Amphiphilic hyaluronic acid derivative with the bioreducible bond: Synthesis and its implication for intracellular drug delivery

Polysaccharide nanoparticles: from fabrication to applications

The present review highlights the developments in polysaccharide nanoparticles with a particular focus on applications in biomedicine, cosmetics and food.

Redox-Responsive Coordination Polymers of Dopamine-Modified Hyaluronic Acid with Copper and 6-Mercaptopurine for Targeted Drug Delivery and Improvement of Anticancer Activity against Cancer Cells

Dopamine-modified hyaluronic acid (HA-DOP) was chosen as the drug carrier in this study, and Cu²⁺ was selected from among Cu²⁺, Zn²⁺, Fe²⁺, and Ca²⁺ as the central atom. 6-Mercaptopurine (6-MP) was conjugated with HA through a coordination reaction. HA-DOP-copper-MP (HA-DOP-Cu-MP), a redox-responsive coordination polymer prodrug, was prepared. The drug loading was 49.5 mg/g, the encapsulation efficiency was 70.18%, and the particle size was 173.5 nm. HA-DOP-Cu-MP released rapidly in the release medium containing reduced glutathione (GSH), and the accumulated release exceeded 94% in 2 h. In the release medium without GSH, the drug release rate was slow, with only 15% of the 6-MP released in 24 h. Cell uptake experiments revealed the CD44 targeting of HA. Cell viability assays showed that the cytotoxicity of HA-DOP-Cu-MP was higher than that of free 6-MP. Indeed, HA-DOP-Cu-MP is very toxic to cancer cells. In this paper, the redox-responsive drug delivery system was synthesized by a coordination reaction. The tumour targeting and tumour cytotoxicity of 6-MP were improved.

Metal-Phenolic Network-Coated Hyaluronic Acid Nanoparticles for pH-Responsive Drug Delivery

Although self-assembled nanoparticles (SNPs) have been used extensively for targeted drug delivery, their clinical applications have been limited since most of the drugs are released into the blood before they reach their target site. In this study, metal-phenolic network (MPN)-coated SNPs (MPN-SNPs), which consist of an amphiphilic hyaluronic acid derivative, were prepared to be a pH-responsive nanocarrier to facilitate drug release in tumor microenvironments (TME). Due to their amphiphilic nature, SNPs were capable of encapsulating doxorubicin (DOX), chosen as the model anticancer drug. Tannic acid and FeCl₃ were added to the surface of the DOX-SNPs, which allowed them to be readily coated with MPNs as the diffusion barrier. The pH-sensitive MPN corona allowed for a rapid release of DOX and effective cellular SNP uptake in the mildly acidic condition (pH 6.5) mimicking TME, to which the hyaluronic acid was exposed to facilitate receptor-mediated endocytosis. The DOX-loaded MPN-SNPs exhibited a higher cytotoxicity for the cancer cells, suggesting their potential use as a drug carrier in targeted cancer therapy.

A carboxymethyl dextran-based polymeric conjugate as the antigen carrier for cancer immunotherapy

BACKGROUND

Antigen-specific cytotoxic T lymphocytes (CTLs), which eliminate target cells bearing antigenic peptides presented by surface major histocompatibility complex (MHC) class I molecules, play a key role in cancer immunotherapy. However, the majority of tumors are not immunologically rejected since they express self-antigens which are not recognized by CTLs as foreign. To foreignize these tumors for CTL-mediated immunological rejection, it is essential to develop carriers that can effectively deliver foreign antigens to cancer cells.

METHODS

A polymeric conjugate, composed of a carboxymethyl dextran (CMD) as the backbone and ovalbumin (OVA) as a model foreign antigen, was prepared to investigate its potential as the antigen carrier for cancer immunotherapy.

RESULTS

An in vitro cellular uptake study showed that the conjugate was successfully taken up by TC-1 cervical cancer cells. When CMD-OVA was systemically administered to tumor-bearing mice, the strong fluorescence signal was observed at the tumor site over the whole period of time period, suggesting high tumor targetability of the conjugate. Compared to free OVA, CMD-OVA induced significantly higher antigen presentation at the tumor site.

CONCLUSIONS

The CMD-OVA conjugate can effectively deliver the antigen to the tumor site, implying its high potential as the antigen carrier for cancer immunotherapy.

A PEGylated hyaluronic acid conjugate for targeted cancer immunotherapy

The cell-free approach to foreignizing tumor cells with non-self antigens has received increasing attention as a method to induce cytotoxic T lymphocyte (CTL)-mediated immunological rejection of tumors, because the clinical translation of the conventional CTL-based cancer immunotherapies has been limited by a complicated manufacturing process and autotransplantation. In this study, we prepared matrix metalloproteinase 9 (MMP9)-responsive polymeric conjugates consisting of PEGylated hyaluronic acid (HA) as the targeting moiety and ovalbumin (OVA) as the model foreign antigen. The MMP9-cleavable linker was introduced between PEG and the HA backbone to facilitate the detachment of the PEG corona from the conjugate at the tumor site. From the in vitro cellular uptake study, it was revealed that the conjugate was effectively taken up by the CD44-expressing TC-1 cancer cells in the presence of MMP9 via receptor-mediated endocytosis. When the conjugate was systemically administered into the tumor-bearing mice with endogenous OVA-specific CTLs, the tumor growth was markedly inhibited, which was attributed to the significant antigen presentation on the tumor cells. Overall, the MMP9-responsive conjugates bearing foreign antigens might have the potential as an alternative to CTL-based cancer immunotherapeutics.

Hyaluronic acid and its derivatives in drug delivery and imaging: Recent advances and challenges

Hyaluronic acid (HA) is a biodegradable, biocompatible, nontoxic, and non-immunogenic glycosaminoglycan used for various biomedical applications. The interaction of HA with the CD44 receptor, whose expression is elevated on the surface of many types of tumor cells, makes this polymer a promising candidate for intracellular delivery of imaging and anticancer agents exploiting a receptor-mediated active targeting strategy. Therefore, HA and its derivatives have been most investigated for the development of several carrier systems intended for cancer diagnosis and therapy. Nonetheless, different and important delivery applications of the polysaccharide have also been described, including gene and peptide/protein drugs delivery. The aim of this review was to provide an overview of the existing recent literature on the use of HA and its derivatives for drug delivery and imaging. Notable attention is given to nanotheranostic systems obtained after conjugation of HA to nanocarriers as quantum dots, carbon nanotubes and graphene. Meanwhile, attention is also paid to some challenging aspects that need to be addressed in order to allow translation of preclinical models based on HA and its derivatives for drug delivery and imaging purposes to clinical testing and further their development.

Reduction-sensitive polymeric nanocarriers in cancer therapy: a comprehensive review

Redox potential is regarded as a significant signal to distinguish between the extra-cellular and intra-cellular environments, as well as between tumor and normal tissues. Taking advantage of this physiological differentiation, various reduction-sensitive polymeric nanocarriers (RSPNs) have been designed and explored to demonstrate excellent stability during blood circulation but rapidly degrade and effectively trigger drug release in tumor cells. Therefore, this smart RSPN delivery system has attracted much attention in recent years, as it represents one of the most promising drug delivery strategies in cancer therapy. In this review, we will provide a comprehensive overview of RSPNs with various reducible linkages and functional groups up to date, including their design and synthetic strategies, preparation methods, drug release behavior, and their in vitro and in vivo efficacy in cancer therapy. In addition, dual- and triple-sensitive nanocarriers based on reducible disulfide bond-containing linkages will also be discussed.