Light-regulated release of recombinant Nerve Growth Factor from Bacterial Hydrogels

• Applicant: Dr. Shrikrishnan Sankaran
• Subject Area: Biological and Biomimetic Chemistry
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 455063657

Nerve growth factor (NGF) is a highly versatile protein that promotes the growth and survival of several types of nerve cells apart from regulating various processes in epithelial, immune and stem cells. Approaches for therapeutic application of NGF have been explored for decades with greatest success achieved in treating topical eye and skin diseases. However, clinical translation of NGF-based therapies is limited by three major obstacles: (i) High cost - as a large and complex protein, cost of production, purification, storage and delivery is very high and impractical for chronic diseases, where prolonged availability is required(ii) Low stability - NGF is degraded by proteases in the body due to which large doses and repetitive administration is often required, leading to side-effects(iii) Inefficient delivery - The loading capacity of NGF in drug-release materials and the control over release are very poorThe proposed project aims to address these issues by developing bacterial hydrogels that can produce and deliver NGF in a controlled manner. The bacteria will be optogenetically engineered for long-term supply of freshly produced NGF, whose production and secretion can be precisely controlled, remotely by light. This will be achieved by (i) genetically fusing a recombinant NGF gene with a carrier protein/signal peptide, capable of transporting it out of the bacteria. (ii) encoding NGF-secretion in optogenetic plasmids(iii) engineering antibiotic-free plasmid retention systems by knocking-out vital metabolic enzyme genes from the bacterial genome and encoding them within the optogenetic plasmids Notably, these genetic circuits will be engineered in 2 types of bacteria – (i) E. coli, for which these genetic modules are readily available and (ii) L. plantarum, which is a probiotic beneficial for the skin and eye but for which the genetic modules need considerable adaptation and optimization. These engineered bacteria will then be encapsulated within hydrogel constructs for sustaining long-term bacterial survival and NGF release, while preventing bacterial escape. This project will result in the development of a novel light-regulated NGF delivery system, whose applicability for chronic skin and eye diseases will be explored in the future. The fundamental insights gained from this project will lay the foundation for a new strategy to enhance the applicability of therapeutic proteins.

• DFG Programme: Research Grants