Separation of binary and ternary oil/water mixtures from a highly hydrophobic metal mesh.

A highly hydrophobic metal mesh has great potential for its application in oil/water separation due to its special wettability. However, most current oil/water separation devices are simple with limited separation capacity. A separation device based on a highly hydrophobic metal mesh was constructed for different types of oil/water mixtures. Experimental results show that the device not only can be used for the continuous separation of binary oil/water mixtures of any density ratios but also can realize the simultaneous separation of heavy oil/water/light oil ternary mixtures. This achievement is meaningful for practical applications, which will gain great interest in the future.

Delta and jagged are candidate target genes of RNAi biopesticides for the control of Nilaparvata lugens.

The brown planthopper (BPH; Nilaparvata lugens) is an important pest in rice cultivation, and chemical pesticide over-use and ineffectiveness of existing Bt transgenic rice against piercing-sucking insects make novel control methods necessary. RNA interference (RNAi) biopesticide is a new type of product with high efficiency and specificity and are simple to use. The Notch signaling pathway has extensive and important physiological functions and plays a key role in the development of insects. In this study, two key ligand genes of the Notch signaling pathway, delta (dl) and jagged (jag), were selected and their lethal effects and functional analysis were systematically evaluated using a stable short-winged population (Brachypterous strain) and a long-winged population (Macropterous strain) of BPHs. The full-length coding sequences of Nldl and Nljag comprised 1,863 and 3,837 base pairs, encoding 620 and 1,278 amino acids, respectively. The nucleic acid sequences of Nldl and Nljag were identical between the two strains. The expression levels of Nldl and Nljag were relatively high in the head of the nymphs, followed by those in the abdomen. Through RNAi treatment, we found that injection of BPH nymphs of both strains with dsNldl (10-50 ng/nymph) or dsNljag (100 ng/nymph) produced lethal or teratogenic effects. dsRNA treatment showed excellent inhibitory effects on the expression of target genes on days 1 and 5, suggesting that RNAi rapidly exhibits effects which persist for long periods of time in BPHs. Taken together, our results confirm the potential of Nldl and Nljag as target genes of RNAi biopesticides, and we propose optimized dosages for the control of BPHs.

Biomimetic electrodynamic nanoparticles comprising ginger-derived extracellular vesicles for synergistic anti-infective therapy.

Nanotechnology enlightens promising antibacterial strategies while the complex in vivo infection environment poses a great challenge to the rational design of nanoplatforms for safe and effective anti-infective therapy. Herein, a biomimetic nanoplatform (EV-Pd-Pt) integrating electrodynamic Pd-Pt nanosheets and natural ginger-derived extracellular vesicles (EVs) is proposed. The introduction of ginger-derived EVs greatly endows EV-Pd-Pt with prolonged blood circulation without immune clearance, as well as accumulation at infection sites. More interestingly, EV-Pd-Pt can enter the interior of bacteria in an EV lipid-dependent manner. At the same time, reactive oxygen species are sustainably generated in situ to overcome the limitations of their short lifetime and diffusion distance. Notably, EV-Pd-Pt nanoparticle-mediated electrodynamic and photothermal therapy exhibit synergistic effects. Furthermore, the desirable biocompatibility and biosafety of the proposed nanoplatform guarantee the feasibility of in vivo applications. This proof-of-concept work holds significant promise for developing biomimetic nanoparticles by exploiting their intrinsic properties for synergistic anti-infective therapy.

Ciprofloxacin conjugated gold nanorods with pH induced surface charge transformable activities to combat drug resistant bacteria and their biofilms.

