Effect of Hydrothermal Aging on the Tribological Performance of Nitrile Butadiene Rubber Seals.

High temperature and humidity affect the tribological performance of nitrile butadiene rubber (NBR) seals, which affects the precise positioning of cylinder systems. Therefore, it is crucial to study the effect of hydrothermal aging on the tribological performance of the NBR seals. In this study, the changes in the tribological performance of the NBR seals under hydrothermal aging conditions were investigated. The results show that the volatilization of additives and the increase in crosslink density of the NBR seals occurs in the hydrothermal aging environment, leading to the deterioration of their surface quality, elastic deformability, and tribological performance. The formation of surface micropores due to additive volatilization is the main factor in the degradation of tribological performance.

Effect of Geometric Error on Friction Behavior of Cylinder Seals.

The tribological characteristics of the cylinder directly affect the operation accuracy of the pneumatic servo system. However, the geometric error has a significant effect on its tribological behavior and the related research is insufficient. Thus, the dynamic friction process of rubber seals has been investigated considering the influence of geometric errors. Firstly, based on the self-made friction test platform, the friction force of the rubber seals was studied and the influence law of geometric error on the contact area of the rubber seal ring was revealed. Secondly, the numerical model of the friction and contact of the rubber seals for the cylinder segment was developed by using the finite element simulation method and the influence laws of machining errors, such as roundness and straightness on the friction characteristics, were revealed. Finally, synergy effects of roundness and straightness in the friction behavior of rubber seals considering geometric errors was investigated, which lays a foundation for the accurate prediction of cylinder dynamic mechanical properties.

A ruthenium nanoframe/enzyme composite system as a self-activating cascade agent for the treatment of bacterial infections.

The cascade catalytic strategy could effectively enhance the antibacterial activity by regulating the production of hydroxyl radicals (˙OH) in the sites of bacterial infection. In this work, a ruthenium metal nanoframe (Ru NF) was successfully synthesized via the palladium template method. The cascade catalysis in the bacterial infection microenvironment was achieved by physically adsorbed natural glucose oxidase (GOx), and hyaluronic acid (HA) was coated on the outer layer of the system for locating the infection sites accurately. Eventually, a composite nano-catalyst (HA-Ru NFs/GOx) based on the ruthenium nanoframe was constructed, which exhibited excellent cascade catalytic activity and good biocompatibility. The prepared HA-Ru NFs/GOx enhances the antibacterial activity and inhibits bacterial regeneration through the outbreak of reactive oxygen species (ROS) caused by self-activating cascade reactions. In addition, in vivo experiments indicate that HA-Ru NFs/GOx could efficiently cause bacterial death and significantly promote wound healing/skin regeneration. Accordingly, ruthenium metal framework nanozymes could be used as an effective cascade catalytic platform to inhibit bacterial regeneration and promote wound healing, and have great potential as new antibacterial agents against antibiotic-resistant bacteria.

Photosensitive properties, synergistic antibacterial abilities of intelligent response-type self-assembled nanoparticle TiO2@V2O5.

Representative pathogenic bacteria such as Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) are widespread in nature and pose a threat to human health. To control the propagation of these pathogens from the source, the key is to design broad-spectrum antibacterial materials to reduce the serious damage of pathogenic bacteria. At present, more and more nanoparticles are widely researched and applied due to their multi-pathway antibacterial properties, such as regulating physiology, biochemistry and physical chemistry. In this work, we synthesized a uniformly dispersed and stable spherical nanoparticle (TiO2@V2O5) synthesized by self-assembly of tianium dioxide and vanadium pentoxide. Based on its excellent photosensitive properties, TiO2@V2O5 nanoparticles have showed excellent antibacterial properties under the light irradiation due to the production of hydroxyl radicals in antibacterial and mechanism tests. In addtion, related cell and plant experiments have showed that TiO2@V2O5 nanoparticles are excellent biocompatible materials, it could be widely used in environmental pollution control, limiting the serious damage caused by pathogens.

