Metal Free Reversible-Deactivation Radical Polymerizations: Advances, Challenges, and Opportunities

Nanotoxicity of multifunctional stoichiometric cobalt oxide nanoparticles (SCoONPs) with repercussions toward apoptosis, necrosis, and cancer necrosis factor (TNF-α) at nano-biointerfaces

Introduction

Apoptosis, necrosis, and cancer necrosis factor (TNF-a) are all impacted by the nanotoxicity of multifunctional stoichiometric cobalt oxide nanoparticles (SCoONPs) at nano-biointerfaces. The creation of multi-functional nanoparticles has had a considerable impact on the transport of drugs and genes, nanotheranostics (in-vivo imaging, concurrent diagnostics), interventions for external healing, the creation of nano-bio interfaces, and the instigation of desired changes in nanotherapeutics.

Objectives

The quantitative structure-activity relationships, chemical transformations, biological interactions as well as toxicological analyses are considered as main objectives. Discrete dimensions of SCoNPs-cell interaction interfaces, their characteristic physical features (size, shape, shell structure, and surface chemistry), impact on cell proliferation and differentiation are the key factors responsible for nanotoxicity.

Methods

The development of multi-functional nanoparticles has been significant in drug/gene delivery, nanotheranostics (in-vivo imaging, coinciding diagnostics), and external healing interventions, designing a nano-bio interface, as well as inciting desired alterations in nanotherapeutics. Every so often, the cellular uptake of multi-functional cobalt [Co, CoO, Co2(CO)8 and Co3O4] nanoparticles (SCoONPs) influences cellular mechanics and initiates numerous repercussions (oxidative stress, DNA damage, cytogenotoxicity, and chromosomal damage) in pathways, including the generation of dysregulating factors involved in biochemical transformations.

Results

The concerns and influences of multifunctional SCoNPs on different cell mechanisms (mitochondria impermeability, hydrolysis of ATP, the concentration of Ca2+, impaired calcium clearance, defective autophagy, apoptosis, and necrosis), and interlinked properties (adhesion, motility, and internalization dynamics, role in toxicity, surface hydrophilic and hydrophobicity, biokinetics and biomimetic behaviors of biochemical reactions) have also been summarized. SCoONPs have received a lot of interest among the nanocarriers family because of its advantageous qualities such as biodegradability, biocompatibility, nontoxicity, and nonimmunogenicity.

Conclusion

Various applications, such as bio-imaging, cell labeling, gene delivery, enhanced chemical stability, and increased biocompatibility, concerning apoptosis, necrosis, and nano-bio interfaces, along with suitable examples. In this analysis, the multi-functional cobalt [Co, CoO, Co2(CO)8 and Co3O4] nanoparticles (SCoNPs) intricacies (cytogenotoxicity, clastogenicity, and immunomodulatory), nanotoxicity, and associated repercussions have been highlighted and explained.

Photoinduced Organocatalyzed Atom Transfer Radical Polymerization (O-ATRP): Precision Polymer Synthesis Using Organic Photoredox Catalysis

The development of photoinduced organocatalyzed atom transfer radical polymerization (O-ATRP) has received considerable attention since its introduction in 2014. Expanding on many of the advantages of traditional ATRP, O-ATRP allows well-defined polymers to be produced under mild reaction conditions using organic photoredox catalysts. As a result, O-ATRP has opened access to a range of sensitive applications where the use of a metal catalyst could be of concern, such as electronics, certain biological applications, and the polymerization of coordinating monomers. However, key limitations of this method remain and necessitate further investigation to continue the development of this field. As such, this review details the achievements made to-date as well as future research directions that will continue to expand the capabilities and application landscape of O-ATRP.

Surface hydroxyl groups: the key to a CrOx/TiO2 catalyst for efficient catalytic oxidation of 2,2′-hydrazine diisobutyronitrile

Surface hydroxyl groups could contribute to the formation of Cr–O–Ti bonds on the surface of the CrOx/TiO2 catalyst, which thus promote the oxidation of 2,2′-hydrazobis-isobutyronitrile.

Development of targeted micelles and polymersomes prepared from degradable RAFT-based diblock copolymers and their potential role as nanocarriers for chemotherapeutics

Modern polymerisation techniques allow synthesis of functional block copolymers that can self-assemble into degradable nanoparticles (NPs) of different sizes and conformations.

Highly efficient oxidation of 2,2'-hydrazobis-isobutyronitrile to 2,2'-azobis-isobutyronitrile over a CrOx/TiO2 catalyst with hydrogen peroxide

Green oxidation of 2,2'-hydrazobis-isobutyronitrile (HAIBN) to 2,2'-azobis-isobutyronitrile (AIBN) over a recyclable solid catalyst was a significant challenge. A titanium dioxide-supported chromium oxide (CrOx/TiO2) catalyst was, for the first time, developed for oxidation of HAIBN with hydrogen peroxide and achieved complete conversion of HAIBN with a high (94.8%) yield of AIBN.

