Tissue engineering in the post-injury brain represents a promising option for cellular replacement and rescue, providing a cell scaffold for either transplanted or resident cells. We have characterized the use of methylcellulose (MC) as a scaffolding material, whose concentration and solvent were varied to manipulate its physical properties. MC solutions were produced to exhibit low viscosity at 23 degrees C and form a soft gel at 37 degrees C, thereby making MC attractive for minimally invasive procedures in vivo. Degradation and swelling studies in vitro demonstrated a small amount of initial polymer erosion followed by relative polymer stability over the 2-week period tested as well as increased hydrogel mass due to solvent uptake. Concentrations up to 8% did not elicit cell death in primary rat astrocytes or neurons at 1 or 7 days. Acellular 2% MC (30 microl) was microinjected into the brains of rats 1 week after cortical impact injury (velocity = 3 m/s, depth = 2 mm) and examined at 2 days (n = 8; n = 3, vehicle injected) and 2 weeks (n = 5; n = 3, vehicle injected). The presence of MC did not alter the size of the injury cavity or change the patterns of gliosis as compared to injured, vehicle-injected rats (detected using antibodies against GFAP and ED1). Collectively, these data indicate that MC is well suited as a biocompatible injectable scaffold for the repair of defects in the brain.