EPR: Evidence and fallacy

A nanoplatform based on mesoporous silica-coated gold nanorods for cancer triplex therapy

To enhance the efficacy of nanoparticle-based cancer therapy with reduced side effects and promote its clinical translation, a biocompatible nanocomposite based on mesoporous silica-coated gold nanorods (AuNR@MSN) for triple tumor therapy is reported in this study. The gold core served as a hyperthermia agent, while the MSN shell acted as a reservoir of chemotherapeutics owing to its excellent loading capacity. Cytochrome c with the apoptosis inducing function was anchored on the surface of AuNR@MSN to prevent drug leakage through redox-responsive disulfide bonds. The successful construction of a nanocomposite was confirmed by characterization of the physicochemical properties. In vitro and in vivo studies demonstrated that the nanocomposite displayed an optimizing anti-tumor effect with a synergistic strategy of excellent photothermal therapy, chemotherapy and protein therapy. Therefore, this cooperative strategy paves the way for high-efficiency oncotherapy with reduced side effects.

Fe3O4-Au Core-Shell Nanoparticles as a Multimodal Platform for In Vivo Imaging and Focused Photothermal Therapy

In this study, we report the synthesis of gold-coated iron oxide nanoparticles capped with polyvinylpyrrolidone (Fe@Au NPs). The as-synthesized nanoparticles (NPs) exhibited good stability in aqueous media and excellent features as contrast agents (CA) for both magnetic resonance imaging (MRI) and X-ray computed tomography (CT). Additionally, due to the presence of the local surface plasmon resonances of gold, the NPs showed exploitable "light-to-heat" conversion ability in the near-infrared (NIR) region, a key attribute for effective photothermal therapies (PTT). In vitro experiments revealed biocompatibility as well as excellent efficiency in killing glioblastoma cells via PTT. The in vivo nontoxicity of the NPs was demonstrated using zebrafish embryos as an intermediate step between cells and rodent models. To warrant that an effective therapeutic dose was achieved inside the tumor, both intratumoral and intravenous routes were screened in rodent models by MRI and CT. The pharmacokinetics and biodistribution confirmed the multimodal imaging CA capabilities of the Fe@AuNPs and revealed constraints of the intravenous route for tumor targeting, dictating intratumoral administration for therapeutic applications. Finally, Fe@Au NPs were successfully used for an in vivo proof of concept of imaging-guided focused PTT against glioblastoma multiforme in a mouse model.

Recent Advances in Preclinical Research Using PAMAM Dendrimers for Cancer Gene Therapy

Carriers of genetic material are divided into vectors of viral and non-viral origin. Viral carriers are already successfully used in experimental gene therapies, but despite advantages such as their high transfection efficiency and the wide knowledge of their practical potential, the remaining disadvantages, namely, their low capacity and complex manufacturing process, based on biological systems, are major limitations prior to their broad implementation in the clinical setting. The application of non-viral carriers in gene therapy is one of the available approaches. Poly(amidoamine) (PAMAM) dendrimers are repetitively branched, three-dimensional molecules, made of amide and amine subunits, possessing unique physiochemical properties. Surface and internal modifications improve their physicochemical properties, enabling the increase in cellular specificity and transfection efficiency and a reduction in cytotoxicity toward healthy cells. During the last 10 years of research on PAMAM dendrimers, three modification strategies have commonly been used: (1) surface modification with functional groups; (2) hybrid vector formation; (3) creation of supramolecular self-assemblies. This review describes and summarizes recent studies exploring the development of PAMAM dendrimers in anticancer gene therapies, evaluating the advantages and disadvantages of the modification approaches and the nanomedicine regulatory issues preventing their translation into the clinical setting, and highlighting important areas for further development and possible steps that seem promising in terms of development of PAMAM as a carrier of genetic material.

Polymeric Nanoparticles with a Sera-Derived Coating for Efficient Cancer Cell Uptake and Killing

Nanoparticle-mediated cancer drug delivery remains an inefficient process. The protein corona formed on nanoparticles (NPs) controls their biological identity and, if optimized, could enhance cancer cell uptake. In this study, a hyperbranched polyester polymer (HBPE) was synthesized from diethyl malonate and used to generate NPs that were subsequently coated with normal sera (NS) collected from mice. Cellular uptake of NS-treated HBPE-NPs was compared to PEGylated HBPE-NPs and was assessed using MDA-MB-231 triple-negative breast cancer (TNBC) cells as well as endothelial and monocytic cell lines. NS-treated HBPE-NPs were taken up by TNBC cells more efficiently than PEGylated HBPE-NPs, while evasion of monocyte uptake was comparable. NS coatings facilitated cancer cell uptake of HBPE-NPs, even after prior interaction of the particles with an endothelial layer. NS-treated HBPE-NPs were not inherently toxic, did not induce the migration of endothelial cells that could lead to angiogenesis, and could efficiently deliver cytotoxic doses of paclitaxel (taxol) to TNBC cells. These findings suggest that HBPE-NPs may adsorb select sera proteins that improve uptake by cancer cells, and such NPs could be used to advance the discovery of novel factors that improve the bioavailability and tissue distribution of drug-loaded polymeric NPs.

Targeted liposomal drug delivery: a nanoscience and biophysical perspective

Liposomes are a unique platform for drug delivery, and a number of liposomal formulations have already been commercialized. Doxil is a representative example, which uses PEGylated liposomes to load doxorubicin for cancer therapy. Its delivery relies on the enhanced permeability and retention (EPR) effect or passive targeting. Drug loading can be achieved using both standard liposomes and also those containing a solid core such as mesoporous silica and poly(lactide-co-glycolide) (PLGA). Developments have also been made on active targeted delivery using bioaffinity ligands such as small molecules, antibodies, peptides and aptamers. Compared to other types of nanoparticles, the surface of liposomes is fluid, allowing dynamic organization of targeting ligands to achieve optimal binding to cell surface receptors. This review article summarizes development of liposomal targeted drug delivery systems, with an emphasis on the biophysical properties of lipids. In both passive and active targeting, the effects of liposome size, charge, fluidity, rigidity, head-group chemistry and PEGylation are discussed along with recent examples. Most of the examples are focused on targeting tumors or cancer cells. Finally, a few examples of commercialized formulations are described, and some future research opportunities are discussed.

Radiolabelling of nanomaterials for medical imaging and therapy

Nanomaterials offer unique physical, chemical and biological properties of interest for medical imaging and therapy. Over the last two decades, there has been an increasing effort to translate nanomaterial-based medicinal products (so-called nanomedicines) into clinical practice and, although multiple nanoparticle-based formulations are clinically available, there is still a disparity between the number of pre-clinical products and those that reach clinical approval. To facilitate the efficient clinical translation of nanomedicinal-drugs, it is important to study their whole-body biodistribution and pharmacokinetics from the early stages of their development. Integrating this knowledge with that of their therapeutic profile and/or toxicity should provide a powerful combination to efficiently inform nanomedicine trials and allow early selection of the most promising candidates. In this context, radiolabelling nanomaterials allows whole-body and non-invasive in vivo tracking by the sensitive clinical imaging techniques positron emission tomography (PET), and single photon emission computed tomography (SPECT). Furthermore, certain radionuclides with specific nuclear emissions can elicit therapeutic effects by themselves, leading to radionuclide-based therapy. To ensure robust information during the development of nanomaterials for PET/SPECT imaging and/or radionuclide therapy, selection of the most appropriate radiolabelling method and knowledge of its limitations are critical. Different radiolabelling strategies are available depending on the type of material, the radionuclide and/or the final application. In this review we describe the different radiolabelling strategies currently available, with a critical vision over their advantages and disadvantages. The final aim is to review the most relevant and up-to-date knowledge available in this field, and support the efficient clinical translation of future nanomedicinal products for in vivo imaging and/or therapy.

