Hydrophilic polymeric coatings for enhanced, serial-siphon based flow control on centrifugal lab-on-disc platforms

In this paper, we implement rotational flow control on a polymeric microfluidic “lab-on-a-disc” device by combining serial siphoning and capillary valving for sequential release of on-board stored liquid reagents. The functionality of this integrated, multi-step centrifugal assay platform is tightly linked by the capability to establish reproducible, capillary-driven priming of the innately hydrophobic siphon microchannels. We here demonstrate for the first time that spin-coated hydrophilic polymeric films of poly(vinyl alcohol) and (hydroxylpropyl)methylcellulose provide stable contact angles

Cluster size distribution of cancer cells in blood using stopped-flow centrifugation along scale-matched gaps of a radially inclined rail

There is increasing evidence that, in addition to their presence, the propensity of circulating tumour cells to form multi-cellular clusters bears significant information about both cellular resistance to chemotherapy and overall prognosis. We present a novel two-stage, stopped-flow, continuous centrifugal sedimentation strategy to measure the size distributions of events (defined here as cells or clusters thereof) in a blood sample. After off-chip removal of red blood cells, healthy white blood cells are sequestered by negative-immunocapture. The purified events are then resolved along a radially inclined rail featuring a series of gaps with increasing width, each connected to a designated outer collection bin. The isolation of candidate events independent of target-specific epitopes is successfully demonstrated for HL60 (EpCAM positive) and sk-mel28 (EpCAM negative) cells using identical protocols and reagents. The propensity to form clusters was quantified for a number of cell lines, showing a negligible, moderate or elevated tendency towards cluster formation. We show that the occupancy distribution of the collection bins closely correlates with the range of cluster sizes intrinsic to the specific cell line

Paper imbibition for timing of multi-step liquid handling protocols on event-triggered centrifugal microfluidic lab-on-a-disc platforms

This document is the Accepted Manuscript version of the following article: David J. Kinahan, Sinéad M. Kearney, Olivier P. Faneuil, Macdara T. Glynn, Nikolay Dimov, and Jens Ducrée, ‘Paper imbibition for timing of multi-step liquid handling protocols on event-triggered centrifugal microfluidic lab-on-a-disc platforms’, RSC Advances, Vol. 5 (3): 1818-1826, 2015, doi: https://doi.org/10.1039/C4RA14887H, published by the Royal Society of Chemistry.Rotational microfluidic platforms have attracted swiftly growing interest over the last decade due to their suitability for integration and automation of sample preparation and detection. Valving is of pivotal importance on these compact "Lab-on-a-Disc" (LoaD) platforms as all liquids are exposed to the same centrifugal field. A number of valving technologies have been developed to coordinate timing of serial and/or parallel multi-step/multi-liquid assay protocols comprising of laboratory unit operations (LUOs) such as the release, metering and mixing of sample and reagents. So far these valving techniques could be broadly categorised into rotationally controlled or externally actuated schemes. Only recently a new, "event-triggered" flow control has been introduced. In this approach, a valve is opened upon arrival of a liquid at a defined destination on the disc; this innovative mechanism for the first time permits the cascading of LUOs independent of the spin rate. In one technology, dissolvable films (DFs) are configured with a pneumatic chamber to offer function akin to an electrical relay. Dissolving one DF, termed the control film (CF), results in the release of liquid at a distal location through a so-called load film (LF). In this paper, a new method for temporal control of actuating DF-based, event-triggered CFs which are serially aligned at defined distances along a paper strip is introduced. Liquids are transported through the paper strip at a given velocity, thus setting well-defined intervals between subsequent LUOs, e.g. incubation steps. As a proof-of-concept, we present a disc with integrated metering and mixing which can perform a prototypical, 4-fold serial dilution; a common function in bioanalytical protocols. Imbibition of the paper strip sequentially opens five valves for serial dilution and mixing. To illustrate an unprecedented level of on-disc automation, this is followed by a branched cascade of 17 event-triggered valves (for a total of 22 liquid handling steps) which completes the serial dilution protocol.Peer reviewedFinal Accepted Versio

Development of an autonomous algal toxin analytical platform for aquatic monitoring

Cyclic peptide cyanobacterial toxins, in particular Microcystis aeruginosa, pose a serious health risk to humans and animals alike [1], [2]. Occurring mostly in fresh and brackish water, they have been identified to cause cancer promotion and liver damage [3]. Herein, we describe a portable, microfluidic-based system for in-situ detection of algal toxins in fresh water. The technology development presented here is a fully integrated and portable sample-to-answer centrifugal microfluidics-based system for the detection of toxic cyanobacteria – Microcystin-LR in fresh water. Our unique system employs highly-specific recombinant chicken anti-microcystin antibodies, prepared in-house, with a 3D-printed ‘LASER-photo¬diode’ fluorescent detection technique, also developed in-house. The system has high analytical specificity and sensitivity for detection of toxins below the regulatory limit with intra/inter day coefficient of variation of less than 20%. Dissolvable-film based valving technique was used for flow actuation and integration of multiple assays on the centrifugal cartridge. This new approach forms the basis of a cost efficient, USB-controlled water quality monitoring system. Technically, this integrated system consists of two components; a microfluidic disc (figure 1.A), the disc-holder fabricated and assembled from a 3D-printed casing, with electronic components housed in device. The 5-layered microfluidic disc consists of five reservoirs (figure 1.B), each with a separate venti-lation, aligned radially with inter-connected microchannels. A competitive immunoassay format is utilised to detect free toxin (figure 1.C). Sensitivity, reproducibility and ease-of-use are key features of this monitoring device. The ‘top-down’ optical detection system has been modified for improved detection sensitivity, as well as the elimination of external noise

