Macromolecular Rapid Communications

Front Cover: A cross-polarized image of composite microgel-poly(vinylpyrrolidone) electrospun nanofibers. The microgels, encapsulated in the beads along the fibers, allow a precise tuning of the swelling dynamics of this composite material, rendering it a good candidate for applications in drug delivery, active filtering, and so on. Further details can be found in the article by J. E. Díaz, A. Barrero, M. Márquez, A. Fernández-Nieves, and I. G. Loscertales^*on page 183.

We present microfluidic approaches for the fabrication of non-spherical particles. Single and multiple emulsions are transformed into non-spherical particles through arrested coalescence, asymmetric polymer solidification, polymerization in microfluidic flow, and clustering of inner droplets. With these highly versatile and scalable approaches, production of non-spherical particles in large quantities may be attainable for commercial applications.

These studies showed for the first time that using a two-step emulsion polymerization process particles consisting of p-MMA/nBA and p-nBA/PFS distinct phases within one acorn-shaped particle can be produced. The phase separation within one particle is driven by the interfacial surface tension of individual polymers and morphologies are retained throughout the entire synthesis. The colloidal particles self-assemble on surfaces, and depending upon the surface energy of the substrate, are able to create hydrophobic or hydrophilic surfaces.

We report the microfluidic synthesis of soft, functional biomimetic hydrogel particles with variable deformability. Using stop flow lithography, we independently control the shape, chemistry, and mechanical flexibility of photopolymerized red blood cell sized hydrogel particles. We demonstrate the ability to vary the mechanical properties over four orders of magnitude by altering the nano- and micro-structure of the hydrogel particles.

The surface charge of “stealth” polymersomes is tuned to mimic that of erythrocytes by incorporating an anionic diblock copolymer. The effect of varying surface charge on in vivo biodistribution is tracked by incorporation of a near-infrared fluorophore (NIRF) into the polymersome membrane. This NIRF allows for the visualization of polymersomes in the microvasculature of freshly excised tissues.

Intracellular transport and localization of PLGA particles with different shapes in HUVECs. Spheres and elliptical disks of PLGA were internalized by HUVECs and finally accumulated in the perinuclear region. Interestingly, elliptical disk-shaped particles oriented tangentially to the nucleus.

Frontispiece: The image shows a schematic of patchy particles and their futuristic applications in supraparticular assembly, directed assembly, and as phoretic motors. Further details can be found in the article by A. B. Pawar and I. Kretzschmar^*on page 150.

Recent advances in particle fabrication techniques have led to a new generation of building blocks, so-called patchy particles. Patchy particles can be fabricated with various innovative techniques, such as glancing-angle deposition, particle lithography, electrohydrodynamic co-jetting, and colloidal assembly. Future applications for patchy particles are in assembly into well-defined, pre-determined structures, which is fueling research into the discovery of newer, simpler, and more inexpensive ways for patchy particle fabrication and manipulation.

A generic method to obtain polymer-modified Janus nanoparticles (NPs) is presented by using polymer single crystals substrates as the templates. Three types of NPs were successfully immobilized on the surface of polymer single crystals of poly(ethylene oxide), polycaprolactone, and polyethylene-block-poly(ethylene oxide). Selectively modifying the top surface of NPs led to hybrid nanoclusters with Janus properties.

Gold nanocrystals are compartmentalized in a single hemisphere of polymer particles by electrohydrodynamic co-jetting (TEM image). The cartoon depicts an anisotropic particle, which has two fluorescent dyes in each hemisphere and also gold nanocrystals well distributed in one hemisphere.

Encapsulating microgels within crosslinked polymer nanofibers allows the design of composite materials that might retain the characteristics of the polymer nanofibers but whose absorbance may be tuned according to some particular ambient stimulus (i.e., temperature, pH, etc.). While the absorbance can be made as large as 17, it dramatically reduces when the stimulus disappears.

Droplets of micro- and nanoparticle suspensions dispensed on superhydrophobic substrates act as templates for the fabrication of 3D hierarchical assemblies. Shape and composition anisotropy are achieved by varying system parameters and application of external magnetic field during the drying process. The technique has potential for the large-scale fabrication of supraparticles with applications in catalysis, microfluidic mixing, drug delivery, and as model systems for studying self-assembly. The scale bars are 500µm each.

Pentamer particles, a colloidal building block from which interesting two-dimensional arrays with open (non-closed packed) structures can be assembled, are introduced. The internal bond angle of the five rigidly fused spheres of the pentamer is controlled through microfluidic synthesis. The steric constraints introduced by the variable bond angle lead to assembly of the open structures.

The factors governing the development of cancer (tumorigenesis) reveal the need for systems-approaches to cancer diagnostics and therapeutics. Recent efforts to tap into the remarkable potential of nanotechnology for sensing the molecular signatures of tumorigenesis and targeting a combination of therapeutics for cancer cells are reviewed. The salient role of polymeric biomaterials and their physicochemical characteristics are highlighted, and the emerging role of macromolecular biophysics and computational nanotechnology in engineering spatiotemporally regulated anti-cancer systems are discussed.

Optodes were used as a sensor platform for monitoring cellular ion flux with attendant implications in the field of drug screening and toxicology. The optodes were created on the microscale and monitored extracellular potassium flux during cardiomyocyte beating. The presence of the potassium channel blocker Haloperidol was detected by fluorescently monitoring potassium flux.

Dissolution of CO₂ bubbles in an aqueous solution containing a mixture of biopolymers leads to the formation of a robust shell on the surface of the shrunken bubbles. The proposed approach offers a way to produce bubbles with long-term stability as well as small dimensions (<10 μm in diameter).

Magnetoplasmonics anticancer agents were made by a simple particle assembly approach. A multifunctional superparticle is made from silica-encapsulated magnetic core surrounded in a corona-like fashion with plasmonic gold nanoparticles. Unlike all the previous magnetoplasmonic agents, the assemblies were carrying anticancer drug, whose bioavailability and curing effect exceeded the free form of the same drug 5 times.

Back Cover: The image shows an optical microscopy image of an array of anisotropic porous magnetic supraparticles. A simple, efficient, and scalable method for the formation of such particles in droplets suspended on superhydrophobic surfaces is presented. The color rings on the surfaces of the supraparticles arise from light diffraction in their highly organized structure. Further details can be found in the article by V. Rastogi, A. A. García, M. Marquez, and O. D. Velev^*on page 190.