Abstract
Point-of-care diagnostics will rely upon the development of low-cost, noncomplex, and easily integrated systems in order to examine biological samples such as blood and urine obtained from the patient. The development of metal ion sensors is a subject of significant relevance for physiological samples. The level of different blood electrolytes, mainly H+, Na+, K+ and Cl− is considerably used to monitor irregular physiologies. The particular challenge in biosensing, and in fact for any other sensor, is signal differentiation between non-specifically bound material and the specific detecting of the target molecule/ion. The biosensors described in this paper are fabricated by a holographic recording of surface relief structures in a photopolymer material. The surface structures are modified by coating with either dibenzo-18-crown-6 (DC) or tetraethyl 4-tert-butylcalix[4]arene (TBC), which are embedded in a polymer matrix. Interrogation of these structures by light allows indirect measurement of the concentration of the analyte. The influence of polymer matrices with different porosities, plasticised polyvinyl chloride (PVC) and a sol-gel matrix, on the performance of the sensors for detection of K+ and Na+ is examined. Here we demonstrate a proof of concept that by using a matrix with higher porosity one can increase the sensitivity of the sensor. The results showed that the DC sensing layer provides a selective response to K+ over Na+ and the TBC modified grating is more responsive to Na+ over K+. The sensor responds to K+ and Na+ within the physiological concentration ranges.
Highlights
There is an urgent need for low-cost mass producible clinical diagnostic devices that allow measurements on site
In order to overcome these challenges, we propose the use of transmission surface relief grating (SRG) fabricated in a low-cost self-developing photopolymer material, which production does not require stability on a nanometer scale
The amplitude observed in the structures of SRG is in the range of 350–400 nm, and line spacing 3.54 μm ± 3% was observed by AFM
Summary
There is an urgent need for low-cost mass producible clinical diagnostic devices that allow measurements on site. Much effort has been devoted to decreasing the expense and time allocated to the measurement of physiologically important ions. The development of selective metal ions sensors is a focus of significant interest because of their clinical relevance. In future biosensors will become an essential part of modern healthcare because the demand for personalised medicine is increasing [1]. Many challenges of the healthcare system can be resolved by new sensor technologies. It is expected that biosensors will become essential in the future [2]. Biosensor development is prompted by the development of new materials that can be used as functionalising materials [3]
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