Bio-inspired antimicrobial surfaces fabricated by glancing angle deposition.

This paper describes the fabrication of cicada-wing-inspired antimicrobial surfaces using Glancing Angle Deposition (GLAD). From the study of an annual cicada (Neotibicen Canicularis, also known as dog-day cicada) in North America, it is found that the cicada wing surfaces are composed of unique three-dimensional (3D) nanofeature arrays, which grant them extraordinary properties including antimicrobial (antifouling) and antireflective. However, the morphology of these 3D nanostructures imposes challenges in artificially synthesizing the structures by utilizing and scaling up the template area from nature. From the perspective of circumventing the difficulties of creating 3D nanofeature arrays with top-down nanofabrication techniques, this paper introduces a nanofabrication process that combines bottom-up steps: self-assembled nanospheres are used as the bases of the features, while sub-100 nm pillars are grown on top of the bases by GLAD. Scanning electron micrographs show the resemblance of the synthesized cicada wing mimicry samples to the actual cicada wings, both quantitatively and qualitatively. The synthetic mimicry samples are hydrophobic with a water contact angle of 125˚. Finally, the antimicrobial properties of the mimicries are validated by showing flat growth curves of Escherichia coli (E. coli) and by direct observation under scanning electron microscopy (SEM). The process is potentially suitable for large-area antimicrobial applications in food and biomedical industries.

The effect of C2-3 disc angle on postoperative adverse events in cervical spondylotic myelopathy.

OBJECTIVEComplete radiographic and clinical evaluations are essential in the surgical treatment of cervical spondylotic myelopathy (CSM). Prior studies have correlated cervical sagittal imbalance and kyphosis with disability and worse health-related quality of life. However, little is known about C2-3 disc angle and its correlation with postoperative outcomes. The present study is the first to consider C2-3 disc angle as an additional radiographic predictor of postoperative adverse events.METHODSA retrospective chart review was performed to identify patients with CSM who underwent surgeries from 2010 to 2014. Data collected included demographics, baseline presenting factors, and postoperative outcomes. Cervical sagittal alignment variables were measured using the preoperative and postoperative radiographs. Univariable logistic regression analyses were used to explore the association between dependent and independent variables, and a multivariable logistic regression model was created using stepwise variable selection.RESULTSThe authors identified 171 patients who had complete preoperative and postoperative radiographic and outcomes data. The overall rate of postoperative adverse events was 33% (57/171), and postoperative C2-3 disc angle, C2-7 sagittal vertical axis, and C2-7 Cobb angle were found to be significantly associated with adverse events. Inclusion of postoperative C2-3 disc angle in the analysis led to the best prediction of adverse events. The mean postoperative C2-3 disc angle for patients with any postoperative adverse event was 32.3° ± 17.2°, and the mean for those without any adverse event was 22.4° ± 11.1° (p < 0.0001).CONCLUSIONSIn the present retrospective analysis of postoperative adverse events in patients with CSM, the authors found a significant association between C2-3 disc angle and postoperative adverse events. They propose that C2-3 disc angle be used as an additional parameter of cervical spinal sagittal alignment and predictor for operative outcomes.

Biomechanics of L5/S1 in Long Thoracolumbosacral Constructs: A Cadaveric Study.

STUDY DESIGN: In vitro cadaveric biomechanical study. OBJECTIVES: Despite numerous techniques employed to establish solid lumbosacral fixation, there are little biomechanical data correlating fixation methods at L5/S1 to thoracolumbosacral (TLS) construct length. We aimed to determine the optimal construct with the hypothesis that under physiological loads, lumbosacral constructs can be stabilized by L5/S1 anterior lumbar interbody fusion (ALIF) alone, without iliac screw fixation (ISF), and that TLS constructs would require ISF, with or without ALIF. METHODS: By using a robot capable of motion in 6 axes, force-moment sensor, motion-tracking camera system and software, we simulated the spinal loading effects in flexion-extension, axial rotation, and lateral bending, and compared torques in different construct groups of T4-S1, T10-S1, and L2-S1. By conducting multidirectional flexibility testing we assessed the effects of constructs of various lengths on the L5/S1 segment. RESULTS: L2-S1 constructs may be equivalently stabilized by L5/S1 ALIF alone without ISF. Longer TLS constructs exerted increasing motion at L5/S1, exhibiting trends in favor of ISF when extending to T10 and statistically improved fixation when extending to T4. Lastly, TLS constructs with ISF exhibited a statistically significant reduction in L5-S1 range of motion from the addition of ALIF when extending to T4-pelvis but not T10-pelvis. CONCLUSIONS: We found that ALIF alone may sufficiently support the L2-S1 construct, reducing L5/S1 range of motion and transmitting loads instead to the sacropelvis. Furthermore, ALIF was found to add significant stability to the T4-pelvis construct when added to ISF. This difference was not significant for the T10-pelvis construct.

