Studies that require biomaterials with well-controlled
physical and biological properties have increased dramatically
since the concept of tissue engineering was first
proposed. Cellular activities are often composite
responses to multiple environmental stimuli [1,2]. To
study how individual stimuli affect cellular response,
precise control over the microenvironment is crucial.
However, this control is often very difficult to achieve
in vivo. On the other hand, a defined in vitro microenvironment
could be easily created from biomaterials with
controlled properties. Efforts have been made to create
such biomaterials with synthetic polymers, including
poly(lactic-co-glycolic acid) [3] and poly(ethylene glycol)