Development and characterization of immuno-nanocarriers targeting the cancer stem cell marker AC133

Cancer Stem Cells in Colorectal Cancer: Implications for Targeted Immunotherapies

PURPOSE

Colorectal cancers are composed of heterogeneous cell populations in the concepts of genetic and functional degrees that among them cancer stem cells are identified with their self-renewal and stemness capability mediating primary tumorigenesis, metastasize, therapeutic resistance, and tumor recurrence. Therefore, understanding the key mechanisms of stemness in colorectal cancer stem cells (CRCSCs) provides opportunities to discover new treatments or improve existing therapeutic regimens.

METHODS

We review the biological significance of stemness and the results of potential CRCSC-based targeted immunotherapies. Then, we pointed out the barriers to targeting CRCSCs in vivo and highlight new strategies based on synthetic and biogenic nanocarriers for the development of future anti-CRCSC trials.

RESULTS

The CSCs' surface markers, antigens, neoantigens, and signaling pathways supportive CRCSCs or immune cells that are interacted with CRCSCs could be targeted by immune monotherapy or in formulation with developed nanocarriers to overcome the resistant mechanisms in immune evader CRCSCs.

CONCLUSION

Identification molecular and cellular cues supporting stemness in CRCSCs and their targeting by nanoimmunotherpy can improve the efficacy of existed therapies or explore novel therapeutic options in future.

Self-Renewal Inhibition in Breast Cancer Stem Cells: Moonlight Role of PEDF in Breast Cancer

Breast cancer is the leading cause of death among females in developed countries. Although the implementation of screening tests and the development of new therapies have increased the probability of remission, relapse rates remain high. Numerous studies have indicated the connection between cancer-initiating cells and slow cellular cycle cells, identified by their capacity to retain long labeling (LT+). In this study, we perform new assays showing how stem cell self-renewal modulating proteins, such as PEDF, can modify the properties, percentage of biomarker-expressing cells, and carcinogenicity of cancer stem cells. The PEDF signaling pathway could be a useful tool for controlling cancer stem cells' self-renewal and therefore control patient relapse, as PEDF enhances resistance in breast cancer patient cells' in vitro culture. We have designed a peptide consisting of the C-terminal part of this protein, which acts by blocking endogenous PEDF in cell culture assays. We demonstrate that it is possible to interfere with the self-renewal capacity of cancer stem cells, induce anoikis in vivo, and reduce resistance against docetaxel treatment in cancer patient cells in in vitro culture. We have also demonstrated that this modified PEDF protein produces a significant decrease in the percentage of expressed cancer stem cell markers.

Study of surfactant cross-linking by click chemistry on a model water/oil interface

In this study, we explored how chemical reactions of amphiphile compounds can be characterized and followed-up on model interfaces. A custom-made surfactant containing three alkyne sites was first adsorbed and characterized at a water/oil interface. These amphiphiles then underwent interfacial crosslinking by click chemistry upon the addition of a second reactive agent. The monolayer properties and dilatational elasticity, were compared before and after the polymerization. Using bulk phase exchange, the composition of the aqueous bulk phase was finely controlled and washed to specifically measure the interfacial effects of the entities adsorbed and trapped at the interface. In this study, we aim to emphasize an original experimental approach to follow complex phenomena occurring on model interfaces, and also show the potential of this method to characterize multifactorial processes.

Surface Modification of Lipid-Based Nanoparticles

There is a growing interest in the development of lipid-based nanocarriers for multiple purposes, including the recent increase of these nanocarriers as vaccine components during the COVID-19 pandemic. The number of studies that involve the surface modification of nanocarriers to improve their performance (increase the delivery of a therapeutic to its target site with less off-site accumulation) is enormous. The present review aims to provide an overview of various methods associated with lipid nanoparticle grafting, including techniques used to separate grafted nanoparticles from unbound ligands or to characterize grafted nanoparticles. We also provide a critical perspective on the usefulness and true impact of these modifications on overcoming different biological barriers, with our prediction on what to expect in the near future in this field.

