Dynamic surface tension measurements as general approach to the analysis of animal blood plasma and serum

Prediction of subcutaneous drug absorption - characterization of subcutaneous interstitial fluids as a basis for developing biorelevant in vitro models

Unlike orally administered drugs, the absorption profile of subcutaneously injectable drugs in humans is difficult to predict from preclinical studies. Since the subcutaneous interstitial fluid (ISF) is the first fluid interacting with the administered formulation before the respective drug is absorbed, it could critically affect bioavailability. The aim of the present study was to gain a better understanding of the similarities and differences of ISF of different species. For this purpose, ISF was isolated from subcutaneous tissues of five preclinical animal species, i.e., mice, rats, minipig, landrace pig, non-human primates, and humans, using a centrifugation method, and characterized with respect to its major constituents and physicochemical properties. The results show trends between animal species, with ISF from non-human primates differing significantly from that of the other preclinical species for most parameters analyzed and showing similarities to ISF of human origin. Although from a statistical point of view it will be necessary to further increase the existing data sets, the presented data provide valuable information for the development of biorelevant in vitro models to predict the in vivo performance of subcutaneously administered formulations, as they provide fundamental information for the design of biorelevant ISF media for both preclinical species and humans.

Synthesis and physicochemical properties of sodium oleyl sulfate

In this paper, sodium oleyl sulphate (SOS) was successfully synthesised by reacting octyl alcohol (OA) with gaseous sulphur trioxide (SO3) as a sulphating reagent in a falling film reactor. The structure was determined by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1HNMR) spectroscopy. The dynamic adsorption and aggregation behaviour of SOS was systematically investigated to reveal the relationship between the structure and properties of SOS. The physicochemical properties of SOS were determined by measuring the equilibrium surface tension, dynamic surface tension and dynamic contact angle, respectively. A laser particle size analyser and a transmission electron microscope (TEM) were used to analyse the aggregation behaviour of SOS. Compared to sodium dodecyl sulphate (SDS) and sodium n-octadecyl sulphate (C18H37OSO3Na), which have a similar structure to SOS, the increase in hydrophobic chain size and tighter molecular packing enabled by the polar head conformation caused a decrease in CMC and an increase in surface activity. The efficiency of the surface activity was controlled by a mixed diffusion kinetic adsorption mechanism. Moreover, SOS in aqueous solution showed efficient wettability on the surface of the low-energy paraffin film at concentration above the CMC. In addition, SOS molecules can spontaneously form spheroidal aggregates with increasing concentration, and the size of the aggregates increased with the concentration.

The role of plasma in the yield stress of blood

BACKGROUND

Yielding and shear elasticity of blood are merely discussed within the context of hematocrit and erythrocyte aggregation. However, plasma might play a substantial role due its own viscoelasticity.

OBJECTIVE

If only erythrocyte aggregation and hematocrit would determine yielding, blood of different species with comparable values would present comparable yield stresses.

METHODS

rheometry (SAOS: amplitude and frequency sweep tests; flow curves) of hematocrit-matched samples at 37°C. Brillouin Light Scattering Spectroscopy at 38°C.

RESULTS

Yield stress for pig: 20mPa, rat: 18mPa, and human blood: 9mPa. Cow and sheep blood were not in quasi-stationary state supporting the role of erythrocyte aggregation for the development of elasticity and yielding. However, pig and human erythrocytes feature similar aggregability, but yield stress of porcine blood was double. Murine and ruminant erythrocytes both rarely aggregate, but their blood behavior was fundamentally different. Pig plasma was shear-thinning and murine plasma was platelet-enriched, supporting the role of plasma for triggering collective effects and gel-like properties.

CONCLUSIONS

Blood behavior near zero shear flow is not based solely on erythrocyte aggregation and hematocrit, but includes the hydrodynamic interaction with plasma. The shear stress required to break down elasticity is not the critical shear stress for dispersing erythrocyte aggregates, but the shear stress required to fracture the entire assembly of blood cells within their intimate embedding.

