Publication information Biomaterials, 33 (26): 6132-6139Publisher Elsevier Item record/more information

Dipicolinic acid (DPA) is an excellent marker compound for bacterial spores, including those of Bacillus anthracis (anthrax). Surface-enhanced Raman spectroscopy (SERS) potentially has the sensitivity and discrimination needed for trace DPA analysis, but mixing DPA solutions with citrate-reduced silver colloid only yielded measurable SERS spectra at much higher (>80 ppm) concentrations than would be desirable for anthrax detection. Aggregation of the colloid with halide salts eliminated even these small DPA bands but aggregation with Na2SO4(aq) resulted in a remarkable increase in the DPA signals. With sulfate aggregation even 1 ppm solutions gave detectable signals with 10 s accumulation times, which is in the sensitivity range required. Addition of CNS- as an internal standard allowed quantitative DPA analysis, plotting the intensity of the strong DPA 1010 cm(-1) band (normalised to the ca. 2120 cm(-1) CNS- band) against DPA concentration gave a linear calibration (R2 = 0.986) over the range 0-50 ppm DPA. The inclusion of thiocyanate also allows false negatives due to accidental deactivation of the enhancing medium to be detected.

Bacterial cellulose (BC) is a polysaccharide produced by Acetobacter Xylinum bacteria with interesting properties for arterial grafting and vascular tissue engineering including high-burst pressure, high-water content, high crystallinity, and an ultrafine highly pure fibrous structure similar to that of collagen. Given that compliance mismatch is one of the main factors contributing to the development of intimal hyperplasia in vascular replacement conduits, an in depth investigation of support mechanical properties of BC is required to further supporting its use in cardiovascular-grafting applications. The aim of this study was to mechanically characterize BC and also study its potential to accommodate vascular cells. To achieve these aims, inflation tests and uniaxial tensile tests were carried out on BC samples. In addition, dynamic compliance tests were conducted on BC tubes, and the results were compared to that of arteries, saphenous vein, expanded polytetrafluoroethylene, and Dacron grafts. BC tubes exhibited a compliance response similar to human saphenous vein with a mean compliance value of 4.27 × 10(-2) % per millimeter of mercury over the pressure range of 30-120 mmHg. In addition, bovine smooth muscle cells and endothelial cells were cultured on BC samples, and histology and fluorescent imaging analysis were carried out showing good adherence and biocompatibility. Finally, a method to predict the mechanical behavior of BC grafts in situ was established, whereby a constitutive model for BC was determined and used to model the BC tubes under inflation using finite element analysis.

Percutaneous stent implantation has revolutionized the clinical treatment of occluded arteries. Nevertheless, there is still a large unmet need to prevent re-occlusion after implantation. Consequently, a niche exists for a cost-effective pre-clinical method of evaluating novel interventional devices in human models. Therefore, the development of a coronary model artery offers tremendous potential for the treatment of endothelial cell dysfunction and restenosis. As a first step, we employ tissue-engineering principles to examine the effect of stent deployment upon endothelial cells in a tubular in vitro system capable of replicating the coronary artery biomechanical environment. In particular, the cellular and molecular changes pertaining to inflammation, proliferation, and death were assessed after stent deployment. Real-time quantitative PCR demonstrated increased expression of genes encoding for E-Selectin, ICAM-1, and VCAM-1; markers associated with an inflammatory response in vivo. Further, an increase in the pro-apoptotic protein Bax was paralleled with a decrease in the anti-apoptotic protein Bcl-2; however, apoptotic morphology was not observed. Interestingly, transcription of c-fos increased, whereas Ki67 levels fell over the same period. One hypothesis is that these results are in response to the altered local hemodynamic environment induced by stent deployment. Most significantly, this study highlights the potential of a biomimetic hemodynamic bioreactor combined with a gene expression analysis to evaluate, with greater specificity, the performance and interaction of stents with the endothelial layer in a controlled environment.

In an effort to reduce organ replacement and enhance tissue repair, there has been a tremendous effort to create biomechanically optimized scaffolds for tissue engineering applications. In contrast, the development and characterization of electroactive scaffolds has attracted little attention. Consequently, the creation and characterization of a carbon nanotube based poly(lactic acid) nanofiber scaffold is described herein. After 28 d in physiological solution at 37 °C, a change in the mass, chemical properties and polymer morphology is seen, while the mechanical properties and physical integrity are unaltered. No adverse cytotoxic affects are seen when mesenchymal stem cells are cultured in the presence of the scaffold. Taken together, these data auger well for electroactive tissue engineering.