Organelle targeting: third level of drug targeting

Acid-brightening fluorescent protein (abFP) for imaging acidic vesicles and organelles

Acidic organelles and vesicles, such as endosomes, lysosomes, autophagosomes, trans-Golgi network, and synaptic vesicles, are known to play important roles in a broad range of cellular events. To facilitate studying these multifunctional systems, we describe here an acid-brightening fluorescent protein (abFP), which fluoresces strongly at acidic pH, but is almost nonfluorescent at or above physiological pH, making it well suited for imaging molecules residing in acidic microenvironment in live cells. Specifically, a quinoline-containing unnatural amino acid Qui is incorporated into the chromophore of EGFP via genetic code expansion to generate the abFP. When being exposed to acidic environment, protonation of Qui results in a cationic chromophore and fluorescence increase. Protocols are presented to express abFP in E. coli and mammalian cells, and to fluorescently image the endocytosis of δ opioid receptor-abFP fusion protein in mammalian cells. This strategy may be similarly applicable to other fluorescent proteins to enable acidic imaging.

Breaking the selectivity-uptake trade-off of photoimmunoconjugates with nanoliposomal irinotecan for synergistic multi-tier cancer targeting

BACKGROUND

Photoimmunotherapy involves targeted delivery of photosensitizers via an antibody conjugate (i.e., photoimmunoconjugate, PIC) followed by light activation for selective tumor killing. The trade-off between PIC selectivity and PIC uptake is a major drawback limiting the efficacy of photoimmunotherapy. Despite ample evidence showing that photoimmunotherapy is most effective when combined with chemotherapy, the design of nanocarriers to co-deliver PICs and chemotherapy drugs remains an unmet need. To overcome these challenges, we developed a novel photoimmunoconjugate-nanoliposome (PIC-Nal) comprising of three clinically used agents: anti-epidermal growth factor receptor (anti-EGFR) monoclonal antibody cetuximab (Cet), benzoporphyrin derivative (BPD) photosensitizer, and irinotecan (IRI) chemotherapy.

RESULTS

The BPD photosensitizers were first tethered to Cet at a molar ratio of 6:1 using carbodiimide chemistry to form PICs. Conjugation of PICs onto nanoliposome irinotecan (Nal-IRI) was facilitated by copper-free click chemistry, which resulted in monodispersed PIC-Nal-IRI with an average size of 158.8 ± 15.6 nm. PIC-Nal-IRI is highly selective against EGFR-overexpressing epithelial ovarian cancer cells with 2- to 6-fold less accumulation in low EGFR expressing cells. Successful coupling of PIC onto Nal-IRI enhanced PIC uptake and photoimmunotherapy efficacy by up to 30% in OVCAR-5 cells. Furthermore, PIC-Nal-IRI synergistically reduced cancer viability via a unique three-way mechanism (i.e., EGFR downregulation, mitochondrial depolarization, and DNA damage).

CONCLUSION

It is increasingly evident that the most effective therapies for cancer will involve combination treatments that target multiple non-overlapping pathways while minimizing side effects. Nanotechnology combined with photochemistry provides a unique opportunity to simultaneously deliver and activate multiple drugs that target all major regions of a cancer cell-plasma membrane, cytoplasm, and nucleus. PIC-Nal-IRI offers a promising strategy to overcome the selectivity-uptake trade-off, improve photoimmunotherapy efficacy, and enable multi-tier cancer targeting. Controllable drug compartmentalization, easy surface modification, and high clinical relevance collectively make PIC-Nal-IRI extremely valuable and merits further investigations in living animals.

Active Cellular and Subcellular Targeting of Nanoparticles for Drug Delivery

Nanoparticle (NP)-mediated drug delivery (NMDD) for active targeting of diseases is a primary goal of nanomedicine. NPs have much to offer in overcoming the limitations of traditional drug delivery approaches, including off-target drug toxicity and the need for the administration of repetitive doses. In the last decade, one of the main foci in NMDD has been the realization of NP-mediated drug formulations for active targeted delivery to diseased tissues, with an emphasis on cellular and subcellular targeting. Advances on this front have included the intricate design of targeted NP-drug constructs to navigate through biological barriers, overcome multidrug resistance (MDR), decrease side effects, and improve overall drug efficacy. In this review, we survey advancements in NP-mediated drug targeting over the last five years, highlighting how various NP-drug constructs have been designed to achieve active targeted delivery and improved therapeutic outcomes for critical diseases including cancer, rheumatoid arthritis, and Alzheimer's disease. We conclude with a survey of the current clinical trial landscape for active targeted NP-drug delivery and how we envision this field will progress in the near future.

Mechanoregulation of titanium dioxide nanoparticles in cancer therapy

Titanium dioxide (TiO₂) nanoparticles (NPs), first developed in the 1990s, have been applied in numerous biomedical fields such as tissue engineering and therapeutic drug development. In recent years, TiO₂-based drug delivery systems have demonstrated the ability to decrease the risk of tumorigenesis and improve cancer therapy. There is increasing research on the origin and effects of pristine and doped TiO₂-based nanotherapeutic drugs. However, the detailed molecular mechanisms by which drug delivery to cancer cells alters sensing of gene mutations, protein degradation, and metabolite changes as well as its associated cumulative effects that determine the microenvironmental mechanosensitive metabolism have not yet been clearly elucidated. This review focuses on the microenvironmental influence of TiO₂-NPs induced various mechanical stimuli on tumor cells. The differential expression of genome, proteome, and metabolome after treatment with TiO₂-NPs is summarized and discussed. In the tumor microenvironment, mechanosensitive DNA mutations, gene delivery, protein degradation, inflammatory responses, and cell viability affected by the mechanical stimuli of TiO₂-NPs are also examined.

Antitumor Effect of Lonidamine-Polypeptide-Peptide Nanoparticles in Breast Cancer Models

Biomaterials folded into nanoparticles (NPs) can be utilized as targeted drug delivery systems for cancer therapy. NPs may provide a vehicle for the anticancer drug lonidamine (LND), which inhibits glycolysis but was suspended from use at the clinical trial stage because of its hepatotoxicity due to poor solubility and pharmacokinetic properties. The NPs prepared by coassembly of the anionic polypeptide poly gamma glutamic acid (γ-PGA) and a designed amphiphilic and positively charged peptide (designated as mPoP-NPs) delivered LND to the mitochondria in cell cultures. In this study, we demonstrate that LND-mPoP-NP effective drug concentrations can be increased to reach therapeutically relevant concentrations. The self-assembled NP solution was subjected to snap-freezing and lyophilization and the resultant powder was redissolved in a tenth of the original volume. The NP size and their ability to target the proximity of the mitochondria of breast cancer cells were both maintained in this new formulation, C-LND-mPoP-NPs. Furthermore, these NPs exhibited 40% better cytotoxicity, relative to the nonlyophilized LND-mPoP-NPs and led to tumor growth inhibition with no adverse side effects upon intravenous administration in a xenograft breast cancer murine model.

