Fibrous Polymer-Based Composites Obtained by Electrospinning for Bone Tissue Engineering

Currently, the significantly developing fields of tissue engineering related to the fabrication of polymer-based materials that possess microenvironments suitable to provide cell attachment and promote cell differentiation and proliferation involve various materials and approaches. Biomimicking approach in tissue engineering is aimed at the development of a highly biocompatible and bioactive material that would most accurately imitate the structural features of the native extracellular matrix consisting of specially arranged fibrous constructions. For this reason, the present research is devoted to the discussion of promising fibrous materials for bone tissue regeneration obtained by electrospinning techniques. In this brief review, we focus on the recently presented natural and synthetic polymers, as well as their combinations with each other and with bioactive inorganic incorporations in order to form composite electrospun scaffolds. The application of several electrospinning techniques in relation to a number of polymers is touched upon. Additionally, the efficiency of nanofibrous composite materials intended for use in bone tissue engineering is discussed based on biological activity and physiochemical characteristics

Powders Based on Ca₂P₂O₇-CaCO₃-H₂O System as Model Objects for the Development of Bioceramics

Nanoscale powders of hydrated Ca2P2O7, CaCO3, and a product of mixed-anionic composition containing P2O74− and CO32− anions were synthesized from aqueous solutions of Ca(CH3COO)2, pyrophosphoric acid (H4P2O7), and/or (NH4)2CO3. Pyrophosphoric acid was previously obtained on the basis of the ion exchange process from Na4P2O7 solution and H+-cationite resin for further introduction into the reactions as an anionic precursor. The phase composition of powders after the syntheses was represented by bioresorbable phases of X-ray amorphous hydrated Ca2P2O7 phase, calcite and vaterite polymorphs of CaCO3. Based on synthesized powders, simple cylindrical constructions were prepared via mechanical pressing and fired in the temperature range of 600–800 °C. Surface morphology observation showed the presence of bimodal porosity with pore sizes up to 200 nm and 2 μm, which is likely to ensure tight particle packing and roughness of the sample surface required for the differentiation of osteogenic cells. Thus, the prepared ceramic samples can be further examined as model objects for bone tissue repair

Ceramics based on calcium pyrophosphate nanopowders

Present work is aimed at the fabrication of resorbable bioceramics based on calcium pyrophosphate (CPP) from the synthesized powders of amorphous hydrated calcium pyrophosphate (AHCPP). Amorphous hydratedcalcium pyrophosphate in the form of nanopowders was precipitated from Ca(NO3 )2 and (NH4 )4P2O7 solutions at room temperature in the presence of PO3– ions. Crystalline CPP powder was fabricated from AHCPP by its thermal decomposition at 600 °C and consisted of β- and α- phase. Small particles, with the size less than 200 nm, were formed promoting sintering of the ceramic material. The final sample, sintered at 900 °C, exhibits microstructure with submicron grains, apparent density of 87% of theoretical density (TD) and demonstrates tensile strength of 70 MPa

A Novel Proline-Rich Cathelicidin from the Alpaca Vicugna pacos with Potency to Combat Antibiotic-Resistant Bacteria: Mechanism of Action and the Functional Role of the C-Terminal Region

Over recent years, a growing number of bacterial species have become resistant to clinically relevant antibiotics. Proline-rich antimicrobial peptides (PrAMPs) having a potent antimicrobial activity and a negligible toxicity toward mammalian cells attract attention as new templates for the development of antibiotic drugs. Here, we mined genomes of all living Camelidae species and found a novel family of Bac7-like proline-rich cathelicidins which inhibited bacterial protein synthesis. The N-terminal region of a novel peptide from the alpaca Vicugna pacos named VicBac is responsible for inhibition of bacterial protein synthesis with an IC50 value of 0.5 µM in the E. coli cell-free system whereas the C-terminal region allows the peptide to penetrate bacterial membranes effectively. We also found that the full-length VicBac did not induce bacterial resistance after a two-week selection experiment, unlike the N-terminal truncated analog, which depended on the SbmA transport system. Both pro- and anti-inflammatory action of VicBac and its N-terminal truncated variant on various human cell types was found by multiplex immunoassay. The presence of the C-terminal tail in the natural VicBac does not provide for specific immune-modulatory effects in vitro but enhances the observed impact compared with the truncated analog. The pronounced antibacterial activity of VicBac, along with its moderate adverse effects on mammalian cells, make this molecule a promising scaffold for the development of peptide antibiotics

Materials in the CaO-K₂O-SO₃-H₂O System Based on Powder Mixtures including Calciolangbeinite K₂Ca₂(SO₄)₃ and Calcium Sulfate Anhydrite CaSO₄

