Sergei I. Tverdokhlebov

Surface modification of biomaterials based on high-molecular polylactic acid and their effect on inflammatory reactions of primary human monocyte-derived macrophages: Perspective for personalized therapy

Polylactic acid (PLA) based implants can cause inflammatory complications. Macrophages are key innate immune cells that control inflammation. To provide higher biocompatibility of PLA-based implants with local innate immune cells their surface properties have to be improved. In our study surface modification technique for high-molecular PLA (MW=1,646,600g/mol) based biomaterials was originally developed and successfully applied. Optimal modification conditions were determined. Treatment of PLA films with toluene/ethanol=3/7 mixture for 10min with subsequent exposure in 0.001M brilliant green dye (BGD) solution allows to entrap approximately 10(-9)mol/cm(2) model biomolecules. The modified PLA film surface was characterized by optical microscopy, SERS, FT-IR, UV and TG/DTA/DSC analysis. Tensile strain of modified films was determined as well. The effect of PLA films modified with BGD on the inflammatory reactions of primary human monocyte-derived macrophages was investigated. We developed in vitro test-system by differentiating primary monocyte-derived macrophages on a coating material. Type 1 and type 2 inflammatory cytokines (TNFα, CCL18) secretion and histological biomarkers (CD206, stabilin-1) expression were analyzed by ELISA and confocal microscopy respectively. BGD-modified materials have improved thermal stability and good mechanical properties. However, BGD modifications induced additional donor-specific inflammatory reactions and suppressed tolerogenic phenotype of macrophages. Therefore, our test-system successfully demonstrated specific immunomodulatory effects of original and modified PLA-based biomaterials, and can be further applied for the examination of improved coatings for implants and identification of patient-specific reactions to implants.

A new approach for the immobilization of poly(acrylic) acid as a chemically reactive cross-linker on the surface of poly(lactic) acid-based biomaterials

A new approach for the immobilization of poly(acrylic) acid (PAA) as a chemically reactive cross-linker on the surface of poly(lactic) acid-based (PLA) biomaterials is described. The proposed technique includes non-covalent attachment of a PAA layer to the surface of PLA-based biomaterial via biomaterial surface treatment with solvent/non-solvent mixture followed by the entrapment of PAA from its solution. Surface morphology and wettability of the obtained PLA-PAA composite materials were investigated by AFM and the sitting drop method respectively. The amount of the carboxyl groups on the composites surface was determined by using the fluorescent compounds (2-(5-aminobenzo[d]oxazol-2-yl)phenol (ABO) and its acyl derivative N-(2-(2-hydroxyphenyl)benzo[d]oxazol-5-yl)acetamide (AcABO)). It was shown that it is possible to obtain PLA-PAA composites with various surface relief and tunable wettability (57°, 62° and 66°). The capacity of the created PAA layer could be varied from 1.5nmol/cm2 to 0.1μmol/cm2 depending on the modification conditions. Additionally, using bovine serum albumin (BSA) it was demonstrated that such composites could be modified with proteins with high binding density (around 0.18nmol/cm2). Obtained fluoro-labeled PLA-PAA materials, as well as PLA-PAA composites themselves, are valuable since they can be used for biodegradable polymer implants tracking in living systems and as drug delivery systems.

Hybrid calcium phosphate coatings for implants

Monophasic biomaterials cannot provide all the necessary functions of bones or other calcined tissues. It is necessary to create for cancer patients the multiphase materials with the structure and composition simulating the natural bone. Such materials are classified as hybrid, obtained by a combination of chemically different components. The paper presents the physical, chemical and biological studies of coatings produced by hybrid technologies (HT), which combine primer layer and calcium phosphate (CaP) coating. The first HT type combines the method of vacuum arc titanium primer layer deposition on a stainless steel substrate with the following micro-arc oxidation (MAO) in phosphoric acid solution with addition of calcium compounds to achieve high supersaturated state. MAO CaP coatings feature high porosity (2–8%, pore size 5–7 µm) and surface morphology with the thickness greater than 5 µm. The thickness of Ti primer layer is 5–40 µm. Amorphous MAO CaP coating micro-hardness was measured at maximum nor...

