Comparison of passive targeted delivery of inorganic and organic nanocarriers among different types of tumors

In this study, we have considered four types of nanoparticles (NPs): polylactic acid (PLA), gold (Au), calcium carbonate (CaCO3), and silica (SiO2) with similar sizes (TEM: 50-110 nm and DLS: 110-140 nm) to examine their passive accumulation in three different tumors: colon (CT26), melanoma (B16-F10), and breast (4T1) cancers. Our results demonstrate that each tumor model showed a different accumulation of NPs, in the following order: CT26 > B16-F10 > 4T1. The Au and PLA NPs were evidently characterized by a higher delivery efficiency in case of CT26 tumors compared to CaCO3 and SiO2 NPs. The Au NPs demonstrated the highest accumulation in B16-F10 cells compared to other NPs. These results were verified using SPECT, ex vivo fluorescence bioimaging, direct radiometry and histological analysis. Thus, this work contributes to new knowledge in passive tumor targeting of NPs and can be used for the development of new strategies for delivery of bioactive compounds.

Facile adipocyte uptake and liver/adipose tissue delivery of conjugated linoleic acid-loaded tocol nanocarriers for a synergistic anti-adipogenesis effect

Obesity is a major risk to human health. Adipogenesis is blocked by α-tocopherol and conjugated linoleic acid (CLA). However, their effect at preventing obesity is uncertain. The effectiveness of the bioactive agents is associated with their delivery method. Herein, we designed CLA-loaded tocol nanostructured lipid carriers (NLCs) for enhancing the anti-adipogenic activity of α-tocopherol and CLA. Adipogenesis inhibition by the nanocarriers was examined using an in vitro adipocyte model and an in vivo rat model fed a high fat diet (HFD). The targeting of the tocol NLCs into adipocytes and adipose tissues were also investigated. A synergistic anti-adipogenesis effect was observed for the combination of free α-tocopherol and CLA. Nanoparticles with different amounts of solid lipid were developed with an average size of 121‒151 nm. The NLCs with the smallest size (121 nm) showed greater adipocyte internalization and differentiation prevention than the larger size. The small-sized NLCs promoted CLA delivery into adipocytes by 5.5-fold as compared to free control. The nanocarriers reduced fat accumulation in adipocytes by counteracting the expression of the adipogenic transcription factors peroxisome proliferator activated receptor (PPAR)γ and CCAAT/enhancer-binding protein (C/EBP)α, and lipogenic enzymes acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS). Localized administration of CLA-loaded tocol NLCs significantly reduced body weight, total cholesterol, and liver damage indicators in obese rats. The biodistribution study demonstrated that the nanoparticles mainly accumulated in liver and adipose tissues. The NLCs decreased adipocyte hypertrophy and cytokine overexpression in the groin and epididymis to a greater degree than the combination of free α-tocopherol and CLA. In conclusion, the lipid-based nanocarriers were verified to inhibit adipogenesis in an efficient and safe way.

Biomimetic nanomedicines for precise atherosclerosis theranostics

Atherosclerosis (AS) is a leading cause of the life-threatening cardiovascular disease (CVD), creating an urgent need for efficient, biocompatible therapeutics for diagnosis and treatment. Biomimetic nanomedicines (bNMs) are moving closer to fulfilling this need, pushing back the frontier of nano-based drug delivery systems design. This review seeks to outline how these nanomedicines (NMs) might work to diagnose and treat atherosclerosis, to trace the trajectory of their development to date and in the coming years, and to provide a foundation for further discussion about atherosclerotic theranostics.

Targeted drug delivery systems for elemene in cancer therapy: The story thus far

Elemene (ELE) is a group of broad-spectrum anticancer active ingredients with low toxicity extracted from traditional Chinese medicines (TCMs), such as Curcumae Rhizoma and Curcuma Radix, which can exert antitumour activities by regulating various signal pathways and targets. However, the strong hydrophobicity, short half-life, low bioavailability and weak in vivo targeting ability of ELE restrict its use. Targeted drug delivery systems based on nanomaterials are among the most viable methods to overcome these shortcomings. In this review, we first summarize recent studies on the clinical uses of ELE as an adjunct antitumour drug. ELE-based combination strategies have great promise for enhancing efficacy, reducing adverse reactions, and improving patients' quality of life and immune function. Second, we summarize recent studies on the antitumour mechanisms of ELE and ELE-based combination strategies. The potential mechanisms include inducing pyroptosis and ferroptosis, promoting senescence, regulating METTL3-mediated m6A modification, suppressing the Warburg effect, and inducing apoptosis and cell cycle arrest. Most importantly, we comprehensively summarize studies on the combination of targeted drug delivery systems with ELE, including passively and actively targeted drug delivery systems, stimuli-responsive drug delivery systems, and codelivery systems for ELE combined with other therapies, which have great promise in improving drug bioavailability, increasing drug targeting ability, controlling drug release, enhancing drug efficacy, reducing drug adverse effects and reversing MDR. Our summary will provide a reference for the combination of TCMs such as ELE with advanced targeted drug delivery systems in the future.