Engineered Polymeric Materials for Biological Applications: Overcoming Challenges of the Bio-Nano Interface

Nanomedicine has generated significant interest as an alternative to conventional cancertherapy due to the ability for nanoparticles to tune cargo release. However, while nanoparticletechnology has promised significant benefit, there are still limited examples of nanoparticles inclinical practice. The low translational success of nanoparticle research is due to the series ofbiological roadblocks that nanoparticles must migrate to be effective, including blood and plasmainteractions, clearance, extravasation, and tumor penetration, through to cellular targeting,internalization, and endosomal escape. It is important to consider these roadblocks holistically inorder to design more effective delivery systems. This perspective will discuss how nanoparticlescan be designed to migrate each of these biological challenges and thus improve nanoparticledelivery systems in the future. In this review, we have limited the literature discussed to studiesinvestigating the impact of polymer nanoparticle structure or composition on therapeutic deliveryand associated advancements. The focus of this review is to highlight the impact of nanoparticlecharacteristics on the interaction with different biological barriers. More specific studies/reviewshave been referenced where possible.

Direct Drug Targeting into Intracellular Compartments: Issues, Limitations, and Future Outlook

Intracellular compartment drug delivery is a promising strategy for the treatment of diseases. By this way, medicines can delivered to particular intracellular compartments. This maximizes the therapeutic efficacy and safety of medicines, particularly of anticancer and antiviral drugs. Intracellular compartment drug delivery is either indirectly by targeting of cell nucleus as central compartment of the cell or directly through the targeting of compartments itself. Drugs or nanoshuttles labeled with compartment's localization signal represent a smart tactic for subcellular compartment targeting. There are several boundaries prevent the arrival of shuttles to the specified intracellular compartments. These boundaries include selective permeability of biomembranes, efflux transporters, and lysosomes. The utilization of specific ligands during design of drug delivery nanoshuttles permits the targeting of specified intracellular compartment. Therefore drugs targeting could correct the diseases associated organelles. This review highlights the direct targeting of the medicines into subcellular compartment as a promising therapeutic strategy.

Approaches to CNS Drug Delivery with a Focus on Transporter-Mediated Transcytosis

Drug delivery to the central nervous system (CNS) conferred by brain barriers is a major obstacle in the development of effective neurotherapeutics. In this review, a classification of current approaches of clinical or investigational importance for the delivery of therapeutics to the CNS is presented. This classification includes the use of formulations administered systemically that can elicit transcytosis-mediated transport by interacting with transporters expressed by transvascular endothelial cells. Neurotherapeutics can also be delivered to the CNS by means of surgical intervention using specialized catheters or implantable reservoirs. Strategies for delivering drugs to the CNS have evolved tremendously during the last two decades, yet, some factors can affect the quality of data generated in preclinical investigation, which can hamper the extension of the applications of these strategies into clinically useful tools. Here, we disclose some of these factors and propose some solutions that may prove valuable at bridging the gap between preclinical findings and clinical trials.

Organelle-Targeted BODIPY Photocages: Visible-Light-Mediated Subcellular Photorelease

Photocaging facilitates non-invasive and precise spatio-temporal control over the release of biologically relevant small- and macro-molecules using light. However, sub-cellular organelles are dispersed in cells in a manner that renders selective light-irradiation of a complete organelle impractical. Organelle-specific photocages could provide a powerful method for releasing bioactive molecules in sub-cellular locations. Herein, we report a general post-synthetic method for the chemical functionalization and further conjugation of meso-methyl BODIPY photocages and the synthesis of endoplasmic reticulum (ER)-, lysosome-, and mitochondria-targeted derivatives. We also demonstrate that 2,4-dinitrophenol, a mitochondrial uncoupler, and puromycin, a protein biosynthesis inhibitor, can be selectively photoreleased in mitochondria and ER, respectively, in live cells by using visible light. Additionally, photocaging is shown to lead to higher efficacy of the released molecules, probably owing to a localized and abrupt release.

Targeting strategies for improving the efficacy of nanomedicine in oncology

The use of nanoparticles as drug carriers has provided a powerful weapon in the fight against cancer. These nanocarriers are able to transport drugs that exhibit very different nature such as lipophilic or hydrophilic drugs and big macromolecules as proteins or RNA. Moreover, the external surface of these carriers can be decorated with different moieties with high affinity for specific membrane receptors of the tumoral cells to direct their action specifically to the malignant cells. The selectivity improvement yielded by these nanocarriers provided a significative enhancement in the efficacy of the transported drug, while the apparition of side effects in the host was reduced. Additionally, it is possible to incorporate targeting moieties selective for organelles of the cell, which improves even more the effect of the transported agents. In the last years, more sophisticated strategies such as the use of switchable, hierarchical or double targeting strategies have been proposed for overcoming some of the limitations of conventional targeting strategies. In this review, recent advances in the development of targeted nanoparticles will be described with the aim to present the current state of the art of this technology and its huge potential in the oncological field.

Engineering Theranostic Microbubbles Using Microfluidics for Ultrasound Imaging and Therapy: A Review

Microbubbles interact with ultrasound in various ways to enable their applications in ultrasound imaging and diagnosis. To generate high contrast and maximize therapeutic efficacy, microbubbles of high uniformity are required. Microfluidic technology, which enables precise control of small volumes of fluid at the sub-millimeter scale, has provided a versatile platform on which to produce highly uniform microbubbles for potential applications in ultrasound imaging and diagnosis. Here, we describe fundamental microfluidic principles and the most common types of microfluidic devices used to produce sub-10 μm microbubbles, appropriate for biomedical ultrasound. Bubbles can be engineered for specific applications by tailoring the bubble size, inner gas and shell composition and by functionalizing for additional imaging modalities, therapeutics or targeting ligands. To translate the laboratory-scale discoveries to widespread clinical use of these microfluidic-based microbubbles, increased bubble production is needed. We present various strategies recently developed to improve scale-up. We conclude this review by describing some outstanding problems in the field and presenting areas for future use of microfluidics in ultrasound.

