•Chitosan nanoparticles were prepared using TPP as a cross-linking agent.•A membrane was used for micromixing the TTP and chitosan solutions.•The anti-Alzheimer's drug tacrine was loaded in the ...chitosan nanoparticles.•Nanoparticles had a mean size of 90–100nm and a polydispersity index of 0.22.•Tacrine encapsulation efficiency was found to equal 66.1%.
Chitosan nanoparticles were prepared by a novel technique based on ionic gelation using sodium tripolyphosphate (TPP) as cross-linking agent. In this method, the TPP solution flows through the pores of a microengineered membrane into the chitosan solution put in a stirred cell. It is shown that favorable micromixing conditions are created on top of the membrane surface to form chitosan–TPP nanoparticles. The influence of several formulation parameters (chitosan and TPP concentrations, ratio between volumes of the two solutions, pH of the two solutions, chitosan molecular weight) and process parameters (membrane characteristics, injection speed, stirring rate) were investigated. Under optimum conditions, chitosan–TPP nanoparticles had a mean size around 90–100nm, polydispersity index around 0.22, and zeta potential close to +31mV. The encapsulation of the anti-Alzheimer's drug tacrine did not change the mean size and polydispersity index of unloaded nanoparticles, whereas the zeta potential was increased to +38mV due to the positively charge of tacrine. Under optimum conditions, tacrine encapsulation efficiency into nanoparticles was found equal to 66.1%. In addition, chitosan–TPP nanoparticles were shown to be stable at least during 25 days in an acidic medium at 4 or 25°C. This study demonstrates that ionic gelation using a stirred cell with microengineered membrane is a suitable technique for preparation of chitosan–TPP nanoparticles.
. Preparation of liposomes using a membrane contactor.
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► We present a novel liposome preparation strategy using a hollow fiber module. ► The technique is fast, reproducible and has a ...potential for industrial production. ► We studied the influence of process parameters on liposome characteristics. ► High entrapment efficiency was achieved when filling liposomes with spironolactone. ► Spironolactone release from liposomes was rapid and complete within 5
h.
In this study, we present a novel liposome preparation technique suitable for the entrapment of pharmaceutical and cosmetic agents. This new method uses a membrane contactor in a hollow fiber configuration. In order to investigate the process, key parameters influence on the liposome characteristics was studied. It has been established that the vesicle size distribution decreased with the organic phase pressure decrease, the phospholipid concentration decreases and the aqueous to organic phase volume ratio increases. Liposomes were filled with a hydrophobic drug model, spironolactone that could be used for a paediatric medication. The mean size of drug-free and drug-loaded liposomes was, respectively, 113
±
4
nm and 123
±
3
nm. The zeta potential of drug-free and drug-loaded liposomes was, respectively, −43
±
0.7
mV and −23
±
0.6
mV. High entrapment efficiency values were successfully achieved (93
±
1.12%). Transmission electron microscopy images revealed nanometric sized and spherical shaped oligo-lamellar vesicles. The release profile showed a rapid and complete release within about 5
h. Additionally, special attention was paid on process reproducibility and long term lipid vesicles stability. Results confirmed the robustness of the hollow fiber module based technique. Moreover, the technique is simple, fast and has a potential for continuous production of nanosized liposome suspensions at large scale.
The membrane emulsification process-a review Charcosset, C; Limayem, I; Fessi, H
Journal of chemical technology and biotechnology (1986),
March 2004, Letnik:
79, Številka:
3
Journal Article
Vitamin E or α-tocopherol is widely used as a strong antioxidant in many medical and cosmetic applications, but is rapidly degraded, because of its light, heat and oxygen sensitivity. In this study, ...we applied the nanoprecipitation method to prepare vitamin E-loaded nanocapsules, at laboratory-scale and pilot-scale. We scaled-up the preparation of nanocapsule with the membrane contactor technique. The effect of several formulation variables on the vitamin E-loaded nanocapsules properties (mean diameter, zeta potential, and drug entrapment efficiency) was investigated. The optimized formulation at laboratory-scale and pilot-scale lead to the preparation of vitamin E-loaded nanocapsules with mean diameter of 165 and 172nm, respectively, and a high encapsulation efficiency (98% and 97%, respectively).
The growing scarcity of freshwater is driving the implementation of desalination on an increasingly large scale. However, the energy required to run desalination plants remains a drawback. The idea ...of using renewable energy sources is fundamentally attractive and many studies have been done in this area. Membrane processes are also gaining much interest for their scaled-up ability and their economic feasibility. This article provides a state-of-theart review on membrane processes associated with renewable energies for seawater and brackish water desalination. The membrane processes include reverse osmosis, membrane distillation and electrodialysis. They are coupled with renewable energies such as solar, wind, wave, and hydrostatic pressure. This article presents the main results in this field including principles, plant design and implementation, mathematical models and economic feasibility.
This paper presents numerical simulations and experimental data on the iodide–iodate reaction in a hollow fiber membrane device. The principle of reactive mixing in a membrane device is the ...following. Component
A flows through the inlet of the lumen side and component
B comes from the membrane pores (shell side). Components
A and
B then mix and react inside the lumen side. Experimental measurements of the segregation index were carried out under various experimental conditions and for two different hollow fiber devices. The numerical and experimental segregation indexes,
X
S
, were found in the range 10
−2–10
−3, indicating effective mixing. The numerical simulations showed that
I
3
−
ions were produced mainly in the first part of the lumen side of the hollow fiber. This confirmed our previous results on precipitation which showed that high supersaturation data and experimental fouling were obtained in this part of the hollow fibers.
