Electrostatic Cell Trapping for Enhanced Sample Yield in Brush Cytology.

Brush cytology is widely used for sampling mucosal surfaces, particularly during gastrointestinal endoscopy to detect malignancies in the pancreas and bile ducts. During brushing, mucus and detached cells are collected in the bristles through capillary action and flow eddies. However, a low cellular yield often limits diagnostic sensitivity. This work explores electrostatic interactions between cancer cells and oppositely charged bristles to enhance cell capture. Modifying the polyamide (PA) bristles with the polycation poly(ethylenimine) (PEI) enhanced their electrostatic affinity for negatively charged cancer cells. A physical analysis of electrostatic attraction and brushing induced hydrodynamic drag quantified forces on epithelial cancer cells near a charged bristle and the mucosal surface. Hydrodynamic drag increased with brushing velocity, and specific regions were identified where electrostatic attraction significantly contributes to cell trapping and balances the hydrodynamic forces. In vitro experiments with HeLa cells showed a 2-fold increase in attachment to the modified brush. Ex vivo brushing of porcine stomach tissue confirmed the approach, showing an ≈5-fold increase in cellularity, as verified by histology. These findings indicate that exploiting electrostatic attraction between cancer cells and oppositely charged bristles can significantly enhance the sensitivity and specificity of cytological brushing in a simple, efficient, and cost-effective manner.