Source:
JOURNAL OF DRUG TARGETING, Volume 3, Number 3, p.209-216 (1995)
Abstract:
A self regulating delivery device, responsive to glucose, has been
shown to operate successfully in vitro. This comprises a gel membrane
which determines the delivery rate of insulin from a reservoir. The gel
consists of a synthetic polysucrose and the lectin, concanavalin A. The
mechanism is one of displacement of the branched polysaccharide from
the lectin receptors by incoming glucose. The gel loses its high
viscosity as a result but reforms on removal of glucose, thus providing
the switch controlling the drug diffusion rate. The drug does not
require to be chemically modified and thus the device is adaptable to
other anti-hyperglycaemic drugs. However, results here indicate that
the molecular weight of the solute may be an important parameter.
Others include path length, gel formulation and temperature. It had
been hypothesised that the reversal might be improved by the use of a
non-aqueous reservoir of insulin. However, with the use of insulin, the
switching off was found to be superior to that found with other test
solutes used in previous studies, irrespective of the reservoir
solvent. The advantages in the use of the non-aqueous system include,
however, more reproducibility in the magnitude of response and a
reduced temperature sensitivity.
