Cork-derived hierarchically porous hydroxyapatite with different stoichiometries for biomedical and environmental applications

abstract

Hydroxyapatite (HA, Ca-10(PO4)(6)(OH)(2)) is the major mineral component of human bone, but has a wide range of interesting and useful properties, and many applications beyond biomedicine. Here we produce HA-based materials from a naturally templated precursor which can have a variety of tailored microstructures and hierarchical porosities, and we investigate their use as designed functional materials for several applications. HA-based materials with different stoichiometries of Ca/P = 1.67 (HA) and 1.5 (Ca-deficient HA) were successfully synthesised from a previously prepared and reported cork-derived CaCO3. The CaCO3 was reacted with a phosphorus containing precursor solution at 60 degrees C, and also successively recalcined at 700 degrees C. The samples prepared at 60 degrees C maintained the 3D honeycomb structure of similar to 20 mu m hexagonal cells typical of cork, and showed high specific surface areas (SSA > 85 m(2) g(-1)) and a high mesoporosity (average mesopores similar to 10-15 nm). These features made them suitable for environmental remediation applications such as heavy metals (i.e. lead) removal from water, with calcium-deficient HA (higher degree of mesoporosity) adsorbing >99% of Pb(ii) ions from solutions containing up to 1.5 g of lead per L. Recalcined samples (SSA = 29 m(2) g(-1)), on the other hand, had very low cytotoxicity towards MG-63 osteoblasts, showing them to be biocompatible for biomaterials. All had cell viabilities of over 70% against a control, and the calcium-deficient HA proved to be even less cytotoxic than the control (>100% viability after 24 and 48 h). Therefore, cork was shown to be an excellent template agent for the design of HA materials with varied properties, tailored for different applications in the environmental and biomedical fields.

keywords

CALCIUM-CARBONATE; CERAMICS; ECOCERAMICS; LEAD; ADSORPTION; MORPHOLOGY; PHOSPHATE; REMOVAL; CADMIUM; ENHANCE

subject category

Chemistry, Multidisciplinary; Materials Science, Multidisciplinary

authors

Scalera, F; Quarta, A; Tobaldi, DM; Pullar, RC; Piccirillo, C

Groups

G4 - Renewable Materials and Circular Economy

Projects

Solar thermochemical production of hydrogen based on cork Ecoceramics (H2CORK)

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Collaboratory for Emerging Technologies, CoLab (EMERGING TECHNOLOGIES)

acknowledgements

Clara Piccirillo and Francecsa Scalera would like to thank Fondazione con il Sud for funding the HApECOrk project (project 2015-0243). Robert Pullar would like to thank the FCT (FundacAo para a Ciencia e a Tecnologia, Portugal) Grant IF/00681/2015 for supporting this work, along with FCT project H2CORK (PTDC/CTM-ENE/6762/2014), and this work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement. Alessandra Quarta would like to thank Tecnopolo per la medicina di precisione (TecnoMed Puglia) - Regione Puglia: DGR no. 2117 del 21/11/2018, CUP: B84I18000540002 and Tecnopolo di Nanotecnologia e Fotonica per la medicina di precisione (TECNOMED) - FISR/MIUR-CNR: delibera CIPE no. 3449 del 7-08-2017, CUP: B83B17000010001. David M. Tobaldi was funded by the project EleGaNTe - PON ARS01_01007. The authors would like to thank Dr. I. Vilarinho for her help with the surface area measurements.