Block copolymer self-assembly assisted fabrication of laterally organized- and stacked- nanoarrays.

Block copolymer (BCP) self-assembly processes are often seen as reliable techniques for advanced nanopatterning to achieve functional surfaces and create templates for nanofabrication. By taking advantage of the tunability in pitch, diameter and feature-to-feature separation of the self-assembled BCP features, complex, laterally organized- and stacked- multicomponent nanoarrays comprising of gold and polymer have been fabricated. The approaches not only demonstrate nanopatterning of up to two levels of hierarchy but also investigate how a variation in the feature-to-feature gap at the first hierarchy affects the self-assembly of polymer features at the second. Such BCP self-assembly enabled multicomponent nanoarray configurations are rarely achieved by other nanofabrication approaches and are particularly promising for pushing the boundaries of block copolymer lithography and in creating unique surface architectures and complex morphologies at the nanoscale.

Characterisation of Hybrid Polymersome Vesicles Containing the Efflux Pumps NaAtm1 or P-Glycoprotein.

Investigative systems for purified membrane transporters are almost exclusively reliant on the use of phospholipid vesicles or liposomes. Liposomes provide an environment to support protein function; however, they also have numerous drawbacks and should not be considered as a "one-size fits all" system. The use of artificial vesicles comprising block co-polymers (polymersomes) offers considerable advantages in terms of structural stability; provision of sufficient lateral pressure; and low passive permeability, which is a particular issue for transport assays using hydrophobic compounds. The present investigation demonstrates strategies to reconstitute ATP binding cassette (ABC) transporters into hybrid vesicles combining phospholipids and the block co-polymer poly (butadiene)-poly (ethylene oxide). Two efflux pumps were chosen; namely the Novosphingobium aromaticivorans Atm1 protein and human P-glycoprotein (Pgp). Polymersomes were generated with one of two lipid partners, either purified palmitoyl-oleoyl-phosphatidylcholine, or a mixture of crude E. coli lipid extract and cholesterol. Hybrid polymersomes were characterised for size, structural homogeneity, stability to detergents, and permeability. Two transporters, NaAtm1 and P-gp, were successfully reconstituted into pre-formed and surfactant-destabilised hybrid polymersomes using a detergent adsorption strategy. Reconstitution of both proteins was confirmed by density gradient centrifugation and the hybrid polymersomes supported substrate dependent ATPase activity of both transporters. The hybrid polymersomes also displayed low passive permeability to a fluorescent probe (calcein acetomethoxyl-ester (C-AM)) and offer the potential for quantitative measurements of transport activity for hydrophobic compounds.

[Analysis of three antipyretic analgesic drugs by open-tubular capillary electrochromatography].

The advantages of capillary electrophoresis, such as small sample consumption, high separation efficiency, and multiple separation modes, have been known for decades. However, exploring unique capillary electrophoresis techniques for the analysis of fluid drugs in living bio-systems remains an important and urgent task. Owing to the similar structures and mass-to-charge ratios of antipyretic analgesic drugs, efficient baseline separation of these analytes by capillary zone electrophoresis method cannot be easily achieved. Micellar electrokinetic chromatography can improve the baseline separation of these drugs, but the substantial amounts of non-volatile surfactants (such as sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium deoxycholate and cetylammonium bromide) in running buffer solutions would pollute the ion source during mass spectrometric analysis. For this reason, it is difficult to analyze unknown drugs by capillary electrophoresis-electrospray ionization-mass spectrometry. To overcome these drawbacks, much attention has been paid to capillary electrochromatography (CEC) because combines the high separation efficiency of capillary electrophoresis with the high selectivity of high performance liquid chromatography (HPLC). Recent challenges encountered in open-tubular capillary electrochromatography (OT-CEC) expanding the range of suitable functional polymer monomers and improvement of the separation efficiency by tuning the characteristics of the polymer coatings without using any organic solvent additives. In this study, a protocol based on OT-CEC using a block co-polymer coating is proposed for the analysis of three test antipyretic analgesic drugs (4-aminoantipyrine, antipyrine and phenacetin), without adding organic solvents and surfactants in the running buffer solutions. First, an amphiphilic block co-poly(styrene-co-glycidyl methacrylate) (P(St-GMA)), was synthesized by reversible addition-fragmentation chain transfer polymerization under mild conditions. Then, P(St-GMA) was coated onto the capillary surface, and an OT-CEC analysis was performed. Next, the effect of some key factors, including the polymerization time for obtaining P(St-GMA) with different molecular weights, coating concentrations of the block copolymer, the species of the running buffer solutions, pH and concentrations of the running buffer solutions, and organic solvent additives, on the OT-CEC separation efficiency were investigated. Under the optimized conditions with 50.0 mmol/L NaAc-HAc as the running buffer solution at pH 5.7, the three test antipyretic analgesic drugs were base-line separated by the constructed OT-CEC system. Good linear relationships between peak area and concentration of the test analytes in the range of 8.0-2.5×103 µmol/L were obtained (R2 ≥ 0.995). The limits of detection (LODs) were 1.0-2.5 µmol/L. Furthermore, the reason for the OT-CEC separation efficiency was clarified based on the decreased electro-osmotic flow in the coated capillary compared with that in the uncoated capillary. Finally, the proposed OT-CEC assay without using any organic solvents and surfactants as additives was applied for analysis of the three test antipyretic analgesic drugs in rat serum samples. Importantly, it was found that despite peak tailing, the OT-CEC separation efficiency of the drugs was dramatically enhanced because the block co-polymer could self-assemble in the solution and form pseudo-micelles, which further increased the interactions between the P(St-GMA) and these drugs. Our results not only reveal the great potential of block co-polymer coatings in OT-CEC for the analysis of drugs in real biological samples, but also serve asa platform for the preparation of diverse block co-polymers to be used in OT-CEC analysis. We believe that in the near future, the peak tailing problem in OT-CEC analysis can be resolved by using the designed unique block co-polymers, which possess a greater number of functional sites, as coatings and by appropriately tuning the interactions between the analytes and the coatings.

