Intracellular uptake and trafficking of Pluronic micelles in drug-sensitive and MDR cells: effect on the intracellular drug localization

Canvassing Prospects of Glyco-Nanovaccines for Developing Cross-Presentation Mediated Anti-Tumor Immunotherapy

In view of the severe downsides of conventional cancer therapies, the quest of developing alternative strategies still remains of critical importance. In this regard, antigen cross-presentation, usually employed by dendritic cells (DCs), has been recognized as a potential solution to overcome the present impasse in anti-cancer therapeutic strategies. It has been established that an elevated cytotoxic T lymphocyte (CTL) response against cancer cells can be achieved by targeting receptors expressed on DCs with specific ligands. Glycans are known to serve as ligands for C-type lectin receptors (CLRs) expressed on DCs, and are also known to act as a tumor-associated antigen (TAA), and, thus, can be harnessed as a potential immunotherapeutic target. In this scenario, integrating the knowledge of cross-presentation and glycan-conjugated nanovaccines can help us to develop so called 'glyco-nanovaccines' (GNVs) for targeting DCs. Here, we briefly review and analyze the potential of GNVs as the next-generation anti-tumor immunotherapy. We have compared different antigen-presenting cells (APCs) for their ability to cross-present antigens and described the potential nanocarriers for tumor antigen cross-presentation. Further, we discuss the role of glycans in targeting of DCs, the immune response due to pathogens, and imitative approaches, along with parameters, strategies, and challenges involved in cross-presentation-based GNVs for cancer immunotherapy. It is known that the effectiveness of GNVs in eradicating tumors by inducing strong CTL response in the tumor microenvironment (TME) has been largely hindered by tumor glycosylation and the expression of different lectin receptors (such as galectins) by cancer cells. Tumor glycan signatures can be sensed by a variety of lectins expressed on immune cells and mediate the immune suppression which, in turn, facilitates immune evasion. Therefore, a sound understanding of the glycan language of cancer cells, and glycan-lectin interaction between the cancer cells and immune cells, would help in strategically designing the next-generation GNVs for anti-tumor immunotherapy.

Formulation of Nanomicelles Loaded with Cannabidiol as a Platform for Neuroprotective Therapy

The present study is focused on the development of cannabidiol-loaded polymeric nanomicelles as a drug delivery system with neuroprotective effects. Cannabidiol was loaded in Pluronic micelles (Pluronic P123 or its combination with Pluronic F127) possessing an average diameter smaller than 50 nm and high encapsulation efficiency for the hydrophobic drug (80% and 84%, respectively). The successful encapsulation and transformation of cannabidiol in amorphous phase were observed by IR spectroscopy and X-ray diffraction, respectively. Studies with neuroblastoma cells (SH-SY5Y and Neuro-2a) showed that the pure cannabidiol caused a dose-dependent reduction of cell viability, whereas its loading into the micelles decreased cytotoxicity. Further, neuroprotective effects of pure and micellar cannabidiol were examined in a model of H₂O₂-induced oxidative stress in both neuroblastoma cells. The pre-treatment of cell lines with cannabidiol loaded into the mixed Pluronic P123/F127 micelles exerted significantly stronger protection against the oxidative stress compared to pure cannabidiol and cannabidiol in single Pluronic P123 micelles. Interestingly, the empty mixed P123/F127 micelles demonstrated protective activity against the oxidative stress. In conclusion, the study revealed the opportunity to formulate a new drug delivery system of cannabidiol, in particular nanosized micellar aqueous dispersion, that could be considered as a perspective platform for cannabidiol application in neurodegenerative diseases.

Emerging nanotechnology-based therapeutics to combat multidrug-resistant cancer

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

New Advances in Biomedical Application of Polymeric Micelles

In the last decade, nanomedicine has arisen as an emergent area of medicine, which studies nanometric systems, namely polymeric micelles (PMs), that increase the solubility and the stability of the encapsulated drugs. Furthermore, their application in dermal drug delivery is also relevant. PMs present unique characteristics because of their unique core-shell architecture. They are colloidal dispersions of amphiphilic compounds, which self-assemble in an aqueous medium, giving a structure-type core-shell, with a hydrophobic core (that can encapsulate hydrophobic drugs), and a hydrophilic shell, which works as a stabilizing agent. These features offer PMs adequate steric protection and determine their hydrophilicity, charge, length, and surface density properties. Furthermore, due to their small size, PMs can be absorbed by the intestinal mucosa with the drug, and they transport the drug in the bloodstream until the therapeutic target. Moreover, PMs improve the pharmacokinetic profile of the encapsulated drug, present high load capacity, and are synthesized by a reproducible, easy, and low-cost method. In silico approaches have been explored to improve the physicochemical properties of PMs. Based on this, a computer-aided strategy was developed and validated to enable the delivery of poorly soluble drugs and established critical physicochemical parameters to maximize drug loading, formulation stability, and tumor exposure. Poly(2-oxazoline) (POx)-based PMs display unprecedented high loading concerning water-insoluble drugs and over 60 drugs have been incorporated in POx PMs. Among various stimuli, pH and temperature are the most widely studied for enhanced drug release at the site of action. Researchers are focusing on dual (pH and temperature) responsive PMs for controlled and improved drug release at the site of action. These dual responsive systems are mainly evaluated for cancer therapy as certain malignancies can cause a slight increase in temperature and a decrease in the extracellular pH around the tumor site. This review is a compilation of updated therapeutic applications of PMs, such as PMs that are based on Pluronics^®, micelleplexes and Pox-based PMs in several biomedical applications.

