Angeles Villanueva

The influence of surface functionalization on the enhanced internalization of magnetic nanoparticles in cancer cells

The internalization and biocompatibility of iron oxide nanoparticles surface functionalized with four differently charged carbohydrates have been tested in the human cervical carcinoma cell line (HeLa). Neutral, positive, and negative iron oxide nanoparticles were obtained by coating with dextran, aminodextran, heparin, and dimercaptosuccinic acid, resulting in colloidal suspensions stable at pH 7 with similar aggregate size. No intracellular uptake was detected in cells incubated with neutral charged nanoparticles, while negative particles showed different behaviour depending on the nature of the coating. Thus, dimercaptosuccinic-coated nanoparticles showed low cellular uptake with non-toxic effects, while heparin-coated particles showed cellular uptake only at high nanoparticle concentrations and induced abnormal mitotic spindle configurations. Finally, cationic magnetic nanoparticles show excellent properties for possible in vivo biomedical applications such as cell tracking by magnetic resonance imaging (MRI) and cancer treatment by hyperthermia: (i) they enter into cells with high effectiveness, and are localized in endosomes; (ii) they can be easily detected inside cells by optical microscopy, (iii) they are retained for relatively long periods of time, and (iv) they do not induce any cytotoxicity.

MTT assay for cell viability: Intracellular localization of the formazan product is in lipid droplets

Although MTT is widely used to assess cytotoxicity and cell viability, the precise localization of its reduced formazan product is still unclear. In the present study the localization of MTT formazan was studied by direct microscopic observation of living HeLa cells and by colocalization analysis with organelle-selective fluorescent probes. MTT formazan granules did not colocalize with mitochondria as revealed by rhodamine 123 labeling or autofluorescence. Likewise, no colocalization was observed between MTT formazan granules and lysosomes labeled by neutral red. Taking into account the lipophilic character and lipid solubility of MTT formazan, an evaluation of the MTT reaction was performed after treatment of cells with sunflower oil emulsions to induce a massive occurrence of lipid droplets. Under this condition, lipid droplets revealed a large amount of MTT formazan deposits. Kinetic studies on the viability of MTT-treated cells showed no harmful effects at short times. Quantitative structure-activity relations (QSAR) models were used to predict and explain the localization of both the MTT tetrazolium salt and its formazan product. These predictions were in agreement with experimental observations on the accumulation of MTT formazan product in lipid droplets.

Morphological criteria to distinguish cell death induced by apoptotic and necrotic treatments.

We present a comparative study of apoptotic and necrotic morphology (light and scanning electron microscopy), induced by well known experimental conditions (photodynamic treatments, etoposide, hydrogen peroxide, freezing-thawing and serum deprivation) on cell cultures. Our results indicate that morphological criteria (apoptotic cell rounding and shrinkage, and appearance of membrane bubbles in early necrosis) allow to distinguish these cell death mechanisms, and also show that, independently of the damaging agents, the necrotic process occurs in a characteristic sequence (coalescence of membrane bubbles in a single big one that detaches from cells remaining on the substrate).

Porphycenes: Facts and Prospects in Photodynamic Therapy of Cancer

The photodynamic process induces cell damage and death by the combined effect of a photosensitizer (PS), visible light, and molecular oxygen, which generate singlet oxygen ((1)O(2)) and other reactive oxygen species that are responsible for cytotoxicity. The most important application of this process with increasing biomedical interest is the photodynamic therapy (PDT) of cancer. In addition to hematoporphyrin-based drugs, 2nd generation PSs with better photochemical properties are now studied using cell cultures, experimental tumors and clinical trials. Porphycene is a structural isomer of porphyrin and constitutes an interesting new class of PS. Porphycene derivatives show higher absorption than porphyrins in the red spectral region (lambda > 600 nm, epsilon > 50000 M-(1)cm(-1)) owing to the lower molecular symmetry. Photophysical and photobiological properties of porphycenes make them excellent candidates as PSs, showing fast uptake and diverse subcellular localizations (mainly membranous organelles). Several tetraalkylporphycenes and the tetraphenyl derivative (TPPo) induce photodamage and cell death in vitro. Photodynamic treatments of cultured tumor cells with TPPo and its palladium(II) complex induce cytoskeletal changes, mitotic blockage, and dose-dependent apoptotic or necrotic cell death. Some pharmacokinetic and phototherapeutic studies on experimental tumors after intravenous or topical application of lipophilic alkyl-substituted porphycene derivatives are known. Taking into account all these features, porphycene PSs should be very useful for PDT of cancer and other biomedical applications.

