A target-triggered strand displacement-assisted target recycling based on carbon dots-based fluorescent probe and MSNs@PDA nanoparticles for miRNA amplified detection and fluorescence imaging.

A target-triggered strand displacement-assisted target recycling based on carbon dots-based fluorescent probe and mesoporous silica nanoparticles@polydopamine (MSNs@PDA) was established to detect miRNA. The surface of MSNs rich in mesopores was coated with a layer of PDA, which can adsorb and quench the fluorescence of single-stranded Fuel DNA with fluorescent carbon dots (CDs) modified at the end through fluorescence resonance energy transfer (FRET). After adding double-stranded DNA-gold nanoparticles (dsDNA-AuNPs) and target let-7a, it will trigger two toehold-mediated strand displacement reactions (TSDR), leading to the recovery of fluorescence and the recycling of target let-7a (excitation wavelength: 380 nm; emission wavelength: 458 nm). The recovery value of fluorescence is proportional to the logarithm of the target microRNA let-7a concentration, thus realizing the sensitivity amplification detection of disease markers. The MSNs@PDA@Fuel DNA-CDs/dsDNA-AuNPs nanoplatform based on the strategy of "on-off-on" and TSDR cyclic amplification may hold great potential as an effective and safe nanoprobe for accurate fluorescence imaging of diseases related to miRNA with low abundances.

Surface micropatterning of 3D printed PCL scaffolds promotes osteogenic differentiation of BMSCs and regulates macrophage M2 polarization.

Micropatterned structures on the surface of materials possessing biomimetic properties to mimic the extracellular matrix and induce cellular behaviors have been widely studied. However, it is still a major challenge to obtain internally stable and controllable micropatterned 3D scaffolds for bone repair and regeneration. In this study, 3D scaffolds with regular grating arrays using polycaprolactone (PCL) as a matrix material were prepared by combining 3D printing and soft lithography, and the effects of grating micropatterning on osteogenic differentiation of BMSCs and M1/M2 polarization of macrophages were investigated. The results showed that compared with the planar group and the 30um grating spacing group, PCL with a grating spacing of 20um significantly promoted the osteogenic differentiation of BMSCs, induced the polarization of RAW264.7 cells toward M2 type, and suppressed the expression of M1-type pro-inflammatory genes and markers. In conclusion, we successfully constructed PCL-based three-dimensional scaffolds with stable and controllable micrographs (grating arrays) inside, which possess excellent osteogenic properties and promote the formation of an immune microenvironment conducive to osteogenesis. This study is a step forward to the exploration of bone-filling materials affecting cell behavior, and makes a new contribution to the provision of high-quality materials.