Poloxamer 188 - quercetin formulations amplify in vitro ganciclovir antiviral activity against cytomegalovirus

Treatment of human cytomegalovirus (CMV) infection requires long-term administration of nucleoside analog antivirals such as ganciclovir (GCV), a therapy frequently limited by GCV-induced toxicity. Here, combining GCV treatment with two bioactive excipients, poloxamer 188 and quercetin, was investigated in vitro to reduce GCV dosage. Quercetin is a natural flavonoid exhibiting antiviral activity against CMV by a mechanism distinct from GCV, but is poorly soluble, limiting its use as a therapeutic. To overcome this challenge, quercetin was co-formulated with poloxamer 188 (P188, Pluronic ® F68). Quercetin-P188 (QP188) formulations yielded only modest CMV viral inhibition, with a selectivity index of 11.4, contrasted with a GCV selectivity index of 95. More significantly, when coadministered with GCV, QP188 exhibited an additive or synergistic interaction in subtherapeutic ranges of GCV. Fluorescence microscopy revealed QP188 accumulation in fibroblast mitochondria, suggesting that the excipient may modulate mitochondrial processes relevant to CMV infection. GCV antiviral therapy augmented with poloxamer-solubilized quercetin may be a viable approach to maintain CMV inhibition while lowering GCV doses, translating to reduced associated toxicity.

Study on the preparation and activity of intelligent response poly(lactic-co-glycolic acid)-ss-polyethylene glycol copolymer micelles

Amphiphilic polymer micellar carriers are the most commonly used nanocarriers for oral delivery of hydrophobic drugs because their hydrophilic shell can avoid the recognition of the reticuloendothelial system (RES), has excellent drug-carrying capacity, and protect the drug from inactivation in the gastrointestinal fluid. The polymer micelle shell can enter cancer cells by endocytosis, and autophagy in cells, degradation by lysosomal pathway, so as to release drugs, prolong the circulation time of drugs in vivo, and then achieve the effect of drug sustained release. In this study, the glutathione-responsive PLGA-ss-PEG loaded paclitaxel (PTX) micelles (PLGA-ss-PEG-PTX) were developed for anticancer therapy. With its long-term circulation and EPR (enhanced permeability and retention) effect, and the micelle had disulfide bond, which could be used as the recognition group of tumor microenvironment, so that the PLGA-ss-PEG-PTX could specifically accumulate at the tumor site, so as to produce better anti-tumor effect. The PLGA-ss-PEG-PTX was formulated by the emulsification method in this study. The drug loading was about 21.54%, the entrapment efficiency was about 94.2%, and the particle size range was about 90 nm with narrow particle size distribution. Cytotoxicity and embryonic toxicity experiments were carried out using mouse lung cancer cells (LLC) and zebrafish fertilized eggs. It was proved that the low concentration of blank micelles had little cytotoxicity, but high concentration of blank micelles had adverse effects on zebrafish embryonic development, resulting in embryonic malformation. The uptake of drugs by cancer cells was studied by a high connotation cell imaging analysis system. The experiments showed that the drug molecules encapsulated in micelles could achieve higher uptake by cells compared with free drug molecules. In addition, in the in vivo evaluation experiment of drugs, the PLGA-ss-PEG-PTX could significantly enhance the therapeutic effect of the PTX, improve its water solubility, and improve its oral bioavailability.

Comprehensive review on ultrasound-responsive theranostic nanomaterials: mechanisms, structures and medical applications

The field of theranostics has been rapidly growing in recent years and nanotechnology has played a major role in this growth. Nanomaterials can be constructed to respond to a variety of different stimuli which can be internal (enzyme activity, redox potential, pH changes, temperature changes) or external (light, heat, magnetic fields, ultrasound). Theranostic nanomaterials can respond by producing an imaging signal and/or a therapeutic effect, which frequently involves cell death. Since ultrasound (US) is already well established as a clinical imaging modality, it is attractive to combine it with rationally designed nanoparticles for theranostics. The mechanisms of US interactions include cavitation microbubbles (MBs), acoustic droplet vaporization, acoustic radiation force, localized thermal effects, reactive oxygen species generation, sonoluminescence, and sonoporation. These effects can result in the release of encapsulated drugs or genes at the site of interest as well as cell death and considerable image enhancement. The present review discusses US-responsive theranostic nanomaterials under the following categories: MBs, micelles, liposomes (conventional and echogenic), niosomes, nanoemulsions, polymeric nanoparticles, chitosan nanocapsules, dendrimers, hydrogels, nanogels, gold nanoparticles, titania nanostructures, carbon nanostructures, mesoporous silica nanoparticles, fuel-free nano/micromotors.

Polymeric micelles in drug delivery: An insight of the techniques for their characterization and assessment in biorelevant conditions

Polymeric micelles, i.e. aggregation colloids formed in solution by self-assembling of amphiphilic polymers, represent an innovative tool to overcome several issues related to drug administration, from the low water-solubility to the poor drug permeability across biological barriers. With respect to other nanocarriers, polymeric micelles generally display smaller size, easier preparation and sterilization processes, and good solubilization properties, unfortunately associated with a lower stability in biological fluids and a more complicated characterization. Particularly challenging is the study of their interaction with the biological environment, essential to predict the real in vivo behavior after administration. In this review, after a general presentation on micelles features and properties, different characterization techniques are discussed, from the ones used for the determination of micelles basic characteristics (critical micellar concentration, size, surface charge, morphology) to the more complex approaches used to figure out micelles kinetic stability, drug release and behavior in the presence of biological substrates (fluids, cells and tissues). The techniques presented (such as dynamic light scattering, AFM, cryo-TEM, X-ray scattering, FRET, symmetrical flow field-flow fractionation (AF4) and density ultracentrifugation), each one with their own advantages and limitations, can be combined to achieve a deeper comprehension of polymeric micelles in vivo behavior. The set-up and validation of adequate methods for micelles description represent the essential starting point for their development and clinical success.

