Ligand Conformation Dictates Membrane and Endosomal Trafficking of Arginine-Glycine-Aspartate (RGD)-Functionalized Mesoporous Silica Nanoparticles

Engineered mesoporous silica nanoparticles, new insight nanoplatforms into effective cancer gene therapy

The use of nucleic acid to control the expression of genes relevant to tumor progression is a key therapeutic approach in cancer research. Therapeutics based on nucleic acid provide novel concepts for untreatable targets. Nucleic acids as molecular medications must enter the target cell to be effective and obstacles in the systemic delivery of DNA or RNA limit their use in a clinical setting. The creation of nucleic acid delivery systems based on nanoparticles in order to circumvent biological constraints is advancing quickly. The ease of synthesis and surface modification, biocompatibility, biodegradability, cost-effectiveness and high loading capability of nucleic acids have prompted the use of mesoporous silica nanoparticles (MSNs) in gene therapy. The unique surface features of MSNs facilitate their design and decoration for high loading of nucleic acids, immune system evasion, cancer cell targeting, controlled cargo release, and endosomal escape. Reports have demonstrated successful therapeutic outcomes with the administration of a variety of engineered MSNs capable of delivering genes to tumor sites in laboratory animals. This comprehensive review of studies about siRNA, miRNA, shRNA, lncRNA and CRISPR/Cas9 delivery by MSNs reveals engineered MSNs as a safe and efficient system for gene transfer to cancer cells and cancer mouse models.

Engineering core-shell mesoporous silica and Fe3O4@Au nanosystems for targeted cancer therapeutics: a review

The extensive utilization of nanoparticles in cancer therapies has inspired a new field of study called cancer nanomedicine. In contrast to traditional anticancer medications, nanomedicines offer a targeted strategy that eliminates side effects and has high efficacy. With its vast surface area, variable pore size, high pore volume, abundant surface chemistry and specific binding affinity, mesoporous silica nanoparticles (MPSNPs) are a potential candidate for cancer diagnosis and treatment. However, there are several bottlenecks associated with nanoparticles, including specific toxicity or affinity towards particular body fluid, which can cater by architecting core-shell nanosystems. The core-shell chemistries, synergistic effects, and interfacial heterojunctions in core-shell nanosystems enhance their stability, catalytic and physicochemical attributes, which possess high performance in cancer therapeutics. This review article summarizes research and development dedicated to engineering mesoporous core-shell nanosystems, especially silica nanoparticles and Fe3O4@Au nanoparticles, owing to their unique physicochemical characteristics. Moreover, it highlights state-of-the-art magnetic and optical attributes of Fe3O4@Au and MPSNP-based cancer therapy strategies. It details the designing of Fe3O4@Au and MPSN to bind with drugs, receptors, ligands, and destroy tumour cells and targeted drug delivery. This review serves as a fundamental comprehensive structure to guide future research towards prospects of core-shell nanosystems based on Fe3O4@Au and MPSNP for cancer theranostics.

Engineering mesoporous silica nanoparticles for drug delivery: where are we after two decades?

The present review details a chronological description of the events that took place during the development of mesoporous materials, their different synthetic routes and their use as drug delivery systems. The outstanding textural properties of these materials quickly inspired their translation to the nanoscale dimension leading to mesoporous silica nanoparticles (MSNs). The different aspects of introducing pharmaceutical agents into the pores of these nanocarriers, together with their possible biodistribution and clearance routes, would be described here. The development of smart nanocarriers that are able to release a high local concentration of the therapeutic cargo on-demand after the application of certain stimuli would be reviewed here, together with their ability to deliver the therapeutic cargo to precise locations in the body. The huge progress in the design and development of MSNs for biomedical applications, including the potential treatment of different diseases, during the last 20 years will be collated here, together with the required work that still needs to be done to achieve the clinical translation of these materials. This review was conceived to stand out from past reports since it aims to tell the story of the development of mesoporous materials and their use as drug delivery systems by some of the story makers, who could be considered to be among the pioneers in this area.

