Synthesis of Graphene-Hydroxyapatite Nanocomposites for Potential Use in Bone Tissue Engineering

This work explains the strategy to fabricate novel composites of nano hydroxyapatite and graphene nanoribbons with opposite orientations. These biomaterials are significant for developing bone tissue engineering scaffolds. This is a simple one pot synthesis.

It is a rapid, effective, and economical method. This work is extremely relevant with the context of treating bone injuries and associated ailments where more bone tissue regeneration will promote rapid healing. To begin, synthesize the pristine nanoparticles of hydroxyapatite using 50 milliliters of the reaction mixture.

Dropwise, add 25%ammoniumhydroxide to maintain a pH of around 10. Thereafter, agitate the reaction mixture by ultrasound irradiation for 30 minutes. Allow the resulting solution to mature for 120 hours at room temperature until the white precipitate of nanoparticles of hydroxyapatite settles out.

Recover the nanoparticles of hydroxyapatite by centrifugation at 1, 398 x g for five minutes at room temperature. Wash the precipitate with deionized water three times. To prepare the nHAP/GNR nanocomposite, use a cofunctionalization strategy, start with dissolving five milligrams of graphene nanoribbons in a mixture of one molar calcium nitrate tetrahydrate and 0.67 molar diammonium hydrogen phosphate to a 50 milliliter final volume.

During this reaction, add 25%of ammonium hydroxide dropwise to maintain the pH at approximately 10. Agitate the resulting mixture by ultrasonication for 30 minutes. After completion of the reaction, leave the solution undisturbed for 120 hours at room temperature until maturation.

Observe for the formation of a gelatinous precipitate of nanoparticles of hydroxyapatite, which coats the graphine nanoribbons, following which a white precipitate of nHAP/GNR settles. Wash the precipitate three times by centrifugation at 1, 398 x g for five minutes at room temperature followed by redispersion in deionized water. To synthesize GNR/nHAP nanocomposites, suspend commercially available nanoparticles of hydroxyapatite at a concentration of five milligrams per milliliter in 50 milliliters of deionized water, supplemented with five milligrams of graphine nanoribbons.

Agitate the resulting mixture by ultrasonication for 30 minutes, and thereafter, leave the mixture undisturbed for 120 hours at room temperature. After maturation, recover the white precipitate of the resulting GNR/nHAP by centrifugation at 1, 398 x g for five minutes at room temperature. Wash the sample three times using deionized water.

The HRTEM analysis of nHAP/GNR nanocomposite showed nHAP patches between 150 to 250 nanometers in length and width. Elemental mapping confirmed that the intermediated nodal patches on the GNRs were indeed nHAP due to the presence of elemental calcium and phosphorus. In GNR/nHAP nanocomposites, the GNR formed thin films on the surface of the spherical nHAP nanoparticles.

The EDS analysis showed a clear increase in the carbon content due to GNRs, while the peaks specific to calcium and phosphorus were due to nHAP. The marked increase in the carbon content in the nHAP/GNR spectrum is due to the majority of the GNRs onto which only small patches of freshly synthesized nHAP were observed. XRD analysis confirmed the hexagonal crystal structure of the nHAP strong peaks corresponding to 002, 102, 211, 300, 202, 310, 113, 222, and 213 planes, respectively, confirmed the purity of the as-synthesized nHAP.

TGA analysis showed a steady decrease in mass after 200 degrees Celsius up to 500 degrees Celsius due to the crystallization of nHAP. Further heating led to the decomposition of the complexes. Lost due to the presence of GNRs was found to be between 0.5 and 0.98%in GNR/nHAP and nHAP/GNR.

The sequence of addition of reagents and reaction conditions are most critical to get the desired reverse orientation of the nanocomposites. Cell lines-based studies can be performed to check the potential of the nanocomposites to promote osteogenesis. This will open a new area of orientation-mediated modulation of cellular response for tissue engineering.