The sophisticated design of primers and the use of enzymes are capable of gene amplification at one constant temperature, eliminating the effort for complicated temperature controller. To address this issue, isothermal amplification techniques have been developed such as LAMP, rolling circle amplification, recombinase polymerase amplification, and helicase dependent amplification. Although polymerase chain reaction (PCR) is accepted as a gold standard method in clinical laboratories due to its high sensitivity and reliability, the precise control of temperature for thermal cycling and fluorescence-based detection system render the whole system bulky and expensive, making the PCR assay unsuitable for POC DNA testing. However, the previous studies used a limited function of the smartphone and its accessories, and few reports have been published for the genetic analysis, which is indispensable for the definite diagnosis of pathogens. ![]() uses the smartphone flash as an excitation source and a luminescent phosphor as a reporter for quantitative and rapid detection of human chorionic gonadotropin in urine 4. employed a camera of a smartphone for identifying Zika virus in a whole blood sample by using a reverse-transcription loop-mediated isothermal amplification (RT-LAMP) and a fluorescence detection 3. uses the camera of smartphone and a series of optical accessories for CD4 detection under a bright field. The utilization of the smartphone for bio-diagnostics is rapidly growing due to the increasing popularity of the smartphone as well as the superb specification of the smartphone such as excellent CMOS sensors, computing capabilities, customized mobile apps, data transfer and storage 2. Recent progress of the POCT diagnostics moves towards the combination of ICT with the microfluidic device. Such a POCT platform is important for the global healthcare monitoring, especially for those who are in need of prompt medical decisions 1. Microfluidic based POCT systems have been proposed for genomic and cellular analysis and have reached a mature stage for commercialization. On the other hand, microfluidic technology has attracted huge attention due to its miniaturization, fast analysis time, low consumption of reagents, high integration, and full automation capability. ![]() Thus, the adoption of the ICT to the medical diagnostic fields is a future trend, and it will be the next-generation diagnostic technology. Mobile communication via a smartphone or an internet of thing (IOT) device enables us to connect human network anytime anywhere, so the patient can have a person-to-person talk with doctors in case of need. Owing to the tremendous progress of Information & Communication Technology (ICT), the paradigm for medical diagnostics is shifting from the centralized medical centers to the individual home or ubiquitous places. We believe that this advanced colorimetric approach and the mobile app can expand the potentials of the smartphone for the future POCT system in the bio-diagnostic fields. ![]() Thus, the proposed mobile platform can inform us of not only qualitative but also quantitative results of the pathogens. ![]() A calibration curve could be generated by plotting the logarithm of the known concentration of the DNA templates versus the threshold time, and it can be used to predict the copy number of nucleic acids in the test samples. To keep track of the progress of the color change, we developed a novel mobile app in which a hue value was accepted as an indicator for color transition and for determining the threshold time of the amplification reaction. Upon the amplification of the target gene by an Eriochrome Black T-mediated LAMP reaction, the color of the LAMP reaction was changed from violet to blue that was real-time recorded by a smartphone camera. The whole system consists of a hand-held box equipped with a smartphone, a film heater, a white LED, a loop-mediated isothermal amplification (LAMP) chip, and a DC converter, and all the processes were powered by a portable battery of 5 V. Here, we describe a methodology for colorimetric quantitative analysis of nucleic acid using an easy-to-build smartphone-based platform, offering low-cost, portability, simplicity in operation, and user-friendliness. The increasing risk of infectious pathogens, especially in the under-developed countries, is demanding the development of point-of-care (POC) nucleic acid testing in the low-resource setting conditions.
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