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In this review, we provide a brief history, progress, and applications, and discuss the remaining challenges of photocontrolled reversible addition–fragmentation chain transfer (RAFT) polymerization (i.e., photoinduced electron/energy transfer-RAFT (PET-RAFT), photoiniferter, and photomediated cationic RAFT polymerization). Among these, visible-light-driven RAFT polymerization has attracted particular attention in recent years due to its benefits, including low energy consumption and the safe reaction procedure. Moreover, the incorporation of visible-light photocatalysis in the polymerization has conferred attractive features, such as spatiotemporal control and oxygen tolerance; however, a clear understanding of the reaction mechanism has not been completely provided. We also present recent research efforts to elucidate the polymerization mechanisms with the aid of quantum chemical calculations combined with experimental evidence. This review offers an insight into the better design of polymerization systems for desired applications and helps realize the full potential of photocontrolled RAFT polymerization in both academic- and industrial-scale applications. [ABSTRACT FROM AUTHOR]

To fight nosocomial infections, the excessive use of antibiotics has led to the emergence of multidrug-resistant microorganisms, which are now considered a relevant public health threat by the World Health Organization. To date, most antibacterial systems are based on the use of petro-sourced polymers, but the global supplies of these resources are depleting. Besides, silver NPs are widely accepted as the most active biocide against a wide range of bacterial strains but their toxicity is an issue. The growing interest in natural products has gained increasing interest in the last decade. Therefore, the design of functional antibacterial materials derived from biomass remains a significant challenge for the scientific community. Consequently, attention has shifted to naturally occurring substances such as essential oils (EOs), which are classified as Generally Recognized as Safe (GRAS). EOs can offer an alternative to the common antimicrobial agents as an inner solution or biocide agent to inhibit the resistance mechanism. Herein, this review not only aims at providing developments in the antibacterial modes of action of EOs against various bacterial strains and the recent advances in genomic and proteomic techniques for the elucidation of these mechanisms but also presents examples of biobased polymer resource-based EO materials and their antibacterial activities. Especially, we describe the antibacterial properties of biobased polymers, e.g. cellulose, starch, chitosan, PLA PHAs and proteins, associated with EOs (cinnamon (CEO), clove (CLEO), bergamot (BEO), ginger (GEO), lemongrass (LEO), caraway (CAEO), rosemary (REO), Eucalyptus globulus (EGEO), tea tree (TTEO), orange peel (OPEO) and apricot (Prunus armeniaca) kernel (AKEO) essential oils). Finally, we discuss the influence of EOs on the mechanical strength of bio-based materials. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) is an essential signaling molecule with a number of biological functions and holds great promise in biomedical applications. However, NO delivery technologies have been complicated due to the inherent properties of NO which include short half-life and limited transport distance in human tissues. In addition, the biofunctionality of NO is strongly dependent on its concentrations and locations where it is delivered. To achieve controlled NO delivery, many studies have focused on encapsulating NO donors into macromolecular scaffolds or using catalysts to realize in situ NO generation from NO prodrugs. Successful applications have been shown, however NO donor-loaded platforms experience the limitation of finite NO storage capacity. The present study reports the synthesis of a catalyst, copper-doped zeolitic imidazolate framework ZIF-8 (Cu2+/ZIF-8), that is designed to generate NO from naturally occurring endogenous NO donors. By tuning the copper doping percentages, we achieved controlled NO generation from S-nitrosoglutathione (GSNO) and S-nitrosocysteine (CysNO). Cu2+/ZIF-8 particles retained their catalytic potency after 5 NO generation cycles and we showed that our copper-doped ZIF-8 catalyst produced a 10-fold increased amount of NO compared with previous reports. As a proof-of-concept study, we demonstrated the ability of copper-doped ZIF-8 to disperse bacterial biofilms in the presence of GSNO. [ABSTRACT FROM AUTHOR]

Docetaxel (DTX) is a widely used chemotherapy drug that is associated with numerous side effects and limited bioavailability. Macromolecular conjugates of DTX may improve drug targeting, solubility, reduce off-target toxicity, and overcome mechanisms of multidrug resistance. However, most polymer conjugates of DTX investigated to date make use of biopolymers, which are of fixed structure and are not well suited to optimisation and subsequent reaction to introduce further functionality. Here, we show the preparation of synthetic copolymer conjugates of DTX with drug loading of up to 20% w/w that also has potential for tuning backbone hydrophilicity and the number of reactive sites for conjugation. The intermediates produced are comprehensively characterised, as are the macromolecular conjugates, which are tested in the MCF-7 human breast adenocarcinoma cell line to assess toxicity and anticancer efficacy. The conjugates produced have IC50 values within one order of magnitude of DTX, as expected for slow release of DTX by ester hydrolysis. The results suggest that the system is promising for delivery of DTX and future work may examine conjugates of a wider molecular weight range, optimisation of DTX and PEG conjugation efficiency, and in vivo biodistribution. [ABSTRACT FROM AUTHOR]