Photodynamic Therapy-Current Limitations and Novel Approaches

Photodynamic therapy (PDT) mostly relies on the generation of singlet oxygen, via the excitation of a photosensitizer, so that target tumor cells can be destroyed. PDT can be applied in the settings of several malignant diseases. In fact, the earliest preclinical applications date back to 1900’s. Dougherty reported the treatment of skin tumors by PDT in 1978. Several further studies around 1980 demonstrated the effectiveness of PDT. Thus, the technique has attracted the attention of numerous researchers since then. Hematoporphyrin derivative received the FDA approval as a clinical application of PDT in 1995. We have indeed witnessed a considerable progress in the field over the last century. Given the fact that PDT has a favorable adverse event profile and can enhance anti-tumor immune responses as well as demonstrating minimally invasive characteristics, it is disappointing that PDT is not broadly utilized in the clinical setting for the treatment of malignant and/or non-malignant diseases. Several issues still hinder the development of PDT, such as those related with light, tissue oxygenation and inherent properties of the photosensitizers. Various photosensitizers have been designed/synthesized in order to overcome the limitations. In this Review, we provide a general overview of the mechanisms of action in terms of PDT in cancer, including the effects on immune system and vasculature as well as mechanisms related with tumor cell destruction. We will also briefly mention the application of PDT for non-malignant diseases. The current limitations of PDT utilization in cancer will be reviewed, since identifying problems associated with design/synthesis of photosensitizers as well as application of light and tissue oxygenation might pave the way for more effective PDT approaches. Furthermore, novel promising approaches to improve outcome in PDT such as selectivity, bioengineering, subcellular/organelle targeting, etc. will also be discussed in detail, since the potential of pioneering and exceptional approaches that aim to overcome the limitations and reveal the full potential of PDT in terms of clinical translation are undoubtedly exciting. A better understanding of novel concepts in the field (e.g. enhanced, two-stage, fractional PDT) will most likely prove to be very useful for pursuing and improving effective PDT strategies.

Virus-Mimicking Mesoporous Silica Nanoparticles with an Electrically Neutral and Hydrophilic Surface to Improve the Oral Absorption of Insulin by Breaking Through Dual Barriers of the Mucus Layer and the Intestinal Epithelium

Protein and peptide drugs orally suffer from extremely low bioavailability principally for the complicated gastrointestinal environment along with the difficulty of passing through the mucus layer and the underlying epithelium. In our work, we fabricated mesoporous silica nanoparticles with modification groups (MSN-NH₂@COOH/CPP5) that effectively penetrated the mucus layer and passed through the intestinal epithelium by mimicking the virus surface. Naked nanoparticles were prepared with inner pores of 6 nm diameter to allow efficient insulin loading and coated with the cationic cell-penetrating KLPVM peptide and the anionic glutaric anhydride to yield hydrophilic MSN-NH₂@COOH/CPP5 with a ζ-potential of -0.49 mV. The apparent permeability coefficient of virus-mimicking nanoparticles was 14.61 × 10^-5 cm/s. The virus-mimicking nanoparticles showed dramatically lower binding to mucin and faster penetration of the mucus layer than positively charged nanoparticles (MSN@NH₂) with a ζ-potential of +35.00 mV. The KLPVM peptide enhanced the uptake of MSN-NH₂@COOH/CPP5 by coculturing Caco-2 and E12 cells as an intestinal epithelium model. MSN-NH₂@COOH/CPP5 enhanced apical-to-basal transcytosis for being internalized primarily through caveolae-mediated endocytosis. Indeed, for MSN-NH₂@COOH/CPP5, the transepithelial transport of the Caco-2 cell monolayer was 2.4-fold higher than MSN@NH₂ and 2.0-fold higher than MSN-NH₂@COOH. In vitro, loading insulin into nanoparticles maintained the bioactivity of the protein under simulated intestinal conditions. Insulin loaded into MSN-NH₂@COOH/CPP5 reduced the diabetic rats' blood glucose level by nearly 50%. The bioavailability of insulin encapsulated in the MSN-NH₂@COOH/CPP5 nanoparticles was 2.1-fold more than insulin when administered directly into the jejunum. Nanoparticles with modifications indicated no significant toxicity in in vitro or in vivo preliminary studies. The obstacles of the mucus layer and intestinal epithelium may be effectively conquered by these virus-mimicking nanoparticles for oral delivery of protein and peptide drugs.

