Calcium Orthophosphate (CaPO4) Containing Composites for Biomedical Applications: Formulations, Properties, and Applications

The goal of this review is to present a wide range of hybrid formulations and composites containing calcium orthophosphates (abbreviated as CaPO4) that are suitable for use in biomedical applications and currently on the market. The bioactive, biocompatible, and osteoconductive properties of various CaPO4-based formulations make them valuable in the rapidly developing field of biomedical research, both in vitro and in vivo. Due to the brittleness of CaPO4, it is essential to combine the desired osteologic properties of ceramic CaPO4 with those of other compounds to create novel, multifunctional bone graft biomaterials. Consequently, this analysis offers a thorough overview of the hybrid formulations and CaPO4-based composites that are currently known. To do this, a comprehensive search of the literature on the subject was carried out in all significant databases to extract pertinent papers. There have been many formulations found with different material compositions, production methods, structural and bioactive features, and in vitro and in vivo properties. When these formulations contain additional biofunctional ingredients, such as drugs, proteins, enzymes, or antibacterial agents, they offer improved biomedical applications. Moreover, a lot of these formulations allow cell loading and promote the development of smart formulations based on CaPO4. This evaluation also discusses basic problems and scientific difficulties that call for more investigation and advancements. It also indicates perspectives for the future.

Calcium Orthophosphate-Containing Biocomposites and Hybrid Biomaterials for Biomedical Applications

The state-of-the-art on calcium orthophosphate (CaPO4)-containing biocomposites and hybrid biomaterials suitable for biomedical applications is presented. Since these types of biomaterials offer many significant and exciting possibilities for hard tissue regeneration, this subject belongs to a rapidly expanding area of biomedical research. Through the successful combinations of the desired properties of matrix materials with those of fillers (in such systems, CaPO4 might play either role), innovative bone graft biomaterials can be designed. Various types of CaPO4-based biocomposites and hybrid biomaterials those are either already in use or being investigated for biomedical applications are extensively discussed. Many different formulations in terms of the material constituents, fabrication technologies, structural and bioactive properties, as well as both in vitro and in vivo characteristics have been already proposed. Among the others, the nano-structurally controlled biocomposites, those containing nanodimensional compounds, biomimetically fabricated formulations with collagen, chitin and/or gelatin, as well as various functionally graded structures seem to be the most promising candidates for clinical applications. The specific advantages of using CaPO4-based biocomposites and hybrid biomaterials in the selected applications are highlighted. As the way from a laboratory to a hospital is a long one and the prospective biomedical candidates have to meet many different necessities, the critical issues and scientific challenges that require further research and development are also examined.

A novel chlorhexidine-releasing composite bone cement: Characterization of antimicrobial effectiveness and cement strength

The addition of calcium phosphate fillers or antimicrobials to bone cements seems to produce inferior materials. In this study, a two-solution bone cement composite was designed for high viscosity and high pseudoplasticity to improve injection and mitigate the risk of extravasation. By pre-mixing these cements, the fillers are incorporated into the matrix and should not detrimentally affect the performance properties. To expand the functionality of this cement system, the addition of bioactive and antimicrobial phases were explored. Brushite and chlorhexidine were used as calcium phosphate filler and the antimicrobial phase, respectively. By controlling the free radical quenching mechanism provided by the chlorhexidine molecule, it was possible to achieve high polymer conversion rates. This phenomenon led to cement strength retention while successfully preventing microbial proliferation in an environment exposed to the cement surface. Based on these results, two-solution cement composite prepared with high concentrations of brushite and chlorhexidine diacetate salt hydrate may provide an attractive bioactive and antimicrobial cement for load-bearing applications.

Effect of PLGA/lecithin hybrid microspheres and β-tricalcium phosphate granules on the physicochemical properties, in vitro degradation and biocompatibility of calcium phosphate cement

CPC with beta-TCP granules and PLGA/Lec microspheres reveals better degradability and cell affinity along with proper physicochemical properties.

Intermolecular interactions between salmon calcitonin, hyaluronate, and chitosan and their impact on the process of formation and properties of peptide-loaded nanoparticles

