NIR-Controlled Treatment of Multidrug-Resistant Tumor Cells by Mesoporous Silica Capsules Containing Gold Nanorods and Doxorubicin

Two-pronged reversal of chemotherapy resistance by gold nanorods induced mild photothermal effect

Chemotherapy treatment outcomes are severely restricted by multidrug resistance (MDR), in which tumors develop a multiple cross-resistance toward drug involving the pump and nonpump resistance mechanisms, resulting in drug efflux and defending against drug toxicity. Herein, we constructed a pH and near infrared (NIR) light responsive nanomedicine DOX@FG based on gold nanorods (GNRs) that demonstrated the potential to improve chemotherapy outcomes by overcoming MDR. DOX@FG was constructed by conjugating folic acid (FA) and doxorubicin (DOX) derivatives onto GNRs, where the DOX derivatives possessed an acid-labile hydrazone bond. Stimulated by the acidic media in endocytic organelles, DOX@FG exhibited a responsive dissociation for the controlled release of chemotherapeutic DOX. Surprisingly, we found the mild photothermal effect elicited by GNRs under NIR irradiation simultaneously inhibited the pump and nonpump resistance mechanisms, enhancing the intracellular DOX accumulation and sensitizing the cancer cells to DOX, collectively amplify the chemotherapy efficacy and delay the MCF-7/ADR breast tumor growth. This intelligent DOX@FG nanomedicine with the potential for two-pronged reversal of MDR may provide a prospective way to encourage chemotherapy efficacy.

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.

Metal-Organic Framework-Capped Gold Nanorod Hybrids for Combinatorial Cancer Therapy

Recently, nanomaterials have attracted extensive attention in cancer-targeting therapy and as drug delivery vehicles owing to their unique surface and size properties. Multifunctional combinations of nanomaterials have become a research hotspot as researchers aim to provide a full understanding of their nanomaterial characteristics. In this study, metal-organic framework-capped gold nanorod hybrids were synthesized. Our research explored their ability to kill tumor cells by locally increasing the temperature via photothermal conclusion. The specific peroxidase-like activity endows the hybrids with the ability to disrupt the oxidative balance in vitro. Simultaneously, chemotherapeutic drugs are administered and delivered by loading and transportation for effective combinatorial cancer treatment, thereby enhancing the curative effect and reducing the unpredictable toxicity and side effects of large doses of chemotherapeutic drugs. These studies can improve combinatorial cancer therapy and enhance cancer treatment.

Progress of Mesoporous Silica Coated Gold Nanorods for Biological Imaging and Cancer Therapy

For unique surface plasmon absorption and fluorescence characteristics, gold nanorods have been developed and widely employed in the biomedical field. However, limitations still exist due their low specific surface area, instability and tendency agglomerate in cytoplasm. Mesoporous silica materials have been broadly applied in field of catalysts, adsorbents, nanoreactors, and drug carriers due to its unique mesoporous structure, highly comparative surface area, good stability and biocompatibility. Therefore, coating gold nanorods with a dendritic mesopore channels can effectively prevent particle agglomeration, while increasing the specific surface area and drug loading efficiency. This review discusses the advancements of GNR@MSN in synthetic process, bio-imaging technique and tumor therapy. Additionally, the further application of GNR@MSN in imaging-guided treatment modalities is explored, while its promising superior application prospect is highlighted. Finally, the issues related to in vivo studies are critically examined for facilitating the transition of this promising nanoplatform into clinical trials.

Tailored Drug Delivery Platforms: Stimulus-Responsive Core-Shell Structured Nanocarriers

Core-shell structured nanocarriers have come into the scientific spotlight in recent years due to their intriguing properties and wide applications in materials chemistry, biology, and biomedicine. Tailored core-shell structures to achieve desired performance have emerged as a research frontier in the development of smart drug delivery system. However, systematic reviews on the design and loading/release mechanisms of stimulus-responsive core-shell structured nanocarriers are uncommon. This review starts with the categories of core-shell structured nanocarriers with different means of drug payload, and then highlights the controlled release mechanism realized through stimulus-response processes triggered under different environments. Finally, some multifaceted perspectives on the design of core-shell structured materials as drug carriers are addressed. This work aims to provide new enlightenments and prospects in the drug delivery field for further developing advanced and smart nanocarriers.