Mesoporous silica nanoparticles: synthesis methods and their therapeutic use-recent advances

Mesoporous silica nanoparticles (MSNPs) are a particular example of innovative nanomaterials for the development of drug delivery systems. MSNPs have recently received more attention for biological and pharmaceutical applications due to their capability to deliver therapeutic agents. Due to their unique structure, they can function as an effective carrier for the delivery of therapeutic agents to mitigate diseases progress, reduce inflammatory responses and consequently improve cancer treatment. The potency of MSNPs for the diagnosis and management of various diseases has been studied. This literature review will take an in-depth look into the properties of various types of MSNPs (e.g. shape, particle and pore size, surface area, pore volume and surface functionalisation), and discuss their characteristics, in terms of cellular uptake, drug delivery and release. MSNPs will then be discussed in terms of their therapeutic applications (passive and active tumour targeting, theranostics, biosensing and immunostimulative), biocompatibility and safety issues. Also, emerging trends and expected future advancements of this carrier will be provided.

Multimodal Decorations of Mesoporous Silica Nanoparticles for Improved Cancer Therapy

The presence of leaky vasculature and the lack of lymphatic drainage of small structures by the solid tumors formulate nanoparticles as promising delivery vehicles in cancer therapy. In particular, among various nanoparticles, the mesoporous silica nanoparticles (MSN) exhibit numerous outstanding features, including mechanical thermal and chemical stability, huge surface area and ordered porous interior to store different anti-cancer therapeutics with high loading capacity and tunable release mechanisms. Furthermore, one can easily decorate the surface of MSN by attaching ligands for active targeting specifically to the cancer region exploiting overexpressed receptors. The controlled release of drugs to the disease site without any leakage to healthy tissues can be achieved by employing environment responsive gatekeepers for the end-capping of MSN. To achieve precise cancer chemotherapy, the most desired delivery system should possess high loading efficiency, site-specificity and capacity of controlled release. In this review we will focus on multimodal decorations of MSN, which is the most demanding ongoing approach related to MSN application in cancer therapy. Herein, we will report about the recently tried efforts for multimodal modifications of MSN, exploiting both the active targeting and stimuli responsive behavior simultaneously, along with individual targeted delivery and stimuli responsive cancer therapy using MSN.

Targeted and stimuli-responsive mesoporous silica nanoparticles for drug delivery and theranostic use

For cancer therapy, the usefulness of mesoporous silica nanoparticles (MPSNPs) has been widely discussed, likely due to its inorganic nature and excellent structural features. The MPSNPs-based chemotherapeutics have been promisingly delivered to their target sites that help to minimize side effects and improve therapeutic effectiveness. A wide array of studies have been conducted to functionalize drug-loaded MPSNPs using targeting ligands and stimuli-sensitive substances. In addition, anticancer drugs have been precisely delivered to their target sites using MPSNPs, which respond to multi-stimuli. Furthermore, MPSNPs have been extensively tested for their safety and compatibility. The toxicity level of MPSNPs is substantially lower as compared to that of colloidal silica; however, in oxidative stress, they exhibit cytotoxic features. The biocompatibility of MPSNPs can be improved by modifying their surfaces. This article describes the production procedures, functionalization, and applications of biocompatible MPSNPs in drug delivery.

Bioceramics: from bone substitutes to nanoparticles for drug delivery

Since the second half of the 20th century, bioceramics are used for bone repair and regeneration. Inspired by bones and teeth, and aimed at mimicking their structure and composition, several artificial bioceramics were developed for biomedical applications. And nowadays, in the 21st century, with the increasing prominence of nanoscience and nanotechnology, certain bioceramics are being used to build smart drug delivery systems, among other applications. This minireview will mainly describe both tendencies through the research work carried out by the research team of María Vallet-Regí.

Engineering docetaxel-loaded micelles for non-small cell lung cancer: a comparative study of microfluidic and bulk nanoparticle preparation

Bulk preparation of micelles has the drawbacks of facile formation of large aggregates and heterogeneous particle size distribution. Microfluidic technology has shown clear potential to address these challenges for robust nanomedicine applications. In this study, docetaxel-loaded PLGA-PEG-Mal-based micelles were prepared by microfluidics and dialysis methods and their physicochemical properties were analyzed. The biological behaviors of these micelles were also investigated in the non-small cell lung cancer (NSCLC) cell line A549 in vitro as well as in vivo. Encouragingly, the mean particle size of the micelles prepared by microfluidics (DMM) was smaller, with an average size of 72 ± 1 nm and a narrow size distribution with a polydispersity index (PDI) of 0.072; meanwhile, micelles prepared by the dialysis method (DMD) had larger particle sizes (range, 102 to 144 nm) and PDIs (up to 0.390). More importantly, significantly high drug loading was achieved using the microfluidic process. The IC50 value of DMM was lower than that of DMD. Whole-body fluorescence imaging of live mice showed that DMM achieved higher accumulation in tumors compared with DMD. DMM showed superior antitumor efficacy, with a tumor inhibition rate of 91.5%. Moreover, pathological histology analysis revealed that no evident biological toxicity was caused by the micelles. In addition, Arg-Gly-Asp (RGD) was employed as a targeting agent on the basis of DMM to prepare targeting micelles, and the targeting micelles exhibited stronger cytotoxicity and obvious antitumor efficacy. In conclusion, DMM may have obvious clinical advantages for the treatment of NSCLC due to its optimized physiochemical properties. Therefore, microfluidic technology-based micelles are a promising platform as an effective drug delivery system for incorporating anticancer agents.

