Peptide-based carbon nanotubes for mitochondrial targeting

Fanarraga M. Carbon nanotubes targeted to the tumor microenvironment inhibit metastasis in a preclinical model of melanoma

Despite notable progress in cancer therapy, metastatic diseases continue to be the primary cause of cancer-related mortality. Multi-walled carbon nanotubes (MWCNTs) can enter tissues and cells and interfere with the dynamics of the cytoskeletal nanofilaments biomimetically. This endows them with intrinsic anti-tumoral effects comparable to those of microtubule-binding chemotherapies such as Taxol®. In this study, our focus was on exploring the potential of oxidized MWCNTs in selectively targeting the vascular endothelial growth factor receptor (VEGFR). Our objective was to evaluate their effectiveness in inhibiting metastatic growth by inducing anti-proliferative, anti-migratory, and cytotoxic effects on both cancer and tumor microenvironment cells. Our findings demonstrated a significant reduction of over 80 % in malignant melanoma lung metastases and a substantial enhancement in overall animal welfare following intravenous administration of the targeted biodegradable MWCNTs. Furthermore, the combination of these nanomaterials with the conventional chemotherapy agent Taxol® yielded a remarkable 90 % increase in the antimetastatic effect. These results highlight the promising potential of this combined therapeutic approach against metastatic disease and are of paramount importance as metastasis is responsible for nearly 60,000 deaths each year.

Engineering metabolism to modulate immunity

Metabolic programming and reprogramming have emerged as pivotal mechanisms for altering immune cell function. Thus, immunometabolism has become an attractive target area for treatment of immune-mediated disorders. Nonetheless, many hurdles to delivering metabolic cues persist. In this review, we consider how biomaterials are poised to transform manipulation of immune cell metabolism through integrated control of metabolic configurations to affect outcomes in autoimmunity, regeneration, transplant, and cancer. We emphasize the features of nanoparticles and other biomaterials that permit delivery of metabolic cues to the intracellular compartment of immune cells, or strategies for altering signals in the extracellular space. We then provide perspectives on the potential for reciprocal regulation of immunometabolism by the physical properties of materials themselves. Lastly, opportunities for clinical translation are highlighted. This discussion contributes to our understanding of immunometabolism, biomaterials-based strategies for altering metabolic configurations in immune cells, and emerging concepts in this evolving field.

The Promoting Role of HK II in Tumor Development and the Research Progress of Its Inhibitors

Increased glycolysis is a key characteristic of malignant cells that contributes to their high proliferation rates and ability to develop drug resistance. The glycolysis rate-limiting enzyme hexokinase II (HK II) is overexpressed in most tumor cells and significantly affects tumor development. This paper examines the structure of HK II and the specific biological factors that influence its role in tumor development, as well as the potential of HK II inhibitors in antitumor therapy. Furthermore, we identify and discuss the inhibitors of HK II that have been reported in the literature.

The Dysregulated MAD in Mad: A Neuro-theranostic Approach Through the Induction of Autophagic Biomarkers LC3B-II and ATG

The word mad has historically been associated with the psyche, emotions, and abnormal behavior. Dementia is a common symptom among psychiatric disorders or mad (schizophrenia, depression, bipolar disorder) patients. Autophagy/mitophagy is a protective mechanism used by cells to get rid of dysfunctional cellular organelles or mitochondria. Autophagosome/mitophagosome abundance in autophagy depends on microtubule-associated protein light chain 3B (LC3B-II) and autophagy-triggering gene (ATG) which functions as an autophagic biomarker for phagophore production and quick mRNA disintegration. Defects in either LC3B-II or the ATG lead to dysregulated mitophagy-and-autophagy-linked dementia (MAD). The impaired MAD is closely associated with schizophrenia, depression, and bipolar disorder. The pathomechanism of psychosis is not entirely known, which is the severe limitation of today's antipsychotic drugs. However, the reviewed circuit identifies new insights that may be especially helpful in targeting biomarkers of dementia. Neuro-theranostics can also be achieved by manufacturing either bioengineered bacterial and mammalian cells or nanocarriers (liposomes, polymers, and nanogels) loaded with both imaging and therapeutic materials. The nanocarriers must cross the BBB and should release both diagnostic agents and therapeutic agents in a controlled manner to prove their effectiveness against psychiatric disorders. In this review, we highlighted the potential of microRNAs (miRs) as neuro-theranostics in the treatment of dementia by targeting autophagic biomarkers LC3B-II and ATG. Focus was also placed on the potential for neuro-theranostic nanocells/nanocarriers to traverse the BBB and induce action against psychiatric disorders. The neuro-theranostic approach can provide targeted treatment for mental disorders by creating theranostic nanocarriers.

