Line patterns from cylinder-forming photocleavable block copolymers

Metal nanoparticle arrays via a water-based lift-off scheme using a block copolymer template

Metalnanoparticles(NPs) can exhibit unique electronic, magnetic, optical, and catalytic properties. Highly ordered, dense arrays of non-close-packed, surface-supported metal NPs are thus of potential use in a wide range of applications. Implementing such arrays over large surfaces can, however, be both technologically challenging and prohibitively expensive using conventional top-down nanofabrication techniques. Moreover, many existing patterning methods are too harsh for sensitive substrate surfaces and their applications. To address this, we here investigate a fabrication protocol involving a water-based lift-off scheme in which the template pattern generation is rapidly and inexpensively achieved throughblock copolymer(BCP) self-assembly. A three-layer lift-off stack consisting of, from top to bottom, a poly(styrene-block-2-vinyl pyridine) template, a SiO_xintermediate hardmask, and a water-soluble poly(vinyl alcohol) sacrificial layer is employed in this endeavor.Solvent-induced surface reconstruction(SISR) is used to generate an initial surface topography in the BCP template which is subsequently transferred to the layers beneath in a sequence of reactive ion etching steps. Through judicious selection of stack materials and dry etch chemistries, a layered, high-aspect-ratio, nanoporous mask is thus implemented. After metal deposition, the mask and excess material are simply removed in a lift-off step by dissolving the bottommost sacrificial layer in water. The incorporation of an intermediate hardmask and a water-soluble sacrificial layer obviates the need for harmful and/or corrosive lift-off solvents and decouples the BCP self-assembly process from the influence of substrate properties. We demonstrate the generation of well-ordered arrays of Au NPs capable of supporting sharp, localized surface plasmon resonances. We also investigate improvements to large-scale uniformity, as this is found sensitive to the SISR termination step in the original protocol. Extensions of the technique to other BCP morphologies and materials deposited ought to be straightforward.

Sensitive and precise visually guided drug delivery nanoplatform with dual activation of pH and light

Controlled-release drug carriers in cancer therapy are the most ideal way to reduce toxicity and improve drug efficacy. Since light stimulation is precise and operable, most multi-stimulation response carriers utilize phototherapy to enhance release efficiency. However, phototoxicity severely limits the application of phototherapy. Herein, we designed and synthesized a Cou-ONB lipid with sensitive fluorescence feedback and multi-stimulus response. COBL liposomes prepared from Cou-ONB lipids will passively aggregate at the tumor and guide phototherapy by fluorescence. More importantly, it can reflect the drug release effect in vivo through its own sensitive fluorescence changes, further enabling precise phototherapy and reducing phototoxicity. In this paper, the multi-stimulus superimposed response and precise fluorescence-guided performance of COBL liposomes were investigated at the molecular, liposome, cellular, and animal levels. Finally, tumor treatment experiments showed that the d-COBL-UV group had the best tumor suppression effect (5.3-fold). This paper highlights a real-time fluorescence-guided multi-stimulus superposition strategy and provides a design idea to precisely implement exogenous stimuli by displaying the degree of drug release, aiming to achieve less toxic and more efficient cancer therapy through timely and precise multi-stimulation. STATEMENT OF SIGNIFICANCE: Multi-stimulus responsive drug carriers have been extensively developed in the last decade. Visual guidance is an important tool to achieve precision medicine and precise control of drug release. However, the available visualization materials are more aimed at directing stimulation at the optimal moment. There is little discussion on when to stop exogenous stimulation and how to minimize the damage of stimulation to the patient. Here, we provide a Cou-ONB lipid that not only responds to multiple stimuli, but also provides sensitive feedback on its own dissociation with a fluorescent signal so that physicians can adjust exogenous stimuli in a timely manner. This paper provides insights to facilitate precision drug delivery systems, providing viable design ideas for precise, efficient, and less toxic cancer therapies.

Magnetic Resonance Imaging-Guided Multi-Stimulus-Responsive Drug Delivery Strategy for Personalized and Precise Cancer Treatment

The emergence of nano-targeted controlled release liposomal drug carriers has provided a breakthrough in cancer therapy. However, their clinical efficacy is unsatisfactory, which is related to individualized differences in targeted drugs and poor in vivo release efficiency. In this paper, we prepared a class of personalized targeted and precisely controlled-release therapeutic drug carriers (GF liposomes) by co-assembling targeting and traceable o-nitrobenzyl ester lipids to propose a magnetic resonance imaging (MRI)-guided personalized in vivo targeted drug screening strategy and a multi-stimulus superimposed controlled-release strategy. Furthermore, by following the drug release process of drug-loaded liposomes (GF-D), it was found that these liposomes could rely on energy superposition to achieve more sensitive and efficient controlled drug release. In addition, the indispensable adjustment of liposome formulation for personalized MRI-based targeted therapy was verified by differential cellular uptake and in vivo magnetic resonance imaging. In the end, the 10.22-fold tumor suppression effect in the stimulus superposition group (GF-D-UV) indicates that the multi-stimulus cumulative response strategy and MRI-guided in vivo screening strategy can more effectively treat cancer. This contribution provides a concise and clever design idea for the future development of personalized precise and efficient clinical cancer therapies.