Nano-Bio Interactions in Cancer: From Therapeutics Delivery to Early Detection

Understanding the interactions between nanomaterials and biological systems plays a pivotal role in enhancing the efficacy of nanomedicine and advancing the disease diagnosis. The nanoparticle-protein corona, an active biomolecular layer, is formed around nanoparticles (NPs) upon mixing with biological fluid. The surface layer which consists of rapidly exchanged biomolecules is called the "soft" corona. The inner layer which is more stable and tightly packed is called the "hard" corona. It has been suggested that the NP-protein corona has a decisive effect on the in vivo fate of nanomedicine upon intravenously administration into the mouse. Furthermore, the features of the NP-protein corona make it a powerful platform to enrich low-abundance proteins from serum/plasma for downstream mass-spectrometry (MS)-based proteomics for biomarker discovery and disease diagnosis.Herein, we summarize our recent work on the development of nanomedicine and disease detection from the level of nano-bio interactions between nanoparticles and biological systems. Nanomedicine has made substantial progress over the past two decades. However, the significant enhancement of overall patient survival by nanomedicine remains a challenge due to the lack of a deep understanding of nano-bio interactions in the clinical setting. The pharmacokinetic effect of the protein corona on PEGylated NPs during blood circulation indicated that the adsorbed apolipoproteins could prolong the circulation time of NPs. This mechanistic understanding of the protein corona (active biomolecule) formed around polymeric NPs offered insights into enhancing the efficacy of nanomedicine from the biological interactions point of view. Moreover, we discuss the basic rationale for developing bioresponsive cancer nanomedicine by exploiting the pathophysiological environment around the tumor, typically the pH, reactive oxygen species (ROS), and redox-responsive supramolecular motifs based on synthetic amphiphilic polymers. The protein corona in vivo determines the biological fate of NPs, whereas it opens a new avenue to enrich low abundant proteins in a biospecimen ex vivo to render them "visible" for downstream analytical workflows, such as MS-based proteomics. Blood serum/plasma, due to easy accessibility and great potential to uncover and monitor physiological and pathological changes in health and disease, has remained a major source of detecting protein biomarker candidates. Inspired by the features of the NP-protein corona, a Proteograph platform, which integrates multi-NP-protein coronas with MS for large-scale efficient and deep proteome profiling has been developed. Finally, we conclude this Account with a better understanding of nano-bio interactions to accelerate the nanomedicine translation and how MS-based proteomics can boost our understanding of the corona composition and facilitate the identification of disease biomarkers.

Mechanochemical Cellular Membrane Internalization of Nanohydrogels: A Large-Scale Mesoscopic Simulation

By combining large-scale dissipative particle dynamics and steered molecular dynamics simulations, we investigate the mechanochemical cellular internalization pathways of homogeneous and heterogeneous nanohydrogels and demonstrate that membrane internalization is determined by the crosslink density and encapsulation ability of nanohydrogels. The homogeneous nanohydrogels with a high crosslink density and low encapsulation ability behave as soft nanoparticles partially wrapped by the membrane, while those with a low crosslink density and high encapsulation ability permeate into the membrane. Regardless of the crosslink density, the homogeneous nanohydrogels undergo typical dual morphological deformations. The local lipid nanodomains are identified at the contacting region between the membrane and nanohydrogels because of different diffusion behaviors between lipid and receptor molecules during the internalization process. The yolk@shell heterogeneous nanohydrogels present a different mechanochemical cellular internalization pathway. The yolk with strong affinity is directly in contact with the membrane, resulting in partial membrane wrapping, and the contacting area is much reduced when compared to homogenous nanohydrogels, leading to a smaller lipid nanodomain and thus avoiding related cellular toxicity. Our findings provide a critical mechanism understanding of the biological pathways of nanohydrogels and may guide the molecular design of the hydrogel-based materials for controlled release drug delivery, tissue engineering, and cell culture.

The Brief Analysis of Peptide-combined Nanoparticle: Nanomedicine's Unique Value

Therapeutic peptides (TPs) are biological macromolecules which can act as neurotransmitters, hormones, ion channel ligands and growth factors. Undoubtedly, TPs are crucial in modern medicine. But low bio-stability and some special adverse reactions reduce their places to the application. With the development of nanotechnology, nanoparticles (NPs) in pharmaceutical science gained much attention. They can encapsulate the TPs into their membrane or shell. Therefore, they can protect the TPs against degradation and then increase the bioavailability, which was thought to be the biggest advantage of them. Additionally, targeting was also studied to improve the effect of TPs. However, there were some drawbacks of nano TPs like low loading efficiency and difficulty to manufacture. Nowadays, lots of studies focused on improving effect of TPs by preparing nanoparticles. In this review, we presented a brief analysis of peptide-combined nanoparticles. Their advantages and disadvantages were listed in terms of mechanism. And several examples of applications were summarized.

MRI-traceable theranostic nanoparticles for targeted cancer treatment

Current cancer therapies, including chemotherapy and radiotherapy, are imprecise, non-specific, and are often administered at high dosages - resulting in side effects that severely impact the patient's overall well-being. A variety of multifunctional, cancer-targeted nanotheranostic systems that integrate therapy, imaging, and tumor targeting functionalities in a single platform have been developed to overcome the shortcomings of traditional drugs. Among the imaging modalities used, magnetic resonance imaging (MRI) provides high resolution imaging of structures deep within the body and, in combination with other imaging modalities, provides complementary diagnostic information for more accurate identification of tumor characteristics and precise guidance of anti-cancer therapy. This review article presents a comprehensive assessment of nanotheranostic systems that combine MRI-based imaging (T1 MRI, T2 MRI, and multimodal imaging) with therapy (chemo-, thermal-, gene- and combination therapy), connecting a range of topics including hybrid treatment options (e.g. combined chemo-gene therapy), unique MRI-based imaging (e.g. combined T1-T2 imaging, triple and quadruple multimodal imaging), novel targeting strategies (e.g. dual magnetic-active targeting and nanoparticles carrying multiple ligands), and tumor microenvironment-responsive drug release (e.g. redox and pH-responsive nanomaterials). With a special focus on systems that have been tested in vivo, this review is an essential summary of the most advanced developments in this rapidly evolving field.

Multifunctional biomolecule nanostructures for cancer therapy

Biomolecule-based nanostructures are inherently multifunctional and harbour diverse biological activities, which can be explored for cancer nanomedicine. The supramolecular properties of biomolecules can be precisely programmed for the design of smart drug delivery vehicles, enabling efficient transport in vivo, targeted drug delivery and combinatorial therapy within a single design. In this Review, we discuss biomolecule-based nanostructures, including polysaccharides, nucleic acids, peptides and proteins, and highlight their enormous design space for multifunctional nanomedicines. We identify key challenges in cancer nanomedicine that can be addressed by biomolecule-based nanostructures and survey the distinct biological activities, programmability and in vivo behaviour of biomolecule-based nanostructures. Finally, we discuss challenges in the rational design, characterization and fabrication of biomolecule-based nanostructures, and identify obstacles that need to be overcome to enable clinical translation.

