Soluble polymeric dual sensor for temperature and pH value

Glow discharge plasma stabilization of azo dye on PMMA polymer

The effects of argon gas glow discharge plasma on the surface of DR1 dye-loaded PMMA polymer films are examined in this work. Plasma immobilizes the dye on the surface of polymer without using stabilizers. Argon plasma activates the surface through breaking some bonds and generation of radical sites. It affects the acrylate groups of PMMA leading to covalent bonds between dye and surface of polymer. In addition, plasma treatment and contact with ambient air may result in the creation of new polar components, such as carbonyl and carboxyl compounds and links that enhance the dye attachment to the polymer matrix. Besides, the dye adsorption on the polymer film is impacted by changes in surface topography. Furthermore, plasma modifies the dye conformation, which affects the adherence of the dye to the polymer surface through bringing the dye to the higher energy state. The chemical and topographical modification of dye-loaded PMMA films by plasma are investigated by spectroscopic and AFM methods. Furthermore, aging process was used to confirm dye retention on the polymer film after plasma modification as opposed to dye-loaded polymer film that was left untreated as a reference sample. Finally, investigated method suggests a novel and very affordable technique for fabrication of poly(MMA-co-DR1) copolymer in the form of a homogeneous surface layer.

Thermal Response and Thermochromism of Methyl Red-Based Copolymer Systems - Coupled Responsiveness in Critical Solution Behaviour and Optical Absorption Properties

Until now, only limited experimental knowledge and sparse theoretical treatment about the mechanisms of thermochromism of azo dyes in solution has been available. Especially the coupling of thermoresponsiveness of polymers...

RAFT Emulsion Polymerization of Styrene Using a Poly((N,N-dimethyl acrylamide)-co-(N-isopropyl acrylamide)) mCTA: Synthesis and Thermosensitivity

Thermoresponsive poly((N,N-dimethyl acrylamide)-co-(N-isopropyl acrylamide)) (P(DMA-co-NIPAM)) copolymers were synthesized via reversible addition−fragmentation chain transfer (RAFT) polymerization. The monomer reactivity ratios were determined by the Kelen–Tüdős method to be r_NIPAM = 0.83 and r_DMA = 1.10. The thermoresponsive properties of these copo-lymers with varying molecular weights were characterized by visual turbidimetry and dynamic light scattering (DLS). The copolymers showed a lower critical solution temperature (LCST) in water with a dependence on the molar fraction of DMA in the copolymer. Chaotropic and kosmotropic salt anions of the Hofmeister series, known to affect the LCST of thermoresponsive polymers, were used as additives in the aqueous copolymer solutions and their influence on the LCST was demonstrated. Further on, in order to investigate the thermoresponsive behavior of P(DMA-co-NIPAM) in a confined state, P(DMA-co-NIPAM)-b-PS diblock copolymers were prepared via polymerization induced self-assembly (PISA) through surfactant-free RAFT mediated emulsion polymerization of styrene using P(DMA-co-NIPAM) as the macromolecular chain transfer agent (mCTA) of the polymerization. As confirmed by cryogenic transmission electron microscopy (cryoTEM), this approach yielded stabilized spherical micelles in aqueous dispersions where the PS block formed the hydrophobic core and the P(DMA-co-NIPAM) block formed the hydrophilic corona of the spherical micelle. The temperature-dependent behavior of the LCST-type diblock copolymers was further studied by examining the collapse of the P(DMA-co-NIPAM) minor block of the P(DMA-co-NIPAM)-b-PS diblock copolymers as a function of temperature in aqueous solution. The nanospheres were found to be thermosensitive by changing their hydrodynamic radii almost linearly as a function of temperature between 25 °C and 45 °C. The addition of kosmotropic salt anions, as a potentially useful tuning feature of micellar assemblies, was found to increase the hydrodynamic radius of the micelles and resulted in a faster collapse of the micelle corona upon heating.

