Ultrasound-Mediated Atom Transfer Radical Polymerization (ATRP)

A novel label-free impedance biosensor for KRAS G12C mutations detection based on PET-RAFT and ROP synergistic signal amplification

The KRAS G12C mutations, as crucial biomarkers, are closely associated with non-small cell lung cancer. Here, a novel label-free electrochemical biosensor with synergistic signal amplification of photocell energy transfer-reversible addition fragmentation chain transfer (PET-RAFT) and ring-opening polymerization (ROP) was developed for the first time for sensitive detection of KRAS G12C mutations. Specifically, hairpin DNA (hDNA), which act as biomolecular probe, was self-assembled on Au electrode surface by Au-S bond. 4-cyano-4-[(dodecylsulfanylthiocarbonyl) sulfanyl] pentanoic acid (CDTPA), the chain transfer agent of PET-RAFT reaction, was then attached to hDNA via amide bond. After that, the target DNA (tDNA) was captured on the electrode surface by complementary base pairing with hDNA. Subsequently, large numbers of electro-active monomers N-acryloxysuccinimide (NAS) were successfully grafted to the electrode surface via PET-RAFT reaction, which provided plenty of junction sites for doxorubicin-polycaprolactone (Dox-PCL) synthesized by ROP. Finally, the Dox-PCL was connected to the electrode surface by ester bond, significantly amplifying the electrochemical signal. Under optimized conditions, the biosensor has a wide linear detection range of 0.1 pM to 1 μM, with a detection limit of 86.9 fM. Attribute to its high sensitivity, specificity, reproducibility and stability, this biosensor possesses considerable potential in early diagnosis of disease and biomedical research.

Photo-Deactivation Strategy for Switchable ATRP with the Assistance of Molecular Switches

Light irradiation is an external stimulus, rapidly developed in switchable atom transfer radical polymerization (ATRP) via photo-activation methods in recent years. Herein, a photo-deactivation strategy is introduced to regulate ATRP with the assistance of photoswitchable hexaarylbiimidozole (HABI). Under visible light irradiation and in the presence of HABI, ATRP is greatly decelerated or quenched depending on the concentration of HABI. Interestingly, with visible light off, ATRP can proceed smoothly and follow a first-order kinetics. Moreover, photo-switchable ATRP alternatively with light off and on is demonstrated. Besides, the mechanism of photo-deactivation ATRP involving radical quenching is proposed in the presence of HABI.

Emerging Advancements in Piezoelectric Nanomaterials for Dynamic Tumor Therapy

Cancer is one of the deadliest diseases, having spurred researchers to explore effective therapeutic strategies for several centuries. Although efficacious, conventional chemotherapy usually introduces various side effects, such as cytotoxicity or multi−drug resistance. In recent decades, nanomaterials, possessing unique physical and chemical properties, have been used for the treatment of a wide range of cancers. Dynamic therapies, which can kill target cells using reactive oxygen species (ROS), are promising for tumor treatment, as they overcome the drawbacks of chemotherapy methods. Piezoelectric nanomaterials, featuring a unique property to convert ultrasound vibration energy into electrical energy, have also attracted increasing attention in biomedical research, as the piezoelectric effect can drive chemical reactions to generate ROS, leading to the newly emerging technique of ultrasound−driven tumor therapy. Piezoelectric materials are expected to bring a better solution for efficient and safe cancer treatment, as well as patient pain relief. In this review article, we highlight the most recent achievements of piezoelectric biomaterials for tumor therapy, including the mechanism of piezoelectric catalysis, conventional piezoelectric materials, modified piezoelectric materials and multifunctional piezoelectric materials for tumor treatment.

Rapid RAFT Polymerization of Acrylamide with High Conversion

Rapid RAFT polymerization can significantly improve production efficiency of PAM with designed molecular structure. This study shows that ideal Reversible Addition–Fragmentation Chain Transfer (RAFT) polymerization of acrylamide is achieved in dimethyl sulfoxide (DMSO) solution at 70 °C. The key to success is the appropriate choice of both a suitable RAFT chain transfer agent (CTA) and initiating species. It is illustrated that dodecyl trithiodimethyl propionic acid (DMPA) is a suitable trithiocarbonate RAFT CTA and is synthesized more easily than other CTAs. Compared to other RAFT processes of polymers, the reaction system shortens reaction time, enhances conversion, and bears all the characteristics of a controlled radical polymerization. The calculation result shows that high concentrations can reduce high conversions, accelerate the reaction rate, and widen molecular weight distributions slightly. This work proposes an excellent approach for rapid synthesis of PAMs with a restricted molecular weight distribution.

