{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,26]],"date-time":"2026-02-26T06:40:35Z","timestamp":1772088035525,"version":"3.50.1"},"reference-count":42,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2026,2,17]],"date-time":"2026-02-17T00:00:00Z","timestamp":1771286400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>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\u2019s 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\u2013Golay (SG) filter to post-process the data. By reducing noise without attenuating chemiluminescent peaks, the Savitzky\u2013Golay 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.<\/jats:p>","DOI":"10.3390\/s26041294","type":"journal-article","created":{"date-parts":[[2026,2,17]],"date-time":"2026-02-17T09:22:46Z","timestamp":1771320166000},"page":"1294","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Label-Free Detection of HeLa Cells Activity Excited by Blue LED"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8632-254X","authenticated-orcid":false,"given":"Vera","family":"Gradi\u0161nik","sequence":"first","affiliation":[{"name":"Faculty of Engineering, University of Rijeka, Vukovarska 58, HR-51000 Rijeka, Croatia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Darko","family":"Gumbarevi\u0107","sequence":"additional","affiliation":[{"name":"Independent Researcher, HR-51000 Rijeka, Croatia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9263-7946","authenticated-orcid":false,"given":"Petar","family":"Kolar","sequence":"additional","affiliation":[{"name":"VERN University, Palmoti\u0107eva ulica 82\/1, HR-10000 Zagreb, Croatia"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,2,17]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"4063","DOI":"10.1039\/c1lc20362b","article-title":"Microspot-based ELISA in microfluidics: Chemiluminescence and colorimetriy detection using integrated thin-film hydrogenated amorphous silicon photodiodes","volume":"11","author":"Novo","year":"2011","journal-title":"Lab Chip"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"210","DOI":"10.1038\/nrd1985","article-title":"Lab-on-a-chip: Microfluidics in drug discovery","volume":"5","author":"Dittrich","year":"2006","journal-title":"Nat. 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