A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)

Meeting abstrac

Synthesis and properties of a novel anisotropic self-inflating hydrogel tissue expander.

The advent of self-inflating hydrogel tissue expanders heralded a significant advance in the reconstructive techniques available for the surgical restoration of a wide variety of soft tissue defects. However, their use in specific applications such as cleft palate surgery is limited on account of their isotropic expansion. An anisotropic self-inflating hydrogel tissue expander has been developed which markedly increases the potential indications for which this restorative tool may be employed. These include complex pediatric soft tissue reconstructions of the palate, nose, ear and digits. Anisotropic expansion in a hydrogel polymer network composed of methyl methacrylate and vinylpyrrolidone has been achieved by annealing the xerogel under a compressive load for a specified time period. By controlling the anisotropic processing conditions and composition we have been able to accurately tailor the ultimate expansion ratio up to 1500%. The expansion rate of the xerogel has also been significantly reduced by encapsulating the polymer within a semi-permeable silicone membrane. The structure and properties of the novel anisotropic hydrogel were characterized by attenuated total reflectance infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis and small-angle neutron scattering

Development of a novel anisotropic self-inflating tissue expander: in vivo submucoperiosteal performance in the porcine hard palate.

BACKGROUND: The advent of self-inflating hydrogel tissue expanders heralded a significant advance in the reconstructive potential of this technique. Their use, however, is limited by their uncontrolled isotropic (i.e., uniform in all directions) expansion. METHODS: Anisotropy (i.e., directional dependence) was achieved by annealing a hydrogel copolymer of poly(methyl methacrylate-co-vinyl pyrrolidone) under a compressive load for a specified time period. The expansion ratio is dictated by the percentage of vinyl pyrrolidone content and the degree of compression. The expansion rate is modified by incorporating the polymer within a silicone membrane. The in vivo efficacy of differing prototype devices was investigated in juvenile pigs under United Kingdom Home Office Licence. The devices were implanted within a submucoperiosteal pocket in a total of six porcine palates; all were euthanized by 6 weeks after implantation. A longitudinal volumetric assessment of the expanded tissue was conducted, in addition to postmortem analysis of the bony and mucoperiosteal palatal elements. RESULTS: Uncoated devices caused excessive soft-tissue expansion that resulted in mucoperiosteal ulceration, thus necessitating animal euthanasia. The silicone-coated devices produced controlled soft-tissue expansion over the 6-week study period. There was a statistically significant increase in the volume of expanded soft tissue with no evidence of a significant acute inflammatory response to the implant, although peri-implant capsule formation was observed. Attenuation of the bony palatal shelf was noted. CONCLUSION: A unique anisotropic hydrogel device capable of controlled expansion has been developed that addresses a number of the shortcomings of the technology hitherto available

Amplified optical nonlinearity in a self-assembled double-strand conjugated porphyrin polymer ladder.

Addition of 4,4'-bipyridyl to a solution of a meso-meso butadiyne-linked conjugated zinc porphyrin polymer in chloroform results in self-assembly of a double-strand ladder complex. Excess ligand causes this duplex to dissociate into single strands. These binding processes were elucidated by near-IR and NMR titrations, as well as by gel permeation chromatography and small-angle neutron scattering. Ladder-making and -breaking are highly cooperative, with Hill coefficients of 3.0 and 3.7, respectively. Self-assembly of the ladder holds the pi-system in a planar conformation, enhancing the conjugation, resulting in a red-shift and intensification of the Q-band. Both the real and imaginary parts of the third-order susceptibility per macrocycle are amplified by ladder formation, as revealed by degenerate four-wave mixing measurements at 1064 nm. At this wavelength, the double-strand polymer complex has |chi(3)xyyx| = 6.0 x 10-17 m2 V-2 per macrocycle, compared with 6.6 x 10-18 m2 V-2 for the single-strand polymer under the same conditions