Effect of the surface chemistry of insulin fibrils on the aggregation rate.

Structure transition cascade: Insulin fibrils undergo a secondary structural transition-from the α-rich to the ß-rich form-upon progressively increasing the incubation time from 0.5 to ten hours. Atomic force microscopy measurements show that the fibril surface chemistry changes from hydrophilic to hydrophobic and the aggregation rate increases fivefold.

Use of laxative-augmented contrast medium in the evaluation of colorectal foci at FDG PET.

PURPOSE: To compare the diagnostic accuracy of fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) in the detection of colon lesions with that of delayed PET/computed tomography (CT) performed after the administration of a laxative-augmented contrast medium. MATERIALS AND METHODS: All patients gave written informed consent according to the guidelines issued by the institutional review board. In a prospective study performed from November 2005 to December 2006, images obtained in 847 patients were reviewed by two physicians in consensus. Colorectal FDG uptake on initial PET images that exceeded background FDG accumulation was graded as minimal, equivocal, or positive. When the initial PET scan revealed a colorectal region of increased uptake, either oral or anal laxative-augmented contrast medium was administered on the basis of the site of colorectal FDG focus and delayed PET/CT was performed. Initial PET findings were reevaluated and revised when necessary. Comparison was performed on a per-patient basis. Findings at histopathologic analysis and clinical follow-up served as the reference standard. The accuracy of PET was compared with that of PET/CT by using the McNemar test. RESULTS: Colorectal FDG foci were seen on initial images in 137 patients. Uptake on the initial images was reported as minimal in 14 patients, equivocal in 68, and positive in 55. With use of a laxative-augmented contrast medium and delayed PET/CT, the proportions of equivocal and positive results decreased by 84% (57 of 68 patients) and 58% (18 of 31 patients), respectively. The accuracy of delayed PET/CT in the depiction of colorectal cancer was greater than that of initial PET (93.4% [128 of 137 patients] vs 71.5% [98 of 137 patients], respectively; P < .01). CONCLUSION: Delayed PET/CT with laxative-augmented contrast medium is more accurate than initial PET alone in the detection of colorectal cancer. This approach has promise as a tool for guiding decisions about how to treat patients with colorectal FDG foci. SUPPLEMENTAL MATERIAL: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101193/-/DC1.

Gold nanoparticles as amyloid-like fibrillogenesis inhibitors.

Amyloid aggregates are one of the likely key factors leading to the development of Alzheimer's disease (AD) and other amyloidosis associated diseases. Several recent studies have shown that some anti-diabetic drugs have a positive therapeutic effect on AD patients by crossing the blood brain barrier (BBB) and preventing or reducing insulin resistance. Nanoparticles (NPs) or nanoscale objects (<600Da.), are able to cross the BBB at low concentrations, and can specifically target amyloidogenic structures. Thus, NPs are fast becoming indispensable tools for directed drug delivery, particularly when targeting structures or regions in the brain. Here, we have explored the inhibitory effect of gold nanoparticles (AuNPs) on the fibrillogenesis process of insulin fibrils. We found that when AuNPs were co-incubated with insulin, the structural transformation into amyloid-like fibrils was delayed by about a week. Further, the fibrils that formed, exhibited altered structure, shape, and dynamics, which further reduced fibril growth, and the stability of available amyloid-like fibrils with cross-ß structure for aggregation. Our results demonstrate that AuNPs disrupt insulin amyloid fibrillation resulting in fibrils that are shorter and more compact, and thus may serve a useful role in new therapeutic and diagnostic strategies for amyloid-related disorders.

Hydrogen peroxide treatment of eggshell membrane to control porosity.

The eggshell membrane (ESM) is a naturally occurring biological polymer, which can be extracted from eggshells, and has been used for adsorption of dyes or heavy metals, as a semipermeable membrane to control particle transport, and as a natural biocompatible material for tissue replacement. In this study, we used hydrogen peroxide to control the pore size and fibre crossing density of the ESM. Structural and chemical properties were investigated using AFM, optical microscopy, contact angle, and FTIR. We show that the structure and permeability of the ESM can be controlled by timed exposure to H2O2 and we demonstrate this effect using red blood cells. This process provides a simple method for preparing biocompatible membranes, with controlled selectivity for biofiltration applications.