Modified supercritical antisolvent method with enhanced mass transfer to fabricate drug nanoparticles

The main aim of this study was to modify the supercritical antisolvent precipitation method to enhance the mass transfer in order to prepare smaller nanoparticles of drugs. The supercritical antisolvent apparatus was customized by introducing a titanium horn in the precipitation chamber for generation of the ultrasonic field for enhanced mass transfer and the method was called supercritical antisolvent with enhanced mass transfer (SAS-EM). The effects of flow rate, ultrasonic amplitude, drug concentration and flow time on the particle size were investigated. The results showed that increasing the flow rate, incrementing the ultrasonic power up to an optimum point, decreasing the drug concentration and reducing the flow time helped to achieve smaller quercetin particles in the range of 120–450 nm. It is also shown that there is a tradeoff between the particle size and the yield; therefore the process parameters can be selected based on the particle size requirement. DSC studies suggested that the crystallinity of SAS-EM prepared quercetin nanoparticles decreased as compared to original quercetin powder. The dissolution of SAS-EM prepared nanoparticles increased significantly in comparison with the original quercetin powder. However, there was no significant difference in the dissolution of various quercetin nanoparticles samples prepared by the SAS-EM process. The best dissolution percent achieved was 75% for the smallest size sample prepared at the flow rate of 5 ml/min, power supply of 200 W, drug concentration of 10 mg/ml, and flow time of 4 min.     

Synthesis and characterization of TiO2 powders by electrospray pyrolysis method

Electrospray pyrolysis, i.e. combination of electrospray and in-flight thermal treatment, has attracted much attention as a preparation method of functional ceramic particles. In this paper, we report the processing detail of spherical TiO₂ nano- and microparticles by the electrospray pyrolysis method as well as their photocatalytic activity for hydrogen evolution. Titanium(IV) bis(ammonium lactato)dihydroxide aqueous solutions (TALH aq., 0.2–20 wt%) were injected into a capillary nozzle by a syringe pump (0.15–0.59 mL/min), and were electrosprayed by using DC 4 kV voltage, followed by the pyrolysis at 300–500 °C. Spherical TiO₂ nano- and microparticles were successfully obtained. Effects of precursor-liquid concentration, liquid flow-rate, and pyrolysis temperature on the particle size, microstructure and functions were discussed.     

Gas anti-solvent precipitation assisted salt leaching for generation of micro- and nano-porous wall in bio-polymeric 3D scaffolds

The mass transport through biocompatible and biodegradable polymeric 3D porous scaffolds may be depleted by non-porous impermeable internal walls. As consequence the concentration of metabolites and growth factors within the scaffold may be heterogeneous leading to different cell fate depending on spatial cell location, and in some cases it may compromise cell survival.In this work, we fabricated polymeric scaffolds with micro- and nano-scale porosity by developing a new technique that couples two conventional scaffold production methods: solvent casting-salt leaching and gas antisolvent precipitation. 10–15 w/w solutions of a hyaluronic benzyl esters (HYAFF11) and poly-(lactic acid) (PLA) were used to fill packed beds of 0.177–0.425 mm NaCl crystals. The polymer precipitation in micro and nano-porous structures between the salt crystals was induced by high-pressure gas, then its flushing extracted the residual solvent. The salt was removed by water-wash. Morphological analysis by scanning electron microscopy showed a uniform porosity (~ 70%) and a high interconnectivity between porous. The polymeric walls were porous themselves counting for 30% of the total porosity. This wall porosity did not lead to a remarkable change in compressive modulus, deformation, and rupture pressure. Scaffold biocompatibility was tested with murine muscle cell line C2C12 for 4 and 7 days. Viability analysis and histology showed that micro- and nano-porous scaffolds are biocompatible and suitable for 3D cell culture promoting cell adhesion on the polymeric wall and allowing their proliferation in layers. Micro- and nano-scale porosities enhance cell migration and growth in the inner part of the scaffold.     

