Enhancing the Stability and Photothermal Conversion Efficiency of ICG by Pillar[5]arene-Based Host-Guest Interaction.

Yue Ding,Yong Yao,Bing Lu,Chenwei Wang

doi:10.3389/fchem.2021.775436

Abstract

Indocyanine green (ICG) is a classical near-infrared (NIR) photothermal reagent that can be employed in clinical medical detection. Under neutral conditions, ICG can adsorb NIR light effectively for photothermal (PTT) and photodynamic (PDT) therapy. However, ICG is easily degraded in weak acid environments, which seriously restricts its application. In this work, a cationic water-soluble pillar[5]arene (WP5) was selected as the stabilizing agent for ICG. Thanks to the host-guest interaction between WP5 and alkyl sulfonate, the stability and the photothermal conversion efficiency of ICG increased remarkably upon addition of WP5 as investigated by UV-vis spectrum and photothermal studies. Furthermore, an in vitro study showed higher efficiency of WP5&ICG in killing cancer cells in a shorter treatment time than the free ICG. Hence, it is hopeful that WP5 can be a new type of supramolecular host in enhancing the stability and photothermal conversion efficiency of photosensitizers.

Highlights

In today’s society, cancer is one of the world’s most concerning health problems to humans, and the main means of cancer treatment are operation, radiotherapy, and chemotherapy (Issels, 2008; Mcguire, 2016; Song et al, 2015)
The above results showed that the linear guest C penetrated into the cavity of water-soluble pillar[5]arene (WP5) to form a [2]pseudorotaxane, the anion head of C was close to the trimethylammonium groups of WP5, and the Hal in the middle of alkyl chain lay in the cavity of pillar[5]arene, the H at the tail of C was outside the cavity (Figure 1A)
From the UV-vis spectra, we found that Indocyanine green (ICG) exhibited a strong absorption peak in the wavelength range of 600–900 nm (Figure 2A), which indicated that ICG could absorb near-infrared light well, and provided the possibility for photothermal therapy

Summary

Introduction

In today’s society, cancer is one of the world’s most concerning health problems to humans, and the main means of cancer treatment are operation, radiotherapy, and chemotherapy (Issels, 2008; Mcguire, 2016; Song et al, 2015). Near-infrared radiation (NIR) is beneficial for photothermotherapy because near-infrared light penetrates deeply through tissues, and endogenous biomolecules absorb fewer photons and cause less cell damage in this wavelength range (Cen et al, 2020). ICG can effectively absorb near-infrared light and convert it into singlet oxygen and heat. Combined with the excellent tissue penetrating ability of near-infrared light and little effect on the tissue itself, ICG can be used in photothermal therapy (PTT) and photodynamic therapy (PDT) (Shafirstein et al, 2012)

Methods

Results

Conclusion