title: Phosphate-modified TiO2 nanoparticles for selective detection of dopamine, levodopa, adrenaline, and catechol based on fluorescence quenching.
abstract: For the first time, an aqueous solution, comprising 6-nm phosphate-modified titanium dioxide (P-TiO2) nanoparticles (NPs) and fluorescein, has been used for sensing dopamine (DA), levodopa (L-DOPA), adrenaline, and catechol. The complexes obtained by means of chelation of surface Ti(IV) ions with an enediol group exhibit strong absorption at 428 nm; thus, they can be designed as efficient quenchers for fluorescein. The fluorescence of a fluorescein solution containing 1.4 mM P-TiO2 NPs at pH 8.0 decreases if the solution comprises DA, L-DOPA, adrenaline, and catechol, but not noradrenaline, ascorbic acid, and salicylic acid. We consider that P-TiO2 NPs have a number of advantages over bare TiO2 NPs, such as ease of preparation, high selectivity, and high stability. By measuring fluorescence quenching, the limits of detection at a signal-to-noise ratio of 3 are calculated as 33.5, 81.8, 20.3, and 92.1 nM for DA, L-DOPA, adrenaline, and catechol, respectively. In contrast, UV-vis absorption reveals the relatively poor sensitivity of these compounds. We have validated the applicability of our method by means of analyses of DA in urine samples. High-performance liquid chromatography in combination with an electrochemical cell has been used to further confirm our results. We believe that this approach has great potential for diagnostic purposes.
authors.affiliation: Department of Chemistry, National Sun Yat-sen University, Taiwan, Faculty of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Hsin-Pin
authors.initials: HP
authors.lastname: Wu
authors.forename: Tian-Lu
authors.initials: TL
authors.lastname: Cheng
authors.forename: Wei-Lung
authors.initials: WL
authors.lastname: Tseng
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods*; D002396:Catechols / Q000032:analysis; D004298:Dopamine / Q000032:analysis; D004837:Epinephrine / Q000032:analysis; D005453:Fluorescence; D007980:Levodopa / Q000032:analysis; D053758:Nanoparticles / Q000737:chemistry*; D004364:Pharmaceutical Preparations / Q000032:analysis*; D010710:Phosphates / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence; D014025:Titanium / Q000737:chemistry*
chemical_list: D002396:Catechols; D004364:Pharmaceutical Preparations; D010710:Phosphates; C009495:titanium dioxide; D007980:Levodopa; D014025:Titanium; C034221:catechol; D004298:Dopamine; D004837:Epinephrine