Nanomedicines: intervention in inflammatory pathways of cancer

Inflammation is a complex defense process that maintains tissue homeostasis. However, this complex cascade, if lasts long, may contribute to pathogenesis of several diseases. Chronic inflammation has been exhaustively studied in the last few decades, for its contribution in development and progression of cancer. The intrinsic limitations of conventional anti-inflammatory and anti-cancer therapies triggered the development of nanomedicines for more effective and safer therapies. Targeting inflammation and tumor cells by nanoparticles, encapsulated with active therapeutic agents, offers a promising outcome with patient survival. Considerable technological success has been achieved in this field through exploitation of tumor microenvironment, and recognition of molecules overexpressed on endothelial cells or macrophages, through enhanced vascular permeability, or by rendering biomimetic approach to nanoparticles. This review focusses on the inflammatory pathways in progression of a tumor, and advancement in nanotechnologies targeting these pathways. We also aim to identify the gaps that hinder the successful clinical translation of nanotherapeutics with further clinical studies that will allow oncologist to precisely identify the patients who may be benefited from nanotherapy at time when promotion or progression of tumor initiates. It is postulated that the nanomedicines, in near future, will shift the paradigm of cancer treatment and improve patient survival.

Advances in nuclei targeted delivery of nanoparticles for the management of cancer

A carrier is inserted into the appropriate organelles (nucleus) in successful medication transport, crucial to achieving very effective illness treatment. Cell-membrane targeting is the major focus of using nuclei to localize delivery. It has been demonstrated that high quantities of anticancer drugs can be injected directly into the nuclei of cancer cells, causing the cancer cells to die and increasing the effectiveness of chemotherapy. There are several effective ways to functionalize Nanoparticles (NPs), including changing their chemical makeup or attaching functional groups to their surface to increase their ability to target organelles. To cause tumor cells to apoptosis, released medicines must engage with molecular targets on particular organelles when their concentration is high enough. Targeted medication delivery studies will increasingly focus on organelle-specific delivery.

Active targeting schemes for nano-drug delivery systems in osteosarcoma therapeutics

Osteosarcoma, the most common malignant tumor of the bone, seriously influences people's lives and increases their economic burden. Conventional chemotherapy drugs achieve limited therapeutic effects owing to poor targeting and severe systemic toxicity. Nanocarrier-based drug delivery systems can significantly enhance the utilization efficiency of chemotherapeutic drugs through targeting ligand modifications and reduce the occurrence of systemic adverse effects. A variety of ligand-modified nano-drug delivery systems have been developed for different targeting schemes. Here we review the biological characteristics and the main challenges of current drug therapy of OS, and further elaborate on different targeting schemes and ligand selection for nano-drug delivery systems of osteosarcoma, which may provide new horizons for the development of advanced targeted drug delivery systems in the future.

Size-switchable polymer-based nanomedicines in the advanced therapy of rheumatoid arthritis

Chronic inflammatory diseases such as rheumatoid arthritis represent a substantial socio-economic impact and have a high prevalence in the modern world. Nano-sized polymer therapeutics have shown suitable characteristics for becoming the next generation of anti-inflammatory nanomedicines. Here, we present biocompatible and stimuli-sensitive N-(2-hydroxypropyl)methacrylamide based polymer conjugates with the anti-inflammatory drug dexamethasone (DEX), which has been tailored for prolonged blood circulation, enhanced inflammatory site accumulation, site-specific drug release and subsequent elimination of the carrier via urine excretion. The hydrodynamic size of novel polymer-DEX nanomedicine was adjusted to prolong its blood circulation whilst maintaining the renal excretability of the polymer carrier after drug release in inflamed tissue. The therapeutic efficacy of the studied polymer nanomedicines was evaluated in a model of dissipated chronic arthritis, i.e. collagen II-induced arthritis, in mice. The pH-sensitive drug attachment enabled enhanced blood circulation with minimal systemic drug release, as well as rapid drug activation in affected joints. Importantly, unlike free DEX, the polymer nanomedicines were able to diminish joint inflammation and arthritis-induced bone damage - even at a reduced dosing regimen - as evaluated by micro computed tomography (micro-CT).