Synthesis of the pH-sensitive nanoparticles based on the acylhydrazone bonds conjugated doxorubicin and studies on their in vivo anti-tumor effects

The purpose of this study was to synthesize DHPD polymers through the conjugation of doxorubicin (DOX) molecules onto poly(ethylene glycol) (PEG) chains via acylhydrazone bonds, and to fabricate pH-responsive DHPD nanoparticles (NPs) for investigation of their biosecurity and in vivo anti-tumor activity. The morphology, size distribution, stability, pH-responsiveness, biosecurity, and in vivo anti-tumor effects of the DHPD NPs were evaluated. Characterization of the DHPD polymers using 1H NMR, FTIR, and Raman spectra confirmed their successful synthesis. The DHPD NPs exhibited a round morphology with an average diameter of 144.4 ± 1.7 nm and a polydispersity index (PDI) of 0.23 ± 0.02. Biosecurity studies indicated that the DHPD NPs were non-toxic to treated mice, and in vitro cell tests demonstrated their ability to be taken up by 4T1 cells. Under the acidic microenvironment of 4T1 cells, the acylhydrazone bonds were cleaved, resulting in increased DOX delivery to tumor cells and improved in vivo anti-tumor effects. Animal experiments confirmed that the DHPD NPs reduced DOX toxicity while enhancing its anti-tumor activity. Furthermore, results from the analysis of γ-interferon (INF-γ), tumor necrosis factor-α (TNF-α), epidermal growth factor (EGF), and vascular endothelial growth factor (VEGF) indicated that the DHPD NPs improved the anti-4T1 tumor effect of DOX, suggesting their potential application in the treatment of breast cancer.

A Dual Concentration-Tailored Cytokine-Chemo Nanosystem to Alleviate Multidrug Resistance and Redirect Balance of Cancer Proliferation and Apoptosis

Background

Cancer multidrug resistance (MDR) is an important factor that severely affects the chemotherapeutic efficacy. Among various methods to bypass MDR, usage of cytokines, such as tumor necrosis factor alpha (TNFα) is attractive, which exerts antitumor effects of immunotherapeutic response and apoptotic/proinflammatory pathways. Nevertheless, the challenges remain how to implement targeted delivery of TNFα to reduce toxicity and manifest the involved signaling mechanism that subdues MDR.

Methods

We synthesized a multifunctional nanosytem, in which TNFα covalently bound to doxorubicin (Dox)-loaded pH-responsive mesoporous silica nanoparticles (MSN) through bi-functional polyethylene glycol (TNFα-PEG-MSN-Hydrazone-Dox) as a robust design to overcome MDR.

Results

The salient features of this nanoplatform are: 1) by judicious tailoring of TNFα concentration conjugated on MSN, we observed it could lead to a contrary effect of either proliferation or suppression of tumor growth; 2) the MSN-TNFα at higher concentration serves multiple functions, besides tumor targeting and inducer of apoptosis through extrinsic pathway, it inhibits the expression level of p-glycoprotein (P-gp), a cell membrane protein that functions as a drug efflux pump; 3) the enormous surface area of MSN provides for TNFα functionalization, and the nanochannels accommodate chemotherapeutics, Dox; 4) targeted intracellular release of Dox through the pH-dependent cleavage of hydrazone bonds induces apoptosis by the specific intrinsic pathway; and 5) TNFα-PEG-MSN-Hydrazone-Dox (MSN-Dox-TNFα) could infiltrate deep into the 3D spheroid tumor model through disintegration of tight junction proteins. When administered intratumorally in a Dox-resistant mouse tumor model, MSN-Dox-TNFα exhibited a synergistic therapeutic effect through the collective performances of TNFα and Dox.

Conclusion

We hereby develop and demonstrate a multifunctional MSN-Dox-TNFα system with concentration-tailored TNFα that can abrogate the drug resistance mechanism, and significantly inhibit the tumor growth through both intrinsic and extrinsic apoptosis pathways, thus making it a highly potential nanomedicine translated in the treatment of MDR tumors.

