Modified Surface Relief Layer Created by Holographic Lithography: Application to Selective Sodium and Potassium Sensing

• Published in: Sensors (Basel, Switzerland) Vol. 19; no. 5; p. 1026
• Main Authors: Gul, Sabad-E, O’Neill, Luke, Cassidy, John, Naydenova, Izabela
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI 28.02.2019; MDPI AG
• Subjects: biomedical sensors; blood serum; diffractive optical sensors; holographic sensors; holography; photopolymers; potassium ion detection; PVC; sensors; sodium ion detection; sol gel; diffractive optical sensors; sensors; sol gel; blood serum; holography; PVC; biomedical sensors; sodium ion detection; holographic sensors; photopolymers; potassium ion detection
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s19051026

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.