Particle Lithography Enables Fabrication of Multicomponent Nanostructures

New Means to Control Molecular Assembly

While self-assembly of molecules is relatively well-known and frequently utilized in chemical synthesis and material science, controlled assembly of molecules represents a new concept and approach. The present work demonstrates the concept of controlled molecular assembly using a non-spherical biomolecule, heparosan tetrasaccharide (MW = 1.099 kD). The key to controlled assembly is the fact that ultra-small solution droplets exhibit different evaporation dynamics from those of larger ones. Using an independently controlled microfluidic probe in an atomic force microscope, sub-femtoliter aqueous droplets containing designed molecules produce well-defined features with dimensions as small as tens of nanometers. The initial shape of the droplet and the concentration of solute within the droplet dictate the final assembly of molecules due to the ultrafast evaporation rate and dynamic spatial confinement of the droplets. The level of control demonstrated in this work brings us closer to programmable synthesis for chemistry and materials science which can be used to develop vehicles for drug delivery three-dimensional nanoprinting in additive manufacturing.

Anisotropic Nano-/Microparticles from Diversified Copolymers by Solvent-Mediated Self-Assembly

Effective synthesis of anisotropic nano-/microparticles (APs) by the copolymers is of great significance in nanomaterials and nanotechnology. However, achieving regulation of the morphology, composition, property, and particle size of anisotropic nano-/microparticles (APs) with diversified copolymers is difficult due to complex mechanism and formation conditions. In this work, a versatile one-pot solvent-mediated self-assembly (SmSa) strategy had been proposed for the facile one-pot synthesis of shape-tunable anisotropic nano-/microparticles (StAPs). In addition, the formation mechanism of StAPs was determined through numerous characterization methods related to morphology and element distribution. The results revealed that the anisotropic architectures of StAPs were closely related to the nature of poly(methylacrylic acid-methyl methacrylate-butyl acrylate) (L₁) and poly(butyl acrylate-styrene) (L₂) polymer chains imparted by polymer blocks of different domains. Therefore, the ordered assembly of the rigid and hydrophobic L₂ polymer chains in micelles consisting of the flexible and amphiphilic L₁ and solvent could be successfully carried out under the mediation of increasing solvent polarity and the strong adsorption of poly(vinylpyrrolidone) for L₂. Furthermore, the developed versatile SmSa strategy and the obtained StAPs play an essential role in the development of nanoscience and nanotechnology. Particularly given its adjustable emulsifying properties at different pH values, as well as numerous sites for further modification by fluorescent or other components, it can be employed to synthesize a wide range of functional materials.

Controlled Molecular Assembly via Dynamic Confinement of Solvent

Assembly from ultrasmall solution droplets follows a different dynamic from that of larger scales. Using an independently controlled microfluidic probe in an atomic force microscope, subfemtoliter aqueous droplets containing polymers produce well-defined features with dimensions as small as tens of nanometers. The initial shape of the droplet and the concentration of solute within the droplet play significant roles in the final assembly of polymers due to the ultrafast evaporation rate and spatial confinement by the small droplets. These effects are used to control the final molecular assembly in terms of feature geometry and distribution and packing of individual molecules within the features. This work introduces new means of control over molecular assembly, bringing us closer to programmable synthesis for chemistry and materials science. The outcomes pave the way for three-dimensional (3D) nanoprinting in additive manufacturing.

Clickable Multifunctional Dumbbell Particles for in Situ Multiplex Single-Cell Cytokine Detection

We report a novel strategy for fabrication of multifunctional dumbbell particles (DPs) through click chemistry for monitoring single-cell cytokine releasing. Two different types of DPs were prepared on a large scale through covalent bioorthogonal reaction between methyltetrazine and trans-cyclooctene on a microchip under a magnetic field. After collection of the DPs, the two sides of each particle were further functionalized with different antibodies for cell capturing and cytokine detection, respectively. These DPs labeled with different fluorescent dyes have been used for multiplex detection and analysis of cytokines secreted by single live cells. Our results show that this new type of DPs are promising for applications in cell sorting, bioimaging, single-cell analysis, and biomedical diagnostics.

Three-Dimensional Nanoprinting via Scanning Probe Lithography-Delivered Layer-by-Layer Deposition

Three-dimensional (3D) printing has been a very active area of research and development due to its capability to produce 3D objects by design. Miniaturization and improvement of spatial resolution are major challenges in current 3D printing technology development. This work reports advances in miniaturizing 3D printing to the nanometer scale using scanning probe microscopy in conjunction with local material delivery. Using polyelectrolyte polymers and complexes, we have demonstrated the concept of layer-by-layer nanoprinting by design. Nanometer precision is achieved in all three dimensions, as well as in interlayer registry. The approach enables production of designed functional 3D materials with nanometer resolution and, as such, creates a platform for conducting scientific research in designed 3D nanoenvironments as well. In doing so, it enables production of nanomaterials and scaffolds for photonics devices, biomedicine, and tissue engineering.

Janus particles for biological imaging and sensing

Janus particles, named after the two-faced Roman god Janus, have different surface makeups, structures or compartments on two sides. This review highlights recent advances in employing Janus particles as novel analytical tools for live cell imaging and biosensing. Unlike conventional particles used in analytical science, two-faced Janus particles provide asymmetry and directionality, and can combine different or even incompatible properties within a single particle. The broken symmetry enables imaging and quantification of rotational dynamics, revealing information beyond what traditional measurements offer. The spatial segregation of molecules on the surface of a single particle also allows analytical functions that would otherwise interfere with each other to be decoupled, opening up opportunities for novel multimodal analytical methods. We summarize here the development of Janus particles, a few general methods for their fabrication and, more importantly, the emerging and novel applications of Janus particles as multi-functional imaging probes and sensors.

Engineered Nanostructures of Haptens Lead to Unexpected Formation of Membrane Nanotubes Connecting Rat Basophilic Leukemia Cells

A recent finding reports that co-stimulation of the high-affinity immunoglobulin E (IgE) receptor (FcεRI) and the chemokine receptor 1 (CCR1) triggered formation of membrane nanotubes among bone-marrow-derived mast cells. The co-stimulation was attained using corresponding ligands: IgE binding antigen and macrophage inflammatory protein 1α (MIP1 α), respectively. However, this approach failed to trigger formation of nanotubes among rat basophilic leukemia (RBL) cells due to the lack of CCR1 on the cell surface (Int. Immunol. 2010, 22 (2), 113-128). RBL cells are frequently used as a model for mast cells and are best known for antibody-mediated activation via FcεRI. This work reports the successful formation of membrane nanotubes among RBLs using only one stimulus, a hapten of 2,4-dinitrophenyl (DNP) molecules, which are presented as nanostructures with our designed spatial arrangements. This observation underlines the significance of the local presentation of ligands in the context of impacting the cellular signaling cascades. In the case of RBL, certain DNP nanostructures suppress antigen-induced degranulation and facilitate the rearrangement of the cytoskeleton to form nanotubes. These results demonstrate an important scientific concept; engineered nanostructures enable cellular signaling cascades, where current technologies encounter great difficulties. More importantly, nanotechnology offers a new platform to selectively activate and/or inhibit desired cellular signaling cascades.