Development of an IOT based portable biosensor for rapid detection of E. coli O157:H7

Foodborne pathogens are a growing concern for human illness and death. There is an increasing demand to ensure safe food supply and can make early detection for diseases. Escherichia coli O157:H7 is a severe bacterium that can cause dangerous disease to a human. Conventional development process requires prolonged and tedious compulsory additional method. Thus, this research study focus on developing completed system which are capable of sensing Escherichia coli O157:H7 at a low concentration level. The development of the system was divided into biosensor, electronic reader and IOT system. The silanization with (3-Aminopropyl) Triethoxysilane (APTES), immobilization of Probe ssDNA target were used as the step for preparation the biosensor. Then, t h e biosensor was hybridized with complementary, non-complementary, and single base mismatch ssDNA to performed selectivity measurement. Sensitivity measurement was accomplished using different concentration of complementary target ssDNA, which are from 1 fM to1 µM concentration and this approach was stable with fentomolar detection limit. In this research, an in-house, hand-held, ultra-sensitive, selective and rapid electronic reader has been demonstrated to detect the electrical signal generated by biosensor that convert the biological reaction into electrical signal. The in-house electronic reader can be used for two electrode amperometric electrical biosensors and is capable of multiplex detection, identifying three samples of E. coli O157:H7 bacteria simultaneously. The in-house electronic reader consists of a sensor interface circuit, a main control circuit, a DC power supply circuit, a sensor circuit and a display circuit. The in-house electronic reader design was focused on designing a sensor interface circuit to capture, filter and amplify different ranges of current and convert them to a detectable voltage range as an output voltage signal. A NodeMCU circuit reads and shows the output voltage value from the sensor interface circuit. The I-V characteristic was performed for each step such as bare Al IDE, salinization, immobilization and hybridization using source meter Keithley 2450 and compared using an in-house electronic reader. The current measurement ranges of the in-house electronic reader for nanoamperes were 0 to 300 nA and the percentage accuracy for the in-house electronic reader was 97 % compared with source meter Keithley 2450. The limit of detection of this system was 1 fM. The current value of 1 fM E. coli O157:H7 complementary target which equals to 3.5 nA, has been set in Arduino programming as an indicator (YES/NO) on display circuit. When the reading captured by the electronic reader is equal and higher than the set output value of 3.5 nA, a “YES” indicator will appear to indicate the presence of a E. coli O157:H7 bacteria on the sample. The results will show food safety levels for taking immediate action. Moreover, this approach system successfully minimized the time required compared with the conventional of E. coli O157:H7 detection.