Preparation of spray-dried microparticles using Gelucire 44/14 and porous calcium silicate or spherical microcrystalline cellulose to enhance transport of water-insoluble pranlukast hemihydrate across Caco-2 monolayers

The aim of this work was to prepare spray-dried microparticles using Gelucire®44/14 (GLC) and porous calcium silicate (FLR) or spherical crystalline cellulose (M06) to enhance transport of poorly water-soluble pranlukast hemihydrate (PLH) across Caco-2 monolayers. FLR or M06 were added to the PLH–GLC aqueous mixture prepared by adding distilled water at 60 °C to a melted mixture of PLH/GLC (1/1) at a PLH–GLC/carrier ratio of 1/1 or 1/17. Spray-dried FLR microparticles have the PLH–GLC solid dispersion (SD) in their pores and spray-dried M06 microparticles have the PLH–GLC SD on their surface. The dissolutions of PLH from the spray-dried FLR (SD/FLR = 1/1), spray-dried M06 (SD/M06 = 1/1), and spray-dried M06 (SD/M06 = 1/17) microparticles in Tween 80 aqueous solution were markedly fast. The transport of PLH from the spray-dried FLR (SD/FLR = 1/1) across Caco-2 monolayers was hardly observed. The transport of PLH across Caco-2 monolayers from the spray-dried M06 (SD/M06 = 1/17) increased with time, and the transport was significantly higher compared to that from PLH powder. The addition of polyethylene glycol 1500 into GLC of the spray-dried M06 was effective to increase the transport of PLH across Caco-2 monolayers. Spray-dried microparticles of PLH using GLC and M06 are a feasible means of enhancing transport across Caco-2 monolayers.     

Doughnut-shaped hierarchical Cu2ZnSnS4 microparticles synthesized by cyclic microwave irradiation

For the first time, hierarchical doughnut-shaped Cu₂ZnSnS₄ (CZTS) microparticles were synthesized by microwave-assisted solution method. N,N-dimethylformamide and polyvinylpyrrolidone (PVP) were used as solvent and stabilizing agent respectively, and the results showed that PVP played an important role in the formation of hierarchical nanostructures. Structural analysis by X-ray diffraction and Raman studies confirmed the formation of single phase kesterite CZTS. Morphological analysis by scanning electron microscope showed doughnut-shaped CZTS microparticles composed of large number of interpenetrating nanoplates. Optical analysis by UV–Vis diffused reflectance spectra showed strong absorption in the visible region with an optical band gap of 1.54 eV. Asymmetric broad emission bands around 1.55 eV and 1.30 eV were observed in the photoluminescence spectrum. A possible formation mechanism for doughnut-shaped CZTS microparticles was put forward and discussed briefly.     

Preparation of hydroxypropyl methyl cellulose phthalate nanoparticles with mixed solvent using supercritical antisolvent process and its application in co-precipitation of insulin

To obtain hydroxypropyl methyl cellulose phthalate (HPMCP)/insulin nanospheres by supercritical antisolvent process, the formation of HPMCP nanoparticles was first investigated. The effects of ratio of the mixed solvent, pressure, temperature, concentration, flow rate of CO₂ and solution on forming HPMCP nanoparticles are discussed. It was found that different morphologies of HPMCP could be produced by varying the ratio of DMSO to acetone in the solvent. The operating parameters were optimized for making HPMCP nanoparticles. Formation of HPMCP/insulin nanospheres was further inspected. The nanospheres with the size ranging from 138 nm to 342 nm were obtained. The loading of insulin in the nanospheres ranged from 10.76% to 16.04% and the encapsulation efficiency reached 100%. The release of insulin is also discussed.     

Preparation of aluminum foil-supported nano-sized ZnO thin films and its photocatalytic degradation to phenol under visible light irradiation

The zinc oxide thin films on aluminum foil have been successfully prepared by sol–gel method with methyl glycol as solvent. The film was characterized by means of XRD, TG, UV–vis, SEM and AFM, which show that the ZnO/Al film is formed by a layer of ZnO nano-sized particles with average diameter of 52.2 nm. Under the initial concentration of 20 mg/L phenol solution (500 mL) and visible light irradiation time of 3 h, more than 40% of the initial phenol was totally mineralized using two pieces of ZnO/Al thin film as photocatalyst with an efficient irradiation area of 400 cm². It is a promising visible light responded photocatalyst for the activation of O₂ at room temperature to degrade organic pollutants.     

