Sophorolipid-toluidine blue conjugates for improved antibacterial photodynamic therapy through high accumulation.

Anti-bacterial photodynamic therapy is the most promising treatment protocol for bacterial infection, but low accumulation of photosensitizers has seriously hindered their development in clinical application. Here, with inherent outstanding affinity to bacterial cell envelope, sophorolipid produced from Candida bombicola has been conjugated to toluidine blue (SL-TB) through amidation reaction. The structure of SL-TB conjugates was identified by 1H-NMR, FT-IR and ESI-HRMS. The interfacial assembly and photophysical properties of SL-TB conjugates have been disclosed through surface tension, micro-polarity, electronic and fluorescence spectra. After light irradiation, the log10 (reduced CFU) of free toluidine blue to P. aeruginosa and S. aureus were 4.5 and 7.9, respectively. In contrast, SL-TB conjugates showed a higher bactericidal activity, with a reduction of 6.3 and 9.7 log10 units of CFU against P. aeruginosa and S. aureus, respectively. The fluorescence quantitative results showed that SL-TB could accumulate 2850 nmol/1011 cells and 4360 nmol/1011 cells by P. aeruginosa and S. aureus, which was much higher than the accumulation of 462 nmol/1011 cells and 827 nmol/1011 cells of free toluidine blue. Through the cooperation of triple factors, including sophorose affinity to bacterial cells, hydrophobic association with plasma membrane, and electrostatic attraction, higher SL-TB accumulation was acquired, which has enhanced antibacterial photodynamic efficiencies.

Emulsifying Properties of Rhamnolipids and Their In Vitro Antifungal Activity against Plant Pathogenic Fungi.

Rhamnolipids have significant emulsifying activity and the potential to become a component of pesticide emulsifier. Rhamnolipids are usually composed of two main components: mono-rhamnolipids (Rha-C10-C10) and di-rhamnolipids (Rha2-C10-C10). The proportion of di-rhamnolipids in the products ranged between 15% and 90%, affected by the production strains and fermentation process. In this paper, three kinds of rhamnolipid products containing di-rhamnolipids proportions, of 25.45, 46.46 and 89.52%, were used to test their emulsifying ability toward three conventional solvents used in pesticide (S-200, xylene, cyclohexanone) and antifungal activities against five strains of plant pathogenic fungi (Phytophthora capsici, Phytophthora parasitica var.nicotianae, Colletotrichum destructivum, Colletotrichum sublineolum, Fusarium oxysporum). The results indicated that although the CMC of the three rhamnolipids were significantly different, their emulsification properties had no remarkable differences, at a concentration of 10 g/L. However, their antifungal activities were significantly different: the more di-rhamnolipids, the stronger the antifungal activity. This work helps to promote the application of rhamnolipids as pesticides adjuvants.

Effect of Rhamnolipid Amidation on Biosurfactant Adsorption Loss and Oil-Washing Efficiency.

Surfactant adsorption loss seriously hinders the economy of surfactant binary flooding technology for enhancing oil recovery, especially for biosurfactants with higher manufacturing costs. Here, biosurfactant rhamnolipid (RL) is chemically modified to develop a more efficient surfactant, rhamnolipid monoethanol amide (RL-MEA), which is characterized by decreased adsorption loss and increased oil-washing efficiency for enhanced oil recovery at a laboratory scale. Synthesis and characterization of the rhamnolipid monoethanol amide are carried out using high-performance liquid chromatography (HPLC), HPLC/MS, 1H nuclear magnetic resonance (NMR), and Fourier transform infrared (FTIR) spectroscopy. The aggregation behavior is disclosed by surface tension, dynamic light scattering, and fluorescence spectra with pyrene as the probe. The applied performances of RL-MEA in the simulated enhanced oil recovery are researched, including the efficiency of oil washing, wettability to crude oil, and adsorption isotherms on silicates. Compared with the critical micelle concentration (CMC) of rhamnolipid of 14.23 × 10-5 M in pure water and 9.02 × 10-5 M in 0.2 M NaCl solution, the modified RL-MEA shows a significantly lower CMC of 7.15 × 10-5 M in pure water and 5.34 × 10-5 M in 0.2 M NaCl solution. More importantly, the modified RL-MEA reduces adsorption loss by 20% and enhanced oil-washing efficiency at higher temperatures and salt concentrations compared with the parent RLs. These findings would provide valuable information for developing efficient surfactant flooding agents for harsh reservoir geological conditions.

