Current Nanoscience - Volume 7, Issue 3, 2011

Today, liposomes are among the most applied technologies for the encapsulation and delivery of bioactive agents and many different compounds in biological, pharmaceutical, medical and nutritional research. In this review, classification of liposomal vesicles, methods of their preparation and encapsulation, as well as their applications in food, cosmetics and pharmaceutical industries are reviewed. In addition, the main analytical approaches used to study liposome characteristics such as size, transition temperature, surface charge, fluidity, lamellarity, stability and encapsulation efficiency are presented. In the final part of the article, mechanisms of liposome targeting are discussed.

Stimuli-responsive (pH, temperature and magnetic field) 4-vinylpyridine (4-VP)-based nanoparticles in copolymeric formulation with core-shell morphology were synthesized using N-isopropylacrylamide (NIPAM), 2-hydroxyethyl methacrylate (HEMA), acrylic acid (AAc), and methacrylic acid (MAc) as shell-forming monomers. Keeping the 4-VP ratio constant and varying the comonomer amounts produced particles with variant shell thickness. Multi-responsive p(4-VP)-based nanoparticles were further modified by reacting with different functional groups containing bromoalkanes by quaternization. These p(4-VP)-based particles were also utilized to include composite materials by encapsulating separately prepared magnetic ferrites. To demonstrate the potential usage of the synthesized particles and their modified forms as drug delivery devices, naproxene sodium salt as an antibacterial drug was used for in vitro release studies in PBS.

In this short review paper, surface energy and site dependent cohesive energy of several Ag clusters are investigated via broken bonds theory and density functional theory simulation. The theoretical and simulation results shows that surface energy of Ag clusters γs(N) are almost equal to the Ag bulk value γs(∞), which shows no size dependence. Considering specific sites, cohesive energy of surface atoms Ecsx(N) are related to their coordinated numbers Zsx(N). While cohesive energy of interior atoms Ecix(N) are influenced by the high pressure existing in clusters.

Nanoliter-droplet breakup in either symmetrically or asymmetrically confined T-shaped junctions is experimentally studied. The critical condition with which nanoliter droplets will break equally is theoretically analyzed based on the pressure-driven mechanism. The scaling analysis is experimentally confirmed, implying that the droplet breakup in a confined T-shaped junction is a pressure-driven process when the capillary number is less than ∼0.1. A semi-empirical correlation is obtained for predicting the equal breakup in symmetric T-shaped junctions. The critical condition is found to be dependent on the initial droplet length, channel depth and capillary number. Besides the equal breakup of nanoliter droplets, a new droplet breakup pattern, unequal breakup, is observed in the symmetric T-shaped junction. In asymmetric T-shaped junctions the nanoliter-droplet breakup is found to be very difficult.

We synthesize multifunctional nanofluids by incorporating fluorescent dyes into magnetite nanoparticles. The synthesis is carried out in two different routes, in which nanoparticles with two sizes are coated by two different kinds of stabilizers. The structures of coating layers of the as-synthesized nanoparticles are characterized by the analysis of Fourier transform infrared spectra. Magneticinteraction- induced aggregation still exits and is traced by the DLS. Thermal conductivities of the synthesized nanofluids are measured under day-light, in the dark and under the UV irradiation. The fluid thermal conductivity varies in a wave-like shape as a function of particle concentration due to the existence of aggregation. Furthermore, the measured thermal conductivity under UV light is higher than those with the other conditions. The collapse of aggregates under UV irradiation due to the unidirectional non-radiative energy transfer increases the number of single magnetite particles and is thus assumed to be responsible for the increase of fluid thermal conductivity.

The effects of evaporative drying and annealing processes on the wettability and morphology characteristics of vapordeposited self-assembled 1H,1H,2H,2H-perfluorooctyltrichlorosilane (CF3(CF2)5(CH2)2SiCl3) (FOTS) thin film on glass substrate were investigated. Removal and desorption of FOTS were found to occur during alcohol rinsing/drying and low temperature annealing at 80°C, as evidenced by the increase in the FOTS oxygen/carbon (O/C) elemental ratio based on X-ray photoelectron spectroscopy study. The surfaces of FOTS thin film were reconstructed and a mechanism was proposed that accounts for the effect of solvent penetration through defect sites of FOTS thin film. The resulting topography increased the water static contact angle by as much as 26° whereas the contact angle hysteresis remained unchanged. A concurrent increase in water dynamic contact angles of 14°was also observed. In addition to the topography effect, the increase in contact angles was also attributed to the changes of the proportions of hydrophobic and hydrophilic area fraction (static and dynamic) and pinning effect (dynamic).