Natural bacterial biofilms are made of bacteria embedded in complex polymeric matrices that protect them from external stresses in harsh environments. Mechanical and adhesive interactions play prominent roles in enabling the biofilms to provide a protective physical barrier and regulate bacterial metabolic activity, growth, division and viability but how they do so is poorly understood. Since natural biofilms grow with microscopically heterogenous mechanical properties, studying theses effects on bacterial behavior is a formidable task. As simplified models, artificial biofilms have been fabricated by encapsulating bacteria within polymeric matrices of defined formulations. Apart from using such systems to study bacterial behavior under biofilm-mimetic confined conditions, such matrices have further been used for the shielded delivery of probiotics in the body and for biocatalysis in industrial settings. Recently, with the growth of synthetic biology tools, bacterial encapsulation has extensively pervaded other fields in the form of “Living materials”, wherein they are being developed for applications such as self-healing concrete, environmental remediation, smart fabrics, energy generation, biosensing and drug delivery. For such applications, polymeric matrices are being studied and designed to sustain bacterial activity, regulate their proliferation, prevent their escape and protect them from environmental insults, while being compatible with processing techniques such as coating, 3D printing and microfabrication. In this intro lecture, I will touch upon biophysical aspects of bacterial confinement and provide a glimpse into the above mentioned applications. Particularly, living materials for biomedical applications will be elaborated upon on . Finally, I will highlight my own work in developing optogenetically-engineered bacterial hydrogels capable of producing and releasing proteins [1] or metabolically synthesized drugs [2] regulated by light.
 
[1] Sankaran, S. & del Campo, A. Optoregulated Protein Release from an Engineered Living Material. Advanced Biosystems 3, 1800312 (2019).
[2] Sankaran, S., Becker, J., Wittmann, C. & del Campo, A. Optoregulated Drug Release from an Engineered Living Material: Self-Replenishing Drug Depots for Long-Term, Light-Regulated Delivery. Small 15, 1804717 (2019).