Challenging applicability of ISO 10993-5 for calcium phosphate biomaterials evaluation: Towards more accurate in vitro cytotoxicity assessment.

Research on biomaterials typically starts with cytocompatibility evaluation, using the ISO 10993-5 standard as a reference that relies on extract tests to determine whether the material is safe (cell metabolic activity should exceed 70 %). However, the generalized approach within the standard may not accurately reflect the material's behavior in direct contact with cells, raising concerns about its effectiveness. Calcium phosphates (CaPs) are a group of materials that, despite being highly biocompatible and promoting bone formation, still exhibit inconsistencies in basic cytotoxicity evaluations. Hence, in order to test the cytocompatibility dependence on different experimental setups and material-cell interactions, we used amorphous calcium phosphate, α-tricalcium phosphate, hydroxyapatite, and octacalcium phosphate (0.1 mg/mL to 5 mg/mL) with core cell lines of bone microenvironment: mesenchymal stem cells, osteoblast-like and endothelial cells. All materials have been characterized for their physicochemical properties before and after cellular contact and once in vitro assays were finalized, groups identified as 'cytotoxic' were further analyzed using a modified Annexin V apoptosis assay to accurately determine cell death. The obtained results showed that indirect contact following ISO standards had no sensitivity of tested cells to the materials, but direct contact tests at physiological concentrations revealed decreased metabolic activity and viability. In summary, our findings offer valuable guidelines for handling biomaterials, especially in powder form, to better evaluate their biological properties and avoid false negatives commonly associated with the traditional standard approach.

Apatite/Chitosan Composites Formed by Cold Sintering for Drug Delivery and Bone Tissue Engineering Applications.

In the biomedical field, nanocrystalline hydroxyapatite is still one of the most attractive candidates as a bone substitute material due to its analogies with native bone mineral features regarding chemical composition, bioactivity and osteoconductivity. Ion substitution and low crystallinity are also fundamental characteristics of bone apatite, making it metastable, bioresorbable and reactive. In the present work, biomimetic apatite and apatite/chitosan composites were produced by dissolution-precipitation synthesis, using mussel shells as a calcium biogenic source. With an eye on possible bone reconstruction and drug delivery applications, apatite/chitosan composites were loaded with strontium ranelate, an antiosteoporotic drug. Due to the metastability and temperature sensitivity of the produced composites, sintering could be carried out by conventional methods, and therefore, cold sintering was selected for the densification of the materials. The composites were consolidated up to ~90% relative density by applying a uniaxial pressure up to 1.5 GPa at room temperature for 10 min. Both the synthesised powders and cold-sintered samples were characterised from a physical and chemical point of view to demonstrate the effective production of biomimetic apatite/chitosan composites from mussel shells and exclude possible structural changes after sintering. Preliminary in vitro tests were also performed, which revealed a sustained release of strontium ranelate for about 19 days and no cytotoxicity towards human osteoblastic-like cells (MG63) exposed up to 72 h to the drug-containing composite extract.

Doxorubicin loaded octacalcium phosphate particles as controlled release drug delivery systems: Physico-chemical characterization, in vitro drug release and evaluation of cell death pathway.

Mastering new and efficient ways to obtain successful drug delivery systems (DDS) with controlled release became a paramount quest in the scientific community. Increase of malignant bone tumors and the necessity to optimize an approach of localized drug delivery require research to be even more intensified. Octacalcium phosphate (OCP), with a number of advantages over current counterparts is extensively used in bone engineering. The aim of the present research was to synthesize bioactive and biocompatible doxorubicin (DOX) containing OCP particles. DOX-OCP was successfully obtained in situ in an exhaustive range of added drug (1-20 wt%, theoretical loading). Based on XRD, above 10 wt% of DOX, OCP formation was inhibited and the obtained product was low crystalline α-TCP. In-vitro drug release was performed in pH 7.4 and 6.0. In both pH environments DOX had a continuous release over six weeks. However, the initial drug burst for pH 7.4, in the first 24 h, ranged from 15.9 ± 1.3 % to 33.5 ± 12 % and for pH 6.0 23.7 ± 1.5 % to 36.2 ± 12 %.The DOX-OCP exhibited an inhibitory effect on viability of osteosarcoma cell lines MG63, U2OS and HOS. In contrast, MC3T3-E1 cells (IC50 > 0.062 µM) displayed increased viability and proliferation from 3rd to 7th day. Testing of the DDS on ferroptotic markers (CHAC1, ACSL4 and PTGS2) showed that OCP-DOX does not induce ferroptotic cell death. Moreover, the evaluation of protein levels of cleaved PARP, by western blotting analysis, corroborated that apoptosis is the main pathway of programmed cell death in osteosarcoma cells induced by DOX-OCP.