Flexible, Wearable and Fully-printed Smart Patch for pH and Hydration Sensing in Wounds

Wound healing is a complex and dynamic regeneration process, wherein the physical and chemical parameters are continuously changing. Its management and monitoring can provide immense benefits, especially for bed-ridden patients. This work reports a low-cost, flexible, and fully printed on-skin patch sensor to measure the change in pH and fluid content in a wound. Such a bendable sensor can also be easily incorporated in a wound dressing. The sensor consists of different electrodes printed on polydimethylsiloxane (PDMS) substrate for pH and moisture sensing. The fabricated sensor patch has a sensitivity of 7.1 ohm/pH for wound pH levels. The hydration sensor results showed that moisture levels on a semi-porous surface can be quantified through resistance change.

Advances and opportunities in the exciting world of azobenzenes

Azobenzenes are archetypal molecules that have a central role in fundamental and applied research. Over the course of almost two centuries, the area of azobenzenes has witnessed great achievements; azobenzenes have evolved from simple dyes to 'little engines' and have become ubiquitous in many aspects of our lives, ranging from textiles, cosmetics, food and medicine to energy and photonics. Despite their long history, azobenzenes continue to arouse academic interest, while being intensively produced for industrial purposes, owing to their rich chemistry, versatile and straightforward design, robust photoswitching process and biodegradability. The development of azobenzenes has stimulated the production of new coloured and light-responsive materials with various applications, and their use continues to expand towards new high-tech applications. In this Review, we highlight the latest achievements in the synthesis of red-light-responsive azobenzenes and the emerging application areas of photopharmacology, photoswitchable adhesives and biodegradable materials for drug delivery. We show how the synthetic versatility and adaptive properties of azobenzenes continue to inspire new research directions, with limits imposed only by one's imagination.

Upper and Apparent Lower Critical Solution Temperature Branches in the Phase Diagram of Polymer:Small Molecule Semiconducting Systems

Solution-processable semiconducting materials are complex materials with a wide range of applications. Despite their extensive study and utility, their molecular interactions as manifested, for example, in phase behavior are poorly understood. Here, we aim to understand the phase behavior of conjugated systems by determining phase diagrams spanning extensive temperature ranges for various combinations of the highly disordered semiconducting polymer (PTB7-Th) with crystallizable (IT-M and PC₆₁BM) and noncrystallizable (di-PDI) small molecule acceptors (SMAs), with polystyrene as an amorphous control, a nonsemiconducting commodity polymer. We discover that the apparent binodal of the studied blends frequently consists of an upper critical solution temperature (UCST) and lower critical solution temperature (LCST) branch, exhibiting a sharp kink where the branches join. Our work suggests that phase diagrams might be a probe in combination with sophisticated models to understand the complexity of semiconducting materials, including microstructure and molecular interactions.

Thermoresponsive properties of polyacrylamides in physiological solutions

We show that the cloud point temperature (TCP) of thermoresponsive polyacrylamides is considerably lower in physiologically relevant solvents (phosphate-buffered saline, serum) than in pure water. This decrease of TCP may be critical for some biomedical applications.

Triple-Responsive Polyampholytic Graft Copolymers as Smart Sensors with Varying Output

Three triggers result in two measurable outputs from polymeric sensors: multiresponsive polyampholytic graft copolymers respond to pH-value and temperature, as well as the type and concentration of metal cations and therefore, allow the transformation of external triggers into simply measurable outputs (cloud point temperature (T_CP ) and surface plasmon resonance (SPR) of encapsulated silver nanoparticles). The synthesis relies on poly(dehydroalanine) (PDha) as the reactive backbone and gives straightforward access to materials with tunable composition and output. In particular, a rather high sensitivity toward the presence of Cu²⁺ , Co²⁺ , and Pb²⁺ metal cations is found.