Nanomedicine in cancer therapy

Cancer remains a highly lethal disease in the world. Currently, either conventional cancer therapies or modern immunotherapies are non-tumor-targeted therapeutic approaches that cannot accurately distinguish malignant cells from healthy ones, giving rise to multiple undesired side effects. Recent advances in nanotechnology, accompanied by our growing understanding of cancer biology and nano-bio interactions, have led to the development of a series of nanocarriers, which aim to improve the therapeutic efficacy while reducing off-target toxicity of the encapsulated anticancer agents through tumor tissue-, cell-, or organelle-specific targeting. However, the vast majority of nanocarriers do not possess hierarchical targeting capability, and their therapeutic indices are often compromised by either poor tumor accumulation, inefficient cellular internalization, or inaccurate subcellular localization. This Review outlines current and prospective strategies in the design of tumor tissue-, cell-, and organelle-targeted cancer nanomedicines, and highlights the latest progress in hierarchical targeting technologies that can dynamically integrate these three different stages of static tumor targeting to maximize therapeutic outcomes. Finally, we briefly discuss the current challenges and future opportunities for the clinical translation of cancer nanomedicines.

Biomedicine Innovations and Its Nanohydrogel Classifications

As one of the most cutting-edge and promising polymer crosslinked network nanoparticle systems. Polymer nano-sized hydrogels (nanogels) have been a hot topic in the biomedical field over the last few decades. Due to their unique characteristics, which include their relatively high drug encapsulation efficiency, ease of preparation, high tunability, low toxicity, high stability in serum and responsive behavior to a range of stimuli to facilitate drug release. Nanogels are thought to be the next generation of drug delivery systems that can completely change the way that drug delivery systems have an impact on patients' lives. Nanogels have demonstrated significant potential in a variety of fields, including chemotherapy, diagnosis, organ targeting, and delivery of bioactive molecules of different dimensions. However, the lack of substantial clinical data from nanogels becomes one of the major barriers to translating the nanogel concept into a practical therapeutic application for many disease conditions. In addition, nanogel safety profiles have been the major concern that hinders it advancement to the clinical trial phase. This review aims to emphasize the unique properties of nanogels as delivery systems for a variety of bioactive molecules over other nano-delivery systems. Also, this review attempts to give insight into the recent progress in nanogels as a carrier in the field of nanomedicine to overcome complex biological barriers. Relevant scientific data and clinical rationale for the development and the potential use of nanogel as a carrier for targeted therapeutic interventions are discussed. Finally, the concluding points of this review highlight the importance of understanding the long-term toxicity profile of nanogel within the biological system to fully understand their biocompatibility.

Polymer-coated carbon nanotube hybrids with functional peptides for gene delivery into plant mitochondria

The delivery of genetic material into plants has been historically challenging due to the cell wall barrier, which blocks the passage of many biomolecules. Carbon nanotube-based delivery has emerged as a promising solution to this problem and has been shown to effectively deliver DNA and RNA into intact plants. Mitochondria are important targets due to their influence on agronomic traits, but delivery into this organelle has been limited to low efficiencies, restricting their potential in genetic engineering. This work describes the use of a carbon nanotube-polymer hybrid modified with functional peptides to deliver DNA into intact plant mitochondria with almost 30 times higher efficiency than existing methods. Genetic integration of a folate pathway gene in the mitochondria displays enhanced plant growth rates, suggesting its applications in metabolic engineering and the establishment of stable transformation in mitochondrial genomes. Furthermore, the flexibility of the polymer layer will also allow for the conjugation of other peptides and cargo targeting other organelles for broad applications in plant bioengineering.

The delivery of genetic material into plants is challenging due to the cell wall barrier. Here, the authors hybridize polymer-coated carbon nanotubes with functional peptides to deliver plasmid DNA cargo into intact plant mitochondria for transient expression and homologous recombination at high efficiency.

An understanding of mitochondria and its role in targeting nanocarriers for diagnosis and treatment of cancer

Nanotechnology has changed the entire paradigm of drug targeting and has shown tremendous potential in the area of cancer therapy due to its specificity. In cancer, several targets have been explored which could be utilized for the better treatment of disease. Mitochondria, the so-called powerhouse of cell, portrays significant role in the survival and death of cells, and has emerged as potential target for cancer therapy. Direct targeting and nanotechnology based approaches can be tailor-made to target mitochondria and thus improve the survival rate of patients suffering from cancer. With this backdrop, in present review, we have reemphasized the role of mitochondria in cancer progression and inhibition, highlighting the different targets that can be explored for targeting of disease. Moreover, we have also summarized different nanoparticulate systems that have been used for treatment of cancer via mitochondrial targeting.

