Fig. 1.

Monitoring the in vivo behaviour of siRNA by Au-DR-siRNA@LNPs based on FRET principle. (A) The siRNA was conjugated with Cy5 at the 3′-end of the antisense strand, then with Au by the strong coordination between Au and the thiol group (-SH) at the 5′ end of the sense chain, and wrapped into LNPs (Au-DR-siRNA@LNPs) by microfluidic technology. Au-AQ-siRNA@LNPs were prepared as the control by modifying both thiol group and Cy5 to the 5′-end of the siRNA sense chain, whose fluorescence is always quenched by Au after Dicer enzyme cleavage. (B) When siRNA was released from LNPs and cleaved by the intracellular Dicer enzyme, siRNA along with Cy5 falls away from the surface of Au to restore the fluorescence of Cy5, thereby monitoring the in vivo pharmacokinetic properties of siRNA. Besides, the survivin siRNA LNPs could be used for the treatment of tumour by silencing the survivin gene and for CT imaging by Au.