Wen-Fei Dong

Multifunctional superparamagnetic iron oxide nanoparticles: design, synthesis and biomedical photonic applications

Superparamagnetic iron oxide nanoparticles (SPIONs) have shown great promise in biomedical applications. In this review, we summarize the recent advances in the design and fabrication of core-shell and hetero-structured SPIONs and further outline some exciting developments and progresses of these multifunctional SPIONs for diagnosis, multimodality imaging, therapy, and biophotonics.

Dynamically tunable protein microlenses.

Proteins have been utilized in numerous photonic and optoelectronic devices, for example, in optical computation, organic light emitting diodes (OLEDs), waveguides, biomicro/nanolasers, organic field effect transistors (OFETs), and memory devices, because their unique optical, mechanical, electrical, and chemical properties are easily tailored to each application. The performance of as-prepared proteinbased photonic devices has been demonstrated to exceed that of devices that are made with currently available organic materials. The underlying motivation for the use of proteins in microdevices is not only abundance, inexpensiveness, and biodegradability, but also biocompatibility and the capacity to tune their properties through appropriate external stimuli. These features are highly desirable for biologically inspired microdevices, for example delicate miniaturized lenses that are similar to the “camera-type” eyes of human beings, the compound eyes of insects, the photosensitive microlens arrays of brittlestars, or the infrared-sensitive microlens receptor arrays of the fire beetle (Melanophila acuminata). Scientists have been highly motivated to fabricate these lens-like micro/nanostructures with the aim of producing small, multifunctional, artificial eyes by using dynamically adjustable and fully biocompatible proteins. However, the preparation of protein microlenses that have controlled geometry and precise positioning still poses a challenge. Herein, we report a promising approach for the production of biomimetic protein microlenses by facile and rapid maskless femtosecond laser direct writing (FsLDW). FsLDW is a well-known method for producing complicated 3D structures with nanometric resolution. Recently, pioneering work from Shear and co-workers demonstrated that protein hydrogel-based microstructures fabricated by FsLDWexhibit a unique responsiveness to chemical signals. This responsiveness could result in rapid and reversible changes in the size and shape of the structures after stimulation by environmental triggers. However, to our knowledge there are few reports on the development of practical and useful devices, such as a tunable microlens, that are made from this class of proteins. In this study, commercial bovine serum albumin (BSA, 300–500 mgmL 1 in aqueous solution) and a photosensitizer (methylene blue, MB, 0.6 mgmL ) were used to fabricate micro/nanoarchitectures. The cross-linking reaction is initiated through the excitation of photosensitive molecules to their triplet states. The photoexcited molecules then react directly with oxidizable moieties (type I process) or transfer the energy to ground state molecular oxygen (type II process) to form a reactive oxygen species, such as singlet oxygen (O2). In either case, excited-state intermediates catalyze the inter or intramolecular covalent cross-linking of oxidizable protein residues (see Scheme S1 in the Supporting Information). In other words, proteins with photooxidizable groups, such as Tyr, Trp, His, Met, and Cys, can absorb infrared or UV light to form reactive or ionized species that are capable of cross-linking with other oxidizable moieties. This mechanism appears to play a role in the formation of some types of cataracts and in the aging of skin. BSA and other proteins with oxidizable side chains “inherit” this photo-cross-linking ability, and can thus be used for multiphoton fabrication (Figure 1). Proof-of-concept protein microlenses were fabricated by using a FsLDW system of our own construction (Figure 1). The system was composed of a femtosecond titanium/ sapphire laser (Spectra Physics 3960-X1BB), a piezo stage with a precision of 1 nm (Physik Instrumente P-622.ZCD), and a set of two galvano mirrors. The 3D shapes of the microstructures were designed by using 3Ds Max and then the designs were converted into computer processing programs. Prior to the photo-cross-linking of the proteins at the focal spot, the beam from the femtosecond laser (80 MHz repetition rate, 120 fs pulse width, 780 nm central wavelength) was tightly focused by a high-numerical-aperture (NA= 1.35) oilimmersion objective lens (60 ). The horizontal and vertical scanning movements of the focused laser spot were achieved simultaneously by the two-galvano-mirror set and the piezo stage. After cross-linking, the sample was rinsed in water several times to remove unreacted proteins. Then the asformed protein microstructures were left on the chip. Surface topography (shape and roughness) plays an important role in the optical properties of protein microoptics. However, the surface roughness of BSA microstruc[*] Y. L. Sun, Prof. Dr. W. F. Dong, R. Z. Yang, X. Meng, L. Zhang, Prof. Dr. Q. D. Chen, Prof. Dr. H. B. Sun State Key Laboratory on Integrated Optoelectronics College of Electronic Science and Engineering Jilin University, 2699 Qianjin Street Changchun 130012 (China) E-mail: dongwf@jlu.edu.cn hbsun@jlu.edu.cn

