Near-infrared Light-Induced Polymerizations: Mechanisms and Applications.

Photopolymerizations have garnered significant attention in polymer science due to their low polymerization temperature, high production efficiency, environmental friendliness, and spatial controllability. Despite these merits, the poor penetration and severe chemical damage from ultraviolet/visible (UV/Vis) light resources pose significant barriers to their success in conventional photopolymerizations. A recent breakthrough involving the utilization of near-infrared (NIR) laser with long wavelength has been exploited for diverse applications. With the combination of a NIR photosensitizer (PS), NIR-induced photopolymerizations have been successfully developed to alleviate the challenges in conventional methods. The enhancement of penetration depth and safety of NIR-induced photopolymerizations can contribute significantly to improving the efficiency of polymerization for production of intricate structures across various scales. In this concept, the typical types of PSs and polymerization mechanisms (PMs) within the NIR-induced photopolymerization systems have been classified in detail. Additionally, the applications of various polymers achieved by NIR-induced photopolymerizations are summarized. Furthermore, research directions and future challenges of this field are also discussed comprehensively.

Surface Chain-Transfer Ring-Opening Metathesis Polymerization.

Ring-opening metathesis polymerization (ROMP) is a powerful method to graft various types of polymer chains to a given surface. While surface-initiated ROMP (SI-ROMP) serves as an efficient tool for surface modification and is therefore widely reported, the method requires grafting (1) the olefin substrate and (2) the metathesis catalyst to the surface prior to the polymerization with multiple synthetic and work up steps. To overcome this difficulty, we proposed the use of the chain-transfer reaction as an alternative method for surface modification. Terminal olefins are grafted to the surface without the need to graft the metathesis catalysts, and polymers with olefin backbones are polymerized and grafted simultaneously via both ROMP and chain transfer (cross-metathesis between olefins from backbones and surfaces). Compared to SI-ROMP, this surface-chain transfer ROMP (SC-ROMP) method avoids grafting the catalyst and growing polymer chains from the surface and could be achieved in a single step. Various types of surfaces like carbon nanotubes, carbon fibers, graphene nanosheets, and silica microspheres are used for demonstration. We envision that this work could bring a convenient and effective solution to surface modification via ROMP.

Covalent Triazine Frameworks and Porous Carbons: Perspective from an Azulene-Based Case.

Covalent triazine frameworks (CTFs) are among the most valuable frameworks owing to many fantastic properties. However, molten salt-involved preparation of CTFs at 400-600 °C causes debate on whether CTFs represent organic frameworks or carbon. Herein, new CTFs based on the 1,3-dicyanoazulene monomer (CTF-Azs) are synthesized using molten ZnCl2 at 400-600 °C. Chemical structure analysis reveals that the CTF-Az prepared at low temperature (400 °C) exhibits polymeric features, whereas those prepared at high temperatures (600 °C) exhibit typical carbon features. Even after being treated at even higher temperatures, the CTF-Azs retain their rich porosity, but the polymeric features vanish. Although structural de-conformation is a widely accepted outcome in polymer-to-carbon rearrangement processes, the study evaluates such processes in the context of CTF systems. A proof-of-concept study is performed, observing that the as-synthesized CTF-Azs exhibit promising performance as cathodes for Li- and K-ion batteries. Moreover, the as-prepared NPCs exhibit excellent catalytic oxygen reduction reaction (ORR) performance; hence, they can be used as air cathodes in Zn-air batteries. This study not only provides new building blocks for novel CTFs with controllable polymer/carbon features but also offers insights into the formation and structure transformation history of CTFs during thermal treatment.

Correction: A mesoporous polydopamine nanoparticle enables highly efficient manganese encapsulation for enhanced MRI-guided photothermal therapy.

Correction for 'A mesoporous polydopamine nanoparticle enables highly efficient manganese encapsulation for enhanced MRI-guided photothermal therapy' by Yan Wu et al., Nanoscale, 2021, 13, 6439-6446, DOI: D1NR00957E.

