BR102019008249A2 - PROCESS OF OBTAINING HYDROGEL COMPOSITION, HYDROGEL COMPOSITION AND USE OF HYDROGEL COMPOSITION - Google Patents

Abstract

process of obtaining the hydrogel composition, hydrogel composition and use of the hydrogel composition. the present invention relates to the hydrogel composition comprising cellulose derivatives and a mixture of encapsulated botanical compounds, the process of obtaining said hydrogel composition and its use in combating and controlling agricultural pests. said hydrogel composition proved to be stable and effective in combating and controlling two agricultural pests: whitefly and spotted mite.

Description

PROCESS OF OBTAINING HYDROGEL COMPOSITION, HYDROGEL COMPOSITION AND USE OF HYDROGEL COMPOSITION Field of invention

[001] The present invention relates to the hydrogel composition comprising cellulose derivatives and a mixture of encapsulated botanical compounds, to the process of obtaining said hydrogel composition and to its use in combating and controlling agricultural pests.

[002] The said hydrogel composition proved to be stable and effective in encapsulation and in combating and controlling two agricultural pests: whitefly and spotted mite.

Fundamentals of the invention

[003] Pests are the main factor that decreases the productivity of agriculture around the world, due to losses during harvest and storage. The damage caused by these organisms depends on a number of factors including the species grown, the technology employed and the management of the plague. Pests can cause damage directly to plants by feeding on them or indirectly when they act as vectors.

[004] Considering this scenario, the use of chemical control using pesticides and repellents is generally the main way to combat these pests and their overuse has contaminated the environment (water, air and soil), leading to an increase in production costs, in addition to losses in productive areas and human and animal poisoning.

[005] Chemical control using pesticides and repellents (eg organophosphates, carbamates and thiadiazines) is generally the main way to combat these pests. However, its use can lead to serious adverse effects including pest resistance, toxic effects on humans and animals, soil and water contamination, etc.

[006] Therefore, the use of strategies to reduce the environmental impact and the cost related to the control of these pests and that contribute to the development of sustainable agriculture is necessary.

[007] In this context, the use of botanical insecticides has shown to be a promising alternative to these synthetic compounds. Botanical insecticides are generally produced through the secondary metabolism of plants, being important in the defense against pathogens and pests. Examples of these botanical insecticides include geraniol (3,7-dimethyloca-trans-2,6-dien-1-ol), citronella (3,7-dimethyloct-6-en-1-al), both of which are made up of the essential oil of citronella, eugenol (4-allyl-2-methoxyphenol) present in cloves and cinnamon and cinnamaldehyde (2E) -3-phenylpro-2-enal, both consisting of the essential oil of cinnamon.

[008] However, despite its advantages over synthetic insecticides, the use of these natural compounds can be limited, due to high temperatures, high degradability and low stability, which makes their effective use difficult.

[009] Therefore, the encapsulation of botanical compounds has been an important strategy to improve the stability and effectiveness of these natural compounds. These systems can be produced using a variety of different matrices, for example, biodegradable polymers, lipids and proteins. Zeine is a protein recognized as safe and has promising characteristics such as biocompatibility, biodegradability, low toxicity and low production costs.

[010] Additionally, the use of polymeric systems has been employed as a strategy for the release of active compounds, as they allow a slow, gradual release directed to the desired location, in addition to being easy to apply and non-occlusive. These materials allow the delivery of compounds, trapped or encapsulated in the polymeric matrix, which offers advantages compared to conventional pharmaceutical forms, such as improved efficiency, reduced toxicity and modified release of the compounds.

[011] Thus, polymeric hydrogels are materials formed by three-dimensional networks of hydrophilic polymers capable of absorbing water at levels above 50% of the total weight and characterized by strong affinity with water due to the presence of hydrophilic groups. Such properties allow the application of these materials in several areas, being used as biodegradable vehicles in different sectors.

[012] Physical and chemical cross-linking of polymer chains is usually crucial to maintaining the structure of hydrogels. Hydrogels based on natural polymers such as cellulose and its derivatives have attracted attention and shown application with great potential in many fields, including medicine, pharmacy and biotechnology.

[013] Citric acid is widely used in the food and pharmaceutical industries as a crosslinking agent and is used to modulate structures and properties for potential new hydrogel applications.

