Orientation of Pterin-6-Carboxylic Acid on Gold Capped Silicon Nanopillars Platforms: Surface Enhanced Raman Spectroscopy and Density Functional Theory Studies

Abstract

The orientation of pterin-6-carboxylic acid on gold nanopillars was investigated by surface enhanced Raman spectroscopy and density functional theory methods. The experimentally vibrations from pterin-6-COOH free and attached to the Au surface display vibration features indicating chemical interaction of the pterin with the metal surface. The spectral feature evidenced that the pterin would adsorb on gold surface with a "lying down" configuration through the high intensity vibration of NH scissoring and rocking OH modes. The orientation study of pterins on gold nanopillars presented herein is believed to lead to new applications in biosensing field for detecting pterins of physiological importance.

Folic acid and sodium folate salts: Thermal behavior and spectroscopic (IR, Raman, and solid-state 13C NMR) characterization

“…Based on DFT and in agreement with Kokaislová et al [30] and Braga et al [41], it is assigned to the C-C stretching of phenylene ring of p-ABA group. For FA and Na 2 HFol, the bands in the 1570 cm -1 region of infrared and Raman spectra are attributed to vibrations from pteroic acid unit (Table 2), consistent with experimental and theoretical results reported for guanine [64,69], p-ABA [71], PT [70], and FA [41]. A broadening of bands is observed from FA to Na 2 HFol, possibly due to the H-bonds and - interactions, as discussed previously.…”

“…The detailed assignment of FA and folates bands is not straightforward due to the structural complexity of the molecule/anions and because many vibrational modes are combined. Hence, a tentative attribution of vibration modes presented in Table2is proposed considering the changes observed according to the protonation degree of the compound, in the light of DFT calculations for the species in vacuum, as well as from data in the literature[30,33,[41][42][43][44][62][63][64][65][66][67][68][69][70][71][72][73][74].The comparison between experimental and theoretical spectra is shown inFigures A.As displayed in Figure A.12, a good linear correlation (R 2 > 0.998) is observed between the experimental and calculated energy (in wavenumber). In the following, the main distinct regions of vibrational spectra of FA, Na 2 HFol and Na 3 Fol are discussed while some less relevant bands are considered in SM (Figures A.9-A.11).…”

Insights into Molecular Structure of Pterins Suitable for Biomedical Applications

“…Regarding oxidized pterins, the potential for their detection using metal nanostructures should allow for a LOD of several nM. Both silver and gold nanostructures have been established as potential tools [ 161 , 162 , 163 ]. The second aspect is the utilization of oxidized pterins in PDT both as a component of synergistic systems [ 205 ] and as a part of nano-sized delivery systems [ 282 ].…”

“…In addition to silver, nanostructured gold is often used for surface modification and SERS. The article by Castillo et al [ 163 ] showed how Cap and gold-capped nanopillars interacted. A comparison of the SERS spectra and DFT calculations demonstrated that Cap mainly interacts with gold through the nitrogen of the amino group.…”

“…They are also used in diagnostics of diseases such as phenylketonuria [ 69 ], vitiligo [ 279 ], hyperphenylalaninemia [ 280 ], cancer [ 70 , 93 ], etc. Spectroscopic methods, along with noble metal nanostructures, can be used for the detection of oxidized pterins [ 162 , 163 , 281 ].…”