Fusion and classification algorithm of octacalcium phosphate production based on XRD and FTIR data.

The present manuscript tested an automated analysis sequence to provide a decision support system to track the OCP synthesis from [Formula: see text]-TCP over time. Initially, the XRD and FTIR signals from a hundredfold scaled-up hydrolysis of OCP from [Formula: see text]-TCP were fused and modeled by the curve fitting based on the significantly established maxima from the literature and nine features extracted from the fitted shapes. Afterward, the analysis sequence enclosed the machine learning techniques for feature ranking, spatial filtering, and dimensionality reduction to support the automatic recognition of the synthesis stages. The proposed analysis pipeline for OCP identification might be the foundation for a decision support system explicitly targeting OCP synthesis. Future projects will exploit the suggested methodology for pinpointing the OCP production over time (including the intermediary phases present in the OCP formation) and for evaluating whether biological variables might be merged with biomaterial properties to build a unified model of tissue response to the implant.

Octacalcium phosphate phase forming cements as an injectable bone substitute materials: Preparation and in vitro structural study.

In the realm of regenerating damaged or degenerated bones through minimally invasive techniques, injectable materials have emerged as exceptionally promising. Among these, calcium phosphate bone cements (CPCs) have garnered significant interest due to their remarkable bioactivity, setting it apart from non-degradable alternatives such as polymethyl methacrylate cements. α-Tricalcium phosphate (α-TCP) is a widely used solid phase component in CPCs. It can transform into calcium-deficient hydroxyapatite (CDHAp) when it comes in contact with water. In this study, we aimed to create an injectable, self-setting bone cement using low-temperature synthesized α-TCP powder as a single precursor of the powder phase. We found that changes in the pH of the liquid phase (pH 6.0, pH 6.2, pH 7.0 and pH 7.4) significantly altered the cement's setting, handling, and mechanical properties. The formation of the octacalcium phosphate (OCP) phase was identified in our study, which positively affects the osteoblastic cell response. Hardened OCP-forming bone cements prepared using a liquid phase with pH 7.0 and 7.4 showed better osteogenic cell attachment and proliferation than those prepared with pH 6.0 and 6.2. Our study suggests that changes in the pH of the liquid phase can significantly affect the properties of α-TCP-based bone cement, and the presence of the OCP phase is crucial for optimal cement performance.

Octacalcium Phosphate-Laden Hydrogels on 3D-Printed Titanium Biomaterials Improve Corrosion Resistance in Simulated Biological Media.

The inflammatory-associated corrosion of metallic dental and orthopedic implants causes significant complications, which may result in the implant's failure. The corrosion resistance can be improved with coatings and surface treatments, but at the same time, it might affect the ability of metallic implants to undergo proper osteointegration. In this work, alginate hydrogels with and without octacalcium phosphate (OCP) were made on 3D-printed (patterned) titanium alloys (Ti Group 2 and Ti-Al-V Group 23) to enhance their anticorrosion properties in simulated normal, inflammatory, and severe inflammatory conditions in vitro. Alginate (Alg) and OCP-laden alginate (Alg/OCP) hydrogels were manufactured on the surface of 3D-printed Ti substrates and were characterized with wettability analysis, XRD, and FTIR. The electrochemical characterization of the samples was carried out with open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). It was observed that the hydrophilicity of Alg/OCP coatings was higher than that of pure Alg and that OCP phase crystallinity was increased when samples were subjected to simulated biological media. The corrosion resistance of uncoated and coated samples was lower in inflammatory and severe inflammatory environments vs. normal media, but the hydrogel coatings on 3D-printed Ti layers moved the corrosion potential towards more nobler values, reducing the corrosion current density in all simulated solutions. These measurements revealed that OCP particles in the Alg hydrogel matrix noticeably increased the electrical charge transfer resistance at the substrate and coating interface more than with Alg hydrogel alone.

Exploring the Interplay of Antimicrobial Properties and Cellular Response in Physically Crosslinked Hyaluronic Acid/ε-Polylysine Hydrogels.