New water-soluble colorimetric pH and metal ione sensor based on graphene quantum dot modified with alizarine red S

A new colorimetric sensor was designed for the screening pH changes in solutions, as well as, detection of some cations. The sensor preparation includes the chemical binding of alizarine red S (ARS) as a sensor of pH and cation to graphene quantum dots (GQD). Loading ARS on GQD led to the formation of water soluble sensor which finally responded to the colorimetric detection of some cations in water. Solubility and stability of the sensor in water indicate that the sensor is an ideal system for the biological and environmental applications. To demonstrate the applicability of the new sensor, the colorimetric responds of sensor were examined for some cations including Fe³⁺, Co²⁺, Ca²⁺, As³⁺, Cd²⁺, Hg²⁺, Pb²⁺, Sn²⁺, Al³⁺, and Cr³⁺. The colorimetric detections of all the ions were performable individually in a solution. In addition, GQD-ARS as a colorimetric sensor detected Co²⁺ at pH < 0.6 with limit of quantification 0.08 mM and Fe³⁺ at 0.6 < pH < 4.0 with limit of quantification 0.03 mM in the mixture of cations.

Confined Microenvironments from Thermoresponsive Dendronized Polymers

Confined microenvironments in biomacromolecules arising from molecular crowding account for their well-defined biofunctions and bioactivities. To mimick this, synthetic polymers to form confined structures or microenvironments are of key scientific value, which have received significant attention recently. To create synthetic confined microenvironments, molecular crowding effects and topological cooperative effects have been applied successfully, and the key is balance between self-association of structural units and self-repulsion from crowding-induced steric hindrance. In this article, formation of confined microenvironments from stimuli-responsive dendronized polymers carrying densely dendritic oligoethylene glycols (OEGs) moieties in their pendants is presented. These wormlike thick macromolecules exhibit characteristic thermoresponsive properties, which can provide constrained microenvironments to encapsulate effectively guest molecules including dyes, proteins, or nucleic acids to prevent their protonation or biodegradation. This efficient shielding effect can also mediate chemical reactions in aqueous phase, and even enhance chirality transferring efficiency. All of these can be switched off simply through the thermally-induced dehydration and collapse of OEG dendrons due to the amphiphilicity of OEG chains. Furthermore, the switchable encapsulation and release of guests can be greatly enhanced when these dendronized polymers are used as major constituents for fabricating bulk hydrogels or nanogels, which provide a higher-level confinement.

Oxidative instability of boronic acid-installed polycarbonate nanoparticles

Oxidative stress, caused by the overproduction of reactive oxygen species (ROS), is often observed in degenerative and/or metabolic diseases, tumors, and inflamed tissues. Boronic acids are emerging as a unique class of responsive biomaterials targeting ROS because of their reactivity toward H2O2. Herein, we examine the oxidative reactivity of nanoparticles from a boronic acid-installed polycarbonate. The extent of oxidation under different concentrations of H2O2 was tracked by the change in fluorescence intensity of an encapsulated solvatochromic reporter dye, demonstrating their sensitivity to biologically-relevant concentrations of hydrogen peroxide. Oxidation-triggered particle destabilization, however, was shown to be highly dependent on the concentration of the final oxidized polymer product, and was only achieved if it fell below polymer critical micelle concentration. Our results indicate that these nanocarriers serve as an excellent dual pH/H2O2 responsive vehicle for drug delivery.

AIE-active non-conjugated poly(N-vinylcaprolactam) as a fluorescent thermometer for intracellular temperature imaging

Since temperature is one of the most significant physiological parameters that dictate the cellular status of living organisms, accurate intracellular temperature measurement is crucial and a valuable biomarker for the diagnosis and treatment of diseases. Herein, we introduce the foremost example of a non-conjugated polymer as a next generation fluorescent thermometer which is capable of addressing the key shortcomings including toxicity and thermal-induced fluorescence quenching associated with π-π conjugated system-based thermometers developed so far. We revealed, for the first time, the unique photophysical and aggregation-induced emission (AIE) characteristics of well-known thermoresponsive poly(N-vinylcaprolactam) (PNVCL) devoid of any classical fluorophore entity. PNVCL underwent a coil to globular conformational transition in an aqueous medium and appeared to be fluorescent above its lower critical solution temperature (LCST) near body temperature (38 °C). Eventually, this intriguing aspect enabled higher cellular uptake of PNVCL at the LCST boundary. By virtue of the AIE effect, the thermo-induced aggregation phenomenon has been ingeniously utilized to apply PNVCL as a novel fluorescent thermometer for intracellular temperature determination.

