Colloidal Polymer-Templated Formation of Inorganic Nanocrystals and their Emerging Applications.

Inorganic nanocrystals possess unique physicochemical properties compared to their bulk counterparts. Stabilizing agents are commonly used for the preparation of inorganic nanocrystals with controllable properties. Particularly, colloidal polymers have emerged as general and robust templates for in situ formation and confinement of inorganic nanocrystals. In addition to templating and stabilizing inorganic nanocrystals, colloidal polymers can tailor their physicochemical properties such as size, shape, structure, composition, surface chemistry, and so on. By incorporating functional groups into colloidal polymers, desired functions can be integrated with inorganic nanocrystals, advancing their potential applications. Here, recent advances in the colloidal polymer-templated formation of inorganic nanocrystals are reviewed. Seven types of colloidal polymers, including dendrimer, polymer micelle, stare-like block polymer, bottlebrush polymer, spherical polyelectrolyte brush, microgel, and single-chain nanoparticle, have been extensively applied for the synthesis of inorganic nanocrystals. Different strategies for the development of these colloidal polymer-templated inorganic nanocrystals are summarized. Then, their emerging applications in the fields of catalysis, biomedicine, solar cells, sensing, light-emitting diodes, and lithium-ion batteries are highlighted. Last, the remaining issues and future directions are discussed. This review will stimulate the development and application of colloidal polymer-templated inorganic nanocrystals.

Engineering the Hydrophobic Microenvironment in Polystyrene-Supported Artificial Catalytic Triad Nanocatalysts: An Effective Strategy for Improving Catalytic Performance.

Hydrophobic environments have been identified as one of the main parameters affecting the catalytic performance of artificial catalytic triads but are often ignored as an approach to engineering these catalysts. Here, we have developed a simple yet powerful strategy to engineer the hydrophobic environment in polystyrene-supported artificial catalytic triad (PSACT) nanocatalysts. Hydrophobic copolymers containing either oligo(ethylene glycol) side chains or hydrocarbon side chains were synthesized and used for the preparation of nanocatalysts through nanoprecipitation in aqueous media. By using the hydrolysis of 4-nitrophenyl acetate (4NA) as a model reaction, we studied the influence of chemical structures and effective constituent ratios of hydrophobic copolymers on the catalytic performance of PSACT nanocatalysts. Additionally, PSACT nanocatalysts could catalyze the hydrolysis of a few carboxylic esters, even polymers, and be reused for five consecutive runs without significant loss of catalytic activity. This strategy may open an avenue for engineering other artificial enzymes, and these PSACT nanocatalysts have potential applications for the hydrolysis of carboxylic esters.

Wide-Field and Real-Time Super-Resolution Optical Imaging By Titanium Dioxide Nanoparticle-Assembled Solid Immersion Lens.

Super-resolution optical imaging techniques can break the optical diffraction limit, thus providing unique opportunities to visualize the microscopic world at the nanoscale. Although near-field optical microscopy techniques have been proven to achieve significantly improved imaging resolution, most near-field approaches still suffer from a narrow field of view (FOV) or difficulty in obtaining wide-field images in real time, which may limit their widespread and diverse applications. Here, the authors experimentally demonstrate an optical microscope magnification and image enhancement approach by using a submillimeter-sized solid immersion lens (SIL) assembled by densely-packed 15 nm TiO2 nanoparticles through a silicone oil two-step dehydration method. This TiO2 nanoparticle-assembled SIL can achieve both high transparency and high refractive index, as well as sufficient mechanical strength and easy-to-handle size, thus providing a fast, wide-field, real-time, non-destructive, and low-cost solution for improving the quality of optical microscopic observation of a variety of samples, including nanomaterials, cancer cells, and living cells or bacteria under conventional optical microscopes. This study provides an attractive alternative to simplify the fabrication and applications of high-performance SILs.

Recent advances in mixing-induced nanoprecipitation: from creating complex nanostructures to emerging applications beyond biomedicine.

