Non-encapsulated Counterparts Research Articles

Protocell Flow Reactors for Enzyme and Whole-Cell Mediated Biocatalysis.

The design and construction of continuous flow biochemical reactors comprising immobilized biocatalysts have generated great interest in the efficient synthesis of value-added chemicals. Living cells use compartmentalization and reaction-diffusion processes for spatiotemporal regulation of biocatalytic reactions, and implementing these strategies into continuous flow reactors can offer new opportunities in reactor design and application. Herein, the fabrication of protocell-based continuous flow reactors for enzyme and whole-cell mediated biocatalysis is demonstrated. Semipermeable membranized coacervate vesicles are employed as model protocells that spontaneously sequester enzymes or accumulate living bacteria to produce embodied microreactors capable of single- or multiple-step catalytic reactions. By packing millions of the enzyme/bacteria-containing coacervate vesicles in a glass column, a facile, cost-effective, and modular methodology capable of performing oxidoreductase, peroxidase and lipolytic reactions, enzyme-mediated L-DOPA synthesis, and whole-cell glycolysis under continuous flow conditions, is demonstrated. It is shown that the protocell-nested enzymes and bacterial cells exhibit enhanced activities and stability under deleterious operating conditions compared with their non-encapsulated counterparts. These results provide a step toward the engineering of continuous flow reactors based on cell-like microscale agents and offer opportunities in the development of green and sustainable industrial bioprocessing.

Block Copolymer Micelles Encapsulating Au(III) Bis(Dithiolene) Complexes as Promising Nanostructures with Antiplasmodial Activity.

Block copolymer micelles (BCMs) can be used to improve the solubility of lipophilic drugs and increase their circulation half-life. Hence, BCMs assembled from MePEG-b-PCL were evaluated as drug delivery systems of gold(III) bis(dithiolene) complexes (herein AuS and AuSe) to be employed as antiplasmodial drugs. These complexes exhibited remarkable antiplasmodial activity against liver stages of the Plasmodiumberghei parasite, and low toxicity in a model of zebrafish embryos. To improve the complexes' solubility, BCMs were loaded with AuS, AuSe, and the reference drug primaquine (PQ). PQ-BCMs (Dh = 50.9 ± 2.8 nm), AuSe-BCMs (Dh = 87.1 ± 9.7 nm), and AuS-BCMs (Dh = 72.8 ± 3.1 nm) were obtained with a loading efficiency of 82.5%, 55.5%, and 77.4%, respectively. HPLC analysis and UV-Vis spectrophotometry showed that the compounds did not suffer degradation after encapsulation in BCMs. In vitro release studies suggest that AuS/AuSe-BCMs present a more controlled release compared with PQ-loaded BCMs. The antiplasmodial hepatic activity of the drugs was assessed in vitro and results indicate that both complexes present higher inhibitory activity than PQ, although encapsulated AuS and AuSe presented lower activity than their non-encapsulated counterparts. Nevertheless, these results suggest that the use of BCMs as delivery vehicles for lipophilic metallodrugs, particularly AuS and AuSe, could enable the controlled release of complexes and improve their biocompatibility, constituting a promising alternative to conventional antimalarial treatments.

Amoebicidal and trichomonicidal capacity of polymeric nanoparticles loaded with extracts of the plants Curcuma longa (Zingiberaceae) and Berberis vulgaris (Berberidaceae)

Introduction: In tropical and developing countries, pathogenic protozoa are a major public health problem. Objective: The main objective of this study was the evaluation of ethanol extracts of Curcuma longa and Berberis vulgaris, as well as their main components curcumin (Cur) and berberine (Ber) in non-encapsulated form and encapsulated into polymeric nanoparticles (NPs) on Entamoeba histolytica and Trichomonas vaginalis trophozoites as well as to evaluate the hemolytic activity. Additionally, we studied the morphology of the NPs, average particle size, polydispersity index (PDI), and encapsulation percentages (%EE) of the formulations. Methods: For this purpose, the activity of the encapsulated and non-encapsulated treatments against E. histolytica and T. vaginalis was evaluated by the microassay technique (in-vitro). In addition, the cytotoxic capacity was determined by the hemolysis technique in healthy erythrocytes. The size and morphology of the NPs were determined by photon correlation spectroscopy and scanning electron microscopy (SEM). Results: Phytochemical analysis of the extracts showed that C. longa had mainly tannins, phenols and flavonoids, and B. vulgaris alkaloids. The NPs were significantly (P < 0.001) more effective compared to their non-encapsulated counterparts, but CurNPs and BerNPs were the most efficient treatments. CurNPs showed IC50 values (μg/mL) of 9.48 and 4.25, against E. histolytica and T. vaginalis respectively, and BerNPs 0.24 and 0.71. The respective particle sizes and encapsulation percentages for CurNPs and BerNPs were 66.5 and 73.4 nm, 83.59 and 76.48 %, respectively. SEM shows that NPs had a spherical morphology. Finally, we analyzed whether ethanolic extracts and NPs induced hemolytic activity and found that significantly NPs reduced hemolysis compared to the non-encapsulated extracts. Conclusions: Therefore, these findings suggest that the use of NPs represent a valuable and novel source of administration of bioactive compounds for the therapeutic treatment of diseases caused by protozoa of clinical interest since they potentiate the amebicidal and trichomonicidal activity of the administered products without significant hemolytic activity.

