Erick F. de Oliveira

Chitosan/cashew gum nanogels for essential oil encapsulation

Nanogels based on chitosan and cashew gum were prepared and loaded with Lippia sidoides oil. Several parameters such as cashew gum concentration and relative oil content in the matrix had their influence on nanogel properties investigated. Nanogels were characterized regarding their morphologies, particle size distributions, zeta potential, Fourier transform infrared spectroscopy and essential oil contents. The release profile was investigated by UV/vis spectroscopy and its efficacy was determined through bioassays. Results showed that samples designed using relative ratios matrix:oil 10:2, gum:chitosan 1:1 and 5% gum concentration showed high loading (11.8%) and encapsulation efficiency (70%). Nanogels were found to exhibit average sizes in the range 335-558 nm. In vitro release profiles showed that nanoparticles presented slower and sustained release. Bioassays showed that larval mortality was related mainly to oil loading, with samples presenting more effective larvicide efficacies than the pure L. sidoides oil.

Alginate/cashew gum nanoparticles for essential oil encapsulation.

Alginate/cashew gum nanoparticles were prepared via spray-drying, aiming at the development of a biopolymer blend for encapsulation of an essential oil. Nanoparticles were characterized regarding to their hydrodynamic volume, surface charge, Lippia sidoides essential oil content and release profile, in addition to being analyzed by infrared spectroscopy (FT-IR), thermal analysis (TGA/DSC) and X-ray diffractometry. Nanoparticles in solution were found to have averaged sizes in the range 223-399 nm, and zeta potential values ranging from -30 to -36 mV. Encapsulated oil levels varied from 1.9 to 4.4% with an encapsulation efficiency of up to 55%. The in vitro release profile showed that between 45 and 95% of oil was released within 30-50h. Kinetic studies revealed that release pattern follow a Korsmeyer-Peppas mechanism.

Activity of chitosan-encapsulated Eucalyptus staigeriana essential oil on Haemonchus contortus

Phytotherapy has been described as an alternative method for the control of gastrointestinal nematodes in small ruminants. Goal of the encapsulation of essential oils in biopolymer matrices is to optimize the biological effects of these oils. The aim of the present study was to evaluate the in vitro and in vivo anthelmintic activity of encapsulated Eucalyptus staigeriana essential oil (EncEs) on the eggs and larvae of Haemonchus contortus. Therefore, the egg hatching test (EHT), larval development test (LDT) and worm load evaluation were performed to evaluate Meriones unguiculatus experimentally infected with H. contortus. The chemical constituents of E. staigeriana essential oil (EsEO) and the in vitro oil release profile from the chitosan matrix at a pH of 1.2 and 7.0 were also characterized. EncEs and EsEO inhibited larval hatching by 97.19% and 99.96% at doses of 1.5 and 1.0 mg ml(-1), respectively. In the LDT, EncEs and EsEO induced a larvicidal effect greater than 95% at concentrations of 5.8 and 8 mg ml(-1), respectively. EncEs and EsEO decreased H. contortus load in M. unguiculatus by 40.51% and 46.44%, respectively. The major chemical constituents of EsEO were (+)-Limonene (72.9%), 1,8-Cineole (9.5%) and o-Cimene (4.6%). The release profile of EsEO was 30% in acid and 25% at neutral pH. The similar efficacy of EncEs and EsEO demonstrates that there was no optimization of anthelmintic action following the encapsulation process. Therefore, the use of new encapsulation matrices with controlled release in the pH of the abomasum should be investigated.

Esferas (beads) de alginato como agente encapsulante de óleo de croton zehntneri Pax et Hoffm

Alginate beads (ALG) crosslinked with calcium and coated with cashew gum (GC) were prepared and loaded with an essential oil from Croton zehntneri Pax et Hoffm (Cz). The beads were characterized by FTIR, thermal properties, with respect to their size, shape, larvicide loading, swelling, and in vitro and in vivo release kinetics. Results showed that beads with ALG:Cz =1:1 relative ratio showed higher loading and encapsulation efficiency, although presenting a faster release kinetics. On the other hand, ALG beads coated with GC showed Q values from 10 to 12, representing a significant increase in the hydrophilic character of the matrix. Infrared spectroscopy and thermal analysis confirmed the presence of essential oil encapsulated in beads. Morphologic investigation by SEM revealed a highly spherical and porous surface. The in vitro profile showed that the Cz oil encapsulated had a prolonged release in ALG-GC beads, probably due to the crosslinking. In vivo tests showed that the mortality degree was related to the mass of the beads, where beads having oil content from 1.81 to 4.25 mg caused larvae mortalities from 72 to 100% after 24 h. The control release system was found to be effective up to 70 days. These results showed that ALG-GC beads loaded with Cz are promising candidate for the control of Stegomyia aegypti larvae.

