Mean Hydrodynamic Diameter Research Articles

Magnetophoretic mobility of iron oxide nanoparticles stabilized by small carboxylate ligands

Iron oxide nanoparticles were synthesized by the co-precipitation method and subjected to an adsorption and functionalization process at controlled pH with five different small carboxylate ligands, namely: citrate, tartrate, gluconate, succinate and β-alanine. The efficiency of the functionalization was evaluated by infrared spectroscopy and thermogravimetric measurements, finding that the presence of hydroxyl groups in the organic molecule is essential to achieve good levels of adhesion. In the three cases with higher levels of adhesion, the nanoparticles remain permanently stabilized and the system behaves like a ferrofluid at neutral pH. Colloidal properties such as the mean hydrodynamic diameter and the surface electrokinetic potential were studied over a wide pH range, being able to establish a clear correlation between the speciation equilibria of the adsorbed species, the surface charge and the formation of agglomerates between the particles.Finally, a magnetophoretic experiment was designed to evaluate and compare the mobility of the nanoparticles under a magnetic field gradient. In systems with individually stabilized nanoparticles, no magnetophoretic mobility was observed due to the low limit velocity reached by the particles. This result is consistent with a theoretical limit speed calculated considering the different parameters of the experiment and the ferrofluids. In systems with agglomerated nanoparticles it was found that the magnetophoretic mobility and the limit speed increase with the hydrodynamic diameter. In turn, this property varies strongly with the pH of the system according to the protonation / deprotonation equilibria of the surface of the nanoparticles and the formation or rupture of the agglomerates.

PLGA nanoparticles optimized by Box-Behnken for efficient encapsulation of therapeutic Cymbopogon citratus essential oil

This study aimed to optimize Cymbopogon citratus essential oil loaded into PLGA-nanoparticles by investigating the effect of processing variables (sonication time, ultrasound power, and essential oil/polymer ratio) on encapsulation efficiency and particle mean hydrodynamic diameter using Box-Behnken design. Nanoparticles were prepared by an emulsification/solvent diffusion method and physicochemically characterized by FTIR, DSC and TGA/DTA. Cytotoxicity was evaluated in human HaCat keratinocytes by WST-1 and LDH assays. The optimized formulation had a hydrodynamic mean diameter of 277 nm, a polydispersity index of 0.18, a Zeta potential of −16 mV and an encapsulation efficiency of 73%. Nanoparticle characterization showed that only citral was incorporated in nanocarriers, with some amount adsorbed on their surface, and highlighted the potential in increasing the oil thermal stability. The drug release profile demonstrated a biphasic pattern with a substantial sustained release depending on diffusion from the polymeric matrix. Toxicity effects on cell viability of pure essential oil at low concentrations were significantly eliminated when encapsulated. Results revealed the ability of PLGA-nanoparticles to improve essential oil physicochemical characteristics, by controlling release and reducing toxicity, suggesting their potential use in pharmaceutical preparations.

Diminishing bioavailability and toxicity of P25 TiO2 NPs during continuous exposure to marine algae Chlorella sp.

Titanium dioxide nanoparticles (TiO2 NPs) find applications in our day-to-day life because of unique physicochemical properties. Their release into the aquatic environment poses a possible risk to the organisms. However, the continuing exposure of NPs might reduce their bioavailability to marine organisms owing to aggregation and sedimentation in the aqueous systems thus significantly reducing their toxic impact. In this regard, the present study investigates the effect of continuous exposure of TiO2 NPs to marine microalgae Chlorella sp. under UV-A irradiation through “tanks in series” mode of experiments. In a three-cycle experiment, concentration of TiO2 NPs in the first cycle was fixed at 62.6 μM, and the interacted nanoparticles was subsequently exposed to fresh batches of algae in the next two cycles. After the interaction, the NPs underwent severe aggregation (mean hydrodynamic diameter 3000 ± 18.2 nm after cycle I) leading to gravitational settling in the medium and thus decreased bioavailability. The aggregation can be attributed to interactions between the particles themselves (homo-aggregation) further aggravated by the presence of the algal cells (hetero-aggregation). Cellular viability after cycle I was found to be only 24.2 ± 2.5%, and it was enhanced to 96.5 ± 2.8% after the cycle III in the course of continuous exposure. The results were validated with estimation of oxidative stress markers such as intracellular ROS (total ROS, superoxide and hydroxyl radicals) and LPO after each cycle of exposure. The continuing decrease in the EPS across the cycles further confirmed the diminishing toxicity of the NPs.

