Upscale Synthesis of Magnetic Mesoporous Silica Nanoparticles and Application to Metal Ion Separation: Nanosafety Evaluation

The synthesis of core-shell magnetic mesoporous nanoparticles (MMSNs) through a phase transfer process is usually performed at the 100-250 mg scale. At the gram scale, nanoparticles without cores or with multicore systems are observed. Iron oxide core nanoparticles (IO) were synthesized through a thermal decomposition procedure of α-FeO(OH) in oleic acid. A phase transfer from chloroform to water was then performed in order to wrap the IO nanoparticles with a mesoporous silica shell through the sol-gel procedure. MMSNs were then functionalized with DTPA (diethylenetriaminepentacetic acid) and used for the separation of metal ions. Their toxicity was evaluated. The phase transfer procedure was crucial to obtaining MMSNs on a large scale. Three synthesis parameters were rigorously controlled: temperature, time and glassware. The homogeneous dispersion of MMSNs on the gram scale was successfully obtained. After functionalization with DTPA, the MMSN-DTPAs were shown to have a strong affinity for Ni ions. Furthermore, toxicity was evaluated in cells, zebrafish and seahorse cell metabolic assays, and the nanoparticles were found to be nontoxic. We developed a method of preparing MMSNs at the gram scale. After functionalization with DTPA, the nanoparticles were efficient in metal ion removal and separation; furthermore, no toxicity was noticed up to 125 µg mL-1 in zebrafish.

Small anticancer drug release by light: Photochemical internalization of porphyrin-β-cyclodextrin nanoparticles

Aiming to engineer simple, neutral, strongly amphiphilic photoactive nanoparticles (NPs) to specifically target cancer cell lysosomes for drug transport and light-controlled release, new conjugates of β-cyclodextrin with highly hydrophobic triphenylporphyrin bearing different alkyl chains, were synthesized. Although differently sized, all conjugates self-assemble into ~60 nm NPs in water and display similar photoactivity. The NPs target selectively the lysosomes of breast adenocarcinoma MCF-7 cells, embedding in vesicular membranes, as experiments with model liposomes indicate. Either empty or drug-loaded, the NPs lack dark toxicity for 48 h. They bind with differently structured anticancer drugs tamoxifen and gemcitabine as its N-adamantyl derivative. Red light irradiation of cells incubated with drug-loaded NPs results in major reduction of viability (>85 %) for 48 h displaying significant synergy of photo-chemotoxicity, as opposed to empty NPs, and to loaded non-irradiated NPs, in manifestation of photochemical internalization (PCI). Our approach expands the field of PCI into different small molecule chemotherapeutics.

Myeloperoxidase exerts anti-tumor activity in glioma after radiotherapy

Background

Host immune response is a critical component in tumorigenesis and immune escape. Radiation is widely used for glioblastoma (GBM) and can induce marked tissue inflammation and substantially alter host immune response. However, the role of myeloperoxidase (MPO), a key enzyme in inflammation and host immune response, in tumorigenesis after radiotherapy is unclear. In this study, we aimed to determine how post-radiation MPO activity influences GBM and outcome.

Methods

We injected C57BL/6J or MPO-knockout mice with 005 mouse GBM stem cells intracranially. To observe MPO's effects on post-radiation tumor progression, we then irradiated the head with 10 Gy unfractionated and treated the mice with a specific MPO inhibitor, 4-aminobenzoic acid hydrazide (ABAH), or vehicle as control. We performed semi-quantitative longitudinal molecular MRI, enzymatic assays and flow cytometry to assess changes in inflammatory response and tumor size, and tracked survival. We also performed cell culture experiments in murine and human GBM cells to determine the effect of MPO on these cells.

Results

Brain irradiation increased the number of monocytes/macrophages and neutrophils, and boosted MPO activity by ten-fold in the glioma microenvironment. However, MPO inhibition dampened radiation-induced inflammation, demonstrating decreased MPO-specific signal on molecular MRI and attenuated neutrophil and inflammatory monocyte/macrophage recruitment to the glioma. Compared to saline-treated mice, both ABAH-treated and MPO-knockout mice had accelerated tumor growth and reduced survival. We further confirmed that MPO decreased tumor cell viability and proliferation in cell cultures.