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The targeted release of drugs intended for pulmonary delivery is a research field which has been so far rather unexploited but is currently becoming increasingly attractive. Liquid ...dispersions encapsulating vitamin E (liposomes, micelles, nano-emulsion, and solid lipid particles) were prepared using various methods based on membrane contactor. The dispersions were nebulized and aerodynamic characteristics of the generated aerosols were assessed using two different methods: laser light scattering and cascade impaction. When the laser diffraction technique was used, results showed that fine particle fractions (<5μm) were 19, 29, 38 and 71% for solid lipid particles, micelles, nano-emulsion and liposomes, respectively. When the impaction method was applied, using a next generation pharmaceutical impactor operated at 30l/min, results showed that fine particle fractions were 39, 78, 82 and 87% for solid lipid particles, micelles, nano-emulsion and liposomes, respectively. The differences observed between the results obtained from both methods confirm that the laser diffraction method is not always suitable for aerodynamic characterization of aerosols and should be validated against an impaction method. Nebulization of the drug-carrier systems led to an increase of their size most likely due to aggregation phenomena. The size was increased by a factor of 2–26 depending on the encapsulation system. The most important aggregation was obtained with nano-emulsion; the less one with solid lipid particles. The mass median aerodynamic diameter (MMAD) of the generated aerosols ranged from 1.76 to 6.10μm. The application of a mathematical model, the Multiple-Path Particle Dosimetry (MPPD), for the prediction of the pulmonary deposit gave encouraging results. The rate of vitamin E able to reach the lung ranged from 37.6 (for the liposomes) to 51.6% (for the micelles). The obtained results showed that the different systems developed for vitamin E encapsulation were suitable to target the lung after pulmonary administration by nebulization.
Removal of fluoride ions using cuttlefish bones Ben Nasr, A.; Walha, K.; Charcosset, C. ...
Journal of fluorine chemistry,
2011, 2011-1-00, 20110101, Letnik:
132, Številka:
1
Journal Article
Recenzirano
This work investigates the possibility of eliminating, by adsorption, the excess of fluoride in overloaded water using cuttlefish bone. The optimal conditions for the use of cuttlefish bone were ...determined on synthetic sodium fluoride solutions. The effectiveness of the adsorption process on the cuttlefish bone on natural waters loaded with fluoride was verified. Following regeneration, the adsorbent can be used for further removal of fluoride.
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▶ Cuttlefish bone was characterized. Elemental analysis shows that the cuttlebone is formed mainly by calcium carbonate. ▶ Cuttlefish bone was effective towards fluoride removal from naturally fluoridated water. ▶ Regeneration studies (adsorption–desorption studies) indicated that cuttlefish bone may be regenerated.
Because of the high toxicity of fluoride to mankind, there is an urgent need to treat fluoride-contaminated drinking water to make it safe for human consumption. This work investigated the possibility of eliminating, by sorption, the excess of fluoride in overloaded water according to World Health Organization WHO recommendations. We tested the cuttlefish bone as an adsorbent material (available in Tunisia) for the defluoridation of water. Initially, we determined the optimal conditions of use (contact time, pH effect, adsorbent dose, initial fluoride concentration) of the cuttlefish bone on synthetic solutions of sodium fluoride. The second step was to verify the effectiveness of the sorption process on the cuttlefish bone by testing it on natural waters loaded with fluoride. The results obtained showed that sorption on the cuttlefish bone could be an effective method for the removal of fluoride. The efficacy of cuttlefish bone to remove fluoride from water was found to be 80% at pH 7.2, 1
h contact time, 15
g
L
−1 adsorbent dose and 5
mg
L
−1 initial fluoride concentration. Despite the different anions (Cl
− and SO
4
2−) generally present in natural waters, a fluoride concentration in agreement with the norm (<1.5
mg
L
−1) could be reached whatever the water treated. The regeneration of the cuttlefish bone was performed with a NaOH solution (10
g of cuttlefish bone/1000
mL NaOH 3
M). After 1
h of agitation, 95% of fluorides were desorbed. Following regeneration, the adsorbent can be used for further removal of fluoride.
•Uniform POPC and Lipoid® E80 liposomes were produced using microengineered membrane.•Three different methods of generating shear stress on the membrane surface were used.•POPC vesicles with 80nm ...size were made using a ring membrane oscillating at 40Hz.•The mean vesicle size increased with increasing the pore size and injection time.•The mean vesicle size of 80–86nm and a CV of 26–36% was suitable for drug delivery.
A novel ethanol injection method using microengineered nickel membrane was employed to produce POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) and Lipoid® E80 liposomes at different production scales. A stirred cell device was used to produce 73ml of the liposomal suspension and the product volume was then increased by a factor of 8 at the same transmembrane flux (140lm−2h−1), volume ratio of the aqueous to organic phase (4.5) and peak shear stress on the membrane surface (2.7Pa). Two different strategies for shear control on the membrane surface have been used in the scaled-up versions of the process: a cross flow recirculation of the aqueous phase across the membrane surface and low frequency oscillation of the membrane surface (∼40Hz) in a direction normal to the flow of the injected organic phase. Using the same membrane with a pore size of 5μm and pore spacing of 200μm in all devices, the size of the POPC liposomes produced in all three membrane systems was highly consistent (80–86nm) and the coefficient of variation ranged between 26 and 36%. The smallest and most uniform liposomal nanoparticles were produced in a novel oscillating membrane system. The mean vesicle size increased with increasing the pore size of the membrane and the injection time. An increase in the vesicle size over time was caused by deposition of newly formed phospholipid fragments onto the surface of the vesicles already formed in the suspension and this increase was most pronounced for the cross flow system, due to long recirculation time. The final vesicle size in all membrane systems was suitable for their use as drug carriers in pharmaceutical formulations.
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