[014] Thus, the present invention presents the preparation and characterization as well as demonstrating the repellent activity of hydrogel compositions based on cellulose derivatives containing the mixture of encapsulated botanical compounds. As will be demonstrated throughout this report, the prepared nanostructured systems have adequate physico-chemical properties, being successfully incorporated into hydrogel compositions, through a two-stage preparation process (modeling and cross-linking).

[015] For crosslinking the hydrogel compositions, a citric acid solution (8 mol / L) was used, which guaranteed high crosslinking and adequate rheological properties. The hydrogel compositions showed high repellent activity against whiteflies and spotted mites, two important pests in different agricultural systems in the world, highlighting the fact that these two pests can occur simultaneously in several agricultural crops, such as soybeans, cotton, tomatoes , beans, among others.

[016] Additionally, these hydrogel compositions make a great contribution to the development of sustainable agriculture, as they are not put in contact with plants directly, which decreases the amount of residues on food when compared to conventional pesticide sprays.

State of the art

[017] Some state-of-the-art documents describe the encapsulation of botanical compounds in order to improve the stability and efficiency of these natural compounds as well as a method of preparing cellulose-based hydrogel compositions.

[018] US patent application 20150004102 describes the preparation and characterization of zein-based nanoparticle formulations for the encapsulation of bioactive compounds, including botanical compounds.

[019] Patent application CA 2805581 describes a method for obtaining zein nanoparticles based on the use of surfactants as stabilizers, including the possibility of incorporating biologically active compounds soluble in water or fat soluble.

[020] US patent application 2006239956 describes a method for preparing hydrogel based on hydroxypropylmethylcellulose containing active ingredient, preferably aroma or fragrance molecules.

[021] Different from the state of the art, the present invention relates to hydrogel compositions which are based on the mixture of two biopolymers: carboxymethylcellulose (CMC) and hydroxyethylcellulose (HEC) crosslinked in the presence of a citric acid solution. It is also noteworthy that the hydrogel compositions were prepared with the incorporation of a mixture of botanical compounds, eugenol, geraniol and cinnamaldehyde, encapsulated in zein nanoparticles. Said hydrogel composition proved to be stable and effective in combating and controlling two agricultural pests: whitefly and spotted mite.

Brief description of the invention

[022] It is a first object of the present invention to provide stable and effective hydrogel compositions comprising cellulose derivatives and a mixture of encapsulated botanical compounds.

[023] It is a second object of the present invention to provide a process for obtaining said hydrogel compositions.

[024] It is a third object of the present invention to provide the use of said hydrogel compositions in the combat and control against two agricultural pests.

Brief description of the figures

[025] To obtain a total and complete visualization of the object of this invention, the figures referenced are presented as follows.

[026] Figure 1 refers to the experimental model used to carry out the tests with spotted mite (Tetranychus urticae).

[027] Figure 2 deals with the schematic representation of the process for preparing hydrogel compositions.

[028] Figure 3 refers to the degree of swelling for hydrogel compositions in the presence or absence of encapsulated botanical compounds, in which are presented: control hydrogel compositions; hydrogel compositions containing zein nanoparticles in the absence of botanical compound (NP); hydrogel compositions containing geraniol and eugenol encapsulated in zein nanoparticles (NP_GRL + EGL); hydrogel compositions containing geraniol and cinnamaldehyde encapsulated in zein nanoparticles (NP_GRL + CND).

[029] Figure 4 refers to the reogram of the hydrogel compositions containing the formulations of zein nanoparticles, in which are presented: elastic modulus (G '), viscous modulus (G' ') and viscosity (η) - (insert) determined from a frequency ramp (1-10 Hz) at two temperatures (25 and 40 ° C), being: A) control hydrogel composition (water); B) Hydrogel composition containing zein nanoparticles; C) Hydrogel composition containing geraniol + eugenol encapsulated in zein nanoparticles; D) Hydrogel composition containing geraniol + cinnamaldehyde encapsulated in zein nanoparticles.

[030] Figure 5 shows the effect index (IF) against whitefly of hydrogel compositions containing the mixture of encapsulated botanical compounds.

[031] Figure 6 demonstrates the cumulative release curves for botanical compounds (%) through hydrogel compositions, in which A) the hydrogel compositions containing the encapsulated geraniol and eugenol mixture and B) the hydrogel compositions containing the geraniol and cinnamaldehyde, encapsulated.

