TAT-Modified Gold Nanoparticle Carrier with Enhanced Anticancer Activity and Size Effect on Overcoming Multidrug Resistance

Self-Assembly of Peptides as an Alluring Approach toward Cancer Treatment and Imaging

Cancer is a severe threat to humans, as it is the second leading cause of death after cardiovascular diseases and still poses the biggest challenge in the world of medicine. Due to its higher mortality rates and resistance, it requires a more focused and productive approach to provide the solution for it. Many therapies promising to deliver favorable results, such as chemotherapy and radiotherapy, have come up with more negatives than positives. Therefore, a new class of medicinal solutions and a more targeted approach is of the essence. This review highlights the alluring properties, configurations, and self-assembly of peptide molecules which benefit the traditional approach toward cancer therapy while sparing the healthy cells in the process. As targeted drug delivery systems, self-assembled peptides offer a wide spectrum of conjugation, biocompatibility, degradability-controlled responsiveness, and biomedical applications, including cancer treatment and cancer imaging.

ABC transporter-mediated MXR mechanism in fish embryos and its potential role in the efflux of nanoparticles

ATP-binding cassette (ABC) transporters are believed to protect aquatic organisms by pumping xenobiotics out, and recent investigation has suggested their involvement in the detoxification and efflux of nanoparticles (NPs), but their roles in fish embryos are poorly understood. In this regard, this paper summarizes the recent advances in research pertaining to the development of ABC transporter-mediated multi-xenobiotic resistance (MXR) mechanism in fish embryos and the potential interaction between ABC transporters and NPs. The paper focuses on: (1) Expression, function, and modulation mechanism of ABC proteins in fish embryos; (2) Potential interaction between ABC transporters and NPs in cell models and fish embryos. ABC transporters could be maternally transferred to fish embryos and thus play an important role in the detoxification of various chemical pollutants and NPs. There is a need to understand the specific mechanism to benefit the protection of aquatic resources.

Emerging nanotechnology-based therapeutics to combat multidrug-resistant cancer

Cancer often develops multidrug resistance (MDR) when cancer cells become resistant to numerous structurally and functionally different chemotherapeutic agents. MDR is considered one of the principal reasons for the failure of many forms of clinical chemotherapy. Several factors are involved in the development of MDR including increased expression of efflux transporters, the tumor microenvironment, changes in molecular targets and the activity of cancer stem cells. Recently, researchers have designed and developed a number of small molecule inhibitors and derivatives of natural compounds to overcome various mechanisms of clinical MDR. Unfortunately, most of the chemosensitizing approaches have failed in clinical trials due to non-specific interactions and adverse side effects at pharmacologically effective concentrations. Nanomedicine approaches provide an efficient drug delivery platform to overcome the limitations of conventional chemotherapy and improve therapeutic effectiveness. Multifunctional nanomaterials have been found to facilitate drug delivery by improving bioavailability and pharmacokinetics, enhancing the therapeutic efficacy of chemotherapeutic drugs to overcome MDR. In this review article, we discuss the major factors contributing to MDR and the limitations of existing chemotherapy- and nanocarrier-based drug delivery systems to overcome clinical MDR mechanisms. We critically review recent nanotechnology-based approaches to combat tumor heterogeneity, drug efflux mechanisms, DNA repair and apoptotic machineries to overcome clinical MDR. Recent successful therapies of this nature include liposomal nanoformulations, cRGDY-PEG-Cy5.5-Carbon dots and Cds/ZnS core–shell quantum dots that have been employed for the effective treatment of various cancer sub-types including small cell lung, head and neck and breast cancers.

Orthogonal Design of Supramolecular Prodrug Vesicles via Water-Soluble Pillar[5]arene and Betulinic Acid Derivative for Dual Chemotherapy

Supramolecular prodrug vesicles with efficient property for dual chemotherapy have been successfully constructed based on the orthogonal self-assembly between a water-soluble pillar[5]arene host (WP5) and a betulinic acid guest (BA-D) as well as doxorubicin (DOX). Under the acidic microenvironment of cancer cells, both the encapsulated anticancer drug DOX and prodrug BA-D can be effectively released from DOX-loaded WP5⊃BA-D prodrug vesicles for combinational chemotherapy. Furthermore, bioexperiments indicate that DOX-loaded prodrug vesicles can obviously enhance the anticancer efficiency based on the cooperative effect of DOX and BA-D, while remarkably reducing the systematic toxicity in tumor-mice, displaying great potential applications in combinational chemotherapy for cancer treatments.

Reversing tumor multidrug resistance with a catalytically active covalent organic framework

We report here a catalytically active nano covalent organic framework [COF(Fe)] with high drug loading capacity for reversing tumor multidrug resistance (MDR). The Fe catalytic sites in COF(Fe) could convert intracellular overexpressed H₂O₂ into highly reactive ˙OH to induce oxidation stress and down-regulate MDR protein. Therefore, COF(Fe) could enhance the intracellular drug accumulation to overcome MDR, which was demonstrated both in vitro and in vivo.

