Large 3D porous scaffolds made of active hydroxyapatite obtained by biomorphic transformation of natural structures and process for obtaining them

Inventors

Tampieri, Anna • Sprio, Simone • Ruffini, Andrea

Assignees

Greenbone Ortho Srl • Consiglio Nazionale delle Richerche CNR

Abstract

The present disclosure relates to a hydroxyapatite obtained from porous wood, having high compressive strength and dimensions suitable for clinical applications. The porous wood has a porosity of between about 60% and about 95%, said porosity being measured after subjecting the wood to a step of pyrolysis, and is selected from among rattan, pine, abachi, balsa, sipo, oak, rosewood, kempas and walnut wood. The hydroxyapatite may be substituted with one or more ions such as magnesium, strontium, silicon, titanium, carbonate, potassium, sodium, silver, gallium, copper, iron, zinc, manganese, europium, gadolinium. Also disclosed is a bone substitute comprising hydroxyapatite obtained from porous wood. The bone substitute is utilized for the substitution and regeneration of a bone or a bone portion, preferably for bones subjected to mechanical loads, such as long bones of the leg and arm, preferably the tibia, fibula, femur, humerus and radius. The invention relates also to a process for manufacturing a biomorphic hydroxyapatite scaffold from wood.

Core Innovation

The invention provides a biomorphic hydroxyapatite scaffold obtained from a wood template, where the wood is subjected to pyrolysis prior to measuring total porosity. The resulting scaffold is defined by a maximum length dimension greater than or equal to 2 cm and a total porosity of at least 20%, with an emphasized range of 60% to 95% in one embodiment. The porous wood template yields a biomorphic hydroxyapatite with a hierarchically organized pore architecture.

The scaffold derived from pyrolyzed wood has a hierarchically organized pore structure, including channel-like pores with interconnectivity between micro- and nano-pores. In one described refinement, 30% to 80% of total porosity corresponds to pores smaller than 150 μm in diameter, with the remaining porosity corresponding to pores larger than 150 μm in diameter. These structural constraints are directed to clinically relevant scaffold dimensions and pore organization.

The invention additionally defines enhanced mechanical strength and performance related to bone substitution and cellular response. The scaffold includes compressive strength measured along the longitudinal direction greater than 5 MPa, with described outcomes including longitudinal compressive strength up to about 16 MPa and an increased specific surface area in the range of about 9–20 m²/g. The described transformation process is multistep, including pyrolysis followed by carburization, oxidation, hydration, carbonation, and phosphatization, with a reduced-pressure carburization step stated to preserve micro/nano-porosity and improve pore distribution during scale-up to scaffolds with length ≥ 2 cm.

Claims Coverage

The independent claims cover two closely related subject matters: a biomorphic hydroxyapatite scaffold derived from pyrolyzed wood with a total porosity of at least 20% and a maximum length dimension of at least 2 cm, and a biomorphic hydroxyapatite derived from pyrolyzed wood with total porosity between 60% and 95%, a hierarchically organized pore structure, and longitudinal compressive strength greater than 5 MPa. Across the claim set, the main inventive elements are the pyrolysis-defined porous wood-to-hydroxyapatite biomorphic conversion with clinically relevant size, hierarchical pore structure, and directional compressive strength, optionally further specifying pore-size fractions, specific surface area, selected ion substitution, and enumerated wood sources.

Across the independent claims, the coverage focuses on biomorphic hydroxyapatite obtained from pyrolyzed porous wood with total porosity constraints and clinically relevant maximum length (≥ 2 cm in one claim), while also requiring a hierarchically organized pore structure and a longitudinal-direction compressive strength greater than 5 MPa. Dependent claims further narrow the subject matter by specifying pore-diameter fractions, a specific surface area threshold, partial hydroxyapatite ion substitution with selected ions, and enumerated wood species.

Stated Advantages

Documented Applications