The reduction of tissue cytotoxicity and the improvement of cell viability are of utmost significance, particularly in the realm of green chemistry. Despite substantial progress, the threat of local infections remains a concern. Therefore, hydrogel systems that provide mechanical support and a harmonious balance between antimicrobial efficacy and cell viability are greatly needed. Our study explores the preparation of physically crosslinked, injectable, and antimicrobial hydrogels using biocompatible hyaluronic acid (HA) and antimicrobial ε-polylysine (ε-PL) in different weight ratios (10 wt% to 90 wt%). The crosslinking was achieved by forming a polyelectrolyte complex between HA and ε-PL. The influence of HA content on the resulting HA/ε-PL hydrogel physicochemical, mechanical, morphological, rheological, and antimicrobial properties was evaluated, followed by an inspection of their in vitro cytotoxicity and hemocompatibility. Within the study, injectable, self-healing HA/ε-PL hydrogels were developed. All hydrogels showed antimicrobial properties against S. aureus, P. aeruginosa, E. coli, and C. albicans, where HA/ε-PL 30:70 (wt%) composition reached nearly 100% killing efficiency. The antimicrobial activity was directly proportional to ε-PL content in the HA/ε-PL hydrogels. A decrease in ε-PL content led to a reduction of antimicrobial efficacy against S. aureus and C. albicans. Conversely, this decrease in ε-PL content in HA/ε-PL hydrogels was favourable for Balb/c 3T3 cells, leading to the cell viability of 152.57% for HA/ε-PL 70:30 and 142.67% for HA/ε-PL 80:20. The obtained results provide essential insights into the composition of the appropriate hydrogel systems able to provide not only mechanical support but also the antibacterial effect, which can offer opportunities for developing new, patient-safe, and environmentally friendly biomaterials.

Exploring the Formation Kinetics of Octacalcium Phosphate from Alpha-Tricalcium Phosphate: Synthesis Scale-Up, Determination of Transient Phases, Their Morphology and Biocompatibility.

Even with decades of research studies behind octacalcium phosphate (OCP), determination of OCP phase formation has proved to be a cumbersome challenge. Even though obtaining a large quantity of OCP is important for potential clinical uses, it still remains a hindrance to obtain high yields of pure OCP. Taking that into consideration, the purpose of this study was to scale-up OCP synthesis for the first time and to use a multi-technique approach to follow the phase transformation pathway at multiple time points. In the present study, OCP has been synthesized from α-tricalcium phosphate (α-TCP), and subsequently scaled-up tenfold and hundredfold (100 mg → 10 g). The hydrolysis mechanism has been followed and described by using XRD and FTIR spectroscopy, as well as Raman and SEM. Gradual transformation into the OCP phase transpired through dicalcium phosphate dihydrate (brushite, DCPD, up to ~36%) as an intermediary phase. Furthermore, the obtained transitional phases and final OCP phases (across all scale-up levels) were tested with human bone marrow-derived mesenchymal stem cells (hBMSCs), in order to see how different phase mixtures affect the cell viability, and also to corroborate the safety of the scaled-up product. Twelve out of seventeen specimens showed satisfactory percentages of cell viability and confirmed the prospective use of scaled-up OCP in further in vitro studies. The present study, therefore, provides the first scale-up process of OCP synthesis, an in depth understanding of the formation pathway, and investigation of the parameters able to contribute in the OCP phase formation.

Calcium phosphate bone cements as local drug delivery systems for bone cancer treatment.

Bone cancer is usually a metastatic disease, affecting people of all ages. Its effective therapy requires a targeted drug administration locally at the cancer site so that the surrounding healthy organs and tissues stay unharmed. Upon a thorough literature search, a tremendous number of published articles are reporting on development of calcium phosphate cements (CPCs) for the treatment of a variety of diseases, such as osteoporosis, osteoarthritis, osteomyelitis, and other musculoskeletal disorders. However, just a limited number of research employs CPCs specifically for bone cancer treatment. In this review article, we study the factors influencing the local drug release from CPCs and particularly focus on bone cancer therapy. Finally, we locate the deficiencies in the literature regarding this specific topic and propose which other perspectives should be considered and discussed in future articles.

Injectable bone cements: What benefits the combination of calcium phosphates and bioactive glasses could bring?

