Advantages and disadvantages of (non)metallic nanoparticles and liposomes application in cancer research.
Cell models for the study of antiproliferative and/or cytotoxic properties of engineered nanoparticles are valuable tools in cancer research. Several techniques and methods are readily available for the study of nanoparticles’ properties regarding selective toxicity and/or antiproliferative effects. Setting up of those techniques, however, needs to be carefully monitored. Harmonization of the wide range of methods available is necessary for assay comparison and replicability. Although individual or core laboratory capabilities play a role in selection and availability of techniques, data arising from cancer cell models are useful in guiding further research. The variety of cell lines available and the diversity of metabolic routes involved in cell responses make in vitro cell models suitable for the study of the biological effect of nanoparticles at the cell level and a valid approach for further in vivo and clinical studies. The present systematic review looks at the in vitro biological effects of different types of nanoparticles in cancer cell models.
Toxicity studies are needed for nanoparticles’ (NPs) intended application on biomedical theranostics. Nanostructures are being designed and fabricated with a wide range of potentialities, including those in cancer therapeutics, medical imaging and diagnostics. Thus, research on cell models and
Earlier and recent toxicity studies on human cell lines have found a range of nanostructures that might be selectively toxic for particular cellular lines, including cancerous ones [2, 3]. This selective toxicity against specific types of cancer is a promising research field with potential implications in (pro)diagnosis and therapeutics [4, 5]. Human cell models are available for a variety of malignancies, serving as suitable platforms for exploring antiproliferative and cytotoxic effects of nanostructures . Data from cancer cell models and NP exposure are valuable for guiding and designing
In this review, we compile and discuss the findings of several recent works using cancer cell models and exploring selective NP toxicity and/or antiproliferative effects for potential therapeutic applications in cancer. We looked for particularly interesting scientific papers from indexed journals published within 2015–2017. The focus of this review is on methodological aspects of NP treatment on human cell–based models, i.e. viability assessment techniques, experimental design for investigation of mechanisms of cellular damage, cell culture protocols and NP stability assessment, including in biological media. Results of this review are presented by nature of NPs. Studies exploring new cell culture techniques for assessment of NP toxicity on cancer cell lines were also included.
2. Physicochemical characteristics of nanomaterials and their influence on toxicity
The potential for biomedical applications of several NPs is enormous. There are, however, several shortcomings regarding interactions of engineered NPs with biological environments. Toxicity concerns for NPs intended for use in biomedicine have limited their translation into clinical settings. NP properties such as size, surface-to-volume ratio, shape, surface functionalization and stability on biological media, among others, have been demonstrated to influence the toxicological profile of the nanostructures and their biocompatibility in general [7, 8]. It has been also demonstrated that the level of toxicity varies depending upon cell type, which reflects on particular cell line biology and genetics .
Interactions of NPs inside a biological environment, e.g. eukaryotic cells, have been widely studied . Proteins, lipids or any biomolecule may be absorbed by NPs, affecting not only the original synthetic structure but its biological effect. Assessing antitumor properties of NPs requires stability in investigation under
In general, smaller NPs are more toxic than larger ones . Several works have confirmed this relationship and some authors have identified NP sizes that correlate well with the level of toxicity observed on
Several coating strategies have been tested for lowering the cytotoxic effects of many engineered NPs intended for medical applications. Metallic NPs have been extensively investigated and are excellent candidates as drug nanocarriers, for imaging strategies and for immunological platforms in biomedicine . Toxicity concerns have, however, slowed their faster development and translation. Green chemistry or biologically mediated synthesis of coated metallic NPs is on the rise, and consequently their nanotoxicity evaluation on biological media has been pursued and published [15, 16].
Nanostructures such as semiconductor quantum dots (QDs) are also being investigated for biomedical purposes. Since the toxicity of these nanostructures is known, different coating procedures have been investigated in order to reduce their toxicity. For instance, zinc sulfide (ZnS) QDs functionalized with chitosan have shown no toxic effects on human leukocytes, contrary to the highly toxic cadmium sulfide (CdS) QDs that, even coated with biocompatible chitosan, showed to be toxic in a concentration and time-dependent manner . A summary of the
|Metallic and nonmetallic nanoparticles||Naked [94, 95]||• High antitumor activity
• Storage and release of energy to other molecules quite effectively
• Improvement of sensitive single-molecule detection techniques
• External stimuli responsive, e.g. light and magnetism modulate its activity
• Tunable physical and chemical properties
|• Conformational changes
• Stabilizers do not function properly in different solvents
• In a large extent, synthesized with toxic chemicals for health and/or environment
|Coated [13, 16, 96]||• Easy conjugation to drugs, proteins, and/or nucleotides
• Attenuated cytotoxicity against normal cells due to surface functionalization
• Specific site of action
|• Biological effect varies among different coatings
• Formation of a protein corona
• Sedimentation and/or aggregation
|Liposomes ||• High biocompatibility
• Capability of conjugation with soluble and insoluble drugs
• Targeted drug release
• Low toxicity
|• Colloidal stability and biodegradability
• Complex and expensive synthesis
3. The selective toxicity of nanomaterials on
in vitro cancer cell models
Several mechanisms are involved in NP-mediated
In spite of the number of studies providing useful information on nanotoxicological profiling, there remains particular information with regard to cell-NP specificity interactions. In addition, investigation on the toxicity of nanostructures and biointeractions rely on data from a wide variety of experiments with several different methods and techniques that are chosen on the basis of laboratory capabilities and researchers´ technical expertise [21, 22]. Then, there are, as today, no standard cell panels or defined protocols available for assessment of cancer cell responses to NPs; therefore, data arising from those studies are difficult to compile and integrate. Moreover, there is still the risk that the toxicological picture from a particular study on specific NPs and cell lines might not be “complete” enough and that toxic risks may be overlooked.
Apoptosis is a common response of cells to NP treatment. Azizi and colleagues found that albumin-coated silver NPs (AgNPs) LD50 were several times lower for breast cancer cells than for normal white blood cells. Apoptosis assays such as Annexin V and microscopy counts of apoptotic bodies demonstrated that albumin-coated AgNPs exert proapoptotic selective effects on breast cancer cells while normal blood cells remained viable at the tested concentrations and times of exposure .
In a recent work on several murine cancer cell lines, Namvar and colleagues investigated the antitumor properties of biosynthesized zinc oxide NPs (ZnONPs). They found that cancer cell proliferation was inhibited by NPs in a time- and concentration-dependent manner and that the mechanism of cell death was primarily apoptosis via procaspases activation and intrinsic mitochondrial pathway triggering .