Conclusion

Local radiation to the brain initiated an acute systemic inflammatory response with increased MPO-carrying cells both in the periphery and the GBM, resulting in increased MPO activity in the tumor microenvironment. Inhibition or absence of MPO activity increased tumor growth and decreased host survival, revealing that elevated MPO activity after radiation has an anti-tumor role.

Reactive Species from Two-Signal Activated Macrophages Interfere with Their Oxygen Consumption Measurements

Metabolic modulation of macrophage activation has emerged as a promising strategy lately in immunotherapeutics. However, macrophages have a broad spectrum of functions and thus, understanding the exact metabolic changes that drive a particular immune response, is of major importance. In our previous work, we have reported a key role of nitric oxide (NO^●) in two(2)-signal activated macrophages [M(2-signals)]. Further characterization using metabolic analysis in intact cells, showed that the basal and maximal respiration levels of M(2-signals) were comparable, with cells being unresponsive to the injections-inducd mitochondrial stress. Here, we show that excessive NO^● secretion by the M(2-signals) macrophages, interferes with the oxygen (O₂) consumption measurements on cells using the seahorse metabolic analyzer. This is attributed mainly to the consumption of ambient oxygen by NO^● to form NO₂⁻ and/or NO₃⁻ but also to the reduction of O₂ to superoxide anion (O₂^●−) by stray electrons from the electron transport chain, leading to the formation of peroxynitrite (ONOO⁻). We found that reactive species-donors in the absence of cells, produce comparable oxygen consumption rates (OCR) with M(2-signals) macrophages. Furthermore, inhibition of NO^● production, partly recovered the respiration of activated macrophages, while external addition of NO^● in non-activated macrophages downregulated their OCR levels. Our findings are crucial for the accurate metabolic characterization of cells, especially in cases where reactive nitrogen or oxygen species are produced in excess.

Predictive biomarkers for 5-ALA-PDT can lead to personalized treatments and overcome tumor-specific resistances

BACKGROUND

Photodynamic therapy (PDT) is a minimally invasive, clinically approved therapy with numerous advantages over other mainstream cancer therapies. 5-aminolevulinic acid (5-ALA)-PDT is of particular interest, as it uses the photosensitiser PpIX, naturally produced in the heme pathway, following 5-ALA administration. Even though 5-ALA-PDT shows high specificity to cancers, differences in treatment outcomes call for predictive biomarkers to better stratify patients and to also diversify 5-ALA-PDT based on each cancer's phenotypic and genotypic individualities.

AIMS

The present study seeks to highlight key biomarkers that may predict treatment outcome and simultaneously be exploited to overcome cancer-specific resistances to 5-ALA-PDT.

METHODS AND RESULTS

We submitted two glioblastoma (T98G and U87) and three breast cancer (MCF7, MDA-MB-231, and T47D) cell lines to 5-ALA-PDT. Glioblastoma cells were the most resilient to 5-ALA-PDT, while intracellular production of 5-ALA-derived protoporphyrin IX (PpIX) could not account for the recorded PDT responses. We identified the levels of expression of ABCG2 transporters, ferrochelatase (FECH), and heme oxygenase (HO-1) as predictive biomarkers for 5-ALA-PDT. GPX4 and GSTP1 expression vs intracellular glutathione (GSH) levels also showed potential as PDT biomarkers. For T98G cells, inhibition of ABCG2, FECH, HO-1, and/or intracellular GSH depletion led to profound PDT enhancement. Inhibition of ABCG2 in U87 cells was the only synergistic adjuvant to 5-ALA-PDT, rendering the otherwise resistant cell line fully responsive to 5-ALA-PDT. ABCG2 or FECH inhibition significantly enhanced 5-ALA-PDT-induced MCF7 cytotoxicity, while for MDA-MB-231, ABCG2 inhibition and intracellular GSH depletion conferred profound synergies. FECH inhibition was the only synergism to ALA-PDT for the most susceptible among the cell lines, T47D cells.

CONCLUSION

This study demonstrates the heterogeneity in the cellular response to 5-ALA-PDT and identifies biomarkers that may be used to predict treatment outcome. The study also provides preliminary findings on the potential of inhibiting specific molecular targets to overcome inherent resistances to 5-ALA-PDT.

