Design And Implementation Of Portable Immunoassay Test Strip Reader

Gastric cancer is one of the most common malignant tumors thatthreatens human life and health. The incidence and mortality rate of gastriccancer rank4th and2nd at malignant tumors respectively. Nowadays in China,most of the diagnosed gastric cancers had been in progressive stage, but therate of early diagnosis is less than10%. While the survival rate of earlytreatment is much higher than progressive stage. Aimed at to diagnose gastriccancer in early stage, the pathogen can be a start point. There has been apositive correlation between the infection of helicobacter pylori and thepopularity of gastric cancer, while the helicobacter pylori which expressescytotoxin-associated gene A is more cancerigenic. Therefore, detection ofcytotoxin-associated protein A is significant to the early warning and diagnosisof gastric cancer, while setting up the accurate test method is mostly needed.With the advantages of simplicity, speediness, high specificity and fitnessfor point of care test, lateral flow immunoassay has become an importantmethod in detecting the biomarker of disease, food toxins and drug residue and environment pollutants. Traditional lateral flow immunoassay can onlydetermine a qualitative result, while there has been an increasing demand forquantitative immunoassay reader which can assay the accurate concentrationof biomarkers. With the character of photoluminescence, the nanoparticlescombined with the biology molecule are used as the fluorescence reporter onimmunoassay test strips. With the advantage of fluorescence stability and highintensity, quantum dots have a bright application prospect in the field ofassaying the ultra-low concentration of molecules.Currently, the optic system of most immunoassay readers are based onCCD imaging whose advantage is single capture, high speed imaging, whilethe shortcoming is image processing and the resolution of CCD sensor limitsthe reader’s detection sensitivity. Herein, aimed at to overcome thedisadvantage of CCD imaging, we utilized the light emitting diode, opticaltransistor and confocal principle based optical sensor, and under the assistanceof stepper motor module to accomplishthe real-time excitation and transitionof fluorescence of quantum dots labeled immunoassay test strip. The opticalsensor converts the fluorescence intensity into numerical value directly,eliminates the error of image processing and improves the accuracy ofdetection. Also, in order to operate the reader in more occasions, based onembedded development principle, we utilized STM32microprocessor to control the fluorescence capture and stepper motor, drive the color LCDdisplaying human machine interface and implement the data transmissionbetween the reader and host computer. For the functions of the reader, wechosethe appropriate hardware and then conducted circuit design and softwaredevelopment, finally tested functions of prototype reader. The developedprototype reader read the results of assaying cytotoxin-associated protein Aand finished the initial experiment exploration.In conclusion, we developed a portable immunoassay test strip reader.The confocal principle based optical sensor made up of the shortcoming ofCCD based optical system, and the application of embedded design reducedthe size of the reader and strengthened its portability. The prototype readerimplemented the designed functions and achieved the requirements.