Facile synthesis of water-stable magnetite nanoparticles for clinical MRI and magnetic hyperthermia applications

AIMS

Superparamagnetic magnetite nanoparticles have been under intensive investigation in nanomedicine. However, it is still a challenge to synthesize high-quality water-stable magnetite nanoparticles for better magnetic performance and less side effects in medical MRI and nanothermotherapy.

MATERIALS & METHODS

We successfully synthesized hydrophilic magnetite nanoparticles through thermal decomposition of Fe(acac)(3) in triethylene glycol, which were coated with a triethylene glycol layer and thus demonstrated excellent water stability.

RESULTS

The optimized deposition temperature has been found to be 250°C (IO-250 NPs). The magnetic and thermal properties as well as the cytotoxicity of IO-250 NPs were investigated. In vitro experiments have demonstrated high cellular uptake and low cytotoxicity. The hyperthermia experiments showed effectiveness in temperature rise and cancer cell death. IO-250 NPs showed promising MRI with relaxivity r(2)* as high as 617.5 s(-1) mM(-1) Fe. In vivo MRI showed excellent tumor imaging.

CONCLUSION

The IO-250 NPs have great potential to be applied for clinical MRI and magnetic thermotherapy.

Nanomedicine: enhancement of chemotherapeutical efficacy of docetaxel by using a biodegradable nanoparticle formulation

The clinical dosage formulation of Paclitaxel and Docetaxel, Taxol and Taxotere, while having high efficacy, can cause serious side effects due to the adjuvant used. We have developed a system of nanoparticles (NPs) of biodegradable copolymer, poly(lactic acid)-d- -tocopheryl polyethylene glycol 1000 succinate (PLA-TPGS), for Docetaxel formulation to achieve enhanced, sustainable and controlled chemotherapeutic effectiveness and reduce the undesirable side actions. Docetaxel-loaded PLA-TPGS NPs were synthesized with desired size and physicochemical and pharmaceutical properties. In vitro studies using MCF-7 cancer cells have demonstrated the cellular uptake and lack of cytotoxicity of the NP formulation. In vivo pharmacokinetics and biodistribution analysis have shown that one dose of the NP formulation of Docetaxel can achieve a 360-h effective chemotherapy with 3.44-fold higher therapeutic effect and 4.42- fold lower side effect than that of Taxotere at the same dose of 10 mg/kg, as indicated by the larger area-under-the-curve and better biodistribution.

Synthesis of hydrophilic superparamagnetic magnetite nanoparticles via thermal decomposition of Fe(acac), in 80 vol% TREG + 20 vol% TREM

In this paper, we report single step synthesis of hydrophilic superparamagnetic magnetite nanoparticles by thermolysis of Fe(acac)3 and their characterization of the properties relevant to biomedical applications like hyperthermia and magnetic resonance imaging (MRI). Size and morphology of the particles were determined by Transmission electron microscopy (TEM) while phase purity and structure of the particles were identified by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Magnetic properties were evaluated using vibrating sample magnetometer (VSM) and superconducting quantum interference device (SQUID) measurements. The as prepared nanoparticles were found to be superparamagnetic with the blocking temperature of 136 K and were easily suspendable in water. Cytotoxicity studies on human cervical (SiHa), mouse melanoma (B16F10) and mouse primary fibroblast cells demonstrated that up to a dose of 0.1 mg/ml, the magnetite nanoparticles were nontoxic to the cells. To evaluate the feasibility of their uses in hyperthermia and MRI applications, specific absorption rate (SAR) and spin-spin relaxation time (T2) were measured respectively. SAR has been calculated to be above 80 Watt/g for samples with the iron concentration of 5-20 mg/ml at 10 kA/m AC magnetic field and 425 kHz frequency. r2 relaxivity value was measured as 358.4 mM(-1)S(-1) which is almost double as compared to that of the Resovist, a commercially available MRI contrast agent. Thus the as-prepared magnetite nanoparticles may be used for hyperthermia and MRI applications due to their promising SAR and r2 values.

