RESUMO
Platelet-rich plasma (PRP) associated with high molecular weight hyaluronic acid (HA) has been clinically used for tissue regeneration in orthopedics. Despite the recognized beneficial clinical outcomes (e.g., early pain control, improvement of patients' functional limitation and longer-term effectiveness compared to PRP and HA alone in mild and moderate osteoarthritis treatments), its use is still challenging and controversial due to lack of standardization of association practical protocols. Moreover, most studies neglect the matrix structure, that generates the ultimate properties of the association among platelets, fibrin network and the microparticles. In the present work, we aimed to analyze the influence of the PRP/HA association with a controlled matrix structure on the stability, rheological behavior, release of growth factors and in vitro proliferation of human adipose-derived mesenchymal cells (h-AdMSCs). The attenuation of the negative charge of HA was also evaluated. Pure PRP (P-PRP) (i.e., plasma enriched with platelets and poor in leukocytes) was prepared by centrifugation and activated with serum and calcium chloride (AP-PRP). Autocrosslinked hyaluronic acid (AHA) was prepared by organocatalyzed auto-esterification and structured in microparticles (MPAHA) by shearing. The attenuation of the negative charge of MPAHA was performed with chitosan (CHT) by polyelectrolyte complexation yielding MPAHA-CHT. The results showed that microparticles (MPs) have viscoelastic properties, extrusion force and swelling ratio appropriate for injectable applications. The association of AP-PRP with the controlled structure of MPAHA and MPAHA-CHT formed a matrix composed of platelets and of a fibrin network with fibers around 160 nm located preferably on the surface of the MPs with an average diameter of 250 µm. Moreover, AP-PRP/MPAHA and AP-PRP/MPAHA-CHT associations were non-toxic and supported controlled growth factor (PDGF-AB and TGF-ß1) release and in vitro proliferation of h-AdMSC with a similar pattern to that of AP-PRP alone. The best h-AdMSC proliferation was obtained with the AP-PRP/MPAHA-CHT75:25 indicating that the charge attenuation improved the cell proliferation. Thus, the association of AP-PRP with the controlled structure of HA can be a valuable approach for orthopedic applications.
RESUMO
This work evaluated the effects of UV irradiation, plasma radiation, steam and 70% ethanol treatments on the sterilization and integrity of auto-crosslinked hyaluronic acid (HA-ACP) scaffolds structured in microparticles and sponges aiming in vivo applications for regenerative medicine of bone tissue. The integrity of the microparticles was characterized by rheological behavior, while for the sponges, it was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and differential scanning calorimetry. The effectiveness of the sterilization treatment was verified by the number of microorganism colonies in the samples after the treatments. In conclusion, plasma radiation was the best treatment for the sponges, while steam sterilization in the autoclave at 126°C (1.5 kgf/cm2) for 5 min was the best treatment for the microparticles.