced neurodegenerative diseases. In the present study, in vitro copper-mediated lipid peroxidation was induced. Melatonin (5 mM) protected against copper-mediated lipid peroxidation in liver homogenates. Electron micrographs of in vivo administered Cu2+ and melatonin show that melatonin affords some protection to rat hepatocytes in the presence of copper. Electrochemical studies performed show that melatonin, in addition to binding Cu2+, may provide protection against copper-mediated free radical damage by binding Cu1+. The findings of these studies provide further evidence for the neuroprotective role of melatonin.

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Resonant and acoustic wave devices have been researched for several decades for application in the gravimetric sensing of a variety of biological and chemical analytes. These devices operate by coupling the measurand (e.g. analyte adsorption) as a modulation in the physical properties of the acoustic wave (e.g. resonant frequency, acoustic velocity, dissipation) that can then be correlated with the amount of adsorbed analyte. These devices can also be miniaturized with advantages in terms of cost, size and scalability, as well as potential additional features including integration with microfluidics and electronics, scaled sensitivities associated with smaller dimensions and higher operational frequencies, the ability to multiplex detection across arrays of hundreds of devices embedded in a single chip, increased throughput and the ability to interrogate a wider range of modes including within the same device. Additionally, device fabrication is often compatible with semiconductor volume batch manufacturing techniques enabling cost scalability and a high degree of precision and reproducibility in the manufacturing process. Integration with microfluidics handling also enables suitable sample pre-processing/separation/purification/amplification steps that could improve selectivity and the overall signal-to-noise ratio. Three device types are reviewed here: (i) bulk acoustic wave sensors, (ii) surface acoustic wave sensors, and (iii) micro/nano-electromechanical system (MEMS/NEMS) sensors.