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Description:
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The need for overnight and continuous monitoring of glucose levels in diabetic
patients is profound , especially among juveniles . Implantation of a chemical assay
which responds optically to changes in glucose concentration shows promise as a
technology capable of continuously monitoring blood sugar with little invasion into the
body . Previous fluorescent chemical assays , based on the affinity binding reaction
between Concanavalin A protein and dextran , performed well but suffered from limited
dermal penetration . In this work , a novel replacement for the dextran molecule
(glycosylated dendrimer ) was fabricated and tested to determine if it would improve the
overall response of the sensing chemistry to glucose . Experiments were carried out and it
was found that the assayâ  s functionality was based on the controlled aggregation of the
Con A protein and the modified dendrimer molecule . This new assay proved to be
specific to glucose , reversible , and independent of fluorophore dye attached to the
protein .
This research was furthered by encapsulation of the new assay into a PEG
hydrogel which showed response to glucose but , due to leeching , did not perform well under repeated exposures . A new method for encapsulation was proposed based on
poration of the hydrogel to create micropores capable of holding the assay chemistry and
allowing it to react to incoming glucose , while the surrounding polymer restricted
leeching . Preliminary results with previous assays proved the potential of a mannitol
based poration procedure , but unforeseen complications in lyophilization of the new
sensor assay restricted its completion . Due to instability of Con A in solution , it was
hypothesized that the immobilization of it onto the surface of an active substrate would
increase its stability overtime as seen in previous works . The immobilization procedure
was performed on Con A for both polystyrene spheres and gold (nanoshells and colloid ) .
Both results showed an adequate amount of protein on the surface of the particles , but
little binding activity was demonstrated . Overall , the improvements to the sensor
chemistry response were notable and the potential for stabilization and enhancement of
the response through the use of an active substrate is promising . |