Nanotechnology for Boosting Cancer Immunotherapy and Remodeling Tumor Microenvironment: The Horizons in Cancer Treatment

Immunotherapy that harnesses the human immune system to fight cancer has received widespread attention and become a mainstream strategy for cancer treatment. Cancer immunotherapy not only eliminates primary tumors but also treats metastasis and recurrence, representing a major advantage over traditional cancer treatments. Recently with the development of nanotechnology, there exists much work applying nanomaterials to cancer immunotherapy on the basis of their excellent physiochemical properties, such as efficient tissue-specific delivery function, huge specific surface area, and controllable surface chemistry. Consequently, nanotechnology holds significant potential in improving the efficacy of cancer immunotherapy. Nanotechnology-based immunotherapy mainly manifests its inhibitory effect on tumors via two different approaches: one is to produce an effective anti-tumor immune response during tumorigenesis, and the other is to enhance tumor immune defense ability by modulating the immune suppression mechanism in the tumor microenvironment. With the success of tumor immunotherapy, understanding the interaction between the immune system and smart nanomedicine has provided vigorous vitality for the development of cancer treatment. This review highlights the application, progress, and prospect of nanomedicine in the process of tumor immunoediting and also discusses several engineering methods to improve the efficiency of tumor treatment.

Recent advances in drug delivery systems for targeting cancer stem cells

Cancer stem cells (CSCs) are a subpopulation of cancer cells with functions similar to those of normal stem cells. Although few in number, they are capable of self-renewal, unlimited proliferation, and multi-directional differentiation potential. In addition, CSCs have the ability to escape immune surveillance. Thus, they play an important role in the occurrence and development of tumors, and they are closely related to tumor invasion, metastasis, drug resistance, and recurrence after treatment. Therefore, specific targeting of CSCs may improve the efficiency of cancer therapy. A series of corresponding promising therapeutic strategies based on CSC targeting, such as the targeting of CSC niche, CSC signaling pathways, and CSC mitochondria, are currently under development. Given the rapid progression in this field and nanotechnology, drug delivery systems (DDSs) for CSC targeting are increasingly being developed. In this review, we summarize the advances in CSC-targeted DDSs. Furthermore, we highlight the latest developmental trends through the main line of CSC occurrence and development process; some considerations about the rationale, advantages, and limitations of different DDSs for CSC-targeted therapies were discussed.

Novel hybrid lipid nanocapsules loaded with a therapeutic monoclonal antibody - Bevacizumab - and Triamcinolone acetonide for combined therapy in neovascular ocular pathologies

The aim of this study was to design and develop a novel hybrid formulation based on lipid nanocapsules containing bevacizumab (BVZ), an effective therapeutic antibody, on the surface and triamcinolone acetonide (TA) in the inner core (BVZ-TA-LNC) intended to improve ocular therapy. Hence, a phase inversion-insertion one step method was developed to drug loading and surface modification of lipid nanocapsules by post-insertion of a bifunctional polymer, followed by antibody coupling using "click" chemistry. The covalent bond and antibody capacity binding to its specific antigen were confirmed by thermal analysis and immunoassay, respectively. BVZ-TA-LNC presented nanometric size (102 nm), negative surface potential (-19 mV) and exhibiting 56% of TA in the lipid core. BVZ-TA-LNC tended to prevent the endothelial cell migration and significantly prevented the capillary formation induced by the vascular endothelium growth factor (VEGF). The novel hybrid system allowed the co-loading of two different therapeutic molecules and may be promising to improve the therapy of eye disorders that occur with inflammation and/or neovascularization.

A nano-based thermotherapy for cancer stem cell-targeted therapy

Cancer stem cells (CSCs) exhibit high resistance to conventional therapy and are responsible for cancer metastasis and tumor relapse.

