How successful is nuclear targeting by nanocarriers?

Enhanced intracellular and intranuclear drug delivery mediated by biomimetic peptide SVS-1 for anticancer therapy

Tumor cell nucleus is the ultimate target of many first-line chemotherapeutics and therapeutic genes. However, nuclear drug delivery is always hampered by multiple intracellular obstacles especially low efficiency of cellular uptake and insufficient nuclear trafficking. It is urgent to establish novel nuclear drug delivery systems to simultaneously overcome barriers including cell membranes and nuclear envelope. Herein, an N-(2-hydroxypropyl) methacrylamide (HPMA) polymer-based drug delivery system was designed to achieve enhanced intracellular and intranuclear drug delivery. A biomimetic peptide (SVS-1), derived from antimicrobial peptides, which was reported to efficiently penetrate cell membranes and translocate rapidly into nucleus without decreasing cell viability, was conjugated to the HPMA copolymer backbone. The in vitro studies showed that SVS-1 could enhance the uptake and nuclei accumulation of HPMA copolymer by 4.1 and 7.0-fold on human cervical cancer cells (HeLa) separately compared with corresponding non-SVS-1 modified HPMA copolymers (P-DOX). This also transferred to greater DNA damage, more apoptosis and superior cytotoxicity (2.4-fold) of doxorubicin which was chosen as the model drug and attached to SVS-1 modified HPMA copolymer (SVS-1-P-DOX). Furthermore, the in vivo investigation revealed that compared with free doxorubicin, SVS-1-P-DOX not only showed prolonged blood circulation and preferential tumor accumulation, but also suppressed tumor growth more efficiently with tumor growth inhibition of 78.7% in HeLa tumor-bearing BALB/c nude mice without causing noticeable physiological change in major organs. These results demonstrated that the SVS-1 modification was a promising strategy for contemporaneously overcome cell membranes and nuclear envelope, which might provide new opportunities for constructing nucleus-targeted anticancer therapy.

Direct Nucleus-Targeted Drug Delivery Using Cascade pHe /Photo Dual-Sensitive Polymeric Nanocarrier for Cancer Therapy

The cell nucleus-targeted delivery of therapeutic agents plays a critical role in cancer therapy, since the biological target of many anticancer therapeutics is the cell nucleus. However, multiple physiological barriers limit the delivery efficiency of free drugs, resulting in unsatisfactory therapeutic effects. Herein, thioketal crosslinked polyphosphoester-based nanoparticles with a tumor acidity (pH_e )-sensitive transactivator of transcription (TAT) peptide (DA-masked TAT-decorating reactive oxygen species (ROS)-sensitive Ce6/DOX-loaded hyperbranched nanoparticles (^D TRCD)) are explored for cascade nucleus-targeted drug delivery. Following administration, ^D TRCD experiences prolonged circulation by masking the targeting effect of its TAT peptide and then achieves enhanced tumor cell uptake and improved translocation into the perinuclear region by reactivating the TAT targeting capability in tumor tissue. Subsequently, ROS generated by ^D TRCD under 660 nm laser not only disrupts the nuclear membrane to allow entry into the nuclei but also triggers intracellular release of the payload in the nuclei. As evidenced by in vivo experiments, such pH_e /photo dual-sensitive polymeric nanocarriers offer remarkable therapeutic effects, efficiently suppressing tumor growth. This multistage cascade nucleus-targeted drug delivery concept provides new avenues to develop nucleus-targeted drug delivery systems.

A stage-specific cancer chemotherapy strategy through flexible combination of reduction-activated charge-conversional core-shell nanoparticles