Targeting cancer stem cells with polymer nanoparticles for gastrointestinal cancer treatment

Nanomaterials are developing rapidly in the medical field, bringing new hope for treating various refractory diseases. Among them, polymer nanomaterials, with their excellent properties, have been used to treat various diseases, such as malignant tumors, diabetes, and nervous system diseases. Gastrointestinal cancer is among the cancers with the highest morbidity and mortality worldwide. Cancer stem cells are believed to play an important role in the occurrence and development of tumors. This article summarizes the characteristics of gastrointestinal cancer stem cells and reviews the latest research progress in treating gastrointestinal malignant tumors using polymer nanoparticles to target cancer stem cells. In addition, the review article highlights the potential of polymer nanoparticles in targeting gastrointestinal cancer stem cells.

Delivery of triptolide: a combination of traditional Chinese medicine and nanomedicine

As a natural product with various biological activities, triptolide (TP) has been reported in anti-inflammatory, anti-tumor and anti-autoimmune studies. However, the narrow therapeutic window, poor water solubility, and fast metabolism limit its wide clinical application. To reduce its adverse effects and enhance its efficacy, research and design of targeted drug delivery systems (TDDS) based on nanomaterials is one of the most viable strategies at present. This review summarizes the reports and studies of TDDS combined with TP in recent years, including passive and active targeting of drug delivery systems, and specific delivery system strategies such as polymeric micelles, solid lipid nanoparticles, liposomes, and stimulus-responsive polymer nanoparticles. The reviewed literature presented herein indicates that TDDS is a multifunctional and efficient method for the delivery of TP. In addition, the advantages and disadvantages of TDDS are sorted out, aiming to provide reference for the combination of traditional Chinese medicine and advanced nano drug delivery systems (NDDS) in the future.

From Passive Targeting to Personalized Nanomedicine: Multidimensional Insights on Nanoparticles' Interaction with the Tumor Microenvironment

Nanomedicine is revolutionizing the treatment of cancer and has achieved unprecedented outcomes over the past decades. The accumulation of Nanoparticles (NPs) in different tumors relies mainly on the Enhanced Permeability and Retention (EPR) effect benefiting from the wide fenestrae of the tumor vasculature and the lack of lymphatic drainage. However, the EPR effect is recognized as a heterogeneous phenomenon resulting in heterogeneous outcomes of clinical trials. Extensive efforts are exerted to enhance the outcomes of nanomedicine in a larger cohort of patients by employing active targeting strategies. However, actively targeted NPs accumulate in tumors by the EPR effect and hence fail to achieve convincing therapeutic outcomes. These obstacles are gradually being removed by improving the understanding of the Tumor Microenvironment (TME) and the mechanistic interaction of the NPs with its different components. In this review, we provide detailed insights into the past concerns of drug targeting, the current trends of TME reengineering, and the future implications for overcoming past hurdles. Strategies explored in this regard included the use of companion diagnostics and the modulation of the protein corona associated with the systemic administration of NPs and their interaction with biological macromolecules.

Multi-organ targeting of HIV-1 viral reservoirs with etravirine loaded nanostructured lipid carrier: An in-vivo proof of concept

The inadequate bioavailability and toxicity potential of antiretroviral therapy limit their effectiveness in the complete eradication of HIV from viral reservoirs. The penetration of these drugs into the brain is challenging because of the unfavorable physicochemical properties required to cross the membranes, limiting the transport of the drugs. Thus, in the current study, the authors report a nanocarrier-based drug delivery of a highly hydrophobic drug to overcome the existing limitations of the conventional therapies. An explicitly simple approach was used to overcome the limitations of existing anti-HIV therapies. The monophasic hot homogenized solution of lipid, drug, and solubilizer was diluted with the predetermined hot surfactant solution followed by the ultrasonication to generate the polydisperse nanoparticles with the size range of 50-1000 nm. The anti-HIV1 potential of nanostructured lipid carriers of Etravirine on HIV-infected cell lines showed efficacy with an appreciable increase in the therapeutic index as compared with the plain drug. Further, the results obtained from confocal microscopy along with flow cytometry exhibited efficient uptake of the nanocarrier loaded with coumarin-6 in cells. The pharmacokinetics of Etravirine nanostructured carriers was significantly better in all aspects compared to the plain drug solution, which could be attributed to molecular dispersion in the lipid matrix of the nanocarrier. A significant enhancement of Etravirine concentration of several-fold was also observed in the liver, ovary, lymph node, and brain, respectively, as compared to plain drug solution when assessed by biodistribution studies in rats. In conclusion, ETR-NLC systems could serve as a promising approach for simultaneous multi-site targeting and could provide therapeutic benefits for the efficient eradication of HIV/AIDS infections.