Design, optimization, characterization, and in vivo evaluation of sterosomes as a carrier of metformin for treatment of lung cancer

The present study aimed to formulate and evaluate metformin sterosomes. Sterosomes were prepared by incorporating stearylamine and cholesterol in different ratios. Sterosomes were characterized using size, zeta potential, entrapment efficiency (EE%) and in vitro release. Aerosol generated by nebulization was evaluated by a cooled Andersen cascade impactor (ACI) at 15 L/min. In vitro cytotoxicity of free and metformin-containing sterosomes was tested against human cancer cell lines. A comparative pharmacokinetic study between sterosomal formulation and free drug solution (750 mg) was performed. Spirometry was performed before and at time intervals after inhalation. The mean hydrodynamic diameter of the formulated vesicles was in the range of 288.7–578 nm. The EE% varied from 71 ± 1.4% to 89 ± 5.2%, with an optimum EE% of 89 ± 5.2at a lipid ratio of 2/1 stearylamine/cholesterol. Metformin sterosomes displayed an inhibitory effect on A549 lung cancer cell lines which significantly (p < 0.05) increased depending on dose and prolonged exposure time. Spirometric data were minimally changed before and after inhalation without a statistically significant difference in the forced expiratory volume in one second (FEV1), forced vital capacity (FVC) or FEV1/FVC ratio (p > 0.05). Metformin-loaded sterosomes resulted in a significant increase in biological half-life (t1/2) with a mean value of 7.31 ± 1.04 h compared to 3.99 ± 0.17 h of the solution form. However, the peak plasma concentration of metformin sterosomes was lower than that achieved by metformin-free solution aerosol, and the difference was statistically significant (p < 0.05).The eligibility of sterosomes for aerosol delivery by nebulization would provide a novel strategy for delivery of metformin by inhalation as a potentially effective inhalation treatment of lung cancer.

Investigation of fouling mechanisms of virus filters during the filtration of protein solutions using a high throughput filtration screening device.

The downstream process development of novel antibodies (Abs) is often challenged by virus filter fouling making a better understanding of the underlying mechanisms highly desirable. The present study combines the protein characterization of different feedstreams with their virus filtration performance using a novel high throughput filtration screening system. Filtration experiments with Ab concentrations of up to 20 g/L using either low interacting or hydrophobically interacting pre-filters indicate the existence of two different fouling mechanisms, an irreversible and a reversible one. At the molecular level, size exclusion chromatography revealed that the presence of large amount of high molecular weight species-considered as irreversible aggregates-correlates with irreversible fouling that caused reduced Ab throughput. Results using dynamic light scattering show that a concentration dependent increase of the mean hydrodynamic diameter to the range of dimers (17 nm at 20 g/L) together with a negative DLS interaction parameter kD (-18 mL/g) correlate with the propensity to form reversible aggregates and to cause reversible fouling, probably by a decelerated Ab transport velocity within the virus filter. The two fouling mechanisms are further supported by buffer flush experiments. Finally, concepts for reversible and irreversible fouling mechanisms are discussed together with strategies for respective fouling mitigation. © 2019 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2776, 2019.

Poly (ɛ-Caprolactone) Nanoparticles with pH-Responsive Behavior Improved the In Vitro Antitumor Activity of Methotrexate.

A promising approach to achieve a more efficient antitumor therapy is the conjugation of the active molecule to a nanostructured delivery system. Therefore, the main objective of this research was to prepare nanoparticles (NPs), with the polymer poly (ε-caprolactone) (PCL), as a carrier for the antitumor drug methotrexate (MTX). A pH-responsive behavior was obtained through conjugation of the amino acid-based amphiphile, 77KL, to the NP matrix. The NPs showed mean hydrodynamic diameter and drug entrapment efficiency of 178.5nm and 20.52%, respectively. Owing to its pH-sensitivity, the PCL-NPs showed membrane-lytic behavior upon reducing the pH value of surrounding media to 5.4, which is characteristic of the endosomal compartments. The in vitro antitumor assays demonstrated that MTX-loaded PCL-NPs have higher antiproliferative activity than free drug in MCF-7 cells and, to a lesser extent, in HepG2 cells. This same behavior was also achieved at mildly acidic conditions, characteristic of the tumor microenvironment. Altogether, the results evidenced the pH-responsive properties of the designed NPs, as well as the higher in vitro cytotoxicity compared to free MTX, representing thus a promising alternative for the antitumor therapy.

