Hyaluronic acid encapsulated silver metal organic framework for the construction of a slow-controlled bifunctional nanostructure: Antibacterial and anti-inflammatory in intrauterine adhesion repair.

Intrauterine adhesion (IUA) is a common gynecological disease caused by endometrial injury, which might result in abnormal menstruation, miscarriage, and even fetal deaths. Nevertheless, existing treatment strategies such as intrauterine device and uterine cavity balloons only provide a physical barrier, and not circumvent inflammation of endometrial microenvironment and retrograde infection. In this study, a slow-controlled bifunctional nanostructure was developed via encapsulating hyaluronic acid (HA) on surface of silver-metal organic framework (Ag-MOF), and then loaded in poly lactic-co-glycolic acid scaffold to prevent IUA. In therapy, macro-molecule of HA provided anti-inflammatory function by the adjustment of signal transduction pathways of macrophage surface receptors, whereas Ag-MOF inactivated bacteria by destroying bacterial membrane and producing reactive oxygen. Significantly, the coated HA effectively avoided burst release of Ag+, thus achieving long-term antibacterial property and good biocompatibility. Antibacterial results showed antibacterial rate of the scaffold reached 87.8 % against staphylococcus aureus. Anti-inflammatory assays showed that the scaffold inhibited the release of inflammatory cytokines and promoted the release of anti-inflammatory cytokines. Moreover, in vitro cell tests revealed that the scaffold effectively inhibited fibroblast growth, indicating its good ability to prevent IUA. Taken together, the scaffold may be a promising candidate for IUA treatment.

Highly Dispersed Cu Produced by Mechanical Stress-Activated Redox Reaction to Establish Galvanic Corrosion in Fe Implant.

Fe has immense potential for biodegradable orthopedic applications, but it degrades slowly in the physiological environment. Inducing galvanic couple by alloying Cu to Fe using ball milling is a promising approach. However, the ductile nature of Cu leads to the cold welding of a large amount of Cu powder during ball milling, which makes it difficult to disperse uniformly in the Fe matrix. Here, a Fe-CuO implant with highly dispersed Cu particles in the matrix was developed by shift-speed ball milling and selective laser melting. Specifically, copper oxide (CuO) particles were selected as precursors and dispersed in Fe powders by ball milling since they were brittle and would not be cold-welded during ball milling. After further milling in higher energy, it was found that CuO particles reacted with Fe and generated Cu particles through a stress-activated redox reaction. Subsequently, the obtained powders were prepared into a Fe-CuO implant using selective laser melting. Microstructure examination revealed that the Cu phases in the implant were dispersed evenly in the Fe matrix, which was considered to establish a large number of galvanic couples and aggravated the galvanic corrosion tendency. Electrochemical tests indicated that the implant had improved performance in degradation behavior in terms of high corrosion current density (22.4 µA/cm2), low corrosion resistance (1319 Ω cm2), and good degradation stability. In addition, it presented antibacterial effects against Escherichia coli and Staphylococcus aureus by diffusion mechanisms with killing rates of 90.7 and 96.7%, respectively, as well as good cytocompatibility.

Photoexcited wireless electrical stimulation elevates nerve cell growth.

Electrical stimulation was restrained by an external power supply and wires, despite its ability to promote nerve cell growth. Bismuth sulfide (Bi2S3) offered a novel prospect for achieving wireless electrical stimulation due to its photoelectric effect. Herein, silver nanoparticles (Ag NPs) were in-situ grown on Bi2S3 surface (Ag/Bi2S3) and then mixed with poly-L-lactic acid (PLLA) powders to fabricate PLLA-Ag/Bi2S3 conduits. On the one hand, Bi2S3 would generate photocurrent under light excitation, forming a wireless electrical stimulation. On the other hand, Ag NPs would form localized electrical fields under light excitation to inhibit rapid electron-hole recombination of Bi2S3. Moreover, Ag NPs would act as electron mediators to accelerate electron transfer, further elevating photocurrent. Electrochemical tests and FDTD simulations revealed the localized electrical fields generated by Ag NPs acted on Bi2S3, resulting in a boosted electron-hole separation evidenced by a reduction in photoluminescence intensity. EIS measurements demonstrated a faster electron transfer occurred on Ag/Bi2S3. As a result, the photocurrent of PLLA-Ag/Bi2S3 increased from 0.26 to 1.03 µA as compared with PLLA-Bi2S3. The enhanced photocurrent effectively promoted cell differentiation by up-regulating Ca2+ influx and nerve growth-related protein SYN1 expression. This work suggested a promising countermeasure in the design of photocurrent stimulation conduits for nerve repair.

A Codispersed Nanosystem of Silver-anchored MoS2 Enhances Antibacterial and Antitumor Properties of Selective Laser Sintered Scaffolds.