Detailed description of the invention

[032] According to the first object of the present invention, stable hydrogel compositions are provided comprising cellulose derivatives and a mixture of encapsulated botanical compounds.

[033] To obtain these compositions, the compounds geraniol (GRL), eugenol (EGL), trans-cinnamaldehyde (CND) (botanical compounds), zein, carboxymethylcellulose (CMC) and hydroxyethylcellulose (HEC) were initially obtained, all from the company Sigma-Aldrich.

[034] Subsequently, nanoparticle solutions were prepared and characterized as described in the next step.

Preparation and characterization of nanoparticle solutions

[035] The preparation of the zein nanoparticles containing the mixture of botanical compounds was carried out using the precipitation method with antisolvents. A zein solution (2% w / v) was prepared in hydroethanolic solution (85% v / v), remaining under stirring overnight. An aqueous solution of the polyoxyethylene-polyoxypropylene surfactant (Poloxamer) (2% w / v) was also prepared by adjusting the pH to 4. Before preparing the formulations, the zein solution underwent a purification process, which consisted of centrifugation ( 30 minutes at 4500 rpm), heat treatment (15 minutes at 75 ° C) and filtration (0.45 μm - Milipore). In preparing the particles, 600 mg of each asset was added to 10 mL of the zein solution. Mixtures of geraniol with eugenol and geraniol with cinnamaldehyde were made and with the aid of a syringe (10 mL without the use of a needle) the zein solution (10 mL) was injected into the poloxamer solution, under magnetic stirring. The colloidal dispersion was stirred (800 rpm) for the evaporation of ethanol (room temperature). In the control formulations, the addition of active compounds did not occur in the zein solution. Also, in relation to formulations with nanoparticles, the loss of active compound during the preparation process was also investigated.

[036] The prepared formulations were characterized by their hydrodynamic diameter, polydispersity index, zeta potential, particle concentration and encapsulation efficiency. The analysis of size distribution and polydispersity index was performed using the photon correlation spectroscopy (DLS) technique. The zeta potential was determined by the microelectrophoresis method. For both techniques, a ZetaSizer Nano ZS90 system (Malvern Instruments, UK) was used at a fixed angle of 90 ° and 25 ° C, and the samples were diluted about 100 to 500 times. The encapsulation efficiency was determined using the ultrafiltration / centrifugation method as described by Oliveira et al., In Zein Nanoparticles as EcoFriendly Carrier Systems for Botanical Repellents Aiming Sustainable Agriculture. Journal of Agricultural and Food Chemistry, v. 66, n. 6, p. 1330-1340, Feb 14 2018. The quantification of botanical compounds was performed using high performance liquid chromatography (HPLC). It is noteworthy that the total amounts of botanical compounds (100%) present in the formulations were calculated taking into account the total amount added, as well as the losses during the preparation process.

[037] The results for mean diameter (MD, nm), polydispersity index (PDI), zeta potential (ZP, mV), particle concentration (CT, particles / mL) and encapsulation efficiency (EE,%) are presented in Table 1.

Observação: diâmetro médio (DM) pela técnica de espalhamento de luz dinâmico (DLS) e rastreamento de nanopartículas (NTA), índice de polidispersão (IPD), potencial zeta (PZ), concentração (CT) e eficiência de encapsulação (EE). Os valores são expressos como média de três determinações.[038] Notes that nanoparticles containing botanical compounds were smaller in size than zein nanoparticles alone, as well as high zeta potential values, which provides these systems with good colloidal stability. It is also noteworthy that the values of encapsulation efficiency observed for all nanoparticles containing botanical compounds were high (> 95%).

Note: medium diameter (DM) by dynamic light scattering (DLS) and nanoparticle tracking (NTA), polydispersion index (IPD), zeta potential (PZ), concentration (CT) and encapsulation efficiency (EE). Values are expressed as an average of three determinations.

[039] According to the second object of the present invention, after the preparation and characterization of the nanoparticle formulations, the process of preparing the hydrogel compositions began.