Microencapsulation and Bioaccessibility of Phenolic Compounds of Vaccinium Leaf Extracts.

In recent years, Vaccinium spp. (bilberry-VMT, lingonberry-VVIT, and blueberry-VCS) have sparked particular interest for their prospective health benefits. The latest investigations have place them as important alternative sources of nutraceuticals as their leaves are the main by-products of berry harvesting. The present study is aimed at investigating the bioaccessibility of phenolic compounds from leaves of the Vaccinium species, both as microencapsulated powder and aqueous extracts, following exposure to in vitro simulated digestion. Moreover, the impact of maltodextrin and glucose microencapsulation carriers on the extracts’ phenolic content was assessed. Prior to encapsulation, the viscosity of the emulsions was shown at a shear stress of 50 s−1 dilatant and a Newtonian behaviour above this value with a final viscosity between 1.024 and 1.049 mPa·s. The final microencapsulation yield for the samples ranged between 79 and 81%. Although the microencapsulated forms presented a targeted release at the intestinal level, the phenolic content decreased after gastrointestinal digestion. The bioaccessibility of the microencapsulated extracts showed higher values than their non-encapsulated counterparts, with the highest value of 45.43% in the VVIT sample, followed by VCS with 41.07%. However, the non-encapsulated VCS sample presented high bioaccessibility after in vitro digestion (38.65%). As concluded, further in vivo research should be conducted on the leaves of the Vaccinium species.

Efficient protection of microorganisms for delivery to the intestinal tract by cellulose sulphate encapsulation

BackgroundGut microbiota in humans and animals play an important role in health, aiding in digestion, regulation of the immune system and protection against pathogens. Changes or imbalances in the gut microbiota (dysbiosis) have been linked to a variety of local and systemic diseases, and there is growing evidence that restoring the balance of the microbiota by delivery of probiotic microorganisms can improve health. However, orally delivered probiotic microorganisms must survive transit through lethal highly acid conditions of the stomach and bile salts in the small intestine. Current methods to protect probiotic microorganisms are still not effective enough.ResultsWe have developed a cell encapsulation technology based on the natural polymer, cellulose sulphate (CS), that protects members of the microbiota from stomach acid and bile. Here we show that six commonly used probiotic strains (5 bacteria and 1 yeast) can be encapsulated within CS microspheres. These encapsulated strains survive low pH in vitro for at least 4 h without appreciable loss in viability as compared to their respective non-encapsulated counterparts. They also survive subsequent exposure to bile. The CS microspheres can be digested by cellulase at concentrations found in the human intestine, indicating one mechanism of release. Studies in mice that were fed CS encapsulated autofluorescing, commensal E. coli demonstrated release and colonization of the intestinal tract.ConclusionTaken together, the data suggests that CS microencapsulation can protect bacteria and yeasts from viability losses due to stomach acid, allowing the use of lower oral doses of probiotics and microbiota, whilst ensuring good intestinal delivery and release.

Design, Fabrication, Characterization, and In Vitro Digestion of Alkaloid-, Catechin-, and Cocoa Extract-Loaded Liposomes.

Liposomes containing theobromine, caffeine, catechin, epicatechin, and a cocoa extract were fabricated using microfluidization and sonication. A high encapsulation efficiency and good physicochemical stability were obtained by sonication (75% amplitude, 7 min). Liposomes produced at pH 5.0 had mean particle diameter ranging from 73.9 to 84.3 nm. The structural and physicochemical properties of the liposomes were characterized by transmission electron microscopy, confocal fluorescence microscopy, and antioxidant activity assays. The release profile was measured by ultra-high performance liquid chromatography coupled to diode array detection. The bioaccessibility of the bioactive compounds encapsulated in liposomes was determined after exposure to a simulated in vitro digestion model. Higher bioaccessibilities were measured for all catechins-loaded liposome formulations as compared to nonencapsulated counterparts. These results demonstrated that liposomes are capable of increasing the bioaccessibility of flavan-3-ols, which may be important for the development of nutraceutical-enriched functional foods.