Pluronic-based nanovehicles: Recent advances in anticancer therapeutic applications

Pluronics are a class of amphiphilic tri-block copolymers with wide pharmaceutical applicability. In the past decades, the ability to form biocompatible nanosized micelles was exploited to formulate stable drug nanovehicles with potential use in antitumor therapy. Due to the great potential for tuning physical and structural properties of Pluronic unimers, a panoply of drug or polynucleotide-loaded micelles was prepared and tested for their antitumoral activity. The attractive inherent antitumor properties of Pluronic polymers in combination with cell targeting and stimuli-responsive ligands greatly improved antitumoral therapeutic effects of tested drugs. In spite of that, the extraordinary complexity of biological challenges in the delivery of micellar drug payload makes their therapeutic potential still not exploited to the fullest. In this review paper we attempt to present the latest developments in the field of Pluronic based nanovehicles and their application in anticancer therapy with an overview of the chemistry involved in the preparation of these nanovehicles.

Surface-modified polymeric nanoparticles for drug delivery to cancer cells

INTRODUCTION

The utilization of polymeric nanoparticles, as drug payloads, has been extensively prevailed in cancer therapy. However, the precise distribution of these nanocarriers is restrained by various physiological and cellular obstacles. Nanoparticles must avoid nonspecific interactions with healthy cells and in vivo compartments to circumvent these barriers. Since in vivo interactions of nanoparticles are mainly dependent on surface properties of nanoparticles, efficient control on surface constituents is necessary for the determination of nanoparticles' fate in the body.

AREAS COVERED

In this review, the surface-modified polymeric nanoparticles and their utilization in cancer treatment were elaborated. First, the interaction of nanoparticles with numerous in vivo barriers was highlighted. Second, different strategies to overcome these obstacles were described. Third, some inspiring examples of surface-modified nanoparticles were presented. Later, fabrication and characterization methods of surface-modified nanoparticles were discussed. Finally, the applications of these nanoparticles in different routes of treatments were explored.

EXPERT OPINION

Surface modification of anticancer drug-loaded polymeric nanoparticles can enhance the efficacy, selective targeting, and biodistribution of the anticancer drug at the tumor site.

Multifunctional cubic liquid crystalline nanoparticles for chemo- and photodynamic synergistic cancer therapy

With the aim of engineering multifunctional nanoparticles useful for cancer therapy, a diketopyrrolopyrrole-porphyrin based photosensitizer was here conjugated to a block copolymer (Pluronic F108), and used to stabilize in water lipidic cubic liquid crystalline nanoparticles (cubosomes), also loaded with the antineoplastic agent docetaxel. The physicochemical characterization by SAXS, DLS, and cryo-TEM demonstrated that the formulation consisted of cubosomes, about 150 nm in size, possessing a bicontinuous cubic structure (space group Pn3m). The cellular imaging experiments proved that these nanoparticles localized in lysosomes and mitochondria, while cytotoxicity tests evidenced a slight but significant synergistic effect which, after irradiation, increased the toxicity induced by docetaxel alone, allowing further reduction of cell viability.

Evaluation of polyvinylpyrrolidone and block copolymer micelle encapsulation of serine chlorin e6 and chlorin e4 on their reactivity towards albumin and transferrin and their cell uptake

Encapsulation of porphyrinic photosensitizers (PSs) into polymeric carriers plays an important role in enhancing their efficiency as drugs in photodynamic therapy (PDT). Porphyrin aggregation and low solubility as well as the preservation of the advantageous photophysical properties pose a challenge on the design of efficient PS-carrier systems. Block copolymer micelles (BCMs) and polyvinylpyrrolidone (PVP) are promising drug delivery vehicles for physical entrapment of PSs. BCMs exhibit enhanced dynamics as compared to the less flexible PVP network. In the current work the question is addressed how these different dynamics affect PS encapsulation, release from the carrier, reaction with serum proteins, and cellular uptake. The porphyrinic compounds serine-amide of chlorin e6 (SerCE) and chlorin e4 (CE4) were used as model PSs with different lipophilicity and aggregation properties. ¹H NMR and fluorescence spectroscopy were applied to study their interactions with PVP and BCMs consisting of Kolliphor P188 (KP). Both chlorins were well encapsulated by the carriers and had improved photophysical properties. Compared to SerCE, the more lipophilic CE4 exhibited stronger hydrophobic interactions with the BCM core, stabilizing the system and preventing exchange with the surrounding medium as was shown by NMR NOESY and DOSY experiments. PVP and BCMs protected the encapsulated chlorins against interaction with human transferrin (Tf). However, SerCE and CE4 were released from BCMs in favor of binding to human serum albumin (HSA) while PVP prevented interaction with HSA. Fluorescence spectroscopic studies revealed that HSA binds to the surface of PVP forming a protein corona. PVP and BCMs reduced cellular uptake of the chlorins. However, encapsulation into BCMs resulted in more efficient cell internalization for CE4 than for SerCE. HSA significantly lowered both, free and carrier-mediated cell uptake for CE4 and SerCE. In conclusion, PVP appears as the more universal delivery system covering a broad range of host molecules with respect to polarity, whereas BCMs require a higher drug-carrier compatibility. Poorly soluble hydrophobic PSs benefit stronger from BCM-type carriers due to enhanced bioavailability through disaggregation and solubilization allowing for more efficient cell uptake. In addition, increased PS-carrier hydrophobic interactions have a stabilizing effect. For more hydrophilic PSs, the main advantage of polymeric carriers like PVP or poloxamer micelles lies in their protection during the transport through the bloodstream. HSA binding plays an important role for drug release and cell uptake in carrier-mediated delivery to the target tissue.

