Development of an Electrochemical Biosensor to Detect miRNA Encapsulated in Lipid Nanoparticles

Lipid nanoparticles (LNPs) represent a versatile delivery platform proposed for a wide range of therapies based on nucleic acids, including microRNA (miRNAs). The ability of LNPs to encapsulate and protect RNA from degradation, as well as their ability to promote cellular uptake, has led to their clinical use with the approval of RNA-based medicinal products, i.e., COVID vaccines. In this context, a growing number of LNP formulations with improved transfection and biocompatibility are under development, requiring rapid, sensitive, and robust quality control tests, e.g., for the quantification of the encapsulated RNA. Nowadays, classical analytical approaches such as fluorescence, ultraviolet-visible (UV-vis) spectrophotometry, and chromatography are mainly used for the quantification of the encapsulated drug. However, the user-friendly and cost-effective quantification of the encapsulation efficacy within LNPs represents an important research focus, as it would allow monitoring of the amount of encapsulated RNA, thus providing immediate quality control. In this work, we present the adaptation of an electrochemical strip to quantify the encapsulation of a miRNA, i.e., miR-218, whose antitumor effect has been widely reported in the literature within LNPs. We provide a rapid and sensitive method to assess the concentrations of miRNA actually encapsulated, obtaining satisfactory agreement compared to the traditional fluorimetric approach. Specifically, the platform is based on a commercial gold-screen-printed electrode modified with a DNA probe designed to be fully complementary to the target miRNA-218. The electrochemical system was successfully combined with a 3D-printed chamber that allowed the use of multiple electrodes simultaneously and the use of Triton X-100 surfactant to disrupt the LNPs and release the encapsulated miRNA-218 achieving a detection limit as low as 1 nM.