Colloidal Nanobioconjugate with Complementary Surface Chemistry for Cellular and Subcellular Targeting

Chemically and biochemically functionalized colloidal nanoparticles with appropriate surface chemistry are essential for various biomedical applications. Although a variety of approaches are now available in making such functional nanoparticles and nanobioconjugates, the lack of complementary surface chemistry often leads to poor performance with respect to intended biomedical applications. This feature article will focus on our efforts to make colloidal nanobioconjugates with appropriate/complementary surface chemistry for better performance of a designed nanoprobe with respect to cellular and subcellular targeting applications. In particular, we emphasize polyacrylate-based coating chemistry followed by a conjugation strategy for transforming <10 nm inorganic nanoparticle to colloidal nanoprobe of 20-50 nm hydrodynamic size. We show that a colloidal nanoprobe can be chemically designed to control the cell-nanoparticle interaction, cellular endocytosis, and targeting/labeling of subcellular compartments. Further study should be directed to adapt this surface chemistry to different nanoparticles, fine tune the surface chemistry for targeting/imaging on the subcellular/molecular length scale, and develop a delivery nanocarrier for subcellular compartments.

Building Block Based Construction of Membrane-Organelle Double Targeted Nanosystem for Two-Drug Delivery

Despite the claim that encapsulation of drugs improves the therapeutic profile of free drugs, there are still important limitations in drug delivery. With respect to cancer treatment, two promising implementations are combination therapy and targeted devices, which are aimed at increasing the drug effect either by achieving higher cell death rates or by discriminating between cell populations. However, for the time being, the scope of combining both approaches is unknown. To advance this knowledge, a two-drug-delivery system with dual cell-organelle targeting based on mesoporous silica nanoparticles, which are known to be able to host drugs within their pores, has been designed. In vitro results show a synergistic effect and high efficacy, demonstrating that the combination of dual therapy and targeting could still advance the development of drug-delivery nanodevices against difficult-to-treat cancers.

Nanolipid Formulations of Benzoporphyrin Derivative: Exploring the Dependence of Nanoconstruct Photophysics and Photochemistry on Their Therapeutic Index in Ovarian Cancer Cells

With the rapidly emerging designs and applications of light-activated, photodynamic therapy (PDT)-based nanoconstructs, photonanomedicines (PNMs), an unmet need exists to establish whether conventional methods of photochemical and photophysical characterization of photosensitizers are relevant for evaluating new PNMs in order to intelligently guide their design. As a model system, we build on the clinical formulation of benzoporphyrin derivative (BPD), Visudyne^® , by developing a panel of nanolipid formulations entrapping new lipidated chemical variants of BPD with differing chemical, photochemical and photophysical properties. These are 16:0 and 20:0 lysophosphocholine-BPD (16:0/20:0 BPD-PC), DSPE-PEG-BPD and BPD-cholesterol. We show that Visudyne^® was the most phototoxic formulation to OVCAR-5 cells, and the least effective was liposomal DSPE-PEG-BPD. However, these differences did not match their optical, photophysical and photochemical properties, as the static BPD quenching was highest in Visudyne, which also exhibited the lowest generation of singlet oxygen. Furthermore, we establish that OVCAR-5 cell phototoxicity also does not correlate with rates of photosensitizer photobleaching and fluorescence quantum yields in any nanolipid formulations. These findings warrant critical future studies into subcellular targets and molecular mechanisms of phototoxicity of photodynamic nanoconstructs, as more reliable prognostic surrogates for predicting efficacy to appropriately and intelligently guide their design.

Mitochondria-targeting nanoparticles for enhanced microwave ablation of cancer

Although microwave ablation is widely used in the treatment of hepatocellular carcinoma, it is only recommended for the therapy of cancer with a diameter of 3 cm or less because of the limited heat transmission radius. Mitochondria play an important role in the apoptotic events of tumor cells. Here, we developed mitochondria-targeting zirconia (ZrO2) complex nanoparticles (MZCNs) as nanoagents for efficient cancer therapy by microwave ablation. The MZCNs are composed of ZrO2 nanoparticles encapsulating the microwave-sensitive ionic liquid (IL) and co-decorated with the mitochondria-targeting molecule of triphenylphosphonium (TPP), and the tumor cell-targeting peptide iRGD. The cell experiment results reveal that the amount of MZCNs accumulated in the tumor is obviously increased by the synergistically targeted delivery of TPP and iRGD peptide after administration by intravenous injection. Besides, the in vitro experiments demonstrate that MZCNs are distributed preferentially in the mitochondria with the assistance of TPP molecules. More importantly, the in vivo experiments in mice administered with MZCNs show that the effective area with a temperature above 42 °C was about 2.8-fold larger than that of the controls due to the targeting effect and better microwave sensitivity of the MZCNs. As such, the cancer in mice can be eradicated without recurrence, demonstrating the MZCNs as promising nanoagents for efficient cancer therapy by microwave ablation.

Enzymatic Assemblies Disrupt the Membrane and Target Endoplasmic Reticulum for Selective Cancer Cell Death

The endoplasmic reticulum (ER) is responsible for the synthesis and folding of a large number of proteins, as well as intracellular calcium regulation, lipid synthesis, and lipid transfer to other organelles, and is emerging as a target for cancer therapy. However, strategies for selectively targeting the ER of cancer cells are limited. Here we show that enzymatically generated crescent-shaped supramolecular assemblies of short peptides disrupt cell membranes and target ER for selective cancer cell death. As revealed by sedimentation assay, the assemblies interact with synthetic lipid membranes. Live cell imaging confirms that the assemblies impair membrane integrity, which is further supported by lactate dehydrogenase (LDH) assays. According to transmission electron microscopy (TEM), static light scattering (SLS), and critical micelle concentration (CMC), attaching an l-amino acid at the C-terminal of a d-tripeptide results in the crescent-shaped supramolecular assemblies. Structure-activity relationship suggests that the crescent-shaped morphology is critical for interacting with membranes and for controlling cell fate. Moreover, fluorescent imaging indicates that the assemblies accumulate on the ER. Time-dependent Western blot and ELISA indicate that the accumulation causes ER stress and subsequently activates the caspase signaling cascade for cell death. As an approach for in situ generating membrane binding scaffolds (i.e., the crescent-shaped supramolecular assemblies), this work promises a new way to disrupt the membrane and to target the ER for developing anticancer therapeutics.

Polysaccharide-modified nanoparticles with intelligent CD44 receptor targeting ability for gene delivery

BACKGROUND

Hyaluronic acid (HA) and chondroitin sulfate (CD) are endogenous polysaccharides. In recent years, they have aroused the interest of scientists because of specific binding to CD44 receptors, which are overexpressed in several types of tumors.