A versatile modular preparation strategy for targeted drug delivery systems against multidrug-resistant cancer cells

Nanotechnology is widely used in targeted drug delivery, but different drug delivery systems need to 're-determine' different synthesis schemes, which greatly limits the further expansion of targeted nanomedicine applications. In this study, we propose a facile and versatile modular stacking strategy to fabricate targeted drug delivery systems to enable tailored designs for patient-specific therapeutic responses. The systems were constructed by a pH-sensitive prodrug module and a mitochondrial targeting module via self-assembly. Using this modular strategy, we successfully prepared two targeting nano-drug delivery systems, TPP-DOX and PK-DOX, where the mitochondrial targeting molecules were triphenylphosphonium (TPP) and 1-(2-Chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxamide (PK11195), respectively. Confocal laser microscopy and flow cytometry tests revealed that TPP-DOX and PK-DOX exhibited high mitochondria targeting capability and greatly improved the drug retention in drug-resistant cells. The antitumor activity tests showed that the IC50 values of TPP-DOX and PK-DOX in MCF-7/ADR cells were 2.5- and 8.2-fold lower than that of free DOX, respectively. These results indicated that PK was more effective than TPP. The studies on their therapeutic effects on human breast cancer resistant cells verified the feasibility of the modular approach, indicated that the two modular targeted drug delivery systems: (1) retain the drug toxicity and cell-killing effect of the prodrug module, (2) have precise targeting capabilities due to mitochondrial targeting module, (3) enhance drug uptake, reduce drug efflux and reverse the multidrug resistance effect to a certain extent. The results show that modular stacking is a practical, effective and versatile method for preparing targeting drugs with broad application prospects. This study provides an easy approach on preparing customizable targeted drug delivery systems to improve precision therapies.

Nanotherapeutics approaches to overcome P-glycoprotein-mediated multi-drug resistance in cancer

Multidrug resistance (MDR) in cancer chemotherapy is a growing concern for medical practitioners. P-glycoprotein (P-gp) overexpression is one of the major reasons for multidrug resistance in cancer chemotherapy. The P-gp overexpression in cancer cells depends on several factors like adenosine triphosphate (ATP) hydrolysis, hypoxia-inducible factor 1 alpha (HIF-1α), and drug physicochemical properties such as lipophilicity, molecular weight, and molecular size. Further multiple exposures of anticancer drugs to the P-gp efflux protein cause acquired P-gp overexpression. Unique structural and functional characteristics of nanotechnology-based drug delivery systems provide opportunities to circumvent P-gp mediated MDR. The primary mechanism behind the nanocarrier systems in P-gp inhibition includes: bypassing or inhibiting the P-gp efflux pump to combat MDR. In this review, we discuss the role of P-gp in MDR and highlight the recent progress in different nanocarriers to overcome P-gp mediated MDR in terms of their limitations and potentials.

Safety Evaluation of Nanotechnology Products

Nanomaterials are now being used in a wide variety of biomedical applications. Medical and health-related issues, however, have raised major concerns, in view of the potential risks of these materials against tissue, cells, and/or organs and these are still poorly understood. These particles are able to interact with the body in countless ways, and they can cause unexpected and hazardous toxicities, especially at cellular levels. Therefore, undertaking in vitro and in vivo experiments is vital to establish their toxicity with natural tissues. In this review, we discuss the underlying mechanisms of nanotoxicity and provide an overview on in vitro characterizations and cytotoxicity assays, as well as in vivo studies that emphasize blood circulation and the in vivo fate of nanomaterials. Our focus is on understanding the role that the physicochemical properties of nanomaterials play in determining their toxicity.

Enhanced Cytotoxic Effect of Doxorubicin Conjugated to Glutathione-Stabilized Gold Nanoparticles in Canine Osteosarcoma-In Vitro Studies

Osteosarcoma (OSA) is the most common malignant bone neoplasia in humans and dogs. In dogs, treatment consists of surgery in combination with chemotherapy (mostly carboplatin and/or doxorubicin (Dox)). Chemotherapy is often rendered ineffective by multidrug resistance. Previous studies have revealed that Dox conjugated with 4 nm glutathione-stabilized gold nanoparticles (Au-GSH-Dox) enhanced the anti-tumor activity and cytotoxicity of Dox in Dox-resistant feline fibrosarcoma cell lines exhibiting high P-glycoprotein (P-gp) activity. The present study investigated the influence of Au-GSH-Dox on the canine OSA cell line D17 and its relationship with P-gp activity. A human Dox-sensitive OSA cell line, U2OS, served as the negative control. Au-GSH-Dox, compared to free Dox, presented a greater cytotoxic effect on D17 (IC₅₀ values for Au-GSH-Dox and Dox were 7.9 μg/mL and 15.2 μg/mL, respectively) but not on the U2OS cell line. All concentrations of Au-GSH (ranging from 10 to 1000 μg/mL) were non-toxic in both cell lines. Inhibition of the D17 cell line with 100 μM verapamil resulted in an increase in free Dox but not in intracellular Au-GSH-Dox. The results indicate that Au-GSH-Dox may act as an effective drug in canine OSA by bypassing P-gp.

