Design and fabrication of a centrifugally driven microfluidic disk for fully integrated metabolic assays on whole blood

For the first time, we present a novel and fully integrated centrifugal microfluidic “ lab-on-a-disk” for rapid metabolic assays in human whole blood. All essential steps comprising blood sampling, metering, plasma extraction and the final optical detection are conducted within t = 150 s in passive structures integrated on one disposable disk. Our technology features a novel plasma extraction structure (V = 500 nL, CV < 5%) without using any hydrophobic microfluidics where the purified plasma (cRBC< 0.11%) is centrifugally separated and subsequently extracted through a capillarily primed extraction channel into the detection chamber. While this capillary extraction requires precisely defined, narrow micro-structures, the reactive mixing and detection is most efficient within larger cavities. The corresponding manufacturing technique of these macro- and micro structures in the range of 30 µ m to 1000 µ m is also presented for the first time: A novel, cost-efficient hybrid prototyping technique of a multiscale epoxy master for subsequent hot embossing of polymer disks

Optical beam guidance in monolithic polymer chips for miniaturized colorimetric assays

For the first time, we present a simple and robust optical concept to enable precise and sensitive read-out of colorimetric assays in flat lab-on-a-chip devices. The optical guidance of the probe beam through an incorporated measurement chamber to the detector is based on the total internal reflection at V-grooves in the polymer chip. This way, the optical path length through the flat measurement chamber and thus the performance of the measurements are massively enhanced compared to direct (perpendicular) beam incidence. This is demonstrated by a chip-based, colorimetric glucose-assay on serum. Outstanding features are an excellent reproducibility (CV= 1.91 %), a competitive lower limit of detection (cmin = 124 μM), and a high degree of linearity (R2 = 0.998) within a working range extending over nearly three orders of magnitude

Direct hemoglobin measurement by monolithically integrated optical beam guidance

We present a concept for optical beam guidance by total internal reflection (TIR) at V-grooves as retro reflectors which are monolithically integrated on a microfluidic "lab-on-a-disk". This way, the optical path length through a measurement chamber and thus the sensitivity of colorimetric assays is massively enhanced compared to direct (perpendicular) beam incidence. With this rugged optical concept, we determine the concentration of hemoglobin (Hb) in human whole blood. Outstanding features are a high degree of linearity (R2 = 0.993) between the optical signal and the Hb together with a reproducibility of CV= 2.9 %, and a time-to-result of 100 seconds, only

Parallelization of chip-based fluorescence immuno-assays with quantum-dot labelled beads

This paper presents an optical concept for the read-out of a parallel, bead-based fluorescence immunoassay conducted on a lab-on-a-disk platform. The reusable part of the modular setup comprises a detection unit featuring a single LED as light source, two emission-filters, and a color CCD-camera as standard components together with a spinning drive as actuation unit. The miniaturized lab-on-a-disk is devised as a disposable. In the read-out process of the parallel assay, beads are first identified by the color of incorporated quantum dots (QDs). Next, the reaction-specific fluorescence signal is quantified with FluoSpheres-labeled detection anti-bodies. To enable a fast and automated read-out, suitable algorithms have been implemented in this work. Based on this concept, we successfully demonstrated a Hepatitis-A assay on our disk-based lab-on-a-chip

Validation of an LC-MS/MS method for the quantitative analysis of 1P-LSD and its tentative metabolite LSD in fortified urine and serum samples including stability tests for 1P-LSD under different storage conditions

A variety of hallucinogens of the lysergamide type has emerged on the drug market in recent years and one such uncontrolled derivative of lysergic acid diethylamide (LSD) is 1 propionyl LSD (1P LSD). Due to the high potency of LSD and some of its derivatives (common doses: 50-200 µg), sensitive methods are required for the analysis of biological samples such as serum and urine. The occurrence of an intoxication case required the development of a fully validated, highly sensitive method for the quantification of 1P LSD and LSD in urine and serum using LC-MS/MS. Given that LSD is unstable in biological samples when exposed to light or elevated temperatures, we also conducted stability tests for 1P LSD in urine and serum under different storage conditions. The validation results revealed that the analysis method was accurate and precise with good linearity over a wide calibration range (0.015-0.4 ng mL-1). The limit of detection (LOD) and the lower limit of quantification (LLOQ) of 1P-LSD and LSD in serum and urine were 0.005 ng mL-1 and 0.015 ng mL-1, respectively. The stability tests showed no major degradation of 1P LSD in urine and serum stored at -20 °C, 5 °C or at room temperature for up to five days, regardless of protection from light. However, LSD was detected in all samples stored at room temperature showing a temperature-dependent hydrolysis of 1P LSD to LSD to some extent (up to 21% in serum). Serum samples were particularly prone to hydrolysis possibly due to enzymatically catalyzed reactions. The addition of sodium fluoride prevented the enzymatic formation of LSD. The method was applied to samples obtained from the intoxication case involving 1P LSD. The analysis uncovered 0.51 ng mL-1 LSD in urine and 3.4 ng mL-1 LSD in serum, whereas 1P LSD remained undetected. So far pharmacokinetic data of 1P LSD is missing, but with respect to the results of our stability tests and the investigated case rapid hydrolysis to LSD in vivo seems more likely than instabilities of 1P¬LSD in urine and serum samples