Nanotherapeutic approaches to target mitochondria in cancer

Treatment of cancer cells exemplifies a difficult test in the light of challenges associated with the nature of cancer cells and the severe side effects too. After making a large number of trials using both traditional and advanced therapies (immunotherapy and hormone therapy), approaches to design new therapies have reached a saturation level. However, nanotechnology-based approaches exhibit higher efficacy and great potential to bypass many of such therapeutic limitations. Because of their higher target specificity, the use of nanoparticles offers incredible potential in cancer therapeutics. Mitochondria, acting as a factory of energy production in cells, reveal an important role in the death as well as the survival of cells. Because of its significant involvement in the proliferation of cancer cells, it is being regarded as an important target for cancer therapeutics. Numerous studies reveal that nanotechnology-based approaches to directly target the mitochondria may help in improving the survival rate of cancer patients. In the current study, we have detailed the significance of mitochondria in the development of cancer phenotype, as well as indicated it as the potential targets for cancer therapy. Our study further highlights the importance of different nanoparticle-based approaches to target mitochondria of cancer cells and the associated outcomes of different studies. Though, nanotechnology-based approaches to target mitochondria of cancer cells demonstrate a potential and efficient way in cancer therapeutics. Yet, further study is needed to overcome the linked limitations.

Novel Strategies for Disrupting Cancer-Cell Functions with Mitochondria-Targeted Antitumor Drug-Loaded Nanoformulations

Any variation in normal cellular function results in mitochondrial dysregulation that occurs in several diseases, including cancer. Such processes as oxidative stress, metabolism, signaling, and biogenesis play significant roles in cancer initiation and progression. Due to their central role in cellular metabolism, mitochondria are favorable therapeutic targets for the prevention and treatment of conditions like neurodegenerative diseases, diabetes, and cancer. Subcellular mitochondria-specific theranostic nanoformulations for simultaneous targeting, drug delivery, and imaging of these organelles are of immense interest in cancer therapy. It is a challenging task to cross multiple barriers to target mitochondria in diseased cells. To overcome these multiple barriers, several mitochondriotropic nanoformulations have been engineered for the transportation of mitochondria-specific drugs. These nanoformulations include liposomes, dendrimers, carbon nanotubes, polymeric nanoparticles (NPs), and inorganic NPs. These nanoformulations are made mitochondriotropic by conjugating them with moieties like dequalinium, Mito-Porter, triphenylphosphonium, and Mitochondria-penetrating peptides. Most of these nanoformulations are meticulously tailored to control their size, charge, shape, mitochondriotropic drug loading, and specific cell-membrane interactions. Recently, some novel mitochondria-selective antitumor compounds known as mitocans have shown high toxicity against cancer cells. These selective compounds form vicious oxidative stress and reactive oxygen species cycles within cancer cells and ultimately push them to cell death. Nanoformulations approved by the FDA and EMA for clinical applications in cancer patients include Doxil, NK105, and Abraxane. The novel use of these NPs still faces tremendous challenges and an immense amount of research is needed to understand the proper mechanisms of cancer progression and control by these NPs. Here in this review, we summarize current advancements and novel strategies of delivering different anticancer therapeutic agents to mitochondria with the help of various nanoformulations.

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.

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.

Characterizing the Cellular Response to Nitrogen-Doped Carbon Nanocups

Carbon nanomaterials, specifically, carbon nanotubes (CNTs) have many potential applications in biology and medicine. Currently, this material has not reached its full potential for application due to the potential toxicity to mammalian cells, and the incomplete understanding of how CNTs interface with cells. The chemical composition and structural features of CNTs have been shown to directly affect their biological compatibility. The incorporation of nitrogen dopants to the graphitic lattice of CNTs results in a unique cup shaped morphology and minimal cytotoxicity in comparison to its undoped counterpart. In this study, we investigate how uniquely shaped nitrogen-doped carbon nanocups (NCNCs) interface with HeLa cells, a cervical cancer epithelial cultured cell line, and RPE-1 cells, an immortalized cultured epithelial cell line. We determined that NCNCs do not elicit a cytotoxic response in cells, and that they are uptaken via endocytosis. We have conjugated fluorescently tagged antibodies to NCNCs and shown that the protein-conjugated material is also capable of entering cells. This primes NCNCs to be a good candidate for subsequent protein modifications and applications in biological systems.