The reversal of chemotherapy-induced multidrug resistance by nanomedicine for cancer therapy

Multidrug resistance (MDR) of cancer is a persistent problem in chemotherapy. Scientists have considered the overexpressed efflux transporters responsible for MDR and chemotherapy failure. MDR extremely limits the therapeutic effect of chemotherapy in cancer treatment. Many strategies have been applied to solve this problem. Multifunctional nanoparticles may be one of the most promising approaches to reverse MDR of tumor. These nanoparticles can keep stability in the blood circulation and selectively accumulated in the tumor microenvironment (TME) either by passive or active targeting. The stimuli-sensitive or organelle-targeting nanoparticles can release the drug at the targeted-site without exposure to normal tissues. In order to better understand reversal of MDR, three main strategies are concluded in this review. First strategy is the synergistic effect of chemotherapeutic drugs and ABC transporter inhibitors. Through directly inhibiting overexpressed ABC transporters, chemotherapeutic drugs can enter into resistant cells without being efflux. Second strategy is based on nanoparticles circumventing over-expressed efflux transporters and directly targeting resistance-related organelles. Third approach is the combination of multiple therapy modes overcoming cancer resistance. At last, numerous researches demonstrated cancer stem-like cells (CSCs) had a deep relation with drug resistance. Here, we discuss two different drug delivery approaches of nanomedicine based on CSC therapy.

Involvement of ABC transporters in the detoxification of non-substrate nanoparticles in lung and cervical cancer cells

This paper aimed to systemically investigate the role of adenosine triphosphate-binding cassette (ABC transporters) in the detoxification of non-substrate nanoparticles including titanium dioxide (n-TiO₂, 5-10 nm) and gold (AuNPs, 3 nm, 15 nm, and 80 nm, named as Au-3, Au-15 and Au-80) in human lung cancer (A549) and human cervical cancer (HeLa) cells. All these nanoparticles were of larger hydrophilic diameters than the channel sizes of ABC transporters, thus should not be the substrates of membrane proteins. After 24-h treatment, they induced significant cytotoxicity as reflected by the reduction in cell viability and glutathione (GSH) contents, as well as the increase in reactive oxygen species (ROS) level. At median-lethal concentrations (10 mg/L n-TiO₂, 2 mg/L Au-3, 5 mg/L Au-15, and 10 mg/L Au-80 for A549 cells; 20 mg/L n-TiO₂, 2 mg/L Au-3, 5 mg/L Au-15, and 10 mg/L Au-80 for Hela cells), all the nanoparticles significantly induced the gene expressions and activities of ABC transporters including P-glycoprotein (PGP) and multidrug resistance associated protein 1 (MRP1). Addition of transporter inhibitors enhanced the ROS levels produced by nanoparticles, but didn't alter their death-inducing effects and intracellular accumulations. With specific suppressors, transcription factors like nuclear factor-erythroid 2-related factor-2 (NRF2) and pregnane X receptor (PXR) were proved to be important in the induction of ABC transporters by nanoparticles. After all, this paper revealed a damage-dependent modulation of ABC transporters by non-substrate nanoparticles. The up-regulated ABC transporters could help in reducing the oxidative stress produced by nanoparticles. Such information should be useful in assessing the environmental risk of nanoparticles, as well as their interactions with other chemical toxicants or drugs.

A Tubular DNA Nanodevice as a siRNA/Chemo-Drug Co-delivery Vehicle for Combined Cancer Therapy

Using the DNA origami technique, we constructed a DNA nanodevice functionalized with small interfering RNA (siRNA) within its inner cavity and the chemotherapeutic drug doxorubicin (DOX), intercalated in the DNA duplexes. The incorporation of disulfide bonds allows the triggered mechanical opening and release of siRNA in response to intracellular glutathione (GSH) in tumors to knockdown genes key to cancer progression. Combining RNA interference and chemotherapy, the nanodevice induced potent cytotoxicity and tumor growth inhibition, without observable systematic toxicity. Given its autonomous behavior, exceptional designability, potent antitumor activity and marked biocompatibility, this DNA nanodevice represents a promising strategy for precise drug design for cancer therapy.

The critical size of gold nanoparticles for overcoming P-gp mediated multidrug resistance