Targeted and Synergic Glioblastoma Treatment: Multifunctional Nanoparticles Delivering Verteporfin as Adjuvant Therapy for Temozolomide Chemotherapy

Despite advances in cancer therapies, glioblastoma multiforme treatment remains inefficient due to the brain-blood barrier (BBB) inhibitory activity and to the low temozolomide (TMZ) chemotherapeutic selectivity. To improve therapeutic outcomes, in this work we propose two strategies, (i) photodynamic therapy (PDT) as adjuvant treatment and (ii) engineering of multifunctional theranostic/targeted nanoparticles ( m-NPs) that integrate biotin as a targeting moiety with rhodamine-B as a theranostic agent in pluronic P85/F127 copolymers. These smart m-NPs can surmount the BBB and coencapsulate multiple cargoes under optimized conditions. Overall, the present study conducts a rational m-NP design, characterization, and optimizes the formulation conditions. Confocal microscopy studies on T98-G, U87-MG, and U343 glioblastoma cells and on NIH-3T3 normal fibroblast cells show that the m-NPs and the encapsulated drugs are selectively taken up by tumor cells presenting a broad intracellular distribution. The formulations display no toxicity in the absence of light and are not toxic to healthy cells, but they exert a robust synergic action in cancer cells in the case of concomitant PDT/TMZ treatment, especially at low TMZ concentrations and higher light doses, as demonstrated by nonlinear dose-effect curves based on the Chou-Talalay method. The results evidenced different mechanisms of action related to the disjoint cell cycle phases at the optimal PDT/TMZ ratio. This effect favors synergism between the PDT and the chemotherapy with TMZ, enhances the antiproliferative effect, and overcomes cross-resistance mechanisms. These results point out that m-NP-based PDT adjuvant therapy is a promising strategy to improve TMZ-based glioblastoma multiforme treatments.

Interaction Pathways between Plasma Membrane and Block Copolymer Micelles

In this work, the interactions between block copolymer micelles (BCMs) and plasma membranes were investigated by performing coarse-grained molecular dynamics (CGMD) simulations. Different binding strengths between the BCMs and the membranes were tested, and four interaction pathways were discovered: attachment, semiendocytosis, endocytosis, and fusion. Endocytosis was the most efficient way for the BCMs to be taken up, and fusion could lead to cytotoxicity. Unlike rigid particles, deformation of the BCMs strongly affected the interaction pathways. We examined the effects of changing the aggregation number of the BCMs (N_agg), the chain length of the polymer (N_b), and the chain stiffness of the hydrophobic block (k_a), and we learned that smaller N_agg and lower N_b could lead to weaker cellular uptake capacities, whereas larger N_agg and higher N_b gave rise to higher cytotoxicities. Moreover, a weaker chain stiffness of the hydrophobic block could be more favorable for obtaining BCMs with higher internalization efficacies and lower cytotoxicities. The results of these simulations could aid in the design of BCMs with desirable cellular internalization capacities and lower cytotoxicities. Such BCMs could be useful in drug-delivery systems.

Post-polymerization functionalization of poly(ethylene oxide)–poly(β-6-heptenolactone) diblock copolymers to tune properties and self-assembly

Copolymers were synthesized and functionalized with a variety of moieties to tune self-assembly and install drugs or fluorescent dyes.

Multifunctional theranostic Pluronic mixed micelles improve targeted photoactivity of Verteporfin in cancer cells

Nanotechnology development provides new strategies to treat cancer by integration of different treatment modalities in a single multifunctional nanoparticle. In this scenario, we applied the multifunctional Pluronic P123/F127 mixed micelles for Verteporfin-mediated photodynamic therapy in PC3 and MCF-7 cancer cells. Micelles functionalization aimed the targeted delivery by the insertion of biotin moiety on micelle surface and fluorescence image-based through rhodamine-B dye conjugation in the polymer chains. Multifunctional Pluronics formed spherical nanoparticulated micelles that efficiently encapsulated the photosensitizer Verteporfin maintaining its favorable photophysical properties. Lyophilized formulations were stable at least for 6months and readily reconstituted in aqueous media. The multifunctional micelles were stable in protein-rich media due to the dual Pluronic mixed micelles characteristic: high drug loading capacity provided by its micellar core and high kinetic stability due its biocompatible shell. Biotin surface functionalized micelles showed higher internalization rates due biotin-mediated endocytosis, as demonstrated by competitive cellular uptake studies. Rhodamine B-tagged micelles allowed monitoring cellular uptake and intracellular distribution of the formulations. Confocal microscopy studies demonstrated a larger intracellular distribution of the formulation and photosensitizer, which could drive Verteporfin to act on multiple cell sites. Formulations were not toxic in the dark condition, but showed high Verteporfin-induced phototoxicity against both cancer cell lines at low drug and light doses. These results point Verteporfin-loaded multifunctional micelles as a promising tool to further developments in photodynamic therapy of cancer.

Targeted Drug Delivery in Cancer Therapy

Chemotherapy has been the main modality of treatment for cancer patients; however, its success rate remains low, primarily due to limited accessibility of drugs to the tumor tissue, their intolerable toxicity, development of multi-drug resistance, and the dynamic heterogeneous biology of the growing tumors. Better understanding of tumor biology in recent years and new targeted drug delivery approaches that are being explored using different nanosystems and bioconjugates provide optimism in developing successful cancer therapy. This article reviews the possibilities and challenges for targeted drug delivery in cancer therapy.

Interactions of Pluronic nanocarriers with 2D and 3D cell cultures: Effects of PEO block length and aggregation state

This work reveals how the physicochemical properties of Pluronic block copolymers influence significantly their interactions with cancer cells, whether in monolayer or spheroid cultures, and how different clinical applications can be foreseen. Two-dimensional (2D) and three-dimensional (3D) cell culture models were used to investigate the interactions of Pluronic carriers with different PEO block length and aggregation state (unimers versus cross-linked micelles) in HeLa and U87 cancer cells. Stabilized micelles of Pluronic P94 or F127 were obtained by polymerization of a crosslinking agent in the micelles hydrophobic core. Nanocarriers were functionalized with a fluorescent probe for visualization, and with a chelator for radiolabeling with Indium-111 and gamma-quantification. The 2D cell models revealed that the internalization pathways and ultimate cellular localization of the Pluronic nanocarriers depended largely on both the PEO block size and aggregation state of the copolymers. The smaller P94 unimers with an average radius of 2.1nm and the shortest PEO block mass (1100gmol(-1)) displayed the highest cellular uptake and retention. 3D tumor spheroids were used to assess the penetration capacity and toxicity potential of the nanocarriers. Results showed that cross-linked F127 micelles were more efficiently delivered across the tumor spheroids, and the penetration depth depends mostly on the transcellular transport of the carriers. The Pluronic P94-based carriers with the shortest PEO block length induced spheroid toxicity, which was significantly influenced by the spheroid cellular type.

