Cell Surface Engineering by Phase‐Separated Coacervates for Antibody Display and Targeted Cancer Cell Therapy

Abstract Cell therapies such as CAR−T have demonstrated significant clinical successes, driving the investigation of immune cell surface engineering using natural and synthetic materials to enhance their therapeutic performance. However, many of these materials do not fully replicate the dynamic nature of the extracellular matrix (ECM). This study presents a cell surface engineering strategy that utilizes phase‐separated peptide coacervates to decorate the surface of immune cells. We meticulously designed a tripeptide, Fmoc−Lys−Gly−Dopa−OH (KGdelta; Fmoc=fluorenylmethyloxycarbonyl; delta=Dopa, dihydroxyphenylalanine), that forms coacervates in aqueous solution via phase separation. These coacervates, mirroring the phase separation properties of ECM proteins, coat the natural killer (NK) cell surface with the assistance of Fe 3+ ions and create an outer layer capable of encapsulating monoclonal antibodies (mAb), such as Trastuzumab. The antibody‐embedded coacervate layer equips the NK cells with the ability to recognize cancer cells and eliminate them through enhanced antibody‐dependent cellular cytotoxicity (ADCC). This work thus presents a unique strategy of cell surface functionalization and demonstrates its use in displaying cancer‐targeting mAb for cancer therapies, highlighting its potential application in the field of cancer therapy.