Calling Biomarkers in Milk Using a Protein Microarray on Your Smartphone

• Published in: PloS one 2015-08, Vol.10 (8), p.e0134360-e0134360
• Main Authors: Ludwig, Susann K J, Tokarski, Christian, Lang, Stefan N, van Ginkel, Leendert A, Zhu, Hongying, Ozcan, Aydogan, Nielen, Michel W F
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Animals; Antibodies; Bioindicators; Biomarkers; Biomarkers - analysis; BU Dierbehandelingsmiddelen; BU Veterinary Drugs; Cattle; CBLB Bodembiologie; Chemical Biological Soil Laboratory - Soil Biology; Chemisch Biologisch Laboratorium Bodem - Bodembiologie; Directie; Electrical engineering; Environmental monitoring; Fluorescence; Food safety; Growth Hormone - analysis; Growth hormones; Immunoassay; Infectious diseases; Insulin; Insulin-like growth factor I; Insulin-like growth factors; Laboratories; Laboratorium voor Organische chemie; Laboratory for Organic Chemistry; Light emitting diodes; Methyltestosterone; Milk; Milk - chemistry; Multiplexing; Onsite; Organic Chemistry; Organische Chemie; Protein Array Analysis - methods; Protein arrays; Proteins; Quantum dots; RIKILT - Business unit Dierbehandelingsmiddelen; RIKILT Directie; Sheep; Smartphone; Smartphones; Three dimensional printing; U.V. radiation; Ultraviolet radiation; VLAG; Wireless networks
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0134360

Here we present the concept of a protein microarray-based fluorescence immunoassay for multiple biomarker detection in milk extracts by an ordinary smartphone. A multiplex immunoassay was designed on a microarray chip, having built-in positive and negative quality controls. After the immunoassay procedure, the 48 microspots were labelled with Quantum Dots (QD) depending on the protein biomarker levels in the sample. QD-fluorescence was subsequently detected by the smartphone camera under UV light excitation from LEDs embedded in a simple 3D-printed opto-mechanical smartphone attachment. The somewhat aberrant images obtained under such conditions, were corrected by newly developed Android-based software on the same smartphone, and protein biomarker profiles were calculated. The indirect detection of recombinant bovine somatotropin (rbST) in milk extracts based on altered biomarker profile of anti-rbST antibodies was selected as a real-life challenge. RbST-treated and untreated cows clearly showed reproducible treatment-dependent biomarker profiles in milk, in excellent agreement with results from a flow cytometer reference method. In a pilot experiment, anti-rbST antibody detection was multiplexed with the detection of another rbST-dependent biomarker, insulin-like growth factor 1 (IGF-1). Milk extract IGF-1 levels were found to be increased after rbST treatment and correlated with the results obtained from the reference method. These data clearly demonstrate the potential of the portable protein microarray concept towards simultaneous detection of multiple biomarkers. We envisage broad application of this 'protein microarray on a smartphone'-concept for on-site testing, e.g., in food safety, environment and health monitoring.