Quantitative detection system for immunostrips in 180nm standard CMOS technology
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Quantitative detection system for immunostrips in 180nm standard CMOS technology Engincan Tekin1 • Caner Celikdemir1 • Busra Ucar1 • Ozgur Gul2 • Baykal Sarioglu1 Received: 17 February 2020 / Revised: 17 February 2020 / Accepted: 3 September 2020 Ó Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In this work, a CMOS based optical read-out system for biomarker on immunostrips detection is presented. For the proposed system, a CMOS integrated circuit containing an on-chip photodiode is designed in standard 180 nm UMC CMOS Technology. The system also contains cost-effective 3D Printed structures for holding both IC and the sample immunostrip together. The proposed system can be operated in two modes (1) light reflectance and (2) light transmittance. In the system, a laser with a wavelength of 637 nm is applied to the CMOS IC through immunostrip. Photovoltaic and photoconductive measurements are carried out for each mode on a custom Gluten biomarker immunostrip. Sensing operation of the biomarker is successfully realized with optical powers from 5 mW to 8 mW. Biomaterial density on the immunostrip is sensed and images of the biomarker with varying intensities are constructed from the measurements. Feasibility of the system for low power biomarker sensing applications is demonstrated. Keywords Biosensing CMOS Optical sensor Biomarker
1 Introduction Biosensors are one of the key instruments for diagnosis and detection of diseases and biological elements. One of the biggest advantages of biosensors is the point of care (PoC) diagnostic abilities [1, 2] . Immunostrips are one of the most used biosensor systems in PoC diagnosis. Immunostrips are defined as biosensors that function based on a interaction between antibodies and antigens which in turn gives them high specificity and selectivity for their specific analyte. Most common immunostrip test format is the sandwich model where the biomarker is captured between two antibodies, one as a capture and the other one as a detection agent (Fig. 1) [3, 4]. Gold nanoparticles (GNPs) are used in literature to construct immunosensors because of their ability to bind with antibodies [5–7]. Using gold nanoparticles, & Baykal Sarioglu [email protected] 1
Department of Electrical and Electronics Engineering, Istanbul Bilgi University, Istanbul, Turkey
2
Department of Genetics and Bioengineering, Istanbul Bilgi University, Istanbul, Turkey
colorimetric immunoassays can be built upon the idea that different amounts of antibodies labeled with gold nanoparticles can result in different observable color changes. The main problem with this kind of detection is its low sensitivity [5]. With an optical detection system depending on a camera or a laser, portable and accurate reading of the immunostrips can be achieved. There are several examples of optical immunostrip reading devices such as using smartphones as an optical detection devices with antibody bound gold nanoparticles to detect cancer antigen CA125 [8] or using an Wi-Fi enabled lens
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