Cell Type Specific Microspheres Incorporating Growth Factors as Injectable Cell Carriers for Tissue Repair

The detection, isolation and sorting of cells holds an important role in cell therapy

and regenerative medicine. Also, injectable systems have been explored for tissue

regeneration in vivo, because it allows repairing complex shaped tissue defects

through minimally invasive procedures.

Here, we report the use of polymeric microspheres to simultaneously isolate and

enrich specific cell types that can be also used as an injectable cell carrier system to

form small tissue constructs in situ. The rationale was to functionalize the particles

with antibodies to target specific cell types and release growth factors (GFs), first to

increase the number of cells growing over the particle surface and then induce the

differentiation of these cells by a sustained release from the particle core.

GFs loaded microspheres of photocrosslinkable chitosan were fabricated using a

flow focusing microfluidic chip. The droplets produced were crosslinked by UV while

flowing inside a Tygon tube before being collected into an eppendorf. Monoclonal

antibodies against cell surface antigens specific to endothelial cells and stem cells

were immobilized on the surface of the microspheres. Experimental results showed

that the microfabricated spheres provide suitable surfaces to capture a target cell

type and subsequent expansion of the captured cells. The aggregation of the

functionalized microspheres has been also shown to successfully form 3D robust

structures upon injection into a mold.