Comparison of Gold Nanoparticles Prepared Using Monobasic Sodium Citrate or Sodium Borohydride for Neomycin Determination in Saliva after Solid-Phase Extraction (SPE) on a Molecularly Imprinted Polymer (MIP)

Abstract

Two distinct spherical gold nanoparticles (AuNPs) were compared for the spectrophotometric determination of neomycin in saliva. The AuNPs were produced using AuCl₃ and monobasic sodium citrate (in water bath at 100 °C) under magnetic stirring (AuNPs-citrate) and using HAuCl₄ and NaBH₄, at room-temperature under mechanical agitation in a commercial reactor (AuNPs-H). Both AuNPs were spherical with diameters of 7.7 nm (AuNPs-H) and 26.1 nm (AuNPs-citrate) and the maximum wavelength of the localized surface plasmon resonance (LSPR) bands were at 511 nm (AuNPs-H) and 529 nm (AuNPs-citrate). Equivalent spectral extinctions were found despite the fact the large difference in concentrations of AuNPs in dispersions: 4.2 × 10⁻⁹mol L⁻¹ for the AuNPs-H and 8.7 × 10⁻¹¹mol L⁻¹ for the AuNPs-citrate. Both AuNPs interacted with aminoglycosides (AMG), affecting intensity of the LSPR band as the concentration of AMG increased. The response of the AuNPs-H was more sensitive toward AMG covering the following ranges: 0.6–600 µg L⁻¹ (gentamicin), 7.3–550 µg L⁻¹ (neomycin) and 14–520 µg L⁻¹ (kanamycin). AuNPs-H optical response was more robust in function of the pH with AuNPs-citrate response only observed in acid solution, favoring electrostatic interaction with AMG. Catalytic activity of AuNPs-H, in reducing the 4-phenolate ion, presented a higher rate constant (4.3 × 10⁻³ s⁻¹) and was used as analytical probe to determine neomycin in saliva after solid phase extraction with a commercially available AMG imprinted polymer enabling quantification to 0.36 μg of the analyte.

Keywords:

• Aminoglycosides
• gold nanoparticles
• localized surface plasmon resonance (LSPR)
• saliva analysis
• spectrophotometry

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES-Brazil) – Finance Code 001 is acknowledged. Aucelio thanks scholarships from Brazilian agencies FAPERJ (E-26/200.810/2021, E-26/010.000980/2019) and CNPq (306108/2021-6) also for scientific grant from FAPERJ (E-210.104/2020), E-26/010.101131/2018 and (SEI-260003/011317/2021). Pedrozo-Peñafiel acknowledges FAPERJ (E-26/202.408/2021) and Letichevsky acknowledges FAPERJ (E-26/010.000982/2019). Analytical facilities from the Chemistry Department at PUC-Rio (CALPH PUC-Rio) and from multiuser MackGraphe Multiuser Laboratory (Mackenzie Presbyterian University) were used.