Mesoporous silica nanoparticles in nanomedicine applications

In the last few years mesoporous silica nanoparticles (MSNs) have gained the attention of the nanomedicine research community, especially for the potential treatment of cancer. Although this topic has been reviewed before, periodic updates on such a hot topic are necessary due to the dynamic character of this field. The reasons that make MSNs so attractive for designing controlled drug delivery systems lie beneath their physico-chemical stability, easy functionalisation, low toxicity and their great loading capacity of many different types of therapeutic agents. The present brief overview tries to cover some of the recent findings on stimuli-responsive mesoporous silica nanocarriers together with the efforts to design targeted nanosystems using that platform. The versatility of those smart nanocarriers has promoted them as very promising candidates to be used in the clinic in the near future to overcome some of the pitfalls of conventional medicine.

Anticancer Efficacy of Targeted Shikonin Liposomes Modified with RGD in Breast Cancer Cells

Shikonin (SHK) has been proven to have a good anti-tumor effect. However, poor water solubility and low bioavailability limit its wide application in clinical practice. In this study, to overcome these drawbacks, RGD-modified shikonin-loaded liposomes (RGD-SSLs-SHK) were successfully prepared. It exhibited excellent physicochemical characteristics including particle size, zeta potential, encapsulation efficiency, and delayed release time. Meanwhile, the targeting activity of the RGD-modified liposomes was demonstrated by flow cytometry and confocal microscopy in the α_vβ₃-positive MDA-MB-231 cells. Besides exhibiting greater cytotoxicity in vitro, compared with non-targeted shikonin-loaded liposomes (SSLs-SHK), RGD-SSLs-SHK could also evidently induce apoptosis by decreasing the expression of Bcl-2 and increasing the expression of Bax. It could also inhibit cell proliferation, migration, invasion, and adhesion by reducing the expression of MMP-9 and the level of NF-κB p65, but did not affect the expression of MMP-2 in the MDA-MB-231 cells. Therefore, these findings indicated that the strategy to use RGD-modified liposomes as carriers for targeted delivery of shikonin is a very promising approach to achieve breast cancer targeted therapy.

Mesoporous Silica Nanoparticles for Drug Delivery: Current Insights

This manuscript reviews the recent progress on mesoporous silica nanoparticles as drug delivery systems. Their intrinsic structural, textural and chemical features permit to design versatile multifunctional nanosystems with the capability to target the diseased tissue and release the cargo on demand upon exposition to internal or external stimuli. The degradation rate of these nanocarriers in diverse physiological fluids is overviewed obeying their significance for their potential translation towards clinical applications. To conclude, the balance between the benefits and downsides of this revolutionary nanotechnological tool is also discussed.

Serum Protein Adsorption Enhances Active Leukemia Stem Cell Targeting of Mesoporous Silica Nanoparticles