Recent Advances in Targeted Tumor Chemotherapy Based on Smart Nanomedicines

Efficacy and safety of chemotherapeutic drugs constitute two major criteria in tumor chemotherapy. Nanomedicines with tumor-targeted properties hold great promise for improving the efficacy and safety. To design targeted nanomedicines, the pathological characteristics of tumors are extensively and deeply excavated. Here, the rationale, principles, and advantages of exploiting these pathological characteristics to develop targeted nanoplatforms for tumor chemotherapy are discussed. Homotypic targeting with the ability of self-recognition to source tumors is reviewed individually. In the meanwhile, the limitations and perspective of these targeted nanomedicines are also discussed.

Application of nanodiagnostics and nanotherapy to CNS diseases

Alzheimer's disease, Parkinson's disease and stroke are the most common CNS diseases, all characterized by progressive cellular dysfunction and death in specific areas of the nervous system. Therapeutic development for these diseases has lagged behind other disease areas due to difficulties in early diagnosis, long disease courses and drug delivery challenges, not least due to the blood-brain barrier. Over recent decades, nanotechnology has been explored as a potential tool for the diagnosis, treatment and monitoring of CNS diseases. In this review, we describe the application of nanotechnology to common CNS diseases, highlighting disease pathogenesis and the underlying mechanisms and promising functional outcomes that make nanomaterials ideal candidates for early diagnosis and therapy. Moreover, we discuss the limitations of nanotechnology, and possible solutions.

Thermodynamics of Helix-Coil Transitions of Polyalanine in Open Carbon Nanotubes

Understanding structure formation in polypeptide chains and synthetic polymers encapsulated in pores is important in biology and nanotechnology. We present replica exchange molecular dynamics studies of the phase diagram for α-helix formation of capped polyalanine in nanotubes (NT) open to a water reservoir as a function of the NT diameter and hydrophobicity. A helix forms only in a narrow range of diameters, which surprisingly is comparable to the width of the ribosome tunnel. Increasing the hydrophobicity enhances helicity in the NT. Helix formation in polyalanine is driven by a small negative enthalpy and a positive entropy change at ≈300 K, in contrast to the large negative entropy change that destabilizes the helix and favors the coiled state in bulk water. There is an anticorrelation between water density inside the nanotube and structure formation. Confinement-induced helix formation depends on amino acid sequence. There is complete absence of helix in polyglutamine and polyserine confined to a open carbon nanotube.

Mitochondrial diseases: Yeast as a model for the study of suppressors

Mitochondrial (mt) tRNA gene mutations are an important cause of human morbidity and are associated with different syndromes. We have previously shown that the mitochondrial protein synthesis elongation factor EF-Tu and isolated sequences from the carboxy-terminal domain of yeast and human mt leucyl-tRNA synthetases (LeuRS), have a wide range of suppression capability among different yeast mt tRNA mutants having defective respiratory phenotype. Here we show that the rescuing capability can be restricted to a specific sequence of six amino acids from the carboxy-terminal domain of mt LeuRS. On the other hand by overexpressing a mutated version of mt EF-Tu in a yeast strain deleted for the endogenous nuclear gene we identified the specific region involved in suppression. Results support the possibility that a small peptide could correct defects associated with many mt tRNA mutations, suggesting a novel therapy for mitochondrial diseases treatment. The involvement of the mt EF-Tu in cellular heat stress response has also been suggested.

Dispersed single wall carbon nanotubes do not impact mitochondria structure or function, but technical issues during analysis could yield incorrect results

Mitochondria, which generate cellular energy, are not influenced by purified carbon nanotubes. Many traditional biological assays to determine mitochondria function give false results because of nanotube surface activity and optical interference.

Mitochondrial-targeted photosensitizer-loaded folate-albumin nanoparticle for photodynamic therapy of cancer

The objective of this study was to develop a mitochondria-targeted photosensitizer (PS) for photodynamic therapy (PDT). Herein, a porphyrin-derivative photosensitizer, pheophorbide-a (PheoA), was conjugated to carboxybutyltriphenylphosphonium (TPP) via a carbodiimide linkage to enhance mitochondrial targeting and TPP-PheoA conjugate was further loaded into folate-cholesteryl albumin (FA-chol-BSA) nanoparticles (NPs) to improve its biocompatibility. Cellular uptake results showed that TPP-PheoA and TPP-PheoA@FA-chol-BSA NPs were readily taken up by B16F10 and HeLa cells. Further in vitro studies exhibited that TPP-PheoA and its nanoparticle primarily accumulate in the mitochondria, greatly generate ROS, lead mitochondrial disruption and cell apoptosis, and have higher phototoxicity against cancer cells. In vivo bioimaging and the in vivo antitumor studies indicated that TPP-PheoA@FA-chol-BSA NP greatly accumulated in the tumor area and significantly suppress the tumor growth as compared to PheoA@FA-chol-BSA NP in tumor-bearing mice. Taken together, TPP-PheoA@FA-chol-BSA NP could be a promising mitochondria-targeted PS for image-guided PDT.

