RF plasma-enhanced conducting Polymer/W₅O₁₄ based self-propelled micromotors for miRNA detection

Functionalized micro/nanomotors having immobilized biological molecules provide excellent and powerful tools for the detection of target molecules. Based on surface modifications and mobilities of micromotors, we report herein a new experimental design of high-speed, self-propelled and plasma modified micromotors for biomedical applications. Within this scope, in the first step, poly (3,4-ethylenedioxythiophene) (PEDOT) was in-situ synthesized onto W₅O₁₄ (tungsten trioxide) wires by using radio frequency (RF) rotating plasma reactor. Then, W₅O₁₄/PEDOT-Platinum (Pt) hybrid micromotors were fabricated by using magnetron sputtering technique. The detection of miRNA-21 was performed using both single-stranded DNA (ssDNA) (probe DNA) immobilized W₅O₁₄–Pt and W₅O₁₄/PEDOT-Pt micromotors. The fluorescence signals were determined after hybridization of probe DNA immobilized these novel W₅O₁₄–Pt and W₅O₁₄/PEDOT-Pt micromotors with different molar concentrations of the synthetic target (6-carboxyfluorescein dye (FAM)-labeled miRNA-21). The changes in the micromotor speeds after the hybridization process were also evaluated. W₅O₁₄/PEDOT-Pt micromotors presented better sensor properties compared to the W₅O₁₄–Pt micromotors. A good linearity for miRNA-21 concentration between 0.1 nM and 100 nM was obtained for these micromotors based on their fluorescence intensities. The detection limit was found as 0.028 nM for W₅O₁₄/PEDOT-Pt micromotors (n = 3). Thus, sensor and motor characteristics of the W₅O₁₄–Pt micromotors were improved by RF plasma enhanced PEDOT coatings. The new catalytic W₅O₁₄ based micromotors demonstrated here had great potential for the development of sensitive and simple sensing platforms for detection of miRNA-21.