METHODS

In this study, HA- and CD-modified poly(D,L-lactide-co-glycolide)-poly(ethylene glycol) (PLGA-PEG) copolymers were synthesized and applied to encapsulate 1,2-Dioleoyl-3-trimethylammonium-propane (DOTAP)/pDNA (D/P) lipoplex as CD44 receptor targeting gene delivery nanoparticles (NPs).

RESULTS

The particle size of CD-PEG-PLGA-D/P (186.8 ± 21.7 nm) was smaller than that of HA-PEG-PLGA-D/P (270.2 ± 13.8 nm), with narrow size distribution, and both HA-PEG-PLGA-D/P NPs and CD-PEG-PLGA NPs possessed negative zeta potentials (-39.63 ± 5.44 mV and -38.9 ± 2.0 mV, respectively), which prevent erythrocytes from agglutination. Both NPs exhibited pH-dependent release and had faster release in pH 4.0 than in pH 7.4. Generally, the CD-PEG-PLGA-D/P NPs possessed less cytotoxicity than HA-PEG-PLGA-D/P NPs. The D/P-loaded HA-PEG-PLGA and CD-PEG-PLGA NPs expressed significantly higher transfection in CD44 high-expressed U87 (30.1% ± 2.1% and 40.7% ± 4.3%, respectively) than in CD44-negative HepG2 (3.3% ± 1.5% and 1.4% ± 1.0%, respectively) (p < 0.001). It was revealed that the endocytosis of HA-PEG-PLGA-D/P NPs was majorly dominated by macropinocytosis and the endocytosis of CD-PEG-PLGA-D/P NPs was dominated by clathrin-mediated endocytosis pathway (p < 0.001).

CONCLUSION

The high selectivity to CD44-positive U87 cancer cells and low cytotoxicity in L929 normal cells assured the promising potential of CD-PEG-PLGA NPs as gene delivery nano-carriers.

Design and biological characterization of novel cell-penetrating peptides preferentially targeting cell nuclei and subnuclear regions

Within this study, we report about the design and biological characterization of novel cell-penetrating peptides (CPPs) with selective suborganelle-targeting properties. The nuclear localization sequence N50, as well as the nucleoli-targeting sequence NrTP, respectively, were fused to a shortened version of the cell-penetrating peptide sC18. We examined cellular uptake, subcellular fate and cytotoxicity of these novel peptides, N50-sC18* and NrTP-sC18*, and found that they are nontoxic up to a concentration of 50 or 100 µM depending on the cell lines used. Moreover, detailed cellular uptake studies revealed that both peptides enter cells via energy-independent uptake, although endocytotic processes cannot completely excluded. However, initial drug delivery studies demonstrated the high versatility of these new peptides as efficient transport vectors targeting specifically nuclei and nucleoli. In future, they could be further explored as parts of newly created peptide-drug conjugates.

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.

Functional disruption of the Golgi apparatus protein ARF1 sensitizes MDA-MB-231 breast cancer cells to the antitumor drugs Actinomycin D and Vinblastine through ERK and AKT signaling

Increasing evidence indicates that the Golgi apparatus plays active roles in cancer, but a comprehensive understanding of its functions in the oncogenic transformation has not yet emerged. At the same time, the Golgi is becoming well recognized as a hub that integrates its functions of protein and lipid biosynthesis to signal transduction for cell proliferation and migration in cancer cells. Nevertheless, the active function of the Golgi apparatus in cancer cells has not been fully evaluated as a target for combined treatment. Here, we analyzed the effect of perturbing the Golgi apparatus on the sensitivity of the MDA-MB-231 breast cancer cell line to the drugs Actinomycin D and Vinblastine. We disrupted the function of ARF1, a protein necessary for the homeostasis of the Golgi apparatus. We found that the expression of the ARF1-Q71L mutant increased the sensitivity of MDA-MB-231 cells to both Actinomycin D and Vinblastine, resulting in decreased cell proliferation and cell migration, as well as in increased apoptosis. Likewise, the combined treatment of cells with Actinomycin D or Vinblastine and Brefeldin A or Golgicide A, two disrupting agents of the ARF1 function, resulted in similar effects on cell proliferation, cell migration and apoptosis. Interestingly, each combined treatment had distinct effects on ERK1/2 and AKT signaling, as indicated by the decreased levels of either phospho-ERK1/2 or phospho-AKT. Our results suggest that disruption of Golgi function could be used as a strategy for the sensitization of cancer cells to chemotherapy.

Intracellular Mechanistic Understanding of 2D MoS2 Nanosheets for Anti-Exocytosis-Enhanced Synergistic Cancer Therapy

Emerging two-dimensional (2D) nanomaterials, such as transition-metal dichalcogenide (TMD) nanosheets (NSs), have shown tremendous potential for use in a wide variety of fields including cancer nanomedicine. The interaction of nanomaterials with biosystems is of critical importance for their safe and efficient application. However, a cellular-level understanding of the nano-bio interactions of these emerging 2D nanomaterials ( i. e., intracellular mechanisms) remains elusive. Here we chose molybdenum disulfide (MoS2) NSs as representative 2D nanomaterials to gain a better understanding of their intracellular mechanisms of action in cancer cells, which play a significant role in both their fate and efficacy. MoS2 NSs were found to be internalized through three pathways: clathrin → early endosomes → lysosomes, caveolae → early endosomes → lysosomes, and macropinocytosis → late endosomes → lysosomes. We also observed autophagy-mediated accumulation in the lysosomes and exocytosis-induced efflux of MoS2 NSs. Based on these findings, we developed a strategy to achieve effective and synergistic in vivo cancer therapy with MoS2 NSs loaded with low doses of drug through inhibiting exocytosis pathway-induced loss. To the best of our knowledge, this is the first systematic experimental report on the nano-bio interaction of 2D nanomaterials in cells and their application for anti-exocytosis-enhanced synergistic cancer therapy.

Metal-based NanoEnhancers for Future Radiotherapy: Radiosensitizing and Synergistic Effects on Tumor Cells

Radiotherapy is one of the major therapeutic strategies for cancer treatment. In the past decade, there has been growing interest in using high Z (atomic number) elements (materials) as radiosensitizers. New strategies in nanomedicine could help to improve cancer diagnosis and therapy at cellular and molecular levels. Metal-based nanoparticles usually exhibit chemical inertness in cellular and subcellular systems and may play a role in radiosensitization and synergistic cell-killing effects for radiation therapy. This review summarizes the efficacy of metal-based NanoEnhancers against cancers in both in vitro and in vivo systems for a range of ionizing radiations including gamma-rays, X-rays, and charged particles. The potential of translating preclinical studies on metal-based nanoparticles-enhanced radiation therapy into clinical practice is also discussed using examples of several metal-based NanoEnhancers (such as CYT-6091, AGuIX, and NBTXR3). Also, a few general examples of theranostic multimetallic nanocomposites are presented, and the related biological mechanisms are discussed.