Carbon nanotubes allow capture of krypton, barium and lead for multichannel biological X-ray fluorescence imaging

The desire to study biology in situ has been aided by many imaging techniques. Among these, X-ray fluorescence (XRF) mapping permits observation of elemental distributions in a multichannel manner. However, XRF imaging is underused, in part, because of the difficulty in interpreting maps without an underlying cellular 'blueprint'; this could be supplied using contrast agents. Carbon nanotubes (CNTs) can be filled with a wide range of inorganic materials, and thus can be used as 'contrast agents' if biologically absent elements are encapsulated. Here we show that sealed single-walled CNTs filled with lead, barium and even krypton can be produced, and externally decorated with peptides to provide affinity for sub-cellular targets. The agents are able to highlight specific organelles in multiplexed XRF mapping, and are, in principle, a general and versatile tool for this, and other modes of biological imaging.

Mitochondria targeting nano agents in cancer therapeutics

Mitochondria have emerged as noteworthy therapeutic targets as their physiological functions are often altered in pathological conditions such as cancer. The electronic databases of MEDLINE, EMBASE and PubMed were searched for recent studies reporting the importance of mitochondria targeting nanoagents in cancer therapeutics. The concluding remarks of the above papers mostly confirmed the growing potential of these novel nanoagents in the area of anticancer research. Furthermore, numerous studies demonstrated the immense potential of nanocarriers in delivering mitochondria-acting compounds to their target site. Among the assemblage of nanomaterials, carbon nanotubes (CNTs) are becoming more prominent for drug delivery due to favorable attributes including their unique shape, which promotes cellular uptake, and large aspect ratio that facilitates conjugation of bioactive molecules on their surface. The present review focused on the current view of variable options available in mitochondria-targeting anticancer therapeutics. It may be concluded that improvements are essential for its establishment as a gold standard therapeutic option especially in the clinical setting.

Mitochondria-Targeted Hydroxyapatite Nanoparticles for Selective Growth Inhibition of Lung Cancer in Vitro and in Vivo

Lung cancer is the leading cause of cancer-related mortality worldwide. Most patients have metastases at the time of diagnosis, thus demanding development of more effective and specific agents. In this study, the specific anticancer effect of hydroxyapatite nanoparticles (HAPNs) to human lung cancer cells (A549) and the underlying mechanisms were investigated, using normal bronchial epithelial cells (16HBE) as the control. Rod-shaped HAPNs (∼10 nm in width and 50 nm in length) were prepared by aqueous precipitation method. Without any further functionalization and drug loading, HAPNs selectively inhibited cancer-cell proliferation. Their efficient mitochondrial targeting correlated strongly with decreased mitochondrial membrane potential and induction of mitochondria-dependent apoptosis in A549 cells. Caveolae-mediated endocytosis via lysosome trafficking was observed to be a prominent internalization pathway for HAPNs in both A549 and 16HBE cells. However, more nanoparticles were taken up into A549 cells. HAPNs triggered a sustained elevation of intracellular calcium concentration ([Ca²⁺]_i) in cancer cells but only a transitory increase in normal control cells. In a nude mouse lung cancer model with xenotransplanted A549 cells, HAPN treatment demonstrated nearly 40% tumor growth inhibition without apparent side effect. These results demonstrated that the enhanced cellular uptake and mitochondrial targeting of HAPNs, together with the prolonged elevation of [Ca²⁺]_i in A549 cells, could result in the cancer-specific cytotoxicity of HAPNs. Thus, HAPNs might be a promising agent or mitochondria-targeted delivery system for effective lung cancer therapy.

A Mitocentric View of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease with an increasing morbidity, mortality, and economic cost. Plaques formed by amyloid beta peptide (Aβ) and neurofibrillary tangles formed by microtubule-associated protein tau are two main characters of AD. Though previous studies have focused on Aβ and tau and got some progressions on their toxicity mechanisms, no significantly effective treatments targeting the Aβ and tau have been found. However, it is worth noting that mounting evidences showed that mitochondrial dysfunction is an early event during the process of AD pathologic changes. What is more, these studies also showed an obvious association between mitochondrial dysfunction and Aβ/tau toxicity. Furthermore, both genetic and environmental factors may increase the oxidative stress and the mitochondria are also the sensitive target of ROS, which may form a vicious feedback between mitochondrial dysfunction and oxidative stress, eventually resulting in deficient energy, synaptic failure, and cell death. This article reviews the previous related studies from different aspects and concludes the critical roles of mitochondrial dysfunction in AD, suggesting a different route to AD therapy, which may guide the research and treatment direction.

