Synthesis and encapsulation of magnetite nanoparticles in PLGA: effect of amount of PLGA on characteristics of encapsulated nanoparticles

Oleic acid-coated superparamagnetic iron oxide nanoparticles (Fe₃O₄) encapsulated within poly(d,l-lactide-co-glycolide) (PLGA) particles were prepared by the w/o/w emulsion technique using poly(vinyl alcohol) as a dispersant. The concentration of PLGA in the oil phase was varied (5, 15, 30, 45, and 60?mg/ml) at constant magnetite concentration in the oil phase (5?mg/ml) to study the properties of composite Fe₃O₄–PLGA nanoparticles. Even though PLGA concentration varied widely in the oil phase, the weight percent of 7–16?nm diameter magnetite in the particles varied only from 56 to 62?% (23–28?vol.%). The obtained composite nanoparticles were essentially spherical with magnetite spatially uniformly dispersed in individual PLGA particles, as measured by transmission electron microscopy (TEM). Also, the magnetite concentration in each particle did not vary widely as determined qualitatively via microscopy. Hydrodynamic diameters of the composite nanoparticles as measured by dynamic light scattering increased by approximately 10?% with added magnetite, with a smaller relative increase in diameter measured by TEM. The zeta potential of the particles was about ?26?mV, independent of Fe₃O₄ loading. Relatively high saturation magnetizations (36–45?emu/g) were measured for these highly loaded particles, with the latter value only 7?emu/g lower than the value measured for the oleic acid-coated particles alone.     

Effect of trimethylamine-<Emphasis Type="Italic">N</Emphasis>-oxide demethylase from lizardfish kidney on biochemical changes of haddock natural actomyosin stored at 4 and −10 °C

The addition of partially purified trimethylamine-N-oxide demethylase (TMAOase) from lizardfish kidney to haddock natural actomyosin (NAM) in the presence of cofactors (FeCl₂, ascorbate, and cysteine) accelerated formaldehyde (FA) formation throughout the storage either at 4 or −10 °C (p < 0.05). ¹H NMR spectroscopic study revealed that the formation of dimethylamine was enhanced with a concomitant decrease in trimethylamine oxide (TMAO) content when TMAOase was added, particularly at higher concentration. The loss of protein solubility increased as the result of FA formation, which was associated with the increased denaturation/aggregation of proteins. Lipid oxidation determined as hexanal content occurred during extended storage at different degrees. Generally, simulated systems without TMAOase and TMAO contained the highest hexanal content. Differential scanning calorimetry of NAM after storage at 4 and −10 °C for 15 days and for 8 weeks, respectively, showed the lower T _m and enthalpy of endothermic peaks corresponding to myosin and actin, suggesting the conformational changes induced by FA formed. Therefore, TMAOase exhibited the detrimental impact on haddock NAM, mainly caused by FA formation.     

Raman spectroscopic analysis and rheological measurements on natural actomyosin from haddock (Melanogrammus aeglefinus) during refrigerated (4 °C) and frozen (−10 °C) storage in the presence of trimethylamine-N-oxide demethylase from kidney of lizardfish (Saurida tumbil)

Changes in viscoelasticity and structure of haddock natural actomyosin (NAM) treated with partially purified trimethylamine-N-oxide demethylase (TMAOase) in the presence of cofactors (FeCl₂, ascorbate and cysteine), after refrigerated storage (4 °C) for 15 days or after frozen storage (−10 °C) for eight weeks, were elucidated using FT-Raman spectroscopy and dynamic viscoelastic measurement. Greater increases in the final storage modulus (G′) and loss modulus (G″), reflecting protein aggregation, were observed in the simulated NAM systems, containing NAM, trimethylamine oxide (TMAO) and cofactors, stored at −10 °C, compared to those stored at 4 °C, particularly in the system with a higher concentration of TMAOase (p < 0.05). Raman spectroscopy revealed that amide I and amide III bands of NAM were affected by TMAOase added as well as by storage temperature. The decrease in the CH₂ bending region near 1450 cm⁻¹, in the presence of TMAOase upon storage, suggested an increase in hydrophobic interactions of aliphatic residues. Changes in a doublet near 830 and 850 cm⁻¹ indicated an involvement of tyrosine residues as hydrogen bond donors in the system containing TMAOase after storage at both temperatures. The systems stored at −10 °C generally showed greater structural alteration than those kept at 4 °C, especially in the presence of 15 units of TMAOase/g. Therefore, TMAOase played an important role in the structural alteration and aggregation of haddock muscle proteins, mainly by the induction of formaldehyde formation.     

