Jianfei Sun

A Novel Magnetic Hydrogel with Aligned Magnetic Colloidal Assemblies Showing Controllable Enhancement of Magnetothermal Effect in the Presence of Alternating Magnetic Field

A novel magnetic hydrogel is formed via the field-directed assembly of magnetic nanomaterials during the gelation process. The novel magnetic hydrogel exhibits direction-dependent thermogenesis in an alternating magnetic field. The specific absorption rate value in the direction along the assemblies can be 2.1-fold as much as that in the direction normal to the assemblies while the heating rate is 6-8-fold. Due to the anisotropic thermogenesis, the novel magnetic hydrogel also shows a direction-dependent release of drugs that has a 3.4-fold difference between the two directions.

Controllable Preparation of Core–Shell Au–Ag Nanoshuttles with Improved Refractive Index Sensitivity and SERS Activity

Recent studies have conclusively shown that the plasmonic performance of Au nanostructures can be enhanced by incorporating Ag. Here, we developed a simple and robust approach for preparing core-shell Au-Ag nanoshuttles (NSs) using single-crystal Au nanorods (NRs) as cores. Upon tailoring the temperature of the reaction system containing alkaline glycine buffer (pH 8.5), exceptionally monodisperse Au-Ag NSs with sharp tips and tunable shell thickness could be routinely achieved in high yield through an epitaxial growth process. In particular, high-resolution transmission electron microscopy and nitric acid corrosive experiments revealed that the shells of these NSs consisted of a homogeneous Au-Ag alloy, rather than pure Ag or Au as previously reported. It was found that glycine played an important role in determining the final metal contents of the shell by regulating the reduction kinetics. In addition, the obatined Au-Ag NSs with sharp tips were shown to have significantly improved refractive index sensitivity and surface-enhanced Raman scattering activity relative to the original Au NRs, making these materials promising for biomedical applications, such as biosensing and biolabeling.

Bubble Microreactors Triggered by an Alternating Magnetic Field as Diagnostic and Therapeutic Delivery Devices

Advances in the medical treatment of a wide variety of pathophysiological conditions require the development of better therapeutic agents, as well as a combination of the required therapeutic agentswith diagnostic-integrated devices. With the development of microand nanotechnologies, the better intelligentmedical systems and devices have profoundly impacted medical theranostic techniques. Based on multifunctional device platforms, the interests of these studies mainly focusonmultimodal imagingand simultaneous therapy, which provide patients with imaging (ultrasound, computed tomography, magnetic resonance imaging (MRI), etc.) and effective therapeutic agents responding directly at the disease sites. In recent years, microand nanoscale intelligent systems have become a desirable method to maximize the efficacy of therapeutic treatments in numerous ways, because they can release their contents in a ‘‘smart or intelligent’’ way by responding to external triggers or biomarkers. Thesedelivery vehicles include polymeric micelles, gels, liposomes, small colloidal particles, and nanoengineered polymeric or polyelec-

Magnetic assembly-mediated enhancement of differentiation of mouse bone marrow cells cultured on magnetic colloidal assemblies.

Here we reported an interesting phenomenon that the field-induced assemblies of magnetic nanoparticles can promote the differentiation of primary mouse bone marrow cells into osteoblasts. The reason was thought to lie in the remnant magnetic interaction inside the assemblies which resulted from the magnetic field-directed assembly. Influence of the assemblies on the cells was realized by means of interface effect rather than the internalization effect. We fabricated a stripe-like assemblies array on the glass plate and cultured cells on this surface. We characterized the morphology of assemblies and measured the mechanic property as well as the magnetic property. The cellular differentiation was measured by staining and quantitative PCR. Finally, Fe uptake was excluded as the reason to cause the phenomenon.

Quasi-One-Dimensional Assembly of Magnetic Nanoparticles Induced by a 50 Hz Alternating Magnetic Field

The control of assembly from building blocks into ordered structures is a promising and interesting issue in nanoscience and nanotechnology. Recently, we reported that alternating magnetic field of tens of kHz can induce the fibrous assembly of magnetic nanoparticles and the formation of discrete particulate monolayers of non-magnetic nanoparticles. However, in daily life, there is another important alternating magnetic field, namely power–frequency alternating magnetic fields. This is because the human body is exposed to this field at all times (consider power lines and electric appliances). Therefore, the study of colloidal behavior under such a field is vital to the biomedical applications of magnetic nanoparticles. Moreover, the investigation of assembly under low-frequency alternating fields also plays a role in the study of frequency responses of nanoparticle assembly, which is vital to understanding the mechanism. According to the Maxwell–Faraday equation [Eq. (1)]:

Sliced Magnetic Polyacrylamide Hydrogel with Cell-Adhesive Microarray Interface: A Novel Multicellular Spheroid Culturing Platform

Cell-adhesive properties are of great significance to materials serving as extracellular matrix mimics. Appropriate cell-adhesive property of material interface can balance the cell-matrix interaction and cell-cell interaction and can promote cells to form 3D structures. Herein, a novel magnetic polyacrylamide (PAM) hydrogel fabricated via combining magnetostatic field induced magnetic nanoparticles assembly and hydrogel gelation was applied as a multicellular spheroids culturing platform. When cultured on the cell-adhesive microarray interface of sliced magnetic hydrogel, normal and tumor cells from different cell lines could rapidly form multicellular spheroids spontaneously. Furthermore, cells which could only form loose cell aggregates in a classic 3D cell culture model (such as hanging drop system) were able to be promoted to form multicellular spheroids on this platform. In the light of its simplicity in fabricating as well as its effectiveness in promoting formation of multicellular spheroids which was considered as a prevailing tool in the study of the microenvironmental regulation of tumor cell physiology and therapeutic problems, this composite material holds promise in anticancer drugs or hyperthermia therapy evaluation in vitro in the future.