Heterologous Expression and Immunogenic Potential of the Most Abundant Phospholipase A2 from Coral Snake Micrurus dumerilii to Develop Antivenoms

Micrurus dumerilii is a coral snake of clinic interest in Colombia. Its venom is mainly composed of phospholipases A₂ being MdumPLA₂ the most abundant protein. Nevertheless, Micrurus species produce a low quantity of venom, which makes it difficult to produce anticoral antivenoms. Therefore, in this work, we present the recombinant expression of MdumPLA₂ to evaluate its biological activities and its immunogenic potential to produce antivenoms. For this, a genetic construct rMdumPLA₂ was cloned into the pET28a vector and expressed heterologously in bacteria. His-rMdumPLA₂ was extracted from inclusion bodies, refolded in vitro, and isolated using affinity and RP-HPLC chromatography. His-rMdumPLA₂ was shown to have phospholipase A₂ activity, a weak anticoagulant effect, and induced myonecrosis and edema. The anti-His-rMdumPLA₂ antibodies produced in rabbits recognized native PLA₂, the complete venom of M. dumerilii, and a phospholipase from another species of the Micrurus genus. Antibodies neutralized 100% of the in vitro phospholipase activity of the recombinant toxin and a moderate percentage of the myotoxic activity of M. dumerilii venom in mice. These results indicate that His-rMdumPLA₂ could be used as an immunogen to improve anticoral antivenoms development. This work is the first report of an M. dumerilii functional recombinant PLA₂.

Correlations between the Total Antioxidant Activity and Biochemical Parameters of Cow Milk Depending on the Number of Somatic Cells

The aim of the work was to study the correlations between the total amount of water-soluble antioxidants (TAWSA) and biochemical parameters (BC) of cow milk depending on the somatic cell count (SCC). The BC and TAWSA values of cow milk were measured by spectroscopic and amperometric methods, respectively. The milk samples from the black-and-white cows (Moscow region) were divided according to SCС values: (1) ≤200, (2) 200-499, (3) 500-999, and (4) ≥1000 thousand units/mL. The average TAWSA values for groups 1, 2, 3, and 4 (33, 15, 13, and 12 milk samples) were the following: $15.95\pm 0.74$ , $14.45\pm 0.84$ , $16.04\pm 0.63$ , and $14.58\pm 1.18$ . The correlations between TAWSA and BC (group 1) were the following: total fat percentage (TFP) -0.305; true protein percentage (TP1) -0.197; total nitrogen percentage (TN2) -0.210; lactose -0.156; solids-not-fat (SNF) -0.276; total dry matter (TDM) -0.399; freezing point (FP) -0.112; pH -0.114; somatic cell count (SCC) - (-0,052). The correlations between TAWSA and BC (group 2) were the following: TFP -0.332; TP1 -0.296; TN2 -0.303; lactose - (-0.308); SNF -0.159; TDM -0.391; FP -0.226; pH - (-0.211); SCC -0.193. The correlations between TAWSA and BC (group 3) were the following: TFP - (-0.352); TP1 - (-0.411); TN2 – (-0.401); lactose - (-0.166); SNF - (-0.462); TDM - (-0.504); FP - (-0.766); pH - (-0.047); SCC - (-0.698). The correlations between TAWSA and BC (group 4) were the following: TFP -0.159; TP1 -0.046; TN2 – 0.077; lactose - (-0.317); SNF - (-0.237); TDM -0.058; FP - (-0.036); pH - (-0.477); SCC - (-0.072). These data are important in assessing the physiological-biochemical status and state of the antioxidant defense system of cows’ organism.