Block-Co-polymer-Assisted Synthesis of All Inorganic Highly Porous Heterostructures with Highly Accessible Thermally Stable Functional Centers.

Here, we propose a simple approach for the design of highly porous multicomponent heterostructures by infiltration of block-co-polymer templates with inorganic precursors in swelling solvents followed by gas-phase sequential infiltration synthesis and thermal annealing. This approach can prepare conformal coatings, free-standing membranes, and powders consisting of uniformly sized metal or metal oxide nanoparticles (NPs) well dispersed in a porous oxide matrix. We employed this new, versatile synthetic concept to synthesize catalytically active heterostructures of uniformly dispersed ∼4.3 nm PdO nanoparticles accessible through three-dimensional pore networks of the alumina support. Importantly, such materials reveal high resistance against sintering at 800 °C, even at relatively high loadings of NPs (∼10 wt %). At the same time, such heterostructures enable high mass transport due to highly interconnected nature of the pores. The surface of synthesized nanoparticles in the porous matrix is highly accessible, which enables their good catalytic performance in methane and carbon monoxide oxidation. In addition, we demonstrate that this approach can be utilized to synthesize heterostructures consisting of different types of NPs on a highly porous support. Our results show that swelling-based infiltration provides a promising route toward the robust and scalable synthesis of multicomponent structures.

Tuneable Metamaterial-like Platforms for Surface-Enhanced Raman Scattering via Three-Dimensional Block Co-polymer-Based Nanoarchitectures.

Surface-enhanced Raman spectroscopy (SERS) pushes past the boundaries and inherent weaknesses of Raman spectroscopy, with a great potential for a broad range of applications particularly, for sensing. Yet, current real world applications are limited due to poor reproducibility, low-throughput, and stability issues. Here, we present the design and fabrication of self-assembly guided structures based on adjustable block co-polymer (BCP) nanomorphologies and demonstrate reproducible SERS enhancement across large areas. Golden three-dimensional (3D) nanostructured morphologies with controllable dimensions and morphologies exhibit high chemical stability, enhanced plasmonic properties and are highly suitable for SERS substrates due to the strong enhancement of the electromagnetic field. Adjustable, free standing porous nanostructures, continuous in 3D space are achieved by removal of selected BCP constituents. Four BCP morphologies and the corresponding achievable enhancement factors are investigated at 633 and 785 nm excitation wavelengths. The choice of excitation laser is shown to greatly affect the observed signal enhancement, highlighting the sensitivity of the technique to the underlying surface architecture and length scales. By using BCP assemblies, it is possible to reliably tune these parameters to match specific applications, thus bridging the gap toward the realization of applied metamaterials. The fabricated SERS platforms via three-dimensional block co-polymer-based nanoarchitectures provide a recipe for intelligent engineering and design of optimized SERS-active substrates for utilization in the Raman spectroscopy-based devices toward enabling the next-generation technologies fulfilling a multitude of criteria.

Morphology of block copolymer micelles formed via electrospray enabled interfacial instability.

