The present review briefly outlines the most recent patents and journals on various aspects of porous calcium phosphate bioceramics including techniques of preparation, properties and bone implant applications. Bioactive ceramics are a class of materials that have capability to bond directly with the host bone. These materials can be easily assimilated by the body and are considered to be biodegradable. Researches have revealed that artificial bones made from hydroxyapatite or a combination of hydroxyapatite (HA) and tricalcium phosphate (TCP) is a perfect substitute for natural bone owing to its excellent biocompatibility and properties close to that of human bone. Bioceramics made of HA are available in dense and porous forms. Several efforts on the fabrication of porous calcium phosphate bioceramics have been carried upon in the field of clinical orthopaedics. The realisation of these efforts can be observed from the fact that numerous patents have been filed on methods of preparing porous calcium phosphate bioceramics for bone implant applications. A number of porous HA ceramics have been developed for applications in both tissue engineering and drug delivery systems. Porous bodies are decomposable in human body and provide a surface for proliferation and growth of cells that are infiltrated from the surrounding tissues so that a new bone grows into the pores and prevents any movement or loosening of the implants. Consequently, these can be used for filling the damaged bone, repair of fractured bone and even can be used as hard tissue replacements. Several processing techniques have been employed for fabrication of porous scaffolds. Among prominent techniques are gel casting, slip casting, camphene-based freeze casting and polymeric-sponge method.
Biphasic calcium phosphate powders doped with zinc (Zn-doped BCP) were synthesized via sol-gel technique. Different concentrations of Zn have been successfully incorporated into biphasic calcium (BCP) phases namely: 1%, 2%, 3%, 5%, 7%, 10% and 15%. The synthesized powders were calcined at temperatures of 700-900°C. The calcined Zn-doped BCP powders were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential and thermogravimetric analysis (TG/DTA) and field-emission scanning electron microscopy (FESEM). X-ray diffraction analysis revealed that the phases present in Zn-doped are hydroxyapatite, β- TCP and parascholzite. Moreover, FTIR analysis of the synthesized powders depicted that the bands of HPO4 increased meanwhile O-H decreased with an increase in the calcination temperature. Field emission scanning electron microscopy (FESEM) results showed the agglomeration of particles into microscale aggregates with size of the agglomerates tending to increase with an increase in the dopant concentration.
The present study was aimed at fabricating porous ceramic scaffolds via polymeric sponge method for biomedical applications using as synthesized Zinc doped Hydroxyapatite (ZnHA) powders. Zn doped HA powders were prepared via sol-gel method using diammonia hydrogen phosphate [(NH4)2HPO4] and calcium nitrate tetrahydrate [Ca (NO3)2.4H2 as starting materials. The obtained powders were then used for the preparation of porous ZnHA scaffolds via polymeric sponge method. The green porous bodies so developed by impregnating cellulosic sponges with HA slurries, were subjected to sintering process at a temperature of 1300 Field-emission scanning electron microscopy (FESEM) was used to observe the surface morphology of the powder and sintered porous sample. The structure and crystallinity of (Zn)HA powder and the sintered porous samples was analyzed using X-ray diffractometer whereas Fourier transform infrared spectroscopy (FTIR) was used to determine the presence of various phases in the powder. FESEM results showed the formation of agglomerates at an increased Zn concentration. The morphology of the porous samples showed high degree of fusion and densification with an increase in Zn concentration. Preliminary mechanical testing results show that maximum compression strength of HA porous bodies was 0.12 MPa.
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