Metal-free atom transfer radical polymerization with ppm catalyst loading under sunlight

Organocatalytic atom transfer radical polymerization (O-ATRP) is recently emerging as an appealing method for the synthesis of metal-free polymer materials with well-defined microstructures and architectures. However, the development of highly effective catalysts that can be employed at a practical low loading are still a challenging task. Herein, we introduce a catalyst design logic based on heteroatom-doping of polycyclic arenes, which leads to the discovery of oxygen-doped anthanthrene (ODA) as highly effective organic photoredox catalysts for O-ATRP. In comparison with known organocatalysts, ODAs feature strong visible-light absorption together with high molar extinction coefficient (ε455nm up to 23,950 M-1 cm-1), which allow for the establishment of a controlled polymerization under sunlight at low ppm levels of catalyst loading.

From 0-dimension to 1-dimensions: Au nanocrystals as versatile plasmonic photocatalyst for broadband light induced RAFT polymerization

Gold nanoparticles and nanorods were utilized as the catalyst for photo-induced RAFT polymerization, because of their strong LSPR performance.

Imidazole based dual photo/thermal initiators for highly efficient radical polymerization under air with a metal-free approach

A metal-free visible LED photopolymerization process, initiated by imidazole based charge transfer complexes under mild conditions (room temperature, without an inert atmosphere, monomer purification or stabilizer removal), is reported.

New Variants of Nitroxide Mediated Polymerization

Nitroxide-mediated polymerization is now a mature technique, at 35 years of age. During this time, several variants have been developed: enhanced spin capture polymerization (ESCP), photoNMP (NMP2), chemically initiated NMP (CI-NMP), spin label NMP (SL-NMP), and plasmon-initiated NMP (PI-NMP). This mini-review is devoted to the features and applications of these variants.

Trends in Polymers 2017/2018: Polymer Synthesis

Polymer synthesis is a substantial area in polymer science and marks the starting point for all sorts of polymer materials that have a plethora of applications in everyday life but also in academic research [...].

Polymers for Regenerative Medicine Structures Made via Multiphoton 3D Lithography

Multiphoton 3D lithography is becoming a tool of choice in a wide variety of fields. Regenerative medicine is one of them. Its true 3D structuring capabilities beyond diffraction can be exploited to produce structures with diverse functionality. Furthermore, these objects can be produced from unique materials allowing expanded performance. Here, we review current trends in this research area. We pay particular attention to the interplay between the technology and materials used. Thus, we extensively discuss undergoing light-matter interactions and peculiarities of setups needed to induce it. Then, we continue with the most popular resins, photoinitiators, and general material functionalization, with emphasis on their potential usage in regenerative medicine. Furthermore, we provide extensive discussion of current advances in the field as well as prospects showing how the correct choice of the polymer can play a vital role in the structure’s functionality. Overall, this review highlights the interplay between the structure’s architecture and material choice when trying to achieve the maximum result in the field of regenerative medicine.

Precise Synthesis of Ultra-High-Molecular-Weight Fluoropolymers Enabled by Chain-Transfer-Agent Differentiation under Visible-Light Irradiation

Ultra-high-molecular-weight (UHMW) polymers display outstanding properties and hold potential for wide applications. However, their precise synthesis remains challenging. Herein, we developed a novel reversible-deactivation radical polymerization based on the strong and selective fluorine-fluorine interaction, allowing chain-transfer agents to spontaneously differentiate into two groups that take charge of the chain growth and reversible deactivation of the growing chains, respectively. This method enables dramatically improved livingness of propagation, providing UHMW polymers with a surprisingly narrow molecular weight distribution (Đ≈1.1) from a variety of fluorinated (meth)acrylates and acrylamide at quantitative conversions under visible-light irradiation. In situ chain-end extensions from UHMW polymers facilitated the synthesis of well-defined block copolymers, revealing the excellent chain-end fidelity achieved by this method.

Structural Engineering of Graphitic Carbon Nitrides for Enhanced Metal-Free PET-RAFT Polymerizations in Heterogeneous and Homogeneous Systems

Developing visible-light-regulated controlled/living radical polymerization techniques for the synthesis of polymers with a predictable molecular weight, spatial and temporal control, and well-defined end-group functionality is being pursued by the macromolecular community worldwide. In this study, a new metal-free photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization system was developed for controlled macromolecular synthesis in both heterogeneous and homogeneous systems by structural engineering of graphitic carbon nitrides (g-C3N4) to improve the textural, optical, and electronic properties. A heteroatom-mediated synthesis enabled the preparation of g-C3N4 with improved structural properties and increased absorption in the visible light region. Enhanced PET-RAFT polymerization of vinyl monomers with low dispersity (Đ < 1.2), temporal control, and high chain-end fidelity was achieved under mild blue light irradiation (λmax = 465 nm, 3 mW/cm2). Moreover, we demonstrate, for the first time, that the g-C3N4-catalyzed RAFT polymerization could be realized in a homogeneous system after structural evolution of bulk g-C3N4 into soluble nanosheets with enhanced photocatalytic efficiency up to high monomer conversion. This study provides new insights into the structure-performance relationship of g-C3N4 for photoregulated PET-RAFT polymerization under visible light. Moreover, the development of a homogeneous g-C3N4-catalyzed photosynthesis system should broaden the application scope of these fascinating photocatalysts while benefiting synthetic upscaling by continuous flow and/or microfluidic reactors.

