Dendrimer-coated Magnetic Nanoparticles Research Articles

Targeted Dendrimer-Coated Magnetic Nanoparticles for Selective Delivery of Therapeutics in Living Cells.

Nanoparticles are widely used as theranostic agents for the treatment of various pathologies, including cancer. Among all, dendrimers-based nanoparticles represent a valid approach for drugs delivery, thanks to their controllable size and surface properties. Indeed, dendrimers can be easily loaded with different payloads and functionalized with targeting agents. Moreover, they can be used in combination with other materials such as metal nanoparticles for combinatorial therapies. Here, we present the formulation of an innovative nanostructured hybrid system composed by a metallic core and a dendrimers-based coating that is able to deliver doxorubicin specifically to cancer cells through a targeting agent. Its dual nature allows us to transport nanoparticles to our site of interest through the magnetic field and specifically increase internalization by exploiting the T7 targeting peptide. Our system can release the drug in a controlled pH-dependent way, causing more than 50% of cell death in a pancreatic cancer cell line. Finally, we show how the system was internalized inside cancer cells, highlighting a peculiar disassembly of the nanostructure at the cell surface. Indeed, only the dendrimeric portion is internalized, while the metal core remains outside. Thanks to these features, our nanosystem can be exploited for a multistage magnetic vector.

Poly(amidoamine) dendrimer-coated magnetic nanoparticles for the fast purification and selective enrichment of glycopeptides and glycans.

Glycosylated proteins modulate various important functions of organisms. To reveal the functions of glycoproteins, in-depth characterization studies are necessary. Although mass spectrometry is a very efficient tool for glycoproteomic and glycomic studies, efficient sample preparation methods are required prior to analyses. In the study, poly(amidoamine) dendrimer-coated magnetic nanoparticles were presented for the specific enrichment and fast purification of glycopeptides and glycans. The enrichment and purification performance of the developed method was evaluated both at the glycopeptide, and the glycan level using several standard glycoprotein digests and released glycan samples. The poly(amidoamine) dendrimer-coated magnetic nanoparticles not only showed selective affinity (Immunoglobulin G/Bovine Serum Albumin, 1/10 by weight) to glycopeptides and released glycans but also good sensitivity (0.4ng/µL for Immunoglobulin G) for glycoproteomic and glycomic applications. Thirty-five glycopeptides of Immunoglobulin G were detected after enrichment with poly(amidoamine) dendrimer-coated magnetic nanoparticles. In addition, 55 18 O tagged deamidated glycopeptides belonging to human plasma glycoproteome were confirmed. Finally, fifty 2-aminobenzoic acid, and 30 procainamide-labelled human plasma N-glycans released from human plasma glycoproteins were determined after purifications. The results indicate that the proposed enrichment and purification method using poly(amidoamine) dendrimer-coated magnetic nanoparticles could be simply adjusted to sample preparation methods.

Photoresponsive molecularly imprinted dendrimer-based magnetic nanoparticles for photo-regulated selective separation of azathioprine

This research describes the development of a poly (amidoamine) (PAMAM) dendrimer-based photoresponsive molecularly imprinted polymers (P-MIPs) for selective separation and determination of azathioprine. This study is the first involving a PAMAM dendrimer-coated magnetic nanoparticles (MNPs) used during the imprinting process to enhance a number of recognition sites in the polymer matrix to advance the recognition ability. The photoresponsive MIP was fabricated using azathioprine as the template, water-soluble 5-[(4-(methacryloyloxy) phenyl) diazenyl] isophthalic acid as the functional monomer, and ethylene glycol dimethacrylate as the cross-linker. The dendrimer-magnetic nanoparticles and PAMAM dendrimer-based P-MIPs were characterized by different spectroscopic and nano structural techniques. Quantitatively release and uptake of azathioprine from the P-MIP is photoregulated by alternate irradiation with ultraviolet and visible light. This means that trans–cis isomerization could regulate the affinity for azathioprine and azobenzene groups placed inside the binding sites. Hence, this material could be used as a chemical sorbent. The recoveries for analyte were higher than 95% and relative standard deviation values were found to be in the range of 1.24–1.72%, indicating that the prepared nano-sorbent has high accuracy and precision for determining trace of azathioprine in complex biological and pharmaceutical samples.

