# Label-Free Detection of HeLa Cells Activity Excited by Blue LED

## TL;DR

This paper introduces a new label-free method using a special photodiode to detect light from HeLa cells excited by blue LED, helping study cell activity without chemical labels.

## Contribution

A novel label-free biosensing method using a-Si:H photodiodes and SG filtering to detect HeLa cell chemiluminescence is proposed.

## Key findings

- HeLa cell light emission is attributed to chemiluminescence from NO and H2O2 reactions.
- SG filtering improves signal accuracy by reducing noise in low-intensity biological signals.
- a-Si:H photodiodes show potential for real-time, non-destructive cell activity monitoring.

## Abstract

Label-free detection of HeLa cells’ intrinsic chemiluminescence.Characteristic or resonance frequency of HeLa cell light emission.a-Si:H p-i-n photodiodes are posted below and laterally of the analyte as a transducer.a-Si:H DOS responsible for weak light biological signal detection.a-Si:H photodiode as a transducer for label-free biosensors.

Label-free detection of HeLa cells’ intrinsic chemiluminescence.

Characteristic or resonance frequency of HeLa cell light emission.

a-Si:H p-i-n photodiodes are posted below and laterally of the analyte as a transducer.

a-Si:H DOS responsible for weak light biological signal detection.

a-Si:H photodiode as a transducer for label-free biosensors.

This paper investigates a novel optical method that uses a high-responsivity a-Si:H photodiode for label-free detection of luminescence from HeLa cervical cancer cells excited by a blue LED. We examine the energy distribution of the energy-gap density of states (DOS) from the photodiode’s long-time transient current, which shows exponential decay kinetics in the HeLa cell reaction. We analysed the transient response of a-Si:H p-i-n photodiode upon the illumination of the analyte with a pulsed blue LED light to better understand the HeLa cells activity and the fundamental defect kinetics processes in the a-Si:H material. Results suggest that the characteristic very low-level, time-varying light response of HeLa cells is due to chemiluminescence within cells, resulting from the reaction between nitric oxide (NO) and hydrogen peroxide (H2O2). Given the low signal intensity and noise, we applied a Savitzky–Golay (SG) filter to post-process the data. By reducing noise without attenuating chemiluminescent peaks, the Savitzky–Golay filter enabled accurate, reproducible quantification of the photocurrent response, reflecting the kinetics of cellular reactions. Further studies and more precise measurement instruments are needed for this real-time, label-free, non-destructive method, which applies SG-filtered signal processing to microfluidic optical biosensors.