Asymmetric Core-Shell Gold Nanoparticles and Controllable Assemblies for SERS Ratiometric Detection of MicroRNA

Janus nanogap gold nanoparticles (JAuNNPs) with varying proportions of Au shell coverage of (ca. 100/75/50/25 %) are presented. The internal nanogap between the partial Au shell and core caused asymmetric optical behavior; tunability depends on the degree of Au shell coverage and structural asymmetry. The shell-to-shell or core-to-core JAuNNDs(50 %) were self-assembled from amphiphilic JAuNNPs(50 %) by tuning the hydrophilic and hydrophobic polymer brushes on the Au core or shell. The positions of electromagnetic field enhancement of JAuNNDs varied with geometrical configurations because of hybridized plasmonic coupling effects. Furthermore, DNA linkers were utilized to form JAuNND(12)(50 %). By combining with Raman molecules, ratiometric SERS signals could be generated, enabling JAuNND(12)(50 %) to image the distribution of miR-21 in living cells and tumors. Asymmetric JAuNNPs allowed facile conjugation of various linkage molecules to fabricate dimeric nanostructures.

Automated summary

The study showed that Janus nanogap gold nanoparticles with varying proportions of Au shell coverage exhibit asymmetric optical behavior, with tunability depending on the degree of shell coverage and structural asymmetry. By tuning hydrophilic and hydrophobic polymer brushes, shell-to-shell or core-to-core structures can be formed, leading to enhanced electromagnetic field effects. Additionally, the use of DNA linkers enabled the successful fabrication of dimeric nanostructures.