Dopamine polymerization-mediated surface functionalization of living cells for advanced therapeutic applications.

The engineering of living cells represents a promising biomedical frontier that enables the design of cells with tailored functionalities for advanced therapeutic applications. Genetic manipulation serves as a primary approach in cell engineering, yet it faces inherent limitations, including the complexity of multigene editing and poor cross-species applicability, which restrict the development of cells with sophisticated functionalities. Therefore, flexible and versatile engineering strategies capable of functionalizing living cells to address diverse therapeutic requirements are highly desirable. Given its pivotal role in mediating cellular interactions, the cell surface is an attractive target for directing cell engineering. The diverse functional groups present in surface biomolecules offer abundant chemical modification sites, making them highly amenable to functionalization. Leveraging this inherent chemical accessibility, we have recently developed a flexible and versatile platform for surface functionalization of living cells through in situ dopamine polymerization that allows us to design personalized living cells with customizable functions by tuning the surface components. Here we provide a detailed protocol describing two distinct methods for bacterial functionalization. The first method uses dopamine polymerization-mediated mono-functionalization to construct mucus-penetrating bacteria that can reinforce intestinal mucosal barrier to prevent colitis. The second method uses dopamine polymerization-mediated dual-functionalization to generate synergy-immunoactivation bacteria that can simultaneously induce anticancer and antiviral immunity to treat cancer and prevent infection. Excluding bacterial culture, preparation of mucus-penetrating bacteria and synergy-immunoactivation bacteria takes ~3 h and 1 h, respectively. We anticipate that this protocol can offer valuable guidance for the engineering of living cells with designable and tailorable functionalities for innovative cell-based therapy.