Biqiang Chen

Self-assembled serum albumin–poly(L-lactic acid) nanoparticles: a novel nanoparticle platform for drug delivery in cancer

We developed a new self-assembled bovine serum albumin–poly(L-lactic acid) nanoparticle platform for anticancer drug delivery made from a bovine serum albumin–poly(L-lactic acid) polymer conjugate. Depending on the ratio of bovine serum albumin (BSA) to poly(L-lactic acid) (PLLA), these conjugates self-assemble into uniform spherical nanoparticles with different sizes. Then, BA-loaded BSA–PLLA nanoparticles (BSA–PLLA/BA NPs) were prepared by using BSA–PLLA conjugates as prototype materials, and betulinic acid (BA) as a model drug. In vitro cytotoxicity studies with human lung cancer cell lines (A549) and murine Lewis lung carcinoma (LLC) cell lines suggested that the BSA–PLLA/BA NPs were significantly superior to the model drug BA in antitumor activity and the BSA–PLLA NPs were non-toxic. Compared to free BA, the BSA–PLLA/BA NPs provided significantly higher blood circulation half-time of free BA (5.02-fold). The antitumor effect of the BSA–PLLA/BA NPs in a mouse tumor xenograft model showed much better tumor inhibition efficacy and fewer side effects than that of free BA. It may be attributed to the preferential tumor accumulation and increases the solubility of the drug in water, strongly supporting their use as high-performance carriers for anti-cancer therapy.

Using imidazolium-based ionic liquids as dual solvent-catalysts for sustainable synthesis of vitamin esters: inspiration from bio- and organo- catalysis†

Vitamin E (VE) has significant biological activities and thus its acylation to increase its stability is of extreme interest. We developed an efficient and sustainable approach using imidazolium-based ionic liquids as dual solvent-catalysts for the esterification between α-tocopherol (the most active form of VE) and succinic anhydride. Although in literature it is reported that lipase can catalyze this reaction, hereby we demonstrate that the reaction observed in DMSO and DMF is catalyzed by the histidyl residues of the protein. Histidine and its analogue containing an imidazole ring were tested as organocatalysts for the production of α-tocopherol succinate. In light of the imidazole organocatalysis, commercially-available 3-alkyl-1-methyl imidazolium ILs [CnC1Im][X−] were investigated as dual solvent-catalysts for the esterification of α-tocopherol with succinic anhydride, and provided satisfactory yields and reaction rates. [C5C1Im][NO3−] can be recycled by water extraction, instead of organic solvent extraction to separate α-tocopherol succinate from [C5C1Im][NO3−], with an average yield of 94.1% for 4 subsequent batches, while the catalytic activity of the recycled ILs showed almost no loss after 4 batches. The developed protocol for the synthesis of α-tocopherol esters and IL recycling bears industrial potential due to the ease of use and the efficient recycling.

Theoretical and experimental studies on activity of Yarrowia lipolytica lipase in methanol/water mixtures.

Methanol is regularly used as a substrate for biodiesel synthesis. Excess methanol can however inhibit the lipase activity. In the present work, the activity and conformational changes of Yarrowia lipolytica lipase (LIP2) at different concentrations of methanol were investigated by measuring fluorescence, UV-vis spectra, and molecular dynamics simulations. The lipase tended to expand at higher concentrations of methanol, and the methanol molecules were able to enter into the LIP2, leading to microenvironment changes around the aromatic amino acids. More hydrophobic groups were exposed to the solvents at high methanol concentrations, and the original hydrophobic interaction in the protein was destroyed, thus resulting in the tertiary structure change of the lipase.

Immobilization of Yarrowia lipolytica lipase Ylip2 for the biocatalytic synthesis of phytosterol ester in a water activity controlled reactor.

