Slow-release agricultural pesticide formulations: state of the art

The need for a long-term sustaining of optimal concentrations of applied pesticides in the soil in agriculture resulted in the development of systems for controlled release of active substances. Such systems are based on the use of eco-friendly carrier materials that are harmless to plants, humans and environment. Inorganic substances (e.g., clays or alike substances), biodegradable polymers of natural or synthetic origin, blends of such polymers and their composites with inorganic fillers can be used as carriers. The deposited pesticides are released by diffusion or, in the case of systems based on biodegradable polymers, by degradation of the carrier. Inorganic carriers are usually impregnated with a pesticide. As for polymers, there is a wide range of methods for obtaining forms. Namely, these are the microsphere and nanoparticle formation, film casting, tablet pressing, form gelatinizing, and coprecipitation of a pesticide and a polymer from a solution. Co-extrusion of pesticides with polymers or their composites at temperatures below the degradation temperature of the components is another promising method for obtaining pesticide carriers

Improvement of biocompatibility of high molecular weight poly-3-hydroxybutyrate by blending with its functionalized oligomers

Oligomers of poly-3-hydroxybutyrate (PHB) were prepared by aminolysis of high molecular weight PHB with ethylenediamine and 1,4-diaminobutane. Polymer-oligomer blends (10, 30, and 50% content of the oligomers) were prepared as films by solution casting. As the content of oligomers increased, a gradual increase in the hydrophilicity of the polymer surface was observed, resulting reflected in the water contact angle decrease from 84° to 72–76°. In addition, a moderate decrease in elongation at break, Young's modulus, and tensile strength for the blends were observed as more oligomer was added to the film. Finally, the viability of NIH-3T3 mouse fibroblasts was higher compared to intact PHB when growing in non-prepared polymer/oligomer mixtures. These findings confirm the benefits of the introduction of a hydrophilic functionalized oligomer into the PHB matrix in terms of improving the biocompatibility of the resulting polymer/oligomer blends

Investigation of Biodegradation of Polylactide Product Samples under Various Temperature and Soil Conditions

In this work, the biodegradation of polylactide films, granules and tapes at temperatures of 23 °C and 8 °C in humus and chernozem soils was investigated. It was found that under the conditions studied, polylactide products are poorly biodegradable – for 84 days of exposure in the soil, the weight loss of all products did not exceed 10%. According to the results of microbiological assessment of the microflora of soils in which destruction occurred, no destructors of this type of biodegradable polymer were identified by inoculation in nutrient media containing polymer as the only carbon source

Comparative study of physical and chemical properties of PLA-based films obtained by solution casting and flat-slot die melt extrusion

In this study the effect of processing methods on physical and chemical properties of polylactide (PLA) (Mn 130 kDa, L-93/ D-7) was investigated. PLA-films were obtained by solution casting and melt extrusion using Bestfiilament extruder equipped with flat-slot die. SEM, AFM, FTIR-spectroscopy and DSC were used for characterization of the films. The films obtained by flat-slot die melt extrusion had a relief surface with prominent strands and inclusions, while the cast films had a smooth surface with pores or gaps ranging in size from 20 to 60 μm. The average roughness (Ra) and root-mean-square roughness (Rq) of the surface of cast films were at the level of 45-48 and 37-39 nm, respectively. Meanwhile, for the melt films these values increased and corresponded to 122 and 65 nm, respectively. According to FTIR, both types of films were characterized by an increase in the absorption peaks at 1800-1700, 1450-1470 and 1350-1320 cm-1, which correspond to stretch vibrations of ester bond and bending vibrations of the C-H bond, respectively. DSC data showed decrease in crystallinity of PLA and change in its internal structure from amorphous-crystalline to amorphous after the processing

Продукция двух- и трехкомпонентных полигидроксиалканоатов светящимися бактериями рода Photobacterium

