Theranostic magnetite cluster@silica@albumin double-shell particles as suitable carriers for water-insoluble drugs and enhanced T2 MR imaging contrast agents.

Design of new multifunctional nanosystems to integrate diagnostic and therapeutic functions is a major area of interest in the field of nanobiotechnology and nanomedicine. In this study, application of a new magnetic multilayered nanobiohybrid system composed of magnetite nanoparticles, silica, and albumin as a theranostic agent was investigated. Once the clusters of magnetite nanoparticles were coated with a silica shell, bovine serum albumin was conjugated to the surface of activated amine-MS particles (BMS). Afterwards, a curcumin-loaded albumin shell was formed on BMS particles (CBBMS). The curcumin loading capacity and efficiency of the nanobiohybrid particles were 93 ±â€¯6 (mg drug/g particles) and 24 ±â€¯1.7 (wt%), respectively. A sustained release profile was observed for the curcumin in PBS which followed the first-order kinetic model. Cytotoxicity evaluation of CBBMS showed a striking reduced IC50 value (9.9 µM) in comparison to that of the free curcumin (16.2 µM), tested on SH-SY5Y cells using MTT assay. Finally, the in vitro relaxivity experiments indicated a high transverse relaxivity (r2) of 369.7 mM-1 s-1 for the superparamagnetic nanobiohybrid particles in magnetic resonance imaging (MRI) tests. The obtained results in drug delivery and MRI tests recommend the as-prepared multilayered nanobiohybrid particles as an efficient and suitable system for theranostic applications.

Physicochemical characterization of fish protein adlayers with bacteria repelling properties.

Materials coated with aqueous fish protein extracts can reduce bacterial adhesion, but the mechanism behind the observed effect is not fully understood. In this study we explore the physicochemical properties of fish muscle protein adlayers on four substrates: gold, stainless steel, polystyrene and silicon dioxide. The aims were (i) to determine if the anti-adhesive effect is independent of the underlying substrate chemistry, (ii) to link the physicochemical properties of the adlayer to its ability to repel bacteria, and (iii) to elucidate the mechanism behind this effect. The main proteins on all surfaces were the muscle proteins troponin, tropomyosin, and myosin, and the lipid binding protein apolipoprotein. The quantity, viscoelasticity, and hydration of the protein adlayers varied greatly on the different substrates, but this variation did not affect the bacterial repelling properties. Our results imply that these proteins adsorb to all substrates and provide a steric barrier towards bacterial adhesion, potentially providing a universal antifouling solution.

Electrostatic and capillary force directed tunable 3D binary micro- and nanoparticle assemblies on surfaces.

We report a simple, rapid and cost-effective method based on evaporation induced assembly to grow 3D binary colloidal assemblies on a hydrophobic/hydrophilic substrate by simple drop casting. The evaporation of a mixed colloidal drop results in ring-like or uniform area deposition depending on the concentration of particles, and thus assembly occurs at the periphery of a ring or uniformly all over the drop area. Binary colloidal assemblies of different crystal structure are successfully prepared over a wide range of size ratios (γ = small/large) from 0.06 to 0.30 by tuning the γ of the micro- and nanoparticles used during assembly. The growth mechanism of 3D binary colloidal assemblies is investigated and it is found that electrostatic forces facilitate assembly formation until the end of the evaporation process, with capillary forces also playing a role. In addition, the effects of solvent type, humidity, and salt concentration on crystal formation and ordering behaviour are also examined. Furthermore, long range, highly ordered binary colloidal assemblies can be fabricated by the choice of a low conducting solvent combined with evaporation induced assembly.

Surface modification of chromatography adsorbents by low temperature low pressure plasma.

In this study we show how low temperature glow discharge plasma can be used to prepare bi-layered chromatography adsorbents with non-adsorptive exteriors. The commercial strong anion exchange expanded bed chromatography matrix, Q HyperZ, was treated with plasmas in one of two general ways. Using a purpose-designed rotating reactor, plasmas were employed to either: (i) remove anion exchange ligands at or close to the exterior surface of Q HyperZ, and replace them with polar oxygen containing functions ('plasma etching and oxidation'); or (ii) bury the same surface exposed ligands beneath thin polymer coatings ('plasma polymerization coating') using appropriate monomers (vinyl acetate, vinyl pyrrolidone, safrole) and argon as the carrier gas. X-ray photoelectron spectroscopy analysis (first ∼10 nm depth) of Q HyperZ before and after the various plasma treatments confirmed that substantial changes to the elemental composition of Q HyperZ's exterior had been inflicted in all cases. The atomic percent changes in carbon, nitrogen, oxygen, yttrium and zirconium observed after being exposed to air plasma etching were entirely consistent with: the removal of pendant Q (trimethylammonium) functions; increased exposure of the underlying yttrium-stabilised zirconia shell; and introduction of hydroxyl and carbonyl functions. Following plasma polymerization treatments (with all three monomers tested), the increased atomic percent levels of carbon and parallel drops in nitrogen, yttrium and zirconium provided clear evidence that thin polymer coats had been created at the exteriors of Q HyperZ adsorbent particles. No changes in adsorbent size and surface morphology, nor any evidence of plasma-induced damage could be discerned from scanning electron micrographs, light micrographs and measurements of particle size distributions following 3 h exposure to air (220 V; 35.8 W L(-1)) or 'vinyl acetate/argon' (170 V; 16.5 W L(-1)) plasmas. Losses in bulk chloride exchange capacity before and after exposure to plasmas enabled effective modification depths within hydrated Q HyperZ adsorbent particles to be calculated as 0.2-1.2 µm, depending on the conditions applied. The depth of plasma induced alteration was strongly influenced by the power input and size of the treated batch, i.e. dropping the power or increasing the batch size resulted in reduced plasma penetration and therefore shallower modification. The selectivity of 'surface vs. core' modification imparted to Q HyperZ by the various plasma treatments was evaluated in static and dynamic binding studies employing appropriate probes, i.e. plasmid DNA, sonicated calf thymus DNA and bovine serum albumin. In static binding studies performed with adsorbents that had been exposed to plasmas at the 5 g scale (25 g L(-1) of plasma reactor), the highest 'surface/core' modification selectivity was observed for Q HyperZ that had been subjected to 3 h of air plasma etching at 220 V (35.8 W L(-1)). This treatment removed ∼53% of 'surface' DNA binding at the expense of a 9.3% loss in 'core' protein binding. Even more impressive results were obtained in dynamic expanded bed adsorption studies conducted with Q HyperZ adsorbents that had been treated with air (220 V, 3 h) and 'vinyl acetate/argon' (170 V, 3 h) plasmas at 10.5 g scale (52.5 g L(-1) of plasma reactor). Following both plasma treatments: the 10% breakthrough capacities of the modified Q HyperZ adsorbents towards 'surface' binding DNA probes dropped very significantly (30-85%); the DNA induced inter-particle cross-linking and contraction of expanded beds observed during application of sonicated DNA on native Q HyperZ was completely eradicated; but the 'core' protein binding performance remained unchanged cf. that of the native Q HyperZ starting material.