The increased applications of lanthanide-doped upconversion nanoparticles (UCNPs) in areas such as biomedical imaging and therapy have raised the demand for high quality nanocrystals with strong and controllable luminescence intensity. Whilst several different approaches including core/shell arrangement, dye sensitization and plasmonic metallic nanostructures have been employed to improve the upconversion luminescence of UCNPs, they may be impractical for scale-up production and applications. Herein, a mathematical model that was developed using multivariate statistical analysis shows that the key to optimising the NIR and blue light emission of NaY1−(x+y)YbxF4:Tmy UCNPs is dopant balancing, where the composition of both ytterbium (Yb3+) sensitizer and thulium (Tm3+) activator is controlled in a way that the concentration and proximity of the dopants to each other can reduce cross-relaxation between Tm3+ and self-quenching that is due to sub-optimal Yb3+ concentrations, and consequently, favours efficient energy transfer between the Yb3+ sensitizers and Tm3+ activators. The data driven approach gives better understanding of the role of dopant balancing in the upconversion process and presents a general yet effective strategy to enhance the optical properties of UCNPs by manipulating the relative concentrations of the lanthanide dopants. This systematic approach will have important implications and it can be integrated with other emission enhancing strategies to produce high quality UCNPs for diverse applications in photonics, imaging, sensing, drug delivery and solar energy conversion. [ABSTRACT FROM AUTHOR]

The use of polyphenol-rich plant extracts is well established for the green synthesis of silver nanoparticles (AgNPs). However, the size of the AgNPs varies substantially depending on the extract used and many researchers report sizes above 20 nm, which are not optimal for antimicrobial activity. Herein, using catechin as a model polyphenol, we have explored two techniques to improve its stabilising capacity and therefore decrease the subsequent AgNP size: cross-linking catechin with sodium tetraborate (borax); and preparation of a water soluble oligomer from catechin (polycat). The prepared AgNPs from the three stabilising systems, cat@AgNPs, cat-borax@AgNPs and polycat@AgNPs, were characterised by UV-Vis spectroscopy, dynamic light scattering (DLS), X-ray diffraction (XRD), transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry (ICP-MS). Cat-borax produced smaller AgNPs (18.4 nm) than catechin (42.3 nm) but the smallest particles were prepared with polycat (8.5 nm). Antimicrobial efficacy was assessed against Gram positive and Gram negative bacteria and was compared with 10 nm sodium citrate capped AgNPs (citrate@AgNPs). Polycat@AgNPs showed superior antimicrobial activity to cat@AgNPs and cat-borax@AgNPs as well as citrate@AgNPs, exhibiting MICs of only 1.25 μg mL−1 (Ag) for Pseudomonas aeruginosa and Acinetobacter baumannii. Polycat@AgNPs also demonstrated substantially enhanced antibiofilm activity. An Ag concentration of only 5 μg mL−1, was sufficient for a 99.9% reduction in biofilm cell viability and a 99.1% reduction in biofilm biomass with polycat@AgNPs. Uptake of polycat@AgNPs by bacteria was determined to be significantly higher than for citrate@AgNPs and tomographic and SEM images showed evidence of destruction of bacteria cells by polycat@AgNPs. [ABSTRACT FROM AUTHOR]

The necessity of sustainable development in the chemical industry has continuously drawn attention to find safe, environmentally friendly and atom-economic chemical processes, which is defined in the 12 principles of green chemistry. Merging photoredox catalysis and reversible addition–fragmentation chain transfer (RAFT) polymerisation, the photoinduced electron/energy transfer (PET)-RAFT process has opened up a new way of performing reversible deactivation radical polymerisation for well-defined polymer synthesis using light as an external stimulus. While providing an increased level of control (spatiotemporal, wavelength, and intensity control) over the polymerisation, PET-RAFT has many attractive attributes (abundant catalyst availability, catalyst recyclability, selectivity and oxygen tolerance) to be green and sustainable, which is intriguing for precision polymer manufacturing in industry. [ABSTRACT FROM AUTHOR]

