Nanodrug delivery systems and cancer stem cells: From delivery carriers to treatment

Engineering a pH-responsive polymeric micelle co-loaded with paclitaxel and triptolide for breast cancer therapy

Breast cancer has overtaken lung cancer as the number one cancer worldwide. Paclitaxel (PTX) is a widely used first-line anti-cancer drug, but it is not very effective in clinical breast cancer therapy. It has been reported that triptolide (TPL) can enhance the anticancer effect of paclitaxel, and better synergistic therapeutic effects are seen with concomitant administration of PTX and TPL. In this study, we developed pH-responsive polymeric micelles for co-delivery of PTX and TPL, which disassembling in acidic tumour microenvironments to target drug release and effectively kill breast cancer cells. Firstly, we synthesized amphiphilic copolymer mPEG2000-PBAE through Michael addition reaction, confirmed by various characterizations. Polymer micelles loaded with TPL and PTX (TPL/PTX-PMs) were prepared by the thin film dispersion method. The average particle size of TPL/PTX-PMs was 97.29 ± 1.63 nm, with PDI of 0.237 ± 0.003 and Zeta potential of 9.57 ± 0.80 mV, LC% was 6.19 ± 0.21%, EE% was 88.67 ± 3.06%. Carrier material biocompatibility and loaded micelle cytotoxicity were assessed using the CCK-8 method, demonstrating excellent biocompatibility. Under the same drug concentration, TPL/PTX-PMs were the most toxic to tumour cells and had the strongest proliferation inhibitory effect. Cellular uptake assays revealed that TPL/PTX-PMs significantly increased intracellular drug concentration and enhanced antitumor activity. Overall, pH-responsive micellar co-delivery of TPL and PTX is a promising approach for breast cancer therapy.

Enhanced Efficacy against Drug-Resistant Tumors Enabled by Redox-Responsive Mesoporous-Silica-Nanoparticle-Supported Lipid Bilayers as Targeted Delivery Vehicles

Multidrug resistance (MDR) is frequently induced after long-term exposure to reduce the therapeutic effect of chemotherapeutic drugs, which is always associated with the overexpression of efflux proteins, such as P-glycoprotein (P-gp). Nano-delivery technology can be used as an efficient strategy to overcome tumor MDR. In this study, mesoporous silica nanoparticles (MSNs) were synthesized and linked with a disulfide bond and then coated with lipid bilayers. The functionalized shell/core delivery systems (HT-LMSNs-SS@DOX) were developed by loading drugs inside the pores of MSNs and conjugating with D-α-tocopherol polyethylene glycol 1000 succinate (TPGS) and hyaluronic acid (HA) on the outer lipid surface. HT-LMSNs-SS and other carriers were characterized and assessed in terms of various characteristics. HT-LMSNs-SS@DOX exhibited a dual pH/reduction responsive drug release. The results also showed that modified LMSNs had good dispersity, biocompatibility, and drug-loading capacity. In vitro experiment results demonstrated that HT-LMSNs-SS were internalized by cells and mainly by clathrin-mediated endocytosis, with higher uptake efficiency than other carriers. Furthermore, HT-LMSNs-SS@DOX could effectively inhibit the expression of P-gp, increase the apoptosis ratios of MCF-7/ADR cells, and arrest cell cycle at the G0/G1 phase, with enhanced ability to induce excessive reactive oxygen species (ROS) production in cells. In tumor-bearing model mice, HT-LMSNs-SS@DOX similarly exhibited the highest inhibition activity against tumor growth, with good biosafety, among all of the treatment groups. Therefore, the nano-delivery systems developed herein achieve enhanced efficacy towards resistant tumors through targeted delivery and redox-responsive drug release, with broad application prospects.

Fabrication of folic acid-modified bovine serum albumin cloaked dual-drug loaded hollow mesoporous silica nanoparticles for pH-responsive and targeted delivery of gastric cancer therapy

Combination therapy is a highly successful way to address the limitations of using a single treatment method and improve therapy's overall efficacy. In this study, we developed a unique hollow mesoporous silica nanoparticle (HMSN) coated with folic acid (FA)-modified bovine serum albumin (FA-BSA). This nanoparticle, referred to as HFB, was designed to target cancer cells and release dual therapeutic drugs, Indocyanine green (ICG) and Paclitaxel (PTX), in response to specific stimuli termed as HFB@IP. The BSA protein acts as a "gatekeeper" to prevent early drug releases and cargo leakage by detaching from BSA in reaction to GSH. The FA facilitates the targeted transport of the drug into cancer cells that express folate receptors (FR), enhancing the effectiveness of chemo-photodynamic treatment (PDT). The drug nanocarrier demonstrated in vitro pH/redox-triggered drug release from HFB@IP due to breaking the imine bonds between aldehyde-functionalized HMSN (CHO-HMSN) and FA-BSA with the disulfide bond inside BSA. In addition, various biological assessments, including cell uptake experiments, demonstrated that HFB@IP effectively targets SGC-7901 cells and induces apoptosis in vitro. Further, it exhibits remarkable efficiency in synergistically killing cancer cells through chemo-photodynamic therapy, as indicated by a combination index (CI) of 0.328. The results showed that combining HMSN with biodegradable stimuli-responsive BSA molecules could offer a promising approach for precise chemo-photodynamic therapy in treating gastric cancer, allowing for the controlled release of drugs as necessary.

