Search

One of the key physicochemical parameters of polyelectrolyte microcapsules (PMCs) is their buffer capacity (BC). The BC of the microcapsules allows for an assessment of the change in protonation state across the entire polyelectrolyte system, which directly impacts the buffer barrier of PMCs, as well as the stability and physical properties of their shell. However, the buffer capacity of PMCs and their behavior under changes in ionic strength and temperature can differ depending on the type of core used to form the microcapsules. As part of this study, we revealed the buffer capacity (BC) of polyelectrolyte microcapsules formed on polystyrene cores (PMC Ps ) and studied the influence of ionic strength and environmental temperature on the BC of these capsules. We found that the buffer capacity of PMC Ps differs from the BC of water at a pH above 8; the addition of sodium chloride leads to an increase in buffer capacity in alkaline conditions, and conversely, thermal treatment leads to its decrease at a pH of 9. The results obtained are different from the BC of polyelectrolyte microcapsules formed on CaCO 3 cores, which suggests a difference in the physicochemical properties of these types of capsules. The buffer capacity of polyelectrolyte microcapsules depends on the type of template used.

There are many studies devoted to the application of polyelectrolyte microcapsules (PMC) in various fields; however, there are significantly fewer studies devoted to the study of the polyelectrolyte microcapsules themselves. The study examined the mutual arrangement of the polyelectrolytes in 13-layered PMC capsules composed of (PAH/PSS) 6 PAH. The research showed that different layers of the polyelectrolyte microcapsules dissociate equally, as in the case of 13-layered PMC capsules composed of (PAH/PSS) 6 PAH with a well-defined shell, and in the case of 7-layered PMC capsules composed of (PAH/PSS) 3 PAH, where the shell is absent. The study showed that polyallylamine layers labeled with FITC migrate to the periphery of the microcapsule regardless of the number of layers. This is due to an increase in osmotic pressure caused by the rapid flow of ions from the interior of the microcapsule into the surrounding solution. In addition, FITC-polyallylamine has a lower charge density and less interaction with polystyrene sulfonate in the structure of the microcapsule. Meanwhile, the hydrophilicity of FITC-polyallylamine does not change or decreases slightly. The results suggest that this effect promotes the migration of labeled polyallylamine to a more hydrophilic region of the microcapsule, towards its periphery.

Phenols are widely used in industries despite their toxicity, which requires governments to limit their concentration in water to 5 mg/L before discharge to the city sewer. Thus, it is essential to develop a rapid, simple, and low-cost detection method for phenol. This study explored two pathways of peroxidase immobilization to develop a phenol detection system: peroxidase encapsulation into polyelectrolyte microcapsules and peroxidase captured by CaCO 3 . The encapsulation of peroxidase decreased enzyme activity by 96%; thus, this method cannot be used for detection systems. The capturing process of peroxidase by CaCO 3 microspherulites did not affect the maximum reaction rate and the Michaelis constant of peroxidase. The native peroxidase-Vmax = 109 µM/min, Km = 994 µM; CaCO 3 -peroxidase-Vmax = 93.5 µM/min, Km = 956 µM. Ultimately, a reusable phenol detection system based on CaCO 3 microparticles with immobilized peroxidase was developed, capable of detecting phenol in the range of 700 ng/mL to 14 µg/mL, with an error not exceeding 5%, and having a relatively low cost and production time. The efficiency of the system was confirmed by determining the content of phenol in a paintwork product.

Anthropogenic activity negatively affects the environment by polluting it with the salts of various metals. One of the ways to reduce this influence is to use water purification methods for the salts of various metals. Water purification methods based on nanomaterials are promising. In this regard, we proposed to study polyelectrolyte microcapsules (PMC) as a promising sorption agent for the salts of various metals. It was found that the polystyrene sulfonate-polyallylamine (PSS-PAH) polyelectrolyte complex and polyelectrolyte microcapsules of different compositions are not able to adsorb salts CuSO 4 , Pb(NO) 3 , FeCl 3 , and CuCl 2 . At the same time, it was found that all types of capsules, except for (PSS/PAH) 2 /PSS, are capable of sorbing about 420 µg of K 3 [Fe(CN) 6 ] and about 500 µg of K 4 [Fe(CN) 6 ] from solution. The adsorption of polyelectrolyte microcapsules has an electrostatic nature which is confirmed by increases in the sorption capacity of PMC of K 3 [Fe(CN) 6 ] and K 4 [Fe(CN) 6 ] with decreases in the pH of the solution. Also, It was confirmed that the sorption process of PMC of K 3 [Fe(CN) 6 ] and K 4 [Fe(CN) 6 ] is concentration dependent and has the limitation of the number of binding sites.

