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

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.

An Indirect Colorimetric Method for Potassium Determination in Soil Using a Paper Device and Smartphone

“…The ion-pair extraction of potassium ions uses dibenzo-18-crown-6 as the complexing agent and excess calmagite as the counter ion. It is well known that K + , which has a radius of 133 pm, fits very well into the cavity of 18-crown-6 (Frański et al, 2009;Gul et al, 2019). As a result, K + can be chelated well with dibenzo-18-crown-6.…”

Holographic Sensors in Biotechnology

“…Naydenova et al demonstrate a methodology whereby holographic surface relief structures are formed and coated in an ionophore containing polyvinyl chloride (PVC) matrices. [81,82] The methodology described within the paper illustrates that the grating is initially formed utilizing an Nd:YAG laser which is separated and directed onto the photopolymer surface. To sensitize the grating structure a secondary layer is spin coated onto the surface containing the binding ligand dibenzo-18-crown-6 (DC) or tetraethyl 4-tertbutylcalix [4]arene (TBC) PVC and plasticizers to give rise to a sensitized coating.…”