pH-Responsive globular poly(ethylene glycol) for photodynamic tumor therapy

Cyclic RGD-Conjugated Hyaluronate Dot Bearing Cleavable Doxorubicin for Multivalent Tumor Targeting

In this study, we developed an extremely small-sized water-soluble hyaluronate dot (dHA) conjugated with cyclic RGD (cRGD) and cleavable doxorubicin (DOX, as a model antitumor drug), named cRGD@dHA-c-DOX. This dot with HA moieties (as specific ligands to tumor CD44 receptors) and cRGD moieties (as specific ligands to tumor integrin α_vβ₃) was designed to enable multivalent tumor targeting. In particular, the imine bonds, linking the DOX and dHA, can exhibit cleavage performance at endosomal pH, resulting in pH-triggered DOX release from cRGD@dHA-c-DOX. We demonstrated that cRGD@dHA-c-DOX resulted in highly improved cellular uptake and cell death in MDA-MB-231 tumor cells (CD44+, integrin α_vβ₃+) compared to those in Huh7 tumor cells (CD44-, integrin α_vβ₃-). In vivo studies using MDA-MB-231 tumor-bearing mice revealed that cRGD@dHA-c-DOX enhanced the tumor inhibition efficacy. These results suggest that cRGD@dHA-c-DOX can be utilized as a promising multivalent tumor-targeting drug carrier for highly efficient tumor treatment.

Honeycomb-like pH-responsive γ-cyclodextrin electrospun particles for highly efficient tumor therapy

We report here the tumor-implantable microparticles with a honeycomb-like porous structure. These microparticles were prepared by electrospinning using γ-cyclodextrin (γ-CD) conjugated with 3-(diethylamino)propylamine (DEAP, as a pH-responsive moiety), named γ-CD-DEAP. The resulting microparticles had pore channels (constructed using γ-CD-DEAP) extending into the deep compartment of the microparticles and allowing efficient paclitaxel (PTX, as a chemotherapeutic model drug) entrapment by a simple hole-filling encapsulation process. Importantly, the hydrophobic DEAP (at pH 7.4) in the γ-CD-DEAP microparticles changed to hydrophilic DEAP (at pH 6.8) because of its acidic pH-induced protonation. This phenomenon resulted in an acidic pH-activated particle destruction by a charge-charge repulsion between the protonated DEAP moieties and allowed a pH-triggered release of the encapsulated PTX from the collapsed microparticles. Consequently, γ-CD-DEAP microparticles implanted at the tumor site caused a significant enhancement of the in vitro/in vivo tumor cell ablation, suggesting their significant potential as a chemotherapeutic implant for tumor therapy.

Poisonous Caterpillar-Inspired Chitosan Nanofiber Enabling Dual Photothermal and Photodynamic Tumor Ablation

As caterpillars detect the presence of predators and secrete poison, herein, we show an innovative and highly effective cancer therapeutic system using biocompatible chitosan nanofiber (CNf) installed with a pH-responsive motif that senses tumor extracellular pH, pH_e, prior to delivering dual-modal light-activatable materials for tumor reduction. The filamentous nanostructure of CNf is dynamic during cell interaction and durable in blood circulation. Due to its amine group, CNf uptakes a large amount of photothermal gold nanoparticles (AuNPs, >25 wt %) and photodynamic chlorin e6 (Ce6, >5 wt %). As the innovative CNf approaches tumors, cationic CNf effectively discharges AuNPs connected to the pH-responsive motif via electrostatic repulsion and selectively binds to tumor cells that are generally anionic, via the electrostatic attraction accompanied by CNf. We demonstrated via these actions that the endocytosed Ce6 (on CNf) and AuNPs (free from CNf) significantly elicited tumor cell death under light irradiation. As a result, the synergistic interplay of thermogenesis and photodynamic action was observed to switch on at the pH_e, resulting in a striking reduction in tumor formation and growth rate upon light exposure.