Multidrug resistance (MDR) remains a huge obstacle during cancer treatment. One of the most studied MDR mechanisms is P-glycoprotein (P-gp) mediated drug efflux. Based on the three-dimensional structural characteristics of P-gp, gold nanoparticles (AuNPs) with average sizes of 4.1 nm and 5.4 nm were designed for the construction of nanodrug delivery systems (NanoDDSs), with the anticancer molecules 2-(9-anthracenylmethylene)-hydrazinecarbothioamide (ANS) and 6-mercaptopurine (6-MP) modified on the AuNP surfaces through the thiol group. In vitro cytotoxicity results suggested that the larger sized AuNPs can effectively decrease the drug resistance index of MCF-7/ADR cells to ∼2. Verapamil and P-gp antibody competitive experiments, combined with the cellular uptake of AuNPs, indicated that larger NanoDDSs were more conducive to intracellular drug accumulation and thus had improved anticancer activities, due to a size mismatch between the nanoparticles and the active site of P-gp, and, therefore, reduced drug efflux was seen. Measurements of ATPase activity and intracellular ATP levels indicated that the larger nanoparticles do not bind well to P-gp, thus avoiding effective recognition by P-gp. This was further evidenced by the observation that 4.1 nm and 5.4 nm NanoDDS-treated MCF-7/ADR cells showed remarkable differences in energy-related metabolic pathways. Therefore, the critical size of AuNPs for overcoming MDR was identified to be between 4.1 nm and 5.4 nm. This provides a more accurate description of the composite dimension requirements for NanoDDSs that are designed to overcome MDR.

Gold nanospheres and nanorods for anti-cancer therapy: comparative studies of fabrication, surface-decoration, and anti-cancer treatments

Various gold nanoparticles have been explored as cancer therapeutics because they can be widely engineered for use as efficient drug carriers and diagnostic agents, and in photo-irradiation therapy. In the current review, we focused on shape-dependent biomedical applications of gold nanoparticles including gold nanospheres and nanorods. Fabrication and functionalization strategies of two different gold nanoparticles for anti-cancer therapy are introduced and the distinguishing performance depending on the shape is discussed to suggest the best carrier shape for specific applications. Moreover, recent advances in anti-cancer immunotherapy using gold nano-carriers are discussed. Thus, this comparative review can be helpful in deciding on suitable shapes and surface-modification strategies for preparing various gold nanoparticle-based therapeutics in anti-cancer therapy.

Supramolecular combination chemotherapy: a pH-responsive co-encapsulation drug delivery system

Most cancer chemotherapy regimens rely on the use of two or more chemotherapeutic agents. However, achieving the best possible dosing of the individual drugs can be challenging due to differences in metabolism, uptake, and clearance among other factors. Here we describe a supramolecular strategy for achieving drug delivery in which the loading ratio of two active components is easily defined. Specifically, we report the formation of aggregates comprised of self-assembled amphiphiles between carboxylatopillar[6]arene (CP6A) and an oxaliplatin (OX)-type Pt(iv) prodrug (PtC10). The association constant (K a) for the underlying host-guest interaction at pH 7.4 ((1.16 ± 0.03) × 104 M-1) is an order of magnitude higher than at pH 5.0 ((1.73 ± 0.15) × 103 M-1). A second chemotherapeutic, doxorubicin (DOX), may be encapsulated in the resulting vesicles (PtC10⊂CP6A) to give a supramolecular combination chemotherapeutic system DOX@PtC10⊂CP6A. Drug release studies served to confirm that PtC10 and DOX are released in acidic environments. Support for a synergistic antiproliferative effect relative to PtC10 + DOX came from cellular studies of DOX@PtC10⊂CP6A using the human liver hepatocellular carcinoma (HepG-2) cell line. In vivo studies revealed that DOX@PtC10⊂CP6A is not only able to retard tumor growth efficiently but also reduce drug-related toxic side effects in BALB/c nude mice bearing HepG-2 subcutaneous tumor xenografts. These favorable findings are attributed to the formation of a ternary complex that benefits from an enhanced permeability and retention (EPR) effect in vivo while allowing for the pH-based release of PtC10 and DOX at the tumor site.

Aptamer-Based Erythrocyte-Derived Mimic Vesicles Loaded with siRNA and Doxorubicin for the Targeted Treatment of Multidrug-Resistant Tumors

Multidrug resistance (MDR) remains one of the most important challenges to clinical chemotherapeutics. In this study, versatile mimic vesicles (MVs) derived from erythrocytes were investigated as delivery systems for siRNA and doxorubicin (DOX) to treat MDR tumors. The carriers could be readily obtained through extruding erythrocyte membranes and had the advantages of biological homogeneity, high output, controllable size, low cost, and excellent biocompatibility. Moreover, aptamers modified on the MVs endowed the carriers with tumor-targeting capacity. DOX and P-glycoprotein (P-gp) siRNA were loaded onto the MVs through incubation and cholesterol-mediated methods, achieving high loading rates and targeted tumor delivery. The drug-loaded carriers could successfully overcome drug resistance and synergistically kill MDR tumors through P-gp silencing and DOX-induced growth inhibition. This MV-based drug delivery system therefore provides new insights into the synergistic targeting of MDR tumors and offers an alternative delivery strategy to overcome MDR.

Advances in Lipid and Metal Nanoparticles for Antimicrobial Peptide Delivery

Antimicrobial peptides (AMPs) have been described as excellent candidates to overcome antibiotic resistance. Frequently, AMPs exhibit a wide therapeutic window, with low cytotoxicity and broad-spectrum antimicrobial activity against a variety of pathogens. In addition, some AMPs are also able to modulate the immune response, decreasing potential harmful effects such as sepsis. Despite these benefits, only a few formulations have successfully reached clinics. A common flaw in the druggability of AMPs is their poor pharmacokinetics, common to several peptide drugs, as they may be degraded by a myriad of proteases inside the organism. The combination of AMPs with carrier nanoparticles to improve delivery may enhance their half-life, decreasing the dosage and thus, reducing production costs and eventual toxicity. Here, we present the most recent advances in lipid and metal nanodevices for AMP delivery, with a special focus on metal nanoparticles and liposome formulations.

