Calcium polyphosphate endows silk fibroin hydrogels with enhanced osteogenesis for bone function restoration

Area of Science:

• Biomaterials Science
• Regenerative Medicine
• Biochemistry

Background:

• Conventional crystalline calcium phosphates have limitations in bone defect repair due to poor solubility and slow resorption.
• Developing biomaterials with both mechanical strength and osteogenic potential is crucial for effective bone regeneration.

Purpose of the Study:

• To develop and characterize novel amorphous, hydrophilic, and bioactive calcium polyphosphate (CaPP) and regenerated silk fibroin (RSF) composite hydrogels.
• To investigate the influence of CaPP's degree of polymerization (DP) on the composite hydrogel properties and osteogenic performance.

Main Methods:

• Amorphous CaPP particles with tunable DP were synthesized using precursor ratio modulation and ion exchange.
• RSF-CaPP composite hydrogels were fabricated via covalent and physical crosslinking using enzyme and ethanol treatment.
• Mechanical properties, Ca2+ release, in vitro degradation, and in vitro/in vivo osteogenesis were evaluated.

Main Results:

• Composite hydrogels exhibited tunable mechanical properties, Ca2+ release kinetics, and degradation rates dependent on CaPP's DP.
• In vitro and in vivo studies demonstrated significantly enhanced osteogenic performance of the RSF-CaPP composites.
• The degree of polymerization of CaPP critically influenced the hydrogel's bioactivity and bone regeneration capacity.

Conclusions:

• Amorphous calcium polyphosphate (CaPP) with controlled chain length acts as a key bioactive component in composite hydrogels.
• Regenerated silk fibroin (RSF)-CaPP hydrogels show great potential as advanced biomaterials for bone defect repair and functional restoration.