Abstract
Thailand has become an aging society. Old age people risk of developing dementia including Alzheimer's disease (AD). Therefore, early diagnosis is crucial in order to prevent the serious health problem. Herein, the rapid simple and low cost detection method have been developed for screening test of Aß1-42 which is essential biomarker of AD. Firstly, the antibodies used were investigated and selected to perform in the assay. The gold nanoparticles (AuNPs) was used as a labelling materials because the results can be seen by naked eye and provide the stability. The dot-blot with direct and sandwich immunoassay were developed for measurement the level of Aß1-42. However, the sandwich immunoassay provides higher sensitivity when compared with the direct assay which was then selected to use in further work. For the assay, the anti-rabbit Aß pAb was immobilized on nitrocellulose membrane. To test, the sample was dropped on the test zone and incubated for 10 min. After that, 2 µL of anti-rabbit Aß mAb conjugate- AuNPs was applied on the test zone and incubated for 10 min following by washing. The results can be visualized in few min. Under optimized conditions, the limit of detection was found to be 5 µg/mL. In order to enhance the signal, the silver enhancer was applied in the system after test. In the present of silver enhancement solution, the darker color in signal becomes more strengthened due to silver precipitation on the AuNPs which providing better sensitivity. The limit of detection was observed at 1 µg/mL. Moreover, the approached assay would be applied to detect of Aß1-42 antigen in real blood sample and the results showed the different between the sample with and with out Aß1-42. However, the further development to increase the sensitivity of detect tool still need more study to apply for the measurement of the plasma Aß in clinical sample.
