Ultralong purely organic aqueous phosphorescence supramolecular polymer for targeted tumor cell imaging

Wei-Lei Zhou,Jing-Jing Li,Yu Liu,Qilin Yu,Zhi-Xue Liu,Xian-Yin Dai,Yong Chen,Haoyang Zhang

doi:10.1038/s41467-020-18520-7

Abstract

Purely organic room-temperature phosphorescence has attracted attention for bioimaging but can be quenched in aqueous systems. Here we report a water-soluble ultralong organic room-temperature phosphorescent supramolecular polymer by combining cucurbit[n]uril (CB[7], CB[8]) and hyaluronic acid (HA) as a tumor-targeting ligand conjugated to a 4-(4-bromophenyl)pyridin-1-ium bromide (BrBP) phosphor. The result shows that CB[7] mediated pseudorotaxane polymer CB[7]/HA–BrBP changes from small spherical aggregates to a linear array, whereas complexation with CB[8] results in biaxial pseudorotaxane polymer CB[8]/HA–BrBP which transforms to relatively large aggregates. Owing to the more stable 1:2 inclusion complex between CB[8] and BrBP and the multiple hydrogen bonds, this supramolecular polymer has ultralong purely organic RTP lifetime in water up to 4.33 ms with a quantum yield of 7.58%. Benefiting from the targeting property of HA, this supramolecular polymer is successfully applied for cancer cell targeted phosphorescence imaging of mitochondria.

Highlights

Organic room-temperature phosphorescence has attracted attention for bioimaging but can be quenched in aqueous systems
In the isothermal titration calorimetry (ITC) titrations (Supplementary Fig. 3A), the calculations were repeated as a 1:1 complex formation, and the titration data could be fitted well with a model characterized by one set of binding sites, giving a Ks value of (3.81 ± 0.22) × 106 M−1
In summary, two pseudorotaxane polymers were constructed by means of host–guest interactions between CB[8]: BrBP ratios (CB) and hyaluronic acid (HA)–BrBP, and these purely organic materials showed Room-temperature phosphorescence (RTP) in aqueous solution

Summary

Introduction

Organic room-temperature phosphorescence has attracted attention for bioimaging but can be quenched in aqueous systems. We report a water-soluble ultralong organic room-temperature phosphorescent supramolecular polymer by combining cucurbit[n]uril (CB[7], CB[8]) and hyaluronic acid (HA) as a tumor-targeting ligand conjugated to a 4-(4bromophenyl)pyridin-1-ium bromide (BrBP) phosphor. Room-temperature phosphorescence (RTP) emitted by purely organic molecules has been attracting increasing attention owing to its advantages over fluorescence, such as longer lifetime, larger Stokes shift, and the involvement of triplet states. Room-temperature phosphorescence (RTP) emitted by purely organic molecules has been attracting increasing attention owing to its advantages over fluorescence, such as longer lifetime, larger Stokes shift, and the involvement of triplet states1–6 Such phosphorescent materials have been widely used in organic light-emitting diodes, data-security, sensing, and bioimaging applications, among others.

Methods

Results

Conclusion