Mixing-induced nanoprecipitation (MINP) is an efficient, controllable, scalable, versatile, and cost-effective technique for the preparation of nanoparticles. In addition to the formulation of drugs, MINP has attracted tremendous interest in other fields. In this review, we highlight recent advances in the preparation of nanoparticles with complex nanostructures via MINP and their emerging applications beyond biomedicine. First, the mechanisms of nanoprecipitation and four mixing approaches for MINP are briefly discussed. Next, three strategies for the preparation of nanoparticles with complex nanostructures including sequential nanoprecipitation, controlling phase separation, and incorporating inorganic nanoparticles, are summarized. Then, emerging applications including the engineering of catalytic nanomaterials, environmentally friendly photovoltaic inks, colloidal surfactants for the preparation of Pickering emulsions, and green templates for the synthesis of nanomaterials, are reviewed. Furthermore, we discuss the structure-function relationships to gain more insight into design principles for the development of functional nanoparticles via MINP. Finally, the remaining issues and future applications are discussed. This review will stimulate the development of nanoparticles with complex nanostructures and their broader applications beyond biomedicine.

Protein-supported transition metal catalysts: Preparation, catalytic applications, and prospects.

The immobilization of transition metal catalysts onto supports enables their easier recycling and improves catalytic performance. Protein supports not only support and stabilize transition metal catalysts but also enable the incorporation of biocompatibility and enzymatic catalysis into these catalysts. Consequently, the engineering of protein-supported transition metal catalysts (PTMCs) has emerged as an effective approach to improving their catalytic performance and widening their catalytic applications. Here, we review the recent development of the preparation and applications of PTMCs. The preparation of PTMCs will be summarized and discussed in terms of the types of protein supports, including proteins, protein assemblies, protein-polymer conjugates, and cross-linked proteins. Then, their catalytic applications including organic synthesis, photocatalysis, polymerization, and biomedicine, will be surveyed and compared. Meanwhile, the established catalytic structures-function relationships will be summarized. Lastly, the remaining issues and prospects will be discussed. By surveying a wide range of PTMCs, we believe that this review will attract a broad readership and stimulate the development of PTMCs.

Cooperative catalysis of Cu/2,2,6,6-tetramethyl-1-piperidine-N-oxyl nanocatalysts supported by ultraviolet light-responsive polyimides.

The development of ultraviolet (UV) light-regulated cooperative catalysts has attracted wide attention and increased the understanding of structure-activity relationships. Here, we have used azobenzene-containing polyimides as supports for the controllable synthesis of Cu/2,2,6,6-tetramethyl-1-piperidine-N-oxyl (TEMPO) nanocatalysts. Of these nanocatalysts, the catalytic components bearing a pyrene moiety were immobilized onto polyimides containing azobenzene and naphthalene diimide (NDI) moieties via aromatic stacking interactions and hydrophobic interactions in nanoprecipitation. Aromatic stacking clusters were formed and randomly distributed inside nanocatalysts, bringing catalytic components in close proximity for cooperative catalysis. The size of aromatic stacking clusters might be regulated by the UV light-responsive azobenzene units of polyimides. This strategy may find applications in the design and engineering of other multifunctional heterogeneous catalysts with controllable UV light-responsive behaviors.

Polyimide-supported Cu/2,2,6,6-tetramethyl-1-piperidine-N-oxyl catalytic systems: Aromatic donor-acceptor interaction-directed cooperative catalysis.

Non-covalent immobilization of multifunctional catalysts onto polymer supports is a promising technique to build highly efficient heterogeneous cooperative catalysts. Here, we present a strategy to build polyimide-supported Cu/2,2,6,6-tetramethyl-1-piperidine-N-oxyl (TEMPO) catalytic systems based on hydrophobic interactions and aromatic donor-acceptor interactions. Pyrene-containing catalytic species and naphthalene diimide (NDI)-based polyimides were chosen for the preparation of nanoparticle catalysts using the nanoprecipitation technique. The cooperative behaviors of catalytic components were evaluated by the catalytic activities of aerobic oxidation of benzyl alcohol (BnOH) in water. We studied the influence of effective constituent ratio of polymers, chain length of monomer, and the incorporation of a second monomer on catalytic activities. The aggregate structures were investigated by X-ray powder diffraction (XRD) patterns and small angle X-ray scattering (SAXS), and speculated to be random distributions of aromatic stacking clusters within nanoparticle catalysts. This strategy will find applications in the construction of other multifunctional heterogeneous catalysts.

