Salicylimine-Based Fluorescent Chemosensor for Aluminum Ions and Application to Bioimaging

Chemosensors for selective detection of various biologically and environmentally relevant metal ions have recently attracted great attention. The widespread use of aluminum in food additives, aluminum-based pharmaceuticals, and storage/cooking utensils often exposes people to aluminum ions. In addition, frequent use of aluminum foil, vessels, and trays for convenience results in moderate increases in the Al3+ concentration in food. After absorption, aluminum ions would be distributed to all tissues in humans and animals and eventually accumulate in the bone. The iron binding protein is known to be the main carrier of Al3+ in plasma, and Al3+ can enter the brain and reach the placenta and fetus. Aluminum ions may stay for a very long time in various organs and tissues before being excreted through the urine. In addition, aluminum ions have been implicated as a causative factor of Alzheimer’s disease and associated with damage to the central nervous system in humans. Although trace amounts of aluminum ions are present in the drinking water, low-dose chronic exposure to the ions may cause Alzheimer’s disease possibly due to accumulation of oxidative damage induced by the ions. Sensitive bioimaging of Al3+ in the cell is a prerequisite for understanding the underlying mechanism about how aluminum ions cause aluminum-induced human diseases including Alzheimer’s disease.Thus, detection of Al3+ is important to control the concentration levels in the biosphere and minimize direct affects on human health.

In recent years, fluorescent chemosensors have attracted significant interest because of their potential use in medicinal and environmental research. The most commonly employed method used for chemosensor detection is the development of probe molecules that consist of a photon interaction site as a fluorophore and a metal binding site. In the presence of specific metal ions, the fluorophore–receptor communication gets turned on as a result of the binding of the metal ions at the receptor site. Until recently, only a few fluorescent chemosensors have been developed for detection of Al3+.Most fluorescent sensors for Al3+ have good selectivity, but this approach has several disadvantages including complicated synthetic procedures and poor water solubility. Meanwhile, some Schiff base compounds coordinated to metal ions were reported to have antitumor and antioxidative activities. Although many Schiff base derivatives incorporating a fluorescent moiety have been used to detect various metal ions, Schiff base-type Al3+ chemosensors are very rare and no examples of water-soluble devices as well as sensors that can be used for cell imaging have been developed. Possible utilization of PSI (o-phenolsalicylimine) as intracellular sensors of Al3+ was also examined by confocal fluorescence microscopy.

Kim, S. Young, J. Kim, Ka(et.al.).Salicylimine-Based Fluorescent Chemosensor for Aluminum Ions and Application to Bioimaging March 2, 2012. Inorg. Chem,Article ASAP. http://pubs.acs.org/doi/suppl/10.1021/ic2024583