Detecting a secreted gastric cancer biomarker molecule by targeted nanoparticles for real-time diagnostics

Purpose: A real time detection of gastric cancer-associated biomarker molecules in the lumen of the stomach could assist in early detection of this multi-step malignancy. Methods: Employing α1-antitrypsin precursor (A1AT) as a secreted biomarker model, a platform with immunoassay capabilities, comprising sensing and detecting compartments was developed. It was made of a microarray-type functionalized glass, containing a high density of amine groups. Trypsin, the capturing moiety, was immobilized to the glass surface with the aid of a PEG-based spacer mixture, identified as being crucial for both capturing and detecting properties. The detecting compartment contained near infrared fluorescently labeled nanoparticles conjugated to A1AT-specific antibodies, aimed at generating an optical signal, detectable by a conventional endoscope or a video capsule. Results: The specific recognition reaction between the captured A1AT and the immuno-nanoparticles generated a profound fluorescence with a signal to noise ratio (SNR) of 12-32, in a biomarker-concentration dependent manner. Moreover, the optical recognition signal was intense enough to be detected by a video capsule simulator (with optical detection capabilities of a video capsule) with a SNR of 6-20. Conclusions: This platform could serve as a real time diagnostic kit for early detection of a secreted biomarker of gastric cancer.