Self-Assembled Coumarin Nanoparticle in Aqueous Solution as Selective Mitochondrial-Targeting Drug Delivery System

The development of specifically targeted nanoparticles for subcellular organelles modified with a low-molecular-weight organic compound as drug nanocarriers can bring about wide applications in cancer therapy. However, their utility has been hampered by low selectivity, poor biodistribution, and limited efficiency. Herein, we report the aggregation behavior of a triphenylphosphonium-appended coumarin probe (TPP-C) in an aqueous solution and its applications as a mitochondria-targeting probe, and drug delivery carrier, which is a rare example for a low molecular-weight organic compound. The TPP-C formed homogeneous nanoparticles with small diameters in water as well as in mixtures of organic solvents and water. In pure water, the homogeneous nanoparticles induced J-aggregation, whereas in mixed solvents, the homogeneous nanoparticles induced H-aggregation. The luminescence intensities of nanoparticles originated from the aggregation-induced emission (AIE) effect in pure water and also in mixtures of organic solvents and water. These findings indicate that the AIE effect of TPP-C was dependent on the solvent. More interestingly, the TPP-C nanoparticles selectively accumulated in mitochondria. The TPP-C nanoparticles alone exhibited noncytotoxicity toward cancer cells. However, with the encapsulation of the anticancer drug doxorubicin (DOX) into the TPP-C nanoparticles, the DOX was efficiently delivered to the mitochondria. These results indicated that the proposed system demonstrates promise as a platform for future clinical medication, particularly for specific suborganelle-targeted drug delivery systems for cancer therapy.

The Platin-X series: activation, targeting, and delivery

Anticancer platinum (Pt) complexes have long been considered to be one of the biggest success stories in the history of medicinal inorganic chemistry. Yet there remains the hunt for the "magic bullet" which can satisfy the requirements of an effective chemotherapeutic drug formulation. Pt(iv) complexes are kinetically more inert than the Pt(ii) congeners and offer the opportunity to append additional functional groups/ligands for prodrug activation, tumor targeting, or drug delivery. The ultimate aim of functionalization is to enhance the tumor selective action and attenuate systemic toxicity of the drugs. Moreover, an increase in cellular accumulation to surmount the resistance of the tumor against the drugs is also of paramount importance in drug development and discovery. In this review, we will address the attempts made in our lab to develop Pt(iv) prodrugs that can be activated and delivered using targeted nanotechnology-based delivery platforms.

Subcellular co-delivery of two different site-oriented payloads based on multistage targeted polymeric nanoparticles for enhanced cancer therapy

Smart nanoparticles which encapsulated two different site-oriented therapeutic agents for multistage targeted delivery and enhanced antitumor therapy.

Crosstalk of Nanosystems Induced Extracellular Vesicles as Promising Tools in Biomedical Applications

Hybrid vesicles are considered as a bridge between natural nanosystems (NNSs) and artificial nanosystems (ANSs). NNSs are extracellular vesicles (EVs), membranous, bio-formed endogenously, which act as endogenous cargoes, and reflecting cellular dynamics. EVs have cellular tropism, permeate tight junctions, and are non-immunogenic. EVs are used as tools in the development of diagnostic and therapeutic agents. ANSs can induce biogenesis of hybrid vesicles as promising smart diagnostic agents, and innovative drug cargoes. EVs can encapsulate small molecules, macromolecules, and ANSs. The manipulation of EVs during biogenesis was suggested for engineering hybrid EVs. This review article highlights the role of ANSs in the biogenesis of NNSs, and introduces hybrid nanosystems research.

Intracellular Fate of Nanoparticles with Polydopamine Surface Engineering and a Novel Strategy for Exocytosis-Inhibiting, Lysosome Impairment-Based Cancer Therapy

Polydopamine (PDA) coating as a bioinspired strategy for nanoparticles (NPs) has been extensively applied in cancer theranostics. However, a cellular-level understanding of nano-biointeraction of these PDA-coated NPs (PDNPs), which drives the fate of them and acts as a critical step to determine their efficacy, still remains unknown. Herein, we utilized the representative mesoporous silica NPs (MSNs) to be coated with PDA and study their nano-bioactivities in cancer cells. HeLa cell line was utilized as a model in this study. The PDNPs were discovered to be internalized through three specific pathways, that is, Caveolae-, Arf6-dependent endocytosis, and Rab34-mediated macropinocytosis (55%, 20% and 37% of uptake inhibition by nystatin, Arf6 knockdown, and rottlerin, respectively). Autophagy-mediated accumulation of PDNPs in lysosomes was observed and the formed PDA shells shedded in the lysosomes. Almost 40% of the NPs were transported out of cells via Rab8/10- and Rab3/26-mediated exocytosis pathways at our tested level. On the basis of these results, a novel combined cancer treatment strategy was further proposed using drug-loaded MSNs-PDA by (i) utilizing naturally intracellular mechanism-controlled PDA shedding for organelle-targeted release of drugs in lysosomes to generate lysosome impairment and (ii) blocking the demonstrated exocytosis pathways for enhanced therapeutic efficacy.

Cancer: Linking Powerhouses to Suicidal Bags

Membrane-bound organelles are integrated into cellular networks and work together for a common goal: regulating cell metabolism, cell signaling pathways, cell fate, cellular maintenance, and pathogen defense. Many of these interactions are well established, but little is known about the interplay between mitochondria and lysosomes, and their deregulation in cancer. The present review focuses on the common signaling pathways of both organelles, as well as the processes in which they both physically interact, their changes under pathological conditions, and the impact on targeting those organelles for treating cancer.

Development of nanomaterials for bone-targeted drug delivery

Bone is one of the major organs of the human body; it supports and protects other organs, produces blood cells, stores minerals, and regulates hormones. Therefore, disorders in bone can cause serious morbidity, complications, or mortality of patients. However, despite the significant occurrence of bone diseases, such as osteoarthritis (OA), osteoporosis (OP), non-union bone defects, bone cancer, and myeloma-related bone disease, their effective treatments remain a challenge. In this review, we highlight recent progress in the development of nanotechnology-based drug delivery for bone treatment, based on its improved delivery efficiency and safety. We summarize the most commonly used nanomaterials for bone drug delivery. We then discuss the targeting strategies of these nanomaterials to the diseased sites of bone tissue. We also highlight nanotechnology-based drug delivery to bone cells and subcellular organelles. We envision that nanotechnology-based drug delivery will serve as a powerful tool for developing treatments for currently incurable bone diseases.