Materials (cement stone samples) in the CaO-K2O-SO3-H2O system with the target phase compositions, including syngenite K2Ca(SO4)2·H2O and calcium sulfate dihydrate CaSO4·2H2O, were prepared from powder mixtures of calcium sulfate anhydrite CaSO4, and/or calciolangbeinite K2Ca2(SO4)3, and potassium sulfate K2SO4 via hydration reactions at a water/powder ratio within an interval of 0.5–0.9. It was revealed that samples with contents of 25, 50, 75 and 100 mol% of syngenite K2Ca(SO4)2·H2O demonstrated a nonlinear dependence of their respective microstructures on their phase compositions. The microstructures of samples with phase compositions of 25 and 75 mol% of syngenite K2Ca(SO4)2·H2O consisted of pillar crystals. The microstructures of samples with phase compositions of 50 and 100 mol% of syngenite K2Ca(SO4)2·H2O consisted of plate crystals. An explanation of microstructure formation was set forth, taking into account equilibria of the dissolution–crystallization processes during cement stone formation. Materials obtained in the CaO-K2O-SO3-H2O system consisting of biocompatible and resorbable (soluble in water) phases can be recommended for testing as potential substances for bone defect treatments

RIAM: A Universal Accessible Protocol for the Isolation of High Purity DNA from Various Soils and Other Humic Substances

A single universal open protocol RIAM (named after Research Institute for Agricultural Microbiology) for the isolation of high purity DNA from different types of soils and other substrates (high and low in humic, clay content, organic fertilizer, etc.) is proposed. The main features of the RIAM protocol are the absence of the sorption–desorption stage on silica columns, the use of high concentrations of phosphate in buffers, which prevents DNA sorption on minerals, and DNA precipitation using CTAB. The performance of RIAM was compared with a reference commercial kit and showed very good results in relation to the purity and quantity of DNA, as well as the absence of inhibitory activity on PCR. In all cases, the RIAM ensured the isolation of DNA in quantities much greater than the commercial kit without the effect of PCR inhibition up to 50 ng DNA per reaction in a volume of 15 µL. The latter circumstance along with the ability of the protocol to extract low molecular weight DNA fractions makes the method especially suitable for those cases where quantitative assessments, detection of minor components of soil microbiota, and completeness of isolation of all DNA fractions are required

Dimerization of the β-Hairpin Membrane-Active Cationic Antimicrobial Peptide Capitellacin from Marine Polychaeta: An NMR Structural and Thermodynamic Study

Capitellacin is the β-hairpin membrane-active cationic antimicrobial peptide from the marine polychaeta Capitella teleta. Capitellacin exhibits antibacterial activity, including against drug-resistant strains. To gain insight into the mechanism of capitellacin action, we investigated the structure of the peptide in the membrane-mimicking environment of dodecylphosphocholine (DPC) micelles using high-resolution NMR spectroscopy. In DPC solution, two structural forms of capitellacin were observed: a monomeric β-hairpin was in equilibrium with a dimer formed by the antiparallel association of the N-terminal β-strands and stabilized by intermonomer hydrogen bonds and Van der Waals interactions. The thermodynamics of the enthalpy-driven dimerization process was studied by varying the temperature and molar ratios of the peptide to detergent. Cooling the peptide/detergent system promoted capitellacin dimerization. Paramagnetic relaxation enhancement induced by lipid-soluble 12-doxylstearate showed that monomeric and dimeric capitellacin interacted with the surface of the micelle and did not penetrate into the micelle interior, which is consistent with the “carpet” mode of membrane activity. An analysis of the known structures of β-hairpin AMP dimers showed that their dimerization in a membrane-like environment occurs through the association of polar or weakly hydrophobic surfaces. A comparative analysis of the physicochemical properties of β-hairpin AMPs revealed that dimer stability and hemolytic activity are positively correlated with surface hydrophobicity. An additional positive correlation was observed between hemolytic activity and AMP charge. The data obtained allowed for the provision of a more accurate description of the mechanism of the oligomerization of β-structural peptides in biological membranes

Powder Synthesized from Aqueous Solution of Calcium Nitrate and Mixed-Anionic Solution of Orthophosphate and Silicate Anions for Bioceramics Production

