Dextran-Functionalized Super-nanoparticle Assemblies of Quantum Dots for Enhanced Cellular Immunolabeling and Imaging

Abstract

Colloidal semiconductor quantum dots (QDs) are a popular material for applications in bioanalysis and imaging. Although individual QDs are bright, some applications benefit from the use of even brighter materials. One approach to achieve higher brightness is to form super-nanoparticle (super-NP) assemblies of many QDs. Here, we present the preparation, characterization, and utility of dextranfunctionalized super-NP assemblies of QDs. Amphiphilic dextran was synthesized and used to encapsulate many hydrophobic QDs via a simple emulsion-based method. The resulting super-NP assemblies or "super-QDs" had hydrodynamic diameters of ca. 90−160 nm, were characterized at the ensemble and single-particle levels, had orders-ofmagnitude superior brightness compared to individual QDs, and were non-blinking. Additionally, binary mixtures of red, green, and blue (RGB) colors of QDs were used to prepare super-QDs, including colors difficult to obtain from individual QDs (e.g., magenta). Tetrameric antibody complexes (TACs) enabled simple antibody conjugation for selective cellular immunolabeling and imaging with both an epifluorescence microscope and a smartphone-based platform. The technical limitations of the latter platform were overcome by the increased per-particle brightness of the super-QDs, and the super-QDs outperformed individual QDs in both cases. Overall, the super-QDs are a very promising material for bioanalysis and imaging applications where brightness is paramount.

Supra-Quantum Dot Assemblies to Maximize Color-Based Multiplexed Fluorescence Detection with a Smartphone Camera

“…Shifting data points further from the origin thus yields higher classification accuracies. Some possible strategies for higher brightness with QD materials include preparation of larger supra-QDs for more QDs per SiO 2 NP (assuming colloidal utility can be maintained), preparation of supra-QDs with QDs that retain their native hydrophobic ligands (exchange with hydrophilic ligands, as done here, frequently lowers quantum yields), , and substitution of supra-QDs with superparticle assemblies of QDs that pack more QDs per unit volume . Device refinements, such as higher intensity excitation and higher numerical aperture optics, will also increase PL signal levels, as would static imaging instead of imaging under flow (a longer exposure time is possible for more signal in static imaging).…”

“…For PL measurements with smartphone-based devices, the higher brightness of quantum dots (QDs) provides superior analytical performance versus fluorescent dyes by better compensating for the technical limitations of smartphone cameras that were not designed and optimized for this purpose. , Moreover, their narrow, symmetric, and tunable PL emission spectracombined with the ability to induce PL from multiple colors of QDs using a single excitation wavelengthare ideal for multiplexed detection via the red-green-blue (RGB) color channels of smartphone cameras. , The recent development of supra-nanoparticle and super-nanoparticle assemblies of QDs now offers this multiplexing advantage with even greater brightness, permitting immunofluorescent single-cell detection and flow cytometry on a smartphone. − These recent developments lead to the question: What level of color multiplexing is possible with PL imaging on a smartphone? To date, examples of multiplexing have been limited to only two or three targets. ,,, …”

Dual-Mode Fluorescent/Intelligent Lateral Flow Immunoassay Based on Machine Learning Algorithm for Ultrasensitive Analysis of Chloroacetamide Herbicides

“…13 The fluorescent LFIA has been regarded as better suited for quantitative analysis. In general, the fluorescent LFIA can be performed by the use of fluorescent materials, such as organic dyes, 14 quantum dots (QDs), 15 up-converting phosphors, 16 and time-resolved fluorescent nanoparticles (TRFNPs). 17 Although organic dyes (e.g., rhodamine) have sufficient fluorescence brightness, they often suffer from the trouble of photobleaching.…”

Spontaneous Emulsification of Organometallic Complexes Applied to the Synthesis of Nanocapsules Active for H2 Release from Ammonia-Borane

“…Well-organized superstructures require complex synthetic procedures to control and achieve the desired functionalities. , In this respect, methodology developments broaden the horizons of material synthesis and applications. − Notably, efforts have been made to create spherical shells of inorganic materials. To date, the most widespread strategies consist in assembling preformed nanoparticles (NPs) at the surface of either solid particles or emulsion droplets. , Hollow capsules were either derived from colloidosomes by sacrificing the core particle or from alternative processes such as spray drying .…”