NP exposure may cause cancer cell death by oxidative stress through varied mechanisms, including ROS production, inhibition of antioxidant enzymes, mitochondrial damage and lipid peroxidation . For instance, Matulionyte, et al. demonstrated that photoluminescent gold nanoclusters have specific toxicity against MCF-7 breast cancer cells and were less toxic on MDA-MB 231 breast cancer cells, a highly drug-resistant cell line. The mechanism of cell death was apoptosis, necrosis and generation of ROS, effects that were more evident in MCF-7 cells .
Several other mechanisms are involved in the selective toxicity of NPs against different cancer cell lines. Endoplasmic reticulum (ER) autophagy is a well-known process related with NP exposure. A study by Wei, et al. found that silica NPs (SiNPs) induced ER autophagy in colon cancer cells. The authors showed a time-dependent effect of NP exposure, but interestingly, autophagy was present only at either low or high NP concentrations .
Due to the complexity of cell responses to NPs, it is important to evaluate the biological effect of NPs from different perspectives, from toxicology assessment to both
In the following sections, we discuss the cytotoxic and antiproliferative
3.1. Metallic nanoparticles: noble metals and selective antitumor properties
Inorganic nanostructures exhibit interesting physical properties such as magnetism, fluorescence and localized surface plasmon resonance, which in combination with NPs’ small dimensions make them suitable for biological applications. An advantage over other types of nanostructures is that inorganic NPs could respond to external stimulation with light or magnetic fields . Among inorganic NPs, noble metals have been commonly used for the synthesis of nanomaterials. For instance, silver, gold and platinum NPs are of interest in cancer research as multifunctional anticancer agents due to their particular properties [25, 26]. In the subsequent sections, antitumor properties of noble metallic NPs are discussed focusing on their
3.1.1. Silver nanoparticles
Silver nanoparticles (AgNPs) possess particular physicochemical properties that determine their extent of cytotoxicity in biological systems . It is well documented that AgNPs exert an antiproliferative effect on cancer cell lines [19, 28]. According to Choi, et al., AgNPs develop a potential cytotoxic effect on A2780 ovarian carcinoma cells and ovarian cancer stem cells (OvCSCs) at high concentrations. The inhibitory effect on cellular viability is caused by the upregulation of p53 and caspase-3 genes. In contrast, AgNPs might promote cell proliferation at low concentrations. The relevance of these findings is that OvCSCs present more sensitivity to the treatment with AgNPs, which is particularly interesting due to the fact that CSCs might increase the risk of acquired resistance to chemotherapy .
The therapeutic effect of AgNPs in multidrug resistant (MDR)-cancer cells has also been investigated. Kovacs, et al. demonstrated that AgNPs induce apoptosis-mediated cell death in drug-sensitive (Colo 205) and drug-resistant (Colo 320) colon adenocarcinoma cell lines, in a dose-dependent manner . The internalization of AgNPs was observed in both cell types; thus, they remained in the cytoplasm. In addition, AgNPs may act synergistically with anticancer drugs to enhance their tumor-killing effects in MDR cells due to their capability of modulating efflux activity . It is important to highlight the risk of exposing normal cells to AgNPs. To illustrate, a hippocampal neuronal cell model (HT22) was treated with AgNPs, obtaining a decrease in cell viability, oxidative damage and hypermethylation in DNA due to the internalization of AgNPs. These effects in normal cells may be prolonged since harmful impacts remain after AgNP removal . Similar reports were found by Gao, et al., demonstrating that AgNPs can potentially damage mouse embryonic stem cells . A novel approach to reduce cytotoxicity against normal cells is the functionalization or modification of AgNP surface . Extensive research has been conducted to validate the hypothesis that AgNPs could inhibit angiogenesis, a complex process that is involved in the formation of new blood vessels and tumor progression . For instance, Gurunathan, et al. concluded that the treatment of bovine retinal endothelial cells (BRECs) with AgNPs might activate PI3K/Akt pathway resulting in the inhibition of capillary formation . Based on this evidence, AgNPs are potent antineoplastic agents with acute cytotoxic effects that modulate several metabolic pathways leading to decreased cell viability, independently or in combination with other anticancer drugs. This synergistic effect will be further discussed along this chapter.
3.1.2. Gold nanoparticles
Compatibility of gold with biosystems has been well demonstrated since metallic nanoscale materials were originally developed . In recent years, synthesis and application of gold NPs (AuNPs) in the biomedical field have substantially increased due to their ductility physicochemical properties and biocompatibility. AuNPs can be synthesized in different shapes including spheres, rods, cubes, triangles, cones and shells . Therefore, based on their size and shape, “naked” AuNPs possess several applications, e.g. as antitumor agents, drug nanocarriers, hyperthermia enhancers and radio sensitizers [1, 35].
In addition, AuNPs could act as enhancers of hyperthermia-targeted therapy because they efficiently absorb laser light and convert it into thermal energy . The synergistic effect of AuNPs and laser-induced thermotherapy renders thermally exposed cancer cells susceptible to be ablated with minimal exposure times and lower laser intensities . Rau, et al. showed that AuNPs could cause severe damage in the cytoskeleton of MG63 osteosarcoma cells in combination with laser treatment, increasing the calcium content inside the cells and leading to mineralization . Another technique to induce hyperthermia in tumors is directed ultrasound. Kosheleva, et al. discovered that the combined treatment of ultrasound and AuNPs exerted a more acute cytotoxic effect on A549 lung cancer cells compared to BEAS-2B normal lung cells when cultivated separately and in coculture . These findings suggested that AuNP-assisted thermotherapy could cause targeted cancer cell ablation, while avoiding damage to surrounding noncancerous cells.
AuNPs can be uptaken by cancer cells via endocytosis and trigger apoptotic events . As a consequence, an improvement in radiation therapy has been observed when cancer cells are previously exposed to AuNPs . Likewise, high atomic number in AuNPs increases radiation absorption from the target tumor . Literature suggests that AuNPs act as radiosensitizers in several cancer cell lines, such as U251 glioblastoma, which in clinical practice could increase radiotherapy efficacy and prevent the development of drug-resistant tumors . Another approach thoroughly studied by Rezaee, et al. showed that electroporation enhances radiosensitizing effect of AuNPs in HT-29 colon adenocarcinoma cells as a result of increasing cell membrane permeability. In this study, AuNPs’ radiosensitizing effect was more prominent in cancer cells than in normal counterparts .