Photodynamic Efficacy of Cercosporin in 3D Tumor Cell Cultures

In the present work, we study the photodynamic action of cercosporin (cerco), a naturally occurring photosensitizer, on human cancer multicellular spheroids. U87 spheroids exhibit double the uptake of cerco than T47D and T98G spheroids as shown by flow cytometry on the single cell level. Moreover, cerco is efficiently internalized by cells throughout the spheroid as shown by confocal microscopy, for all three cell lines. Despite their higher cerco uptake, U87 spheroids show the least vulnerability to cerco-PDT, in contrast to the other two cell lines (T47D and T98G). While 300 μm diameter spheroids consistently shrink and become necrotic after cerco PDT, bigger spheroids (>500 μm) start to regrow following blue-light PDT and exhibit high viability. Cerco-PDT was found to be effective on bigger spheroids reaching 1mm in diameter especially under longer exposure to yellow light (~590 nm). In terms of metabolism, T47D and T98G undergo a complete bioenergetic collapse (respiration and glycolysis) as a result of cerco-PDT. U87 spheroids also experienced a respiratory collapse following cerco-PDT, but retained half their glycolytic activity.

Simultaneous defeat of MCF7 and MDA-MB-231 resistances by a hypericin PDT-tamoxifen hybrid therapy

Currently the greatest challenge in oncology is the lack of homogeneity of the lesions where different cell components respond differently to treatment. There is growing consensus that monotherapies are insufficient to eradicate the disease and there is an unmet need for more potent combinatorial treatments. We have previously shown that hypericin photodynamic therapy (HYP-PDT) triggers electron transport chain (ETC) inhibition in cell mitochondria. We have also shown that tamoxifen (TAM) enhances cytotoxicity in cells with high respiration, when combined with ETC inhibitors. Herein we introduce a synergistic treatment based on TAM chemotherapy and HYP-PDT. We tested this novel combinatorial treatment (HYPERTAM) in two metabolically different breast cancer cell lines, the triple-negative MDA-MB-231 and the estrogen-receptor-positive MCF7, the former being quite sensitive to HYP-PDT while the latter very responsive to TAM treatment. In addition, we investigated the mode of death, effect of lipid peroxidation, and the effect on cell metabolism. The results were quite astounding. HYPERTAM exhibited over 90% cytotoxicity in both cell lines. This cytotoxicity was in the form of both necrosis and autophagy, while high levels of lipid peroxidation were observed in both cell lines. We, consequently, translated our research to an in vivo pilot study encompassing the MDA-MB-231 and MCF7 tumor models in NOD SCID-γ immunocompromised mice. Both treatment cohorts responded very positively to HYPERTRAM, which significantly prolonged mice survival. HYPERTAM is a potent, synergistic modality, which may lay the foundations for a novel, composite anticancer treatment, effective in diverse tumor types.

Cytotoxic and Photocytotoxic Effects of Cercosporin on Human Tumor Cell Lines

Cercosporin is a naturally occurring perylenequinone. Although other perylenequinones have been extensively studied as photosensitizers in photodynamic therapy of cancer (PDT), cercosporin has been studied in this light only within the remits of phytopathology. Herein, we investigated the photocytotoxicity of cercosporin against two glioblastoma multiforme (T98G and U87) and one breast adenocarcinoma (MCF7) human cell lines. Cercosporin was found to be a potent singlet oxygen producer upon 532 nm excitation, while its cell loading was similar for MCF7 and U87, but approximately threefold higher for T98G cells. The subcellular localization of cercosporin was in all cases in both mitochondria and the endoplasmic reticulum. Light irradiation of cercosporin-incubated cells around 450 nm showed that T98G cells were more susceptible to cercosporin PDT, mainly due to their higher cercosporin uptake. Metabolic studies before and 1 h following cercosporin PDT showed that cercosporin PDT instigated a bioenergetic collapse in both the respiratory and glycolytic activities of all cell lines. In the dark, cercosporin exhibited a synergistic cytotoxicity with copper only in the most respiratory cell lines (MCF7 and T98G). Cercosporin is a potent photosensitizer, but with a short activation wavelength, mostly suitable for superficial PDT treatments, especially when it is necessary to avoid perforations.

Artesunate shows potent anti-tumor activity in B-cell lymphoma

BACKGROUND

Although chemo-immunotherapy has led to an improved overall survival for most B-cell lymphoma types, relapsed and refractory disease remains a challenge. The malaria drug artesunate has previously been identified as a growth suppressor in some cancer types and was tested as a new treatment option in B-cell lymphoma.