Surface engineering of nanomaterials with phospholipid-polyethylene glycol-derived functional conjugates for molecular imaging and targeted therapy

In recent years, phospholipid-polyethylene glycol-derived functional conjugates have been widely employed to decorate different nanomaterials, due to their excellent biocompatibility, long blood circulation characteristics, and specific targeting capability. Numerous in vivo studies have demonstrated that nanomedicines peripherally engineered with phospholipid-polyethylene glycol-derived functional conjugates show significantly increased selective and efficient internalization by target cells/tissues. Targeting moieties including small-molecule ligands, peptides, proteins, and antibodies are generally conjugated onto PEGylated phospholipids to decorate liposomes, micelles, hybrid nanoparticles, nanocomplexes, and nanoemulsions for targeted delivery of diagnostic and therapeutic agents to diseased sites. In this review, the synthesis methods of phospholipid-polyethylene glycol-derived functional conjugates, biophysicochemical properties of nanomedicines decorated with these conjugates, factors dominating their targeting efficiency, as well as their applications for in vivo molecular imaging and targeted therapy were summarized and discussed.

Detection of CD133-marked cancer stem cells by surface plasmon resonance: Its application in leukemia patients

Here, we reported the development of a label-free and real-time surface plasmon resonance (SPR) based biosensor for cancer stem cells (CSCs) detection using cell surface biomarker; CD133. The fabricated biosensor was used for detection of this marker in some acute myeloid leukemia (AML) patients and the results were compared with those obtained from flow cytometry (FC) method. CD133 antibody was immobilized on the gold chip surface via EDC/NHS coupling method and binding of the candidate cells to the modified gold sensor surface was monitored after isolation of mononuclear cells from bone marrow of the patients. The method was validated in terms of various parameters such as CD133- antibody concentration and cell density. The CD133-marked cells were investigated in seven AML patients. All SPR results were compared with those obtained from FC method. A very good correlation (R² = 0.96) was obtained between SPR and FC responses related to CD133-marked cells densities. In conclusion, in this study, a label-free and real-time SPR cytometry method was developed to detect CD133 and it was successfully applied to follow this cancer stem cell biomarker in AML patients.

Model Affitin and PEG modifications onto siRNA lipid nanocapsules: cell uptake and in vivo biodistribution improvements

Malignant melanoma is an aggressive tumor, associated with the presence of local and/or distant metastases. The development of gene therapy by the use of small interfering RNA (siRNA) represents a promising new treatment. However, the protection of this biomolecule is necessary in order for it to be intravenously administrated, for example via its incorporation into nanomedicines. In parallel to the passive targeting usually obtained by pegylation, various studies have aimed at developing “smart” nanomedicines to efficiently deliver the drug to tumor sites. In this work, siRNA loaded lipid nanocapsules (LNCs) were modified with DSPE-polyethylene glycol (DSPE-PEG), tetraether-PEG (TE-PEG) and/or with an Affitin model, to assay multiple targeting strategies. The uptake of fluorescently labelled LNCs, nanocarrier integrity and siRNA release into human SK-Mel28 melanoma cells were studied by flow cytometry, conventional confocal microscopy and by confocal spectral imaging in a Förster Resonance Energy Transfer (FRET) mode. Surface modified siRNA LNCs were followed after human plasma incubation and after intravenous injection, in order to compare the stealth properties. Finally, the biodistribution of the different siRNA LNCs in healthy and melanoma tumor bearing mice models was assessed by in vivo biofluorescence imaging (BFI), to evaluate the potential tumor targeting ability. The post-insertion of DSPE-PEG induced a strong decrease of the internalization into melanoma cells compared to TE-PEG modification. Both PEG polymer decorations induced a great plasma protection of siRNA but only DSPE-PEG led to stealth properties, even at low concentration (5 mM). The Affitin grafting by thiolation of DSPE-PEG was validated on siRNA LNCs. DSPE-PEG-Affitin LNCs were not detected in this melanoma tumor model but did not show unspecific accumulation in organs. DSPE-PEG and TE-PEG LNCs induced a significant intratumoral accumulation of modified LNCs.

Surface modifications of siRNA LNCs were assessed with innovative TE-PEG polymers and an Affitin model, in comparison to classic DSPE-PEG LNCs, in order to evaluate the potential tumor targeting of siRNA after intravenous administration.