Process of preparing hydrogel compositions

[040] The process of preparing the hydrogel compositions comprises two stages: the first is carried out by dispersing the polymers in an aqueous medium (according to the composition of the formulation) with 5% CMC and HEC in the proportion of 5: 1 (CMC: HEC, m: m), until complete hydration mixing in a nanoparticle solution or water (control). Compositions containing nanoparticles were then prepared with the mixture of geraniol and eugenol (NP_GRL + EGL), nanoparticles with the mixture of geraniol and cinnamaldehyde (NP_GRL + CND), nanoparticles without the presence of active compounds (NP_Z), and control compositions (CTL) . The solution was mixed using a mechanical stirrer at 500 rpm for 10 minutes. The obtained CMC / HEC hydrogel was then placed in a mold (2.5 x 3.5 cm), pressed to remove air bubbles and molded into the desired shape. At this stage, there is no crosslinking process. In the second stage, the molds were immersed in a citric acid solution (8 mol / L) for 6 hours for crosslinking the hydrogel. During this stage, the Na + of the sodium carboxylate (R-COONa) linked to the main chain of CMC are gradually replaced by H +, which diffuses out of the paste. The 3D network structure of the hydrogel is then constructed through physical cross-linking, together with the formation of hydrogen bonds between the polymer chains.

[041] The referred process of preparing said hydrogel compositions is outlined in Figure 2. In the first step (molding), the CMC / HEC paste is prepared (by mixing with deionized water or nanoparticle solutions) and placed in the molds. In the second stage (cross-linking), after the acidification process with citric acid (immersion), the CMC / HEC hydrogels are obtained. The scheme exemplifies the hydrogen bonds between the polymer chains.

[042] Following the step of preparing the hydrogel compositions, the characterization of these compositions was carried out in which the degree of swelling and the rheological properties were analyzed.

Characterization of hydrogel compositions Degree of swelling

[043] The degree of swelling was one of the parameters investigated for the characterization of hydrogel compositions. Initially, three replicates of each hydrogel were oven dried (30 ° C, for 24 hours), and frequent weighing was carried out in order to evaluate the complete drying and stabilization of the hydrogel mass. The dry hydrogels were immersed in deionized water (100 mL) for the swelling process (at room temperature). Depending on the time, the hydrogels were weighed and the excess water was removed with the aid of a paper towel. The degree of swelling (GI) of the hydrogels was calculated as a function of time, using equation 1.
GI = [mi-ms) / ms] x 100% (1)
where, mi is the mass of the swollen hydrogel and ms is the mass of the dry hydrogel.

[044] Figure 3 shows the results of degree of swelling for hydrogels prepared in the presence or not of the botanical compounds encapsulated in the nanoparticles. The control hydrogels showed a swelling degree of about 27 ± 0.4% with 180 minutes, respectively. It is observed that with the addition of the encapsulated compounds there was a slight increase in the degree of swelling, however, no significant differences were observed between the formulations. Low values for the degree of swelling contribute to an increase in the mechanical properties of hydrogels. In addition, a high concentration of acid leads to a high concentration of cross-links and a limited rate of expansion of the polymeric network. In the present invention a high concentration of citric acid was used in the crosslinking (8 mol / L).

Rheological properties

[045] Rheological properties were analyzed using a rotational rheometer (Kinexus Lab, Malvern Instruments Ltd) with cone and plate geometry (diameter 20 mm, angle 0.5 rad and space between plates 1 mm) and temperature control Peltier. To determine the elastic modulus (G ') and the viscous modulus (G "), about 500 mg of the hydrogel was transferred to the sample holder and a frequency range of 0.1-10 Hz was applied to assess stability of the material, the shear stress was 1 Pa. The rheological properties were studied at two temperatures 25 ° C and 40 ° C, with each experiment being repeated three times and analyzed using the rSpace software.

[046] Figure 4 presents the graphs of the rheological analysis for the different hydrogel compositions prepared containing the nanoparticle formulations with the botanical compounds.

Observação: Controle - Composição de hidrogel controle (Água); NP - Composição de hidrogel contendo nanopartículas de zeína; NP_GRL+EGL - Composição de hidrogel contendo geraniol+eugenol encapsulados em nanopartículas de zeína; NP_GRL+CND - Composição de hidrogel contendo geraniol+cinamaldeído encapsulados em nanopartículas de zeína.[047] Table 2 shows the rheological parameters for hydrogel compositions containing zein nanoparticle formulations, at a frequency of 1 Hz.

Observation: Control - Control hydrogel composition (Water); NP - Hydrogel composition containing zein nanoparticles; NP_GRL + EGL - Hydrogel composition containing geraniol + eugenol encapsulated in zein nanoparticles; NP_GRL + CND - Hydrogel composition containing geraniol + cinnamaldehyde encapsulated in zein nanoparticles.