Enhanced stability of red-fleshed apple anthocyanins by copigmentation and encapsulation.

Red-fleshed apples are a great source of natural colorants and functional food ingredients because of their high anthocyanin content. Generally, anthocyanins are highly unstable after extraction, which limits their wide applications in the food and pharmaceutical industries. This study was aimed at investigating the effects of combining copigmentation with encapsulation on the stability of anthocyanins from red-fleshed apples. In this study, red-fleshed apple anthocyanins were copigmented with caffeic acid, and then the copigmented complexes were encapsulated using gum arabic and maltodextrin using spray drying and freeze drying. All anthocyanin microcapsules had high encapsulation efficiencies ranging from 93.84 to 96.85% with mean hydrodynamic diameter smaller than 350 nm. After heating at 80 °C for 2 h, the dispersions of microencapsulated anthocyanins with copigments exhibited the highest absorbance values at λmax (515 nm) (P < 0.05). Light stability experiments demonstrated that the half-life of the red-fleshed apple anthocyanins increased from 5 to 12 days after being treated with copigmentation and encapsulation. The drying methods (spray/freeze drying) did not significantly influence the stability of the microencapsulated anthocyanins. Applying copigmentation and spray-drying encapsulation in tandem has great potential for enhancing the stability of red-fleshed apple anthocyanins. Thus, such anthocyanins with enhanced stability may be increasingly used in the food and pharmaceutical industries as value-added natural food pigments. © 2018 Society of Chemical Industry.

Biocompatible superparamagnetic carriers of chondroitin sulfate

The present study reports on the fabrication, morphological and structural characterizations, magnetic and biological tests of a biocompatible superparamagnetic carrier comprising iron oxide nanoparticle (ION) surface-functionalized with chondroitin sulfate (ChS), labelled ION@ChS. The reported ION@ChS sample is produced by alkaline coprecipitation of Fe2+ and Fe3+ ions in aqueous media in the presence of ChS. Fourier Transform infrared, Raman and x-ray photoelectron spectroscopies provide evidences for coordination of the ChS molecule (mainly through sulfonic groups) onto the ION’s surface. Transmission electron microscopy reveals that the ION@ChS are nearly spherical (mean diameter = 8.2 nm ± 0.1) and almost monodispersed (diameter dispersity = 0.11 ± 0.01), while dynamic light scattering and electrophoretic mobility measurements confirm the presence of ChS at the ION’s surface, providing mean hydrodynamic diameter (∼100 nm) and very high negative zeta potential (around −50 mV). Moreover, the ION@ChS is superparamagnetic at room temperature, with no coercivity or remanence. Cell viability tests performed by means of the MTT assay indicates that ION@ChS shows no cytotoxiciy effect (p < 0.05). Therefore, one can anticipate potential biotechnological applications of the ION@ChS sample for site-specific delivery of ChS as well as a contrast agent in magnetic resonance imaging.

Fluorescence Enhancement of Tb3+ in the Tb3+‐Trimesic Acid‐Gd3+ Complex: Role of Polynuclear Structures

AbstractThe mechanism of fluorescence enhancement of Tb3+ in Tb3+‐trimesic acid‐Gd3+ systems has been explored using dynamic light scattering. In earlier work, the mechanism of fluorescence enhancement of Tb3+ in these systems was proposed to be due to the formation of a polynuclear complex involving Tb3+, trimesic acid and Gd3+. However, no direct experimental evidence was presented for the mechanism in that work. In this work, we have used dynamic light scattering (DLS), to measure changes in the mean hydrodynamic diameter (Zavg) of the Tb3+‐trimesic acid‐Gd3+ complex, as a function of time. The Zavg was found to increase monotonically as a function of time, indicating a continuous growth in the particle size. The Eu3+‐β‐diketones‐Gd3+ system also shows enhancement of Eu3+ fluorescence; though a different mechanism was believed to be operating in this case; namely intermolecular energy transfer. If the two systems followed different mechanisms for fluorescence enhancement, the Eu3+‐β‐diketones‐Gd3+ system, is expected to show a different time evolution of particle size. The DLS study showed that the Zavg increased rapidly to a maximum value and then remained nearly constant throughout our measurements; that is, no gradual increase in Zavg was seen as in the Tb3+‐trimesic acid‐Gd3+ system. These DLS studies of the Tb3+‐trimesic acid‐Gd3+ and Eu3+‐β‐diketones‐Gd3+ systems, therefore confirms that different mechanisms of fluorescence enhancement are operative in the two systems.