Solvent Coordination Effect on Copper-Based Molecular Catalysts for Controlled Radical Polymerization

The equilibrium of copper-catalyzed atom transfer radical polymerization was investigated in silico with the aim of finding an explanation for the experimentally observed solvent effect. Various combinations of alkyl halide initiators and copper complexes in acetonitrile (MeCN) and dimethyl sulfoxide (DMSO) were taken into consideration. A continuum model for solvation, which does not account for the explicit interactions between the solvent and metal complex, is not adequate and does not allow the reproduction of the experimental trend. However, when the solvent molecules are included in the coordination sphere of the copper(I,II) species and the continuum description of the medium is still used, a solvent dependence of process thermodynamics emerges, in fair agreement with experimental trends.

Electrochemical Investigation of Iron-Catalyzed Atom Transfer Radical Polymerization

Use of iron-based catalysts in atom transfer radical polymerization (ATRP) is very interesting because of the abundance of the metal and its biocompatibility. Although the mechanism of action is not well understood yet, iron halide salts are usually used as catalysts, often in the presence of nitrogen or phosphorous ligands (L). In this study, electrochemically mediated ATRP (eATRP) of methyl methacrylate (MMA) catalyzed by FeCl3, both in the absence and presence of additional ligands, was investigated in dimethylformamide. The electrochemical behavior of FeCl3 and FeCl3/L was deeply investigated showing the speciation of Fe(III) and Fe(II) and the role played by added ligands. It is shown that amine ligands form stable iron complexes, whereas phosphines act as reducing agents. eATRP of MMA catalyzed by FeCl3 was investigated in different conditions. In particular, the effects of temperature, catalyst concentration, catalyst-to-initiator ratio, halide ion excess and added ligands were investigated. In general, polymerization was moderately fast but difficult to control. Surprisingly, the best results were obtained with FeCl3 without any other ligand. Electrogenerated Fe(II) effectively activates the dormant chains but deactivation of the propagating radicals by Fe(III) species is less efficient, resulting in dispersity > 1.5, unless a high concentration of FeCl3 is used.

Action of Mechanical Forces on Polymerization and Polymers

In this review, we summarize recent developments in the field of the mechanochemistry of polymers. The aim of the review is to consider the consequences of mechanical forces and actions on polymers and polymer synthesis. First, we review classical works on chemical reactions and polymerization processes under strong shear deformations. Then, we analyze two emerging directions of research in mechanochemistry-the role of mechanophores and, for the first time, new physical phenomena, accompanying external impulse mechanical actions on polymers. Mechanophores have been recently proposed as sensors of fatigue and cracks in polymers and composites. The effects of the high-pressure pulsed loading of polymers and composites include the Dzyaloshinskii-Moriya effect, emission of superradiation and the formation of metal nanoparticles. These effects provide deeper insight into the mechanism of chemical reactions under shear deformations and pave the way for further research in the interests of modern technologies.

High chain-end fidelity in sono-RAFT polymerization

This study presents the preparation of well-defined multi-block copolymers and understanding of the chain-end fidelity of polymers prepared via sono-RAFT technique.

Solid-state molecular oxygen activation using ball milling and a piezoelectric material for aerobic oxidation of thiols

The agitation of BaTiO₃via ball milling converts mechanical energy into electrical energy, leading to the reduction of molecular oxygen via a single electron transfer pathway analogous to the photocatalytic reaction. This mechanoredox strategy for the oxidative coupling of thiols could eliminate waste and develop a recyclable methodology to accomplish organic transformations in a greener fashion, exhibiting promising potential for large-scale chemical manufacturing.

The agitation of BaTiO₃via ball milling converts mechanical energy into electrical energy, leading to the reduction of molecular oxygen via a single electron transfer pathway analogous to the photocatalytic reaction.

