Early diagnostic of renal diseases plays very important role in their effective therapy. Biomarkers present in body fluids, which are currently used for diagnosis of kidney dysfunction, are strongly affected with different non-renal factors (e.g. patient age, gender, diet etc.). That’s why search for new biomarkers, and methods of their determination, are still a very important tasks. One of such prospective biomarkers of renal dysfunctions is asymmetric dymethylarginine (ADMA)1 as its normal concentration level in blood serum is independent of age or gender.
It is worth mentioning that one of the important trends in modern analytical chemistry is integration of recognition and sample processing elements in one “lab on chip” systems based on microfluidic technologies. This approach gain interest as promising and important diagnostic tool for clinical use.2
The aim of the presented work was to devise microfluidic electrochemical cell with molecularly imprinted polymer (MIP) recognition layer for selective determination of ADMA.
To develop the ADMA-imprinted polymer benzoic acid and 18-crown-6-appended bis(bithienyl)methane derivatives were used as functional monomers. Structure of pre-polymerization complex of ADMA with these monomers has been optimized by density functional theory (DFT) method using the B3LYP/6-31G functional and basis set. The calculations indicated formation of very stable complex with DG reaching –499 kJ/mol.
Before deposition on electrodes of microfluidic cell the MIP and control non-imprinted polymer (NIP) films were tested in batch condition. For that purpose, the MIP and NIP films were deposited on Pt disk electrode by electrochemical polymerization in potentiodynamic conditions. Removal of template was proved by differential pulse voltammetry (DPV) and Surface Enhanced Raman Spectroscopy. Subsequently, the analytical performance of the devised chemosensor has been tested by using DPV and electrochemical impedance spectroscopy (EIS) and showed sensitivity reaching 1.98·10-2 µA/µM and limit of detection of 0.3 µM when DPV was used as transduction technique, while impedimetric sensor exhibited sensitivity of 86.1 Ω/µM and limit of detection 0.4 µM.
In the next step, devised MIP film was deposited on electrode in microfluidic electrochemical cell, which consisted of glass layer with Au working and counter electrodes, as well as Ag pseudo-reference electrode and polydimethylsiloxane (PDMS) layer with two rectangular shaped 400 ´ 400 µm channels. Layers were bonded after treatment with oxygen plasma. Complete microfluidic cheap contains three complete sets of electrodes. Assembled microfluidic device has been tested with injection of red-ox probe in flow-injection analysis conditions.
Figure 1 – (a) Complete electrochemical microfluidic cell. and (b) chronoamperometric curves recorded after injection of red-ox probe solution.
MIP and NIP polymer films were deposited on working electrodes in microfluidic cell by electrochemical polymerization in potentiodynamic conditions. Subsequently, the analytical performance of the devised chemosensor was tested by using EIS transduction.
This work was partially supported via Polish National Science Centre grant No. 2014/15/B/ST4/04642.
- Fleck C, Schweitzer F, Karge E, Busch M, Stein G (2003) Serum concentration of asymmetric (ADMA) and symmetric (SDMA) dimethylarginine in patients with chronic kidney diseases. Clinica Chimica Acta 336: 1-12.
- Baker1 C A, Duong1 C T, Grimley1 A, Roper M G (2009) Recent advances in microfluidic detection systems. Bioanalysis 1(5): 967–975