Responsive functionalized MoSe2 nanosystem for highly efficient synergistic therapy of breast cancer.

The photothermal/photodynamic synergistic therapy is a promising tumor treatment, but developing nanosystems that achieve synchronous photothermal/photodynamic functions is still quite challenging. Here, we use a simple method to synthesize molybdenum selenide nanoparticles (MoSe2 NPs) with a photothermal effect as a carrier, and load a photosensitizer ICG to form a nanosystem (MoSe2@ICG-PDA-HA)with dual photothermal/photodynamic functions under near-infrared irradiation. In addition, the surface modification of the nanosystem with acid-responsive release polydopamine (PDA) and tumor-targeted hyaluronic acid (HA) enhanced the stability of the photosensitizer ICG and the accumulation of ICG at tumor sites. The multicellular sphere assay simulated solid tumors and demonstrated that MoSe2@ICG-PDA-HA could significantly inhibit the 4T1 cell growth. The anti-tumor experiments in tumor-bearing mice showed that MoSe2@ICG-PDA-HA not only significantly inhibited the growth of 4T1 subcutaneous tumors, but also inhibited their metastasis. This study presented a nanosystem that could improve the photostability of optical materials and enhance the photothermal/photodynamic synergy effect, providing a new idea for finding a way to effectively treat breast cancer.

Bacteria-Responsive Biomimetic Selenium Nanosystem for Multidrug-Resistant Bacterial Infection Detection and Inhibition.

Multidrug-resistant (MDR) bacterial infections are a severe threat to public health owing to their high risk of fatality. Noticeably, the premature degradation and undeveloped imaging ability of antibiotics still remain challenging. Herein, a selenium nanosystem in response to a bacteria-infected microenvironment is proposed as an antibiotic substitute to detect and inhibit methicillin-resistant Staphylococcus aureus (MRSA) with a combined strategy. Using natural red blood cell membrane (RBCM) and bacteria-responsive gelatin nanoparticles (GNPs), the Ru-Se@GNP-RBCM nanosystem was constructed for effective delivery of Ru-complex-modified selenium nanoparticles (Ru-Se NPs). Taking advantage of natural RBCM, the immune system clearance was reduced and exotoxins were neutralized efficiently. GNPs could be degraded by gelatinase in pathogen-infected areas in situ; therefore, Ru-Se NPs were released to destroy the bacteria cells. Ru-Se NPs with intense fluorescence imaging capability could accurately monitor the infection treatment process. Moreover, excellent in vivo bacteria elimination and a facilitated wound healing process were confirmed by two kinds of MRSA-infected mice models. Overall, the above advantages proved that the prepared nanosystem is a promising antibiotic alternative to combat the ever-threatening multidrug-resistant bacteria.

A core-shell structure QRu-PLGA-RES-DS NP nanocomposite with photothermal response-induced M2 macrophage polarization for rheumatoid arthritis therapy.

Rheumatoid arthritis (RA) is a degenerative joint disease caused by autoimmunity; for the effective treatment of RA while avoiding the side effects of conventional drugs, we have proposed a new therapeutic strategy to eliminate the inflammatory response in RA by regulating the immune system that promotes the transformation of M1-type macrophages to M2-type macrophages. Herein, we designed and synthesized a core-shell nanocomposite (QRu-PLGA-RES-DS NPs), which showed an effective therapeutic effect on RA by accurately inducing the polarization of M2 macrophages. In this system, the quadrilateral ruthenium nanoparticles (QRuNPs) with a photothermal effect were utilized as a core and the thermosensitive molecular poly (lactic-co-glycolic acid) (PLGA) modified with the targeted molecule dextran sulfate (DS) was employed as a shell. Then, the nanocarrier QRu-PLGA-DS NPs effectively improved the water solubility and targeting of resveratrol (RES) through self-assembly. Therefore, the QRu-PLGA-RES-DS NPs significantly enhanced the ability of RES to reverse the M1 type macrophages to the M2 type macrophages through an accurate release. In vivo experiments further demonstrated that the QRu-PLGA-RES-DS NPs could effectively accumulate in the lesion area with an exogenous stimulus, and this significantly enhanced the transformation of the M2 type macrophages and decreased the recruitment of the M1 type macrophages. Furthermore, the QRu-PLGA-RES-DS NPs effectively treated RA by eliminating the inflammatory response; in addition, photoacoustic imaging (PA) of the QRu NPs provided image guidance for the distribution and analysis of nanomedicine in inflammatory tissues. Hence, this therapeutic strategy promotes the biological applications of Ru-based nanoparticles in disease treatment.