Active Targeting of the Nucleus Using Nonpeptidic Boronate Tags

Active intracellular transport is a central mechanism in cell biology, directed by a limited set of naturally occurring signaling peptides. Here, we report the first nonpeptide moiety that recruits intracellular transport machinery for nuclear targeting. Proteins synthetically modified with a simple aromatic boronate motif are actively trafficked to the nucleus via the importin α/β pathway. Significantly, proteins too large to passively diffuse through nuclear pores were readily imported into the nucleus through this boronate-mediated pathway. The use of this simple motif to provide active intracellular targeting provides a promising strategy for directing subcellular localization for therapeutic and fundamental applications.

Bioreducible Poly(ethylene glycol)-Triphenylphosphonium Conjugate as a Bioactivable Mitochondria-Targeting Nanocarrier

Bioactivable nanocarrier systems have favorable characteristics such as high cellular uptake, target specificity, and an efficient intracellular release mechanism. In this study, we developed a bioreducible methoxy polyethylene glycol (mPEG)-triphenylphosphonium (TPP) conjugate (i.e., mPEG-(ss-TPP)₂ conjugate) as a vehicle for mitochondrial drug delivery. A bioreducible linkage with two disulfide bond-containing end groups was used at one end of the hydrophilic mPEG for conjugation with lipophilic TPP molecules. The amphiphilic mPEG-(ss-TPP)₂ self-assembled in aqueous media, which thereby formed core-shell structured nanoparticles (NPs) with good colloidal stability, and efficiently encapsulated the lipophilic anticancer drug doxorubicin (DOX). The DOX-loaded mPEG-(ss-TPP)₂ NPs were characterized in terms of their physicochemical and morphological properties, drug-loading and release behaviors, in vitro anticancer effects, and mitochondria-targeting capacity. Our results suggest that bioreducible DOX-loaded mPEG-(ss-TPP)₂ NPs can induce fast drug release with enhanced mitochondrial uptake and have a better therapeutic effect than nonbioreducible NPs.

Gold Nanoparticles in Single-Cell Analysis for Surface Enhanced Raman Scattering

The need for new therapeutic approaches in the treatment of challenging diseases such as cancer, which often consists of a highly heterogeneous and complex population of cells, brought up the idea of analyzing single cells. The development of novel techniques to analyze single cells has been intensively studied to fully understand specific alternations inducing abnormalities in cellular function. One of the techniques used for single cell analysis is surface-enhanced Raman spectroscopy (SERS) in which a noble metal nanoparticle is used to enhance Raman scattering. Due to its low toxicity and biocompatibility, gold nanoparticles (AuNPs) are commonly preferred as SERS substrates in single cell analysis. The intracellular uptake, localization and toxicity issues of AuNPs are the critical points for interpretation of data since the obtained SERS signals originate from molecules in close vicinity to AuNPs that are taken up by the cells. In this review, the AuNP-living cell interactions, cellular uptake and toxicity of AuNPs in relation to their physicochemical properties, and surface-enhanced Raman scattering from single cells are discussed.

A Dual Anticancer Efficacy Molecule: A Selective Dark Cytotoxicity Photosensitizer

Unlike traditional binary nanostructures that construct chemotherapy drugs and photodynamic therapy photosensitizers, we introduce a molecule with a chemo-photodynamic dual therapy function. A water-soluble aggregation-induced emission enhancement (AIEE) fluorogen, NV-12P, was designed and synthesized based on asymmetric 1,6-disubstituted naphthalene and can generate particular reactive oxygen species to undergo type I photodynamic therapy under irradiation. Furthermore, this compound can specifically localize in mitochondria and, after biological evaluation, can cause mitochondrial dysfunction and potent cytotoxicity to cancer cells but not normal cells. We conclude that this compound is a potential dual-toxic efficacy molecule because it exhibits selective dark cytotoxicity and efficient photodamage in cancer cells. Additionally, we also supported the optimal combinational treatment course for the best chemo-phototherapy efficacy.

Decoration of pH-sensitive copolymer micelles with tumor-specific peptide for enhanced cellular uptake of doxorubicin

To improve the targeting efficacy of hyaluronic acid (HA)-based micelles, pH-sensitive mixed micelles based on HA-g-poly(L-histidine) (PHis) and d-α-tocopheryl polyethylene glycol 2000 copolymers were prepared and decorated with human epidermal growth factor receptor 2 (Her2) peptide, a tumor cell-specific peptide ligand, on their surface. The doxorubicin-loaded micelles (HA-PHis/peptide–d-α-tocopheryl polyethylene glycol 2000 mixed micelles [PHTM]) were characterized to have a unimodal size distribution and pH-dependent drug release pattern. In vitro tumor targeting studies demonstrated that PHTM exhibited the pronounced cytotoxicity and efficient internalization in MDA-MB-231 cells overexpressing CD44 and Her2 receptors. In vivo investigation into micelles in MDA-MB-231 tumor-bearing mice confirmed that PTHM could reach the tumor site more effectively and exert excellent tumor killing activity. In general, Her2 peptide decoration can enhance the selective cytotoxicity and antitumor activity of HA-based micelles.

Efficiency of calcium phosphate composite nanoparticles in targeting Ehrlich carcinoma cells transplanted in mice

The present study aimed to investigate the mode of action of nano-CaPs in vivo as a therapy for solid tumor in mice. To achieve this goal, Ehrlich Ascites Carcinoma (EAC) was transplanted into 85 Swiss male albino mice. After nine days, the mice were divided into 9 groups. Groups 1 and 2 were allocated as the EAC control. Groups 3 and 4 were injected once intratumorally (IT) by nano-calcium phosphate (nano-CaP). Groups 5 and 6 received once intraperitoneal injection (IP) of nano-CaP. Groups 7, 8, and 9 received nano-CaP (IP) weekly. Blood samples and thigh skeletal muscle were collected after three weeks from groups 1, 3, 5, and 7 and after four weeks from groups 2, 4, 6, and 8. On the other hand, group 9 received nano-CaP (IP) for four weeks and lasted for three months to follow up the recurrence of tumor and to ensure the safety of muscle by histopathological analysis. Tumor growth was monitored twice a week throughout the experiment. DNA fragmentation of tumor cells was evaluated. In thigh tissue, noradrenaline, dopamine, serotonin (5HT), and gamma-aminobutyric acid (GABA) were measured. In serum, 8-Hydroxy-deoxyguanosine (8-OHDG), adenosine triphosphate (ATP), and vascular endothelial growth factor (VEGF) were analyzed. Histopathological and biochemical results showed a significant therapeutic effect of nano-CaP on implanted solid tumor and this effect was more pronounced in the animals treated IP for four weeks. This improvement was evident from the repair of fragmented DNA, the significant decrease of caspase-3, 8-OHDG, myosin, and VEGF, and the significant increase of neurotransmitters (NA, DA, 5HT, and GABA). Additionally, histopathological examination showed complete recovery of cancer cells in the thigh muscle after three months.

