Interfacial interactions in biphasic polymeric fluids confined in a nanochannel are studied by using dissipative particle dynamics. The effects of an arrested nanotube at the interfaces of short-chain polymer models are elucidated, and its interactions with the polymers are varied systematically. The results confirm the experimental notion that a particle can bear an excess of anisotropic interfacial stresses and consequently stabilize interface curvatures. In the presence of limited capillary effects in nanofluidic channels, the solvation shells in the vicinity of the nanotube and their related interactions become more dominant. The solvation shells are characterized by the density oscillations around the nanotube. While the oscillation intensity depends on the polymer nanotube interactions, its characteristic length is only a function of the molecular structure of the polymer. The oscillations disappear within a certain number of shells away from the nanotube that is comparable to experimental values for low molecular weight liquids. Detailed analyses of the interface shape based on capillary wave theory reveal the impacts of such solvation forces. This study offers insights into how the polymeric solvation shells around nanoparticles can influence the interface shape, the nanoparticle-nanoparticle interactions, and the nanoparticle-wall interactions. Our findings can lead to promising applications in nanofluidics and in drug delivery using nanoparticles.