Microencapsulation Of an Optimized 4-Component Tsetse-Repellent Blend into Β-Cyclodextrin and Laboratory Assessment of Its Efficacy
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Date
2019
Authors
Ratemo, Bernadatte Moraa
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
Microencapsulation and nano-encapsulation techniques have been applied in pharmaceutical
industry for more than half a century to facilitate controlled-release of drugs in the body. It is a
novel and vital technique that aims to deliver active ingredients over extended periods. In
addition, microencapsulation can prevent degradation and premature losses as a result of
exposure of the active ingredients to the environment. Thus, other fields have also embraced
nanotechnology, including cosmetic industry, biotechnology, fluid science, molecular physics
and mechanics, energy science and technology. Tsetse flies (Glossina spp.) are amongst the chief
stern vectors of parasites of trypanosome origin that threaten over 60 million individuals with
Human African Trypanosomiasis (sleeping sickness/ HAT) and 45-50 million livestock with
Animal African Trypanosomiasis (Nagana/ AAT) yearly in the sub-Saharan Africa. It is
projected that at least 50,000 persons and three million livestock perish from trypanosomiasis
ailment yearly in this region. Research on development of vaccine for the control of this parasite
has proved futile owing to antigenic variations of the trypanosome parasite. A superior ecofriendly
alternative to control both HAT and AAT is substantial reduction of vectors, such as in
the use of attractant blends to trap the flies and repellent blends to protect the hosts, and
integration of the two in ‘push-pull’ tactics. Previous studies have led to the characterization of
odour blends from tsetse-refractory bovids like waterbuck (Kobus defassa) that are repellent to
these vectors. An optimized 4-component tsetse-repellent (4-cTRB) blend (δ-nonalactone,
heptanoic acid, 4-methylguaiacol and geranylacetone) in the ratio of 6:4:2:1, showed high
efficiency in protecting cattle and other host animals from tsetse. In an effort to come up with an
effective controlled-release downstream deployment of the 4-component blend,
microencapsulation of the blend into β-cyclodextrin (β-CD) was undertaken using four different
techniques (kneading, co-precipitation, heating in a sealed container and freeze-drying). The
microcapsules, based on UV-Visible spectroscopy results, showed successful incorporation of
the repellent blend into the β-CD in all the four methods. This was also confirmed by Fourier
Transform-Infra Red spectroscopy. Gas chromatography with a flame ionization detection (GCFID),
showed that kneaded microcapsules had highest levels of the blend constituents; with
heptanoic acid having significantly higher release rate (1.2 x 10-5 mgml-1s-1) as compared to δ-
nonalactone (8.2 x 10-6 mgml-1s-1), 4-methylguaiacol (9.7 x 10-6 mgml-1s-1) and geranyl acetone
(5.7 x 10-6 and 4.4 x 10-6 mgml-1s-1). Behavioral responses of tsetse flies carried out in a wind
tunnel reported a range of 87.04-89.67 % repellency. This is approximately 5 % higher than the
earlier reported, 84.77 % repellency. The tsetse responses to the inclusion compounds of
different methods were not significantly different (p > 0.05) to those of the un-encapsulated
blend (89.02 %). β-Cyclodextrin matrix did not affect the aversive behavior of tsetse. Thus,
encapsulation of the 4-cTRB blend into β-cyclodextrin does not negatively affect its release and
its repellence to tsetse. The findings of this study provides a method for controlled release of
tsetse and other ectoparasite’s repellent blends which is useful in large-scale controls. Therefore,
microencapsulation should be embraced in control of ectoparasites and their related diseases in
livestock and humans.
Description
A Thesis Submitted In Partial Fulfillment of the Requirements for the Award of the Degree of Master of Science (Applied Analytical Chemistry) In the School of Pure and Applied Sciences of Kenyatta University, November, 2019