Synthesis of Monodisperse ZIF-67@CuSe@PVP Nanoparticles for pH-Responsive Drug Release and Photothermal Therapy.

In recent years, the combination treatment of chemotherapy and photothermal therapy (PTT) has emerged as an efficient approach to improve anticancer activity. Here, we combine zeolitic imidazolate framework-67 (ZIF-67) and CuSe to build a multifunctional therapeutic platform (ZIF-67@CuSe@PVP) with an efficient chemo-photothermal therapy for cancer treatment. ZIF-67@CuSe@PVP nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), dynamic light scattering (DLS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis, Fourier transform infrared (FT-IR), and nitrogen adsorption-desorption isotherms. These nanoparticles exhibited excellent pH-responsive doxorubicin hydrochloride (DOX) releases due to the decomposition of ZIF-67 and excellent photothermal conversion efficiency (36%) without apparent deterioration during three cycles. In vivo biodistribution evaluation revealed the passive tumor-targeting ability of ZIF-67@CuSe@PVP@DOX via the enhanced permeability and retention (EPR) effect. Both in vitro and in vivo data demonstrated excellent anticancer efficacy of ZIF-67@CuSe@PVP in tumor-bearing mice. This multifunctional therapeutic platform could have certain clinical application potential.

Multifunctional phototheranostic nanoplatform based on polydopamine-manganese dioxide-IR780 iodide for effective magnetic resonance imaging-guided synergistic photodynamic/photothermal therapy.

Multifunctional phototheranostics combining diagnostic and therapeutic modalities may provide a revolutionary opportunity for cancer treatment. As a promising tumor phototheranostic molecule, IR780 iodide (IR780) shows excellent photodynamic and photothermal performance under near-infrared laser irradiation; however, its hydrophobicity and instability limit its further use in organisms. This work demonstrates the design and development of a multifunctional nanoplatform (PMIDA, referring to polydopamine (PDA)-manganese dioxide (MnO2)-IR780) for imaging-guided phototherapy. The good biocompatibility of PDA greatly improves the water solubility and photostability of IR780, and its excellent photothermal properties make PMIDA a dual photothermal therapy (PTT). MnO2-induced generation of oxygen in the tumor microenvironment improves the hypoxia effect and photodynamic therapy (PDT) of IR780. Moreover, Mn2+ serves as a decent T1-weighted magnetic resonance imaging (MRI) probe to guide treatment. Notably, in relevant cellular assays, PMIDA shows high photodynamic and photothermal effects contributing to the final therapeutic effect. The MRI-guided PDT/PTT synergistic therapy effect in vivo is demonstrated by precise tumor diagnosis and complete tumor elimination outcomes. Based on these experiments, PMIDA nanoparticles display promising effects in facilitating intravenous injection of IR780 and achieving magnetic resonance imaging (MRI)-guided phototheranostic efficacy for tumor treatment.

Highly Luminescent Copper Nanoclusters Stabilized by Ascorbic Acid for the Quantitative Detection of 4-Aminoazobenzene.

As one of the widely studied metal nanoclusters, the preparation of copper nanoclusters (Cu NCs) by a facile method with high fluorescence performance has been the interest of researchers. In this paper, a simple, green, clean, and time-saving chemical etching method was used to synthesize water-soluble Cu NCs using ascorbic acid (AA) as the reducing agent. The as-prepared Cu NCs showed strong green fluorescence (with a quantum yield as high as 33.6%) and high ion stability, and good antioxidant activity as well. The resultant Cu NCs were used for the detection of 4-aminoazobenzene (one of 24 kinds of prohibited textile compounds) in water with a minimum detection limit of 1.44 µM, which has good potential for fabric safety monitoring.