Systematics of Fission Barriers in Superheavy Elements

We investigate the systematics of fission barriers in superheavy elements in the range Z = 108-120 and N = 166-182. Results from two self-consistent models for nuclear structure, the relativistic mean-field (RMF) model as well as the non-relativistic Skyrme-Hartree-Fock approach are compared and discussed. We restrict ourselves to axially symmetric shapes, which provides an upper bound on static fission barriers. We benchmark the predictive power of the models examining the barriers and fission isomers of selected heavy actinide nuclei for which data are available. For both actinides and superheavy nuclei, the RMF model systematically predicts lower barriers than most Skyrme interactions. In particular the fission isomers are predicted too low by the RMF, which casts some doubt on recent predictions about superdeformed ground states of some superheavy nuclei. For the superheavy nuclei under investigation, fission barriers drop to small values around Z = 110, N = 180 and increase again for heavier systems. For most of the forces, there is no fission isomer for superheavy nuclei, as superdeformed states are in most cases found to be unstable with respect to octupole distortions.Comment: 17 pages REVTEX, 12 embedded eps figures. corrected abstrac

New Outlook on the Possible Existence of Superheavy Elements in Nature

A consistent interpretation is given to some previously unexplained phenomena seen in nature in terms of the recently discovered long-lived high spin super- and hyper-deformed isomeric states. The Po halos seen in mica are interpreted as due to the existence of such isomeric states in corresponding Po or nearby nuclei which eventually decay by gamma- or beta-decay to the ground states of 210Po, 214Po and 218Po nuclei. The low-energy 4.5 MeV alpha-particle group observed in several minerals is interpreted as due to a very enhanced alpha transition from the third minimum of the potential-energy surface in a superheavy nucleus with atomic number Z=108 (Hs) and atomic mass number around 271 to the corresponding minimum in the daughter.Comment: 8 pages, 8 figures, 5 tables. Paper presented at VII Int. School-Seminar on Heavy Ion Physics, May 27 - June 1, 2002, Dubna, Russi

Faecal and Urinary Incontinence after Multimodality Treatment of Rectal Cancer

Marilyne Lange and Cornelis van de Velde discuss the differential diagnosis and management of incontinence after rectal cancer treatment

Event-triggered logical flow control for comprehensive process integration of multi-step assays on centrifugal microfluidic platforms

Content in the UH Research Archive is made available for personal research, educational, and non-commercial purposes only. Unless otherwise stated, all content is protected by copyright, and in the absence of an open license, permissions for further re-use should be sought from the publisher, the author, or other copyright holder.The centrifugal "lab-on-a-disc" concept has proven to have great potential for process integration of bioanalytical assays, in particular where ease-of-use, ruggedness, portability, fast turn-around time and cost efficiency are of paramount importance. Yet, as all liquids residing on the disc are exposed to the same centrifugal field, an inherent challenge of these systems remains the automation of multi-step, multi-liquid sample processing and subsequent detection. In order to orchestrate the underlying bioanalytical protocols, an ample palette of rotationally and externally actuated valving schemes has been developed. While excelling with the level of flow control, externally actuated valves require interaction with peripheral instrumentation, thus compromising the conceptual simplicity of the centrifugal platform. In turn, for rotationally controlled schemes, such as common capillary burst valves, typical manufacturing tolerances tend to limit the number of consecutive laboratory unit operations (LUOs) that can be automated on a single disc. In this paper, a major advancement on recently established dissolvable film (DF) valving is presented; for the very first time, a liquid handling sequence can be controlled in response to completion of preceding liquid transfer event, i.e. completely independent of external stimulus or changes in speed of disc rotation. The basic, event-triggered valve configuration is further adapted to leverage conditional, large-scale process integration. First, we demonstrate a fluidic network on a disc encompassing 10 discrete valving steps including logical relationships such as an AND-conditional as well as serial and parallel flow control. Then we present a disc which is capable of implementing common laboratory unit operations such as metering and selective routing of flows. Finally, as a pilot study, these functions are integrated on a single disc to automate a common, multi-step lab protocol for the extraction of total RNA from mammalian cell homogenate.Peer reviewe