Polydiacetylenes are a class of polymers with unique optical properties. Upon photopolymerization, monomers form a deep blue, nonfluorescent polymer, which transitions to a red, fluorescent polymer in response to various environmental factors such as pH, temperature, or molecular binding. The chromatic and emissive properties of polydiacetylenes have generated considerable popularity for their use in biosensing applications over the past three decades. The versatility of polydiacetylene forms has also allowed for a wide range of sensors including liposome bacterial sensors, films for detecting influenza virus, hydrogels for protein detection, and printed ink for the detection of volatile organic compounds. In this article, we review the wide range of techniques employed in the development of polydiacetylene sensors and summarize methods to modify, characterize, and analyze polydiacetylene-based sensing systems. Additionally, we discuss the recent directions of polydiacetylene materials outside of sensing applications as versatile tools in biomedicine and tissue engineering.

In paper-based microfluidics, the simplest devices are colorimetric, giving qualitative results. However, getting quantitative data can be quite a bit more difficult. Distance-based devices provide a user-friendly means of obtaining quantitative data without the need for any additional equipment, simply by using an included ruler or calibrated markings. This article details the development of a quantitative DNA detection device that utilizes the aggregation of polystyrene microspheres to affect the distance that microspheres wick through filter paper. The microspheres are conjugated to single-stranded DNA (ssDNA) oligomers that are partially complementary to a target strand and, in the presence of the target strand, form a three-strand complex, resulting in the formation of aggregates. The higher the concentration of the target strand, the larger the aggregate, and the shorter the distance wicked by the microspheres. This behavior was investigated across a wide range of target concentrations and under different incubation times to understand aggregate formation. The device was then used to successfully detect a target strand spiked in extracted plant DNA.

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