Analytical Evaluation of Portable and Simple FREND Fluorescent Immunoassay for Rapid Quantification of Thyroid-Stimulating Hormone and Free Thyroxine.

BACKGROUND: The FREND™ thyroid stimulating hormone (TSH) and free thyroxine (FT4) assays are newly developed rapid quantitative immunoassays utilizing antibody-conjugated fluorescent nanoparticles in a microfluidic flow system. The FREND system is a simple and portable fluorescence reader with rapid turnaround time (4 - 10 minutes). METHODS: The analytical sensitivity, precision, and linearity were evaluated. For the method comparison, FREND TSH and FT4 levels were compared with those from ADVIA Centaur XP and Abbott ARCHITECT i2000. RESULTS: The limit of detection was 0.047 mIU/L and 5.031 pmol/L in FREND TSH and FT4 assays. FREND system had acceptable linearity and precision of  10% across the assay range (0.05 - 25.0 mIU/L for TSH and 1.4 - 96.8 pmol/L for FT4). The functional sensitivity was 0.057 mIU/L for the TSH assay and 4.644 pmol/L for the FT4 assay. Passing-Bablok regression analysis of TSH data showed good correlation among the three assays. For the FT4 assay, FREND FT4 displayed good correlation with the ARCHITECT FT4 assay, but the intercepts and slopes significantly differed between FREND and Centaur results: [FREND FT4] = 4.799 + 0.600 [Centaur FT4]. CONCLUSIONS: The analytical performance of FREND TSH and FT4 assays was satisfactory for use in the clinical laboratory. The FREND FT4 assay was in concordance with ARCHITECT FT4, but it needs further investigation and harmonization.

A modified squeeze equation for predicting the filling ratio of nanoimprint lithography.

A numerical method using the modified squeeze model is proposed in this paper in order to overcome the limitation of the established squeeze equation and obtain filling ratios for nanoimprint lithography (NIL). Because the imprinting velocity is overestimated when the ratio of indenter width to polymer thickness is close to unity, the modified equation is critical. For verification, the numerical results are compared with the experimental data according to the various stamp geometries and pressure variation rates, for which a maximum difference of 10% is indicated. Based on these results, additional studies are conducted using the modified squeeze equation in order to obtain filling ratios according to the polymer thickness and temperature. The filling rates are enhanced through the increases in the temperature and the polymer thickness. The results demonstrate that the modified squeeze equation can be used to obtain and predict the filling ratio of sub-nanoscale NIL fabrication. It is expected that this study will assist in optimizing the experimental conditions and approaches for roll-to-roll NIL and step-and-flash NIL.

Nanoimprint lithography with a focused laser beam for the fabrication of nanopatterned microchannel molds.

We present a process based on nanoimprint lithography for the fabrication of a microchannel mold having nanopatterns formed at the bottoms of its microchannels. A focused laser beam selectively cures the resist in the micrometer scale during nanoimprint lithography. Nanopatterns within the microchannels may be used to control microfluidic behavior.