The effect of phospho-peptide on the stability of gold nanoparticles and drug delivery

BACKGROUND

Gold nanoparticles (AuNPs) have been proposed for many applications in medicine and bioanalysis. For use in all these applications, maintaining the stability of AuNPs in solution by suppressing aggregation is paramount. Herein, the effects of amino acids were investigated in stabilizing AuNPs by rationally designed peptide scaffolds.

RESULTS

Compared to other tested amino acids, phosphotyrosine (pY) significantly stabilized AuNPs. Our results indicated that pY modified AuNPs presented a high level of stability in various solutions, and had good biocompatibility. When a pY-peptide was used in stabilizing AuNPs, the phosphate group could be removed by phosphatases, which subsequently caused the aggregation and the cargo release of AuNPs. In vitro study showed that AuNPs formed aggregation in a phosphatase concentration depending manner. The aggregation of AuNPs was well correlated with the enzymatic activity (R² = 0.994). In many types of cancer, a significant increase in phosphatases has been observed. Herein, we demonstrated that cancer cells treated with pY modified AuNPs in conjunction with doxorubicin killed SGC-7901 cells with high efficiency, indicating that the pY peptide stabilized AuNPs could be used as carriers for targeted drug delivery.

CONCLUSION

In summary, pY peptides can act to stabilize AuNPs in various solutions. In addition, the aggregation of pY-AuNPs could be tuned by phosphatase. These results provide a basis for pY-AuNPs acting as potential drug carriers and anticancer efficacy.

Functionalized gold nanostructures: promising gene delivery vehicles in cancer treatment

Surface-modified gold nanoparticles are recognized as promising gene delivery vehicles in the treatment of cancer owing to their excellent biocompatibility with biomolecules (like DNA or RNA) and their unique optical and structural properties. In this context, this review article focuses on the diverse transfection abilities of the gene to the targeted cell on the basis of different shapes and sizes of gold nanoparticles in order to promote its effective expression for cancer treatment. In addition, recent trends in gold nanoparticle mediated gene silencing, gene delivery, detection and combinatory therapies are highlighted considering their cytotoxic effects on healthy human cells.

ABC Transporters: Regulation and Association with Multidrug Resistance in Hepatocellular Carcinoma and Colorectal Carcinoma

For most cancers, the treatment of choice is still chemotherapy despite its severe adverse effects, systemic toxicity and limited efficacy due to the development of multidrug resistance (MDR). MDR leads to chemotherapy failure generally associated with a decrease in drug concentration inside cancer cells, frequently due to the overexpression of ABC transporters such as P-glycoprotein (P-gp/MDR1/ABCB1), multidrug resistance-associated proteins (MRPs/ABCCs), and breast cancer resistance protein (BCRP/ABCG2), which limits the efficacy of chemotherapeutic drugs. The aim of this review is to compile information about transcriptional and post-transcriptional regulation of ABC transporters and discuss their role in mediating MDR in cancer cells. This review also focuses on drug resistance by ABC efflux transporters in cancer cells, particularly hepatocellular carcinoma (HCC) and colorectal carcinoma (CRC) cells. Some aspects of the chemotherapy failure and future directions to overcome this problem are also discussed.

Molecular mechanism of HIV-1 TAT peptide and its conjugated gold nanoparticles translocating across lipid membranes

The trans-acting activator of transcription (TAT) peptide, which is derived from human immunodeficiency virus-1 (HIV-1), has been widely used as an effective nanocarrier to transport extracellular substances into cells. However, the underlying translocation mechanism of TAT peptide across cell membranes still remains controversial. Besides, the molecular process of TAT peptide facilitating the transport of extracellular substances into cells is largely unknown. In this study, we explore the interactions of TAT peptides and their conjugated gold nanoparticles with lipid membranes by coarse-grained molecular dynamics simulations. It is found that the TAT peptides can hardly penetrate through the membrane at low peptide concentrations; after the concentration increases to a threshold value, they can cross the membrane through an induced nanopore due to the transmembrane electrostatic potential difference. The translocation of TAT peptides is mainly caused by the overall structural changes of membranes. Furthermore, we demonstrate that the translocation of gold nanoparticles (AuNPs) across the membrane is significantly affected by the number of grafted TAT peptides on the particle surface. The transmembrane efficiency of AuNPs may even be reduced when a small number of peptides modify them; whereas, when the number of grafted peptides increases to a certain value, the TAT-AuNP complex can translocate across the membrane in a pore-mediated way. Based on our findings, an effective strategy has been proposed to enhance the delivery efficiency of AuNPs. The present study can improve our understanding of the interactions between TAT peptides and cell membranes; it may also give some insightful suggestions on the design and development of nanocarriers with high efficiency for the delivery of nanoparticles and drugs.

