4-Aminohippuric acid

4-Aminohippuric acid (p-Aminohippuric acid) is a coordination ligand for metal ions (such as Cu²⁺, Fe³⁺, Hg²⁺) and a functionalization reagent for nanomaterials. 4-Aminohippuric acid can coordinate with metal ions or modify the surface of materials such as carbon nanotubes and gold nanoparticles through amino and carboxyl groups. 4-Aminohippuric acid can form stable complexes with metal ions or participate in the synthesis of nanomaterials as a reducing agent/stabilizer, enriching metal ions or giving nanoparticles peroxidase-mimicking activity. 4-Aminohippuric acid can be used to construct highly sensitive electrochemical sensors or colorimetric sensors to detect and quantitatively analyze heavy metal ions such as copper, iron, and mercury in environmental water samples and biological samples. 4-Aminohippuric acid may also be a biomarker for attention-deficit/hyperactivity disorder (ADHD)^[1][2][3]. In Vitro:1. Electrochemical sensor experiment:
4-Aminohippuric acid (10 mg/mL; 3 h) was covalently coupled to multi-walled carbon nanotubes (MWNTs) in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). After modification of glassy carbon electrode, it was used for anodic stripping voltammetry to detect Cu²⁺ with a linear detection range of 1.0-230.0 μg/L and a detection limit as low as 0.4 μg/L^[1].
2. Nanoparticle synthesis and colorimetric detection experiments:
4-Aminohippuric acid (0.5 mM; 1 h) was used as a reducing agent and stabilizer to synthesize gold nanoparticles (4-AHA@AuNPs) at pH 6.5-6.8 and 70°C. The nanoparticles have peroxidase mimetic activity and the linear detection ranges for Fe³⁺ and Hg²⁺ are 5-50 ppb and 5-200 ppb, respectively, with detection limits of 4.0 ppb and 2.5 ppb, respectively^[2].
3. Plasma metabolism experiment:
4-Aminohippuric acid is differentially expressed in the plasma of attention-deficit/hyperactivity disorder (ADHD) models, and the level of 4-Aminohippuric acid is higher than that of the control group. The plasma concentration of 4-Aminohippuric acid can be used as a biomarker to identify ADHD and reflect the disease state, and its level is significantly correlated with the clinical symptoms of ADHD^[3].