Facile Fabrication of Hyperbranched Polyacetal Quaternary Ammonium with pH-Responsive Curcumin Release for Synergistic Antibacterial Activity

In the current global crisis of antibiotic resistance,persuit of an effective multi-pathway collaborative approach to enhance antibacterial activity is urgently needed.Here,a kind of hyperbranched polyacetal quaternary ammonium(Hyper-ace-QA)with efficiently antibacterial function were synthesized by a succession of efficient click strategies.The high molecular weights can be obtained just after UV irradiation for 3 h,and the grafting ratio can be easily adjusted through controlling solvent system,molar ratio,and temperature.Cytotoxicity studies indicated that Hyper-ace-QA had good biocompatibility and can be used as a potential antibacterial dressing.More importantly,after in situ encapsulation of bioactive curcumin drugs into the hyperbranched intramolecular cavities,the acid-liable acetal linkers within the hyperbranched backbone made the loading antibacterial drugs rapidly release with pH-or bacterial-responsive behaviors since many bacteria can produce acids at the infection site by the combined actions of immune response and bacterial metabolism.Therefore,the integration of quaternary ammonium characteristics and pH-triggered curcumin release could facilitate the antibacterial activity against gram-positive Staphylococcus aureus.This work represents a synergistic strategy on offering important guidance to rational design of multifunctional antimicrobial vehicles,which would be promising therapeutic alternatives for first aid treatment of wound infection in critical situations.

Layer Thickness-Dependent Hardness and Strain Rate Sensitivity of Cu–Al/Al Nanostructured Multilayers

Cu-Al/Al nanostructured metallic multilayers with Al layer thickness hAl varying from 5 to 100 nm were prepared, and their mechanical properties and deformation behaviors were studied by nanoindentation testing. The results showed that the hardness increased drastically with decreasing hAl down to about 20 nm, whereafter the hardness reached a plateau that approaches the hardness of the alloyed Cu-Al monolithic thin films. The strain rate sensitivity （SRS, m）, however, decreased monotonically with reducing hAl. The layer thickness-dependent strengthening mechanisms were discussed, and it was revealed that the alloyed Cu-Al nanolayers dominated at hAl≤ 20 nm, while the crystalline Al nanolayers dominated at hAl 〉 20 nm. The plastic deformation was mainly related to the ductile Al nanolayers, which was responsible for the monotonic evolution of SRS with hAl. In addition, the hAFdependent hardness and SRS were quanti- tatively modeled in light of the strengthening mechanisms at different length scales.

Dendrimer-based Hydrogels with Controlled Drug Delivery Property for Tissue Adhesion

In recent years,the hydrogel-based tissue adhesives have been extensively investigated for their excellent biocompatibility and the ability to be administered directly within the adherent tissue.To meet the requirement for more controllable release in various physiological settings,the components of hydrogel adhesive should be more precisely tailored.In this work,the POSS-ace-PEG hydrogel adhesive was fabricated with the polyacetal dendrimer G1’-[NH3 Cl]16 and poly(ethylene glycol)succinimidyl carbonate(PEG-SC)due to the regular peripheral amino structure of G1’-[NH3 Cl]16.Rheological and adhesion tests demonstrated that the hydrogel adhesive had good mechanical and adhesive properties,which could effectively adhere to the pigskin and severed nerves.Moreover,the tissue adhesive exhibited good stability under neutral conditions and the rapid degradation under acidic conditions,allowing for the release of doxycycline hydrochloride(DOX)drug in response to pH.Together,these results suggested that the POSS-ace-PEG adhesive had the potential to provide an alternative to tissue adhesives for applications in pathological environments(inflammation,tumors,etc.).

Contributions of internal climate variability in driving global and ocean temperature variations using multi-layer perceptron neural network

Roles of internal climate variabilities regulating global and ocean temperature changes is a hot but complex issue of scientific concern,infuencing the comprehensive policy-making in response to global and regional warming.In this study,the time series of monthly global and ocean mean surface temperature(GST and OST,respectively)since 1866 is successflly reconstructed via natural and anthropogenic forcing factors and internal climate variability by using a Multi-Layer Perceptron(MLP)neural network technique.The MLP demonstrates prominent monthly GST and OST reconstruction skills on both interannual and annual time scales.Most of the warming in GST and OST since 1866 is found to be attributable to anthropogenic forcing,while the multidecadal and interannual GST and OST variations are considerably dominated by Atlantic Multidecadal Oscillation(AMO).Internal climate variabilities like Interdecadal Pacific Oscillation(IPO)can amplify the GST and OST changes and explain the global warming slowdown since 1998.Southern Oscillation Index(SOI)performs a similar role as IPO but to a lesser extent.Changes in OST caused by solar forcing are more considerable than those in GST.Moreover,the"biased warmth"during the Second World War is successfully reconstructed in MLP.AMO and IPO can explain most annual and even sub-annual temperature variations during this period,offering an explanation for the existence of this abnormal warm period other than that it was entirely caused by instrumental errors.The generally high accuracy of reconstructions on interannual and annual time scales can enhance the ability to monitor the prompt feedback of specific external radiative forcings and internal variabilities to changes in climate.