Are o ‐nitrobenzyl (meth)acrylate monomers polymerizable by controlled‐radical polymerization?

Improved Dye Survival in Expansion Microscopy through Stabilizer-Conjugated Linkers

Expansion microscopy (ExM) has been widely used to detect biomolecules in cultured cells and tissue samples due to its enablement of super resolution imaging with conventional microscopes, via physical expansion of samples. However, reaction conditions inherent to the process bring about strong fluorescent signal loss during polymerization and digestion and thus limit the brightness of the signal obtained post expansion. Here, we explore the impact of stabilizer-containing organic fluorophores in ExM, as a mitigation strategy for this radical-induced dye degradation. Through direct conjugation of 4-nitrophenylalanine (NPA) to our previously developed trifunctional reagents, we validate and demonstrate that these multifunctional linkers enable visualization of different organelles with improved fluorescent intensity, owning to protection of the dyes to radical induced degradation as well as to photoprotection upon imaging. At this point, we cannot disentangle the relative contribution of both mechanisms. Furthermore, we report anchoring linkers that allow straightforward application of NPA or Trolox to commercially available fluorophore-conjugated antibodies. We show that these anchoring linkers enable complete retention of biological targets while increasing fluorophore photostability. Our results provide guidance in exploring these stabilizer-modified agents in ExM and methods for increased signal survival through the polymerization steps of the ExM protocols.

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.

Stimuli-responsive destructible polymeric hydrogels based on irreversible covalent bond dissociation

Covalently crosslinked stimuli-destructible hydrogels with the ability of irreversible bond dissociation have attracted great attentions due to their biodegradability, stability against hydrolysis, and controlled solubility upon insertion of desired triggers.

Synthesis of multiple stimuli-responsive degradable block copolymers via facile carbonyl imidazole-induced postpolymerization modification

A robust approach that centers on carbonyl imidazole chemistry was used to synthesize a triple-stimuli-responsive degradable block copolymer labeled with acetal, disulfide, and o-nitrobenzyl groups exhibiting acid, reduction, and light responses.

Applying an Oleophobic/Hydrophobic Fluorinated Polymer Monolayer Coating from Aqueous Solutions

Despite major advancements in the fabrication of low-surface-energy surfaces, the environmental consequences of their fabrication can be a serious issue, particularly in an industrial context. This is especially the case for fluorine-based coatings, which often require fluorinated solvents for their processing and applications. These solvents are not only detrimental to the ozone layer but also represent a potential workplace hazard because they tend to bioaccumulate. We describe the design, synthesis, and characterization of a new fluorinated-polymer coating that can be simply applied to surfaces from an aqueous environment using a dip-coating technique. This was made possible by copolymerizing three different methacrylate monomers, each serving a specific function. Namely, fluorinated methacrylate providing oleo/hydrophobicity, photocleavable polyethylene glycol (PEG) methacrylate promoting water solubility of the copolymer, and thioether-based methacrylate serving as an anchoring unit to a number of different substrates. This copolymer is initially grafted to the surface as a monolayer from an aqueous solvent, after which the system is treated with ultraviolet (UV) light, cleaving away the protecting PEG moieties to yield an oleo/hydrophobic surface.

Nanogels Capable of Triggered Release

This chapter provides an overview of soft and environmentally sensitive polymeric nanosystems, which are widely known as nanogels. These particles keep great promise to the area of drug delivery due to their high biocompatibility with body fluids and tissues, as well as due to their ability to encapsulate and release the loaded drugs in a controlled manner. For a long period of time, the controlled drug delivery systems were designed to provide long-termed or sustained release. However, some medical treatments such as cancer chemotherapy, protein and gene delivery do not require the prolonged release of the drug in the site of action. In contrast, the rapid increase of the drug concentration is needed for gaining the desired biological effect. Being very sensitive to surrounding media and different stimuli, nanogels can undergo physico-chemical transitions or chemical changes in their structure. Such changes can result in more rapid release of the drugs, which is usually referred to as triggered drug release. Herein we give the basic information on nanogel unique features, methods of sensitive nanogels preparation, as well as on main mechanisms of triggered release. Additionally, the triggered release of low-molecular drugs and biomacromolecules are discussed.

Hybrid silica micro-particles with light-responsive surface properties and Janus-like character

The present work highlights the synthesis and post-modification of silica-based micro-particles containing photo-responsive polymer brushes with photolabile o-nitrobenzyl ester (o-NBE) chromophores.