An innovative approach to assessing the integral parameters of the hybrid pig blood for the methodological support of animal husbandry development

The main aims of research were: to measure the surface tension (ST) values of hybrid pig blood; to establish the relationships between these ST-values and obtained biochemical parameters of the same blood samples. All studied animals (n=43) were healthy and grown at the feeding stations (Russia). The ST-values (measured using PAT-device) of the pig blood were obtained at initial (n=30) and final (n=13) points of animal fattening. The following correlations between eST at final (or initial) point of pig fattening and the biochemical parameters were obtained: +0.80 (+0.19) with the ratio of albumins to globulins (A/G), -0.39 with globulins (-0.38) with phospholipids, +0.32 (+0.40) with the “de Ritis” coefficient, -0.52 (+0.35) with Cl. The correlations between eTA at same fattening points and the biochemical parameters were obtained: +0.32 with A/G ratio, +0.18 with globulins, +0.36 with phospholipids, +0.28 (+0.17) with the “de Ritis” coefficient, -0.32 (+0.21) with Mg, +0.35 with Fe, +0.30 with Cl, +0.31 (+0.34) with the ratio of calcium to phosphorus (Ca/P). Such tendency indicated the stabilization of pig physiological-biochemical status during their fattening. The authors recommended the following eST (42-46 mN/m) and eTA (10-30 mN·m-1·s-½) blood parameters as reference values for further applications in husbandry.

Radial Wicking of Biological Fluids in Paper

In this study, we analyze stain growth kinetics from droplets of biological fluids such as blood, plasma, and protein solutions on paper both experimentally and numerically. The primary difference of biological fluids from a simple fluid is a significant wetting/dewetting hysteresis in paper. This becomes important in later stages of droplet wicking, after the droplet has been completely absorbed into paper. This is shown by anomalous power dependence of area with time in the later stages of radial wicking. At early stages, current numerical wicking models can predict stain growth of biological fluids. However, at later stages, the introduction of hysteresis complicates modeling significantly. We show that the cause of the observed hysteresis is due to contact angle effects and that this is the dominant mechanism that leads to the anomalous stain growth kinetics measured uniquely in biological fluids. Results presented will streamline the design process of paper-based diagnostics, allowing a modeling approach instead of a trial and error method.

Comparative Study of the Water-Soluble Antioxidants in Fodder Additives and Sheep Blood Serum by Amperometric and Biochemical Methods

The effects of chitosan as feed additive for animals (FAFAs) on various digestive processes are an important to study because of the animal nutrition and production quality, healthcare and farming. The aims of this study were to evaluate the total amount of water-soluble antioxidants (TAWSA) of chitosan and high protein microbiologically synthesized concentrate as FAFAs; to assess the effect of these FAFAs on TAWSA values, parameters of sheep blood serum and rumen content by biochemical, physical and chemical methods. The laboratory studies of TAWSA values of feed components based on chitosan from different manufacturers or/and a high-protein concentrate were implemented. The animal experiments were carried out on six rumen-fistulated ewes (in three rounds of 14 days each, i.e., three groups) to confirm the results of the laboratory studies. The particular differences of the TAWSA of sheep blood by using both FAFAs by amperometric method were determined. A strong negative correlation -0.67 (or -0.86) was observed between TAWSA and the total protein (globulin's) content in the blood for the Group 3 of animals. A moderate (0.40) or strong (0.73) positive correlation between TAWSA and total protein content in the blood for the Group 2 of animals than weak correlation 0.23 (or 0.26) for the control Group 1. In conclusion, the correlations between the value changes of TAWSA vs. major biochemical parameters of a blood serum of rumen-fistulated ewes (Group 3 > Group 2 > Group 1) or some indicators of the rumen content (ingesta pH, total content of volatile fatty acids, etc.) were found for the first time.

Optical coherence tomography for evaluating capillary waves in blood and plasma

Capillary waves are associated with fluid mechanical properties. Optical coherence tomography (OCT) has previously been used to determine the viscoelasticity of soft tissues or cornea. Here we report that OCT was able to evaluate phase velocities of capillary waves in fluids. The capillary waves of water, porcine whole blood and plasma on the interfacial surface, air-fluid in this case, are discussed in theory, and phase velocities of capillary waves were estimated by both our OCT experiments and theoretical calculations. Our experiments revealed highly comparable results with theoretical calculations. We concluded that OCT would be a promising tool to evaluate phase velocities of capillary waves in fluids. The methods described in this study could be applied to determine surface tensions and viscosities of fluids for differentiating hematological diseases in the future potential biological applications.

