The home kit developed for this project is a prototype designed to enable individuals to detect arsenic contamination in rice using a portable, paper-based testing system. The kit comprises a test strip fabricated by mixing TXO, DFHBI fluorophore, plasmid, and 10% trehalose, which is then spotted onto paper, frozen at -80°C, and lyophilized overnight for stability. Stored dry in a desiccant pouch at room temperature, the strip is prepared for use by users who take 1 gram of rice, grind it into a powder, and add it to a solvent containing citric acid for safety.
A very small drop of this mixture is then applied to the lyophilized biosensor using a tiny disposable pipette. Following a 30-minute incubation period at ambient or 37°C, users illuminate the strip with a flashlight while capturing a snapshot through a small filter placed over the camera app, allowing for visual interpretation of the resulting fluorescence or quantitative analysis via a smartphone application. This design ensures a practical and accessible testing method for household application.
As a prototype, the home kit is currently in an experimental phase, offering a proof-of-concept for at-home arsenic detection. The system leverages the fluorescence properties of the Broccoli aptamer, as described in the Svensen et al. (2014) study, to activate the DFHBI fluorophore, providing a sensitive indicator of arsenic presence. While the kit demonstrates promising functionality, further refinement is required to optimize sensitivity, durability, and user instructions. This prototype serves as a foundation for future iterations, with potential enhancements to include automated quantification and expanded testing for additional contaminants, aligning with the broader objectives of the citizen science initiative outlined in the accompanying app functionality.
In the development of our prototype end-user kit for the Riceguard biosensor, selecting an appropriate light source to excite DHFBI-1T at its optimal wavelength posed a significant challenge. After thorough evaluation, we acquired two potential options: a laser and an LED flashlight. Testing revealed that the LED flashlight was the safer choice, as the laser posed risks of eye damage. Given that the emission wavelength differs, we also procured a plastic filter, which we cut into small strips and secured with tape over the cellphone camera lens to block unwanted light. This filter was readily available and proved to be a practical solution. The selected items include the LED flashlight and the compatible plastic filter, enhancing the kit's functionality for fluorescence detection.
Products we procured for our prototype included:
- Waterproof 488nm Cyan-Blue Focusable Dot Laser Module
- UltraFire Blue Light Flashlight Hunting Torch 256 Yard 470 nm
- Color Correction Gel Light Filter
Color Correction Gel Light Filter