Effects of surface modification on delivery efficiency of biodegradable nanoparticles across the blood–brain barrier

Aim: The aim of this work was to investigate the effect of surface modification of biodegradable nanoparticles on their cellular uptake, cytotoxicity and biodistribution for the delivery of imaging and therapeutic agents across the blood–brain barrier. Materials & methods: Coumarin-6- and docetaxel-encapsulated poly(D,L-lactide-co-glycolide) nanoparticles were prepared by a modified single emulsion method using polyvinyl alcohol or D-α-tocopheryl polyethylene glycol 1000 succinate (vitamin E TPGS or TPGS) as emulsifier. The nanoparticles’ surface was further modified with surfactants such as polysorbate-80 (Tween® 80), poloxamer 188 (F68) and poloxamer 407 (F127) to enhance cellular uptake of the NPs. Results: The F68-coated poly(D,L-lactide-co-glycolide) nanoparticles demonstrated the greatest cellular uptake and achieved highest fluorescence concentration in the brain tissues over those with T80 and F127 surface modification. Conclusion: Surface modification is a feasible and efficient strategy for nanoparticles made of biodegradable polymers to deliver diagnostic and therapeutic agents across the blood–brain barrier.

Multimodal tumor imaging by iron oxides and quantum dots formulated in poly (lactic acid)-D-alpha-tocopheryl polyethylene glycol 1000 succinate nanoparticles

This work developed a multimodal imaging system by co-encapsulating superparamagnetic iron oxides (IOs) and quantum dots (QDs) in the nanoparticles of poly (lactic acid) - d-α-tocopheryl polyethylene glycol 1000 succinate (PLA-TPGS) for concurrent imaging of the magnetic resonance imaging (MRI) and the fluorescence imaging to combine their advantages and to overcome their disadvantages as well as to promote a sustained and controlled imaging with passive targeting effects to the diseased cells. The QDs and IOs-loaded PLA-TPGS NPs were prepared by a modified nanoprecipitation method, which were then characterized for their size and size distribution, zeta potential and the imaging agent encapsulation efficiency. The transmission electron microscopy (TEM) images showed direct evidence for the well-dispersed distribution of the QDs and IOs within the PLA-TPGS NPs. The cellular uptake and the cytotoxicity of the PLA-TPGS NPs formulation of QDs and IOs were investigated in vitro with MCF-7 breast cancer cells, which were conducted in close comparison with the free QDs and IOs at the same agent dose. The Xenograft model was also conducted for biodistribution of the QDs and IOs-loaded PLA-TPGS NPs among the various organs, which showed greatly enhanced tumor imaging due to the passively targeting effects of the NPs to the tumor. Images of tumors were acquired in vivo by a 7T MRI scanner. Further ex vivo images of the tumors were obtained by confocal laser scanning microscopy. Such a multimodal imaging system shows great advantages of both contrast agents making the resultant probe highly sensitive with good depth penetration, which confirms the diagnosis obtained from each individual imaging. With therapeutics co-encapsulation and ligand conjugation, such nanoparticles system can realize a multi-functional system for medical diagnosis and treatment.

Doxorubicin conjugated to D-alpha-tocopheryl polyethylene glycol succinate and folic acid as a prodrug for targeted chemotherapy

