Applications of biomaterials in regenerative medicine and tissue engineering – concepts and perspective

Abstract

Regenerative medicine (RM) exploits the innate potential of the human body to effectively repair and regenerate damaged tissues and organs with the help of various biomaterials. Tissue engineering (TE) makes it possible to replace damaged tissues and organs with new ones. Research in the field of biomaterials has significantly improved the area of RM and TE. Biomaterials are used as orthopedic, dental, cardiovascular implants, medical devices, in the fields of reconstructive and regenerative medicine, among others. Important preconditions for the biomaterial to be used for implantation are its biocompatibility and biofunctionality. Biomaterials should enable adhesion, migration, proliferation and differentiation of cells. The biological properties of biomaterials are a reflection of their physicochemical properties, such as internal architecture, surface characteristics and charge. Biomaterials used in tissue regeneration should mimic the natural structure of the extracellular matrix and represent a physiological microenvironment for normal cellular functions. These biomaterials should also have adequate biodegradability properties to facilitate the formation and growth of new tissue. Biomaterials for use in RM can be of natural or synthetic origin, polymers by structural properties, ceramic and composite type, and based on bioreactivity they can be bioinert or bioactive. In RM and TE, polymers of different classes, natural and synthetic, are used, which can be made as intelligent materials. The structure of hydrogels in the form of a porous network represents a good matrix for cell activity. Ceramic biomaterials based on hydroxyapatite (HAp) are selected for use in RM and TE, especially solid tissues. Properties, such as composition, particle size, material shape, porosity, surface charge, topography, etc., are relevant for the proper use of HAp materials. The properties of HAp allow modification of its structure, surface, particle size design at the micro and nano level, hybridization with polymers, metals, etc. which is very important for its applications. Designed micro-nanohybrid HAp structure is most similar to the bone structure, making the cell environment closest to natural. Bone tissue engineering (BTE) is based on the combined use of cells, osteostimulating (osteoinductive) factors and biomaterials as a scaffolds and carriers for bone regeneration and defects repair. In BTE adipose-derived mesenchymal stem cells (ADSCs) are often used that are induced in vitro towards osteogenic cells or endothelial cells, and freshly isolated stromal vascular fraction can also be used. Blood components (PRP, blood plasma or blood clot) can be included in the composition of the BTE construct as a source of osteoinductive factors. In vitro models and methods were used to examine the biocompatibility, immunomodulatory and regenerative potential of biomaterials, as well as their influence on cellular functions. After in vitro methods, and before clinical studies, various in vivo animal models are used to examine the regenerative potential of biomaterials, such as subcutaneous implantations and bone defects in tibia, femur and calvaria in experimental animals (mouse, rat, rabbit).