A mesoporous polydopamine nanoparticle enables highly efficient manganese encapsulation for enhanced MRI-guided photothermal therapy.

Theranostic agents based on magnetic resonance imaging (MRI) and photothermal therapy (PTT) play an important role in tumor therapy. However, the available theranostic agents are facing great challenges such as biocompatibility, MRI contrast effect and photothermal conversion efficiency (η). In this work, mesoporous polydopamine nanoparticles (MPDAPs/Mn) were prepared on MRI and PTT combined theranostic nanoplatforms, of which the high loading manganese ions and specific surface areas enable good MRI contrast and excellent photothermal conversion efficiency, respectively. The MPDAPs/Mn have uniform morphology, good stability and biocompatibility. Meanwhile, in vitro and in vivo studies have confirmed their superior T1-weighted MRI effect and photothermal conversion efficiency. Furthermore, MPDAPs/Mn have excellent antitumor efficacy in HeLa tumor-bearing mice. Therefore, this developed MPDAPs/Mn theranostic nanoplatform could be a promising candidate for MRI-guided photothermal cancer therapy.

A room-temperature interfacial approach towards iron/nitrogen co-doped fibrous porous carbons as electrocatalysts for the oxygen reduction reaction and Zn-Air batteries.

The development of nonprecious and efficient catalysts to boost the oxygen reduction reaction (ORR) is imperative. However, the majority of previously reported approaches suffered from a complicated fabrication procedure, both time consuming and difficult to scale up. Herein, large-scale iron ion embedded polyaniline fibers were successfully fabricated as precursors for preparing iron/nitrogen co-doped fibrous porous carbons (Fe/NPCFs) through an interfacial engineering strategy at room temperature. As ORR electrocatalysts in an alkaline medium (0.1 M KOH), Fe/NPCFs display a positive half-wave potential of 0.827 V (vs. RHE), and high limited current density (up to 5.76 mA cm-2), which are better than those of commercial Pt/C (E1/2 = 0.815 V, JL = 5.47 mA cm-2). Also, Fe/NPCFs exhibit a high ORR catalysis activity (E1/2 = 0.632 V, JL = 5.07 mA cm-2) in acidic medium (0.5 M H2SO4). When used as an air cathode in a primary Zn-air battery, high power density (158.5 mW cm-2) and specific capacity (717.8 mA h g-1) can be easily achieved, outperforming the commercial Pt/C.

Nucleoside Analogue-Based Supramolecular Nanodrugs Driven by Molecular Recognition for Synergistic Cancer Therapy.

The utilization of nanotechnology for the delivery of a wide range of anticancer drugs has the potential to reduce adverse effects of free drugs and improve the anticancer efficacy. However, carrier materials and/or chemical modifications associated with drug delivery make it difficult for nanodrugs to achieve clinical translation and final Food and Drug Administration (FDA) approvals. We have discovered a molecular recognition strategy to directly assemble two FDA-approved small-molecule hydrophobic and hydrophilic anticancer drugs into well-defined, stable nanostructures with high and quantitative drug loading. Molecular dynamics simulations demonstrate that purine nucleoside analogue clofarabine and folate analogue raltitrexed can self-assemble into stable nanoparticles through molecular recognition. In vitro studies exemplify how the clofarabine:raltitrexed nanoparticles could greatly improve synergistic combination effects by arresting more G1 phase of the cell cycle and reducing intracellular deoxynucleotide pools. More importantly, the nanodrugs increase the blood retention half-life of the free drugs, improve accumulation of drugs in tumor sites, and promote the synergistic tumor suppression property in vivo.

Polysaccharide Nanoparticles for Targeted Cancer Therapies.