Polymer-conjugated glucosamine complexed with boric acid shows tumor-selective accumulation and simultaneous inhibition of glycolysis

We synthesized unique water-soluble synthetic-polymer, styrene-maleic acid copolymer (SMA) conjugated glucosamine (SG); which formed a stable complex with boric acid (BA). This complex had a mean particle size of 15 nm by light scattering, and single peak in gel permeation chromatography. The particles were taken up by tumor cells five times faster than free BA in vitro and liberated BA at acidic tumor pH (5-7). Liberated BA inhibited glycolysis and resulted in tumor suppression in vivo. Intravenously injected SGB-complex did bind with albumin, and plasma half-life was about 8 h in mice, and accumulated to tumor tissues about 10 times more than in normal organs. IC₅₀ of SGB-complex for HeLa cells under pO₂ of 6-9% was about 20 μg/ml (free BA equivalent), 150 times more potent than free BA. Neutron irradiation of human oral cancer cells with SGB-complex resulted in 16 times greater cell-killing than that without SGB-complex. In vivo antitumor effect was evaluated after neutron irradiation only once in SCC VII tumor bearing mice and significant tumor suppression was confirmed. These results indicate that SGB-complex is a unique multifunctional anticancer agent with much more potent activity under low pO₂ conditions as in large advanced cancers.

Nanomedicine: A Useful Tool against Glioma Stem Cells

The standard of care therapy of glioblastoma (GBM) includes invasive surgical resection, followed by radiotherapy and concomitant chemotherapy. However, this therapy has limited success, and the prognosis for GBM patients is very poor. Although many factors may contribute to the failure of current treatments, one of the main causes of GBM recurrences are glioma stem cells (GSCs). This review focuses on nanomedicine strategies that have been developed to eliminate GSCs and the benefits that they have brought to the fight against cancer. The first section describes the characteristics of GSCs and the chemotherapeutic strategies that have been used to selectively kill them. The second section outlines the nano-based delivery systems that have been developed to act against GSCs by dividing them into nontargeted and targeted nanocarriers. We also highlight the advantages of nanomedicine compared to conventional chemotherapy and examine the different targeting strategies that have been employed. The results achieved thus far are encouraging for the pursuit of effective strategies for the eradication of GSCs.

Erlotinib entrapped in cholesterol-depleting cyclodextrin nanoparticles shows improved antitumoral efficacy in 3D spheroid tumors of the lung and the liver

Erlotinib (ERL), a tyrosine kinase inhibitor approved for therapeutic use in non-small cell lung cancer is further researched for eventual liver cancer treatment. However, conventional ERL has important bioavailability problems resulting from oral administration, poor solubility and gastrointestinal degradation into inactive metabolites. Alternative administration routes and nanoparticulate drug delivery systems are studied to prevent or reduce these drawbacks. In this study, ERL-loaded CD nanosphere and nanocapsule formulations capable of cholesterol depletion in resistant cancer cells were evaluated for ERL delivery. Drug loading and release profile depended largely on the surface charge of nanoparticles. Antiproliferative activity data obtained from 2D and 3D cell culture models demonstrated that polycationic βCD nanocapsules were the most effective formulation for ERL delivery to lung and liver cancer cells. 3D tumour tumoral penetration studies further revealed that nanocapsule formulations penetrated deeper into the tumour through the multilayered cells. Furthermore, all formulations were able to extract membrane cholesterol from lung and liver cancer cell lines, indicating the induction of apoptosis and overcoming drug resistance. In conclusion, given their tumoral penetration and cell membrane cholesterol depletion abilities, amphiphilic CD nanocapsules emerge as promising alternatives to improve the safety and efficiency of ERL treatment of both liver and lung tumours.

Nanostructured Polymeric, Liposomal and Other Materials to Control the Drug Delivery for Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the leading cause of death globally, taking an estimated 17.9 million lives each year, representing one third of global mortality. As existing therapies still have limited success, due to the inability to control the biodistribution of the currently approved drugs, the quality of life of these patients is modest. The advent of nanomedicine has brought new insights in innovative treatment strategies. For this reason, several novel nanotechnologies have been developed for both targeted and prolonged delivery of therapeutics to the cardiovascular system tο minimize side effects. In this regard, nanoparticles made of natural and/or synthetic nanomaterials, like liposomes, polymers or inorganic materials, are emerging alternatives for the encapsulation of already approved drugs to control their delivery in a targeted way. Therefore, nanomedicine has attracted the attention of the scientific community as a potential platform to deliver therapeutics to the injured heart. In this review, we discuss the current types of biomaterials that have been investigated as potential therapeutic interventions for CVDs as they open up a host of possibilities for more targeted and effective therapies, as well as minimally invasive treatments.

Mitochondria-Targeted Polyamidoamine Dendrimer-Curcumin Construct for Hepatocellular Cancer Treatment

Mitochondrial malfunction plays a crucial role in cancer development and progression. Cancer cells show a substantially higher mitochondrial activity and greater mitochondrial transmembrane potential than normal cells. This concept can be exploited for targeting cytotoxic drugs to the mitochondria of cancer cells using mitochondrial-targeting compounds. In this study, a polyamidoamine dendrimer-based mitochondrial delivery system was prepared for curcumin using triphenylphosphonium ligands to improve the anticancer efficacy of the drug in vitro and in vivo. For the in vitro evaluations, various methods, such as viability assay, confocal microscopy, flow cytometry, reactive oxygen species (ROS), and real-time polymerase chain reaction analyses, were applied. Our findings showed that the targeted-dendrimeric curcumin (TDC) could successfully deliver and colocalize the drug to the mitochondria of the cancer cells, and selectively induce a potent apoptosis and cell cycle arrest at G2/M. Moreover, at a low curcumin dose of less than 25 μM, TDC significantly reduced adenosine triphosphate and glutathione, and increased the ROS level of the isolated rat hepatocyte mitochondria. The in vivo studies on the Hepa1-6 tumor-bearing mice also indicated a significant tumor suppression effect and the highest median survival days (Kaplan-Meier survival estimation and log-rank test) after treatment with the TDC construct compared to the free curcumin and untargeted construct. Besides its targeted nature and safety, the expected improved solubility and stability represent the prepared targeted-dendrimeric construct as an up-and-coming candidate for cancer treatment. The results of this study emphasize the promising route of mitochondrial targeting as a practical approach for cancer therapy, which can be achieved by optimizing the delivery method.

Ligand-Targeted Delivery of Photosensitizers for Cancer Treatment

Photodynamic therapy (PDT) is a promising cancer treatment which involves a photosensitizer (PS), light at a specific wavelength for PS activation and oxygen, which combine to elicit cell death. While the illumination required to activate a PS imparts a certain amount of selectivity to PDT treatments, poor tumor accumulation and cell internalization are still inherent properties of most intravenously administered PSs. As a result, common consequences of PDT include skin photosensitivity. To overcome the mentioned issues, PSs may be tailored to specifically target overexpressed biomarkers of tumors. This active targeting can be achieved by direct conjugation of the PS to a ligand with enhanced affinity for a target overexpressed on cancer cells and/or other cells of the tumor microenvironment. Alternatively, PSs may be incorporated into ligand-targeted nanocarriers, which may also encompass multi-functionalities, including diagnosis and therapy. In this review, we highlight the major advances in active targeting of PSs, either by means of ligand-derived bioconjugates or by exploiting ligand-targeting nanocarriers.

