Abstract
3 min readRecently, the delivery of growth factors (GFs) through controlled release systems is one of the top approaches for combined tissue engineering (TE) and regenerative medicine strategies. Polysaccharides have been motif of interest for their versatility and superior functional properties and can be used to design new protein delivery systems since they are capable of preserving the bioactive conformation and even enhancing the potency of the proteins. In this work, a polyelectrolyte complex (PEC) based on the electrostatic interaction of two oppositely charged polysaccharides, chitosan (CH) and chondroitin sulfate (CS) is proposed for the encapsulation of proteins, specifically platelet lysate (PL). PL is a promising source of GFs due to its autologous nature and rich composition, leading to synergistic GF actions. By a harmless and quick procedure for the entrapped proteins, spherical nanoparticles (NPs) slightly smaller than 200 nm were developed. The PL-loaded NPs were cultured with human adipose derived stem cells (hASCs) and it was observed a positive influence over cell viability and proliferation. The NPs were then included in a threedimensional polyD,L lactic acid (PDLLA) scaffold to address the possibility of creating a multifunctional scaffold able to stimulate the proliferation and differentiation of seeded cells. Different protein delivery rates were achieved, which suggests this system as a promising approach for TE strategies. INTRODUCTION The emerging next generation of engineered tissues relies on the development of loaded scaffolds containing bioactive molecules in order to provide the necessary information or signalling for cell attachment, proliferation and differentiation to meet the requirement of dynamic reciprocity for Tissue Engineering (TE). This justifies the importance of delivery systems in TE applications (Causa et al., 2007). Natural based chitosan/chondroitin sulfate nanoparticles (CH/CS NPs) were developed with the ultimate goal of encapsulating bioactive agents to promote and enhance bone and cartilage regeneration. In the present study we investigate the potential of the CH/CS NPs to act as a controlled release system for PL, in order to stimulate the proliferation of human adipose-derived stem cells (hASCs) in 2D cultures. The introduction of autologous platelet concentrate into clinical practice was previously suggested, underlining the several advantages of using this source of growth factors (GFs) for tissue healing. Besides their autologous nature, these concentrates do not present risks of disease transmission neither immunogenic reactions. The use of single GFs is not as effective as the application of combined GFs, which can act synergistically towards tissue healing, with a low cost (Hokugo et al, 2005). The main disadvantages come from the complexity of the cocktail of GFs present in the mixture, which are involved in different pathways and therefore might diverge the cell differentiation from the lineage we intend. There are some contradictory studies in the literature reporting the effects of platelet lysate (PL) on the osteogenic and chondrogenic differentiation of stem cells, resulting from different protocols for isolation of platelets and their further activation (Anitua et al., 2010). We have also addressed the use of the developed NPs in a combinatory strategy with other 3D scaffolds based on PolyD,L lactic acid (PDLLA), to influence the viability, proliferation and differentiation of seeded hASCs. The combination of a NP releasing system with a supercritical fluid-produced 3D structure might result in an appropriate delivery system for TE strategies. MATERIALS AND METHODS Semana de Engenharia 2010 Guimaraes, 11 a 15 de Outubro
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