BACKGROUND: Despite extensive advances have been made in constructing polysaccharide-based nanomedicines for target cancer therapy due to their biocompatibility, easy-functionalizability and high targeting property, there is no review concentrating the significance of the intrinsic targeting properties of polysaccharides. This review mainly focuses on the recent progress on polysaccharide-based nanoparticles which have been applied in gene delivery, drug delivery and theranostics for targeted cancer therapies. Notably, representative polysaccharides with intrinsic targeting capability used as targeting ligand are well discussed. CONCLUSION: It has been found that polysaccharides have become a class of promising biopolymer carrier materials to deliver anti-cancer therapeutic molecules. Among all of polysaccharides, those who are with intrinsic properties of targeting are most frequently used. Therefore, this review revealed the importance of understanding the natural functions of polysaccharides to tailor nanocarrier platforms and ultimately surmount challenges in targeted cancer therapy.

"Bottom-Up" Fabrication of BODIPY-Functionalized Fluorescent Hyperbranched Glycopolymers for Hepatoma-Targeted Imaging.

A novel type of multivalent and highly specific fluorescent hyperbranched glycopolymers h-P(GalEA-co-VBPT-co-BYMA) (hPGVB) is designed and prepared successfully via a facile "bottom-up" strategy. The acetylated hPGVB is prepared by one-pot reversible addition-fragmentation chain transfer (RAFT) copolymerization of acrylate-type galactose monomers AcGalEA and methacrylate-type fluorescent monomers BYMA in presence of an inimer-type RAFT chain transfer agent. After deacetylation, the resulting amphiphilic hPGVB can self-assemble into stable nanoparticles in aqueous media, showing strong green fluorescence with relative high quantum yields and good photostability. The cell viability study indicates the excellent biocompatibility of the hPGVB fluorescent nanoparticles (FNPs) against HepG2 and NIH3T3 cells. More importantly, comparing with the galactose-free fluorescent hyperbranched polymers h-P(OEGMA-co-VBPT-co-BYMA), hPEVB FNPs can be selectively internalized by asialoglycoprotein (ASGP) receptor-rich HepG2 cells, indicating their potential application in the bioimaging fields.

Star polymer-based unimolecular micelles and their application in bio-imaging and diagnosis.

As a novel kind of polymer with covalently linked core-shell structure, star polymers behave in nanostructure in aqueous medium at all concentration range, as unimolecular micelles at high dilution condition and multi-micelle aggregates in other situations. The unique morphologies endow star polymers with excellent stability and functions, making them a promising platform for bio-application. A variety of functions including imaging and therapeutics can be achieved through rational structure design of star polymers, and the existence of plentiful end-groups on shell offers the opportunity for further modification. In the last decades, star polymers have become an attracting platform on fabrication of novel nano-systems for bio-imaging and diagnosis. Focusing on the specific topology and physicochemical properties of star polymers, we have reviewed recent development of star polymer-based unimolecular micelles and their bio-application in imaging and diagnosis. The main content of this review summarizes the synthesis of integrated architecture of star polymers and their self-assembly behavior in aqueous medium, focusing especially on the recent advances on their bio-imaging application and diagnosis use. Finally, we conclude with remarks and give some outlooks for further exploration in this field.

A Crosslinked Nucleic Acid Nanogel for Effective siRNA Delivery and Antitumor Therapy.

Functional siRNAs are employed as cross-linkers to direct the self-assembly of DNA-grafted polycaprolactone (DNA-g-PCL) brushes to form spherical and nanosized hydrogels via nucleic acid hybridization in which small interfering RNAs (siRNAs) are fully embedded and protected for systemic delivery. Owing to the existence of multivalent mutual crosslinking events inside, the crosslinked nanogels with tunable size exhibit not only good thermostability, but also remarkable physiological stability that can resist the enzymatic degradation. As a novel siRNA delivery system with spherical nucleic acid (SNA) architecture, the crosslinked nanogels can assist the delivery of siRNAs into different cells without any transfection agents and achieve the gene silencing effectively both in vitro and in vivo, through which a significant inhibition of tumor growth is realized in the anticancer treatment.

Synthesis of Multiarm Star Polymer Based on Hyperbranched Polyester Core and Poly(ε-caprolactone) Arms and Its Application in UV-Curable Coating.