3.1.3. Platinum nanoparticles
Several investigations have addressed the antiproliferative effect of platinum nanoparticles (PtNPs) in cell models [45–48]. Bendale, et al. concluded that the harmful effect of PtNPs on cancer cell viability depends on the cell type. At the same PtNP concentration, an acute cytotoxic effect was observed in lung (A549), ovary (PA-1) and pancreatic (Mia-Pa-Ca-2) cancer cells  . In this study, no significative effect on cell viability was observed in breast, renal, colon and leukemia cancer cell lines. Interestingly, peripheral blood mononuclear cells (PBMCs) were not affected either, suggesting that PtNPs could preferably target tumor cells . According to Kutwin, et al., PtNPs severely affect the proliferation rate and morphology of U118 and U87 human malignant glioma cell lines, and as a consequence, cells suffer from membrane disruption, reduced density and decreased migration . Gehrke, et al. did not find any adverse effect on cellular viability when HT29 colon carcinoma cells were treated with PtNPs. It was observed, however, that smaller PtNPs enter the cells and remain in the cytoplasm or inside intracellular vesicles, either individually or in aggregates. Additionally, PtNPs released Pt ions that may bind to DNA leading to strand cleavage damage . Another important feature is the synergistic antitumor activity between platinum and gold NPs. Ahamed, et al. reported that platinum-coated gold nanorods (AuNRs-Pt) affected cell viability on MCF7 breast cancer cells at relatively low doses. The mechanism of action of AuNRs-Pt involved impairment of normal morphology resulting in rounded cells, cell cycle detention at SubG1 phase, increased expression levels of proapoptotic genes caspase-3 and caspase-9 and generation of ROS . Manikandan, et al. demonstrated that PtNPs could improve photothermal treatment in cancer cells. Neuro-2a brain neuroblastoma cells were exposed to the combined scheme of laser irradiation and PtNPs, which resulted in induction of apoptosis . There was no significative effect on cellular viability when PtNPs and laser treatment were applied separately .
3.1.4. Other metal-based nanomaterials
Titanium dioxide (TiO2), zinc (Zn), copper (Cu) and iron (Fe) are used in several industrial applications such as cosmetics, paint chemicals, food additives, pharmacological coatings, drug delivery systems, biosensor technologies and body implants. These nanomaterials have been also tested in cancer research and development of new therapeutics [22, 50].
Xia and coworkers reported the cytotoxic effect of cuprous oxide nanoparticles (CONPs) on HeLa, SiHa and MS751 human cervical cancer cell lines. Results demonstrated that CONPs are uptaken by cells and internalized into the cytoplasm, mitochondria and lysosomes; as a result, cell morphology alterations and decreased cellular viability were observed. Cell cycle arrest in the G1/G0 phase, induction of apoptosis and autophagy were also reported .
The antineoplastic effect of CONPs in PC-3, LNCaP FGC and DU145 human prostate carcinoma cells was investigated by Wang, et al. The results of this study suggest that CONPs might induce cytotoxicity selectively on cancerous cells without affecting normal prostate epithelial cells (RWPE-1). Moreover, a significant decrease in the expression of Oct4, Sox2 and KLF4 transcription factors related with stem-cell proliferation capability was observed .
Superparamagnetic iron oxide nanoparticles (SPIONs) are also included in a large extent in nanomedical products . SPIONs develop magnetic properties within a magnetic field; therefore, they are able to act in specific target sites . Several studies demonstrated that SPIONS can be approached as hyperthermia enhancers, contrast agents in magnetic resonance imaging, drug nanocarriers and anticancer candidates . For instance, Du, et al. studied the combined effect of SPIONs and spinning magnetic field (SMF) on the survival rate of U-2 OS and Saos-2 osteosarcoma cell lines. This combined treatment exerts a more effective cytotoxic response triggering the intracellular ROS generation, autophagic cell death and apoptosis, than SPION treatment alone .
3.2. Nonmetallic and organically coated metallic nanomaterials: antiproliferative and cytotoxic properties
3.2.1. Green synthesis–based nanomaterials
Production of materials at the nanometric scale (1–100 nm) has been performed using several approaches . The most common synthesis method involves the use of three elements: capping agent, reducing agent and solvent . However, most of these elements are toxic, flammable, corrosive and even dangerous for the natural environment and living organisms. For this reason, a new green chemistry tendency emerged in the nanotechnology area to modify chemical processes and reduce or minimize the use of hazardous reagents . The green-synthesis approach has been focused on finding nontoxic elements to develop a more eco-friendly design with improved efficiency . Some of these new techniques require the use of solvents such as water, supercritical CO2 or ionic liquids [56, 57]. For example, silver and gold nanoscale structures, due to their chemical and biological properties, have been widely used in green synthesis in combination with medicinal plants (photosynthesis) or bacterial/fungi/viral proteins (microbial-synthesis) . This section provides further interesting examples of green-synthetized nanomaterials.
The importance of developing an alternative nanosynthesis protocol is not only for an environmental footprint reduction, but contributes also for the simplification of industrial production with the lack of expensive organic solvents and toxic chemicals . The use of innocuous plant extracts with solvents such as water facilitates the production and further evaluation of green nanomaterials, which are fundamental for biological applications in critical areas e.g. drug production . There are several nanoscale structures coated with plant extracts and their effect on living systems has been extensively studied . For instance, Krishnaraj, et al. reported that Ag/Au biosynthesized NPs with
188.8.131.52. Microbial synthesis
Bacterial survival in the presence of heavy metals is caused by a transformation (reduction/precipitation) of metal ions into insoluble nontoxic metal nanoclusters. These detoxification reactions are mediated by intracellular accumulation or a physicochemical process–denominated extracellular biosorption, which facilitates the concentration of contaminants, e.g. heavy metals, and binds them in their cellular structure, with variable levels of dispersity . Based on these bacterial properties, Klaus, et al. described AgNP production in
3.2.2. Organically coated metallic and nonmetallic nanomaterials
Nanobiotechnology as a mature biomedical field emerged in the last years ; for example, from gene-delivery systems to targeted drug delivery, it has several applications in cancer treatment, diagnosis (biomarkers), molecular biology and genetic/cell engineering [70, 71]. A nanomedicine-based therapeutic approach might be built on nanocarriers, e.g. liposomes and NPs that improve chemotherapeutic biodistribution  and have been useful for treating diseases such as cancer  and microbial infections . In 1989, Matsumura and Maeda described the enhanced permeation and retention (EPR) effect, a controversial concept based on the passive accumulation of macromolecular drugs in tumors due to the presence of a high number of abnormal blood vessels (angiogenesis), which lack lymphatic drainage, affecting in turn as a drug delivery system . Despite the fact that this effect has been extensively studied but has failed in clinical trials , EPR is still one of the most used concepts in nanobiodistribution . With this information in mind, this section discusses relevant aspects of metallic and nonmetallic coated nanomaterials, including liposomes as novel therapeutic agents for cancer.