Giant "Breathing" Proteinosomes with Jellyfish-like Property

The design and construction of "breathing" self-assemblies has been a rather popular topic due to their potential in materials science and nanotechnology. Inspired by the "breathing" behavior of natural jellyfish, herein, we presented the construction of a giant "breathing" proteinosome through an interfacial self-assembly of proteins and surfactants at the oil/water interface of emulsions: The proteinosome displays "breathing" behavior and can swell and shrink for multiple cycles by protein folding and unfolding through the alternate addition and removal of denaturant; more importantly, when green fluorescent proteins were selected as alternative protein building blocks, the fluorescence of proteinosome can be reversibly switched on/off just like the behavior of jellyfish. Moreover, accompanied by reversible swelling and shrinking and on/off fluorescence, the expanded and shrunk membrane pore can be tuned for distinguishing quantum dots of different sizes. The folding-responsive breathing behavior of intelligent proteinosomes provides a platform for functional biomaterials.

Responsive Polymers as Smart Nanomaterials Enable Diverse Applications

Responsive polymers undergo reversible or irreversible physical or chemical modifications in response to a change in environment or stimulus, e.g., temperature, pH, light, and magnetic or electric fields. Polymeric nanoparticles (NPs), which constitute a diverse set of morphologies, including micelles, vesicles, and core-shell geometries, have been successfully prepared from responsive polymers and have shown great promise in applications ranging from drug delivery to catalysis. In this review, we summarize pH, thermo-, photo-, and enzymatic responsiveness for a selection of polymers. We then discuss the formation of NPs made from responsive polymers. Finally, we highlight how NPs and other nanomaterials are enabling a wide range of smart applications with improved efficiency, as well as improved sustainability and recyclability of polymeric systems.

Artificial Microbial Arenas: Materials for Observing and Manipulating Microbial Consortia

From the smallest ecological niche to global scale, communities of microbial life present a major factor in system regulation and stability. As long as laboratory studies remain restricted to single or few species assemblies, however, very little is known about the interaction patterns and exogenous factors controlling the dynamics of natural microbial communities. In combination with microfluidic technologies, progress in the manufacture of functional and stimuli-responsive materials makes artificial microbial arenas accessible. As habitats for natural or multispecies synthetic consortia, they are expected to not only enable detailed investigations, but also the training and the directed evolution of microbial communities in states of balance and disturbance, or under the effects of modulated stimuli and spontaneous response triggers. Here, a perspective on how materials research will play an essential role in generating answers to the most pertinent questions of microbial engineering is presented, and the concept of adaptive microbial arenas and possibilities for their construction from particulate microniches to 3D habitats is introduced. Materials as active and tunable components at the interface of living and nonliving matter offer exciting opportunities in this field. Beyond forming the physical horizon for microbial cultivates, they will enable dedicated intervention, training, and observation of microbial consortia.

