Matthew Chapman

A Variable Cross-section Pore for Screening Cells for Specific Markers

Nanopores have emerged as a versatile tool for performing highly sensitive single-molecule measurements to probe the properties of proteins and nucleic acids. Interactions within a nanopore (due to pore functionalization with metals, oxides, or organic species) can result in slower translocation rates, thereby realizing “smart” nanopore sensors that provide insight into the properties of the particles that are transiting the pore. At the same time, while greatly enhancing its utility, functionalizing a pore with only one type of species limits the broader applicability of pores for biosensing.

Label-free Screening of Niche-to-niche Variation in Satellite Stem Cells Using Functionalized Pores

Understanding embryonic organogenesis and adult tissue regeneration relies on the ability to isolate and characterizing stem cells. However, these cells are difficult to study because they constitute minute populations in organ niches and express multiple cell-surface markers, few of which are identified. Furthermore, the properties of these cells change quickly in vitro and possibly even during isolation procedures. Perturbations introduced during sample isolation and processing, and the difficulty in determining gene-expression levels accurately in the low starting stem-cell numbers within the micro-anatomical niche further add further complications. Because they are better suited for large numbers of cells, fluorescence-activated cell sorting (FACS) and magnetic-activated cell sorting (MACS) do not easily enable niche-specific characterization or even separate hind-leg muscle groups in the case of muscle (satellite) stem cells. Microscopy, although capable of imaging stem cells in their niches, is labor intensive and quantifying expression levels is difficult. Adding to the overall complexity is the fact that FACS, MACS, and fluorescence microscopy depend on irreversible antibody binding to stem-cell surface proteins, potentially altering cell properties, including gene expression and regenerative capacity. To address these challenges, we have developed a unique, label-free method for the objective, quantitative screening and characterization of single, functional organ stem cells. We demonstrate the power of our method by quantitatively screening satellite cells directly isolated from single muscle fibers.

The Northwestern Hawaiian Islands coral reef ecosystem reserve: Ephemeral protection

As part of his administrations efforts to preserve environmentally valuable national areas for future generations, President Clinton issued two Executive Orders in late 2000 to begin the process of designating a vast tract of oceans and reefs in the Northwestern Hawaiian Islands as a National Marine Sanctuary, and Congress lent some support to this effort in the National Marine Sanctuaries Amendments Act of 2000. A sanctuary of this scale is unprecedented. Clintons use of Executive Orders as the vehicle for the creation of this Reserve, however, has left these marine resources vulnerable, and the environmental statutes cited in the EOs provide little real power to preserve the coral reefs. As a vision, the NHICRER is an important development in marine protection, but as a reality, it is far from home free.