Weiwei He

Protein modified upconversion nanoparticles for imaging-guided combined photothermal and photodynamic therapy.

In this work, we develop a multifunctional nano-platform by coating upconversion nanoparticles (UCNPs) with bovine serum albumin (BSA), obtaining UCNP@BSA nanoparticles with great solubility and stability in physiological environments. Two types of dye molecules, including a photosensitizer, Rose Bengal (RB), and an NIR-absorbing dye, IR825, can be simultaneously loaded into the BSA layer of the UCNP@BSA nanoparticles. In this carefully designed UCNP@BSA-RB&; IR825 system, RB absorbs green light emitted from UCNPs under 980-nm excitation to induce photodynamic cancer cell killing, while IR825 whose absorbance shows no overlap with upconversion excitation and emission wavelengths, offers nanoparticles a strong photothermal perform under 808-nm laser irradiation. Without showing noticeable dark toxicity, the obtained dual-dye loaded nanoparticles are able to kill cancer via combined photothermal and photodynamic therapies, both of which are induced by NIR light with high tissue penetration, by a synergetic manner both in vitro and in vivo. In addition, the intrinsic paramagnetic and optical properties of Gd(3+)-doped UCNPs can further be utilized for in vivo dual modal imaging. Our study suggests that UCNPs with well-designed surface engineering could serve as a multifunctional nano-platform promising in cancer theranostics.

Atom transfer radical polymerization of hydrophilic monomers and its applications

Atom transfer radical polymerization (ATRP) has become one of the most widely used living radical polymerization techniques for preparation of polymers with pre-designed compositions, topologies and functionalities. Hydrophilic (co)polymers are broadly used in various fields, such as hybrid materials, surface modification and delivery carriers in biomedical areas because of their diverse functionalities and ideal characters, including their non-toxicity, biocompatibility and environmentally friendly nature. Polymerization of hydrophilic monomers by ATRP provides polymers with more colorful structures, as well as novel properties and extends the application scope of hydrophilic polymers due to its facile operation and commercially available catalysts, ligands and initiators of the methodology. This review focuses on ATRP of hydrophilic monomers, as well as its application as detailed in five aspects: (1) basic understanding of the ATRP mechanism and polymerization kinetics of hydrophilic monomers; (2) polymerization media for hydrophilic monomers; (3) topologies of polymers based on hydrophilic monomers; (4) polymerization by combination of ATRP with other techniques, and (5) applications of polymerization of hydrophilic monomers.

Facile Iron-Mediated AGET ATRP for Water-Soluble Poly(ethylene glycol) Monomethyl Ether Methacrylate in Water

An environmentally friendly iron catalyst system was successfully developed in water for the AGET ATRP (activator generated by electron transfer for atom transfer radical polymerization) of water-soluble monomer poly(ethylene glycol) monomethyl ether methacrylate (PEGMA) for the first time. A kinetic study indicated that the polymerization was a living/controlled process in which molecular weight increased linearly with monomer conversion. A lower molecular weight distribution (M(w)/M(n) < 1.5) was maintained. The nontoxic and biocompatible characteristics of the iron catalyst facilitate its mediated polymerization to be used in the preparation of functional polymer materials for biomedical use.

A versatile Fe3O4 based platform via iron-catalyzed AGET ATRP: towards various multifunctional nanomaterials

In this work, iron-catalyzed atom transfer radical polymerization with activators generated by electron transfer (AGET ATRP) of poly(ethylene glycol) monomethyl ether methacrylate (PEGMA) and 2-((ethoxycarbonothioyl)thio)ethyl methacrylate (ETCEMA) followed by reduction were performed to modify Fe3O4@SiO2 nanoparticles (NPs) for introducing thiol groups on the surface of the NPs. Gold NPs and two near infra-red (NIR) organic dyes with different quantum yields were covalently fixed into the polymer shells independently to afford magnetic NPs with surface-enhanced Raman spectroscopy (SERS), NIR fluorescence imaging and photo-thermal therapy (PTT) functionalities, respectively. In addition, all of these NPs are able to display as contrast agents for magnetic resonance imaging (MRI) because of the existence of the paramagnetic Fe3O4 cores.

Facile Fabrication of Biocompatible and Tunable Multifunctional Nanomaterials via Iron-Mediated Atom Transfer Radical Polymerization with Activators Generated by Electron Transfer

A novel strategy of preparing multifunctional nanoparticles (NPs) with near infra red (NIR) fluorescence and magnetism showing good hydrophilicity and low toxicity was developed via surface-initiated atom transfer radical polymerization with activators generated by electron transfer (AGET ATRP) of poly(ethylene glycol) monomethyl ether methacrylate (PEGMA) and glycidyl methacrylate (GMA) employing biocompatible iron as the catalyst on the surface of silica coated iron oxide (Fe3O4@SiO2) NPs. The small molecules (CS2), a NIR fluorescent chromophore, can be fixed into the covalently grafted polymer shell of the NPs by chemical reaction through a covalent bond to obtain stable CS2 dotted NPs Fe3O4@SiO2@PPEGMA-co-PGMA@CS2. The fluorescence intensity of the as-prepared NPs could be conveniently regulated by altering the silica shell thickness (varying the feed of silica source TEOS), CS2 feed, or the feed ratio of VPEGMA/VGMA, which are easily realized in the preparation process. Thorough investigation of the properties of the final NPs including in vivo dual modal imaging indicate that such NPs are one of the competitive candidates as imaging agents proving a promising potential in the biomedical area.

Retracted article: Hydrophilic hybrid materials with magnetism & NIR fluorescence via surface-initiated RAFT polymerization

In the current work, one monomer (denoted as MHB) capable of emitting near infrared (NIR) fluorescence under UV light excitation is prepared and employed to perform (co)polymerization with a commercial hydrophilic and biocompatible monomer, poly(ethylene glycol) monomethyl ether methacrylate (PEGMA), on the surface of silica coated iron oxide nanoparticles (NPs). PEGMA is used to either copolymerize or chain-extend MHB after polymerization to improve the hydrophilicity of the NPs which is essential for practical application in bio-related areas. The as-prepared NPs in different surface modification steps were investigated by Fourier transfer infrared (FT-IR), thermogravimetric analysis (TGA), transmission electron microscope (TEM) and UV-vis spectroscopic techniques. The crystal form of the NPs was checked by powder X-ray diffraction (XRD) and it showed that the magnetic core is made up of ferroferric oxide. The magnetic properties of the NPs were measured by vibrating-sample magnetometer (VSM) and all NPs exhibited superparamagnetism. The final NPs possessing magnetic and NIR fluorescent properties have potential applications in biological areas as dual-model imaging agents, and their application as contrast agents for magnetic resonance imaging (MRI) is investigated.