| ObjectiveIt is generally accepted that growth factors have an essential role in the healing process and tissue formation.In fact,all stages of the repair process are controlled by a wide variety of cytokines and growth factors acting locally as regulators of the most basic cell functions,using endocrine,paracrine,autocrine and intracrine mechanisms.These findings have led to a significant research effort aimed at testing different growth factors and cytokines as therapeutic molecules for the repair or regeneration of a wide range of tissues.The molecules that have been most intensively investigated in orthopedic research include bone morphogenetic proteins(BMPs),transforming growth factor-β(TGF-β),platelct-derived growth factor(PDGF),insulin-like growth factor (IGF),vascular endothelial growth factor(VEGF) and fibroblast growth factors(FGF). But some limiting factors are related to both the mode of growth factor delivery and the requirements for multiple signals to drive the regeneration process to completion.The latter is essential,assuming that no single exogenous agent can mediate,effectively,all aspects needed for tissue repair.Thus,delivery of a wide range of biological mediators is required if complete tissue engineering is to be achieved.Furthermore,the way these growth factors are made available is of paramount importance.Ideally,they should be delivered locally,following specific and distinct kinetics,to mimic,as far as possible, the requirements of the injured tissue during the different regeneration phases in situ.Platelets contribute to haemostasis by preventing blood loss at sites of vascular injury,and they contain a large number of growth factors and cytokines that have a key role in bone regeneration and soft-tissue maturation.The source of the new preparation, known as platelet-rich plasma(PRP),consists of a limited volume of plasma enriched in platelets,which is obtained from the patient.Once the platelet concentrate is activated by way of thrombin generation with calcium,a three-dimensional and biocompatible fibrin scaffold is formed,and a myriad of growth factors and proteins are released,progressively,to the local environment,contributing to the accelerated postoperative wound healing and tissue repair.Furthermore,this preparation promotes rapid vascularization of the healing tissue and,because it is autologous,it eliminates concerns about immunogenic reactions and disease transmission.Consequently,the use of autologous PRP as a novel therapeutic alternative opens new avenues in other fields such as orthopedics,sports medicine,dentistry,periodontal surgery and plastic and maxillofacial surgery.Othopedics infection is common in open fracture.Traditonal treatment include debridement and broad-spectrum antibiotics were used after operation,but local ischemia and devitalization of bone and soft tissue occurred when open fracture,drug concentration of local fracture is lower than blood.Local application of antibiotics in fracture wound may be a good options,to enhance bactericidal effect and depress toxic and side-effect of antibiotics.PRG has a three-dimensional and biocompatible fibrin scaffold,so it may has the ability of delayd release proterty.This study is execute to probe the treatment of infected bone defects with gentamicin-loaded PRG drug delivery system,controlling the infection and speeding bony growth and healing at one stage.Method1,To compare the different centrifugate terms of PRP preparation,define the ideal condition,Four healthy white rabbits were used include male and female,body weight 3-3.5Kg.Blood is collected in hard of hearing central artery using BD Vacutainer(9NC 0.109M),and centrugugated according to given terms.Platelet concentration is survey using automatic blood cell analyzer.Term that lead to platelet concentration ratios of 5-6 fold have been difined as ideal term.2,Sodium citrate and calcium chloride are used to make PRG or Gentamicin-loaded PRG as an anticoagulant and a clot activator.PRG or Gentamicin-loaded PRG are cultured in PBS.PDGF and TGF in the culture solution at day1,2,4,5,7,14 is measured with ELISA Kit.Culture soltion's gentamicin concentration is measured with ultraviolet spectrophotometry.3,A total of 10 white rabbits were recruited in the study and the model of chronic osteomyelitis of tibia was made by injecting staphylococcus aureus into the bone hole of two legs.PRP and Gentamicin-loaded PRG implanted into the bone defect.The histologic,radiologic and pathology bone changes were evaluated after therapy.Result1,Platelet-rich plasma was obtained by double centrifugation of blood,the term of first centrifuge as B4 and C2 has a coefficient of recovery more than 80%;the term of recentrifuge as K2 and K3 has a 6-fold condense than the blood.2,PRG obtained by activate PRP by thrombin and CaCl2,addition gentamicin added will form Gentamicin-loaded PRG,they have same release curve.3,Sustained release of gentamicin from Gentamicin-loaded PRG was observed,it reach the peak at two days,and till 14th day has a 16ug/ml release.4,The infected bone defect healed at six weeks after operation in Gentamicin-loaded PRG side,the other side is not healed which treated with PRG.Conclusion1,Double centrifuging,1400 rpm/10 minutes first,the blood sublayer was removed and the platelet rich fraction was spun(1,400 rpm/15 minutes) followed by removal of the supernatant platelet poor serum fraction(PPP),could easily and stably obtain PRP which more than 6-times above baseline of original blood.2,There are no significant difference of the release of growth factor of PRP and Gentamicin-loaded PRG. 3,PRG has delayed release characteristics,which can sustained release PDGF, TGF and gentamycin more than 7 days.4,Gentamycin-loaded PRG is effective in preventing and treating chronic osteomyelitis of rabit tibia...
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