Half generations magnetic PAMAM dendrimers as an effective system for targeted gemcitabine delivery

Tumor-specific delivery of anticancer drugs by magnetic nanoparticles will maximize the efficacy of the drug and minimize side effects, and reduce systemic toxicity. The magnetic core of these nanoparticles provides an advantage for selective drug targeting as they can be targeted to the tumor site and accumulated in cancer cells by means of an external magnetic field. Magnetic nanoparticles can be coated with Polyamidoamine (PAMAM) dendrimer and loaded with drugs. However, biomedical applications of PAMAM dendrimers are limited due to their toxicity associated with their multiple cationic charges due to terminal NH2 groups. Modifying the positively charged end groups with negatively charged COOH groups, is a satisfactory strategy for obtaining less toxic PAMAM dendrimers. Gemcitabine being an analogue of deoxycytidine, is an effective anticancer drug. However, clinical benefits of Gemcitabine are limited due to its short biological half-life. The aim of this study was to obtain an effective, less toxic targeted delivery system for Gemcitabine. Half generations, between G4.5 and G7.5, of PAMAM dendrimer coated magnetic nanoparticles (DcMNPs) were synthesized and conjugated with Gemcitabine. TEM images showed nanoscale size (12–14nm) of the nanoparticles. The zeta-potential analysis indicated a decreased negativity of surface charge in drug bound dendrimer compared to the empty nanoparticles. Gemcitabine was effectively conjugated successfully onto the surface of half-generations of PAMAM DcMNPs. It was observed Gemcitabine did not effectively bind to Generations G4 and G5. The highest drug loading was obtained for DcMNPs with Generation 5.5. Empty nanoparticles showed no significant cytotoxicity on SKBR-3 and MCF-7 cells. On the other hand, Gemcitabine loaded nanoparticles were 6.0 fold more toxic on SKBR-3 and 3.0 fold more toxic on MCF-7 cells compared to free Gemcitabine. Gemcitabine loaded on Generation 5.5 DcMNPs showed a higher stability than free Gemcitabine. About 94% of the drug was retained over 6 weeks period, at pH 7.2. Due to their targetability under magnetic field, stability, size distribution, cellular uptake and toxicity characteristics the dendrimeric nanoparticles obtained in this study can be useful a delivery system for Gemcitabine in cancer therapy.

Changes in apoptosis-related gene expression and cytokine release in breast cancer cells treated with CpG-loaded magnetic PAMAM nanoparticles

CpG-oligodeoxynucleotide (CpG-ODN) can function as an immune adjuvant. Previously, we showed that stimulation of breast cancer cells with CpG-ODN conjugated with PAMAM dendrimer-coated magnetic nanoparticles (DcMNPs) has induced apoptosis. The aim of the current study was to evaluate the expression levels of some apoptosis-regulating genes in several human breast cancer cells treated with CpG/DcMNPs. Treated MDA-MB231 cells showed an increase in Noxa and Bax gene expression levels, whereas the expression level of Survivin decreased. Similarly, Noxa gene was overexpressed in treated MCF7 cells. In treated SKBR3 cells, a decline in the c-Flip mRNA level was determined. Furthermore, release of cytokines, IL-6, IL-10, and TNF-α, was determined in cell culture supernatants. CpG/DcMNP treatment leads to an increase in the release of IL-6 in MDA-MB231 and SKBR3 cells, whereas release of IL-10 and TNF-α did not change significantly. It is indicated that CpG-ODN may show its cytotoxic effect by regulating the expression of apoptosis-related genes and the release of cytokine in breast cancer cells.

