CORDIS - EU research results

Intelligent nanocomposite for bone tissue repair and regeneration

Final Report Summary - NANOBIOCOM (Intelligent nanocomposite for bone tissue repair and regeneration)

The main objective of the 'Intelligent nanocomposite for bone tissue repair and regeneration' (NANOBIOCOM) project was to establish the scientific and technological basis for the development new 'intelligent' composite scaffold for bone tissue repair and regeneration with bioactive behaviour capable of activating osteoprogenitor cells and genes and within an in vivo environment provide the interface to respond to physiological and biological changes, with mechanical and structural properties similar to a healthy bone and with size and shape required for reconstructing big skeletal defects.

The main objectives proposed were:
- To optimise osteoblast activation (such as cell proliferation, collagen type I formation, and > 50% accumulation of calcium-containing mineral in the extracellular matrix) pertinent to new bone formation.
- To achieve an 'intelligent' malleable composite for 3D scaffold with match mechanical bone properties. Mechanical properties: compressive/tensile strength, and Young's modulus close to normal cortical bone it should maintain while new bone formation and macroporosity Between 200-400 micrometre to allow for nutrient transport as well as the tailoring of polymer surface chemistry for biological recognition.
- Genetic analysis of the processes controlling bone regeneration. The objective is to understand the temporal and spatial organisation of bone regeneration occurring in fracture repair and to use this understanding to inform the engineering of novel scaffolding materials.
- Increase the potential medical applications. The main application targeted concern large loss of segments of bone in order to increase the rate of new bone formation but this knowledge could be apply to other skeletal defects (cartilages etc).

NANOBIOCOM has developed an intelligent material with the following challenges:
- The bioactivity of the composite, which is rendered by the bioactive components (nanoparticles, carbon nanotubes, polymers) in the composite and/or by external stimulation (BMP's, Electrical Fields, biofunctionalitation) will active osteoprogenitor cells and genes, and consequently promote the tissue growth adjacent to the implant.
- Mechanical and structural properties of the scaffold equal to a healthy bone synchronous with new bone formation. By the incorporation of nanoparticles as carbon nanotubes and nanohidroxiapatite into the composite are expected to be highly suitable reinforcement for the implants of the load bearing structures of our body such as bone and cartilage.
- The size and shape of biodegradable implants. We are going made large segments of implants required for reconstructing big defects capable of supplying similar physical properties and behaviour of healthy bone to be replaced, in contrast with the small implants that are made at present.
- Understanding the genetic programming of bone regeneration. To realise the potential for novel 'intelligent' composite materials to serve as scaffolds for bone regeneration requires that the innate programming mechanisms involved in bone development and repair are effectively harnessed.

The project was structured into 5 work packages (WP), as follows:

WP1- Main nanocomposite requirements
NANOBIOCOM material requirements were defined in the deliverable 1.1 'User requirements report'; the characteristics of proposed materials were explained in the deliverable 1.2 'List of possible polymers, nanoparticles and BMP's'. Deliverable 1.3 presented a list of every material that will be used by the partners in the Nanobiocom's project.

WP2- Production and characterisation of nanocomposite
The original objective was to develop an 'intelligent' bone substitute material matching thefollowing mechanical healthy bone properties:
- Intrinsic mechanical properties (dense material) close to those of cortical healthy bone
- Apparent mechanical properties (macroporous material) close to those of healthy cancellous bone
- Material incorporating an interconnected macroporous network, with a minimum pore diameter of 200…400 micrometers in order to enable early vascularisation and cell penetration in the bulk of the material
- Bioresorbable material, preferably through a process close to bone remodelling
- Osteoconductive material, i. e. allowing new bone growth in close apposition to the residual material.

WP3- Specific cells activation
This workpackage was the core of project and its main objective was to optimise osteoblast activation (such as cell proliferation, collagen type I formation, and accumulation > 50% of calcium-containing mineral in the extracellular matrix) pertinent to new bone formation. The WP3 can be considered as the main working line as it is dedicated to specific cells activation. WP3 was divided in four sub-workpackages:
WP 3.1- Genetic analysis of the processes controlling
WP 3.2- Electrical stimulation
WP 3.3- Morphogenetic factors
WP 3.4- Biofunctionalitation

WP4- Integration and matrix validationfinal report
- Integration of cells activation WP's results.
- Isolation, expansion and characterisation in vitro of human primary boneforming cells.
- Seeding of the 3D composites and analysis of the bone-forming activities on the constructs Mechanical and histomorphometrical evaluation of the 3D cultures.
- Complete in vitro testing of bone-forming cell/composite construct.

WP5 - Preclinical test
- To establish an experimental model of fracture healing and non-union by means of a critical size long bone defect.
- To perform experimental surgery in animals reproducing the bioactivity and non-union model.
- To implant the matrix 3D culture and assure his restoration capability
- To evaluate bone quality at the fracture site of different experimental groups by means of several analysis.
- Assure the viability of nanocomposite as medical device.
- Assure the safety of use of potential future industrial application

The main outputs of NANOBIOCOM project, from the biomedical point of view, are:
- An appropriate cell bioactive system to initiate repair and regeneration of bone.
- Intelligent composite for 3D scaffold, which is able to support physiological loading until sufficient tissue regeneration occurs and will be possible manufacture large segments of material.
- A comprehensive gene expression profiles of the temporal regulation of genes during bone development were obtained 'in vitro' (human, rabbit and mouse) even 'in vivo' experiments.

In addition,
- Long time cell culture is possible with this type of materials. The control of the material properties developed during the project let obtain tailored microstructures able to support long time cell cultures and act as cellular scaffolds.
- No sign of toxicity, induced by the composite material has been observed. These promising results encourage further developments of this technology for clinical applications.