Preparation, physicochemical characterization and swelling properties of composite hydrogel microparticles based on gelatin and pectins with different structure.

Composite hydrogel microparticles based on pectins with different structures (callus culture pectin (SVC) and apple pectin (AU)) and gelatin were developed. Hydrogel microparticles were formed by the ionotropic gelation and electrostatic interaction of COO- groups of pectin and NH3+ groups of gelatin, which was confirmed by FTIR spectroscopy. The addition of gelatin to pectin-based gel formulations resulted in a decrease in gel strength, whereas increasing gelatin concentration enhanced this effect. The microparticle gel strength increased in proportion to the increase in the pectin concentration. The DSC and TGA analyzes showed that pectin-gelatin gels had the higher thermal stability than individual pectins. The gel strength, Ca2+ content and thermal stability of the microparticles based on gelatin and SVC pectin with a lower degree of methylesterification (DM) (14.8 %) were higher compared to that of microparticles based on gelatin and AU pectin with a higher DM (40 %). An increase in the SVC concentration, Ca2+ content and gel strength of SVC-gelatin microparticles led to a decrease in the swelling degree in simulated gastrointestinal fluids. The addition of 0.5 % gelatin to gels based on AU pectin resulted in increased stability of the microparticles in gastrointestinal fluids, while the microparticles from AU without gelatin were destroyed.

Force spectroscopy of interactions between Yersinia pseudotuberculosis and Yersinia pestis cells and monoclonal antibodies using optical tweezers.

The interactions of a microbial cell with host cells and humoral factors play an important role in the development of infectious diseases. The study of these mechanisms contributes to the development of effective methods for the treatment of bacterial infections. One of the possible approaches to studying bacterial adhesion to host cells is based on the use of the optical trap method. The aim of this work was to assess the significance of lipopolysaccharide O-antigen on the adhesiveness of Yersinia pseudotuberculosis using a model system including a bacterial cell captured by a laser beam and monoclonal antibodies (mAbs) bound covalently to a glass substrate. Registered interaction forces between Y. pseudotuberculosis cells and complementary antibodies to the O-antigen of lipopolysaccharide (LPS) or the B antigen outer membrane protein were 5.9 ± 3.3 and 2.0 ± 1.8 pN, respectively. Interaction forces between O-antigen deficient Y. pestis cells and the mentioned mAbs were 4.2 ± 2.9 and 9.6 ± 4.9 pN. The results are qualitatively consistent with earlier data obtained by using a model system based on polymer beads sensitized with LPS from Y. pseudotuberculosis and Y. pestis and surfaces coated by the aforementioned antibodies. This indicates that the immunochemical activity of Y. pseudotuberculosis cells is mediated mainly by the lipopolysaccharide. The model described can be used in similar studies of physicochemical and immunochemical mechanisms of bacterial adhesiveness.

Characterization and swelling properties of composite gel microparticles based on the pectin and κ-carrageenan.

The aim of this research was to produce composite gel microparticles based on the pectin (campion callus culture (SVC) and commercial apple (AU) pectins) and κ-carrageenan and investigate the relationship between the characteristics and swelling properties of the composite microparticles. The microparticles were obtained using emulsion dehydration techniques with successive incubation in calcium chloride solution. A significant positive correlation between the Ca2+ content and the SVC concentration in gel formulations was shown. Decreasing degree of methyl esterification (DM) of the SVC pectin promoted Ca2+ binding in comparison with the AU pectin. Increasing concentration of the pectin promoted increasing gel strength of the composite microparticles. The higher gel strength of the composite microparticles based on the SVC pectin was probably due to the lower DM and a higher linearity in comparison with the AU pectin. The microparticle gel formulations with a higher pectin concentration had a lower swelling degree in the simulated digestive fluids. The addition of the carrageenan to the gel formulations led to an increase in the swelling degree in comparison with that without carrageenan. The correlation analysis indicated that increasing initial Ca2+ content and gel strength of the microparticles promoted decreasing swelling degree of the composite microparticles.

Physicochemical and swelling properties of composite gel microparticles based on alginate and callus cultures pectins with low and high degrees of methylesterification.

Composite gel microparticles based on alginate and callus culture pectins with low and high degrees of methylesterification or apple pectin were produced. By varying the chemical composition of the pectic samples and the ratio of alginate to pectin, the gel strength, morphology, and swelling properties of composite microparticles can be altered. The inclusion of increasing concentrations of alginate in gel formulations promoted an increase in the microparticle gel strength and the formation of a smoother surface microrelief independently of the pectin chemical composition. Microparticles based on the pectin with a low degree of methylesterification (DM) and a higher concentration of alginate exhibited an increased swelling degree in the simulated digestive fluids. Microparticles based on the pectin with high DM and low alginate concentration were destroyed in the simulated intestinal fluid within 1 h due to the low Ca2+ content, gel strength, and grooved and rough surface of these microparticles. An increase in alginate concentration of gel formulations based on pectin with high DM led to increased stability of the microparticles in the simulated intestinal and colonic fluids due to increased Ca2+ content, microparticle gel strength and degree of crosslinking.

