Evaluation of the Direct Interaction between Amino Acids and Glutathione-Coated CdTe Quantum Dots and Application in Urinalysis for Histidine Determination

AUTOR(ES)
FONTE

J. Braz. Chem. Soc.

DATA DE PUBLICAÇÃO

2021-03

RESUMO

The present work aimed to direct amino acid (AA) sensing by quantum dots (QD) and development of an analytical method for potential fast clinical tests. Notably, AA with a positive charge or neutral polar chains, namely L-histidine (His) and L-threonine (Thr), responded to glutathione-coated CdTe (GSH-CdTe) (ΔF ≤ 90%, variation of fluorescence intensity). However, in ammoniacal buffer (0.25 mol L-1) at pH 8.0, 2.2 nm GSH-CdTe responded only to His. Static quenching with complex association constant (Ksv) varying from 2.81 to 0.94 (10 L mol-1) as well as van der Waals forces and/or hydrogen bonding were predicted for His-QD quenching mechanism and binding type. Additionally, thermodynamic parameters as ΔH = -76.5 kJ mol-1 (enthalpy), ΔS = -227.4 J K-1 mol-1 (entropy) and ΔG from -9.8 until -6.4 kJ mol-1 (Gibbs free energy) at 20 to 35 °C were estimated by van’t Hoff equation. Under optimal conditions, the developed method presented a linear range from 0.42 to 35 mmol L-1 (with correlation coefficient (r) of 0.9970, n = 7), good precision (relative standard deviations (RSD) < 2.5% for 2.5 and 20 mmol L-1; n = 6) and limit of detection 1.6 × 10-4 mol L-1 (0.025 mg mL-1). Recovery tests were performed on artificial urine and human urine samples with recoveries ranging from 78.7 to 127.6%.

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