Boronate-mediated covalent and oriented immobilization of antibodies on the PDMS surface toward improved capture of circulating tumor cells

Microfluidic immunoassays are crucial for early detection and capture of circulating tumor cells (CTCs). The method of immobilizing functional receptors, such as antibodies (Abs), plays a critical role in determining the effectiveness of these systems. In this study, we present a microfluidic channel functionalized with boronic acids to facilitate the directed immobilization of native Abs, thereby improving their interaction with target antigens and cells. We evaluated the selectivity and efficiency of CTC capture using the anti-epithelial cell adhesion molecule (EpCAM) as the capture Ab. Using EpCAM-positive PC-9 human pulmonary adenocarcinoma cells and EpCAM-negative HeLa cervical cancer cells as models, our comparisons revealed that oriented Ab immobilization through covalent boronate formation resulted in approximately 5.2 times more PC-9 cell capture compared to random covalent Ab immobilization. Additionally, directional Ab immobilization demonstrated a roughly 30.8-fold increase in selectivity for EpCAM-expressing CTCs. This versatile Ab immobilization platform offers a promising approach for selective cell capture under dynamic flow conditions.