Possible contribution of sialic acid to the enhanced tumor targeting efficiency of nanoparticles engineered with doxorubicin

Doxorubicin (DOX)-engineered poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) including phloretin (PHL) were designed and the feasible contribution of sialic acid (SA) to the improved tumor targeting and penetration capabilities was elucidated in lung adenocarcinoma models. DOX has been clinically used as liposomal formulations after its introduction to the inner side of vehicles, however DOX is anchored in the outer surface of PLGA NPs for improved tumor penetration by interactions with SA in this study. DOX (positively charged at physiological pH) was adsorbed onto the negatively charged PLGA NPs via electrostatic interactions and consequent binding of SA (negatively charged at physiological pH) to DOX located in NPs was also elucidated. DOX layer in DOX@PLGA NPs rendered improved endocytosis and partial contribution of SA (expressed in cancer cells) to that endocytosis was demonstrated. DOX@PLGA/PHL NPs provided enhanced antiproliferation potentials in A549 cells rather than single agent (DOX or PHL)-installed NPs. In addition, DOX-SA interactions seemed to play critical roles in tumor infiltration and accumulation of DOX@PLGA NPs in A549 tumor-xenografted mouse model. All these findings support the novel use of DOX which is used for the surface engineering of NPs for improved tumor targeting and penetration.

Noninvasive Molecular Imaging of the Enhanced Permeability and Retention Effect by 64Cu-Liposomes: In vivo Correlations with 68Ga-RGD, Fluid Pressure, Diffusivity and 18F-FDG

Background

The accumulation of liposome encapsulated chemotherapy in solid cancers is dependent on the presence of the enhanced permeability and retention (EPR) effect. Positron emission tomography (PET) imaging with a liposome encapsulated radioisotope, such as liposome encapsulated Cu-64 (⁶⁴Cu-liposome) may help to identify tumors with high liposome accumulation, and thereby stratify patients based on expected benefit from liposomal chemotherapy. However, intravenous administration of liposomes without a cytotoxic content is complicated by the accelerated blood clearance (ABC) phenomenon for succeeding therapeutic liposome dosing. Alternative markers for assessing the tumor’s EPR level are therefore warranted.

Materials and Methods

To increase our understanding of EPR variations and to ultimately identify an alternative marker for the EPR effect, we investigated the correlation between ⁶⁴Cu-liposome PET/CT (EPR effect) and ⁶⁸Ga-RGD PET/CT (neoangiogenesis), ¹⁸F-FDG PET/CT (glycolysis), diffusion-weighted MRI (diffusivity) and interstitial fluid pressure in two experimental cancer models (CT26 and COLO 205).

Results

⁶⁴Cu-liposome and ⁶⁸Ga-RGD SUV_max displayed a significant moderate correlation, however, none of the other parameters evaluated displayed significant correlations. These results indicate that differences in neoangiogenesis may explain some EPR variability, however, as correlations were only moderate and not observed for SUV_mean, ⁶⁸Ga-RGD is probably insufficient to serve as a stand-alone surrogate marker for quantifying the EPR effect and stratifying patients.

Receptor-based targeting of engineered nanocarrier against solid tumors: Recent progress and challenges ahead

Background In past few decades, the research on engineered nanocarriers (NCs) has gained significant attention in cancer therapy due to selective delivery of drug molecules on the diseased cells thereby preventing unwanted uptake into healthy cells to cause toxicity. Scope of review The applicability of enhanced permeability and retention (EPR) effect for the delivery of nanomedicines in cancer therapy has gained limited success due to poor accessibility of the drugs to the target cells where non-specific payload delivery to the off target region lack substantial reward over the conventional therapeutic systems. Major conclusions In spite of the fact, nanomedicines fabricated from the biocompatible nanocarriers have reduced targeting potential for meaningful clinical benefits. However, over expression of receptors on the tumor cells provides opportunity to design functional nanomedicine to bind substantially and deliver therapeutics to the cells or tissues of interest by alleviating the bio-toxicity and unwanted effects. This critique will give insight into the over expressed receptor in various tumor and targeting potential of functional nanomedicine as new therapeutic avenues for effective treatment. General significance This review shortly shed light on EPR-based drug targeting using nanomedicinal strategies, their limitation, and advances in therapeutic targeting to the tumor cells.

What Went Wrong with Anticancer Nanomedicine Design and How to Make It Right

The three design criteria of anticancer nanomedicines to improve anticancer efficacy and to reduce toxicity have been debated for decades: (1) Nanomedicines increase drug accumulation through enhanced permeability and retention (EPR) in tumors to improve anticancer efficacy. (2) Long systemic circulation of nanomedicines with high plasma concentration reduces reticuloendothelial system (RES) clearance and decreases drug accumulation in the normal organs to reduce toxicity, and to enhance the EPR effect. (3) A universal nanodelivery platform based on EPR and long systemic circulation can be developed to deliver different anticancer drugs. Although these criteria have repeatedly been confirmed in preclinical xenograft cancers, the majority of anticancer nanomedicines have failed to improve clinical efficacy, while the clinical efficacies/safety of successful nanomedicines are inconsistent with these design criteria. First, the debate over tumor EPR may have mixed two different questions and missed more clinically relevant comparisons for nanomedicines versus free drugs. When tumors are compared with normal tissues, tumor EPR has been confirmed in both mouse xenograft tumors and human cancers. However, nanomedicines may not enhance drug accumulation in human tumors compared with free drugs, despite outstanding improvement in preclinical cancers. Heterogeneity of enhanced permeability and retention in human cancers occurs for small/large molecules and nanomedicines, which cannot fully explain the poor translation of nanomedicines' efficacy from preclinical cancer models to cancer patients. Second, long-circulation nanomedicine should not be used as a universal design criterion because it does not further improve tumor accumulation by tumor EPR in human patients nor universally reduce distribution in normal organs. In contrast, nanomedicines change the drug tissue distribution to alter anticancer efficacy/safety. Third, a universal nanodelivery platform that uses the same design criteria for different drugs is not feasible. Rather, drug-specific nanodelivery systems are required to overcome the intrinsic shortcomings of delivered drugs, which are determined by the physicochemical, pharmacokinetic, and pharmacodynamic properties of the delivered drugs and nanocarriers to improve their efficacy/safety.

Nanoparticle-Mediated Delivery of 2-Deoxy-D-Glucose Induces Antitumor Immunity and Cytotoxicity in Liver Tumors in Mice

BACKGROUND & AIMS

Immune checkpoint inhibitors have shed light on the importance of antitumor immunity as a therapeutic strategy for hepatocellular carcinoma (HCC). The altered glucose metabolism known as the Warburg effect recently has gained attention as a cancer immune-resistance mechanism. Considering glycolysis inhibitors as therapeutic agents, their specific delivery to cancer cells is critical not to induce adverse effects. Thus, we investigated antitumor effects of a glycolysis inhibitor, consisting of 2-deoxy-D-glucose (2DG)-encapsulated poly(lactic-co-glycolic acid) (PLGA) nanoparticles (2DG-PLGA-NPs), against hepatocellular carcinoma in mice.

METHODS

The antitumor effects of 2DG-PLGA-NPs were examined using hepatoma cell lines, xenograft tumors, and hepatocarcinogenic and syngeneic mouse models.

