Microfluidic immunoassays as rapid saliva-based clinical diagnostics

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 104; no. 13; pp. 5268 - 5273
• Main Authors: Herr, Amy E, Hatch, Anson V, Throckmorton, Daniel J, Tran, Huu M, Brennan, James S, Giannobile, William V, Singh, Anup K
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 27.03.2007; National Acad Sciences
• Subjects: Anatomy & physiology; Antibodies; Bioassays; Biological markers; Biological Sciences; biomarkers; Biomarkers - metabolism; Body fluids; Chemistry, Clinical - methods; Collagen - metabolism; Computers, Handheld; diagnostic techniques; Diagnostic tests; Disease; disease course; Disease progression; electrophoresis; Electrophoresis - methods; Enzyme-Linked Immunosorbent Assay; Enzymes; Equipment Design; Gels; health status; Human subjects; Humans; Image Processing, Computer-Assisted; Immunoassay; Immunoassay - methods; Immunoassays; Matrix Metalloproteinase 8 - metabolism; Microfluidics - methods; mixing; Mouth diseases; P branes; Periodontal diseases; Periodontal Diseases - diagnosis; Periodontal Diseases - metabolism; Periodontics; Physical Sciences; pregnancy; Saliva; Saliva - metabolism; Ultraviolet Rays
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0607254104

At present, point-of-care (POC) diagnostics typically provide a binary indication of health status (e.g., home pregnancy test strip). Before anticipatory use of diagnostics for assessment of complex diseases becomes widespread, development of sophisticated bioassays capable of quantitatively measuring disease biomarkers is necessary. Successful translation of new bioassays into clinical settings demands the ability to monitor both the onset and progression of disease. Here we report on a clinical POC diagnostic that enables rapid quantitation of an oral disease biomarker in human saliva by using a monolithic disposable cartridge designed to operate in a compact analytical instrument. Our microfluidic method facilitates hands-free saliva analysis by integrating sample pretreatment (filtering, enrichment, mixing) with electrophoretic immunoassays to quickly measure analyte concentrations in minimally pretreated saliva samples. Using 20 μl of saliva, we demonstrate rapid (<10 min) measurement of the collagen-cleaving enzyme matrix metalloproteinase-8 (MMP-8) in saliva from healthy and periodontally diseased subjects. In addition to physiologically measurable indicators of periodontal disease, conventional measurements of salivary MMP-8 were used to validate the microfluidic assays described in this proof-of-principle study. The microchip-based POC diagnostic demonstrated is applicable to rapid, reliable measurement of proteinaceous disease biomarkers in biological fluids.