Polydopamine-mediated bio-inspired synthesis of copper sulfide nanoparticles for T1-weighted magnetic resonance imaging guided photothermal cancer therapy.

Copper sulfide nanoparticles(CuS NPs) have attracted considerable interest in the field of photothermal therapy(PTT) due to its low cost, easy preparation and favorable photothermal effect. However, lack of reliable visualization and relatively poor biocompatibility restrict its further bio-application. To overcome these limitations, polydopamine(PDA, a melanin-like biopolymer) stabilized CuS NPs and further chelated with iron ions (denoted as CuPDF) were designed as a versatile nanoplatform for T1-weighted MR imaging-guided PTT. In this system, PDA served as both bio-template to synthesis CuS NPs and an active platform to give MRI diagnostic capability. The as-prepared CuPDF NPs demonstrated strong absorption at NIR region, nearly three times higher than that of pure PDA NPs at 808 nm. Moreover, toxicity studies and histology evalution verified that CuPDF NPs possess excellent biocompatibility. In addition, CuPDF NPs showed significant MRI signal enhancement with high longitudinal relaxivity (r1 = 4.59 mM-1 s-1). In vivo MRI and biodistribution test confirmed the efficient accumulation of CuPDF NPs in the tumor region. After intravenous injection of CuPDF, irreversible tumor ablation was successfully achieved without inducing any obvious side effects by using 808-nm laser irradiation. All in all, these results indicated that the developed CuPDF NPs hold great potential as an effective theranostic agent for MR imaging guided PTT in vivo.

Synthesis of platinum nanoparticles templated by dendrimers terminated with alkyl chains.

We devised a new approach to synthesize platinum nanoparticles (PtNPs) templated by dendrimers terminated with alkyl chains. Such PtNPs were monodisperse and stable in solution for a couple of weeks without any obvious sediment. The use of hydrogen as a reducing agent was crucial for their successful preparation, likely causing a relatively low concentration of Pt0 atoms that facilitated the nucleation and growth of PtNPs within dendrimers. This approach extended the size range of PtNPs encapsulated within dendrimers and enabled the synthesis of PtNPs with sizes approaching those of dendrimers.

One-pot synthesis of albumin-gadolinium stabilized polypyrrole nanotheranostic agent for magnetic resonance imaging guided photothermal therapy.

Theranostic agents with perfect properties are needed urgently for the development of imaging guided photothermal therapy (PTT). In this work, Gd-integrated polypyrrole nanotheranostic agent (PPy@BSA-Gd) was successfully built through selecting bovine serum albumin (BSA) as both stabilizers for polymerization and biomimetic mineralization in "one pot". The obtained PPy@BSA-Gd possessed high stability and excellent photothermal property. Besides, relevant cellular assays indicated that PPy@BSA-Gd had fantastic cytocompatibility which could be further internalized by cancer cells. Due to their high longitudinal relaxivity value (r1 = 10.203 mM-1 s-1), PPy@BSA-Gd could serve as considerable probe for T1-weighted magnetic resonance imaging (MRI). After tail vein injection of PPy@BSA-Gd, the MR signal of tumor section exhibited a time-dependent increase, indicating effective tumor accumulation of PPy@BSA-Gd. Notably, when exposed to 808 nm laser, the tumor growth of PPy@BSA-Gd treated mice could be inhibited by photothermal ablation successfully. All the results demonstrated the well-designed PPy@BSA-Gd have the potential for tumor diagnose and photothermal therapy.

Albumin/sulfonamide stabilized iron porphyrin metal organic framework nanocomposites: targeting tumor hypoxia by carbonic anhydrase IX inhibition and T1-T2 dual mode MRI guided photodynamic/photothermal therapy.