Engineered Nanoparticles Against MDR in Cancer: The State of the Art and its Prospective

Cancer is a highly heterogeneous disease at intra/inter patient levels and known as the leading cause of death worldwide. A variety of mono and combinational therapies including chemotherapy have been evolved over the years for its effective treatment. However, advent of chemotherapeutic resistance or multidrug resistance (MDR) in cancer is a major challenge researchers are facing in cancer chemotherapy. MDR is a complex process having multifaceted non-cellular or cellular-based mechanisms. Research in the area of cancer nanotechnology over the past two decade has now proven that the smartly designed nanoparticles help in successful chemotherapy by overcoming the MDR and preferentially accumulate in the tumor region by means of active and passive targeting therefore reducing the offtarget accumulation of payload. Many of such nanoparticles are in different stages of clinical trials as nanomedicines showing promising result in cancer therapy including the resistant cases. Nanoparticles as chemotherapeutics carriers offer the opportunity to have multiple payload of drug and or imaging agents for combinational and theranostics therapy. Moreover, nanotechnology further bring in notice the new treatment strategies such as combining the NIR, MRI and HIFU in cancer chemotherapy and imaging. Here, we discussed the cellular/non-cellular factors constituting the MDR in cancer and the role of nanomedicines in effective chemotherapy of MDR cases of cancers. Moreover, recent advancements like combinational payload delivery and combined physical approach with nanotechnology in cancer therapy have also been discussed.

The challenges facing block copolymer micelles for cancer therapy: In vivo barriers and clinical translation

The application of block copolymer micelles (BCMs) in oncology has benefitted from advances in polymer chemistry, drug formulation and delivery as well as in vitro and in vivo biological models. While great strides have been made in each of these individual areas, there remains some disappointment overall, citing, in particular, the absence of more BCM formulations in clinical evaluation and practice. In this review, we aim to provide an overview of the challenges presented by in vivo systems to the effective design and development of BCMs. In particular, the barriers posed by systemic administration and tumor properties are examined. The impact of critical features, such as the size, stability and functionalization of BCMs is discussed, while key pre-clinical endpoints and models are critiqued. Given clinical considerations, we present this work as a means to stimulate a renewed focus on the unique chemical versatility bestowed by BCMs and a measured grasp of representative in vitro and in vivo models.

Which polymer is more suitable for etoposide: A comparison between two kinds of drug loaded polymeric micelles in vitro and in vivo?

In this paper, we systemly compared the two kinds of VP16 (etoposide) loaded polymers micelles, monomethyl poly (ethylene glycol)-poly (lactic acid) (MPEG-PDLLA) and monomethyl poly (ethylene glycol)-poly (ϵ-caprolactone) (MPEG-PCL) in vitro and in vivo. Molecular modeling study was used as a novel means to compare the two formulations. In vitro, the micelle samples were fully characterized by TEM, XRD, drug loading (DL), Encapsulation efficiency (EE), stability and MTT. The stability study revealed that MPEG-PDLLA-VP16 had the significant advantage of 100% drug retention within 48 h compared to MPEG-PCL-VP16 with 40%, conform to the computer simulation model results. Cellular uptake figured that MPEG-PDLLA-VP16 had a 7 times larger uptake rate in the H460 cell line. In vivo, pharmacodynamics results showed MPEG-PDLLA-VP16 perform no significant difference with VP16 clinical formulations (10, 20mg/kg). However, MPEG-PCL-VP16 had no difference between different dosages on anticancer activities. Plasma pharmacokinetics results showed that the two micelle formulations prolong the half-life of VP16 twice than that of VP16 clinical formulations. In conclusion, micelle were better choice for cancer treatment on reducing drug toxic. In this study, the results also indicated that MPEG-PDLLA was more suitable for VP16 than MPEG-PCL as a more promising formulation for clinical cancer treatment.

Polymeric micelles and nanoemulsions as tumor-targeted drug carriers: Insight through intravital imaging

Intravital imaging of nanoparticle extravasation and tumor accumulation has revealed, for the first time, detailed features of carrier and drug behavior in circulation and tissue that suggest new directions for optimization of drug nanocarriers. Using intravital fluorescent microscopy, the extent of the extravasation, diffusion in the tissue, internalization by tissue cells, and uptake by the RES system were studied for polymeric micelles, nanoemulsions, and nanoemulsion-encapsulated drug. Discrimination of vascular and tissue compartments in the processes of micelle and nanodroplet extravasation and tissue accumulation was possible. A simple 1-D continuum model was suggested that allowed discriminating between various kinetic regimes of nanocarrier (or released drug) internalization in tumors of various sizes and cell density. The extravasation and tumor cell internalization occurred much faster for polymeric micelles than for nanoemulsion droplets. Fast micelle internalization resulted in the formation of a perivascular fluorescent coating around blood vessels. A new mechanism of micelle extravasation and internalization was suggested, based on the fast extravasation and internalization rates of copolymer unimers while maintaining micelle/unimer equilibrium in the circulation. The data suggested that to be therapeutically effective, nanoparticles with high internalization rate should manifest fast diffusion in the tumor tissue in order to avoid generation of concentration gradients that induce drug resistance. However an extra-fast diffusion should be avoided as it may result in the flow of extravasated nanoparticles from the tumor to normal organs, which would compromise targeting efficiency. The extravasation kinetics were different for nanodroplets and nanodroplet-encapsulated drug F-PTX suggesting a premature release of some fraction of the drug from the carrier. In conclusion, the development of an "ideal" drug carrier should involve the optimization of both drug retention and carrier diffusion parameters.

