Tag Archives: Stellenbosch University

Quantum dots as pollen labels: tracking pollinators

Caption: This bee was caught after it visited a flower of which the pollen grains were labelled with quantum dots. Under the microscope one can see where the pollen was placed, and actually determine which insects carry the most pollen from which flower. Credit: Corneile Minnaar

Fascinating, yes? Next, the news and, then, the video about the research,

A February 14, 2019 news item on ScienceDaily announces research from South Africa,

A pollination biologist from Stellenbosch University in South Africa is using quantum dots to track the fate of individual pollen grains. This is breaking new ground in a field of research that has been hampered by the lack of a universal method to track pollen for over a century.

A February 13, 2019 Stellenbosh University press release (also on EurekAlert but published February 14, 2019) by Wiida Fourie-Basson, which originated the news item, expands on the theme,

In an article published in the journal Methods in Ecology and Evolution this week, Dr Corneile Minnaar describes this novel method, which will enable pollination biologists to track the whole pollination process from the first visit by a pollinator to its endpoint – either successfully transferred to another flower’s stigma or lost along the way.

Despite over two hundred years of detailed research on pollination, Minnaar says, researchers do not know for sure where most of the microscopically tiny pollen grains actually land up once they leave flowers: “Plants produce massive amounts of pollen, but it looks like more than 90% of it never reaches stigmas. For the tiny fraction of pollen grains that make their way to stigmas, the journey is often unclear–which pollinators transferred the grains and from where?”

Starting in 2015, Minnaar decided to tread where many others have thus far failed, and took up the challenge through his PhD research in the Department of Botany and Zoology at Stellenbosch University (SU).

“Most plant species on earth are reliant on insects for pollination, including more than 30% of the food crops we eat. With insects facing rapid global decline, it is crucial that we understand which insects are important pollinators of different plants–this starts with tracking pollen,” he explains.

He came upon the idea for a pollen-tracking method after reading an article on the use of quantum dots to track cancer cells in rats (https://doi.org/10.1038/nbt994). Quantum dots are semiconductor nanocrystals that are so small, they behave like artificial atoms. When exposed to UV light, they emit extremely bright light in a range of possible colours. In the case of pollen grains, he figured out that quantum dots with “fat-loving” (lipophilic) ligands would theoretically stick to the fatty outer layer of pollen grains, called pollenkitt, and the glowing colours of the quantum dots can then be used to uniquely “label” pollen grains to see where they end up.

The next step was to find a cost-effective way to view the fluorescing pollen grains under a field dissection microscope. At that stage Minnaar was still using a toy pen from a family restaurant with a little UV LED light that he borrowed from one of his professors.
“I decided to design a fluorescence box that can fit under a dissection microscope. And, because I wanted people to use this method, I designed a box that can easily be 3D-printed at a cost of about R5,000, including the required electronic components.” (view video at https://youtu.be/YHs925F13t0

[or you can scroll down to the bottom of this post]

So far, the method and excitation box have proven itself as an easy and relatively inexpensive method to track individual pollen grains: “I’ve done studies where I caught the insects after they have visited the plant with quantum-dot labelled anthers, and you can see where the pollen is placed, and which insects actually carry more or less pollen.”
But the post-labelling part of the work still requires hours and hours of painstaking counting and checking: “I think I’ve probably counted more than a hundred thousand pollen grains these last three years,” he laughs.

As a postdoctoral fellow in the research group of Prof Bruce Anderson in the Department of Botany and Zoology at Stellenbosch University, Minnaar will continue to use the method to investigate the many unanswered questions in this field.

Here’s a link to and a citation for the paper,

Using quantum dots as pollen labels to track the fates of individual pollen grains by Corneile Minnaar and Bruce Anderson. Methods in Ecology and Evolution DOI: https://doi.org/10.1111/2041-210X.13155 First published: 25 January 2019

This paper is behind a paywall.

Here is the video,

Cleaning dirty water

Two news items about cleaning dirty water and the Canadian nanotech scene in two days! First, I got news of a Canada-China-India-Israel Roundtable on Sustainable Water Management via Nano- and Emerging Technologies held February 22-23, 2011 in Edmonton, Alberta. [Note: The information about the participant countries is directly from the ISTP website and there is no mention of the US as there is in the following article. This may be due to a late entrance to the event.] From the Feb. 22, 2011 article by Dave Cooper in the Vancouver Sun,

Canada joined hands with four other nations Tuesday in a partnership aimed at harnessing the potential of nanotechnology to improving the world’s water supply.

“Applying advanced technology to the problems of water is a serious issue. This is not a sideshow, it is a fundamental issue,” said Henri Rothschild, CEO of federally backed International Science and Technology Partnerships (ISTP) Canada.

