Simultaneous determination of levodopa, NADH, and tryptophan using carbon paste electrode modified with carbon nanotubes and ferrocenedicarboxylic acid

Electroanalytical Overview: The Determination of Levodopa (L-DOPA)

L-DOPA (levodopa) is a therapeutic agent which is the most effective medication for treating Parkinson's disease, but it needs dose optimization, and therefore its analytical determination is required. Laboratory analytical instruments can be routinely used to measure L-DOPA but are not always available in clinical settings and traditional research laboratories, and they also have slow result delivery times and high costs. The use of electroanalytical sensing overcomes these problems providing a highly sensitivity, low-cost, and readily portable solution. Consequently, we overview the electroanalytical determination of L-DOPA reported throughout the literature summarizing the endeavors toward sensing L-DOPA, and we offer insights into future research opportunities.

Preparation of Dawson heteropolyacid-embedded silver nanoparticles/graphene oxide nanocomposite thin film used to modify pencil graphite electrode as a sensor for trace electrochemical sensing of levodopa

Measurement of levodopa (LD) as the most efficient treatment accessible for controlling the symptoms of Parkinson's disease was investigated. The electrocatalytic measurement of LD was performed at the surface of pencil graphite electrode (PGE) modified with graphene oxide (GO) and silver nanoparticle@Dawson heteropolyacid (AgNPs@DHPA). For this purpose, GO and the intermediate (AgNPs@DHPA) were first synthesized using a simple, cost-effective and straightforward method. The synthetic compounds, morphology, and surface characteristics of the modified sensor were evaluated. The results demonstrated that AgNPs@DHPA well-dispersed on the GO/PGE surface with a mean size of 6.27 nm and thickness of 42 nm. The electrochemical behavior of the modified PGE was also investigated. The heterogeneous charge transfer rate constant (k_s) and transfer coefficient (α) for the electron transfer between AgNPs@DHPA/GO and PGE were obtained as 16.44 s^-1 and 0.59, respectively. Also, the diffusion coefficient of LD for AgNPs@DHPA/GO/PGE thin film was calculated using chronoamperometric experiments (D = 9.05 × 10^-6 cm² s^-1). Optimal parameters were obtained to access the best response for the measurement of LD. The results revealed that the modified PGE was able to measure the trace amounts of LD in phosphate buffer solution (pH = 6.0) in the concentration ranges from 3.0 × 10^-9 to 1.0 × 10^-7 M and 1.0 × 10^-7 to 1.0 × 10^-5 M. The calculated limit of detection was obtained 7.6 × 10^-10 M which was much better than the previously reported electrochemical sensors. The modified electrode was used to measure LD in tablet, blood serum and urine.

A highly selective and sensitive chemosensor forl-tryptophan by employing a Schiff based Cu(ii) complex

Construction of a new Cu(ii) complex (1) based modified glassy carbon electrode (1-GCE) for highly selective and sensitive detection ofl-tryptophan (l-Trp).

A novel electrochemical sensor of tryptophan based on silver nanoparticles/metal–organic framework composite modified glassy carbon electrode

A familiar metal–organic framework MIL-101(Fe) and silver nanoparticles composite acted as a novel electrode modified material for the detection of tryptophan.

One-pot in situ synthesis of a CoFe2O4nanoparticle-reduced graphene oxide nanocomposite with high performance for levodopa sensing

We demonstrate that a new nanocomposite of CoFe₂O₄-reduced graphene oxide can be used as an enhanced electrochemical sensing platform for levodopa.