The functionalization of nanoparticles with a ligand targeting receptors overexpressed by the target cells is a commonly used strategy when aiming at nanoparticle-based, cell type-specific drug delivery.1-4 However, the influence of particle surface chemistry on the targetability has received much less attention. The surface charge is known to directly or indirectly affect the nanoparticle cellular uptake kinetics by influencing serum protein adsorption.5-7 Thus, it is fair to assume that both the specificity and cellular uptake kinetics of targeted nanoparticles are influenced by the nanoparticle charge, both of which are important parameters for controlling cell-specific drug delivery efficiency. We therefore studied the influence of the surface chemistry of mesoporous silica nanoparticles (MSNs) carrying identical amounts of a specific antibody (anti-B220) on the selectivity toward B220-positive leukemia stem cells. The uptake by these cells was higher compared to the nanoparticle uptake by B220-negative leukemia stem cells, demonstrating uptake specificity. In addition, the adsorption of serum proteins onto the differently charged MSNs was studied by SDS-PAGE. Interestingly, the highest selectivity was not observed for the MSNs with the lowest level of serum protein adsorption, which suggests that proteins present in the protein corona of the MSNs may positively influence the selective uptake of targeted nanoparticles. For the particles exhibiting the highest selectivity, successful selective delivery of cargo to the B220-positive cells was demonstrated. Taken together, our results indicate that nanoparticle surface charge and adsorption of serum proteins is an important factor for enhancing selectivity in targeted delivery of drugs using nanoparticulate vectors, an observation tentatively attributed to enhanced cellular internalization kinetics in the presence of adsorbed serum proteins on the nanoparticles.

Biocompatibility of Multi-Imaging Engineered Mesoporous Silica Nanoparticles: In Vitro and Adult and Fetal In Vivo Studies

Despite potentially serious adverse effects of engineered nanoparticles on maternal health and fetal development, little is known about their transport across the placenta. Human and animal studies are primarily limited to ex vivo approaches; the lack of a real-time, minimally invasive tool to study transplacental transport is clear. We have developed functionalized mesoporous silica nanoparticles (MSN) for use in magnetic resonance, ultrasound, and fluorescent imaging. This material is designed as a model for, or a carrier of, environmental toxicants, allowing for in vivo evaluation. To establish a baseline of biocompatibility, we present data describing MSN tolerance using in vitro and in vivo models. In cultured cells, MSN were tolerated to a dose of 125 µg/mL with minimal effect on viability and doubling time. For the 42 day duration of the study, none of the mice exhibited behaviors usually indicative of distress (lethargy, anemia, loss of appetite, etc.). In gravid mice, the body and organ weights of MSN-exposed dams were equivalent to those of control dams. Embryos exposed to MSN during early gestation were underweight by a small degree, while embryos exposed during late gestation were of a slightly larger weight. The rate of spontaneous fetal resorptions were equivalent in exposed and control mice. Maternal livers and sera were screened for a complement of cytokines/chemokines and reactive oxygen/nitrogen species (ROS/RNS). Only granulocyte-colony stimulating factor was elevated in mice exposed to MSN during late gestation, while ROS/RNS levels were elevated in mice exposed during early/mid gestation. These findings may usher future experiments investigating environmental toxicants using real-time assessment of transport across the placenta.

Intracellular pH-responsive and rituximab-conjugated mesoporous silica nanoparticles for targeted drug delivery to lymphoma B cells

Background

One of the main problems in B cell lymphoma treatment is severe adverse effects and low therapeutic efficacy resulting from systemic chemotherapy. A pH-sensitive controlled drug release system based on mesoporous silica nanoparticles was constructed for targeted drug delivery to tumor cells to reduce systemic toxicity and improve the therapeutic efficacy.

Methods

In this study, the doxorubicin (DOX) was filled into the mesopores of the functional MSNs (DMSNs). Furthermore, rituximab was introduced as the targeted motif of functional DMSNs using an avidin-biotin bridging method to evaluate the targetability to tumor cells. Then, the cell viability and apoptosis efficiency after treatment with rituximab-conjugated DMSNs (RDMSNs) were estimated by using CCK-8 assay and flow cytometry, respectively. Additionally, the research in vivo was performed to evaluate the enhanced antitumor efficacy and the minimal toxic side effects of RDMSNs. Also, TUNEL staining assay was employed to explore the mechanism of antitumor effects of RDMSNs.

Results

This targeted drug delivery system exhibited low premature drug release at a physiological pH and efficient pH-responsive intracellular release under weakly acidic conditions. The in vitro tests confirmed that targeted RDMSNs could selectively adhere to the surface of lymphoma B cells via specific binding with the CD20 antigen and be internalized into CD20 positive Raji cells but few CD20 negative Jurkat cells, which leads to increased cytotoxicity and apoptosis of the DOX in Raji cells due to the release of the entrapped DOX with high efficiency in the slightly acidic intracellular microenvironment. Furthermore, the in vivo investigations confirmed that RDMSNs could efficiently deliver DOX to lymphoma B cells by pH stimuli, thus inducing cell apoptosis and inhibiting tumor growth, while with minimal toxic side effects.

