This microfluidic-optical fiber sensor is an experimental system designed to transport and monitor 3D cell cultures, facilitating medical research and technology. This system includes a photonic crystal fiber with a hollow core diameter of 22 µm, which functions as a bridge between two microfluidic devices. The purpose of this system was to transport 3T3 cells (of diameters from 15 µm to 23 µm) between the two devices. At low Reynold's and capillary numbers, spectroscopic analysis confirmed the presence of cellular aggregation at the interface of the fiber and microfluidic device. The transcapillary conductance, T C, is a separate analysis that models the behavior of a cellular aggregate through the hollow channel of a photonic crystal fiber. For the experimental system, conventional fluid mechanics theory is limited and requires special treatment of conditions at the microscale, such that transcapillary conductance treatment was employed. The transcapillary conductance, T C, was empirically derived to model cellular transport at the microfluidic scale and is useful for comparing transport events. For example, for a pressure differential of Δ p=1.5⋅103 c m H 2 O, the transcapillary conductance values were determined to be 10-12<T C<10-9, which were then compared to other literature values, such as the transport of circulating tumor cells (CTCs) at 33<Δ p<80c m H 2 O, with corresponding transcapillary conductance values at 10-7<T C<10-5. These transcapillary conductance values for both the literature and the experimental system are consistent, indicating that an increase in pressure differential does not promote microfluidic transport.