Exploring Electrochemically Mediated ATRP of Styrene

Electrochemically mediated atom transfer radical polymerization (eATRP) of styrene was studied in detail by using CuBr2/TPMA (TPMA = tris(2-pyridylmethyl)amine) as a catalyst. Redox properties of various Cu(II) species were investigated in CH3CN, dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) both in the absence and presence of 50% (v/v) styrene. This investigation together with preliminary eATRP experiments at 80 °C indicated DMF as the best solvent. The effects of catalyst, monomer, and initiator concentrations were also examined. The livingness of the polymerization was studied by chain extension and electrochemical temporal control of polymerization.

Sonochemical fabrication of inorganic nanoparticles for applications in catalysis

Catalysis covers almost all the chemical reactions or processes aiming for many applications. Sonochemistry has emerged in designing and developing the synthesis of nano-structured materials, and the latest progress mainly focuses on the synthetic strategies, product properties as well as catalytic applications. This current review simply presents the sonochemical effects under ultrasound irradiation, roughly describes the ultrasound-synthesized inorganic nano-materials, and highlights the sonochemistry applications in the inorganics-based catalysis processes including reduction, oxidation, degradation, polymerization, etc. Or all in all, the review hopes to provide an integrated understanding of sonochemistry, emphasize the great significance of ultrasound-assisted synthesis in structured materials as a unique strategy, and broaden the updated applications of ultrasound irradiation in the catalysis fields.

Surface-initiated mechano-ATRP as a convenient tool for tuning of bidisperse magnetorheological suspensions toward extreme kinetic stability

Magnetic NPs grafted via mechano-ATRP served as a powerful agent for enhancing performance and stability of magnetorheological suspensions.

Electro-Mechanochemical Atom Transfer Radical Cyclizations using Piezoelectric BaTiO3

The formation and regeneration of active CuI species is a fundamental mechanistic step in copper-catalyzed atom transfer radical cyclizations (ATRC). Typically, the presence of the catalytically active CuI species in the reaction mixture is secured by using high CuI catalyst loadings or the addition of complementary reducing agents. In this study it is demonstrated how the piezoelectric properties of barium titanate (BaTiO3 ) can be harnessed by mechanical ball milling to induce electrical polarization in the strained piezomaterial. This strategy enables the conversion of mechanical energy into electrical energy, leading to the reduction of a CuII precatalyst into the active CuI species in copper-catalyzed mechanochemical solvent-free ATRC reactions.

Stimuli-Responsive Rifampicin-Based Macromolecules

This paper presents the modification of the antibiotic rifampicin by an anionic polyelectrolyte using a simplified electrochemically mediated atom transfer radical polymerization (seATRP) technique to receive stimuli-responsive polymer materials. Initially, a supramolecular ATRP initiator was prepared by an esterification reaction of rifampicin hydroxyl groups with α-bromoisobutyryl bromide (BriBBr). The structure of the initiator was successfully proved by nuclear magnetic resonance (1H and 13C NMR), Fourier-transform infrared (FT-IR) and ultraviolet-visible (UV-vis) spectroscopy. The prepared rifampicin-based macroinitiator was electrochemically investigated among various ATRP catalytic complexes, by a series of cyclic voltammetry (CV) measurements, determining the rate constants of electrochemical catalytic (EC') process. Macromolecules with rifampicin core and hydrophobic poly (n-butyl acrylate) (PnBA) and poly(tert-butyl acrylate) (PtBA) side chains were synthesized in a controlled manner, receiving polymers with narrow molecular weight distribution (Mw/Mn = 1.29 and 1.58, respectively). "Smart" polymer materials sensitive to pH changes were provided by transformation of tBA into acrylic acid (AA) moieties in a facile route by acidic hydrolysis. The pH-dependent behavior of prepared macromolecules was investigated by dynamic light scattering (DLS) determining a hydrodynamic radius of polymers upon pH changes, followed by a control release of quercetin as a model active substance upon pH changes.