Folate-Targeted Nanocarriers Co-Deliver Ganciclovir and miR-34a-5p for Combined Anti-KSHV Therapy

Kaposi's sarcoma-associated herpesvirus (KSHV) can cause a variety of malignancies. Ganciclovir (GCV) is one of the most efficient drugs against KSHV, but its non-specificity can cause other side effects in patients. Nucleic acid miR-34a-5p can inhibit the transcription of KSHV RNA and has great potential in anti-KSHV therapy, but there are still problems such as easy degradation and low delivery efficiency. Here, we constructed a co-loaded dual-drug nanocomplex (GCV@ZIF-8/PEI-FA+miR-34a-5p) that contains GCV internally and adsorbs miR-34a-5p externally. The folic acid (FA)-coupled polyethyleneimine (PEI) coating layer (PEI-FA) was shown to increase the cellular uptake of the nanocomplex, which is conducive to the enrichment of drugs at the KSHV infection site. GCV and miR-34a-5p are released at the site of the KSHV infection through the acid hydrolysis characteristics of ZIF-8 and the "proton sponge effect" of PEI. The co-loaded dual-drug nanocomplex not only inhibits the proliferation and migration of KSHV-positive cells but also decreases the mRNA expression level of KSHV lytic and latent genes. In conclusion, this co-loaded dual-drug nanocomplex may provide an attractive strategy for antiviral drug delivery and anti-KSHV therapy.

Liquid exfoliation of ultrasmall zirconium carbide nanodots as a noninflammatory photothermal agent in the treatment of glioma

Photothermal therapy (PTT), like other clinical translational tumor ablation techniques, requires a temperature increase above 50 °C to cause necrosis and death of tumor cells. Although the tumor can be eliminated rapidly by PTT, the inflammatory response is triggered by the large amounts of released reactive oxygen species (ROS). Therefore, liquid exfoliation was used to create ultrasmall zirconium carbide nanodots (NDs) with an average diameter of approximately 4.5 nm as noninflammatory/anti-inflammatory photosensitizers for PTT of glioma. Ultrasmall ZrC NDs showed excellent photothermal stability and biocompatibility but no obvious toxicity. Moreover, the ultrasmall ZrC NDs effectively ablated glioma at relatively low concentrations and inhibited tumor migration and proliferation in vitro and in vivo. Furthermore, the excellent ROS-scavenging ability of ultrasmall ZrC NDs suppressed the inflammatory response to PTT. Intriguingly, we found that ZrC had the capability of performing CT imaging. We demonstrated that the ultrasmall ZrC NDs created in this study could effectively and safely treat glioma without inflammation.

Ultrasmall zirconium carbide nanodots for synergistic photothermal-radiotherapy of glioma

Glioma is characterized by highly invasive, progressive, and lethal features. In addition, conventional treatments have been poorly effective in treating glioma. To overcome this challenge, synergistic therapies combining radiotherapy (RT) with photothermal therapy (PTT) have been proposed and extensively explored as a highly feasible cancer treatment strategy. Herein, ultrasmall zirconium carbide (ZrC) nanodots were successfully synthesized with high near-infrared absorption and strong photon attenuation for synergistic PTT-RT of glioma. ZrC-PVP nanodots with an average size of approximately 4.36 nm were prepared by the liquid exfoliation method and modified with the surfactant polyvinylpyrrolidone (PVP), with a satisfactory absorption and photothermal conversion efficiency (53.4%) in the near-infrared region. Furthermore, ZrC-PVP nanodots can also act as radiosensitizers to kill residual tumor cells after mild PTT due to their excellent photon attenuating ability, thus achieving a significant synergistic therapeutic effect by combining RT and PTT. Most importantly, both in vitro and in vivo experimental results further validate the high biosafety of ZrC-PVP NDs at the injected dose. This work systematically evaluates the feasibility of ZrC-PVP NDs for glioma treatment and provides evidence of the application of zirconium-based nanomaterials in photothermal radiotherapy.