Exploring Borate-Modified Calcium Phosphate Ceramics: Antimicrobial Potential and Cytocompatibility Assessment.

Addressing periprosthetic infections, which present significant healing challenges that often require revision surgeries, necessitates the development of novel antibacterial materials and implants. Current research focuses on creating materials that hinder bacterial adhesion, colonization, and proliferation in surrounding tissues. Boron (B)-containing compounds are known for their antibacterial properties and potential in bone metabolism for regenerative medicine. In this study, we synthesized B-containing tricalcium phosphate (0.3B-TCP) with 1.1 wt.% B content via precipitation from aqueous solutions and sintering at 1100 °C. X-ray diffraction confirmed the ceramic's primary crystalline phase as ß-TCP, with B evenly distributed according to energy-dispersive spectroscopy data. Electron paramagnetic resonance (EPR) data verified stable paramagnetic borate anions, indicating successful BO33- substitution for phosphate groups. The microstructural properties of 0.3B-TCP ceramic were assessed before and after soaking in a saline solution. Its bending strength was approximately 30 MPa, and its porosity was about 33%. 0.3B-TCP ceramic demonstrated significant antimicrobial efficacy against various bacterial strains and a fungus. Cytotoxicity evaluation using equine adipose tissue-derived mesenchymal stem cells and osteogenic differentiation assessment were conducted. The combination of antibacterial efficacy and good cytocompatibility suggests 0.3B-TCP ceramic as a promising bone substitute material.

Magnetic Resonance-Based Analytical Tools to Study Polyvinylpyrrolidone-Hydroxyapatite Composites.

The synthesis of biocompatible and bioresorbable composite materials, such as a "polymer matrix-mineral constituent," stimulating the natural growth of living tissues and the restoration of damaged parts of the body, is one of the challenging problems in regenerative medicine and materials science. Composite films of bioresorbable polymer of polyvinylpyrrolidone (PVP) and hydroxyapatite (HA) were obtained. HA was synthesized in situ in the polymer solution. We applied electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) approaches to study the composite films' properties. The application of EPR in two frequency ranges allowed us to derive spectroscopic parameters of the nitrogen-based light and radiation-induced paramagnetic centers in HA, PVP and PVP-HA with high accuracy. It was shown that PVP did not significantly affect the EPR spectral and relaxation parameters of the radiation-induced paramagnetic centers in HA, while light-induced centers were detected only in PVP. Magic angle spinning (MAS) 1H NMR showed the presence of two signals at 4.7 ppm and -2.15 ppm, attributed to "free" water and hydroxyl groups, while the single line was attributed to 31P. NMR relaxation measurements for 1H and 31P showed that the relaxation decays were multicomponent processes that can be described by three components of the transverse relaxation times. The obtained results demonstrated that the applied magnetic resonance methods can be used for the quality control of PVP-HA composites and, potentially, for the development of analytical tools to follow the processes of sample treatment, resorption, and degradation.

Polyvinylpyrrolidone-Alginate Film Barriers for Abdominal Surgery: Anti-Adhesion Effect in Murine Model.

Surgical operations on the peritoneum are often associated with the formation of adhesions, which can interfere with the normal functioning of the internal organs. The effectiveness of existing barrier materials is relatively low. In this work, the effectiveness of soluble alginate-polyvinylpyrrolidone (PVP-Alg) and non-soluble Ca ion cross-linked (PVP-Alg-Ca) films in preventing these adhesions was evaluated. Experiments in vivo were performed on mice via mechanical injury to the adjacent peritoneum wall and the caecum, followed by the application of PVP-Alg or PVP-Alg-Ca films to the injured area. After 7 days, samples from the peritoneal wall and caecum were analyzed using histology and quantitative polymerase chain reaction (qPCR). It was shown that the expression of genes responsible for adhesion formation in the caecum in the PVP-Alg group was comparable to that in the control group, while in the PVP-Alg-Ca group, it increased by 5-10 times. These results were consistent with the histology: in the PVP-Alg group, the adhesions did not form, while in the PVP-Alg-Ca group, the adhesions corresponded to five points on the adhesion scale. Therefore, the formation of intraperitoneal adhesions can be effectively prevented by non-crosslinked, biodegradable PVP-Alg films, whereas cross-linked, not biodegradable PVP-Alg-Ca films cause inflammation and adhesion formation.

Polyvinylpyrrolidone-Alginate-Carbonate Hydroxyapatite Porous Composites for Dental Applications.