Synthesis and Characterization of a New Bifunctionalized, Fluorescent, and Amphiphilic Molecule for Recruiting SH-Containing Molecules to Membranes

This study describes the synthesis and characterization of an amphiphilic construct intended to recruit SH-containing molecules to membranes. The construct consists of 1) an aliphatic chain to enable anchoring within membranes, 2) a maleimide moiety to react with the sulfhydryl group of a soluble (bio)molecule, and 3) a fluorescence moiety to allow the construct to be followed by fluorescence spectroscopy and microscopy. It is shown that the construct can be incorporated into preformed membranes, thus allowing application of the approach with biological membranes. The close proximity between the fluorophore and the maleimide moiety within the construct causes fluorescence quenching. This allows monitoring of the reaction with SH-containing molecules by measurement of increases in fluorescence intensity and lifetime. Notably, the construct distributes into laterally ordered membrane domains of lipid vesicles, which is probably triggered by the length of its membrane anchor. The advantages of the new construct can be employed for several biological, biotechnological, and medicinal applications.

Targeted Delivery of siRNA Therapeutics to Malignant Tumors

Over the past 20 years, a diverse group of ligands targeting surface biomarkers or receptors has been identified with several investigated to target siRNA to tumors. Many approaches to developing tumor-homing peptides, RNA and DNA aptamers, and single-chain variable fragment antibodies by using phage display, in vitro evolution, and recombinant antibody methods could not have been imagined by researchers in the 1980s. Despite these many scientific advances, there is no reason to expect that the ligand field will not continue to evolve. From development of ligands based on novel or existing biomarkers to linking ligands to drugs and gene and antisense delivery systems, several fields have coalesced to facilitate ligand-directed siRNA therapeutics. In this review, we discuss the major categories of ligand-targeted siRNA therapeutics for tumors, as well as the different strategies to identify new ligands.

Locoregional Confinement and Major Clinical Benefit of 188Re-Loaded CXCR4-Targeted Nanocarriers in an Orthotopic Human to Mouse Model of Glioblastoma

PURPOSE

Gold standard beam radiation for glioblastoma (GBM) treatment is challenged by resistance phenomena occurring in cellular populations well prepared to survive or to repair damage caused by radiation. Among signals that have been linked with radio-resistance, the SDF1/CXCR4 axis, associated with cancer stem-like cell, may be an opportune target. To avoid the problem of systemic toxicity and blood-brain barrier crossing, the relevance and efficacy of an original system of local brain internal radiation therapy combining a radiopharmaceutical with an immuno-nanoparticle was investigated.

EXPERIMENT DESIGN

The nanocarrier combined lipophilic thiobenzoate complexes of rhenium-188 loaded in the core of a lipid nanocapsule (LNC¹⁸⁸Re) with a function-blocking antibody, 12G5 directed at the CXCR4, on its surface. The efficiency of 12G5-LNC¹⁸⁸Re was investigated in an orthotopic and xenogenic GBM model of CXCR4-positive U87MG cells implanted in the striatum of Scid mice.

RESULTS

We demonstrated that 12G5-LNC¹⁸⁸Re single infusion treatment by convection-enhanced delivery resulted in a major clinical improvement in median survival that was accompanied by locoregional effects on tumor development including hypovascularization and stimulation of the recruitment of bone marrow derived CD11b- or CD68-positive cells as confirmed by immunohistochemistry analysis. Interestingly, thorough analysis by spectral imaging in a chimeric U87MG GBM model containing CXCR4-positive/red fluorescent protein (RFP)-positive- and CXCR4-negative/RFP-negative-GBM cells revealed greater confinement of DiD-labeled 12G5-LNCs than control IgG2a-LNCs in RFP compartments. Main conclusion: These findings on locoregional impact and targeting of disseminated cancer cells in tumor margins suggest that intracerebral active targeting of nanocarriers loaded with radiopharmaceuticals may have considerable benefits in clinical applications.