Enzyme-Responsive Mesoporous Ruthenium for Combined Chemo-Photothermal Therapy of Drug-Resistant Bacteria.

The rapid mutation of drug-resistant bacteria and the serious lag of development of new antibiotics necessitate research on novel antibacterial agents. Nanomaterials with unique size effect and antibacterial mechanism could serve as an alternative for antibiotics, since they showed low possibility to develop drug-resistant bacteria. Here, an enzyme-responsive nanosystem, AA@Ru@HA-MoS2, with a synergistic chemo-photothermal therapy function is proposed to treat bacterial infections. Mesoporous ruthenium nanoparticles (Ru NPs) were used as nanocarriers, loading prodrug ascorbic acid (AA) and encapsulated by hyaluronic acid (HA). Then, molybdenum disulfide (MoS2) precoated with ciprofloxacin was used as a catalyst with targeting effect binding to the outer surface. When the nanosystem gathered at the infection site, Hyal secreted by bacteria could degrade the HA capping and trigger the release of AA and then generated hydroxyl radicals (•OH) in situ by the catalysis of MoS2. In addition, taking advantage of the good photothermal property of Ru NPs, combined chemo-photothermal antibacterial therapy could be achieved. The nanosystem exhibited potent bactericidal activity against drug-resistant Gram-positive and Gram-negative bacteria. Furthermore, it could break down the biofilm, inhibit the contained bacteria, and prevent the formation of a new biofilm. The in vivo bacterium-infected model also proved accelerated wound healing. The study showed a high potential of AA@Ru@HA-MoS2 as a novel enzyme-responsive nanosystem for combating drug-resistant bacterial infection.

Folic acid-modified mesoporous silica nanoparticles with pH-responsiveness loaded with Amp for an enhanced effect against anti-drug-resistant bacteria by overcoming efflux pump systems.

Efflux pump system-mediated bacterial multidrug resistance is one of the main causes of antibiotic failure. Therefore, it is necessary to develop a novel nanocarrier that could effectively inhibit drug-resistant bacteria by increasing the intake and retention time of antibiotics. Herein, we constructed a pH-responsive nanocarrier (MSN@FA@CaP@FA) with double folic acid (FA) and calcium phosphate (CaP) covered on the surface of mesoporous silica (MSN) by electrostatic attraction and biomineralization, respectively. Afterward, loading the nanocomposites with ampicillin (Amp) effectively increased the uptake and reduced the efflux effect in Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) by the specific targeting of FA. Moreover, Amp-MSN@FA@CaP@FA could specifically transport Amp to the bacterial infection site. Similarly, antibacterial experiments revealed that the Amp-MSN@FA@CaP@FA could significantly enhance the activity of Amp for inhibiting drug-resistant bacteria, without producing drug resistance. Additionally, the Amp-MSN@FA@CaP@FA could reduce the content of protein and inhibit the protein activity in drug-resistant bacteria, so that it destroyed the bacterial membrane and led to the bacteria death. In vivo antibacterial experiments showed that the Amp-MSN@FA@CaP@FA could effectively reduce the mortality of drug-resistant E. coli infection and promote wound healing of drug-resistant S. aureus infection. In summary, Amp-MSN@FA@CaP@FA has a potential for application in sustained-release nanostructures and to inhibit drug-resistant bacteria.