Amphiphilic di-cationic methylene blue for improving antibacterial photodynamic efficiency through high accumulation and low aggregation on bacterial cell surfaces.

The aggregation state of photosensitizers on the surface of bacterial cells is an important scientific problem for antibacterial photodynamic therapy (APDT). High accumulation and high photoactive state maintenance of photosensitizers are the prerequisite of high APDT efficiency. In this study, an amphiphilic di-cationic methylene blue photosensitizer (C12-MB) was synthesized through quaternization, and its structure, interface properties, photophysical properties and antibacterial photodynamic properties were studied. The results showed that C12-MB could reduce 4.27 log10 CFU and 4.8 log10 CFU for P. aeruginosa and S. aureus under irradiation of light at 660 nm, higher than the parent methylene blue. Through a spectroscopic study on photosensitizer adsorption over the bacterial surface, C12-MB can be accumulated with higher concentration, and the photo-active monomer content is 73% and 70% over P. aeruginosa and S. aureus, higher than those of methylene blue: 25% and 49%, respectively. The higher content of non-aggregated photo-active monomer could contribute to higher antibacterial photodynamic efficiency. For C12-MB adsorbed over bacterial surfaces, planar packing inhibition and electrostatic repulsion could contribute to lower C12-MB aggregation, which provides an useful reference for the structural design of high-efficiency photosensitizers.

Near-Infrared-Fluorescent Probe for Turn-On Lipopolysaccharide Analysis Based on PEG-Modified Gold Nanorods with Plasmon-Enhanced Fluorescence.

Lipopolysaccharide (LPS), as the major component of the outer membrane of Gram-negative bacteria, can trigger a variety of biological effects such as sepsis, septic shock, and even multiorgan failure. Herein, we developed a near-infrared-fluorescent probe for fluorescent turn-on analysis of LPS based on plasmon-enhanced fluorescence (PEF). Gold nanorods (Au NRs) modified polyethylene glycol (PEG) was used as PEF materials. Au NRs were prepared with different longitudinal surface plasmon resonance (LSPR), and their fluorescence enhancement was investigated. Three kinds of molecular weights (1000, 5000, and 10000) of polyethylene glycol (PEG) were employed to control the distance between the Au NRs and the fluorescence substances of cyanine 7 (Cy7). Experimental analysis showed that the enhancement was related to the spectral overlap between the plasmon resonance of Au NRs and the extinction/emission of fluorophore. The three-dimensional finite-difference time-domain (3D-FDTD) simulation further revealed that the enhancement was caused by local electric field enhancement. Furthermore, the probe was used for the ultrasensitive analysis of LPS with a detection limit of 3.85 ng/mL and could quickly distinguish the Gram-negative bacterium-Escherichia coli (E. coli) (with LPS in the membrane) from Gram-positive bacterium-Staphylococcus aureus (S. aureus) (without LPS), as well as quantitative determination of E. coli with a detection limit of 1.0 × 106 cfu/mL. These results suggested that the prepared probe has great potential for biomedical diagnosis and selective detection of LPS from different bacterial strains.

Surfactin-methylene blue complex under LED illumination for antibacterial photodynamic therapy: Enhanced methylene blue transcellular accumulation assisted by surfactin.