Different hydration states and passive tumor targeting ability of polyethylene glycol-modified dendrimers with high and low PEG density

It has been reported that the amount of intermediate water, defined as water molecules loosely bound to a material, is a useful index of the material's bio-inert properties. Polyethylene glycol (PEG) is a well-known biocompatible polymer with a large amount of intermediate water. Many researchers have showed that PEGylated nanoparticles are passively accumulated in tumor tissues owing to their enhanced permeability and retention (EPR) effects. Dendrimers are regularly branched polymers with highly controllable size and structure, which can be exploited as potent drug carriers. In this study, we investigated the tripartite relationship among the PEG density, the hydration state, and the passive tumor targeting property, using PEGylated dendrimers. The fully PEGylated dendrimer, PEG64-den, showed similar hydration behavior to PEG and a passive tumor targeting property. In contrast, the hydration state of the partly PEGylated dendrimer, PEG5-den, was different from that of PEG64-den, and the passive tumor targeting property was not observed. This is the first report to show the hydration state of a drug carrier as well as discuss a relationship between the hydration state and biodistribution.

Conventional Nanosized Drug Delivery Systems for Cancer Applications

Clinical responses and tolerability of conventional nanocarriers (NCs) are sometimes different from those expected in anticancer therapy. Thus, new smart drug delivery systems (DDSs) with stimuli-responsive properties and novel materials have been developed. Several clinical trials demonstrated that these DDSs have better clinical therapeutic efficacy in the treatment of many cancers than free drugs. Composition of DDSs and their surface properties increase the specific targeting of therapeutics versus cancer cells, without affecting healthy tissues, and thus limiting their toxicity versus unspecific tissues. Herein, an extensive revision of literature on NCs used as DDSs for cancer applications has been performed using the available bibliographic databases.

Lipoamino acid-based cerasomes for doxorubicin delivery: Preparation and in vitro evaluation

Cerasomes are hybrid organic-inorganic nanoparticles (NPs) that could be considered as liposomes with rather durable silicon shell. In this study, several cerasome-forming lipoamino acids (CFLA) were synthesized and used as structural blocks for cerasome preparation. Pure cerasomes which contained only CFLA, and mixed cerasomes based on a mixture of CFLA with a disintegrating dipalmitoylphosphatidylcholine (DPPC) lipid were fabricated and characterized in terms of morphology, mean size, ζ-potential, stability at storage. All obtained cerasome samples were found to be much more stable at storage than conventional liposomes (120 and 10 days, respectively). The cerasomes were loaded with doxorubicin (DOX) and tested in vitro using human breast adenocarcinoma MCF-7. Effects of the lipid composition on the physical-chemical properties and cellular uptake of the cerasomes both in 2D (monolayer culture) and 3D (multicellular tumor spheroids) were studied. The biggest accumulation efficiencies as well as the highest cytotoxicity level were found for the mixed cationic cerasomes. These cerasomes could be proposed as promising drug delivery system for cancer treatment.

Facile synthesis of pH-responsive polymersomes based on lipidized PEG for intracellular co-delivery of curcumin and methotrexate

pH-responsive polymersomes were obtained by self-assembling of a carboxyl-terminated PEG amphiphile achieved via esterification of PEG diacid with PEG40stearate. The obtained vesicular systems had spherical shape and a mean diameter of 70 nm. The pH sensitivity was assessed by measuring the variations of particles mean diameter after incubation in media mimicking the physiological (pH 7.4) or tumor (pH 5.0) conditions, recording a significant increase of the vesicles dimensions at acidic pH. The ability of the polymersomes to carry both hydrophobic and hydrophilic drugs was evaluated by loading the vesicles with curcumin and methotrexate, respectively, obtaining high encapsulation efficiencies and pH-dependent release profiles. The drug-loaded polymeric vesicles exhibited improved cytotoxic potential against MCF-7 cancer cell line and were found to be highly hemocompatible. Finally, cellular uptake experiments on MCF-7 cancer cells were conducted to demonstrate the ability of the designed polymersomes to enhance drug penetration inside the cells.

PEGylated crushed gold shell-radiolabeled core nanoballs for in vivo tumor imaging with dual positron emission tomography and Cerenkov luminescent imaging

BACKGROUND

Radioactive isotope-labeled gold nanomaterials have potential biomedical applications. Here, we report the synthesis and characterization of PEGylated crushed gold shell-radioactive iodide-124-labeled gold core nanoballs (PEG-¹²⁴I-Au@AuCBs) for in vivo tumor imaging applications through combined positron emission tomography and Cerenkov luminescent imaging (PET/CLI).

RESULTS

PEG-¹²⁴I-Au@AuCBs showed high stability and sensitivity in various pH solutions, serum, and in vivo conditions and were not toxic to tested cells. Combined PET/CLI clearly revealed tumor lesions at 1 h after injection of particles, and both signals remained visible in tumor lesions at 24 h, consistent with the biodistribution results.

CONCLUSION

Taken together, the data provided strong evidence for the application of PEG-¹²⁴I-Au@AuCBs as promising imaging agents in nuclear medicine imaging of various biological systems, particularly in cancer diagnosis.

