Study shows how a mixture of chitin
and silver nanoparticles inhibits growth of mosquito larvae
Date: May 11, 2017
Source: Springer
A non-toxic mixture of
chitin-rich crab shell powder and nanosized silver particles could be an
environmentally friendly way of curbing the spread of disease-carrying mosquitoes,
and malaria in particular. This is according to a series of experiments led by
Jiang-Shiou Hwang of the National Taiwan Ocean University. The findings are
published in Springer's journal Hydrobiologia.
Mosquitoes carry diseases such as
malaria, dengue fever, yellow fever, the Zika virus and encephalitis. Despite
more than 100 years of research on the subject, malaria remains a global health
problem, especially in Sub-Saharan Africa and Asia. In 2013, the number of
malaria cases was estimated at 198 million, and the number of malaria-related
deaths at 548,000. According to the World Health Organization, one child dies
every minute from malaria in Africa. Products such as organophosphates, insect
growth regulators, microbial control agents and organic solutions are used in
efforts to control mosquito populations and the spread of the disease.
Hwang's team turned their
attention to chitosan or chitin, a non-toxic natural substance that has been
used in wound healing, as drug carriers and in manufacturing membrane water
filters and biodegradable food package coating. Chitin is found in animal
tissues, such as the exoskeletons of arthropods, bird beaks and insect eggs. It
can easily be chemically changed, is quite strong and, because of its abundance
in nature, is cost-effective to use.
The research team first crushed
and oven-dried the exoskeletons of a number of hydrothermal vent crabs
(Xenograpsus testudinatus) before extracting the chitin and other minerals. The
subsequent creamy-white filtrate was then mixed with silver nitrate (AgNO3) to
obtain a brown-yellow solution of silver nanoparticles (AgNP).
The solution was sprayed over six
water reservoirs at the National Institute of Communicable Disease Centre in
Coimbatore in India. Even in small concentrates it killed mosquito larvae and
pupa quite effectively. It had the greatest effect during the early stages of
the mosquito larvae's development.
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