Programmable microbial therapeutics: advances in engineered bacteria for targeted in vivo delivery and precision medicine.

backgroundBioengineered bacteria have emerged as versatile, programmable platforms for in vivo drug delivery. By integrating gene editing, synthetic gene circuits, targeted surface modifications, and environment‑responsive triggers, these living vectors can home to specific tissues and dynamically release therapeutic molecules in response to local cues. Recent advances have demonstrated their potential across oncology, immunomodulation, infectious disease control, and inflammatory disorders, yet challenges in stability, biosafety, and regulatory approval remain. AIM OF REVIEW: This review synthesizes the latest developments in programmable microbial therapeutics, focusing on engineering strategies and delivery system designs that enhance precision, efficacy, and safety. We evaluate proof‑of‑concept applications in disease models and identify critical bottlenecks hindering clinical translation, with the goal of guiding future research toward robust, personalized microbial interventions. KEY SCIENTIFIC CONCEPTS OF REVIEW: This review centers on four main areas. First, programmable gene circuits and biosensors enable conditional drug release only when desired. Second, targeting strategies-such as adhesion molecules and microenvironmental cues-guide bacteria to disease sites. Third, delivery system designs (e.g., encapsulation and surface coating) improve bacterial survival and payload stability. Fourth, expression-optimization methods fine-tune therapeutic output levels. We also discuss biosafety measures like kill-switches and auxotrophy, and outline future directions including intelligent feedback loops, multifunctional circuits, and streamlined regulatory pathways.