Paper-based microfluidic devices for analysis of clinically relevant analytes present in urine and saliva

Abstract

We report the use of paper-based microfluidic devices fabricated from a novel polymer blend for the monitoring of urinary ketones, glucose, and salivary nitrite. Paper-based devices were fabricated via photolithography in less than 3 min and were immediately ready for use for these diagnostically relevant assays. Patterned channels on filter paper as small as 90 microm wide with barriers as narrow as 250 microm could be reliably patterned to permit and block fluid wicking, respectively. Colorimetric assays for ketones and nitrite were adapted from the dipstick format to this paper microfluidic chip for the quantification of acetoacetate in artificial urine, as well as nitrite in artificial saliva. Glucose assays were based on those previously demonstrated (Martinez et al., Angew Chem Int Ed 8:1318-1320, 1; Martinez et al., Anal Chem 10:3699-3707, 2; Martinez et al., Proc Nat Acad Sci USA 50:19606-19611, 3; Lu et al., Electrophoresis 9:1497-1500, 4; Abe et al., Anal Chem 18:6928-6934, 5). Reagents were spotted on the detection pad of the paper device and allowed to dry prior to spotting of samples. The ketone test was a two-step reaction requiring a derivitization step between the sample spotting pad and the detection pad, thus for the first time, confirming the ability of these paper devices to perform online multi-step chemical reactions. Following the spotting of the reagents and sample solution onto the paper device and subsequent drying, color images of the paper chips were recorded using a flatbed scanner, and images were converted to CMYK format in Adobe Photoshop CS4 where the intensity of the color change was quantified using the same software. The limit of detection (LOD) for acetoacetate in artificial urine was 0.5 mM, while the LOD for salivary nitrite was 5 microM, placing both of these analytes within the clinically relevant range for these assays. Calibration curves for urinary ketone (5 to 16 mM) and salivary nitrite (5 to 2,000 microM) were generated. The time of device fabrication to the time of test results was about 25 min.

Calligraphy paper-based analytical devices

“…In healthy people, urine nitrite ions should not be detected in urine samples and urine glucose levels should range from 0 -0.8 mM [23,25]. The LOD of our nitrite assay was similar to the LOD of PADs (LOD = 0.005 mM) and 5.6 times lower than the LOD of poly(dimethylsiloxane) (PDMS)-based analytical devices (LOD = 0.045 mM) [25,26]. The LOD of our glucose assay was compatible for the current criteria of urine glucose, was better than the LOD of PADs (which could only recognize glucose levels above 0.5 mM), and was 7 times lower than the LOD of PDMS-based analytical devices (LOD = 0.56 mM) [27,28].…”

Diagnosis of communicable diseases using papepr microfluidic platforms

“…width and length) of the device. The conventional methods used for creating hydrophobic barriers are inkjet printing [17][18][19], wax printing [20,21], flexographic printing [22], photolithography [23], wax dipping [24], plasma treatment [19,25], screenprinting of poly(dimethylsiloxane) (PDMS) [15], lacquer spraying [26] and using a permanent marker [27]. The details of these fabrication methods have been studied comprehensively by several researchers [11,28,29].…”

A low cost design and fabrication method for developing a leak proof paper based microfluidic device with customized test zone

“…40,41 The development achieved in this area along with new detection systems using colorimetry to electrochemical, chemiluminescence, electrochemiluminescence, fluorescence, and electrical methods has opened avenues for new sensing technologies. 12,34,[42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] Paper-based microfluidic systems, however, suffer from two major drawbacks: first is the leakage of sample from the rear side of the channels during sample analysis and second is the difficulty in precise incorporation of reagents in the test zone without the inherent spreading of reagents to the surrounding areas including the microchannels. Additionally, covalent immobilization of certain detection reagents (e.g., antibodies, aptamers, enzymes, etc.)…”