Development of bioactive constructs through cell crosslinking for tissue regeneration

Injectable systems are particularly attractive for a minimally invasive approach in tissue engineering applications. Many different methods for in situ crosslinking have been investigated however the ability of cells to promote hydrogel formation has not been fully explored. This study addressed the hypothesis that cells can promote crosslinking of chitosan microparticles forming a tridimensional network. Through covalent immobilization we were able to functionalize particles with specific antibodies, used to promote the attachment of cells and growth factors of interest. CD90 anti-human antibodies that are highly expressed by human adipose stem cells (hASCs) were successfully con- jugated with chitosan microparticles. A tridimensional hydrogel was obtained by the assembly of the modified chitosan microparticles with hASCs and was stabilized by the crosslinks established by the entrapped cells. The degree of crosslinking of the structure could be regulated by the cell concentration in each construct. Moreover we believe that a combination of microparticles tailored with specific growth factors will increase the stability of the construct and promote cell differentiation. It is well established that platelets are an important source of autologous growth factors that can modulate cell growth and differentiation. In this study we propose antibody-conjugated particles as a method to select specific growth factors from the mixture obtained from platelet lysates. The obtained construct simultaneously provides support for stem cell growth as well localized and sustained presentation of factors to modulate cell differentiation. We intend to design a novel multifunctional injectable system that may be custom- ized by combining particles with different growth factors for a specific application.