Dual subcellular compartment delivery of doxorubicin to overcome drug resistant and enhance antitumor activity

In order to overcome drug resistant and enhance antitumor activity of DOX, a new pH-sensitive micelle (DOX/DQA-DOX@DSPE-hyd-PEG-AA) was prepared to simultaneously deliver DOX to nucleus and mitochondria. Drug released from DOX/DQA-DOX@DSPE-hyd-PEG-AA showed a pH-dependent manner. DOX/DQA-DOX@DSPE-hyd-PEG-AA induced the depolarization of mitochondria and apoptosis in MDA-MB-231/ADR cells and A549 cells, which resulted in the high cytotoxicity of DOX/DQA-DOX@DSPE-hyd-PEG-AA against MDA-MB-231/ADR cells and A549 cells. Confocal microscopy confirmed that DOX/DQA-DOX@DSPE-hyd-PEG-AA simultaneously delivered DQA-DOX and DOX to the mitochondria and nucleus of tumor cell. After DOX/DQA-DOX@DSPE-hyd-PEG-AA was injected to the tumor-bearing nude mice by the tail vein, DOX was mainly found in tumor tissue. But DOX was widely distributed in the whole body after the administration of free DOX. Compared with free DOX, the same dose of DOX/DQA-DOX@DSPE-hyd-PEG-AA significantly inhibited the growth of DOX-resistant tumor in tumor-bearing mice without obvious systemic toxicity. Therefore, dual subcellular compartment delivery of DOX greatly enhanced the antitumor activity of DOX on DOX-resistant tumor. DOX/DQA-DOX@DSPE-hyd-PEG-AA has the potential in target therapy for DOX-resistant tumor.

A novel high-throughput activity assay for the Trypanosoma brucei editosome enzyme REL1 and other RNA ligases

The protist parasite Trypanosoma brucei causes Human African trypanosomiasis (HAT), which threatens millions of people in sub-Saharan Africa. Without treatment the infection is almost always lethal. Current drugs for HAT are difficult to administer and have severe side effects. Together with increasing drug resistance this results in urgent need for new treatments. T. brucei and other trypanosomatid pathogens require a distinct form of post-transcriptional mRNA modification for mitochondrial gene expression. A multi-protein complex called the editosome cleaves mitochondrial mRNA, inserts or deletes uridine nucleotides at specific positions and re-ligates the mRNA. RNA editing ligase 1 (REL1) is essential for the re-ligation step and has no close homolog in the mammalian host, making it a promising target for drug discovery. However, traditional assays for RELs use radioactive substrates coupled with gel analysis and are not suitable for high-throughput screening of compound libraries. Here we describe a fluorescence-based REL activity assay. This assay is compatible with a 384-well microplate format and sensitive, satisfies statistical criteria for high-throughput methods and is readily adaptable for other polynucleotide ligases. We validated the assay by determining kinetic properties of REL1 and by identifying REL1 inhibitors in a library of small, pharmacologically active compounds.

Fungal-specific subunits of the Candida albicans mitochondrial complex I drive diverse cell functions including cell wall synthesis

Our published research has focused on the role of Goa1p, an apparent regulator of the Candida albicans mitochondrial complex I (CI). Lack of Goa1p affects optimum cell growth, CI activity and virulence. Eukaryotic CI is composed of a core of 14 alpha-proteobacterial subunit proteins and a variable number of supernumerary subunit proteins. Of the latter group of proteins, one (NUZM) is fungal specific and the other (NUXM) is found in fungi, algae and plants, but is not a mammalian CI subunit protein. We have established that NUXM is orf19.6607 and NUZM is orf19.287 in C. albicans. Herein, we validate both subunit proteins as NADH:ubiquinone oxidoreductases (NUO) and annotate their gene functions. To accomplish these objectives, we compared null mutants of each with wild type (WT) and gene-reconstituted strains. Genetic mutants of genes NUO1 (orf19.6607) and NUO2 (orf19.287), not surprisingly, each had reduced oxygen consumption, decreased mitochondrial redox potential, decreased CI activity, increased reactive oxidant species (ROS) and decreased chronological ageing in vitro. Loss of either gene results in disassembly of CI. Transcriptional profiling of both mutants indicated significant down-regulation of genes of carbon metabolism, as well as up-regulation of mitochondrial-associated gene families that may occur to compensate for the loss of CI activity. Profiling of both mutants also demonstrated a loss of cell wall β-mannosylation but not in a conserved CI subunit (ndh51Δ). The profiling data may indicate specific functions driven by the enzymatic activity of Nuo1p and Nuo2p. Of importance, each mutant is also avirulent in a murine blood-borne, invasive model of candidiasis associated with their reduced colonization of tissues. Based on their fungal specificity and roles in virulence, we suggest both as drug targets for antifungal drug discovery.

Mitochondria-targeting particles

Mitochondria are a promising therapeutic target for the detection, prevention and treatment of various human diseases such as cancer, neurodegenerative diseases, ischemia-reperfusion injury, diabetes and obesity. To reach mitochondria, therapeutic molecules need to not only gain access to specific organs, but also to overcome multiple barriers such as the cell membrane and the outer and inner mitochondrial membranes. Cellular and mitochondrial barriers can be potentially overcome through the design of mitochondriotropic particulate carriers capable of transporting drug molecules selectively to mitochondria. These particulate carriers or vectors can be made from lipids (liposomes), biodegradable polymers, or metals, protecting the drug cargo from rapid elimination and degradation in vivo. Many formulations can be tailored to target mitochondria by the incorporation of mitochondriotropic agents onto the surface and can be manufactured to desired sizes and molecular charge. Here, we summarize recently reported strategies for delivering therapeutic molecules to mitochondria using various particle-based formulations.