Polyelectrolyte microcapsules are used in the development of new forms of targeted delivery systems, self-healing materials, sensors, and smart materials. Nevertheless, their buffer capacity has not been practically studied, although that characteristic makes it possible to estimate the change in the state of protonation of the entire polyelectrolyte system. This is necessary both for creating a buffer barrier system for pH-sensitive compounds (metals, enzymes, polyelectrolytes, drugs) and for the correct interpretation of the results of research and studying of the PMC structure. The buffer capacity of a PMC can be affected by the concentration of microcapsules in solution and the number of shell layers since the listed parameters affect other physicochemical properties of the PMC shell. This includes, for example, the electrical conductivity, permeability (of ions), osmotic pressure, charge density, etc. In this regard, we studied the change in the buffer capacity of polyelectrolyte microcapsules depending on their concentration and the number of shell layers. As a result, it was found that with an increasing concentration of microcapsules, the buffering capacity of the PMC increases, but at the same time, in the pH range from 4 to 5.5, the calculated buffering capacity of 1 billion capsules decreases with increasing their concentration. This effect may be associated with a decrease in the available -NH 2 groups of the PMC's shell. In addition, it was found that the main contribution to the buffer capacity of a PMC is made by the entire shell of the microcapsule and not just its surface. At the same time, the buffer capacity of the capsules has non-linear growth with an increase in the number of PMC shell layers. It is presumably associated either with a decrease in the polyelectrolyte layer with an increase in their number or with a decrease in the permeability of hydrogen protons.

Polyelectrolyte microcapsules (PMCs) are used in the development of new forms of drugs, coatings and diagnostic systems. Their buffer capacity, depending on the conditions of the medium, has not been practically studied, although it can affect the structure of both the capsule itself and the encapsulated agents. In this connection, we studied the buffer capacity of polyelectrolyte microcapsules of the composition (polystyrene sulfonate/polyallylamine) 3 ((PSS/PAH) 3 ) depending on the concentration and the type of salt in solution, as well as the microcapsule incubation temperature. It was found that the buffer capacity of microcapsules in the presence of mono- and di-valent salts of the same ionic strength did not differ practically. Increasing the NaCl concentration to 1 M led to an increase of buffer capacity of PMCs at pH ≥ 5, and an increase in NaCl concentration above 1 M did not change buffer capacity. The study of the buffer capacity of pre-heated PMCs showed that buffer capacity decreased with increasing incubation temperature, which was possibly due to the compaction of the PMCs and an increase in the number of compensated PAH sites. The addition of 1 M sodium chloride to heated PMCs presumably reversed the process described above, since an increase in the ionic strength of the solution led to an increase of the buffer capacity of the PMCs. The effects described above confirm the hypothesis put forward that the buffer properties of microcapsules are determined by uncompensated PAH regions in their composition.

Polyelectrolyte microcapsules can be applied as microcontainers for the delivery of a wide range of substances, and it is important to search for new methods for capsule destruction and releasing substances from them. In this work, we studied the possibility of using sodium dodecyl sulfonate (SDS) for the release of fluorescein isothiocyanate-dextran from six-layer microcapsules composed of PAH and PSS. It was shown that the presence of SDS in the medium, at a concentration of 3000 μg/ml, leads to the destruction of polyelectrolyte microcapsules and the release of the substance from them (54% of the amount of the encapsulated substance), while the main part of the FITC-dextran released during the first hours of incubation. At an SDS concentration of 100 μg/ml, the substance released is uniform and is 44% in 24 h. At SDS concentrations from 50 to 100 μg/ml, the process of destruction of microcapsules proceeds more slowly. At SDS concentrations from 10 to 50 μg/ml, microcapsules are not degraded., (© 2022. The Author(s).)

