Fluorescent Ion‐Sensing Microspheres for Multiplexed Chemical Analysis of Clinical and Biological Samples

Abstract

This review summarizes recent advances in the development of chemically selective microspheres with a view to developing new, attractive methodologies in clinical and biomedical analysis. In particular, the development of fluorescent ion-selective microspheres that function analogously to established bulk optodes is discussed. The fluorescent signal is dependent on a selective ion extraction process into a hydrophobic bulk phase doped with selective complexing agents. A mild preparation process for making large numbers of such microspheres is reported. Among a multitude of different applications, these beads may be applied in analytical flow cytometry in order to form part of a total bead-based suspension array analysis system. Applications toward low detection limit measurements, as well as advances in polymer chemistry to develop plasticizer-free ion sensing beads, are also discussed.

Surface Modified Thread-Based Microfluidic Analytical Device for Selective Potassium Analysis

“…The diffusion transport at medium/high analyte concentration and the convective mass transport at low concentration explain the response time. 3,4 Different strategies have been devised to reduce the response time of IBOS, with the most common ones including the ionophore chemistry in micro/nano sized spherical particles obtained by techniques such as heterogeneous polymerization, 7 sonic casting, 8 polymer swelling, 9 physical adsorption on the surface of microspheres 10 or O/W emulsion forming micelles. 11 The increase in the surface from the micro/nano particles and the reduction in the molecular diffusion distance enhance the mass transport and reduce the response time.…”

“…One of the drawbacks of planar film ionophore-based optical sensors (IBOS) working in equilibrium mode is the long response time, from minutes to hours depending on the analyte concentration, − both in flow and disposable mode, due to the need to extract the target species from the solution to the bulk of the membrane. The diffusion transport at medium/high analyte concentration and the convective mass transport at low concentration explain the response time. , Different strategies have been devised to reduce the response time of IBOS, with the most common ones including the ionophore chemistry in micro/nanosized spherical particles obtained by techniques such as heterogeneous polymerization, sonic casting, polymer swelling, physical adsorption on the surface of microspheres, or O/W emulsion forming micelles . The increase in the surface from the micro/nanoparticles and the reduction in the molecular diffusion distance enhance the mass transport and reduce the response time.…”

Enzyme Substrates Protective Encapsulation within Polymeric Microspheres

“…This has been proven by numerous research on polyacrylate based ion-selective electrodes [e.g. 17,18] as well as on polymeric microspheres [4,6,16].…”

“…Incorporation of molecules into the polymeric microspheres, in principle, can be achieved either during polymerization [4,6] or afterwards by absorption of molecules to ready spheres, e.g. during microspheres contact with mixed water/THF based solution containing the molecule of choice [15,16].…”

“…The applicability of these systems for fluorimetirc analysis is also well proven [4][5][6][7][8][9][10][11][12][13][14].…”