**3.3 Platelet rich in growth factors (PRGF)**

Platelet-rich growth factors were first described in 1999 by Eduardo Anitua, who patented PRGF within Biotechnology Institute, BTI, Vitoria, Spain, a dental implant company. For PRGF to be made, it requires one centrifugation only coupled by multiple pipetting to ensure precise isolation of the centrifugation end-products. The result is a preparation rich in growth factors, however, with no leukocytes [10, 11].

The procedure requires the following equipment: PRGF system centrifuge, four calibrated test tubes with anticoagulants, Plasmatherm (heating device), micropipettes, and activator (calcium chloride). The preparation phases are the following (**Figure 2**):


#### **Figure 2.**

*The PRGF preparation process. (A) Blood drawing into 3.2% sodium citrate vacuum test tubes. (B) BTI centrifuge (PRGF system centrifuge. (C) Micropipetting PPGF, PGF, and PRGF fractions. (D) Three fractions transferred into calibrated tubes and activated with CaCl2 and heating device (Plasmatherm).*

PRGF prepared in this way is activated by procoagulant calcium chloride, whereby 50 μl of calcium chloride is used in 1 ml of PRGF. It takes 6 minutes for PRGF to transition from a liquid to a gel-like state upon activation and, as such, it becomes an autologous biomaterial ready for use. Plasmatherm (a device used for heating) should be set at 37°C to accelerate the transition.

In contrast to the previous, this protocol requires one centrifugation only. Instead of using bovine thrombin, it requires using calcium chloride to activate coagulation, while coagulation acceleration is achieved by using Plasmatherm. The greatest difference between PRGF and other platelet concentrates is the absence of leukocytes in the final product that is used as a biomaterial. Anitua et al., however, consider this as an advantage as they argue that proinflammatory activity is thereby prevented. This question remains controversial since there are many conflicting opinions among scientists.