Purification of yeast alcohol dehydrogenase by using immobilized metal affinity cryogels

In this study, poly(2-hydroxyethyl methacrylate–glycidylmethacrylate) [poly(HEMA–GMA)] cryogels were prepared by radical cryocopolymerization of HEMA with GMA as a functional comonomer and N,N′-methylene-bisacrylamide (MBAAm) as a crosslinker. Iminodiacetic acid (IDA) functional groups were attached via ring opening of the epoxy group on the poly(HEMA–GMA) cryogels and then Zn(II) ions were chelated with these structures. Characterization of cryogels was performed by FTIR, SEM, EDX and swelling studies. These cryogels have interconnected pores of 30–50 μm size. The equilibrium swelling degree of Zn(II) chelated poly(HEMA–GMA)-IDA cryogels was approximately 600%. Zn(II) chelated poly(HEMA–GMA)-IDA cryogels were used in the adsorption of alcohol dehydrogenase from aqueous solutions and adsorption was performed in continuous system. The effects of pH, alcohol dehydrogenase concentration, temperature, and flow rate on adsorption were investigated. The maximum amount of alcohol dehydrogenase adsorption was determined to be 9.94 mg/g cryogel at 1.0 mg/mL alcohol dehydrogenase concentration and in acetate buffer at pH 5.0 with a flow rate of 0.5 mL/min. Desorption of adsorbed alcohol dehydrogenase was carried out by using 1.0 M NaCI at pH 8.0 phosphate buffer and desorption yield was found to be 93.5%. Additionally, these cryogels were used for purification of alcohol dehydrogenase from yeast with a single-step. The purity of desorbed alcohol dehydrogenase was shown by silver-stained SDS–PAGE. This purification process can successfully be used for the purification of alcohol dehydrogenase from unclarified yeast homogenates and this work is the first report about the usage of the cryogels for purification of alcohol dehydrogenase.     

Immobilization of cholesterol esterase in mesoporous silica materials and its hydrolytic activity toward diethyl phthalate

Cholesterol esterase (CE, cholesteryl ester hydrolase, EC 3.1.1.13) from porcine pancreas (molecular weight 400–500 kDa) exhibits hydrolytic activity toward various toxic organic phthalate esters. CE was confined in the nanospace (diameter 3–30 nm) of five types of mesoporous silica (MPS) that differ in structural properties such as pore diameter, pore volume, and particle morphology. These structural properties were characterized by transmission electron microscopy, small-angle X-ray diffraction, N₂ adsorption–desorption experiments, solid-state ¹³C nuclear magnetic resonance (NMR), and solid-state ²⁹Si NMR. Catalytic activities of immobilized and free CE were evaluated by the hydrolysis of diethyl phthalate in phosphate buffer solutions containing an organic cosolvent. Optimal activity recovery was achieved when CE was immobilized in n-decane-functionalized MPS, which had a large pore size (22.5 nm). The immobilization also protected against effects of temperature within the range 30 °C–60 °C; CE immobilized in n-decyl-functionalized MPS exhibited better thermal stability than in non-functionalized MPS or free CE. Moreover, it retained approximately 60% of its catalytic activity even after six catalytic cycles.     

Preparation,characterization and dissolution behavior of artemisinin microparticles

In the present study, a modified 4-fluid nozzle spray drier was used to prepare microparticles of a poorly water soluble drug, artemisinin with the aim of improving its solubility. We also investigated the effect of process variables on the physical properties and dissolution rate of spray dried artemisinin. A full factorial experimentally designed study was performed to investigate the following spray drying variables: inlet temperature and feed concentration. The artemisinin powder and spray dried artemisinin microparticles were characterized by scanning electron microscopy (SEM), differential scanning calorimetric (DSC), X-ray diffraction (XRD) and dissolution. SEM study suggested that the inlet temperature and feed concentration impacted on the particle size of the spray dried particles. The crystallinity of spray dried particles was slightly decreased with increasing inlet temperature and concentration. The dissolution of spray dried particles was markedly improved as compared to commercial artemisinin. A dissolution surface-response model was used to elucidate the significant and direct relationships between drug feed concentration and inlet temperature on one hand and dissolution on the other hand. The best dissolution was found to be 117.00 ± 5.15 μg/mL at the drug feed concentration of 10 g/L and inlet temperature of 140 °C.     