Adhesion of food-borne bacteria to stainless steel is reduced by food conditioning films.

AIMS: Preconditioning of stainless steel with aqueous cod muscle extract significantly impedes subsequent bacterial adhesion most likely due to repelling effects of fish tropomyosin. The purpose of this study was to determine if other food conditioning films decrease or enhance bacterial adhesion to stainless steel. METHODS AND RESULTS: Attachment of Pseudomonas fluorescens AH2 to stainless steel coated with water-soluble coatings of animal origin was significantly reduced as compared with noncoated stainless steel or stainless steel coated with laboratory substrate or extracts of plant origin. Coating with animal extracts also decreases adhesion of other food-relevant bacteria. The manipulation of adhesion was not attributable to growth inhibitory effects. Chemical analysis revealed that the stainless steels were covered by homogenous layers of adsorbed proteins. The presence of tropomyocin was indicated by appearance of proteins with similar molecular weight based in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, in several extracts that reduced adhesion but also extracts not containing this protein reduced bacterial adhesion, indicating that several molecular species may be involved in the phenomenon. CONCLUSIONS: It is a common perception that food materials facilitate bacterial adhesion to surfaces; however, this study demonstrates that aqueous coatings of food origin may actually reduce bacterial adhesion. SIGNIFICANCE AND IMPACT OF THE STUDY: Compounds from food extracts may potentially be used as nontoxic coatings to reduce bacterial attachment to inert surfaces.

DNA binding during expanded bed adsorption and factors affecting adsorbent aggregation.

DNA-induced aggregation and contraction of expanded bed adsorption chromatography beds have been examined using strong anion exchanger Q HyperZ and calf thymus DNA in buffers containing added NaCl. Two batches of adsorbent with different ionic capacities were used allowing the effects of different ligand densities to be examined. Very high dynamic binding capacities at 10% breakthrough were found in the absence of added salt. However, the highest binding capacities (approximately 10 and approximately 19 mg DNA ml(-1) gel) were found in buffers containing added salt at concentrations of either 0.25 or 0.3 5M, for the low and high ligand density adsorbents, respectively. Bed contraction was observed, but did not correlate with dynamic binding capacity or with the amount of DNA loaded. No differences in bed contraction were seen by varying the concentration of DNA loaded in the range of 20-80 microg ml(-1) even though the dynamic binding capacity was reduced as DNA concentration was increased. The extent of bed contraction during DNA loading was found to be a function of added salt concentration and ligand density of the adsorbent. The results imply that ligand density significantly affects the salt tolerance of anion exchangers when binding DNA. However, more importantly, with the adsorbents examined here, attempts to reduce bed aggregation by feedstock conditioning with added salt may increase DNA binding leading to a reduction in expanded bed adsorption performance compromising protein capture in real feedstocks.

Critical evaluation and comparison of fluid distribution systems for industrial scale expanded bed adsorption chromatography columns.

The hydrodynamic properties of an expanded bed contactor with 30 cm or 150 cm internal diameter, which employs a rotating or oscillating fluid distributor, were compared to prototype columns of 60 cm or 150 cm diameter employing local stirring (fixed wall nozzles plus central bottom mounted stirrer) for fluid distribution. Fluid introduction through a rotating fluid distributor was found to give superior hydrodynamic characteristics in the 30 cm and 150 cm diameter column compared to using the local stirrer in both the 60 cm and 150 cm diameter columns. The shortcomings of the local stirring distributor at large scale were apparent: dead zones were present which could not be removed by increasing rotation rates or flow rates, and such changes led to a deterioration in hydrodynamic properties. In contrast, during fluid introduction through a rotating distributor no dead zones were observed, and residence time distribution tests showed that plate numbers remained constant or increased slightly as flow rate was raised from 200 cm h(-1) to 470 cm h(-1). Under the conditions studied, oscillation of the rotating fluid distributor led to increased mixing and poorer performance than rotary movement. The results imply that further improvement in distributor design is needed and careful attention should be given to the trade off between turbulence and adequate fluid distribution.