Empowering Point-of-Care Diagnostics through Nanotechnologies: Enhanced Sensitivity at Diminished Cost

Abstract

The detection of disease biomarkers has become essential for the timely identification of various pathological conditions, offering valuable insights into the progression and severity of diseases. Advances in immunoassay techniques enable highly sensitive and specific quantification of protein biomarkers and antibody serology. However, the current gold standard for immunoassays, the enzyme-linked immunosorbent assay (ELISA), is largely confined to clinical settings. This is due to its reliance on trained personnel and the necessity of performing multiple steps, including reagent additions and extensive washing procedures. These requirements limit ELISA’s accessibility, particularly in resource-limited environments.The field of point-of-care testing (POCT) is rapidly evolving, with the potential to democratize clinical diagnostics by making it accessible outside of hospital settings. POCT could have a transformative impact on a wide range of applications, including rapid testing for infectious diseases, early detection of life-threatening conditions in resource-limited areas, and remote monitoring of chronic conditions. Currently, the most widely available POCT format based on immunological testing of biomarkers is the lateral flow assay (LFA), which has proven highly effective in delivering rapid, low-cost results for a range of applications, including COVID-19 antigen testing, pregnancy and ovulation tests, and HIV self-testing. However, despite their simple design and low cost, LFAs primarily provide binary (yes/no) results and are limited in their ability to perform multiplexed detection of multiple biomarkers simultaneously. This limitation restricts their diagnostic potential, particularly in applications requiring precise quantification of biomarker concentrations for monitoring disease progression or treatment response.To address this limitation, this dissertation introduces two innovative approaches for the sensitive and cost-effective detection of biomarkers, with a focus on heart failure monitoring. Both diagnostic technologies employ plasmonic nanoparticles to enhance optical readout, achieving a balance between assay sensitivity and system cost. Chapter 2 introduces the plasmonically enhanced (PE-D4) assay, which incorporates a plasmonic nanopatch antenna nanocavity into the previously developed D4 microarray immunoassay. The PE-D4 demonstrates unprecedented signal amplification, enabling multiplexed detection of heart failure biomarkers—NT-proBNP, NGAL, and Galectin-3—with sufficient sensitivity to be detected by a standard smartphone camera. Chapter 3 presents an alternative approach, the PAL-D4 assay, which offers a minimalistic method for quantifying biomarker concentrations. This technique uses light-scattering gold nanoparticles as labels, allowing for simple, low-cost, and sensitive detection of NT-proBNP via a smartphone equipped with a basic 3D-printed attachment.