title: Measurement artifacts identified in the UV-vis spectroscopic study of adduct formation within the context of molecular imprinting of naproxen.
abstract: The ultraviolet-visible spectroscopy has been assessed as a technique for the evaluation of the strength of template-precursor adduct in the development of molecular imprints of the non-steroidal anti-inflammatory drug naproxen (NAP). The commonly employed approach relies on the collection of UV spectra of drug+precursor mixtures at different proportions, the spectra being recorded against blanks containing the same concentration of the precursor. The observation of either blue or red band-shifts and abatement of a major band are routinely attributed to template-precursor adduct formation. Following the described methodology, the precursors 1-(triethoxysilylpropyl)-3-(trimethoxysilylpropyl)-4,5-dihydroimidazolium iodide (AO-DHI(+)) and 4-(2-(trimethoxysilyl)ethyl)pyridine (PETMOS) provoked a blue-shift and band abatement effect on the NAP spectrum. Molecular dynamics simulations indicated a reasonable affinity between NAP and these precursors (coordination numbers 0.33 for AO-DHI(+) and 0.18 for PETMOS), hence showing that NAP-precursor complexation is in fact effective. However, time dependent density functional theory (TD-DFT) calculations of the spectra of both free and precursor-complexed NAP were identical, thus providing no theoretical basis for the complexation-induced effects observed. We realized that the intense spectral bands of AO-DHI(+) and PETMOS (at around 265 nm) superimpose partially with the NAP bands, and the apparent "blue-shifting" in the NAP spectra when mixed with AO-DHI+ and PETMOS was in this case a spurious effect of the intense background subtraction. Therefore, extreme care must be taken when interpreting other spectroscopic results obtained in a similar fashion.
authors.affiliation: REQUIMTE, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal.
authors.forename: Martin
authors.initials: M
authors.lastname: Perez
authors.affiliation: REQUIMTE, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Concu
authors.affiliation: CIQ-UP, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal.
authors.forename: Mariana
authors.initials: M
authors.lastname: Ornelas
authors.affiliation: REQUIMTE, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal.
authors.forename: M Natália D S
authors.initials: MN
authors.lastname: Cordeiro
authors.affiliation: CIQ-UP, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal. Electronic address: mazenha@fc.up.pt.
authors.forename: Manuel
authors.initials: M
authors.lastname: Azenha
authors.affiliation: CIQ-UP, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal.
authors.forename: A Fernando
authors.initials: AF
authors.lastname: Silva
mesh_terms: D016477:Artifacts; D004583:Electrons; D056004:Molecular Dynamics Simulation; D054802:Molecular Imprinting; D009288:Naproxen / Q000737:chemistry*; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet
chemical_list: D009288:Naproxen
keywords: Measurement artifacts; Molecular dynamics; Molecular imprinting; Time dependent density functional theory; UV spectroscopy