Faculty Bibliography

This paper describes research addressing the question of whether microscopic hydrogels can be created from poly(ethylene glycol) [PEG 6800] and poly(ethylene oxide) [PEO 200K] using spatially resolved radiation from a scanning electron microscope with an approach similar to that used in the electron-beam patterning of polymeric photoresists. We demonstrate that, indeed, PEG hydrogels with micrometer and submicrometer feature sizes can be created by this approach, and we call these microhydrogels. Using solvent-free PEG 6800 and PEO 200K films similar to50-100-nm thick, we have identified sets of irradiation conditions where sufficient cross-linking occurs so that the exposed patterned polymer remains while the unexposed polymer dissolves during a post-irradiation solvent rinse. Arbitrary spatial patterns can be made. We have generated patterned dots with diameters below 200 rim. Using atomic force microscopy, in air and water, to study similar to5 x 5 mum PEG and PEO pads on silicon, we show that the patterned features generated by electron-beam cross-linking swell when exposed to water. The extent of swelling depends on the incident electron dose. Maximum swelling ratios of 14-16 have been observed. The swelling ratio decreases with increasing dose toward a limit of unity at the highest doses studied. Because of the significance of PEG in biomaterials applications, we examined the adsorption of fibronectin fragments onto the PEG microhydrogels using immunofluoresence optical microscopy. Undetectable Fn levels are observed on microhydrogels subjected to the lowest radiative exposure conditions where maximum swelling occurs. Fn adsorption increases with increasing dose and reaches a maximum at the highest doses where swelling ratios of unity are observed. This approach opens a new means for arbitrarily patterning the spatial distribution of proteins on surfaces and may be useful for controlling surface bioactivity

Congenital heart block (CHB), a life-threatening manifestation of neonatal lupus, offers aunique opportunity to study the effect or arm of immunity and define the pathogenicity of an autoantibody in mediating tissue injury. This review focuses on our recent in vitro model which supports a cascade from antibody insult to unchecked fibrosis. In brief, it is proposed that the fetal cardiac myocyte undergoes apoptosis which facilitates transfer of intracellular Ro and La antigens to the surface where they are bound by circulating maternal autoantibodies (anti-SSA/Ro-SSB/La antibodies). Scavenging macrophages phagocytose these inadvertently 'opsonized' cardiocytes, leading to the secretion of pro-inflammatory and pro-fibrotic cytokines, the latter of which transdifferentiate fibroblasts into myofibroblasts and thereby promote scarring. Immunohistologic study of a heart from a neonate dying of CHB supports this model in that macrophages and myofibroblasts were demonstrated. To facilitate both basic and clinical research, a Research Registry for Neonatal Lupus was established in 1994 by the U.S. National Institute of Arthritis, Musculoskeletal and Skin Diseases. Maternal and fetal outcomes are addressed as well as recurrence rates. Laboratory evaluation and management decisions during pregnancy are provided