Photodynamic therapy (PDT) involves the action of photons on photosensitive molecules, where atomic oxygen or OH− molecular species are locally released on pathogenic human cells, which are mainly carcinogenic, thus causing cell necrosis. The efficacy of PDT depends on the local nanothermodynamic conditions near the cell/nanodrug system that control both the level of intracellular translocation of nanoparticles in the pathogenic cell and their agglomeration on the cell membrane. Dendrimers are considered one of the most effective and promising drug carriers because of their relatively low toxicity and negligible activation of complementary reactions. Polyamidoamine (PAMAM) dendrite delivery of PDT agents has been investigated in the last few years for tumour selectivity, retention, pharmacokinetics and water solubility. Nevertheless, their use as drug carriers of photosensitizing molecules in PDT for cardiovascular disease, targeting the selective necrosis of macrophage cells responsible for atheromatous plaque growth, has never been investigated. Furthermore, the level of aggregation, translocation and nanodrug delivery efficacy of PAMAM dendrimers or PAMAM/zinc phthalocyanine (ZnPc) conjugates on human atheromatous tissue and endothelial cells is still unknown.In this work, the aggregation of PAMAM zero generation dendrimers (G0) acting as drug delivery carriers, as well as conjugated G0 PAMAM dendrimers with a ZnPc photosensitizer, to symptomatic and asymptomatic human carotid tissues was investigated by using atomic force microscopy (AFM). For the evaluation of the texture characteristics of the AFM images, statistical surface morphological and fractal analytical methodologies and Minkowski functionals were used. All statistical quantities showed that the deposition of nanodrug carriers on healthy tissue has an inverse impact when comparing to the deposition on atheromatous tissue with different aggregation features between G0 and G0/ZnPc nanoparticles and with considerably larger G0/ZnPc aggregations on the atheromatous plaque. The results highlight the importance of using PAMAM dendrimer carriers as a novel and promising PDT platform for atherosclerosis therapies.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-015-0904-5) contains supplementary material, which is available to authorized users.

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Ultraviolet photons can damage microorganisms, which rarely survive prolonged irradiation. In addition to the need for intact DNA, cell viability is directly linked to the functionality of the cell wall and membrane. In this work, Cladosporium herbarum spore monolayers exhibit high viability (7%) when exposed to 157 nm laser irradiation (412 kJm−2) or vacuum-ultraviolet irradiation (110–180 nm) under standard pressure and temperature in a nitrogen atmosphere. Spore viability can be determined by atomic-force microscopy, nano-indentation, mass, μ-Raman and attenuated reflectance Fourier-transform far-infrared spectroscopies and DNA electrophoresis. Vacuum ultraviolet photons cause molecular damage to the cell wall, but radiation resistance in spores arises from the activation of a photon-triggered signaling reaction, expressed via the exudation of intracellular substances, which, in combination with the low penetration depth of vacuum-ultraviolet photons, shields DNA from radiation. Resistance to phototoxicity under standard conditions was assessed, as was resistance to additional environmental stresses, including exposure in a vacuum, under different rates of change of pressure during pumping time and low (10 K) temperatures. Vacuum conditions were far more destructive to spores than vacuum-ultraviolet irradiation, and UV-B photons were two orders of magnitude more damaging than vacuum-ultraviolet photons. The viability of irradiated spores was also enhanced at 10 K. This work, in addition to contributing to the photonic control of the viability of microorganisms exposed under extreme conditions, including decontamination of biological warfare agents, outlines the basis for identifying bio-signaling in vivo using physical methodologies.

The efficiency of penetration of nanodrugs through cell membranes imposes further complexity due to nanothermodynamic and entropic potentials at interfaces. Action of nanodrugs is effective after cell membrane penetration. Contrary to diffusion of water diluted common molecular drugs, nanosize imposes an increasing transport complexity at boundaries and interfaces (e.g., cell membrane). Indeed, tiny dimensional systems brought the concept of "nanothermodynamic potential," which is proportional to the number of nanoentities in a macroscopic system, from either the presence of surface and edge effects at the boundaries of nanoentities or the restriction of the translational and rotational degrees of freedom of molecules within them. The core element of nanothermodynamic theory is based on the assumption that the contribution of a nanosize ensemble to the free energy of a macroscopic system has its origin at the excess interaction energy between the nanostructured entities. As the size of a system is increasing, the contribution of the nanothermodynamic potential to the free energy of the system becomes negligible. Furthermore, concentration gradients at boundaries, morphological distribution of nanoentities, and restriction of the translational motion from trapping sites are the source of strong entropic potentials at the interfaces. It is evident therefore that nanothermodynamic and entropic potentials either prevent or allow enhanced concentration very close to interfaces and thus strongly modulate nanoparticle penetration within the intracellular region. In this work, it is shown that nano-sized polynuclear iron (III)-hydroxide in sucrose nanoparticles have a nonuniform concentration around the cell membrane of macrophages in vivo, compared to uniform concentration at hydrophobic prototype surfaces. The difference is attributed to the presence of entropic and nanothermodynamic potentials at interfaces.

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