Creasensor: SIMPLE technology for creatinine detection in plasma
Graphical abstract
Introduction
Since their introduction more than twenty years ago, lab-on-a-chip (LOC) devices generated high interest and expectations within the microfluidics community and beyond [1], [2], [3]. In particular, their intrinsic properties such as miniaturization, integration of different laboratory processes, rapid time-to-result (TTR) and low cost fabrication, envisaged their bright future for point-of-care (POC) testing [3], [4]. However, despite the initial excitement, the LOC devices that found their way to the POC market continue to be greatly outnumbered by those remaining in the research environment. This phenomenon can be mostly explained with two arguments. First, researchers have been often focusing on increasing the versatility and thus also the complexity of the microfluidic chips without simultaneously working on their integration with pumps and readout systems. As a consequence, lab-on-a-chip became chip-in-a-lab and resulted in small microfluidic chips needing bulky instrumentation to operate, which is suitable for research purposes but not for POC applications [3], [5]. Second, the trend in the LOC community for many years was to develop new technologies rather than to integrate the existing ones with biological applications and make them more robust and user-friendly for non-technical users [6], [7].
Number of autonomous and self-powered microfluidic approaches tried to address the integration and portability aspects. For instance, systems based on capillary forces of intricate microstructures were introduced as capable of drawing liquids into a microfluidic network and performing complicated multi-step assays [8]. However, these systems required hydrophilization of the surfaces to obtain the capillary effect increasing the complexity and cost of the fabrication. Other platforms were based on the so called “degas-driven flow” concept [9], [10], [11], [12], [13], which takes advantage of the inherent high porosity and air solubility of PDMS. However, this approach was limited to permeable materials while the control over flow rate and timing was challenging. A third promising approach was paper-based microfluidics where paper is exploited as pumping element relying on capillary action to move liquids. The paper strip was often patterned with different reagents at different locations with the final goal to perform multi-step tests [14], [15], [16], [17]. Although promising, the performance of the bio-assay integrated on the paper-based microfluidic platforms is often hampered by the irreproducible fluid control, the narrow range of flow rates and the interaction of the sample with the matrix.
More recently, a new self-powered pumping concept has been introduced, being the Self-powered Imbibing Microfluidic Pump by Liquid Encapsulation (SIMPLE) [18] which works in pulling mode. Although the potential of this technology for POC applications is enormous due to its versatility in terms of flow rate and liquid volume, autonomy in liquid manipulation, low cost, ease-of-fabrication and suitability for mass-replication it has not been combined so far with any biological application. Therefore, in this paper we show for the first time that the SIMPLE platform can be effectively integrated with a model bioassay, i.e. an enzymatic assay for quantification of creatinine. Creatinine is the golden standard biomarker for chronic kidney disease (CKD) and it is sufficient for diagnosing this disease and monitoring of its progress [19], [20], [21], which is a medical condition associated with the gradual loss of kidney function, leading to kidney transplantation in the acute cases [22]. Moreover, starting from the previously published SIMPLE concept, in this paper we improve the fabrication and design process. To validate the robustness of the SIMPLE technology, we further combine SIMPLE-based microfluidic cartridge (Creacard) with colorimetric read-out system into the fully integrated Creasensor device. Using Creasensor, we quantify creatinine directly in a plasma matrix within the entire clinically relevant concentration range and we validate on-field the performance of the device in a single-blind study. We finally benchmark the performance of the newly developed SIMPLE biosensor with the well-established laboratory-based and POC platforms for creatinine diagnostics.
Section snippets
Reagents and materials
All buffer reagents and creatinine anhydrous (98% purity) were purchased from The Merck group - Sigma Aldrich (Belgium), as well as creatinine standard solutions, creatinine assay buffer, creatinine probe, creatininase, creatinase and creatinine enzyme mix, which were obtained from the Creatinine Assay kit (MAK080). Bovine plasma heparin NA was supplied by Tebu-Bio (Belgium). All solutions were prepared using deionized water purified with a Milli-Q 50 ultrapure water system (Millipore,
Development of the microfluidic cartridge and Creasensor device
To develop a fully integrated SIMPLE-based biosensor for creatinine quantification, two main parts were designed and built in this work: (i) the Creacard (Fig. 2), a microfluidic cartridge based on the SIMPLE concept [18] and (ii) a portable colorimetric read-out system. The main role of the SIMPLE-based cartridge was to efficiently pull the sample into the microfluidic network in order to obtain a standardized filling of the detection zone. The cartridge was prefilled with working liquid
Conclusions
In this paper, we presented a fully integrated SIMPLE-based biosensor, named Creasensor, engineered to detect creatinine in blood plasma samples. The Creasensor combines fast bioassay on a self-powered SIMPLE microfluidic cartridge (Creacard) with integrated signal processing unit and a simple but robust colorimetric read-out. The Creacard was designed to provide efficient sample manipulation and optimal conditions for the read-out system. The enzymatic bioassay was optimized to (i) meet POC
Acknowledgements
The research leading to these results has received funding from the KU Leuven (PDM/17/093, C3 project 3E150475, C3 project C32/17/007) and the FWO-Flanders Postdoctoral Fellow Devin Daems 12U1618N. These results were obtained in the context of the SensUs 2016 competition (http://sensus.org/).
References (36)
- et al.
Lab-on-a-chip or chip-in-a-lab: challenges of commercialization lost in translation
Procedia Technol.
(2015) - et al.
Commercialization of microfluidic devices
Trends Biotechnol.
(2014) - et al.
Creatinine sensors
TrAC - Trends Anal. Chem.
(2013) - et al.
Emerging technologies for next-generation point-of-care testing
Trends Biotechnol.
(2015) - et al.
Determination of reference intervals for serum creatinine, creatinine excretion and creatinine clearance with an enzymatic and a modified Jaffé method
Clin. Chim. Acta
(2004) - et al.
Creatinine biosensors: principles and designs
Trends Biotechnol.
(2000) - et al.
Characterization of a new ionophore-based ion-selective electrode for the potentiometric determination of creatinine in urine
Biosens. Bioelectron.
(2017) - et al.
A facile low-cost enzymatic paper-based assay for the determination of urine creatinine
Talanta
(2015) - et al.
Lab-on-a-chip devices: how to close and plug the lab?
Microelectron. Eng.
(2014) - et al.
Commercialization of microfluidic point-of-care diagnostic devices
Lab. Chip
(2012)