A new Co(II)-metalloviologen-based electrochromic material integrated in thin multilayer films

A metallosupramolecular coordination polyelectrolyte prepared by the reaction of cobalt(II) with a novel bisterpyridine ligand has been assembled as the active component in electrochromic films by sequential deposition using electrostatic layer-by-layer self-assembly.

Enhanced Raman imaging and optical spectra of gold nanoparticle doped microcapsules

Gold nanoparticle doped hollow polyelectrolyte microcapsules (gold-doped capsules) were prepared by the layer-by-layer self-assembly method. After sequential adsorption of oppositely charged polyelectrolytes of poly(styrenesulfonate) sodium salt (PSS), poly(allylamine hydrochloride) (PAH) or gold nanoparticles onto melamine formaldehyde particles (MF), intact gold-doped capsules were obtained by dissolving the MF templates via low pH. The maximum absorbance peaks of gold-doped capsules shifted to long wavelengths with increasing filling factor of the gold nanoparticles in accordance with Maxwell–Garnet theory. Due to protection of the nanoparticle surfaces by the polyelectrolyte multilayer surroundings, stable optical properties of gold-doped capsules were observed in low pH solution or organic solvent. Gold nanoparticles in the multilayer enhance the Raman spectra of the polyelectrolyte multilayers, in contrast with the weak Raman signal, which was observed for normal capsules. High-resolution surface Raman imaging was performed by controlling the filling factor.

Microfluidic Electroporation-Facilitated Synthesis of Erythrocyte Membrane-Coated Magnetic Nanoparticles for Enhanced Imaging-Guided Cancer Therapy

Biomimetic cell membrane-coated nanoparticles (CM-NPs) with superior biochemical properties have been broadly utilized for various biomedical applications. Currently, researchers primarily focus on using ultrasonic treatment and mechanical extrusion to improve the synthesis of CM-NPs. In this work, we demonstrate that microfluidic electroporation can effectively facilitate the synthesis of CM-NPs. To test it, Fe3O4 magnetic nanoparticles (MNs) and red blood cell membrane-derived vesicles (RBC-vesicles) are infused into a microfluidic device. When the mixture of MNs and RBC-vesicles flow through the electroporation zone, the electric pulses can effectively promote the entry of MNs into RBC-vesicles. After that, the resulting RBC membrane-capped MNs (RBC-MNs) are collected from the chip and injected into experimental animals to test the in vivo performance. Owing to the superior magnetic and photothermal properties of the MN cores and the long blood circulation characteristic of the RBC membrane shells, core-shell RBC-MNs were used for enhanced tumor magnetic resonance imaging (MRI) and photothermal therapy (PTT). Due to the completer cell membrane coating, RBC-MNs prepared by microfluidic electroporation strategy exhibit significantly better treatment effect than the one fabricated by conventional extrusion. We believe the combination of microfluidic electroporation and CM-NPs provides an insight into the synthesis of bioinpired nanoparticles to improve cancer diagnosis and therapy.

