| AVS 58th Annual International Symposium and Exhibition | |
| Biomaterial Interfaces Division | Monday Sessions |
| Session BI-MoA |
| Session: | Sensors and Fluidics for Biomedical Applications |
| Presenter: | Yuji Wang, The Ohio State University |
| Authors: | Y. Wang, The Ohio State University W. Lu, The Ohio State University |
| Correspondent: | Click to Email |
AlGaN/GaN heterojunction features two-dimensional electron gas which is highly sensitive to proximal charges and excellent stability against chemicals. These unique advantages imply the potential of AlGaN/GaN based field effect transistor (FET) in facilitating various biological and chemical studies. We have previously reported the detection of hybridization between probe DNAs and fully complementary target DNAs with AlGaN/GaN HFET biosensors. To further improve the sensitivity, comprehensive understanding of the working principle is necessary. In this work, we focus on a systematical investigation on the effects of the distance between the charged layer and the sensing surface, i.e., the distance from target DNA biomocules to the AlGaN surface. We immobilized a monolayer of single-strand probe DNAs modified with thiol groups on the Au-coated active gate surface of an AlGaN/GaN HFET. Different target ssDNA molecules were designed so that distance between the hybridization sites and the AlGaN surface varied. Experimental results show an explicit relationship between the detection sensitivity and the charge layer distance.
Six types of synthesized 25-mer oligonucletides (Allele) solutions were prepared, including a probe DNA, a fully complementary target DNA, a 21-bp complementary DNA, a 13-bp complementary DNA, a 9-bp complementary DNA and a mismatched DNA. The amount of charges is assumed identical for DNAs with a constant length. The distance of the charge layer can be well controlled by varying the hybridization sites of target DNAs to the probe DNAs. For example, the 21-bp complementary DNA is 4-bp further away from the surface than the fully complementary DNA.
We compared the IDS-VDS characteristics of devices before and after hybridization. A decrease of drain current was noticed, revealing the binding of negatively charged DNAs. More importantly, the decreases in IDS-VDS demonstrated a clear dependence of charge layer distance by an observation of the current change ratio, defined by ΔIDS / IDS, (gate bias: -1 V): 16.1% for fully complementary target DNA (0.1 µ mol), 14.9% for 21-bp complementary DNA, 10.9% for 13-bp complementary DNA, 6.89 % for 9-bp complementary DNA, and 0.75% for mismatch DNA, which was comparably insignificant. The current change decreases with the distance between the target DNA and sensing surface, although the amount of charges for the target DNA is constant. These results demonstrate that the detection sensitivity is significantly dependent on the charge layer distance. Theoretical analysis for varying charge layer distances of target DNAs will also be studied and compared with the experimental results.