Effects of Nanoscale Structures on Photothermal Heating Behaviors of Surface-Modified Fe3O4 Nanoparticles

In this investigation, the photothermal heating of superparamagnetic Fe3O4 nanoparticles was carried out by irradiating with either 785[Formula: see text]nm or 808[Formula: see text]nm near infrared (NIR) lasers. The effects of nanoparticle configuration, arrangement, and surface coating on the photothermal heating behavior were investigated for different Fe3O4 nanoparticle systems. Depending on the preparation method, Fe3O4 nanoparticles with mean hydrodynamic diameter ranging from 30[Formula: see text]nm to 250[Formula: see text]nm were synthesized. Photothermal transduction efficiency is a measure of light to thermal energy conversion; the highest efficiency obtained was 56% by 785[Formula: see text]nm and 42% by 808[Formula: see text]nm light irradiation for poly(acrylic) acid (PAA) coated Fe3O4 samples. With this conversion efficiency, the PAA-coated Fe3O4 nanoparticles raised the solution temperature [Formula: see text] [Formula: see text]C above physiological temperature, which is sufficient for cancer therapeutics. Photothermal transduction efficiency was found to decrease as the particle hydrodynamic diameter increased. Nanoparticle absorption and scattering properties were found different due to surface modifications. UV-VIS-NIR absorption spectroscopy was carried out and results were analyzed using the Mie scattering theory. Experimental photothermal transduction efficiency was found to scale with the theoretical results for a particular wavelength. These results have significance in the design and development of the Fe3O4 nanoparticle systems for effective cancer therapy with NIR light.

Development of an aqueous two-phase emulsion using hydrophobized whey proteins and erythritol

Formation of aqueous two-phase (ATP) emulsions relies on the immiscibility of two (bio)polymeric phases. Herein, we report that hydrophobization of whey proteins via a pre-acetylation and succeeding acetylation/heating combined process makes solutions of whey protein isolate (WPI) immiscible with alginate solutions. Erythritol was also added at different concentrations (0, 52, 105, and 158 mg/g) into the hydrophobized WPI solution. Subsequently, emulsions at an alginate to WPI weight ratio of 0.1–0.9 were prepared. Erythritol supplementation facilitated emulsification and increased emulsion stability, so that at the erythritol concentration of 105 mg/g, the emulsion was stable for a minimum duration of 7 days. The droplet size evolved and reached to ≈5 μm during this period. The hydrophobized protein had a mean hydrodynamic diameter of 80 nm, ζ-potential of −39 mV, and intrinsic fluorescence emission peak of 335 nm. Erythritol addition did not influence any of the above-mentioned characteristics. However, the hydrophobized WPI solution changed from Newtonian to a more viscous and shear-thinning fluid by adding erythritol at concentrations ≥105 mg/g, due probably to the induction of interaction among protein particles. A diameter of 150 nm was calculated for the air-dried hydrophobized protein particles using atomic force microscopy images, supporting the assumption that exclusion of erythritol from the protein particles surface induced inter-particle interactions. Erythritol addition at 105 mg/g had a twofold larger influence on the surface tension of hydrophobized WPI compared to water. It decreased the surface tension of hydrophobized WPI to 45 mN/m after droplet ageing for 350 s.

