The current bioassay development literature lacks the use of statistically robust methods for calculating the limit of detection of a given assay. Instead, researchers often employ simple methods that provide a rough estimate of the limit of detection, often without a measure of the confidence in the estimate. This scarcity of robust methods is likely due to a realistic preference for simple and accessible methods and to a lack of such methods that have reduced the concepts of limit of detection theory to practice for the specific application of bioassays. Here, we have developed a method for determining limits of detection for bioassays that is statistically robust and reduced to practice in a clear and accessible manner geared at researchers, not statisticians. This method utilizes a four-parameter logistic curve fit to translate signal intensity to analyte concentration, which is a curve that is commonly employed in quantitative bioassays. This method generates a 95% confidence interval of the limit of detection estimate to provide a measure of uncertainty and a means by which to compare the analytical sensitivities of different assays statistically. We have demonstrated this method using real data from the development of a paper-based influenza assay in our laboratory to illustrate the steps and features of the method. Using this method, assay developers can calculate statistically valid limits of detection and compare these values for different assays to determine when a change to the assay design results in a statistically significant improvement in analytical sensitivity.

Imine-linked covalent organic frameworks (COFs) have received widespread attention because of their structure features such as high crystallinity and tunable pores. However, the intrinsic reversibility of the imine bond leads to the poor stability of imine-linked COFs under strong acid conditions. Also, their thermal stability is significantly lower than that of many other COFs. Herein, we report for the first time that the reversible imine bonds in the skeleton of COFs can be locked through the asymmetric hydrophosphonylation reaction of phosphite. The functionalized COFs not only retain the crystallinity and porous structure but also exhibit evidently improved chemical and thermal stabilities. In addition, the phosphorous acid groups generated by acidic hydrolysis attached to the skeleton endow the COFs with good intrinsic proton conductivity. Due to the diversity of phosphite derivatives and imine-linked COFs, this work may provide an avenue for extending the COF structures and functions through the asymmetric hydrophosphonylation reaction.

Nanostructured silver films of different thicknesses were deposited on surfaces of polypropylene nonwovens by magnetron sputter coating to obtain antibacterial and electrical conductive properties. The surface morphology of nanostructured silver films was investigated by atomic force microscopy (AFM). The antibacterial properties of the nonwovens coated with relatively thinner films were evaluated using the shake flask test. The conductivity of the nonwovens coated with relatively thicker films was examined using an ohm-meter. The results of the antibacterial test revealed that the antibacterial performance improved gradually as the film thickness increased from 0.5 to 3 nm. It is believed that the total amount of silver ions released from the coating was increased along with the increase in film thickness. As sputtering time prolonged, the grain sizes of the silver particles were increased and the coating became more compact. The results of the electrical conductivity test showed that the increased film thickness led to the improved electrical conductivity when the film was relatively thicker. The AFM images clearly revealed the change in surface morphology formed by sputter coating. The growth and coverage of the coating layer contributed to the improvement in its antibacterial and conductive properties.

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