METHODS

We included artesunate in a cancer sensitivity drug screen in B lymphoma cell lines. The preclinical properties of artesunate was tested as single agent in vitro in 18 B-cell lymphoma cell lines representing different histologies and in vivo in an aggressive B-cell lymphoma xenograft model, using NSG mice. Artesunate-treated B lymphoma cell lines were analyzed by functional assays, gene expression profiling, and protein expression to identify the mechanism of action.

RESULTS

Drug screening identified artesunate as a highly potent anti-lymphoma drug. Artesunate induced potent growth suppression in most B lymphoma cells with an IC50 comparable to concentrations measured in serum from artesunate-treated malaria patients, while leaving normal B-cells unaffected. Artesunate markedly inhibited highly aggressive tumor growth in a xenograft model. Gene expression analysis identified endoplasmic reticulum (ER) stress and the unfolded protein response as the most affected pathways and artesunate-induced expression of the ER stress markers ATF-4 and DDIT3 was specifically upregulated in malignant B-cells, but not in normal B-cells. In addition, artesunate significantly suppressed the overall cell metabolism, affecting both respiration and glycolysis.

CONCLUSIONS

Artesunate demonstrated potent apoptosis-inducing effects across a broad range of B-cell lymphoma cell lines in vitro, and a prominent anti-lymphoma activity in vivo, suggesting it to be a relevant drug for treatment of B-cell lymphoma.

Functionalized Hyperbranched Polyethylenimines as Thermosensitive Drug Delivery Nanocarriers with Controlled Transition Temperatures

The low critical solution temperature phase transition (T_c) that is exhibited by thermosensitive polymers is strongly dependent on polymer concentration, pH, ionic strength, as well as the presence of specific molecules or ions in solution. Therefore, polymers with T_c values above 37 °C that are useful for hyperthermia therapy are not readily available. In the present study, temperature-sensitive hyperbranched polyethylenimine derivatives were developed through stepwise functionalization with isobutylamide groups. Although factors such as the concentration of polymer, sodium chloride, phosphate ions, and pH considerably affect the transition temperature, it was possible to obtain a hyperbranched derivative having the required T_c (38-39 °C) for the given aqueous medium required in cell experiments through careful selection of the degree of substitution. This thermosensitive derivative can encapsulate doxorubicin (DOX), a well-known anticancer agent, and was further studied as a temperature-triggered drug delivery system. Although the polymeric carrier showed no notable toxicity at temperatures either below or above the transition temperature, the thermoresponsive drug-loaded formulation exhibited increased DOX cellular uptake and improved in vitro cytotoxicity at 40 °C.

The diverse roles of glutathione-associated cell resistance against hypericin photodynamic therapy

The diverse responses of different cancers to treatments such as photodynamic therapy of cancer (PDT) have fueled a growing need for reliable predictive markers for treatment outcome. In the present work we have studied the differential response of two phenotypically and genotypically different breast adenocarcinoma cell lines, MCF7 and MDA-MB-231, to hypericin PDT (HYP-PDT). MDA-MB-231 cells were 70% more sensitive to HYP PDT than MCF7 cells at LD50. MCF7 were found to express a substantially higher level of glutathione peroxidase (GPX4) than MDA-MB-231, while MDA-MB-231 differentially expressed glutathione-S-transferase (GSTP1), mainly used for xenobiotic detoxification. Eighty % reduction of intracellular glutathione (GSH) by buthionine sulfoximine (BSO), largely enhanced the sensitivity of the GSTP1 expressing MDA-MB-231 cells to HYP-PDT, but not in MCF7 cells. Further inhibition of the GSH reduction however by carmustine (BCNU) resulted in an enhanced sensitivity of MCF7 to HYP-PDT. HYP loading studies suggested that HYP can be a substrate of GSTP for GSH conjugation as BSO enhanced the cellular HYP accumulation by 20% in MDA-MB-231 cells, but not in MCF7 cells. Studies in solutions showed that L-cysteine can bind the GSTP substrate CDNB in the absence of GSTP. This means that the GSTP-lacking MCF7 may use L-cysteine for xenobiotic detoxification, especially during GSH synthesis inhibition, which leads to L-cysteine build-up. This was confirmed by the lowered accumulation of HYP in both cell lines in the presence of BSO and the L-cysteine source NAC. NAC reduced the sensitivity of MCF7, but not MDA-MB-231, cells to HYP PDT which is in accordance with the antioxidant effects of L-cysteine and its potential as a GSTP substrate. As a conclusion we have herein shown that the different GSH based cell defense mechanisms can be utilized as predictive markers for the outcome of PDT and as a guide for selecting optimal combination strategies.

