PRGF-Modified Collagen Membranes for Guided Bone Regeneration: Spectroscopic, Microscopic and Nano-Mechanical Investigations

By C. Ratiu, Simona Cavalu et al.

The aim of our study was to evaluate the properties of different commercially available resorbable collagen membranes for guided bone regeneration, upon addition of plasma rich in growth factors (PRGF). The structural and morphological details, mechanical properties, and enzymatic degradation were investigated in a new approach, providing clinicians with new data in order to help them in a successful comparison and better selection of membranes with respect to their placement and working condition. Copyright Simona Cavalu et al.

Whole blood separation upon centrifugation at 580 G for 8 minutes at room temperature (a) and subsequent platelets rich in growth factor (PRGF) separation by pipetting (b); membrane immersion in PRGF (c). Copyright C. Ratiu, Simona Cavalu et al.

Hematology parameters of whole blood and PRGF fraction:

ComponentWhole bloodPRGF
Leukocytes (x 103/μL)5.9 ± 1.20.3 ± 0.2
Erythrocytes (x 106/μL)4.5 ± 0.40.01 ± 0.0
Platelets (x 103/μL)210 ± 20655 ± 85
Hematology parameters of whole blood and PRGF fraction. Copyright Simona Cavalu et al.
Growth factor contentValue
Transforming growth factor TGFβ1: enhances the proliferative activity of fibroblasts and stimulates the biosynthesis of collagen and fibronectin43 ng/mL
Vascular endothelial growth factor VEGF: induces angiogenesis via migrating endothelial cells220 pg/mL
Insulin –like growth factor IGF-1:  is a primary mediator of the effects of growth hormone ; can also regulate cellular DNA synthesis105 ng/mL
Platelet-derived growth factor PDGR: enhances collagen synthesis and bone cells proliferation14 ng/mL
Quantitative assessment of the main growth factors, cytokines, and chemokines in PRGF fraction. Copyright Simona Cavalu et al.
Cross-sectional scanning electron microscopy (SEM) images of different commercial collagen membranes before (a,d,g) and after (b,e,h) PRGF treatment; AFM 3D topography of the membrane surface after PRGF treatment (c,f,i) showing the details of collagen fibers. The images correspond to Biocollagen® (ac), CovaTM Max (df), and Jason® (gi). Copyright Simona Cavalu et al.
Nanoindentation measurements: load–displacement curves recorded for each membrane before (a,c,e) and after (b,d,f) PRGF treatment. The images correspond to Jason® (a,b), Biocollagen® (c,d), and CovaTM Max (e,f). Legend: MC1/MC2 = Jason® membrane before/after PRGF treatment; MCP1/MCP2 = Biocollagen® membrane before/after PRGF treatment; MPP1/MPP2 = CovaTM Max membrane before/after PRGF treatment. Copyright Simona Cavalu et al.
Young modulus calculations with respect to the three collagen membranes before (a) and after PRGF treatment (b). Legend: MPP1/MPP2 = CovaTMMax membrane before/after PRGF treatment; MC1/MC2 = Jason® membrane before/after PRGF treatment; MCP1/MCP2 = Biocollagen® membrane before/after PRGF treatment. Copyright Simona Cavalu et al.
Results of enzymatic degradation test of native (unmodified) and PRGF-modified collagen membranes. Copyright Simona Cavalu et al.

PRGF-modified collagen membranes investigated in our study present new evidence of several advantages, with respect to a rapid and predictable soft tissue healing. The structural and morphological features of three different commercial collagen membranes for GBG/GTR were investigated upon PRGF treatment, revealing that particular characteristics such as porosity, fiber density, and surface topography may influence the mechanical behavior and performance of the membranes. By FTIR spectroscopy, it was demonstrated that the collagen matrix may act as a natural reservoir for growth factor delivery. Nanoindentation measurements revealed that, upon PRGF treatment, the changes of Young modulus values are correlated with the ultrastructural properties of each membrane type, especially the porosity. The mechanical properties of the membranes were analyzed in a comparative manner, before and after PRGF modification. The enzymatic (trypsin) degradation test also emphasized a different behavior—PRGF-modified membranes exhibited a slower degradation compared with the native ones. Within the limitations of the present study, the results are important with respect to the regulation and kinetic release of multiple growth factors that can be adapted to specific therapeutic conditions. Copyright Simona Cavalu et al.