Overcoming Cancer Multi-drug Resistance (MDR): Reasons, mechanisms, nanotherapeutic solutions, and challenges

Multi-drug resistance (MDR) in cancer cells, either intrinsic or acquired through various mechanisms, significantly hinders the therapeutic efficacy of drugs. Typically, the reduced therapeutic performance of various drugs is predominantly due to the inherent over expression of ATP-binding cassette (ABC) transporter proteins on the cell membrane, resulting in the deprived uptake of drugs, augmenting drug detoxification, and DNA repair. In addition to various physiological abnormalities and extensive blood flow, MDR cancer phenotypes exhibit improved apoptotic threshold and drug efflux efficiency. These severe consequences have substantially directed researchers in the fabrication of various advanced therapeutic strategies, such as co-delivery of drugs along with various generations of MDR inhibitors, augmented dosage regimens and frequency of administration, as well as combinatorial treatment options, among others. In this review, we emphasize different reasons and mechanisms responsible for MDR in cancer, including but not limited to the known drug efflux mechanisms mediated by permeability glycoprotein (P-gp) and other pumps, reduced drug uptake, altered DNA repair, and drug targets, among others. Further, an emphasis on specific cancers that share pathogenesis in executing MDR and effluxed drugs in common is provided. Then, the aspects related to various nanomaterials-based supramolecular programmable designs (organic- and inorganic-based materials), as well as physical approaches (light- and ultrasound-based therapies), are discussed, highlighting the unsolved issues and future advancements. Finally, we summarize the review with interesting perspectives and future trends, exploring further opportunities to overcome MDR.

Subcellular-Targeted Near-Infrared-Responsive Nanomedicine with Synergistic Chemo-photothermal Therapy against Multidrug Resistant Cancer

Multidrug resistance (MDR) is a major obstacle to effective cancer treatment. Therefore, developing effective approaches for overcoming the limitation of MDR in cancer therapy is very essential. Chemotherapy combined with photothermal therapy (PTT) is a potential therapeutic option against MDR. Herein, we developed a subcellular-targeted near-infrared (NIR)-responsive nanomedicine (Fe₃O₄@PDA-TPP/S₂-PEG-hyd-DOX, abbreviated as Fe₃O₄-ATSPD) as a new photothermal agent with improved photothermal stability and efficiency. This system demonstrates high stability in blood circulation and can be accumulated at the tumor site by magnetic targeting enhanced permeability and retention effect (EPR). Near-infrared (NIR) irradiation at the tumor site generates a photothermal effect from the photosensitizer Fe₃O₄@PDA, leading to a dramatic decrease in mitochondrial membrane potential. Simultaneously, the conjugated drugs released under low pH condition in endosomes or lysosomes cause nucleus DNA damage and cell apoptosis. This subcellular-targeted NIR-responsive nanomedicine with efficient integration of diagnosis and therapy could significantly enhance MDR cancer treatment by combination of chemotherapy and PTT.

Biomedical applications and prospects of temperature‐orchestrated photothermal therapy

Photothermal therapy (PTT) has been regarded as a promising strategy considering its advantages of high inherent specificity and a lower invasive burden. Since the photothermal killing of cells/bacteria showed different patterns of death depending on the varying temperature in PTT, the temperature change of PTT is vital to cell/tissue response in scientific research and clinical application. On one hand, mild PTT has received substantial attention in the treatment of cancer and soft/hard tissue repair. On the other hand, the high temperature induced by PTT is capable of antibacterial capacity, which is better than conventional antibiotic therapy with drug resistance. Herein, we summarize the recent developments in the application of temperature‐dependent photothermal biomaterials, mainly covering the temperature ranges of 40–42°C, 43–50°C, and over 50°C. We highlight the biological mechanism of PTT and the latest progress in the treatment of different diseases. Finally, we conclude by discussing the challenges and perspectives of biomaterials in addressing temperature‐orchestrated PTT. Given a deep understanding of the interaction between temperature and biology, rationally designed biomaterials with sophisticated photothermal responsiveness will benefit the outcomes of personalized PTT toward various diseases.

Rose bengal-modified gold nanorods for PTT/PDT antibacterial synergistic therapy

In this study, Rose Bengal (RB) was loaded onto mesoporous silica coated gold nanorods (AuNR@SiO₂-NH₂) to form a novel multifunctional platform for antimicrobial therapy (AuNR@SiO₂-NH₂-RB). The platform combines the photothermal functions of AuNR and the photodynamic functions of RB to effectively inactivate bacteria under irradiation. Moreover, AuNR@SiO₂-NH₂-RB showed negligible cytotoxicity and good blood compatibility. Therefore, this work has potential significance for the development of new antibacterial agents.

