Nanoplasmonic Biosensors for Clinical Diagnosis at the Point of Care

Maria Soler Aznar

Prof. Laura M. Lechuga Dr. M. Carmen Estévez

Nanobiosensors & Bioanalytical Applications (NanoB2A) (ICN2)

This Doctoral Thesis focuses on the development of novel analytical methodologies in optical biosensors as alternative solutions for diagnosis or therapy monitoring of relevant diseases, such as allergy, celiac disease or cancer. In particular, we propose the use of nanoplasmonic biosensors for a rapid, sensitive and label-free detection of biomarkers present in human fluids. Both the well-known Surface Plasmon Resonance (SPR) biosensor and an innovative nanoplasmonic biosensor based on gold nanodisks surfaces have been evaluated for their real application in the clinical field. The different biosensor methodologies make use of antibodies, either as biorecognition elements in immunoassays or as specific disease biomarkers for diagnostics. First, an indepth study of two site-directed antibody immobilization strategies is presented for the direct immunoassay of protein biomarkers in biological fluids. In second place, a novel immunosensing strategy is proposed for the detection of gluten-derivative peptides in urine as a rapid and non-invasive technique for dietary control in celiac patients. On the other hand, two assays have been developed employing the nanoplasmonic biosensor to detect blood circulating antibodies as disease biomarkers. First, we have designed an alternative approach for drug allergy diagnosis (in particular for amoxicillin) based on dendrimer-based receptors, which enable the detection IgE antibodies directly in serum. And second, a new biosensing strategy is assessed to quantify specific tumor-related autoantibodies for the early diagnosis of colorectal cancer. The work in this Thesis combines the wide knowledge of the research group in the design and fabrication of powerful biosensor technology with the development of surface activation chemistry and bioanalytical techniques to overcome current challenges related to costly and time-consuming clinical analysis. Besides, the strong experience of our research group in technological transfer and the established collaborations during this doctoral work with companies as Biomedal S.L. or Protein Alternatives S.L. open up interesting opportunities to facilitate the technology-transfer process for the real implementation of Point-of-Care biosensors.

Among the research projects developed during the doctoral thesis, two stand out due to their industrial and commercial relevance. 1. Point-of-Care Biosensor for Gluten Detection in Urine This project, in collaboration with Biomedal S.L., focused on developing a portable biosensor for detecting gluten-derived peptides in urine as a non-invasive dietary monitoring tool for celiac patients. The method enables rapid, user-friendly detection, addressing a major unmet clinical need—real-time dietary compliance assessment. The biosensor demonstrated high sensitivity, capable of detecting minimal gluten intake, with strong correlation to clinical data provided by Hospital del Valme (Seville). Following promising results, a prototype is under negotiation with Biomedal for clinical validation and home-use deployment. 2. Point-of-Care Biosensor for Early Diagnosis of Colorectal Cancer Conducted in partnership with Protein Alternatives S.L. (ProAlt), this project aimed to create a blood-based diagnostic biosensor for the early detection of colorectal cancer through the identification of specific tumor-related antibodies. The platform enables non-invasive, rapid analysis of small blood volumes, potentially replacing colonoscopies and facilitating routine screening, particularly in genetically predisposed individuals. The biosensor's accuracy was validated with patient samples from Cabueñes Hospital (Gijón), showing good agreement with conventional techniques. Technology Transfer and Industrial Collaboration Based on these results, the colorectal cancer biosensor work progressed within the COLONTEST project (Retos-Colaboración RTC-2014-1518-1), involving ProAlt, the thesis research group, and Hospital Clínic de Barcelona. The technology is being integrated into nanophotonic bimodal waveguide (BiMW) devices, patented by the thesis group. These platforms support high sensitivity, miniaturization, and multiplexing, ideal for Lab-on-a-Chip and POC applications. BiMW technology is exclusively licensed to Promax Electrónica S.L., a Catalan SME with over 50 years in analytical device manufacturing. The research group maintains active tech transfer agreements with Promax for commercialization.

Doctoral Thesis; Novel Analytical Methodologies; Optical Biosensors; Alternative Solutions; Diagnosis; Therapy Monitoring; Relevant Diseases; Allergy; Celiac Disease; Cancer; Nanoplasmonic Biosensors; Rapid Detection; Sensitive Detection; Label-Free Detection; Biomarkers; Human Fluids; Surface Plasmon Resonance (SPR) biosensor; Innovative Nanoplasmonic Biosensor; Gold Nanodisks Surfaces; Clinical Field; Biosensor Methodologies; Antibodies; Biorecognition Elements; Immunoassays; Specific Disease Biomarkers; Diagnostics; Site-Directed Antibody Immobilization Strategies; Direct Immunoassay; Protein Biomarkers; Biological Fluids; Novel Immunosensing Strategy; Gluten-Derivative Peptides; Urine; Rapid Technique; Non-Invasive Technique; Dietary Control; Celiac Patients; Blood Circulating Antibodies; Disease Biomarkers; Drug Allergy Diagnosis; Amoxicillin; Dendrimer-Based Receptors; IgE Antibodies; Serum; Biosensing Strategy; Quantify; Specific Tumor-Related Autoantibodies; Early Diagnosis; Colorectal Cancer; Biosensor Technology; Surface Activation Chemistry; Bioanalytical Techniques; Costly Clinical Analysis; Time-Consuming Clinical Analysis; Technological Transfer; Collaborations; Biomedal S.L.; Protein Alternatives S.L.; Technology-Transfer Process; Point-of-Care Biosensors