[048] It can be seen in Figure 4 that for all hydrogel compositions, there was a decrease in viscosity (inset), as the frequency increased. Thus, the prepared compositions follow the rheology of a non-Newtonian fluid of the pseudoplastic type. It is known that the main characteristic of pseudoplastics is the decrease in apparent viscosity, with an increase in the shear rate. This is mainly due to the hydrodynamic forces, which become more intense and cause a progressive rupture and an elongation of the system. This results in a new alignment with the flow of the material and, therefore, a reduction in viscosity.

[049] Also, it can be seen in Figure 4 and Table 2 that the elastic modulus (G ') is greater than the viscous modulus (G ") for both temperatures. Such results indicate that the hydrogel is highly cross-linked.

[050] When the hydrogel compositions were incorporated with the nanoparticle formulations in the presence and absence of botanical compounds - (Figure 4 and Table 1) there was an increase in the viscoelastic parameters, especially the G '/ G "ratio, be suggestive of a substantial interaction between the hydrogel matrix and the nanoparticles. The incorporation of only the nanoparticles increased the rheological parameters compared to those containing the botanical repellents. The increase in the G '/ G "ratio indicates a greater interaction between the chains of polymers during the crosslinking process, which is due to the presence of zein, improving the structure and the possible long-term stability of the hydrogel. Thus, proteins have a strong tendency to adsorb on oil-water interfaces, so during the cross-linking process it allowed for better interaction between polymers. This data set shows that the prepared hydrogel compositions are promising for carrying encapsulated botanical compounds. In addition, the prepared compositions showed excellent properties for applications in the environment, since there is no shear from external sources, such as the mechanical pressure caused by excessive handling. It is noteworthy that the fact that they also resist shear at high temperatures is an important property, considering agricultural applications.

[051] According to the third object of the present invention, having the hydrogel compositions demonstrated stability, their repellent activity was evaluated as described below.

Evaluation of the repellent activity of hydrogel compositions Repellent activity against whitefly (Bemisia tabaci)

[052] The repellent activity tests against whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), were conducted in a four-way arena olfactometer in a room without light. The evaluated samples were the same as described in the item preparing the hydrogel compositions, and for each bioassay 1.0 cm2 was removed from each hydrogel. The treatments were arranged in glass connectors coupled to the olfactometer pathways, in which the flow rate of 1 L / min of air was regulated. The air flow was obtained by a vacuum pump connected to the central outlet of the olfactometer. In this way, the air entered through the four pathways of the olfactometer, converging at the central point of release of the insects B. tabaci. The treatments on the olfactometer were distributed with a 50% chance of choice (treatment vs. control). Therefore, two copies corresponded to the treatment and two copies corresponded to the control, positioned interchangeably.

[053] Each repetition corresponded to a fly and was introduced into the center of the olfactometer by means of a micropipette tip and, for 10 minutes, the residence time in each quadrant was observed. It was considered as "non-response" the time the insect stayed in the central area of the olfactometer, as it is the place where the convergence and mixture of the volatiles of the four pathways occurs. At each change of treatment, the glass connectors and hoses were changed. 10 repetitions were conducted for the repellency test.

[054] The results were calculated using the effect index (IF), equation 2, the results being expressed as a function of the control hydrogels (water only). It is noteworthy that the IF was calculated according to the repellent, attractive and also "non-response" effect.
IF = (Et-Ec) / Ec (2)
where, Et is the% of effect for the treatment and Ec is the% of effect for the control hydrogel. It is noteworthy that positive results indicate that the treatment showed an effect superior to the control, whereas negative results indicate that the control showed an effect superior to the treatment.

[055] Hydrogel compositions containing encapsulated botanical compounds show positive IF for repellency, with values between 1.1 and 1.5% (Figure 5). The compositions containing the mixture of geraniol and cinnamaldehyde showed slightly higher values. These compositions showed a significant repellent effect compared to the control compositions. It is also noteworthy that the repellent effect was also significantly and surprisingly superior to the effect of compositions containing only the zein nanoparticles. Such result may be due mainly to the presence and interaction between botanical compounds.

[056] In this way, the mixture of active compounds is a promising alternative in order to increase the spectrum of action of botanical compounds.