Evaluation of intermolecular forces between lipopolysaccharides and monoclonal antibodies using atomic force microscopy.

Understanding of interactions between a bacterium and an immune or non-immune host organism at the cellular and subcellular level is important in order to improve new and existing immunobiological tools for the treatment of bacterial infections (including pseudotuberculosis). The aim of this work was to quantify the interaction force between Yersinia pseudotuberculosis and monoclonal antibodies (mAbs) in the model system "lipopolysaccharide (LPS) - mAbs" by atomic force microscopy (AFM). Our research findings provided the methodical approaches to force measurements between an AFM probe, which was functionalized with Y. pseudotuberculosis LPS, and mica coated by different mAbs. Based on the criteria for force estimation there was shown a greater binding force in the system "LPS - complementary mAbs" than in the system "LPS - heterologous mAbs". In both cases binding force increase followed by increase a contact time between the functionalized AFM probe and mica from 1 to 5 s. It has been shown that single bonds between LPS and complementary mAbs molecules also included a clearly defined non-specific component along with immunochemically specific one. The evidence suggests a significant proportion of applied force exerted to unfolding of high-molecular aggregates whose length may attain many hundreds of nanometers.

Preparation and properties of the pectic gel microparticles based on the Zn2+, Fe3+ and Al3+ cross-linking cations.

The aim of this work was to evaluate the relationship between the cross-linking cation content in the microparticles, chemical characteristics of pectins and swelling properties of the gel microparticles based on the Zn2+, Fe3+ and Al3+ cross-linking cations. A significant negative correlation between the Zn2+ content and DM of pectin indicated that decreasing DM of pectin promoted Zn2+ binding. The microparticles from the pectins with a higher linearity had a higher content of Fe3+. The microparticles from the pectins with a lower Mw, branching of rhamnogalacturonan I, amount of RG, specific viscosity and a higher linearity had a higher content of Al3+. The content of the Fe3+ ions in the microparticles was higher than the Zn2+ content. The Al3+ content in the microparticles was lowest. The Fe3+ and Zn2+ ions, which are more electronegative, bind more strongly to pectin in comparison with the less electronegative Al3+ cations. The microparticles with a higher Zn2+, Fe3+, and Al3+ content had a lower swelling degree in the simulated digestive fluids. Moreover, the higher swelling of the microparticles can be due to their porous or wrinkled surface. Variation of specific cations and pectins can influence the functionality of the gel microparticles, in particular swelling properties.

Preparation and release characteristics of mesalazine loaded calcium pectin-silica gel beads based on callus cultures pectins for colon-targeted drug delivery.

The aim of this work is to produce calcium pectin-silica gel beads containing mesalazine as a drug model in order to control the drug release in the colon. The mesalazine loaded calcium pectin-silica gel beads were prepared using the ionotropic gelation method. Energy-dispersive X-ray analysis revealed that increasing the Na2SiO3 concentration led to an increase of the silicon content on the surface and in the cross-sections of the beads. The addition of Na2SiO3 to the gel formulations made from the duckweed callus culture pectin led to a decrease in the swelling degree that appeared to be related to the higher gel strength of these beads. The beads made from pectins of campion and duckweed callus cultures with adding of 22.2 mg/ml of Na2SiO3 showed the lowest release of mesalazine in simulated gastric and intestinal fluids. An increase in the reaction time up to 60 min during incubation in the cross-linking solution of CaCl2 led to a slower release of drug from the beads. An elevated release of mesalazine was achieved in the simulated colonic fluid. Prepared calcium pectin-silica gel beads containing mesalazine as a drug model can be proposed for controlled drug release in the colon.

Adhesive properties of calcium pectinate gels prepared from callus cultures pectins.

The aim of this research is to investigate the influence of the surface morphology of the calcium pectinate gel (CaPG) beads as well as the physicochemical characteristics of pectins and the CaPG beads on the adhesive properties of gels against the Gram-negative bacteria Escherichia coli and the Gram-positive bacteria Bacillus subtilis. The adhesion of the bacteria depends on the type of pectin and the surface morphology of the beads. The faster adhesion on CaPG beads appeared to be related to a lower degree of methyl esterification (DE), a higher molecular weight (Mw) and specific viscosity of the pectin and a higher gel strength. Surface roughness measurements were performed using an atomic force microscope. The beads from pectins with a higher Mw, a higher specific viscosity and a lower DE had a higher surface roughness. The surface roughness was one of the factors promoting adhesion of the bacteria onto the calcium pectinate gels. The surface morphology was observed under a scanning electron microscope (SEM). SEM images illustrated that E. coli and B. subtilis adhered on the beads with a rough surface. CaPG beads obtained from callus culture pectins can be proposed for the preparation of gels with adhesive and antiadhesive properties.