title: A novel optical DNA biosensor for detection of trace amounts of mercuric ions using gold nanoparticles introduced onto modified glass surface.
abstract: In this work we report a DNA spectrophotometric biosensor for detection of Hg2+ ions in which a pair of oligonucleotides with four thymine-thymine (T-T) mismatched bases was immobilized onto modified glass surface. Firstly, glass surface modified with 3-(mercaptopropyl) trimethoxysilane (MSPT) and gold nano-particles respectively and then one oligonucleotide (P1) modified with hexanthiol at 5-terminal was immobilized on gold nano-particles via self-assembly and inserted in methylene blue. Methylene blue can intercalate on single strand DNA (ss-DNA) and its absorption peak can measure spectrophotometrically. Then the other oligonucleotide was able to hybridize with P1 by forming thymine-Hg2+-thymine (T-Hg2+-T) complexes in the presence of Hg2+, and absorption signal of methylene blue reduced upon Hg2+ increasing concentration because inaccessibility of guanine base in DNA duplex. However, when Hg2+ was absent, the two oligonucleotides could not hybridize due to the T-T mismatched bases, and P2 could not be fixed on the modified glass surface and any change in absorption peak of methylene blue takes place. The UV-Vis spectrum showed a linear correlation between the absorption peak of methylene blue and the concentration of Hg2+ over the range from 10 nM to 10 μM (R2=0.9985) with a detection limit of 6 nM. This spectrophotometric biosensor could be widely used for selective detection of Hg2+.
authors.affiliation: Faculty of Chemistry, Kharazmi University, Tehran, Iran. Electronic address: mashhadizadeh@khu.ac.ir.
authors.forename: Mohammad Hossein
authors.initials: MH
authors.lastname: Mashhadizadeh
authors.affiliation: Faculty of Chemistry, Kharazmi University, Tehran, Iran.
authors.forename: Rasoul Pourtaghavi
authors.initials: RP
authors.lastname: Talemi
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods*; D005898:Glass / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D007477:Ions; D008628:Mercury / Q000032:analysis*; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D008751:Methylene Blue / Q000737:chemistry; D055620:Optical Phenomena; D013053:Spectrophotometry; D014867:Water / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D007477:Ions; D014874:Water Pollutants, Chemical; D014867:Water; D006046:Gold; D008628:Mercury; D008751:Methylene Blue
keywords: DNA biosensor; Gold nano-particles; Hg(2+); Methylene blue; Modified glass surface; Self-assembly