Repellent activity against striped mite (Tetranychus urticae)

[057] Mites Tetranychus urticae Koch (Acari: Tetranychidae) used in the experiment came from a breed kept in an air-conditioned room (temperature 25 ± 1 ° C, humidity 70 ± 10% and photoperiod of 12 hours) on Phaseolus vulgaris bean plants L.

onde, Nc é o número de ácaros encontrados na planta controle (sem gel) e Nt é o número de ácaros encontrados na planta contendo os géis. Ot é o número de ovos encontrados na planta contendo os géis e Oc é o número de ovos encontrados nas plantas sem a presença dos géis. As médias do índice de repelência e também de impedimento de oviposição foram atribuídas a classes distintas, sendo: Classe 0 (0,01% -0,1%), Classe I (0,1% -20%), Classe II (20,1% -40%), Classe III (40,1% -60%), Classe IV (60,1% -80%) e Classe V (80,1% a 100%). O número de ácaros, bem como de ovos, nas plantas tratadas e controle foram analisados por testes t para comparações pareadas. Os dados foram transformados em log antes da análise para atender aos pressupostos da estatística paramétrica.[058] Initially, seeds of P. vulgaris beans were planted in 500 mL plastic cups. At 30 days after germination, the plants were taken to the laboratory under the same climatic conditions mentioned for the creation of mites and placed in 6 L plastic containers. The gels were fixed to a 25.0 cm high wooden toothpick, attached with a fastener, and placed inside the glass containing the plants. The containers were assembled in pairs at a distance of 17.0 cm from each other, with the gel on one side and not on the other. The containers were connected through a hole containing a 1.0 cm diameter transparent plastic hose (Figure 1). In the center of the hose, an opening of 0.5 cm2 was made, and after 12 hours in this opening, 50 adult females of T. urticae were transferred with the aid of a brush with only one hair and a stereomicroscope. Then, the opening was sealed with "sheer" fabric. Twenty-four hours (24 h) after the mite transfer, the leaves of the plants in each plastic container were cut and the number of mites and eggs present in each plant was counted under a stereomicroscope. The repellency index (IR) and the oviposition impediment index (IO) were calculated according to equations 3 and 4.

where, Nc is the number of mites found in the control plant (without gel) and Nt is the number of mites found in the plant containing the gels. Ot is the number of eggs found in the plant containing the gels and Oc is the number of eggs found in the plants without the gels. The averages of the repellency index and also of preventing oviposition were attributed to different classes, being: Class 0 (0.01% -0.1%), Class I (0.1% -20%), Class II (20 , 1% -40%), Class III (40.1% -60%), Class IV (60.1% -80%) and Class V (80.1% to 100%). The number of mites, as well as eggs, in the treated and control plants were analyzed by t tests for paired comparisons. The data were transformed into a log before analysis to meet the assumptions of parametric statistics.

Observação: Testemunha (sem adição de composições); Composições de hidrogel controle (apenas água); composições de hidrogel contendo nanopartículas de zeína na ausência de composto botânico (NP); composições de hidrogel contendo geraniol e eugenol encapsulados em nanopartículas de zeína (NP_GRL+EGL); composições de hidrogel contendo geraniol e cinamaldeído encapsulados em nanopartículas de zeína (NP_GRL+CND).

Observação1: a Média de nove repetições. DP= desvio padrão. b Testes estatísticos referem-se ao teste-t para comparação de pares entre plantas tratadas e controle. c IR= índice de repelência.
Observação2: Testemunha (sem adição de dispositivos); Dispositivos hidrogéis controle (apenas água); dispositivos hidrogéis contendo nanopartículas de zeína na ausência de composto botânico (NP); dispositivos hidrogéis contendo geraniol e eugenol encapsulados em nanopartículas de zeína (NP_GRL+EGL); dispositivos hidrogéis contendo geraniol e cinamaldeído encapsulados em nanopartículas de zeína (NP_GRL+CND).[059] Table 3 presents the results for the number of mites found in the plant with the device (treated) and in the control. With the obtained data it was possible to calculate the repellency index (IR). On the other hand, Table 4 presents the results for the number of eggs found in the plant with the device and in the control, being calculated the oviposition impediment index (IO).