Mitochondria and neurodegenerative diseases: the promising role of nanotechnology in targeted drug delivery

INTRODUCTION

Neurodegenerative diseases (NDs) represent a group of different clinical entities that, despite the specific primary etiologies, share a common signature in terms of a general mitochondrial dysfunction with consequent oxidative stress accumulation. As these two events occur early during neurodegenerative process, they could be considered ideal therapeutic targets. Areas covered: This review describes the nanotechnologies explored for the specific targeted delivery of drugs, in order to precisely direct molecules into the intended site, where they can practice their therapeutic effects. Expert opinion: Conventional drug delivery systems cannot provide adequate restoration and connection patterns that are essential for a functional recovery in NDs. Since orally delivered antioxidants are easily destroyed by acids and enzymes, only a small portion of consumed antioxidants gets absorbed, leading to low bioavailability and low concentration at the target site. In this scenario, the identification of new proenergetic drugs, in combination with the development of methods for selectively delivering biologically active molecules into mitochondria, will potentially launch new therapeutic approaches for the treatment of NDs, where energetic imbalance plays a central role.

Delivering Single-Walled Carbon Nanotubes to the Nucleus Using Engineered Nuclear Protein Domains

Single-walled carbon nanotubes (SWCNTs) have great potential for cell-based therapies due to their unique intrinsic optical and physical characteristics. Consequently, broad classes of dispersants have been identified that individually suspend SWCNTs in water and cell media in addition to reducing nanotube toxicity to cells. Unambiguous control and verification of the localization and distribution of SWCNTs within cells, particularly to the nucleus, is needed to advance subcellular technologies utilizing nanotubes. Here we report delivery of SWCNTs to the nucleus by noncovalently attaching the tail domain of the nuclear protein lamin B1 (LB1), which we engineer from the full-length LMNB1 cDNA. More than half of this low molecular weight globular protein is intrinsically disordered but has an immunoglobulin-fold composed of a central hydrophobic core, which is highly suitable for associating with SWCNTs, stably suspending SWCNTs in water and cell media. In addition, LB1 has an exposed nuclear localization sequence to promote active nuclear import of SWCNTs. These SWCNTs-LB1 dispersions in water and cell media display near-infrared (NIR) absorption spectra with sharp van Hove peaks and an NIR fluorescence spectra, suggesting that LB1 individually disperses nanotubes. The dispersing capability of SWCNTs by LB1 is similar to that by albumin proteins. The SWCNTs-LB1 dispersions with concentrations ≥150 μg/mL (≥30 μg/mL) in water (cell media) remain stable for ≥75 days (≥3 days) at 4 °C (37 °C). Further, molecular dynamics modeling of association of LB1 with SWCNTs reveal that the exposure of the nuclear localization sequence is independent of LB1 binding conformation. Measurements from confocal Raman spectroscopy and microscopy, NIR fluorescence imaging of SWCNTs, and fluorescence lifetime imaging microscopy show that millions of these SWCNTs-LB1 complexes enter HeLa cells, localize to the nucleus of cells, and interact with DNA. We postulate that the modification of native cellular proteins as noncovalent dispersing agents to provide specific transport will open new possibilities to utilize both SWCNT and protein properties for multifunctional subcellular targeting applications. Specifically, nuclear targeting could allow delivery of anticancer therapies, genetic treatments, or DNA to the nucleus.

Evaluation of the efficacy of carbon nanotubes for delivering peptides into mitochondria

Future therapy for mitochondrial pathologies: CKKSFLSPRTALINFLVK peptide from mitochondrial-LeuRS has a mitochondrial targeting activity when conjugated with multi-walled carbon nanotubes.

Tumor therapy: targeted drug delivery systems

The review highlights the main targeted drug delivery systems for tumor therapy, including the targeting sites, strategies, mechanisms and preclinical/clinical trials.

Under the lens: carbon nanotube and protein interaction at the nanoscale

The combination of the very different chemical natures of carbon nanotubes (CNTs) and proteins gives rise to systems with unprecedented performance, thanks to a rich pool of very diverse chemical, electronic, catalytic and biological properties. Here we review recent advances in the field, including innovative and imaginative aspects from a nanoscale point of view. The tubular nature of CNTs allows for internal protein encapsulation, and also for their external coating by protein cages, affording bottom-up ordering of molecules in hierarchical structures. To achieve such complex systems it is imperative to master the intermolecular forces between CNTs and proteins, including geometry effects (e.g. CNT diameter and curvature) and how they translate into changes in the local environment (e.g. water entropy). The type of interaction between proteins and CNTs has important consequences for the preservation of their structure and, in turn, function. This key aspect cannot be neglected during the design of their conjugation, be it covalent, non-covalent, or based on a combination of both methods. The review concludes with a brief discussion of the very many applications intended for CNT-protein systems that go across various fields of science, from industrial biocatalysis to nanomedicine, from innovative materials to biotechnological tools in molecular biology research.