RESULTS

The 2DG-PLGA-NPs induced cytotoxic effects and antitumor immunity through enhanced T-cell trafficking. In addition, 2DG-PLGA-NPs induced decreased lactate production and increased interferon-γ-positive T cells in liver tumors. Human CD8⁺ T cells cocultured with 2DG-PLGA-NP-treated Huh7 cells showed their increased interferon-γ production and glucose uptake compared with the CD8⁺ T cells co-cultured with PLGA-NP-treated Huh7 cells. Chemotaxis of CD8⁺ T cells was suppressed by lactate and enhanced by glucose. Interferon-γ enhanced CD8⁺ T-cell chemotaxis in both an autocrine and paracrine manner. Notably, the 2DG-PLGA-NPs augmented chemokine (CXCL9/CXCL10) production in liver tumors via interferon-γ-Janus kinase-signal transducers and activator of transcription pathway and 5' adenosine monophosphate-activated protein kinase-mediated suppression of histone H3 lysine 27 trimethylation. These 2DG-PLGA-NPs not only amplified antitumor effects induced by sorafenib or an anti-programmed death-1 antibody, but also suppressed anti-programmed death-1-resistant tumors.

CONCLUSIONS

The newly developed 2DG-PLGA-NPs showed antitumor immunity and cytotoxicity in liver tumors in mice, suggesting the potential of 2DG-PLGA-NPs for future clinical applications.

Advances in nanomedicines for diagnosis of central nervous system disorders

In spite of a great improvement in medical health services and an increase in lifespan, we have witnessed a skyrocket increase in the incidence of central nervous system (CNS) disorders including brain tumors, neurodegenerative diseases (Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, Huntington's disease), ischemic stroke, and epilepsy, which have seriously undermined the quality of life and substantially increased economic and societal burdens. Development of diagnostic methods for CNS disorders is still in the early stage, and the clinical outcomes suggest these methods are not ready for the challenges associated with diagnosis of CNS disorders, such as early detection, specific binding, sharp contrast, and continuous monitoring of therapeutic interventions. Another challenge is to overcome various barrier structures during delivery of diagnostic agents, especially the blood-brain barrier (BBB). Fortunately, utilization of nanomaterials has been pursued as a potential and promising strategy to address these challenges. This review will discuss anatomical and functional structures of BBB and transport mechanisms of nanomaterials across the BBB, and special emphases will be placed on the state-of-the-art advances in the development of nanomedicines from a variety of nanomaterials for diagnosis of CNS disorders. Meanwhile, current challenges and future perspectives in this field are also highlighted.

Comprehensive Survey on Nanobiomaterials for Bone Tissue Engineering Applications

One of the most important ideas ever produced by the application of materials science to the medical field is the notion of biomaterials. The nanostructured biomaterials play a crucial role in the development of new treatment strategies including not only the replacement of tissues and organs, but also repair and regeneration. They are designed to interact with damaged or injured tissues to induce regeneration, or as a forest for the production of laboratory tissues, so they must be micro-environmentally sensitive. The existing materials have many limitations, including impaired cell attachment, proliferation, and toxicity. Nanotechnology may open new avenues to bone tissue engineering by forming new assemblies similar in size and shape to the existing hierarchical bone structure. Organic and inorganic nanobiomaterials are increasingly used for bone tissue engineering applications because they may allow to overcome some of the current restrictions entailed by bone regeneration methods. This review covers the applications of different organic and inorganic nanobiomaterials in the field of hard tissue engineering.

Mesoporous Silica Nanoparticles as Theranostic Antitumoral Nanomedicines

Nanoparticles have become a powerful tool in oncology not only as carrier of the highly toxic chemotherapeutic drugs but also as imaging contrast agents that provide valuable information about the state of the disease and its progression. The enhanced permeation and retention effect for loaded nanocarriers in tumors allow substantial improvement of selectivity and safety of anticancer nanomedicines. Additionally, the possibility to design stimuli-responsive nanocarriers able to release their payload in response to specific stimuli provide an excellent control on the administered dosage. The aim of this review is not to present a comprehensive revision of the different theranostic mesoporous silica nanoparticles (MSN) which have been published in the recent years but just to describe a few selected examples to offer a panoramic view to the reader about the suitability and effectiveness of these nanocarriers in the oncology field.

Chondroitin sulfate-hybridized zein nanoparticles for tumor-targeted delivery of docetaxel

Chondroitin sulfate-hybridized zein nanoparticles (zein/CS NPs) were developed for targeted delivery of docetaxel, which exhibited mean diameters of 157.8 ± 3.6 nm and docetaxel encapsulation efficiency of 64.2 ± 1.9 %. Docetaxel was released from the NPs in a sustained manner (∼72 h), following first-order kinetics. The zein/CS NPs showed improved colloidal stability, maintaining the initial size in serum for 12 h. The pre-treatment of CS reduced the uptake efficiency of the NPs by 23 % in PC-3 cells, suggesting the involvement of CD44-mediated uptake mechanism. The NPs showed 2.79-fold lower IC₅₀ values than free docetaxel. Enhanced tumor accumulation of the NPs was confirmed in PC-3 xenograft mice by near-infrared fluorescence imaging (35.3-fold, versus free Cy5.5). The NPs exhibited improved pharmacokinetic properties (9.5-fold longer terminal half-life, versus free docetaxel) and anti-tumor efficacy comparable to Taxotere with negligible systemic toxicity, suggesting zein/CS NPs could be a promising nanoplatform for targeted cancer therapy.

Innovatory role of nanomaterials as bio-tools for treatment of cancer

Conventional treatment modes like chemotherapy, thermal and radiations aimed at cancerous cells eradication are marked by destruction pointing the employment of nanomaterials as sustainable and auspicious materials for saving human lives. Cancer has been deemed as the second leading cause of death on a global scale. Nanomaterials employment in cancer treatment is based on the utilization of their inherent physicochemical characteristics in addition to their modification for using as nano-carriers and nano-vehicles eluted with anti-cancer drugs. Current work has reviewed the significant role of different types of nanomaterials in cancer therapeutics and diagnostics in a systematic way. Compilation of review has been done by analyzing voluminous investigations employing ERIC, MEDLINE, NHS Evidence and Web of Science databases. Search engines used were Google scholar, Jstore and PubMed. Current review is suggestive of the remarkable performance of nanomaterials making them candidates for cancer treatment for substitution of destructive treatment modes through investigation of their physicochemical characteristics, utilization outputs and long term impacts in patients.

Gold-based therapy: From past to present

Despite an abundant literature on gold nanoparticles use for biomedicine, only a few of the gold-based nanodevices are currently tested in clinical trials, and none of them are approved by health agencies. Conversely, ionic gold has been used for decades to treat human rheumatoid arthritis and benefits from 70-y hindsight on medical use. With a view to open up new perspectives in gold nanoparticles research and medical use, we revisit here the literature on therapeutic gold salts. We first summarize the literature on gold salt pharmacokinetics, therapeutic effects, adverse reactions, and the present repurposing of these ancient drugs. Owing to these readings, we evidence the existence of a common metabolism of gold nanoparticles and gold ions and propose to use gold salts as a "shortcut" to assess the long-term effects of gold nanoparticles, such as their fate and toxicity, which remain challenging questions nowadays. Moreover, one of gold salts side effects (i.e., a blue discoloration of the skin exposed to light) leads us to propose a strategy to biosynthesize large gold nanoparticles from gold salts using light irradiation. These hypotheses, which will be further investigated in the near future, open up new avenues in the field of ionic gold and gold nanoparticles-based therapies.

