Table 3: The most recent and significant studies on degradation profile, osteoconductivity and mechanical properties of synthetic nanohydroxyapatite incorporated into various types of synthetic polymers.

Author Scaffold Fabrication Technique Major Tests Significant Findings
Degradation Dong et al. (2009) [51] nHA/PU Foaming SBF, in vitro, in vivo SBF test indicated that urethanes degrade through chemical breakage of castor oil followed by the hydrolysis of urethane bonds joining the hard and soft segment.
in vivo degradation of the construct was mainly due to the enzyme digestion of n-HA.
Han et al. (2013) [52] PLLA, NF-PLLA & nHA/NF-PLLA Thermally induced phase separation Physiochemical & in vitro Nanofibrous poly(L-lactide) and nHA/poly(L-lactide) had a significantly faster degradation rate, due to their much larger SSA, compared to poly(L-lactide).
Huang et al. (2013) [95] nHA/ PLLA Melt blending In vitro nHA/PLLA scaffold had a slower rate of degradation than the PLLA scaffold. The nHA/PLLA material sustained its initial mechanical strength better than the pure PLLA scaffold.
Diaz et al. (2014) [96] PLLA & nHA/PLLA Lyophilization Phosphate buffer
Solution
By forming a physical barrier, the nHA nanoparticles decreased the rate of degradation of PLLA scaffolds.
Diaz & Puerto
(2015) [53]
PLCL & nHA/PLCL Thermally induced phase separation In vitro The concentration of nHA significantly affected the degradation rate. The rate of degradation of the scaffolds was significantly slower with the increase of nHA content compared to lower nHA concentrations and that of pure PLCL
Osteoconductivity Tong et al. (2011) [59] Electrospun PHBV & CHA/PHBV Nanomulsion/electrospinning In vitro CHA/PHBV scaffolds exhibited a significantly higher ALP activity of SaOS-2 cells than the PHBV scaffolds, therefore, suggesting that the presence of CHA nanospheres in electrospun CHA/PHBV nanocomposite fibers was useful for encouraging the cells for the expression of ALP activity.
Fu et al. (2012) [97] PCEC & nHA/PCEC Melt blending/ electrospinning In vitro & in vivo The nHA/PCEC composite scaffolds, implanted in 12 New Zealand white rabbits, had a higher ability to promote guided bone regeneration than that of self-healing control group with no implant.
Zhang et al. (2014) [60] PCL & nHA/PCL Air drying/coagulation In vitro Scaffolds supported hFOBs adhesion, viability and proliferation but ALP activity and mineralised matrix synthesis of these cells was significantly increased on the nHA/PCL scaffolds compared to pristine control. nHA/PCL nanocomposite scaffolds had a higher level of osteogenic differentiation markers and the effect was nHA dose dependent.
Selvakumar et al. (2015) [61] TPU & nanorods nHA/TPU non-ionic surfactant & in situ In vitro Enhanced osteoconductivity of the nanocomposites by successful formation of an apatite layer on the surface of the scaffolds was reported after immersion into SBF.
Mechanical Properties Liu et al. (2010) [63] nHA/PLGA & Wet chemistry precipitation Physiochemical Well-dispersed nHA in PLGA significantly improved tensile modulus, tensile stress at yield, ultimate tensile strength and compressive modulus of the constructs.
Nathanael
et al. (2011) [64]
nHA nanorods/HMWPE & HMWPE Horizontal injection
moulding
Physiochemical Studied nHA nanorods reinforced with high molecular weight polyethylene (HMWPE) and found that the tensile strength and the abrasion resistance were improved in these scaffolds compared to pure HMWPE specimen and nHA.
Sajjadi et al. (2011) [65] nHA/PMMA & PMMA Compression molding Physiochemical It was shown that increased nHA concentration of PMMA/nHA scaffolds decreased wear rate in both atmosphere and artificial saliva, as the presence of nHA has high hardness that can improve sliding wear rate.
Shokrollahi
et al. (2014) [66]
HApUPy & SP PCL/naked nHA Drying under reduced pressure Physiochemical & in vitro Unusually improved mechanical properties were observed in nHA/PCL scaffolds which was explained by the formation of supramolecular clusters around nHA nanoparticles.
Jiang et al. (2014) [67] Unmodified nHA/PLGA, g1-n-HA & g2-n-HA Surface grafting DLLA with and without citric acid Physiochemical A novel method of surface-grafting for nHA incorporated into PLGA showed a 20% improvement on the bending strength and tensile strength of nHA/PLGA scaffolds modified with citric acid compared to pure PLGA with 3 wt% nHA.