Genetically engineered bacterial biofilm materials enhances portable whole cell sensing.

In recent years, whole-cell biosensors (WCBs) have emerged as a potent approach for environmental monitoring and on-site analyte detection. These biosensors harness the biological apparatus of microorganisms to identify specific analytes, offering advantages in sensitivity, specificity, and real-time monitoring capabilities. A critical hurdle in biosensor development lies in ensuring the robust attachment of cells to surfaces, a crucial step for practical utility. In this study, we present a comprehensive approach to tackle this challenge via engineering Escherichia coli cells for immobilization on paper through the Curli biofilm pathway. Furthermore, incorporating a cellulose-binding peptide domain to the CsgA biofilm protein enhances cell adhesion to paper surfaces, consequently boosting biosensor efficacy. To demonstrate the versatility of this platform, we developed a WCB for copper, optimized to exhibit a discernible response, even with the naked eye. To confirm its suitability for practical field use, we characterized our copper sensor under various environmental conditions-temperature, salinity, and pH-to mimic real-world scenarios. The biosensor-equipped paper discs can be freeze-dried for deployment in on-site applications, providing a practical method for long-term storage without loss of sensitivity paper discs demonstrate sustained functionality and viability even after months of storage with 5 µM limit of detection for copper with visible-to-naked-eye signal levels. Biofilm-mediated surface attachment and analyte sensing can be independently engineered, allowing for flexible utilization of this platform as required. With the implementation of copper sensing as a proof-of-concept study, we underscore the potential of WCBs as a promising avenue for the on-site detection of a multitude of analytes.

A living material platform for the biomineralization of biosilica.

Nature has a vast array of biomineralization mechanisms. The commonly shared mechanism by many living organisms to form hardened tissues is the nucleation of mineral structures via proteins. Living materials, thanks to synthetic biology, are providing many opportunities to program cells for many functionalities. Here we have demonstrated a living material system for biosilicification. Silaffins are utilized to synthesize silicified cell walls by one of the most abundant organism groups called diatoms. The R5 peptide motif of the silaffins is known for its ability to precipitate silica in ambient conditions. Therefore, various studies have been conducted to implement the silicification activity of R5 in different application areas, such as regenerative medicine and tissue engineering. However, laborious protein purification steps are required prior to silica nanoparticle production in recombinant approaches. In this study, we aimed to engineer an alternative bacterial platform to achieve silicification using released and bacteria-intact forms of R5-attached fluorescent proteins (FP). Hence, we displayed R5-FP hybrids on the cell surface of E. coli via antigen 43 (Ag43) autotransporter system and managed to demonstrate heat-controllable release from the surface. We also showed that the bacteria cells displaying R5-FP can be used in silicification reactions. Lastly, considering the stimulating effect of silica on osteogenic differentiation, we treated human dental pulp stem cells (hDPSCs) with the silica aggregates formed via R5-FP hybrids. Earlier calcium crystal deposition around the hDPSCs was observed. We envision that our platform can serve as a faster and more economical alternative for biosilicification applications, including endodontics.

Combating Infectious Diseases with Synthetic Biology.

Over the past decades, there have been numerous outbreaks, including parasitic, fungal, bacterial, and viral infections, worldwide. The rate at which infectious diseases are emerging is disproportionate to the rate of development for new strategies that could combat them. Therefore, there is an increasing demand to develop novel, specific, sensitive, and effective methods for infectious disease diagnosis and treatment. Designed synthetic systems and devices are becoming powerful tools to treat human diseases. The advancement in synthetic biology offers efficient, accurate, and cost-effective platforms for detecting and preventing infectious diseases. Herein we focus on the latest state of living theranostics and its implications.

Cellular Biosensors with Engineered Genetic Circuits.

An increasing interest in building novel biological devices with designed cellular functionalities has triggered the search of innovative tools for biocomputation. Utilizing the tools of synthetic biology, numerous genetic circuits have been implemented such as engineered logic operation in analog and digital circuits. Whole cell biosensors are widely used biological devices that employ several biocomputation tools to program cells for desired functions. Up to the present date, a wide range of whole-cell biosensors have been designed and implemented for disease theranostics, biomedical applications, and environmental monitoring. In this review, we investigated the recent developments in biocomputation tools such as analog, digital, and mix circuits, logic gates, switches, and state machines. Additionally, we stated the novel applications of biological devices with computing functionalities for diagnosis and therapy of various diseases such as infections, cancer, or metabolic diseases, as well as the detection of environmental pollutants such as heavy metals or organic toxic compounds. Current whole-cell biosensors are innovative alternatives to classical biosensors; however, there is still a need to advance decision making capabilities by developing novel biocomputing devices.