Recent Trends in Applying Rrtho-Nitrobenzyl Esters for the Design of Photo-Responsive Polymer Networks

Polymers with light-responsive groups have gained increased attention in the design of functional materials, as they allow changes in polymers properties, on demand, and simply by light exposure. For the synthesis of polymers and polymer networks with photolabile properties, the introduction o-nitrobenzyl alcohol (o-NB) derivatives as light-responsive chromophores has become a convenient and powerful route. Although o-NB groups were successfully exploited in numerous applications, this review pays particular attention to the studies in which they were included as photo-responsive moieties in thin polymer films and functional polymer coatings. The review is divided into four different sections according to the chemical structure of the polymer networks: (i) acrylate and methacrylate; (ii) thiol-click; (iii) epoxy; and (iv) polydimethylsiloxane. We conclude with an outlook of the present challenges and future perspectives of the versatile and unique features of o-NB chemistry.

Photoinduced Modulation of Polymeric Interfacial Behavior Controlling Thin-Film Block Copolymer Wetting

The tunable surface-wetting properties of photosensitive random copolymer mats were used to spatially control the orientations of thin-film block copolymer (BCP) structures. A photosensitive mat was produced via thermal treatment on spin-coated random copolymers of poly(styrene-ran-2-nitrobenzyl methacrylate-ran-glycidyl methacrylate), synthesized via reversible-deactivation radical polymerization. The degree of UV-induced deprotection of the nitrobenzyl esters in the mat was precisely controlled through the amount of UV-irradiation energy imparted to the mat. The resulting polarity switching of the constituents collectively altered the interfacial wetting properties of the mat, and the tunability allowed lamellar or cylinder-forming poly(styrene-b-methyl methacrylate) BCP thin films, applied over the mat, to change the domain orientation from perpendicular to parallel at proper UV exposures. UV irradiation passing through a photomask was capable of generating defined regions of BCP domains with targeted orientations.

Preparation of a Series of Photoresponsive Polymersomes Bearing Photocleavable a 2-nitrobenzyl Group at the Hydrophobic/Hydrophilic Interfaces and Their Payload Releasing Behaviors

In this study, the structure-function relationships of a series of polymersomes composed of well-defined amphiphilic diblock copolymers were investigated. The building blocks were synthesized by clicking hydrophobic polymers, synthesized beforehand, and commercially available poly(ethylene glycol) with photocleavable 2-nitrobenzyl compounds bearing alkyne and maleimide functionalities. All of the tested polymersomes preserved their hollow structures even after sufficient photoirradiation. Nevertheless, the release rate of an entrapped anionic fluorophore was highly dependent on the molecular weight and the type of hydrophobic polymer, as well as on the presence or absence of the charged end groups. Moreover, the polymersomes with a 2-nitrosobenzyl photolysis residue within the hydrophobic shells exhibited photo-induced payload release after complete photolysis. It was concluded that the payload release was mediated by photo-induced permeability changes of the hydrophobic shells rather than the decomposition of their overall structures.

UV-induced vesicle to micelle transition: a mechanistic study

The morphology of self-assembled block copolymer aggregates is highly dependent on the relative volume fraction of the hydrophobic block.

Polymeric Micelles Based on Light-Responsive Block Copolymers for the Phototunable Detection of Mercury(II) Ions Modulated by Morphological Changes

Polymeric micelles based on light-responsive block copolymers were prepared and used for the phototunable detection of mercury(II) ions. 2-Nitrobenzyl acrylate (NBA) and ( E)-2-((4-((4-formylphenyl)diazenyl)phenyl)(methyl)amino) ethyl acrylate (FPDEA) were copolymerized from a poly(ethylene oxide) (PEO) macroinitiator via atom transfer radical polymerization (ATRP), leading to a well-defined block copolymer of PEO₁₁₃- b-[p(NBA₁₀- co-FPDEA₃)] with a low polydispersity index (PDI = 1.16). After polymerization, the aldehyde groups of PEO- b-[p(NBA- co-FPDEA)] were converted to aldoxime groups by reacting with hydroxylamine, leading to the formation of a final oxime-containing polymeric probe, PEO- b-[p(NBA- co-HPDEA)], P1. The resulting block copolymer, P1, was self-assembled in water to yield spherical micelles that consist of a PEO block forming a hydrophilic shell and a copolymer of light-responsive NBA and a mercury(II) ion-detecting HPDEA block forming a hydrophobic core. Upon the addition of mercury(II) ions to this micellar solution, no detection was observed since water-soluble mercury(II) ions have limited accessability to the oxime units of P1, which are located in the hydrophobic core. After UV light irradiation, however, the photolabile 2-nitrobenzyl moieties were cleaved, and hydrophobic PNBA was transformed to hydrophilic poly(acrylic acid) (PAA), leading to the photoinduced dissociation of micelles to unimers. As a result, the oxime units of P1 were exposed to a hydrophilic environment and could react with mercury(II) ions to form nitrile groups, resulting in the turn-on detection of mercury(II) ions by UV light irradiation.