Evaluating Nanomedicines: Obstacles and Advancements

Continued advancements in nanotechnology are expanding the boundaries of medical research, most notably as drug delivery agents for treatment against cancer. Drug delivery with nanotechnology can offer greater control over the biodistribution of therapeutic agents to improve the therapeutic index. In the last 20 years, a number of nanomedicines have transitioned into the clinic. As nanomedicines evolve, techniques to properly evaluate their safety and efficacy must also evolve. Characterization methods for nano-based materials must be adapted to the demands of nanomedicine developers and regulators. This second edition book provides updated characterization protocols designed to address the clinical potential of nanomedicines during their preclinical development. In this chapter, the characterization challenges of nanoparticles intended for drug delivery will be discussed, along with examples of advancements and improvements in nanomedicine characterization.

RGD modified and PEGylated lipid nanoparticles loaded with puerarin: Formulation, characterization and protective effects on acute myocardial ischemia model

CONTEXT

Puerarin has been widely used as a therapeutic agent for the treatment of cardiovascular diseases. However, its rapid elimination half-life in plasma and poor water solubility limits its clinical efficacy.

OBJECTIVE

RGD modified and PEGylated solid lipid nanoparticles loaded with puerarin (RGD/PEG-PUE-SLN) were developed to improve bioavailability of PUE, to prolong retention time in vivo and to enhance its protective effect on acute myocardial ischemia model.

METHODS

In the present study, RGD-PEG-DSPE was synthesized. RGD/PEG-PUE-SLN were prepared by the solvent evaporation method with some modifications. The physicochemical properties of NPs were characterized, the pharmacokinetics, biodistribution, pharmacodynamic behavior of RGD/PEG-PUE-SLN were evaluated in acute MI rats.

RESULTS

The mean diameter, zeta potential, entrapment efficiency and drug loading capacity for RGD/PEG-PUE-SLN were observed as 110.5nm, -26.2mV, 85.7% and 16.5% respectively. PUE from RGD/PEG-PUE-SLN exhibited sustained drug release with a burst release during the initial 12h and a followed sustained release. Pharmacokinetics results indicated that AUC increased from 52.93 (μg/mLh) for free PUE to 176.5 (μg/mLh) for RGD/PEG-PUE-SLN. Similarly, T_1/2 increased from 0.73h for free PUE to 2.62h for RGD/PEG-PUE-SLN. RGD/PEG-PUE-SLN exhibited higher drug concentration in the heart and plasma compared with other PUE formulations. It can be clearly seen that the infarct size of RGD/PEG-PUE-SLN is the lowest among all the formulation.

CONCLUSION

We conclude that RGD modified and PEGylated SLN are promising candidate delivery vehicles for cardioprotective drugs in treatment of myocardial infarction.

Efficient ferrocifen anticancer drug and Bcl-2 gene therapy using lipid nanocapsules on human melanoma xenograft in mouse

Metastatic melanoma has been described as a highly aggressive cancer with low sensibility to chemotherapeutic agents. New types of drug, such as metal-based drugs (ferrocifens) have emerged and could represent an alternative for melanoma treatment since they show interesting anticancer potential. Furthermore, molecular analysis has evidenced the role of apoptosis in the low sensibility of melanomas and especially of the key regulator, Bcl-2. The objective of this study was to combine two strategies in the same lipid nanocapsules (LNCs): i) gene therapy to modulate anti-apoptotic proteins by the use of Bcl-2 siRNA, and ii) ferrocifens as a new type of anticancer agent. The efficient gene silencing with LNCs was verified by the specific extinction of Bcl-2 in melanoma cells. The cellular toxicity of ferrocifens (ferrociphenol (FcDiOH) or Ansa-FcDiOH) was demonstrated, showing higher efficacy than dacarbazine. Interestingly, the association of siBcl-2 LNCs with Ansa-FcDiOH demonstrated a significant effect on melanoma cell viability. Moreover, the co-encapsulation of siRNA and ferrocifens was successfully performed into LNCs for animal experiments. A reduction of tumor volume and mass was proved after siBcl-2 LNC treatment and Ansa-FcDiOH LNC treatment, individually (around 25%). Finally, the association of both components into the same LNCs increased the reduction of tumor volume to about 50% compared to the control group. In conclusion, LNCs appeared to provide a promising tool for the co-encapsulation of a metal-based drug and siRNA.

Size effect of Au/PAMAM contrast agent on CT imaging of reticuloendothelial system and tumor tissue

Polyamidoamine (PAMAM)-entrapped Au nanoparticles were synthesized with distinct sizes to figure out the size effect of Au-based contrast agent on CT imaging of passively targeted tissues. Au/PAMAM nanoparticles were first synthesized with narrow distribution of particles size of 22.2 ± 3.1, 54.2 ± 3.7, and 104.9 ± 4.7 nm in diameters. Size effect leads no significant difference on X-ray attenuation when Au/PAMAM was ≤0.05 mol/L. For CT imaging of a tumor model, small Au/PAMAM were more easily internalized via endocytosis in the liver, leading to more obviously enhanced contrast. Similarly, contrast agents with small sizes were more effective in tumor imaging because of the enhanced permeability and retention effect. Overall, the particle size of Au/PAMAM heavily affected the efficiency of CT enhancement in imaging RES and tumors.

