Two-photon lithography-fabricated deterministic lateral displacement microfluidic system for efficient minicell purification in cancer therapy

Chromosome-less minicells, derived from aberrant polar division events of bacterial cells, have emerged as promising nanocarriers for targeted cancer drug delivery due to their unique characteristics. A major challenge in their purification process lies in effectively isolating such spherical minicells (< 1 μm) from their rod-shaped parental cells (1-10 μm). This study investigates the use of Deterministic Lateral Displacement (DLD) microfluidic systems for minicell purification, leveraging Two-Photon Lithography (TPL) for the rapid prototyping of high-resolution designs optimized for this purpose. Under laminar flow conditions, we investigated key DLD design parameters including symmetric and asymmetric post gaps, outlet widths, dual post arrays, fluidic-resistance-optimized design. To enhance separation efficiency, we developed a two-stage microfluidic separation system combining a spiral inertial chip and an optimized DLD chip in series. Utilizing high-resolution TPL for chip fabrication of an inertial chip with 12 spirals and an asymmetric DLD chip with a 2 μm downstream post gap, we achieved a separation efficiency of 94%. This high efficiency achieved using microfluidics for the separation of cells differing in both shape and size, demonstrates the potential of advanced microfluidic systems in cell sorting.