Photodiode array for characterizing optical fibers.

An innovative approach is proposed and demonstrated for measuring the attenuation of light in optical fibers. The technique utilizes a silicon device containing a v-groove that positions the fiber and detector array along the v-groove. The detectors within the v-groove are designed to partially surround the fiber in order to maximize the coupling of scattered light from the fiber into each detector.

Central Sensitization Inventory as a Predictor of Worse Quality of Life Measures and Increased Length of Stay Following Spinal Fusion.

BACKGROUND: Central sensitization is abnormal and intense enhancement of pain mechanism by the central nervous system. Patients with central sensitization may be at higher risk of poor outcomes after spinal fusion. The Central Sensitivity Inventory (CSI) was developed to identify and quantify key symptoms related to central sensitization. METHODS: In 664 patients who underwent thoracic and/or lumbar fusion, we evaluated retrospectively pretreatment CSI as a predictor of postoperative quality of life measures, length of stay, and discharge status. RESULTS: Preoperative Pain Disability Questionnaire scores, Patient Health Questionnaire-9 scores, and EuroQol-5 Dimensions index scores were significantly worse in patients with preoperative CSI ≥40 compared with patients with preoperative CSI <40 (P < 0.0001 for all). After adjusting for demographic variables, operation duration, and preoperative health status, preoperative CSI was significantly associated with higher postoperative Pain Disability Questionnaire total score (unadjusted P < 0.001, adjusted P = 0.009), higher postoperative Patient Health Questionnaire-9 score (unadjusted P < 0.001, adjusted P = 0.001), and lower postoperative EuroQol-5 Dimensions index (unadjusted P < 0.001, adjusted P = 0.001). For each 10-unit increase in CSI, average length of stay increased by 6.4% (95% confidence interval 0.4%-12.6%, P = 0.035). The odds of being discharged home after adjusting for confounders was not statistically related to preoperative CSI (P = 0.0709). CONCLUSIONS: Preoperative CSI was associated with worse quality of life outcomes and increased length of stay after spinal fusions. CSI may be an additional measure in evaluating patients preoperatively to better predict successful spinal fusion outcomes.

Spinal cord stimulation: a review of the safety literature and proposal for perioperative evaluation and management.

BACKGROUND CONTEXT: There is currently no consensus on appropriate perioperative management of patients with spinal cord stimulator implants. Magnetic resonance imaging (MRI) is considered safe under strict labeling conditions. Electrocautery is generally not recommended in these patients but sometimes used despite known risks. PURPOSE: The aim was to discuss the perioperative evaluation and management of patients with spinal cord stimulator implants. STUDY DESIGN: A literature review, summary of device labeling, and editorial were performed, regarding the safety of spinal cord stimulator devices in the perioperative setting. METHODS: A literature review was performed, and the labeling of each Food and Drug Administration (FDA)-approved spinal cord stimulation system was reviewed. The literature review was performed using PubMed and the FDA website (www.fda.gov). RESULTS: Magnetic resonance imaging safety recommendations vary between the models. Certain systems allow for MRI of the brain to be performed, and only one system allows for MRI of the body to be performed, both under strict labeling conditions. Before an MRI is performed, it is imperative to ascertain that the system is intact, without any lead breaks or low impedances, as these can result in heating of the spinal cord stimulation (SCS) and injury to the patient. Monopolar electrocautery is generally not recommended for patients with SCS; however, in some circumstances, it is used when deemed required by the surgeon. When cautery is necessary, bipolar electrocautery is recommended. Modern electrocautery units are to be used with caution as there remains a risk of thermal injury to the tissue in contact with the SCS. As with MRI, electrocautery usage in patients with SCS systems with suspected breaks or abnormal impedances is unsafe and may cause injury to the patient. CONCLUSIONS: Spinal cord stimulation is increasingly used in patients with pain of spinal origin, particularly to manage postlaminectomy syndrome. Knowledge of the safety concerns of SCS and appropriate perioperative evaluation and management of the SCS system can reduce risks and improve surgical planning.

