Wettability Engendered Templated Self-Assembly (WETS) for the Fabrication of Biocompatible, Polymer-Polyelectrolyte Janus Particles.

Fabrication of charged, multiphasic, polymeric micro- and nanoparticles with precise control over their composition, size, and shape is critical for developing the next generation of drug carriers for combinatorial therapies and theranostics. The addition of charged polyelectrolyte multilayers on the surface of polymeric particles can significantly improve their stability, targeting efficacy, drug-release kinetics, and their ability to encapsulate different drugs within a single particle. Many of the traditional methods for multilayer functionalization of multiphasic polymeric particles are time and energy intensive which significantly limits their scalability, and therefore therapeutic potential. In this work, we combine the bulk layer-by-layer polyelectrolyte application methodology with our previously developed technique of fabricating multiphasic polymeric particles on substrates with patterned wettability to synthesize biocompatible, monodisperse, Janus polymer-polyelectrolyte particles.

Wettability engendered templated self-assembly (WETS) for fabricating multiphasic particles.

Precise control over the geometry and chemistry of multiphasic particles is of significant importance for a wide range of applications. In this work, we have developed one of the simplest methodologies for fabricating monodisperse, multiphasic micro- and nanoparticles possessing almost any composition, projected shape, modulus, and dimensions as small as 25 nm. The synthesis methodology involves the fabrication of a nonwettable surface patterned with monodisperse, wettable domains of different sizes and shapes. When such patterned templates are dip-coated with polymer solutions or particle dispersions, the liquids, and consequently the polymer or the particles, preferentially self-assemble within the wettable domains. Utilizing this phenomenon, we fabricate multiphasic assemblies with precisely controlled geometry and composition through multiple, layered depositions of polymers and/or particles within the patterned domains. Upon releasing these multiphasic assemblies from the template using a sacrificial layer, we obtain multiphasic particles. The templates can then be readily reused (over 20 times in our experiments) for fabricating a new batch of particles, enabling a rapid, inexpensive, and easily reproducible method for large-scale manufacturing of multiphasic particles.

Transparent, superhydrophobic surfaces from one-step spin coating of hydrophobic nanoparticles.

We study the nonwettability and transparency from the assembly of fluorosilane modified silica nanoparticles (F-SiO(2) NPs) via one-step spin-coating and dip-coating without any surface postpassivation steps. When spin-coating the hydrophobic NPs (100 nm in diameter) at a concentration ≥ 0.8 wt % in a fluorinated solvent, the surface exhibited superhydrophobicity with an advancing water contact angle greater than 150° and a water droplet (5 µL) roll-off angle less than 5°. In comparison, superhydrophobicity was not achieved by dip-coating the same hydrophobic NPs. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images revealed that NPs formed a nearly close-packed assembly in the superhydrophobic films, which effectively minimized the exposure of the underlying substrate while offering sufficiently trapped air pockets. In the dip-coated films, however, the surface coverage was rather random and incomplete. Therefore, the underlying substrate was exposed and water was able to impregnate between the NPs, leading to smaller water contact angle and larger water contact angle hysteresis. The spin-coated superhydrophobic film was also highly transparent with greater than 95% transmittance in the visible region. Further, we demonstrated that the one-step coating strategy could be extended to different polymeric substrates, including poly(methyl methacrylate) and polyester fabrics, to achieve superhydrophobicity.

Synthesis and morphological study of thick benzyl methacrylate-styrene diblock copolymer brushes.

We demonstrate, for the first time, the synthesis of model poly(benzyl methacrylate) [P(BnMA)] brushes of very high thickness (>300 nm) on silicon wafer. P(BnMA) brush is also synthesized from the surface of silica nanoparticles, from a covalently anchored initiator monolayer, using ambient temperature ATRP. The kinetic studies and block copolymerization from the surface anchored P(BnMA)-Br macroinitiator showed that the polymerization was controlled in nature. AFM, ellipsometry, and water contact angle were used for the characterization of the polymer brush. The grafting density of the P(BnMA) brush, formed by immersion in a dilute monomer solution, was relatively less (∼11% less) in comparison to that obtained by immersion in neat monomer under similar conditions. The P(BnMA)-Br macroinitiator brushes were used to synthesize P(BnMA-b-S) diblock copolymer brushes by the ATRP of styrene at 95 °C. The P(BnMA-b-S) brushes showed stimulus response to a selective solvent and various nanopatterns were observed according to the composition of the block copolymer.

