Bi2S3@MoS2 Nanoflowers on Cellulose Fibers Combined with Octahedral CeO2 for Dual-Mode Microfluidic Paper-Based MiRNA-141 Sensors.

An effective dual-mode microfluidic paper-based analysis device (μPAD) was proposed via Bi2S3@MoS2 nanoflowers combined with octahedral CeO2 for ultrasensitive miRNA-141 bioassay. To obtain the amplified electrochemical signal, Bi2S3@MoS2 nanoflowers were first in situ grown onto the surface of cellulose fibers to promote the reduction of H2O2. The prism-anchored octahedral CeO2 nanoparticles with a great catalytic function on the reduction of H2O2 were linked up to the functionalized cellulose fibers through the hybridization chain reaction to further enhance the electrochemical signal. By means of the catalysis effect of Bi2S3@MoS2 nanoflowers and octahedral CeO2 nanoparticles, the obtained signal was amplified, thereby achieving ultrasensitive electrochemical detection of the target. With the help of duplex specific nuclease, the octahedral CeO2 could be released from the electrochemical detection area and flow to the color channel through capillary action, which could initiate the oxidation reaction of 3,3',5,5'-tetramethylbenzidine in the existence of H2O2 to generate a blue visual band, avoiding the error of distinguishing color depth caused by the naked eye and thus improving the accuracy of the visual method. Under the optimal conditions, satisfactory prediction and accurate detection performance were achieved in the range of 10 fM-1 nM and 0.5 fM-1 nM, respectively, by measuring the length of the blue product and the electrochemical signal intensity. The electrochemical/visual detection limits of the proposed μPAD for miRNA-141 were as low as 0.12 and 2.65 fM (S/N = 3). This work provides great potential for the construction of low-cost and high-performance dual-mode biosensors for the detection of biomarkers.