Encapsulation of polyphenolic antioxidants obtained from Momordica charantia fruit within zein/gelatin shell core fibers via coaxial electrospinning

Abstract This study dealt with fabricating and characterizing nano fibrillar bilayer structures encapsulated with Momordica charantia fruit extract. Coaxial shell core zein/ gelatin nano fiber structure was successfully produced at 20 kV, 0.5 ml/h and 10 cm of voltage, flow rate and emitter/collector distance, respectively. The gelatin fiber was encapsulated with bitter gourd extract (BGE) at 5–15% (w/w%) loading rate. Statistical analysis of scanning electron micrographs showed the encapsulation process resulted in a non-significant (P > 0.05) increase in average fiber diameter. Morphological analysis through transmission electron microscopy (TEM) confirmed fabrication of the bilayer structure as well as encapsulation of the extract. Furthermore, spectroscopic analysis by FTIR illustrated the formation of composite coaxial fibers through electrospinning process. However, encapsulation at various loading rates did not result in any chemical interaction between core and wall materials. Thermogravimetric graphs of encapsulated fibers, at all core loadings, illustrated an additional third phase, absent in non-encapsulated fibers, which confirms encapsulation occurrence. Moreover, glass transition temperature decreased in both first and second heating scans of differential scanning calorimetry (DSC) thermograms due to BGE encapsulation process. Furthermore, coaxial encapsulation process managed to conserve an average of 88% of antioxidative content and potency in all cases. Besides this, shelf stability of the encapsulated extract at both refrigerated and ambient conditions were significantly extended when compared to their non-encapsulated counterparts.

Dioxovanadium(V) complexes of Schiff and tetrahydro-Schiff bases encapsulated in zeolite-Y for the aerobic oxidation of styrene

A series of dioxovanadium(V) complexes of Schiff and tetrahydro-Schiff bases were encapsulated into the supercages of zeolite-Y and were characterized by X-ray diffraction, SEM, N2 adsorption/desorption, FT-IR, UV-vis spectroscopy, ICPAES, pair distribution function (PDF) and X-ray absorption near edge structure (XANES) measurements. The encapsulation is achieved by a flexible ligand method in which the transition metal cations were first ion-exchanged into zeolite-Y and then complexed with ligands. The dioxovanadium-exchanged zeolite, dioxovanadium complexes encapsulated in zeolite-Y plus non-encapsulated homogeneous counterparts were all screened as catalysts for the aerobic oxidation of styrene under mild conditions. It was found that the encapsulated complexes showed better activity than their respective nonencapsulated counterparts in most cases. All encapsulated dioxovanadium tetrahydro-Schiff base complexes showed much higher activity in aerobic oxidation of styrene than their corresponding Schiff base complexes.

Surface modification of gold and quantum dot nanoparticles with chitosan for bioapplications

Gold (Au) and quantum dot (QD) nanoparticles, which have been extensively used in many fields, were encapsulated with a natural polymer, chitosan, to improve their biocompatibility. Characterization was performed using ultraviolet-visible, dynamic light scattering, atomic force microscopy, and transmission electron microscope analyses. It was found that a Au/chitosan ratio of 1:1 and smaller produced chitosan-encapsulated Au nanoparticles of a sufficiently small size, and this result was then applied in the chitosan encapsulation of QDs. The biocompatibility of both types of nanoparticles was assessed in cell culture studies using HT29 human colon carcinoma and NIH 3T3 mouse fibroblast cells. MTT and trypan blue exclusion assays revealed that both chitosan-encapsulated Au nanoparticles and QDs exhibited improved biocompatibility over their bare, nonencapsulated counterparts. Therefore, this study showed that chitosan could be used to encapsulate both Au nanoparticles and QDs in order to enhance their biocompatibility. The approaches developed in this study can also be extended to other nanoparticles for bioapplications as well.

Inhibition in vitro de la croissance de Chlamydia trachomatis par des cyclines encapsulées dans les liposomes

The antichlamydial activity of tetracycline (Tet) and doxycycline (Dox) encapsulated in cationic (CaL), anionic (AnL) and neutral (NtL) liposomes has been evaluated in vitro by adding serial dilutions of antibiotics (minimum inhibitory concentration, MIC: 0.12–0.007 μg/ml; MBC: 4 to 0.25 μg/ml) to HeLa 229 cell monolayers inoculated with Chlamydia trachomatis L 2/434/Bu (10 3 ufi/ml). Following 72 h incubation at 37°C under a 5% CO 2 atmosphere, the chlamydial inclusions were stained by the May-Giemsa method to determine the MICs. After a second and third passage, the MBC 1 and MBC 2 were determined in antibiotic-free medium. The chlamydial inclusions were then counted to assess the degree of growth inhibition at each antibiotic dilution tested for MBC 1 and MBC 2 determinations. The MIC, MBC 1 and MBC 2 of the various antichlamydial agents were as follows: Tet (0.12; 4; 4), AnL-Tet (0.01; 1; 1), NtL-Tet (0.03; 1; 2), Dox (0.06; 1; 2), CaL-Dox (0.03; 0.5; 2), AnL-Dox (0.01; 1; 2), and NtL-Dox (0.03; 0.5; 0.5). It was found that Tet and Dox liposome-encapsulated antibiotics were more active than their non-encapsulated counterparts, and the inclusion count showed a higher inhibitory activity of the former antibiotics on chlamydial growth. The inhibition of chlamydial growth by AnL-Tet may be of bactericidal nature. In conclusion, liposome-encapsulated drugs could be of value in the treatment of chlamydial infections