Supramolecular Systems Based on Novel Amphiphiles and a Polymer: Aggregation and Selective Solubilization

AbstractSupramolecular systems based on novel triazole‐containing and pyrimidine‐containing amphiphiles bearing OH‐groups and a hydrophilic polymer (polyethyleneimine, PEI) were fabricated. Aggregation threshold of individual amphiphile solutions and a surfactant/polymer binary mixture were determined to be equal to 2 and 0.05 mM, respectively, using tensiometry and conductometry techniques. It was found, that PEI addition to surfactant aqueous solutions induces the transition from open to closed association mode accompanying the decrease of mean hydrodynamic diameter of particles (D H) from 100 nm to D H ≤ 5 nm. Polymer addition to the system results in the leveling of pH decrease with surfactant concentration and increase of the electrokinetic potential values from 10 mV up to 40 mV. It was established that solubilization capacity of the supramolecular system formed could be increased by transition from surfactant individual solutions to the amphiphile/polymer binary system. The solubilization properties of the system strongly depend on the nature of the hydrophobic guest solubilized and differ by two orders of magnitude for hydrophobic azodye and lipophilic oxime.

Molecular origin of surface-enhanced Raman spectra of E. coli suspensions excited at 532 and 785 nm using silver nanoparticle sols as sers substrates

Research into the molecular origin of surface-enhanced Raman spectra (SERS) of bacteria is a crucial step in assessing the future of SERS-based discrimination and identification of bacteria in clinical analysis, food quality control, etc. Previous studies have revealed that at 785 nm excitation wavelength SERS of bacterial cells placed on a solid surface functionalized with in-situ grown aggregated gold nanoparticles covered with SiO2 originate from a mixture of 6 purine derivatives (adenine, guanine, AMP, hypoxanthine, xanthine, and uric acid) that are released by the cells into the medium. The aim of the present work was to investigate whether such interpretation is possible with a different class of SERS substrates: silver nanoparticle sols at excitation wavelengths of 785 and 532 nm. The suspension of the Escherichia coli DH5α strain was used as a model bacterium. Sols of silver nanoparticles were obtained by reducing silver nitrate in the presence of alkaline hydroxylamine hydrochloride. Number-weighted mean hydrodynamic diameter of the particles was 43±2 nm. We confirm that at both excitation wavelengths the spectra can be best described as a superposition of 4 purine derivatives: adenine, guanine, hypoxanthine, and xanthine. Importantly, we have discovered that 1) the spectra of the purine mixture are characteristic of viable cells only; 2) due to the variations in the concentrations of purine metabolites released by the cells into the surrounding medium the spectra of a bacterial strain can vary significantly when a silver nanoparticle sol is used as a SERS substrate.

Síntesis de nanopartículas de plata con extractos acuosos de tejocote como agente reductor y pasivante

Introduction: Biosynthesis has emerged as an option for obtaining nanometric materials due to the need to use more environmentally-friendly synthesis methods. Objective: To synthesize silver nanoparticles (Ag NPs) with aqueous Crataegus gracilior Phipps (tejocote) bark extract as precursor. Methodology: Ag NPs were synthesized with AgNO3 and aqueous Crataegus gracilior bark extracts, and later characterized by ultraviolet-visible spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and X-ray diffraction (XRD). In addition, their size distribution and zeta potential were obtained. Results: The presence of Ag NPs reached maximum values at concentrations of 10 % (w/v). Mostly spherical nanoparticles were found in the range of 20 to 50 nm in size. FTIR confirmed the stabilization of the nanoparticles through their interactions with functional groups of carbohydrates and proteins. XRD and TEM results were explained by their face-centered cubic (FCC) structure with a size of 26 nm, a mean hydrodynamic diameter of 108 nm and polydispersity index of 0.24. The zeta potential values in the dispersions were -21.9 ± 5.11 mV, denoting colloidal stability. Limitations of the study: The characteristics of the nanoparticles obtained are only valid under the following synthesis conditions: 10 % (w/v) solids and pH 10. Originality: A non-reported plant material was used, capable of acting as a reducing and passivating agent of silver nanoparticles. Conclusions: Biosynthesis of Ag NPs with tejocote extract is an efficient, low-cost and environmentally-friendly method.

