As nanotechnology moves towards widespread commercialization, new technologies are needed to adequately address the potential health impact of nanoparticles (NPs). Assessing the safety of over 30000 NPs through animal testing would not only be expensive, but it would also raise a number of ethical considerations. Furthermore, existing in vitro cell-based assays are not sufficient in scope to adequately address the complexity of cell–nanoparticle interactions including NP translocation, accumulation and co-transport of e.g. allergens. In particular, classical optical/fluorescent endpoint detection methods are known to provide irreproducible, inaccurate and unreliable results since these labels can directly react with the highly catalytic surfaces of NP. To bridge this technological gap we have developed a lab-on-a-chip capable of continuously and non-invasively monitoring the collagen production of primary human fibroblast cells (NHDF) using contactless dielectric microsensors. Human dermal fibroblast cells are responsible for the maintenance of soft tissue integrity, are found throughout the human body and their primary function is collagen expression. We show that cellular collagen production can be readily detected and used to assess cellular stress responses to a variety of external stimuli, including exposure to nanoparticles. Results of the study showed a 20% and 95% reduction of collagen production following 4 hour exposure to 10 μg mL⁻¹ gold and silver nanoparticles (dia.10 nm), respectively. Furthermore a prolonged perfusion of sub-toxic concentrations (0.1 μg mL⁻¹) of silver NP reduced NHDF collagen production by 40% after 10 h indicating increased NP take up and accumulation. We demonstrate that the application of microfluidics for the tailored administration of different NP treatments constitutes a powerful new tool to study cell–nanoparticle interactions and nanoparticle accumulation effects in small cell populations.