Dimercaptosuccinic acid-coated magnetite nanoparticles for magnetically guided in vivo delivery of interferon gamma for cancer immunotherapy

As radio- and chemotherapy-based cancer treatments affect both tumors and healthy tissue, cancer immunotherapy attempts to specifically enhance the natural immune response to tumor cells. In mouse models of cancer, we tested uniform dimercaptosuccinic acid (DMSA)-coated monodisperse magnetic nanoparticles as a delivery system for the anti-tumorigenic cytokine IFN-γ. IFN-γ-adsorbed DMSA-coated magnetic nanoparticles were targeted to the tumor site by application of an external magnetic field. We analyzed nanoparticle biodistribution before and after IFN-γ conjugation, as well as the efficiency of nanoparticle accumulation in tumors, IFN-γ release in the area of interest, and the effects of both on tumor development. At the tumor site, we observed a high degree of nanoparticle accumulation and of cytokine delivery, which led to increased T cell and macrophage infiltration and promoted an anti-angiogenic effect. The combined action led to a notable reduction in tumor size. Our findings indicate that IFN-γ-adsorbed DMSA-coated magnetite nanoparticles can be used as an efficient in vivo drug delivery system for tumor immunotherapy.

Efficient and safe internalization of magnetic iron oxide nanoparticles: two fundamental requirements for biomedical applications.

UNLABELLED We have performed a series of in vitro tests proposed for the reliable assessment of safety associated with nanoparticles-cell interaction. A thorough analysis of toxicity of three different coating iron oxide nanoparticles on HeLa cells has been carried out including, methyl thiazol tetrazolium bromide (MTT) and Trypan blue exclusion tests, cell morphology observation by optical and Scanning Electron Microscopy (SEM), study of cytoskeletal components, analysis of cell cycle and the presence of reactive oxygen species (ROS). We have quantified magnetic nanoparticle internalization, determined possible indirect cell damages and related it to the nanoparticle coating. The results confirm a very low toxicity of the analyzed iron oxide nanoparticles into HeLa cells by multiple assays and pave the way for a more successful cancer diagnostic and treatment without secondary effects. FROM THE CLINICAL EDITOR In this paper, three different iron oxide nanoparticles are studied and compared from the standpoint of safety and toxicity in HeLa cells, demonstrating low toxicity for each preparation, and paving the way to potential future clinical applications.

Efficient treatment of breast cancer xenografts with multifunctionalized iron oxide nanoparticles combining magnetic hyperthermia and anti-cancer drug delivery

IntroductionTumor cells can effectively be killed by heat, e.g. by using magnetic hyperthermia. The main challenge in the field, however, is the generation of therapeutic temperatures selectively in the whole tumor region. We aimed to improve magnetic hyperthermia of breast cancer by using innovative nanoparticles which display a high heating potential and are functionalized with a cell internalization and a chemotherapeutic agent to increase cell death.MethodsThe superparamagnetic iron oxide nanoparticles (MF66) were electrostatically functionalized with either Nucant multivalent pseudopeptide (N6L; MF66-N6L), doxorubicin (DOX; MF66-DOX) or both (MF66-N6LDOX). Their cytotoxic potential was assessed in a breast adenocarcinoma cell line MDA-MB-231. Therapeutic efficacy was analyzed on subcutaneous MDA-MB-231 tumor bearing female athymic nude mice.ResultsAll nanoparticle variants showed an excellent heating potential around 500 W/g Fe in the alternating magnetic field (AMF, conditions: H = 15.4 kA/m, f = 435 kHz). We could show a gradual inter- and intracellular release of the ligands, and nanoparticle uptake in cells was increased by the N6L functionalization. MF66-DOX and MF66-N6LDOX in combination with hyperthermia were more cytotoxic to breast cancer cells than the respective free ligands. We observed a substantial tumor growth inhibition (to 40% of the initial tumor volume, complete tumor regression in many cases) after intratumoral injection of the nanoparticles in vivo. The proliferative activity of the remaining tumor tissue was distinctly reduced.ConclusionThe therapeutic effects of breast cancer magnetic hyperthermia could be strongly enhanced by the combination of MF66 functionalized with N6L and DOX and magnetic hyperthermia. Our approach combines two ways of tumor cell killing (magnetic hyperthermia and chemotherapy) and represents a straightforward strategy for translation into the clinical practice when injecting nanoparticles intratumorally.

