**6. Autologous platelet rich plasma (PRP)**

The application of growth factors in medical practice is one of the areas where basic clinical research has focused its attention but there are many problems associated with their local administration. For example, recombinant human growth factors are not cost effective, they have limited shelf life, and ineffectively delivered to target cells and in addition, to get efficient therapy, large doses are needed. The use of autologous platelets concentrates for tissue regeneration and wound healing has now become an alternative easy and cheap way to obtain high concentrations of these growth factors (34).

The autologous blood collected from a patient just before surgery can be prepared as platelet concentrates, platelet-rich plasma (PRP) and platelet gel for the treatment the patient specifically needs (35). These forms are prepared by gradient density centrifugation techniques to obtain high (x5) concentration of platelets (36). This autologous concentration includes a large amount of growth factors, especially PRP is an easy and inexpensive technique to accelerate the wound healing (37).

This quite new field is open for research, there are a lot of techniques still under development stage such as platelet gels can be obtained by adding thrombin to autologous platelet-rich plasma. The initiation of fibrin polymerization and the release of platelets factors and cytokines can be achieved by the specific activators such as thrombin, glass, freeze-thaw cycle to platelet-rich plasma depending on what is required during the surgery (35).

In spite of the distinct features of platelet-rich plasma (PRP) and its use by different fields of medicine, no adverse reactions were documented until now(38, 39, 40, 41).