In this work, phytosterol ester was synthesized using Yarrowia lipolytica lipase Ylip2 that had been immobilized on inorganic support in a solvent-free system and reacted in a computer-aided water activity controlled bioreactor. The immobilization of Ylip2 on celite led to a remarkable increase in the phytosterol conversion compared to that of free lipase. An investigation of the reaction conditions were oleic acid as the fatty acid variety, 10,000U/g substrate, and a temperature of 50°C for phytosterol ester synthesis. Controlling of the water activity at a set point was accomplished by the introduction of dry air through the reaction medium at a digital feedback controlled flow rate. For the esterification of phytosterol ester, a low (15%) water activity resulted in a considerable improvement in phytosterol conversion (91.1%) as well as a decreased reaction time (78h). Furthermore, Ylip2 lipase immobilized on celite retained 90% esterification activity for the synthesis of phytosterol oleate after reused 8 cycles, while free lipase was only viable for 5 batches with 90% esterification activity remained. Finally, the phytosterol oleate space time yield increased from 1.65g/L/h with free lipase to 2.53g/L/h with immobilized lipase. These results illustrate that the immobilized Yarrowia lipolytica lipase Ylip2 in a water activity controlled reactor has great potential for the application in phytosterol esters synthesis.

Synergistic effects of amine and protein modified epoxy-support on immobilized lipase activity

We have developed an improved and effective method to immobilize Yarrowia lipolytica lipase Lip2 (YLIP2) on an epoxy poly-(glycidylmethacrylate-triallyisocyanurate-ethyleneglycoldimethacrylate) (PGMA-TAIC-EGDMA) support structure with or without amine or/and protein modifications. Our results show that there is an increase in the activity of the immobilized lipase on n-butylamine (BA) modified support (420U/g support) and the biocompatible gelatin modified support (600U/g support) when compared to the support without modification (240U/g support). To further study the influences of BA and gelatin modification on the activity of the immobilized lipase, gelatin and BA were concurrently used to decorate the support structure. Lipase immobilized on 2% BA/gelatin (1:1) modified support obtained the highest activity (1180U/g support), which was five-fold higher than that on a native support structure. These results suggest that the activity of a support-immobilized lipase depends on the support surface properties and a moderate support surface micro-environment was crucial for elevated activity. Collectively, these data show that a combined gelatin and BA modification regulates the support surface more suitable for immobilizing YLIP2.

Enhancing trimethylolpropane esters synthesis through lipase immobilized on surface hydrophobic modified support and appropriate substrate feeding methods.

Candida sp. 99-125 lipase immobilized on surface hydrophobic modified support and appropriate substrate feeding methods were used to improve the synthesis of tri-substituted trimethylolpropane (TMP) esters, which can be used as raw materials for biodegradable lubricants. The proposed novel production method is environmentally friendly. Lipase was adsorbed on surface hydrophobic silk fibers that were pretreated by amino-modified polydimethylsiloxane. A 5-level-4-factors central composite model, including reaction time, temperature, enzyme amount, and molar ratio of fatty acid to TMP, was designed to evaluate the interaction of process variables in the enzymatic esterification. The water activity was kept constant using a LiCl-saturated salt solution. Under the optimum conditions with 30% enzyme amount and substrates molar ratio 8.4 at 45°C for 47h, the total conversion of caprylic acid is 97.3% and the yield of tri-substituted TMP esters is 95.5%. The surface hydrophobic treatment resulted in less cluster water accumulated on the surface immobilized lipase, which was demonstrated by near-infrared spectra. Consequently, the optimum temperature and water tolerance of immobilized lipase were increased. Two TMP-feeding methods were used to maintain high molar ratio of fatty acid to TMP, and increase the final tri-substituted TMP esters content exceeding 85% (w/w) in reactant.