184.108.40.206. Organically coated nanomaterials
Organic coating is used to stabilize NPs and maintain a balance between electrostatic and electrosteric repulsion forces . NPs of different shapes might be covered with diverse capping agents such as citric acid, polysaccharides, surfactants, proteins, polymers and nucleic acids [77, 78]. However, despite the fact that they have the same core material, coated-NPs exert different biological responses. For instance, viability, genotoxicity and mutagenicity evaluation of AgNPs coated with anionic (citrate, SDS), neutral (disperbyk, tween) or cationic (byk and chitosan) compounds were performed by Kun, et al. using lymphoblast TK6 cell line and Chinese hamster lung fibroblasts. The methodology used for testing involved trypan blue exclusion assay, relative growth activity, cell morphology, HPRT mutation and comet assay. The results determined that AgNPs_byk and AgNPs_chitosan were the most cytotoxic, affecting cell morphology, inhibiting proliferation and inducing cell death through apoptosis or necrosis. Furthermore, AgNPs_byk showed significant mutagenic effects by inducing DNA strand breaks and oxidation. It is important to note that AgNPs_byk formed the smallest agglomerates in medium solution in comparison to other coated AgNPs, suggesting that size is an important factor in toxicity. To sum up, coated NPs display various biological
One of the well-known NP biointeractions is that with bovine serum albumin (BSA), which relies on principle that a protein corona is dynamically formed around NPs when they enter a biological environment . A recent investigation performed by Zhou, et al. determined that ZnONPs bound to BSA elicited interleukin-6 (IL-6) production-mediated anti-inflammatory responses in HepG2 liver cancer cell line. Additionally, synthesized NPs induced mitochondria and lysosomal damage by increasing intracellular Zn ions production . However, the analysis of the biological effect of ZnONPs bound to α-linolenic acid (LNA) did not show the same response . Another interesting example is the evaluation of the response of SPIONs conjugated to the antitumor peptide ATWLPPR (A7R) on HUVEC human umbilical vein endothelial cells and MDA-MB-231 human breast adenocarcinoma . These NPs might be adjusted carriers for targeted drug delivery systems using their magnetic properties. Furthermore, the presence of cell receptors for the A7R peptide facilitates the uptake of the nanocarriers. This is particularly important because the role of the receptor is to repress the vascular endothelial growth factor A (VEGF A). Consequently, NPs affect angiogenic events and impair cell proliferation .
The study of commercial anticancer drug formulations in nanoform has also been evaluated, with positive results in many cases. For instance, tamoxifen, an anticancer agent used in estrogen receptor-positive (ER+) breast cancer, has been commonly used before surgery to reduce tumor volume . However, tamoxifen resistance has become a significant problem in cancer treatment . Devulapally, et al. synthesized biodegradable polymer NPs loaded with the active compound of tamoxifen (4-hydroxytamoxifen-4OHT) and the noncoding RNA (anti-miR-21). NPs showed antiproliferative and proapoptotic effects in human breast (MCF7, ZR-751, BT-474) and mouse mammary (4 T1) carcinoma cells .
220.127.116.11. Nonmetallic nanomaterials
Despite the fact that most widely used nanomaterials have metal cores, a number of industry-relevant nonmetallic nanoscale particles such as SiO2 and carbon NPs have been engineered. For instance, silica NPs have been extensively used in food additives , toothpaste and skin care products . However, their use requires toxicology screening to determine their innocuity. According to Wittig, et al., commercially available nanosilica (Ø 12 nm) increases the growth of GXF251L human gastric carcinoma cells. The results showed an important proliferative effect through the activation of cellular epidermal growth factor receptor (EGFR) and mitogen-activated protein kinase (MAPK) signaling pathways .
On the contrary, research on antiproliferative properties have found that cerium oxide nanocrystals (nanoceria: CeO2-NCs) can act as an anticancer drug . The investigation conducted by Khan, et al. found that fluorescence microscopy assessments of nanoceria displayed a marked
Liposomes were firstly described in the middle 1960s as spherical vesicles constituted with phospholipid bilayers . These lipid-based nanoparticles have been used in several fields from biophysics to biology for many years . With the advances of nanotechnology, liposomes have evolved in order to assure controlled delivery of active molecules to a specific site of action. For instance, a radiation therapy scheme in use for more than 50 years is boron neutron capture (BNCT), which is based on the specific delivery of the isotope (boron-10) undergoing a nuclear reaction to form boron-11, through exposure to a laser beam (neutron source ). This reaction causes a release of an -particle that has a high linear energy transfer (LET) and kills the equivalent of one cell diameter . In the above research, conducted by Maitz, et al., the effect of unilamellar liposomes (composed of cholesterol, 1, 2-distearoyl-sn-glycero-3-phosphocholine, K [nido-7-CH3 (CH2)15-7, 8-C2B9H11] and core Na3 [1-(2′-B10H9)-2-NH3B10H8]) on mice bearing tumors (breast carcinoma EMT6 and colon carcinoma CT26) was studied. The results showed a 50% tumor reduction after 45 min of radiation, despite lower boron concentrations inside EMT6 tumor, in comparison to CT26. The average time for tumor growth, set as three times the pretreatment volume, was 38 days for BNCT-treated mice in comparison to 4 days for untreated controls. In conclusion, the authors found that liposomes were useful elements for increasing inherent radiosensitivity in selected tumors .
