Hyaluronic acid prodrug micelles for tumour therapy

Hyaluronic acid (HA), an important component of the extracellular matrix, has high water solubility and biocompatibility, and good application prospects in biomedicine. Especially in tumour treatment, prodrug polymer micelles prepared from HA and chemotherapeutics can increase water solubility, prolong drug release time, improve organ distribution and therapeutic effects, and show good tumour targeting and biocompatibility. Therefore, this study introduces strategies for using HA to prepare prodrug polymer micelles and discusses recent research on HA prodrug micelles for antitumor applications.

Development of pH-responsive starch–glycol chitosan nanogels for proapoptotic (KLAKLAK)2 peptide delivery

In this study, we report pH-responsive polysaccharidic nanogels for cytosolic peptide delivery. We conjugated starch to water-soluble glycol chitosan and pH-responsive 3-diethylaminopropylamine (starch–(glycol chitosan–3-diethylaminopropylamine)). Starch–(glycol chitosan–3-diethylaminopropylamine) self-organizes in aqueous solution, with the glycol chitosan blocks on the hydrophilic outer shell and starch and 3-diethylaminopropylamine blocks in the hydrogel inner core. The experimental results demonstrated that the protonation of 3-diethylaminopropylamine at pH 6.0 (endosomal pH) allowed for accelerated release of the encapsulated D-(KLAKLAK)2 proapoptotic peptide from the nanogels as a result of electrostatic repulsion between D-(KLAKLAK)2 and 3-diethylaminopropylamine. A hemolysis test using red blood cell membranes (as an endosomal membrane model) revealed the excellent endosomolytic activity of these nanogels, which likely stems from the proton-sponge effect of 3-diethylaminopropylamine at pH 6.0. As a result, these nanogels resulted in increased KB tumor cell ablation.

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.

Facile fabrication of highly soluble, extremely small-sized drug carriers using globular poly(ethylene glycol)

We report extremely small-sized drug-carrying globular poly(ethylene glycol) particles. These particles were prepared using fullerene (C60) as a backbone structure and poly(ethylene glycol) as a hydrophilic shell. All π–π carbon bonds in C60 were combined with poly(ethylene glycol), which form a “globular nano-cage” with a hollow core (originating from the soccer-ball-shaped truncated icosahedron of C60) and the poly(ethylene glycol) shell. Subsequently, we constructed chlorin e6-conjugated globular poly(ethylene glycol). The obtained globular poly(ethylene glycol)–chlorin e6 (average 3.6 nm in diameter) was soluble in aqueous solution and enabled improved singlet oxygen generation. The preferential cellular uptake of globular poly(ethylene glycol)–chlorin e6 resulted in significant enhancement of in vitro or in vivo photodynamic tumor cell ablation under light illumination. Our approach offers a versatile strategy to create extremely small-sized drug carriers using a biocompatible polymer for various biomedical applications.

Hoechst 33258–conjugated hyaluronated fullerene for efficient photodynamic tumor therapy and necrotic tumor targeting

In this study, we synthesized a Hoechst 33258–conjugated hyaluronated fullerene consisting of Hoechst 33258 (as a target moiety to detect necrotic tumor cells), hyaluronic acid (as a target polymer to bind the CD44 receptor overexpressed on the surface of tumor cells), and fullerene (as a photosensitizing agent). This conjugate self-assembled to form nanoparticles consisting of a hydrophilic block (Hoechst 33258 and hyaluronic acid) and a lipophilic block (fullerene). We utilized these nanoparticles to improve the antitumor efficacy via photodynamic tumor therapy. The HCT-116 cells that were damaged after the first photodynamic tumor therapy (using hyaluronated fullerene nanoparticles) were again targeted using Hoechst 33258–conjugated hyaluronated fullerene nanoparticles (detecting necrotic tissues). The experimental results revealed that the second photodynamic tumor therapy using Hoechst 33258–conjugated hyaluronated fullerene nanoparticles caused significant increases in the in vitro phototoxicity and the in vivo tumor inhibition, thereby suggesting their pharmaceutical potential for designing effective multiple photodynamic tumor therapy treatments.

Dual passively active tumor-targeting micelles for pH-triggered intracellular anticancer drug release

Novel passive–active dual tumor-targeting micelles for pH-triggered intracellular nitrogen mustard release were developed based on hydrophobic cores conjugated with anticancer drugs and shells functionalized with folic acid ligands for tumor cell targeting. The amphiphilic triblock copolymer, 4-( bis(2-chloroethyl)amino)benzaldehyde, N-(2-hydroxypropyl)methacrylamide, and folic acid copolymer (poly(mustard-acetal)- b-PHPMA- b-PFA), was synthesized via reversible addition fragmentation chain transfer polymerization. The amphiphilic copolymer was subsequently self-assembled into nanosized micelles of 83 nm with the nitrogen mustard drug safely encapsulated in the core. The cleavage of anticancer drug within the cores of micelles was effectively actuated under biologically relevant conditions, mildly acidic microenvironments (endosomal/lysosomal pH in the cytosol). 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays and fluorescence microscopy image analysis revealed that folate-conjugated nanosized micelles exhibited at least ~2.2-fold higher cellular uptake than folate unconjugated micelles against KB cells overexpressing folate receptors on the surface. Thus, poly(mustard-acetal)- b-PHPMA- b-PFA micelles could potentially be used as a promising system for triggering the release of nitrogen mustard drug.

A molecular zipping/unzipping nano-vehicles sensitive to tumor extracellular pH

A new class of pH- responsive multivalent host–guest interactions to manipulate polypeptide-based nano-vehicles was developed. Poly(l-lysine) (poly(Lys)) grafted with β-cyclodextrin and 2,3-dimethylmaleic acid was coupled with oleic acid. This new polymer was utilized to fabricate pH-responsive nano-vehicles for antitumor drug doxorubicin delivery. The host–guest (zipping) interaction between β-cyclodextrin and 2,3-dimethylmaleic acid moieties and the hydrophobic interaction between the oleic acid molecules contributed to form self-assembled nano-vehicles. 2,3-Dimethylmaleic acid moieties were highly degradable at a slightly acidic pH (~pH 6.8). These nano-vehicles increased the release of the encapsulated doxorubicin content (by the unzipping interaction between β-cyclodextrin and degraded 2,3-dimethylmaleic acid moieties) when the pH of the solution decreased to 6.8. This event caused a significant increase in the efficiency of cellular doxorubicin uptake and in vitro tumor inhibition.