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

Abstract

Nanoparticle (NP)-based targeted drug delivery is intended to transport therapeutically active molecules to specific cells and particular intracellular compartments. However, there is limited knowledge regarding the complete route of NPs in this targeting scenario. In this study, simultaneously performing motion and dynamic pH sensing using single-particle tracking (SPT) leads to an alternative method of gaining insights into the mesoporous silica nanoparticle's (MSN) journey in targeting lysosome. Two different pH-sensitive dyes and a reference dye are incorporated into mesoporous silica nanoparticles (MSNs) via co-condensation to broaden the measurable pH range (pH 4−7.5) of the nanoprobe. The phosphonate, amine, and lysosomal sorting peptides (YQRLGC) are conjugated onto the MSN's surface to study intracellular nano-biointeractions of two oppositely charged and lysosome-targetable MSNs. The brightness and stability of these MSNs allow their movement and dynamic pH evolution during their journey to be simultaneously monitored in real time. Importantly, a multidimensional analysis of MSN's movement and local pH has revealed new model intracellular dynamic states and distributions of MSNs, previously inaccessible when using single parameters alone. A key result is that YQRLGC-conjugated MSNs took an alternative route to target lysosomes apart from the traditional one, which sped up to 4 h and enhanced their targeting efficiency (up to 32%). The findings enrich our understanding of the intracellular journey of MSNs. This study offers complementary information on correlating the surface design with the full pathway of nanoparticles to achieve targeted delivery of therapeutic payload.

Evaluation of Nanoparticle Penetration in the Tumor Spheroid Using Two-Photon Microscopy

“…To improve our understanding of the influence of NP physicochemistry in passive diffusion to their accumulation in spheroids, we further adopted the zombie cell method developed by Warren et al [ 35 , 36 ]. Spheroids were fixed overnight under 4% PFA to ensure that all the cellular dynamics and cellular uptake processes were halted, allowing only NP diffusion to dominate the penetration process.…”

Revealing the Phagosomal pH Regulation and Inflammation of Macrophages after Endocytosing Polyurethane Nanoparticles by A Ratiometric pH Nanosensor

“…>5000) within the matrix of mesoporous silica nanoparticle (MSNs) [ 44 ] and the compartmentations by the pores of MSNs prevented aggregation‐induced self‐quenching and photobleaching of the encapsulated dyes and minimize sensing interference from cell components. [ 34 ] These overall excellent properties made them suitable probes for long‐term monitoring of dynamic pH values throughout the phagocytosis using single‐particle tracking.…”

“…The synthesis of FRMSNs was based on a Stöber-like process developed by Mou and co-workers. [33,34] To generate wide-range ratiometric pH sensing which covers pH values of phagocytosis, double pH sensitive dyes FITC (pK a = 6.7) and OG (pK a = 4.1), and one reference RITC were cocondensed with a silica precursor to form triple dye-labeled MSNs. The chemical structure of the FRMSN +/− (FRMSN + or FRMSN − ) synthesized in this study is demonstrated in Figure 1B.…”

“…[33] Two different pH-sensitive dyes, fluorescein isothiocyanate (FITC) and oregon green (OG), and a reference rhodamine B isothiocyanate (RITC) dye were cocondensed with a silica precursor forming fluorescent MSN so-called FRMSN (abbreviation for FITC, OG, and RITC in MSN). [33,34] This specially designed MSN shows high sensitivity, brightness, and photostability in a broad pH range. The positively charged FRMSN (FRMSN + ), which contained a mix of polyethylene glycol (PEG) and polyethylene amine (PEI), was used as the pH reporter due to its biocompatibility.…”

Zn2+-Depletion Enhances Lysosome Fission in Cultured Rat Embryonic Cortical Neurons Revealed by a Modified Epifluorescence Microscopic Technique

“…1a). More details can be found in the Supplementary Material and a recent publication (Chang et al, 2020). In that design, the authors successfully tracked the constant spatial movement and morphological changes of a single fluorescent nanoparticle inside a cell.…”