A. S. Fomin

Use of a synthetic foot-and-mouth disease virus peptide conjugated to gold nanoparticles for enhancing immunological response

Foot-and-mouth disease is an acute, highly contagious infection of domestic and wild cloven-hoofed animals, which can be transmitted to humans. In many cases, the existing vaccines are not quite effective. The purpose of this study was to test the possibility of using gold nanoparticles as an antigen carrier and an adjuvant. The immunogenic properties of gold nanoparticles were assessed by conjugating the particles to a synthetic peptide of the VP1 capsid protein of the foot-and-mouth disease virus. The resulting conjugate (with or without the use of complete Freund’s adjuvant), a commercial vaccine, and the native peptide served to immunize guinea pigs. The titer and sensitivity of the raised antibodies were maximal for the combination comprising the nanoparticle–peptide conjugate and complete Freund’s adjuvant. Antibody biosynthesis was accompanied by increased production of proinflammatory cytokines (especially IFN-γ) and by stimulation of the respiratory activity of peritoneal macrophages. The use of gold nanoparticles as a hapten carrier enhanced the immune response even when complete Freund’s adjuvant was not used.

Stabilization of Carbonate Hydroxyapatite by Isomorphic Substitutions of Sodium for Calcium

Carbonate hydroxyapatite (CHA) is an analogue of the mineral component of bone tissue. Synthetic CHA is thermally unstable: it readily decomposes with carbon oxide evolution when sintered to ceramics. Its thermal stability has been studied as affected by partial isomorphic substitution of sodium for calcium intended to compensate a possible charge imbalance induced by CO32− groups. Investigative tools were thermogravimetry and FTIR spectroscopy of the condensed vapor produced by heating CHA samples doped with 0.4 and 0.8 wt % sodium. Sodium does not improve the thermal stability of CHA: weight loss on heating increases with increasing sodium level; evolution of carbon oxides occurs at lower temperatures and more intensively. Sodium enhances the generation of B-type defects (CO32− → PO43− substitutions); these defects are thermodynamically less stable than AB-type defects (2CO32− → PO43−, OH− substitutions), which are characteristic of sodium-free CHA.

Hydroxyapatite of platelet morphology synthesized by ultrasonic precipitation from solution

Hydroxyapatite (HA) synthesis by precipitation with urea from aqueous solutions of calcium nitrate and ammonium hydrogenphosphate is studied. Ultrasonication during the synthesis decreases the size of platelet HA crystals from several micrometers to 200–300 nm. At low calcium concentrations in solution, the crystallizing phase is carbonate-hydroxyapatite, whereas at high calcium concentrations, octacalcium phosphate (OCP) precedes hydroxyapatite crystallization.

Silicon-containing hydroxylapatite nanopowders

Silicon-substituted hydroxylapatite nanopowders containing 0.14–1.4 wt % Si have been synthesized by the heterophase reaction between calcium hydroxide, diammonium hydrogen phosphate, tetraethoxysilane, and water and by precipitation from aqueous solutions of calcium nitrate, diammonium hydrogen phosphate, and tetraethoxysilane. The products have been characterized by specific surface area (SBET) measurements, X-ray powder diffraction, chemical analysis, and IR spectroscopy. The phase composition of the products depends on the synthesis method. The heterophase reaction yields nanopowders with SBET = 20–24 m2/g in which the main crystalline phase is silicon-substituted hydroxylapatite. The product synthesized by precipitation from solution has an SBET of up to 73 m2/g and an increased tricalcium phosphate content, which crystallizes from the amorphous phase during heat treatment.

The Bone Building Blues: Self-hardening copper-doped calcium phosphate cement and its in vitro assessment against mammalian cells and bacteria

A blue calcium phosphate cement with optimal self-hardening properties was synthesized by doping whitlockite (β-TCP) with copper ions. The mechanism and the kinetics of the cement solidification process were studied using energy dispersive X-ray diffraction and it was found out that hardening was accompanied by the phase transition from TCP to brushite. Reduced lattice parameters in all crystallographic directions resulting from the rather low (1:180) substitution rate of copper for calcium was consistent with the higher ionic radius of the latter. The lower cationic hydration resulting from the partial Ca→Cu substitution facilitated the release of constitutive hydroxyls and lowered the energy of formation of TCP from the apatite precursor at elevated temperatures. Addition of copper thus effectively inhibited the formation of apatite as the secondary phase. The copper-doped cement exhibited an antibacterial effect, though exclusively against Gram-negative bacteria, including E. coli, P. aeruginosa and S. enteritidis. This antibacterial effect was due to copper ions, as demonstrated by an almost negligible antibacterial effect of the pure, copper-free cement. Also, the antibacterial activity of the copper-containing cement was significantly higher than that of its precursor powder. Since there was no significant difference between the kinetics of the release of copper from the precursor TCP powder and from the final, brushite phase of the hardened cement, this has suggested that the antibacterial effect was not solely due to copper ions, but due to the synergy between cationic copper and a particular phase and aggregation state of calcium phosphate. Though inhibitory to bacteria, the copper-doped cement increased the viability of human glial E297 cells, murine osteoblastic K7M2 cells and especially human primary lung fibroblasts. That this effect was also due to copper ions was evidenced by the null effect on viability increase exhibited by the copper-free cements. The difference in the mechanism of protection of dehydratases in prokaryotes and eukaryotes was used as a rationale for explaining the hereby evidenced selectivity in biological response. It presents the basis for the consideration of copper as a dually effective ion when synergized with calcium phosphates: toxic for bacteria and beneficial for the healthy cells.

