Efficient Polymer Pendant Approach toward High Stable Organic Fluorophore for Sensing Ultratrace Hg2+ with Improved Biological Compatibility and Cell Permeability.

A convenient and efficient method to eliminate the aggregation effect of organic photoelectric sensing materials and to improve biological compatibility and cell permeability as well was developed by hanging organic fluorophores on a polymer chain, for example, fluorescein fluorophores had been controllably hung on polyacrylamide main chains with a 1:2 stoichiometric ratio by a simple copolymerization strategy. The results showed that introduction of water-soluble bioactive polyacrylamide main chains into fluorescein fluorophores via covalent bonds could effectively improve their optical stability by deteriorating π-π stack and charge-transfer interactions among different fluorophores. More importantly, the resultant materials possessed low toxicity and excellent cell permeability ten times larger than their precursor fluorescein fluorophore, which made it express an especially turn-on fluorescent response to ultratrace Hg2+ both in aqueous and living cells by forming stable 5-member-ring complexes with Hg2+ with a correlation coefficient of 0.997 and a low detection limit of 4.0 × 10-10 mol·L-1. This work provides promising insight into constructing some practical sensing materials for environmentally-friendly biological analyses.

A modified fluorescein derivative with improved water-solubility for turn-on fluorescent determination of Hg2+ in aqueous and living cells.

To improve the water-solubility of heavy-metal sensing materials, a modified fluorescein-based derivative, acryloyl fluorescein hydrazine (ACFH), was designed and developed by incorporating a non-hydrogen-bonding group into the conjugated molecule for weakening intermolecular hydrogen-bonding interactions. In neutral water environments, ACFH presented a fluorescence-enhancement performance at λmax=512nm in the presence of Hg2+, which could be visualized by naked-eyes. Under the optimized conditions, the linear range of Hg2+ detection was 1.0-100×10-9molL-1 with a correlation coefficient of 0.9992 and a detection limit of 0.86×10-9molL-1. The recognition mechanism was confirmed to be a stable and irreversible 1:1 five-member ring complex between ACFH and Hg2+ with a coordination constant of 3.36×109. ACFH would possess a potential application in detecting Hg2+ for biological assay with low cytotoxicity.