BackgroundPhotodynamic therapy (PDT) combines light, molecular oxygen and a photosensitizer to induce oxidative stress in target cells. Certain hydrophobic photosensitizers, such as aluminium-phthalocyanine chloride (AlPc), have significant potential for antitumor PDT applications. However, hydrophobic molecules often require drug-delivery systems, such as nanostructures, to improve their pharmacokinetic properties and to prevent aggregation, which has a quenching effect on the photoemission properties in aqueous media. As a result, this work aims to develop and test the efficacy of an AlPc in the form of a nanoemulsion to enable its use in anticancer PDT.ResultsThe nanoemulsion was developed using castor oil and Cremophor ELP®, and a monodisperse population of nanodroplets with a hydrodynamic diameter of approximately 25 nm was obtained. While free AlPc failed to show significant activity against human breast adenocarcinoma MCF-7 cells in an in vitro PDT assay, the AlPc in the nanoemulsion showed intense photodynamic activity. Photoactivated AlPc exhibited a 50 % cytotoxicity concentration (CC50) of 6.0 nM when applied to MCF-7 cell monolayers and exerted a powerful cytotoxic effect on MCF-7 cell spheroids.ConclusionThrough the use of spontaneous emulsification, a stable AlPc nanoemulsion was developed that exhibits strong in vitro photodynamic activity on cancer cells.Electronic supplementary materialThe online version of this article (doi:10.1186/s12951-015-0095-3) contains supplementary material, which is available to authorized users.

In this study Surface Enhanced Raman Spectroscopy (SERS) data recorded from mouse mammary glands cancer cells (4T1 cell line) was used to assess information regarding differences between control, death and viable cells after Photodynamic Therapy (PDT) treatment. The treatment used nanoemulsions (NE/PS) loaded with different chloroaluminumphthalocyanine (ClAlP) photosensitizer (PS) contents (5 and 10 µmol × L−1) and illumination (660 nm wavelength) at 10 J × cm−2 (10 minutes). The SERS data revealed significant molecular alterations in proteins and lipids due to the PDT treatment. Principal Component Analysis (PCA) was applied to analyze the data recorded. Three-dimensional and well reproductive PCA scatter plots were obtained, revealing that two clusters of dead cells were well separated from one another and from control cluster. Overlap between two clusters of viable cells was observed, though well separated from control cluster. Moreover, the data analysis also pointed out necrosis as the main cell death mechanism induced by the PDT, in agreement with the literature. Finally, Raman modes peaking at 608 cm−1 (proteins) and 1231 cm−1 (lipids) can be selected for follow up of survival rate of neoplastic cells after PDT. We envisage that this finding is key to contribute to a quick development of quantitative infrared thermography imaging.

Three-dimensional electronic properties of multiple vertically stacked In As ∕ Ga As self-assembled quantum dots

We investigated the optical properties of self-assembled InP/GaAs quantum dots using continuous-wave and time-resolved photoluminescence spectroscopy. The thermal activation energy, which is directly related to the exciton binding energy in this system, was obtained by photoluminescence measurements as a function of temperature. We obtained thermal activation energies of 6-9 meV for undoped quantum dots and 13 meV for the modulation-doped sample. Those values are in good agreement with calculated results. The dots presented a recombination time of ~ 0.8-1.1 ns, which is surprisingly small for a type-II system.1 Introduction Quantum dots (QDs) have attracted much attention due to its technological application in opto-electronic devices, such as QD lasers [1]. The strong localization of the electronic wave function on those systems leads to an atomic-like electronic density of states [2] and to the possibility of novel and improved photonic and electronic devices, and also to the study of fundamental physics in low-dimensional systems.InP/GaAs QDs present a type-II band alignment (Fig. 1a) so that the excitonic state is composed of an electron confined inside the InP quantum dot and a hole localized around it, in the GaAs layers. The electron and the hole are, therefore, spatially separated, which reduces the Coulomb interaction and the electron-hole wave-function overlap as compared to type-I QDs. In the latter, the repulsive and attractive interactions on excitonic complexes consisting of more than two carriers are of the same order of magnitude, whereas in type-II systems, the attractive interaction becomes much smaller than the repulsive one, resulting in much larger energies for bi-excitons or charged excitons relative to the single exciton [3]. Type-II structures are, therefore, interesting systems to investigate many-body effects. Nonetheless, there are only few reports on InP/GaAs QDs and some fundamental points such as the exciton binding energy and its lifetime are still unknown. In this work, we present an experimental and theoretical investigation of excitons in type-II InP/GaAs QDs.

No abstract