A Miniature Bio-Photonics Companion Diagnostics Platform for Reliable Cancer Treatment Monitoring in Blood Fluids.

In this paper, we present the development of a photonic biosensor device for cancer treatment monitoring as a complementary diagnostics tool. The proposed device combines multidisciplinary concepts from the photonic, nano-biochemical, micro-fluidic and reader/packaging platforms aiming to overcome limitations related to detection reliability, sensitivity, specificity, compactness and cost issues. The photonic sensor is based on an array of six asymmetric Mach Zender Interferometer (aMZI) waveguides on silicon nitride substrates and the sensing is performed by measuring the phase shift of the output signal, caused by the binding of the analyte on the functionalized aMZI surface. According to the morphological design of the waveguides, an improved sensitivity is achieved in comparison to the current technologies (<5000 nm/RIU). This platform is combined with a novel biofunctionalization methodology that involves material-selective surface chemistries and the high-resolution laser printing of biomaterials resulting in the development of an integrated photonics biosensor device that employs disposable microfluidics cartridges. The device is tested with cancer patient blood serum samples. The detection of periostin (POSTN) and transforming growth factor beta-induced protein (TGFBI), two circulating biomarkers overexpressed by cancer stem cells, is achieved in cancer patient serum with the use of the device.

A Direct Assay for Measuring Free 25-Hydroxyvitamin D.

Recent studies suggest that the concentration and genotype of vitamin D binding protein (VDBP) are important factors that determine the bioavailability of 25-hydroxyvitamin D [25(OH)D] in blood. Accumulating data indicate that, e.g., in pregnant women, hemodialysis patients, chronic kidney disease, liver failure, and bladder and pancreatic cancers, the measurement of free 25(OH)D in serum provides more relevant diagnostic information than measurement of total 25(OH)D. The aim of this study was to develop and validate an ELISA for direct measurement of free 25(OH)D in serum. A simple and direct ELISA was developed, based on a two-step immunoassay procedure performed in a microtiter plate. The assay has been characterized in terms of precision (4-10% CV, according to concentration), sensitivity (limits of blank = 0.5-1.0 pg/mL and LODs = 1.3-1.8 pg/mL), accuracy (correlation to dialysis, ELISA = 0.99xdialysis-0.5 pg/mL, r2 = 0.74), cross-reactivity of the antibody for the D2 form (77%), and addition of both VDBP and albumin (35-38% recovery upon addition of VDBP, 53-58% upon addition of albumin). The assay has already been used in multiple studies, including its comparison with calculation methods and in studies of patients with liver failure, different ethnic groups, supplemented mice, respiratory diseases, and obesity. The free 25(OH)D ELISA can be used in studies as a valuable tool to establish the clinical relevance of free 25(OH)D.