HYPOTHESIS: Elongated micelles may be preferred over spherical because of their increased loading capacity, differential mass transport and biodistribution. Although morphological transitions of block co-polymer (BCP) micelles have been extensively investigated in batch systems, research on continuous or semi-continuous scalable approaches such as flash nanoprecipitation and coaxial electrospray-enabled interfacial instability (Aero-IS) have primarily focused on producing spherical micelles. This paper investigates whether process changes intended to increase micelle production via Aero-IS also induce morphological transitions. EXPERIMENTS: BCP micelles were synthesized from carboxylated polystyrene-block-poly(ethylene oxide) (PS-b-PEO) (PS 9.5 kDa:PEO 18.0 kDa) using Aero-IS. Volumetric flowrates, polymer concentrations, and emulsion temperature were varied to investigate their effect on the micelle production rate and resulting micelle structure, including transitions to worm-like micelles. FINDINGS: These findings report the first worm-like micelles formed via a scalable, interfacial instability approach. The morphological transitions obtained by increasing polymer concentration occurred at lower nominal values than in corresponding batch processes. Optimizing operating conditions also led to a 12-fold increase in micelle production rates over prior electrospray reports (Duong, 2014). Thus, the Aero-IS approach holds promise for scalable nanomanufacturing of worm-like micelles, potentially enabling applications in drug delivery, imaging, diagnostics, and separations.

Evaluation of a Novel Thermal Accelerant for Augmentation of Microwave Energy during Image-guided Tumor Ablation.

The primary challenge in thermal ablation of liver tumors (e.g. hepatocellular carcinoma and hepatic colorectal cancer) is the relatively high recurrence rate (~30%) for which incomplete ablation at the periphery of the tumor is the most common reason. In an attempt to overcome this, we have developed a novel thermal accelerant (TA) agent capable of augmenting microwave energy from a distance normally unattainable by a single microwave ablation antenna. This cesium-based block co-polymer compound transforms from a liquid to a gel at body temperature and is intrinsically visible by computed tomography. Using an agarose phantom model, herein we demonstrate that both the rate and magnitude of temperature increase during microwave ablation were significantly greater in the presence of TA when compared with controls. These results suggest robust augmentation of microwave energy, and may translate into larger ablation zone volumes within biologic tissues. Further work using in vivo techniques is necessary to confirm these findings.

RAFT polymerization of 4-vinylphenylboronic acid as the basis for micellar sugar sensors.

Well-defined homo and mPEGylated block (co)polymers of the commercially available unprotected 4-vinylphenylboronic acid (4-VBA) monomer are reported based on reversible addition-fragmentation chain transfer (RAFT) polymerization. The polymerization kinetics are studied in detail for homo and block (co)polymerizations with different chain transfer agents (CTAs) to optimize the preparation of well-defined polymer structures, eventually leading to comparatively low dispersities (D ≤ 1.25). Subsequently, block (co)polymers with methoxy poly(ethylene glycol) mPEG-b-P(4-VBA) are prepared using a mPEG-functionalized CTA. The formed block copolymer mPEG114 -b-P(4-VBA)30 is demonstrated to be pH and glucose responsive as its micellization behavior is dictated by pH as well as the presence of glucose. The glucose-responsive pH window of mPEG114 -b-P(4-VBA)30 is found to be pH 9-10 based on the DLS and TEM measurement.

Effect of the hydrophobic basal layer of thermoresponsive block co-polymer brushes on thermally-induced cell sheet harvest.

Thermoresponsive poly(benzyl methacrylate)-b-poly(N-isopropylacrylamide) (PBzMA-b-PIPAAm) block co-polymer brush surfaces were prepared by surface-initiated two-step reversible addition-fragmentation chain transfer radical (RAFT) polymerization. PBzMA brushes were fabricated on azoinitiator-immobilized glass substrates in the presence of dithiobenzoate (DTB) compound as a RAFT agent. The amount of grafted polymer was regulated by initial monomer concentrations. The second thermoresponsive blocks were added to the RAFT-related DTB groups located at PBzMA termini through the propagation of PIPAAm chains, resulting in formation of PBzMA-b-PIPAAm brushes. Surface characteristics of the block co-polymer brushes and its influence on thermally regulated cellular behavior were investigated using bovine carotid artery endothelial cells (BAECs), compared with PIPAAm brush surfaces. Cell adhesion/detachment behavior on thermoresponsive polymer brush surfaces significantly depended on their individual polymer architectures and chemical compositions of grafted polymers. Low-temperature treatment at 20°C, below the phase-transition temperature of PIPAAm, induced the spontaneous detachment of adhering cells from the PBzMA-b-PIPAAm brush surfaces with a higher rate than that from PIPAAm brush surfaces. In addition, the cell-repellent effect of the hydrophobic basal layer successfully accelerated for harvesting BAEC sheets from the block co-polymer brush surfaces. Unique features of thermoresponsive block co-polymer brush architectures can be applied to control cell-adhesion strength for enhancing cell adhesion or accelerating cell detachment.