The use of liposomes has also been found useful for drug delivery systems . Sadhu, et al. evaluated the cytotoxicity and antiproliferative effects of liposomes designed to increase the intracellular glutathione disulfide (GSSG) on B16 murine metastatic melanoma tumor cells (B16F10), human metastatic lung carcinoma cells (NCI-H226) and
Drewes, et al. demonstrated that lipid-core nanocapsules containing poly(ε-caprolactone), capric/caprylic triglyceride, sorbitan monostearate and polysorbate 80 affected cell proliferation and triggered cell cycle arrest on SK-Mel-28 human melanoma cells. Furthermore, nanocapsules induced apoptosis and necrosis on a murine model B16F10 (H2b) bearing B16 melanoma cell line . To sum up, GSSG liposomes and lipid-core nanocapsules are potentially useful for antimetastatic treatment and as drug delivery systems for melanoma treatment, respectively . Organically coated nanostructures, including liposomes, might exert antiproliferative cytotoxic properties against cancer cells/tumors but may also induce cell proliferation depending on the type of tumor and nanostructure used.
The wide spectrum of known cancer cellular responses to nanomaterials is summarized in Table 2.
|Type||Nanoparticles||Coating material||Cell type||Biological effect||Ref.|
|Metallic||AgNPs||Naked||A2780 ovarian carcinoma||Cytotoxic|||
|OvCSCs ovarian cancer stem cells|
|Colo 205 colon adenocarcinoma||Proapoptotic, synergic with anticancer drugs|||
|Colo 320 drug-resistant colon adenocarcinoma|
|HT22 hippocampal neuronal model||Antiproliferative, DNA hypermethylation and oxidative stress damage|||
|Mouse embryonic stem cells||Transcriptomic alterations|||
|Bovine retinal endothelia||Angiogenesis inhibition|||
|MCF7 breast cancer||Cytotoxic|||
|HepG2 hepatocellular carcinoma|
|A549 lung cancer|||
|MDA-MB-231 human breast adenocarcinoma||Cytotoxic, proapoptotic|||
|AuNPs||Naked||HeLa cervical carcinoma||Cytotoxic||[3, 36–38]|
|PC-3 prostate cancer|
|HepG2 hepatocellular carcinoma|
|MDA-MB-231 human breast adenocarcinoma|
|Calu-1 epidermoid carcinoma||Proapoptotic, synergistic effect with anticancer molecules, DNA fragmentation and mitochondrial fission|||
|MG63 osteosarcoma||Cytoskeleton damage in combination with laser treatment|||
|A549 lung cancer||Cytoskeleton damage in combination with ultrasound|||
|U251 glioblastoma||Proapoptotic, radiosensitizer||[43, 44]|
|HT-29 colon adenocarcinoma|
|Platinum coated||MCF7 breast cancer||Proapoptotic, ROS production and cell cycle arrest|||
|MDA-MB-231 human breast adenocarcinoma||Cytotoxic, proapoptotic|||
|PtNPs||Naked||A549 lung cancer||Cytotoxic|||
|PA-1 human ovarian teratocarcinoma|
|Mia-Pa-Ca-2 human pancreas carcinoma|
|U118/U87 human malignant glioma||Antiproliferative|||
|Neuro-2a brain neuroblastoma||Proapoptotic in combination with laser treatment|||
|Cuprous oxide CONPs||Naked||SiHa cervical squamous carcinoma||Cytotoxic, autophagy and proapoptotic|||
|HeLa cervical carcinoma|
|MS751 cervical cancer|
|LNCaP FGC human prostate carcinoma||Cytotoxic, reduction in transcription factors for proliferation|||
|PC-3 prostate cancer|
|Metallic||DU145 prostate carcinoma|
|Iron oxide, SPIONs||Naked||U-2 OS osteosarcoma||Cytotoxic, autophagy and proapoptotic|||
|antiangiogenic peptide ATWLPPR (A7R)||MDA-MB-231 human breast adenocarcinoma||Reduce angiogenesis and proliferation|||
|ZnO||Bovine serum albumin||HepG2 hepatocellular carcinoma||Anti-inflammatory and mitochondria-lysosome damage inducer|||
|Nonmetallic||Biopolymer||4-hydroxytamoxifen and noncoding RNA (anti-miR-21)||MCF7, ZR-751, BT-474 breast cancer||Antiproliferative and proapoptotic|||
|4 T1 mouse mammary carcinoma|
|SiO2||Naked Ø 12 nm||GXF251L gastric carcinoma||Increase proliferation|||
|Cerium oxide CeO||Naked||HT29 human colorectal adenocarcinoma||Cytotoxic, antiproliferative and proapoptotic|||
|Cytochrome C (Cyt C) and hyaluronic acid (HA)||Naked||A549 lung cancer||Antiproliferative|||
|Liposomes||Core: Na3 [1-(2′-B10H9)-2-NH3B10H8]||Cholesterol, 1, 2-distearoyl-sn-glycero-3-phosphocholine, K [nido-7-CH3 (CH2)15–7, 8-C2B9H11]||EMT6 breast carcinoma||Increase radiosensitivity of tumors|||
|CT26 colon carcinoma|
|Lipid-core||Poly(ε-caprolactone), capric/caprylic triglyceride, sorbitan monostearate and polysorbate 80||SK-Mel-28 human melanoma||Cytotoxic, proapoptotic and cell cycle arrest|||
Several techniques and methods are readily available for investigation of nanostructured particle properties regarding their selective cytotoxicity and/or antiproliferative effects. Setting up of those techniques, however, needs to be carefully monitored. Harmonization of the wide range of methods available is necessary for assay comparison and replicability.
