Agriculture Reference
In-Depth Information
rigid and unbranched structure. After cellulose, chitosan is the second most abun-
dant natural polymer in nature and can be found mainly in crustaceans and to a
minor extent in fungi and bacteria. This polysaccharide has been used for many
biological applications because it is biocompatible (Agnihotri et al.
2004
). Chitosan
is recognized in agriculture for its antimicrobial properties, inhibiting fungal and
bacterial pathogens and also stimulating defense responses in plants (Harish
et al.
2007
). However, chitosan has attracted particular attention as a biodegradable
material for mucosal delivery systems, due to its adhesive properties, facilitating
the transport of drugs across cellular membranes.
Gelatin is also an interesting polymeric material for development of
nanoparticles for drug delivery. Gelatin is nontoxic, low cost, biocompatible, and
highly biodegradable. In addition, it is easy to cross-link and to modify chemically,
and its molecules contain both cationic and anionic groups, which guarantee
functionality to encapsulate both acid and basic substances (Li et al.
2011
;
Karthikeyan et al.
2013
). Therefore, gelatin encloses a great potential to be used
for the preparation of antimicrobial delivery systems for application in food and
agriculture.
6.3.4 Solid Lipid Nanoparticles
SLNs are another antimicrobial delivery system that has attracted attention as an
efficient and a nontoxic alternative lipophilic colloidal carrier prepared either with
physiological lipids or lipid molecules used as common pharmaceutical excipients
(Almeida and Souto
2007
). SLNs are essentially composed of lipids that are in solid
phase at room temperature and surfactants for emulsification. Solid lipids utilized in
SLN formulations include fatty acids (e.g., palmitic acid, decanoic acid, and
behenic acid), triglycerides (e.g., trilaurin, trimyristin, and tripalmitin), steroids
(e.g., cholesterol), partial glycerides (e.g., glyceryl monostearate and glyceryl
behenate), and waxes (e.g., cetyl palmitate). Several types of surfactants are
frequently used as emulsifiers to stabilize lipid dispersion, including soybean
lecithin, phosphatidylcholine, poloxamer 188, sodium cholate, and sodium
glycocholate (Zhang et al.
2010a
). Several methods are available for preparing
SLNs, including spray drying, high shear mixing, and ultra-sonication, but the high-
pressure homogenization (HPH) and microemulsion-based techniques are the most
important. Simple manufacturing techniques such as HPH make it possible to
produce SLNs in a large-scale and reproducible manner. Moreover, unlike most
polymeric nanoparticles, SLN production techniques do not need to employ poten-
tially toxic organic solvents, which may also have deleterious effect on some active
ingredients (Almeida and Souto
2007
; Weiss et al.
2008
).
Due to their occlusive properties, SLNs are a promising antimicrobial delivery
system for topical applications. SLNs contain occlusive excipients that upon appli-
cation can induce thin film formation that reduce water evaporation and extend
residence time on the skin. The administration of azole antifungal drugs such as
