Comparison of In Vivo Properties of Hydroxyapatite-Polyhydroxybutyrate Composites Assessed for Bone Substitution

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.

Biodegradable Polymers in Veterinary Medicine-A Review

During the past two decades, tremendous progress has been made in the development of biodegradable polymeric materials for various industrial applications, including human and veterinary medicine. They are promising alternatives to commonly used non-degradable polymers to combat the global plastic waste crisis. Among biodegradable polymers used, or potentially applicable to, veterinary medicine are natural polysaccharides, such as chitin, chitosan, and cellulose as well as various polyesters, including poly(ε-caprolactone), polylactic acid, poly(lactic-co-glycolic acid), and polyhydroxyalkanoates produced by bacteria. They can be used as implants, drug carriers, or biomaterials in tissue engineering and wound management. Their use in veterinary practice depends on their biocompatibility, inertness to living tissue, mechanical resistance, and sorption characteristics. They must be designed specifically to fit their purpose, whether it be: (1) facilitating new tissue growth and allowing for controlled interactions with living cells or cell-growth factors, (2) having mechanical properties that address functionality when applied as implants, or (3) having controlled degradability to deliver drugs to their targeted location when applied as drug-delivery vehicles. This paper aims to present recent developments in the research on biodegradable polymers in veterinary medicine and highlight the challenges and future perspectives in this area.

In vitro characterization of hydroxyapatite and cobalt ferrite nanoparticles compounds and their biocompatibility in vivo

Bioactive materials in combination with antibiotics have been widely developed for the treatment of bone infection. Thus, this work aims to characterize six biomaterials formulated with different concentrations of hydroxyapatite and cobalt ferrite nanoparticles, in addition to the antibiotic ciprofloxacin, using X-ray diffraction (XRD), scanning electron microscopy (SEM), and the antibiotic diffusion test on agar. Furthermore, in vivo biocompatibility and the reabsorption process of these materials were analyzed. XRD showed that both hydroxyapatite and cobalt ferrite present high crystallinity. The photomicrographs obtained by SEM revealed that composites have a complex surface, evidenced by the irregular arrangement of the hydroxyapatite and cobalt ferrite granules, besides demonstrating the interaction between their components. The antibiotic-diffusion test showed that all biomaterials produced an inhibition halo in Staphylococcus aureus cultures. For the biocompatibility study, composites were surgically implanted in the dorsal region of rabbits. At 15, 30, 70, and 100 days, biopsies of the implanted regions were performed. The biomaterials were easily identified during histological analysis and no significant inflammatory process, nor histological signs of toxicity or rejection by the adjacent tissue were observed. We can conclude that the biomaterials analyzed are biocompatible, degradable, and effective in inhibiting the in vitro growth of Staphylococcus aureus. Graphical abstract.

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.

An in vivo study of osteoplastic properties of resorbable poly-3-hydroxybutyrate in models of segmental osteotomy and chronic osteomyelitis

A series of 3D implants and filling materials prepared from powdered biodegradable polymers, polyhydroxyalkanoates (PHAs), have been designed for the purposes of reparative osteogenesis. The 3D implants are made of resorbable polymer of hydroxybutyric acid (poly-3-hydroxybutyrate, P3HB) and a composite of this polymer with hydroxyapatite (HA) (P3HB/HA). The properties of the implants were studied in vivo in a model of segmental osteotomy and compared with commercial material Bio-Oss(®). All implants containing P3HB as the main component facilitate reconstructive osteogenesis. P3HB and P3HB/HA show pronounced osteoplastic properties; their in vivo degradation is slow and corresponds to the growth of a new bone tissue, facilitating normal reparative osteogenesis. Also, powdered P3HB and P3HB/tienam can be used as filling materials for osteoplasty of bone cavities infected by Staphylococcus aureus. Biodegradable 3D implants and P3HB-based filling materials show pronounced osteoplastic properties and degrade in vivo at a slow rate, enabling normal reparative osteogenesis.

Guided tissue regeneration using rigid absorbable membranes in the dog model of chronic furcation defect

OBJECTIVE

Absorbable membranes are used to promote the regeneration of periodontal defects by Guided Tissue Regeneration (GTR). However, their collapse into the defect is commonly reported, impairing regeneration. Therefore, absorbable but rigid membranes aiming at preventing such collapse were developed and analyzed in periodontal regeneration.

MATERIALS AND METHODS

Membranes were analyzed in class II furcation defects in dogs; procedures included periodontal disease induction, prophylaxis and GTR (treated groups) or open flap debridement alone (control group). For GTR, the membranes were made of either 25% hydroxyapatite (HA) in polyhydroxybutyrate matrix (PHB) or 35% HA in PHB. Animals were clinically evaluated for gingival recession, clinical attachment level (CAL) and biopsies were collected at 60 and 120 days. Bone volume, trabeculae number, trabecular thickness and trabecular separation were quantified by micro-computed tomography, followed by histology.

RESULTS

Membrane exposure was observed in both treated groups (25 and 35% HAP) from the 8(th) day after surgery, continuously progressing until 120 days. Mean CAL for all groups remained above normal values for dogs. Bone volumetric values were not significantly different. Partial formation of bone, cementum and periodontal ligament was observed in treated groups. An inflammatory infiltrate was observed in the dense connective tissue that partially filled the center of the treated defects with active osteoclasts on bone surface.

CONCLUSION

Although partial regeneration of the defect was observed, it was limited by wound contamination. Consequently, rigid absorbable membranes made of HA and PHB failed to improve the regeneration of class II furcation defects in dogs.

Desenvolvimento e caracterização de membranas rígidas, osteocondutoras e reabsorvíveis de polihidroxibutirato e hidroxiapatita para regeneração periodontal

A regeneração tecidual guiada (RTG) utiliza membranas para favorecer a regeneração dos tecidos periodontais danificados pela doença periodontal. As membranas usadas ainda apresentam limitações, principalmente quanto à capacidade de manter o espaço do defeito. Dois biomateriais de origem brasileira, a hidroxiapatita (HAP) e o polihidroxibutirato (PHB), foram utilizados para fabricar membranas rígidas para RTG, contendo 25, 35 ou 50% de HAP em matriz de PHB pelo método de moldagem por injeção. As membranas apresentaram alta cristalinidade, sendo que, inicialmente, a topografia de superfície era pouco complexa em que os grânulos de HAP não estavam expostos. As membranas foram desgastadas com broca odontológica, de modo similar à cirurgia para sua implantação in vivo. Este procedimento resultou na exposição dos grânulos de HAP numa superfície com poros e estruturas lineares de dimensões que variaram de 3,55 µm ± 1,14 a 75,98 µm ± 30,76, portanto, característica microtopográfica. Observou-se, ainda, que a HAP é responsável por conferir uma topografia de superfície mais complexa às membranas. Portanto, espera-se que membranas com as características de rigidez e superfície microtopográfica possam proporcionar estabilidade ao defeito periodontal e permitir migração celular mais intensa, assim favorecendo a regeneração periodontal.