The ever-growing threat of drug-resistant pathogens and their biofilms based persistent, chronic infections has created an urgent call for new strategies to deal with multidrug resistant bacteria (MDR). Near-infrared (NIR) laser-induced photothermal treatment (PTT) of gold nanorods (AuNRs) disinfects microbes by local heating with low possibility to develop resistant. However, PTT disinfection strategy of AuNRs alone shows less efficiency in killing multidrug resistant strains (i.e. Methicillin-resistant Staphylococcus aureus, MRSA) and their matured biofilms. Herein, a novel synergistic chemo-photothermal integrated antimicrobial platform (P(Cip-b-CB)-AuNRs) was fabricated which show enhanced killing efficiency against MRSA in both planktonic and biofilm phenotypes. Polymethacrylate copolymers with pendant ciprofloxacin (Cip) and the carboxyl betaine groups (P(Cip-b-CB)) were synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization. P(Cip-b-CB) was decorated onto AuNRs via gold-thiol bond which resulted in AuNRs with acidic-induced surface charge-switchable activities and lipase triggered Cip release properties (P(Cip-b-CB)-AuNRs). The lower pH value and overexpress of lipase are characteristics for microenvironment of microbial infections and their biofilms, which ensure the targeting on, penetration into and on-demand release of Cip from the nanocomposites in bacterial infection sites and their biofilms. The bacterial cell membrane was disrupt by photothermal therapy which could improve its permeability and sensitivity to antibiotics, meanwhile lipase-triggered release of Cip ensures a high concentration of antibiotics at the site of bacterial infection. Besides their NIR induced PTT disinfection activities, the increased local temperature generated by NIR light irradiation accelerated Cip release which further enhanced the antibacterial efficiency, leading to synergistic antibacterial activities of chemo-photothermal therapy. Taken together, the designed synergistic chemo-photothermal integrated antimicrobial platform is a promising antibacterial agent for fighting MDR bacterial infections and their biofilms.

Gold nanorods with surface charge-switchable activities for enhanced photothermal killing of bacteria and eradication of biofilm.

The increasing growth and severity of bacterial biofilm infections and the appearance of multidrug-resistant bacteria pose alarming threats to public healthcare systems, mainly due to their formidable tolerance to conventional antibiotics. Different from the antibacterial mechanisms of antibiotics, gold nanorods (AuNRs) disinfect microbes by local heating induced by near-infrared (NIR) light irradiation; thus, they are potential disinfection agents. In an attempt to increase the biocompatibility and antibacterial activities of AuNRs against organisms in both planktonic and biofilm phenotypes, polymethacrylate with pendant carboxyl betaine groups was decorated on AuNRs (PCB-AuNRs) to afford AuNRs with pH-induced surface charge-transformable activities. The zwitterion-modified AuNRs demonstrated a pH-responsive transition from negative charge to positive charge; this confers the AuNRs with a change in functionality from biocompatible zwitterionic nanocomposites in healthy tissues (pH = ∼7.4) to enhanced antimicrobial cationic nanocomposites at acidic bacterial infection sites (pH = ∼5.5). AuNRs coated by polymethacrylate with pendant mPEG (PPEGMA-AuNRs) without surface charge transition activities were used for comparison. PCB-AuNRs presented better antimicrobial activity against Gram-negative bacteria (E. coli), Gram-positive bacteria (S. aureus) and their drug-resistant strains (MRSA and EBSL E. coli) than PPEGMA-AuNRs as a result of their pH-responsive surface charge transition activities. Moreover, PCB-AuNRs demonstrated deeper penetration into mature biofilms and better biofilm elimination activities than their non-surface charge-transformable counterparts. The results indicate that the designed zwitterion-coated AuNRs are a promising antibacterial agent for fighting bacterial infections.

Dopamine-assisted one-pot synthesis of gold nanoworms and their application as photothermal agents.