Precision medicine has increased the demand for stage-specific cancer chemotherapy. Drugs with different properties are needed for different stages of tumor development, which is, inducing rapid destruction in the early stage and facilitating deep penetration in the advanced stage. Herein, we report a novel reduction-activated charge-conversional core-shell nanoparticle (CS NP) formula based on ring-closing metathesis of the thiamine disulfide system (TDS) to deliver the chemotherapeutic agent-gambogic acid (GA). Methods: The shell consisted of hyaluronic acid-all-trans retinoid acid with a disulfide bond as the linker (HA-SS-ATRA). The core was selected from poly (γ-glutamic acid) with different grafting rates of the functional group (Fx%) of TDS. GA/CF100%S NPs, with the strongest reduction-responsive drug release, and GA/CF60%S NPs with the strongest penetration have been finally screened. On this basis, a stage-specific administration strategy against a two-stage hepatocellular carcinoma was proposed. Results: The developed CS NPs have been confirmed as inducing reduction-activated charge conversion from about -25 to +30 mV with up to 95% drug release within 48 h. The administration strategy, GA/CF100%S NPs for the early-stage tumor, and sequential administration of GA/CF60%S NPs followed by GA/CF100%S NPs for the advanced-stage tumor, achieved excellent tumor inhibition rates of 93.86±2.94% and 90.76±6.43%, respectively. Conclusions: Our CS NPs provide a novel platform for charge conversion activated by reduction. The stage-specific administration strategy showed great promise for cancer therapy.

Paclitaxel-tyroserleutide Conjugates Self-assembly into Nanocarrier for Drug Delivery

Background:

The drug-drug self-assembly was considered as a simple and efficient approach to prepare high drug loading nano-drug carriers and present new opportunities for cancer therapeutics. The strategy of PTX amphiphiles preparation would be a possible way to solve the poor water solubility of PTX.

Methods:

The PTX-YSL conjugate were synthesized and characterized. The PTX-YSL nanocarriers was prepared by a simple self-assembly method. In vitro cell studies and pharmacokinetic studies were evaluated for their in vitro anti-tumor activities and blood retention time.

Results:

The structures of PTX-YSL conjugate were confirmed by LC-MS, 1H NMR and FTIR. The size and morphology of the PTX-YSL self-assembled nanocarriers were observed with TEM and DLS. PTX-YSL nanocarriers could facilitate cellular uptake and had low cytotoxicity. PTX-YSL nanocarriers have longer blood retention for enhancing accumulation in the tumor tissues via EPR effect.

Conclusion:

This drug delivery system formed by PTX-YSL conjugates constitutes a promising and effective drug carrier in cancer therapy.

Strategies to target bioactive molecules to subcellular compartments. Focus on natural compounds

Many potential pharmacological targets are present in multiple subcellular compartments and have different pathophysiological roles depending on location. In these cases, selective targeting of a drug to the relevant subcellular domain(s) may help to sharpen its impact by providing topological specificity, thus limiting side effects, and to concentrate the compound where needed, thus increasing its effectiveness. We review here the state of the art in precision subcellular delivery. The major approaches confer "homing" properties to the active principle via permanent or reversible (in pro-drug fashion) modifications, or through the use of special-design nanoparticles or liposomes to ferry a drug(s) cargo to its desired destination. An assortment of peptides, substituents with delocalized positive charges, custom-blended lipid mixtures, pH- or enzyme-sensitive groups provide the main tools of the trade. Mitochondria, lysosomes and the cell membrane may be mentioned as the fronts on which the most significant advances have been made. Most of the examples presented here have to do with targeting natural compounds - in particular polyphenols, known as pleiotropic agents - to one or the other subcellular compartment.

Recent Advances in Subcellular Targeted Cancer Therapy Based on Functional Materials

Recently, diverse functional materials that take subcellular structures as therapeutic targets are playing increasingly important roles in cancer therapy. Here, particular emphasis is placed on four kinds of therapies, including chemotherapy, gene therapy, photodynamic therapy (PDT), and hyperthermal therapy, which are the most widely used approaches for killing cancer cells by the specific destruction of subcellular organelles. Moreover, some non-drug-loaded nanoformulations (i.e., metal nanoparticles and molecular self-assemblies) with a fatal effect on cells by influencing the subcellular functions without the use of any drug molecules are also included. According to the basic principles and unique performances of each treatment, appropriate strategies are developed to meet task-specific applications by integrating specific materials, ligands, as well as methods. In addition, the combination of two or more therapies based on multifunctional nanostructures, which either directly target specific subcellular organelles or release organelle-targeted therapeutics, is also introduced with the intent of superadditive therapeutic effects. Finally, the related challenges of critical re-evaluation of this emerging field are presented.

