Chemosensors and biosensors based on polyelectrolyte microcapsules containing fluorescent dyes and enzymes

Abstract

The concept of enzyme-assisted substrate sensing based on use of fluorescent markers to detect the products of enzymatic reaction has been investigated by fabrication of micron-scale polyelectrolyte capsules containing enzymes and dyes in one entity. Microcapsules approximately 5 μm in size entrap glucose oxidase or lactate oxidase, with peroxidase, together with the corresponding markers Tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) dichloride (Ru(dpp)) complex and dihydrorhodamine 123 (DHR123), which are sensitive to oxygen and hydrogen peroxide, respectively. These capsules are produced by co-precipitation of calcium carbonate particles with the enzyme followed by layer-by-layer assembly of polyelectrolytes over the surface of the particles and incorporation of the dye in the capsule interior or in the multilayer shell. After dissolution of the calcium carbonate the enzymes and dyes remain in the multilayer capsules. In this study we produced enzyme-containing microcapsules sensitive to glucose and lactate. Calibration curves based on fluorescence intensity of Ru(dpp) and DHR123 were linearly dependent on substrate concentration, enabling reliable sensing in the millimolar range. The main advantages of using these capsules with optical recording is the possibility of building single capsule-based sensors. The response from individual capsules was observed by confocal microscopy as increasing fluorescence intensity of the capsule on addition of lactate at millimolar concentrations. Because internalization of the micron-sized multi-component capsules was feasible, they could be further optimized for in-situ intracellular sensing and metabolite monitoring on the basis of fluorescence reporting.

Probing the surface microstructure of layer-by-layer self-assembly chitosan/poly( l -glutamic acid) multilayers: A grazing-incidence small-angle X-ray scattering study

“…Polyelectrolyte multilayers (PEMs) formed by the layer-by-layer technique [1,2] have attracted considerable interest because of their potential applications in optical devices [3][4][5], sensing [6][7][8], drug release [9,10], and biologically active coatings [11][12][13][14][15]. The PEM film is based on the alternating adsorption of oppositely charged polyions onto a charged surface.…”

Pharmacological aspects of release from microcapsules — from polymeric multilayers to lipid membranes

“…Sensing pH in cells [106] or oxygen [107] is relevant for sensoring part of theranostics [97]. This can be implemented by designing a semipermeable capsule which would permit ions to go through its shell [108], but would protect and preserve inside the larger molecules (proteins), which are used as indicators or sensors.…”

Influence of the Ionic and Non-Ionic Additives on the Acid Strength of Neutral Red in the Aqueous Solutions of Poly (Sodium 4-Styrenesulfonate)

“…It is widely used in the creation of biosensors [11,12] or the polyelectrolyte titration [13]. Moreover, Baumgartner et al [14] reported the decreasing in the indices of the apparent ionization constant of neutral red, app a pK , by 1.7 units in NaPSS solution on adding aprotic solvent dioxane (2.0 M).…”