Improving the Sensitivity of Colorimetric DNA Sensors via Catalytic Disassembly of Gold Nanoparticles

Biotechnology is quickly progressing in the medical field; however, its applicability is limited by the lack of early detection in a few diseases/cancers, which is essential for effective care. Since biotechnology is rising, sensitive detection approaches are increasingly developed with gold nanoparticles (NPs). One technique commonly used for DNA amplification is polymerase chain reaction (PCR), which can be used to diagnose a variety of diseases and cancers. The shortcomings of PCR are that it requires sensitive enzymes, expensive equipment such as a thermocycler, and employees being trained on this equipment, which makes this process very time-consuming. Because of these disadvantages, this method is inapt as a simple procedure for DNA amplification. Previous sensor designs used nanoparticle aggregation-based methods via plasmonic coupling to exploit the colorimetric properties of gold NPs. However, few possibilities have been explored in which nanoparticle aggregates are formed first and then disassembled via catalytic DNA networks in the presence of a target sequence. In this work, a non-enzymatic, simple technique is proposed via catalytic disassembly of the DNA reaction mechanism. Our catalytic DNA network can be used as a colorimetric DNA sensor by implementing gold NPs onto a polymer microbead. This allows the gold nanoparticle linkages to be released at minimal detectable concentrations from the polymer microbead, and the resultant colorimetric change can be detected in the supernatant without using costly instrumentation. The primary objective of this project is to create a disassembly-based colorimetric sensor system that can elicit a measurable signal when small segments of nanoparticles disassemble into a solution. Two colorimetric sensor designs as well as two gold NP sizes were prepared and tested to find the combination that produced the lowest detection limit. Results have been reported, and the minimum amount of detectable DNA signal was as low as 0.2 nM. A low enough detection limit could potentially allow researchers to distinguish trace amounts of analytes that are characteristic of a variety of diseases