Continuous, Nondestructive Detection of Microorganism Growth at Buried Interfaces with Vascularized Polymers

Abstract

Evaluating surface bacterial growth at buried interfaces can be problematic due to the difficulties associated with obtaining samples. In this work, we present a new method to detect signals from microorganisms at buried interfaces that is nondestructive and can be conducted continuously. Inspired by vascular systems in nature that permit chemical communication between the surface and underlying tissues of an organism, we created a system in which an inert carrier fluid could be introduced into an empty vascular network embedded in a polymer matrix. When a microorganism layer was grown on top, small molecules produced by the growth process would diffuse down into the carrier fluid, which could then be collected and analyzed. We used this system to nondestructively detect signals from a surface layer of Escherichia coli using conductivity, ultraviolet−visible (UV−vis) absorbance spectroscopy, and high-performance liquid chromatography (HPLC) for organic acids, methods that ranged in sensitivity, time-to-result, and cost. Carrier fluid from sample vascularized polymers with surface bacterial growth recorded significantly higher values in both conductivity and absorbance at 350 nm compared to controls with no bacteria after 24 h. HPLC analysis showed three clear peaks that varied between the samples with bacteria and the controls without. Tests tracking the change in signals over 48 h showed clear trends that matched the bacterial growth curves, demonstrating the system's ability to monitor changes over time. A 2D finite element model of the system closely matched the experimental results, confirming the predictability of the system. Finally, tests using clinically relevant Staphylococcus aureus and Pseudomonas aeruginosa yielded differences in conductivity, absorbance, and HPLC peak areas unique to each species. This work lays the foundation for the use of vascularized polymers as an adaptive system for the continuous, nondestructive detection of surface microorganisms at buried interfaces in both industry and medicine.

Multi-component liquid-infused systems: a new approach to functional coatings

“…2 Such a thin layer is instrumental in keeping the liquid associated with the solid surface rather than flowing away; however, this thinness (and therefore, low volume) can also limit the quantity of a secondary component that can be present within the liquid at the surface. Strategies such as incorporating a vascular network into the solid to use as a means to deliver additional liquid and/or secondary components to 124 or from 125 the surface may help to mitigate this issue; however, designers of multi-component liquid-infused surfaces should be aware of this limitation and plan accordingly. Another limitation is the solubility and/or stability of the secondary components within the liquid.…”