Hyperbranched polymers have attracted much attention in the field of UV-curable coatings because of its low viscosity, highly branched structure, and rich functional moieties. However, hyperbranched polymers also have some limitations. For example, the spherical structure increases the crosslinking hindrance, resulting in surplus functional moieties. In this study, a multiarm star polymer with hyperbranched polyester core and linear polymer arms was synthesized and used as UV-curable coating. H40, the fourth generation of the hyperbranched polyester, was chosen as the core owing to its low viscosity and high chemical reactivity. Poly(ε-caprolactone) (PCL) arms were introduced to increase the content of flexible segments and reduce the cross-linking hindrance. The terminal hydroxyls were then replaced with methacrylate groups to endow the star polymer with UV curable ability, yielding HPCLn-M. This multiarm star polymer was considered as a promising candidate to make up for the shortcomings of UV-curable coating made from the hyperbranched polymer. The properties, such as hardness, adhesion, acid resistance, and alkali resistance of cured films were enhanced obviously after the grafting of PCL. Moreover, to further explore the effect of the length of PCL grafts on the coating, star polymers with different degree of polymerization (DP) were synthesized. Through the performance tests of cured films, it was found that the multiarm star polymer HPCLn-M could make up for the limitations of the hyperbranched polymer when the DP of PCL was suitable, and the comprehensive performance of cured film reached the best when the DP of PCL was 20. Overall, this multiarm star polymer could combine the advantages of the hyperbranched polymer and linear polymer and has the potential to be the next environmentally friendly UV-curable coating.

Mustard-inspired delivery shuttle for enhanced blood-brain barrier penetration and effective drug delivery in glioma therapy.

Effective penetration through the blood-brain barrier (BBB) remains a challenge for the treatment of many brain diseases. In this study, a small molecule, sinapic acid (SA), extracted from mustard, was selected as a novel bioinspired BBB-permeable ligand for efficient drug delivery in glioma treatment. SA was conjugated on the surface of zwitterionic polymer poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC)-encapsulated bovine serum albumin (BSA)-based nanoparticles, yielding nBSA-SA. The PMPC shell serves as a protective layer to prolong the in vivo blood circulation time with a better chance to cross the BBB. Furthermore, temozolomide (TMZ), which can be loaded onto the nanoparticles via electrostatic interactions with acrylic acid (AA) to generate AA-nBSA-SA-TMZ, was applied as an excellent chemotherapeutic drug for glioma therapy. The obtained nanoparticles with a distinct size show great BBB permeability. Through the mechanism study, it was found that the cell internalization of the SA-conjugated nanoparticles is an energy-dependent process with only transient disruption of the BBB. The biological evaluation results unambiguously suggest that drug-loaded nanoparticles can lead to strong apoptosis on the tumor site and increase the median survival time of glioma-bearing mice. Overall, this novel BBB-permeable ligand SA paves the way for the delivery of cargo into the brain and provides a powerful nanoplatform for glioma therapy via intravenous administration.

Zwitterionic gold nanorods: low toxicity and high photothermal efficacy for cancer therapy.

Novel "zwitterionic" gold nanorods (Au NRs) were constructed through a facile ligand exchange process between cetyltrimethylammonium bromide (CTAB)-Au NRs and the zwitterionic block polymer {poly(2-methacryloyloxyethyl phosohorylcholine)-b-poly(lipoic methacrylate) (pMPC-b-pLA)}. In vitro, they exhibited low dark cytotoxicity and a high therapeutic efficacy to cancer cells. Their blood circulation half-life in vivo (t1/2, ∼10 h) was 20-fold longer than that of CTAB-Au NRs (t1/2, <30 min). After intravenous administration, they accumulated in tumour sites via an enhanced permeability and retention (EPR) effect and enabled destruction of human xenograft tumours in mice after exposure of the tumour location to NIR laser irradiation at 808 nm. These studies showed that the "zwitterionic" Au NRs had low toxicity and high photothermal efficacy both in vitro and in vivo due to the suprahydrophilic, biocompatible zwitterionic polymer coating layer. They may have the potential to be a promising NIR PTT agent in the biomedical field.