Anti-tumour activity of low molecular weight heparin doxorubicin nanoparticles for histone H1 high-expressive prostate cancer PC-3M cells

Nucleus-targeting drug delivery systems (NTDDs) deliver chemotherapeutic agents to nuclei in order to improve the efficacy of anti-tumour therapy. Histone H1 (H1) plays a key role in establishing and maintaining higher order chromatin structures and could bind to cell membranes. In the present study, we selected H1 as a target to prepare a novel H1-mediated NTDD. Low molecular weight heparin (LMHP) and doxorubicin (DOX) were combined to form LMHP-DOX. Then, a novel NTDD consisting of LMHP-DOX nanoparticles (LMHP-DOX NPs) was prepared by self-assembly. The characteristics of LMHP-DOX and LMHP-DOX NPs were investigated. Histone H1 high-expressive prostate cancer PC-3M cell line was selected as the cell model. Cellular uptake, and the in vitro and in vivo anti-tumour activity of LMHP-DOX NPs were evaluated on H1 high-expressive human prostate cancer PC-3M cells. Our results indicated that intact LMHP-DOX NPs mediated by H1 could be absorbed by H1 high-expressive PC-3M cells, escape from the lysosomes to the cytoplasm, and localize in the perinuclear region via H1-mediated, whereby DOX could directly enter the cell nucleus and quickly increase the concentration of DOX in the nuclei of H1 high-expressive PC-3M cells to enhance the apoptotic activity of cancer cells. The anti-coagulant activity of LMHP-DOX NPs was almost completely diminished in rat blood compared with that of LMHP, indicating the safety of LMHP-DOX NPs. Compared to traditional NTDD strategies, LMHP-DOX NPs avoid the complicated modification of nucleus-targeting ligands and provide a compelling solution for the substantially enhanced nuclear uptake of chemotherapeutic agents for the development of more intelligent NTDDs.

Self-Assembled Double-Bundle DNA Tetrahedron for Efficient Antisense Delivery

DNA nanostructures are promising biomaterials capable of arranging multiple functional components with nanometer precision. Here, a double-bundle DNA tetrahedron is rationally designed to integrate with antisense oligonucleotides silencing proto-oncogene c-raf and nuclear targeting peptides. The functionalized DNA tetrahedron can be internalized by A549 cells and assists the delivery of antisense oligonucleotides toward the nucleus to increase the chance to downregulate target mRNA in nucleus and cytoplasm. Antisense strands released from the tetrahedron in response to the intracellular reducing environment can inhibit cell proliferation at a low concentration without transfection reagent. Finally, efficient knockdown of c-raf gene is observed, which verified our design. This designer DNA-based nanocarrier system will open a new avenue for efficient delivery of nucleic acid drugs.

Strategies for the enhanced intracellular delivery of nanomaterials

The intracellular delivery of nanomaterials and drugs has been attracting increasing research interest, mainly because of their important effects and functions in several organelles. Targeting specific organelles can help treat or decrease the symptoms of diabetes, cancer, infectious, and autoimmune diseases. Tuning biological and chemical properties enables the creation of functionalized nanomaterials with enhanced intracellular uptake, ability to escape premature lysosome degradation, and to reach a specific target. Here, we provide an update of recent advances in the intracellular delivery mechanisms that could help drugs reach their target more efficiently.

The combination of endolysosomal escape and basolateral stimulation to overcome the difficulties of "easy uptake hard transcytosis" of ligand-modified nanoparticles in oral drug delivery