Altered Gene expression of ABC transporters, nuclear receptors and oxidative stress signaling in zebrafish embryos exposed to CdTe quantum dots

Adenosine triphosphate-binding cassette (ABC) transporters, including P-glycoprotein (Pgp) and multi-resistance associated proteins (Mrps), have been considered important participants in the self-protection of zebrafish embryos against environmental pollutants, but their possible involvement in the efflux and detoxification of quantum dots (QDs), as well as their regulation mechanism are currently unclear. In this work, gene expression alterations of ABC transporters, nuclear receptors, and oxidative stress signaling in zebrafish embryos after the treatment of mercaptopropionic acid (MPA)CdTe QDs and MPA-CdSCdTe QDs were investigated. It was observed that both QDs caused concentration-dependent delayed hatching effects and the subsequent induction of transporters like mrp1&2 in zebrafish embryos, indicating the protective role of corresponding proteins against CdTe QDs. Accompanying these alterations, expressions of nuclear receptors including the pregnane X receptor (pxr), aryl hydrocarbon receptor (ahr) 1b, and peroxisome proliferator-activated receptor (ppar)-β were induced by QDs in a concentration- and time-dependent manner. Moreover, elevated oxidative stress, reflected by the reduction of glutathione (GSH) level and superoxide dismutase (SOD) activities, as well as the dramatic induction of nuclear factor E2 related factor (nrf) 2, was also found. More importantly, alterations of pxr and nrf2 were more pronounced than that of mrps, and these receptors exhibited an excellent correlation with delayed hatching rate in the same embryos (R² > 0.8). Results from this analysis demonstrated that the induction of mrp1 and mrp2 could be important components for the detoxification of QDs in zebrafish embryos. These transporters could be modulated by nuclear receptors and oxidative stress signaling. In addition, up-regulation of pxr and nrf2 could be developed as toxic biomarkers of CdTe QDs.

1988-2018: Thirty years of drug smuggling at the nano scale. Challenges and opportunities of cell-penetrating peptides in biomedical research

In 1988, two unrelated papers reported the discovery of peptide vectors with innate cell translocation properties, setting the ground for a new area of research that over the years has grown into considerable therapeutic potential. The vectors, named cell-penetrating peptides (CPPs), constitute a now large and diversified family, sharing the extraordinary ability to diffuse unaltered across cell membranes while ferrying diverse associated cargos. Such properties have made CPPs ideal tools for delivery of nucleic acids, proteins and other therapeutic/diagnostic molecules to cells and tissues via covalent conjugation or complexation. This year 2018 marks the 30^th anniversary of a peptide research landmark opening new perspectives in drug delivery. Given its vastness, exhaustive coverage of the main features and accomplishments in the CPP field is virtually impossible. Hence this manuscript, after saluting the above 30^th jubilee, focuses by necessity on the most recent contributions, providing a comprehensive list of recognized CPPs and their latest-reported applications over the last two years. In addition, it thoroughly reviews three areas of peptide vector research of particular interest to us, namely (i) efficient transport of low-bioavailability drugs into the brain; (ii) CPP-delivered disruptors of G protein-coupled receptor (GPCRs) heteromers related to several disorders, and (iii) CPP-mediated delivery of useful but poorly internalized drugs into parasites.

Cancer Chemoradiotherapy Duo: Nano-Enabled Targeting of DNA Lesion Formation and DNA Damage Response

Both production of DNA damage and subsequent prevention of its repair are crucial in concluding the therapeutic outcome of radiotherapy (RT). However, nearly all current strategies for improving RT focus only on one of the two aspects and overlook the necessity of their combinations. In this work, we introduce a concept of DNA-dual-targeting nanomedicine (NM) to simultaneously enhance DNA lesion formation and prevent the succeeding repair. Briefly, the cisplatin prodrug loaded in NM can form platinated DNA in cell nuclei, making DNA more vulnerable to the ionizing radiation generated by RT. Concomitantly, the spatial-temporally codelivered vorinostat, a histone deacetylase inhibitor, prolongs the build-up of double-strand breaks and causes cell apoptosis en masse, probably due to the suppressed expression of DNA repair proteins. Furthermore, this nanoplatform is suitable for fluorescence and magnetic resonance imaging techniques, enabling accurate trafficking of the NM as well as reliable real-time imaging-guided precision RT. Finally, results from in vitro and in vivo jointly reveal that this dual-action system attains a remarkably enhanced radiotherapeutic outcome. In conclusion, our imaging-guided DNA-dual-targeting design represents a novel strategy for efficient cancer precision RT.