Observation: Witness (without adding compositions); Control hydrogel compositions (water only); hydrogel compositions containing zein nanoparticles in the absence of botanical compound (NP); hydrogel compositions containing geraniol and eugenol encapsulated in zein nanoparticles (NP_GRL + EGL); hydrogel compositions containing geraniol and cinnamaldehyde encapsulated in zein nanoparticles (NP_GRL + CND).

Observation1: the Average of nine repetitions. SD = standard deviation. b Statistical tests refer to the t-test for comparing pairs between treated plants and control. c IR = repellency index.
Observation2: Witness (without adding devices); Hydrogel control devices (water only); hydrogel devices containing zein nanoparticles in the absence of botanical compound (NP); hydrogel devices containing geraniol and eugenol encapsulated in zein nanoparticles (NP_GRL + EGL); hydrogel devices containing geraniol and cinnamaldehyde encapsulated in zein nanoparticles (NP_GRL + CND).

[060] As can be seen, only the compositions containing the encapsulated botanical active compounds showed a significant difference between the number of mites and eggs found in the treated plants compared to the control (Tables 3 and 4). The compositions containing the encapsulated compounds (NP_GRL + CND and NP_GRL + EGL) showed an IR of 81% (t = 3.24, df = 16, p = 0.005) and 90% (t = 3.98, df = 16, p <0.001), respectively. The compositions containing the encapsulated botanical compounds had a maximum rating (V), indicating an excellent repellent capacity. Both the control (without adding compositions), the control compositions (water only) and those containing only the zein nanoparticles (NP) did not show a significant repellent effect, presenting p values> 0.1, in addition to low IR. Similar results are found when we evaluate the number of eggs deposited (Table 4). The compositions NP_GRL + CND and NP_GRL + EGL showed an OI of 97% (t = 4.57, df = 112, p <0.001) and 94% (t = 6.17, df = 112, p <0.001), respectively. Therefore, it received maximum classification, to prevent oviposition of mites. No deterrent effect of oviposition was observed for the control and for the control and NP compositions, with low or negative IO values.

[061] In this context, as observed for the tests with whitefly (Bemisia tabaci), the compositions containing the encapsulated botanical compounds showed a significant and surprising repellent effect against the pests, being also able to prevent the oviposition of the mites.

[062] Therefore, the compositions containing the encapsulated botanical compounds showed repellent activity against the striped mite, as demonstrated for the whitefly. In addition, the mixture of active compounds may have improved the repellent effect, being a promising alternative in order to increase the spectrum of action. In this way, in vitro release tests were carried out in order to investigate the release profile of the active compounds from the compositions.

In vitro release tests

[063] A hydrogel (4.50 g on average) containing the nanoparticle suspension was added in 100 mL of a 3% (w / v) Poloxamer solution and subjected to shaker shaking (150 rpm) . As a function of time, aliquots (1 mL) of the solution were collected, the volume being removed, replaced with a 3% Poloxamer solution in order to maintain the final volume of the acceptor compartment. The amount of botanical compound released was then quantified using HPLC, the results being expressed in%. In order to avoid any loss by evaporation, the beakers were covered, only being discovered during sampling (performed in triplicate).

[064] Figure 6 shows the graph of cumulative release of botanical compounds as a function of time. It is observed that for the compositions containing the mixture of GRL and CND, the release (with 24 hours) of GRL and CND was 23.4 ± 1.4% and 48.4 ± 1.3%, respectively. Regarding the compositions containing the mixture of GRL and EGL, the release was 21.1 ± 1.0% and 29.3 ± 1.3%, respectively. It is observed, therefore, that all the compositions presented a biphasic release profile, with a faster release initially, followed by a sustained release. The faster release is initially associated with the non-encapsulated or adsorbed fraction on the surface of the particles. Thus, the incorporation of nanoparticles in the hydrogel limits the mobility of botanical compounds in the polymeric network of the gel.

Advantages of the present invention

[065] Therefore, the present invention highlights the development of a hydrogel composition based on cellulose derivatives, such as CMC and HEC, containing a mixture of encapsulated botanical compounds.

• a) modelagem e incorporação dos bioativos e
• b) moldagem e reticulação final com possível rápida remoção aquosa do agente reticulante, tendo também a possibilidade de moldagem em diferentes formatos.