Disulfide proteinoid micelles responsive to reduction

Proteinoid composed of aspartic acid (Asp) and Leucine (Leu) (Prot(Asp-Leu)) and of Asp, Leu, and dithiopropionic acid (DTPA) (Prot(Asp-Leu-DTPA)) were prepared by melt-condensation method. 1H NMR spectroscopy confirmed the successful synthesis of the proteinoids. The air/water interfacial tension of Prot(Asp-Leu-DTPA) solution increased when dithiothreitol (DTT, a reducing agent) was in the solution, possibly due to the breakdown of the disulfide bond of the proteinoid. On transmission electron micrograph, the proteinoid micelles were round and the diameter was less than 200 nm. Sulfur signal was found in the energy-dispersive X-ray spectrum of Prot(Asp-Leu-DTPA) micelle, indicating that the disulfide compound (i.e., DTPA) was successfully included in the proteinoid. As the pH value increased, the mean hydrodynamic diameter of the proteinoid micelle increased. The release degree of doxorubicin (DOX) loaded in Prot(Asp-Leu-DTPA) micelle was relatively low (3.5%–5.8%) and it was not affected by a reducing agent (i.e., DTT), possibly because of electrostatic attraction between DOX and the proteinoid. DTT had a significant effect on the release degree of amaranth (a negatively charged dye) loaded in Prot(Asp-Leu-DTPA) micelle. Prot(Asp-Leu-DTPA) has disulfide bonds so it can be broken into thiol proteinoids via DTT-caused reduction, giving rise to the micellar shell loosening and the promoted release.

Bio-inspired keratin-based core-crosslinked micelles for pH and reduction dual-responsive triggered DOX delivery

Facile bio-inspired approach has been developed to prepare novel DOX-loaded chicken feather keratin-based core-crosslinked micelles (DOX/Ker-PEG CCMs) for pH and reduction dual-responsive tumor-specific intracellular triggered DOX delivery, by oxidation crosslinking the DOX/Ker-PEG micelles which were simply self-assembled by adjusting solution pH value to 10. The final DOX/Ker-PEG CCMs with a mean hydrodynamic diameter of 152 nm were obtained with a drug loading capacity (DLC) of 24.8%. The in vitro controlled release profiles demonstrated the pH and reduction dual-responsive triggered release of DOX from the developed bio-inspired drug delivery system (DDS), with a cumulative release of 58% within 3 days in a sustained release manner in the stimulated tumor intracellular microenvironment, while a low premature drug leakage of 14% occurred in the normal physiological medium. Furthermore, the MTT assays demonstrated that the graft copolymer Ker-PEG58 possessed excellent cytocompatibility, while the DOX/Ker-PEG CCMs exhibited an enhanced anti-tumor efficacy on the HepG2 cells than the free DOX.

Betulin silver nanoparticles qualify as efficient antimelanoma agents in in vitro and in vivo studies

The current study was purported to assess the: (i) in vitro toxicity of betulin silver nanoparticles (AgNPs-B), bare and capped with polyethylene glycol (PEG), on two murine melanoma cell lines (B164A5 and B16Ova) and on healthy cell lines (keratinocytes and melanocytes), and (ii) in vivo antitumor efficacy of PEGylated AgNPs-B in an experimental melanoma model. Bare and PEG-capped AgNPs-B were synthesized by a chemical reduction method resulting in stable and non-aggregated spherical AgNPs-B and PEG-AgNPs-B, of narrow size distributions and mean hydrodynamic diameters of 25 nm and 75 nm, respectively. In vitro assessments were achieved by MTT and Annexin V-FITC assays and in vivo evaluation involved non-invasive techniques for the surveillance of the physiological skin parameters changes and histopathological examination of the harvested organs. The in vitro results revealed selective cytotoxicity against melanoma cells, at low doses that are nontoxic to normal cells; higher doses were associated with the loss of selectivity and toxicity for healthy cells. PEGylated formulation of betulin exerted a dose-dependent pro-apoptotic effect, more obvious in the case of B164A5 cells. Histopathological analysis suggested that PEGylated AgNPs-B developed relevant in vivo effects as antimelanoma agents by decreasing the tumor volume and inhibiting the development of secondary tumors.