To sum up, extended cell-based testing (
Henriksen-Lacey M, Carregal-Romero S, Liz-Marzán LM. Current challenges toward in vitro cellular validation of inorganic nanoparticles. Bioconjugate Chemistry. Jan. 2017; 28(1):212-221
Namvar F, et al. Cytotoxic effects of biosynthesized zinc oxide nanoparticles on murine cell lines. Evidence-Based Complementary and Alternative Medicine. 2015; 2015:593014
Moses SL, Edwards VM. Cytotoxicity in MCF-7 and MDA-MB-231 breast cancer cells, without harming MCF-10A healthy cells. Journal of Nanomedicine & Nanotechnology. 2016; 7(2):369
Ortega FG, et al. Study of antitumor activity in breast cell lines using silver nanoparticles produced by yeast. International Journal of Nanomedicine. 2015; 10:2021-2031
Azizi M, Ghourchian H, Yazdian F, Bagherifam S, Bekhradnia S, Nyström B. Anti-cancerous effect of albumin coated silver nanoparticles on MDA-MB 231 human breast cancer cell line. Scientific Reports. Jul. 2017; 7(1):5178
Chang J-S, Kuo H-P, Chang KLB, Kong Z-L. Apoptosis of hepatocellular carcinoma cells induced by nanoencapsulated polysaccharides extracted from Antrodia camphorata. PLoS One. 2015; 10(9):e0136782
Liu G, et al. Cytotoxicity of various types of gold-mesoporous silica nanoparticles in human breast cancer cells. International Journal of Nanomedicine. 2015; 10:6075-6087
Saifullah B, Hussein MZB. Inorganic nanolayers: Structure, preparation, and biomedical applications. International Journal of Nanomedicine. 2015; 10:5609-5633
Joris F, et al. The impact of species and cell type on the nanosafety profile of iron oxide nanoparticles in neural cells. Journal of Nanobiotechnology. Sep. 2016; 14(1):69
Foglia S, et al. In vitro biocompatibility study of sub-5 nm silica-coated magnetic iron oxide fluorescent nanoparticles for potential biomedical application. Scientific Reports. Apr. 2017; 7:46513
Niescioruk A, et al. Physicochemical properties and in vitro cytotoxicity of iron oxide-based nanoparticles modified with antiangiogenic and antitumor peptide A7R. Journal of Nanoparticle Research. 2017; 19(5):160
Huk A, et al. Impact of nanosilver on various DNA lesions and HPRT gene mutations—Effects of charge and surface coating. Particle and Fibre Toxicology. Jul. 2015; 12:25
Shannahan JH, Lai X, Ke PC, Podila R, Brown JM, Witzmann FA. Silver nanoparticle protein corona composition in cell culture media. PLoS One. Sep. 2013; 8(9):e74001
Joksić G, Stašić J, Filipović J, Šobot AV, Trtica M. Size of silver nanoparticles determines proliferation ability of human circulating lymphocytes in vitro. Toxicology Letters. Apr. 2016; 247:29-34
Guo X, et al. Size- and coating-dependent cytotoxicity and genotoxicity of silver nanoparticles evaluated using in vitrostandard assays. Nanotoxicology. Oct. 2016; 10(9):1373-1384
Das B, et al. Surface modification minimizes the toxicity of silver nanoparticles: An in vitro and in vivo study. Journal of Biological Inorganic Chemistry. Aug. 2017; 22(6):893-918
Mansur AA, Mansur HS, de Carvalho SM, Lobato ZI, Guedes MI, Leite MF. Surface biofunctionalized CdS and ZnS quantum dot nanoconjugates for nanomedicine and oncology: To be or not to be nanotoxic? International Journal of Nanomedicine. 2016; 11:4669-4690
Patil NA, Gade WN, Deobagkar DD. Epigenetic modulation upon exposure of lung fibroblasts to TiO2 and ZnO nanoparticles: Alterations in DNA methylation. International Journal of Nanomedicine. 2016; 11:4509-4519
Choi Y-J, et al. Differential cytotoxic potential of silver nanoparticles in human ovarian cancer cells and ovarian cancer stem cells. International Journal of Molecular Sciences. Dec. 2016; 17(12):2077
Abdal Dayem A, et al. The role of reactive oxygen species (ROS) in the biological activities of metallic nanoparticles. International Journal of Molecular Sciences. Jan. 2017; 18(1):120
Yang F, et al. Real-time, label-free monitoring of cell viability based on cell adhesion measurements with an atomic force microscope. Journal of Nanobiotechnology. Mar. 2017; 15(1):23
Kuku G, Culha M. Investigating the origins of toxic response in TiO2 nanoparticle-treated cells. Nanomaterials. 2017; 7(4):83
Matulionyte M, Dapkute D, Budenaite L, Jarockyte G, Rotomskis R. Photoluminescent gold nanoclusters in cancer cells: Cellular uptake, toxicity, and generation of reactive oxygen species. International Journal of Molecular Sciences. Feb. 2017; 18(2):378
Wei F, Wang Y, Luo Z, Li Y, Duan Y. New findings of silica nanoparticles induced ER autophagy in human colon cancer cell. Scientific Reports. Feb. 2017; 7:42591
Rai M, Ingle AP, Birla S, Yadav A, Dos Santos CA. Strategic role of selected noble metal nanoparticles in medicine. Critical Reviews in Microbiology. Sep. 2016; 42(5):696-719
Fekrazad R, Naghdi N, Nokhbatolfoghahaei H, Bagheri H. The combination of laser therapy and metal nanoparticles in cancer treatment originated from epithelial tissues: A literature review. Journal of Lasers in Medical Science. Mar. 2016; 7(2):62-75
Vimbela GV, Ngo SM, Fraze C, Yang L, Stout DA. Antibacterial properties and toxicity from metallic nanomaterials. International Journal of Nanomedicine. 2017; 12:3941-3965
Kovacs D, et al. Silver nanoparticles modulate ABC transporter activity and enhance chemotherapy in multidrug resistant cancer. Nanomedicine. Apr. 2016; 12(3):601-610
Mytych J, Zebrowski J, Lewinska A, Wnuk M. Prolonged effects of silver nanoparticles on p53/p21 pathway-mediated proliferation, DNA damage response, and methylation parameters in HT22 hippocampal neuronal cells. Molecular Neurobiology. Mar. 2017; 54(2):1285-1300
Gao X, Topping VD, Keltner Z, Sprando RL, Yourick JJ. Toxicity of nano- and ionic silver to embryonic stem cells: A comparative toxicogenomic study. Journal of Nanobiotechnology. Apr. 2017; 15(1):31
Mukherjee S, Patra CR. Therapeutic application of anti-angiogenic nanomaterials in cancers. Nanoscale. Jul. 2016; 8(25):12444-12470
Gurunathan S, Lee K-J, Kalishwaralal K, Sheikpranbabu S, Vaidyanathan R, Eom SH. Antiangiogenic properties of silver nanoparticles. Biomaterials. Oct. 2009; 30(31):6341-6350
