Abstract: Crosslinkable polymers, such as dendritic macromolecules and their in vitro, in vivo, and in situ uses are disclosed. These biomaterials/polymers are likely to be an effective sealant/glue for a variety of surgical procedures where the site of the wound is not easily accessible or when sutureless surgery is desirable. Crosslinkable dendritic macromolecules can be fabricated into cell scaffold/gel/matrix of specified shapes and sizes using chemical techniques. The polymers, after being crosslinked, can be seeded with cells and then used to repair or replace organs, tissue, or bones. Alternatively, the polymers and cells can be mixed and then injected into the in vivo site and crosslinked in situ for organ, tissue, or bone repair or replacement. The crosslinked polymers provide three dimensional templates for new cell growth that is suitable for a variety of reconstructive procedures, including custom molding of cell implants to reconstruct three dimensional tissue defects.