Iron Chelation Nanoparticles with Delayed Saturation as an Effective Therapy for Parkinson Disease.

Iron accumulation in substantia nigra pars compacta (SNpc) has been proved to be a prominent pathophysiological feature of Parkinson's diseases (PD), which can induce the death of dopaminergic (DA) neurons, up-regulation of reactive oxygen species (ROS), and further loss of motor control. In recent years, iron chelation therapy has been demonstrated to be an effective treatment for PD, which has shown significant improvements in clinical trials. However, the current iron chelators are suboptimal due to their short circulation time, side effects, and lack of proper protection from chelation with ions in blood circulation. In this work, we designed and constructed iron chelation therapeutic nanoparticles protected by a zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) to delay the saturation of iron chelators in blood circulation and prolong the in vivo lifetime, with HIV-1 trans-activating transcriptor (TAT) served as a shuttle to enhance the blood-brain barrier (BBB) permeability. We explored and investigated whether the Parkinsonian neurodegeneration and the corresponding symptoms in behaviors and physiologies could be prevented or reversed both in vitro and in vivo. The results demonstrated that iron chelator loaded therapeutic nanoparticles could reverse functional deficits in Parkinsonian mice not only physiologically but also behaviorally. On the contrary, both untreated PD mice and non-TAT anchored nanoparticle treated PD mice showed similar loss in DA neurons and difficulties in behaviors. Therefore, with protection of zwitterionic polymer and prolonged in vivo lifetime, iron chelator loaded nanoparticles with delayed saturation provide a PD phenotype reversion therapy and significantly improve the living quality of the Parkinsonian mice.

Aptamer-Functionalized and Backbone Redox-Responsive Hyperbranched Polymer for Targeted Drug Delivery in Cancer Therapy.

A novel type of backbone redox-responsive hyperbranched poly(2-((2-(acryloyloxy)ethyl)disulfanyl)ethyl 4-cyano-4-(((propylthio)carbonothioyl)-thio)-pentanoate-co-poly(ethylene glycol) methacrylate) (HPAEG) has been designed and prepared successfully via the combination of reversible addition-fragmentation chain-transfer (RAFT) polymerization and self-condensing vinyl polymerization (SCVP). Owing to the existence of surface vinyl groups, HPAEG could be efficiently functionalized by DNA aptamer AS1411 via Michael addition reaction to obtain an active tumor targeting drug delivery carrier (HPAEG-AS1411). The amphiphilic HPAEG-AS1411 could form nanoparticles by macromolecular self-assembly strategy. Cell Counting Kit-8 (CCK-8) assay illustrated that HPAEG-AS1411 nanoparticles had low cytotoxicity to normal cell line. Flow cytometry and confocal laser scanning microscopy (CLSM) results demonstrated that HPAEG-AS1411 nanoparticles could be internalized into tumor cells via aptamer-mediated endocytosis. Compared with pure HPAEG nanoparticles, HPAEG-AS1411 nanoparticles displayed enhanced tumor cell uptake. When the HPAEG-AS1411 nanoparticles loaded with anticancer drug doxorubicin (DOX) were internalized into tumor cells, the disulfide bonds in the backbone of HPAEG-AS1411 were cleaved by glutathione (GSH) in the cytoplasm, so that DOX was released rapidly. Therefore, DOX-loaded HPAEG-AS1411 nanoparticles exhibited a high tumor cellular proliferation inhibition rate and low cytotoxicity to normal cells. This aptamer-functionalized and backbone redox-responsive hyperbranched polymer provides a promising platform for targeted drug delivery in cancer therapy.

Toward Scalable Fabrication of Hierarchical Silica Capsules with Integrated Micro-, Meso-, and Macropores.

