A Gold Nanoparticle Bio-Optical Transponder to Dynamically Monitor Intracellular pH

Abstract

A pH-sensitive bio-optical transponder (pH-BOT) capable of simultaneously reporting the timing of intracellular DNA cargo release from a gold nanoparticle (AuNP) and the evolving intracellular pH (pH i) during endosomal maturation is demonstrated. The pH-BOT is designed with a triple-dye-labeled duplex DNA appended to a 6.6 nm AuNP, utilizing pH-responsive fluorescein paired with DyLight405 as a surface energy transfer (SET) coupled dye pair to ratiometrically report the pH at and after cargo release. A non-SET-coupled dye, DyLight 700, is used to provide dynamic tracking throughout the experiment. The pH-BOT beacon of the cargo uptake, release, and processing was visualized using live-cell confocal fluorescent microscopy in Chinese hamster ovary cells, and it was observed that while maturation of endosomes carrying pH-BOT is slowed significantly, the pH-BOT is distributed throughout the endolysosomal system while remaining at pH ∼6. This observed decoupling of endosomal maturation from acidification lends support to those models that propose that pH alone is not sufficient to explain endosomal maturation and may enable greater insight into our understanding of the fundamental processes of biology.

pH‐Triggered Aggregation of Gold Nanoparticles for Enhanced Labeling and Long‐Term CT Imaging Tracking of Stem Cells in Pulmonary Fibrosis Treatment

“…As demonstrated by previous work, most AuNPs enter cells via endocytosis. [ 18 ] Once internalized into cells, the AuNPs will undergo fast acidification, beginning from endosomes (with a pH of 5.2–6) to lysosomes (with a pH of 4.5–5.2) during the endosome maturation. [ 19 ] This mildly acidic environment could be used as an endogenic stimulus to change the properties of nanoparticles by triggering the aggregation of small nanoparticles, thus facilitating stem cell labeling and tracking.…”

Simultaneous Single-Particle Tracking and Dynamic pH Sensing Reveal Lysosome-Targetable Mesoporous Silica Nanoparticle Pathways

“…Evaluating the Dynamic Movements of MSNs in Different Regions of the Cell Using a Multidimensional Analysis. Even though many reports have examined the endocytosis process of NPs by monitoring either the motility type 3,60 or pH value, 4 separately, studying the correlation between these two parameters is important to obtain insight into NPs' internalization process. The 3D-scatter graphs shown in Figure 8 were established by plotting the histograms of velocity, α-coefficients, and pH slopes projecting on the x-, y-, and z-axes, respectively.…”

“…1−3 Most NPs enter cells via endocytosis. 4 Once they are internalized, fast acidification of encapsulated NPs via modulation of V-ATPase proton pump activity takes place during the endosome maturation. 5 The process begins from early endosomes (EEs), with a pH value of around 6−6.8, then proceeds to late endosomes (LEs), with a pH of approximately 5.2−6, and finally to, the lysosome (Lys), capable of acidification to a pH of 4.5−5.2.…”

Recent advances of smart acid‐responsive gold nanoparticles in tumor therapy

“…Strouse and coworkers reported a pH-sensitive AuNPs probe that can monitor the dynamic change in intracellular pH (Carnevale, Riskowski, & Strouse, 2018). Briefly, a triple-dye-labeled duplex DNA was loaded onto the surface of Guo et al (2010).…”