Team:Brown/Project/Overview

Inspired by the need for a simple, inexpensive, and portable means of toxin detection, Brown University’s Team Toxipop wanted to create a biosensor that utilizes a novel method to detect the presence of a toxin in a solution of bacteria. After a great deal of brainstorming, our team finalized the design for our project. A gene cassette coding for cell lysis in E. Coli will be placed under the control of an inducible promoter such as a pBAD promoter. Once cell lysis has occurred, the charged intracellular contents of the cells will become part of the extracellular solution, increasing the solution’s conductance and indicating the presence of the inducer.

Strategy

After doing research on current toxin detection systems in the market and seeing what is missing from these systems, our team compiled a list of guidelines for an ideal biosensor that our system is designed to meet:

Biological

• Uses minimal biological machinery
• Direct induction of system by inducer creates a sensitive system
• Versatile construct

Engineering

• Compact and user-friendly system for sample analysis
• Economically feasible

Minimal biological machinery

Our biological construct consists of three interacting proteins under the control of a single promoter. Such a simple construct increases efficiency and minimizes sources of error in the system.

Direct induction of system by inducer optimizes sensitivity

The triggering of the lysis gene cassette is directly influenced by inducer presence, creating a sensitive system that should maintain a constant gain.

Versatile construct

The simplicity of our construct lends to its versatility. The promoter controlling the lysis cassette can easily be interchanged, optimizing our system's potential to detect several different types of toxins and other substances. For example, a mercury-induced, arsenic-induced, or lead-induced promoter, all of which have been introduced by iGEM teams in the past, could be placed in control of the lysis cassette, creating three separate and specific toxin detection systems.

Compact and user-friendly

The physical bio-sensor envisioned by our team would be hand-held, consisting of a small compartment of bacterial cells with electrical probes fixed in this compartment. The probes feed information to a simple circuit within the sensor which monitors conductance of the bacterial solution and outputs an increase in conductance via a simple LED light signal (See our "Application" page for more details). This set-up would enable any person with little or no knowledge of the machinery of the bio-sensor to utilize it effectively.

Economically feasible

E. coli bacteria, which provide the main machinery of the bio-sensor, are inexpensive to obtain, grow, and store. Additionally, after consultation with mechanical engineers, we discovered that the circuit required for our proposed system would be simple to create and inexpensive to produce, in the range of a few dollars.