Stefan Marian Iordache

Nanobioarchitectures based on chlorophyll photopigment, artificial lipid bilayers and carbon nanotubes

Summary In the last decade, building biohybrid materials has gained considerable interest in the field of nanotechnology. This paper describes an original design for bionanoarchitectures with interesting properties and potential bioapplications. Multilamellar lipid vesicles (obtained by hydration of a dipalmitoyl phosphatidylcholine thin film) with and without cholesterol were labelled with a natural photopigment (chlorophyll a), which functioned as a sensor to detect modifications in the artificial lipid bilayers. These biomimetic membranes were used to build non-covalent structures with single-walled carbon nanotubes. Different biophysical methods were employed to characterize these biohybrids such as: UV–vis absorption and emission spectroscopy, zeta potential measurements, AFM and chemiluminescence techniques. The designed, carbon-based biohybrids exhibited good physical stability, good antioxidant and antimicrobial properties, and could be used as biocoating materials. As compared to the cholesterol-free samples, the cholesterol-containing hybrid structures demonstrated better stability (i.e., their zeta potential reached the value of −36.4 mV), more pronounced oxygen radical scavenging ability (affording an antioxidant activity of 73.25%) and enhanced biocidal ability, offering inhibition zones of 12.4, 11.3 and 10.2 mm in diameter, against Escherichia coli, Staphylococcus aureus and Enterococcus faecalis, respectively.

Effect of UV irradiation on biomimetic membranes labelled with bioporphyrins

ABSTRACT Two kinds of biomimetic membranes labelled with chlorophyll a and chlorophyllide a were obtained through hydration of a phosphatidylcholine thin film. These artificial membranes were subjected to UVC irradiation (253.7 nm) for different times and were characterized by spectral methods (Vis absorption and emission spectroscopy, Dynamic Light Scattering). The stability of the samples was checked by zeta potential measurements. A photo-bleaching effect occurred depending on the exposure time. The two types of membranes exhibited different photo-responses. Both bioporphyrins proved to be excellent sensors for detection of changes occurred in artificial lipid bilayers, at molecular level.

Ecobiophysical Aspects on Nanosilver Biogenerated from Citrus reticulata Peels, as Potential Biopesticide for Controlling Pathogens and Wetland Plants in Aquatic Media

In recent years, a considerable interest was paid to ecological strategies in management of plant diseases and plant growth. Metallic nanoparticles (MNPs) gained considerable interest as alternative to pesticides due to their interesting properties. Green synthesis of MNPs using plant extracts is very advantageous taking into account the fact that plants are easily available and eco-friendly and possess many phytocompounds that help in bioreduction of metal ions. In this research work, we phytosynthesized AgNPs from aqueous extract of Citrus reticulata peels, with high antioxidant, antibacterial, and antifungal potential. These “green” AgNPs were characterized by modern biophysical methods (absorption and FTIR spectroscopy, AFM, and zeta potential measurements). The nanobioimpact of Citrus-based AgNPs on four invasive wetland plants, Cattail (Typha latifolia), Flowering-rush (Butomus umbellatus), Duckweed (Lemna minor), and Water-pepper (Polygonum hydropiper), was studied by absorption spectroscopy, by monitoring the spectral signature of chlorophyll. The invasive plants exhibited different behavior under AgNP stress. Deep insights were obtained from experiments conducted on biomimetic membranes marked with chlorophyll a. Our results pointed out the potential use of Citrus-based AgNPs as alternative in controlling pathogens in aqueous media and in management of aquatic weeds growth.

Graphene layers used as cryogenic temperature sensor

A resistive structure designed with graphene, thin 2D monoatomic layers of graphite, was deposited by dropcast method from a solution, on a ceramic substrate, between Copper electrodes. The obtained structure is proposed as temperature sensor and was tested in the cryogenic field down to 77K. The obtained numerical results from this investigation are compared with previous experimental results of calibrated sensors. The resistance/temperature characteristic shows that on the studied interval it can be numerically interpolated with the use of a polynomial low. The stability against ageing, the reactivation and the perspective to design micro sensors for cryogenic applications is taken in account. The experimental results show the need for structure coating with a polymer protective layer.