Supramolecular assembly of water-soluble poly(ferrocenylsilanes): multilayer structures on flat interfaces and permeability of microcapsules

We report on the layer-by-layer (LBL) supramolecular assembly of redox responsive, organometallic polyion films on planar and curved (spherical) substrates. Organometallic poly(ferrocenylsilane) (PFS) polyanions and polycations were first used to assemble multilayers on planar quartz, silicon and quartz-crystal microbalance (QCM) electrodes. UV/Vis spectroscopy, spectroscopic ellipsometry and quartz-crystal microgravimetry showed a linear increase of UV absorbance, film thickness and frequency shift with increasing the number of deposited bilayers. Additional ellipsometric studies showed a square-root dependence of the film thickness on solution salt (NaCl) concentration. For the preparation of multilayer films on colloidal particles (manganese carbonate, MnCO), relatively high salt concentrations (0.5 M) were employed. PFS microcapsules were subsequently obtained by colloidal template removal using ethylenediaminetetraacetic acid (EDTA). Following the removal of the spherical template, hollow microcapsules were obtained, whose wall structure-permeability characteristics received particular attention. Atomic force microscopy (AFM) and confocal laser scanning microscopy (CLSM) were used to study the wall thickness, integrity and permeability of the capsules. Capsule-wall thickness obtained from AFM indicated the existence of a linear film growth regime when the number of adsorbed bilayers was larger than four. Capsules made of PFS polyanions and rhodamine-labelled PFS polycations were directly visualized by CLSM. Using tetramethylrhodamine isothiocyanate (TRITC)-labelled dextran (∼ 4 400 g mol) as probe, CLSM showed that capsules containing more than four PFS polycation-polyanion bilayers displayed good stability and integrity. These stable capsules are excellent candidates for the investigation of polyelectrolyte microcapsule permeability control triggered by redox stimuli.

Janus Silver-Mesoporous Silica Nanocarriers for SERS Traceable and pH-Sensitive Drug Delivery in Cancer Therapy.

A facile and cheap strategy was used to fabricate the novel Janus silver-mesoporous silica nanoparticles with excellent SPR and mesoporous properties for simultaneous SERS imaging and pH-responsive drug release, leading to the efficient cancer theranostic with less toxic effects.

Stable ZnO@TiO2 core/shell nanorod arrays with exposed high energy facets for self-cleaning coatings with anti-reflective properties

Nanostructured metal oxides such as ZnO and TiO2 have been extensively employed as self-cleaning coatings due to their large band gaps as well as their hydrophilic and photocatalytic properties. We have developed a simple hydrothermal method to coat thin TiO2 nanosheets with exposed (001) facets onto a ZnO nanorod array. The chemical stability of the ZnO nanorods was great improved due to the existence of the TiO2 layer. Owing to the porous structure of the ZnO@TiO2 nanorod arrays, this thin coating layer possesses anti-reflective properties. A transmittance improvement of ∼5% was observed for one-side coated FTO glass. This coating also exhibits good hydrophilic properties, after addition of the TiO2 nanosheets. More importantly, these ZnO@TiO2 nanorod arrays display excellent photocatalytic properties for the degradation of dye molecules, due to the heterojunction between the ZnO nanorods and TiO2 nanosheets. This heterojunction facilitates the charge separation of photo generated carriers. Based on the above features, the ZnO@TiO2 core/shell nanorod array film has many advantages as a self-cleaning coating.

High-performance magnetic antimicrobial Janus nanorods decorated with Ag nanoparticles

Silver nanoparticle-decorated magnetic-silica Janus nanorods, synthesized by an environmentally friendly in situ approach, show superior magnetic sensitivity, strong affinity binding to bacteria, and highly effective and long-term antimicrobial activity against bacteria. Such antibacterial nanomaterials could have great potential in biomedical applications due to their excellent biocompatibility and non-hemolytic property.

Magnetic colloidosomes fabricated by Fe3O4–SiO2 hetero-nanorods

Magnetic colloidosomes were fabricated by directing self-assembly of magnetic-mesoporous hetero-nanorods at the interface of water-in-oil droplets. Emulsions stabilized by the adsorbed particles without any surfactant indicate that such rod-like nanoparticles have specific advantages in making stable and intact shells than spherical particles. The integrity and emulsion stability of the colloidosomes were strongly influenced by the geometric shape of the hetero-nanorods. The optimum length of the nanorods to construct the colloidosomes was studied and demonstrated. The as-formed magnetic colloidosomes can exhibit unique encapsulation behaviors and show strong magnetic response properties, which will find huge potential application in multicompartment reactor, drug delivery and other biomedical fields.