An alternative approach for the currently used replacement therapy in dentistry is to apply materials that restore tooth tissue. Among them, composites, based on biopolymers with calcium phosphates, and cells can be applied. In the present work, a composite based on polyvinylpyrrolidone (PVP) and alginate (Alg) with carbonate hydroxyapatite (CHA) was prepared and characterized. The composite was investigated by X-ray diffraction, infrared spectroscopy, electron paramagnetic resonance (EPR) and scanning electron microscopy methods, and the microstructure, porosity, and swelling properties of the material were described. In vitro studies included the MTT test using mouse fibroblasts, and adhesion and survivability tests with human dental pulp stem cells (DPSC). The mineral component of the composite corresponded to CHA with an admixture of amorphous calcium phosphate. The presence of a bond between the polymer matrix and CHA particles was shown by EPR. The structure of the material was represented by micro- (30-190 µm) and nano-pores (average 8.71 ± 4.15 nm). The swelling measurements attested that CHA addition increased the polymer matrix hydrophilicity by 200%. In vitro studies demonstrated the biocompatibility of PVP-Alg-CHA (95 ± 5% cell viability), and DPSC located inside the pores. It was concluded that the PVP-Alg-CHA porous composite is promising for dentistry applications.

1H NMR and EPR Spectroscopies Investigation of Alginate Cross-Linking by Divalent Ions.

Alginate is a natural polymer widely applied in materials science, medicine, and biotechnology. Its ability to bind metal ions in order to form insoluble gels has been comprehensively used to create capsules for cell technology, drug delivery, biomedical materials, etc. To modify and predict the properties of cross-linked alginate, knowledge about the mechanism of alginate binding with metal ions and the properties of its gels is necessary. This article presents the results obtained by proton Nuclear Magnetic Resonance Spectroscopy for alginate containing calcium and strontium (alkaline earth metal diamagnetic) ions and by Electron Paramagnetic Resonance Spectroscopy for alginate with copper (Cu) and manganese (Mn) (transition metal paramagnetic) ions. It was found that in the case of calcium (Ca) and Mn ions, their concentration does not affect their distribution in the alginate structure and the cross-linking density. In the case of strontium (Sr) and Cu ions, their number affects the number of binding sites and, accordingly, the cross-linking density. Thus, the cross-linking of alginate depends mainly on the characteristics of specific cations, while the nature of the bond (ionic or coordination type) is less important.

Strontium Substituted ß-Tricalcium Phosphate Ceramics: Physiochemical Properties and Cytocompatibility.

Sr2+-substituted ß-tricalcium phosphate (ß-TCP) powders were synthesized using the mechano-chemical activation method with subsequent pressing and sintering to obtain ceramics. The concentration of Sr2+ in the samples was 0 (non-substituted TCP, as a reference), 3.33 (0.1SrTCP), and 16.67 (0.5SrTCP) mol.% with the expected Ca3(PO4)2, Ca2.9Sr0.1(PO4)2, and Ca2.5Sr0.5(PO4)2 formulas, respectively. The chemical compositions were confirmed by the energy-dispersive X-ray spectrometry (EDX) and the inductively coupled plasma optical emission spectroscopy (ICP-OES) methods. The study of the phase composition of the synthesized powders and ceramics by the powder X-ray diffraction (PXRD) method revealed that ß-TCP is the main phase in all compounds except 0.1SrTCP, in which the apatite (Ap)-type phase was predominant. TCP and 0.5SrTCP ceramics were soaked in the standard saline solution for 21 days, and the phase analysis revealed the partial dissolution of the initial ß-TCP phase with the formation of the Ap-type phase and changes in the microstructure of the ceramics. The Sr2+ ion release from the ceramic was measured by the ICP-OES. The human osteosarcoma MG-63 cell line was used for viability, adhesion, spreading, and cytocompatibility studies. The results show that the introduction of Sr2+ ions into the ß-TCP improved cell adhesion, proliferation, and cytocompatibility of the prepared samples. The obtained results provide a base for the application of the Sr2+-substituted ceramics in model experiments in vivo.

Composite Polyvinylpyrrolidone-Sodium Alginate-Hydroxyapatite Hydrogel Films for Bone Repair and Wound Dressings Applications.

Today, the synthesis of biocompatible and bioresorbable composite materials such as "polymer matrix-mineral constituent," which stimulate the natural growth of living tissues and the restoration of damaged parts of the body, is one of the challenging problems in regenerative medicine. In this study, composite films of bioresorbable polymers of polyvinylpyrrolidone (PVP) and sodium alginate (SA) with hydroxyapatite (HA) were obtained. HA was introduced by two different methods. In one of them, it was synthesized in situ in a solution of polymer mixture, and in another one, it was added ex situ. Phase composition, microstructure, swelling properties and biocompatibility of films were investigated. The crosslinked composite PVP-SA-HA films exhibit hydrogel swelling characteristics, increasing three times in mass after immersion in a saline solution. It was found that composite PVP-SA-HA hydrogel films containing HA synthesized in situ exhibited acute cytotoxicity, associated with the presence of HA synthesis reaction byproducts-ammonia and ammonium nitrate. On the other hand, the films with HA added ex situ promoted the viability of dental pulp stem cells compared to the films containing only a polymer PVP-SA blend. The developed composite hydrogel films are recommended for such applications, such as membranes in osteoplastic surgery and wound dressing.