БИОРАЗЛАГАЕМЫЕ ПОЛИМЕРНЫЕ МАТЕРИАЛЫ ДЛЯ МЕДИЦИНЫ: ОТ ИМПЛАНТА К ОРГАНУ

Development of modern medical technologies would be impossible without the application of various materials with special properties. Over the last decade there has been a marked increase in interest in biodegradable materials for use in medicine and other areas of the national economy. In medicine, biodegradable polymers offer great potential for controlled drug delivery and wound management (e.g., adhesives, sutures and surgical meshes), for orthopedic devices (screws, pins and rods), nonwoven materials and scaffolds for tissue engineering. Among the family of biodegradable polyesters the most extensively investigated and the most widely used polymers are poly(α-hydroxyacid)s: polylactide (i.e. PLA), polyglycolide (i.e. PGA), poly-ε-caprolactone (PCL), polydioxanone and their copolymers. Controlling the molecular and supramolecular structure of biodegradable polymers allows tuning the physico-chemical and mechanical characteristics of the materials as well as their degradation kinetics. This enables selecting the optimal composition and structure of the material for the development of a broad range of biomedical products. Introduction of various functional fillers such as calcium phosphates allows creating bioactive composite materials with improved mechanical properties. To manufacture the highly dispersed biomedical materials for regenerative medicine electrospinning and freeze-drying are employed. Varying the technological parameters of the process enables to produce materials and devices with predetermined pore sizes and various mechanical properties. In order to increase the effectiveness of a great number of drugs the perspective approach is their inclusion into nanosized polymer micelles based on amphiphilic block copolymers of lactide and ethylene oxide. Different crystallization behavior of the lactide blocks and controlled regulation of their length allows producing micelles with various sizes and morphology. In this article we have attempted to provide an overview of works that are under way in the area of biodegradable polymers research and development in our group.Развитие современных медицинских технологий было бы невозможно без применения различных материалов со специальными свойствами. В последнее десятилетие наблюдается все возрастающий интерес к биоразлагаемым материалам для использования в медицине и других областях народного хозяйства. Синтетические биоразлагаемые полимеры широко используются в медицине для создания систем контролируемой доставки лекарственных препаратов, шовных хирургических материалов, для изготовления ортопедических изделий (винты, штифты, стержни), а также нетканых материалов и матриксов для тканевой инженерии. Наиболее востребованными полимерами для изготовления изделий биомедицинского назначения являются сложные полиэфиры α-гидроксикислот: полилактид, полигликолид, поли(ε-капролактон), полидиоксанон, а также их сополимеры. Регулирование молекулярной и надмолекулярной структуры биоразлагаемых полимеров позволяет управлять физико-химическими и физико-механическими характеристиками материалов, а также кинетикой их биодеградации. Это дает возможность подбирать оптимальный состав и структуру материала для разработки широкого ассортимента биомедицинских изделий. Введение различных функциональных наполнителей, таких как кальций-фосфаты, в структуру материала позволяет создавать биоактивные композиционные материалы с улучшенными физико-механическими характеристиками. Для получения высокодисперсных биомедицинских материалов для регенеративной медицины применяют такие методы как электроформование и лиофилизация. Варьирование технологических параметров процесса обеспечивает возможность изготовления материалов и изделий с заданным размером пор и различными механическими характеристиками. Повысить эффективность действия многих лекарственных средств можно путем включения их в наноразмерные полимерные мицеллы на основе амфифильных блочных сополимеров лактида и этиленоксида. Различная способность блоков лактида к кристаллизации и направленное изменение длины блоков позволяет получать мицеллы с различным размером и морфологией. В данной статье мы попытались сделать обзор основных работ, проводимых в нашем научном коллективе в области биоразлагаемых полимеров

Physicochemical Characteristics and Hydrolytic Degradation of Polylactic Acid Dermal Fillers: A Comparative Study

Dermal fillers have gained significant attention in the field of aesthetic medicine due to their ability to restore volume and correct facial wrinkles. Even though such formulations have similar compositions, they can have different microstructure and molecular characteristics, which in turn affect the biodegradation profile. This study presents the results of an investigation of the physicochemical characteristics of four dermal fillers from different manufacturers (Sculptra®, Gana V®, AestheFill®, and Repart PLA®). The molecular and supramolecular characteristics of polylactic acid (L/D isomer ratio, molecular weight, degree of crystallinity), the morphology and size of PLA microparticles were determined. Hydrolytic degradation studies in phosphate buffer revealed differences in the rate of molecular weight reduction in the polymer. The obtained data may be important for the analysis and interpretation of the results of biological studies and clinical outcomes of the PLA dermal fillers

