Enhancing analytical accuracy of intravascular electrochemical oxygen sensors via nitric oxide release using S-nitroso-N-acetyl-penicillamine (SNAP) impregnated catheter tubing.

Implantable medical devices are an integral part of primary/critical care. However, these devices carry a high risk for blood clots, caused by platelet aggregation on a foreign body surface. This study focuses on the development of a simplified approach to create nitric oxide (NO) releasing intravascular electrochemical oxygen (O2) sensors with increased biocompatibility and analytical accuracy. The implantable sensors are prepared by embedding S-nitroso-N-acetylpenacillamine (SNAP) as the NO donor molecule in the walls of the catheter type sensors. The SNAP-impregnated catheters were prepared by swelling silicone rubber tubing in a tetrahydrofuran solution containing SNAP. Control and SNAP-impregnated catheters were used to fabricate the Clark-style amperometric PO2 sensors. The SNAP-impregnated sensors release NO under physiological conditions for 18 d as measured by chemiluminescence. The analytical response of the SNAP-impregnated sensors was evaluated in vitro and in vivo. Rabbit and swine models (with sensors placed in both veins and arteries) were used to evaluate the effects on thrombus formation and analytical in vivo PO2 sensing performance. The SNAP-impregnated PO2 sensors were found to more accurately measure PO2 levels in blood continuously (over 7 and 20 h animal experiments) with significantly reduced thrombus formation (as compared to controls) on their surfaces.

Rodent Skeletal Muscle Metabolomic Changes Associated With Static Cold Storage.

OBJECTIVE: The aim of this study was to evaluate the impact of static cold storage preservation on skeletal muscle metabolism using a rodent model. METHODS: Sixteen male Lewis rats (250 ± 25 g) were distributed into 4 groups, including naive control, warm ischemia for 2 hours, static warm storage for 6 hours, and static cold storage for 6 hours. Energy status, metabolomics profiling, and histopathology of the muscle were analyzed. RESULTS: In the warm ischemia and static warm storage groups, glycolytic pathway metabolites decreased, but the Krebs cycle metabolite of succinate and the purine degradation product of hypoxanthine accumulated. Increased succinate and hypoxanthine levels were associated with increased injury severity scores. During static cold storage, the glycolytic pathway activity and the energy status were preserved. Succinate and hypoxanthine levels showed no significant difference from the naive group. CONCLUSION: Warm ischemia results in reduced glycolysis and Krebs cycle metabolites. Static cold storage preserves the glycolytic pathway and represents a favorable contribution to cellular energy demand. Succinate and hypoxanthine might be used as novel potential biomarkers for the assessment of viability and injury severity.

A small-scale, rolled-membrane microfluidic artificial lung designed towards future large area manufacturing.

Artificial lungs have been used in the clinic for multiple decades to supplement patient pulmonary function. Recently, small-scale microfluidic artificial lungs (µAL) have been demonstrated with large surface area to blood volume ratios, biomimetic blood flow paths, and pressure drops compatible with pumpless operation. Initial small-scale microfluidic devices with blood flow rates in the µl/min to ml/min range have exhibited excellent gas transfer efficiencies; however, current manufacturing techniques may not be suitable for scaling up to human applications. Here, we present a new manufacturing technology for a microfluidic artificial lung in which the structure is assembled via a continuous "rolling" and bonding procedure from a single, patterned layer of polydimethyl siloxane (PDMS). This method is demonstrated in a small-scale four-layer device, but is expected to easily scale to larger area devices. The presented devices have a biomimetic branching blood flow network, 10 µm tall artificial capillaries, and a 66 µm thick gas transfer membrane. Gas transfer efficiency in blood was evaluated over a range of blood flow rates (0.1-1.25 ml/min) for two different sweep gases (pure O2, atmospheric air). The achieved gas transfer data closely follow predicted theoretical values for oxygenation and CO2 removal, while pressure drop is marginally higher than predicted. This work is the first step in developing a scalable method for creating large area microfluidic artificial lungs. Although designed for microfluidic artificial lungs, the presented technique is expected to result in the first manufacturing method capable of simply and easily creating large area microfluidic devices from PDMS.

Extracorporeal support: improves donor renal graft function after cardiac death.

Donors after cardiac death (DCD) could increase the organ pool. Data supports good long-term renal graft survival. However, DCDs are <10% of deceased donors in the United States, due to delayed graft function, and primary nonfunction. These complications are minimized by extracorporeal support after cardiac death (ECS-DCD). This study assesses immediate and acute renal function from different donor types. DCDs kidneys were recovered by conventional rapid recovery or by ECS, and transplanted into nephrectomized healthy swine. Warm ischemia of 10 and 30 min were evaluated. Swine living donors were controls (LVD). ECS-DCDs were treated with 90 min of perfusion until organ recovery. After procurement, kidneys were cold storage 4-6 h. Renal vascular resistance (RVR), urine output (UO), urine protein concentration (UrPr) and creatinine clearance (CrCl), were collected during 4 h posttransplantation. All grafts functioned with adequate renal blood flow for 4 h. RVR at 4 h posttransplant returned to baseline only in the LVD group (0.36 mmHg/mL/min +/- 0.03). RVR was higher in all DCDs (0.66 mmHg/mL/min +/- 0.13), without differences between them. UO was >50 mL/h in all DCDs, except in DCD-30 (6.8 mL/h +/- 1.7). DCD-30 had lower CrCl (0.9 mL/min +/- 0.2) and higher UrPr >200 mg/dL, compared to other DCDs >10 mL/min and <160 mg/dL, respectively. Normothermic ECS can resuscitate kidneys to transplantable status after 30 min of cardiac arrest/WI.