Fabrication of Hydrogel with Cell Adhesive Micropatterns for Mimicking the Oriented Tumor-Associated Extracellular Matrix

For mimicking the fibrous extracellular matrix (ECM), a facile method for patterning anticell adhesive substrate was novelly applied on agarose hydrogel. Without using masks or templates for etching, we applied the magnetic field-induced colloidal assembly of magnetic nanoparticles on the flat agarose hydrogel to form cell-adhesive micropatterns. Meanwhile, tuning the hydrogel substrates modulus to fit real tissue was experimentally demonstrated. Magnetic nanobeads were also assembled on this hydrogel surface and formed more complete and regular patterns. The patterned hydrogel substrate could actually influence behaviors of different cancer cells, including adhesion, growth, and migration.

Assembly-Induced Thermogenesis of Gold Nanoparticles in the Presence of Alternating Magnetic Field for Controllable Drug Release of Hydrogel

Films of gold nanoparticles are easily fabricated by layer-by-layer assembly. With increasing number of layers a transition of the electric property from insulating to conducting can be achieved. This conductivity leads to controllable thermogenesis of the film, which can be employed for drug release of loaded hydrogels.

Growth enhancing effect of LBL-assembled magnetic nanoparticles on primary bone marrow cells

Magnetic field has been considered to have positive effect on growth of bone. Because amagnetic nanoparticle can be regarded as one magnetic dipole, the macroscopic assemblies of magnetic nanoparticles may exhibit magnetic effect on local objects. This paper fabricated macroscopic film of γ-Fe2O3 nanoparticles by layer-by-layer (LBL) assembly on poly-D,L-lactic acid (PLA) scaffold, and studied the magnetic effect of the assembled γ-Fe2O3 nanoparticles film on primary bone marrow cells. The primary bone marrow cells were extracted from a mouse and cultured on the PLA substrate decorated by the film of γ-Fe2O3 nanoparticles after purification. Quantitative PCR (q-PCR) was used to show the cellular effect quantitatively. A just-found magnetosensing protein was employed to verify the magnetic effect of assembled film of nanoparticles on primary cells. It was exhibited that the decoration of nanoparticles enhanced themechanical property of the interface. By acting as the adhesion sites, the LBL-assembled film of nanoparticles seemed beneficial to the cellular growth and differentiation. The expression of magnetosensing protein indicated that there was magnetic effect on the cells which resulted from the assembly of magnetic nanoparticles, implying its potential as a promising interface on scaffold which can integrate the physical effect with good biocompatibility to enhance the growth and differentiation of stem cells. The LBL-assembled film of magnetic nanoparticles may boost the development of novel scaffold which can introduce the physical stimulus into local tissue in vivo.摘要磁场一直以来都被认为对骨生长具有促进作用. 磁性纳米颗粒可以被看作是一个磁偶极子, 因此宏观的磁性纳米颗粒组装膜也可 能对附近的物体具有磁效应. 本文通过层层自组装方法在聚乳酸支架表面制备了宏观γ-Fe2O3纳米颗粒组装膜, 研究了γ-Fe2O3纳米颗粒组 装膜对原代小鼠骨髓细胞的磁作用. 原代小鼠骨髓细胞从小鼠体内新鲜提取, 并在前述生物材料表面培养. 定量PCR用来定量表征细胞效 应, 磁场的影响通过检测一种刚刚发现的磁感应蛋白来指示. 结果表明, 表面纳米颗粒组装可以显著增强聚合物支架的力学性质, 促进细 胞生长和分化. 磁感应蛋白检测结果表明这是由于磁性纳米颗粒组装导致的磁效应引起的. 本文用磁感应蛋白证明了磁性纳米颗粒层层 自组装膜可以通过对细胞的磁效应促进干细胞的生长和分化, 该磁性纳米颗粒组装膜将会促进新一代组织工程支架的研发, 有可能将物 理刺激效应引入到体内局部组织修复中.

A high precision apparatus for intracellular thermal response at single-cell level

In this work, a nanoprobe that is highly thermo-sensitive to tiny temperature changes was prepared based on a thermocouple metal junction. A series of electro-element apparatuses were integrated to accomplish single-cell temperature measurement. The temperature measurement probe (TMP) was constructed by tungsten (W), polyurethane (PU), and platinum (Pt). The tip size of TMP was characterized at less than 500 nm, and the tip angle was between 10 and 20° with the resistance in the range of 500 to 1500 Ω. The single-cell temperature measurement probes were calibrated and calculated with a Seebeck coefficient ranging from 6 to 8 μV °C(-1) at a precision of 0.1 °C. Monitoring the temperature at a single-cell level by inserting the TMP in marine lung epithelia (MLE)-12 cells displayed that the stimulation of lipopolysaccharide (LPS) and cobalt chloride induced different single-cell temperature fluctuation. This investigation could help reveal complex cellular functions and develop novel diagnoses.