Vincent Leung

Pullulan Encapsulation of Labile Biomolecules to Give Stable Bioassay Tablets

A simple and inexpensive method is reported for the long-term stabilization of enzymes and other unstable reagents in premeasured quantities in water-soluble tablets (cast, not compressed) made with pullulan, a nonionic polysaccharide that forms an oxygen impermeable solid upon drying. The pullulan tablets dissolve in aqueous solutions in seconds, thereby facilitating the easy execution of bioassays at remote sites with no need for special reagent handling and liquid pipetting. This approach is modular in nature, thus allowing the creation of individual tablets for enzymes and their substrates. Proof-of-principle demonstrations include a Taq polymerase tablet for DNA amplification through PCR and a pesticide assay kit consisting of separate tablets for acetylcholinesterase and its chromogenic substrate, indoxyl acetate, both of which are highly unstable. The encapsulated reagents remain stable at room temperature for months, thus enabling the room-temperature shipping and storage of bioassay components.

Polyvinylamine―Phenylboronic Acid Adhesion to Cellulose Hydrogel

Pairs of wet, regenerated cellulose films were laminated with polyvinylamine derivatized with phenylboronic acid (PVAm-PBA), and the forces required to delaminate the never-dried laminates were measured as functions of adhesive structure and application conditions. The greatest wet adhesion was obtained with 150 kDa PVAm, with 16% of the amines bearing phenylboronic moieties. The pH at which the PVAm-PBA was adsorbed onto the cellulose was the dominant process parameter. High adsorption pH gave high concentrations of adsorbed adhesive and the maximum adhesion. The specific role of the phenyl boronic groups was illustrated two ways: (a) replacing the B(OH)(2) with OH (i.e., phenol) gave much lower adhesion, and (b) wet adhesion was greatly reduced by the presence of sorbitol, which effectively competes with cellulose for boronate-binding sites.

Diaphragmatic injuries: why do we struggle to detect them?

Diaphragmatic injury is an uncommon traumatic condition. It can be easily missed due to a lack of awareness by both clinicians and radiologists. A high index of suspicion is required for the establishment of an early diagnosis and prevention of life-threatening complications. Multidetector computed tomography (MDCT) is the modality of choice for the detection of diaphragmatic injury. In this review article, we illustrate the MDCT appearance of blunt and penetrating diaphragmatic injuries and emphasize the role of the emergency radiologist in detecting these entities.

Design Rules for Fluorocarbon-Free Omniphobic Solvent Barriers in Paper-Based Devices.

The utility of hydrophobic wax barriers in paper-based lateral flow and multiwell devices for containment of aqueous solvents was extended to organic solvents and challenging aqueous surfactant solutions by preparation of a three layer barrier, consisting of internal pullulan impregnated paper barriers surrounded by external wax barriers. When paper impregnated with pullulan solution dries, the polymer forms solvent blocking lenses in the paper structure. Lens formation was illustrated by forming pullulan lenses in glass capillaries. The lens shapes were less curved compared to the predictions of a model based upon minimizing surface area. For barriers on Whatman # 1 filter paper, the pullulan molecular weight must be greater than ∼70 kDa, the mass fraction of pullulan in the barrier zone must be at least 32%, and there are restrictions on the minimum width of the pullulan impregnated zone.

Imaging of Traumatic Diaphragmatic Rupture: Evaluation of Diagnostic Accuracy at a Level 1 Trauma Centre

Purpose Traumatic diaphragmatic rupture (TDR) is an uncommon injury that can be associated with significant morbidity if not detected and treated in a timely manner. The purpose of our study was to evaluate the diagnostic accuracy of 64-slice multidetector computed tomography (64-MDCT) for the detection of TDR in patients at our level 1 trauma centre. Methods We used our hospitals trauma registry to identify patients with a diagnosis of TDR from January 1, 2008, to December 31, 2012. Only patients with a 64-MDCT scan at presentation who subsequently underwent laparotomy/laparoscopy were included in the study cohort. Using surgical findings as the gold standard, the accuracy of the prospective radiology reports was analyzed. Results Of the 3225 trauma patients who presented to our institution, 38 (1.2%) had a TDR. Fourteen of the 38 were excluded as they did not have MDCT before surgery. The study cohort consisted of 20 males and 4 females with a median age of 34.5 years and a median Injury Severity Score (ISS90) of 26. Fifteen had blunt trauma while 9 had a penetrating injury. The overall sensitivity of the radiology reports was 66.7% (95% confidence interval [CI]: 46.7%-82.0%), specificity was 100% (95% CI: 94.1%-100%), positive predictive value was 100% (95% CI: 80.6%-100%), negative predictive value was 88.4% (95% CI: 78.8%-94.0%), and accuracy was 90.6% (95% CI: 82.5%-95.2%). However, only 3 of 9 patients with penetrating injury had a correct preoperative diagnosis. Two of the 6 missed penetrating trauma cases had only indirect signs of injury. Conclusions The detection of TDR in trauma patients on 64-MDCT can be improved, especially in patients presenting with penetrating injury. A careful search for subtle diaphragmatic defects and indirect evidence of injury is important to avoid missing the diagnosis.