Out of the wide range of calcium phosphate (CaP) biomaterials, calcium phosphate bone cements (CPCs) have attracted increased attention since their discovery in the 1980s due to their valuable properties such as bioactivity, osteoconductivity, injectability, hardening ability through a low-temperature setting reaction and moldability. Thereafter numerous researches have been performed to enhance the properties of CPCs. Nonetheless, low mechanical performance of CPCs limits their clinical application in load bearing regions of bone. Also, the in vivo resorption and replacement of CPC with new bone tissue is still controversial, thus further improvements of high clinical importance are required. Bioactive glasses (BGs) are biocompatible and able to bond to bone, stimulating new bone growth while dissolving over time. In the last decades extensive research has been performed analyzing the role of BGs in combination with different CaPs. Thus, the focal point of this review paper is to summarize the available research data on how injectable CPC properties could be improved or affected by the addition of BG as a secondary powder phase. It was found that despite the variances of setting time and compressive strength results, desirable injectable properties of bone cements can be achieved by the inclusion of BGs into CPCs. The published data also revealed that the degradation rate of CPCs is significantly improved by BG addition. Moreover, the presence of BG in CPCs improves the in vitro osteogenic differentiation and cell response as well as the tissue-material interaction in vivo.

Calcium Phosphate/Hyaluronic Acid Composite Hydrogels for Local Antiosteoporotic Drug Delivery.

Despite the bone ability of self-regeneration, large bone defects require surgical intervention. Likewise, when it comes to osteoporotic bone fractures, new approaches should be considered a supportive mechanism for the surgery. In recent years, more and more attention has been attracted to advanced drug delivery systems for local osteoporosis treatment, combining appropriate biomaterials with antiosteoporotic drugs, allowing simultaneously to regenerate the bone and locally treat the osteoporosis. Within the current research, hyaluronic acid/strontium ranelate (HA/SrRan), HA/calcium phosphate nanoparticles (HA/CaP NPs), and HA/CaP NPs/SrRan hydrogels were prepared. The effect of CaP and SrRan presence in the composites on the swelling behavior, gel fraction, molecular structure, microstructure, and SrRan and Sr2+ release, as well as in vitro cell viability was evaluated. Obtained results revealed that the route of CaP nanoparticle incorporation into the HA matrix had a significant effect on the hydrogel gel fraction, rheological properties, swelling behavior, and microstructure. Nevertheless, it had a negligible effect on the release kinetics of SrRan and Sr2+. The highest cell (3T3) viability (>80%) was observed for HA hydrogels, with and without SrRan. Moreover, the positive effect of SrRan on 3T3 cells was also demonstrated, showing a significant increase (up to 50%) in cell viability if the used concentrations of SrRan were in the range of 0.05-0.2 µg/ml.

Effect of crosslinking strategy on the biological, antibacterial and physicochemical performance of hyaluronic acid and ɛ-polylysine based hydrogels.

The design of multifunctional hydrogels based on bioactive hyaluronic acid (HA) and antibacterial cationic polymer ɛ-poly-l-lysine (ε-PL) is a promising tool in tissue engineering applications. In the current study, we have designed hyaluronic acid and ɛ-polylysine composite hydrogel systems with antibacterial and cell attractive properties. Two distinct crosslinking approaches were used: the physical crosslinking based on electrostatic attractions and the chemical crosslinking of charged functional groups (-NH2 and -COOH). The impact of the crosslinking strategy on fabricated hydrogel molecular structure, swelling behavior, gel fraction, morphology, porosity, viscoelastic properties, antibacterial activity, and in vitro biocompatibility was evaluated. Both chemically and physically crosslinked HA/ԑ-PL hydrogels demonstrated fast swelling behavior and long-term stability for at least 28 days, as well as similar order of stiffness (10-30 kPa). We demonstrated that physically crosslinked hydrogels inhibited over 99.999% of Gram-negative E. coli, while chemically crosslinking strategy led to the antibacterial efficiency decrease. However, cell viability was significantly improved, confirming the importance of the applied crosslinking approach to the antibacterial activity and in vitro biocompatibility. The distinct differences in the physicochemical and biological properties of the developed materials provide new opportunities to design next-generation functional composite hydrogel systems.

Biopharmaceutical-Type Chinese Hamster Ovary Cell Cultivation Under Static Magnetic Field Exposure: A Study of Genotoxic Effect.

