Enhanced Antitumor Effects of Epidermal Growth Factor Receptor Targetable Cetuximab-Conjugated Polymeric Micelles for Photodynamic Therapy.

Nanocarrier-based delivery systems are promising strategies for enhanced therapeutic efficacy and safety of toxic drugs. Photodynamic therapy (PDT)-a light-triggered chemical reaction that generates localized tissue damage for disease treatments-usually has side effects, and thus patients receiving photosensitizers should be kept away from direct light to avoid skin phototoxicity. In this study, a clinically therapeutic antibody cetuximab (C225) was conjugated to the surface of methoxy poly(ethylene glycol)-b-poly(lactide) (mPEG-b-PLA) micelles via thiol-maleimide coupling to allow tumor-targetable chlorin e6 (Ce6) delivery. Our results demonstrate that more C225-conjugated Ce6-loaded polymeric micelles (C225-Ce6/PM) were selectively taken up than Ce6/PM or IgG conjugated Ce6/PM by epidermal growth factor receptor (EGFR)-overexpressing A431 cells observed by confocal laser scanning microscopy (CLSM), thereby decreasing the IC50 value of Ce6-mediated PDT from 0.42 to 0.173 µM. No significant differences were observed in cellular uptake study or IC50 value between C225-Ce6/PM and Ce6/PM groups in lower EGFR expression HT-29 cells. For antitumor study, the tumor volumes in the C225-Ce6/PM-PDT group (percentage of tumor growth inhibition, TGI% = 84.8) were significantly smaller than those in the Ce6-PDT (TGI% = 38.4) and Ce6/PM-PDT groups (TGI% = 53.3) (p < 0.05) at day 21 through reduced cell proliferation in A431 xenografted mice. These results indicated that active EGFR targeting of photosensitizer-loaded micelles provides a possible way to resolve the dose-limiting toxicity of conventional photosensitizers and represents a potential delivery system for PDT in a clinical setting.

Carbon Nanotube-Mediated Photothermal Disruption of Endosomes/Lysosomes Reverses Doxorubicin Resistance in MCF-7/ADR Cells.

Cancer is the leading cause of human death worldwide. Although many scientists work to fight this disease, multiple drug resistance is a predominant obstacle for effective cancer therapy. In drug-resistant MCF-7/ADR cells, the acidic organelles with lower pH value than normal one can cause the protonation of anthracycline drugs, inducing drug accumulation in these organelles. In this study, single-walled carbon nanotubes with polyethylene glycol phospholipids surface modification (PEGylated SWNTs) were utilized as near infrared-activated drug carriers for doxorubicin (DOX) delivery against MCF-7/ADR cells. Our results showed that a concentration-dependent temperature increase was observed in a solution of PEGylated SWNTs with 808 nm laser irradiation, whereas a water solution showed no significant changes in temperature under a thermal camera using the same irradiation dose. Interestingly, PEGylated DOX-SWNTs enhanced the nuclear accumulation of DOX with 808 nm irradiation whereas free DOX or PEGylated DOX-SWNTs revealed discrete red spots in MCF-7/ADR cells by confocal microscopic observation. Cell viability of PEGylated DOX-SWNTs-treated cells was also significantly decreased after 808 nm laser irradiation. Thus, photothermally activated PEGylated SWNTs can be a potential nanocarrier to deliver DOX into cancer cells and successfully overcome drug-resistant behavior in MCF-7/ADR breast cancer cells.

Enhanced cytotoxicity of saporin by polyamidoamine dendrimer conjugation and photochemical internalization.

Because of the lack of membrane binding subunit, type I ribosome-inactivating proteins (RIPs) are not very toxic to cells unless action is taken to allow for toxin internalization to the cytosol. To overcome the potential barriers that greatly hinder the cellular uptake and intracellular release of saporin, a type I RIP, we used generation 4 polyamidoamine (PAMAM) dendrimer as the carrier to improve its endocytic uptake, passive tumor targeting, and implemented the photochemical internalization (PCI) technology to facilitate its cytosolic release. Our results showed that the cellular uptake of saporin was increased after conjugation with the PAMAM dendrimer and the cytotoxic effect was improved by more than 1 order of magnitude. The cytotoxicity of free saporin and PAMAM-saporin was further enhanced by the PCI technology. PCI changed the mechanism of cellular uptake of free saporin and then caused more saporin entering into the cells. After the PCI treatment, PAMAM-saporin was not only internalized into the cytosol but also efficiently entered the nuclei. Our results indicated that conjugating to PAMAM dendrimer is a possible approach to enhance the cellular uptake of saporin. PCI is a promising technology to significantly enhance the cytotoxicity of both free saporin and PAMAM-saporin. Combining both polymer conjugation and PCI approaches may improve the efficacy of RIPs in cancer therapy.

Doxorubicin delivery by polyamidoamine dendrimer conjugation and photochemical internalization for cancer therapy.

Coupling anticancer drugs to synthetic polymers is a promising approach to improve the efficacy and reduce the side effects of these drugs. The pH-activated polymer has been demonstrated to be a successful drug delivery vehicle system, whereas the photochemical internalization (PCI) was invented for site-specific delivery of membrane impermeable macromolecules from endocytic vesicles into the cytosol. In this study, doxorubicin (DOX) was conjugated to polyamidoamine (PAMAM) dendrimers via pH-sensitive and -insensitive linkers and was combined with different PCI strategies to evaluate the cytotoxic effects. Our results showed that both PCI strategies significantly improved the cytotoxicity of free DOX on Ca9-22 cells at higher concentrations. The 'light after' PCI treatment was efficient in releasing DOX from the PAMAM-hyd-DOX conjugates, resulted in more nuclear accumulation of DOX and more cell death through synergistic effects. On the other hand, antagonism was observed when 'light before' PCI combined with PAMAM-hyd-DOX conjugate. The distribution of PAMAM-amide-DOX was mainly cytosolic with or without PCI treatments. Both PCI strategies failed to improve the cytotoxicity of PAMAM-amide-DOX conjugates. Our results provide invaluable information in the future design of drug-polymer complexes for multi-modality cancer treatments.