Noncovalent Ruthenium(II) Complexes-Single-Walled Carbon Nanotube Composites for Bimodal Photothermal and Photodynamic Therapy with Near-Infrared Irradiation

To enhance the efficacy and optimize the treatment of cancers, the integration of multimodal treatment strategies leading to synergistic effects is a promising approach. The coassembly of multifunctional agents for systematic therapies has received considerable interest in cancer treatment. Herein, Ru(II) complex-functionalized single-walled carbon nanotubes (Ru@SWCNTs) are developed as nanotemplates for bimodal photothermal and two-photon photodynamic therapy (PTT-TPPDT). SWCNTs have the ability to load a great amount of Ru(II) complexes (Ru1 or Ru2) via noncovalent π-π interactions. The loaded Ru(II) complexes are efficiently released by the photothermal effect of irradiation from an 808 nm diode laser (0.25 W/cm(2)). The released Ru(II) complexes produce singlet oxygen species ((1)O2) upon two-photon laser irradiation (808 nm, 0.25 W/cm(2)) and can be used as a two-photon photodynamic therapy (TPPDT) agent. Based on the combination of photothermal therapy and two-photon photodynamic therapy, Ru@SWCNTs have greater anticancer efficacies than either PDT using Ru(II) complexes or PTT using SWCNTs in two-dimensional (2D) cancer cell and three-dimensional (3D) multicellular tumor spheroid (MCTS) models. Furthermore, in vivo tumor ablation is achieved with excellent treatment efficacy under a diode laser (808 nm) irradiation at the power density of 0.25 W/cm(2) for 5 min. This study examines an efficacious bimodal PTT and TPPDT nanoplat form for the development of cancer therapeutics.

Discovery, Synthesis, and Optimization of Diarylisoxazole-3-carboxamides as Potent Inhibitors of the Mitochondrial Permeability Transition Pore

The mitochondrial permeability transition pore (mtPTP) is a Ca(2+) -requiring mega-channel which, under pathological conditions, leads to the deregulated release of Ca(2+) and mitochondrial dysfunction, ultimately resulting in cell death. Although the mtPTP is a potential therapeutic target for many human pathologies, its potential as a drug target is currently unrealized. Herein we describe an optimization effort initiated around hit 1, 5-(3-hydroxyphenyl)-N-(3,4,5-trimethoxyphenyl)isoxazole-3-carboxamide, which was found to possess promising inhibitory activity against mitochondrial swelling (EC50 <0.39 μM) and showed no interference on the inner mitochondrial membrane potential (rhodamine 123 uptake EC50 >100 μM). This enabled the construction of a series of picomolar mtPTP inhibitors that also potently increase the calcium retention capacity of the mitochondria. Finally, the therapeutic potential and in vivo efficacy of one of the most potent analogues, N-(3-chloro-2-methylphenyl)-5-(4-fluoro-3-hydroxyphenyl)isoxazole-3-carboxamide (60), was validated in a biologically relevant zebrafish model of collagen VI congenital muscular dystrophies.

Treatment Strategies that Enhance the Efficacy and Selectivity of Mitochondria-Targeted Anticancer Agents

Nearly a century has passed since Otto Warburg first observed high rates of aerobic glycolysis in a variety of tumor cell types and suggested that this phenomenon might be due to an impaired mitochondrial respiratory capacity in these cells. Subsequently, much has been written about the role of mitochondria in the initiation and/or progression of various forms of cancer, and the possibility of exploiting differences in mitochondrial structure and function between normal and malignant cells as targets for cancer chemotherapy. A number of mitochondria-targeted compounds have shown efficacy in selective cancer cell killing in pre-clinical and early clinical testing, including those that induce mitochondria permeability transition and apoptosis, metabolic inhibitors, and ROS regulators. To date, however, none has exhibited the standards for high selectivity and efficacy and low toxicity necessary to progress beyond phase III clinical trials and be used as a viable, single modality treatment option for human cancers. This review explores alternative treatment strategies that have been shown to enhance the efficacy and selectivity of mitochondria-targeted anticancer agents in vitro and in vivo, and may yet fulfill the clinical promise of exploiting the mitochondrion as a target for cancer chemotherapy.

