Evaluating impacts of bambusuril pocket size and sterics on anion binding trends using ChemFET sensors.

Chemically-sensitive Field Effect Transistors (ChemFETs) are a useful tool to evaluate aqueous anion affinity of hydrophobic supramolecular scaffolds. More specifically, ChemFETs can be used to probe impacts of receptor modification to aqueous anion affinity. In this study, ChemFETs are used to evaluate the anion affinity of both dodeca-n-butyl bambus[6]uril and dodecabenzyl bambus[6]uril to assess steric effects in the chemical selectivity of the sensor membrane. The ChemFETs were evaluated through a series of common anions in the Hofmeister series in order to ascertain the difference in detection limit imparted by the specific functionalization of the bambus[6]uril macrocycles, which are quite sensitive to modest steric effects. Significant improvements to perchlorate and nitrate detection limits were observed via n-butyl bambusuril-containing sensor membranes over detection limits recorded with benzyl bambusuril sensors.

Benchmarking the placement of hydrosulfide in the Hofmeister series using a bambus[6]uril-based ChemFET sensor.

Hydrosulfide (HS-) is the conjugate base of gasotransmitter hydrogen sulfide (H2S) and is a physiologically-relevant small molecule of great interest in the anion sensing community. However, selective sensing and molecular recognition of HS- in water remains difficult because, in addition to the diffuse charge and high solvation energy of anions, HS- is highly nucleophilic and readily oxidizes into other reactive sulfur species. Moreover, the direct placement of HS- in the Hofmeister series remains unclear. Supramolecular host-guest interactions provide a promising platform on which to recognize and bind hydrosulfide, and characterizing the placement of HS- in the Hofmeister series would facilitate the future design of selective receptors for this challenging anion. Few examples of supramolecular HS- binding have been reported, but the Sindelar group reported HS- binding in water using bambus[6]uril macrocycles in 2018. We used this HS- binding platform as a starting point to develop a chemically-sensitive field effect transistor (ChemFET) to facilitate assigning HS- to a specific place in the Hofmeister series. Specifically, we prepared dodeca-n-butyl bambus[6]uril and incorporated it into a ChemFET as the HS- receptor motif. The resultant device provided an amperometric response to HS-, and we used this device to measure the response of other anions, including SO42-, F-, Cl-, Br-, NO3-, ClO4-, and I-. Using this response data, we were able to experimentally determine that HS- lies between Cl- and Br- in the Hofmeister series, which matches recent theoretical computational work that predicted a similar placement. Taken together, these results highlight the potential of using molecular recognition coupled with ChemFET architectures to develop new approaches for direct and reversible HS- detection and measurement in water and further advance our understanding of different recognition approaches for this challenging anion.

Using Watershed Boundaries to Map Adverse Health Outcomes: Examples From Nebraska, USA.

In 2009, a paper was published suggesting that watersheds provide a geospatial platform for establishing linkages between aquatic contaminants, the health of the environment, and human health. This article is a follow-up to that original article. From an environmental perspective, watersheds segregate landscapes into geospatial units that may be relevant to human health outcomes. From an epidemiologic perspective, the watershed concept places anthropogenic health data into a geospatial framework that has environmental relevance. Research discussed in this article includes information gathered from the literature, as well as recent data collected and analyzed by this research group. It is our contention that the use of watersheds to stratify geospatial information may be both environmentally and epidemiologically valuable.