The present invention is directed to surface functionalization of polymeric fibers. Surface biofunctionalization is achieved by covalent conjugation of biofunctional igands and/or cell growth factors that are crucial for cell attachment, proliferation and functions. Biofunctional fibers could be fabricated into three-dimensional scaffolds. Polymer fibers described here comprise of biocompatible polymers that are either biodegradable ornon-biodegradable. This patent also describes a series of new biodegradable polyphosphoramidates for the processing of biodegradable fibers. Scaffolds made of non-biodegradable functional fibers could be used for in vitro cell culture (for example, ex vivo cell expansion), while biodegradable functional fibers could be fabricated into tissue engineering scaffolds.