Gradual attenuation of a congenital extrahepatic portosystemic shunt with a self-retaining polyacrylic acid-silicone device in 6 dogs.

OBJECTIVE: To determine the ability of a polyacrylic acid-silicone radiolucent self-retaining gradual occlusion device (PAS-OD) to attenuate congenital extrahepatic portosystemic shunts (EHPSS) in dogs. STUDY DESIGN: Prospective clinical trial. ANIMALS: Six client-owned dogs with single, congenital EHPSS. METHODS: Serum bile acids (SBA), abdominal ultrasonography, and computed tomographic angiography (CTA) were performed preoperatively and at 4 and 8 weeks postoperatively. Each dog was treated for EHPSS by placement of a PAS-OD. RESULTS: PAS-OD were placed without complication an average of 4.3 seconds (range, 3-7) after isolation of the shunt. Median surgical time was 38.5 minutes (range, 28-84) including concurrent procedures. All dogs recovered from surgery without complications. SBA were normal in 5 of 6 dogs at 4 and 8 weeks after surgery. The shunt was completely attenuated in 2 of 6 dogs at 4 weeks and in 4 of 6 dogs at 8 weeks, without evidence of acquired shunt formation in any dog. The size and velocity of the portal vasculature were improved in 5 of 6 dogs according to 8-week postoperative CTA and ultrasonography results, respectively. The remaining dog had a persistently decreased portal vasculature size but a normal velocity according to 8-week postoperative CTA and ultrasound results, respectively. CONCLUSION: The PAS-OD led to complete attenuation in 4 of 6 dogs and partial attenuation with mild residual flow of 2 EHPSS over an 8-week period in dogs. CLINICAL SIGNIFICANCE: The PAS-OD is a new option for gradual occlusion of congenital EHPSS over 8 weeks.

Silk-based resorbable electronic devices for remotely controlled therapy and in vivo infection abatement.

A paradigm shift for implantable medical devices lies at the confluence between regenerative medicine, where materials remodel and integrate in the biological milieu, and technology, through the use of recently developed material platforms based on biomaterials and bioresorbable technologies such as optics and electronics. The union of materials and technology in this context enables a class of biomedical devices that can be optically or electronically functional and yet harmlessly degrade once their use is complete. We present here a fully degradable, remotely controlled, implantable therapeutic device operating in vivo to counter a Staphylococcus aureus infection that disappears once its function is complete. This class of device provides fully resorbable packaging and electronics that can be turned on remotely, after implantation, to provide the necessary thermal therapy or trigger drug delivery. Such externally controllable, resorbable devices not only obviate the need for secondary surgeries and retrieval, but also have extended utility as therapeutic devices that can be left behind at a surgical or suturing site, following intervention, and can be externally controlled to allow for infection management by either thermal treatment or by remote triggering of drug release when there is retardation of antibiotic diffusion, deep infections are present, or when systemic antibiotic treatment alone is insufficient due to the emergence of antibiotic-resistant strains. After completion of function, the device is safely resorbed into the body, within a programmable period.

Transient, biocompatible electronics and energy harvesters based on ZnO.

The combined use of ZnO, Mg, MgO, and silk provides routes to classes of thin-film transistors and mechanical energy harvesters that are soluble in water and biofluids. Experimental and theoretical studies of the operational aspects and dissolution properties of this type of transient electronics technology illustrate its various capabilities. Application opportunities range from resorbable biomedical implants, to environmentally dissolvable sensors, and degradable consumer electronics.

Multiple congenital PSS in a dog: case report and literature review.

A 4 yr old spayed female mixed-breed dog presented with a 2 yr history of recurring increases in liver enzymes. Two congenital portosystemic shunts (PSSs) were identified using computed tomography (CT) angiography, which included a portoazygous and portorenal extrahepatic shunt. Double right renal veins were also identified. The shunts were successfully identified and attenuated with cellophane banding. Multiple congenital PSS is a rare phenomenon, but should be considered during exploratory laparotomy for PSS and in dogs with poor response to surgical attenuation of a single PSS. CT proved to be a crucial part of accurate diagnosis and surgical planning for this dog with multiple congenital PSS.

Materials and designs for wirelessly powered implantable light-emitting systems.

Strategies are presented to achieve bendable and stretchable systems of microscale inorganic light-emitting diodes with wireless powering schemes, suitable for use in implantable devices. The results include materials strategies, together with studies of the mechanical, electronic, thermal and radio frequency behaviors both in vitro and in in-vivo animal experiments.

Stretchable, transparent graphene interconnects for arrays of microscale inorganic light emitting diodes on rubber substrates.

This paper describes the fabrication and design principles for using transparent graphene interconnects in stretchable arrays of microscale inorganic light emitting diodes (LEDs) on rubber substrates. We demonstrate several appealing properties of graphene for this purpose, including its ability to spontaneously conform to significant surface topography, in a manner that yields effective contacts even to deep, recessed device regions. Mechanics modeling reveals the fundamental aspects of this process, as well as the use of the same layers of graphene for interconnects designed to accommodate strains of 100% or more, in a completely reversible fashion. These attributes are compatible with conventional thin film processing and can yield high-performance devices in transparent layouts. Graphene interconnects possess attractive features for both existing and emerging applications of LEDs in information display, biomedical systems, and other environments.