Ultrafine porous fibers electrospun from cellulose triacetate

Ultrafine porous cellulose triacetate (CTA) fibers were prepared by electrospinning with methylene chloride (MC) and a mixed solvent of MC/ethanol (EtOH) and their intra- and inter-fiber pore structures was investigated. Ultrafine porous CTA fibers electrospun with MC had isolated circular shape pores with a narrow size distribution in the range of 50–100 nm. In the case of ultrafine CTA fibers electrospun with MC/EtOH (90 / 10 v/v), they had interconnected larger pores in the range of 200–500 nm. These porous structures were induced by phase separation resulting from the rapid evaporation of solvent during the electrospinning process. However, non-porous corrugated fibers were obtained from MC/EtOH (85 / 15 v/v) and MC/EtOH (80 / 20 v/v) due to their lower vapor pressure. The pore sizes in ultrafine CTA fibers electrospun with MC showed a bimodal distribution centered at ∼17 and ∼64 nm. CTA fibers electrospun with MC/EtOH (90 / 10 v/v) showed the greatest porosity due to their larger intra-fiber pores and fiber diameter.     

Extensive in vitro activity of guanidine hydrochloride polymer analogs against antibiotics-resistant clinically isolated strains

Polyhexamethylene guanidine hydrochloride (PHMG) possesses great potential in the development of covalently bound permanent sterile-surface materials for hospital infection control. This study aimed at evaluating the extensive activity of PHMG and its three novel analogs, including polybutamethylene guanidine hydrochloride, polyoctamethylene guanidine hydrochloride (POMG) and poly(m-xylylene guanidine hydrochloride), against 370 clinical strains, especially 96 isolates of which were antibiotics-resistant. Their in vitro antimicrobial activities were determined by testing the minimal inhibitory concentration (MIC) and time-killing curves. POMG, the novel oligoguanidine had significantly lower MIC values (0.5–16 mg/L) against 370 antibiotics-susceptible and -resistant clinical strains compared to PHMG (1–64 mg/L) and chlorhexidine digluconate (2–64 mg/L). Interestingly, POMG displayed excellent activity against meticillin resistant-Staphylococcus aureus (1–8 mg/L) and -coagulase-negative staphylococci (1–2 mg/L), vancomycin resistant Enterococcus faecium (2–4 mg/L), multidrug resistant Pseudomonas aeruginosa (8–16 mg/L), ceftazidime resistant-Citrobacter spp. (1–4 mg/L) and -Enterobacter spp. (2–4 mg/L). PHMG was especially efficient against methicillin resistant-S. aureus and -coagulase-negative staphylococci (1–8 mg/L). The presented extensive activity of POMG and PHMG against antibiotic-resistant bacteria provides encouraging reference information for the using and further development of cationic guanidine-based polymers in the biomedical material field.     

Gibbs–Thomson relationship for the precipitation in Cu–Ti alloys

A diffusion-couple Cu/Cu–Ti alloy was prepared in order to obtain a macroscopic composition gradient in the Cu–Ti alloy system. This couple was solution treated subsequently water quenched and aged at 837 K for 600 s. The precipitation process was analyzed with an EDS-TEM. The Gibbs–Thomson relation was used to analyze the precipitation of the metastable and semicoherent β′ phase in Cu–Ti alloys and this relationship enabled us to estimate the interfacial free energy between matrix and precipitates to be about 0.31 ± 0.02 J m^− 2.     