Liver-targeting liposome drug delivery system and its research progress in liver diseases

Liposome-based targeted therapy is mainly divided into active targeting, passive targeting, and physical and chemical targeting. In terms of liver targeting, because of specificity, active liver-targeting liposomes have received more and more attention, and these types of liposomes can be used in liver fibrosis, hepatitis and other chronic liver diseases. In addition, the particle size could control the passive liver targeting of liposomes, while the liver-targeted liposomes of the physical and chemical targeting type have advantages in treating hepatic carcinoma. In this paper, we focus on the basics and application of liver-targeting liposome drug delivery system in hepatic diseases.

Trends on polymer- and lipid-based nanostructures for parenteral drug delivery to tumors

PURPOSE

The dawn of the state-of-the-art methods of cancer treatments, nano-based delivery systems, has dispensed with the mainstream chemotherapy for being inadequate in yielding productive results and the numerous reported side effects. The popularity of this complementary approach in the course of the last two decades has been primarily attributed to its capacity to elevate the therapeutic index of anticancer drugs as well as removing the impassable delivery barriers in solid tumors with the minimal damage to the normal tissues.

METHODS

The PubMed database was consulted to compile this review.

RESULTS

A wide range of minuscule organic and inorganic nanomaterials, with dimensions not exceeding hundred nanometers, has led to hope for cancer therapy to flare-up once again due to possessing a number of exclusive traits for passive and active tumor targeting, some of which are EPR effect, high interstitial pressure of tumor, overexpressed receptors and angiogenesis. Although a limited number of liposomal and polymer-based therapeutic nanoparticles have gained applicability, a vast number of nanoparticles are still being trailed in order to be fully developed.

CONCLUSIONS

This study provides an overview of the advantages/disadvantages of nanocarriers for cancer drug delivery.

Targeted polymer-drug conjugates: Current progress and future perspective

The combination of polymer technology and targeted drug delivery may pave the way for more effective yet safer therapeutic options for cancer therapy. Polymer-drug conjugates belonging to polymer therapeutics represent an emerging approach for drug delivery. The development of smart targeted polymer-drug conjugates that can specifically deliver drugs at a sustained rate to tumor cells may substantially improve the therapeutic index of anticancer agents. In this update, we provide an overview of the most important targeting molecules, and systemically summarize the recent advances in the development of tumor-targeted polymer-drug conjugates. Additionally, several promising approaches for the future will also be presented.

SOD1 nanozyme salvages ischemic brain by locally protecting cerebral vasculature

Copper/zinc superoxide dismutase (CuZnSOD; SOD1) is widely considered as a potential therapeutic candidate for pathologies involving oxidative stress, but its application has been greatly hindered by delivery issues. In our previous study, nanoformulated SOD1 (cl-nanozyme) was shown to decrease infarct volume and improve sensorimotor functions after a single intravenous (IV) injection in a rat middle cerebral artery occlusion (MCAO) model of ischemia/reperfusion (I/R) injury (stroke). However, it remained unclear how cl-nanozyme was able to deliver SOD1 to the brain and exert therapeutic efficacy. The present study aims to answer this question by exploring micro-distribution pattern of cl-nanozyme in the rat brain after stroke. Immunohistochemistry studies demonstrated cl-nanozyme co-localization with fibrin along damaged arteries and capillaries in the ischemic hemisphere. We further found that cl-nanozyme can be cross-linked into thrombi formed after I/R injury in the brain, and this effect is independent of animal species (rat/mouse) used for modeling I/R injury. This work is also the first report reinforcing therapeutic potential of cl-nanozyme in a well-characterized mouse MCAO model of I/R injury.

Cancer targeted therapeutics: From molecules to drug delivery vehicles

The pitfall of all chemotherapeutics lies in drug resistance and the severe side effects experienced by patients. One way to reduce the off-target effects of chemotherapy on healthy tissues is to alter the biodistribution of drug. This can be achieved in two ways: Passive targeting utilizes shape, size, and surface chemistry to increase particle circulation and tumor accumulation. Active targeting employs either chemical moieties (e.g. peptides, sugars, aptamers, antibodies) to selectively bind to cell membranes or responsive elements (e.g. ultrasound, magnetism, light) to deliver its cargo within a local region. This article will focus on the systemic administration of anti-cancer agents and their ability to home to tumors and, if relevant, distant metastatic sites.