RAFT polymerization to form stimuli-responsive polymers

Stimuli-responsive polymers respond to a variety of external stimuli, which include optical, electrical, thermal, mechanical, redox, pH, chemical, environmental and biological signals. This paper is concerned with the process of forming such polymers by RAFT polymerization.

Photo-responsive polymers: synthesis and applications

Photo-responsive polymers are able to change their structure, conformation and properties upon light irradiation.

Chemically Patterned Inverse Opal Created by a Selective Photolysis Modification Process

Anisotropic photonic crystal materials have long been pursued for their broad applications. A novel method for creating chemically patterned inverse opals is proposed here. The patterning technique is based on selective photolysis of a photolabile polymer together with postmodification on released amine groups. The patterning method allows regioselective modification within an inverse opal structure, taking advantage of selective chemical reaction. Moreover, combined with the unique signal self-reporting feature of the photonic crystal, the fabricated structure is capable of various applications, including gradient photonic bandgap and dynamic chemical patterns. The proposed method provides the ability to extend the structural and chemical complexity of the photonic crystal, as well as its potential applications.

Tuning core vs. shell dimensions to adjust the performance of nanoscopic containers for the loading and release of doxorubicin

Detailed studies were performed to probe the effects of the core and shell dimensions of amphiphilic, shell crosslinked, knedel-like polymer nanoparticles (SCKs) on the loading and release of doxorubicin (DOX), a widely-used chemotherapy agent, in aqueous buffer, as a function of the solution pH. Effects of the nanoparticle composition were held constant, by employing SCKs constructed from a single type of amphiphilic diblock copolymer, poly(acrylic acid)-b-polystyrene (PAA-b-PS). A series of four SCK nanoparticle samples, ranging in number-average hydrodynamic diameter from 14-30 nm, was prepared from four block copolymers having different relative block lengths and absolute degrees of polymerization. The ratios of acrylic acid to styrene block lengths ranged from 0.65 to 3.0, giving SCKs with ratios of shell to core volumes ranging from 0.44 to 2.1. Although the shell thicknesses were calculated to be similar (1.5-3.1 nm by transmission electron microscopy (TEM) calculations and 3.5-4.9 nm by small angle neutron scattering (SANS) analyses), two of the SCK nanoparticles had relatively large core diameters (19±2 and 20±2 nm by TEM; 17.4 and 15.3 nm by SANS), while two had similar, smaller core diameters (11±2 and 13±2 nm by TEM; 9.0 and 8.9 nm by SANS). The SCKs were capable of being loaded with 1500-9700 DOX molecules per each particle, with larger numbers of DOX molecules packaged within the larger core SCKs. Their shell-to-core volume ratio showed impact on the rates and extents of release of DOX, with the volume occupied by the poly(acrylic acid) shell relative to the volume occupied by the polystyrene core correlating inversely with the diffusion-based release of DOX. Given that the same amount of polymer was used to construct each SCK sample, SCKs having smaller cores and higher acrylic acid vs. styrene volume ratios were present at higher concentrations than were the larger core SCKs, and gave lower final extents of release., Higher final extents of release and faster rates of release were observed for all DOX-loaded particle samples at pH 5.0 vs. pH 7.4, respectively, ca. 60% vs. 40% at 60 h, suggesting promise for enhanced delivery within tumors and cells. By fitting the data to the Higuchi model, quantitative determination of the kinetics of release was made, giving rate constants ranging from 0.0431 to 0.0540 h⁻¹/² at pH 7.4 and 0.106 to 0.136 h⁻¹/² at pH 5.0. In comparison, the non-crosslinked polymer micelle analogs exhibited rate constants for release of DOX of 0.245 and 0.278 h⁻¹/² at pH 7.4 and 5.0, respectively. These studies point to future directions to craft sophisticated devices for controlled drug release.

Evaluation of Isoprene Chain Extension from PEO Macromolecular Chain Transfer Agents for the Preparation of Dual, Invertible Block Copolymer Nanoassemblies

Two RAFT-capable PEO macro-CTAs, 2 and 5 kDa, were prepared and used for the polymerization of isoprene which yielded well-defined block copolymers of varied lengths and compositions. GPC analysis of the PEO macro-CTAs and block copolymers showed remaining unreacted PEO macro-CTA. Mathematical deconvolution of the GPC chromatograms allowed for the estimation of the blocking efficiency, about 50% for the 5 kDa PEO macro-CTA and 64% for the 2 kDa CTA. Self assembly of the block copolymers in both water and decane was investigated and the resulting regular and inverse assemblies, respectively, were analyzed with DLS, AFM, and TEM to ascertain their dimensions and properties. Assembly of PEO-b-PIp block copolymers in aqueous solution resulted in well-defined micelles of varying sizes while the assembly in hydrophobic, organic solvent resulted in the formation of different morphologies including large aggregates and well-defined cylindrical and spherical structures.