The field of 3D printing is an area of active research, with a substantial focus given to the design and construction of customized tools for applications in technology. There exists a particular need in these developing areas of opportunity for new multi-functional soft materials that are biologically compatible for the growth and directed culturing of cells. Herein, a composite material consisting of gold nanoparticles with useful plasmonic properties embedded within a highly hydrophilic poly-2-hydroxyethylmethacrylate matrix is described and characterized. This composite material serves dual functions as both host framework scaffold for cell lines such as pre-osteoblasts as well as a plasmonic biosensor for in situ measurements of living cells. The plasmonic properties of this system are characterized as a function of the material properties and related to compositional features of the material through a proposed light-directed mechanism. This chemistry provides a tunable, 3D printable plasmonic composite material of encapsulated gold nanoparticles in a biologically-compliant, acrylate-based hydrogel matrix. Surface-enhanced Raman scattering studies of 3D-microcultures supported by the scaffolds are carried out and the strong influence of perm-selective molecular diffusion in its analytical responses is established. Most notably, specific, largely hydrophilic, cellular metabolites are detected within the supported live cultures.