Aroma Molecules as Dynamic Volatile Surfactants: Functionality beyond the Scent

Understanding of nonequilibrium processes at dynamic interfaces is indispensable for advancing design and fabrication of solid-state and soft materials. The research presented here unveils specific interfacial behavior of aroma molecules and justifies their usage as multifunctional volatile surfactants. As nonconventional volatile amphiphiles, we study commercially available poorly water-soluble compounds from the classes of synthetic and essential flavor oils. Their disclosed distinctive feature is a high dynamic interfacial activity, so that they decrease the surface tension of aqueous solutions on a time scale of milliseconds. Another potentially useful property of such amphiphiles is their volatility, so that they notably evaporate from interfaces on a time scale of seconds. This behavior allows for control of wetting and spreading processes. A revealed synergetic interfacial behavior of mixtures of conventional and volatile surfactants is attributed to a decrease of the activation barrier as a result of high statistical availability of new sites at the surface upon evaporation of the volatile component. Our results offer promising advantages in manufacturing technologies which involve newly creating interfaces, such as spraying, coating technologies, ink-jet printing, microfluidics, laundry, and stabilization of emulsions in cosmetic and food industry, as well as in geosciences for controlling aerosol formation.

Surface tension and intrinsic amyloid fluorescence of serum and cerebrospinal fluid samples in Alzheimer´s disease

AIM

Surface tension of biological fluids can be influenced by changes in oligomerization or aggregation of surfactant peptides or proteins. Amphiphilic peptides of amyloid-β or other amyloidogenic peptides/proteins display properties of surfactants, oligomerization and aggregation increase also their fluorescence intensity compared with native structures. Results/methodology: We estimated surface tension and native/ThioflavinT-based/intrinsic amyloid fluorescence intensity in serum and cerebrospinal fluid samples for their evalution as diagnostic biomarkers for Alzheimer´s disease (AD).

DISCUSSION/CONCLUSION

Our results indicate that values of surface tension are not a suitable biomarker for AD. However, the ratio of ThioflavinT-based fluorescence to intrinsic amyloid fluorescence in cerebrospinal fluid appears to be an acceptable supportive diagnostic biomarker for AD (its sensitivity was 61.1%, and the specificity 70.8% when compared with aged controls).

Interfacial tensiometry and dilational surface visco-elasticity of biological liquids in medicine

Dynamic surface tensions and dilational visco-elasticity are easy accessible parameters of liquids. For human body liquids, such as urine, blood serum, amniotic fluid, gastric juice, saliva and others, these parameters are very characteristic for the health status of people. In case of a disease the composition of certain liquids specifically changes and the measured characteristics of dynamic surface tension of the dilational surface elasticity and viscosity reflect these changes in a clear way. Thus, this kind of physico-chemical measurements represent sensitive tools for evaluating the severity of a disease and can serve as control tool for the efficiency of applied therapies. The overview summarises the results of a successful work over about 25years on this subject and gives specific insight into a number of diseases for which the diagnostics as well as the therapy control have been significantly improved by the application of physico-chemical experimental techniques.

Surface Tension and Adsorption Studies by Drop Profile Analysis Tensiometry

Surface tension and dilational viscoelasticity of solutions of various surfactants measured with bubble and drop profile analysis tensiometry are discussed. The study also includes experiments on the co-adsorption of surfactant molecules from a solution drop and alkane molecules from saturated alkane vapor phase. Using experimental data for 12 surfactants with different surface activities, it is shown that depletion due to adsorption of surfactant from the drop bulk can be significant. An algorithm is proposed quantitatively to take into consideration the depletion effect which is required for a correct description of the co-adsorption of alkanes on the solution drop surface and the correct analysis of experimental dynamic surface tension data to determine the adsorption mechanism. Bubble and drop profile analysis tensiometry is also the method of choice for measuring the dilational viscoelasticity of the adsorbed interfacial layer. The same elasticity moduli are obtained with the bubble and drop method only when the equilibrium surface pressures are sufficiently small (Π < 15 mN m-1). When the surface pressure for a surfactant solution is larger than this value, the viscoelasticity moduli determined from drop profile experiments become significantly larger than those obtained from bubble profile measurements.