The lack of a sufficient research base is the reason for the ongoing discussion regarding the genotoxic effect of magnetic field (MF) exposure on mammalian cell cultures. Chinese hamster ovary (CHO) suspension-type cells, which are widely used for biopharmaceutical production, are potentially subjected to an increased MF when cultivated in bioreactors equipped with bottom-placed magnetically coupled stirring mechanisms. The main challenge for conducting research in this field remains the availability of a suitable experimental setup that generates an appropriate MF for the raised research question. In the present study, a simple and cost-effective experimental setup was developed that generated a static MF, similar to what has been modeled in large-scale bioreactors and, at the same time, was suitable for experimental cell cultivation in laboratory conditions. The measured maximum magnetic flux density to which the cells were exposed was 0.66 T. To assess the possible genotoxic effect, cells were continuously subcultivated in laboratory petri dishes for a period of 14 days, corresponding to a typical duration of a biopharmaceutical production process in a conventional fed-batch regime. The genotoxic effect was assessed using the cytokinesis-block micronucleus assay with fluorescent staining. Results showed that a 0.66-T static MF exposure had no significant long-term effect on cell viability and chromosomal damage but demonstrated a short-term effect on cell apoptosis. Significant increase in nuclear bud formation was observed. These findings may encourage other researchers in future studies investigating cellular responses to MF exposure and contribute relevant data for comparison.

Incorporation of Barium Ions into Biomaterials: Dangerous Liaison or Potential Revolution?

In the present manuscript, a brief overview on barium, its possible utilization, and the aftermath of its behavior in organisms has been presented. As a bivalent cation, barium has the potential to be used in a myriad of biochemical reactions. A number of studies have exhibited both the unwanted outcome barium displayed and the advantages of barium laden compounds, tested in in vitro and in vivo settings. The plethora of prospective manipulations covered the area of hydrogels and calcium phosphates, with an end goal of examining barium's future in the tissue engineering. However, majority of data revert to the research conducted in the 20th century, without investigating the mechanisms of action using current state-of-the-art technology. Having this in mind, set of questions that are needed for possible future research arose. Can barium be used as a substitute for other biologically relevant divalent cations? Will the incorporation of barium ions hamper the execution of the essential processes in the organism? Most importantly, can the benefits outweigh the harm?

Octacalcium phosphate: Innovative vehicle for the local biologically active substance delivery in bone regeneration.

Disadvantages of conventional drug delivery systems (DDS), such as systemic circulation, interaction with physiochemical factors, reduced bioavailability, and insufficient drug concentration at bone defect site, have underlined the importance of developing efficacious local drug delivery systems. Octacalcium phosphate (OCP) is presumed to be the precursor of biologically formed apatite, owing to its similarity to hydroxyapatite (HAp) and readiness to convert to it. Specific crystal structure of OCP is constructed of compiled apatite layers and water layers, which make possible the incorporation of various ions in its structure, making it feasible to alter the overall effect OCP has in the system. Next to that intrinsic property, characteristics as high solubility, biodegradability and osteoconductivity have made it indispensable to tailor OCP as a carrier material. In this review, we present the main characteristics and progress done on utilizing OCP as an innovative vehicle and provide suggestions for possible research pathways and advantages for local drug delivery in bone tissue engineering. STATEMENT OF SIGNIFICANCE: Octacalcium phosphate (OCP), being a precursor to biologically formed apatite, has many assets when compared to other calcium phosphates. Owing to its highly pertinent structure, it is being used as a vehicle for biologically active substances or ions for bone regeneration. However, orchestrating drug delivery systems with OCP, in order to achieve the best possible outcome, is still a pioneering concept, and the all-encompassing data is still scarce. Although several articles have been published on this matter, to this date there is no systematic overview pointing out the benefits that OCP can bring in the field of drug delivery. Here we offer a comprehensive overview, starting from the OCP synthesis to its structure, morphology, and the biological significance OCP has.

Development of local strontium ranelate delivery systems and long term in vitro drug release studies in osteogenic medium.

It has been recognized that the operative stabilization of osteoporotic fractures should be followed up with an appropriate osteoporosis treatment in order to decrease the risk of repeated fractures. Despite the good clinical results of strontium ranelate (SrRan) towards the osteoporosis treatment, high drug doses and long treatment period cause an increased risk of serious side effects. Novel local SrRan/poly(lactic acid) (SrRan/PLA) delivery systems containing from 3.57 ± 0.28 wt% to 24.39 ± 0.91 wt% of active substance were developed. In order to resemble the naturally occurring processes, osteogenic media (OM) was used as a release medium for long term (121 days) in vitro drug release studies and UV/VIS method for the determination of SrRan content in OM was developed and validated. Biomimetic calcium phosphate precipitates were found on the surface and in the pores of prepared delivery system after microcapsule exposure to OM for 121 days as well as SrRan particles, indicating that the release of the drug have not been completed within 121 days. In vitro cell viability evaluation approved no cytotoxic effects of microcapsule suspensions and extracts.