This research developed a prodrug strategy to conjugate doxorubicin (DOX) to D-alpha-tocopheryl polyethylene glycol succinate (TPGS) and folic acid (FOL) for targeted chemotherapy to enhance the therapeutic effects and reduce the side effects of the drug. We synthesized two conjugates, TPGS-DOX and TPGS-DOX-FOL, to quantitatively evaluate the advantages of TPGS conjugation and FOL conjugation through passive and active targeting effects. The successful conjugation was confirmed by (1)H nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy. The in vitro drug release was found pH dependent, which is in favor of cancer treatment. The in vitro cellular uptake and cytotoxicity were evaluated with MCF-7 breast cancer cells. It was found that the cellular uptake of DOX increased 15.2% by TPGS conjugation and further 6.3% by FOL conjugation after 0.5-h cell culture. The IC(50) after 24-h cell culture with MCF-7 cancer cells showed that TPGS-DOX conjugate could be 1.19-fold effective versus DOX and that TPGS-DOX-FOL could be 38.6-fold effective than TPGS-DOX and thus 45.0-fold more effective versus DOX. In vivo experiment showed that the half-life of TPGS-DOX and TPGS-DOX-FOL were increased 3.79- and 3.9-fold than the free DOX, and the area under the curve were increased 19.2- and 14.5-fold than the DOX, respectively. The biodistribution data showed that TPGS-DOX and TPGS-DOX-FOL significantly lowered drug accumulation in the heart, thereby reducing the cardiotoxicity, which is the main side effect of the DOX. Furthermore, TPGS-DOX can limit, and TPGS-DOX-FOL can further deduce, the gastrointestinal side effect of the drug.

A strategy for precision engineering of nanoparticles of biodegradable copolymers for quantitative control of targeted drug delivery

Research on quantitative control of targeting effect for the drug delivery system of ligand-conjugated nanoparticles of biodegradable polymers is at the cutting edge in the design of drug delivery device. In this work, we developed a post-conjugation strategy, which makes the ligand conjugation after the preparation of the drug-loaded nanoparticles of two copolymers blend. We synthesized the PLGA-PEG copolymer with PEG functioning as the linker molecule needed for herceptin conjugation. Docetaxel-loaded nanoparticles of the PLGA-PEG/PLGA copolymer blend were prepared by the nanoprecipitation method. Anti-HER2 antibody (heceptin), which targets the breast cancer cells of HER2 receptor overexpression, was conjugated on the drug-loaded PLGA-PEG/PLGA nanoparticles for sustained, controlled and targeted delivery of docetaxel. We demonstrated that the targeting effect can be quantitatively controlled by two ways, i.e. (1) adjusting the copolymer blend ratio of the nanoparticle matrix, which showed within the range of 20% PLGA/PEG in the copolymer blend a linear relation with the ligand density on the nanoparticle surface, and (2) adjusting the herceptin feed molar ratio to NH2 in the linker molecules appearing on the nanoparticle surface, which also showed a linear relation. Compared with the pre-conjugation strategy developed recently in the literature, in which the ligand was firstly conjugated onto the PLGA-PEG copolymer before preparation of the nanoparticles of the PLGA-PEG/PLGA copolymer blend, the post-conjugation strategy provides more efficient use of the ligand and protects its bioactivity in the nanoparticle preparation process, thus resulting in much better performance in drug targeting, which was assessed in vitro with SK-BR-3 breast cancer cells of HER2 receptor overexpression and MCF7 breast cancer cells of HER2 receptors moderate expression.

Superparamagnetic iron oxide--loaded poly(lactic acid)-D-alpha-tocopherol polyethylene glycol 1000 succinate copolymer nanoparticles as MRI contrast agent

We developed a strategy to formulate supraparamagnetic iron oxides (SPIOs) in nanoparticles (NPs) of biodegradable copolymer made up of poly(lactic acid) (PLA) and d-alpha-tocopherol polyethylene glycol 1000 succinate (TPGS) for medical imaging by magnetic resonance imaging (MRI) of high contrast and low side effects. The IOs-loaded PLA-TPGS NPs (IOs-PNPs) were prepared by the single emulsion method and the nanoprecipitation method. Effects of the process parameters such as the emulsifier concentration, IOs loading in the nanoparticles, and the solvent to non-solvent ratio on the IOs distribution within the polymeric matrix were investigated and the formulation was then optimized. The transmission electron microscopy (TEM) showed direct visual evidence for the well dispersed distribution of the IOs within the NPs. We further investigated the biocompatibility and cellular uptake of the IOs-PNPs in vitro with MCF-7 breast cancer cells and NIH-3T3 mouse fibroblast in close comparison with the commercial IOs imaging agent Resovist. MRI imaging was further carried out to investigate the biodistribution of the IOs formulated in the IOs-PNPs, especially in the liver to understand the liver clearance process, which was also made in close comparison with Resovist. We found that the PLA-TPGS NPs formulation at the clinically approved dose of 0.8 mg Fe/kg could be cleared within 24 h in comparison with several weeks for Resovist. Xenograft tumor model MRI confirmed the advantages of the IOs-PNPs formulation versus Resovist through the enhanced permeation and retention (EPR) effect of the tumor vasculature.