Facile One-Step Fabrication of Phthalocyanine-Graphene-Bacterial-Cellulose Nanocomposite with Superior Catalytic Performance

It is generally accepted that the convenient fabrication of a metal phthalocyanine-based heterogeneous catalyst with superior catalytic activity is crucial for its application. Herein, a novel and versatile ultrasonic-assisted biosynthesis approach (conducting ultrasonic treatment during biosynthesis process) was tactfully adopted for the direct immobilization of a sulfonated cobalt phthalocyanine (PcS) catalyst onto a graphene-bacterial cellulose (GBC) substrate without any modification. The prepared phthalocyanine-graphene-bacterial-cellulose nanocomposite, PcS@GBC, was characterized by field emission scanning electron microscope (FESEM) and X-ray photoelectron spectroscopy (XPS). The catalytic activity of the PcS@GBC was evaluated based on its catalytic oxidation performance to dye solution, with H₂O₂ used as an oxidant. More than a 140% increase of dye removal percentage for the PcS@GBC heterogeneous catalyst was found compared with that of PcS. The unique hierarchical architecture of the GBC substrate and the strong interaction between PcS and graphene, which were verified experimentally by ultraviolet-visible light spectroscopy (UV-vis) and Fourier transform infrared spectroscopy (FT-IR) and theoretically by density functional theory (DFT) calculation, were synergistically responsible for the substantial enhancement of catalytic activity. The accelerated formation of the highly reactive hydroxyl radical (·OH) for PcS@GBC was directly evidenced by the electron paramagnetic resonance (EPR) spin-trapping technique. A possible catalytic oxidation mechanism for the PcS@GBC-H₂O₂ system was illustrated. This work provides a new insight into the design and construction of a highly reactive metal phthalocyanine-based catalyst, and the practical application of this functional nanomaterial in the field of environmental purification is also promising.

Mixed Polymer Brushes for "Smart" Surfaces

Mixed polymer brushes (MPBs) are composed of two or more disparate polymers covalently tethered to a substrate. The resulting phase segregated morphologies have been extensively studied as responsive "smart" materials, as they can be reversible tuned and switched by external stimuli. Both computational and experimental work has attempted to establish an understanding of the resulting nanostructures that vary as a function of many factors. This contribution highlights state-of-the-art MPBs studies, covering synthetic approaches, phase behavior, responsiveness to external stimuli as well as novel applications of MPBs. Current limitations are recognized and possible directions for future studies are identified.

Low Ppm Atom Transfer Radical Polymerization in (Mini)Emulsion Systems

In the last decade, unceasing interest in atom transfer radical polymerization (ATRP) has been noted, especially in aqueous dispersion systems. Emulsion or miniemulsion is a preferred environment for industrial polymerization due to easier heat dissipation and lower production costs associated with the use of water as a dispersant. The main purpose of this review is to summarize ATRP methods used in emulsion media with different variants of initiating systems. A comparison of a dual over single catalytic approache by interfacial and ion pair catalysis is presented. In addition, future development directions for these methods are suggested for better use in biomedical and electronics industries.

Surface Modifications of Poly(Ether Ether Ketone) via Polymerization Methods-Current Status and Future Prospects

Surface modification of poly(ether ether ketone) (PEEK) aimed at applying it as a bone implant material aroused the unflagging interest of the research community. In view of the development of implantology and the growing demand for new biomaterials, increasing biocompatibility and improving osseointegration are becoming the primary goals of PEEK surface modifications. The main aim of this review is to summarize the use of polymerization methods and various monomers applied for surface modification of PEEK to increase its bioactivity, which is a critical factor for successful applications of biomedical materials. In addition, the future directions of PEEK surface modifications are suggested, pointing to low-ppm surface-initiated atom transfer radical polymerization (SI-ATRP) as a method with unexplored capacity for flat surface modifications.

Effects of various Cu(0), Fe(0), and proanthocyanidin reducing agents on Fe(iii)-catalysed ATRP for the synthesis of PMMA block copolymers and their self-assembly behaviours

Well-defined PMMA, PMMA-b-PBzMA and PMMA-b-PBMA polymers were obtained via green Fe-ATRP with the aid of proanthocyanidins. Interestingly, microphase separation was observed in PMMA-b-PBMA polymer with upper critical ordering temperature behaviour.