Chen C-H, Chan T-M, Wu Y-J, Chen J-J. Review: Application of nanoparticles in urothelial cancer of the urinary bladder. Journal of Medical and Biological Engineering. 2015; 35(4):419-427
Amendola V, Pilot R, Frasconi M, Marago OM, Iati MA. Surface plasmon resonance in gold nanoparticles: A review. Journal of Physics Condensed Matter. May 2017; 29(20):203002
Orlando A, et al. Evaluation of gold nanoparticles biocompatibility: A multiparametric study on cultured endothelial cells and macrophages. Journal of Nanoparticle Research. Feb. 2016; 18(3):58
Wozniak A, et al. Size and shape-dependent cytotoxicity profile of gold nanoparticles for biomedical applications. Journal of Materials Science. Materials in Medicine. Jun. 2017; 28(6):92
Malugin A, Ghandehari H. Cellular uptake and toxicity of gold nanoparticles in prostate cancer cells: A comparative study of rods and spheres. Journal of Applied Toxicology. Apr. 2010; 30(3):212-217
Paino IMM, Marangoni VS, de Oliveira R d CS, Antunes LMG, Zucolotto V. Cyto and genotoxicity of gold nanoparticles in human hepatocellular carcinoma and peripheral blood mononuclear cells. Toxicology Letters. 2012; 215(2):119-125
Ke S, et al. Gold nanoparticles enhance TRAIL sensitivity through Drp1-mediated apoptotic and autophagic mitochondrial fission in NSCLC cells. International Journal of Nanomedicine. 2017; 12:2531-2551
Popp MK, Oubou I, Shepherd C, Nager Z, Anderson C, Pagliaro L. Photothermal therapy using gold nanorods and near-infrared light in a murine melanoma model increases survival and decreases tumor volume. Journal of Nanomaterials. 2014; 2014Article ID 450670, 8 pages
Rau L-R, Huang W-Y, Liaw J-W, Tsai S-W. Photothermal effects of laser-activated surface plasmonic gold nanoparticles on the apoptosis and osteogenesis of osteoblast-like cells. International Journal of Nanomedicine. 2016; 11:3461-3473
Kosheleva OK, Lai T-C, Chen NG, Hsiao M, Chen C-H. Selective killing of cancer cells by nanoparticle-assisted ultrasound. Journal of Nanobiotechnology. Jun. 2016; 14(1):46
Rezaee Z, Yadollahpour A, Bayati V, Negad Dehbashi F. Gold nanoparticles and electroporation impose both separate and synergistic radiosensitizing effects in HT-29 tumor cells: An in vitro study. International Journal of Nanomedicine. 2017; 12:1431-1439
Liu P, et al. Silver nanoparticles outperform gold nanoparticles in radiosensitizing U251 cells in vitro and in an intracranial mouse model of glioma. International Journal of Nanomedicine. 2016; 11:5003-5014
Bendale Y, Bendale V, Paul S. Evaluation of cytotoxic activity of platinum nanoparticles against normal and cancer cells and its anticancer potential through induction of apoptosis. Integrative Medicine Research. Jun. 2017; 6(2):141-148
Kutwin M, et al. Assessment of the proliferation status of glioblastoma cell and tumour tissue after nanoplatinum treatment. PLoS One. 2017; 12(5):e0178277
Ahamed M, Akhtar MJ, Khan MAM, Alhadlaq HA, Alrokayan SA. Cytotoxic response of platinum-coated gold nanorods in human breast cancer cells at very low exposure levels. Environmental Toxicology. Nov. 2016; 31(11):1344-1356
Manikandan M, Hasan N, Wu H-F. Platinum nanoparticles for the photothermal treatment of Neuro 2A cancer cells. Biomaterials. Jul. 2013; 34(23):5833-5842
Gehrke H, et al. Platinum nanoparticles and their cellular uptake and DNA platination at non-cytotoxic concentrations. Archives of Toxicology. Jul. 2011; 85(7):799-812
Schrand AM, Rahman MF, Hussain SM, Schlager JJ, Smith DA, Syed AF. Metal-based nanoparticles and their toxicity assessment. Wiley Interdisciplinary Reviews: Nanomedicine and Nanobiotechnology. 2010; 2(5):544-568
Xia L, et al. Cuprous oxide nanoparticles inhibit the growth of cervical carcinoma by inducing autophagy. Oncotarget. May 2017; 8(37):61083-61092
Wang Y, et al. Cuprous oxide nanoparticles inhibit prostate cancer by attenuating the stemness of cancer cells via inhibition of the Wnt signaling pathway. International Journal of Nanomedicine. 2017; 12:2569-2579
Du S, Li J, Du C, Huang Z, Chen G, Yan W. Overendocytosis of superparamagnetic iron oxide particles increases apoptosis and triggers autophagic cell death in human osteosarcoma cell under a spinning magnetic field. Oncotarget. Feb. 2017; 8(6):9410-9424
Fedlheim DL, Foss CA. Metal Nanoparticles: Synthesis, Characterization, and Applications. Marcel Dekker Inc. New York; 2002
Poinern GEJ. A Laboratory Course in Nanoscience and Nanotechnology. CRC Press, Taylor & Francis Group, Boca Raton, FL; 2014
Duan H, Wang D, Li Y. Green chemistry for nanoparticle synthesis. Chemical Society Reviews. 2015; 44(16):5778-5792
Kumar B, Smita K, Seqqat R, Benalcazar K, Grijalva M, Cumbal L. In vitro evaluation of silver nanoparticles cytotoxicity on hepatic cancer (Hep-G2) cell line and their antioxidant activity: Green approach for fabrication and application. Journal of Photochemistry and Photobiology B: Biology. Jun. 2016; 159:8-13
Krishnaraj C, Muthukumaran P, Ramachandran R, Balakumaran MD, Kalaichelvan PT. Acalypha indica Linn: Biogenic synthesis of silver and gold nanoparticles and their cytotoxic effects against MDA-MB-231, human breast cancer cells. Biotechnology Reports. 2014; 4(1):42-49
Dauthal P, Mukhopadhyay M. Phyto-synthesis and structural characterization of catalytically active gold nanoparticles biosynthesized using Delonix regia leaf extract. 3 Biotech. Dec. 2016; 6(2):118
Ahmed S, Ahmad M, Swami BL, Ikram S. A review on plants extract mediated synthesis of silver nanoparticles for antimicrobial applications: A green expertise. Journal of Advanced Research. Jan. 2016; 7(1):17-28
Gengan RM, Anand K, Phulukdaree A, Chuturgoon A. A549 lung cell line activity of biosynthesized silver nanoparticles using Albizia adianthifolia leaf. Colloids and Surfaces B: Biointerfaces. May 2013; 105:87-91
Daisy P, Saipriya K. Biochemical analysis of Cassia fistula aqueous extract and phytochemically synthesized gold nanoparticles as hypoglycemic treatment for diabetes mellitus. International Journal of Nanomedicine. Mar. 2012; 7:1189-1202
