Development of a Rapid-Onset, Acid-Labile Linkage Polyplex-Mixed Micellar System for Anticancer Therapy.

Shiou-Fen Hung,Yi-Ting Chiang,Hsin-Cheng Chiu,Lu-Yi Yu,Chun-Liang Lo,Yu-Han Wen

doi:10.3390/polym13111823

Shiou-Fen Hung, Yi-Ting Chiang + Show 4 more

Open Access

https://doi.org/10.3390/polym13111823

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Abstract

In the treatment of cancers, small interfering ribonucleic acids (siRNAs) are delivered into cells to inhibit the oncogenic protein’s expression; however, polyanions, hydrophilicity, and rapid degradations in blood, endosomal or secondary lysosomal degradation hamper clinal applications. In this study, we first synthesized and characterized two copolymers: methoxy poly(ethylene glycol)-b-poly(2-hydroxy methacrylate-ketal-pyridoxal) and methoxy poly(ethylene glycol)-b-poly(methacrylic acid-co-histidine). Afterwards, we assembled two polymers with the focal adhesion kinase (FAK) siRNA, forming polyplex-mixed micelles for the treatment of the human colon cancer cell line HCT116. In terms of the physiological condition, the cationic pyridoxal molecules that were conjugated on the copolymer with ketal bonds could electrostatically attract the siRNA. Additionally, the pyridoxal could form a hydrophobic core together with the hydrophobic deprotonated histidine molecules in the other copolymer and the hydrophilic polyethylene glycol (PEG) shell to protect the siRNA. In an acidic condition, the pyridoxal would be cleaved from the polymers due to the breakage of the ketal bonds and the histidine molecules can simultaneously be protonated, resulting in the endosome/lysosome escape effect. On the basis of our results, the two copolymers were successfully prepared and the pyridoxal derivatives were identified to be able to carry the siRNA and be cleavable by the copolymers in an acidic solution. Polyplex-mixed micelles were prepared, and the micellar structures were identified. The endosome escape behavior was observed using a confocal laser scanning microscopy (CLSM). The FAK expression was therefore reduced, and the cytotoxicity of siRNA toward human colon cancer cells was exhibited, rapidly in 24 h. This exceptional anticancer efficiency suggests the potential of the pH-sensitive polyplex-mixed micellar system in siRNA delivery.

Highlights

The copolymer was dried and characterized using 1 H-NMR and Fourier transform infrared spectroscopy (FT-IR) as respectively shown in Figure S1a,b in Supporting Information
The C–O ether stretching of polyethylene glycol (PEG) was found. These results indicate the successful conjugation of VB6 onto the copolymer and that the cationic mPEG-b-P(HEMA-ketal-VB6 ) was synthesized
It is noticeable that when the cells were treated with 100 μg/mL of the free small interferingRNA (siRNA), only 10% of cell death occurred as a result

Summary

Introduction

Even when an siRNA is permitted entry into a cell, its ability to escape from endosomes or secondary lysosomes is another concern [9]. In order to overcome these natural obstacles, the siRNA is often packaged into a carrier for the treatment of cancer [9,12,13]. These carriers are required to impede the siRNA from the nuclease during blood circulation, ensure internalization into cancer cells and escape from the endosomes or secondary lysosomes in cells [12,13,14]

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