Gold-based nanomaterials of various sizes and geometries have been prepared for use as photothermal agents due to their unique physical and chemical properties. Here we report a simple one-step synthesis of gold nanoworms (NWs) and characterized them with transmission electron microscopy, X-ray photoelectron spectroscopy, UV-Visible spectroscopy, and Fourier transform infrared spectroscopy. The results showed that small gold nanounits were first formed by reducing chloroaurate ions (AuCl4-) with sodium borohydride (NaBH4), and then fused together to form NWs assisted by dopamine (DA), which served a structure-director due to an oriented attachment mechanism. Then DA in the solution was further polymerized into polydopamine (PDA) to form a coating layer on the surface of gold NWs. Moreover, further experiments showed that gold NWs had low cytotoxicity and excellent performance as a photothermal bactericidal on both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. These results show that the synthesized gold NWs are a promising photothermal agent.

Layer-by-Layer Assembled Multilayer Films with Multiple Antibacterial and pH-Induced Self-Cleaning Activities Based on Polyurethane Micelles.

Layer-by-layer assembled multilayer films with antifouling and pH induced self-cleaning activities were constructed by polyurethane micelles with dense PEG brush coronas (PEG-g-PUM) and polyethylenimine (bPEI). The dense PEG brush coronas and acidic induced surface charge transform activities of PEG-g-PUM rendered the multilayer films (PEG-g-PUM/bPEI)n with antifouling and self-cleaning activities, respectively. Multilayer films constructed from polyurethane micelles without surface charge switchable properties (PEG-c-PUM, PEG-b-PUM), showed negligible pH induced surface release of PU micelles. Furthermore, Triclosan encapsulation in the multilayer films ((PEG-g-PUM-TLS/bPEI)n) further improved the antibacterial performance, as a result of pH and lipase triggered release of payloads from the surfaces. The antifouling properties of PEG-g-PUM and the on-demand release of payloads and PU micelles, may account for their excellent multiple antibacterial performance and pH-induced self-cleaning activities.

Silver nanoparticles with pH induced surface charge switchable properties for antibacterial and antibiofilm applications.

Silver nanoparticles (AgNPs) are widely used as antibacterial agents because of their significant antimicrobial activities and little sign of antimicrobial resistance. However, the relatively high toxicity to healthy cells and low penetration efficiency into bacterial biofilms prevent their further use in biomedical applications. In order to decrease the cytotoxicity of the AgNPs to mammalian cells while increasing their antibacterial and antibiofilm efficiency, a novel nanocomposite composed of AgNPs decorated with carboxyl betaine groups (AgNPs-LA-OB) was prepared. The zwitterion modified AgNPs showed a pH responsive transition from a negative charge to a positive charge, which enabled the AgNPs to be compatible with mammalian cells and red blood cells (RBCs) in healthy tissues (pH ∼ 7.4), while strongly adhering quickly to negatively charged bacterial surfaces at infectious sites (pH ∼ 5.5) based on electrostatic attraction. The AgNPs penetrated deeply into bacterial biofilms and killed the bacteria living in an acidic environment. The results indicated that the designed zwitterion NPs for antibacterial applications and eradication of bacterial biofilms, which also had particles that did not harm the healthy cells showed promise for future use in humans. The satisfactory selectivity for bacteria compared to RBCs, together with their potent eradication of bacterial biofilms make AgNPs-LA-OB a promising antibacterial nanomedicine in biomedical fields.

Triclosan loaded polyurethane micelles with pH and lipase sensitive properties for antibacterial applications and treatment of biofilms.

Three different kinds of polyurethane (PU) micelles, i.e. PEG-c-PU, PEG-g-PU and PEG-b-PU, with hydrophobic PCL core and hydrophilic PEG corona were prepared by self-assembly method. DLS studies illustrated that PEG-g-PU micelles showed pH dependent surface charge switching properties while no obvious surface charge switching activities were found for PEG-b-PU and PEG-c-PU micelles. Triclosan was loaded into PCL core by dialysis method with pretty high encapsulate content and efficiency and the payloads were released at an accelerate rate in the presence of lipase. MIC and MBC studies demonstrated an enhanced antibacterial activity of encapsulated Triclosan against planktonic bacteria than free Triclosan. CLSM images of S. aureus biofilms treated with Nile red loaded PU micelles illustrated the penetration and accumulation of PEG-g-PU micelles inside the bacterial biofilms at an acidic environment. In addition, Triclosan loaded into PEG-g-PU micelles showed more potent antibiofilm activities than that loaded into PEG-c-PEG and PEG-b-PU micelles. Therefore, the PEG-g-PU micelles can be potentially used as hydrophobic antibiotic carriers to treat bacterial infections and biofilms.