CpG oligodeoxynucleotide-loaded PAMAM dendrimer-coated magnetic nanoparticles promote apoptosis in breast cancer cells

One major application of nanotechnology in cancer treatment involves designing nanoparticles to deliver drugs, oligonucleotides, and genes to cancer cells. Nanoparticles should be engineered so that they could target and destroy tumor cells with minimal damage to healthy tissues. This research aims to develop an appropriate and efficient nanocarrier, having the ability of interacting with and delivering CpG-oligodeoxynucleotides (CpG-ODNs) to tumor cells. CpG-ODNs activate Toll-like receptor 9 (TLR9), which can generate a signal cascade for cell death. In our study, we utilized three-layer magnetic nanoparticles composed of a Fe3O4 magnetic core, an aminosilane (APTS) interlayer and a cationic poly(amidoamine) (PAMAM) dendrimer. This will be a novel targeted delivery system to enhance the accumulation of CpG-ODN molecules in tumor cells. The validation of CpG-ODN binding to DcMNPs was performed using agarose gel electrophoresis, UV-spectrophotometer, XPS analyses. Cytotoxicity of conjugates was assessed in MDA-MB231 and SKBR3 cancer cells based on cell viability by XTT assay and flow cytometric analysis. Our results indicated that the synthesized DcMNPs having high positive charges on their surface could attach to CpG-ODN molecules via electrostatic means. These nanoparticles with the average sizes of 40±10nm bind to CpG-ODN molecules efficiently and induce cell death in MDA-MB231 and SKBR3 tumor cells and could be considered a suitable targeted delivery system for CpG-ODN in biomedical applications. The magnetic core of these nanoparticles represents a promising option for selective drug targeting as they can be concentrated and held in position by means of an external magnetic field.

Development of poly (I:C) modified doxorubicin loaded magnetic dendrimer nanoparticles for targeted combination therapy

The objective of this study was to develop and evaluate the anticancer activity and the safety of a combinational drug delivery system using polyamidoamine (PAMAM) dendrimer-coated iron oxide nanoparticles for doxorubicin and poly I:C delivery in vitro. Dendrimer-coated magnetic nanoparticles (DcMNPs) are suitable for drug delivery system as nanocarriers with their following properties, such as surface functional groups, symmetry perfection, internal cavities, nano-size and magnetization. These nanoparticles could be targeted to the tumor site under a magnetic field since they have a magnetic core. DcMNPs were found as a convenient vehicle for targeted doxorubicin delivery in cancer therapy. Poly (I:C) binding on doxorubicin loaded DcMNPs (DcMNPs-Dox) was reported for the first time in the literature. It was also demonstrated that loading of doxorubicin into the cavities of DcMNPs increases the binding efficiency of poly (I:C) to the surface functional groups of dendrimer up to 10 times. When we compare the in vitro cytotoxic properties of doxorubicin, poly (I:C) and poly (I:C) bound doxorubicin loaded DcMNPs (PIC-DcMNPs-Dox), it was observed that PIC-DcMNPs-Dox show the highest cytotoxic effect by passing the cell resistance mechanisms on doxorubicin resistant MCF7 (MCF7/Dox) cells. Results demonstrated that applying PIC-DcMNPs-Dox would improve the efficacy by increasing the biocompatibility of system in blood stream and the toxicity inside tumor cells. These results provide invaluable information and new insight for the design and optimization of a novel combinational drug delivery system for targeted cancer therapy.

Effect of gemcitabine and retinoic acid loaded PAMAM dendrimer-coated magnetic nanoparticles on pancreatic cancer and stellate cell lines