Recently, increased attention has been focused on antibacterial photodynamic therapy (APDT) to treat multidrug-resistant bacterial infection due to the antibiotic abuse. Methylene blue has been used as a kind of efficient and cheap commercial photosensitizer in APDT. However, due to high hydrophilicity, methylene blue is not able to be transcellular intaken and accumulated efficiently. To promote accumulation and APDT efficiency of methylene blue, lipopeptide surfactin-methylene blue complex has been prepared through electrostatic interaction. The complex under LED irradiation was found to effectively reduce 5.0 Log10 CFU and 7.6 Log10 CFU for P. aeruginosa and S. aureus, respectively. The bacterial reduction efficiency is slightly higher than free methylene blue. The photosensitizers accumulation and APDT targeting protein have been characterized by fluorescence spectroscopy, fluorescence microscopy and protein electrophoresis techniques. These results demonstrated that more surfactin-methylene blue complex could be accumulated more into the cell, and inactivate bacteria through destroying intracellular protein under LED illumination. In comparison, free methylene blue under light could inactivate bacteria through destroying membrane protein and lipid structures. These results would provide valuable insight for developing advanced clinical medicine and designing photo-drug for photodynamic therapy.

Acetoin modulates conformational change of surfactin: Interfacial assembly and crude oil-washing performance.

Due to its special structure, the cyclic lipopeptide surfactin showed remarkable responsiveness to stimuli such as pH, temperature and metal ions. However, few studies investigated the effect of fermented by-products on the conformational change and interfacial assembly of surfactin. Here, the effect of acetoin, a primary metabolite of Bacillus subtilis, on the conformational change and interfacial assembly of surfactin was studied in detail. Surface tension measurements showed that the critical micelle concentration (CMC) of surfactin increased from 1.14 × 10-5 to 4.32 × 10-5 M in the presence of acetoin. Moreover, acetoin has increased the interfacial tension of surfactin aqueous solution-crude oil from 1.08 mN/m to 3.01 mN/m. Circular dichroism (CD) spectra and dynamic light-scattering (DLS) further demonstrated that acetoin had induced the conformational transition of surfactin from ß-sheet to ß-turn structure, and caused surfactin forming some larger micelle aggregations. Afterwards, it was further found that acetoin decreased the oil sand cleaning efficiency of surfactin from 59.7% to 6.6%, and deteriorated the O/W emulsion stability and altered the silicate wettability toward less water wet state. Based on the experimental results, a possible mechanism of the interaction between surfactin and acetoin was proposed.

Synthesis of hyaluronic acid hydrogels by crosslinking the mixture of high-molecular-weight hyaluronic acid and low-molecular-weight hyaluronic acid with 1,4-butanediol diglycidyl ether.

High molecular weight hyaluronic acid (HMW-HA) and low molecular weight hyaluronic acid (LMW-HA) were mixed at different ratios and cross-linked with 1,4-butanediol diglycidyl ether (BDDE) to prepare five hyaluronic acid hydrogels A-E. Enzymolysis stability, swelling rate, crosslinking degree, rheological characteristics, BDDE residual rate, surface microstructure, and cytotoxicity of different hydrogels were investigated. The results showed that hydrogel B obtained by 10% HA (w/v, HMW-HA and LMW-HA having a mass ratio of 4 : 1) crosslinking with 1% BDDE (v/v) had stronger in vitro anti-degradation ability, better mechanical properties and lower cytotoxicity than those prepared by mixing in different proportions. Hydrogel B has potential applications in regenerative medicine and tissue engineering.

Synthesis of functional ionic liquid modified magnetic chitosan nanoparticles for porcine pancreatic lipase immobilization.