Highly transparent superhydrophobic surfaces from the coassembly of nanoparticles (≤100 nm).

We report a simple and versatile approach to creating a highly transparent superhydrophobic surface with dual-scale roughness on the nanoscale. 3-Aminopropyltrimethoxysilane (APTS)-functionalized silica nanoparticles of two different sizes (100 and 20 nm) were sequentially dip coated onto different substrates, followed by thermal annealing. After hydrophobilization of the nanoparticle film with (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trichlorosilane for 30 min or longer, the surface became superhydrophobic with an advancing water contact angle of greater than 160° and a water droplet (10 µL) roll-off angle of less than 5°. The order of nanoparticles dip coated onto the silicon wafer (i.e., 100 nm first and 20 nm second or vice versa) did not seem to have a significant effect on the resulting apparent water contact angle. In contrast, when the substrate was dip coated with monoscale nanoparticles (20, 50, and 100 nm), a highly hydrophobic surface (with an advancing water contact angle of up to 143°) was obtained, and the degree of hydrophobicity was found to be dependent on the particle size and concentration of the dip-coating solution. UV-vis spectra showed nearly 100% transmission in the visible region from the glass coated with dual-scale nanoparticles, similar to the bare one. The coating strategy was versatile, and superhydrophobicity was obtained on various substrates, including Si, glass, epoxy resin, and fabrics. Thermal annealing enhanced the stability of the nanoparticle coating, and superhydrophobicity was maintained against prolonged exposure to UV light under ambient conditions.

Attachment of polymer films to solid surfaces via thermal activation of self-assembled monolayers containing sulphonyl azide group.

We report on a simple and effective way to attach thin polymer films to solid surfaces. The system is based on a thermosensitive sulphonyl azide derivative that is immobilized to SiO(2) surfaces via chlorosilane anchoring group and subsequently covered with a polymer film. Upon heating the sulfonyl azide decomposes, leading to a C-H insertion reaction from the adjacent polymer chain resulting in a covalent attachment of the polymer to the surface. Any nonbound polymer can be removed by extraction. The method allows to attach a wide spectrum of polymers to solid surfaces. The film thickness of the monolayers can be tuned by adjusting the molecular weight of the polymer used and to some extent, the thermolysis conditions. The film thickness increases linearly with the radius of gyration of the polymers used for attachment. We have successfully attached thin layers of poly (styrene), poly (dimethylacryl amide) and poly (heptadecafluorodecylacrylate).

Surface-initiated atom transfer radical polymerization of methyl methacrylate from magnetite nanoparticles at ambient temperature.

The synthesis of methyl methacrylate (MMA) brush from the surface of magnetite nanoparticles (core-shell structure), from initiator moieties anchored covalently to the nanoparticles, via room temperature atom transfer radical polymerization (ATRP) is described. The surface-initiated polymerization was carried out from a surface-confined initiator containing a 2-bromoisobutyrate moiety with Cu(I)Br/PMDETA catalytic system. The initiator moiety was covalently anchored to the nanoparticles via a two step modification reaction scheme. Controlled polymerization was observed if ethyl-2-bromoisobutyrate (2-EiBrB) was added as a free/sacrificial initiator. A linear increase of molecular weight and a narrow molecular weight distribution of the PMMA formed in solution, provide evidence for a controlled surface-initiated polymerization, leading to surface-attached polymer brushes under mild conditions. The grafted PMMA provides good stability and dispersibility for the nanoparticles in organic solvents.

Hyperpyrexia and prolonged postoperative disorientation following methylene blue infusion during parathyroidectomy.

A 65-year-old man underwent parathyroidectomy for hyperparathyroidism secondary to renal failure. Intra-operatively he received methylene blue infusion (7.5 mg.kg(-1), a total of 650 mg in 500 ml 0.9% sodium chloride) for visualisation of parathyroid glands. At the end of surgery, following extubation he developed agitation, intense shivering and hyperpyrexia, and his level of consciousness decreased to a Glasgow Coma score of 7. The differential diagnoses included methylene blue toxicity or malignant hyperpyrexia. His lungs were ventilated, and intravenous dantrolene was administered to control hyperpyrexia. Haemodialysis was started to remove the methylene blue dye. We review the literature on the pharmacological actions of methylene blue, and discuss the differential diagnosis and management of this patient.