Antimicrobial resistance is a global public health threat. One of the possible ways to solve this problem is phage therapy, but the instability of bacteriophages hinders the development of this approach. A bacteriophage delivery system that stabilizes the phage is one of the possible solutions to this problem. This study is dedicated to exploring methods to create encapsulated forms of bacteriophages for delivery. We studied the effect of proteolytic enzymes on the destruction of the polyelectrolyte microcapsule shell and revealed that protease from Streptomyces griseus was able to destroy the membrane of the microcapsule (dextran sulfate/polyarginine) 3 ((DS/PArg) 3 ). In addition, the protease decreased the activity of the bacteriophage in the second hour of incubation, and the phage lost activity after 16 h. It was found that a medium with pH 9.02 did not affect the survival of the bacteriophage or E. coli . The bacteriophages were encapsulated into polyelectrolyte microcapsules (DS/PArg) 3 . It was established that it is impossible to use microcapsules as a means of delivering bacteriophages since the bacteriophages are inactivated. When bacteriophages were included inside a CaCO 3 core, it was demonstrated that the phage retained activity before and after the dissolution of the CaCO 3 particle. From the results of this study, we recommend using CaCO 3 microparticles as a container for bacteriophage delivery through the acidic stomach barrier.

Sodium dodecyl sulfate (SDS) is the most widely used anionic surfactant. Its frequent use causes environmental pollution and negative effects on living organisms (even at low concentrations ≈ 20 μg/ml). Thus, cheap and fast methods are needed to detect this surfactant in wastewater and surface waters in order to prevent the negative effects of SDS on the environment and human beings. We discovered that sodium dodecyl sulfate is capable of destroying polyelectrolyte microcapsules, which has been demonstrated by the number of sedimented polyelectrolyte microcapsules (PMC) before and after incubation in SDS solution. Therefore, it was proposed to use PMCs to create qualitative and quantitative diagnostic systems for the determination of SDS in solution. The qualitative system is a polyelectrolyte microcapsules containing polyallylamine labeled with a fluorescent dye-FITC. An excess SDS concentration of more than 5 μg/ml in the analyzed medium leads to the destruction of PMC and an increase in the fluorescence intensity of the solution, which is recorded by a fluorometer. The quantitative diagnostic system is based on turbidimetry of the PMC suspension before and after incubation in an anionic surfactant solution. This system has a range of detectable SDS concentrations from 10 to 50 μg/ml, with a standard deviation of no more than 11%., (© 2022. The Author(s).)

Polyelectrolyte microcapsules, which are obtained by the method of alternate adsorption of oppositely charged polyelectrolytes onto colloidal particles of micron size, are widely used in science and industry. Nevertheless, the properties of microcapsules are still poorly understood. In particular, there is no information in the literature on the buffer capacity. However, information on the presence of a buffer capacity and an understanding of its mechanisms can both simplify the use of microcapsules and expand the scope of their application. In this regard, the buffer capacity of various types of microcapsules was studied. It was found that polyelectrolyte microcapsules consisting of polyallylamine, and polystyrene sulfonate have a buffer capacity. In addition, in an acidic medium, the buffer capacity of microcapsules containing BSA is significantly greater than that of microcapsules without protein. This is due to the fact that BSA contributes to the buffering of microcapsules. Differences in the behaviour of the buffer capacity of microcapsules with the composition (PAH/PSS) 3 and (PSS/PAH) 3 were found. In addition, a hypothesis has been proposed that regions of unbound polyallylamine are responsible for the buffering properties of polyelectrolyte microcapsules. This hypothesis is confirmed by the fact that incubation of microcapsules in 0.5 M NaCl increases the amount of unbound polyallylamine, which leads to an increase in the buffer capacity of microcapsules at alkaline pH values higher than the buffer capacity of capsules in an aqueous solution.

In this work, the mutual arrangement of polyelectrolytes of multilayer polyelectrolyte microcapsules (with layers-[PAH/PSS] 3 PAH) by determination of the dissociation level of polyallylamine (PAH) from the surface of a polyelectrolyte microcapsules (PMC) of various types was studied: PMC with a dissolved CaCO 3 core after preparation, PMC with an undissolved CaCO 3 core and PMC with an encapsulated protein. It was concluded that the polyelectrolyte layers are mixed in the entire shell of the capsules with a dissolved CaCO 3 core. In the case of the PMC with an undissolved CaCO 3 core, such mixing of polyelectrolyte layers does not occur. That fact allows us to conclude that the mixing of polyelectrolytes layers mixing at the stage of dissolution of CaCO 3 core. The PMC with encapsulated protein has partial mixing of polyelectrolytes layers. That phenomenon may be due to the fact that seven-layered protein-containing microcapsules already have a dense and well-formed shell. The obtained data correlate with the data on the study of the surface charge of microcapsules.