Photochemical internalization of tamoxifens transported by a "Trojan-horse" nanoconjugate into breast-cancer cell lines

Photochemical internalization (PCI) has shown great promise as a therapeutic alternative for targeted drug delivery by light-harnessed activation. However, it has only been applicable to therapeutic macromolecules or medium-sized molecules. Herein we describe the use of an amphiphilic, water-soluble porphyrin-β-cyclodextrin conjugate (mTHPP-βCD) as a "Trojan horse" to facilitate the endocytosis of CD-guest tamoxifens into breast-cancer cells. Upon irradiation, the porphyrin core of mTHPP-βCD expedited endosomal membrane rupture and tamoxifen release into the cytosol, as documented by confocal microscopy. The sustained complexation of mTHPP-βCD with tamoxifen was corroborated by 2D NMR spectroscopy and FRET studies. Following the application of PCI protocols with 4-hydroxytamoxifen (4-OHT), estrogen-receptor β-positive (Erβ+, but not ERβ-) cell groups exhibited extensive cytotoxicity and/or growth suspension even at 72 h after irradiation.

A versatile δ-aminolevulinic acid (ΑLA)-cyclodextrin bimodal conjugate-prodrug for PDT applications with the help of intracellular chemistry

Grafting of δ-aminolevulinic acid (1) moieties on the narrow periphery of a β-cyclodextrin (β-CD) derivative through hydrolysable bonds was implemented, in order to generate a water-soluble, molecular/drug carrier with the capacity to undergo intracellular transformation into protoporphyrin IX (PpIX), an endogenous powerful photosensitizer for photodynamic therapy (PDT). The water-soluble derivative 2 was prepared by esterifying δ-azidolevulinic acid with heptakis(6-hydroxyethylamino-6-deoxy)-β-cyclodextrin, with an average degree of substitution, DS = 3. Delivery of water-soluble, colorless 2 to cells resulted in intense red fluorescence registered by confocal microscopy, evidently due to the engagement of the intracellular machinery towards formation of PpIX. Conjugate 2 was further complexed with a fluorescein-labeled model guest molecule which was successfully transported into the cells, thereby demonstrating the bimodal action of the derivative. The present work shows the versatility of CDs in smart applications and constitutes advancement to our previously shown PpIX-β-CD conjugation both in terms of water solubility and lack of aggregation.

Molecular basis for increased risk for late-onset Alzheimer disease due to the naturally occurring L28P mutation in apolipoprotein E4

The apolipoprotein (apo) E4 isoform has consistently emerged as a susceptibility factor for late-onset Alzheimer disease (AD), although the exact mechanism is not clear. A rare apoE4 mutant, apoE4[L28P] Pittsburgh, burdens carriers with an added risk for late-onset AD and may be a useful tool for gaining insights into the role of apoE4 in disease pathogenesis. Toward this end, we evaluated the effect of the L28P mutation on the structural and functional properties of apoE4. ApoE4[L28P] was found to have significantly perturbed thermodynamic properties, to have reduced helical content, and to expose a larger portion of the hydrophobic surface to the solvent. Furthermore, this mutant is thermodynamically destabilized and more prone to proteolysis. When interacting with lipids, apoE4[L28P] formed populations of lipoprotein particles with structural defects. The structural perturbations brought about by the mutation were accompanied by aberrant functions associated with the pathogenesis of AD. Specifically, apoE4[L28P] promoted the cellular uptake of extracellular amyloid β peptide 42 (Aβ42) by human neuroblastoma SK-N-SH cells as well as by primary mouse neuronal cells and led to increased formation of intracellular reactive oxygen species that persisted for at least 24 h. Furthermore, lipoprotein particles containing apoE4[L28P] induced intracellular reactive oxygen species formation and reduced SK-N-SH cell viability. Overall, our findings suggest that the L28P mutation leads to significant structural and conformational perturbations in apoE4 and can induce functional defects associated with neuronal Aβ42 accumulation and oxidative stress. We propose that these structural and functional changes underlie the observed added risk for AD development in carriers of apoE4[L28P].

