Fluorescent nanoparticles for ratiometric pH-monitoring in the neutral range

Abstract

This article describes the synthesis and characterisation of poly(acrylamide) nanoparticles (NPs) with a covalently immobilised pH-sensitive fluorophore. With a pK(a) of 6.7, good photostability, emission in the visible spectral range and large Stokes' shift the naphthalimide-based pH-indicator is well suited for bio-analytical applications. Additionally, the nanosensors contain a pH-insensitive reference fluorophore that allows the ratiometric monitoring of pH e.g. inside living cells. In order to enhance the cellular uptake and endosomal escape of the beads, novel core-shell nanoparticles bearing a positive z-potential are synthesised and evaluated

Facing the Design Challenges of Particle-Based Nanosensors for Metabolite Quantification in Living Cells

“…168 The monomer N,N-dimethylaminopropylacrylamide (DMAPA) have been used to produce nanoparticles with a polyamine core gel (copolymerization of DMAPA/MBA) surrounded by a PAA gel including copolymerized sensor and reference dyes. 16 The obtained d H was 30−40 nm; however, the study contained no structural evidence for the core−shell structure.…”

Augmenting Automated Analytics Using Fluorescent Nanosensors

“…Optical nanosensors are probes that have nanometre-scale sizes in all three dimensions [11] that utilise light in many forms, such as ultra-violet light, visible light, near-infrared and infra-red, to elucidate a vast amount of detail about the inner workings of microenvironments. Of the number of optical nanosensors reported in the literature, probes that utilise the principles of fluorescence and phosphorescence have shown the most promise [12][13][14][15]. This is largely due to: Due to the diversity of fluorescent sensing elements available, and ability of the versatile nanoparticle matrix to protect the sensing element, development of fluorescent nanosensors has been taken on by several research groups around the world and has permitted the development of ratiometric fluorescent nanosensors (Figure 1).…”

A broad range fluorescent pH sensor based on hollow mesoporous silica nanoparticles, utilising the surface curvature effect

“…13 Generally, a ratiometric uorescence method comprises of one pH sensitive dye and a second insensitive dye which are used on a nanoscale to achieve local sensing capability. 17 Coreshell structured uorescent nanoparticles based on silica or polymer were reported by Wiesner et al 15 and Mohr et al 18 respectively, with an immobilized reference dye in the core and a pH sensitive dye on the shell. Jin et al developed a quantum dot based ratiometric pH sensor by conjugating uorescein isothiocyanate (FITC) with CdSe-CdZnS nanocrystals.…”

“…[9][10][11][12] For robust local pH measurement, ratiometric uorescence nanoparticles have been used to detect pH accurately. [14][15][16][17][18] The method is based on the two emission peaks from the disparate dyes and the results of the measurements are recorded in terms of the intensity ratio of the two peaks. [14][15][16][17][18] The method is based on the two emission peaks from the disparate dyes and the results of the measurements are recorded in terms of the intensity ratio of the two peaks.…”

“…19,20 Mou and co-workers reported a ratiometric pH sensor based on MSN and studied its cellular uptake in HeLa cells. [12][13][14][15][16][17][18][19][20] When one uses these pH nanosensors for intracellular pH measurement, intending to cover both cytosol and endosome-lysosome systems, one may nd that the pH values are outside the limit of the pH-sensing range. The range, mainly determined by the acid dissociation constant (K a ) of the pH sensitive probe, is normally pK a AE 1, which means that the working pH range of most sensors is approximately two pH units.…”