Multiple overlapping stents as monotherapy in the treatment of 'blister' pseudoaneurysms arising from the supraclinoid internal carotid artery: a single institution series and review of the literature.

BACKGROUND: The 'blister-type' aneurysm is one of the most devastating cerebrovascular lesions. Flow diversion with stent reconstruction is an emerging treatment and has shown promising initial results. OBJECTIVE: To evaluate the experience of one institution using stent reconstruction for pseudoaneurysms of the supraclinoid internal carotid artery and to compare with a review of the literature. METHODS: A retrospective review from one institution identified eight patients with 'blister' aneurysms over a 47-month period. The Raymond scale was used to classify the aneurysms. Clinical data were obtained using the modified Rankin Scale (mRS) and the National Institute of Health Stroke Scale. A literature review was performed and compared with our results. Clinical and angiographic data were obtained. RESULTS: After treatment, two aneurysms were Raymond class 1 (25%) and six were class 3 (75%). Of the class 3 aneurysms, two required retreatment, three (50%) progressed to complete occlusion and three (50%) had persistent aneurysm filling. Clinical data revealed two patients with mRS score of 0 (25%), five with mRS score of 1 (62.5%) and one with mRS score of 2 (12.5%). From the literature review, residual filling was evident in nine patients (64.3%) and complete occlusion in four (28.6%). On follow-up angiography, nine (64.3%) were occluded, two (14.3%) had residual neck filling and one (7.1%) had persistent aneurysm filling. Thirteen patients (92.9%) had an mRS score of 2 or better. Combining the available experience, patients demonstrated either improvement (n=9, 41%) or stability (n=11, 50%). Only two (9%) had progression requiring retreatment. CONCLUSIONS: Endovascular stent remodeling of 'blister-type' aneurysms is a safe and effective strategy.

Fully integrated three-dimensional electrodes for electrochemical detection in microchips: fabrication, characterization, and applications.

A scalable and rather inexpensive solution to producing microanalytical systems with "on-chip" three-dimensional (3D) microelectrodes is presented in this study, along with applicability to practical electrochemical (EC) detection scenarios such as preconcentration and interferant removal. This technique to create high-aspect-ratio (as much as 4:1) gold microstructures in constrained areas involved the modification of stud bump geometry with microfabricated silicon molds via an optimized combination of temperature, pressure, and time. The microelectrodes that resulted consisted of an array of square pillars approximately 18 microm tall and 20 microm wide on each side, placed at the end of a microfabricated electrophoresis channel. This technique increased the active surface area of the microelectrodes by as much as a factor of 50, while mass transfer and, consequently, preconcentration collection efficiencies were increased to approximately 100%, compared to approximately 30% efficiency for planar nonmodified microelectrodes (samples that were used included the neurotransmitters dopamine and catechol). The 3D microelectrodes were used both in a stand-alone configuration, for direct EC detection of model catecholamine analytes, and, more interestingly, in dual electrode configurations for EC sample processing prior to detection downstream at a second planar electrode. In particular, the 3D electrodes were shown to be capable of performing coulometry or complete (100%) redox conversion of analyte species over a wide range of concentrations, from 4.3 microM to 4.4 mM, in either plug-flow or continuous-flow formats.

Room temperature UV adhesive bonding of CE devices.

A simple low temperature adhesive 'stamp-and-stick' bonding procedure for lab-on-a-chip glass devices has been tested for capillary electrophoresis applications. This technique involves use of a mask aligner to transfer a UV-curable adhesive selectively onto the top CE substrate which is then aligned with and bonded to the bottom CE wafer. The entire bonding process can be carried out at room temperature in less than 30 minutes, involved only user-friendly laboratory operations, and provided a near 100% success rate. CE microchips made in this manner exhibited similar electroosmotic flow and separation characteristics as ones made via conventional high temperature thermal bonding. Equally important, the devices provided stable long-term performance over weeks of use, encompassing hundreds of individual CE runs without structural failure or any apparent change in operating characteristics. Finally, these devices exhibited excellent chip-to-chip reproducibility. Successful adaptation of the stamp-and-stick approach did require the development and testing of new but easily implemented structural features which were incorporated into the chip design and whose nature is described in detail.

Fabrication of a glass capillary electrophoresis microchip with integrated electrodes.