The principal aim of this work was to study the formulation of a ternary complex comprising salmon calcitonin (sCT), hyaluronate (HA), and chitosan (CS) in a nanoparticle (NP) format. As interactions between the constituents are possible, their presence and component mass mixing ratio (MMR) and charge mixing ratio (CMR) were investigated to tune the properties of NPs. Intermolecular interactions between sCT and HA as well as sCT and CS were studied by infrared spectroscopy (FTIR) and dynamic viscosity. The impact of MMR, CMR, and HA molecular weight on the sCT loading capacity in NPs and in vitro release properties was determined. sCT complexes to HA via electrostatic interactions and a support for hydrophobic interactions between sCT and HA as well as sCT and CS was found by FTIR. The sCT/HA complex is soluble but, depending on the mass mixing ratio between sCT and HA, NPs and microparticles were also formed indicative of associative phase separation between HA and sCT. The negatively charged HA/CS/sCT NPs were characterized by very high values (above 90%) of peptide association for the systems tested. Also, high sCT loading up to 50% were achieved. The peptide loading capacity and in vitro release properties were dependent on the NP composition. The zeta potential of the NPs without sCT was negative and ranging from -136 to -36 mV, but increased to -84 to -19 mV when the peptide was loaded. The particle size was found to be smaller and ranging 150-230 nm for sCT/NPs in comparison to NPs without sCT (170-260 nm). Short-term storage studies in liquid dispersions showed that the colloidal stability of NPs was acceptable and no release of sCT was observed for up to 3 days. In conclusion, a range of NP systems comprising sCT, HA, and CS was successfully developed and characterized. Such NPs may be considered as a suitable nanoparticulate format for the delivery of sCT.

Biodegradable uniform microspheres based on solid-in-oil-in-water emulsion for drug delivery: A comparison of homogenization and fluidic device

Based on solid-in-oil-in-water emulsification, we fabricated biodegradable poly(ϵ-caprolactone) microspheres containing gentamicin using conventional homogenization and a fluidic device. The feasibility of the poly(ϵ-caprolactone) microspheres as drug carriers was evaluated in terms of encapsulation efficiency, release behavior of gentamicin, and antimicrobial activity. The poly(ϵ-caprolactone) microspheres prepared using a fluidic device (fluidic device microspheres) had a uniform diameter and a smooth surface, whereas the poly(ϵ-caprolactone) microspheres prepared using conventional homogenization (conventional homogenization microspheres) exhibited polydisperse and a porous structure. At 0.3 wt% of gentamicin concentration, the encapsulation efficiencies of the conventional homogenization and fluidic device microspheres were 39.5% and 72.0%, respectively. In addition, a significant amount of gentamicin was only released initially from the conventional homogenization microspheres, whereas the fluidic device microspheres released gentamicin in a sustained manner for 28 days. These results confirmed the superior performances of the uniform fluidic device microspheres for drug delivery system. We further proposed a model for microsphere formation to explain the difference in performance of the conventional homogenization and fluidic device microspheres.

Sustained release of antibiotics from uniform poly (ε-caprolactone) microspheres prepared by a simple fluidic device with a tapered glass capillary

Uniform poly(ε-caprolactone) microspheres containing a variety of water-soluble antibiotics, such as tobramycin, vancomycin, and gentamicin, were prepared by a simple fluidic device with a pristine or tapered glass capillary. Each type of antibiotic was dispersed in an organic solvent by ball-milling prior to microsphere preparation. The poly(ε-caprolactone) organic solution containing the powder of each antibiotic was introduced as the discontinuous phase into the fluidic device, where an aqueous phase containing surfactant served as the continuous phase. The poly(ε-caprolactone) microspheres were obtained after solvent evaporation. A tapered glass capillary was tested to produce poly(ε-caprolactone) microspheres, leading to the size reduction of the microspheres from 47.46 ± 0.72 to 25.49 ± 1.05 µm without destroying size uniformity. This size range should be suitable for parenteral injection into the human body. The release analysis revealed that gentamicin and vancomycin were released from the poly(ε-caprolactone) microspheres up to approximately 2 months in a more sustained manner than tobramycin, which is due to the solubility difference in the antibiotics in water. The antimicrobial activities of each type of antibiotic released from the poly(ε-caprolactone) microspheres were evaluated using Staphylococcus aureus and Escherichia coli.

Biodegradable poly(butylene-carbonate) porous membranes for guided bone regeneration: In vitro and in vivo studies

Poly(butylene-carbonate) is a potential alternative to poly(ε-caprolactone) for biomedical application. Although mechanical properties of porous poly(butylene-carbonate) membranes were inferior to poly(ε-caprolactone), its contact angles (47.41° ± 1.17°) were lower than poly(ε-caprolactone) (77.24° ± 0.54°) (p < 0.001). It degraded faster than poly(ε-caprolactone) during a 10-week in vitro experiment (p < 0.01). Moreover, it had excellent bioactivity during simulated body fluid immersion. Cell spreading on poly(butylene-carbonate) was better than that on poly(ε-caprolactone). Cell behavior tests including cytotoxicity, proliferation, and differentiation were performed. The poly(butylene-carbonate) is more compatible with cells and promotes cell differentiation. In vivo, the defects covered by poly(butylene-carbonate) and poly(ε-caprolactone) membranes had a similar degree of regeneration at 4 weeks. It was concluded that poly(butylene-carbonate) could potentially be used to guide bone regeneration, and it is a potential new biodegradable polymer.