Phenylboronic acid-decorated chondroitin sulfate A-based nanoparticles for solid tumor targeting and penetration

Abstract

For effective chemotherapy, it is crucial for anti-cancer drugs to gain adequate access to tumor tissues. Despite numerous efforts to improve tumor targeting including drug-loaded nanoparticles (NPs), the homogeneous distribution of the drug molecules across the entire tumor tissue—particularly in the hypoxic region distant from functioning blood vessels—is not readily achieved due to unfavorable tumor microenvironments. In this thesis work, we hypothesized that the tumor-targetable chondroitin sulfate A (CSA)-based NP system with phenylboronic acid (PBA) moiety added (targeting the hypoxic region of tumors) may achieve enhanced tumor targeting and penetration of anticancer drugs, thereby improving anticancer efficacy. To test the validity of our hypothesis, we designed NPs that consist of PBA-functionalized amphiphilic chondroitin sulfate A (CSA) derivatives. Briefly, deoxycholic acid (DOCA) was conjugated to the CSA backbone via ethylenediamine (EDA) linker, followed by the introduction of (3-aminomethylphenyl)boronic acid (AMPB) to CSA-DOCA. Successful synthesis of the developed graft copolymers was verified using proton nuclear magnetic resonance spectroscopy (1H-NMR). The amphiphilic CSA-DOCA and CSA-DOCA-AMPB conjugates were loaded with doxorubicin (DOX). The resulting self-assembled NPs displayed an average diameter of approximately 200 nm with narrow size distribution, negative zeta potential, and spherical morphology. With the relatively high drug entrapment efficiency (approximately 80%), the developed NPs exhibited an increased DOX release at acidic pH (pHs 5.5 and 6.8) compared to at pH 7.4. Further experiments using confocal laser scanning microscopy and flow cytometry indicated that the developed NPs have an enhanced cellular uptake, penetration into spheroids and enhanced cytotoxic effects, likely via the CSA-CD44 and PBA-sialic acid interactions. Using near-infrared fluorescence (NIRF) imaging in mouse xenograft models, we also observed that the developed NPs have an improved tumor targeting and drug penetration in vivo, potentially leading to improved anti-tumor efficacy and reduced systemic toxicity of DOX. In summary, our results showed that the CSA-DOCA-AMPB NPs can achieve improved tumor targeting and drug penetration, thereby a promising nanoplatform potentially applicable to the treatment of various solid cancers.