Using Molecular Detection Technology to Help Doctors Make Patient Diagnoses Faster and More Accurate

The market growth of point-of-care molecular diagnostics (PoC) is mainly driven by the following factors: High prevalence of infectious diseases; Rising awareness and acceptance of personalized medicine; Accuracy and portability of diagnostic results with advancements in molecular technology Sexual improvement. PoC molecular diagnostic technology can help doctors make quick diagnosis and treatment decisions at the first visit of a patient, and patients do not have to wait days for test results, thereby improving the level of medical care. This article will briefly describe this detection method and detail some of the practical components in the main modules of this type of instrument.

The market growth of point-of-care molecular diagnostics (PoC) is mainly driven by the following factors: High prevalence of infectious diseases; Rising awareness and acceptance of personalized medicine; Accuracy and portability of diagnostic results with advancements in molecular technology Sexual improvement. PoC molecular diagnostic technology can help doctors make quick diagnosis and treatment decisions at the first visit of a patient, and patients do not have to wait days for test results, thereby improving the level of medical care. This article will briefly describe this detection method and detail some of the practical components in the main modules of this type of instrument.

Using Molecular Detection Technology to Help Doctors Make Patient Diagnoses Faster and More Accurate

Figure 1: Simplified workflow of PoC molecular diagnostic analyzer

At a higher level, biological samples may not have enough target DNA to be detected by optical fluorescence means. Therefore, DNA amplification (cloning/replication) is required for analysis. The two main amplification techniques are polymerase chain reaction (PCR) and loop-mediated isothermal amplification (LAMP).

PCR and LAMP amplification techniques require the use of some heating and cooling elements. The PCR amplification technique requires the use of a thermoelectric cooler (TEC), which thermally cycles through three independent changes in temperature conditions, including heating the sample to 95°C, cooling to 50°C-56°C, and holding the sample at 72°C C at constant temperature. Repeating this cyclic process can generate billions of DNA copies. During LAMP amplification, heating and cooling elements maintain the sample at a constant temperature of 60°C-65°C. Avoiding thermal cycling helps speed up this reaction, but requires a more advanced set of primers.

Figure 2 shows a schematic diagram of the sensor front end/TEC unit of the PoC molecular diagnostic analyzer, which is based on the TIDDC112 current input analog-to-digital converter (ADC) and TI current driver, precision amplifier and temperature sensor.

Using Molecular Detection Technology to Help Doctors Make Patient Diagnoses Faster and More Accurate

Figure 2: Block diagram of the sensor front-end system of the PoC molecular diagnostic analyzer

Proper operation of the TEC unit requires a high level of temperature accuracy to monitor the heating and cooling required for the nucleic acid amplification process. The TMP117 digital sensor achieves a typical accuracy of ±0.1°C and a maximum accuracy of ±0.2°C over the -40°C to 100°C temperature range. The device features an integrated 16-bit ADC that communicates with digital components via I2C or SMBus. Specifically designed for battery-operated systems, the TMP117 features a quiescent current consumption of 150 nA in shutdown and requires only 3.5µA per 1Hz conversion cycle.

The TPS54201 provides constant current (1.5A) to drive the DRV8873 to operate the efficient heating and cooling elements to drive the TEC. The DRV8873 consists of four N-channel MOSFETs that bidirectionally drive the motor with peak currents up to 10A, and features such as integrated current sensing that eliminates the need for two external parallel resistors, saving BOM cost and space. For more information, please refer to the following application notes.

When amplification occurs, a fluorescent tag against the pathogen tag sequence is excited by a light source; a single photodiode or group of photodiodes can detect the fluorescence. Signal levels vary with amplification time or cycle, indicating the initial concentration of a specific pathogen in the sample. This signal level can be detected with just a few target DNA fragments in the sample early in the amplification process, further reducing the time required to obtain a positive result (identification of target genomic material). The DDC112 family of devices can sample current from 1 to 256 diodes and integrate a current amplifier and ADC into a single circuit. These devices feature very low input-referred noise (in the rms ferroampere range), low input bias current (0.1 pA), and high linearity ADCs with up to 24-bit resolution.

The complexities involved in such detection span multiple scientific fields and are not discussed in depth here. Nonetheless, we hope this article will help you in choosing the more critical electronics for your instrument design.

Other resources

Read the following application report, “Advanced Digital Temperature Sensor for Field Emitters Achieves Class AA RTD Accuracy.”
See the DRV8873xEVM and DDC11xEVM-PDK user guides.
See In Vitro Diagnostics for more information.

The Links:   NL2432HC17-05B LB104S01-TL02

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