Copper complex of a thienyl-hydrazone rhodamine derivative is a highly selective colorimetric sensor for pyrophosphate

Green and sustainable smart wooden system integrated with cellulose nanowhiskers-supported polyvinyl alcohol and anthocyanin biomolecules to monitor food freshness

Smart packaging materials have been used to protect human health from environmental hazards by sending real-time colorimetric signals for changes in the food packaging environment. However, the colorimetric material sensors use synthetic sensor dyes, which are toxic, expensive, non-biodegradable, and difficult to prepare. Herein, a simple strategy is presented for the development of an environmentally-friendly halochromic wood able to change color upon exposure to spoilage of food. A combination of anthocyanin (Ac)/aluminum (Al) mordant (Ac/Al) nanoparticles and cellulose nanowhiskers (CNW)-reinforced polyvinyl alcohol (PVA) was infiltrated into a delignified wood to produce a translucent wood with halochromic properties. CNW were employed as reinforcement agent to improve the mechanical performance of PVA. Additionally, CNW function as a dispersing agent to prevent agglomeration of Ac/Al nanoparticles. The diameters of CNW are in the range of 12-19 nm, whereas Ac/Al particles showed diameters of 9-22 nm. The smart wood changed color from purplish to colorless when exposed to food spoilage. A hypsochromic change from 539 nm to 370 nm was shown by the anthocyanin receptor when the spoilage level of food increased. This could be attributed to the pH-driven molecular switching of anthocyanin, leading to charge delocalization.

Dual amplification-based ultrasensitive and highly selective colorimetric detection of miRNA

In this study, we combined a Pradeep Kumar (PK)-probe with a ligation-transcription-ramified RCA (LTR) dual-amplification system for the isothermal colorimetric detection of miRNA 25-3P, where the PK-probe transformed from its pink color to colorless in the presence of the amplification byproduct pyrophosphate (PPi), thereby allowing the simple naked-eye qualitative detection of the miRNA. Through this double-amplification strategy, the limit of detection reached as low as 91.4 aM-quite extraordinary sensitivity for a colorimetric miRNA detection system based on absorbance readings. Our detection system also operated with high specificity, the result of using two different target-selective ligation steps (linear DNA ligation and circular DNA ligation) mediated by SplintR ligase, and so could discriminate single-mismatched from perfectly matched target sequences. We suspect that this ultrasensitive and selective PK-probe/LTR dual-amplification system should be a great colorimetric diagnostic for the detection of any miRNA with high efficiency.

Multiple ligation–Assisted recombinase polymerase amplification for highly sensitive and selective colorimetric detection of SARS-CoV-2

In this paper we present a new method for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), targeting a specific region “N gene.” Under isothermal reaction conditions, we integrated ligation (Lig; high selectivity) and recombinase polymerase amplification (RPA; high sensitivity) processes, obtaining a robust method of detection. For point-of-care testing, we incorporated our laboratory-produced pyrophosphate ion (PPi)–sensing probe (PK-probe) for colorimetric analysis of the reaction. The total detection system was efficient and effective at diagnosing this RNA virus–mediated disease rapidly (30 min). In a full-genome SARS-CoV-2 study, our PK-probe/Lig-RPA system functioned with a limit of detection of 1160 copies/ml, with a single-mismatch level of selectively, and it was highly selective even in the presence of bacterial genomes commonly found in the human mouth and nose. This robust, straightforward, selective, efficient, and ultrasensitive colorimetric detection method, with potential for point-of-care analysis, should also be effective in detecting a diverse range of other RNA-based diseases.