Agriculture Reference
In-Depth Information
Phototoxicity in presence of light suggests that cell death was due to NO release
from the complex under light irradiation (Gomes et al. 2008 ). It is clear from the
literature that this material presents an interesting system for carrying and locally
delivering NO, under irradiation, with a great potential for its use in plants. Sunlight
can enhance the rates of NO release from the material and promote a cytotoxic
effect against plant parasites.
9.3.6 Dendrimers
Poly(etherhydroxylamine) (PEHAM) dendrimers were used in formulations for
increasing the efficacy of many active agents in agriculture, and this was responsive
to increase the solubility of active agents. As a consequence, several functions in
plants were improved by enhancing water fastness of the active agent to plants or
seeds or reducing enzymatic degradation of the active agent (Hayes et al. 2011 ).
Gene delivery in plants by dendrimers is another interesting platform. In this
context, Pasupathy et al. ( 2008 ) reported the delivery of GFP-encoding plasmid
DNA to turfgrass cells by using poly(amidoamine) dendrimers, which can directly
perform gene delivery in a noninvasive fashion. Plant cells were transfected and the
GFP genes were expressed, as observed by confocal fluorescence microscopy
(Pasupathy et al. 2008 ). Spherical cationic dendrimers such as polyamidoamine
(PAMAM) were designed to introduce plasmids and active molecules into plant
cells. There are many different methods that are provided to genetically modify
plants and to treat or to prevent plant diseases (Samuel et al. 2011 ).
Due to precise control over size and the ability to multifunctionalize their
structures to enable targeting and tracking, dendrimers have become ubiquitous
as drug delivery vehicles in the biomedical arena (Mintzer and Grinstaff 2011 ).
Defined generations of branching and corresponding exponential increase in end
group surface functionalities are inherent to their chain-growth synthesis. As such,
their multifunctionality has been utilized to produce NO-releasing macromolecular
scaffolds with large reservoirs of NO (Stasko and Schoenfisch 2006 ; Stasko
et al. 2008 ). Stasko et al. ( 2008 ) functionalized generation 4 polyamidoamine
(PAMAM) dendrimers with either N -acetyl- D , L -penicillamine or N -acetyl- L -cyste-
ine to yield thiol-terminated dendrimers. Nitrosating these derivatives yielded
S -nitrosothiol-modified dendrimers (G4-SNAP and G4-NACysNO). The loading
was efficient and NO release kinetics varied based on the trigger (i.e., copper ions
concentration, light).
In the same direction and focus, Benini et al. ( 2008 ) have hypothesized a similar
platform, which could be used for local and controlled delivery of NO by using
PAMAM dendrimers functionalized with nitrosyl ruthenium complexes. These
NO-releasing dendrimers might find useful applications in agriculture due to their
capability to load and later deliver high amounts of NO. This characteristic may be
relevant to treat microbial infections in plants, since high doses of NO are known to
present cytotoxic effects against fungi, viruses, and bacteria (Paradise et al. 2010 ).
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