Multifunctional PLGA nanoparticles combining transferrin-targetability and pH-stimuli sensitivity enhanced doxorubicin intracellular delivery and in vitro antineoplastic activity in MDR tumor cells.

Targeted delivery aims to enhance cellular uptake and improve therapeutic outcome with higher disease specificity. The expression of transferrin receptor (TfR) is upregulated on tumor cells, which make the protein Tf and its receptor vastly relevant when applied to targeting strategies. Here, we proposed Tf-decorated pH-sensitive PLGA nanoparticles containing the chemosensitizer poloxamer as a carrier for doxorubicin delivery to tumor cells (Tf-DOX-PLGA-NPs), aiming at alleviating multidrug resistance (MDR). We performed a range of in vitro studies to assess whether targeted NPs have the ability to improve DOX antitumor potential on resistant NCI/ADR-RES cells. All evaluations of the Tf-decorated NPs were performed comparatively to the nontargeted counterparts, aiming to evidence the real role of NP surface functionalization, along with the benefits of pH-sensitivity and poloxamer, in the improvement of antiproliferative activity and reversal of MDR. Tf-DOX-PLGA-NPs induced higher number of apoptotic events and ROS generation, along with cell cycle arrest. Moreover, they were efficiently internalized by NCI/ADR-RES cells, increasing DOX intracellular accumulation, which supports the greater cell killing ability of these targeted NPs with respect to MDR cells. Altogether, these findings supported the effectiveness of the Tf-surface modification of DOX-PLGA-NPs for an improved antiproliferative activity. Therefore, our pH-responsive Tf-inspired NPs are a promising smart drug delivery system to overcome MDR effect at some extent, enhancing the efficacy of DOX antitumor therapy.

pH-Sensitive chitosan-tripolyphosphate nanoparticles increase doxorubicin-induced growth inhibition of cervical HeLa tumor cells by apoptosis and cell cycle modulation.

Delivery systems responsive to pH variations might allow the exploitation of the various pH gradients within the body, e.g. between healthy and tumor tissue, or between the extracellular space and some cell compartments. In previous studies, we designed doxorubicin-loaded pH-responsive chitosan-tripolyphosphate nanoparticles (DOX-CS-NPs) and also performed an extensive in vitro study evidencing its notable antiproliferative activity against different tumor cells. Here, we focus on the understanding of the mechanisms underlying the improved in vitro antitumor activity of these NPs, using experimental conditions simulating both the physiological environments (pH 7.4) and the extracellular space of tumors (pHe 6.6). CS-NPs were obtained by ionotropic gelation method, using the surfactant 77KS, derived from the amino acid lysine, as a pH-sensitive adjuvant. The apoptotic effects on HeLa tumor cells was analyzed by annexin V-FITC quantification using flow cytometry. Likewise, the modulation of the cell cycle and the NP cell uptake rate were assessed by flow cytometry. pH-Responsive NPs augmented DOX cytotoxicity by increasing the number of apoptosis events, thus causing cell cycle arrest in the G2/M or S phase. The apoptotic effects were notably more evident at pH 6.6. It was also demonstrated that DOX-CS-NPs were internalized by HeLa cells in a greater extent than the non-associated drug, especially at pH 6.6. It was proven that the combined physicochemical and pH-responsive properties of CS-NPs allowed an enhanced DOX cell internalization in a tumor cell model, allowing the entrapped drug to induce greater cell cycle arrest and apoptotic effects.

Inclusion of a pH-responsive amino acid-based amphiphile in methotrexate-loaded chitosan nanoparticles as a delivery strategy in cancer therapy.

The encapsulation of antitumor drugs in nanosized systems with pH-sensitive behavior is a promising approach that may enhance the success of chemotherapy in many cancers. The nanocarrier dependence on pH might trigger an efficient delivery of the encapsulated drug both in the acidic extracellular environment of tumors and, especially, in the intracellular compartments through disruption of endosomal membrane. In this context, here we reported the preparation of chitosan-based nanoparticles encapsulating methotrexate as a model drug (MTX-CS-NPs), which comprises the incorporation of an amino acid-based amphiphile with pH-responsive properties (77KS) on the ionotropic complexation process. The presence of 77KS clearly gives a pH-sensitive behavior to NPs, which allowed accelerated release of MTX with decreasing pH as well as pH-dependent membrane-lytic activity. This latter performance demonstrates the potential of these NPs to facilitate cytosolic delivery of endocytosed materials. Outstandingly, the cytotoxicity of MTX-loaded CS-NPs was higher than free drug to MCF-7 tumor cells and, to a lesser extent, to HeLa cells. Based on the overall results, MTX-CS-NPs modified with the pH-sensitive surfactant 77KS could be potentially useful as a carrier system for intracellular drug delivery and, thus, a promising targeting anticancer chemotherapeutic agent.

PEGylated and poloxamer-modified chitosan nanoparticles incorporating a lysine-based surfactant for pH-triggered doxorubicin release.

The growing demand for efficient chemotherapy in many cancers requires novel approaches in target-delivery technologies. Nanomaterials with pH-responsive behavior appear to have potential ability to selectively release the encapsulated molecules by sensing the acidic tumor microenvironment or the low pH found in endosomes. Likewise, polyethylene glycol (PEG)- and poloxamer-modified nanocarriers have been gaining attention regarding their potential to improve the effectiveness of cancer therapy. In this context, DOX-loaded pH-responsive nanoparticles (NPs) modified with PEG or poloxamer were prepared and the effects of these modifiers were evaluated on the overall characteristics of these nanostructures. Chitosan and tripolyphosphate were selected to form NPs by the interaction of oppositely charged compounds. A pH-sensitive lysine-based amphiphile (77KS) was used as a bioactive adjuvant. The strong dependence of 77KS ionization with pH makes this compound an interesting candidate to be used for the design of pH-sensitive devices. The physicochemical characterization of all NPs has been performed, and it was shown that the presence of 77KS clearly promotes a pH-triggered DOX release. Accelerated and continuous release patterns of DOX from CS-NPs under acidic conditions were observed regardless of the presence of PEG or poloxamer. Moreover, photodegradation studies have indicated that the lyophilization of NPs improved DOX stability under UVA radiation. Finally, cytotoxicity experiments have shown the ability of DOX-loaded CS-NPs to kill HeLa tumor cells. Hence, the overall results suggest that these pH-responsive CS-NPs are highly potent delivery systems to target tumor and intracellular environments, rendering them promising DOX carrier systems for cancer therapy.