2D Magnetic Microswimmers for Targeted Cell Transport and 3D Cell Culture Structure Construction.

Cell delivery using magnetic microswimmers is a promising tool for targeted therapy. However, it remains challenging to rapidly and uniformly manufacture cell-loaded microswimmers that can be assembled into cell-supporting structures at diseased sites. Here, rapid and uniform manufacturable 2D magnetic achiral microswimmers with pores were fabricated to deliver bone marrow mesenchymal stem cells (BMSCs) to regenerate articular-damaged cartilage. Under actuation with magnetic fields, the BMSC-loaded microswimmers take advantage of the achiral structure to exhibit rolling or swimming motions to travel on smooth and rough surfaces, up inclined planes, or in the bulk fluid. Cell viability, proliferation, and differentiation tests performed days after cell seeding verified the microswimmers' biocompatibility. Long-distance targeting and in situ assemblies into 3D cell-supporting structures with BMSC-loaded microswimmers were demonstrated using a knee model and U-shaped wells. Overall, combining the advantages of preparing an achiral 2D structured microswimmer with magnetically driven motility results in a platform for cell transport and constructing 3D cell cultures that can improve cell delivery at lesion sites for biomedical applications.

A rolled-up-based fabrication method of 3D helical microrobots.

While the potential of using helical microrobots for biomedical applications, such as cargo transport, drug delivery, and micromanipulation, had been demonstrated, the viability to use them for practical applications is hindered by the cost, speed, and repeatability of current fabrication techniques. Hence, this paper introduces a simple, low-cost, high-throughput manufacturing process for single nickel layer helical microrobots with consistent dimensions. Photolithography and electron-beam (e-beam) evaporation were used to fabricate 2D parallelogram patterns that were sequentially rolled up into helical microstructures through the swelling effect of a photoresist sacrificial layer. Helical parameters were controlled by adjusting the geometric parameters of parallelogram patterns. To validate the fabrication process and characterize the microrobots' mobility, we characterized the structures and surface morphology of the microrobots using a scanning electron microscope and tested their steerability using feedback control, respectively. Finally, we conducted a benchmark comparison to demonstrate that the fabrication method can produce helical microrobots with swimming properties comparable to previously reported microrobots.

High-performance and selective adsorption of ZIF-8/MIL-100 hybrids towards organic pollutants.

Environmental contamination by organic pollutants has become a pressing concern. In this study, metal-organic framework composites with a core-shell structure of MIL-100 wrapped around ZIF-8 (ZIF-MIL hybrids) were synthesized and characterized for their effectiveness to remove organic pollutants. First, a sequence of routine characterizations will examine the ZIF-MIL series samples' physicochemical properties and morphological characteristics. Then, the adsorption capacities of ZIF-MIL towards organic pollutants, including cationic dyes (methylene blue (MB), and rhodamine B (RHB)), anionic dyes (methyl orange (MO)), neutral pollutants (Sudan III (SD-III), tetracycline (TC) and amoxicillin (AMX)), were investigated. Among the ZIF-MIL series, ZIF-MIL-4 has an excellent specific surface area with high uptake of TC (1288 mg g-1) and RHB (1181 mg g-1). Based on the adsorption data from kinetic and dynamic studies, the adsorption process was closest to the pseudo-second-order kinetic model and Freundlich isotherm. In terms of thermodynamic parameter values, the adsorption of TC is an endothermic and spontaneous process, while the adsorption of RHB is an exothermic and spontaneous process. Furthermore, the reusability and selectivity studies of ZIF-MIL-4 towards TC and RHB exhibited significant regeneration ability and high selectivity. The effects of ionic strength and pH on pollutant removal efficiency were also tested. The experimental results showed that the main interactions between ZIF-MIL-4 and RHB or TC were weak coordination, electrostatic, hydrogen bonding, and π-π stacking interactions. Thus, the proposed MOF hybrid, by forming mixtures with other MOFs, can be a potential purifier with improved adsorption capacity and selectivity for organic pollutants as well as self-reusability.

Macrophage-compatible magnetic achiral nanorobots fabricated by electron beam lithography.

With the development and progress of nanotechnology, the prospect of using nanorobots to achieve targeted drug delivery is becoming possible. Although nanorobots can potentially improve nano-drug delivery systems, there remains a significant challenge to fabricating magnetically controllable nanorobots with a size suitable for drug delivery in complex in vivo environments. Most of the current research focused on the preparation and functionalization of microscale and milliscale robots due to the relative difficulties in fabricating nanoscale robots. To address this problem and move towards in vivo applications, this study uses electron beam lithography to fabricate achiral planar L-shaped nanorobots that are biocompatible with immune cells. Their minimal planar geometry enabled nanolithography to fabricate nanorobots with a minimum feature size down to 400 nm. Using an integrated imaging and control system, the locomotive behavior of the L-shaped nanorobots in a fluidic environment was studied by examining their velocity profiles and trajectories. Furthermore, the nanorobots exhibit excellent cell compatibility with various types of cells, including macrophage cells. Finally, the long-term cell culture medium immersion test demonstrated that the L-shaped nanorobots have robust stability. This work will demonstrate the potential to use these nanorobots to operate in vivo without triggering immune cell responses.

Magnetic bio-hybrid micro actuators.

Over the past two decades, there has been a growing body of work on wireless devices that can operate on the length scales of biological cells and even smaller. A class of these devices receiving increasing attention are referred to as bio-hybrid actuators: tools that integrate biological cells or subcellular parts with synthetic or inorganic components. These devices are commonly controlled through magnetic manipulation as magnetic fields and gradients can be generated with a high level of control. Recent work has demonstrated that magnetic bio-hybrid actuators can address common challenges in small scale fabrication, control, and localization. Additionally, it is becoming apparent that these magnetically driven bio-hybrid devices can display high efficiency and, in many cases, have the potential for self-repair and even self-replication. Combining these properties with magnetically driven forces and torques, which can be transmitted over significant distances, can be highly controlled, and are biologically safe, gives magnetic bio-hybrid actuators significant advantages over other classes of small scale actuators. In this review, we describe the theory and mechanisms required for magnetic actuation, classify bio-hybrid actuators by their diverse organic components, and discuss their current limitations. Insights into the future of coupling cells and cell-derived components with magnetic materials to fabricate multi-functional actuators are also provided.

Structural defects in 2D MoS2 nanosheets and their roles in the adsorption of airborne elemental mercury.

In this research, ab initio calculations and experimental approach were adopted to reveal the mechanism of Hg0 adsorption on MoS2 nanosheets that contain various types of defects. The ab initio calculation showed that, among different structural defects, S vacancies (Vs) in the MoS2 nanosheets exhibited outstanding potential to strongly adsorb Hg0. The MoS2 material was then prepared in a controlled manner under conditions, such as temperature, concentration of precursors, etc., that were determined by adopting the new method developed in this study. Characterisation confirmed that the MoS2 material is of graphene-like layered structure with abundant structural defects. The integrated dynamic and steady state (IDSS) testing demonstrated that the Vs-rich nanosheets showed excellent Hg0 adsorption capability. In addition, ab initial calculation on charge density difference, PDOS, and adsorption pathways revealed that the adsorption of Hg0 on the Vs-rich MoS2 surface is non-activated chemisorption.