Gemcitabine is an anticancer drug used in the treatment of different cancer types, including pancreatic ductal adenocarcinoma. The maximum tolerated dose in humans is restricted by its side effects on healty cells. Furthermore, the fibrotic stroma produced by the pancreatic stellate cells prevents effective delivery of chemotherapeutic agents providing a safe-haven for the cancer cells. This becomes more of a problem considering the short half-life of this drug. Magnetic nanoparticle-based targeted drug delivery systems are a promising alternative to overcome the limitations of classical chemotherapies. The aim of this study is to obtain an effective targeted delivery system for gemcitabine using magnetic nanoparticles (MNPs) and all-trans retinoic acid (ATRA). This dual approach targets the tumor cells and its infrastructure – stellate cells – simultaneously. Gemcitabine and ATRA were loaded onto the PAMAM dendrimer-coated magnetic nanoparticles (DcMNPs), which were synthesized and characterized previously. Drug loading and release characteristics, and stability of the nanoparticles were investigated. Gemcitabine and ATRA loaded MNPs are efficiently taken up by pancreatic cancer and stellate cells successfully targeting and eliminating both cells. Results of this study can provide new insights on pancreatic cancer therapy where tumor is seen as a system with its stroma insead of epithelial cells alone.

Poly(ethylene glycol)-Modified PAMAM-Fe3O4-Doxorubicin Triads with the Potential for Improved Therapeutic Efficacy: Generation-Dependent Increased Drug Loading and Retention at Neutral pH and Increased Release at Acidic pH

Polyamidoamine (PAMAM) dendrimer-coated magnetic nanoparticles are a promising drug-delivery system that can enhance the therapeutic effects of chemotherapy drugs, such as doxorubicin (DOX), with minimized side effects. This work explores the optimization of the potential therapeutic efficiency of PAMAM-Fe3O4-DOX triads. Different generations (G3, G5, and G6) of PAMAMs were synthesized and modified with poly(ethylene glycol) (PEG) and then used to encapsulate glutamic acid-modified Fe3O4 nanoparticles. The Fe3O4-dendrimer carriers (Fe3O4-DGx where x = the generation 3, 5, or 6 of dendrimers) were electrostatically conjugated with drug DOX. The loading and releasing efficiencies of DOX increased with the PAMAM generation from 3 to 6. The loading efficiencies of DOX molecules were 87, 93, and 96% for generations 3, 5, and 6, respectively. At pH 5, the DOX release efficiencies within 24 h were approximately 60, 68, and 80% for generations 3, 5, and 6, respectively. At pH 7.4, the DOX releasing efficiency was as low as ∼ 15%. Compared to the negative control, the PAMAM-Fe3O4-DOX triads showed only mild toxicity against human cervical adenocarcinoma cell line HeLa at pH 7.4, which indicated that DOX can be fairly benignly carried and sparingly released until PAMAM-Fe3O4-DOX is taken up into the cell.

Polymer- and Dendrimer-Coated Magnetic Nanoparticles as Versatile Supports for Catalysts, Scavengers, and Reagents

The work-up of chemical reactions by standard techniques is often time consuming and energy demanding, especially when chemists have to guarantee low levels of metal contamination in the products. Therefore, scientists need new ideas to rapidly purify reaction mixtures that are both economically and environmentally benign. One intriguing approach is to tether functionalities that are required to perform organic reactions to magnetic nanoparticles, for example, catalysts, reagents, scavengers, or chelators. This strategy allows researchers to quickly separate active agents from reaction mixtures by exploiting the magnetic properties of the support. In this Account, we discuss the main attributes of magnetic supports and describe how we can make the different nanomagnets accessible by surface functionalization. Arguably the most prominent magnetic nanoparticles are superparamagnetic iron oxide nanoparticles (SPIONs) due to their biologically well-accepted constituents, their established size-selective synthesis methods, and their diminished agglomeration (no residual magnetic attraction in the absence of an external magnetic field). However, nanoparticles made of pure metal have a considerably higher magnetization level that is useful in applications where high loadings are needed. A few layers of carbon can efficiently shield such highly reactive metal nanoparticles and, equally important, enable facile covalent functionalization via diazonium chemistry or non-covalent functionalization through π-π interactions. We highlight carbon-coated cobalt (Co/C) and iron (Fe/C) nanoparticles in this Account and compare them to SPIONs stabilized with surfactants or silica shells. The graphene-like coating of these nanoparticles offers only low loadings with functional groups via direct surface modification, and the resulting nanomagnets are prone to agglomeration without effective steric stabilization. To overcome these restrictions and to tune the dispersibility of the magnetic supports in different solvents, we can introduce dendrimers and polymers on Co/C and Fe/C platforms by various synthetic strategies. While dendrimers have the advantage of being able to array all functional groups on the surface, polymers need fewer synthetic steps and higher molecular weight analogues are easily accessible. We present the application of these promising hybrid materials for the extraction of analytes or contaminates from complex aqueous solutions (e.g. waste water treatments or blood analytics), for metal-, organo-, and biocatalysis, and in organic synthesis. In addition, we describe advanced concepts like magnetic protecting groups, a multistep synthesis solely applying magnetic reagents and scavengers, and thermoresponsive self-separating magnetic catalysts. We also discuss the first examples of the use of magnetic scaffolds manipulated by external magnetic fields in flow reactors on the laboratory scale. These hold promise for future applications of magnetic hybrid materials in continuous flow or highly parallelized syntheses with rapid magnetic separation of the applied resins.