A mitochondrial-targeting and NO-based anticancer nanosystem with enhanced photo-controllability and low dark-toxicity

Compared to the generation of singlet oxygen in photodynamic therapy, photo-generation of nitric oxide (NO) would not be limited by the concentration of molecular oxygen. However, therapeutic applications of exogenous nitric oxide are usually limited by its short half-life and its vulnerability to many biological substances, thus straightforward and precise control over NO delivery may be critical to its therapeutic effects. Herein, we demonstrate a mitochondrial-targeting and photoactive NO-releasing system as an anticancer drug. Fabricated by covalently incorporating a photo-responsive NO-donor and a mitochondrial targeting ligand onto carbon dots, this nanosystem exhibits a multi-functional nature which combines mitochondrial-targeting, photocontrollable NO-releasing and cell imaging. Upon cellular internalization, the nanosystem could target mitochondria effectively. Furthermore, the system displays little dark toxicity under physiological temperature; but upon light irradiation, it could release NO, efficiently damage mitochondria and consequently cause prominent apoptosis of cancer cells. Moreover, evaluated by using MTT assay, this nanosystem shows high cytotoxicity towards two cancer cell lines. These observations provide new insights for exploiting NO in disease therapy.

Targeted nanoparticles in mitochondrial medicine

Mitochondria, the so-called 'energy factory of cells' not only produce energy but also contribute immensely in cellular mortality management. Mitochondrial dysfunctions result in various diseases including but not limited to cancer, atherosclerosis, and neurodegenerative diseases. In the recent years, targeting mitochondria emerged as an attractive strategy to control mitochondrial dysfunction-related diseases. Despite the desire to direct therapeutics to the mitochondria, the actual task is more difficult due to the highly complex nature of the mitochondria. The potential benefits of integrating nanomaterials with properties such as biodegradability, magnetization, and fluorescence into a single object of nanoscale dimensions can lead to the development of hybrid nanomedical platforms for targeting therapeutics to the mitochondria. Only a handful of nanoparticles based on metal oxides, gold nanoparticles, dendrons, carbon nanotubes, and liposomes were recently engineered to target mitochondria. Most of these materials face tremendous challenges when administered in vivo due to their limited biocompatibility. Biodegradable polymeric nanoparticles emerged as eminent candidates for effective drug delivery. In this review, we highlight the current advancements in the development of biodegradable nanoparticle platforms as effective targeting tools for mitochondrial medicine.

Peptide-based biomaterials. Linking l-tyrosine and poly l-tyrosine to graphene oxide nanoribbons

GONRs grafted to tyrosine and poly-tyrosine can be used as biophysical tools for studying the oxidability of proteins or as fluorescent probes for detecting molecular or physical events.

Differential sub-cellular processing of single-wall carbon nanotubes via interfacial modifications

Real-space and fluorescence lifetime imaging reveal that non-covalently attached dispersing agents influence sub-cellular trafficking and localization of carbon nanotubes.

Enhanced cytotoxicity to cancer cells by mitochondria-targeting MWCNTs containing platinum(IV) prodrug of cisplatin

Among the arsenal of nano-materials, carbon nanotubes (CNTs) are becoming more prominent due to favorable attributes including their unique shape, which promotes cellular-uptake, and large aspect-ratio that facilitates functionalization of bioactive molecules on their surface. In this study, multi-walled carbon nanotubes (MWCNTs) were functionalized with either mitochondrial-targeting fluorescent rhodamine-110 (MWCNT-Rho) or non-targeting fluorescein (MWCNT-Fluo). Despite structural similarities, MWCNT-Rho associated well with mitochondria (ca. 80% co-localization) in contrast to MWCNT-Fluo, which was poorly localized (ca. 21% co-localization). Additionally, MWCNT-Rho entrapping platinum(IV) pro-drug of cisplatin (PtBz) displayed enhanced potency (IC50 = 0.34 ± 0.07 μM) compared to a construct based on MWCNT-Fluo (IC50 ≥ 2.64 μM). Concurrently, preliminary in vitro toxicity evaluation revealed that empty MWCNT-Rho neither decreased cell viability significantly nor interfered with mitochondrial membrane-potential, while seemingly being partially expelled from cells. Due to its targeting capability and apparent lack of cytotoxicity, MWCNT-Rho complex was used to co-encapsulate PtBz and a chemo-potentiator, 3-bromopyruvate (BP), and the resulting MWCNT-Rho(PtBz+BP) construct demonstrated superior efficacy over PtBz free drug in several cancer cell lines tested. Importantly, a 2-fold decrease in mitochondrial potential was observed, implying that mitochondrial targeting of compounds indeed incurred additional intended damage to mitochondria.