Hydroxyapatite Nanobelt/polylactic Acid Janus Membrane With Osteoinduction/barrier Dual Functions For Periodontal Bone Regeneration

Background and Objective:Periodontitis is a kind ofinflammatory disease leading to tooth loss,alveolar bone absorption and eventually disorder of masticatory function.Guided tissue regeneration(GTR)is one of the most common strategies for the regeneration of lost periodontium.Hydroxyapatite(HAp)and polylactic acid(PLA)both are biomaterials which could be used in GTR approved by Food and Drug Administration(FDA).HAp can promote bone regeneration,and PLA mainly plays the role of barrier.During surgical process,osteoinduction materials and barrier membrane are usually placed in defect area respectively,which could add the risk of infection and bleeding as well as surgery difficulty.In order to solve this problem,we were inspired by Janus and introduced a new kind of HAp nanobelt modified PLA membrane to achieve barrier/osteoinduction dual functions.The side of HAp is hydrophilic which can inductthe regeneration of bone while the side of PLA canprovide the regenerative space by prohibiting the growth of fibrous connective tissue such as gingiva around defect area.The aim of this study was to produce a new kind of HAp/PLA Janus composite membrane and measure its topographic and physicochemical properties.Then a rat mandible bony defect model was establishedto investigate the barrier and osteoinductive effects of this composite membrane.Materials&Methods:A HAp nanobelt/PLA(HAp/PLA)Janus membrane was prepared in this study by coating PLA on a paper-like HAp nanobelt film with a casting-pervaporation method.The topography of HAp nanobelts,PLA membrane and two sides of the composite membrane were observed underscanning electron microscope(SEM)and transmission electron microscope(TEM).X-ray diffraction(XRD)spectra of HAp nanobelts and PLA were observed by a Bruker D8 advance powder diffractometer.Fourier transform infrared spectroscopy(FTIR)spectra of HAp nanobelts and PLA were obtained on a Thermo Nexus 670 spectrometer.High-resolution transmission electron microscope(HRTEM)image was observed under Philips Tecnai 20U-Twin high resolution electron microscope.A bilateral rat mandible bony defect model was eatablished and covered by PLA membrane or HAp/PLA Janus composite membrane.There was also a negative control group treated with nothing.The mandible samples were collected at 3 days,1,2,4,8 weeks after surgery then the effects of functional cells engraftment and osteoinduction were detected by SEM,histomorphometric measurement,immunohistochemistry(IHC)staining and micro-computed tomography(Micro CT)scanning.Results:After composition,the physicochemical property measurementsindicated that the two sides of the composite membrane did notchange.An area of transition section was also observed under SEM which demonstrated a good combination of these two kinds of materials.Duringthe process of gross anatomy,PLA and HAp/PLA group showed no sign of postoperative adhesion between bones and the adjacent soft tissues,while the negative control group showed serious adhesion.SEM images showed HAp side could engraft more functional cells than PLA side.The histomorphometric measurementshowed HAp/PLA could enhance new bone formation in quantity and quality.The result of IHC staining suggested HAp/PLA could promote the expression of bone-related markers alkaline phosphatase(ALP),osteocalcin(OCN)and collagen I(Col I).Moreover,Micro CT also demonstrated there were more newly formed bones with better quality in HAp/PLA group.Because its barrier/osteoinductiondual functions and low cost of production,this HAp/PLA membrane would be a promising biomaterial in oral tissue engineering for precise bone regeneration.Conclusion:The composite membrane was synthesized by casting PLA to the HAp nanobeltpaper-likefilm.The PLA side possesses hydrophobicity and smooth surface which can prohibit cell attachment thus prevent connective and epithelial tissue growing into defect area during the process of bone regeneration.Therefore,the PLA side of this composite membrane could provide spaces for functional cells to migrate and grow in the defect area while HAp side endows hydrophilicity and rough surface which is beneficial for functional cells such as stem cells or precursor cells adhering,proliferating and differentiating.Since HAp is one of the main components of bone tissue,once implanted in the defect area,it could recruitmorefunctional cells then promote their osteogenic differentiation and increase the expression of bone-related markers.Thus,HAp could enhance new bone formation in quantity and quality which is beneficial to bone repair and regenerationin periodontal defect area.The results in this present study suggested that this HAp/PLA composite membrane with barrier/osteoinduction dual functions had significant potential for oral tissue engineering.