Nano-delivery system targeting to cancer stem cell cluster of differentiation biomarkers

Cancer stem cells (CSCs) are one of the most important origins of cancer progression and metastasis. CSCs have unique self-renewal properties and diverse cell membrane receptors that induced the resistance to the conventional chemotherapeutic agents. Therefore, the therapeutic removal of CSCs could result in the cancer cure with lack of recurrence and metastasis. In this regard, targeting CSCs in accordance to their specific biomarkers is a talented attitude in cancer therapy. Various CSCs surface biomarkers have been described, which some of them exhibited similarities on different cancer cell types, while the others are cancer specific and have just been reported on one or a few types of cancers. In this review, the importance of CSCs in cancer development and therapeutic response has been stated. Different CSCs cluster of differentiation (CD) biomarkers and their specific function and applications in the treatment of cancers have been discussed, Special attention has been made on targeted nano-delivery systems. In this regard, several examples have been illustrated concerning specific natural and artificial ligands against CSCs CD biomarkers that could be decorated on various nanoparticulated drug delivery systems to enhance therapeutic index of chemotherapeutic agents or anticancer gene therapy. The outlook of CSCs biomarkers discovery and therapeutic/diagnostic applications was discussed.

Prostate Cancer Stem Cells and Nanotechnology: A Focus on Wnt Signaling

Prostate cancer is the most common cancer among men worldwide. However, current treatments for prostate cancer patients in advanced stage often fail because of relapse. Prostate cancer stem cells (PCSCs) are resistant to most standard therapies, and are considered to be a major mechanism of cancer metastasis and recurrence. In this review, we summarized current understanding of PCSCs and their self-renewal signaling pathways with a specific focus on Wnt signaling. Although multiple Wnt inhibitors have been developed to target PCSCs, their application is still limited by inefficient delivery and toxicity in vivo. Recently, nanotechnology has opened a new avenue for cancer drug delivery, which significantly increases specificity and reduces toxicity. These nanotechnology-based drug delivery methods showed great potential in targeting PCSCs. Here, we summarized current advancement of nanotechnology-based therapeutic strategies for targeting PCSCs and highlighted the challenges and perspectives in designing future therapies to eliminate PCSCs.

Applications of nanoparticle drug delivery systems for the reversal of multidrug resistance in cancer

Multidrug resistance (MDR) to chemotherapy presents a major obstacle in the treatment of cancer patients, which directly affects the clinical success rate of cancer therapy. Current research aims to improve the efficiency of chemotherapy, whilst reducing toxicity to prolong the lives of cancer patients. As with good biocompatibility, high stability and drug release targeting properties, nanodrug delivery systems alter the mechanism by which drugs function to reverse MDR, via passive or active targeting, increasing drug accumulation in the tumor tissue or reducing drug elimination. Given the potential role of nanodrug delivery systems used in multidrug resistance, the present study summarizes the current knowledge on the properties of liposomes, lipid nanoparticles, polymeric micelles and mesoporous silica nanoparticles, together with their underlying mechanisms. The current review aims to provide a reliable basis and useful information for the development of new treatment strategies of multidrug resistance reversal using nanodrug delivery systems.

POLYMERIC BIOMATERIALS AND NANOMEDICINES

This overview intends to demonstrate the close relationship between the design of smart biomaterials and water-soluble polymer-drug conjugates. First, the discovery and systematic studies of hydrogels based on crosslinked poly(meth)acrylic acid esters and substituted amides is described. Then, the lessons learned for the design of water-soluble polymers as drug carriers are highlighted. The current state-of-the-art in water-soluble, mainly poly[N-(2-hydroxypropyl)methacylamide (HPMA), polymer-drug conjugates is shown including the design of backbone degradable HPMA copolymer carriers. In the second part, the modern design of hybrid hydrogels focuses on the self-assembly of hybrid copolymers composed from the synthetic part (backbone) and biorecognizable grafts (coiled-coil forming peptides or morpholino oligonucleotides) is shown. The research of self-assembling hydrogels inspired the invention and design of drug-free macromolecular therapeutics - a new paradigm in drug delivery where crosslinking of non-internalizating CD20 receptors results in apoptosis in vitro and in vivo. The latter is mediated by biorecognition of complementary motifs; no low molecular weight drug is needed.