Ligand-modified nanoparticles (NPs) are an effective tool to increase the endocytosis efficiency of drugs, but these functionalized NPs face the drawback of "easy uptake hard transcytosis" in the oral delivery of proteins and peptides. Adversely, the resulting deficiency in transcytosis has not attracted much attention. Herein, NPs modified with the low-density lipoprotein receptor (LDLR) ligand NH₂-C6-[cMPRLRGC]c-NH₂, i.e., peptide-22 (P22NPs) were fabricated to investigate strategies related to the enhancement of transcytosis. By systematically studying the intracellular trafficking of NPs, it was found that reduced transcytosis might be associated with the entrapment of P22NPs in endosomes or lysosomes and limited basolateral exocytosis. On this basis, the prevention of the endolysosomal entrapment of NPs and the acceleration of basolateral exocytosis should be considered as strategies to enhance the transcytosis of NPs. By screening chemicals that could help the endosomal/lysosomal escape of chemicals related to LDLR-mediated transcytosis, it was shown that hemagglutinin-2 (HA₂) and metformin had higher abilities to enhance the exocytosis of P22NPs. The transcytosis efficiencies of insulin loaded in P22NPs were also investigated, and a 3.2-fold increase in transcytosis was observed in comparison with free insulin. The transcytosis efficiencies of insulin could be further increased by the addition of metformin or HA₂ (3.6-fold or 4.1-fold higher than that of free insulin). Inspiringly, the simultaneous addition of the abovementioned two chemicals led to the highest transcytosis efficiency of insulin, which was up to 5.1-fold higher than that of free insulin. These results demonstrated that endolysosomal entrapment and basolateral exocytosis are two of the most important limiting steps for the "easy uptake hard transcytosis" of orally administered ligand-modified NPs. Moreover, our work provides a new point of view for the design of novel oral drug delivery systems.

Biosensors for spatiotemporal detection of reactive oxygen species in cells and tissues

Redox biology has become a major issue in numerous areas of physiology. Reactive oxygen species (ROS) have a broad range of roles from signal transduction to growth control and cell death. To understand the nature of these roles, accurate measurement of the reactive compounds is required. An increasing number of tools for ROS detection is available; however, the specificity and sensitivity of these tools are often insufficient. Furthermore, their specificity has been rarely evaluated in complex physiological conditions. Many ROS probes are sensitive to environmental conditions in particular pH, which may interfere with ROS detection and cause misleading results. Accurate detection of ROS in physiology and pathophysiology faces additional challenges concerning the precise localization of the ROS and the timing of their production and disappearance. Certain ROS are membrane permeable, and certain ROS probes move across cells and organelles. Targetable ROS probes such as fluorescent protein-based biosensors are required for accurate localization. Here we analyze these challenges in more detail, provide indications on the strength and weakness of current tools for ROS detection, and point out developments that will provide improved ROS detection methods in the future. There is no universal method that fits all situations in physiology and cell biology. A detailed knowledge of the ROS probes is required to choose the appropriate method for a given biological problem. The knowledge of the shortcomings of these probes should also guide the development of new sensors.

Stimuli-Responsive Nanomedicines for Overcoming Cancer Multidrug Resistance

Chemotherapy is still a main option for cancer therapy, but its efficacy is often unsatisfying due to multidrug resistance (MDR). The tumor microenvironment is considered a dominant factor causing MDR. Stimuli-responsive nanomedicines exhibit many superiorities for reversal of MDR. As smart systems, stimuli-responsive nanomedicines are desirable for achieving site-specific accumulation and triggered drug release in response to slight changes in physicochemical properties in pathological conditions or to exogenous stimuli. In this review, we highlight the current progress of various nanomedicines with different stimuli-responsive capabilities for overcoming MDR. The materials, design, construction as well as efficacy in overcoming MDR of these nanomedicines are discussed. Eventually, we look forward to forthcoming intelligent nanoparticle systems with new mechanisms to deliver drugs for practical applications in conquering cancer MDR.

Enhanced nuclear delivery of anti-cancer drugs using micelles containing releasable membrane fusion peptide and nuclear-targeting retinoic acid

Biodegradable cross-linked N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer micelles can improve the accumulation of drug cargo in tumors by prolonging their circulation time. However, drug delivery can still be ineffective because of intracellular degradation in lysosomes and poor delivery to the nucleus. In this work, we prepared a novel micelle by grafting the hydrophobic HA2 membrane fusion peptide onto hydrophilic HPMA copolymers via a linker that would be cleaved in lysosomes, allowing the HA2 peptide to be released and disrupt lysosome membranes. In addition, we conjugated the drug cargo (H1 peptide) to nucleus-targeting all-trans retinoic acid, and then encapsulated the conjugates into micelles. The drug-loaded micelles efficiently escaped lysosomes and targeted the nucleus in MCF-7 breast cancer cells in culture. They also strongly inhibited tumor growth in mice bearing MCF-7 tumor xenografts, without causing appreciable systemic toxicity. Removing the retinoic acid or preventing the cleavage of HA2 resulted in extremely inefficient lysosomal escape and nuclear delivery, translating into low anti-cancer efficacy in vitro and in vivo. These results suggest that micelle modifications to evade lysosomes and target the nucleus can improve the efficacy of anti-cancer drugs. Our results further suggest that the ability to escape lysosomes improves the nuclear distribution of drug cargos more than the addition of the nuclear-targeting retinoic acid.

