Nanotech Viagra patch

Sildenafil citrate, commonly known as Viagra, is currently the first choice drug for erectile dysfunction but despite its success oral delivery of the drug is hampered by numerous side effects, the long delay before it starts working and the short amount of time it lasts. Researchers in Egypt think they may have a solution via nanotechnology.

Writing in the International Journal of Nanotechnology, the team describes tests on different formulations for sildenafil citrate transdermal nanocarriers as the delivery agent on human skin rather than the user having to swallow a pill. The benefits of such nanocarriers are that the drug gets into the bloodstream through the skin much more quickly than having to be ingested. Moreover, 70% of an oral dose of sildenafil citrate is wasted as it is metabolized by the liver without having any effect. Improved delivery via the transdermal route would avoid several side-effects as well as making onset of activity much quicker.

Pharmaceutical scientist Yosra S.R. Elnaggar of Alexandria University and professors there and at Alexandria and Pharos University, explain how previous attempts to create a Viagra transdermal application have been hampered by the properties of the drug itself. The drug has low oil and water solubility and is loathe to cross membranes, such as human skin, because of this. However, it is possible to encapsulate the drug in nanoemulsion based systems that can cross membranes readily. As such, the team has investigated two types of nanocarriers made using fat-like lipid molecules – the first made by forming an emulsion with the drug using a surfactant compound to allow the lipid molecules and drug to mix, much as soap will emulsify oil and water. The second option is a self-emulsifying nanocarrier that has its own inbuilt surfactant.

The team demonstrated in the laboratory that both formulations would have benefits for oral drug delivery, whereas only the nano-emulsion, rather than the self-emulsifying formulation, shows promise for a Viagra patch, in other words.

Elnaggar, Y., Massik, M., & Abdallah, O. (2011). Sildenafil citrate nanoemulsion vs. self-nanoemulsifying delivery systems: rational development and transdermal permeation International Journal of Nanotechnology, 8 (8/9) DOI: 10.1504/IJNT.2011.041443

Biofilters cut old landfill carbon footprint

Researchers in the US are testing biofilter systems as a viable alternative to releasing methane from passive landfill vents into the atmosphere. The technology could reduce the overall impact of old landfills on global warming. Details are reported in the current issue of the International Journal of Environmental Engineering.

Organic matter rotting in smaller, old landfill sites generates a slow trickle of the potent greenhouse gas, methane, into the atmosphere, amounting to just 2 or 3 kilograms per day per vent. In contrast to controlled methane generate for biofuel from modern, managed landfills, tapping this slow stream of the gas is not viable technologically or economically. However, methane has an infrared activity 21 times greater than carbon dioxide and so represents an important anthropogenic source of this greenhouse gas when attempting to balance the climate change books. Indeed, landfills contribute 12% of worldwide anthropogenic methane emissions due to the decomposition of organic waste.

Old landfills typically have passive gas vents. Methane is simply released into the atmosphere from these vents, or if the rate of emission is high enough it can be burned, or flared. According to Tarek Abichou and Jeffery Chanton of the Florida State University, Jose Morales of Environmental and Geotechnical Specialists, Inc., Tallahassee, Florida and Lei Yuan of Geosyntec Consultants in Columbia, Maryland, methane oxidation has recently been viewed as a more benign alternative to venting or flaring of landfill methane.

The researchers tested two biofilter designs capable of oxidizing methane gas to carbon dioxide and water. Both are packed with so-called methanotrophic bacteria, microbes that digest methane. They found that the radial biofilter design gave a much higher methane oxidation rate than a vertical biofilter. The higher surface area exposed to methane flow led to greater oxygen penetration into the biofilters, essential for microbial digestion. The radial biofilter has a surface area of well over 1.2 square meters whereas the vertical biofilter amounts to just 0.3 square meters area.

The team also found that the average percent oxidation rate of 20% and higher for the radial biofilter was possible when the air temperature was 20 to 36 Celsius, indicating the optimal soil temperature for methanotrophic bacteria to oxidize methane. Vertical biofilters averaged a little over 12% oxidation.

Abichou, T., Yuan, L., Chanton, J., & Morales, J. (2011). Mitigating methane emissions from passive landfill vents: a viable option for older closed landfills International Journal of Environmental Engineering, 3 (3/4) DOI: 10.1504/IJEE.2011.041354

Energy, all at sea

Floating wind turbines could capture the energy of higher wind speeds further out to sea and address some of the noise and unsightliness complained about by those with turbines closer to home.

Wind turbines represent one of the most reliable renewable energy solutions, along with solar power and tidal and hydroelectric power. As wind turbine designs increase their size they also get noisier and become more of an eyesore. The solution is either to site them remotely on dry land or to build them at sea with the tower embedded in the seabed of shallow waters, but this restricts them to near-shore waters with depths no greater than 50 metres, which means they cannot utilise the strong winds further out to sea.

Now, naval architect Dominique Roddier of Berkeley, California-based Marine Innovation & Technology has, together with his team, published a feasibility study of a novel platform design – WindFloat – that, as the name suggests uses floating wind turbines. The study is published in the Journal of Renewable and Sustainable Energy this month.

Floating wind turbines could use stronger offshore winds
Floating wind turbines could use stronger offshore winds (Credit: Roddier et al/JRSE/American Institute of Physics)

Roddier and colleagues, Christian Cermelli, Alexia Aubault, and Alla Weinstein, have tested a 1:65 scale model in a wave tank, which shows that a three-legged floating platform, based on existing gas and oil offshore platform designs. The team explains the main issue: “A floater supporting a large payload (wind turbine and nacelle) with large aerodynamic loads high above the water surface challenges basic naval architecture principles due to the raised centre of gravity and large overturning moment,” they say. In other words at first glance such a rig would capsize very easily. However, after several years work, their results show that the current design is stable enough to support a 5-megawatt wind turbine, the largest turbine that currently exists. These mammoth turbines are 70 metres tall and have rotors the size of a football field. Just one, Roddier says, produces enough energy “to support a small town.”

The next step is to continue construction of a prototype with electricity operator Energias de Portugal that will help the developers understand the life-cycle cost of such projects and to refine the economic model. The prototype will be tested in open water by the end of summer 2012, Roddier says. “The WindFloat [design] is envisioned to be located 15-20 km offshore so as to minimize risks/nuisance to the general public, and to mitigate the view impact from the coastline,” the team adds.

Links

J Renewable Sustainable Energy, 2010, 2, 3, 033104
Marine Innovation & Technology