Selective dispersive liquid–liquid microextraction and preconcentration of Ni(II) into a micro droplet followed by ETAAS determination using a yellow Schiff's base bisazanyl derivative

A simple, rapid and sensitive method was developed for the selective separation and preconcentration of Ni(II) using dispersive liquid–liquid microextraction, by a yellow Schiff's base bisazanyl derivative, as a selective complexing agent. In this method, a mixture of 45 μL chloroform (extraction solvent) and 450 μL tetrahydrofuran (dispersive solvent) is rapidly injected by syringe into a 5 mL aqueous sample containing 3% (w/v) sodium chloride and an appropriate amount of the Schiff's base. As a result, a cloudy solution is formed by entire dispersion of the extraction solvent into the aqueous phase. After centrifuging for 5 min at 5000 rpm, the sedimented phase is directly injected into the electrothermal atomic absorption spectrometry for Ni(II) determination. Some important parameters, such as kind and volume of extraction and dispersive solvents, extraction time, salt effect, pH and concentration of the chelating agent have been optimized. Under the optimum conditions, the enrichment factor for the presented method is 138. The calibration curve was linear over a nickel concentration range of 10–50 ng mL^? 1. The detection limit and relative standard deviation were 0.04 ng mL^? 1 and 2.1%, respectively. The method was successfully applied to the extraction and determination of Ni(II) in different water samples.     

Precipitation in Al–Mg solid solution prepared by solidification under high pressure

The precipitation in Al–Mg solid solution containing 21.6 at.% Mg prepared by solidification under 2 GPa was investigated. The results show that the γ-Al₁₂Mg₁₇ phase is formed and the β′ phase cannot be observed in the solid solution during ageing process. The precipitation of γ and β phases takes place in a non-uniform manner during heating process, i.e. the γ and β phases are first formed in the interdendritic region, which is caused by the inhomogeneous distribution of Mg atoms in the solid solution solidified under high pressure. Peak splitting of X-ray diffraction patterns of Al(Mg) solid solution appears, and then disappears when the samples are aged at 423 K for different times, due to the non-uniform precipitation in Al–Mg solid solution. The direct transformation from the γ to β phase is observed after ageing at 423 K for 24 h. It is considered that the β phase is formed through a peritectoid reaction of α + γ → β which needs the diffusion of Mg atoms across the interface of α/γ phases.     

Preparation of N,O-carboxymethyl chitosan coated alginate microcapsules and their application to Bifidobacterium longum BIOMA 5920

In order to greatly improve vitality of probiotic bacteria within the application, a novel biocompatible vehicle, N,O-carboxymethyl chitosan (NOCs) with appropriate degrees of substitution coat alginate (ALg) microparticles, was prepared by electrostatic droplet generation. The amount of chitosan (Cs) and N,O-carboxymethyl chitosan (NOCs) coated on the ALg microparticles was determined by differential scanning calorimetry. The surface morphology of ALg microparticles, Cs coated ALg microparticles and NOCs coated ALg microparticles was determined using scanning electron microscopy. The coating thickness of Cs coated ALg microparticles and that of NOCs coated ALg microparticles was directly observed with confocal laser scanning microscopy. In order to assess pH sensitivity of microparticles, the bovine serum albumin release from the microspheres was tested in acid solution (pH 2.0) for 2 h and subsequently in alkaline solution (pH 7.0) for 2 h. The survival of Bifidobacterium longum BIOMA 5920 loaded in NOCs coated with ALg microparticle was improved in simulated gastric juice (pH 2.0, for 2 h) compared to that of B. longum BIOMA 5920 loaded in ALg microparticles and Cs coated ALg microparticles. After incubation in simulated intestinal juices (pH 7.0, 2 h), the release of microencapsulated B. longum BIOMA 5920 was investigated.     