MDR in cancer: Addressing the underlying cellular alterations with the use of nanocarriers

Multidrug resistance (MDR) is associated with a wide range of pathological changes at different cellular and intracellular levels. Nanoparticles (NPs) have been extensively exploited as the carriers of MDR reversing payloads to resistant tumor cells. However, when properly formulated in terms of chemical composition and physicochemical properties, NPs can serve as beyond delivery systems and help overcome MDR even without carrying a load of chemosensitizers or MDR reversing molecular cargos. Whether serving as drug carriers or beyond, a wise design of the nanoparticulate systems to overcome the cellular and intracellular alterations underlying the resistance is imperative. Within the current review, we will initially discuss the cellular changes occurring in resistant cells and how such changes lead to chemotherapy failure and cancer cell survival. We will then focus on different mechanisms through which nanosystems with appropriate chemical composition and physicochemical properties can serve as MDR reversing units at different cellular and intracellular levels according to the changes that underlie the resistance. Finally, we will conclude by discussing logical grounds for a wise and rational design of MDR reversing nanoparticulate systems to improve the cancer therapeutic approaches.

Nuclear-Targeted Multifunctional Magnetic Nanoparticles for Photothermal Therapy

The pursuit of multifunctional, innovative, more efficient, and safer cancer treatment has gained increasing interest in the research of preclinical nanoparticle-mediated photothermal therapy (PTT). Cell nucleus is recognized as the ideal target for cancer treatment because it plays a central role in genetic information and the transcription machinery reside. In this work, an efficient nuclear-targeted PTT strategy is proposed using transferrin and TAT peptide (TAT: YGRKKRRQRRR) conjugated monodisperse magnetic nanoparticles, which can be readily functionalized and stabilized for potential diagnostic and therapeutic applications. The monodisperse magnetic nanoparticles exhibit high photothermal conversion efficiency (≈37%) and considerable photothermal stability. They also show a high magnetization value and transverse relaxivity (207.1 mm^-1 s^-1 ), which could be applied for magnetic resonance imaging. The monodisperse magnetic nanoparticles conjugated with TAT peptides can efficiently target the nucleus and achieve the imaging-guided function, efficient cancer cells killing ability. Therefore, this work may present a practicable strategy to develop subcellular organelle targeted PTT agents for simultaneous cancer targeting, imaging, and therapy.

Preparation, cytotoxicity, and in vivo antitumor efficacy of 111In-labeled modular nanotransporters

PURPOSE

Modular nanotransporters (MNTs) are a polyfunctional platform designed to achieve receptor-specific delivery of short-range therapeutics into the cell nucleus by receptor-mediated endocytosis, endosome escape, and targeted nuclear transport. This study evaluated the potential utility of the MNT platform in tandem with Auger electron emitting 111In for cancer therapy.

METHODS

Three MNTs developed to target either melanocortin receptor-1 (MC1R), folate receptor (FR), or epidermal growth factor receptor (EGFR) that are overexpressed on cancer cells were modified with p-SCN-Bn-NOTA and then labeled with 111In in high specific activity. Cytotoxicity of the 111In-labeled MNTs was evaluated on cancer cell lines bearing the appropriate receptor target (FR: HeLa, SK-OV-3; EGFR: A431, U87MG.wtEGFR; and MC1R: B16-F1). In vivo micro-single-photon emission computed tomography/computed tomography imaging and antitumor efficacy studies were performed with intratumoral injection of MC1R-targeted 111In-labeled MNT in B16-F1 melanoma tumor-bearing mice.