We developed magnetic chitosan nanoparticles (CS­Fe3O4) with mean diameter of 15-20 nm. Subsequently, these inorganic-organic composite nanoparticles were modified using an imidazole-based functional ionic liquid (IL). The prepared support (IL­CS­Fe3O4), which was used to immobilize porcine pancreatic lipase (PPL), was characterized using Fourier transform infrared (FTIR) spectroscopy, vibrating sample magnetometry (VSM), thermogravimetry (TG), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Circular dichroism (CD) was used to analyze the secondary structure of immobilized PPL. The immobilized PPL (PPL­IL­CS­Fe3O4) exhibited 1.93-fold higher specific activity than PPL­CS-Fe3O4 when triacetin was used as the substrate, and showed 95 mg/g of lipase immobilization capacity and 382% of activity recovery. The residual activity of PPL­IL­CS­Fe3O4 was above 60% of the initial activity after incubation at 50 °C for 6 h, as was higher than that of PPL­CS­Fe3O4 which showed 40% of the initial activity. In addition, PPL­IL­CS­Fe3O4 retained 84.6% of the initial activity after 10 cycles, whereas PPL­CS­Fe3O4 retained only 75.5% activity. Furthermore, the kinetic parameters, apparent Km and Vmax of PPL­IL­CS­Fe3O4 were 2.51 mg/mL and 1.395 U/mg respectively, these results indicated that the immobilized PPL had better affinity towards the substrate, especially when the nanoparticles were modified by functional IL. Besides, the magnetic chitosan nanoparticles loaded with PPL were easily recovered. A novel, efficient, and practical method for enzyme immobilization was developed.

Mono-acrylated isosorbide as a bio-based monomer for the improvement of thermal and mechanical properties of poly(methyl methacrylate).

Despite its optical clarity and good weatherability, poly(methyl methacrylate) (PMMA) cannot meet the needs of special occasions due to its deficient thermal and mechanical properties. To overcome these shortcomings, a type of novel bio-based monomer, mono-acrylated isosorbide, was used as a comonomer for the poly(methyl methacrylate) via a solution polymerization process. The chemical structure, the thermal and mechanical properties of the copolymerized PMMA were characterized. When the molar content of the mono-acrylated isosorbide was increased from 0% to 15%, the glass transition temperature T g of the copolymerized PMMA was increased from 151.2 °C to 172.5 °C, and the initial decomposition temperature (T 5%) was increased from 323.1 °C to 396.3 °C. Moreover, the impact strength of copolymerized PMMA increased from 10.59 kJ m-2 to 17.19 kJ m-2 and the tensile strength improved from 84.02 MPa to 97.56 MPa when the mono-acrylated isosorbide was incorporated with different contents. The incorporation of rigid and thermally stable isosorbide could contribute to the improved thermal and mechanical properties of PMMA, which would find important applications in the military and aeronautical materials under harsh service environments.

Enhancement of catalytic performance of porcine pancreatic lipase immobilized on functional ionic liquid modified Fe3O4-Chitosan nanocomposites.

Magnetic chitosan nanocomposites were designed and fabricated by combining the magnetic nanoparticles Fe3O4 and chitosan covalently modified by imidazole-based ionic liquids with various functional groups, to be utilized as a support matrix for immobilization of porcine pancreatic lipase (PPL). Ionic liquids modified chitosan was characterized with nuclear magnetic resonance (NMR) and the nanocomposites were characterized with Fourier transform infrared spectroscopy (FTIR), vibrating-sample magnetometer (VSM), thermogravimetry analysis (TGA), Transmission electron microscope (TEM) and Scanning electron microscopy (SEM). The enzymatic properties of PPL were significantly improved by immobilization onto all thus prepared nanocomposites, and among the supports, modified with ionic liquids bearing hydroxyl group exhibited relatively enhanced performance. Particularly, the MCS-IL(8C)-OH-PPL exhibited the highest specific activity which was 6.68 times that of free PPL, and the residual activity of MCS-IL(8C)-OH-PPL remarkably maintained 91.5% of its initial activity even after 10 repeated cycles. The residual activity of MCS-IL(8C)-OH-PPL retained 55.8% after incubated in 6 M urea solution for 1 h and maintained the noticeable initial activity of 75.5% after incubated in phosphate buffer at 50 °C with pH 7.5 for 6 h. In conclusion, the study demonstrated that Fe3O4@Chitosan nanocomposites modified with functional ionic liquids could be utilized as a novel nanosupport for enzyme immobilization.

Microencapsulated sunblock nanoparticles based on zeolitic imidazole frameworks for safe and effective UV protection.

