The control of the surface topography of biomaterials is a key factor for the management of post-implantation recovery processes. The study of the influence of the nanorelief of polyhydroxyalkanoate (PHA) films on the functional state of cells involved in tissue healing process is important for the development of biocompatible materials for tissue engineering. In this work, polymer films based on polyhydroxyalkanoates of various compositions with different surface relief were analyzed. The effect of the nanorelief of PHA films on the morphology, adhesion and proliferation of cells involved in regenerative processes in tissue damage (erythrocytes, macrophages, fibroblasts) was evaluated. According to the obtained results, it was found that all films samples based on polyhydroxyalkanoates of various compositions have high biocompatibility and do not cause any pronounced negative cellular reactions. However, differences in cell morphology, adhesion, and proliferation were noted between film samples. In the case of P3HB films, a slight activation of local inflammatory reactions was noted. Thus, P3HB matrix is less preferable for use in restoration of soft tissues. On the other hand, films based on P3HB3HV demonstrated high biocompatibility, which allows to conclude that this copolymer matrix is promising for use in tissue engineering.

Background 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.

In 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.

Synthesis and characterization process of the PHB granules and film.

Surface of polyhydroxyalkanoate (PHA) films of varying monomer compositions are analyzed using atomic force microscopy (AFM) and unsupervised machine learning (ML) algorithms to investigate and classify films based on global attributes such as the scan size, film thickness, and monomer type. The experiment provides benchmarked results for 12 of the most widely used clustering algorithms via a hybrid investigation approach while highlighting the impact of using the Fourier transform (FT) on high-dimensional vectorized data for classification on various pools of data. Our findings indicate that the use of a one-dimensional (1D) FT of vectorized data produces the most accurate outcome. The experiment also provides insights into case-by-case investigations of algorithm performances and the impact of various data pools. Lastly, we show an early version of our tool aimed at investigating surfaces using ML approaches and discuss the results of our current experiment to configure future improvements.

This study explores the electronic properties of polyhydroxyalkanoates (PHAs), a class of biodegradable polymers. The focus lies in examining the relationship between crystallinity and band gap energies in PHAs. A notable discovery is the identification of a band gap plateau, suggesting a threshold in electronic properties with increasing polymer chain length. DFT calculations were employed to model the complexities of PHA polymers, with the conductor-like polarizable continuum model (CPCM) offering insights into solvent effects. The results demonstrate a strong negative correlation between crystallinity and band gap in both vacuum and CPCM environments. This study underscores the significance of structural order in shaping the electronic properties of PHAs, paving the way for the development of sustainable polymeric materials for various applications.

In the original publication [...].

The results of constructing 3D scaffolds from degradable poly(3-hydrosbutyrpate-co-3-hydroxyvalerate) using FDM technology and studying the structure, mechanical properties, biocompatibility in vitro, and osteoplastic properties in vivo are presented. In the process of obtaining granules, filaments, and scaffolds from the initial polymer material, a slight change in the crystallization and glass transition temperature and a noticeable decrease in molecular weight (by 40%) were registered. During the compression test, depending on the direction of load application (parallel or perpendicular to the layers of the scaffold), the 3D scaffolds had a Young’s modulus of 207.52 ± 19.12 and 241.34 ± 7.62 MPa and compressive stress tensile strength of 19.45 ± 2.10 and 22.43 ± 1.89 MPa, respectively. SEM, fluorescent staining with DAPI, and calorimetric MTT tests showed the high biological compatibility of scaffolds and active colonization by NIH 3T3 fibroblasts, which retained their metabolic activity for a long time (up to 10 days). The osteoplastic properties of the 3D scaffolds were studied in the segmental osteotomy test on a model defect in the diaphyseal zone of the femur in domestic Landrace pigs. X-ray and histological analysis confirmed the formation of fully mature bone tissue and complete restoration of the defect in 150 days of observation. The results allow us to conclude that the constructed resorbable 3D scaffolds are promising for bone grafting.

The needs of modern regenerative medicine for biodegradable polymers are wide and varied. Restoration of the viability of the vascular tree is one of the most important components of the preservation of the usefulness of organs and tissues. The creation of vascular implants compatible with blood is an important task of vascular bioengineering. The function of the endothelial layer of the vessel, being largely responsible for the development of thrombotic complications, is of great importance for hemocompatibility. The development of surfaces with specific characteristics of biomaterials that are used in vascular technologies is one of the solutions for their correct endothelialization. Linear polyhydroxyalkanoates (PHAs) are biodegradable structural polymeric materials suitable for obtaining various types of implants and tissue engineering, having a wide range of structural and physicomechanical properties. The use of PHA of various monomeric compositions in endothelial cultivation makes it possible to evaluate the influence of material properties, especially surface characteristics, on the functional state of cells. It has been established that PHA samples with the inclusion of 3-hydroxyhexanoate have optimal characteristics for the formation of a human umbilical vein endothelial cell, HUVEC, monolayer in terms of cell morphology as well as the levels of expression of vinculin and VE-cadherin. The obtained results provide a rationale for the use of PHA copolymers as materials for direct contact with the endothelium in vascular implants.

Biodegradable 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 polyhydroxyalkanoates, biopolymers of microbiological origin, consisting of 3- and 4-hydroxybutyrate monomers, were used to obtain by electrospinning nanomembranes loaded with drugs (ceftazidime, doripinem, and actovegin) as cell carriers promising for the treatment of wound defects complicated by infection.

The 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.

From 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.

The 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.