Localized Surface Plasmon Resonance Meets Controlled/Living Radical Polymerization: An Adaptable Strategy for Broadband Light-Regulated Macromolecular Synthesis

The photophysical process of localized surface plasmon resonance (LSPR) is, for the first time, exploited for broadband photon harvesting in photo-regulated controlled/living radical polymerization. Efficient macromolecular synthesis was achieved under illumination with light wavelengths extending from the visible to the near-infrared regions. Plasmonic Ag nanostructures were in situ generated on Ag₃ PO₄ photocatalysts in a reversible addition-fragmentation chain transfer (RAFT) system, thereby promoting polymerization of various monomers following a LSPR-mediated electron transfer mechanism. Owing to the LSPR-enhanced broadband photon harvesting, high monomer conversion (>99 %) was achieved under natural sunlight within 0.8 h. The deep penetration of NIR light enabled successful polymerization with reaction vessels screened by opaque barriers. Moreover, by trapping active oxygen species generated in the photocatalytic process, polymerization could be implemented without pre-deoxygenation.

Ten Chemical Innovations That Will Change Our World: IUPAC identifies emerging technologies in Chemistry with potential to make our planet more sustainable

2019 is a very special year in chemistry. 2019 marks two major anniversaries: the 100th anniversary of the founding of the International Union of Pure and Applied Chemistry (IUPAC), and the 150th anniversary of Dimitri Mendeleev’s first publication on the Periodic Table of Elements [1]. IUPAC is the global organization that, among many other things, established a common language for chemistry—enabling scientific research, education, and trade. In a similar manner, Mendeleev’s system classified all the elements that were known at the time, and even predicted the existence of elements that would only come to be discovered years later. These two anniversaries are closely entwined, as IUPAC has played a major role developing of the modern Periodic Table by ensuring that the most authoritative version of the table is accessible to everyone [2], establishing names and symbols for the newly discovered elements, and also constantly reviewing its accuracy through the IUPAC Commission on Isotopic Abundances and Atomic Weights.

Redox-Initiated Reversible Addition–Fragmentation Chain Transfer (RAFT) Polymerization

Reversible addition–fragmentation chain transfer (RAFT) polymerization initiated by a radical-forming redox reaction between a reducing and an oxidizing agent (i.e. ‘redox RAFT’) represents a simple, versatile, and highly useful platform for controlled polymer synthesis. Herein, the potency of a wide range of redox initiation systems including enzyme-mediated redox reactions, the Fenton reaction, peroxide-based reactions, and metal-catalyzed redox reactions, and their application in initiating RAFT polymerization, are reviewed. These redox-RAFT polymerization methods have been widely studied for synthesizing a broad range of homo- and co-polymers with tailored molecular weights, compositions, and (macro)molecular structures. It has been demonstrated that redox-RAFT polymerization holds particular promise due to its excellent performance under mild conditions, typically operating at room temperature. Redox-RAFT polymerization is therefore an important and core part of the RAFT methodology handbook and may be of particular importance going forward for the fabrication of polymeric biomaterials under biologically relevant conditions or in biological systems, in which naturally occurring redox reactions are prevalent.

Molecular bionics - engineering biomaterials at the molecular level using biological principles

Life and biological units are the result of the supramolecular arrangement of many different types of molecules, all of them combined with exquisite precision to achieve specific functions. Taking inspiration from the design principles of nature allows engineering more efficient and compatible biomaterials. Indeed, bionic (from bion-, unit of life and -ic, like) materials have gained increasing attention in the last decades due to their ability to mimic some of the characteristics of nature systems, such as dynamism, selectivity, or signalling. However, there are still many challenges when it comes to their interaction with the human body, which hinder their further clinical development. Here we review some of the recent progress in the field of molecular bionics with the final aim of providing with design rules to ensure their stability in biological media as well as to engineer novel functionalities which enable navigating the human body.

Heteroatom-Doped Carbon Dots (CDs) as a Class of Metal-Free Photocatalysts for PET-RAFT Polymerization under Visible Light and Sunlight

A key challenge of photoregulated living radical polymerization is developing efficient and robust photocatalysts. Now carbon dots (CDs) have been exploited for the first time as metal-free photocatalysts for visible-light-regulated reversible addition-fragmentation chain-transfer (RAFT) polymerization. Screening of diverse heteroatom-doped CDs suggested that the P- and S-doped CDs were effective photocatalysts for RAFT polymerization under mild visible light following a photoinduced electron transfer (PET) involved oxidative quenching mechanism. PET-RAFT polymerization of various monomers with temporal control, narrow dispersity (Đ≈1.04), and chain-end fidelity was achieved. Besides, it was demonstrated that the CD-catalyzed PET-RAFT polymerization was effectively performed under natural solar irradiation.

Externally controlled atom transfer radical polymerization

ATRP can be externally controlled by electrical current, light, mechanical forces and various chemical reducing agents. The mechanistic aspects and preparation of polymers with complex functional architectures and their applications are critically reviewed.