Abstract
The quantitative analysis of tear analytes in point-of-care settings can enable early diagnosis of ocular diseases. Here, a fluorescent scleral lens sensor is developed to quantitatively measure physiological levels of pH, Na+ , K+ , Ca2+ , Mg2+ , and Zn2+ ions. Benzenedicarboxylic acid, a pH probe, displays a sensitivity of 0.12 pH units within pH 7.0-8.0. Crown ether derivatives exhibit selectivity to Na+ and K+ ions within detection ranges of 0-100 and 0-50 mmol L-1 , and selectivities of 15.6 and 8.1 mmol L-1 , respectively. A 1,2 bis(o-aminophenoxy)ethane-N,N,-N',N'-tetraacetic-acid-based probe allows Ca2+ ion sensing with 0.02-0.05 mmol L-1 sensitivity within 0.50-1.25 mmol L-1 detection range. 5-Oxazolecarboxylic acid senses Mg2+ ions, exhibiting a sensitivity of 0.10-0.44 mmol L-1 within the range of 0.5-0.8 mmol L-1 . The N-(2-methoxyphenyl)iminodiacetate Zn2+ ion sensor has a sensitivity of 1 µmol L-1 within the range of 10-20 µmol L-1 . The fluorescent sensors are subsequently multiplexed in the concavities of an engraved scleral lens. A handheld ophthalmic readout device comprising light-emitting diodes (LEDs) and bandpass filters is fabricated to excite as well as read the scleral sensor. A smartphone camera application and an user interface are developed to deliver quantitative measurements with data deconvolution. The ophthalmic system enables the assessment of dry eye severity stages and the differentiation of its subtypes.
Highlights
The quantitative analysis of tear analytes in point-of-care settings can of the dry eye treatment has focused on deficiency in tear production and inflamenable early diagnosis of ocular diseases
Existing dry eye diagnostic approach is application and an user interface are developed to deliver quantitative primarily based on identifying symptoms measurements with data deconvolution
The scleral lens sensor consisted of fluorescent probes to quantitatively measure pH value and electrolyte (Na+, K+, Ca2+, Mg2+, and Zn2+ ions) concentrations within the physiological range
Summary
The scleral lens sensor consisted of fluorescent probes to quantitatively measure pH value and electrolyte (Na+, K+, Ca2+, Mg2+, and Zn2+ ions) concentrations within the physiological range. K+ ion concentration variation was tested with DA18C6 (1–100 μmol L−1) using K+ solutions in tris buffer (pH 7.4, 150 mmol L−1) both in aqueous solutions and on a scleral lens sensor with different ionic strength values (2.5–50 mmol L−1). The fluorescence intensity increased 5.4 fold with increasing Mg2+ ion concentrations, and a 1.2 fold increase within the physiological detection range using the microplate reader, where the results were comparable with the measurements in a scleral lens sensor using an image processing algorithm (Figure 5e). The fluorescence intensity of MPIDA showed a 2.6-fold increase with increasing Zn2+ ion concentration, comparable to the data in the scleral lens concavity. Electronics, which immensely simplifies its working principle and facilitates its clinical utility
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