Thermoresponsive block copolymer micelles with tunable pyrrolidone-based polymer cores: structure/property correlations and application as drug carriers

Residue structure affects the physicochemical properties, drug loading efficiency, and thermoresponsive drug release profiles of block copolymer micelles with pyrrolidone-based polymer cores.

Ultrasonically triggered drug delivery: breaking the barrier

The adverse side-effects of chemotherapy can be minimized by delivering the therapeutics in time and space to only the desired target site. Ultrasound offers one fairly non-invasive method of accomplishing such precise delivery because its energy can disrupt nanosized containers that are designed to sequester the drug until the ultrasonic event. Such containers include micelles, liposomes and solid nanoparticles. Conventional micelles and liposomes are less acoustically sensitive to ultrasound because the strongest forces associated with ultrasound are generated by gas-liquid interfaces, which both of these conventional constructs lack. Acoustically activated carriers often incorporate a gas phase, either actively as preformed bubbles, or passively such as taking advantage of dissolved gasses that form bubbles upon insonation. Newer concepts include using liquids that form gas when insonated. This review focuses on the ultrasonically activated delivery of therapeutics from micelles, liposomes and solid particles. In vitro and in vivo results are summarized and discussed. Novel structural concepts from micelles and liposomes are presented. Mechanisms of ultrasonically activated release are discussed. The future of ultrasound in drug delivery is envisioned.

The use of ultrasound to release chemotherapeutic drugs from micelles and liposomes

Several drug delivery systems have been investigated to reduce the side effects of chemotherapy by encapsulating the therapeutic agent in a nanosized carrier until it reaches the tumor site. Many of these particles are designed to be responsive to the mechanical and thermal perturbations delivered by ultrasound. Once the nanoparticle reaches the desired location, ultrasound is applied to release the chemotherapy drug only in the vicinity of the targeted (cancer) site, thus avoiding any detrimental interaction with healthy cells in the body. Studies using liposomes and micelles have shown promising results in this area, as these nanoparticles with simple, yet effective structures, showed high efficiency as drug delivery vehicles both in vitro and in vivo. This article reviews the design and application of two novel nanosized chemotherapeutic carriers (i.e. micelles and liposomes) intended to be actuated by ultrasound.

Pluronics and MDR reversal: an update

Multidrug resistance (MDR) remains one of the biggest obstacles for effective cancer therapy. Currently there are only few methods that are available clinically that are used to bypass MDR with very limited success. In this review we describe how MDR can be overcome by a simple yet effective approach of using amphiphilic block copolymers. Triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), arranged in a triblock structure PEO-PPO-PEO, Pluronics or “poloxamers”, raised a considerable interest in the drug delivery field. Previous studies demonstrated that Pluronics sensitize MDR cancer cells resulting in increased cytotoxic activity of Dox, paclitaxel, and other drugs by 2–3 orders of magnitude. Pluronics can also prevent the development of MDR in vitro and in vivo. Additionally, promising results of clinical studies of Dox/Pluronic formulation reinforced the need to ascertain a thorough understanding of Pluronic effects in tumors. These effects are extremely comprehensive and appear on the level of plasma membranes, mitochondria, and regulation of gene expression selectively in MDR cancer cells. Moreover, it has been demonstrated recently that Pluronics can effectively deplete tumorigenic intrinsically drug-resistant cancer stem cells (CSC). Interestingly, sensitization of MDR and inhibition of drug efflux transporters is not specific or selective to Pluronics. Other amphiphilic polymers have shown similar activities in various experimental models. This review summarizes recent advances of understanding the Pluronic effects in sensitization and prevention of MDR.

Doxorubicin-conjugated PLA-PEG-Folate based polymeric micelle for tumor-targeted delivery: synthesis and in vitro evaluation

BACKGROUND

Selective delivery of anticancer agents to target areas in the body is desirable to minimize the side effects while maximizing the therapeutic efficacy. Anthracycline antibiotics such as doxorubicin (DOX) are widely used for treatment of a wide variety of solid tumors.This study evaluated the potential of a polymeric micellar formulation of doxorubicin as a nanocarrier system for targeted therapy of a folate-receptor positive human ovarian cancer cell in line.

RESULTS

DOX-conjugated targeting and non-targeting micelles prepared by the dialysis method were about 188 and 182 nm in diameter, respectively and their critical micelle concentration was 9.55 μg/ml. The DOX-conjugated micelles exhibited a potent cytotoxicity against SKOV3 human ovarian cancer cells. Moreover, the targeting micelles showed higher cytotoxicity than that of non-targeting ones (IC₅₀= 4.65 μg/ml vs 13.51 μg/ml).

CONCLUSION

The prepared micelle is expected to increase the efficacy of DOX against cancer cells and reduce its side effects.

Repositioning metformin in cancer: genetics, drug targets, and new ways of delivery

After sitting many years on the shelves of drug stores as a harmless antidiabetic drug, metformin comes back in the spotlight of the scientific community as a surprisingly effective antineoplastic drug. Metformin targets multiple pathways that play pivotal roles in cancer progression, impacting various cellular processes, such as proliferation, cell death, metabolism, and even the cancer stemness features. The biomolecular characteristics of tumors, such as appropriate expression of organic cation transporters or genetic alterations including p53, K-ras, LKB1, and PI3K may impact metformin's anticancer efficiency. This could indicate a need for tumor genetic profiling in order to identify patients most likely to benefit from metformin treatment. Considering that the majority of experimental models suggest that higher, supra-clinical doses of metformin should be used in order to obtain an antineoplastic effect, new ways of drug delivery could be developed, such as metformin-loaded nanoparticles or incorporation of metformin into microparticles used in transarterial chemoembolization, with the aim of obtaining higher intratumoral drug concentrations and a targeted therapy which will ultimately maximize metformin's efficacy.

