Papaya-clay combo could cut cost
of water purification in developing
An inexpensive new material made of clay and papaya seeds
removes harmful metals from water and could lower the cost of
providing clean water to millions of people in developing countries, scientists are reporting. Their study on this “hybrid clay”
appears in the journal ACS Sustainable Chemistry & Engineering.
Emmanuel Unuabonah and colleagues explain that almost 1 billion people in developing countries lack access to reliable supplies of clean water for drinking, cooking, and
other key uses. One health problem resulting from that shortage involves exposure to
heavy metals such as lead, cadmium, and mercury, released from industrial sources into
the water. Technology exists for removing those metals from drinking water, but often is
too costly in developing countries. So these researchers looked for a more affordable and
sustainable water treatment adsorbent.
They turned to two materials readily available in some developing countries. One
was kaolinite clay, used to make ceramics, paint, paper, and other products. The other:
seeds of the Carica papaya fruit. Both had been used separately in water purification in
the past, but until now, they had not been combined in what the scientists term “hybrid
clay.” Their documentation of the clay’s effectiveness established that the material “has a
strong potential for replacing commercial activated carbon in treatment of wastewater in
the developing world.”
The authors acknowledge funding from the Max Planck Institute of Colloids and Inter-
faces, the University of Potsdam, and the Alexander von Humboldt Foundation.
Read more about the research: “Hybrid Clay: A New Highly Efficient Adsorbent for
Water Treatment,” ACS Sustainable Chem. Eng., May 9, 2013 (Web).
First dual-action compound kills cancer
cells, stops them from spreading
Researchers are reporting development and successful lab tests
of the first potential drug to pack a lethal one-two punch against
melanoma skin cancer cells. Hit number one destroys cells in the
main tumor, and the second hit blocks metastasis, according to
their report in the journal ACS Chemical Biology.
Photodynamic therapy (PDT), which involves administering a drug that kills cancer cells
when exposed to light, already is available. But PDT works only on the main tumor and has
other drawbacks. Nathan Luedtke and his team set out to find an improved approach to PDT.
They describe successful tests in laboratory mice of one compound they synthesized,
tetrakis-(diisopropyl-guanidino) zinc phthalocyanine (Zn-DIGP), which not only killed melanoma cells but also stopped them from metastasizing by blocking a key signal inside the
tumor cells. This compound “provides the first example of a PDT agent that facilitates the
photodynamic treatment of primary tumors while at the same time inhibiting the formation of metastatic tumors by a light-independent mode of action,” the authors state.
Read the research article: “Photodynamic Agents with Anti-metastatic Activities,”
ACS Chem. Biol., May 14, 2013 (Web).
on how fluoride
ights tooth decay
n an advance toward solving a
0-year-old mystery, scientists
re reporting new evidence
n how the fluoride in drink-ng water, toothpastes, mouth
nses, and other oral-care prod-cts prevents tooth decay. Their
eport appears in the ACS jour-al Langmuir.
Karin Jacobs and colleagues explain that
spite half a century of scientific research,
ntroversy still exists over exactly how fluoride
mpounds reduce the risk of tooth decay. That
search established long ago that fluoride
elps to harden the enamel coating that pro-cts teeth from the acid produced by decay-using bacteria. Newer studies already found
at fluoride penetrates into and hardens a
uch thinner layer of enamel than previously
elieved, lending credence to other theories
bout how fluoride works.
The report describes new evidence that
uoride also works by impacting the adhesion
rce of bacteria that stick to the teeth and pro-uce the acid that causes cavities. The experi-ents— performed on artificial teeth (
hydroxy-patite pellets) to enable high-precision analy-s techniques — revealed that fluoride reduces
e ability of decay-causing bacteria to stick, so
at it is easier to wash away the bacteria by
liva, brushing, and other activity.
Read more about the research: “Reduced
dhesion of Oral Bacteria on Hydroxyapatite by
uoride Treatment,” Langmuir, 2013, 29 ( 18),
p 5528–5533, April 4, 2013 (Web).