Controlled-release of free bacteriophage nanoparticles from 3D-plotted hydrogel fibrous structure as potential antibacterial wound dressing.

To combat the emergence of drug-resistant bacteria, a locally isolated bacteriophage (HZJ) targeting H5α Escherichia coli was used as an antibacterial agent to make wound dressing samples in this study. The phages were physically embedded within an alginate hydrogel sample so that they could later be released with their tails being free during the infection process, which preserves their lytic activity. The HZJ phage isolated in the study have a 20 min latent period and are stable between pH 6 and pH 9 and at temperatures below 45 °C. The addition of phage to an E. coli culture suppressed over 99% of bacterial growth in 2-h (p < 0.001). Phage-embedded hydrogel fibers were used to create porous wound dressing material using three-dimensional (3D) printing. The majority of phage lytic activity (85%-90%) was preserved after encapsulation. After they were embedded in samples, HZJ lysed 57% to 67% of bacteria (p < 0.001) within 2 h and the antibacterial effects lasted at least 24 h. The small amount of phage released in 2 h was able to quickly replicate and effectively lysed the majority of the bacterial hosts. Phage-embedded alginate samples released 10% of its incorporated phage particles in 24 h. The SEM micrographs show that, compared to phage-free samples, fewer E.coli cells were observed on phage-embedded samples 2 h after bacteria were exposed to the samples. The phage-embedded sample was not cytotoxic to L929 cells. The presence of HZJ in alginate hydrogel promoted cell growth (p < 0.01) and adhesion to the samples. Further, the existence of phage did not alter the tensile strength and modulus of samples (p > 0.05). An antibacterial dressing capable of slowly releasing lytic phages and effectively suppressing bacterial growth for up to 24 h was produced in this study. This model represents an attractive means to reduce use of antibiotics and other additives in conventional dressings.

The mechanical and morphological properties of 6 year-old cranial bone.

Traumatic Brain Injury (TBI) is a leading cause of mortality and morbidity for children in the United States. The unavailability of pediatric cadavers makes it difficult to study and characterize the mechanical behavior of the pediatric skull. Computer based finite element modeling could provide valuable insights, but the utility of these models depends upon the accuracy of cranial material property inputs. In this study, 47 samples from one six year-old human cranium were tested to failure via four point bending to study the effects of strain rate and the structure of skull bone on modulus of elasticity and failure properties for both cranial bone and suture. The results show that strain rate does not have a statistically meaningful effect on the mechanical properties of the six year-old skull over the range of strain rates studied (average low rate of 0.045 s(-1), average medium rate of 0.44 s(-1), and an average high rate of 2.2 s(-1)), but that these properties do depend on the growth patterns and morphology of the skull. The thickness of the bone was found to vary with structure. The bending stiffness (per unit width) for tri-layer bone (12.32±5.18 Nm(2)/m) was significantly higher than that of cortical bone and sutures (5.58±1.46 Nm(2)/m and 3.70±1.88 Nm(2)/m respectively). The modulus of elasticity was 9.87±1.24 GPa for cranial cortical bone and 1.10±0.53 GPa for sutures. The effective elastic modulus of tri-layer bone was 3.69±0.92 GPa. Accurate models of the pediatric skull should account for the differences amongst these three distinct tissues in the six year-old skull.

Splenic rupture as a complication of colonoscopy: report of a case.

Colonoscopy is a common procedure with the rare complication of a splenic injury. The proposed mechanism of injury is excessive splenocolic ligament traction. The diagnosis is made by computed tomography and the treatment is determined by the patient's stability. Here we report a case of splenic injury during colonoscopy with failure to manage conservatively. A review of the literature and suggested guidelines are also provided.