A novel mitotropic oligolysine nanocarrier: Targeted delivery of covalently bound D-Luciferin to cell mitochondria

New and emerging therapeutic approaches focus on the targeted delivery of therapeutic agents to cell mitochondria with high specificity. Herein we present a novel mitotropic nanocarrier based on an oligolysine scaffold by addition of two triphenylphosphonium cations per oligomer. Although the parent oligolysine failed to enter healthy cells, the triphenylphosphonium modified carrier, with or without D-Luciferin, attached as cargo molecule, demonstrated striking mitochondrial specificity. Furthermore, the oligolysine bound d-Luciferin exhibited chemiluminescence, of lower intensity than free d-Luciferin, yet of remarkably longer steady-state temporal profile.

Hypericin hydroquinone: potential as a red-far red photosensitizer?

Hypericin hydroquinone is the product of two-electron reduction of hypericin (quinone), a potent phenanthroperylenequinone photosensitizer. In contrast to the quinone, the hydroquinone exhibits strong absorbance in the far-red spectral region. Herein we provide initial evidence on the potential of hypericin hydroquinone as a far-red photosensitizer.

Guanidinylated dendritic molecular transporters: prospective drug delivery systems and application in cell transfection

In the present review the crucial role of the guanidinium functional group in facilitating the transport of dendritic polymers through liposomal and cell membranes is discussed, along with other structural features of guanidinylated dendritic polymers that fine-tune their transport properties, and even determine their subcellular destinations. In this context, an ideal dendritic molecular transporter would need to possess a dendritic scaffold of the appropriate size and degree of guanidinylation, flexibility of the guanidinium moiety, and should exhibit a proper balance between hydrophilic and hydrophobic moieties located on the dendritic surface. All of the above are illustrated through selected paradigms from the relevant literature, which give a valuable insight into forging successful dendritic delivery systems for both drugs and genes. The main challenge for the future focus of the field is identified as the determination of the key structural and functional characteristics that will enhance cell internalisation, and secure localisation in specific subcellular organelles.

Interactive transport, subcellular relocation and enhanced phototoxicity of hypericin encapsulated in guanidinylated liposomes via molecular recognition

Hypericin (HYP), a photocytotoxic phenanthroperylenquinone was encapsulated in liposomes outfitted with guanidinium-bearing lipids to ensure efficient cell binding through molecular recognition with anionic groups resident on the plasma membrane. The uptake of HYP encapsulated in these liposomes by DU145 human prostate cancer cells, was studied employing fluorescence, versus nonguadinylated liposomes and free HYP. The subcellular localization was in all cases studied by confocal microscopy employing specific subcellular organelle probes. The photocytotoxicity of HYP was assessed, 24 h following irradiation with 15 mWcm(-2) light through a GG 495 Schott filter, by a standard tetrazolium to formazan assay (XTT). HYP uptake by DU145 cells was found to be profoundly enhanced by using guanidinylated liposomes. Also the distance of the guanidinium group from the liposomal surface was found to significantly affect HYP loading, subcellular localization and phototoxicity. The two different modes of liposome cell internalization observed, i.e. plasma membrane fusion and endocytosis, were found to greatly affect the phototoxicity of HYP. Molecular recognition was overall appraised as a promising, novel route for photodynamic therapy, profoundly enhancing its efficacy. HYP encapsulated in liposomes-bearing guanidinium groups was more efficiently taken up by cells, leading to enhanced phototoxicity, in contrast to HYP encapsulated in their nonguanidinylated counterparts.

Novel amiodarone-doxorubicin cocktail liposomes enhance doxorubicin retention and cytotoxicity in DU145 human prostate carcinoma cells

We have developed novel cocktail liposomes bearing doxorubicin in their hydrophilic cores, and amiodarone, a potent multidrug resistance inhibitor, in their lipid bilayers. The efficacy of these liposomes was studied in DU145 human prostate carcinoma cells. Intracellular calcein retention, which is inversely proportional to multidrug resistance activity, significantly increased following cell incubation with amiodarone loaded liposomes. Fluorescence confocal microscopy on cells incubated with the cocktail liposomes revealed enhanced intranuclear doxorubicin accumulation. Two liposomal drug concentration combinations were employed to assess the differential cytotoxicity of the cocktail liposomes, doxorubicin (1.4 microM)-amiodarone (15 microM) and doxorubicin 3 (microM)-amiodarone (45 microM), and two incubation times, 5 and 19 h. Cell toxicity was determined by XTT assays at 24, 48, and 72 h following incubation and was significantly enhanced for incubation with the cocktail liposomes. On the whole, we believe that these liposomes will greatly contribute to the cancer chemotherapy arena.

