Site-Specific Chemistry on Gold Nanorods: Curvature-Guided Surface Dewetting and Supracolloidal Polymerization
Control of interparticle interactions in terms of their direction and strength highly relies on the use of anisotropic ligand grafting on nanoparticle (NP) building blocks. We report a ligand deficiency exchange strategy to achieve site-specific polymer grafting of gold nanorods (AuNRs). Patchy AuNRs with controllable surface coverage can be obtained during ligand exchange with a hydrophobic polystyrene ligand and an amphiphilic surfactant while adjusting the ligand concentration (CPS) and solvent condition (Cwater in dimethylformamide). At a low grafting density of ≤0.08 chains/nm2, d
umbbell-like AuNRs with two polymer domains capped at the two ends can be synthesized through surface dewetting with a high purity of >94%. These site-specifically-modified AuNRs exhibit great colloidal stability in aqueous solution. Dumbbell-like AuNRs can further undergo supracolloidal polymerization upon thermal annealing to form one-dimensional plasmon chains of AuNRs. Such supracolloidal polymerization follows the temperature–solvent superposition principle as revealed by kinetic studies. Using the copolymerization of two AuNRs with different aspect ratios, we demonstrate the design of chain architectures by varying the reactivity of nanorod building blocks. Our results provide insights into the postsynthetic design of anisotropic NPs that potentially serve as units for polymer-guided supracolloidal self-assembly.
Next-generation poly-L-histidine formulations for miRNA mimic delivery
Synthetic miRNA inhibitors have shown promising efficacy in blocking the activity of aberrant miRNAs that are upregulated in disease-specific pathologies. On the other hand, miRNAs that aid in preventing certain diseases and are reduced in expression in the disease state need different strategies. To tackle this, miRNA mimics, which mimic the activity of endogenous miRNAs, can be delivered for those miRNAs downregulated in different disease states. However, the delivery of miRNA mimics remains a challenge. Here, we report a cationic polylactic-co-glycolic acid (PLGA)-poly-L-histidine delivery system to deliver miRNA mimics. We chose miR-34a mimics as a proof of concept for miRNA delivery. miR-34a-loaded PLGA-poly-L-histidine nanoparticles (NPs) were formulated and biophysically characterized to analyze the structural properties of miRNA mimic-loaded NPs. In vitro efficacy was determined by investigating miR-34a and downstream target levels and performing cell viability and apoptosis assays. We confirmed in vivo efficacy through prolonged survival of miR-34a NP-treated A549-derived xenograft mice treated intratumorally. The results of these studies establish PLGA-poly-L-histidine NPs as an effective delivery system for miRNA mimics for treating diseases characterized by downregulated miRNAs.Spontaneous Structural Diagrams of Bicellar Mixtures
Bicellar mixtures are lipid mixtures composed of long- and short- chain lipids, which self-assemble into a variety of stru
ctures including: nanodiscs (known as “bicelles”), unilamellar nano-vesicles, bilayered ribbons, alignable perforated lamellae, multilamellar vesicles, etc. Many features make “bicellar mixtures” attractive to the researchers in biochemical, biophysical and biomedical societies. First, the sizes in many of the nanoparticles are uniform at the nanoscale, e.g., well-defined radii of nanodiscs and nanovesicles, well-defined width of the bilayered ribbons. Moreover, the perforated lamellae of the bicellar mixtures under certain conditions are magnetically alignable, providing a way to align membrane-associated biomolecules in their native states (like a “goniometer”). Furthermore, the systems can serve ideal platforms for theragnostic carriers.