In this chapter, a detailed outline delineating the processing steps for microfabricating capillary electrophoresis (CE) with integrated electrochemical detection (ECD) platforms for performing analyte separation and detection is presented to enable persons familiar with microfabrication to enter a cleanroom and fabricate a fully functional Lab-on-a-Chip (LOC) microdevice. The processing steps outlined are appropriate for the production of LOC prototypes using easily obtained glass substrates and common microfabrication techniques. Microfabrication provides a major advantage over existing macro-scale systems by enabling precise control over electrode placement, and integration of all required CE and ECD electrodes directly onto a single substrate with a small footprint. In the processing sequences presented, top and bottom glass substrates are photolithographically patterned and etched using wet chemical processing techniques. The bottom substrate contains seven electrodes required for CE/ECD operation, whereas the top substrate contains the microchannel network. The flush planar electrodes are created using sputter deposition and lift-off processing techniques. Finally, the two glass substrates are thermally bonded to create the final LOC device.

Chemiresistive vapor sensing with microscale films of gold monolayer protected clusters.

Here we report the stability, conductivity, and vapor-sensing properties of microcontact-printed films of 1.6-nm average diameter hexanethiolate-coated gold monolayer protected clusters (C6 Au MPCs). The C6 Au MPCs were stamped into parallel lines (approximately 1.2 microm wide and 400 nm thick) across two Au electrodes separated by a 1-microm gap. The chemiresistive vapor-sensing properties were measured for saturated toluene and 2-propanol vapors. As-prepared patterned Au MPC films were unstable in the presence of saturated toluene vapor, and their current response was irreversible. Chemically linking the films with vapor-phase hexanedithiol greatly improves their stability and leads to reversible responses. The extent of Au MPC cross-linking and vapor response to organic vapors varies with different exposure times to dithiol vapor. The response to toluene changed from 61 to 8% for exposures of 1 and 60 min, respectively, which is likely due to greater film flexibility with less dithiol exposure. The current measured through the films varies from 10(-11) to 10(-3) Angstroms as a function of the temperature between 250 and 320 degrees C, which correlates with the loss of organic material as measured by FT-IR spectroscopy and the change in thickness and width of the film as measured by atomic force microscopy. The vapor-sensing properties vary with temperature, current, and organic content in the film, which are all interrelated. Response to toluene decreased with increasing temperature and conductivity, while the response to 2-propanol was less predictable. Reducing the size of vapor-sensing devices based on Au MPCs is important for creating highly portable devices that can simultaneously detect multiple analytes. This work demonstrates a simple method for reducing the size of such devices down to the microscale and describes methods for maximizing response, stability, and reversibility.

Portable high-voltage power supply and electrochemical detection circuits for microchip capillary electrophoresis.

Miniaturized, battery-powered, high-voltage power supply, electrochemical (EC) detection, and interface circuits designed for microchip capillary electrophoresis (CE) are described. The dual source CE power supply provides +/- 1 kVDC at 380 microA and can operate continuously for 15 h without recharging. The amperometric EC detection circuit provides electrode potentials of +/-2 VDC and gains of 1, 10, and 100 nA/V. The CE power supply power is connected to the microchip through an interface circuit consisting of two miniature relays, diodes, and resistors. The microchip has equal length buffer and separation channels. This geometry allows the microchip to be controlled from only two reservoirs using fixed dc sources while providing a consistent and stable sample injection volume. The interface circuit also maintains the detection reservoir at ground potential and allows channel currents to be measured likewise. Data are recorded, and the circuits are controlled by a National Instruments signal interface card and software installed in a notebook computer. The combined size (4 in. x 6 in. x 1 in.) and weight (0.35 kg) of the circuits make them ideal for lab-on-a-chip applications. The circuits were tested electrically, by performing separations of dopamine and catechol EC and by laser-induced fluorescence visualization.

Fully integrated on-chip electrochemical detection for capillary electrophoresis in a microfabricated device.

Microfabricated lab-on-a-chip devices employing a fully integrated electrochemical (EC) detection system have been developed and evaluated. Both capillary electrophoresis (CE) channels and all CE/EC electrodes were incorporated directly onto glass substrates via traditional microfabrication techniques, including photolithographic patterning, wet chemical etching, DC sputtering, and thermal wafer bonding. Unlike analogous CE/EC devices previously reported, no external electrodes were required, and critical electrode characteristics, including size, shape, and placement on the microchip, were established absolutely by the photolithography process. For the model analytes dopamine and catechol, detection limits in the 4-5 microM range (approximately 200 amol injected) were obtained with the Pt EC electrodes employed here, and devices gave stable analytical performance over months of usage.