BIODEGRADABLE POLYMER MATERIALS FOR MEDICAL APPLICATIONS: FROM IMPLANTS TO ORGANS

Development of modern medical technologies would be impossible without the application of various materials with special properties. Over the last decade there has been a marked increase in interest in biodegradable materials for use in medicine and other areas of the national economy. In medicine, biodegradable polymers offer great potential for controlled drug delivery and wound management (e.g., adhesives, sutures and surgical meshes), for orthopedic devices (screws, pins and rods), nonwoven materials and scaffolds for tissue engineering. Among the family of biodegradable polyesters the most extensively investigated and the most widely used polymers are poly(α-hydroxyacid)s: polylactide (i.e. PLA), polyglycolide (i.e. PGA), poly-ε-caprolactone (PCL), polydioxanone and their copolymers. Controlling the molecular and supramolecular structure of biodegradable polymers allows tuning the physico-chemical and mechanical characteristics of the materials as well as their degradation kinetics. This enables selecting the optimal composition and structure of the material for the development of a broad range of biomedical products. Introduction of various functional fillers such as calcium phosphates allows creating bioactive composite materials with improved mechanical properties. To manufacture the highly dispersed biomedical materials for regenerative medicine electrospinning and freeze-drying are employed. Varying the technological parameters of the process enables to produce materials and devices with predetermined pore sizes and various mechanical properties. In order to increase the effectiveness of a great number of drugs the perspective approach is their inclusion into nanosized polymer micelles based on amphiphilic block copolymers of lactide and ethylene oxide. Different crystallization behavior of the lactide blocks and controlled regulation of their length allows producing micelles with various sizes and morphology. In this article we have attempted to provide an overview of works that are under way in the area of biodegradable polymers research and development in our group

Experimental-Morphological Study of Several Types of Fibrillar Structured Drainages for Glaucoma Surgery

Purpose: based on the results of an experimental study in vivo, to determine the optimal type of fibrillar structured drainages for glaucoma surgery.Material and methods. An experimental morphological study was performed on 32 rabbits of the chinchilla breed, which were divided into 4 groups of 8 animals each. The rabbits were implanted with fibrillar structured drains from polyurethane, polyethylene terephthalate, polyamide, polylactide. In the postoperative period, a postoperative inflammatory reaction was assessed. After removing the animals from the experiment, the eyes were subjected to morphological examination.Results. In rabbits with drainage from polyurethane, a mild congested hyperemia was noted in visual evaluation compared with the pair eye during the entire follow-up period. The eye reaction to the operation was regarded as a 1st degree. In more distant terms, there was a proliferation of subconjunctival tissue in the projection of the operation zone. In histological examination, the implant was represented by thin fibrous structures throughout the volume of drainage, a uniform distribution of macrophages, lymphocytes, among the fibers. In rabbits with drainage from polyethylene terephthalate, the reaction of the eyeball to the implantation of the polymeric material corresponded to the 0 degree. When a histological study was carried out along the periphery of the drainage, a thin capsule was formed. In rabbits with drainage from polyamide, the reaction of the eyeball corresponded to 1 degree. Histological examination showed that the fibrous structure of drainage was practically not determined, an abundance of cellular elements was observed throughout the drainage: macrophages and multinucleate giants predominated, fibroblasts, fibroblasts, lymphocytes, and newly formed connective tissue fibers between the drainage fibers were present. When analyzing the results obtained during the implantation of the matrix from the polylactide, the reaction of the eyeball corresponded to the 0 degree. Histological examination showed the preservation of fibrous structure of drainage, a moderate accumulation of macrophages was determined between the fibers, single giants, single lymphocytes were present.The conclusion. Fibrillar structured drains based on polylactide due to a stable highly porous structure, high biocompatibility and biodegradability create favorable conditions for transport of aqueous humor and formation of outflow pathways

Theoretical and Experimental Investigation of 3D-Printed Polylactide Laminate Composites’ Mechanical Properties

The purpose of this work is to theoretically and experimentally investigate the applicability of the Tsai–Hill failure criterion and classical laminate theory for predicting the strength and stiffness of 3D-printed polylactide laminate composites with various raster angles in mechanical tests for uniaxial tension and compression. According to the results of tensile and compression tests, the stiffness matrix components of the orthotropic individual lamina and strength were determined. The Poisson’s ratio was determined using the digital image correlation method. It was found that the Tsai–Hill criterion is applicable for predicting the tensile strength and yield strength of laminate polymer composite materials manufactured via fused deposition modeling 3D printing. The calculated values of the elastic moduli for specimens with various raster angles correlate well with the values obtained experimentally. In tensile tests, the error for the laminate with a constant raster angle was 3.3%, for a composite laminate it was 4.4, in compression tests it was 11.9% and 9%, respectively

Cold Crystallization of Glassy Polylactide during Solvent Crazing

Uniaxial tension accompanied by the orientation and crystallization of polymer chains is one of the powerful methods for the improvement of mechanical properties. Crystallization of amorphous isotropic polylactide (PLA) at room temperature is studied for the first time during the drawing of films in the presence of liquid adsorption-active media (ethanol, water–ethanol mixtures, and <i>n</i>-heptane) by the solvent crazing mechanism. The crystalline structure arises only under simultaneous actions of a liquid medium and a tensile stress and does not depend on the nature of the environment. The degree of polymer crystallinity increases nearly linearly with the growth in the fraction of the fibrillar material and reaches a maximum value of 42–45%. It has been stated that polymer crystallization happens in crazes involving nanofibrils with a diameter of about 10–20 nm without affecting the bulk polymer parts. Wide-angle X-ray scattering has been used to confirm that the crazing-induced crystallization is accompanied by the formation of the α′-crystalline phase with crystallite sizes (X-ray coherent scattering region) of 3–5 nm, depending on the nature of the liquid medium. After stretching in liquid media to a high tensile strain, the strength of a PLA film has increased to 200 MPa