Synthesis from mixed-anionic aqueous solutions is a novel approach to obtain active powders for bioceramics production in the CaO-SiO2-P2O5-Na2O system. In this work, powders were prepared using precipitation from aqueous solutions of the following precursors: Ca(NO3)2 and Na2HPO4 (CaP); Ca(NO3)2 and Na2SiO3 (CaSi); and Ca(NO3)2, Na2HPO4 and Na2SiO3 (CaPSi). Phase composition of the CaP powder included brushite CaHPO4‧2H2O and the CaSi powder included calcium silicate hydrate. Phase composition of the CaPSi powder consisted of the amorphous phase (presumably containing hydrated quasi-amorphous calcium phosphate and calcium silicate phase). All synthesized powders contained NaNO3 as a by-product. The total weight loss after heating up to 1000 °C for the CaP sample—28.3%, for the CaSi sample—38.8% and for the CaPSi sample was 29%. Phase composition of the ceramic samples after the heat treatment at 1000 °C based on the CaP powder contained β-NaCaPO4 and β-Ca2P2O7, the ceramic samples based on the CaSi powder contained α-CaSiO3 and Na2Ca2Si2O7, while the ceramics obtained from the CaPSi powder contained sodium rhenanite β-NaCaPO4, wollastonite α-CaSiO3 and Na3Ca6(PO4)5. The densest ceramic sample was obtained in CaO-SiO2-P2O5-Na2O system at 900 °C from the CaP powder (ρ = 2.53 g/cm3), while the other samples had densities of 0.93 g/cm3 (CaSi) and 1.22 (CaPSi) at the same temperature. The ceramics prepared in this system contain biocompatible and bioresorbable phases, and can be recommended for use in medicine for bone-defect treatment

Design of Protegrin-1 Analogs with Improved Antibacterial Selectivity

Protegrin-1 (PG-1) is a cationic β-hairpin pore-forming antimicrobial peptide having a membranolytic mechanism of action. It possesses in vitro a potent antimicrobial activity against a panel of clinically relevant MDR ESKAPE pathogens. However, its extremely high hemolytic activity and cytotoxicity toward mammalian cells prevent the further development of the protegrin-based antibiotic for systemic administration. In this study, we rationally modulated the PG-1 charge and hydrophobicity by substituting selected residues in the central β-sheet region of PG-1 to design its analogs, which retain a high antimicrobial activity but have a reduced toxicity toward mammalian cells. In this work, eight PG-1 analogs with single amino acid substitutions and five analogs with double substitutions were obtained. These analogs were produced as thioredoxin fusions in Escherichia coli. It was shown that a significant reduction in hemolytic activity without any loss of antimicrobial activity could be achieved by a single amino acid substitution, V16R in the C-terminal β-strand, which is responsible for the PG-1 oligomerization. As the result, a selective analog with a ≥30-fold improved therapeutic index was obtained. FTIR spectroscopy analysis of analog, [V16R], revealed that the peptide is unable to form oligomeric structures in a membrane-mimicking environment, in contrast to wild-type PG-1. Analog [V16R] showed a reasonable efficacy in septicemia infection mice model as a systemic antibiotic and could be considered as a promising lead for further drug design

Powder Synthesized from Aqueous Solution of Calcium Nitrate and Mixed-Anionic Solution of Orthophosphate and Silicate Anions for Bioceramics Production

Synthesis from mixed-anionic aqueous solutions is a novel approach to obtain active powders for bioceramics production in the CaO-SiO2-P2O5-Na2O system. In this work, powders were prepared using precipitation from aqueous solutions of the following precursors: Ca(NO3)2 and Na2HPO4 (CaP); Ca(NO3)2 and Na2SiO3 (CaSi); and Ca(NO3)2, Na2HPO4 and Na2SiO3 (CaPSi). Phase composition of the CaP powder included brushite CaHPO4‧2H2O and the CaSi powder included calcium silicate hydrate. Phase composition of the CaPSi powder consisted of the amorphous phase (presumably containing hydrated quasi-amorphous calcium phosphate and calcium silicate phase). All synthesized powders contained NaNO3 as a by-product. The total weight loss after heating up to 1000 °C for the CaP sample—28.3%, for the CaSi sample—38.8% and for the CaPSi sample was 29%. Phase composition of the ceramic samples after the heat treatment at 1000 °C based on the CaP powder contained β-NaCaPO4 and β-Ca2P2O7, the ceramic samples based on the CaSi powder contained α-CaSiO3 and Na2Ca2Si2O7, while the ceramics obtained from the CaPSi powder contained sodium rhenanite β-NaCaPO4, wollastonite α-CaSiO3 and Na3Ca6(PO4)5. The densest ceramic sample was obtained in CaO-SiO2-P2O5-Na2O system at 900 °C from the CaP powder (ρ = 2.53 g/cm3), while the other samples had densities of 0.93 g/cm3 (CaSi) and 1.22 (CaPSi) at the same temperature. The ceramics prepared in this system contain biocompatible and bioresorbable phases, and can be recommended for use in medicine for bone-defect treatment