Hydrogels Containing Core Cross-Linked Block Co-Polymer Micelles.

Poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels loaded with core cross-linked PEG-b-PCL micelles with different morphologies (spherical and rod-like) were prepared and evaluated for use as drugeluting soft contact lenses. The relationship between the composition of micelle-loaded pHEMA hydrogels and properties such as transparency and swelling were determined. The incorporation of core crosslinked micelles into pHEMA hydrogels led to the formation of different internal nanostructures which were dependent on the amount and morphology of the micelles added. 7-Hydroxy-9H-(1,3-dichloro-9,9'-dimethylacridin-2-one) (DDAO), a hydrophobic fluorescent dye, was loaded into the micelles prior to their incorporation within the hydrogel matrix. The in vitro release of DDAO demonstrated the potential of the micelles/pHEMA hydrogels to provide controlled drug delivery for at least 14 days. This study demonstrates the feasibility of both chemical and physical incorporation of block co-polymer micelles within pHEMA hydrogels as a means to achieve sustained release of drugs for potential application in ophthalmic therapies.

Biodegradable Nano-aggregates of Star-Shaped 8-arm PEG-PLLA Block Co-polymers for Encapsulation of Water-Soluble Macromolecules.

A series of amphiphilic 8-arm PEG-b-PLLA co-polymers with star-shaped structure was synthesized through ring-opening polymerization of L-lactide (L-LA) in the presence of 8-arm PEG as a macroinitiator by varying feeding molar rations of L-LA to 8-arm PEG. 8-arm PEG-b-PLLA co-polymers having certain PEG content and PEG length were found to self-assemble into nano-aggregates in aqueous solutions. The size and the morphology of the nano-aggregates were investigated by dynamic light scattering and (1)H-NMR in CDCl3 and D2O. The results indicate that the average diameter was ca. 150 nm, the surface of the nano-aggregates was covered by PEG chains and the PLLA cores formed by hydrophobic interaction are located inside of the nano-aggregates. FITC-dextran molecules, as model for water-soluble macromolecular drugs, were successfully encapsulated into 8-arm PEG-b-PLLA nano-aggregates by simple addition of FITC-dextran to the aqueous phase during the self-assembly process. This result suggests that the nanoaggregates have a vesicle-like morphology. The nano-aggregates dissociated gradually in the order of weeks in PBS (pH 7.4, ionic strength 140 mM) at 37°C. Thus, the novel nano-aggregates of 8-arm PEG-b-PLLA can be expected to have advantages, such as long circulation times, as drug carriers which show sustained release of loaded macromolecular drugs such as antibodies and DNA vaccines in the blood stream.

Amphiphilic block co-polyesters bearing pendant cyclic ketal groups as nanocarriers for controlled release of camptothecin.

Amphiphilic block co-polymers consisting of hydrophilic poly(ethylene glycol) and hydrophobic polyester bearing pendent cyclic ketals were synthesized by ring-opening co-polymerization of ε-caprolactone (CL) and 1,4,8-trioxaspiro-[4,6]-9-undecanone (TSU) using α-hydroxyl, ω-methoxy, poly(ethylene glycol) as the initiator and stannous octoate as the catalyst. Compositional analyses indicate that TSU was randomly distributed in the hydrophobic blocks. When the TSU content in the co-polymers increased, the polymer crystallinity decreased progressively and the glass transition temperature increased accordingly. The hydrophobic, anticancer drug, camptothecin (CPT), was successfully encapsulated in the block copolymer nanoparticles. The CPT encapsulation efficiency and release kinetics were strongly dependent on the co-polymer composition and crystallinity. CPT release from nanoparticles constructed from co-polymers containing 0, 39 and 100 mol% TSU in the hydrophobic block followed the same trend, with an initial burst of approx. 40% within one day followed by a moderate and slow release lasting up to 7 days. At a TSU content of 14 mol%, CPT was released in a continuous and controlled fashion with a reduced initial burst and a 73% cumulative release by day 7. The in vitro cytoxicity assay showed that the blank nanoparticles were not toxic to the cultured bone metastatic prostate cancer cells (C4-2B). Compared to the free drug, the encapsulated CPT was more effective in inducing apoptotic responses in C4-2B cells. Modulating the physical characteristics of the amphiphilic co-polymers via co-polymerization offers a facile method for controlling the bioavailability of anticancer drugs, ultimately increasing effectiveness and minimizing toxicity.