Structure and Function of the CBNAAT Module

The CBNAAT module contains components that enable automated sample processing in the cartridge, and filling of the tube with the sample-reagent mixture for Polymerase Chain Reaction (PCR), followed by PCR amplification and detection.

The structure of the CBNAAT module is described below and shown in Figure 1:

• Syringe pump drive or plunger motor: Dispenses fluids into the different cartridge chambers
• I-CORE module: Performs PCR amplification and detection
• A cartridge loading and unloading mechanism ensures the proper movement of the cartridge in the instrument
• Reaction/PCR tube: Enables rapid thermal cycling and optical excitation and detection of the tube contents. The reaction tube is automatically inserted into the I-CORE module (hardware for PCR amplification and fluorescence detection) when the cartridge is loaded into the instrument.
• Valve drive: Rotates the cartridge valves to align the chambers with the syringe
• Ultrasonic horn: Lyses the sample

Figure 1: Structure of the CBNAAT module

The interior region of the cartridge insertion site also called cartridge bay and is shown in Figure 2.

Figure 2: Interior of the Cartridge Bay

Mode of Operation of the CBNAAT Module 

• The Intelligent Cooling/Heating Optical Reaction (I-CORE) module is the hardware component, within each instrument module, that performs PCR amplification and, fluorescence detection.
• As part of the cartridge load process, the PCR tube is inserted into the ICORE module. 
• As the test starts, the sample and reagent mixture are pushed from the cartridge, into the PCR tube.
• During the amplification process, the ICORE heater heats up and the fan cools down the reaction tube contents.

Within the I-CORE, there is an optical system composed of two blocks: A six colour excitor and detector block excite the dye molecules, and detect the fluorescence emitted.

Figure 3: Mode of operation of the CBNAAT module

Resources

• Training material Cepheid Hbdc 3a GeneXpert technology

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