Upconversion Nanoamplicon With Confined Emitters For Precise Reporting Of Microrna-21 Levels Originated From Cancer Cells

MicroRNA (miRNA) upconversion nanoprobes using organic dyes as acceptors have attracted intensive attention in early cancer diagnosis, but still remains a large challenge from the unsatisfactory luminescence resonance energy transfer (LRET) efficiency. Herein, we proposed to integrate the confined emitters effect and target cycling amplification strategy into a single matrix for establishing the upconversion nanoamplicon with high LRET efficiency, allowing for accurately reporting the levels of miRNA originated from cancer cells. As a proof-of-concept, the emitting ions were confined in the shell of the core-shell upconversion nanoparticles (UCNPs), enabling an enough close distance to its surface energy acceptors. The tentacle DNAs (P-tDNA-M), phosphorylated and methylated at both ends, were immobilized onto the UCNPs surfaces for effectively capturing hairpin DNA1 labeled with BHQ1 (BHQ1-HP1) to form BHQ1-UCNPs energy donor-acceptor pair, achieving similar to 67.9 % of LRET efficiency. Target miRNA-21 could bind with HP1 to open the loop, causing BHQ1 away from UCNPs, thereby restoring the upconversion luminescence, allowing for high sensitively detecting miRNA-21 with a detection limit of 75.3 fM. Interestingly, this naoprobe exhibited good performances for monitoring miRNA-21 in human serum samples and evaluating the expression level of miRNA-21 in various cell lines. This proposed platform gives a new insight to design the efficient upconversion nanoprobes for precisely detecting low-expressed miRNA in complex biological samples.