Single-Walled Carbon Nanohorns as Promising Nanotube-Derived Delivery Systems to Treat Cancer

Cancer has become one of the most prevalent diseases worldwide, with increasing incidence in recent years. Current pharmacological strategies are not tissue-specific therapies, which hampers their efficacy and results in toxicity in healthy organs. Carbon-based nanomaterials have emerged as promising nanoplatforms for the development of targeted delivery systems to treat diseased cells. Single-walled carbon nanohorns (SWCNH) are graphene-based horn-shaped nanostructure aggregates with a multitude of versatile features to be considered as suitable nanosystems for targeted drug delivery. They can be easily synthetized and functionalized to acquire the desired physicochemical characteristics, and no toxicological effects have been reported in vivo followed by their administration. This review focuses on the use of SWCNH as drug delivery systems for cancer therapy. Their main applications include their capacity to act as anticancer agents, their use as drug delivery systems for chemotherapeutics, photothermal and photodynamic therapy, gene therapy, and immunosensing. The structure, synthesis, and covalent and non-covalent functionalization of these nanoparticles is also discussed. Although SWCNH are in early preclinical research yet, these nanotube-derived nanostructures demonstrate an interesting versatility pointing them out as promising forthcoming drug delivery systems to target and treat cancer cells.

Vascular and extracellular matrix remodeling by physical approaches to improve drug delivery at the tumor site

INTRODUCTION

Modern comprehensive studies of tumor microenvironment changes allowed scientists to develop new and more efficient strategies that will improve anticancer drug delivery on site. The tumor microenvironment, especially the dense extracellular matrix, has a recognized capability to hamper the penetration of conventional drugs. Development and co-applications of strategies aiming at remodeling the tumor microenvironment are highly demanded to improve drug delivery at the tumor site in a therapeutic prospect.

AREAS COVERED

Increasing indications suggest that classical physical approaches such as exposure to ionizing radiations, hyperthermia or light irradiation, and emerging ones as sonoporation, electric field or cold plasma technology can be applied as standalone or associated strategies to remodel the tumor microenvironment. The impacts on vasculature and extracellular matrix remodeling of these physical approaches will be discussed with the goal to improve nanotherapeutics delivery at the tumor site.

EXPERT OPINION

Physical approaches to modulate vascular properties and remodel the extracellular matrix are of particular interest to locally control and improve drug delivery and thus increase its therapeutic index. They are particularly powerful as adjuvant to nanomedicine delivery; the development of these technologies could have extremely widespread implications for cancer treatment.[Figure: see text].

Tumor repolarization by an advanced liposomal drug delivery system provides a potent new approach for chemo-immunotherapy

Immunosuppressive cells in the tumor microenvironment allow cancer cells to escape immune recognition and support cancer progression and dissemination. To improve therapeutic efficacy, we designed a liposomal oxaliplatin formulation (PCL8-U75) that elicits cytotoxic effects toward both cancer and immunosuppressive cells via protease-mediated, intratumoral liposome activation. The PCL8-U75 liposomes displayed superior therapeutic efficacy across all syngeneic cancer models in comparison to free-drug and liposomal controls. The PCL8-U75 depleted myeloid-derived suppressor cells and tumor-associated macrophages in the tumor microenvironment. The combination of improved cancer cell cytotoxicity and depletion of immunosuppressive populations of immune cells is attractive for combination with immune-activating therapy. Combining the PCL8-U75 liposomes with a TLR7 agonist induced immunological rejection of established tumors. This combination therapy increased intratumoral numbers of cancer antigen-specific cytotoxic T cells and Foxp3^- T helper cells. These results are encouraging toward advancing liposomal drug delivery systems with anticancer and immune-modulating properties into clinical cancer therapy.

Indocyanine Green and Curcumin Co-Loaded Nano-Fireball-Like Albumin Nanoparticles Based on Near-Infrared-Induced Hyperthermia for Tumor Ablation

Background

Indocyanine green (ICG) has received considerable interest as a biocompatible organic photothermal agent, and curcumin (Cur) is considered an attractive natural chemopreventive and chemotherapeutic compound. However, the in vivo applicability of ICG and Cur is significantly restricted by their poor ability to target tumors and their extremely low solubility.

Materials and Methods

To address these problems, ICG/Cur-loaded albumin nanoparticles (ICG-BSA-Cur-NPs) based on the nab^TM (nanoparticle albumin-bound) technology were applied to neuroblastomas in vivo.

Results

The fabricated ICG-BSA-Cur-NPs were found to be spherical, ~150 nm in size and highly dispersible and stable in aqueous solution. Approximately 80% of the incorporated ICG and Cur were gradually released from the NPs over 48 h. All formulations of ICG-BSA-Cur-NPs (5~20 µg/mL) showed efficient hyperthermia profiles (up to 50–60°C within 5 min) in response to 808-nm NIR laser irradiation in vitro and in vivo. Notably, ICG-BSA-Cur-NPs illuminated with 808-nm laser irradiation (1.5 W/cm²) showed excellent cytotoxicity toward N2a cells in vitro and undisputable antitumor efficacy in N2a-xenografted mice in vivo, compared to other tested sample groups (tumor volumes for PBS, BSA-Cur-NPs, free ICG, and ICG-BSA-Cur-NPs groups were 1408.6 ± 551.9, 1190.6 ± 343.6, 888.6 ± 566.2, and 103.0 ± 111.3 mm³, respectively).

Conclusion

We demonstrate that these hyperthermal chemotherapeutic ICG-BSA-Cur-NPs have potential as a future brain tumor treatment.

Applications and challenges of thermoplasmonics

Over the past two decades, there has been a growing interest in the use of plasmonic nanoparticles as sources of heat remotely controlled by light, giving rise to the field of thermoplasmonics. The ability to release heat on the nanoscale has already impacted a broad range of research activities, from biomedicine to imaging and catalysis. Thermoplasmonics is now entering an important phase: some applications have engaged in an industrial stage, while others, originally full of promise, experience some difficulty in reaching their potential. Meanwhile, innovative fundamental areas of research are being developed. In this Review, we scrutinize the current research landscape in thermoplasmonics, with a specific focus on its applications and main challenges in many different fields of science, including nanomedicine, cell biology, photothermal and hot-electron chemistry, solar light harvesting, soft matter and nanofluidics.

The Biomolecular Corona of Lipid Nanoparticles for Gene Therapy

Gene therapy holds great potential for treating almost any disease by gene silencing, protein expression, or gene correction. To efficiently deliver the nucleic acid payload to its target tissue, the genetic material needs to be combined with a delivery platform. Lipid nanoparticles (LNPs) have proven to be excellent delivery vectors for gene therapy and are increasingly entering into routine clinical practice. Over the past two decades, the optimization of LNP formulations for nucleic acid delivery has led to a well-established body of knowledge culminating in the first-ever RNA interference therapeutic using LNP technology, i.e., Onpattro, and many more in clinical development to deliver various nucleic acid payloads. Screening a lipid library in vivo for optimal gene silencing potency in hepatocytes resulted in the identification of the Onpattro formulation. Subsequent studies discovered that the key to Onpattro's liver tropism is its ability to form a specific "biomolecular corona". In fact, apolipoprotein E (ApoE), among other proteins, adsorbed to the LNP surface enables specific hepatocyte targeting. This proof-of-principle example demonstrates the use of the biomolecular corona for targeting specific receptors and cells, thereby opening up the road to rationally designing LNPs. To date, however, only a few studies have explored in detail the corona of LNPs, and how to efficiently modulate the corona remains poorly understood. In this review, we summarize recent discoveries about the biomolecular corona, expanding the knowledge gained with other nanoparticles to LNPs for nucleic acid delivery. In particular, we address how particle stability, biodistribution, and targeting of LNPs can be influenced by the biological environment. Onpattro is used as a case study to describe both the successful development of an LNP formulation for gene therapy and the key influence of the biological environment. Moreover, we outline the techniques available to isolate and analyze the corona of LNPs, and we highlight their advantages and drawbacks. Finally, we discuss possible implications of the biomolecular corona for LNP delivery and we examine the potential of exploiting the corona as a targeting strategy beyond the liver to develop next-generation gene therapies.

