Silk-Based Encapsulation of Mammalian Cells Integrated with Nitrogen-Vacancy Centers for Protective and Sensing Applications

Mammalian cells are highly sensitive to mechanical and biochemical stresses encountered during in vitro manipulation or in vivo transplantation, which can compromise their viability and function. To address these challenges, we developed a silk fibroin–based encapsulation system that provides both protection and environmental sensing capabilities. Using electrostatic layer-by-layer (LbL) deposition, we encapsulated various types of cells, including immune cells (THP-1), human mesenchymal stem cells, human intestinal organoids, and β-cells islets, within biocompatible silk fibroin coatings that act as a semi-permeable barrier, shielding cells from external forces and immunological attack while preserving physiological activity. To further enhance the functionality of the coating, we incorporated fluorescent nanodiamonds (FNDs) containing nitrogen-vacancy (NV) centers into the silk layers. These NV centers containing atomic-scale quantum defects exhibit stable fluorescence and unique spin-dependent optical signatures that respond selectively to changes in pH, temperature, and redox state. Embedding NV centers within the silk matrix transforms the encapsulation shell into a multifunctional quantum-sensing interface, capable of reporting the microenvironmental dynamics in real time. This platform demonstrates a dual benefit, protecting cells and enabling noninvasive monitoring of their physiological state. Together, this highlights the potential of silk-based cell encapsulation as a versatile approach for cell protection, regenerative medicine and nano-sensing applications.