Calcium phosphate materials (CaPs) are similar to inorganic part of human mineralized tissues (i.e., bone, enamel, and dentin). Owing to their high biocompatibility, CaPs, mainly hydroxyapatite (HA), have been investigated for their use in various medical applications. One of the most widely used ways to improve the biological and physicochemical properties of HA is ionic substitution with trace ions. Recent developments in bioceramics have already demonstrated that introducing foreign ions is also possible in other CaPs, such as tricalcium phosphates (amorphous as well as α and β crystalline forms) and brushite. The purpose of this paper is to review recent achievements in the field of non-apatitic CaPs substituted with various ions. Particular attention will be focused on tricalcium phosphates (TCP) and “additives” such as magnesium, zinc, strontium, and silicate ions, all of which have been widely investigated thanks to their important biological role. This review also highlights some of the potential biomedical applications of non-apatitic substituted CaPs.

Hydroxyapatite materials, due to their high biocompatibility, play a crucial role in orthopaedics and bone surgery as alternatives to autologous bone grafts. It was also found that coatings of metallic implants with hydroxyapatite layer improve significantly their osseointegration. Due to its bioactivity, osteoconductivity and non-toxicity, hydroxyapatite is also widely used as a component of hybrid biomaterials. The implantation of “foreign” materials brings one major concern that is the risk of potential bone tissue infections or chronic osteomyelitis. In turn, the main problem concerning bacterial infection treatment is to obtain an adequate, bactericidal drug concentration maintained for a sufficient period of time in the bone tissue. Therefore, recent developments of materials engineering are focused on delivery antibiotics directly into the affected bone. To achieve this goal, hydroxyapatite-based materials are frequently studied as carriers for antibacterial drugs. For effective support of antibiotic therapy, the antibacterial activity of certain ions (including silver, zinc or copper) may be applied. In our work, we present recent developments on ceramic materials for bacterial bone infections: hydroxyapatite-based carriers for antibiotics and modifications of hydroxyapatite with antibacterial ions. In this review, state-of-the-art and current applications of such materials are presented and discussed. We want to also present our recent results.

In this study, a novel biomaterial, i.e., brushite containing 0.67 wt% of selenium (Se-Bru) was synthesized via a wet precipitation method. Pure, unsubstituted brushite (Bru) was synthesized via the same method and used as a reference material. Different techniques of instrumental analysis were applied to investigate and compare physicochemical properties of both materials. Fourier-Transform Infrared Spectroscopy confirmed the chemical identity of both materials. Scanning Electron Microscopy (SEM) was used to study the morphology and indicated that both samples (Bru and Se-Bru) consisted of plate-like microcrystals. Powder X-ray Diffraction (PXRD) showed that Bru, as well as Se-Bru were crystallographically homogenous. What is more, the data obtained from PXRD studies revealed that the substitution of selenite ions into the crystal structure of the material had clearly affected its lattice parameters. The incorporation of selenium was also confirmed by solid-state 1H→31P CP MAS kinetics experiments. Additionally, studies on the release kinetics of the elements forming Se-Bru and preliminary cytotoxicity tests were conducted. This preliminary research will favor a better understanding of ionic substitution in calcium phosphates and may be a starting point for the development of selenium-doped brushite cements for potential use in bone tissue impairments treatment.

In this work, 3D porous granules based on Zn and Se-containing calcium phosphates (CaPs) were fabricated using a droplet-extrusion technique. The composite beads varied in composition and contained two different natural polymers: sodium alginate (SA) and gelatin (GEL). To analyse and compare their physicochemical properties, such as porosity and morphology, different techniques were applied, including scanning electron microscopy (SEM), sorption of N₂ and mercury porosimetry. Prior to the fabrication of the granules, the properties of CaPs materials, (the bioceramic base of the beads), selenium (IV)-substituted hydroxyapatite (Se-HA) and zinc-substituted dicalcium phosphate dihydrate (Zn-DCPD), were also investigated. The results of cell viability assessment showed that Se-HA powder was non-toxic to human osteoblasts (hFOB 1.19) and simultaneously exhibited high toxicity to tumour cells (Saos-2). Once the cytotoxicity assay was completed, Se-HA and Zn-DCPD were used to prepare 3D materials. The prepared porous granules were used as matrices to deliver simvastatin to bones. Simvastatin was applied in either the lipophilic form or hydrophilic form. The release kinetics of simvastatin from granules of different composition was then assessed and compared.

Wśród nowoczesnych materiałów stosowanych w implantologii i medycynie regeneracyjnej szczególne miejsce zajmuje hydroksyapatyt. Wykorzystuje się go m. in. jako materiał kościozastępczy, powłokę metalicznych implantów oraz składnik dokostnych biomateriałów kompozytowych. W ostatnich latach poszukuje się możliwości tworzenia na jego bazie implantów wielofunkcyjnych, które oprócz roli wypełniającej ubytek kostny mają za zadanie uwalniać substancję leczniczą bezpośrednio w miejscu implantacji. Celem tej pracy jest podsumowanie aktualnej wiedzy w zakresie otrzymywania i możliwości wykorzystania nowoczesnych apatytowych systemów dostarczających antybiotyki do kości.