Alginate/cashew gum floating bead as a matrix for larvicide release

A polymeric floating system composed of Alginate (ALG) and Cashew gum (CG), loaded with an essential oil (Lippia sidoides-Ls) was prepared by ionotropic gelation, characterized regarding its physical-chemistry properties and evaluated on its potential as a controlled release system. The influence of process parameters on the buoyancy, loading, swelling and in vitro and in vivo release kinetics, was investigated. Results showed that beads produced with carbonate and Ls at high level contents exhibit good floatability (up to 5 days) and loading capacity (15.2-23.8%). In vitro release data showed a Fickian diffusion profile and in vivo experiments showed that ALG-CG floating system presented a superior and prolonged larvicide effect, in comparison with non-floating ones, presenting larvae mortality values of 85% and 33%, respectively, after 48 h. These results indicate that ALG-CG floating beads loaded with Ls presented enhanced oil entrapment efficiency, excellent floating ability, and suitable larvicide release pattern.

Enhanced antimicrobial activity based on a synergistic combination of sublethal levels of stresses induced by UV-A light and organic acids

ABSTRACT The reduction of microbial load in food and water systems is critical for their safety and shelf life. Conventionally, physical processes such as heat or light are used for the rapid inactivation of microbes, while natural compounds such as lactic acid may be used as preservatives after the initial physical process. This study demonstrates the enhanced and rapid inactivation of bacteria based on a synergistic combination of sublethal levels of stresses induced by UV-A light and two food-grade organic acids. A reduction of 4.7 ± 0.5 log CFU/ml in Escherichia coli O157:H7 was observed using a synergistic combination of UV-A light, gallic acid (GA), and lactic acid (LA), while the individual treatments and the combination of individual organic acids with UV-A light resulted in a reduction of less than 1 log CFU/ml. Enhanced inactivation of bacteria on the surfaces of lettuce and spinach leaves was also observed based on the synergistic combination. Mechanistic investigations suggested that the treatment with a synergistic combination of GA plus LA plus UV-A (GA+LA+UV-A) resulted in significant increases in membrane permeability and intracellular thiol oxidation and affected the metabolic machinery of E. coli. In addition, the antimicrobial activity of the synergistic combination of GA+LA+UV-A was effective only against metabolically active E. coli O157:H7. In summary, this study illustrates the potential of simultaneously using a combination of sublethal concentrations of natural antimicrobials and a low level of physical stress in the form of UV-A light to inactivate bacteria in water and food systems. IMPORTANCE There is a critical unmet need to improve the microbial safety of the food supply, while retaining optimal nutritional and sensory properties of food. Furthermore, there is a need to develop novel technologies that can reduce the impact of food processing operations on energy and water resources. Conventionally, physical processes such as heat and light are used for inactivating microbes in food products, but these processes often significantly reduce the sensory and nutritional properties of food and are highly energy intensive. This study demonstrates that the combination of two natural food-grade antimicrobial agents with a sublethal level of physical stress in the form of UV-A light can greatly increase microbial load inactivation. In addition, this report elucidates the potential mechanisms for this synergistic interaction among physical and chemical stresses. Overall, these results provide a novel approach to develop antimicrobial solutions for food and water systems.

On mechanism behind UV-A light enhanced antibacterial activity of gallic acid and propyl gallate against Escherichia coli O157:H7

Possible mechanisms behind the enhanced antimicrobial activity of gallic acid (GA) and its ester propyl gallate (PG) in the presence of UV-A light against Escherichia coli O157:H7 were investigated. GA by itself is a mild antimicrobial and has a pro-oxidant ability. We found that the presence of UV-A light increases the uptake of GA by the bacteria. Once GA is internalized, the interaction between GA and UV-A induces intracellular ROS formation, leading to oxidative damage. Concurrently, GA + UV-A also inhibits the activity of superoxide dismutase (SOD), magnifying the imbalance of redox status of E. coli O157:H7. In addition to ROS induced damage, UV-A light and GA also cause injury to the cell membrane of E. coli O157:H7. UV-A exposed PG caused oxidative damage to the cell and significantly higher damage to the cell membrane than GA + UV-A treatment, explaining its higher effectiveness than GA + UV-A treatment. The findings presented here may be useful in developing new antimicrobial sanitation technologies for food and pharmaceutical industries.