Comparative study on proteolysis of two species of bigeye snapper,Priacanthus macracanthus and Priacanthus tayenus

Proteolytic activity in muscle from two species of bigeye snapper (Priacanthus macracanthus and Priacanthus tayenus) was studied. Autolysis of mince and washed mince at 50 and 60 °C was compared. Higher degradation of myosin heavy chain was observed in both mince and washed mince from P macracanthus than in those from P tayenus, especially when the incubation time was increased. Autolysis of washed mince from both species was inhibited by soybean trypsin inhibitor, suggesting that myofibril‐associated proteases were serine proteases. When sarcoplasmic proteolytic activity in P macracanthus muscle was studied, two activity peaks with an optimum temperature of 60 °C were observed at pH 6.5 and 8.5. The activities of both peaks were mostly inhibited by soybean trypsin inhibitor, suggesting that the major protease was a serine protease. Major sarcoplasmic proteolytic activity in P macracanthus muscle was found at M_r 62 000 on sodium dodecyl sulphate substrate gel. For P tayenus sarcoplasmic proteolytic activity, two activity peaks with an optimum temperature of 60 °C were found at pH 5.0 and 8.5. The pH 5.0 peak activity was effectively inhibited by pepstatin A, while the pH 8.5 peak activity was inhibited by several inhibitors. The results indicated that various sarcoplasmic proteases were present in P tayenus muscle. The two species contained different sarcoplasmic proteases in terms of composition and activity level. P macracanthus muscle generally had higher sarcoplasmic proteolytic activities than P tayenus muscle. Copyright © 2003 Society of Chemical Industry     

Effect of some additives on the inhibition of lizardfish trimethylamine-N-oxide demethylase and frozen storage stability of minced flesh

Effects of some additives on the inhibition of trimethylamine‐N‐oxide demethylase (TMAOase) from lizardfish (Saurida tumbil) muscle were investigated. Sodium citrate and pyrophosphate could inhibit TMAOase activity in a concentration‐dependent manner, most likely because of their chelating property. Sodium alginate was the hydrocolloid possessing the inhibitory activity towards TMAOase (P < 0.05). During the storage of lizardfish mince at ?20 °C for 24 weeks, the addition of 0.5% sodium alginate and 0.3% pyrophosphate in combination with 4% sucrose and 4% sorbitol as the cryoprotectants resulted in the retarded increase in TMAOase activities with the coincidental lowered formation of dimethylamine and formaldehyde (FA), compared with the control (without additives) (P < 0.05). The loss in solubility of muscle proteins was also impeded with the addition of those compounds, suggesting their role in the inhibition of TMAOase as well as the retardation of protein denaturation induced by FA.     

Magnetite/poly(D,L-lactide-co-glycolide) and hydroxyapatite/poly(D,L-lactide-co-glycolide) prepared by W/O/W emulsion technique for drug carrier: Evaluation of in vitro release of dexamethasone from composite nanoparticles

Biocompatible polymeric carriers containing inorganic materials for delivering therapeutic agents to a targeted site are promising candidate for drug delivery. Two nanocomposite nanoparticles, magnetite/poly(D,L-lactide-co-glycolide) and hydroxyapatite/poly(D,L-lactide-co-glycolide) (Fe₃O₄/PLGA and HAp/PLGA, respectively), with different weight ratios of inorganics to polymer and different polymer molecular weights were prepared by water-in-oil-in-water (W/O/W) emulsion technique to determine incorporation and in vitro release profile of the small molecule drugs water-insoluble dexamethasone acetate (DEX-Ac) and water-soluble dexamethasone phosphate (DEX-P). The in vitro release for DEX-Ac nanoparticles showed an initial burst release followed by a continuous slower release, whereas DEX-P nanoparticles showed only rapid initial release behavior.     

Initial Oxide Particle Deposition Under Low-Temperature Cooling Water Conditions: Experiments Under Subcooled Boiling at High pH

The deposition behavior of colloidal corrosion-product particles under isothermal conditions and different modes of heat transfer at atmospheric pressure has been reported previously, under conditions where the particles and heat transfer surface had opposite electrostatic charges so the fouling process was under transport control. Reported here are observations from a recirculating loop of the deposition of nickel ferrite from suspension in alkaline water during subcooled boiling at the surface of an Alloy-800 tube. Control was nominally by attachment. The experiment involved tracing the particles with radioactive ⁶⁰Co so that their accumulation on the tube could be monitored remotely. A radioactive scoping test lasting 147 h was followed by a test with three continuous, sequential periods when the surface radioactivity was monitored. The first, for 117 h, involved exposure to a ～5-ppm suspension, followed by a 124-h exposure to a nominally identical but nonradioactive suspension, followed by a 68-h exposure to water nominally devoid of nickel ferrite. The deposition during the first period followed kinetics similar to those measured under transport control in previous experiments and could be described by a mechanistic model developed previously. The surface radioactivity during the second period decreased, even while nonradioactive particles continued to deposit, but tended toward an asymptotic value at a rate that suggested that consolidation of a large portion of the deposit occurred abruptly. The final period saw a further decrease in surface radioactivity, presumably due to dissolution and release of deposit in the solute-free environment. These results are described with a mathematical model and their implications are discussed in the context of the previous experiments.