Recent Progress in Electrochemical pH-Sensing Materials and Configurations for Biomedical Applications

pH-sensing materials and configurations are rapidly evolving toward exciting new applications, especially those in biomedical applications. In this review, we highlight rapid progress in electrochemical pH sensors over the past decade (2008-2018) with an emphasis on key considerations, such as materials selection, system configurations, and testing protocols. In addition to recent progress in optical pH sensors, our main focus in this review is on electromechanical pH sensors due to their significant advances, especially in biomedical applications. We summarize developments of electrochemical pH sensors that by virtue of their optimized material chemistries (from metal oxides to polymers) and geometrical features (from thin films to quantum dots) enable their adoption in biomedical applications. We further present an overview of necessary sensing standards and protocols. Standards ensure the establishment of consistent protocols, facilitating collective understanding of results and building on the current state. Furthermore, they enable objective benchmarking of various pH-sensing reports, materials, and systems, which is critical for the overall progression and development of the field. Additionally, we list critical issues in recent literary reporting and suggest various methods for objective benchmarking. pH regulation in the human body and state-of-the-art pH sensors (from ex vivo to in vivo) are compared for suitability in biomedical applications. We conclude our review by (i) identifying challenges that need to be overcome in electrochemical pH sensing and (ii) providing an outlook on future research along with insights, in which the integration of various pH sensors with advanced electronics can provide a new platform for the development of novel technologies for disease diagnostics and prevention.

Understanding the effect of monomer structure of oligoethylene glycol acrylate copolymers on their thermoresponsive behavior for the development of polymeric sensors

Oligoethylene glycol acrylate (OEGA) polymers are a class of thermoresponsive polymers. Three new OEGA monomer combinations were investigated, which revealed three different types of thermoresponsive behavior as a function of copolymer composition.

Synthesis of next generation dual-responsive cross-linked nanoparticles and their application to anti-cancer drug delivery

Rare earth metal-mediated group transfer polymerisation enables the synthesis of previously inaccessible block copolymers of 2-vinylpyridine, diethyl vinylphosphonate and the new diallyl vinylphosphonate monomer. This precision polymerisation and the selective cross-linking of allyl side groups via thiol-ene click chemistry leads to the formation of well-defined dual-responsive nanoparticles. We demonstrate that these next generation nanocarriers are pH- and temperature-responsive and are capable of efficiently delivering doxorubicin into the nucleus of cancer cells. High anti-cancer activity could be demonstrated via cytotoxicity tests on breast cancer (MCF-7) and cervical cancer (HeLa) cells. These results validate this modular synthesis route as an ideal platform for the development of sophisticated nanocarriers for future drug delivery applications.

Plasma dye coating as straightforward and widely applicable procedure for dye immobilization on polymeric materials

Here, we introduce a novel concept for the fabrication of colored materials with significantly reduced dye leaching through covalent immobilization of the desired dye using plasma-generated surface radicals. This plasma dye coating (PDC) procedure immobilizes a pre-adsorbed layer of a dye functionalized with a radical sensitive group on the surface through radical addition caused by a short plasma treatment. The non-specific nature of the plasma-generated surface radicals allows for a wide variety of dyes including azobenzenes and sulfonphthaleins, functionalized with radical sensitive groups to avoid significant dye degradation, to be combined with various materials including PP, PE, PA6, cellulose, and PTFE. The wide applicability, low consumption of dye, relatively short procedure time, and the possibility of continuous PDC using an atmospheric plasma reactor make this procedure economically interesting for various applications ranging from simple coloring of a material to the fabrication of chromic sensor fabrics as demonstrated by preparing a range of halochromic materials.

Peroxynitrite-biosignal-responsive polymer micelles as intracellular hypersensitive nanoprobes

Copolymerization of a trifluoromethyl ketone-bearing monomer and a rhodamine monomer has led to the formation of peroxynitrite (ONOO⁻) signaling molecule-responsive polymer fluorescent micelles.

Poly(2-isopropenyl-2-oxazoline) as a versatile platform towards thermoresponsive copolymers

Thermoresponsive (co)polymers with LCST behavior based on a well-defined PiPOx scaffold showing high versatility in tuning up the T_CP as well as the interval of response.