Nanoparticle based inner ear therapy

Synthetic nanoparticles can be used to carry drugs, genes, small interfering RNA (siRNA) and growth factors into the inner ear, to repair, restore and induce cellular regeneration. Nanoparticles (NPs) have been developed which are targetable to selected tissue, traceable in vivo, and equipped with controlled drug/gene release. The NPs are coated with a ‘stealth’ layer, and decorated with targeting ligands, markers, transfection agents and endosomal escape peptides. As payloads, genes such as the BDNF-gene, Math1-gene and Prestin-gene have been constructed and delivered in vitro. Short-hairpin RNA has been used in vitro to silence the negative regulator of Math1, the inhibitors of differentiation and DNA binding. In order to facilitate the passage of cargo from the middle ear to the inner ear, the oval window transports gadolinium chelate more efficiently than the round window and is the key element in introducing therapeutic agents into the vestibule and cochlea. Depending upon the type of NPs, different migration and cellular internalization pathways are employed, and optimal carriers should be designed depending on the cargo. The use of NPs as drug/gene/siRNA carriers is fascinating and can also be used as an intraoperative adjunct to cochlear implantation to attract the peripheral processes of the cochlear nerve.

Role of integrated cancer nanomedicine in overcoming drug resistance

Cancer remains a major killer of mankind. Failure of conventional chemotherapy has resulted in recurrence and development of virulent multi drug resistant (MDR) phenotypes adding to the complexity and diversity of this deadly disease. Apart from displaying classical physiological abnormalities and aberrant blood flow behavior, MDR cancers exhibit several distinctive features such as higher apoptotic threshold, aerobic glycolysis, regions of hypoxia, and elevated activity of drug-efflux transporters. MDR transporters play a pivotal role in protecting the cancer stem cells (CSCs) from chemotherapy. It is speculated that CSCs are instrumental in reviving tumors after the chemo and radiotherapy. In this regard, multifunctional nanoparticles that can integrate various key components such as drugs, genes, imaging agents and targeting ligands using unique delivery platforms would be more efficient in treating MDR cancers. This review presents some of the important principles involved in development of MDR and novel methods of treating cancers using multifunctional-targeted nanoparticles. Illustrative examples of nanoparticles engineered for drug/gene combination delivery and stimuli responsive nanoparticle systems for cancer therapy are also discussed.

Nanobubble ultrasound contrast agents for enhanced delivery of thermal sensitizer to tumors undergoing radiofrequency ablation

PURPOSE

Pluronic has been shown to sensitize various tumor cell lines to chemotherapy and hyperthermia by altering the membrane fluidity, depleting ATP, and modulating the heat shock protein 70 expression. In our prior work, Pluronic was also used to formulate nanosized ultrasound contrast agents. In the current study we evaluate the use of these contrast agents as vehicles for image-guided delivery of Pluronic to improve outcomes of tumor radiofrequency (RF) ablation.

METHODS

Lipid-shelled Pluronic nanobubbles were prepared and examined for size distribution, zeta potential, stability, biodistribution, accumulation of nanobubbles in the tumor, and treatment efficacy. LS174-T xenograft tumor-bearing mice were used to evaluate tumor growth suppression and measure treatment efficacy after RF ablation.

RESULTS

The average diameter of Pluronic bubbles was 230 nm, and initial bubble echogenicity was 16 dB. In vitro, cells exposed to Pluronic nanobubbles exhibited low cytotoxicity in the absence of ultrasound, even if heat (43 ºC) was applied. When the cells were exposed to Pluronic nanobubbles, heat, and ultrasound; viability was significantly reduced. In vivo, tumors treated with ultrasound-modulated nanobubbles prior to RF ablation showed a significant reduction in growth compared to the RF alone (P<0.05).

CONCLUSION

Lipid and Pluronic-shelled, echogenic nanobubbles combined with ultrasound modulation can serve as an effective theranostic method for sensitization of tumors to RF ablation.

Ultrasound-mediated drug/gene delivery in solid tumor treatment

Ultrasound is an emerging modality for drug delivery in chemotherapy. This paper reviews this novel technology by first introducing the designs and characteristics of three classes of drug/gene vehicles, microbubble (including nanoemulsion), liposomes, and micelles. In comparison to conventional free drug, the targeted drug-release and delivery through vessel wall and interstitial space to cancerous cells can be activated and enhanced under certain sonication conditions. In the acoustic field, there are several reactions of these drug vehicles, including hyperthermia, bubble cavitation, sonoporation, and sonodynamics, whose physical properties are illustrated for better understanding of this approach. In vitro and in vivo results are summarized, and future directions are discussed. Altogether, ultrasound-mediated drug/gene delivery under imaging guidance provides a promising option in cancer treatment with enhanced agent release and site specificity and reduced toxicity.

Erythrocyte membrane-cloaked polymeric nanoparticles for controlled drug loading and release

Aim: Polymeric nanoparticles (NPs) cloaked by red blood cell membrane (RBCm) confer the combined advantage of both long circulation lifetime and controlled drug release. The authors carried out studies to gain a better understanding of the drug loading, drug-release kinetics and cell-based efficacy of RBCm-cloaked NPs. Materials & methods: Two strategies for loading doxorubicin into the RBCm-cloaked NPs were compared: physical encapsulation and chemical conjugation. In vitro efficacy was examined using the acute myeloid leukemia cell line, Kasumi-1. Results: It was found that the chemical conjugation strategy resulted in a more sustained drug release profile, and that the RBCm cloak provided a barrier, retarding the outward diffusion of encapsulated drug molecules. It was also demonstrated that RBCm-cloaked NPs exhibit higher toxicity in comparison with free doxorubicin. Conclusion: These results indicate that the RBCm-cloaked NPs hold great promise to become a valuable drug-delivery platform for the treatment of various diseases such as blood cancers.