Tumor recurrence and bacterial infection are common problems during bone repair and reconstruction after bone tumor surgery. In this study, silver-anchored MoS2 nanosheets (Ag@PMoS2) were synthesized by in situ reduction, then a composite polymer scaffold (Ag@PMoS2/PGA) with sustained antitumor and antibacterial activity was successfully constructed by selective laser sintering technique. In the Ag@PMoS2 nanostructures, silver nanoparticles (Ag NPs) were sandwiched between adjacent MoS2 nanosheets (MoS2 NSs), which restrained the restacking of the MoS2 NSs. In addition, the MoS2 NSs acted as steric hindrance layers, which prevented the aggregation of Ag NPs. More importantly, MoS2 NSs can provide a barrier layer for Ag NPs, hindering Ag NPs from reacting with the external solution to prevent its quick release. The results showed that Ag@PMoS2/PGA scaffolds have stronger photothermal effect and antitumor function. Meanwhile, the Ag@PMoS2/PGA scaffolds also demonstrated slow control of silver ion (Ag+) release and more efficient long-term antibacterial ability. Besides, composite scaffolds have been proved to kill the MG-63 cells by inducing apoptosis and inhibit bacterial proliferation by upregulating the level of bacterial reactive oxygen species. This kind of novel bifunctional implants with antitumor and antibacterial properties provides better choice for the artificial bone transplantation after primary bone tumor resection.

Selective Laser Melted Rare Earth Magnesium Alloy with High Corrosion Resistance.

Magnesium (Mg) degrades too fast in human body, which limits its orthopedic application. Single-phase Mg-based supersaturated solid solution is expected to possess high corrosion resistance. In this work, rare earth scandium (Sc) was used as alloying element to prepare Mg(Sc) solid solution powder by mechanical alloying (MA) and then shaped into implant using selective laser melting (SLM). MA utilizes powerful mechanical force to introduce numerous lattice defects, which promotes the dissolution of Sc in Mg matrix and forms supersaturated solid solution particles. Subsequently, SLM with fast heating and cooling rate maintains the original supersaturated solid solution structure. Immersion tests revealed that high Sc content significantly enhanced the corrosion resistance of Mg matrix because of the formation of protective corrosion product film, which was also proved by the electrochemical impedance spectroscopy measurements. Thereby, Mg(Sc) alloy showed a relatively low degradation rate of 0.61 mm/year. In addition, cell tests showed that the Mg(Sc) exhibited favorable biocompatibility and was suitable for medical application.

Polydopamine constructed interfacial molecular bridge in nano-hydroxylapatite/polycaprolactone composite scaffold.

Nano-hydroxylapatite (nano-HAP)/polycaprolactone (PCL) composite scaffold is proved to possess great potential for bone tissue engineering application since the biocompatibility of PCL and the osteoinduction ability of nano-HAP. However, the interfacial bonding between nano-HAP and PCL is weak by reason of the difference in thermodynamic properties. Herein, nano-HAP was modified by polydopamine (PDA) and then added to the PCL matrix to enhance their interface bonding in bone scaffold manufactured by selective laser sintering (SLS). The results indicated that PDA acted as an interfacial molecular bridge between PCL and nano-HAP. On one hand, the amino groups of PDA formed hydrogen bonding with the hydroxyl groups of nano-HAP, and on the other hand, the catechol groups of PDA formed hydrogen bonding with the ester groups of PCL. Compared with the HAP/PCL scaffolds, the tensile and compressive strength of the P-HAP/PCL scaffolds loading 12 wt% P-HAP were increased by 10% and 16%, respectively. Meanwhile, the scaffold possessed great bioactivity and cytocompatibility that could accelerate the formation of apatite layers and promote the cell adhesion, proliferation and differentiation.

In Situ Growth of a Metal-Organic Framework on Graphene Oxide for the Chemo-Photothermal Therapy of Bacterial Infection in Bone Repair.

Bacterial infection with high morbidity (>30%) seriously affects the defect's healing after bone transplantation. To this end, chemotherapy and photothermal therapy have been utilized for antibacterial treatment owing to their high selectivity and minimal toxicity. However, they also face several dilemmas. For example, bacterial biofilms prevented the penetration of antibacterial agents and local temperatures (over 70 °C) caused by the photothermal therapy damaged normal tissue. Herein, a co-dispersion nanosystem with chemo-photothermal function was constructed via the in situ growth of zeolitic imidazolate framework-8 (ZIF-8) on graphene oxide (GO) nanosheets. In this nanosystem, GO generates a local temperature (∼50 °C) to increase the permeability of a bacterial biofilm under near-infrared laser irradiation. Then, Zn ions released by ZIF-8 seized this chance to react with the bacterial membrane and inactivate it, thus realizing efficient sterilization in a low-temperature environment. This antibacterial system was incorporated into a poly-l-lactic acid scaffold for bone repair. Results showed that the scaffold showed a high antibacterial rate of 85% against both Escherichia coli and Staphylococcus aureus. In vitro cell tests showed that the scaffold promoted cell proliferation.

Nd-Fe-B Magnets: The Gradient Change of Microstructures and the Diffusion Principle after Grain Boundary Diffusion Process.

The diffusion of Tb in sintered Nd-Fe-B magnets by the grain boundary diffusion process can significantly enhance coercivity. However, due to the influence of microstructures at different depths, the coercivity increment and temperature stability gradually decreases with the increase of diffusion depth, and exhibit good corrosion resistance at a sub-surface layer (300-1000 µm). According to the Electron Probe Micro-analyzer (EPMA) test results and the diffusion mechanism, the grain boundary and intragranular diffusion behavior under different Tb concentration gradients were analyzed, and the diffusion was divided into three stages. The first stage is located on the surface of the magnet, which formed a thick core-shell structure and a large number of RE-rich phases. The second stage is located in the sub-surface layer, forming a uniform and continuous RE-rich phase and thin core-shell structure. The third stage is located deeper in the magnet, and the Tb enrichment only existed at the triangular grain boundary.