Article
Alginate Nanohydrogels as a Biocompatible Platform for the
Controlled Release of a Hydrophilic Herbicide
Fiora Artusio
1
, Dario Casà
1
, Monica Granetto
2
, Tiziana Tosco
2
and Roberto Pisano
1,
*
Citation: Artusio, F.; Casà, D.;
Granetto, M.; Tosco, T.; Pisano, R.
Alginate Nanohydrogels as a
Biocompatible Platform for the
Controlled Release of a Hydrophilic
Herbicide. Processes 2021, 9, 1641.
https://doi.org/10.3390/pr9091641
Academic Editors: Arkadiusz Gola,
Izabela Nielsen and Patrik Grznár
Received: 31 July 2021
Accepted: 9 September 2021
Published: 11 September 2021
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4.0/).
1
Department of Applied Science and Technology (DISAT), Politecnico di Torino, 24 Corso Duca Degli Abruzzi,
10129 Torino, Italy; fiora.artusio@polito.it (F.A.); dario.casa@studenti.polito.it (D.C.)
2
Department of Environment, Land and Infrastructure Engineering (DIATI), Politecnico di Torino, 24 Corso
Duca Degli Abruzzi, 10129 Torino, Italy; monica.granetto@polito.it (M.G.); tiziana.tosco@polito.it (T.T.)
* Correspondence: roberto.pisano@polito.it
Abstract:
The large-scale application of volatile and highly water-soluble pesticides to guarantee
crop production can often have negative impacts on the environment. The main loss pathways are
vapor drift, direct volatilization, or leaching of the active substances. Consequently, the pesticide
can either accumulate and/or undergo physicochemical transformations in the soil. In this scenario,
we synthesized alginate nanoparticles using an inverse miniemulsion template in sunflower oil and
successfully used them to encapsulate a hydrophilic herbicide, i.e., dicamba. The formulation and
process conditions were adjusted to obtain a unimodal size distribution of nanohydrogels of about
20 nm. The loading of the nanoparticles with dicamba did not affect the nanohydrogel size nor
the particle stability. The release of dicamba from the nanohydrogels was also tested: the alginate
nanoparticles promoted the sustained and prolonged release of dicamba over ten days, demonstrating
the potential of our preparation method to be employed for field application. The encapsulation
of hydrophilic compounds inside our alginate nanoparticles could enable a more efficient use of
pesticides, minimizing losses and thus environmental spreading. The use of biocompatible materials
(alginate, sunflower oil) also guarantees the absence of toxic additives in the formulation.
Keywords: miniemulsion; cross-linking; nanoparticle; alginate; nanopesticide; release; hydrogel
1. Introduction
Pesticides are massively used worldwide in agriculture to control pests, including
insects, weeds, rodents, fungi, and any armful organism in crop production and livestock
management [
1
]. Their use is fundamental in enhancing crop yield production in a scenario
of increasing global population, which is expected to reach 9.8 billion by 2050 [
2
,
3
]. Several
studies show how crop management, without the use of pesticides, would averagely
result in 35% loss of potential yields in the pre-harvest phase [
4
], and another 35% during
transformation, transport, and other processing steps [
5
]. On the other hand, 10 to 75%
of applied pesticides does not actually reach the target organisms and is dispersed in
the environment [
6
,
7
]. As a consequence, significantly higher doses, compared to those
really needed to control target pests, must be currently applied for most agrochemicals,
with potential detrimental effects for environmental compartments. Depending on their
specific characteristics, pesticides spread into the environmental matrices, where they can
either undergo physical/chemical transformations (e.g., degradation, hydrolysis, oxidation,
etc.) [
8
] or accumulate [
9
]. Unintended losses and consequent environmental spreading are
particularly relevant for highly soluble and volatile pesticides, having a high potential of
diffusion and dispersion in surface and subsurface water and in the atmosphere. Among
these, dicamba is a prime example. Dicamba is a post-emergence selective herbicide that
is active against broadleaf weeds and currently applied in different crops such as maize,
wheat, and sorghum. It belongs to the family of benzoic acids and is characterized by
a low dissociation constant (pKa = 1.89), high solubility in water (6.5 g/L at pH
≈
2,
Processes 2021, 9, 1641. https://doi.org/10.3390/pr9091641 https://www.mdpi.com/journal/processes
