A Tip Optofluidic Immunoassay System for COVID-19 Immuno-protection Evaluation Using Fingertip Blood

Infectious diseases such as COVID-19 continue posing significant global health challenges, with recurrent re-infections contributing to long-term symptoms such as cardiac issues and anosmia. Effective management of re-infections relies heavily on maintaining high levels of circulating binding and neutralizing antibodies. Traditional methods for antibody quantification, such as ELISA, face significant challenges, including narrow dynamic ranges and complex sample preparation procedures, which hinder their applications in rapid and routine diagnosis. This study introduces a novel optofluidic biosensing technology, tip optofluidic immunoassay (TOI), that addresses these limitations by enabling the quantitative analysis of binding IgG against multiple SARS-CoV-2 strains from only 1 μL of fingertip blood. The proposed TOI system, featuring industrial-grade micro-fabricated immuno-reactors and a portable chemiluminescent imaging station, can provide test results within 12 minutes. For IgG binding assays, TOI possesses a lower limit of detection of 0.1 ng/mL, a dynamic range of 3-4 orders of magnitude, along with a high signal-to-noise ratio (approximately 10,000). This technology not only simplifies the antibody quantification process but also enhances patient compliance and facilitates decentralized testing, which is crucial for infectious disease management. By enabling precise and rapid antibody assessment, this system can support the optimization of vaccination strategies and broader public health responses to COVID-19 and other infectious diseases. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study was supported by the Shenzhen Institute of Advanced Technology, Chinese Academy of Science, and The Key Laboratory of Biomedical Imaging Science and System, Chinese Academy of Sciences. This study was also funded by the Guangdong Province Young Innovative Talents Project (2022KQNCX067), Shenzhen Basic Research Project of Natural Science Foundation (JCYJ20230808105701004), and Shenzhen Science and Technology Innovations Committee (JSGGZD20220822095200001). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The Institutional Review Board (IRB) of Shenzhen Institute of Advanced Technology, Chinese Academy of Science gave ethical approval for this work. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors.