Scaffold-free tissue constructs

Abstract

A tissue construct comprising includes a self-assembled, scaffold-free, high-density cell aggregate. The cell aggregate includes a plurality of cells and a plurality of biocompatible and biodegradable nanoparticles and/or microparticles that are incorporated within the cell aggregate. The nanoparticles and/or microparticles act as a bulking agent within the cell aggregate to increase the cell aggregate size and/or thickness and improve the mechanical properties of the cell aggregate allowing the cell aggregate to be readily manipulated and formed into tissue constructs with defined architectures.

Having described the invention, we claim: 
     
         1 . A tissue construct comprising:
 a self-assembled, scaffold-free, high-density cell aggregate, the cell aggregate including a mixture of a plurality of cells and a plurality of biocompatible and degradable bulking agents, wherein the bulking agents include a plurality of nanoparticles and/or microparticles and the high-density cell aggregate has a shape that is defined by a shape and/or cell adhesive properties of a culture vessel in which the cell aggregate self assembles.   
     
     
         2 . The tissue construct of  claim 1 , the nanoparticles and/or microparticles having a diameter of about 1 nm to about 200 μm. 
     
     
         3 . The tissue construct of  claim 1 , the size, shape, and/or composition of the nanoparticles and/or microparticles provided in the tissue construct being varied. 
     
     
         4 . The tissue construct of  claim 1 , the nanoparticles and/or microparticles comprising a biocompatible and/or degradable polymer. 
     
     
         5 . The tissue construct of  claim 4 , the degradable and/or biocompatible polymer including a hydrogel that comprises macromers, the macromers being optionally cross-linked. 
     
     
         6 . The tissue construct of  claim 5 , wherein the degradable and biocompatible polymer is gelatin and the gelatin is cross-linked with genipin. 
     
     
         7 . The tissue construct of  claim 1 , the nanoparticles and/or microparticles including at least one bioactive agent that is differentially and/or controllably released by the nanoparticles and/or microparticles. 
     
     
         8 . The tissue construct of  claim 7 , the bioactive agent being incorporated in and/or physically associated with the nanoparticles and/or microparticles and spatially presented in specific locations within the aggregate and/or temporally released with a defined release profile from the nanoparticles and/or microparticles. 
     
     
         9 . The tissue construct of  claim 1 , the cells being at least about 30%, by volume of the cell aggregate based on the total volume of the cell aggregate. 
     
     
         10 . The tissue construct of  claim 1 , the cells comprising progenitor cells. 
     
     
         11 . The tissue construct of  claim 1 , comprising a heterogenous cell aggregate that includes defined regions of differing aggregate materials. 
     
     
         12 . The tissue construct of  claim 11 , the heterogenous cell aggregate comprising layers of cell sheets comprising different cells, nanoparticles and/or microparticles, and/or optionally mechanical properties. 
     
     
         13 . The tissue construct of  claim 11 , wherein at least some of the defined regions are modified to form an acellular aggregate that is free of cells. 
     
     
         14 . The tissue construct of  claim 1 , have shape that is defined by or substantially similar to a tissue defect or region being treated. 
     
     
         15 . A method of forming a cell aggregate, the method comprising:
 isolating undifferentiated and/or substantially differentiated progenitor cells;   expanding the undifferentiated and/or substantially differentiated progenitor cells;   combining the undifferentiated and/or substantially differentiated progenitor cells with a plurality of the nanoparticles and/or microparticles so that the nanoparticles and/or microparticles are dispersed and suspended with the undifferentiated and/or substantially differentiated progenitor cells in a culture medium; and culturing the suspension of nanoparticles and/or microparticles and undifferentiated and/or substantially differentiated progenitor cells in a culture so that a self-assembled, scaffold-free, high-density cell aggregate is formed having a shape and/or cell adhesive properties defined by the shape of culture vessel.   
     
     
         16 . The method of  claim 15 , further comprising mechanical stimulating the cell aggregate and/or tissue construct to enhance cell differentiation and tissue formation of the tissue construct. 
     
     
         17 . The method of  claim 15 , the nanoparticles and/or microparticles having a diameter of about 1 nm to about 200 μm. 
     
     
         18 . The method of  claim 15 , the size, shape, and/or composition of the nanoparticles and/or microparticles provided in the tissue construct being varied. 
     
     
         19 . The method of  claim 15 , the nanoparticles and/or microparticles comprising a biocompatible and/or degradable polymer. 
     
     
         20 . The method of  claim 19 , the degradable and/or biocompatible polymer including a hydrogel that comprises macromers, the macromers being optionally cross-linked. 
     
     
         21 . The method of  claim 15 , the nanoparticles and/or microparticles including at least one bioactive agent that is differentially and/or controllably released by the nanoparticles and/or microparticles. 
     
     
         22 . The method of  claim 21 , the bioactive agent being incorporated in and/or physically associated with the nanoparticles and/or microparticles and spatially presented in specific locations within the aggregate and/or temporally released with a defined release profile from the nanoparticles and/or microparticles. 
     
     
         23 . The method of  claim 15 , the cells being at least about 30%, by volume of the cell aggregate based on the total volume of the cell aggregate. 
     
     
         24 . The method of  claim 15 , comprising a heterogenous cell aggregate that includes defined regions of differing aggregate materials. 
     
     
         25 . The method of  claim 15 , the heterogenous cell aggregate comprising layers of cell sheets comprising different cells, nanoparticles and/or microparticles, and/or optionally mechanical properties. 
     
     
         26 . The method of  claim 24 , further modifying at least some of the defined regions to form an acellular aggregate that is free of cells.