# Does a SPR-Based Cell-Based Assay Provide Reliable Results on the Toxicity and Efficacy of Antiviral Drugs?

## TL;DR

A new SPR-based cell assay reliably measures antiviral drug toxicity and efficacy faster than traditional methods.

## Contribution

Grating-based SPR enables accurate, label-free cell-based drug screening by replacing continuous-flow detection with sequential measurements.

## Key findings

- Grating-based SPR detects cell morphological changes with higher accuracy and sensitivity than conventional methods.
- SPR assay identifies biochemical reaction precursors in cells within 48 hours, compared to 96 hours with MTT assays.
- SPR signal variations correlate with cell coverage, compound toxicity, and antiviral effects in VERO E6 cells.

## Abstract

What are the main findings?
A SPR-based cell-based assay provides accurate data on drug cytotoxicity and antiviral efficacy.Grating-based SPR requires sequential signal measurements of SPR slides removed from the medium at fixed hours after seeding, which successfully replaces continuous-flow SPR detection.

A SPR-based cell-based assay provides accurate data on drug cytotoxicity and antiviral efficacy.

Grating-based SPR requires sequential signal measurements of SPR slides removed from the medium at fixed hours after seeding, which successfully replaces continuous-flow SPR detection.

What is the implication of the main finding?
Exploiting the key advantage of grating-based SPR—tuning the excitation wavelength of the resonance from the visible to the near-infrared region—to detect cell morphological changes with increased accuracy and sensitivity;Speed of detection: The SPR assay detects the precursors of biochemical reactions in cells before 48 h, which are detected by the MTT assay at 96 h.

Exploiting the key advantage of grating-based SPR—tuning the excitation wavelength of the resonance from the visible to the near-infrared region—to detect cell morphological changes with increased accuracy and sensitivity;

Speed of detection: The SPR assay detects the precursors of biochemical reactions in cells before 48 h, which are detected by the MTT assay at 96 h.

SPR has been recently established as a powerful tool for studying various cellular processes in real time and without the use of labeling agents. So far, all studies in this area have been performed using the Kretschmann method for SPR excitation. In our studies, we used grating-based SPR. Here, we investigated the feasibility of this approach in a cell-based assay applied for antiviral drug screening. It was found that the continuous-flow SPR detection used in the conventional SPR can be replaced by sequential signal measurements of SPR slides removed from the medium at fixed hours after seeding. A protocol ensuring correct measurements was established. SPR detection was performed up to 48 h after seeding the VERO E6 cell line in three experiments, in which the cells were (i) compound-untreated, (ii) compound-treated, and (iii) infected with human coronavirus type 229E and compound-treated. Therefore, the temporal variation in the SPR signal was determined, induced by the cell coverage on the slide, the compound toxicity, and its antiviral action. MTT analysis and microscopic observations were used as reference methods. The remarkable agreement found in the results of SPR detection proved the effectiveness and reliability of grating-based SPR applied in cell-based assays.