Cell surface markers of cancer stem cells: diagnostic macromolecules and targets for drug delivery

The recognition that the persistence of cancer stem cells (CSCs) in patients following chemotherapy can result in disease relapse underscores the necessity to develop therapeutics against those cells. CSCs display a unique repertoire of cell surface macromolecules, which have proven essential for their characterization and isolation. Additionally, CSC-specific cell surface macromolecules or markers provide targets for the development of specific agents to destroy them. In this review, we compiled those cell surface molecules that have been validated as CSC markers for many common blood and solid tumors. We describe the unique chemical and structural features of the most common cell surface markers, as well as recent efforts to deliver chemotherapeutic agents into CSCs by targeting those macromolecules.

Poly(lactic-co-glycolic acid) nanoparticles conjugated with CD133 aptamers for targeted salinomycin delivery to CD133+ osteosarcoma cancer stem cells

Background

Cancer stem cells (CSCs) possess the characteristics associated with normal stem cells and are responsible for cancer initiation, recurrence, and metastasis. CD133 is regarded as a CSCs marker of osteosarcoma, which is the most common primary bone malignancy in childhood and adolescence. Salinomycin, a polyether ionophore antibiotic, has been shown to kill various CSCs, including osteosarcoma CSCs. However, salinomycin displayed poor aqueous solubility that hinders its clinical application. The objective of this study was to develop salinomycin-loaded nanoparticles to eliminate CD133⁺ osteosarcoma CSCs.

Methods

The salinomycin-loaded PEGylated poly(lactic-co-glycolic acid) nanoparticles (SAL-NP) conjugated with CD133 aptamers (Ap-SAL-NP) were developed by an emulsion/solvent evaporation method, and the targeting and cytotoxicity of Ap-SAL-NP to CD133⁺ osteosarcoma CSCs were evaluated.

Results

The nanoparticles are of desired particle size (~150 nm), drug encapsulation efficiency (~50%), and drug release profile. After 48 hours treatment of the Saos-2 CD133⁺ osteosarcoma cells with drugs formulated in Ap-SAL-NP, SAL-NP, and salinomycin, the concentrations needed to kill 50% of the incubated cells were found to be 2.18, 10.72, and 5.07 μg/mL, respectively, suggesting that Ap-SAL-NP could be 4.92 or 2.33 fold more effective than SAL-NP or salinomycin, respectively. In contrast, Ap-SAL-NP was as effective as SAL-NP, and less effective than salinomycin in Saos-2 CD133⁻ cells, suggesting that Ap-SAL-NP possess specific cytotoxicity toward Saos-2 CD133⁺ cells. Ap-SAL-NP showed the best therapeutic effect in Saos-2 osteosarcoma xenograft mice, compared with SAL-NP or salinomycin. Significantly, Ap-SAL-NP could selectively kill CD133⁺ osteosarcoma CSCs both in vitro and in vivo, as reflected by the tumorsphere formation and proportion of Saos-2 CD133⁺ cells.

Conclusion

Our results suggest that CD133 is a potential target for drug delivery to osteosarcoma CSCs and that it is possible to significantly inhibit the osteosarcoma growth by killing CD133⁺ osteosarcoma CSCs. We demonstrated that Ap-SAL-NP have the potential to target and kill CD133⁺ osteosarcoma CSCs.

Comparative biodistribution in mice of cyanine dyes loaded in lipid nanoparticles

