Springs along the south rim of the Grand Canyon, Arizona, are important ecological and cultural resources in Grand Canyon National Park and are discharge points for regional and local aquifers of the Coconino Plateau. This study evaluated the applicability of electrical resistance (ER) sensors for measuring diffuse, low-stage (<1.0 cm) intermittent and ephemeral flow in the steep, rocky spring-fed tributaries of the south rim. ER sensors were used to conduct a baseline survey of spring flow timing at eight sites in three spring-fed tributaries in Grand Canyon. Sensors were attached to a nearly vertical rock wall at a spring outlet and were installed in alluvial and bedrock channels. Spring flow timing data inferred by the ER sensors were consistent with observations during site visits, with flow events recorded with collocated streamflow gauging stations and with local precipitation gauges. ER sensors were able to distinguish the presence of flow along nearly vertical rock surfaces with flow depths between 0.3 and 1.0 cm. Laboratory experiments confirmed the ability of the sensors to monitor the timing of diffuse flow on impervious surfaces. A comparison of flow patterns along the stream reaches and at springs identified the timing and location of perennial and intermittent flow, and periods of increased evapotranspiration.

Chimeric antigen receptors (CARs) and synthetic Notch (synNotch) receptors are engineered cell-surface receptors that sense a target antigen and respond by activating T cell receptor signaling or a customized gene program, respectively. Here, to expand the targeting capabilities of these receptors, we develop “universal” receptor systems for which receptor specificity can be directed post-translationally via covalent attachment of a co-administered antibody bearing a benzylguanine (BG) motif. A SNAPtag self-labeling enzyme is genetically fused to the receptor and reacts with BG-conjugated antibodies for covalent assembly, programming antigen recognition. We demonstrate that activation of SNAP-CAR and SNAP-synNotch receptors can be successfully targeted by clinically relevant BG-conjugated antibodies, including anti-tumor activity of SNAP-CAR T cells in vivo in a human tumor xenograft mouse model. Finally, we develop a mathematical model to better define the parameters affecting universal receptor signaling. SNAP receptors provide a powerful strategy to post-translationally reprogram the targeting specificity of engineered cells.

Chimeric antigen receptors (CARs) are artificial T cell receptors that re-target patients’ T cells to specifically recognize and kill tumor cells. Despite remarkable success of anti-CD19 CAR therapy against refractory B cell leukemias, there are several limitations to CAR T cell therapies including toxicities and antigen-loss leading to relapse. To address these issues, we previously developed a “universal” CAR, SNAP-CAR, for which antigen-specificity is directed by co-administered tumor-targeted antibodies. Instead of directly recognizing a tumor antigen, the SNAP-CAR carries out an enzymatic reaction to fuse with antibodies conjugated to a benzylguanine (BG) tag. Activation and effector functions of SNAP CAR T cells can be re-targeted by antibody-BG conjugates to several antigens including: CD20, CD19, HER2, and EGFR. We are now developing SNAP-CAR T cells for potential clinical translation including optimization of the CAR expression construct and functional characterization in a human tumor xenograft mouse model. SNAP-CAR-T2A-LNGFR was cloned into a gamma-retroviral expression system, yielding a 10-fold greater expression level in primary human T cells compared to our previous lentiviral vector. SNAP-CAR T cells were potently activated and lysed tumor cells in a target antigen-specific manner in vitro. Challenging NSG mice with CD20+ Raji leukemia cells, significant tumor regression was observed with SNAP-CAR T cells + Rituximab-BG and anti-CD20-CAR positive control T cells but not SNAP-CAR T cells without antibody, as compared to untransduced T cells + Rituximab-BG. The SNAP-CAR provides a powerful system to program the antigen-targeting capability of human T cells with promise for cancer therapy.

Neodymium:YAG laser energy has a pronounced effect on sodium hyaluronate that exceeds the thermal effect seen with BSS when the pressure is monitored in a closed system. These structural changes might contribute to the IOP rise seen clinically.