Photoswitchable fluorescent nanoparticles and their emerging applications

Abstract

Although fluorescence offers ultrasensitivity, real-world applications of fluorescence techniques encounter many practical problems. As a noninvasive means to investigate biomolecular mechanisms, pathways, and regulations in living cells, the intrinsic heterogeneity and inherent complexity of biological samples always generates optical interferences such as autofluorescence. Therefore, innovative fluorescence technologies are needed to enhance measurement reliability while not compromising sensitivity. In this review, we present current strategies that use photoswitchable nanoparticles to address these real-world challenges. The unique feature in these photoswitchable nanoparticles is that fundamental molecular photoswitches are playing the critical role of fluorescence modulation rather than traditional methods like modulating the light source. As a result, new innovative technologies that have recently emerged include super-resolution imaging, frequency-domain imaging, antiphase dual-color correlation, etc. Some of these methods improve imaging resolution down to the nanometer level, while others boost the detection sensitivity by orders of magnitude and confirm the nanoparticle probes unambiguously. These enhancements, which are not possible with non-photoswitching molecular probes, are the central topics of this review.

Photochromic fluorophores at the molecular and nanoparticle levels: fundamentals and applications of diarylethenes

“…For the sake of clarity, this review article will not include all accomplishments related to this research field, and therefore the most important and recent developments will be described by selecting a few representative examples. Many other excellent review papers reported previously will help to cover the wide variety of results reported so far [8][9][10][11][12][13][14][15][16][17] .…”

“…The difference in geometry and electronic structure between the two isomers can be exploited to reversibly control a wide variety of properties. In particular, photoswitching of fluorescence signals has attracted much attention because of its potential in various optoelectronic applications, including optical memories, bioimaging, and photoswitches with high sensitivity [8][9][10][11] . In addition, the recent progress of fluorescence-based imaging technology including super-resolution microscopy 5,10,12,13 , which can achieve higher spatial resolution beyond the diffraction limit of light, further encourages the development of fluorescence photoswitchable molecules.…”

From a Molecular Toolbox to a Toolbox for Photoswitchable Fluorescent Polymeric Nanoparticles

“…The situation becomes even worse in the case that a combinational color, i.e., white light, is the target because it consists of more than two emission colors with a subtle ratio . Although various organic fluorescent molecules have been designed and developed, there remains a lot of issues that must be addressed prior to their practical application, for example, the lack of a photoswitching mechanism that allows the use of the materials in rewritable data storage and photoresponsive optoelectronic devices etc., and high fabrication cost of some molecules with specific emission colors (like white light) . Efficient, photoswitchable fluorescent material toolbox is still not built up yet.…”

An all-photonic full color RGB system based on molecular photoswitches

“…timuli-responsive multicolor luminescent materials attract extensive attention due to their potential applications in areas such as optical memory systems, bioimaging, sensors, whitelight generation, encryption/decryption protocols, and anticounterfeiting [1][2][3][4][5][6][7][8][9] . Additive mixing, that is, changes in the overall emission color of a sample achieved by mixing two or more individual fluorophores in different ratios has been successfully applied [10][11][12][13][14] , whereas other approaches imply exposing the sample to physical or mechanical stimuli such as acid/base, ions, solvent vapor, and grinding/smearing [15][16][17][18][19][20][21][22][23][24][25][26] .…”