Fabrication of PLA/CaCO3 hybrid micro-particles as carriers for water-soluble bioactive molecules

We propose the use of polylactic acid/calcium carbonate (PLA/CaCO3) hybrid micro-particles for achieving improved encapsulation of water-soluble substances. Biodegradable porous CaCO3 microparticles can be loaded with wide range of bioactive substance. Thus, the formation of hydrophobic polymeric shell on surface of these loaded microparticles results on encapsulation and, hence, sealing internal cargo and preventing their release in aqueous media. In this study, to encapsulate proteins, we explore the solid-in-oil-in-water emulsion method for fabricating core/shell PLA/CaCO3 systems. We used CaCO3 particles as a protective core for encapsulated bovine serum albumin, which served as a model protein system. We prepared a PLA coating using dichloromethane as an organic solvent and polyvinyl alcohol as a surfactant for emulsification; in addition, we varied experimental parameters such as surfactant concentration and polymer-to-CaCO3 ratio to determine their effect on particle-size distribution, encapsulation efficiency and capsule permeability. The results show that the particle size decreased and the size distribution narrowed as the surfactant concentration increased in the external aqueous phase. In addition, when the CaCO3/PLA mass ratio dropped below 0.8, the hybrid micro-particles were more likely to resist treatment by ethylenediaminetetraacetic acid and thus retained their bioactive cargos within the polymer-coated micro-particles.

BIOLOGICAL ACTIVITY OF THE IMPLANT FOR INTERNAL FIXATION

Early treatment of bone fractures was performed using implants, which are often used in the form of plates of various types, which are fixed on the bone surface (extracellular fixation) and nails that are located in the medullary canal (intracerebral fixation). The goal of this study was to investigate the features of osseointegration of implants for internal fixation (intramedullary or extramedullary) with various bioactive coating techniques. During experimental study on 20 mongrel dogs, the implant model in the form of 1.0‐mm plate made of titanium alloy (Ti6Al 4V) was placed in the medullary canal (first series) or under the periosteum (second series): the plates had bioactive coating (hydroxyapatite) produced using the technology of magnetron sputtering (six animals), plasma electrolytic oxidation or microarc oxidation technology (PEO; eight animals), and composite technology (six dogs). Anatomic and histological studies have shown that the process of active osseointegration of porous implants with bioactive coating begins after 7 days: at first, granulation tissue – and then fibrous connective tissue – is formed; after 14 days, the osteogenic substrate can be found, and after 28 days, the entire implant area is covered by the lamellar bone tissue, which creates single implant–bone block. The most active formation of bone tissue is observed around implants with bioactive coating produced using the last two technologies. Low traumatic placement of porous implants with bioactive coating in the medullary canal or subperiosteally provides the stimulation of reparative osteogenesis and rapid (especially with PEO technique) osseointegration of the implant.

A first method for preparation of biodegradable fibrous scaffolds containing iodine on the fibre surfaces

Fibrous electrospun scaffolds made of poly(L-lactic acid) (PLLA) and poly(

Comparative Studies of the Physical, Mechanical and Chemical Properties of Hybrid Coatings for Medical Implants

\upvarepsilon

Atmospheric pressure plasma assisted immobilization of hyaluronic acid on tissue engineering PLA-based scaffolds and its effect on primary human macrophages

ε-caprolactone) (PCL) were modified with iodine using ‘solvent/non-solvent’ treatment of the polymer through two-step process. At the first step, the scaffolds were treated with mixture of toluene and ethanol for pre-swelling of the fibre surfaces. Then, treated scaffolds were exposed to iodine vapours to entrap iodine on the polymer surface. Concentration of iodine in obtained materials was measured by means of UV-spectrophotometry. Morphology of the modified scaffolds was characterized by scanning electron microscopy (SEM). Proposed modification had no significant effect on mechanical properties of the scaffolds and their morphologies. Obtained materials demonstrated the E. coli’s antimicrobial activity depending on iodine concentration.