Phage therapy is a great alternative to antibiotic drugs, but it can't effectively overcome the over-acidic medium of the stomach. We offer the use of polyelectrolyte microcapsules as a protective means of bacteriophage. It is necessary to understand the influence of polyelectrolytes on bacteriophage survival. The work studied the effect of polyanions and polycations on the coliprotetic bacteriophage's viability. We have shown that polyallylamine decreased bacteriophage's viability during increasing polyelectrolyte concentration and polyarginine had a lower inhibitory effect (then PAH) on the activity of the bacteriophage due to polyelectrolyte concentration from 0.05 to 5 mg/mL. It was shown that the inhibition of the bacteriophage by polyallylamine had an electrostatic nature and the use of high ionic strength prevented the formation of the PAH-protein capsid complex. Polystyrene sulfonate does not affect bacteriophage viability during increasing polyelectrolyte concentration from 0.05 mg/mL to 1 mg/mL. Polystyrene sulfonate decreases the viability of bacteriophage from 5 mg/mL of polyelectrolyte concentration. Dextran sulfate inhibits bacteriophage activity at 20-30%. Dextran inhibits bacteriophage activity by 80% at diapason concentration from 0.05 to 5 mg/mL and loses the inhibition effect from a concentration of 5 mg/mL.

In this article, the effect of polyallylamine (PAA) on the structure and catalytic characteristics of alcohol dehydrogenase (ADH) was studied. For this research, we used methods of stationary kinetics and fluorescence spectroscopy. It has been shown that PAA non-competitively inhibits ADH activity while preserving its quaternary structure. It was established that 0.1 M ammonium sulfate removes the inhibitory effect of PAA on ADH, which is explained by the binding of sulfate anion (NH 4 ) 2 SO 4 with polyallylamine amino groups. As a result, the rigidity of the polymer chain increases and the ability to bind to the active loop of the enzyme increases. It is also shown that sodium chloride removes the inhibitory effect of PAA on ADH due to an electrostatic screening of the enzyme from polyelectrolyte. The method of encapsulating ADH in polyelectrolyte microcapsules was adapted to the structure and properties of the enzyme molecule. It was found that the best for ADH is its encapsulation by adsorption into microcapsules already formed on CaCO 3 particles. It was shown that the affinity constant of encapsulated alcohol dehydrogenase to the substrate is 1.7 times lower than that of the native enzyme. When studying the affinity constant of ADH in a complex with PAA to ethanol, the effect of noncompetitive inhibition of the enzyme by polyelectrolyte was observed.

One of the prerequisites of successful address delivery is controlling the release of encapsulated drugs. The new method of bacterial spore encapsulation in polyelectrolyte microcapsules allows for degrading the nanoscale membrane shell of microcapsules. The possibility of encapsulating spore forms of Bacillus subtilis in polystyrenesulfonate sodium/ polyallylamine hydrochloride (PSS/PAH) polyelectrolyte microcapsules was demonstrated. The activation and growth on a nutrient medium of encapsulated bacterial spores led to 60% degradation of the microcapsules nanoscale membrane shell. As a result, 18.5% of Fluorescein isothiocyanatedextran was encapsulated into polyelectrolyte microcapsules, and 28.6% of the encapsulated concentration of FITC-dextran was released into the solution., Competing Interests: The authors declare no conflict of interest.

We studied the effect of different concentrations of polyelectrolytes poly(allylamine hydrochloride) (PAH) and polystyrene sulfonate (PSS) as well as the effects of microcapsules coated with these polymers on survival of Ehrlich ascites carcinoma cells and mouse peritoneal macrophages and on ROS production by phagocytes. PAH reduced viability of Ehrlich ascites carcinoma in a concentration-dependent manner (LD 50 =12-15 μg/ml). This effect was presumably determined by its ability to bind phosphates, thereby depleting the culture medium. At the same time, PAH did not affect the viability of macrophages. PSS produced no cytotoxic effect on the examined cells. Polyelectrolyte capsules with the shell architectonics (PAH/PSS) 3 and (PAH/PSS) 3 PAH in the examined concentration range had no effect on the viability of macrophages and tumor cells. PAH microcapsules with positively charged surface much more rapidly and more intensively activated macrophages. The chemiluminescence response directly depended on the amount of capsules in the solution.

Relationship between changes in the erythrocyte sedimentation rate in rats and concentration and charge of polyelectrolyte microcapsules was studied by the Panchenkov method. Positively charged microcapsules reduced erythrocyte sedimentation rate in a concentrationdependent manner. This effect was related to a decrease in the content of high-molecularweight proteins in the plasma due to their adsorption in positively charged microcapsules with polyacrylamide surface layer.