Exploring a nanotheranostic agent with image guided highly efficient therapeutic properties is greatly significant for tumor screening and treatment. Herein, we construct a novel nanoplatform, composed of low cost bovine serum albumin (BSA), sulfonamides (SAs) and iron porphyrin nanoscale metal organic frameworks (NMOFs), which possesses the capability of active targeting to tumor cells and magnetic resonance imaging (MRI) can be used to guide synergetic photodynamic/photothermal therapy. These constructed BSA/SAs-NMOF nanoplatforms can be accumulated more at tumor sites due to modification of the nanoparticles with BSA/SA complexes, allowing this system to achieve long circulation in vivo and to actively target to carbonic anhydrase (CA) IX of tumor cells by the SAs. Moreover, the magnetic iron ion and porphyrin serve as the metal centre and organic ligand of novel NMOFs which exhibit a T1-T2 weighted MRI effect (r1 = 2.7 mM-1 s-1 and r2 = 19.68 mM-1 s-1) and allow synergetic photodynamic/photothermal therapy of tumors. In vitro reactive oxygen species (ROS) detection and photothermal temperature change results revealed that these BSA/SAs-NMOF nanoplatforms could exhibit a great PDT effect in tumor cells, even under hypoxic conditions, and a remarkable PTT effect with a photothermal conversion efficiency of 40.53%. What's more, there was a greater fatality rate of 4T1 cancer cells in the single wavelength induced PDT & PTT group (95%) than in the PDT or PTT monotherapy groups (nearly 80%), and the growth of a solid tumor was more effectively inhibited by PDT & PTT than by single PTT or PDT. This work provides a novel nanoplatform for targeting tumor hypoxia and achieved highly efficient treatment of tumors based on PDT and PTT.

Microwave-assisted preparation of paramagnetic zwitterionic amphiphilic copolymer hybrid molybdenum disulfide for T1-weighted magnetic resonance imaging-guided photothermal therapy.

Magnetic resonance imaging (MRI)-guided photothermal therapy (PTT) has recently attracted tremendous attention. In this study, a paramagnetic zwitterionic amphiphilic copolymer (PZAC) was successfully prepared and utilized as a multifunctional surfactant to form micelles in diethylene glycol to coordinate with a molybdenum disulfide precursor (MoS2). Uniform spherical MoS2 nanohybrids (MoS2@PZAC) were first prepared by a microwave-assisted solvothermal process, which is simpler, easier and more efficient than hydrothermal methods or exfoliation processes. In this nanoplatform, MoS2 serves as a phototherapeutic agent possessing a high photothermal conversion efficiency (33.8%), while PZAC acts as a T1-weighted MRI contrast agent. This nanoplatform has the advantages of ultralow toxicity, prolonged circulation time and bio-imaging guided capability. The cytotoxicity assessment showed the good cytocompatibility of MoS2@PZAC. Furthermore, MoS2@PZAC could effectively kill cancer cells upon 2 W cm-2 808 nm laser irradiation for 10 min in both in vitro and in vivo experiments. This work provides a novel and efficient solution to synthesize a multifunctional and uniform theranostic agent, and the results show that the as-prepared MoS2@PZAC can be used as a promising theranostic agent for T1-weighted MRI-guided PTT of cancer cells.

Magnetic, fluorescent, and thermo-responsive poly(MMA-NIPAM-Tb(AA)3Phen)/Fe3O4 multifunctional nanospheres prepared by emulsifier-free emulsion polymerization.

Magnetic, luminescent, and thermoresponsive multifunctional nanospheres composed of modified Fe3O4 nanoparticles as the core and rare earth complex Tb(AA)3Phen as the shell are synthesized by emulsifier-free emulsion polymerization. The core-shell spherical structure has a size between 140 and 220 nm and exhibits strong green fluorescence of the rare earth complex Tb(AA)3Phen. In the R2 relaxivity and in vivo MRI studies, the R2 relaxivity of the nanospheres is 562.56 mM(-1) s(-1) and enhanced T2-weighted images are observed from the nanospheres in the liver and spleen after injection as a contrast agent. The excellent superparamagnetic, thermosensitive, and fluorescent properties render the nanospheres useful in biomedical engineering and optical imaging.

Self-assembled magnetic fluorescent polymeric micelles for magnetic resonance and optical imaging.

