Minimally invasive surgery for the restoration of bone tissues lost due to diseases and trauma is preferred to reduce patient complications and health care costs. The current challenge is to design material at the site of surgery with specific behaviors for mimicking the natural structures and delivering appropriate signals to cells promoting tissue repair/regeneration. Selection of a suitable injectable is often based on material characteristics (including mechanical properties, drug release kinetics and degradation) that serve for the specific treatment function. Micro or nano-structured materials in the form of gels, nanoparticles and nano-composites have gained increasing interest in regenerative medicine because they are able to mimic the physical features of natural extracellular matrix (ECM) at the sub-micro and nano-scale levels. Different strategies are implemented for engineering bioactive and osteoinductive injectable materials to optimize their interfaces with cells and bone tissue environments.
Here, it discussed injectable bone materials integrating biphasic calcium phosphate nanoparticles prepared by sol-gel synthesis with different polymers, nano-materials and antimicrobial compounds for specific bone infections conditions.
Innovative natural polymer-based double network hydrogels (DNs) were developed by a two-step network-formation procedure to obtain photocrosslinkable methacrylated hyaluronic acid (HAMA) and maleated hyaluronic acid (MAHA). Different chemical modification of hyaluronic acid (HA) followed by the development of nanocomposites hydrogels were directly prepared in situ by sol-gel synthesis . Furthermore, injectable hybrid material based on graphene oxide nanosheets and hydroxyapatite prepared by sol-gel approach is described. The presence of GO increases the bioactive and osteogenic material properties.
One more approach is based on the use of antimicrobial injectable materials . Several systems based on Ionic Liquids (IL) at different alkyl-chain length incorporated in Hydroxyapatite through the sol-gel process were developed to obtain an injectable material with simultaneous opposite responses toward osteoblasts and microbial proliferation.
In vitro cell tests to assess the osteogenic potential of the synthesized biomaterials were performed using human mesenchymal stem cells (hMSC) and the expression of specific osteogenic markers (ALP, OCN) was analyzed.
Nanocomposite materials based on chemically modified HAs and in situ sol-gel CaP, were successfully developed and characterized in terms of physico-chemical, morphological, mechanical and biological properties. Injectable bone materials integrating BCP nanoparticles with HA based materials, GO and IL were successfully synthesized. For HA-GO system, it was found that the spindle-like hydroxyapatite nanoparticles were intercalated between GO nanosheets. The oxygen-containing functional groups of GO sheets play an important role in anchoring calcium ions, as demonstrated by FTIR and TEM investigations, thus improving the bioactive and osteogenic properties. The systems based on CaP-ILs showed a higher osteogenic activity and antimicrobial performance by increasing the IL alkyl chain. These systems are able to induce osteogenic differentiation and also inhibit biofilm formation.
The results indicated that all the proposed injectable materials can be considered a high-performance bone filler in the treatment of bone defects."