BackgroundNanotechnology is a science that involves imaging, measurement, modeling and a manipulation of matter at the nanometric scale. One application of this technology is drug delivery systems based on nanoparticles obtained from natural or synthetic sources. An example of these systems is synthetized from poly(3-hydroxybutyrate-co-3-hydroxyvalerate), which is a biodegradable, biocompatible and a low production cost polymer. The aim of this work was to investigate the uptake mechanism of PHBV nanoparticles in two different epithelial cell lines (HeLa and SKOV-3).ResultsAs a first step, we characterized size, shape and surface charge of nanoparticles using dynamic light scattering and transmission electron microscopy. Intracellular incorporation was evaluated through flow cytometry and fluorescence microscopy using intracellular markers. We concluded that cellular uptake mechanism is carried out in a time, concentration and energy dependent way. Our results showed that nanoparticle uptake displays a cell-specific pattern, since we have observed different colocalization in two different cell lines. In HeLa (Cervical cancer cells) this process may occur via classical endocytosis pathway and some internalization via caveolin-dependent was also observed, whereas in SKOV-3 (Ovarian cancer cells) these patterns were not observed. Rearrangement of actin filaments showed differential nanoparticle internalization patterns for HeLa and SKOV-3. Additionally, final fate of nanoparticles was also determined, showing that in both cell lines, nanoparticles ended up in lysosomes but at different times, where they are finally degraded, thereby releasing their contents.ConclusionsOur results, provide novel insight about PHBV nanoparticles internalization suggesting that for develop a proper drug delivery system is critical understand the uptake mechanism.Electronic supplementary materialThe online version of this article (doi:10.1186/s12951-016-0241-6) contains supplementary material, which is available to authorized users.

Research in fluorescence microscopy presents new challenges, especially with respect to the development of new metal-based fluorophores. In this work, the news fac-[Re(CO) 3 (bpy)L]PF 6 (C3) and fac-[Re(CO) 3 (dmb)L]PF 6 (C4) complexes, where L is an ancillary ligand E-2-((3-amino-pyridin-4-ylimino)-methyl)-4,6-diterbutylphenol, both exhibiting an intramolecular hydrogen bond, have been synthesized for its use as preliminary probes for fluorescence microscopy. The complexes were characterized using chemical techniques such as UV-Vis, 1 H-NMR, TOCSY, FT-IR, cyclic voltammetry, mass spectra (EI-MS 752.22 M + for C3 and 780.26 M + for C4) and DFT calculations including spin-orbit effects. The electron withdrawing nature of the ancillary ligand L in C3 and C4 explains their electrochemical behavior, which shows the oxidation of Re I at 1.84 V for C3 and at 1.88 V for C4. The UV-vis absorption and emission properties have been studied at room temperature in acetonitrile solution. The complexes show luminescent emission with a large Stokes shift (λ ex = 366 nm; λ em = 610 nm for C3 and λ ex = 361 nm; λ em = 560 nm for C4). The TDDFT calculations suggest that an experimental mixed absorption band at 360 nm could be assigned to MLCT (d(Re) →π*(dmb))and LLCT (π(L)→π*(dmb)) transitions. We also assessed the cytotoxicity of C3 and C4 in an epithelial cell line (T84). We found that 12.5 µg/ml of C3 or C4 is the minimum concentration needed to kill the 80% of cell population, as determined by neutral red uptake. Finally, the potential of C3 and C4 as biological dyes for use in fluorescent microscopy was assessed in bacteria (Salmonella enterica) and yeasts (Candida albicans and Cryptococcus spp.), and in an ovarian cancer cell line (SKOV-3). We found that, in all cases, both C3 and C4 are suitable compounds to be used as fluorescent dyes for biological purposes. In addition, we present evidence suggesting that these rhenium (I) tricarbonyl complexes may be also useful as differential fluorescent dyes in yeasts (Candida albicans and Cryptococcus spp.), without the need of antibodies.

Poly(amidoamine) dendrimers are the most recognized class of dendrimer. Amino-terminated (PAMAM-NH2) and hydroxyl-terminated (PAMAM-OH) dendrimers of generation 4 are widely used, since they are commercially available. Both have different properties, mainly based on their different overall charges at physiological pH. Currently, an important function of dendrimers as carriers of short single-stranded DNA has been applied. These molecules, known as antisense oligonucleotides (asODNs), are able to inhibit the expression of a target mRNA. Whereas PAMAM-NH2 dendrimers have shown to be able to transfect plasmid DNA, PAMAM-OH dendrimers have not shown the same successful results. However, little is known about their interaction with shorter and more flexible molecules such as asODNs. Due to several initiatives, the use of these neutral dendrimers as a scaffold to introduce other functional groups has been proposed. Because of its low cytotoxicity, it is relevant to understand the molecular phenomena involving these types of dendrimers. In this work, we studied the behavior of an antisense oligonucleotide in presence of both types of dendrimers using molecular dynamics simulations, in order to elucidate if they are able to form stable complexes. In this manner, we demonstrated at atomic level that PAMAM-NH2, unlike PAMAM-OH, could form a well-compacted complex with asODN, albeit PAMAM-OH can also establish stable interactions with the oligonucleotide. The biological activity of asODN in complex with PAMAM-NH2 dendrimer was also shown. Finally, we revealed that in contact with PAMAM-OH, asODN remains outside the cells as TIRF microscopy results showed, due to its poor interaction with this dendrimer and cell membranes.

Since its discovery, cAMP has been proposed as one of the most versatile second messengers. The remarkable feature of cAMP to tightly control highly diverse physiological processes, including metabolism, homeostasis, secretion, muscle contraction, cell proliferation and migration, immune response, and gene transcription, is reflected by millions of different articles worldwide. Compartmentalization of cAMP in space and time, maintained by mainly phosphodiesterases, contributes to the maintenance of equilibrium inside the cell where one signal can trigger many different events. Novel cAMP sensors seem to carry out certain unexpected signaling properties of cAMP and thereby to permit delicate adaptations of biologic responses. Measuring space and time events with biosensors will increase our current knowledge on the pathophysiology of diseases, such as chronic obstructive pulmonary disease, asthma, cognitive impairment, cancer, and renal and heart failure. Further insights into the cAMP dynamics will help to optimize the pharmacological treatment for these diseases.