Stable and cytocompatible hybrid PEGylated micelles with multimodal imaging capabilities are described. The F3O4-encapsulated polymeric micelles composed of cores containing magnetic nanoparticles and polyethylene glycol (PEG) shells are synthesized by self-assembly of amphiphilic poly(HFMA-co-VBK)-g-PEG copolymers and oleic acid stabilized Fe3O4 nanoparticles. The Fe3O4 magnetic nanoparticles in the core produce T2-weighted MR imaging functionalities, whereas the small fluorescent monomer carbazole in the polymer shell introduces good fluorescent properties. The multifunctional micelles exhibit excellent paramagnetic properties with the maximum saturation magnetization of 9.61 emu/g and transverse relaxivity rate of 157.44 mM(-1) S(-1). In vivo magnetic resonance imaging (MRI) studies reveal enhanced contrast between the liver and spleen. Fluorescence spectra show characteristic emission peaks from carbazole at 350 nm and 365 nm and vivid blue fluorescence can be observed by 2-photon confocal scanning laser microscopy (CLSM). In vivo optical imaging demonstrates the unique fluorescent characteristics of the Fe3O4-encapsulated polymeric micelles in the liver and spleen and the excellent multifunctional properties suggest potential clinical use as nanocarriers in magnetic resonance imaging and optical imaging.

Self-assembled magnetic luminescent hybrid micelles containing rare earth Eu for dual-modality MR and optical imaging.

In this study, we report new water-soluble multifunctional nanomaterials based on amphiphilic poly(HFMA-co-Eu(AA)3Phen)-g-PEG copolymers and oleic acid modified Fe3O4 nanoparticles. The nanoparticles can self-assemble to form magnetic and luminescent hybrid micelles and show a spherical morphology, paramagnetic properties with a maximum saturation magnetization of 7.05 emu g-1, and a high transverse relaxivity of 340 mM-1 s-1. According to in vivo magnetic resonance imaging (MRI) experiments, excellent contrast of the liver and spleen was achieved after injection of the hybrid micelles. Fluorescence spectra show characteristic emission peaks from the rare earth Eu at 616 nm and vivid red fluorescence can be observed by 2-photon confocal laser scanning microscopy (CLSM). In vivo optical imaging demonstrates the unique fluorescent characteristics of the magnetic and luminescent hybrid micelles in the liver and spleen and the excellent multifunctional properties suggest the possibility of clinical use as nanocarriers in magnetic resonance imaging and optical imaging.

Design and preparation of novel fluorescent polyimides containing ortho-linked units and pyridine moieties.

A novel pyridine-containing aromatic diamine monomer, 4-[4-hydroxyphenyl]-2,6-bis[4-(2-aminophenoxy)phenyl]pyridine (p,o-HAPP), was synthesized by a modified Chichibabin reaction of p-Hydroxybenzaldehyde and a substituted acetophenone, 4-(2-nitrophenoxy)acetophenone (p,o-NPAP), followed by a reduction of the resulting dinitro compound 4-[4-hydroxyphenyl]-2,6-bis[4-(2-nitrophenoxy)phenyl]pyridine with Pd/C and hydrazine monohydrate. The aromatic diamine was employed to prepare a series of pyridine-containing polyimides (PIs) by polycondensation with various aromatic dianhydrides in N,N-dimethylformamide (DMF) via the conventional two-step method. The inherent viscosities of the resulting poly(amic acids) and PIs were in range of 0.62-0.76 and 0.52-0.64 dL/g, respectively. The obtained novel PIs exhibited high solubility in common organic solvents, such as m-Cresol, DMF, N,N-dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone (NMP), tetrahydrofuran, and chloroform. Meanwhile, flexible PI films were obtained, which had excellent thermal stability, with the glass transition temperature (T g) of 259.8-323.4 °C and the temperature at 10% weight loss of 485.5-576.4 °C in nitrogen atmosphere. The protonated polymer showed UV-vis absorption in the region 200-400 nm and displayed strong fluorescence intensity (470 nm) in NMP solution.