Interactive transport of guanidinylated poly(propylene imine)-based dendrimers through liposomal and cellular membranes

The ability of guanidinylated poly(propylene imine) dendrimers to translocate across lipid bilayers was assessed by employing either a model phosphate-bearing liposomal membrane system or A549 human lung carcinoma cells. Two dendrimer generations, differing in the number of surface guanidinium groups, were employed, while surface acetylation or the use of spacers affected the binding of the guanidinium group to the phosphate moiety and finally the transport efficiency. Following adhesion of dendrimers with liposomes, fusion or transport occurred. Transport through the liposomal bilayer was observed at low guanidinium/phosphate molar ratios, and was enhanced when the bilayer was in the liquid-crystalline phase. For effective transport through the liposomal membrane, an optimum balance between the binding strength and the degree of hydrophobicity of the guanidinylated dendrimer is required. In experiments performed in vitro with cells, efficient penetration and internalization in subcellular organelles and cytosol was observed.

Second harmonic generation confocal microscopy of collagen type I from rat tendon cryosections

We performed second harmonic generation (SHG) imaging of collagen in rat-tendon cryosections, using femtosecond laser scanning confocal microscopy, both in backscattering and transmission geometries. SHG transmission images of collagen fibers were spatially resolved due to a coherent, directional SHG component. This effect was enhanced with the use of an index-matching fluid (n(i) = 1.52). The average SHG intensity oscillated with wavelength in the backscattered geometry (isotropic SHG component), whereas the spectral profile was consistent with quasi-phase-matching conditions in transmission geometry (forward propagating, coherent SHG component) around 440 nm (lambda(p) = 880 nm). Collagen type I from bovine Achilles tendon was imaged for SHG in the backscattered geometry and its first-order effective nonlinear coefficient was determined (|d(eff)| approximately 0.085(+/-0.025)x10(-12)mV(-1)) by comparison to samples of inorganic materials with known effective nonlinear coefficients (LiNbO3 and LiIO3). The SHG spectral response of collagen type I from bovine Achilles tendon matched that of the rat-tendon cryosections in backscattered geometry. Collagen types I, II, and VI powders (nonfibrous) did not show any detectable SHG, indicating a lack of noncentrosymmetric crystalline structure at the molecular level. The various stages of collagen thermal denaturation were investigated in rat-tendon cryosections using SHG and bright-field imaging. Thermal denaturation resulted in the gradual destruction of the SHG signal.

Mitochondria are a primary target of hypericin phototoxicity: Synergy of intracellular calcium mobilisation in cell killing

Hypericin, a naturally occurring anthraquinone synthesised by hypericum, upon light activation exhibits photodynamic cytotoxicity attributed mainly to the production of reactive oxygen species. This study aimed to elucidate the primary subcellular targets and mechanistic aspects of hypericin photosensitization in human prostate carcinoma cells. Depletion of intracellular glutathione (>85%) via inhibition of gamma-glutamyl-cysteine synthase had no effect on hypericin (5 microM) phototoxicity, thus precluding any direct oxidative involvement of H2O2. There was no change in intracellular SOD activity immediately after hypericin irradiation (1.5-5 J cm(-2)). Evaluation of the lysosomal enzyme hexosaminidase activity showed: (a) 60% cell loss 22 h following irradiation (1.5 J cm(-2)) and (b) a steady rate of lysosomal leakage to the cytosol (25%), at the same time and irradiation. However, lysosomal damage appears to be a slower process compared to the rapid loss of mitochondrial function, as reflected from parallel tetrazolium to formazan assays. The activity of cytosolic and mitochondrial aconitase, an enzyme exquisitely sensitive to oxidation, revealed a dose correlated loss of activity in the mitochondria immediately following hypericin photoactivation. The use of ionomycin, which modulates both internal Ca2+ stores and external Ca2+ transport during hypericin photosensitization, profoundly enhanced photocytotoxicity. Our data supports a direct mitochondrial hypericin phototoxicity that does not involve glutathione/H2O2 homeostasis. Further a potential synergistic treatment combining mitochondrial targeting of photosensitisers and Ca2+ mobilisation was identified.