13 research outputs found
Resorbable Nanomatrices from Microbial Polyhydroxyalkanoates: Design Strategy and Characterization
No full textFrom a series of biodegradable natural polymers of polyhydroxyalkanoates (PHAs)—poly-3-hydroxybutyrate (P(3HB) and copolymers containing, in addition to 3HB monomers, monomers of 3-hydroxyvalerate (3HV), 3-hydroxyhexanoate (3HHx), and 4-hydroxybutyrate (4HB), with different ratios of monomers poured—solvent casting films and nanomembranes with oriented and non-oriented ultrathin fibers were obtained by electrostatic molding. With the use of SEM, AFM, and measurement of contact angles and energy characteristics, the surface properties and mechanical and biological properties of the polymer products were studied depending on the method of production and the composition of PHAs. It has been shown in cultures of mouse fibroblasts of the NIH 3T3 line and diploid human embryonic cells of the M22 line that elastic films and nanomembranes composed of P(3HB-co-4HB) copolymers have high biocompatibility and provide adhesion, proliferation and preservation of the high physiological activity of cells for up to 7 days. Polymer films, namely oriented and non-oriented nanomembranes coated with type 1 collagen, are positively evaluated as experimental wound dressings in experiments on laboratory animals with model and surgical skin lesions. The results of planimetric measurements of the dynamics of wound healing and analysis of histological sections showed the regeneration of model skin defects in groups of animals using experimental wound dressings from P(3HB-co-4HB) of all types, but most actively when using non-oriented nanomembranes obtained by electrospinning. The study highlights the importance of nonwoven nanomembranes obtained by electrospinning from degradable low-crystalline copolymers P(3HB-co-4HB) in the effectiveness of the skin wound healing process
Chitosan-modified ceftazidime loaded polyhydroxyalkanoates microparticles: preparation, characterization and antibacterial evaluation in vitro
Get PDFBackground and purpose: The use of drug delivery systems to enhance the efficacy of existing antimicrobial drugs is one of the promising approaches to combat bacterial resistance. The simultaneous presence of a polycationic biopolymer (chitosan) and an antibacterial drug (ceftazidime) in polyhydroxyalkanoates microparticles is more effective since it allows such carriers to have a more pronounced therapeutic effect. In this study, chitosan-modified ceftazidime-loaded poly(3-hydroxybutyrate-3-hydroxyvalerate-3-hydroxy-hexanoate) (P(3HB-3HV-3HHх)) microparticles were prepared and investigated as a drug delivery system. Experimental approach: The obtained microparticles were characterized in terms of their particle size, polydispersity index (PDI), zeta potential, encapsulation efficiency, drug release studies in vitro, cytotoxicity and antibacterial properties in cell cultures. Key results: The microparticles had spherical shapes with diameters from 0.6 to 1.6 µm. The constructed chitosan-modified ceftazidime-loaded microparticles are a depot form of drug, the release of which in vitro is realized for a long time, without burst releases, corresponds to Korsmeyer-Peppas and Higuchi models. In vitro cell viability and proliferation studies on designed microparticles investigated using HaCaT (human keratinocyte skin cell lines) showed good cell proliferation. The hemolytic activity of chitosan-modified P(3HB- 3HV-3HHх) microparticles evaluated by hemolysis assay demonstrated good blood compatibility. Chitosan-modified microparticles enhanced the antibacterial activity of ceftazidime, being effective against E. coli and St. aureus. Conclusion: Thus, the obtained drug delivery systems based on PHAs and chitosan in the form of microparticles can be promising means in treating infectious skin diseases for topical use
Laser Processing of Polymer Films Fabricated from PHAs Differing in Their Monomer Composition
