{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T01:24:58Z","timestamp":1760059498632,"version":"build-2065373602"},"reference-count":26,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2025,6,17]],"date-time":"2025-06-17T00:00:00Z","timestamp":1750118400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"TecniCov","award":["POCI-01-02B7-FEDER-069745","COMPETE2020","Lisboa2020"],"award-info":[{"award-number":["POCI-01-02B7-FEDER-069745","COMPETE2020","Lisboa2020"]}]},{"name":"FEDER","award":["POCI-01-02B7-FEDER-069745","COMPETE2020","Lisboa2020"],"award-info":[{"award-number":["POCI-01-02B7-FEDER-069745","COMPETE2020","Lisboa2020"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Biosensors"],"abstract":"<jats:p>The COVID-19 pandemic highlighted the need for rapid, cost-effective tools to monitor transmission and immune response. We developed two novel paper-based colorimetric biosensors using glutaraldehyde as a protein dye\u2014its first use in this context. Glutaraldehyde reacts with amino groups to generate a brown color, enabling detection of SARS-CoV-2 antibodies. Wathman filter paper was functionalized with (3-aminopropyl)triethoxysilane (APTES) to immobilize virus-like particles (VLPs) and nucleocapsid protein (N-protein) as biorecognition elements. Upon incubation with antibody-containing samples, glutaraldehyde enabled colorimetric detection using RGB analysis in ImageJ software. Both sensors showed a linear correlation between antibody concentration and RGB values in buffer and serum. The VLP sensor responded linearly within the range of 1.0\u201320 \u00b5g\/mL (green coordinate) in 500-fold diluted serum and the N-protein sensor from 1.0\u201340 \u00b5g\/mL (blue coordinate) in 250-fold diluted serum. Both sensors demonstrated good selectivity, with glucose causing up to 18% interference. These biosensors represent a paradigm shift, as they provide a sensitive, user-friendly, and cost-effective option for semi-quantitative serological analysis. Furthermore, their versatility goes beyond the detection of SARS-CoV-2 antibodies and suggests broader applicability for various molecular targets.<\/jats:p>","DOI":"10.3390\/bios15060390","type":"journal-article","created":{"date-parts":[[2025,6,17]],"date-time":"2025-06-17T10:45:26Z","timestamp":1750157126000},"page":"390","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Cellulose-Based Colorimetric Test Strips for SARS-CoV-2 Antibody Detection"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5232-2384","authenticated-orcid":false,"given":"Mariana P.","family":"Sousa","sequence":"first","affiliation":[{"name":"BioMark\/CEB\/LABBELS\u2014Centre of Biological Engineering, University of Minho, 4710-057 Braga, Portugal"},{"name":"Epidemiology, Outcomes, Economics and Management in Oncology Group\u2014Portuguese Oncology Institute of Porto Research Center (CI-IPOP), Porto Comprehensive Cancer Center (Porto.CCC) & RISE@CI-IPOP (Health Research Network), 4200-072 Porto, Portugal"},{"name":"Experimental Pathology and Therapeutics Group\u2014Research Center, Porto Comprehensive Cancer Center (Porto.CCC) & RISE@CI-IPOP (Health Research Network), Portuguese Oncology Institute of Porto (IPO Porto), 4200-072 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1727-8255","authenticated-orcid":false,"given":"Ana Cl\u00e1udia","family":"Pereira","sequence":"additional","affiliation":[{"name":"Experimental Pathology and Therapeutics Group\u2014Research Center, Porto Comprehensive Cancer Center (Porto.CCC) & RISE@CI-IPOP (Health Research Network), Portuguese Oncology Institute of Porto (IPO Porto), 4200-072 Porto, Portugal"},{"name":"HE-FP\u2014Hospital Fernando Pessoa, CECLIN\u2014Center of Clinical Studies, 4420-096 Gondomar, Portugal"},{"name":"FP-I3ID\u2014Instituto de Investiga\u00e7\u00e3o, Inova\u00e7\u00e3o e Desenvolvimento, FP-BHS\u2014Biomedical and Health Sciences, 4420-096 Gondomar, Portugal"},{"name":"FCS\u2014Faculty of Health Sciences, Fernando Pessoa University, 4249-004 Porto, Portugal"}]},{"given":"B\u00e1rbara","family":"Correia","sequence":"additional","affiliation":[{"name":"BioMark\/CEB\/LABBELS\u2014Centre of Biological Engineering, University of Minho, 4710-057 Braga, Portugal"}]},{"given":"An\u00e1lia","family":"do Carmo","sequence":"additional","affiliation":[{"name":"Center for Innovative Biomedicine and Biotechnology (CIBB) and Center for Neuroscience and Cell Biology (CNC-UC), University of Coimbra, 3000-548 Coimbra, Portugal"},{"name":"CERES\u2014Chemical Engineering and Renewable Resources for Sustainability, Faculty of Sciences and Technology, University of Coimbra, 3030-790 Coimbra, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5764-0023","authenticated-orcid":false,"given":"Ana Miguel","family":"Matos","sequence":"additional","affiliation":[{"name":"CERES\u2014Chemical Engineering and Renewable Resources for Sustainability, Faculty of Sciences and Technology, University of Coimbra, 3030-790 Coimbra, Portugal"},{"name":"FFUC\u2014Laboratory of Pharmacology, Faculty of Pharmacy, University of Coimbra, 3030-790 Coimbra, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9846-6754","authenticated-orcid":false,"given":"Maria Teresa","family":"Cruz","sequence":"additional","affiliation":[{"name":"CERES\u2014Chemical Engineering and Renewable Resources for Sustainability, Faculty of Sciences and Technology, University of Coimbra, 3030-790 Coimbra, Portugal"},{"name":"FFUC\u2014Laboratory of Pharmacology, Faculty of Pharmacy, University of Coimbra, 3030-790 Coimbra, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4237-8952","authenticated-orcid":false,"given":"Felismina T. C.","family":"Moreira","sequence":"additional","affiliation":[{"name":"BioMark\/CEB\/LABBELS\u2014Centre of Biological Engineering, University of Minho, 4710-057 Braga, Portugal"},{"name":"CIETI\u2014LabRISE\/ISEP, Polytechnic of Porto, R. Dr. Ant\u00f3nio Bernardino de Almeida, 431, 4249-015 Porto, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2025,6,17]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Naresh, V., and Lee, N. (2021). A Review on Biosensors and Recent Development of Nanostructured Materials-Enabled Biosensors. 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