An Integrated Smartphone-Based Genetic Analyzer for Qualitative and Quantitative Pathogen Detection

Abstract

The use of the smartphone is an ideal platform to realize the future point-of-care (POC) diagnostic system. Herein, we propose an integrated smartphone-based genetic analyzer. It consists of a smartphone and an integrated genetic analysis unit (i-Gene), in which the power of the smartphone was utilized for heating the gene amplification reaction, and the camera function was used for imaging the colorimetric change of the reaction for quantitative and multiplex foodborne pathogens. The housing of i-Gene was fabricated by using a 3D printer, which was equipped with a macro lens, white LEDs, a disposable microfluidic chip for loop-mediated isothermal amplification (LAMP), a thin-film heater, and a power booster. The i-Gene was installed on the iPhone in alignment with a camera. The LAMP mixture for Eriochrome Black T (EBT) colorimetric detection was injected into the LAMP chip to identify Escherichia coli O157:H7, Salmonella typhimurium, and Vibrio parahaemolyticus. The proportional-integral-derivative controller-embedded film heater was powered by a 5.0 V power bank to maintain 63 °C for the LAMP reaction. When the LAMP proceeded, the color was changed from violet to blue, which was real-time monitored by the smartphone complementary metal oxide semiconductor camera. The images were transported to the desktop computer via Wi-Fi. The quantitative LAMP profiles were obtained by plotting the ratio of green/red intensity versus the reaction time. We could identify E. coli O157:H7 with a limit of detection of 10¹ copies/μL within 60 min. Our proposed smartphone-based genetic analyzer offers a portable, simple, rapid, and cost-effective POC platform for future diagnostic markets.

Figure 1

(A) Schematic illustration of the i-Gene attached on the smartphone. (B) Microfluidic LAMP reaction chip (yellow line channels: vistex coating, blue line channels: no coating). (C) Inside view of the genetic analyzer.

Figure 2

Procedure of the molecular diagnostics by the portable smartphone-based genetic analyzer.

Figure 3

(A) Assembly of the electrical circuit to run the heater and the LED lighting system. (B) Temperature profile for 60 min at 24.0 V input voltage. (C) Full set for the molecular diagnostics consisting of an i-Gene, a smartphone, an LAMP chip, and a power bank. (D) Cross-sectional digital image of the i-Gene.

Figure 4

RGB colorimetric assay for quantifying the EBT-mediated LAMP reaction.

Figure 5

Colorimetric detection and the real-time LAMP profiles by the i-Gene for the (A) monoplex target (E. coli O157:H7), (B) duplex target (E. coli O157:H7 and V. parahaemolyticus), and (C) triplex target (E. coli O157:H7, V. parahaemolyticus, and S. typhimurium).

Figure 6

Quantification calibration curve. (A) LAMP profiles using various amounts of genomic DNAs of E. coli O157:H7 ranging from 10¹ to 10⁶ copies/μL. (B) Linear regression plot of the C_t versus log(the amount of DNA).