ABSTRACT
<p><b>OBJECTIVE</b>To establish a highly sensitive fluorometric nanobiosensor for determination of aqueous mercury ions (Hg(2+)) using optimized mercury-specific oligonucleotide (MSO) probes and graphene oxide (GO).</p><p><b>METHODS</b>The nanobiosensor was assembled by attaching the self-designed MSO(1) (5' end labeled with fluorophore carboxyfluorescein (FAM), denoted as FAM-MSO(1)) and MSO(2) to the surface of GO through strong non-covalent bonding forces. Upon the addition of Hg(2+), the formation of the T-Hg(2+)-T configuration desorbed the FAM-MSO(1) and MSO(2) from the surface of GO, resulting in a restoration of the fluorescence of FAM-MSO(1). Using the specific mispairing of T-Hg(2+)-T and the changes in fluorescent signals in solutions, quantitative analysis of Hg(2+) could be performed.</p><p><b>RESULTS</b>The average thickness of the prepared GO sheets was only 1.4 nm. For the Hg(2+) nanobiosensor, the optimum concentrations of FAM-MSO(1) and MSO(2) were both 1 µmol/L, the optimum volume of 0.5 g/L GO was 5 µL, and the limit of detection was 10 pmol/L; it had low cross-reactivity with 10 other kinds of non-specific metal ions; the fluorescence recovery efficiency was up to 65% in the re-determination of Hg(2+) after addition of Na(2)S(2)O(3).</p><p><b>CONCLUSION</b>The MSO/GO-based nanobiosensor is convenient to operate, highly sensitive, highly specific, highly accurate, and reusable. It can be applied to determine trace amount of Hg(2+) in aqueous solutions.</p>
Subject(s)
Biosensing Techniques , Fluorometry , Graphite , Mercury , Nanotechnology , Oligonucleotide Probes , WaterABSTRACT
<p><b>OBJECTIVE</b>Impact of the presence of bacteria associated with a marine dinoflagellate, Alexandrium tamarense CI01, on the growth and toxin production of the algae in batch culture was investigated.</p><p><b>METHODS</b>Pronounced changes in the activities of the algal culture were observed when the culture was treated with different doses of a mixture of penicillin and streptomycin.</p><p><b>RESULTS</b>In the presence of antibiotics at the initial concentration of 100 u/mL in culture medium, both algal growth and toxin yield increased markedly. When the concentration of antibiotics was increased to 500 u/mL, the microalgal growth was inhibited, but resumed in a few days to eventually reach the same level of growth and toxin production as at the lower dose of the antibiotics. When the antibiotics were present at a concentration of 1 000 u/mL, the algal growth was inhibited permanently.</p><p><b>CONCLUSIONS</b>The results indicate that antibiotics can enhance algal growth and toxin production not only through their inhibition of the growth and hence competition for nutrients, but also through their effects on the physiology of the algae.</p>