Synthesis of polyurethanes with pendant azide groups attached on the soft segments and the surface modification with mPEG by click chemistry for antifouling applications.

Polyurethane with pendant azide groups on the soft segment (PU-GAP) was prepared in this study to further increase the content of reactive azide groups and improve their surfaces enrichment for further functionalization. Polymer diols with pendant azide groups (GAP) were prepared by transforming the pendant chlorine groups at polyepichlorohydrin (PECH) into azide groups with sodium azide. The prepared PECH, GAP and PU-GAP was characterized by GPC, 1H NMR and FTIR. Propargylic mPEG (mPEG-alkyne) was used as model surface modification reagents which was grafted on the prepared azido containing polyurethane films via click chemistry. The surface morphology, chemical composition and wettabilities were studied by SEM, XPS and water contact angle (WCA) analysis, respectively. SEM results demonstrated different surface topologies between mPEG modified PU surface and original PU surface. XPS and WCA analysis proved the successful grafting of mPEG on the pendant azide groups of PUs. The mPEG modified PU surfaces demonstrated good antifouling activities against model bacteria and mPEG with larger molecular weights modified surfaces showed better resistance efficiency to attachment of bacteria. Therefore, the surface reactive polyurethane we prepared can be a universal platform for further functionalization according actual applications.

Reduction responsive and surface charge switchable polyurethane micelles with acid cleavable crosslinks for intracellular drug delivery.

Previously we synthesized redox sensitive polyurethane micelles, core crosslinked by diisocyanates (PU-CCL). To improve the intracellular drug release and tumor cellular toxicity of anticancer drugs loaded into polyurethane micelles, we now describe redox sensitive polyurethane micelles with tunable surface charge switchabilities, crosslinked with pH cleavable Schiff bonds, as anticancer drug carriers. Different amounts of 1,6-diaminohexane were connected onto the pendant carboxyl groups of amphiphilic multi-blocked polyurethane (PU-SS-COOH), resulting in polyurethanes with various ratios of pendant carboxyl and amine groups (denoted as PU-SS-COOH-NH2-1, PU-SS-COOH-NH2-2 and PU-SS-COOH-NH2-3). The surface charge switched as the pH was increased for PU-SS-COOH-NH2-1, PU-SS-COOH-NH2-2 and PU-SS-COOH-NH2-3. Then the PU-SS-COOH-NH2-3 micelles, dissolved in water, were crosslinked by glutaraldehyde resulting in surface charge switchable and reduction responsive polyurethane micelles with acid cleavable crosslinks (PU-ACCL). The crosslinked polyurethane micelles (PU-ACCL) demonstrated superior particle stability in phosphate buffered saline (PBS, pH = 7.4) solution without reducing agents, whereas the drug release rate was markedly accelerated by the addition of glutathione (GSH). Notably, the drug release from PU-ACCL was further accelerated in acidic fluid as the result of acid induced cleavage of the crosslinks. In vitro cytotoxicity studies demonstrated that doxorubicin (DOX)-loaded PU-ACCL micelles displayed increased cytotoxicity against tumor cells which was comparable to that obtained for DOX loaded into uncrosslinked polyurethane micelles. The reduction responsive and surface charge switchable polyurethane micelles with acid cleavable crosslinks, which have superior extracellular stability and provide rapid intracellular drug release, may hold great potential as a bio-triggered drug delivery system for cancer therapy.