Highly Fluorescent, Photostable, Conjugated Polymer Dots with Amorphous, Glassy‐State, Coarsened Structure for Bioimaging

Abstract

have been developed for in vitro and in vivo bioimaging applications. CPDs have attracted considerable attention, because of their potential benefi ts such as relatively facile preparation, high fl uorescence (FL) emission quantum effi ciency, photostability, and low cytotoxicity. [ 2a ] However, CPDs still have some drawbacks, because of the characteristic electronic structures of conjugated polymers. First, in general, π-conjugated polymers have planar geometries and strong intermolecular interactions, because of the extremely stiff and rigid main chains, resulting in highly face-to-face chain packing in the solid state. [ 5 ] Although such an intermolecular π-stacked structure is essential for effective charge-carrier transport in the active layer in thin-fi lm organic optoelectronic devices, [ 6 ] the cofacial packing structure signifi cantly reduces the FL quantum effi ciency in bulk solid fi lms, because it produces crystal domains, and the formed intermolecular excimers have an extremely low transition energy in non-radiative processes. [ 7 ] CPDs are no exception to this rule. [ 2,8 ] Signifi cant FL attenuation has been observed in aqueous colloidal solutions compared with the usual organic solutions. Secondly, although CPDs have much higher photostabilities compared with other fl uorescent materials such as organic dyes [ 9 ] and green fl uorescent In this paper, specifi c molecular design rules are proposed for highly fl uorescent, photostable, conjugated polymer dots (CPDs) applicable for the bioimaging of live cells. CPDs are prepared by nanoprecipitation in water using polydiphenylacetylene (PDPA) derivatives and commercial conjugated polymers. Among these, an amorphous, glassy-state PDPA derivative provides highly porous, coarsened nanoparticles. The nanoparticles are dispersed very well in water, and the polymer chains are either hydrodynamically or thermodynamically stable, with a fully relaxed intramolecular stacked structure. This leads to effective radiative emission decays by restraining collisional quenching and vibrational relaxation to achieve an extremely high fl uorescence (FL) quantum effi ciency. The FL emission quantum yield is as high as 0.76, which is the highest value among those reported for conventional CPDs. The PDPA-based CPD has a very low photobleaching quantum yield (∼10 −9 ), because of its relatively high ionization potential. This aqueous colloidal solution is useful for bioimaging plant and mammalian cells. The excellent FL quantum effi ciency, photostability, and cellular uptake suggest that the present CPD is a very promising probe for bioimaging, particularly for long-term imaging and tracking in live cells or experimental animals.Recently, a wide range of fl uorescent nanoparticles such as inorganic semiconductor quantum dots, [ 1 ] conjugated polymer dots (CPDs), [ 2 ] conjugated polyelectrolyte dots, [ 3 ] and carbon dots [ 4 ]

Conjugated Polymer Nanoparticles for Bioimaging

“…Nevertheless, quantum efficiencies hardly reach values over 50%. The introduction of specific moieties known to exhibit aggregation induced emission seems to be an attractive alternative solution, since those materials exhibit higher emission efficiencies when tight packing can be achieved [ 40 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ].…”

“…A very promising technique was introduced by Kim et al [ 50 ], who showed that the freezing of polydiphenylacetylene (PDPA, 23 and 24 ) into CPNPs in their relaxed state can lead to an extremely high PLQY of 76%. PDPA is an amorphous polymer and the effect of relaxed state freezing is very specific for this polymer of which the backbone is rigid, but highly twisted because of the steric hindrance caused by the phenyl side chains.…”

Novel PSMA-Coated On-Off-On Fluorescent Chemosensor Based on Organic Dots with AIEgens for Detection of Copper (II), Iron (III) and Cysteine

“…The AIE dots were prepared for conjugated polymers by using the nano-precipitation method as described previously [39,40]. The tetrahydrofuran stock solutions of PSMA (1 mg·mL −1 ) and DSA (0.5 mg·mL −1 ) were prepared, respectively.…”

Properties, Functions, Chemical Transformation, Nano-, and Hybrid Materials of Poly(diphenylacetylene)s toward Sensor and Actuator Applications

“…[94][95][96][97] In a previous study, nanoprecipitation was examined using several PDPA derivatives and commercial CPs. 98 Among them, the p-C1-PDPA produced highly porous nanoparticles that dispersed very well in water. The polymer chains therein were either hydrodynamically or thermodynamically stable with the side phenyl rings being relaxed.…”

“…Additionally, the nanoparticles had higher photostability and lower cytotoxicity relative to conventional CPs. 98 The aqueous colloidal solution was suitable for bioimaging of live cells. Cellular uptake of the nanoparticles via endocytosis was observed.…”