Advanced targeted therapies in cancer: Drug nanocarriers, the future of chemotherapy

Cancer is the second worldwide cause of death, exceeded only by cardiovascular diseases. It is characterized by uncontrolled cell proliferation and an absence of cell death that, except for hematological cancers, generates an abnormal cell mass or tumor. This primary tumor grows thanks to new vascularization and, in time, acquires metastatic potential and spreads to other body sites, which causes metastasis and finally death. Cancer is caused by damage or mutations in the genetic material of the cells due to environmental or inherited factors. While surgery and radiotherapy are the primary treatment used for local and non-metastatic cancers, anti-cancer drugs (chemotherapy, hormone and biological therapies) are the choice currently used in metastatic cancers. Chemotherapy is based on the inhibition of the division of rapidly growing cells, which is a characteristic of the cancerous cells, but unfortunately, it also affects normal cells with fast proliferation rates, such as the hair follicles, bone marrow and gastrointestinal tract cells, generating the characteristic side effects of chemotherapy. The indiscriminate destruction of normal cells, the toxicity of conventional chemotherapeutic drugs, as well as the development of multidrug resistance, support the need to find new effective targeted treatments based on the changes in the molecular biology of the tumor cells. These novel targeted therapies, of increasing interest as evidenced by FDA-approved targeted cancer drugs in recent years, block biologic transduction pathways and/or specific cancer proteins to induce the death of cancer cells by means of apoptosis and stimulation of the immune system, or specifically deliver chemotherapeutic agents to cancer cells, minimizing the undesirable side effects. Although targeted therapies can be achieved directly by altering specific cell signaling by means of monoclonal antibodies or small molecules inhibitors, this review focuses on indirect targeted approaches that mainly deliver chemotherapeutic agents to molecular targets overexpressed on the surface of tumor cells. In particular, we offer a detailed description of different cytotoxic drug carriers, such as liposomes, carbon nanotubes, dendrimers, polymeric micelles, polymeric conjugates and polymeric nanoparticles, in passive and active targeted cancer therapy, by enhancing the permeability and retention or by the functionalization of the surface of the carriers, respectively, emphasizing those that have received FDA approval or are part of the most important clinical studies up to date. These drug carriers not only transport the chemotherapeutic agents to tumors, avoiding normal tissues and reducing toxicity in the rest of the body, but also protect cytotoxic drugs from degradation, increase the half-life, payload and solubility of cytotoxic agents and reduce renal clearance. Despite the many advantages of all the anticancer drug carriers analyzed, only a few of them have reached the FDA approval, in particular, two polymer-protein conjugates, five liposomal formulations and one polymeric nanoparticle are available in the market, in contrast to the sixteen FDA approval of monoclonal antibodies. However, there are numerous clinical trials in progress of polymer-protein and polymer-drug conjugates, liposomal formulations, including immunoliposomes, polymeric micelles and polymeric nanoparticles. Regarding carbon nanotubes or dendrimers, there are no FDA approvals or clinical trials in process up to date due to their unresolved toxicity. Moreover, we analyze in detail the more promising and advanced preclinical studies of the particular case of polymeric nanoparticles as carriers of different cytotoxic agents to active and passive tumor targeting published in the last 5 years, since they have a huge potential in cancer therapy, being one of the most widely studied nano-platforms in this field in the last years. The interest that these formulations have recently achieved is stressed by the fact that 90% of the papers based on cancer therapeutics with polymeric nanoparticles have been published in the last 6 years (PubMed search).

Advanced targeted nanomedicine

Targeted drug delivery has been the major topic in drug formulation and delivery. As nanomedicine emerges to create nano scale therapeutics and diagnostics, it is still essential to embed targeting capability to these novel systems to make them useful. Here we discuss various targeting approaches for delivery of therapeutic and diagnostic nano materials in view of search for more universal methods to target diseased tissues. Many diseases are accompanied with hypoxia and acidosis. Coating nanoparticles with pH Low Insertion Peptides (pHLIPs) increases efficiency of targeting acidic diseased tissues. It has been showing promising results to create future nanotheranostics for cancer and other diseases which are dominating in the present world.