Biomechanical evaluation of a non-locking pre-manufactured loop suture technique compared to a three-loop pulley suture in a canine calcaneus tendon avulsion model.

OBJECTIVE: The purpose of this cadaveric study was to compare the strength of a non-locking pre-manufactured loop (SpeedWhip™ [SW]) suture pattern using Fiberwire® with the three-loop pulley (TLP) suture pattern using polypropylene for the surgical repair of canine calcaneal tendon avulsion injuries. METHODS: In vitro biomechanical study using 22 paired tendons collected from 11 canine cadavers. Paired tendons were repaired with either a SW suture pattern using Fiberloop® suture or a TLP suture pattern using polypropylene suture. Tensile loads required to create a 1 mm gap, 3 mm gap, and construct failure were measured. RESULTS: The mean loads to achieve a 1 mm gap in the TLP and SW constructs were not significantly different. Gap formation at 3 mm occurred at significantly lower loads for the SW (106.4 ± 21.5N) than for the TLP (127.2 ± 27.5N) (p = 0.05). The mean loads to construct failure for the TLP (172.8 ± 39.4N) and SW (131.3 ± 34.3N) were significantly different (p = 0.001). CLINICAL SIGNIFICANCE: The TLP with polypropylene suture is superior to the SW using Fiberloop® at resistance to 3 mm gap formation.

In vitro development and evaluation of a polyacrylic acid-silicone device intended for gradual occlusion of portosystemic shunts in dogs and cats.

OBJECTIVE: To develop a device intended for gradual venous occlusion over 4 to 6 weeks. SAMPLE: Silicone tubing filled with various inorganic salt and polyacrylic acid (PAA) formulations and mounted within a polypropylene or polyether ether ketone (PEEK) outer ring. PROCEDURES: 15 polypropylene prototype rings were initially filled with 1 of 5 formulations and placed in PBSS. In a second test, 10 polypropylene and 7 PEEK prototype rings were filled with 1 formulation and placed in PBSS. In a third test, 2 formulations were loaded into 6 PEEK rings each, placed in physiologic solution, and incubated. In all tests, ring luminal diameter, outer diameter, and luminal area were measured over 6 weeks. RESULTS: In the first test, 2 formulations had the greatest changes in luminal area and diameter, and 1 of those had a greater linear swell rate than the other had. In the second test, 6 of 7 PEEK rings and 6 of 10 polypropylene rings closed to a luminal diamater < 1 mm within 6 weeks. Polypropylene rings had a greater increase in outer diameter than did PEEK rings between 4.5 and 6 weeks. In the third test, 11 of 12 PEEK rings gradually closed to a luminal diameter < 1 mm within 6 weeks. CONCLUSIONS AND CLINICAL RELEVANCE: A PAA and inorganic salt formulation in a prototype silicone and polymer ring resulted in gradual occlusion over 4 to 6 weeks in vitro. Prototype PEEK rings provided more reliable closure than did polypropylene rings.

Peri-implant tissue response and biodegradation performance of a Mg-1.0Ca-0.5Sr alloy in rat tibia.

Biodegradable magnesium (Mg) alloys combine the advantages of traditional metallic implants and biodegradable polymers, having high strength, low density, and a stiffness ideal for bone fracture fixation. A recently developed Mg-Ca-Sr alloy potentially possesses advantageous characteristics over other Mg alloys, such as slower degradation rates and minimal toxicity. In this study, the biocompatibility of this Mg-Ca-Sr alloy was investigated in a rat pin-placement model. Cylindrical pins were inserted in the proximal tibial metaphyses in pre-drilled holes orthogonal to the tibial axis. Implant and bone morphologies were investigated using µCT at 1, 3, and 6 weeks after implant placement. At the same time points, the surrounding tissue was evaluated using H&E, TRAP and Goldner's trichrome staining. Although gas bubbles were observed around the degrading implant at early time points, the bone remained intact with no evidence of microfracture. Principle findings also include new bone formation in the area of the implant, suggesting that the alloy is a promising candidate for biodegradable orthopedic implants.

Assessment of the attenuation of an intra-abdominal vein by use of a silicone-polyacrylic acid gradual venous occlusion device in dogs and cats.