Combination of aerosolized curcumin and UV-A light for the inactivation of bacteria on fresh produce surfaces

There is a critical unmet need to improve microbial safety of fresh fruits and vegetables. Current sanitation approaches cannot achieve >2 log inactivation of bacteria on fresh produce. Thus, there is a need to develop antimicrobial strategies that can consistently achieve >2 logs of bacterial inactivation on the surface of diverse fresh produce. Furthermore it is highly desired that these antimicrobial strategies have reduced environmental impact and are clean label solutions for food products. In this study, we evaluated the combination of curcumin and UV-A light radiation for the inactivation of inoculated E. coli O157:H7 and L. innocua bacterial cells on the surface of spinach, lettuce and tomatoes. Curcumin was deposited on the surface of fresh produce by either aerosolization or conventional spray-atomization methods before exposing the contaminated produce to UV-A light for 10 min (total light fluence of 20.4 kJ m-2). Results showed that the proposed combination of aerosolized or sprayed curcumin and UV-A light radiation can reduce the initial Escherichia coli O157:H7 and Listeria innocua load from 6 log CFU cm-2 to approximately 3 log CFU cm-2 on spinach, lettuce and tomato surfaces. Furthermore, there was no significant difference in bacterial reduction between the different types of inoculated fresh produce surfaces (P > .05). Interestingly, subsequent curcumin deposition and UV-A light exposure cycles were not able to further reduce the bacterial load below the observed threshold of approximately 3 log CFU cm-2. Lastly, the combination of aerosolized curcumin and UV-A light radiation did not affect the color or the texture of the treated fresh produce samples. The findings described in this study illustrate the potential of applying aerosolized or sprayed curcumin under UV-A light illumination to improve microbial safety of fresh produce products.

Uso da nanoemulsão de Eucalyptus staigeriana no controle da hemoncose em ovinos

Ribeiro W.L.C., Camurça-Vasconcelos A.L.F., Santos J.M.L., Macedo I.T.F., Ribeiro J.C., Oliveira E.F., Paula H.C.B. & Bevilaqua C.M.L. 2017. The use of Eucalyptus staigeriana nanoemulsion for control of sheep haemonchosis. Pesquisa Veterinária Brasileira 37(3):221-226. Programa de Pós-Graduação em Ciências Veterinárias, Faculdade de Veterinária, Universidade Estadual do Ceará, Avenida Dr. Silas Munguba 1700, Fortaleza, CE 60714-903, Brazil. E-mail: bevilaqua.uece@gmail.com Sustainable control of gastrointestinal nematodes (GIN) in small ruminants has been based on the use of alternative methods, including targeted selective treatment, such as FAMACHA. Another GIN control alternative is the use of herbal medicines, although in many cases their use is based on empirical knowledge. Biopolymer nanoformulations has been investigated to maximize the essential oil effects against sheep gastrointestinal nematodes. The aim of the present study was to combine a Eucalyptus staigeriana essential oil nanoemulsion (EsNano) with FAMACHA as an alternative control for sheep haemonchosis. The study was performed over six months at a commercial sheep farm located in a semiarid region of Northeast Brazil. Initially, a fecal egg count reduction test (FECRT) in sheep with levamisole, ivermectin and oxfendazole in sheep was performed used to determine the most effective anthelmintic to use as the positive control. Levamisole has been selected because it showed efficacy superior to 95%. EsNano was obtained and then its physicochemical properties were characterized. The average (±SE) size of the particles in the nanoemulsion was 276.8 (±12.3) nm with bimodal distribution and polydispersity. Nine visits were performed, from April to September 2013, with an interval of 17 days. One hundred sixty-two male and female sheep were divided into three groups (n=54 each) and were treated when FAMACHA score was 3, 4, or 5: G-EsNano 250mg kg-1 EsNano; G-Lev 7.5mg kg-1 levamisole (positive control), and G-Neg was not treated (negative control). Feces from sheep were collected to quantify the number of eggs per gram of feces (epg) and to identify nematode genera. Sheep weight gain was monitored. The epg data for each group and the average sheep weight gains were analyzed by variance analysis and compared with the Tukey’s test (P<0.05). Significant difference between the number of animals treated with EsNano and levamisole was not observed in any visit (P>0.05). The epg variation was similar in the G-EsNano and G-Lev groups on visits (P>0.05), except the second and fifth evaluation in the epg groups were significantly different (P<0.05). Haemonchus spp. was the most prevalent nematode. There was no significant weight gain in any of the treated groups (P<0.05). The combination of phytotherapy and FAMACHA can be an alternative to minimize the use of synthetic anthelmintics to control resistant GIN populations of small ruminants.