Electrochemical biosensor for the evaluation of monoclonal antibodies targeting the N protein of SARS-CoV-2 virus

The emergence of COVID-19 caused by the coronavirus SARS-CoV-2 has prompted a global pandemic that requires continuous research and monitoring. This study presents a design of an electrochemical biosensing platform suitable for the evaluation of monoclonal antibodies targeting the SARS-CoV-2 nucleocapsid (N) protein. Screen-printed carbon electrodes (SPCE) modified with gold nanostructures (AuNS) were applied to design a versatile and sensitive sensing platform. Electrochemical techniques, including electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV), were used to investigate the interactions between immobilised recombinant N (rN) protein and several monoclonal antibodies (mAbs). The electrochemical characterisation of SPCE/AuNS/rN demonstrated a successful immobilisation of rN, enhancing the electron transfer kinetics. Affinity interactions between immobilised rN and four mAbs (mAb-4B3, mAb-4G6, mAb-12B2, and mAb-1G5) were explored. Although mAb-4B3 showed some non-linearity, the other monoclonal antibodies exhibited specific and well-defined interactions followed by the formation of an immune complex. The biosensing platform demonstrated high sensitivity in the linear range (LR) from 0.2 nM to 1 nM with limits of detection (LOD) ranging from 0.012 nM to 0.016 nM for mAb-4G6, mAb-12B2, and mAb-1G5 and limits of quantification (LOQ) values ranging from 0.035 nM to 0.139 nM, as determined by both EIS and SWV methods. These results highlight the system's potential for precise and selective detection of monoclonal antibodies specific to the rN. This electrochemical biosensing platform provides a promising route for the sensitive and accurate detection of monoclonal antibodies specific to the rN protein.

Electrochemical biosensing based comparative study of monoclonal antibodies against SARS-CoV-2 nucleocapsid protein

In this study, we are reporting an electrochemical biosensor for the determination of three different clones of monoclonal antibodies (mAbs) against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) recombinant nucleocapsid protein (rN). The nucleocapsid protein was chosen as a system component identifying and discriminating antibodies that occur after virus infection instead of S protein used in serological tests to measure antibodies raised after vaccination and infection. The sensing platform was based on a screen-printed carbon electrode (SPCE) covered with gold nanoparticles (AuNP) and subsequently modified with a self-assembled monolayer (SAM) to ensure the covalent immobilization of the rN. The interaction between the protein and three clones of mAbs against SARS-CoV-2 rN with clone numbers 4G6, 7F10, and 1A6, were electrochemically registered in the range of concentrations. Three techniques, cyclic voltammetry (CV), differential pulse voltammetry (DPV), and pulse amperometric detection (PAD) were used for the detection. A gradual change in the responses with an increase in mAbs concentration for all techniques was observed. To assess the performance of the developed electrochemical biosensor, 'complexation constant' (KC), limit of detection (LOD), and limit of quantification (LOQ) were calculated for all assessed clones of mAbs and all used techniques. Our results indicated that DPV possessing higher fitting accuracy illustrated more significant differences in KC constants and LOD/LOQ values. According to the DPV results, 7F10 clone was characterized with the highest KC value of 1.47 ± 0.07 μg/mL while the lowest LOD and LOQ values belonged to the 4G6 clone and equaled 0.08 ± 0.01 and 0.25 ± 0.01 μg/mL, respectively. Overall, these results demonstrate the potential of electrochemical techniques for the detection and distinguishing of different clones of mAbs against SARS-CoV-2 nucleocapsid protein.

The Predictive Value of Tissue Doppler Indices for Early Recurrence of Atrial Fibrillation After Electrical Cardioversion

Purpose

Spectral tissue Doppler-derived E/e’ ratio has been proposed as the best parameter for prediction of atrial fibrillation (AF). Relaxation and contraction are equivalent parts of a continuous cardiac cycle, where systolic and diastolic abnormalities have a variable contribution to the left ventricle (LV) failure. The aim of this study was to investigate whether the E/(e’xs’) ratio is a better index than E/e‘ to predict AF recurrence and to determine the changes of spectral tissue Doppler indices 1 month after the electrical cardioversion (ECV).

Patients and Methods

The study included 77 persistent AF patients with restored sinus rhythm (SR) after ECV. Only patients with normal LV ejection fraction (EF) were included. Echocardiography and NT-proBNP laboratory findings were performed. A primary outcome was the early (within 1 month) recurrence of AF.

Results

After a 1 month follow-up period, 39 patients (50.6%) were in SR. E/e′ (HR=1.74, P=0.001) and E/(e’×s’) ratios (HR=8.17, P=0.01) were significant predictors of AF recurrence. E/(e’×s’) in combination with LV end-diastolic diameter >49.3 mm and NT-proBNP >2000 ng/L demonstrated a higher contribution in the model to predict AF recurrence compared to the E/e’ ratio (18.94, P=0.005 vs 1.95, P=0.001). On ROC analysis, E/(e’×s’) and E/e′ showed similar diagnostic accuracy (E/(e’×s’), AUC=0.71, P=0.002 and E/e′, AUC=0.75, P<0.0001). Average e‘ value significantly decreased after 1 month in SR (from 10.76±1.24 to 8.96±1.47 cm/s, P=0.01), E wave did not change significantly and E/e′ ratio tended to improve. A decrease of average e‘ and an increase of average s‘ values led to significant improvement of E/(e’xs’) ratio.

Conclusion

E/(e’xs’) and E/e’ ratios are comparable to predict early AF recurrence after ECV in patients with persistent AF. The e’ value decreased significantly after 1 month follow-up period after ECV for persistent AF patients.