Conclusions

This targeted and pH-sensitive controlled drug delivery system has the potential for promising application to enhance the therapeutic index and reduce the side effects of B cell lymphoma therapy.

A peptide-decorated and curcumin-loaded mesoporous silica nanomedicine for effectively overcoming multidrug resistance in cancer cells

A robust peptide-functionalized mesoporous silica nanomedicine loading with curcumin and doxorubicin (DOX/CUR@MSN-Pep) has been successfully constructed to effectively overcome multidrug resistance in cancer cells.

Advances in Peptide Functionalization on Mesoporous Silica Nanoparticles for Controlled Drug Release

During the last decade, using versatile, promising, and fascinating mesoporous silica nanoparticles (MSNs) as site-specific and stimuli-responsive drug delivery systems (DDSs) has received concentrated research interest. As one of the most attractive surface modification units, peptides have inherent bioactivity, biodegradability and biocompatibility. Recent progresses in the utilization of versatile peptides for surface functionalization of MSNs to achieve cell-specific targeting, fluorescence imaging, and intracellular diagnosis and treatment of tumors are summarized in this review. The various functional peptides decorated on the MSNs are introduced and classified into three types, including targeting peptides, stimuli-responsive peptides and multifunctional chimeric peptides. The limitations and challenges of peptide modified MSNs and their potential applications are further discussed.

Smart Mesoporous Nanomaterials for Antitumor Therapy

The use of nanomaterials for the treatment of solid tumours is receiving increasing attention by the scientific community. Among them, mesoporous silica nanoparticles (MSNs) exhibit unique features that make them suitable nanocarriers to host, transport and protect drug molecules until the target is reached. It is possible to incorporate different targeting ligands to the outermost surface of MSNs to selectively drive the drugs to the tumour tissues. To prevent the premature release of the cargo entrapped in the mesopores, it is feasible to cap the pore entrances using stimuli-responsive nanogates. Therefore, upon exposure to internal (pH, enzymes, glutathione, etc.) or external (temperature, light, magnetic field, etc.) stimuli, the pore opening takes place and the release of the entrapped cargo occurs. These smart MSNs are capable of selectively reaching and accumulating at the target tissue and releasing the entrapped drug in a specific and controlled fashion, constituting a promising alternative to conventional chemotherapy, which is typically associated with undesired side effects. In this review, we overview the recent advances reported by the scientific community in developing MSNs for antitumor therapy. We highlight the possibility to design multifunctional nanosystems using different therapeutic approaches aimed at increasing the efficacy of the antitumor treatment.

Mesoporous-Silica-Functionalized Nanoparticles for Drug Delivery

The ever-growing interest for finding efficient and reliable methods for treatment of diseases has set a precedent for the design and synthesis of new functional hybrid materials, namely porous nanoparticles, for controlled drug delivery. Mesoporous silica nanoparticles (MSNPs) represent one of the most promising nanocarriers for drug delivery as they possess interesting chemical and physical properties, thermal and mechanical stabilities, and are biocompatibile. In particular, their easily functionalizable surface allows a large number of property modifications further improving their efficiency in this field. This Concept article deals with the advances on the novel methods of functionalizing MSNPs, inside or outside the pores, as well as within the walls, to produce efficient and smart drug carriers for therapy.

A new targeting agent for the selective drug delivery of nanocarriers for treating neuroblastoma

Novel targeting agents against neuroblastoma based on the meta-iodobenzylguanidine (MIBG) moiety were synthesized and biologically evaluated for nanocarrier vectorization. These compounds have been anchored on the surface of drug loaded mesoporous silica nanocarriers, resulting in the improved cellular uptake in tumoral cells. Neuroblastoma (NB) is the most frequent extracranial pediatric tumor. Advanced forms of the disease (metastatic and/or refractory) have a dismal prognosis despite the combination of chemotherapy, radiotherapy, surgery and bone narrow transplants. These treatments carry severe side effects and, in some cases, compromise the life of the patient. MIBG has been widely applied in the medical diagnosis of NB due to its affinity for tumor cells through the norepinephrine transporter (NET), which is expressed in 90% of NB tumors. The exclusive accumulation of MIBG in neuroblastoma has been widely studied; however, its properties have been never exploited as a targeting agent in nanocarrier drug delivery systems. Several structural analogues of MIBG have been prepared and attached on the surface of nanocarriers. Their selective internalization has been tested against human neuroblastoma cells, which show, in the best case, cellular uptake four times higher than that of the naked nanosystem. Furthermore, in vivo experiments showed preferential and selective accumulation and retention of the targeted nanosystem comparing with the naked and only PEGylated counterpart systems. This novel nanosystem could be easily applicable to all kinds of drug delivery nanocarriers, providing a universal tool for neuroblastoma chemotherapies that is superior to classical approaches through a novel nanosystem exclusively designed to target this terrible malignancy.