Two near infrared cyanine dyes, DiD (1,1'-dioctadecyl-3,3,3',3'-tetramethylindotricarbocyanine perchlorate) and ICG (Indocyanine Green) were loaded in lipid nanoparticles (LNP). DiD-LNP and ICG-LNP presented similar physicochemical characteristics (hydrodynamic diameter, polydispersity, zeta potential), encapsulation efficiency, and colloidal stability when stored in PBS buffer. However, whereas DiD had similar biodistribution than cholesteryl-1-(14)C-oleate ([(14)C]CHO, a constituent of the nanoparticle used as a reference radiotracer), ICG displayed a different biodistribution pattern, similar to that of the free dye, indicative of its immediate leakage from the nanovector after blood injection. NMR spectroscopy using Proton NOE (Nuclear Overhauser Effect) measurements showed that the localization of the dye in the lipid nanoparticles was slightly different: ICG, more amphiphilic than DiD, was found both inside the lipid core and at particle interface, whereas DiD, more hydrophobic, appeared exclusively located inside the particle core. The ICG release rate from the particles was 7% per 1 month under storage conditions (4 °C, dark, 10% of lipids), whereas no leakage could be detected for DiD. ICG leakage increased considerably in the presence of BSA 40 g/L (45% leakage in 24h at 100 mg/mL of lipids), because of the high affinity of the fluorophore for plasma proteins. On the contrary, no DiD leakage was observed, until high dilution of the nanoparticles which triggered their dissociation (45% leakage in 24h at 1 mg/mL of lipids). Altogether, the subtle difference in dye localization into the nanoparticles, the partial dissociation of the LNP in diluted media, and more importantly the high ICG affinity for plasma proteins, accounted for the differences observed in the fluorescence biodistribution after tail vein injection of the dye-loaded nanoparticles.

Functionalization of nano-emulsions with an amino-silica shell at the oil–water interface

A new and simple method of modify and functionalize the liquid/liquid interface of nano-emulsion droplets.

An innovative hydrogel of gemcitabine-loaded lipid nanocapsules: when the drug is a key player of the nanomedicine structure

A new method to form a nanoparticle-structured hydrogel is reported; it is based on the drug being loaded into the nanoparticles to form a solid structure. A lipophilic form of gemcitabine (modified lauroyl), an anti-cancer drug, was encapsulated in lipid nanocapsules (LNCs), using a phase-inversion temperature process. A gel was formed spontaneously, depending on the LNC concentration. The drug loading, measured with total entrapment efficiency, and the rheological properties of the gel were assessed. Physical studies (surface tension measurements) showed that modified gemcitabine was localised at the oil-water interface of the LNC, and that the gemcitabine moieties of the prodrug were exposed to the water phase. This particular assembly promoted inter-LNC interactions via hydrogen bonds between gemcitabine moieties that led to an LNC gel structure in water, without a matrix, like a tridimensional pearl necklace. Dilution of the gel produced a gemcitabine-loaded LNC suspension in water, and these nanoparticles presented cytotoxic activity to various cancer cell lines to a greater degree than the native drug. Finally, the syringeability of the formulation was successfully tested and perspectives of its use as a nanomedicine (intratumoural or subcutaneous injection) can be foreseen.

Silencing of miR-21 by locked nucleic acid-lipid nanocapsule complexes sensitize human glioblastoma cells to radiation-induced cell death

The recent discovery of microRNA (miRNA) as major post-transcriptional repressors prompt the interest of developing novel approaches to target miRNA pathways to improve therapy. In this context, although the most significant barrier to their widespread clinical use remains delivery, nuclease-resistant locked nucleic acid (LNA) that bind specifically and irreversibly to miRNA represent interesting weapons. Thus, by focusing on oncongenic miR-21 miRNA, which participate to cancer cell resistance to apoptotic signals, the aim of the present study was to investigate the possibility of silencing miRNA by LNA conjugated to lipid nanocapsules (LNCs) as miRNA-targeted nanomedicines in U87MG glioblastoma (GBM) cells. After synthesis of an amphiphilic lipopeptide affine for nucleic acids, a post-insertion procedure during the LNC phase inversion formulation process allowed to construct peptide-conjugated LNCs. Peptide-conjugated LNCs were then incubated with LNAs to allow the formation of complexes characterized in gel retardation assays and by their physicochemical properties. U87MG cell treatment by LNA-LNC complexes resulted in a marked reduction of miR-21 expression as assessed by RTqPCR. In addition, exposure of U87MG cells to LNA-LNC complexes followed by external beam radiation demonstrated a significant improvement of cell sensitivity to treatment and emphasizes the interest to investigate further this miRNA-targeted strategy.

