Resorbable PCEC/gelatin-bismuth doped bioglass-graphene oxide bilayer membranes for guided bone regeneration

Guided bone regeneration (GBR) is a therapeutic modality applied prior to dental implant placement to increase bone density at the defect site or during placement for directing bone growth around implant. In this study, an asymmetric, bilayer structure was prepared by covalently bonding a dense polycaprolactone-polyethylene glycol-polycaprolactone (PCEC) membrane layer with a hydrogel layer composed of bismuth doped bioactive glass (BG, 45S5) and graphene oxide (GO) particles incorporated in gelatin. Structural and mechanical properties (surface morphology and chemistry, thickness, degradation rate and tensile strength of GBR membranes) were studied. Membranes had a 3D structure having almost 1 mm thickness which is suitable for space filling. Highest tensile strength (TS) (1.71 ± 0.10 MPa, p < 0.001) was observed for membranes having the highest BG containing group (BG20) while lowest TS was observed (1.23 ± 0.11 MPa, p < 0.001) for BG8/GO2 samples. Similarly, hydrolytic degradation of BG20 involving bilayer structures was slower in phosphate buffered saline (PBS) (23% ± 5% in 4 weeks) than other GBR membranes while biodegraded at an equal rate in lipase (BG20 as 72% ± 3%, BG10 as 69% ± 1%, BG8/GO2 as 71% ± 7% and BG2/GO8 as 74% ± 8%). BG8/GO2, displayed lowest gelatin (GEL) release in PBS over 28 d period (175% ± 9% and 164% ± 10% mg_GEL/g_sample, p < 0.001). However, all bilayer membranes displayed a similar rate of degradation in lipase solution and also had similar mineral deposition ability in simulated body fluid. Significantly higher cell proliferation (p < 0.001) and osteogenic differentiation (p < 0.001) of human dental pulp stem cells were observed in BG20 and BG10 membrane groups than all other groups. On the other hand, GO presence decreased both mechanical and osteoinductive properties compared to pure BG counterparts. Collectively, amine introduced (aminolysis) synthetic dense PCEC layer was covalently bonded to composite hydrogel layer to obtain coherent bilayer membranes for GBR. They were successfully produced to have two layers designed to prevent fibrous tissue movement towards bone defect while enabling bone regeneration. BG20 membrane groups demonstrated higher calcium phosphate deposition TS, cellular growth and osteogenic differentiation.