FloraDX Overview

FloraDX’s diagnostic platform offers a simple, affordable, and effective method for detecting and tracking bacterial vaginosis (BV)-associated bacteria. By integrating biological and electronic components, the device captures multiple Amsel’s criteria simultaneously. This is achieved through a dual-sensing system: a hydrogel embedded with engineered bacteria that fluoresces in response to putrescine and an optical pH spot sensor. The results are displayed clearly on an LCD screen via a user-friendly graphical interface, allowing for reliable and accessible monitoring over time. We have also included a bill of materials PDF found at the bottom of this web page in order to increase our project's reproducibility and accessibility.

Figure 1. FloraDX Flow-Diagram

Hydrogel Cassettes

To enable easy and consistent biological sensing, we housed the putrescine-responsive bacteria in hydrogels within circular cassettes. Each cassette is partitioned into seven compartments, one for each day of the week. Bacterial viability is maintained by our alginate-based hydrogel formulation, allowing users to perform daily tests without replacing the hydrogel for an entire week. Hydrogel insertion and replacement is simplified by a sliding tray mechanism, which features a notch to ensure the cassette is correctly aligned within the device.

Figure 2. Sliding Tray and Hydrogel Disk

Figure 3. Cassette with Hydrogel Compartments

Optical Fluorescence System

We developed a compact optical system in our device to quantify GFP expression from our putrescine-responsive bacteria. To excite GFP, we used a high-power 465 nm monochromatic LED (OSRAM OSCONIQ P 3030, GB QSSPA1.13) mounted on a custom PCB, with a copper heatsink to manage thermal resistance. GFP emission was measured using a 525 nm-specific photodiode (Marktech Optoelectronics MTD5052D3). An aspheric lens focused the emitted light, while a longpass filter (HOYA Y52) improved the signal-to-noise ratio.

Figure 4. Optical System

pH Detection System

FloraDX incorporates a PyroScience PHSP5-PK7 pH sensor spot positioned at the top right of the device. Because changes in vaginal pH are a key diagnostic marker for BV, this sensor complements the biological detection system to improve overall diagnostic accuracy. Users insert their swab directly into the small compartment at the top of the device, where it undergoes dilution and comes into contact with the pH sensor spot. The sensor itself is a small sticker placed inside the compartment. An optical system outside the compartment then excites the sticker, measures the emitted fluorescence, and converts it into a pH value. This non-invasive, optical approach enables precise measurements while minimizing contamination, allowing for high-throughput analysis.

Figure 5. pH Sensor Spot

We would like to acknowledge PyroScience for generously donating the PHSP5-PK7 pH sensor spot to Boston University’s 2025 iGEM team, FloraSynse, in support of our project.

LCD Interface

Users interact with FloraDX’s software either through our app or directly via the device. The front of the device features a 2.1-inch LILYGO T-RGB Liquid-Crystal Display (LCD) touchscreen, providing a clear and intuitive interface. By leveraging an RGB graphical display, raw fluorescence and pH data are translated into user-friendly indicators, such as color-coded alerts or numeric readouts, enhancing both confidence and ease of use.

Figure 6. Graphical User Interface

FloraDX Housing

FloraDX is housed in a robust, square enclosure featuring an LCD interface on the front, a hydrogel cassette tray on the side, and sample inserts on the top. The enclosure is constructed from polycarbonate sheets, providing impact resistance, maintaining an isothermal environment for the biological system, shielding the optical components from ambient light, and keeping the device lightweight. These design choices enhance safety, portability, and ease of handling. Internal components are securely mounted to prevent user contact with live bacteria or electronics, and the device supports both single-use and modular reuse. Additionally, sterilization protocols have been implemented to ensure that genetically modified bacteria remain contained within the controlled environment.

Figure 7. FloraDX Housing

Future Directions

Future iterations of FloraDX’s hardware aim to expand its sensing capabilities through:

Miniaturizing the optical fluorescence system to reduce device size while maintaining signal fidelity

Enhancing the touchscreen interface with customizable alerts, trend analysis, and historical data visualization

Refining sterilization protocols to ensure complete containment of genetically modified organisms during disposal