Original submitted 27 February 2012; Revised submitted 27 August 2012; Published online 14 February 2013

Cellular distribution studies of the nitric oxide-generating antineoplastic prodrug O(2) -(2,4-dinitrophenyl)1-((4-ethoxycarbonyl)piperazin-1-yl)diazen-1-ium-1,2-diolate formulated in Pluronic P123 micelles

OBJECTIVE

Nitric oxide (NO) possesses antitumour activity. It induces differentiation and apoptosis in acute myeloid leukaemia (AML) cells. The NO prodrug O(2) -(2,4-dinitrophenyl)1-((4-ethoxycarbonyl)piperazin-1-yl)diazen-1-ium-1,2-diolate, or JS-K, has potent antileukaemic activity. JS-K is also active in vitro and in vivo against multiple myeloma, prostate cancer, non-small-cell lung cancer, glioma and liver cancer. Using the Pluronic P123 polymer, we have developed a micelle formulation for JS-K to increase its solubility and stability. The goal of the current study was to investigate the cellular distribution of JS-K in AML cells.

METHODS

We investigated the intracellular distribution of JS-K (free drug) and JS-K formulated in P123 micelles (P123/JS-K) using HL-60 AML cells. We also studied the S-glutathionylating effects of JS-K on proteins in the cytoplasmic and nuclear cellular fractions.

KEY FINDINGS

Both free JS-K and P123/JS-K accumulate primarily in the nucleus. Both free JS-K and P123/JS-K induced S-glutathionylation of nuclear proteins, although the effect produced was more pronounced with P123/JS-K. Minimal S-glutathionylation of cytoplasmic proteins was observed.

CONCLUSIONS

We conclude that a micelle formulation of JS-K increases its accumulation in the nucleus. Post-translational protein modification through S-glutathionylation may contribute to JS-K's antileukaemic properties.

How do polymeric micelles cross epithelial barriers?

Non-parenteral delivery of drugs using nanotechnology-based delivery systems is a promising non-invasive way to achieve effective local or systemic drug delivery. The efficacy of drugs administered non-parenterally is limited by their ability to cross biological barriers, and epithelial tissues particularly present challenges. Polymeric micelles can achieve transepithelial drug delivery because of their ability to be internalized into cells and/or cross epithelial barriers, thereby delivering drugs either locally or systematically following non-parenteral administration. This review discusses the particular characteristics of various epithelial barriers and assesses their potential as non-parenteral routes of delivery. The material characteristics of polymeric micelles (e.g., size, surface charge, and surface decoration) and of unimers dissociated from polymeric micelles determine their interactions (non-specific and/or specific) with mucus and epithelial cells as well as their intracellular fate. This paper outlines the mechanisms governing the major modes of internalization of polymeric micelles into epithelial cells, with an emphasis on specific recent examples of the transport of drug-loaded polymeric micelles across epithelial barriers.

A simple way to enhance Doxil® therapy: drug release from liposomes at the tumor site by amphiphilic block copolymer

The antitumor efficacy of Doxil® is hindered by the poor release of the active drug from the liposome at the tumor sites. This study investigates a possibility to enhance drug release from the liposomes and increase therapeutic efficacy of Doxil® by administering Pluronic block copolymers once the liposomal drug accumulates in the tumor sites. In our study, the fluorescence de-quenching experiments were designed to investigate the drug release from liposome by Pluronic P85. MTT cytotoxicity assay and confocal microscopy images were carried out to determine whether Pluronic P85 could facilitate release of Dox from Doxil®. Anti-tumor growth and distribution of drug were evaluated when Pluronic P85 was injected 1h, 48h, or 96h after the Doxil® administration in A2780 human ovarian cancer xenografts. Addition of Pluronic P85 resulted in release of Dox from the liposomes accompanied with significant increases of Dox delivery and cytotoxic effect in cancer cells. The greatest anti-tumor effect of single injection of Doxil® was achieved when Pluronic P85 was administered 48h after Doxil®. The confocal tile scanning images of tumor section showed that copolymer treatment induced the release of the drug in the tumors from the vessels regions to the bulk of the tumor. No release of the drug remaining in circulation was observed. Our study has demonstrated a simple approach for localized release of Dox from liposome by Pluronic P85 at the tumor site, which was therapeutically beneficial.

Blood-pool multifunctional nanoparticles formed by temperature-induced phase transition for cancer-targeting therapy and molecular imaging

Multifunctional nanoparticles (NPs) were prepared based on temperature-induced phase transition in a molten mixture of Lipiodol(®), Tween 80, paclitaxel (PTX), and Pluronic F-68, wherein the Lipiodol(®)/Tween 80 mixture is used as a solubilizer for PTX, and Pluronic F-68 is used for the stabilization of the molten mixture. The morphology and size distribution of optimized multifunctional NPs were observed using transmittance electron microscopy (TEM) and a particle size analyzer. In the optical imaging of tumor-bearing mice using a near-infrared fluorescence (NIRF) imaging system, the multifunctional NPs were evaluated in terms of a time-dependent excretion profile, in vivo biodistribution and tumor-targeting capability compared to free fluorescence dye. In addition, the prolonged circulation of multifunctional NPs was confirmed by enhancement of the blood-pool in live animals using a micro-CT imaging system, because iodine-containing Lipiodol(®) has an X-ray enhancement property. Finally, the anti-tumor efficacy of multifunctional NPs was monitored by injecting the multifunctional NPs into the tail veins of tumor-bearing mice. The multifunctional NPs showed excellent tumor targetability and anti-tumor efficacy in tumor-bearing mice, caused by the enhanced permeation and retention (EPR) effect.