Staging the clinical status from blood of cancer patients by chip-based cell enumeration following targeted removal of normal cells

Even though an agreed phenotypic definition of circulating tumor cells (CTCs) remains elusive in the literature, many current detection technologies isolate candidate cells based on molecular recognition of cellular epitopes that may not accurately predict CTC load. Rather than using such an epitope specific “positive-capture” strategy, we present a chip-based, centrifugal microfluidic platform integrating “negative-capture” magnetophoretic removal of normal white blood cells (WBCs) from a sample and subsequent, array-based enumeration of individualized, (untagged) abnormal cells. We compared the numerical recovery of cells on the array with the status of the donor patient, showing that the chip can has the potential to indicate the oncogenic severity of the blood donor

Centrifugal automation of a highly customizable rapid-elisa test towards detection of cervical cancer in point-of-care settings

Infections of high-risk strains of human papilloma virus (HPV16-E7) have been directly linked with cervical carcinogenesis [1]. Despite pervasive HPV testing and vaccinations, resource-poor regions continue to be affected. We present here a fully automated, bead-based Rapid Antigenic Protein In-situ Display (RAPID) Enzyme Linked Immunosorbent Assay (ELISA) for the detection of the onco-proteins of HPV16 E7 [1]. Advanced centrifugal flow control is implemented by a novel router based on lipophilic membranes in an event-trigger valving architecture [2]. By simply replacing the charge of RAPID-functionalized beads in the incubation chamber, the system may be customized for the detection of other biomarkers

A portable centrifugal analyser for liver function screening

Mortality rates of up to 50% have been reported after liver failure due to drug-induced hepatotoxicity and certain viral infections(Gao et al. 2008). These adverse conditions frequently affect HIV and tuberculosis patients on regular medication in resource-poor settings. Here, we report full integration of sample preparation with read-out of a 5-parameter liver assay panel (LAP) on a portable, easy-to-use, fast and cost- efficient centrifugal microfluidic analysis system (CMAS). Our unique, dissolvable-film based centrifugo- pneumatic valving was employed to provide sample-to-answer fashion automation for plasma extraction (from finger-prick of blood), metering and aliquoting into separate reaction chambers for parallelized colorimetric quantification during rotation. The entire LAP completes in less than 20 minutes while using only a tenth the reagent volumes when compared with standard hospital laboratory tests. Accuracy of in-situ liver function screening was validated by 96 separate tests with an average coefficient of variance (CV) of 7.9% compared to benchtop and hospital lab tests. Unpaired two sample statistical t-tests were used to compare the means of CMAS and benchtop reader, on one hand; and CMAS and hospital tests on the other. The results demonstrate no statistical difference between the respective means with 94% and 92% certainty of equivalence, respectively. The portable platform thus saves significant time, labour and costs compared to established technologies, and therefore comply with typical restrictions on lab infrastructure, maintenance, operator skill and costs prevalent in many field clinics of the developing world. It has been successfully deployed in a centralised lab in Nigeria

A centrifugal lab-on-a-disc device for the in situ determination of dissolved reactive phosphate in water.

Phosphorus (P) is an important nutrient to monitor in natural waters as it is a growth limiting nutrient. When levels of phosphorus are elevated, excessive growth of algae occurs. This can lead to hypoxic or anoxic waters, potential release of harmful toxins and it impacts negatively on the ecosystem. Phosphorus measurement in water involves the collection of grab samples, transport and storage of samples, and analysis using expensive analytical instrumentation. This is costly, time and labour intensive and is carried out infrequently as a result. In this work, P is measured as soluble reactive phosphate (SRP), to give an indication of P levels in fresh water. A device for in situ analysis of SRP was fabricated. This device consists of a centrifugal microfluidic lab-on-a-disc platform, with a housing unit. The disc operates by mixing the sample with ascorbic acid method reagents using centrifugal force. The coloured product is presented to an optical detection system consisting of a laser and photodiode. The limit of detection has been optimised by modification of the optical path length. The housing unit is a 3D printed portable box with a built in motor for disc rotation. This box also houses the optical detection system which consists of a laser and photodiode. The box facilitates the alignment of the detection system with the optical pathway of the disc for absorbance measurements in an environment free from ambient light. This device allows for rapid analysis times, compactness, ease of use, low cost analyses and low reagent consumption. Keywords: Phosphate, microfluidics, lab-on-a-disc, optical senso

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