Synthesis of biosafe isosorbide dicaprylate ester plasticizer by lipase in a solvent-free system and its sub-chronic toxicity in mice

In this study, biosafe isosorbide dicaprylate ester based plasticizer was prepared using renewable feedstock with lipase in a solvent-free system. Different kinds of water removal methods and some important factors including molar ratio of the substrates, reaction temperature and catalyst loading were investigated. Bubbling dried air was determined to be the most effective water removal method. The activation energy (E) of hydrolysis and esterification to form di-substituted isosorbide were examined to determine the limiting step in the synthesis of isosorbide dicaprylate ester. The Ehydrolysis (25.51 kJ mol−1) was found to be higher than Esynthesis (35.65 kJ mol−1), demonstrating that the formation of diester from monoester is the critical step in the process. The lipase can be recycled up to 16 times while 80% diester was maintained. Additionally, the properties of poly(vinyl chloride) PVC blends plasticized with isosorbide ester as secondary plasticizer was studied. The results indicated that the thermal stability of plasticized PVC blends was improved, and the tensile strength was increased. Furthermore, the sub-chronic toxicity study in mice showed that the isosorbide ester was safe, indicating its great potential in industrial applications as a plasticizer.

Solvothermal synthesis of FeCo nanoparticles for magneto-controllable biocatalysis

A facile and simple one-step solvothermal method has been developed to synthesize FeCo nanoparticles with well-controlled composition, desired morphology and high saturation magnetization, which exhibit component-dependent magnetic behaviors: the increase of Fe content leads to the increase of saturation magnetization and the decrease of coercivity. Furthermore, due to the availability of a coarse surface for the stable adsorption of targeted cargo, the high saturation magnetization for efficient control and directional separation from a reaction mixture by an external magnetic field, the as-prepared magnetic FeCo nanoparticles could work as a fuel-free magneto-controllable carrier to load biocatalytically-active cargo lipase for magneto-controllable and recyclable biocatalytic synthesis of lauryl laurate under an external magnetic field. By alternate positioning of the FeCo carrier with loaded cargo in and out of the substrate solution, the biocatalysis for esterification from lauric acid and lauryl alcohol to lauryl laurate could be switched between “On” and “Off” states.

Improving performance of Yarrowia lipolytica lipase lip2-catalyzed kinetic resolution of (R, S)-1-phenylethanol by solvent engineering

Abstract Extracellular Yarrowia lipolytica lipase Lip2 (YLIP2) demonstrated an (R)-enantiopreference for efficient resolution of (R,S)-1-phenylethanol by solvent engineering with different kinds of binary solvent. The enantioselectivity was significantly improved by the addition of 1, 4-dioxane. The reaction parameters including co-solvent concentration, reaction temperature, and the reaction time were optimized. When the reaction was carried out with n-hexane in the presence of 0.8% 1,4-dioxane at 50°C for 72 h, the enantiomeric excess of product markedly increased to 99.1% from 66% in pure n-hexane; the enantiomeric ratio was higher than 200, which was 500-fold compared with that in pure n-hexane. The results indicated that it is very important to design the proper co-solvents, especially to create appropriate micro-environment for YLIP2 for catalyzing the resolution of (R,S)-1-phenylethanol.

Environmentally-friendly strategy for separation of 1,3-propanediol using biocatalytic conversion

Glycerol waste from the biodiesel production can be used as a carbon source in the production of 1,3-propanediol (1,3-PD) through microbial fermentation. However, downstream processing is a major bottleneck that restricts its biological production. Here, we investigated an environmentally-friendly method to enzymatically separate 1,3-PD. The transformation of 1,3-PD to an ester was achieved by exploiting the esterification reaction with fatty acids under lipase catalysis. The reaction efficiency was optimized using different poly-alcohols that were existed in the fermentation broth reacted with a fatty acid. Whereas the 1,3-PD conversion reached 62%, only a 0.06% and 0.08% conversion was reached for 2,3-butanediol and glycerol, illustrating the formers more efficient separation. The recovery efficiency of 1,3-PD was 96%. Finally, 1,3-PD was obtained by lipase-directed ester hydrolysis. Taken together, the bio-catalyzed separation process presented here is a novel and promising method for recovering 1,3-PD.