Combining fluidic reservoirs and optical tweezers to control beads/living cells contacts

Abstract

We have developed a complete system based on holographic optical tweezers to realize multiple-point interactions between beads and cells with control of the stimulation places, timing and durations. We introduce microstereolithography as a 3D micromanufacturing approach to the rapid prototyping of three-dimensional fluidic microchambers of complex shapes, comprising wells, channels and walls, that are afterwards placed inside the sample and used to inject beads locally and keep them separated from cells in our assays. A custom reservoir designed to keep beads and cells separated in liquid samples has been realized and successfully tested. This allows us to deposit beads locally on the microscope cover glass placed under the reservoir outlet. Limited dispersion of beads under the outlet has been confirmed, and the ability of the polymeric structures to confine beads in a restricted area has been demonstrated. Examples of manipulations consisting at first in extracting several beads from the reservoir, making them travel to the target cell, and finally depositing on its outer membrane with respect to the shape of the target cell, are finally given.