Toward the two-step microdynamic phase transition mechanism of an oligo(ethylene glycol)methacrylate-based copolymer with a LCST-type poly(ionic liquid) block

A new LCST-type thermoresponsive polyelectrolyte P[P_4,4,4,4][SS], poly(tetrabutyl phosphonium styrene sulfonate), was introduced to PMEO₂MA (poly(2-(2-methoxyethoxy)ethyl methacrylate)) via RAFT polymerization, in order to explore the transition behavior of the block copolymer PMEO₂MA-b-P[P_4,4,4,4][SS] with two distinct LCST-type segments. A relatively sharp LCST-type phase transition with only one transition point is observed in the turbidity curves, while the whole phase transition is completely different from the micro perspective. The phase transition temperature range is relatively broad, according to the unsynchronized changes of different protons of the two blocks in the temperature-variable ¹H NMR analysis. From PCMW analysis, it is found that there exists an obvious two-step phase transition behavior, especially in the region of the C-H groups. Accordingly, we divided the whole transition process into two subregions: 20-40 °C and 40-55 °C in 2Dcos analysis. At the first stage of 20-40 °C, the CH₃ groups mainly belonging to the backbones of PMEO₂MA blocks have the earliest response to the heating and drive the first step of the dehydration process of PMEO₂MA-b-P[P_4,4,4,4][SS], resulting in the formation of an intermediate micelle state composed of the collapsed PMEO₂MA core and hydrophilic P[P_4,4,4,4][SS] corona. In particular, the conformational changes and the more compact structures due to the interaction between the C[double bond, length as m-dash]O groups and P[P_4,4,4,4][SS] segments (ν(C[double bond, length as m-dash]OD₂O-PILs)) were observed using IR analysis. With the continual increase of the temperature, when the second temperature range of 40-55 °C is reached, the P[P_4,4,4,4][SS] segments start to collapse and expel the water molecules, driven by the anions of the poly(ionic liquid)s, with the phosphonium cations being distributed over the relatively hydrophilic outside.

Carbon Dot Nanothermometry: Intracellular Photoluminescence Lifetime Thermal Sensing

Nanoscale biocompatible photoluminescence (PL) thermometers that can be used to accurately and reliably monitor intracellular temperatures have many potential applications in biology and medicine. Ideally, such nanothermometers should be functional at physiological pH across a wide range of ionic strengths, probe concentrations, and local environments. Here, we show that water-soluble N,S-co-doped carbon dots (CDs) exhibit temperature-dependent photoluminescence lifetimes and can serve as highly sensitive and reliable intracellular nanothermometers. PL intensity measurements indicate that these CDs have many advantages over alternative semiconductor- and CD-based nanoscale temperature sensors. Importantly, their PL lifetimes remain constant over wide ranges of pH values (5-12), CD concentrations (1.5 × 10^-5 to 0.5 mg/mL), and environmental ionic strengths (up to 0.7 mol·L^-1 NaCl). Moreover, they are biocompatible and nontoxic, as demonstrated by cell viability and flow cytometry analyses using NIH/3T3 and HeLa cell lines. N,S-CD thermal sensors also exhibit good water dispersibility, superior photo- and thermostability, extraordinary environment and concentration independence, high storage stability, and reusability-their PL decay curves at temperatures between 15 and 45 °C remained unchanged over seven sequential experiments. In vitro PL lifetime-based temperature sensing performed with human cervical cancer HeLa cells demonstrated the great potential of these nanosensors in biomedicine. Overall, N,S-doped CDs exhibit excitation-independent emission with strongly temperature-dependent monoexponential decay, making them suitable for both in vitro and in vivo luminescence lifetime thermometry.

Responsive Boronic Acid-Decorated (Co)polymers: From Glucose Sensors to Autonomous Drug Delivery

Boronic acid-containing (co)polymers have fascinated researchers for decades, garnering attention for their unique responsiveness toward 1,2- and 1,3-diols, including saccharides and nucleotides. The applications of materials that exert this property are manifold including sensing, but also self-regulated drug delivery systems through responsive membranes or micelles. In this review, some of the main applications of boronic acid containing (co)polymers are discussed focusing on the role of the boronic acid group in the response mechanism. We hope that this summary, which highlights the importance and potential of boronic acid-decorated polymeric materials, will inspire further research within this interesting field of responsive polymers and polymeric materials.