Santhoshkumar T, et al. Synthesis of silver nanoparticles using Nelumbo nucifera leaf extract and its larvicidal activity against malaria and filariasis vectors. Parasitology Research. Mar. 2011; 108(3):693-702
Narayanan KB, Sakthivel N. Biological synthesis of metal nanoparticles by microbes. Advances in Colloid and Interface Science. Apr. 2010; 156(1-2):1-13
Klaus T, Joerger R, Olsson E, Granqvist CG. Silver-based crystalline nanoparticles, microbially fabricated. Proceedings of the National Academy of Sciences of the United States of America. Nov. 1999; 96(24):13611-13614
Beveridge TJ, Murray RG. Sites of metal deposition in the cell wall of Bacillus subtilis. Journal of Bacteriology. Feb. 1980; 141(2):876-887
Magdi HM, Bhushan B. Extracellular biosynthesis and characterization of gold nanoparticles using the fungus Penicillium chrysogenum. Microsystem Technologies. 2015; 21(10):2279-2285
Nam KT, et al. Virus-enabled synthesis and assembly of nanowires for lithium ion battery electrodes. Science. May 2006; 312(5775):885-888
Heath JR. Nanotechnologies for biomedical science and translational medicine. Proceedings of the National Academy of Sciences of the United States of America. Nov. 2015; 112(47):14436-14443
De Jong WH, Borm PJA. Drug delivery and nanoparticles: Applications and hazards. International Journal of Nanomedicine. 2008; 3(2):133-149
Rathi Sre PR, Reka M, Poovazhagi R, Arul Kumar M, Murugesan K. Antibacterial and cytotoxic effect of biologically synthesized silver nanoparticles using aqueous root extract of Erythrina indica lam. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 2015; 135:1137-1144
Sharkey RM, Goldenberg DM. Targeted therapy of cancer: New prospects for antibodies and immunoconjugates. CA: A Cancer Journal for Clinicians. 2006; 56(4):226-243
Wesselinova D. Current major cancer targets for nanoparticle systems. Current Cancer Drug Targets. Feb. 2011; 11(2):164-183
Liu L, et al. Self-assembled cationic peptide nanoparticles as an efficient antimicrobial agent. Nature Nanotechnology. Jul. 2009; 4(7):457-463
Maeda H. Macromolecular therapeutics in cancer treatment: The EPR effect and beyond. Journal of Controlled Release. Dec. 2012; 164(2):138-144
Nichols JW, Bae YH. EPR: Evidence and fallacy. Journal of Controlled Release. Sep. 2014; 190:451-464
Sharma VK, Siskova KM, Zboril R, Gardea-Torresdey JL. Organic-coated silver nanoparticles in biological and environmental conditions: Fate, stability and toxicity. Advances in Colloid and Interface Science. Feb. 2014; 204:15-34
Kumar B, et al. One pot phytosynthesis of gold nanoparticles using Genipa americana fruit extract and its biological applications. Materials Science & Engineering. C, Materials for Biological Applications. May 2016; 62:725-731
Zhou Y, et al. The interactions between ZnO nanoparticles (NPs) and α-linolenic acid (LNA) complexed to BSA did not influence the toxicity of ZnO NPs on HepG2 cells. Nanomaterials (Basel, Switzerland). 2017; 7(4):1-15
Chang M. Tamoxifen resistance in breast cancer. Biomolecules & Therapeutics. May 2012; 20(3):256-267
Devulapally R, Sekar TV, Paulmurugan R. Formulation of anti-miR-21 and 4-hydroxytamoxifen co-loaded biodegradable polymer nanoparticles and their antiproliferative effect on breast cancer cells. Molecular Pharmaceutics. Jun. 2015; 12(6):2080-2092
Bouwmeester H, et al. Review of health safety aspects of nanotechnologies in food production. Regulatory Toxicology and Pharmacology. Feb. 2009; 53(1):52-62
Frohlich E, Roblegg E. Models for oral uptake of nanoparticles in consumer products. Toxicology. Jan. 2012; 291(1-3):10-17
Wittig A, et al. Amorphous silica particles relevant in food industry influence cellular growth and associated signaling pathways in human gastric carcinoma cells. Nanomaterials (Basel, Switzerland). Jan. 2017; 7(1):18
Khan S, et al. Evaluation of in vitro cytotoxicity, biocompatibility, and changes in the expression of apoptosis regulatory proteins induced by cerium oxide nanocrystals. Science and Technology of Advanced Materials. 2017; 18(1):364-373
Gao Y, Chen K, Ma J-L, Gao F. Cerium oxide nanoparticles in cancer. OncoTargets and Therapy. 2014; 7:835-840
Figueroa CM, Suárez BN, Molina AM, Fernández JC, Torres Z, Griebenow K. Smart release nano-formulation of cytochrome C and hyaluronic acid induces apoptosis in cancer cells. Journal of Nanomedicine & Nanotechnology. Feb. 2017; 1:8
Akbarzadeh A, et al. Liposome: Classification, preparation, and applications. Nanoscale Research Letters. Feb. 2013; 8(1):102
Maitz CA, et al. Validation and comparison of the therapeutic efficacy of boron neutron capture therapy mediated by boron-rich liposomes in multiple murine tumor models. Translational Oncology. Jul. 2017; 10(4):686-692
Sercombe L, Veerati T, Moheimani F, Wu SY, Sood AK, Hua S. Advances and challenges of liposome assisted drug delivery. Frontiers in Pharmacology. Dec. 2015; 6:286
Sadhu SS, et al. In vitro and in vivo tumor growth inhibition by glutathione disulfide liposomes. Cancer Growth and Metastasis. 2017; 10:1179064417696070
Drewes CC, et al. Novel therapeutic mechanisms determine the effectiveness of lipid-core nanocapsules on melanoma models. International Journal of Nanomedicine. 2016; 11:1261-1279
Fior R, et al. Single-cell functional and chemosensitive profiling of combinatorial colorectal therapy in zebrafish xenografts. Proceedings of the National Academy of Sciences. Aug. 2017; 114(39):E8234-E8243
Mody VV, Siwale R, Singh A, Mody HR. Introduction to metallic nanoparticles. Journal of Pharmacy & Bioallied Sciences. Jun. 2010; 2(4):282-289
Kumar CSSR. Mixed Metal Nanomaterials. Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim; 2009
Lee JJ, Saiful Yazan L, Che Abdullah CA. A review on current nanomaterials and their drug conjugate for targeted breast cancer treatment. International Journal of Nanomedicine. Mar. 2017; 12:2373-2384