Clip Chemistry: Diverse (Bio)(macro)molecular and Material Function through Breaking Covalent Bonds

In the two decades since the introduction of the "click chemistry" concept, the toolbox of "click reactions" has continually expanded, enabling chemists, materials scientists, and biologists to rapidly and selectively build complexity for their applications of interest. Similarly, selective and efficient covalent bond breaking reactions have provided and will continue to provide transformative advances. Here, we review key examples and applications of efficient, selective covalent bond cleavage reactions, which we refer to herein as "clip reactions." The strategic application of clip reactions offers opportunities to tailor the compositions and structures of complex (bio)(macro)molecular systems with exquisite control. Working in concert, click chemistry and clip chemistry offer scientists and engineers powerful methods to address next-generation challenges across the chemical sciences.

Photopatterning of Block Copolymer Thin Films

Block copolymers are potentially useful materials for large-area 2-D patterning applications due to their spontaneous self-assembly into sub-50 nm domains. However, most thin film engineering applications require patterns of prescribed size, shape, and organization. Photopatterning is a logical choice for manipulating block copolymer features since advanced lithography tools can pattern areas as small as a single block copolymer domain. By exposing either the block copolymer or a responsive interfacial surface to patterned radiation, precise control over placement, orientation, alignment, and selective development of block copolymer domains can be achieved. This Viewpoint highlights some of the recent research in photopatterning block copolymer thin films and identifies areas of future opportunity.

O-Nitrobenzyl-alt-(phenylethynyl)benzene copolymer-based nanoaggregates with highly efficient two-photon-triggered degradable properties via a FRET process

This paper reports on O-nitrobenzyl-alt-(phenylethynyl)benzene copolymer-based nanoaggregates which could be efficiently degraded under two-photon excitation.

Nanoscale plasmonic stamp lithography on silicon

Nanoscale lithography on silicon is of interest for applications ranging from computer chip design to tissue interfacing. Block copolymer-based self-assembly, also called directed self-assembly (DSA) within the semiconductor industry, can produce a variety of complex nanopatterns on silicon, but these polymeric films typically require transformation into functional materials. Here we demonstrate how gold nanopatterns, produced via block copolymer self-assembly, can be incorporated into an optically transparent flexible PDMS stamp, termed a plasmonic stamp, and used to directly functionalize silicon surfaces on a sub-100 nm scale. We propose that the high intensity electric fields that result from the localized surface plasmons of the gold nanoparticles in the plasmonic stamps upon illumination with low intensity green light, lead to generation of electron-hole pairs in the silicon that drive spatially localized hydrosilylation. This approach demonstrates how localized surface plasmons can be used to enable functionalization of technologically relevant surfaces with nanoscale control.

Anomalous rapid defect annihilation in self-assembled nanopatterns by defect melting

Molecular self-assembly commonly suffers from dense structural defect formation. Spontaneous defect annihilation in block copolymer (BCP) self-assembly is particularly retarded due to significant energy barrier for polymer chain diffusion and structural reorganization. Here we present localized defect melting induced by blending short neutral random copolymer chain as an unusual method to promote the defect annihilation in BCP self-assembled nanopatterns. Chemically neutral short random copolymer chains blended with BCPs are specifically localized and induce local disordered states at structural defect sites in the self-assembled nanopatterns. Such localized "defect melting" relieves the energy penalty for polymer diffusion and morphology reorganization such that spontaneous defect annihilation by mutual coupling is anomalously accelerated upon thermal annealing. Interestingly, neutral random copolymer chain blending also causes morphology-healing self-assembly behavior that can generate large-area highly ordered 10 nm scale nanopattern even upon poorly defined defective prepatterns. Underlying mechanisms of the unusual experimental findings are thoroughly investigated by three-dimensional self-consistent field theory calculation.

Synthesis, self-assembly, and degradation of amphiphilic triblock copolymers with fully photodegradable hydrophobic blocks

The development of stimuli-responsive materials is of significant interest for many applications including drug delivery, medical imaging, sensors, and microfluidic devices. Among the available stimuli, light is particularly attractive as it can be applied with high spatial and temporal resolution. We describe here the synthesis of amphiphilic triblock copolymers composed of poly(ethylene glycol) and a hydrophobic block containing o-nitrobenzyl esters throughout the backbone using copper-catalyzed azide–alkyne cycloaddition chemistry. These materials were designed to have a high weight fraction of the hydrophobic block to favour nonmicellar aggregates. The self-assembly in water was studied using nanoprecipitation and the resulting assemblies were characterized by dynamic light scattering and transmission electron microscopy. Under optimized conditions, it was possible to prepare polymer vesicles, commonly referred to as polymersomes, with diameters of approximately 100 nm. The degradation of these materials in response to UV light was studied by spectroscopy, light scattering, and electron microscopy, demonstrating that the vesicles were broken down. These results suggest the potential of these materials for applications such as encapsulation and release.

Photocleavable Triblock Copolymers Featuring an Activated Ester Middle Block: "One-Step" Synthesis and Application as Locally Reactive Nanoporous Thin Films

Polystyrene-block-poly(maleimide pentafluorophenyl ester-co-styrene)-block-poly(ethylene oxide) with an o-nitrobenzyl ester junction was synthesized by "one-step" RAFT polymerization. Highly ordered and locally reactive nanoporous thin films were obtained from the photocleavable triblock copolymer after spin coating, solvent annealing, UV exposure, and washing with methanol/water to remove the minor block PEO. The local reactivity in the thin films was demonstrated by fabrication of iron oxide nanotori after post-modification with an amino-functionalized ferrocene and treatment with oxygen plasma.