Lactosaminated mesoporous silica nanoparticles for asialoglycoprotein receptor targeted anticancer drug delivery

BACKGROUND

Mesoporous silica nanoparticles (MSNs) have several attractive properties as a drug delivery system, such as ordered porous structure, large surface area, controllable particle size as well as interior and exterior dual-functional surfaces. The purpose of this study was to develop novel lactosaminated mesoporous silica nanoparticles (Lac-MSNs) for asialoglycoprotein receptor (ASGPR) targeted anticancer drug delivery.

RESULTS

Lac-MSNs with an average diameter of approximately 100 nm were prepared by conjugation of lactose with 3-aminopropyl triethoxysilane modified MSNs. Characterization of Lac-MSNs indicated a huge Brunauer-Emmett-Teller (BET) surface area (1012 m(2)/g), highly ordered 2D hexagonal symmetry, an unique mesoporous structure with average pore size of 3.7 nm. The confocal microscopy and flow cytometric analysis illustrated Lac-MSNs were effectively endocytosed by ASGPR-positive hepatoma cell lines, HepG2 and SMMC7721. In contrast, non-selective endocytosis of Lac-MSNs was found in ASGPR-negative NIH 3T3 cells. The cellular uptake study showed the internalization process was energy-consuming and predominated by clathrin-mediated pathway. Model drug docetaxel (DTX) was loaded in the mesopores of Lac-MSNs by wetness impregnation method. In vitro cytotoxicity assay showed that DTX transported by Lac-MSNs effectively inhibited the growth of HepG2 and SMMC7721 cells in a time- and concentration- dependent manner.

CONCLUSIONS

These results demonstrated that Lac-MSNs could be a promising inorganic carrier system for targeted intracellular anti-cancer drug delivery.

Advances in mesoporous silica nanoparticles for targeted stimuli-responsive drug delivery

INTRODUCTION

Mesoporous silica nanoparticles (MSNPs) are one of the most promising inorganic drug delivery systems (DDSs). The design and development of tumour-targeted MSNPs with stimuli-responsive drug release capability aim at enhancing the efficiency and minimising the side effects of anti-tumour drugs for cancer therapy.

AREAS COVERED

This review provides an overview of the scientific advances in MSNPs for tumour-targeted stimuli-responsive drug delivery. The key factors that govern the passive accumulation of MSNPs within solid tumours such as size, shape and surface functionalisation are roughly described. The different active targeting strategies for the specific retention and uptake of MSNPs by tumour cells are also outlined. The approaches developed so far for the synthesis of smart MSNPs capable of releasing the trapped drugs in response to internal or external stimuli and their applications are reviewed. Critical considerations in the use of MSNPs for the treatment of cancer treatment are discussed. The future prospects and key factors concerning the clinical application of MSNPs are considered throughout the manuscript.

EXPERT OPINION

MSNPs are promising nanocarriers to efficiently transport and site-specifically deliver highly toxic drugs, such as chemotherapeutic agents for cancer treatment. However, there are certain issues that should be overcome to improve the suitability of MSNPs for clinical applications. Increasing the penetration capability of MSNPs within tumour tissues, providing them of appropriate colloidal stability in physiological fluids and ensuring that their active targeting capability and stimuli-responsive performance are preserved in complex biological media are of foremost significance. Few in vivo evaluation tests of MSNPs have been reported and much research effort into this field is mandatory to be able to move from bench to bedside.

