Abstract
A colorimetric polydiacetylene (PDA) paper strip sensor that can specifically recognize Bacillus thuringiensis (BT) HD-73 spores is described in this work. The target-specific aptamer was combined with PDA, and the aptamer-conjugated PDA vesicles were then coated on polyvinylidene fluoride (PVDF) paper strips by a simple solvent evaporation method. The PDA-aptamer paper strips can be used to detect the target without any pre-treatment. Using the paper strip, the presence of BT spores is directly observable by the naked eye based on the unique blue-to-red color transition of the PDA. Quantitative studies using the paper strip were also carried out by analyzing the color transitions of the PDA. The specificity of this PDA sensor was verified with a high concentration of Escherichia coli, and no discernable change was observed. The observable color change in the paper strip occurs in less than 1 h, and the limit of detection is 3 × 107 CFU/mL, much below the level harmful to humans. The PDA-based paper sensor, developed in this work, does not require a separate power or detection device, making the sensor strip highly transportable and suitable for spore analysis anytime and anywhere. Moreover, this paper sensor platform is easily fabricated, can be adapted to other targets, is highly portable, and is highly specific for the detection of BT spores.
Highlights
Certain bacteria can form durable, self-protective spore structures that can survive under harsh conditions
The results of our system complicated pre-processing in our system, and the prepared PDA-aptamer paper strip can be used showed that PDA-aptamer paper-based strips exhibit varying degrees of color changes, depending for immediate detection, as long as the targets are present in a liquid
Our sensor can be used for showed that PDA-aptamer paper-based strips exhibit varying degrees of color changes, depending quantitative analysis, and the color changes are observable by the naked eye
Summary
Certain bacteria can form durable, self-protective spore structures that can survive under harsh conditions. Eliminating bacterial spores with conventional sterilization methods is very difficult because the spore structure can protect it from environmental stresses, including desiccation, high temperature, UV irradiation, enzymatic destruction by drugs and exposure to toxic chemicals [1]. The simple and rapid detection of spores is a widespread concern in food safety. Polymerase chain reaction (PCR) [2,3], immunoassays [4], fluorescence assays using quantum dots [5], and counting methods for Bacillus spores have been demonstrated. Sophisticated methods and non-transportable instruments have limited their use in the field. We developed a simple and transportable paper sensor platform to detect well-known spores from the phylum
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