Label-Free MicroRNA Optical Biosensors

Abstract

MicroRNAs (miRNAs) play crucial roles in regulating gene expression. Many studies show that miRNAs have been linked to almost all kinds of disease. In addition, miRNAs are well preserved in a variety of specimens, thereby making them ideal biomarkers for biosensing applications when compared to traditional protein biomarkers. Conventional biosensors for miRNA require fluorescent labeling, which is complicated, time-consuming, laborious, costly, and exhibits low sensitivity. The detection of miRNA remains a big challenge due to their intrinsic properties such as small sizes, low abundance, and high sequence similarity. A label-free biosensor can simplify the assay and enable the direct detection of miRNA. The optical approach for a label-free miRNA sensor is very promising and many assays have demonstrated ultra-sensitivity (aM) with a fast response time. Here, we review the most relevant label-free microRNA optical biosensors and the nanomaterials used to enhance the performance of the optical biosensors.

Label-Free Biosensors for Laboratory-Based Diagnostics of Infections: Current Achievements and New Trends

“…In the latter, live natural or engineered microorganisms (such as Escherichia coli or Staphylococcus aureus), integrated on a sensory substrate, assimilate target organic compounds from biosubstrates (such as, for example, antibodies from blood serum) and simultaneously act as a sensitive mechanism [25,[68][69][70][71][72]. In this case, a positive reaction to the promoter of the target molecule after its transport through the cell membrane and diffusion inside the bacterial cell causes expression of the reporter gene, which is recorded as a quantitative response via optical [7,24,26,39,56] or electrochemical signals [30,[48][49][50]73].…”

“…This type of biosensors requires only one recognition element, which leads to simplification of the pattern of analysis, reducing both the analysis time and expenditures for reagents. The latest generation of label-free biosensors provides real-time quantification of products of biomolecular reaction, which makes it possible to perform continuous data recording, allowing kinetic monitoring of parameters of the ligand-receptor interaction recognition process [24,32,[77][78][79][80].…”

“…These methods allow you to indirectly determine the analyzed substances and molecules; however, they are laborious and time-consuming. In addition, the markers used affect the passage of chemical reactions in the biodetection system and do not allow measurements in real time [7,24,39].…”

“…In this case, the phenomenon of interaction of electrons with an electromagnetic field is used and this can be represented by a propagating light wave. The high sensitivity of devices of this type is mediated by the ability of biological molecules to cause a change in the speed of light transmitted through the biomaterial and register the effect of the generation of a damped wave [24,26,56,72,75].…”

“…Biosensors have shown great potential for use in medicine, including as a tool for the simultaneous detection in real time of several markers of bacterial and viral infections [5][6][7]23]. In addition, the possibility has arisen to conduct quantitative monitoring of the safety of the environment and the population, the detection of pathogenic biological agents in case of emergencies associated with natural, man-made accidents, or terrorist attacks [24,25].…”