Targeted photodynamic therapy in head and neck squamous cell carcinoma: heading into the future

The aim of this article is to give an insight into the future of photodynamic therapy (PDT) in head and neck squamous cell carcinoma (HNSCC). Through the combination of a photosensitizing agent with light and oxygen, PDT produces highly cytotoxic reactive oxygen species leading to selective tumor eradication. PDT is an attractive treatment for focal therapy of localized tumors, especially in the case of unresectable tumors. In HNSCC, over 1500 patients have been treated by PDT, and the majority of them responded quite favorably to this treatment. However, the non-negligible photosensitization of healthy tissue is a major limitation for the clinical application of PDT. Improvement in tumor selectivity is the main challenge that can be taken up by the use of a new generation of photosensitizing nanoparticles. Passive targeting, by using functionalised nanocarriers to target to overexpressed transmembrane receptors afford attractive solutions. To this day, epidermal growth factor receptor (EGFR) remains the only validated molecular target for HNSCC, and photosensitizer immunoconjugates to EGFR have been developed for the intracellular delivery of photosensitizing agents. Depending on coordinated research between biomarkers, specific ligands, and photosensitizers, similar approaches could be rapidly developed. In addition, some photosensitizers hold high fluorescence yield and therefore could emerge as theranostic agents.

Bioresponsive nanohydrogels based on HEAA and NIPA for poorly soluble drugs delivery

Environmentally sensitive hydrogels have gained considerable attention in recent years as one of the most promising drug delivery systems. In the present study, two new formulations of pH and temperature stimuli-responsive nanogels (NGs) based on poly-N-isopropylacrylamide (NIPA), N-hydroxyethyl acrylamide (HEAA) and tert-butyl 2-acrylamidoethyl carbamate (2AAECM) were synthesized and evaluated for passive targeting of paclitaxel (PTX). Nanogels were prepared by microemulsion polymerization method using N-methylenebis(acrylamide) (NMBA) as crosslinking agent. TEM images and DLS results showed nanosized spherical hydrogels. FTIR spectra confirmed the synthesis of nanogels by radical polymerization among vinyl groups of monomers. The PTX loading capacity, encapsulation efficiency and in vitro release were analyzed by HPLC. The cumulative release profile of the PTX-loaded nanohydrogels within 144h showed a faster drug release at acid pH (pH 5), similar to those observed at lysosome compartment, whereas a fewer PTX amount was released from NGs at pH similar to plasma levels. Cellular uptake assays revealed rapid penetration and intracellular accumulation of those nanogels in MCF7, HeLa and T47D cells after 48h incubation. MTT assays showed cell viability dependence on concentration and time incubation. Finally, the PTX effect on cell viability showed a G2/M cell arrest after using PTX-loaded NGs and pure PTX.

pH and glutathion-responsive hydrogel for localized delivery of paclitaxel

pH and glutathion (GSH)- responsive nanogels (NGs) based on poly-N-isopropylacrilamide (NIPA), N-hydroxyethyl acrylamide (HEAA) and tert-butyl 2-acrylamidoethyl carbamate (2AAECM) were synthesized by a microemulsion polymerization method using N, N'-cystaminebisacrylamide (CBA) as a crosslinking agent and evaluated for passive targeting of paclitaxel (PTX). Physicochemical characterizations of unloaded and PTX-loaded NGs, such as particle size, morphology, encapsulation efficiency and in vitro PTX release were also assessed. Electron microscopy techniques (SEM and TEM) as well as dynamic light scattering (DLS) analysis showed nanosized spherical hydrogels. FTIR spectra confirmed the synthesis of nanogels by free radical polymerization among vinyl groups of monomers. In vitro release was analyzed by high-performance liquid chromatography (HPLC) and differences between two NG formulations were obtained. Nanogels released almost 64% of PTX after 50h at GSH concentrations equivalent to that in the cellular cytosol, whereas less PTX was released from NGs at pH and GSH levels similar to plasma. Cellular uptake and cytotoxicity were also demonstrated by using coumarin-6 and MTT assays, respectively, for three tumor cell lines (MCF7, HeLa and T47D). Cellular uptake assays revealed rapid uptake within 2h and intracellular accumulation of coumarin-6-loaded nanogels after 48 h incubation. MTT assays showed changes in cell viability at different concentrations of PTX formulations, as well as pure PTX (10 μM, 20 μM and 30 μM). To investigate PTX effect on cell viability, changes in cell cycle were examined by flow cytometry and a G2/M cell arrest was demonstrated. Overall, synthesized nanogels may be used as potential carriers for hydrophobic anticancer drugs.

Nanocapsules based on mPEGylated artesunate prodrug and its cytotoxicity

mPEGylated artesunate prodrug was synthesized via esterification between poly(ethylene glycol) monomethyl ether (mPEG) and artesunate (ART). The product was inclined to form nanocapsules in aqueous media due to its amphiphilic nature. These nanocapsules showed narrow size distribution, with an average particle size of 88.7 nm measured by dynamic laser scattering (DLS). Their vesical morphology was further confirmed by transmission electron microscopy (TEM). We found that the release of ART from the nanocapsules was controllable, which was contributed to the easily hydrolyzed property of the ester bond. In addition, the cytotoxicity of the prodrug against L1210 and MCF7 cell lines showed an essential decrease compared with the free ART. These results present a new strategy in designing anti-tumor ART nanocapsules for targeting tumor cells.