RESULTS

The three NOTA-MNT conjugates were labeled with a specific activity of 2.7 GBq/mg with nearly 100% yield, allowing use without subsequent purification. The cytotoxicity of 111In delivered by these MNTs was greatly enhanced on receptor-expressing cancer cells compared with 111In nontargeted control. In mice with B16-F1 tumors, prolonged retention of 111In by serial imaging and significant tumor growth delay (82% growth inhibition) were found.

CONCLUSION

The specific in vitro cytotoxicity, prolonged tumor retention, and therapeutic efficacy of MC1R-targeted 111In-NOTA-MNT suggest that this Auger electron emitting conjugate warrants further evaluation as a locally delivered radiotherapeutic, such as for ocular melanoma brachytherapy. Moreover, the high cytotoxicity observed with FR- and EGFR-targeted 111In-NOTA-MNT suggests further applications of the MNT delivery strategy should be explored.

Leveraging Physiology for Precision Drug Delivery

Physiological characteristics of diseases bring about both challenges and opportunities for targeted drug delivery. Various drug delivery platforms have been devised ranging from macro- to micro- and further into the nanoscopic scale in the past decades. Recently, the favorable physicochemical properties of nanomaterials, including long circulation, robust tissue and cell penetration attract broad interest, leading to extensive studies for therapeutic benefits. Accumulated knowledge about the physiological barriers that affect the in vivo fate of nanomedicine has led to more rational guidelines for tailoring the nanocarriers, such as size, shape, charge, and surface ligands. Meanwhile, progresses in material chemistry and molecular pharmaceutics generate a panel of physiological stimuli-responsive modules that are equipped into the formulations to prepare “smart” drug delivery systems. The capability of harnessing physiological traits of diseased tissues to control the accumulation of or drug release from nanomedicine has further improved the controlled drug release profiles with a precise manner. Successful clinical translation of a few nano-formulations has excited the collaborative efforts from the research community, pharmaceutical industry, and the public towards a promising future of smart drug delivery.

Passage of Magnetic Tat-Conjugated Fe3O4@SiO2 Nanoparticles Across In Vitro Blood-Brain Barrier

Delivery of diagnostic or therapeutic agents across the blood-brain barrier (BBB) remains a major challenge of brain disease treatment. Magnetic nanoparticles are actively being developed as drug carriers due to magnetic targeting and subsequently reduced off-target effects. In this paper, we developed a magnetic SiO2@Fe3O4 nanoparticle-based carrier bound to cell-penetrating peptide Tat (SiO2@Fe3O4-Tat) and studied its fates in accessing BBB. SiO2@Fe3O4-Tat nanoparticles (NPs) exhibited suitable magnetism and good biocompatibility. NPs adding to the apical chamber of in vitro BBB model were found in the U251 glioma cells co-cultured at the bottom of the Transwell, indicating that particles passed through the barrier and taken up by glioma cells. Moreover, the synergistic effects of Tat and magnetic field could promote the efficient cellular internalization and the permeability across the barrier. Besides, functionalization with Tat peptide allowed particles to locate into the nucleus of U251 cells than the non-conjugated NPs. These results suggest that SiO2@Fe3O4-Tat NPs could penetrate the BBB through the transcytosis of brain endothelial cells and magnetically mediated dragging. Therefore, SiO2@Fe3O4-Tat NPs could be exploited as a potential drug delivery system for chemotherapy and gene therapy of brain disease.

Myeloid cells as orchestrators of the tumor microenvironment: novel targets for nanoparticular cancer therapy

Macrophages, myeloid-derived suppressor cells and tolerogenic dendritic cells are central players of a heterogeneous myeloid cell population, with the ability to suppress innate and adaptive immune responses and thus to promote tumor growth. Their influx and local proliferation are mainly induced by the cancers themselves, and their numbers in the tumor microenvironment and the peripheral blood correlate with decreased survival. Therapeutic targeting these innate immune cells, either aiming at their elimination or polarization toward tumor suppressive cells is an attractive novel approach to control tumor progression and block metastasis. We review the current understanding of cancer immunology including immune surveillance and immune editing in the context of these prominent innate suppressor cells, and their targetability by nanoparticular immunotherapy with small molecules or siRNA.