Sunscreen is believed to protect human skin from photo damage due to UV exposure. However, substantial concerns remain associated with skin contact with UV filters and the subsequent reactive oxygen species from photoactivation of UV filters. Herein, we show that the microencapsulation of octyl p-methoxycinnamate (OMC), a typical UV filter, into the nanoporous structure of zeolitic imidazole frameworks (ZIF-8) prevents the skin exposure to UV filters while improving UV protection performance. Meanwhile, the UV filter photostability has been obviously improved due to the nanoconfinement effect. Microencapsulated OMC in ZIF-8 adhered to the stratum corneum could not only reduce OMC transdermal penetration, but also prevent skin exposure to the deleterious reactive oxygen species (ROS) from photoactivation of OMC. Therefore, this microencapsulated UV filter system based on a metal organic frameworks microporous polymer would find important applications in skin care products through providing safe and effective UV protection.

Immobilization of Candida antarctic lipase B on MWNTs modified by ionic liquids with different functional groups.

Multiwalled carbon nanotubes (MWNTs) were modified by imidazole-based ionic liquids with different kinds of functional groups such as alkyl, carboxyl, amino and hydroxyl. The supports were used to immobilize Candida antarctic lipase B (CALB) and the influence of different functional groups of ionic liquids on enzymatic properties was investigated by the hydrolysis reaction of triacetin. The results revealed that the functionalization process did not destroy the structural integrity of MWNTs, and the enzymatic properities of CALB which immobilized on the MWNTs modified by ionic liquids with different kinds of functional groups were all improved. The hydroxyl functionalized ionic liquids which exhibited the best enzymatic properities was selected to investigate the effects of different carbon chain length on the enzymatic properties of immobilized CALB. Among them, CALB which immobilized on MWNTs modified by hydroxyl functionalized ionic liquid with suitable chain length (MWNTs-IL(8C)-OH-CALB) had the highest specific activity, with a specific activity of 18.11 times that of MWNTs-CALB. Furthermore, it also presented best thermal stability and reusability. The residual activity of MWNTs-IL(8C)-OH-CALB held over 64.01% of the initial activity after being incubated for 20min at 70°C, and the residual activity was 85.56% after 4 cycles of use.

Effect of surface modification of low cost mesoporous SiO2 carriers on the properties of immobilized lipase.

To investigate the surface effects of low cost mesoporous SiO2 on the properties of lipase, a series of modified mesoporous SiO2 was synthesized through various alkoxysilanes reacted with hydroxyl of SiO2 (C1-SiO2, C8-SiO2, C16-SiO2, SH-SiO2, Ph-SiO2, NH2-SiO2). Particularly, ionic liquids as novel alkoxysilane were synthesized and subjected to modify the low cost mesoporous SiO2 (CH3IL-SiO2 and COOHIL-SiO2). The porcine pancreas lipase (PPL) was immobilized on the prepared materials. The activity assay indicated that the activation of enzymatic activity site was benefit from the longer alkyl chain of alkoxysilane because of the growing hydrophobic nature. Nevertheless, the loading of lipase decreased from 69% for PPL-C1-SiO2 to 59% for PPL-C16-SiO2, reflecting the growing hydrophobic property limited the immobilization yield. The characteristic of alkoxysilane group (SH-SiO2, Ph-SiO2, NH2-SiO2) was another important factor to influence immobilization efficiency and enzymatic performance besides the alkyl chain length. The immobilization efficiency of PPL-SH-SiO2, PPL-Ph-SiO2 and PPL-NH2-SiO2 maintained at least 93%. Compared with conventional alkoxysilane, the activity of PPL-CH3IL-SiO2 improved to 2.60 folds of PPL-SiO2. The immobilization efficiency of PPL-COOHIL-SiO2 was up to 97% and the relative activity was above 62% after five recycles.

Functionalized ionic liquid modified mesoporous silica SBA-15: a novel, designable and efficient carrier for porcine pancreas lipase.