Doxorubicin Loading, Release, and Stability of Polyamidoamine Dendrimer-Coated Magnetic Nanoparticles

Nanotechnology is a promising alternative to overcome the limitations of classical chemotherapy. As a novel approach, dendrimer-coated magnetic nanoparticles (DcMNPs) maintain suitable drug delivery system because of their buildup of functional groups, symmetry perfection, nanosize, and internal cavities. They can also be targeted to the tumor site in a magnetic field. The aim of this study is to obtain an effective targeted delivery system for doxorubicin, using polyamidoamine (PAMAM) DcMNPs. Different generations (G2 , G3 , G4 , and G7 ) of PAMAM DcMNPs were synthesized. Doxorubicin loading, release, and stability efficiencies in these nanoparticles (NPs) were studied. The results showed that low-generation NPs obtained in this study have pH-sensitive drug release characteristics. G4 DcMNP, which releases most of the drug in lower pH, seems to be the most suitable generation for efficient Doxorubicin delivery. Furthermore, application of doxorubicin-loaded G4 DcMNPs may help to overcome doxorubicin resistance in MCF-7 cells. On the contrary, G2 and G3 DcMNPs would be suitable for the delivery of drugs such as vinca alkaloids (Johnson IS, Armstrong JG, Gorman M, Burnett JP. 1963. Cancer Res 23:1390-1427.) and taxenes (Clarke SJ, Rivory LP. 1999. Clin Pharmacokinet 36(2):99-114.), which show their effects in cytoplasm. The results of this study can provide new insights in the development of pH-sensitive targeted drug delivery systems to overcome drug resistance during cancer therapy.

PAMAM dendrimer-coated iron oxide nanoparticles: synthesis and characterization of different generations

This study focuses on the synthesis and characterization of different generations (G0–G7) of polyamidoamine (PAMAM) dendrimer-coated magnetic nanoparticles (DcMNPs). In this study, superparamagnetic iron oxide nanoparticles were synthesized by co-precipitation method. The synthesized nanoparticles were modified with aminopropyltrimethoxysilane for dendrimer coating. Aminosilane-modified MNPs were coated with PAMAM dendrimer. The characterization of synthesized nanoparticles was performed by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), dynamic light scattering, and vibrating sample magnetometry (VSM) analyses. TEM images demonstrated that the DcMNPs have monodisperse size distribution with an average particle diameter of 16 ± 5 nm. DcMNPs were found to be superparamagnetic through VSM analysis. The synthesis, aminosilane modification, and dendrimer coating of iron oxide nanoparticles were validated by FTIR and XPS analyses. Cellular internalization of nanoparticles was studied by inverted light scattering microscopy, and cytotoxicity was determined by XTT analysis. Results demonstrated that the synthesized DcMNPs, with their functional groups, symmetry perfection, size distribution, improved magnetic properties, and nontoxic characteristics could be suitable nanocarriers for targeted cancer therapy upon loading with various anticancer agents.