Reversing multi-drug resistance by polymeric metformin to enhance antitumor efficacy of chemotherapy

Multi-drug resistance (MDR) in breast cancer poses a great threat to chemotherapy. The expression and function of the ATP binding cassette (ABC) transporter are the major cause of MDR. Herein, a linear polyethylene glycol (PEI) conjugated with dicyandiamide, which called polymeric metformin (PolyMet), was successfully synthesized as a simple and biocompatible polymer of metformin. PolyMet showed the potential to reverse MDR by inhibiting the efflux of the substrate of ATP-binding cassette (ABC) transporter from DOX resistant MCF-7 cells (MCF-7/DOX). To test its MDR reversing effect, PolyMet was combined with DOX to treat mice carrying MCF-7/DOX xenografts. In order to decrease the toxicities of DOX and delivery PolyMet and DOX to tumor at the same time, PolyMet was complexed with poly-γ-glutamic acid-doxorubicin (PGA-DOX) electrostatically at the optimal ratio of 2:3, which were further coated with lipid membrane to form lipid/PolyMet-(PGA-DOX) nanoparticles (LPPD). The particle size of LPPD was 165.8 nm, and the zeta potential was +36.5 mV. LPPD exhibited favorable cytotoxicity and cellular uptake in MCF-7/DOX. Meanwhile, the bioluminescence imaging and immunohistochemical analysis indicated that LPPD effectively conquered DOX-associated MDR by blocking ABC transporters (ABCB1 and ABCC1) via PolyMet. Remarkably, LPPD significantly inhibited the tumor growth and lowered the systemic toxicity in a murine MCF-7/DOX tumor model. This is the first time to reveal that PolyMet can enhance the anti-tumor efficacy of DOX by dampening ABC transporters and activating the AMPK/mTOR pathway, which is a promising strategy for drug-resistant breast cancer therapy.

Biodegradable Metal-Organic-Framework-Gated Organosilica for Tumor-Microenvironment-Unlocked Glutathione-Depletion-Enhanced Synergistic Therapy

The clinical employment of cisplatin (cis-diamminedichloroplatinum(II) (CDDP)) is largely constrained due to the non-specific delivery and resultant serious systemic toxicity. Small-sized biocompatible and biodegradable hollow mesoporous organosilica (HMOS) nanoparticles show superior advantages for targeted CDDP delivery but suffer from premature CDDP leakage. Herein, the smart use of a bimetallic Zn²⁺ /Cu²⁺ co-doped metal-organic framework (MOF) is made to block the pores of HMOS for preventing potential leakage of CDDP and remarkably increasing the loading capacity of HMOS. Once reaching the acidic tumor microenvironment (TME), the outer MOF can decompose quickly to release CDDP for chemotherapy against cancer. Besides, the concomitant release of dopant Cu²⁺ can deplete the intracellular glutathione (GSH) for increased toxicity of CDDP as well as catalyzing the decomposition of intratumoral H₂ O₂ into highly toxic •OH for chemodynamic therapy (CDT). Moreover, the substantially reduced GSH can also protect the yielded •OH from scavenging and thus greatly improve the •OH-based CDT effect. In addition to providing a hybrid HMOS@MOF nanocarrier, this study is also expected to establish a new form of TME-unlocked nanoformula for highly efficient tumor-specific GSH-depletion-enhanced synergistic chemotherapy/chemodynamic therapy.

Silica-Based Nanoframeworks Involved Hepatocellular Carcinoma Theranostic

Silica-based nanoframeworks have been extensively studied for diagnosing and treating hepatocellular carcinoma (HCC). Several reviews have summarized the advantages and disadvantages of these nanoframeworks and their use as drug-delivery carriers. Encouragingly, these nanoframeworks, especially those with metal elements or small molecular drugs doping into the skeleton structure or modifying onto the surface of nanoparticles, could be multifunctional components participating in HCC diagnosis and treatment rather than functioning only as drug-delivery carriers. Therefore, in this work, we described the research progress of silica-based nanoframeworks involved in HCC diagnosis (plasma biomarker detection, magnetic resonance imaging, positron emission tomography, photoacoustic imaging, fluorescent imaging, ultrasonography, etc.) and treatment (chemotherapy, ferroptotic therapy, radiotherapy, phototherapy, sonodynamic therapy, immunotherapy, etc.) to clarify their roles in HCC theranostics. Further, the future expectations and challenges associated with silica-based nanoframeworks were highlighted. We believe that this review will provide a comprehensive understanding for researchers to design novel, functional silica-based nanoframeworks that can effectively overcome HCC.