Multifunctional nanoparticles of biodegradable copolymer blend for cancer diagnosis and treatment

AIMS

A multifunctional nanoparticle (NP) system is developed to provide a sustained, controlled and targeted co-delivery of quantum dots (QDs) as a model imaging agent and docetaxel as a model anticancer drug. The NPs are made of a polymeric blend of poly(lactic-co-glycolic acid), which forms a biodegradable NP matrix, and the novel copolymer D-alpha-tocopheryl polyethylene glycol 1000 succinate-COOH, which facilitates ligand conjugation on the NP surface.

MATERIALS & METHODS

The NPs were prepared by nanoprecipitation and characterized for their size and size distribution, surface morphology, surface charge, QD/drug encapsulation and loading efficiency, and in vitro drug release profile. The targeting effects of such NPs were evaluated both quantitatively and qualitatively through the cellular uptake of the QDs as well as the cytotoxicity of the drug using MCF-7 cells, which overexpress folate receptors and NIH 3T3 cells, which have no folate receptors overexpression.

RESULTS & CONCLUSIONS

NPs with folate conjugated on their surface achieved much higher cellular uptake than those with no folate conjugation in MCF-7 cells while no significant targeting effect could be observed for NIH 3T3 cells. The drug formulated in the folate-conjugated NPs were more efficious compared with NPs with no folate conjugation as well as the current clinical formulation Taxotere.

Nanoparticles of lipid monolayer shell and biodegradable polymer core for controlled release of paclitaxel: effects of surfactants on particles size, characteristics and in vitro performance

This work developed a system of nanoparticles of lipid monolayer shell and biodegradable polymer core for controlled release of anticancer drugs with paclitaxel as a model drug, in which the emphasis was given to the effects of the surfactant type and the optimization of the emulsifier amount used in the single emulsion solvent evaporation/extraction process for the nanoparticle preparation on the particle size, characters and in vitro performance. The drug loaded nanoparticles were characterized by laser light scattering (LLS) for size and size distribution, field-emission scanning electron microscopy (FESEM) for surface morphology, X-ray photoelectron spectroscopy (XPS) for surface chemistry, zetasizer for surface charge, and high performance liquid chromatography (HPLC) for drug encapsulation efficiency and in vitro drug release kinetics. MCF-7 breast cancer cells were employed to evaluate the cellular uptake and cytotoxicity. It was found that phospholipids of short chains such as 1,2-dilauroylphosphatidylocholine (DLPC) have great advantages over the traditional emulsifier poly(vinyl alcohol) (PVA), which is used most often in the literature, in preparation of nanoparticles of biodegradable polymers such as poly(D,L-lactide-co-glycolide) (PLGA) for desired particle size, character and in vitro cellular uptake and cytotoxicity. After incubation with MCF-7 cells at 0.250 mg/ml NP concentration, the coumarin-6 loaded PLGA NPs of DLPC shell showed more effective cellular uptake versus those of PVA shell. The analysis of IC(50), i.e. the drug concentration at which 50% of the cells are killed, demonstrated that our DLPC shell PLGA core NP formulation of paclitaxel could be 5.88-, 5.72-, 7.27-fold effective than the commercial formulation Taxol after 24, 48, 72h treatment, respectively.