Low-temperature calcium carbonate ceramic

Investigations were carried out on development of a calcium carbonate ceramic with addition of potassium carbonate for regeneration of human osseous tissues. The initial materials included various calcium carbonate powders of commercial grade as well as powders obtained by chemical deposition. Porosity and strength were studied as a function of additive content and sintering temperature. The use of the additive resulted in a decrease in sintering temperature below 720°C, which allowed decomposition of calcium carbonate to be eliminated and a dense ceramic to be obtained.

Porous chitosan matrices reinforced by bioactive calcium compounds

In the last decade, a new technology for bone tissue regeneration after damage through accidental injury or surgical operation has been developed. The technology is based on implanting porous resorbable matrices with bone-forming cells cultivated therein at the bone defect site. This matrix is replaced with time by bone tissue de novo, being gradually resorbed in the body. The design of matrices with required microstructure parameters (porosity, pore size and interconnection) and mechanical and biological properties is a key problem. In recent years, considerable attention has been devoted to the development of matrices made of composite materials based on biopolymers [1, 2]. Chitosan-based materials are biocompatible and bioresorbable [3, 4]. Chitosan is prepared from natural chitin, a linear aminopolysaccharide (composed of N -acetyl-2-amino-2-deoxy- D -glycopyranose units). The main raw material sources of chitin are shells of marine and freshwater crustaceans, dead bees, and some fungi [3]. Chitosan is used in medicine both in pure form (films, fibers, capsules, sponges) and as a composite material, e.g., chitosan‐hydroxyapatite. The use as a matrix of porous composite materials based on chitosan containing as fillers bioactive calcium compounds is promising. These composites have higher porosity and elasticity than porous ceramics, which allows filling of a bone defect of any shape without gaps between the bone and the implant. Porous chitosan sponges are obtained most often by freeze-drying. Cross-linking of the chitosan structure after preparation of a porous structure is often performed using toxic compounds (e.g., glutaraldehyde) [4]. In this paper, we describe a simple method for production and the results of studies of structures and properties of porous composite sponges (PCSs) containing bioactive calcium compounds. The method is based on chitosan dissolution, introduction of a filler, foaming, and subsequent replacement of water by a liquid in which chitosan is insoluble. This gives sponges with a porosity of more than 90% containing up to 50 wt % of a filler: hydroxyapatite (HA), carbonate hydroxyapatite (CHA), or calcium carbonate (CC).

Gold nanoparticles as an adjuvant: Influence of size, shape, and technique of combination with CpG on antibody production

ABSTRACT Gold nanoparticles (GNPs) are advantageous as an adjuvant in the design of effective vaccines and in the preparation of high‐affinity antibodies to haptens and complete antigens. Another method of activating immunocompetent cells with colloidal gold is to conjugate GNPs with CpG oligodeoxynucleotides (ODNs). We examined how the size and shape of GNPs and various combinations of GNPs and CpG ODNs 1826 affect the immune response. When animals were injected with a model antigen (BSA) coupled to gold nanospheres (diameters, 15 and 50 nm), nanorods, nanoshells, and nanostars, the titers of the resultant antibodies differed substantially. The antibody titers decreased in the sequence GNPs‐50 nm > GNPs‐15 nm > nanoshells > nanostars > nanorods > native BSA. We conclude that 50 and 15 nm gold nanospheres are the optimal antigen carrier and adjuvant for immunization. The highest titer of anti‐BSA antibodies was detected in the blood serum of mice immunized simultaneously with BSA–GNP and CpG–GNP conjugates. Graphical abstract Figure. No caption available. HighlightA modern trend in the use of GNP for vaccination is the combination of GNP and CpG.Gold nanospheres 15 nm is the optimal antigen carrier and adjuvant for immunization.BSA–GNP and CpG–GNP conjugates are the optimal construction for immunization.

Effect of an Amino Acid on the Formation of Calcium Phosphate Particles on Chitosan Macromolecules

This paper presents a study aimed at producing new mineral–polymer composites for damaged bone tissue restoration after extended surgery and injuries. We have obtained materials based on chitosan and calcium phosphates and determined their likely structure by 13C NMR spectroscopy.

Novel approach to obtain composite poly-L-lactide based films blended with starch and calcium phosphates and their bioactive properties

A novel approach for preparation of composite materials based on the poly-L-lactide (PL), starch and calcium phosphates is provided, applying the polymer crazing process in liquid absorption active medium. For composite films preparation, PL and blends of PL and starch have been chosen as polymeric matrixes. Pores formation in the polymer films occurred during the process of uniaxial stretching in the presence of ethanol or water-ethanol mixtures via the solvent-crazing mechanism. The diameter of pores and fibrils in crazed PL was 20–30 nm. Porous polymer matrixes have been loaded with starch, using crazing mechanism, and filled with calcium phosphates (CP) by the countercurrent diffusion method, the content of starch and CP being up to 11.0 and 14.5 wt%, respectively. The obtained composites were investigated by XRD, SEM-EDS and TEM methods. It was found out that the starch filled the porous crazed structure of polymer, while the CP synthesis in the PL pores resulted in the formation of amorphous particles with the diameter of about 20 nm. These CP nanoparticles aggregated into the submicron particles of 100–300 nm in diameter. The bioactivity of the initial and porous poly-L-lactide films, and composites, based on PL with starch and calcium phosphates, was investigated. It was shown that the bioactivity depends on the chemical composition and surface morphology of the prepared materials. After 10 days of cultivation of the pre-osteoblastic MC3T3E1 cells, an intense, 6 times, growth of osteoblast population was achieved for the composite containing calcium phosphates. This result is perceptibly higher than those obtained for other samples (4 times growth) and for the control sample (5 times growth). Based on the results of in vitro tests, it can be concluded that the prepared materials are promising for biomedical applications.