A. G. Sanin

The informative-capacity phenomenon of drying drops

This investigation shows fundamentally good prospects for the information phenomenon of drying drops in medical diagnostics. The advantages of this method include the high information capacity, the rapid result obtainment, the small invasivity, the possibility of use by individuals without special qualification, and the low cost of the device in mass production. These properties create hope that this technology, after widescale clinical tests and the development of a prototype device, can be useful for making a preliminary diagnosis and extracting a risk group for both screening examinations and home use.

On the existence of regular structures in liquid human blood serum (plasma) and phase transitions in the course of its drying

Experimental data show that regular three-dimensional liquid-crystal protein structures ranging in size from several hundredths to several tenths of a millimeter are present in the whole blood serum (plasma) of patients suffering from various diseases. When a drop of serum dries, some of the structures melt to produce a gel, whereas the rest of them undergo phase transition to form solid crystals. These crystals are shaped like immunoglobulin M molecules enlarged 1000-fold. In the serum (plasma) of ailing people, the amount of the gel formed upon drying increases, breaking the symmetry during the formation of nonequilibrium protein films. It is believed that low-intensity physical factors exert a therapeutic action by changing the phase state of protein in body fluids.

Protein and Salt: Spatiotemporal Dynamics of Events in a Drying Drop

Self-organization processes in biological fluids and aqueous solutions containing protein and salt in various ratios have been studied in drops drying on the surface of a solid substrate. Morphological and histochemical data show that the salt solution exhibits the phase transition in an organic jelly matrix formed in the system. The physical properties of this matrix influence the kinetics of salt crystallization and the morphological features of the observed salt patterns. Controlled UV-radiation-induced protein damage in protein-salt solutions violates the formation of a regular gel and introduces chaotic features into the salt pattern. A new method of investigation of the self-organization processes in drying drops is developed based on acoustomechanical impedance measurements. It is suggested that the dynamic parameters of salt crystallization in drying drops bear information on the composition of the whole biological fluid.

Drops of Biological Fluids Drying on a Hard Substrate: Variation of the Morphology, Weight, Temperature, and Mechanical Properties

The time variation of the morphology, weight, temperature, and integral mechanical properties of drying drops of biological fluids are investigated with the aim of defining more exactly the mechanism of self-organization in the drops. Test fluids in experiments are distilled water, a physiological salt solution (0.9 wt. % NaCl), a solution of bovine serum albumin (BSA) in water, and a solution of BSA (7 wt. %) in the physiological solution. It is shown that the variation of the weight of the drying drops can be described by a sloping straight line with two slightly nonlinear portions at the beginning and at the end of the drying process. The earlier nonlinear portion correlates with a more rapid fall of the temperature, which slows down and stabilizes as a saturated vapor layer forms over the drop. The later nonlinear portion in the drop weight variation is associated with the retardation of water diffusion through the solidifying medium. The temperature variation of the drops is a superposition of endothermal (water evaporation) and exothermal (salt crystallization and gelation) phase transitions. Phase transitions may change the mechanical properties of the drying drops, which can be detected by the method of acoustic impedancemetry.

A new technology for studying multicomponent liquids using a quartz crystal resonator: Theory and applications

A new technique for analyzing multicomponent liquids is suggested. It is based on recording “electronic autographs” of liquids and thereby allows one to identify and certify them. In this technique, information comes from the dynamics of the complex process of self-organization in drying drops, this dynamics being dependent on the composition and structure of the liquid. Detecting the self-organization dynamics as acoustomechanical impedance, one can reveal quantitative distinctions between liquids and thereby test their quality by comparing with a reference.

Dynamics of Phase Transitions in Drying Drops of Human Serum Protein Solutions

The dynamics of structuring of protein solutions in drying drops and their morphology versus the composition of dissolved proteins are studied. An increase in the content of immunoglobulins and fibronectin is shown to have an effect on the physical properties of adsorption layers at the fluid-air interface and thereby changes the dynamic parameters of structuring in drying drops. These changes are embodied in the shape of the acoustomechanical impedance curves of drying drops and can be estimated numerically. Thus, experimental support is provided for the previous phenomenological data indicating that medical diagnosis based on recording the dynamics of the acoustomechanical impedance in drying drops of blood serum is a feasibility.

Thermographic investigation of the temperature field dynamics at the liquid-air interface in drops of water solutions drying on a glass substrate

The temperature field distribution at the liquid-air interface in drops of water and water solutions drying on a glass substrate is studied with thermal imaging means. It is shown that irrespective of the liquid composition, the circumferential temperature of the drops (along the boundary line) is always higher than the temperature on the top. The temperature field on the surface of the drops is nonstationary and varies chaotically during water evaporation. It is found that the dynamics of histograms for albumin-containing and albumin-free liquids differ. Mechanisms behind the origination of thermocapillary liquid flows and their directivity in the drying drops are discussed.

Mechanical Properties of Adsorption Layers in Solutions of Human Blood Serum Proteins: A Comparative Assessment

The mechanical properties of adsorption layers in small volumes (0.1 ml) of protein solutions in a saline are studied using small-diameter indenters. In an albumin solution, the partial substitution of the protein by an equivalent (by weight) amount of immunoglobulins G or M reduces the surface energy, whereas the addition of fibronectin improves the mechanical strength of the layer. The data obtained may provide a deeper insight into the mechanisms of specific dynamic processes responsible for the structuring of biological fluids in drying drops. In particular, such information is of value for medical diagnosis.

Dynamics of mechanical properties of drying drops of biological liquids as a reflection of the features of self-organization of their components from nano- to microlevel

It has been shown that the dynamics of molecular self-organization of the components of liquids drying in the form of drops on a solid wettable surface contains information about their composition and structure. The physical mechanisms of this phenomenon have been considered. A method of recording this dynamics and retrieving useful information has been suggested. Examples of using this method in medical diagnosis and quality assessment of food products, drugs, and liquids of domestic appliance are given.

Method for studying phase transitions in drying drops and its application in assessing the physicochemical properties of water and aqueous solutions

Using microscopy and acoustic impedancemetry, we examine the spatiotemporal features of crystallization of inorganic chlorides in drying drops of aqueous solutions on a solid wettable surface. We discuss the physicochemical mechanisms determining the difference in the “dynamic portraits” of distilled water and salt solutions and the relaxation phenomena in water. We show the drying drop technique to be promising in assessing the changes in water properties under the impact of physical and chemical factors.