Photodegradation of bisphenol-A in a batch TiO2 suspension reactor

In this work, the photocatalytic behaviors of bisphenol-A (BPA), which has been listed as one of endocrine disrupting chemicals, were carried out in a batch TiO₂ suspension reactor. The photodegradation efficiency has been investigated under the controlled process parameters including initial BPA concentration (i.e., 1–50 mg L^?1), TiO₂ dosage (i.e., 5–600 mg/200 cm³), initial pH (i.e., 3–11), and temperature (i.e., 10–70 °C). It was found that the optimal conditions in the photoreaction process could be coped with at initial BPA concentration = 20 mg L^?1, TiO₂ dosage = 0.5 g L^?1 (100 mg/200 cm³), initial pH = 7.0, and temperature = 25 °C. According to the Langmuir–Hinshelwood model, the results showed that the photodegradation kinetics for the destruction of BPA in water also followed the first-order model well. The apparent first-order reaction constants (k_obs), thus obtained from the fittings of the model, were in line with the destruction-removal efficiencies of BPA in all the photocatalytic experiments. Based on the intermediate products identified in the study, the possible mechanisms for the photodegradation of BPA in water were also proposed in the present study.     

PUA/PSS multilayer coated CaCO3 microparticles as smart drug delivery vehicles

Hybrid CaCO₃ microparticles coated by sodium poly(styrene sulfonate) (PSS) and aliphatic poly(urethane-amine) (PUA) were developed as thermal-/pH-responsive drug delivery vehicles via LbL self-assembly technique. The DOX release from the CaCO₃ microparticles was higher than 60% within 36 h, whereas the value of PUA/PSS-coated microparticles was only 20%. The results demonstrated that the PUA/PSS multilayer coating could reduce the drug release rate and significantly assuage the initial burst release of DOX. In addition, the drug release of the hybrid microparticles was found to be thermal-/pH-dual responsive. More interestingly, more than 90% of DOX was released in 36 h at pH 2.1 and 55 °C owing to the combined action of the dissolution of the CaCO₃ core and the shrinkage of aliphatic PUA.     

UV resistibility of a nano-ZnO/glass fibre reinforced epoxy composite

The harmfulness of ultraviolet (UV) radiation (UVR) to human health and polymer degradation has been the focus recently in all engineering industries. A polymer-based composite filled with nano-ZnO particles can enhance its UV resistibility. It has been found that the use of appropriate amount of nano-ZnO/Isopropyl alcohol solvent to prepare a UV resistant nano-ZnO/glass fibre reinforced epoxy (ZGFRE) composite can effectively block the UV transmission with negligible influence on the crystal structure of its resin system. This paper aims at investigating the interfacial bonding behaviour and UV resistibility of a ZGFRE composite. The solvent effect in relation to the dispersion properties of ZnO in the composite is also discussed. XRD results indicated that 20 wt% Isopropyl alcohol was an effective solvent for filling nano-ZnO particles into an epoxy. SEM examination also showed that the bonding behaviour between glass fibre and matrix was enhanced after filling 20 wt% nano-ZnO particles with 20 wt% Isopropyl alcohol into the composite. Samples filled with 20 wt% nano-ZnO/Isopropyl alcohol and 40 wt% nano-ZnO/Isopropyl alcohol has full absorption of UVA (315–400 nm), UVB (280–315 nm) and a part of UVC (190–280 nm).     

Equilibrium and kinetics of cadmium adsorption from aqueous solutions using untreated Pinus halepensis sawdust

Untreated Pinus halepensis sawdust has been investigated as an adsorbent for the removal of cadmium from aqueous solutions. Batch experiments were carried out to investigate the effect of pH, adsorbent dose, contact time, and metal concentration on sorption efficiency. The favorable pH for maximum cadmium adsorption was at 9.0. For the investigated cadmium concentrations (1–50 mg/L), maximum adsorption rates were achieved almost in the 10–20 min of contact. An adsorbent dose of 10 g/L was optimum for almost complete cadmium removal within 30 min from a 5 mg/L cadmium solution. For all contact times, an increase in cadmium concentration resulted in decrease in the percent cadmium removal (100–87%), and an increase in adsorption capacity (0.11–5.36 mg/g). The equilibrium adsorption data were best fitted with the Freundlich isotherm (R² = 0.960). The kinetics of cadmium adsorption was very well described by the pseudo-second-order kinetic model (R² > 0.999).