3D Cell Templates

Broad objectives in this area are  i) to develop technologies that facilitate the production of 3D cell composites with high precision and reliability, for adaption in large scale preparations, ii) to develop synthetic 3D surrogates that mimic cell functions similar to that in the body, and iii) to use these conditions in regenerating tissue of interest. Our hypothesis is that various matrix elements in the body contribute different signals to the cells and they have to be present in an appropriate composition for recreating needed function.  Successful completion of this project will have significant impact on i) the development of synthetic surrogates to test disease states (mechanism of wound healing), and ii) for toxicology studies and to test the effect of pathogens i.e., as real time sensors for detecting biological agents.

Background.  The body's functions are determined by the cells.  Understanding the dynamic changes in cellular activity is of significant importance in a many applications including occurrence of diseases and developmental biology. Petri dish cultures were developed in the early 1900s to understand cellular activity in an environment of reduced complexity when evaluated in the whole body.  Although these insights have been helpful in understanding many concepts, there are many problems with two-dimensional (2D) tissue culture technique.  Tissue culture plastic surface, cells are restricted to spread on a rigid surface. Hence, effects of biophysical properties of the matrix that provide a spatio-temporal effect in the body are not part of the effect. However, biophysical properties significantly influence cell adhesion and functions in 3D environment. Cells do respond differently in attachment, morphology, migration, and proliferation on 3D porous structures. There are also significant differences in many proteins responsible for cell-matrix interactions.  Such differences in cell adhesion between 2D and 3D structures trigger different signaling mechanisms.  Since cells exist in 3D spaces in the human body, developing systems to for the cell colonization in 3D is necessary.  Porous structures generated from natural and synthetic polymers or after removing the cellular components from xenogeneic tissues have been used to support and guide the in-growth of cells.  Examples include small intestinal submucosa (SIS), and acellular dermis.  On the other hand, manufacturing porous templates using pure components allows formation of matrices with required features in addition to large scale production.  Scaffolds are generated from synthetic and natural polymers using various techniques such as controlled rate freezing and lyophilization, porogen-leaching technique, free-form printing and electrospraying.  Each technique has advantages and disadvantages and many not be suitable for all polymers.  Also, altered surface texture and surface charge affects cell spreading.  Current bottleneck in the field is the dearth of biomaterial scaffolds that elicit controlled cellular responses and possess essential mechanical properties.    

Our approach. Our group focuses on innovative methods of dispersing polymeric systems without chemical reactions.  We work on generating scaffolds and injectable hydrogels from blends of natural and synthetic polymers, based on the desired properties.  We innovate and adapt many novel techniques to obtain desirable scaffolds.  We have formed emulsions and blends of synthetic and natural polymers using unique solvents.  We form co-axial and tri-axial fibers to obtain reinforced composites.  We utilize controlled release of stimulants locally to create a heterogeneous microenvironment form differentiating  stem cells.  We have formulated novel temperature sensitive injectable hydrogels.  We use bioprinting to form blood vessels and then co-culture other types of cells.  We perform a wide variety of mechanical tests including tensile, compression, cyclical, stress relaxation testing under physiological conditions and evaluate various mechanical properties.