The self-assembly of inorganic nanoparticles is of great importance in realizing their enormous potentials for broad applications due to the advanced collective properties of nanoparticle ensembles.
Nanoparticle clusters with molecular-like configurations are an emerging class of colloidal materials. Particles decorated with attractive surface patches acting as analogs of functional groups are used to assemble colloidal molecules (CMs); however, high-yield generation of patchy nanoparticles remains a challenge. We show that for nanoparticles capped with complementary reactive polymers, a stoichiometric reaction leads to reorganization of the uniform ligand shell and self-limiting nanoparticle bonding, whereas electrostatic repulsion between colloidal bonds governs CM symmetry. This mechanism enables high-yield CM generation and their programmable organization in hierarchical nanostructures. Our work bridges the gap between covalent bonding taking place at an atomic level and colloidal bonding occurring at the length scale two orders of magnitude larger and broadens the methods for nanomaterial fabrication.
We report a stepwise self-assembly of hollow plasmonic vesicles containing strings of gold nanoparticles (NPs) in vesicular membranes. The formation of chain vesicles can be controlled by tuning the density of polymer ligands on the surface of gold NPs. The strong absorption of chain vesicles in the near-infrared (NIR) range led to a much higher efficiency in photoacoustic (PA) imaging than non-chain vesicles. The chain vesicles were further demonstrated for the encapsulation of drugs and NIR light-triggered release of payloads. This work not only offers a new platform for controlling the hierarchical self-assembly of NPs, but also demonstrates that the control over the spatial arrangement of NPs within the assemblies enables us to tailor the physical properties of the materials for better performance in biomedical applications.
This article describes the fabrication of nanosized magneto-vesicles (MVs) comprising tunable layers of densely packed superparamagnetic iron oxide nanoparticles (SPIONs) in membranes via cooperative assembly of polymer-tethered SPIONs and free poly(styrene)- b-poly(acrylic acid) (PS- b-PAA). The membrane thickness of MVs could be well controlled from 9.8 to 93.2 nm by varying the weight ratio of PS- b-PAA to SPIONs. The increase in membrane thickness was accompanied by the transition from monolayer MVs, to double-layered MVs and to multilayered MVs (MuMVs). This can be attributed to the variation in the hydrophobic/hydrophilic balance of polymer-grafted SPIONs upon the insertion and binding of PS- b-PAA onto the surface of nanoparticles. Therapeutic agents can be efficiently encapsulated in the hollow cavity of MVs and the release of payload can be tuned by varying the membrane thickness of nanovesicles. Due to the high packing density of SPIONs, the MuMVs showed the highest magnetization and transverse relaxivity rate ( r) in magnetic resonance imaging (MRI) among these MVs and individual SPIONs. Upon intravenous injection, doxorubicin-loaded MuMVs conjugated with RGD peptides could be effectively enriched at tumor sites due to synergetic effect of magnetic and active targeting. As a result, they exhibited drastically enhanced signal in MRI, improved tumor delivery efficiency of drugs as well as enhanced antitumor efficacy, compared with groups with only magnetic or active targeting strategy. The unique nanoplatform may find applications in effective disease control by delivering imaging and therapy to organs/tissues that are not readily accessible by conventional delivery vehicles.
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