Vertically Aligned Nitrogen-Doped Carbon Nanotube Carpet Electrodes: Highly Sensitive Interfaces for the Analysis of Serum from Patients with Inflammatory Bowel Disease

Abstract

The number of patients suffering from inflammatory bowel disease (IBD) is increasing worldwide. The development of noninvasive tests that are rapid, sensitive, specific, and simple would allow preventing patient discomfort, delay in diagnosis, and the follow-up of the status of the disease. Herein, we show the interest of vertically aligned nitrogen-doped carbon nanotube (VA-NCNT) electrodes for the required sensitive electrochemical detection of lysozyme in serum, a protein that is up-regulated in IBD. To achieve selective lysozyme detection, biotinylated lysozyme aptamers were covalently immobilized onto the VA-NCNTs. Detection of lysozyme in serum was achieved by measuring the decrease in the peak current of the Fe(CN)6(3-/4-) redox couple by differential pulse voltammetry upon addition of the analyte. We achieved a detection limit as low as 100 fM with a linear range up to 7 pM, in line with the required demands for the determination of lysozyme level in patients suffering from IBD. We attained the sensitive detection of biomarkers in clinical samples of healthy patients and individuals suffering from IBD and compared the results to a classical turbidimetric assay. The results clearly indicate that the newly developed sensor allows for a reliable and efficient analysis of lysozyme in serum.

Aptamer-Based Electrochemical Sensing of Lysozyme

“…Among others, recent approaches based on nanomaterials, such as graphene [105] or nanoceria [106], show promising potentialities; (iv) Validation of novel aptasensors in comparison with methods currently used in clinical and analytical laboratories, such as ELISA and HPLC. So far, only three studies reported comparative results obtained with the aptasensor and by classical methods [73,78,91]. In the particular case of lysozyme, a comparison with other methods should be made with caution, since some methods measure the amount of enzymatically-active lysozyme, while others determine the total amount of protein.…”

“…Recent developments in biosensing research illustrate the applications of aptasensors for the dual detection of lysozyme and other important analytes, such as adenosine [95], thrombin [89,94] and interferon gamma [90]. The usefulness of aptasensors for serum analysis of patients with inflammatory bowel disease was recently demonstrated [73]. Consequently, new studies focused on the parallel analysis and correlations between disease biomarkers and lysozyme levels in biological samples are expected to boost research efforts tapping into the applicative potential of electrochemical aptasensing of lysozyme in the biomedical field.…”

“…For clinical applications [73], testing the performance of the different sensors on real samples is of ultimate necessity. Approximately half of the electrochemical aptasensors for lysozyme developed so far were applied for real sample analysis (Table 2).…”

“…For Strategy (2), an appropriate number of carboxylic functional groups can be introduced on the electrode surface by modification with nanocomposites of graphene oxide-chitosan [61,77], or reduction of diazonium salts of p-aminobenzoic acid on carbon electrodes [44,63], or by attaching vertically-aligned nitrogen-doped carbon nanotubes (VA-NCNTs) [73]. Rohrbach et al modified screen-printed graphite electrodes with multi-walled carbon nanotubes (MWCNTs) containing about 5% carboxylic acid groups [82].…”

Advantages of Carbon Nanomaterials in Electrochemical Aptasensors for Food Analysis

“…For improved performance, controlled deposition of CNTs was pursued by growing the CNTs on electrode surface and vertical alignment in CNTs nanocarpets. Doping of CNTs was further reported to enhance the analytical characteristics of obtained electrochemical aptasensors . The synthesis, properties and applications of carbon nanotubes in electrochemical sensing have been detailed in several reviews .…”