OBJECTIVE To evaluate the closure rate and completeness of closure for a silicone-polyacrylic acid gradual venous occlusion device placed around an intra-abdominal vein to simulate gradual occlusion of an extrahepatic portosystemic shunt. ANIMALS 3 purpose-bred cats and 2 purpose-bred dogs. PROCEDURES The device was surgically placed around an external (cats) or internal (dogs) iliac vein. Computed tomographic angiography was performed at the time of surgery and 2, 4, and 6 weeks after surgery. Ultrasonographic examinations of blood flow through the vein within the device were performed at the time of surgery and at weekly intervals thereafter. Dogs were euthanized 6 weeks after surgery, and the external iliac veins were harvested for histologic examination. RESULTS The prototype gradual venous occlusion device was successfully placed in all animals, and all animals recovered without complications following the placement procedure. The vessel was completely occluded in 2 cats by 6 weeks after surgery, as determined on the basis of results of CT and ultrasonography; there was incomplete occlusion with a luminal diameter of 1.5 mm in the other cat by 6 weeks after surgery. The vessel was completely occluded in both dogs by 6 weeks after surgery. Histologic examination of the external iliac veins obtained from the dogs revealed minimal inflammation of the vessel wall and no thrombus formation. CONCLUSIONS AND CLINICAL RELEVANCE The prototype device induced gradual attenuation of an intra-abdominal vessel over a 6-week period. This device may provide another option for gradual occlusion of extrahepatic portosystemic shunts.

Immunologic and tissue biocompatibility of flexible/stretchable electronics and optoelectronics.

Recent development of flexible/stretchable integrated electronic sensors and stimulation systems has the potential to establish an important paradigm for implantable electronic devices, where shapes and mechanical properties are matched to those of biological tissues and organs. Demonstrations of tissue and immune biocompatibility are fundamental requirements for application of such kinds of electronics for long-term use in the body. Here, a comprehensive set of experiments studies biocompatibility on four representative flexible/stretchable device platforms, selected on the basis of their versatility and relevance in clinical usage. The devices include flexible silicon field effect transistors (FETs) on polyimide and stretchable silicon FETs, InGaN light-emitting diodes (LEDs), and AlInGaPAs LEDs, each on low modulus silicone substrates. Direct cytotoxicity measured by exposure of a surrogate fibroblast line and leachable toxicity by minimum essential medium extraction testing reveal that all of these devices are non-cytotoxic. In vivo immunologic and tissue biocompatibility testing in mice indicate no local inflammation or systemic immunologic responses after four weeks of subcutaneous implantation. The results show that these new classes of flexible implantable devices are suitable for introduction into clinical studies as long-term implantable electronics.

Rugged and breathable forms of stretchable electronics with adherent composite substrates for transcutaneous monitoring.

Research in stretchable electronics involves fundamental scientific topics relevant to applications with importance in human healthcare. Despite significant progress in active components, routes to mechanically robust construction are lacking. Here, we introduce materials and composite designs for thin, breathable, soft electronics that can adhere strongly to the skin, with the ability to be applied and removed hundreds of times without damaging the devices or the skin, even in regions with substantial topography and coverage of hair. The approach combines thin, ultralow modulus, cellular silicone materials with elastic, strain-limiting fabrics, to yield a compliant but rugged platform for stretchable electronics. Theoretical and experimental studies highlight the mechanics of adhesion and elastic deformation. Demonstrations include cutaneous optical, electrical and radio frequency sensors for measuring hydration state, electrophysiological activity, pulse and cerebral oximetry. Multipoint monitoring of a subject in an advanced driving simulator provides a practical example.

Materials for bioresorbable radio frequency electronics.

Materials, device designs and manufacturing approaches are presented for classes of RF electronic components that are capable of complete dissolution in water or biofluids. All individual passive/active components as well as system-level examples such as wireless RF energy harvesting circuits exploit active materials that are biocompatible. The results provide diverse building blocks for physically transient forms of electronics, of particular potential value in bioresorbable medical implants with wireless power transmission and communication capabilities.

Dental care and associated factors among older adults with schizophrenia.

BACKGROUND: Few data are available concerning dental care in older adults with schizophrenia. The authors examined the utilization of dental care and factors related to dental treatment in this population. METHODS: The sample consisted of 198 community-dwelling participants 55 years and older with schizophrenia and a community comparison group of 113 participants. The authors adapted a model of illness behavior in later life as the basis for selection of 18 predictor variables of annual dental care visits. RESULTS: The study results showed no significant differences between the schizophrenia and community comparison groups with regard to the percentage of participants (28 and 31 percent, respectively) reporting having had at least two dental visits in the previous year or one dental visit (48 and 54 percent, respectively). However, the results showed significant differences in the percentage of participants in the schizophrenia and community comparison groups who stated that they experienced problems with their teeth or dentures (41 and 23 percent, respectively). When examining participants in the schizophrenia group separately, the authors found four variables that were significantly associated with having had at least one dental visit: financial well-being (odds ratio [OR] = 1.12), better executive cognitive functioning (OR = 1.11), fewer perceived problems with teeth or dentures (OR = 0.33) and fewer oral dyskinesias (OR = 0.86). CONCLUSIONS: Most older adults with schizophrenia in this study did not receive at least two dental visits per year, although their frequency of care was no worse than that of their age-matched peers. Psychiatric assessments should include questions about dental care. The greatest improvement in dental care for such patients likely is to occur by targeting people who report having more problems with their teeth, including oral dyskinesias; those who have greater cognitive impairments, especially in executive functioning; and those who have diminished financial resources.