Engineering Anticancer Amphipathic Peptide-Dendronized Compounds for Highly-Efficient Plasma/Organelle Membrane Perturbation and Multidrug Resistance Reversal

Discovering new strategies for combating drug-resistant tumors becomes a worldwide challenge. Thereinto, stubborn drug-resistant tumor membrane is a leading obstacle on chemotherapy. Herein, we report a novel tumor-activatable amphipathic peptide-dendronized compound, which could form nanoaggregates in aqueous solutions, for perturbing tumor plasma/organelle membrane and reversing multidrug resistance. Distinguished from classical linear amphipathic peptide drugs for membrane disturbance, dendritic lysine-based architecture is designed as a multivalent scaffold to amplify the supramolecular interactions of cationic compound with drug-resistant tumor membrane. Moreover, arginine-rich residues as terminal groups are hopeful to generate multiple hydrogen bonding and electrostatic interactions with tumor membrane. On the other hand, antitumor molecule (doxorubicin) is devised as a hydrophobic moiety to intensify the membrane-inserting ability owing to the prominent interactions with hydrophobic domains of drug-resistant tumor membrane. As expected, these amphipathic peptide-dendronized compounds within the nanoaggregates could severely disturb both the structures and functions of tumor plasma/organelle membrane system, thereby resulting in the rapid leakage of many critical biomolecules, highly efficient apoptotic activation and antiapoptotic inhibition. This strategy on tumor membrane perturbation demonstrates a bran-new antitumor activity with high contributions to cell cycle arrest (at the S phase), strong apoptosis-inducing ability and satisfying cytotoxicity to a variety of drug-resistant tumor cell lines.

Porphyrin-Gold Nanomaterial for Efficient Drug Delivery to Cancerous Cells

With an aim to overcome multidrug resistance (MDR), nontargeted delivery, and drug toxicity, we developed a new nanochemotherapeutic system with tetrasodium salt of meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) armored on gold nanoparticles (TPPS-AuNPs). The nanocarrier is able to be selectively internalized within tumor cells than in normal cells followed by endocytosis and therefore delivers the antitumor drug doxorubicin (DOX) particularly to the nucleus of diseased cells. The embedment of TPPS on the gold nanosurface provides excellent stability and biocompatibility to the nanoparticles. Porphyrin interacts with the gold nanosurface through the coordination interaction between gold and pyrrolic nitrogen atoms of the porphyrin and forms a strong association complex. DOX-loaded nanocomposite (DOX@TPPS-AuNPs) demonstrated enhanced cellular uptake with significantly reduced drug efflux in MDR brain cancer cells, thereby increasing the retention time of the drug within tumor cells. It exhibited about 9 times greater potency for cellular apoptosis via triggered release commenced by acidic pH. DOX has been successfully loaded on the porphyrin-modified gold nanosurface noncovalently with high encapsulation efficacy (∼90%) and tightly associated under normal physiological conditions but capable of releasing ∼81% of drug in a low-pH environment. Subsequently, DOX-loaded TPPS-AuNPs exhibited higher inhibition of cellular metastasis, invasion, and angiogenesis, suggesting that TPPS-modified AuNPs could improve the therapeutic efficacy of the drug molecule. Unlike free DOX, drug-loaded TPPS-AuNPs did not show toxicity toward normal cells. Therefore, higher drug encapsulation efficacy with selective targeting potential and acidic-pH-mediated intracellular release of DOX at the nucleus make TPPS-AuNPs a "magic bullet" for implication in nanomedicine.

A pre-protective strategy for precise tumor targeting and efficient photodynamic therapy with a switchable DNA/upconversion nanocomposite

Tumor-specific targeting based on folic acid (FA) is one of the most common and significant approaches in cancer therapy. However, the expression of folate receptors (FRs) in normal tissues will lead to unexpected targeting and unsatisfactory therapeutic effect. To address this issue, we develop a pre-protective strategy for precise tumor targeting and efficient photodynamic therapy (PDT) using a switchable DNA/upconversion nanocomposite, which can be triggered in the acidic tumor microenvironment. The DNA/upconversion nanocomposite is composed of polyacrylic acid (PAA) coated upconversion nanoparticles (UCNPs), the surface of which is modified using FA and chlorin e6 (Ce6) functionalized DNA sequences with different lengths. Initially, FA on the shorter DNA was protected by a longer DNA to prevent the bonding to FRs on normal cells. Once reaching the acidic tumor microenvironment, C base-rich longer DNA forms a C-quadruplex, resulting in the exposure of the FA groups and the bonding of FA and FRs on cancer cell membranes to achieve precise targeting. Simultaneously, the photosensitizer chlorin e6 (Ce6) gets close to the surface of UCNPs, enabling the excitation of Ce6 to generate singlet oxygen (1O2) under near infrared light via Förster resonance energy transfer (FRET). In vivo experiments indicated that higher tumor targeting efficiency was achieved and the tumor growth was greatly inhibited through the pre-protective strategy.