Hierarchical porous structures are ubiquitous in biological organisms and inorganic systems. Although such structures have been replicated, designed, and fabricated, they are often inferior to naturally occurring analogues. Apart from the complexity and multiple functionalities developed by the biological systems, the controllable and scalable production of hierarchically porous structures and building blocks remains a technological challenge. Herein, a facile and scalable approach is developed to fabricate hierarchical hollow spheres with integrated micro-, meso-, and macropores ranging from 1 nm to 100 µm (spanning five orders of magnitude). (Macro)molecules, micro-rods (which play a key role for the creation of robust capsules), and emulsion droplets have been successfully employed as multiple length scale templates, allowing the creation of hierarchical porous macrospheres. Thanks to their specific mechanical strength, these hierarchical porous spheres could be incorporated and assembled as higher level building blocks in various novel materials.

Preparation of polydopamine nanocapsules in a miscible tetrahydrofuran-buffer mixture.

A miscible tetrahydrofuran-tris buffer mixture has been used to fabricate polydopamine hollow capsules with a size of 200 nm and with a shell thickness of 40 nm. An unusual non-emulsion soft template mechanism has been disclosed to explain the formation of capsules. The results indicate that the capsule structure is highly dependent on the volume fraction of tetrahydrofuran as well as the solvent, and the shell thickness of capsules can be controlled by adjusting the reaction time and dopamine concentration.

Amorphous carbon dots with high two-photon fluorescence for cellular imaging passivated by hyperbranched poly(amino amine).

Amorphous carbon dots (C-Dots) with high two-photon fluorescence were prepared by using citric acid (CA) as the carbon source and hyperbranched poly(amino amine) (HPAA) as the surface passivation agent through a facile hydrothermal approach. The C-Dots with an average diameter about 10 nm were readily dispersed in water. They exhibited excellent fluorescence properties and excitation-dependent fluorescence behavior with the corresponding quantum yield (QY) of 17.1% in aqueous solution. Interestingly, the C-Dots emitted bright fluorescence even in the solid state with a QY of 16.3%, which is the highest value obtained for carbon-based nanomaterials. Using the MTT assay, the C-Dots showed low cytotoxicity against L929 normal cells. Furthermore, they were easily internalized by HeLa cells and presented high quality one- and two-photon cellular imaging, suggesting significant potential for application in biological imaging.

Physiochemical properties and bioapplication of nano- and microsized hydroxy zinc phosphate particles modulated by reaction temperature.

We investigated the effect of reaction temperature on the particle size and morphology of hydroxy zinc phosphate particles (HZnPPs). The influence of differences in shape on the physiochemical properties of HZnPPs and the possible bioapplications of these particles were also investigated. HZnPPs with both hollow and solid nanospheres and microsized rectangular sheet-like particles were successfully prepared by a wet chemical method using Zn (NO3)2·6H2O and (NH4)2HPO4 as the reactants and ammonia to adjust the pH. The synthesis was performed at temperatures ranging from 0 to 95 °C. The particle size, morphology, crystal structure and thermal properties were analysed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, the Brunauer-Emmett-Teller specific surface area, thermogravimetric analysis and dynamic light scatting. The chemical composition and vibrational spectra were measured using inductively coupled plasma atomic emission spectrometry, Fourier transform infrared spectrometry and Raman spectrometry. The transmission electron microscopy results showed that a hollow spherical structure with a pore size of 20-30 nm was obtained at reaction temperatures <25 °C. With increasing temperature, the nanoparticles changed from hollow to solid spheres of a similar size. Microsized rectangular sheet-like particles were formed when the reaction temperature was >60 °C. The effect of HZnPPs on cell viability in vitro was evaluated by the MTT assay against normal NIH/3T3 cells. The hollow and solid nanospheres had a lower cell cytotoxicity than the microsized sheet-like particles. Both the nanospheres and the rectangular sheet-like particles were able to adsorb heavy metal ions. The hollow nanospheres were also used as a carrier for a high drug-loading of epirubicin. These results clearly show that temperature plays an important part in regulating the nanoscale hierarchical structure of HZnPPs and their properties.