Micromilling is a promising technology for the fabrication of surface profiles with optical quality. We present a highly integrated optofluidic system made of polydimethylsiloxane (PDMS). The system is replicated in a single-step process from a micromilled polymethyl methacrylate master mold. It already includes the reservoirs, the channel system, as well as the optical interconnect surfaces for high numerical aperture objectives. We demonstrate the potential of this approach by laser-based three-dimensional optical manipulation within the replicated system. To our knowledge, this is the first time that a PDMS membrane is used as a well-defined channel wall for an optical trapping setup.