Cicada&Catkin Inspired Dual Biomimetic Antibacterial Structure For The Surface Modification Of Implant Material

Background and Objective: Due to the aging of the population,sports injury and improvement of medical technology,implant-related surgery has been increasing year by year,and various kinds of new implant materials have been created accordingly.Implant-related infection,a common postoperative complication,is a major cause of surgical failure,in particular in orthopaedic.Once the infection occurs,removal of the implants is often needed as well as the multiplied risk of re-infection,sometimes required multiple surgical revision and even amputation,which will greatly increase the rate of disability,bringing a huge financial burden to patients and the health care system.Apart from antibiotics,the surface modification of the implant material is a promising avenue to resolve this global problem.An ideal implant interface is expected to possess good biocompatibility,as well as broad-spectrum and long-term bacterial inhibition capabilities.Here,a delicate cicada & catkin inspired dual biomimetic structure was proposed,for the first time,to improve the antibacterial properties of the implant material.By using PEEK as the model implant,the relative in vitro and in vivo evaluations demonstrated that this dual biomimetic structure could simultaneously provide less bacterial adhesion,wider antimicrobial range and longer antibacterial durability.Meanwhile,the modified implant also remained an ideal biocompatibility.Most importantly,the relative dual biomimetic structure engineering process could be accomplished through a simple,economic and fast hydrothermal chemical reaction,which thus might brought certain impact to the development of future biomedical materials.Methods:(1).Synthesis of porous anodic aluminium oxide(AAO): electrochemical method was used to synthesize AAO;(2).Synthesis of single biomimetic PEEK(SB-PEEK): the synthesis method of cicada-wing like nanopillar structure on PEEK surface was prepared using “template printing” method.(3).Synthesis of dual biomimetic PEEK(DB-PEEK): the ZnO nanoslice was prepared by “water bath heating” method and then drop onto the surface of SB-PEEK to form DB-PEEK.High-resolution electron micrographs of dragonfly wings and cicada wings were also recorded.The normal bacterial morphology and the morphology on original PEEK and SB-PEEK was also observed.The crystalline structure of original PEEK,SB-PEEK and DB-PEEK were determined by X-ray diffraction.The element composition of samples were studied via Energy Disperse Spectroscopy(EDS).(4).Characterization of the nanoarchitecture and bacterial morphology: the original PEEK,SB-PEEK and DB-PEEK were observed using scanning electron microscope(SEM).The nanopillars structure on the surface of the cicada wing and dragonfly wing was also observed,and the bacteria were observed.The normal morphology and morphology of the surface of PEEK and single biomimetic PEEK,while using X-ray diffraction(XRD)techniques to determine the surface modification of the nano-array and energy spectrum techniques to detect their elemental composition;(5).Antibacterial Properties Assay in vitro and Bacterial adhesion experiments: original PEEK,SB-PEEK and DB-PEEK were co-cultured with Gram-positive and Gram-negative bacteria(Staphylococcus aureus and Escherichia coli)for 24 and 48 hours,respectively.The number of bacteria was counted and the inhibition rate was calculated.At the same time,for SB-PEEK,a bacterial adhesion test was performed to examine its resistance to Staphylococcus aureus;(6).Cytotoxicity: It was divided into cytotoxicity and hemolytic test,all using the extract method.(7).In vivo infected studies: original PEEK,SB-PEEK and DB-PEEK were simultaneously implanted subcutaneously with bacteria(Staphylococcus aureus and Escherichia coli)and fed for 8 days.The wound healing,as well as abscess formation around the implant was recorded on the 1st,4th and 8th day,respectively.Then,the implant was taken for bacterial count and the tissue around the implant was subjected to HE staining to observe the inflammation.Results:(1).Results of SEM,XRD and EDS showed the successfully construction of SB-PEEK and DB-PEEK.(2).Plate counting results showed significant antibacterial efficiency of DB-PEEK,not only for Staphylococcus aureus,but also for Escherichia coli,compared with original PEEK( < 0.001),however,SB-PEEK showed selected antibacterial property for Escherichia coli.(3).In in vitro antibacterial experiment,the DB-PEEK showed good antibacterial properties at 24 h and 48h(more preferably at 48h),and the antibacterial ability to Staphylococcus aureus was better than that of Escherichia coli.(4).In in vivo antibacterial experiment,the wound healing speed in DB-PEEK group is favorable,which showed completely healed of incision,while the SB-PEEK group showed a certain degree of delayed healing,and the healing speed of original PEEK was obviously slowly.Plate counting results of bacteria on the surface of PEEK showed obviously superior antibacterial effects of DB-PEEK,compared to the original PEEK(p < 0.001).And the SB-PEEK,due to the resistance to bacteria,the bacteria on surface were also less than original PEEK.HE staining showed intense inflammation of skin tissue around SB-PEEK groupand original PEEK group.However,only a small number of inflammation were found in the tissues surrounding the implant in DB-PEEK group.Conclusion:(1)The single biomimetic structure and the dual biomimetic structure were successfully synthesized on the surface of PEEK by simple “template printing” method and“water bath heating” method.An additional biomimetic structure of catkin-like ZnO nanoslices have been added onto this structure,which compensate the defect of single biomimetic material effectively(selective antibacterial property and comparatively lower antibacterial efficiency);(2)The construction of dual biomimetic materials can provide a new and effective method to reduce the rate of implant-related infection,as well as new approach for reducing the use of antibiotics.