Abstract
This study presents an optical inspection system for detecting a commercial point-of-care testing product and a new detection model covering from qualitative to quantitative analysis. Human chorionic gonadotropin (hCG) strips (cut-off value of the hCG commercial product is 25 mIU/mL) were the detection target in our study. We used a complementary metal-oxide semiconductor (CMOS) sensor to detect the colors of the test line and control line in the specific strips and to reduce the observation errors by the naked eye. To achieve better linearity between the grayscale and the concentration, and to decrease the standard deviation (increase the signal to noise ratio, S/N), the Taguchi method was used to find the optimal parameters for the optical inspection system. The pregnancy test used the principles of the lateral flow immunoassay, and the colors of the test and control line were caused by the gold nanoparticles. Because of the sandwich immunoassay model, the color of the gold nanoparticles in the test line was darkened by increasing the hCG concentration. As the results reveal, the S/N increased from 43.48 dB to 53.38 dB, and the hCG concentration detection increased from 6.25 to 50 mIU/mL with a standard deviation of less than 10%. With the optimal parameters to decrease the detection limit and to increase the linearity determined by the Taguchi method, the optical inspection system can be applied to various commercial rapid tests for the detection of ketamine, troponin I, and fatty acid binding protein (FABP).
Highlights
Human chorionic gonadotropin is an important marker indicating pregnancy
When the Human chorionic gonadotropin (hCG) concentration was increased, larger volumes of the colloid gold were aggregated in the test line and this deepens the color of the test line
After the experiments were designed by the Taguchi method (L12 (211) orthogonal array), the best levels for the factors could be determined through calculation and tabulation
Summary
Human chorionic gonadotropin (hCG) is an important marker indicating pregnancy. HCG is a hormone produced by the syncytiotrophoblast, a component of the fertilized egg after conception. In 1960, the radioimmunoassay (RIA) method was used to detect the hCG concentration [2]. Commercial detection reagents (hCG, ketamine, troponin I, luteinizing hormone, etc.). Were used in the lateral flow immunoassay to detect the specific antigen, and the different color in the test line was observed by the naked eye. The pregnancy test strip was used to detect the hCG concentration in the woman’s urine. The cut-off value of the pregnancy test strip was set to 25 mIU/mL
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