Multiresponsive Behavior of Functional Poly(p-phenylene vinylene)s in Water

The multiresponsive behavior of functionalized water-soluble conjugated polymers (CPs) is presented with potential applications for sensors. In this study, we investigated the aqueous solubility behavior of water-soluble CPs with high photoluminescence and with a particular focus on their pH and temperature responsiveness. For this purpose, two poly(phenylene vinylene)s (PPVs)-namely 2,5-substituted PPVs bearing both carboxylic acid and methoxyoligoethylene glycol units-were investigated, with different amount of carboxylic acid units. Changes in the pH and temperature of polymer solutions led to a response in the fluorescence intensity in a pH range from 3 to 10 and for temperatures ranging from 10 to 85 °C. Additionally, it is demonstrated that the polymer with the largest number of carboxylic acid groups displays upper critical solution temperature (UCST)-like thermoresponsive behavior in the presence of a divalent ion like Ca2+. The sensing capability of these water-soluble PPVs could be utilized to design smart materials with multiresponsive behavior in biomedicine and soft materials.

Influence of the Near Molecular Vicinity on the Temperature Regulated Fluorescence Response of Poly(N-vinylcaprolactam)

A series of new fluorescent dye bearing monomers, including glycomonomers, based on maleamide and maleic esteramide was synthesized. The dye monomers were incorporated by radical copolymerization into thermo-responsive poly(N‑vinyl-caprolactam) that displays a lower critical solution temperature (LCST) in aqueous solution. The effects of the local molecular environment on the polymers' luminescence, in particular on the fluorescence intensity and the extent of solvatochromism, were investigated below as well as above the phase transition. By attaching substituents of varying size and polarity in the close vicinity of the fluorophore, and by varying the spacer groups connecting the dyes to the polymer backbone, we explored the underlying structure⁻property relationships, in order to establish rules for successful sensor designs, e.g., for molecular thermometers. Most importantly, spacer groups of sufficient length separating the fluorophore from the polymer backbone proved to be crucial for obtaining pronounced temperature regulated fluorescence responses.

Amphiphilic gels of solvatochromic fluorescent poly(2-oxazoline)s containing D–π–A pyrenes

We report amphiphilic, fluorescent, solvatochromic poly(2-methyl-2-oxazoline) (POZO-py) and poly(2-ethyl-2-oxazoline) (PEtOZO-py), which contain D–π–A pyrene dye units in their side chains.

Amino-functionalized poly(N-vinylcaprolactam) derived from lysine: a sustainable polymer with thermo and pH dual stimuli response

Lysine, a renewable feedstock with economic feasibility, was tactfully cyclized to its corresponding cyclic lysine and then subjected to a reaction with acetylenes to yield a sustainable N-vinylcaprolactam (VCL) derivative. Well-defined PVCL with pendent amino groups was prepared via MADIX/RAFT polymerization.

A reversible pH-modified fluorescence transition in block copolymer micelles enwrapped with a zinc(ii) fluorescent complex

pH-Modified luminescent micelles and films were prepared and show a reversible green and blue luminescent response to acidic and alkaline atmospheres, respectively.

Design and synthesis of a rhodol isomer and its derivatives with high selectivity and sensitivity for sensing Hg2+ and F− in aqueous media

A fluorescent rhodol isomer has developed as a versatile fluorophore for the molecular design of chemosensors and fluorescent tracers.

Conventional fluorophore-free dual pH- and thermo-responsive luminescent alternating copolymer

Herein, we have designed and synthesized a novel traditional fluorophore-free water-soluble fluorescent copolymer based on a poly(maleimide-alt-styrene) skeleton, which responds to both pH and temperature in aqueous medium.