The requirement for deoxygenation in controlled/living radical polymerisation (CLRP) places significant limitations on its widespread implementation by necessitating the use of large reaction volumes, sealed reaction vessels as well as requiring access to specialised equipment such as a glove box and/or inert gas source. As a result, in recent years there has been intense interest in developing strategies for overcoming the effects of oxygen inhibition in CLRP and therefore remove the necessity for deoxygenation. In this review, we highlight several strategies for achieving oxygen tolerant CLRP including: “polymerising through” oxygen, enzyme mediated deoxygenation and the continuous regeneration of a redox-active catalyst. In order to provide further clarity to the field, we also establish some basic parameters for evaluating the degree of “oxygen tolerance” that can be achieved using a given oxygen scrubbing strategy. Finally, we propose some applications that could most benefit from the implementation of oxygen tolerant CLRP and provide a perspective on the future direction of this field. [ABSTRACT FROM AUTHOR]

The nitric oxide (NO) molecule has gained increasing attention in biological applications to combat biofilm-associated bacterial infections. However, limited NO loading, relatively short half-lives of low molecular weight NO donor compounds, and difficulties in targeted delivery of NO have hindered their practical clinical administration. To overcome these drawbacks, the combination of NO and scaffolds based on biocompatible polymers is an effective way towards realizing the practical utility of NO in biomedical applications. In this regard, the present overview highlights the recent developments in NO-releasing polymeric biomaterials for antimicrobial applications, focusing on antibiofilm treatments and the challenges that need to be overcome. [ABSTRACT FROM AUTHOR]

Polymeric nanoparticles (NPs) of different morphologies (spheres and worms) were synthesized using a visible light mediated polymerization-induced self-assembly (PISA) approach. Spherical and worm-like NPs were subsequently modified to generate diazeniumdiolate functionalized NPs. Interestingly, the NO release rate and the dispersal of biofilms were found to strongly depend on the NP morphology. NPs with a higher aspect ratio (worms) exhibited a slower NO release rate and greater biofilm dispersal after 1 h of incubation. [ABSTRACT FROM AUTHOR]

We investigated the use of crude chlorophyll extracts to catalyze photoinduced electron/energy transfer-reversible addition–fragmentation chain transfer (PET-RAFT) polymerization under red light irradiation. We discovered that Chl a degrades under visible light in the presence of air, which can eliminate the need for catalyst removal after polymerization. [ABSTRACT FROM AUTHOR]

Incorporation of both metal nanoparticles and a polymer layer is proposed to benefit charge transport in a semiconductor in the absence of electron and hole scavengers. Therefore in this work, zinc oxide is deposited with platinum metal and a layer of polymeric species via a photocatalytic route: platinum cation photoreduction and phenol photooxidative polymerization which utilize photogenerated electrons and holes of ZnO, respectively. The photoelectrochemical performances of these photocatalysts follow the order of Poly/Pt/ZnO ＞ Pt/ZnO ＞ bare ZnO, revealing the effectiveness of both the platinum and polymer in enhancing charge separation within ZnO. Although platinum is known to be an excellent electron sink for promoting electron transfer, the performance of Pt/ZnO was limited by the transport of holes to the ZnO surface for oxidation reactions. Thus, the polymer layer plays an important role in facilitating hole transport, resulting in the enhanced performance of Poly/Pt/ZnO. [ABSTRACT FROM AUTHOR]

This review, with over 600 references, summarizes the recent applications of photoredox catalysis for organic transformation and polymer synthesis. Photoredox catalysts are metallo- or organo-compounds capable of absorbing visible light, resulting in an excited state species. This excited state species can donate or accept an electron from other substrates to mediate redox reactions at ambient temperature with high atom efficiency. These catalysts have been successfully implemented for the discovery of novel organic reactions and synthesis of added-value chemicals with an excellent control of selectivity and stereo-regularity. More recently, such catalysts have been implemented by polymer chemists to post-modify polymers in high yields, as well as to effectively catalyze reversible deactivation radical polymerizations and living polymerizations. These catalysts create new approaches for advanced organic transformation and polymer synthesis. The objective of this review is to give an overview of this emerging field to organic and polymer chemists as well as materials scientists. [ABSTRACT FROM AUTHOR]

A novel methodology of visible light regulated ring opening polymerization in the presence of reversible merocyanine-based photoacid was reported for the first time. In combination with a photoinduced radical polymerization technique, a dual wavelength light controlled orthogonal polymerization system was investigated to switch the polymerization between two different monomers and for the preparation of block and graft copolymers in one pot. [ABSTRACT FROM AUTHOR]