Integrating polythiophene derivates to PCN-222(Fe) for electrocatalytic sensing of L-dopa

Porphyrinic Metal-Organic Frameworks (porph-MOFs) are attracting attention due to the redox activity in the porphyrin subunit. Herein, we report the design of a novel core-shell structure hybrid material with a sea-cucumber morphology, namely PMeTh, containing the poly(3-methythiophene) conducting polymer coated on the surface of iron-based porph-MOFs PCN-222(Fe) via in-situ oxidative chemical polymerization. The porous PCN-222(Fe) serves as the electrocatalytic sites, while the poly(3-methythiophene) conducting polymer functions as the charge collector to facilitate the charge transport to the redox active sites. The resulting PMeTh composite demonstrates an excellent electrochemical response towards the levodopa detection. The sensitivity towards the L-dopa detection is estimated to be 1.868 μA ⋅ μM^-1 ⋅ cm^-2 in the linear concentration of 0.05-7.0 μmol ⋅ L^-1 and 0.778 μA ⋅ μM^-1 ⋅ cm^-2 in the linear concentration of 7.00-100 μmol ⋅ L^-1, respectively. Additionally, the levodopa sensor exhibits a low detection limit of 2 nmol L^-1 as well as excellent stability after 120 cycles in 10 μmol L^-1 levodopa. The feasibility of this novel L-dopa sensor was evaluated in human urine samples by standard addition. The satisfactory recoveries were in the range of 97.0-104.5% with the R.S.D. value lower than 4.4%. The method of intergrating porph-MOFs and conducting polymers can efficiently expand the porph-MOFs based composites in bioanalysis.