Enabling cytoplasmic delivery and organelle targeting by surface modification of nanocarriers

Nanocarriers are designed to specifically accumulate in diseased tissues. In this context, targeting of intracellular compartments was shown to enhance the efficacy of many drugs and to offer new and more effective therapeutic approaches. This is especially true for therapies based on biologicals that must be encapsulated to favor cell internalization, and to avoid intracellular endosomal sequestration and degradation of the payload. In this review, we discuss specific surface modifications designed to achieve cell cytoplasm delivery and to improve targeting of major organelles; we also discuss the therapeutic applications of these approaches. Last, we describe some integrated strategies designed to sequentially overcome the biological barriers that separate the site of administration from the cell cytoplasm, which is the drug's site of action.

Image-guided combination chemotherapy and photodynamic therapy using a mitochondria-targeted molecular probe with aggregation-induced emission characteristics

Mitochondria-targeted AIE photosensitizers show multifunctions of targeted and image-guided combination chemotherapy and photodynamic therapy.

Subcellular targeted cancer therapy and in situ monitoring of therapeutic effect are highly desirable for clinical applications. Herein, we report a series of probes by conjugating zero (TPECM-2Br), one (TPECM-1TPP) and two (TPECM-2TPP) triphenylphosphine (TPP) ligands to a fluorogen with aggregation-induced emission (AIE) characteristics. The probes are almost non-emissive as molecularly dissolved species, but they can light up in cell cytoplasm or mitochondria. TPECM-2TPP is found to be able to target mitochondria, depolarize mitochondria membrane potential and selectively exert potent chemo-cytotoxicity on cancer cells. Furthermore, it can efficiently generate singlet oxygen with strong photo-toxicity upon light illumination, which further enhances its anti-cancer effect. On the other hand, TPECM-1TPP can also target mitochondria and generate singlet oxygen to trigger cancer cell apoptosis, but it shows low cytotoxicity in dark. Meanwhile, TPECM-1TPP can report the cellular oxidative stress by visualizing the morphological changes of mitochondria. However, TPECM-2Br does not target mitochondria and shows no obvious anticancer effect either in dark or under light illumination. This study thus highlights the importance of molecular probe design, which yields a new generation of subcellular targeted molecular theranostic agents with multi-function, such as cancer cell imaging, chemotherapy, photodynamic therapy, and in situ monitoring of the therapeutic effect in one go.

Lysosomal targeting with stable and sensitive fluorescent probes (Superior LysoProbes): applications for lysosome labeling and tracking during apoptosis

Intracellular pH plays an important role in the response to cancer invasion. We have designed and synthesized a series of new fluorescent probes (Superior LysoProbes) with the capacity to label acidic organelles and monitor lysosomal pH. Unlike commercially available fluorescent dyes, Superior LysoProbes are lysosome-specific and are highly stable. The use of Superior LysoProbes facilitates the direct visualization of the lysosomal response to lobaplatin elicited in human chloangiocarcinoma (CCA) RBE cells, using confocal laser scanning microscopy. Additionally, we have characterized the role of lysosomes in autophagy, the correlation between lysosome function and microtubule strength, and the alteration of lysosomal morphology during apoptosis. Our findings indicate that Superior LysoProbes offer numerous advantages over previous reagents to examine the intracellular activities of lysosomes.

Quorum-sensing Salmonella selectively trigger protein expression within tumors

Salmonella that secrete anticancer proteins have the potential to eliminate tumors, but nonspecific expression causes damage to healthy tissue. We hypothesize that Salmonella, integrated with a density-dependent switch, would only express proteins in tightly packed colonies within tumors. To test this hypothesis, we cloned the lux quorum-sensing (QS) system and a GFP reporter into nonpathogenic Salmonella. Fluorescence and bacterial density were measured in culture and in a tumor-on-a-chip device to determine the critical density necessary to initiate expression. QS Salmonella were injected into 4T1 tumor-bearing mice to quantify GFP expression in vivo using immunofluorescence. At densities below 0.6 × 10(10) cfu/g in tumors, less than 3% of QS Salmonella expressed GFP. Above densities of 4.2 × 10(10) cfu/g, QS Salmonella had similar expression levels to constitutive controls. GFP expression by QS colonies was dependent upon the distance to neighboring bacteria. No colonies expressed GFP when the average distance to neighbors was greater than 155 µm. Calculations of autoinducer concentrations showed that expression was sigmoidally dependent on density and inversely dependent on average radial distance. Based on bacterial counts from excised tissue, the liver density (0.0079 × 10(10) cfu/g) was less than the critical density (0.11 × 10(10) cfu/g) necessary to initiate expression. QS Salmonella are a promising tool for cancer treatment that will target drugs to tumors while preventing damage to healthy tissue.

Highly stable and sensitive fluorescent probes (LysoProbes) for lysosomal labeling and tracking

We report the design, synthesis and application of several new fluorescent probes (LysoProbes I-VI) that facilitate lysosomal pH monitoring and characterization of lysosome-dependent apoptosis. LysoProbes are superior to commercially available lysosome markers since the fluorescent signals are both stable and highly selective, and they will aid in characterization of lysosome morphology and trafficking. We predict that labeling of cancer cells and solid tumor tissues with LysoProbes will provide an important new tool for monitoring the role of lysosome trafficking in cancer invasion and metastasis.

Off to the organelles - killing cancer cells with targeted gold nanoparticles

Gold nanoparticles (AuNPs) are excellent tools for cancer cell imaging and basic research. However, they have yet to reach their full potential in the clinic. At present, we are only beginning to understand the molecular mechanisms that underlie the biological effects of AuNPs, including the structural and functional changes of cancer cells. This knowledge is critical for two aspects of nanomedicine. First, it will define the AuNP-induced events at the subcellular and molecular level, thereby possibly identifying new targets for cancer treatment. Second, it could provide new strategies to improve AuNP-dependent cancer diagnosis and treatment.

Our review summarizes the impact of AuNPs on selected subcellular organelles that are relevant to cancer therapy. We focus on the nucleus, its subcompartments, and mitochondria, because they are intimately linked to cancer cell survival, growth, proliferation and death. While non-targeted AuNPs can damage tumor cells, concentrating AuNPs in particular subcellular locations will likely improve tumor cell killing. Thus, it will increase cancer cell damage by photothermal ablation, mechanical injury or localized drug delivery. This concept is promising, but AuNPs have to overcome multiple hurdles to perform these tasks. AuNP size, morphology and surface modification are critical parameters for their delivery to organelles. Recent strategies explored all of these variables, and surface functionalization has become crucial to concentrate AuNPs in subcellular compartments.

Here, we highlight the use of AuNPs to damage cancer cells and their organelles. We discuss current limitations of AuNP-based cancer research and conclude with future directions for AuNP-dependent cancer treatment.