Sensitization of drug resistant sarcoma tumors by membrane modulation via short chain sphingolipid-containing nanoparticles

Nanoparticles such as liposomes are able to overcome cancer treatment challenges such as multidrug resistance by increasing the bioavailability of the encapsulated drug, bypassing drug pumps or through targeting resistant cells. Here, we merge enhanced drug delivery by nanotechnology with tumor cell membrane modulation combined in a single formulation. This is achieved through the incorporation of Short chain sphingolipids (SCSs) in the liposomal composition, which permeabilizes cell membranes to amphiphilic drugs such as Doxorubicin (Dxr). To study the mechanism and capability of SCS-containing nanodevices to overcome Dxr resistance, a sensitive uterine sarcoma cell line, MES-SA, and a resistant derived cell line, MES-SA/MX2, were used. The mechanism of resistance was explored by lipidomics and flow cytometry, revealing significant differences in lipid composition and in P glycoprotein (Pgp) expression. In vitro assays show that SCS liposomes were able to reverse cell resistance, and importantly, display a higher net effect on resistant than sensitive cells. SCS lipids modulated the cell membrane of MES-SA/MX2 drug resistant cells, while Pgp expression was not affected. Furthermore, SCS-modified liposomes were evaluated in a sarcoma xenograft model on drug accumulation, pharmacokinetics and efficacy. SCS liposomes improved Dxr levels in tumor nuclei of MES-SA/MX2 tumor cells, which was accompanied by a delay in tumor growth of the resistant model. Here we show that Dxr accumulation in tumor cells by SCS-modified liposomes was especially improved in Dxr resistant cells, rendering Dxr as effective as in sensitive cells. Moreover, this phenomenon translated to improved efficacy when Dxr liposomes where modified with SCSs in the drug resistant tumor model, while no benefit was seen in the sensitive tumors.

On Complex Coacervate Core Micelles: Structure-Function Perspectives

The co-assembly of ionic-neutral block copolymers with oppositely charged species produces nanometric colloidal complexes, known, among other names, as complex coacervates core micelles (C3Ms). C3Ms are of widespread interest in nanomedicine for controlled delivery and release, whilst research activity into other application areas, such as gelation, catalysis, nanoparticle synthesis, and sensing, is increasing. In this review, we discuss recent studies on the functional roles that C3Ms can fulfil in these and other fields, focusing on emerging structure-function relations and remaining knowledge gaps.

Nitric Oxide Nano-Delivery Systems for Cancer Therapeutics: Advances and Challenges

Nitric oxide (NO) plays important roles in various physiological and pathological functions and processes in the human body. Therapeutic application of NO molecules has been investigated in various diseases, including cardiovascular disease, cancer, and infections. However, the extremely short half-life of NO, which limits its clinical use considerably, along with non-specific distribution, has resulted in a low therapeutic index and undesired adverse effects. To overcome the drawbacks of using this gaseous signaling molecule, researchers in the last several decades have focused on innovative medical technologies, specifically nanoparticle-based drug delivery systems (DDSs), because these systems alter the biodistribution of the therapeutic agent through controlled release at the target tissues, resulting in a significant therapeutic drug effect. Thus, the application of nano-systems for NO delivery in the field of biomedicine, particularly in the development of new drugs for cancer treatment, has been increasing worldwide. In this review, we discuss NO delivery nanoparticle systems, with the aim of improving drug delivery development for conventional chemotherapies and controlling multidrug resistance in cancer treatments.

Polydopamine-Incorporated Nanoformulations for Biomedical Applications

Polydopamine (PDA), a pigment in natural melanin, has attracted considerable attention because of its excellent optical properties, extraordinary adhesion, and good biocompatibility, which make it a promising material for application in energy, environmental, and biomedical fields. In this review, PDA-incorporated nanoformulations are focused for biomedical applications such as drug delivery, bioimaging, and tumor therapy. First, the recent advances in PDA-incorporated nanoformulations for drug delivery are discussed. Further, their application in boimaging, such as fluorescence imaging, photothermal imaging, and photoacoustic imaging, is reviewed. Next, their therapeutic applications, including chemotherapy, photodynamic therapy, photothermal therapy, and synergistic therapy are discussed. Finally, other biomedical applications of PDA-incorporated nanoformulations such as biosensing and clinical diagnosis are briefly presented. Finally, the biomedical applications of PDA-incorporated nanoformulations along with their prospects are summarized.

Intratumoral Distribution and pH-Dependent Drug Release of High Molecular Weight HPMA Copolymer Drug Conjugates Strongly Depend on Specific Tumor Substructure and Microenvironment

Stimulus-sensitive polymer drug conjugates based on high molecular weight N-(2-hydroxypropyl) methacrylamide (HPMA) copolymers carrying doxorubicin via a pH-dependent cleavable bond (pHPMA-Dox) were previously shown to be able to overcome multi-drug resistance. Nevertheless, a tumor type dependent differential response was observed. Although an improved and more selective tumor accumulation of pHPMA-Dox is generally achieved due to the enhanced permeability and retention (EPR) effect, little is known about the fate of these conjugates upon entering the tumor tissue, which could explain the different responses. In this study, we compared in vitro and in vivo accumulation and Dox-activation of pHPMA-Dox in three cancer cell line models (1411HP, A2780cis, HT29) and derived xenograft tumors using a near-infrared fluorescence-labeled pHPMA-Dox conjugate. Firstly, cytotoxicity assays using different pH conditions proved a stepwise, pH-dependent increase in cytotoxic activity and revealed comparable sensitivity among the cell lines. Using multispectral fluorescence microscopy, we were able to track the distribution of drug and polymeric carrier simultaneously on cellular and histological levels. Microscopic analyses of cell monolayers confirmed the assumed mechanism of cell internalization of the whole conjugate followed by intracellular cleavage and nuclear accumulation of Dox in all three cell lines. In contrast, intratumoral distribution and drug release in xenograft tumors were completely different and were associated with different tissue substructures and microenvironments analyzed by Azan- and Hypoxisense^®-staining. In 1411HP tumors, large vessels and less hypoxic/acidic microenvironments were associated with a pattern resulting from consistent tissue distribution and cellular uptake as whole conjugate followed by intracellular drug release. In A2780cis tumors, an inconsistent pattern of distribution partly resulting from premature drug release was associated with a more hypoxic/acidic microenvironment, compacted tumor tissue with compressed vessels and specific pre-damaged tissue structures. A completely different distribution pattern was observed in HT29 tumors, resulting from high accumulation of polymer in abundant fibrotic structures, with small embedded vessels featuring this tumor type together with pronounced premature drug release due to the strongly hypoxic/acidic microenvironment. In conclusion, the pattern of intratumoral distribution and drug release strongly depends on the tumor substructure and microenvironment and may result in different degrees of therapeutic efficacy. This reflects the pronounced heterogeneity observed in the clinical application of nanomedicines and can be exploited for the future design of such conjugates.