No full textThe study reports results of using a CO2-laser in continuous wave (3 W; 2 m/s) and quasi-pulsed (13.5 W; 1 m/s) modes to treat films prepared by solvent casting technique from four types of polyhydroxyalkanoates (PHAs), namely poly-3-hydroxybutyrate and three copolymers of 3-hydroxybutyrate: with 4-hydroxybutyrate, 3-hydroxyvalerate, and 3-hydroxyhexanoate (each second monomer constituting about 30 mol.%). The PHAs differed in their thermal and molecular weight properties and degree of crystallinity. Pristine films differed in porosity, hydrophilicity, and roughness parameters. The two modes of laser treatment altered these parameters and biocompatibility in diverse ways. Films of P(3HB) had water contact angle and surface energy of 92° and 30.8 mN/m, respectively, and average roughness of 144 nm. The water contact angle of copolymer films decreased to 80–56° and surface energy and roughness increased to 41–57 mN/m and 172–290 nm, respectively. Treatment in either mode resulted in different modifications of the films, depending on their composition and irradiation mode. Laser-treated P(3HB) films exhibited a decrease in water contact angle, which was more considerable after the treatment in the quasi-pulsed mode. Roughness parameters were changed by the treatment in both modes. Continuous wave line-by-line irradiation caused formation of sintered grooves on the film surface, which exhibited some change in water contact angle (76–80°) and reduced roughness parameters (to 40–45 mN/m) for most films. Treatment in the quasi-pulsed raster mode resulted in the formation of pits with no pronounced sintered regions on the film surface, a more considerably decreased water contact angle (to 67–76°), and increased roughness of most specimens. Colorimetric assay for assessing cell metabolic activity (MTT) in NIH 3T3 mouse fibroblast culture showed that the number of fibroblasts on the films treated in the continuous wave mode was somewhat lower; treatment in quasi-pulsed radiation mode caused an increase in the number of viable cells by a factor of 1.26 to 1.76, depending on PHA composition. This is an important result, offering an opportunity of targeted surface modification of PHA products aimed at preventing or facilitating cell attachment
Correction: Volova et al. Laser Processing of Polymer Films Fabricated from PHAs Differing in Their Monomer Composition. Polymers 2021, 13, 1553
No full textIn the original publication [...
Features of Professional and Psychological Training of an Accountant-Analyst for Making Management Decisions in an Economic Crisis
No full textOtcepljenje putem oružane sile: komparativna studija Čečenije i Kosova
Get PDFTekst se bavi manjkavostima strukturalističkog objašnjenja upotrebe sile
prilikom pokušaja secesije. Uporednom analizom slučajeva secesije Kosova i
Čečenije pokazuje se da pored toga što postoje uporedivi strukturalni uslovi
za primenu oružane sile, secesionistički pokreti, u ova dva slučaja, razlikuju
se značajno u stavu prema upotrebi oružane sile u periodu pre pokušaja
otcepljenja. Autor smatra da pored strukturalnih faktora i ljudski činioci
imaju važnu ulogu pri opredeljivanju za taktiku oružane pobune. Ova teza
se potkrepljuje ulogom secesionističkih vođa Džohara Dudajeva u Čečeniji
i Ibrahima Rugove na Kosovu. Različite biografije, obrazovanje i lične
karakteristike lidera su doprinele da se ovi secesionistički pokreti opredele za
različite političke taktike i preferencije u pogledu upotrebe oružane sile.The paper deals with deficiencies of structural explanation of the use of force
during attempts at secession. Comparative analysis of the cases of Kosovo and
Chechnya has demonstrated that these two secessionist movements differed
in their stances toward the use of armed forces prior the secessionist attempts
even though comparable structural conditions for the use of armed forces
existed in these cases. Alongside of structural factors, the author considers
human factor as performing an important role in selection of tactics of armed
rebellion. This thesis has been corroborated by the roles of the secessionist
leaders Dzhokhar Dudaev in Chechnya and Ibrahim Rugova in Kosovo.