Cellular uptake of multilayered capsules produced with natural and genetically engineered biomimetic macromolecules

Multilayered microcapsules of chitosan and biomimetic elastin-like recombinamers (ELRs) were prepared envisaging the intracellular delivery of active agents. Two ELRs containing either a bioactive RGD sequence or a scrambled non-functional RDG were used to construct two types of functionalized polymeric microcapsules, both of spherical shape ∼4μm in diameter. Cell viability studies with human mesenchymal stem cells (hMSCs) were performed using microcapsule/cell ratios between 5:1 and 100:1. After 3 and 72h of co-incubation, no signs of cytotoxicity were found, but cells incubated with RGD-functionalized microcapsules exhibited higher viability values than RDG cells. The internalization efficacy and bioavailability of encapsulated DQ-ovalbumin were assessed by monitoring the fluorescence changes in the cargo. The data show that surface functionalization did not significantly influence internalization by hMSCs, but the bioavailability of DQ-ovalbumin degraded faster when encapsulated within RGD-functionalized microcapsules. The microcapsules developed show promise for intracellular drug delivery with increased drug efficacy.

MSN anti-cancer nanomedicines: chemotherapy enhancement, overcoming of drug resistance, and metastasis inhibition

In the anti-cancer war, there are three main obstacles resulting in high mortality and recurrence rate of cancers: the severe toxic side effect of anti-cancer drugs to normal tissues due to the lack of tumor-selectivity, the multi-drug resistance (MDR) to free chemotherapeutic drugs and the deadly metastases of cancer cells. The development of state-of-art nanomedicines based on mesoporous silica nanoparticles (MSNs) is expected to overcome the above three main obstacles. In the view of the fast development of anti-cancer strategy, this review highlights the most recent advances of MSN anti-cancer nanomedicines in enhancing chemotherapeutic efficacy, overcoming the MDR and inhibiting metastasis. Furthermore, we give an outlook of the future development of MSNs-based anti-cancer nanomedicines, and propose several innovative and forward-looking anti-cancer strategies, including tumor tissue-cell-nuclear successionally targeted drug delivery strategy, tumor cell-selective nuclear-targeted drug delivery strategy, multi-targeting and multi-drug strategy, chemo-/radio-/photodynamic-/ultrasound-/thermo-combined multi-modal therapy by virtue of functionalized hollow/rattle-structured MSNs.

Novel tumor-targeting, self-assembling peptide nanofiber as a carrier for effective curcumin delivery

The poor aqueous solubility and low bioavailability of curcumin restrict its clinical application for cancer treatment. In this study, a novel tumor-targeting nanofiber carrier was developed to improve the solubility and tumor-targeting ability of curcumin using a self-assembled Nap-GFFYG-RGD peptide. The morphologies of the peptide nanofiber and the curcumin-encapsulated nanofiber were visualized by transmission electron microscopy. The tumor-targeting activity of the curcumin-encapsulated Nap-GFFYG-RGD peptide nanofiber (f-RGD-Cur) was studied in vitro and in vivo, using Nap-GFFYG-RGE peptide nanofiber (f-RGE-Cur) as the control. Curcumin was encapsulated into the peptide nanofiber, which had a diameter of approximately 10-20 nm. Curcumin showed sustained-release behavior from the nanofibers in vitro. f-RGD-Cur showed much higher cellular uptake in αvβ3 integrin-positive HepG2 liver carcinoma cells than did non-targeted f-RGE-Cur, thereby leading to significantly higher cytotoxicity. Ex vivo studies further demonstrated that curcumin could accumulate markedly in mouse tumors after administration of f-RGD-Cur via the tail vein. These results indicate that Nap-GFFYG-RGD peptide self-assembled nanofibers are a promising hydrophobic drug delivery system for targeted treatment of cancer.

Hyaluronic acid modified mesoporous silica nanoparticles for targeted drug delivery to CD44-overexpressing cancer cells

In this paper, a targeted drug delivery system has been developed based on hyaluronic acid (HA) modified mesoporous silica nanoparticles (MSNs). HA-MSNs possess a specific affinity to CD44 over-expressed on the surface of a specific cancer cell line, HCT-116 (human colon cancer cells). The cellular uptake performance of fluorescently labelled MSNs with and without HA modification has been evaluated by confocal microscopy and fluorescence-activated cell sorter (FACS) analysis. Compared to bare MSNs, HA-MSNs exhibit a higher cellular uptake via HA receptor mediated endocytosis. An anticancer drug, doxorubicin hydrochloride (Dox), has been loaded into MSNs and HA-MSNs as drug delivery vehicles. Dox loaded HA-MSNs show greater cytotoxicity to HCT-116 cells than free Dox and Dox-MSNs due to the enhanced cell internalization behavior of HA-MSNs. It is expected that HA-MSNs have a great potential in targeted delivery of anticancer drugs to CD44 over-expressing tumors.