Short-chain PEG molecules strongly bound to magnetic nanoparticle for MRI long circulating agents

This study developed an approach for the synthesis of magnetic nanoparticles coated with three different polyethylene glycol (PEG)-derived molecules. The influence of the coating on different properties of the nanoparticles was studied. Magnetite nanoparticles (7 and 12 nm in diameter) were obtained via thermal decomposition of a coordination complex as an iron precursor to ensure nanoparticle homogeneity in size and shape. Particles were first coated with meso-2,3-dimercaptosuccinic acid by a ligand exchange process to remove oleic acid, followed by modification with three distinct short-chain PEG polymers, which were covalently bound to the nanoparticle surface via 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride activation of the carboxylic acids. In all cases, colloidal suspensions had hydrodynamic sizes <100 nm and low surface charge, demonstrating the effect of PEG coating on the aggregation properties and steric stabilization of the magnetic nanoparticles. The internalization and biocompatibility of these materials in the HeLa human cervical carcinoma cell line were tested. Cells preincubated with PEG-coated iron nanoparticles were visualized outside the cells, and their biocompatibility at high Fe concentrations was demonstrated using a standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Finally, relaxivity parameters (r1 and r2) were used to evaluate the efficiency of suspensions as magnetic resonance imaging contrast agents; the r2 value was similar to that for Resovist and up to four times higher than that for Sinerem, probably due to the larger nanoparticle size. The time of residence in blood of the nanoparticles measured from the relaxivity values, and the Fe content in blood was doubled for rats and rabbits due to the PEG on the nanoparticle surface. The results suggest that this PEGylation strategy for large magnetic nanoparticles (>10nm) holds promise for biomedical applications.

Synthesis of 2,7,12,17-tetraphenylporphycene (TPPo). First aryl-substituted porphycene for the photodynamic therapy of tumors

Abstract We report on the synthesis of 2,7,12,17-tetraphenylporphycene (TPPo), the first example of an aryl-substituted porphycene macrocycle. A modification of the general porphycene synthetic method has been used, thus avoiding an intermediate sublimation. TPPo has an absorption maximum at 659 nm ( e = 50.000 M −1 cm −1 ), and shows good sensitizing properties: it photoproduces singlet oxygen with a quantum yield of ca. 0.25, is phototoxic to cells, and has low dark toxicity. These properties make TPPo a suitable candidate for the photodynamic therapy of tumors.

Pharmacokinetic and tumour-photosensitizing properties of the cationic porphyrin meso-tetra(4N-methylpyridyl)porphine

The pharmacokinetic behaviour and the photodynamic properties of the cationic porphyrin meso-tetra(4N-methylpyridyl)porphine (T4MPyP 2.1 mg/kg) were examined in Balb/c mice bearing an MS-2 fibrosarcoma. The porphyrin shows good tumour localizing properties; 24 h after drug administration the tumour concentration of T4MPyP was approximately 1.2 ng/mg, while the concentrations in normal tissues were substantially lower, except for liver and spleen. In the serum, T4MPyP is preferentially transported by albumin and globulins (80.5%), while minor amounts are associated to lipoproteins (19.5%). The phototherapeutic efficiency of T4MPyP was tested by following the growth curves of fibrosarcoma irradiated by 600-680 nm (450 J/cm2) 24 h after the i.v. injection of T4MPyP (2.1 mg/kg). PDT-treated tumours showed a temporary delay in their growth compared with control tumours. The excellent selectivity of T4MPyP and its antitumour activity on photoexcitation encourage further studies for assessing the usefulness of this porphyrin in photodynamic therapy.