Biodegradable Nanoglobular Magnetic Resonance Imaging Contrast Agent Constructed with Host-Guest Self-Assembly for Tumor-Targeted Imaging

Gadolinium-based macromolecular magnetic resonance imaging (MRI) contrast agents (CAs) have attracted increasing interest in tumor diagnosis. However, their practical application is potentially limited because the long-term retention of gadolinium ion in vivo will induce toxicity. Here, a nanoglobular MRI contrast agent (CA) PAMAM-PG- g-s-s-DOTA(Gd) + FA was designed and synthesized on the basis of the facile host-guest interaction between β-cyclodextrin and adamantane, which initiated the self-assembly of poly(glycerol) (PG) separately conjugated with gadolinium chelates by disulfide bonds and folic acid (FA) molecule onto the surface of poly(amidoamine) (PAMAM) dendrimer, finally realizing the biodegradability and targeting specificity. The nanoglobular CA has a higher longitudinal relaxivity ( r₁) than commercial gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA), showing a value of 8.39 mM^-1 s^-1 at 0.5 T, and presents favorable biocompatibility on the observations of cytotoxicity and tissue toxicity. Furthermore, MRI on cells and tumor-bearing mice both demonstrate the obvious targeting specificity, on the basis of which the effective contrast enhancement at tumor location was obtained. In addition, this CA exhibits the ability of cleavage to form free small-molecule gadolinium chelates and can realize minimal gadolinium retention in main organs and tissues after tumor detection. These results suggest that the biodegradable nanoglobular PAMAM-PG- g-s-s-DOTA(Gd) + FA can be a safe and efficient MRI CA for tumor diagnosis.

A review and outlook in the treatment of osteosarcoma and other deep tumors with photodynamic therapy: from basic to deep

Photodynamic therapy, one of the most promising minimally invasive treatments, has received increasing focus in tumor therapy research, which has been widely applied in treating superficial tumors. Three basic factors - photosensitizer, the light source, and oxidative stress - are responsible for tumor cell cytotoxicity. However, due to insufficient luminous flux and peripheral tissue damage, the utilization of photodynamic therapy is facing a huge limitation in deep tumor therapy. Osteosarcoma is the typical deep tumor, which is the most commonly occurring malignancy in children and adolescents. Despite developments in surgery, high risks of the amputation still threatens the health of osteosarcoma patients. In this review, we summarize recent developments in the field of photodynamic therapy and specifically PDT research in OS treatment modalities. In addition, we also provide some novel suggestions, which could potentially be a breakthrough in PDT-induced OS therapies. PDT has the potential to become an effective therapy while the its limitations still present when applied on the treatment of OS or other types of deep tumors. Thus, more researches and studies in the field are required.

Fluorescence guided photothermal/photodynamic ablation of tumours using pH-responsive chlorin e6-conjugated gold nanorods

Photothermal/photodynamic therapies (PTT/PDT) have been widely accepted as non-invasive therapeutic modalities to erase tumours. However, both therapies face the problem of precisely locating tumours and reducing their side effects. Herein, chlorin e6 conjugated gold nanorod, (Ce6-PEG-AuNR), a type of gold nanorod-photosensitizer conjugate, is designed as a kind of nano-therapeutic agent to simultaneously realize combined PTT/PDT. Compared to free Ce6, the fluorescence of Ce6 adhered to the conjugate is effectively quenched by the longitudinal surface plasmon resonance (LSPR) of in the Ce6-PEG-AuNR. However, the specific fluorescence of Ce6 can be recovered in tumour tissue when Ce6 is separated from the conjugate owing to the cleavage of hydrazone bond between Ce6 and PEG caused by intracellular acidic conditions in tumour tissue. Based on this effect, we can precisely locate tumours and further kill cancer cells by combined PTT/PDT. In addition, the combined therapy (PTT/PDT) function is more efficient in cancer treatment than that of PTT or PDT alone. Therefore, Ce6-PEG-AuNR can serve as a promising dual-modal phototherapeutic agent as well as a tumour-sensitive fluorescent probe to diagnose and treat cancer.