Enzyme and Thermal Dual Responsive Amphiphilic Polymer Core-Shell Nanoparticle for Doxorubicin Delivery to Cancer Cells

Dual responsive polymer nanoscaffolds for administering anticancer drugs both at the tumor site and intracellular compartments are made for improving treatment in cancers. The present work reports the design and development of new thermo- and enzyme-responsive amphiphilic copolymer core-shell nanoparticles for doxorubicin delivery at extracellular and intracellular compartments, respectively. A hydrophobic acrylate monomer was tailor-made from 3-pentadecylphenol (PDP, a natural resource) and copolymerized with oligoethylene glycol acrylate (as a hydrophilic monomer) to make new classes of thermo and enzyme dual responsive polymeric amphiphiles. Both radical and reversible addition-fragmentation chain transfer (RAFT) methodologies were adapted for making the amphiphilic copolymers. These amphiphilic copolymers were self-assembled to produce spherical core-shell nanoparticles in water. Upon heating, the core-shell nanoparticles underwent segregation to produce larger sized aggregates above the lower critical solution temperature (LCST). The dual responsive polymer scaffold was found to be capable of loading water insoluble drug, such as doxorubicin (DOX), and fluorescent probe-like Nile Red. The drug release kinetics revealed that DOX was preserved in the core-shell assemblies at normal body temperature (below LCST, ≤ 37 °C). At closer to cancer tissue temperature (above LCST, ∼43 °C), the polymeric scaffold underwent burst release to deliver 90% of loaded drugs within 2 h. At the intracellular environment (pH 7.4, 37 °C) in the presence of esterase enzyme, the amphiphilic copolymer ruptured in a slow and controlled manner to release >95% of the drugs in 12 h. Thus, both burst release of cargo at the tumor microenvironment and control delivery at intracellular compartments were accomplished in a single polymer scaffold. Cytotoxicity assays of the nascent and DOX-loaded polymer were carried out in breast cancer (MCF-7) and cervical cancer (HeLa) cells. Among the two cell lines, the DOX-loaded polymers showed enhanced killing in breast cancer cells. Furthermore, the cellular uptake of the DOX was studied by confocal and fluorescence microscopes. The present investigation opens a new enzyme and thermal-responsive polymer scaffold approach for DOX delivery in cancer cells.

A Novel Mechanochromic and Photochromic Polymer Film: When Rhodamine Joins Polyurethane

A rhodamine-based molecule, Rh-OH, is synthesized. Rh-OH exhibits a reversible mechanochromic luminescent character but a passivating response to UV light. An elastomeric polymer film based on polyurethane with embedded Rh-OH is prepared via a polycondensation reaction. The film shows mechanochromic and photochromic properties with reversible color change, which originates from the isomerization of the Rh-OH molecule from a twisted spirolactam in the ring-closed form to a planarized zwitterionic structure in the ring-open state.

Multicolor fluorescent graphene quantum dots colorimetrically responsive to all-pH and a wide temperature range

Smart functional nanomaterials colorimetrically responsive to all-pH and a wide temperature range are urgently needed due to their widespread applications in biotechnology, drug delivery, diagnosis and optical sensing. Although graphene quantum dots possess remarkable advantages in biological applications, they are only stable in neutral or weak acidic solutions, and strong acidic or alkaline conditions invariably suppress or diminish the fluorescence intensity. Herein, we report a new type of water-soluble, multicolor fluorescent graphene quantum dot which is responsive to all-pH from 1 to 14 with the naked eye. The synthesis was accomplished by electrolysis of the graphite rod, followed by refluxing in a concentrated nitric and sulfuric acid mixed solution. We demonstrate the novel red fluorescence of quinone structures transformed from the lactone structures under strong alkaline conditions. The fluorescence of the resulting graphene quantum dots was also found to be responsive to the temperature changes, demonstrating their great potential as a dual probe of pH and temperature in complicated environments such as biological media.