Surface modification of lipid nanocapsules with polysaccharides: from physicochemical characteristics to in vivo aspects

Attaching polysaccharides to the surface of nanoparticles offers the possibility of modifying the physicochemical and biological properties of the core particles. The surface of lipid nanocapsules (LNCs) was modified by post-insertion of amphiphilic lipochitosan (LC) or lipodextran (LD). Modelling of these LNCs by the drop tensiometer technique revealed that the positively charged LC made the LNC surface more rigid, whereas the neutral, higher M(W) LD had no effect on the surface elasticity. Both LNC-LC and LNC-LD activated the complement system more than the blank LNC, thus suggesting increased capture by the mononuclear phagocyte system. In vitro, the positively charged LNC-LC were more efficiently bound by the model HEK293(β3) cells compared to LNC and LNC-LD. Finally, it was observed that neither LC nor LD changed the in vivo biodistribution properties of LNCs in mice. These polysaccharide-coated LNCs, especially LNC-LC, are promising templates for targeting ligands (e.g. peptides, proteins) or therapeutic molecules (e.g. siRNA).

Biological rationale for the design of polymeric anti-cancer nanomedicines

Understanding the biological features of cancer is the basis for designing efficient anti-cancer nanomedicines. On one hand, important therapeutic targets for anti-cancer nanomedicines need to be identified based on cancer biology, to address the unmet medical needs. On the other hand, the unique pathophysiological properties of cancer affect the delivery and interactions of anti-cancer nanomedicines with their therapeutic targets. This review discusses several critical cancer biological properties that challenge the currently available anti-cancer treatments, including cancer heterogeneity and cancer stem cells, the complexcity of tumor microenvironment, and the inevitable cancer metastases. In addition, the biological bases of the enhanced permeability and retention (EPR) effect and tumor-specific active targeting, as well as the physiological barriers for passive and active targeting of anti-cancer nanomedicines are covered in this review. Correspondingly, possible nanomedicine strategies to target cancer heterogeneity, cancer stem cells and metastases, to overcome the challenges related to tumor passive targeting and tumor penetration, and to improve the interactions of therapeutic payloads with the therapeutic targets are discussed. The focus is mainly on the designs of polymeric anti-cancer nanomedicines.

Cancer stem cells and drug resistance: the potential of nanomedicine

Properties of the small group of cancer cells called tumor-initiating or cancer stem cells (CSCs) involved in drug resistance, metastasis and relapse of cancers can significantly affect tumor therapy. Importantly, tumor drug resistance seems to be closely related to many intrinsic or acquired properties of CSCs, such as quiescence, specific morphology, DNA repair ability and overexpression of antiapoptotic proteins, drug efflux transporters and detoxifying enzymes. The specific microenvironment (niche) and hypoxic stability provide additional protection against anticancer therapy for CSCs. Thus, CSC-focused therapy is destined to form the core of any effective anticancer strategy. Nanomedicine has great potential in the development of CSC-targeting drugs, controlled drug delivery and release, and the design of novel gene-specific drugs and diagnostic modalities. This review is focused on tumor drug resistance-related properties of CSCs and describes current nanomedicine approaches, which could form the basis of novel combination therapies for eliminating metastatic and CSCs.

Cancer stem cells: in the line of fire

Most tumours appear to contain a sub-population(s) of self-renewing and expanding stem cells known as cancer stem cells (CSCs). The CSC model proposes that CSCs are at the apex of a hierarchically organized cell population, somewhat akin to normal tissue organization. Selection pressures may also facilitate the stochastic clonal expansion of sub-sets of cancer cells that may co-exist with CSCs and their progeny, moreover the trait of stemness may be more fluid than hitherto expected, and cells may switch between the stem and non-stem cell state. A large body of evidence points to the fact that CSCs are particularly resistant to radiotherapy and chemotherapy. In this review we discuss the basis of such resistance that highlights the roles of ABC transporters, aldehyde dehydrogenase (ALDH) activity, intracellular signalling pathways, the DNA damage response, hypoxia and proliferative quiescence as being significant determinants. In the light of such observations, we outline strategies for the successful eradication of CSCs, including targeting the self-renewal controlling pathways (Wnt, Notch and Hedgehog), ALDH activity and ABC transporters, blocking epithelial mesenchymal transition (EMT), differentiation therapy and niche targeting.