Hydroxyapatite composites with carbon allotropes: Preparation, properties, and applications

Hydroxyapatite (HA) and its composites with inorganic additives, dopants, and polymers is a rapidly developing branch in the materials chemistry. In particular, carbon allotropes are widely used in these composites being widely applied for medical purposes. Observing a gap of insufficient generalization of recent achievements in the field of the HA/Carbon composites, in this review we present the state of the art of the field of HA composites and hybrids with classic carbon allotropes and nanocarbons. These composites are known for carbon nanotubes, nanofibers, graphene and its oxidized forms, as well as, in a lesser grade, for graphite, fullerenes, nanodiamonds, carbon nanofoams, etc. These composites can be fabricated by a variety of classic and less-common methods, such as co-precipitation (with or without ultrasonic treatment), CVD, hot isostatic pressing, hydrothermal, spark plasma sintering, biomimetic mineralization, thermal and plasma spray, electrochemical and electrophoretic deposition, selfassembling, 3D printing, electrospinning, and lyophilisation, among others. Combination of various synthesis techniques can be also carried out for composite preparation. Natural or synthetic HA can be used as it is for further interaction with carbon allotropes or it can be first prepared and then reacted with carbon counterpart; similarly, carbon allotropes can be introduced into the interaction with HA directly or they can be first synthesized, in particular from biomass. Resulting biocompatible composites can be produced in the form of coatings, powders, and scaffolds and can additionally contain quantitative amounts of third phases, frequently natural or synthetic polymers. In these composites, especially with O-containing functionalizing groups, HA disadvantages could be considerably decreased with simultaneous enhancement of mechanical properties, becoming similar to human bone, chemical stability and biocompatibility, as well as possessing antibacterial effect. GO/G reduction and higher HA decoration were observed in several experiments. The morphology of polymercontaining HA/GO composites can be tuned by variations of GO:polymer ratios. Predominant number of resulting applications of formed HA composites corresponds to the biomedical area, mainly for orthopedic applications/implants, osteoporosis treatment, myocardial, skin and dental regeneration, etc. Other important uses include applications as adsorbents for the elimination of impurities from wastewaters and/or removal/uptake of heavy metal cations, loading several medicines, and energy storage materials. Biocompatibility and hemocompatibility aspects of HA/Carbon composites are also discussed and future developments are proposed. (c) 2023 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Automated summary

Hydroxyapatite (HA) composites with carbon allotropes and nanocarbons are rapidly developing in materials chemistry, especially for medical applications. These composites can be synthesized using various methods and exhibit biocompatibility and hemocompatibility, making them suitable for bone regeneration and wastewater treatment.