The goal of the participants from Canada, the U.S. [?], China, India and Israel is to discuss “the real opportunities to address these challenges by pooling resources and expertise,” he said, in a spectrum from drinking and waste water to desalinization.

… with plenty of local water research underway to deal with the oilsands, funded by industry and governments, the region is now internationally recognized for its water expertise. “There are a lot of scientists and engineers here who know the subject. It’s leading edge and dealing with some very hard issues,” Rothschild said. “With this roundtable, we are trying to break new ground and create something that takes it to another level, and have it based here in Canada. This is one model under discussion,” he added.

There’s more information about the event on the ISTP roundtable wepage and, for those who are curious about the ISTP itself, here’s a description from their Who We Are page,

STPCanada was incorporated as a not-for-profit organization with the primary objective of strengthening Canada’s science and technology (S&T), business to business relations and ultimately overall economic, trade and political relations. ISTPCanada was selected by the Government of Canada, through the Department of Foreign Affairs and International Trade, to deliver the India, China and Brazil elements of its International Science and Technology Partnerships Program (ISTPP). Reflecting that bilateral S&T agreements are already in place with India and China, funding for these two countries was provided to ISTPCanada in April 2007, with additional funding for Brazil expected in 2008/2009 on completion of a similar bilateral agreement.

I do see the flag for the State of California on the page but it’s  not mentioned as a member of the ISTP. Perhaps they haven’t had time to update the site or they’re not sure how to add the information given that the other members are countries. Also, Brazil which is a member of the ISTP was not at the roundtable.

Getting back to the water, I had no idea the Edmonton region was internationally recognized for its expertise in water.  Meanwhile on the other side of the country, researchers from McGill University have developed a new and inexpensive way to filter water in case of emergencies. From the Feb. 23, 2011 news release,

Disasters such as floods, tsunamis, and earthquakes often result in the spread of diseases like gastroenteritis, giardiasis and even cholera because of an immediate shortage of clean drinking water. Now, chemistry researchers at McGill University have taken a key step towards making a cheap, portable, paper-based filter coated with silver nanoparticles to be used in these emergency settings.

“Silver has been used to clean water for a very long time. The Greeks and Romans kept their water in silver jugs,” says Prof. Derek Gray, from McGill’s Department of Chemistry. But though silver is used to get rid of bacteria in a variety of settings, from bandages to antibacterial socks, no one has used it systematically to clean water before. “It’s because it seems too simple,” affirms Gray.

Prof. Gray’s team, which included graduate student Theresa Dankovich, coated thick (0.5mm) hand-sized sheets of an absorbent porous paper with silver nanoparticles and then poured live bacteria through it. “Viewed in an electron microscope, the paper looks as though there are silver polka dots all over,” says Dankovich, “and the neat thing is that the silver nanoparticles stay on the paper even when the contaminated water goes through.” The results were definitive. Even when the paper contains a small quantity of silver (5.9 mg of silver per dry gram of paper), the filter is able to kill nearly all the bacteria and produce water that meets the standards set by the American Environmental Protection Agency (EPA).

The filter is not envisaged as a routine water purification system, but as a way of providing rapid small-scale assistance in emergency settings. “It works well in the lab,” says Gray, “now we need to improve it and test it in the field.”

This story reminds me of an Aug. 18, 2010  news article by Lin Edwards on physorg.com about ‘nano’ tea bags (excerpted from the article),

Scientists in South Africa have come up with a novel way of purifying water on a small scale using a sachet rather like a tea bag, but instead of imparting flavor to the water, the bag absorbs toxins, filters out and kills bacteria, and cleans the water.

The bag, which fits into the neck of an ordinary water bottle, was developed by scientists at Stellenbosch University in South Africa to help communities with no water purification facilities to clean their water. The bags are made of inexpensive tea bag material but instead of containing tea they contain nano-scale antimicrobial fibers that filter out contaminants and microbes, and granules of activated carbon that kill the bacteria. The nano-fibers are about one hundredth the width of a human hair.

According to researcher Marelize Botes, one sachet can clean a liter of the dirtiest water to about the same water quality of bottled water. Once the bag has been used it is discarded and a new bag is fitted in the neck of the bottle. The discarded bags have no environmental impact as they disintegrate in only a few days and the materials are not toxic to humans.

It’s hard to tell how closely related the research and initiatives are despite the fact that they’re all talking about ‘dirty water’. What I mean is that the water being discussed in the Dave Cooper article is industrial water recycled from sewage and waste, while the McGill researchers and the South African researchers are focused on drinking water that has been contaminated.