Biodegradable Materials and Metallic Implants-A Review.

Recent progress made in biomaterials and their clinical applications is well known. In the last five decades, great advances have been made in the field of biomaterials, including ceramics, glasses, polymers, composites, glass-ceramics and metal alloys. A variety of bioimplants are currently used in either one of the aforesaid forms. Some of these materials are designed to degrade or to be resorbed inside the body rather than removing the implant after its function is served. Many properties such as mechanical properties, non-toxicity, surface modification, degradation rate, biocompatibility, and corrosion rate and scaffold design are taken into consideration. The current review focuses on state-of-the-art biodegradable bioceramics, polymers, metal alloys and a few implants that employ bioresorbable/biodegradable materials. The essential functions, properties and their critical factors are discussed in detail, in addition to their challenges to be overcome.

Fabrication, Properties and Applications of Dense Hydroxyapatite: A Review.

In the last five decades, there have been vast advances in the field of biomaterials, including ceramics, glasses, glass-ceramics and metal alloys. Dense and porous ceramics have been widely used for various biomedical applications. Current applications of bioceramics include bone grafts, spinal fusion, bone repairs, bone fillers, maxillofacial reconstruction, etc. Amongst the various calcium phosphate compositions, hydroxyapatite, which has a composition similar to human bone, has attracted wide interest. Much emphasis is given to tissue engineering, both in porous and dense ceramic forms. The current review focusses on the various applications of dense hydroxyapatite and other dense biomaterials on the aspects of transparency and the mechanical and electrical behavior. Prospective future applications, established along the aforesaid applications of hydroxyapatite, appear to be promising regarding bone bonding, advanced medical treatment methods, improvement of the mechanical strength of artificial bone grafts and better in vitro/in vivo methodologies to afford more particular outcomes.

Calcium phosphate bone cements for local vancomycin delivery.

Among calcium phosphate biomaterials, calcium phosphate bone cements (CPCs) have attracted increased attention because of their ability of self-setting in vivo and injectability, opening the new opportunities for minimally invasive surgical procedures. However, any surgical procedure carries potential inflammation and bone infection risks, which could be prevented combining CPC with anti-inflammatory drugs, thus overcoming the disadvantages of systemic antibiotic therapy and controlling the initial burst and total release of active ingredient. Within the current study α-tricalcium phosphate based CPCs were prepared and it was found that decreasing the solid to liquid phase ratio from 1.89g/ml to 1.23g/ml, initial burst release of vancomycin within the first 24h increased from 40.0±2.1% up to 57.8±1.2% and intrinsic properties of CPC were changed. CPC modification with vancomycin loaded poly(lactic acid) (PLA) microcapsules decreased the initial burst release of drug down to 7.7±0.6%, while only 30.4±1.3% of drug was transferred into the dissolution medium within 43days, compared to pure vancomycin loaded CPC, where 100% drug release was observed already after 12days. During the current research a new approach was found in order to increase the drug bioavailability. Modification of CPC with novel PLA/vancomycin microcapsules loaded and coated with nanosized hydroxyapatite resulted in 85.3±3.1% of vancomycin release within 43days.

Evaluation of the physical and antimicrobial properties of silver doped hydroxyapatite depending on the preparation method.

In the present study, the effect of the preparation method on the physical and antibacterial properties of silver doped hydroxyapatite (HAp/Ag) samples was investigated. HAp/Ag with 0.1-5 % of silver was prepared using two different modified wet chemical precipitation methods. A comparison of thermal stability and thermodynamical properties indicated that the thermal stability and sintering temperature of HAp/Ag were higher than those of pure hydroxyapatite if Ca(NO3)2·4H2O, AgNO3, NH4OH and (NH4)2HPO4 were used as raw materials. Phase composition and silver release were determined by XRD and ICP-MS. The study showed that, after 50 h in simulated body fluid 0.8-1.8 % of silver of the total silver amount was released from compact HAp/Ag scaffolds, and release kinetics strongly depended on the HAp/Ag preparation method. In vitro antibacterial activity of samples from each method against the bacterial strains Staphylococcus epidermidis and Pseudomonas aeruginosa was approved. Results showed that, in the case of using Ca(OH)2, H3PO4 and AgNO3 as raw materials for HAp/Ag synthesis, higher antibacterial activity towards both bacterial strains could be obtained.