Materials based on Mg²⁺-containing phosphates are gaining great relevance in the field of bone tissue repair via regenerative medicine methods. Magnesium ions, together with condensed phosphate ions, play substantial roles in the process of bone remodeling, affecting the early stage of bone regeneration through active participation in the process of osteosynthesis. In this paper we provide a comprehensive overview of the usage of biomaterials based on magnesium phosphate and magnesium calcium phosphate in bone reconstruction. We consider the role of magnesium ions in angiogenesis, which is an important process associated with osteogenesis. Finally, we summarize the biological properties of calcium magnesium phosphates for regeneration of bone.

Currently, the significantly developing fields of tissue engineering related to the fabrication of polymer-based materials that possess microenvironments suitable to provide cell attachment and promote cell differentiation and proliferation involve various materials and approaches. Biomimicking approach in tissue engineering is aimed at the development of a highly biocompatible and bioactive material that would most accurately imitate the structural features of the native extracellular matrix consisting of specially arranged fibrous constructions. For this reason, the present research is devoted to the discussion of promising fibrous materials for bone tissue regeneration obtained by electrospinning techniques. In this brief review, we focus on the recently presented natural and synthetic polymers, as well as their combinations with each other and with bioactive inorganic incorporations in order to form composite electrospun scaffolds. The application of several electrospinning techniques in relation to a number of polymers is touched upon. Additionally, the efficiency of nanofibrous composite materials intended for use in bone tissue engineering is discussed based on biological activity and physiochemical characteristics.

Interest in calcium phosphate cements as materials for the restoration and treatment of bone tissue defects is still high. Despite commercialization and use in the clinic, the calcium phosphate cements have great potential for development. Existing approaches to the production of calcium phosphate cements as drugs are analyzed. A description of the pathogenesis of the main diseases of bone tissue (trauma, osteomyelitis, osteoporosis and tumor) and effective common treatment strategies are presented in the review. An analysis of the modern understanding of the complex action of the cement matrix and the additives and drugs distributed in it in relation to the successful treatment of bone defects is given. The mechanisms of biological action of functional substances determine the effectiveness of use in certain clinical cases. An important direction of using calcium phosphate cements as a carrier of functional substances is the volumetric incorporation of anti-inflammatory, antitumor, antiresorptive and osteogenic functional substances. The main functionalization requirement for carrier materials is prolonged elution. Various release factors related to the matrix, functional substances and elution conditions are considered in the work. It is shown that cements are a complex system. Changing one of the many initial parameters in a wide range changes the final characteristics of the matrix and, accordingly, the kinetics. The main approaches to the effective functionalization of calcium phosphate cements are considered in the review.

The development of electrospun nanofibers based on cellulose and its derivatives is an inalienable task of modern materials science branches related to biomedical engineering. The considerable compatibility with multiple cell lines and capability to form unaligned nanofibrous frameworks help reproduce the properties of natural extracellular matrix and ensure scaffold applications as cell carriers promoting substantial cell adhesion, growth, and proliferation. In this paper, we are focusing on the structural features of cellulose itself and electrospun cellulosic fibers, including fiber diameter, spacing, and alignment responsible for facilitated cell capture. The study emphasizes the role of the most frequently discussed cellulose derivatives (cellulose acetate, carboxymethylcellulose, hydroxypropyl cellulose, etc.) and composites in scaffolding and cell culturing. The key issues of the electrospinning technique in scaffold design and insufficient micromechanics assessment are discussed. Based on recent studies aiming at the fabrication of artificial 2D and 3D nanofiber matrices, the current research provides the applicability assessment of the scaffolds toward osteoblasts (hFOB line), fibroblastic (NIH/3T3, HDF, HFF-1, L929 lines), endothelial (HUVEC line), and several other cell types. Furthermore, a critical aspect of cell adhesion through the adsorption of proteins on the surfaces is touched upon.

The review discusses methods to manufacture osteoconductive inorganic materials based mainly on calcium phosphates with given macroscopic porosity using rapid prototyping. Requirements for...

Methods that are used in regenerative medicine rely on the inherent ability of living organisms to regenerate their tissue. If the size (volume) of a defect exceeds some critical level, regeneration can be initiated and maintained using resorbable porous scaffolds made of natural, artificial, or synthetic materials capable of temporary defect compensation. When modified with pharmaceutical products and specific proteins or cells, such porous scaffolds are referred to as tissue engineering constructs. Inorganic resorbable materials are most frequently used for bone tissue defect repair. Natural bone is a composite having a polymer (collagen) matrix filled with calcium phosphate nanocrystals in the form of insoluble calcium hydroxyapatite. For this reason, calcium phosphate-based materials are leaders of medical inorganic materials research. To date, resorbable biocompatible materials based on tricalcium phosphate, calcium pyrophosphate, brushite, monetite, and octacalcium phosphate have been developed. Calcium hydroxyapatite is known as an inorganic ion exchanger. Because of this, the composition of bone tissue includes, in addition to phosphate and calcium ions, carbonate, silicate, and sulfate ions, as well as sodium, potassium, magnesium, iron, strontium, zinc and some other metal ions. The fact that bone tissue contains anions substituting for orthophosphate ions or hydroxide ions in the calcium hydroxyapatite of bone tissue prompted researchers to produce resorbable materials based on calcium sulfates, calcium carbonate, and calcium phosphates in which orthophosphate ions are replaced by anions mentioned above. Cation substitutions in calcium hydroxyapatite of bone tissue and the chemical composition of the medium of an organism allow one to produce and use resorbable materials for bone implants consisting of cation-substituted calcium phosphates and calcium–biocompatible cation double phosphates, such as sodium-substituted tricalcium phosphate, potassium-substituted tricalcium phosphate, sodium rhenanite, potassium rhenanite, and calcium magnesium double pyrophosphate. The resorption of an inorganic material intended for use as a pharmaceutical product can be controlled via designing a preset phase composition. The above-mentioned biocompatible resorbable phases can be used in various combinations in already existing composite materials or composites under development. The microstructure of a biocompatible resorbable inorganic material can be formed as a result of various physicochemical processes. The phase composition and microstructure of a ceramic material are determined by solid-state and liquid-phase sintering processes, as well as by heterogeneous chemical reactions during firing. The phase composition and microstructure of cement stone are formed as a result of chemical binding reactions initiated by the addition of water or aqueous solutions. Amorphous materials can be prepared via melting of starting reagents or sol–gel processing. The osteoconductivity of a biocompatible resorbable inorganic material is an important property necessary for body fluids and bone cells to be able to penetrate into the implant material. Macroporosity, which determines the osteoconductivity of a resorbable inorganic material, can be produced using various technological approaches. 3D printing methods make it possible to obtain materials with tailored phase composition and microstructure and permeable macroporosity of preset architecture. A large surface area of a porous inorganic material is thought to be a factor of controlling the resorption rate. This review summarizes information about existing biocompatible resorbable inorganic materials for regenerative medicine and considers physicochemical principles of the preparation of such materials with the use of synthetic starting powders and natural materials.