Effectiveness of Parachlorella kessleri cell disruption evaluated with the use of laser light scattering methods

The main objective of this study is to demonstrate the possibilities of using laser light scattering methods, dynamic light scattering and laser Doppler electrophoresis, as suitable methods in investigations of algal production biosystems and biotechnology. This paper highlights the innovative use of the dynamic light scattering (DLS) methods for monitoring the destruction of Parachlorella kessleri cells. Additionally, these results indicate electrophoretic mobility as a new parameter to investigate the effectiveness of cell disruption prior to extraction conducted to optimise the biotechnological processes of recovery of microalgal intracellular metabolites. The efficacy of P. kessleri cell disintegration by ultrasound was determined by measurements of the number of cells with the algal cell reduction (CRns), relative mean hydrodynamic diameter (Rdt) and electrophoretic mobility after applying different lengths of ultrasound exposure to a cell suspension. It was found that stationary-phase cells were the most resistant to the ultrasound treatment, especially at low values of the optical density. Both the relative hydrodynamic diameter and the electrophoretic mobility of cells were correlated statistically significantly with the time of sonication (t) and the algal cell reduction. The relationships allowed estimation of the sonication time needed for total cell disruption.

New insights on the formation of gold nanoparticles and Pluronic nanocomposites: Kinetics and thermodynamics parameters

The present contribution reports new insights into the structure, kinetics, and thermodynamics of gold nanoparticles (AuNP) synthesized in the presence of the block copolymer Pluronic F127 (PLU). AuNP-PLU nanocomposite samples were prepared in the form of aqueous colloidal suspensions by using PLU as a reducing agent of Au(III) ions to Au(0) and stabilizer of the formed AuNP. Transmission electron microscopy reveals that typical AuNP-PLU are nearly polygonal (mean diameter = 18.5 nm ± 0.2) and highly crystalline, while dynamic light scattering provides mean hydrodynamic diameter around 50 nm. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) and Raman spectroscopies indicate that AuNP are located at the more hydrophobic (polypropylene oxide) block of PLU by coordination with oxygen atoms of ether groups. Monitoring the optical absorbance of the localized surface plasmon resonance (LSPR) band of AuNP as a function of the reaction time and PLU concentration suggests the formation of AuNP-PLU is of pseudo first order kinetics, with the observed rate constant being dependent on the PLU concentration. Thus, the concentrations of block copolymer required to form the nanoparticles can be precisely determined. Thermodynamics data collected by isothermal calorimetry titration identified two regimes of molecular interaction: electrostatic, between Au(III) and PLU, and hydrophobic, between Au(0) and PLU, whose energies depend on the PLU concentration. It is concluded that optimal conditions for the synthesis of AuNP-PLU nanocomposites are those in which PLU is provided in concentrations above its critical micellar concentration. At this condition, the Au(III) to Au(0) reaction reaches completion and the establishment of hydrophobic interactions between Au(0) nuclei and polypropylene oxide block becomes feasible.

Study on the dissolution improvement of albendazole using reconstitutable dry nanosuspension formulation

The aim of the study was to improve the solubility and dissolution rate of the poorly water soluble drug albendazole via surfactant assisted media milling process. Preparation of a nanosuspension and then post-processing with a solidification technique applied to improve the applicability of nanosuspension in a solid dosage forms carrier. The dry nanosuspension was obtained using microcrystalline cellulose as solid carrier after tray drying at 40 °C. Both reconstitution from the solid carrier and dissolution profile studies were investigated in biorelevant Artificial Rumen Fluid (ARF) at pH = 6.50 and dissolution media at pH = 1.20 and pH = 6.80. Reconstitution studies have demonstrated that the mean hydrodynamic diameter values of albendazole crystals released from the dry suspension were nanosized (intensity weighted hydrodynamic diameter values: 200.40 ± 2.318 nm in ARF at pH = 6.50, 197.17 ± 0.208 nm in dissolution medium at pH = 6.80). Thermodynamic solubility studies have indicated a 2.98 times increase in water solubility (144.41 ± 0.09 μg/ml milled, 48.38 ± 0.01 μg/ml unmilled, 8.21 ± 0.02 μg/ml albendazole powder) in ARF at pH = 6.50, and 2.33 times in dissolution medium at pH = 6.8: (146.27 ± 0.28 μg/ml milled, 62.71 ± 0.04 μg/ml unmilled, 9.00 ± 0.01 μg/ml albendazole powder), and 13.65% increase at pH = 1.20 (1728.31 ± 3.31 μg/ml milled, 1559.41 ± 0.40 μg/ml unmilled, 1520.70 ± 1.39 μg/ml albendazole powder), dissolution rates have also increased. Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) imaging investigations detected no albendazole nanocrystals on the surface of the carrier, which demonstrated the incorporation of albendazole into the microcrystalline cellulose solid carrier structure.