In-vitro and in-vivo evaluation for the bio-natural Alginate/nano-Hydroxyapatite (Alg/n-HA) injectable hydrogel for critical size bone substitution.

Currently, bio-natural injectable hydrogels are receiving a lot of attention due to their ability to control, adjust, and adapt to random bone defects, in addition, to their ability to mimic the composition of natural bones. From such a viewpoint, this study goal is to prepare and characterize the injectable hydrogels paste based on the natural alginate (Alg) derived from brown sea algae as a polysaccharide polymer, which coupled with nano biogenic-hydroxyapatite (n-HA) prepared from eggshells and enriched with valuable trace elements. The viscosity and mechanical properties of the paste were investigated. As well as the in-vitro study in terms of water absorption and biodegradability in the PBS, biocompatibility and the capability of the injectable Alginate/n-Hydroxyapatite (Alg/n-HA) to regenerate bone for the most suitable injectable form. The injectable hydrogel (BP -B sample) was chosen for the study as it had an appropriate setting time for injecting (13 mins), and suitable compressive strength reached 6.3 MPa. The in vivo study was also carried out including a post-surgery follow-up test of the newly formed bone (NB) in the defect area after 10 and 20 weeks using different techniques such as (SEM/EDX) and histological analysis, the density of the newly formed bone by Dual x-ray absorptiometry (DEXA), blood biochemistry and the radiology test. The results proved that the injectable hydrogels Alginate/n-Hydroxyapatite (Alg/n-HA) had an appreciated biodegradability and bioactivity, which allow the progress of angiogenesis, endochondral ossification, and osteogenesis throughout the defect area, which positively impacts the healing time and ensures the full restoration for the well-mature bone tissue that similar to the natural bone.

Evaluation of Ti/Al alloy coated with biogenic hydroxyapatite as an implant device in dogs' femur bones.

The main target of the present research was a full assessment of the toxicity effects and biocompatibility of a Ti/Al-alloy device coated with biogenic hydroxyapatite (bHA) when implanted in dogs in comparison with those of an uncoated Ti/Al-alloy device. The coating of the alloy was carried out using controlled high-velocity suspension flame spray (HVSFS) technique. Both coated and uncoated devices were implanted in dogs' femur bones for different time periods (45 days and 90 days). Bone-formation ability and healing were followed up, and blood analysis was performed, at Time zero (immediately post surgery), and then at 3 days, 45 days, and 90 days post surgery. Bone mineral density checks, radiological scans of the femur bone, and histological analysis were also conducted. The in-vivo study results proved that implantation of a device made from bHA-coated Ti/Al alloy in dogs' femur bones is completely safe. This is due to the high osteoconductivity of the coated alloy, which enables the formation of new bone and a full connection between new and original bone material. At 90 days post surgery, the coated alloy had been completely digested within the original bone; thus, it appeared as a part of the femur bone and not as a foreign body. Both the scanning electron microscopy with energy-dispersive X-ray and histology analysis findings affirmed the results. Furthermore, the blood tests indicated no toxicity effects during the 90 days of implantation.

In vitro and in vivo study of naturally derived alginate/hydroxyapatite bio composite scaffolds.

Biogenic bioceramics scaffolds are receiving considerable attention for bone restoration applications. Compared with scaffolds of chemical origin, biogenic scaffolds exhibit greater biocompatibility and enhanced bioactive features. In the present study, porous biogenic hydroxyapatite (bHA) was prepared via a polymeric infiltration route and was subsequently coated with alginate to produce alginate/biogenic hydroxyapatite (Alg/bHA) composites. Alginate was used to enhance the mechanical properties as well as the bioactivity and biodegradability of the HA scaffolds. A coating of 3%w/v alginate applied for 10 min was found to result in the best coating for the HA porous scaffolds. The in vitro study demonstrated that the prepared composites had acceptable bioactivity and biodegradability characteristics. The histological study in femur bone of rats indicated that the 3Alg/HA scaffolds capable of supporting both endochondral and intramembranous bone formation. The defect was fully regenerated and mostly filled with the mature lamellar bone after 6 months, with Ca/P atomic ratio similar to the rat's normal bone. The studied scaffolds provide a promising therapeutic option to enhance local bone healing because they do not damage liver or kidney functions and do not induce carcinogenic or inflammatory effects. Accordingly, 3Alg/HA scaffolds are recommended for the tissue engineering applications.

Influence of the thermal treatment on the characteristics of porous geopolymers as potential biomaterials.

Highly porous sodium geopolymer structures were successfully produced through the chemical direct foaming approach at ambient temperature. The impact of the thermal treatment, as well as the influence of various additions of hydrogen peroxide, as a foaming agent, on the porosity, microstructure and mechanical characteristics of the produced geopolymers was investigated. The evaluation of bioactivity was carried out by assessing the formation of an apatite layer on the samples' surface, using scanning electronic microscopy and inductively coupled plasma spectrometry for the simulated body fluid solution, in which the geopolymer samples were kept up to 28 days. In addition, the biodegradability was estimated through the weight change of the samples and pH-measurements. The results demonstrated that the geopolymer foams, produced using 4.5 vol% H2O2 and heat-treated at 500 °C for 1 h, possessed a high open porosity (71 vol %), excellent compressive strength (3.56 ± 0.27 MPa), and suitable chemical stability. The pH value of SBF solutions, in which these geopolymers were immersed for 28 days, remained close to the physiological one. The in vitro study indicated that the developed geopolymer foams possessed bioactivity, as demonstrated by the formation of apatite particles on their surface after immersion in the simulated body fluid solution for 28 days.

Investigation the impact of ZTA addition on the properties of nano biogenic hydroxyapatite.

The target of the recent study is to achieve a significant inexpensive and eco-friendly way for getting ZTA/HA composites, based on the nano-HA derived from the eggshell biogenic source. Combining simultaneously the porous structure; which is considered as a bone formation key, with developed mechanical properties and adequate biocompatibility, is another purpose of this study. Furthermore, the impact of ZTA addition from 10-30 mass-%, fabricated by uniaxial pressing and sintering at 1200-1300 °C for 2 h, on the physical and mechanical properties, microstructure and phase composition of ZTA/HA composite bodies was investigated. The results demonstrated that the increasing of ZTA content increases the bodies' apparent porosity and decreases the bulk density due to the decomposition of HA into ß-TCP. Where the formation of ß-TCP possessed the predominant impact on the mechanical properties of the sintered ZTA/HA composites. ICP, SEM, EDX and thin film XRD results of composites containing 20 mass-% ZTA affirmed the excellent bioactivity of the bodies.