Different biographies, education and personal characteristics of the leaders
have contributed to diverse political tactics and preferences in terms of the
use of armed forces
Modification of Polyhydroxyalkanoates Polymer Films Surface of Various Compositions by Laser Processing
No full textThe results of surface modification of solvent casting films made from polyhydroxyalkanoates (PHAs) of various compositions are presented: homopolymer poly-3-hydroxybutyrate P(3HB) and copolymers comprising various combinations of 3-hydroxybutyrate (3HB), 3-hydroxyvalerate (3HV), 4-hydroxybutyrate(4HB), and 3-hydroxyhexanoate (3HHx) monomers treated with a CO2 laser in continuous and quasi-pulsed radiation modes. The effects of PHAs film surface modification, depending on the composition and ratio of monomers according to the results of the study of SEM and AFM, contact angles of wetting with water, adhesion and growth of fibroblasts have been revealed for the laser radiation regime used. Under continuous irradiation with vector lines, melted regions in the form of grooves are formed on the surface of the films, in which most of the samples have increased values of the contact angle and a decrease in roughness. The quasi-pulse mode by the raster method causes the formation of holes without pronounced melted zones, the total area of which is lower by 20% compared to the area of melted grooves. The number of viable fibroblasts NIH 3T3 on the films after the quasi-pulse mode is 1.5–2.0 times higher compared to the continuous mode, and depends to a greater extent on the laser treatment mode than on the PHAs’ composition. The use of various modes of laser modification on the surface of PHAs with different compositions makes it possible to influence the morphology and properties of polymer films in a targeted manner. The results that have been obtained contribute to solving the critical issue of functional biodegradable polymeric materials
Biodegradable Polyhydroxyalkanoates Formed by 3- and 4-Hydroxybutyrate Monomers to Produce Nanomembranes Suitable for Drug Delivery and Cell Culture
No full textBiodegradable polyhydroxyalkanoates, biopolymers of microbiological origin, formed by 3- and 4-hydroxybutyrate monomers P(3HB-co-4HB), were used to obtain nanomembranes loaded with drugs as cell carriers by electrospinning. Resorbable non-woven membranes from P(3HB-co-4HB) loaded with ceftazidime, doripinem, and actovegin have been obtained. The loading of membranes with drugs differently affected the size of fibers and the structure of membranes, and in all cases increased the hydrophilicity of the surface. The release of drugs in vitro was gradual, which corresponded to the Higuchi and Korsmeyer-Peppas models. Antibiotic-loaded membranes showed antibacterial activity against S. aureus and E. coli, in which growth inhibition zones were 41.7 ± 1.1 and 38.6 ± 1.7 mm for ceftazidime and doripinem, respectively. The study of the biological activity of membranes in the NIH 3T3 mouse fibroblast culture based on the results of DAPI and FITC staining of cells, as well as the MTT test, did not reveal a negative effect despite the presence of antibiotics in them. Samples containing actovegin exhibit a stimulating effect on fibroblasts. Biodegradable polyhydroxyalkanoates formed by 3-hydroxybutyrate and 4-hydroxybutyrate monomers provide electrospinning non-woven membranes suitable for long-term delivery of drugs and cultivation of eukaryotic cells, and are promising for the treatment of wound defects complicated by infection
Biodegradable polymer casting films for drug delivery and cell culture
No full textIn this work, for the first time, films were obtained based on biodegradable polyhydroxyalkanoates (PHAs) - a copolymer of 3-hydroxybutyrate-co-3-hydroxyvalerate P(3HB-co-3HV) and a copolymer of 3-hydroxybutyrate-co-4-hydroxybutyrate P(3HB-co-4HB), containing drugs of different chemical structure and action - antibiotics (ceftazidime, doripenem), antiseptic (chlorhexidine) and tissue regeneration stimulator (Actovegin) for drug delivery and cell culture. Using SEM, AFM and measuring the contact angles of water wetting, it is shown how PHAs composition and loading of films of P(3HB-co-3HV) and P(3HB-co-4HB) with drugs affect the porosity, roughness indicators and adhesive properties of the surface. The constructed films are a depot form of drug, the release of which in vitro is realized for a long time, without burst releases, corresponds to Korsmeyer-Peppas and Higuchi models with diffusion character. Films loaded with antibiotics have pronounced antibacterial activity and suppress the development of pathogens S. aureus and E. coli, without a pronounced negative effect on the adhesion and proliferation of epidermal cells. In the cultures of human keratinocytes HaCaT it was shown that the presence of actovegin, as well as ceftazidime in the films, exhibits a stimulating effect, increasing their number. The results demonstrate the suitability of the depot-films for cellular technologies and are promising for the reconstruction of tissues complicated by infection
