Enhanced Osseointegration Capability of Poly(ether ether ketone) via Combined Phosphate and Calcium Surface-Functionalization.

Sunarso Sunarso,Kunio Ishikawa,Kanji Tsuru,Akira Tsuchiya,Riki Toita

doi:10.3390/ijms21010198

Abstract

Biomedical applications of poly(ether ether ketone) (PEEK) are hindered by its inherent bioinertness and lack of osseointegration capability. In the present study, to enhance osteogenic activity and, hence, the osseointegration capability of PEEK, we proposed a strategy of combined phosphate and calcium surface-functionalization, in which ozone-gas treatment and wet chemistry were used for introduction of hydroxyl groups and modification of phosphate and/or calcium, respectively. Surface functionalization significantly elevated the surface hydrophilicity without changing the surface roughness or topography. The cell study demonstrated that immobilization of phosphate or calcium increased the osteogenesis of rat mesenchymal stem cells compared with bare PEEK, including cell proliferation, alkaline phosphatase activity, and bone-like nodule formation. Interestingly, further enhancement was observed for samples co-immobilized with phosphate and calcium. Furthermore, in the animal study, phosphate and calcium co-functionalized PEEK demonstrated significantly enhanced osseointegration, as revealed by a greater direct bone-to-implant contact ratio and bond strength between the bone and implant than unfunctionalized and phosphate-functionalized PEEK, which paves the way for the orthopedic and dental application of PEEK.

Highlights

Poly(ether ether ketone) (PEEK) has attracted increasing attention as a prime candidate for orthopedic and dental implants due to its distinct advantages over metallic implants, including similar mechanical strength to bone, lack of a metal allergy, radiolucency, excellent chemical and sterilization resistance, and easier manufacturing [1,2,3]
We and other research groups reported that surface modification of bioactive elements and functional groups, including calcium, zinc, magnesium, strontium, and phosphate, elevate the biological performance of implants [18,19,20,21,22,23,24,25], whose osseointegration capabilities were further augmented if combined with surface topographical modification [18]
The O1s peak in bare PEEK consisted of two components, as demonstrated by peaks with binding energies (BE) of 531.9 and 533.0 eV ascribed for O=C and O–C bonds, respectively (Figure 2A)

Summary

Introduction

Poly(ether ether ketone) (PEEK) has attracted increasing attention as a prime candidate for orthopedic and dental implants due to its distinct advantages over metallic implants, including similar mechanical strength to bone, lack of a metal allergy, radiolucency, excellent chemical and sterilization resistance, and easier manufacturing [1,2,3]. We and other research groups reported that surface modification of bioactive elements and functional groups, including calcium, zinc, magnesium, strontium, and phosphate, elevate the biological performance of implants [18,19,20,21,22,23,24,25], whose osseointegration capabilities were further augmented if combined with surface topographical modification [18] These elements and functional groups are recognized by the corresponding cell membrane-bound receptors, including a family of phosphate transporters (PiT) [26,27], a calcium-sensing receptor (CaSR) [28,29], a melastatin-like transient receptor potential 7 [30], and a zinc sensing receptor/GPR39 [31], resulting in enhanced cellular responses. The biological performance of a phosphate and calcium co-functionalized PEEK implant has not been clarified

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Discussion

Conclusion