Natural Hydrogels Applied in Photodynamic Therapy

Natural hydrogels are three-dimensional (3D) water-retaining materials with a skeleton consisting of natural polymers, their derivatives or mixtures. Natural hydrogels can provide sustained or controlled drug release and possess some unique properties of natural polymers, such as biodegradability, biocompatibility and some additional functions, such as CD44 targeting of hyaluronic acid. Natural hydrogels can be used with photosensitizers (PSs) in photodynamic therapy (PDT) to increase the range of applications. In the current review, the pertinent design variables are discussed along with a description of the categories of natural hydrogels available for PDT.

Immune cells as tumor drug delivery vehicles

This review article describes the use of immune cells as potential candidates to deliver anti-cancer drugs deep within the tumor microenvironment. First, the rationale of using drug carriers to target tumors and potentially decrease drug-related side effects is discussed. We further explain some of the current limitations when using nanoparticles for this purpose. Next, a comprehensive step-by-step description of the migration cascade of immune cells is provided as well as arguments on why immune cells can be used to address some of the limitations associated with nanoparticle-mediated drug delivery. We then describe the benefits and drawbacks of using red blood cells, platelets, granulocytes, monocytes, macrophages, myeloid-derived suppressor cells, T cells and NK cells for tumor-targeted drug delivery. An additional section discusses the versatility of nanoparticles to load anti-cancer drugs into immune cells. Lastly, we propose increasing the circulatory half-life and development of conditional release strategies as the two main future pillars to improve the efficacy of immune cell-mediated drug delivery to tumors.

Genotoxic and Cytotoxic Activities of Lantadene A-Loaded Gold Nanoparticles (LA-AuNPS) in MCF-7 Cell Line: An in vitro Assessment

Gold nanoparticles (AuNPs) have been widely used in many applications. Their usage as drug delivery vehicles has also gained considerable attention due to their chemical and optical properties as well as their good biocompatibility. The present study was conducted to evaluate the efficiency of AuNPs in enhancing the cytotoxic and apoptotic induction activity of lantadene A (LA), separated from Lantana camara leaves, on the breast tumor cell line MCF-7 in vitro. By utilizing plant-mediated synthesis method of nanostructures, LA-loaded AuNPs (LA-AuNPs) were prepared and their formation was confirmed by means of ultraviolet–visible spectroscope, atomic force microscope, scanning electron microscope, and zeta potential. The cytotoxic effect of LA-AuNPs was analyzed using a methylthiazol tetrazolium assay and compared to free AuNPs and LA. The results indicated a significant increase in the reduction of MCF-7 cells viability after incubation with LA-AuNPs. As determined by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, LA-AuNPs induced a greater ratio of DNA-fragmented cells compared to LA-treated and untreated cells. Also, by operating real-time polymerase chain reaction, LA-AuNPs-treated cells displayed an increased upregulation of p53 expression and downregulation of BCL-2 expression in addition to a significant reduction in the level of BCL-2-BAX ratio. No significant effect was shown on the expression of BAX. Collectively, our results indicate that LA-AuNPs showed promising cytotoxicity to MCF-7 cells as a novel nanoscale preparation, likely via induction of apoptotic genes and stimulation of DNA fragmentation.

Perfusion-guided sonopermeation of neuroblastoma: a novel strategy for monitoring and predicting liposomal doxorubicin uptake in vivo

Neuroblastoma (NB) is the most common extracranial solid tumor in infants and children, and imposes significant morbidity and mortality in this population. The aggressive chemoradiotherapy required to treat high-risk NB results in survival of less than 50%, yet is associated with significant long-term adverse effects in survivors. Boosting efficacy and reducing morbidity are therefore key goals of treatment for affected children. We hypothesize that these may be achieved by developing strategies that both focus and limit toxic therapies to the region of the tumor. One such strategy is the use of targeted image-guided drug delivery (IGDD), which is growing in popularity in personalized therapy to simultaneously improve on-target drug deposition and assess drug pharmacodynamics in individual patients. IGDD strategies can utilize a variety of imaging modalities and methods of actively targeting pharmaceutical drugs, however in vivo imaging in combination with focused ultrasound is one of the most promising approaches already being deployed for clinical applications. Over the last two decades, IGDD using focused ultrasound with "microbubble" ultrasound contrast agents (UCAs) has been increasingly explored as a method of targeting a wide variety of diseases, including cancer. This technique, known as sonopermeation, mechanically augments vascular permeability, enabling increased penetration of drugs into target tissue. However, to date, methods of monitoring the vascular bioeffects of sonopermeation in vivo are lacking. UCAs are excellent vascular probes in contrast-enhanced ultrasound (CEUS) imaging, and are thus uniquely suited for monitoring the effects of sonopermeation in tumors. Methods: To monitor the therapeutic efficacy of sonopermeation in vivo, we developed a novel system using 2D and 3D quantitative contrast-enhanced ultrasound imaging (qCEUS). 3D tumor volume and contrast enhancement was used to evaluate changes in blood volume during sonopermeation. 2D qCEUS-derived time-intensity curves (TICs) were used to assess reperfusion rates following sonopermeation therapy. Intratumoral doxorubicin (and liposome) uptake in NB was evalauted ex vivo along with associated vascular changes. Results: In this study, we demonstrate that combining focused ultrasound therapy with UCAs can significantly enhance chemotherapeutic payload to NB in an orthotopic xenograft model, by improving delivery and tumoral uptake of long-circulating liposomal doxorubicin (L-DOX) nanoparticles. qCEUS imaging suggests that changes in flow rates are highly sensitive to sonopermeation and could be used to monitor the efficacy of treatment in vivo. Additionally, initial tumor perfusion may be a good predictor of drug uptake during sonopermeation. Following sonopermeation treatment, vascular biomarkers show increased permeability due to reduced pericyte coverage and rapid onset of doxorubicin-induced apoptosis of NB cells but without damage to blood vessels. Conclusion: Our results suggest that significant L-DOX uptake can occur by increasing tumor vascular permeability with microbubble sonopermeation without otherwise damaging the vasculature, as confirmed by in vivo qCEUS imaging and ex vivo analysis. The use of qCEUS imaging to monitor sonopermeation efficiency and predict drug uptake could potentially provide real-time feedback to clinicians for determining treatment efficacy in tumors, leading to better and more efficient personalized therapies. Finally, we demonstrate how the IGDD strategy outlined in this study could be implemented in human patients using a single case study.

N-Alkylisatin-Loaded Liposomes Target the Urokinase Plasminogen Activator System in Breast Cancer

The urokinase plasminogen activator and its receptor (uPA/uPAR) are biomarkers for metastasis, especially in triple-negative breast cancer. We prepared anti-mitotic N-alkylisatin (N-AI)-loaded liposomes functionalized with the uPA/uPAR targeting ligand, plasminogen activator inhibitor type 2 (PAI-2/SerpinB2), and assessed liposome uptake in vitro and in vivo. Receptor-dependent uptake of PAI-2-functionalized liposomes was significantly higher in the uPA/uPAR overexpressing MDA-MB-231 breast cancer cell line relative to the low uPAR/uPAR expressing MCF-7 breast cancer cell line. Furthermore, N-AI cytotoxicity was enhanced in a receptor-dependent manner. In vivo, PAI-2 N-AI liposomes had a plasma half-life of 5.82 h and showed an increased accumulation at the primary tumor site in an orthotopic MDA-MB-231 BALB/c-Fox1nu/Ausb xenograft mouse model, relative to the non-functionalized liposomes, up to 6 h post-injection. These findings support the further development of N-AI-loaded PAI-2-functionalized liposomes for uPA/uPAR-positive breast cancer, especially against triple-negative breast cancer, for which the prognosis is poor and treatment is limited.