A new tool for the selective detection of dopamine in water, with potential applications to urine and serum, has recently been developed by the Chinese research group led by Fang Zeng and Shuizhu Wu.
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The new sensor, with a detection limit of 50 nM, is based on the fluorescence response obtained when dopamine reacts with a molecule containing an o-phtalic hemithioacetal (OPTA). The selectivity of the system over other amino acids and primary amines has been obtained by trapping the OPTA-bearing group within the pores of microporous silica particles and enhanced by anchoring a β-cyclodextrin (β-CD) layer on the surface of the particles.
The β-CD, due to their ability of supporting both hydrogen-bond and hydrophobic interactions, serves as a barrier for most interfering molecules but allows dopamine to reach the pores. The authors believe that this derives from its limited capability of forming both hydrophobic and hydrogen-bonds.
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Repeated tests proved that without the β-CD layer the selectivity is lost and that out of 24 potential interfering molecules, among which common amino acids, epinephrine and others, only two (histidine and norepinephrine) gave responses comparable to dopamine. While the results obtained for norepinephrine can be ascribed to the structural similarities to the target molecule, the reason behind the behaviour of the sensor towards histidine are currently unclear.
Dopamine is an important neurotransmitter involved in behavioural responses, sleep regulation, mood and learning processes among others. A malfunction in the dopamine regulating processes and related disruptions are implicated in the attention deficit disorder, Alzheimer`s disease, schizophrenia and psychosis.
Changmin Yu, Ming Luo, Fang Zeng, Fangyuan Zheng and Shuizhu Wu
Chem. Commun., 2011, Advance Article