Selective Cell Penetrating Peptide-Functionalized Polymersomes Mediate Efficient and Targeted Delivery of Methotrexate Disodium to Human Lung Cancer In Vivo

It is a long challenge to develop nanomedicines that simultaneously possess tumor cell selectivity and penetration functions. Here, it is reported that selective cell penetrating peptide (RLWMRWYSPRTRAYGC)-functionalized polymersomes (SCPP-PS) mediate efficient and targeted delivery of methotrexate disodium (MTX) to human lung cancer in vivo. SCPP-PS with an SCPP density of 18.7% is self-crosslinked, has a small size (63-65 nm), and high MTX loading (up to 19.4 wt%), shows selective uptake and fast penetration into A549 lung cancer cells, and efficiently releases MTX intracellularly. Interestingly, MTX-loaded SCPP-PS (MTX-SCPP-PS) displays much lower IC₅₀ than those of MTX-PS and free MTX. Installing SCPP to polymersomes has no detrimental effect to their long blood circulation time but significantly increases drug accumulation in A549 tumor (5.3% injected dose per gram at 8 h post injection). Remarkably, SCPP-PS exhibits deep penetration in to A549 tumors. MTX-SCPP-PS completely inhibits tumor progression and significantly improves survival rates in mice bearing A549 lung tumor xenografts as compared to MTX-PS and free MTX groups (median survival time: 75 vs 45 and 38 d, respectively), without causing noticeable adverse effects. These results highlight that functionalization of nanomedicines with SCPP is a feasible strategy to achieve efficient and targeted tumor therapy.

Strategies in the design of gold nanoparticles for intracellular targeting: opportunities and challenges

With unique physicochemical properties, gold nanoparticles (Au NPs) have demonstrated their potential as drug carriers or therapeutic agents. Effective guidance of Au NPs into specific intracellular destinations becomes increasingly important as we strive to further improve the efficiency of drug delivery and modulate controllable cellular responses. In this review, we summarized recent advances in designing Au NPs with the capabilities of cellular penetration and internalization, endosomal escape, intracellular trafficking and subcellular localization via various approaches including physical injection, tuning the physiochemical parameters of Au NPs, and surface modification with targeting ligands. Strategies for delivering Au NPs to specific subcellular destinations including the nucleus, mitochondria, endoplasmic reticulum, lysosomes are also discussed. Moreover, current challenges associated with intracellular targeting of Au NPs are discussed with future perspectives proposed.

Targeting brain tumors by intra-arterial delivery of cell-penetrating peptides: a novel approach for primary and metastatic brain malignancy

Computational modeling shows that intra-arterial delivery is most efficient when the delivered drugs rapidly and avidly bind to the target site. The cell-penetrating peptide trans-activator of transcription (TAT) is a candidate carrier molecule that could mediate such specificity for brain tumor chemotherapeutics. To test this hypothesis we first performed in vitro studies testing the uptake of TAT by one primary and three potentially metastatic brain cancer cell lines (9L, 4T-1, LLC, SKOV-3). Then we performed in vivo studies in a rat model where TAT was delivered either intra-arterially (IA) or intravenously (IV) to 9L brain tumors. We observed robust uptake of TAT by all tumor cell lines in vitro. Flow cytometry and confocal microscopy revealed a rapid uptake of fluorescein-labeled TAT within 5 min of exposure to the cancer cells. IA injections done under transient cerebral hypoperfusion (TCH) generated a four-fold greater tumor TAT concentration compared to conventional IV injections. We conclude that it is feasible to selectively target brain tumors with TAT-linked chemotherapy by the IA-TCH method.

Trackable Mitochondria-Targeting Nanomicellar Loaded with Doxorubicin for Overcoming Drug Resistance

Multidrug resistance (MDR) has been recognized as a major obstacle to successful chemotherapy for cancer in the clinic. In recent years, more and more nanoscaled drug delivery systems (DDS) are constructed to modulate drug efflux protein (P-gp) and deliver chemotherapeutic drugs for overcoming MDR. Among them, d-α-tocopheryl polyethylene glycol succinate (TPGS) has been widely used as a drug carrier due to its capability of inhibiting overexpression of P-gp and good amphiphilicity favorable for improving permeation and long-circulation property of DDS. In the present work, a novel kind of mitochondria-targeting nanomicelles-based DDS is developed to integrate chemotherapeutics delivery with fluorescence imaging functionalities on a comprehensive nanoplatform. The mitochondria-targeting nanomicelles are prepared by self-assembly of triphenylphosphine (TPP)-modified TPGS and fluorescent carbon quantum dots (CQDs) in an n-hexane/H₂O mixed solution, named CQDs-TPGS-TPP. Notably, although the drug loading content of doxorubicin (DOX) in the as-prepared nanomicelles is as low as 3.4%, the calculated resistant index (RI) is greatly decreased from 66.23 of free DOX to 7.16 of DOX-loaded nanomicelles while treating both parental MCF-7 cells and drug-resistant MCF-7/ADR cells. Compared with free DOX, the penetration efficiency of DOX-loaded nanomicelles in three-dimensional multicellular spheroids (MCs) of MCF-7/ADR is obviously increased. Moreover, the released DOX from the nanomicelles can cause much more damage to cells of drug-resistant MCs. These results demonstrate that our constructed mitochondria-targeting nanomicelles-based DDS have potential application in overcoming MDR of cancer cells as well as their MCs that mimic in vivo tumor tissues. The MDR-reversal mechanism of the DOX-loaded CQDs-TPGS-TPP nanomicelles is also discussed.