- Aplicação no ambiente, mas sem contato direto com a planta, reduzindo as possibilidades de danos ao cultivo.
- Resistência estrutural à altas temperaturas e tensões de cisalhamento, facilitando a aplicação e a elaboração de embalagens adequadas;
- Efetiva atividade repelente da mistura de compostos botânicos encapsulados contra duas pragas agrícolas: mosca-branca e ácaro-rajado.[066] The said hydrogel composition has the following advantages:
- Possibility of incorporating oily bioactive substances, facilitating their aqueous dispersion;
- It is based on matrices of natural origin, with application in sustainable agriculture;
- It presents a simple preparation process with two steps, being:

• a) modeling and incorporation of bioactive and
• b) molding and final cross-linking with possible rapid aqueous removal of the cross-linking agent, also having the possibility of molding in different formats.

- Application in the environment, but without direct contact with the plant, reducing the chances of damage to the crop.
- Structural resistance to high temperatures and shear stresses, facilitating the application and preparation of suitable packaging;
- Effective repellent activity of the mixture of botanical compounds encapsulated against two agricultural pests: whitefly and spotted mite.

[067] Those skilled in the art will value the knowledge presented here and will be able to reproduce the invention in the modalities presented and in other variants, covered by the scope of the attached claims.

Claims (19)

Process of obtaining the hydrogel composition, characterized by comprising the following steps:

• a) dispersion of cellulose polymers in the nanoparticle solution containing the botanical compounds until complete hydration;
• b) obtaining the resulting hydrogel;
• c) homogenization of the hydrogel;
• d) insertion of the hydrogel into a mold and
• e) immersion of the mold in citric acid solution.

Process for obtaining the hydrogel composition, according to claim 1, characterized by the fact that in step a), said cellulose polymers are selected from the group comprising carboxymethylcellulose and hydroxyethylcellulose. Process for obtaining the hydrogel composition, according to claim 2, characterized by the fact that said polymers are in the proportion of 5: 1 by weight of carboxymethylcellulose to hydroxyethylcellulose. Process for obtaining the hydrogel composition, according to claim 1, characterized by the fact that in step a), the botanical compounds are selected from the group comprising geraniol, eugenol and cinnamaldehyde or their combinations. Process for obtaining the hydrogel composition according to claim 1, characterized by the fact that in step a), said mixture of nanoparticles solution comprising the botanical compounds has an average diameter of 200 to 350 nm; polydispersity index from 0.2 to 0.4; zeta potential of 20 to 50 mV and particle concentration of 1 to 4x1012 particles / mL. Process for obtaining the hydrogel composition according to claim 1, characterized by the fact that in step c), homogenization occurs with a mechanical stirrer at 500 rpm and for 10 minutes. Process for obtaining the hydrogel composition according to claim 1, characterized by the fact that in step d), the molds are 2.5 cm long by 3.5 cm high. Process for obtaining the hydrogel composition according to claim 1, characterized by the fact that in step e), the citric acid solution is in a concentration of 8 mol / L and immersion occurs for 6 hours. Hydrogel composition obtained as defined in claims 1 to 8, characterized in that it comprises 5% cellulose polymers, 2% mixture of botanical compounds, 2% solution of zein nanoparticles and 2% polyoxyethylene-polypropylene. Hydrogel composition according to claim 9, characterized by the fact that cellulose polymers are selected from the group comprising carboxymethylcellulose and hydroxyethylcellulose. Hydrogel composition according to claim 10, characterized in that it has a ratio of 5: 1 by weight of carboxymethylcellulose to hydroxyethylcellulose. Hydrogel composition according to claim 9, characterized by the fact that the botanical compounds are selected from the group comprising geraniol, eugenol and cinnamaldehyde or their combinations. Hydrogel composition according to claims 9 to 12, characterized by the fact that it has a swelling degree of 27-32%, an elastic modulus of 149-253 mPas, viscous modulus of 28-50 mPas and viscosity of 24240-41810 mPas. Hydrogel composition according to claims 9 to 13, characterized by the fact that it does not come into direct contact with the plant. Hydrogel composition according to claims 9 to 14, characterized by the fact that it prevents the oviposition of mites. Hydrogel composition according to claims 9 to 15, characterized by the fact that it presents sustained release. Hydrogel composition according to claims 9 to 16, characterized by the fact that it has a repellent effect. Use of the hydrogel composition as defined in claims 9 to 17, characterized by the fact that it is used to combat and control agricultural pests. Use according to claim 18, characterized by the fact that agricultural pests are selected from the group comprising whitefly and spotted mite.

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