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.

Influence of canal curvature on the amount of apically extruded debris determined by using three-dimensional determination method.

The aim of this study was to introduce a new three-dimensional curvature classification method to evaluate the canal curvature and analyse its effect on the amount of debris extrusion during reciprocating preparation. Freshly extracted mandibular molar teeth were collected. After performing access cavities, periapical radiographs were taken on both mesio-distal and bucco-lingual planes of each tooth using a digital sensor. The radii of the curvature were calculated and a new three-dimensional classification method was used to classify canal curvature, based on radius as follows: Three-dimensionally slight, moderate and severe curve root canal. Fifteen teeth for each curvature sort were randomly chosen for canal instrumentation. The extruded debris was collected in pre-weighed Eppendorf tubes and calculated. A significant difference was noted between root canals with slight and severe three-dimensional curvatures (P < 0.001). It can be concluded that root canal curvature plays a significant role in the amount of extruded debris.