A series of functionalized ionic liquid modified mesoporous silicas SBA-15 (FIL-SBA) were synthesized by modulating the loading and cation/anion ratio of the functionalized ionic liquid (FIL). The prepared materials FIL-SBA were used as a novel carrier system to immobilize porcine pancreas lipase (PPL). Enzymatic activity and reusability of the immobilized enzyme were investigated using the triacetin hydrolysis reaction. The combined advantages of the nano-sized pore diameter, large surface area and high pore volume of SBA-15, and the tunable properties of the FIL for enzymes immobilized in FIL-SBA gave a maximum improvement of 570% in relative activity, with 63% retention of initial activity after five cycles of use. Carriers and immobilized enzymes were characterized using nitrogen adsorption, small-angle X-ray diffraction (SXRD), Fourier transform infrared (FT-IR), elemental analysis, nuclear magnetic resonance (NMR), scanning and transmission electron microscopy (SEM and TEM). It was shown that the introduction of FIL influenced the catalytic behavior of PPL significantly by changing the structure and surface properties of the carriers.

Selective dehydration of bio-ethanol to ethylene catalyzed by lanthanum-phosphorous-modified HZSM-5: influence of the fusel.

Bio-ethanol dehydration to ethylene is an attractive alternative to oil-based ethylene. The influence of fusel, main byproducts in the fermentation process of bio-ethanol production, on the bio-ethanol dehydration should not be ignored. We studied the catalytic dehydration of bio-ethanol to ethylene over parent and modified HZSM-5 at 250°C, with weight hourly space velocity (WHSV) equal to 2.0/h. The influences of a series of fusel, such as isopropanol, isobutanol and isopentanol, on the ethanol dehydration over the catalysts were investigated. The 0.5%La-2%PHZSM-5 catalyst exhibited higher ethanol conversion (100%), ethylene selectivity (99%), and especially enhanced stability (more than 70 h) than the parent and other modified HZSM-5. We demonstrated that the introduction of lanthanum and phosphorous to HZSM-5 could weaken the negative influence of fusel on the formation of ethylene. The physicochemical properties of the catalysts were characterized by ammonia temperature-programmed desorption (NH(3)-TPD), nitrogen adsorption and thermogravimetry (TG)/differential thermogravimetry (DTG)/differential thermal analysis (DTA) (TG/DTG/DTA) techniques. The results indicated that the introduction of lanthanum and phosphorous to HZSM-5 could inhibit the formation of coking during the ethanol dehydration to ethylene in the presence of fusel. The development of an efficient catalyst is one of the key technologies for the industrialization of bio-ethylene.

Temperature-induced solid-phase oriented rearrangement route to the fabrication of NaNbO3 nanowires.

We proposed here a temperature-induced solid-phase oriented rearrangement route to the fabrication of NaNbO(3) nanowires by using sandia octahedral molecular sieves (SOMS) Na(2)Nb(2)O(6) x H(2)O as a precursor. The SOMS precursor was prepared by using metal Nb powder as a raw material through the hydrothermal approach.

Mesoporous nanotubes of iron phosphate: synthesis, characterization, and catalytic property.

Iron phosphate nanotubes with mesoporous walls are solvothermally synthesized using sodium dodecyl sulfate (SDS) as a template. With different template concentrations, various shapes of nanosized iron phosphates can be obtained. When the concentration of SDS is set at the transition regions between the lamellar and the hexagonal mesophases, according to its phase diagram, the coassembly of iron phosphate precursor and SDS forms a flake-type mesoporous iron phosphate. Otherwise, nanoparticles or bulky sheets of iron phosphates are obtained. The followed solvothermal treatments on the mesoporous iron phosphate flakes produce iron phosphate nanotubes with mesoporous walls. The removal of the surfactant by acetate exchange and heat treatment results in the clean mesoporous nanotubes of iron phosphate with diameters of 50-400 nm and lengths of several microns. The nanotubular and mesoporous iron phosphate possesses a specific surface area of 232 m2/g and a bimodal distribution of pore sizes, corresponding to the size of mesopores in the walls and the diameter of the nanotubes, respectively. The novel nanotubular iron phosphate with composite meso-macroporous structure, in favor of the diffusion of reactive molecules, has been tested for direct hydroxylation of benzene with hydrogen peroxide and has shown better catalytic performance compared with the conventional particulate mesoporous iron phosphate.