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.

Transferrin-Conjugated Nanocarriers as Active-Targeted Drug Delivery Platforms for Cancer Therapy.

A lot of effort has been devoted to achieving active targeting for cancer therapy in order to reach the right cells. Hence, increasingly it is being realized that active-targeted nanocarriers notably reduce off-target effects, mainly because of targeted localization in tumors and active cellular uptake. In this context, by taking advantage of the overexpression of transferrin receptors on the surface of tumor cells, transferrin-conjugated nanodevices have been designed, in hope that the biomarker grafting would help to maximize the therapeutic benefit and to minimize the side effects. Notably, active targeting nanoparticles have shown improved therapeutic performances in different tumor models as compared to their passive targeting counterparts. In this review, current development of nano-based devices conjugated with transferrin for active tumor-targeting drug delivery are highlighted and discussed. The main objective of this review is to provide a summary of the vast types of nanomaterials that have been used to deliver different chemotherapeutics into tumor cells, and to ultimately evaluate the progression on the strategies for cancer therapy in view of the future research.

Chitosan-tripolyphosphate nanoparticles functionalized with a pH-responsive amphiphile improved the in vitro antineoplastic effects of doxorubicin.

Delivery systems with pH-responsiveness behavior are of particular interest because they could allow exploring the various pH gradients within the body, for example, between healthy tissue and tumor tissue, or between extracellular tissue and some cell compartments. Likewise, modifications in nanocarriers with polyethylene glycol (PEG) and poloxamer could be a potential approach to improve the effectiveness of cancer treatments. On these premises, we prepared pH-responsive DOX-loaded chitosan-tripolyphosphate nanoparticles (NPs), modified or not with PEG or poloxamer, and incorporating an anionic dyacyl lysine-based surfactant with sodium counterion (77KS) as a pH-sensitive adjuvant. Owing to its pH-sensitivity, the CS-NPs showed membranolytic behavior upon reducing the pH value of surrounding media to 6.6 and 5.4, which are characteristic of the endosomal compartments. The in vitro antiproliferative assays with MCF-7 and HeLa tumor cells indicated that the NPs themselves had no associated significant cytotoxicity, while DOX-loaded NPs induced higher cytotoxicity than free drug. Additionally, DOX-loaded CS-NPs displayed greater selectivity to tumor cells than to the non-tumor 3T3 fibroblasts. The feasibility of using these NPs to target tumor microenvironment was proven, as cytotoxicity against cancer cell models was higher in a mildly acidic environment. Finally, the hemocompatibility of NPs was demonstrated, indicating their suitability for intravenous administration. Altogether, the results suggest that the combination of endosomal acidity with the potential endosomolytic capability of these pH-responsive nanocarriers could increase the intracellular delivery of DOX and, thus, might enhance its antineoplastic efficacy.