The study addresses the ability of luminous bacteria Photobacterium leiognathi Boisvert et al. and Photobacterium phosphoreum (Cohn) Beijerinck to synthesize polyesters of hydroxycarbon acids (polyhydroxyalkanoates, PHAs) as storage macromolecules. The screened strains widely vary in their PHA productivity. Ph. leiognathi (but not Ph. phosphoreum) produces PHAs containing monomers of 3-hydroxyvaleric acid and, in some cases, 3-hydroxyhexanoic acid, in addition to common monomers of 3-hydroxybutyric acid. All studied strains of Ph. phosphoreum produce pure poly-3-hydroxybutyrate only. In the case of Ph. leiognathi, addition of valeric acid as substrate can increase the amounts of medium-chain-length hydroxy acids contained in the produced polymers. The results suggest a conclusion that luminous microorganisms of Photobacterium genus can be considered as producers of multi-component PHAsИсследована способность светящихся бактерий видов Photobacterium leiognathi Boisvert et al. и Photobacterium phosphoreum (Cohn) Beijerinck к синтезу полиэфиров гидроксикарбоновых кислот (полигидроксиалканоатов – ПГА) в качестве резервных макромолекул. Исследованные штаммы значительно различались по их способности к синтезу ПГА. Ph. leiognathi (но не Ph. phosphoreum) синтезировал ПГА, которые, помимо мономеров поли-3-гидроксибутирата, содержали мономеры 3-гидроксивалериановой и, иногда 3-гидроксикапроновой кислот. Все изученные штаммы Ph. phosphoreum образуют только гомополимерный поли-3-гидроксибутират. В случае Ph. leiognathi добавление валериановой кислоты в качестве субстрата может увеличивать содержание 3-гидроксивалериановой и 3-гидроксикапроновой кислот в полимере. Результаты позволяют рассматривать светящиеся микроорганизмы рода Photobacterium в качестве продуцентов многокомпонентных ПГ

Продукция двух- и трехкомпонентных полигидроксиалканоатов светящимися бактериями рода Photobacterium

The study addresses the ability of luminous bacteria Photobacterium leiognathi Boisvert et al. and Photobacterium phosphoreum (Cohn) Beijerinck to synthesize polyesters of hydroxycarbon acids (polyhydroxyalkanoates, PHAs) as storage macromolecules. The screened strains widely vary in their PHA productivity. Ph. leiognathi (but not Ph. phosphoreum) produces PHAs containing monomers of 3-hydroxyvaleric acid and, in some cases, 3-hydroxyhexanoic acid, in addition to common monomers of 3-hydroxybutyric acid. All studied strains of Ph. phosphoreum produce pure poly-3-hydroxybutyrate only. In the case of Ph. leiognathi, addition of valeric acid as substrate can increase the amounts of medium-chain-length hydroxy acids contained in the produced polymers. The results suggest a conclusion that luminous microorganisms of Photobacterium genus can be considered as producers of multi-component PHAsИсследована способность светящихся бактерий видов Photobacterium leiognathi Boisvert et al. и Photobacterium phosphoreum (Cohn) Beijerinck к синтезу полиэфиров гидроксикарбоновых кислот (полигидроксиалканоатов – ПГА) в качестве резервных макромолекул. Исследованные штаммы значительно различались по их способности к синтезу ПГА. Ph. leiognathi (но не Ph. phosphoreum) синтезировал ПГА, которые, помимо мономеров поли-3-гидроксибутирата, содержали мономеры 3-гидроксивалериановой и, иногда 3-гидроксикапроновой кислот. Все изученные штаммы Ph. phosphoreum образуют только гомополимерный поли-3-гидроксибутират. В случае Ph. leiognathi добавление валериановой кислоты в качестве субстрата может увеличивать содержание 3-гидроксивалериановой и 3-гидроксикапроновой кислот в полимере. Результаты позволяют рассматривать светящиеся микроорганизмы рода Photobacterium в качестве продуцентов многокомпонентных ПГ

Свойства и биосовместимость смесей поли-3-гидроксибутирата-3-гидроксивалерата с поли-ε-капролактоном

Blends consisting of the poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) copolymer and poly- ε-caprolactone (PCL) were used to prepare polymer films by casting solution technique. The structure and physical-mechanical, and biological properties of the films were examined as influenced by the ratios of the blend components. The microstructure of the films was determined by the dominant component: the films had porous surface if the percentage of PHBV was higher than that of PCL and were relatively smooth if the dominant component was PCL. The highest elongation at break (190-368 %) was exhibited by the films prepared from the blends containing 5-25 % PHBV; at 25 % PHBV, local maxima of tensile strength (16 MPa) and Young’s modulus (529 MPa) were observed. Biocompatibility of the films prepared from the blends was studied in the culture of NIH 3T3 mouse fibroblast cells. Results of SEM and DAPI staining, determination of the number of attached cells, and MTT assay showed the absence of cytotoxic effects and high cell adhesion and proliferation, which in some cases were higher than on films prepared from pure PHBV and PCL. Thus, PHBV/PCL blends are suitable materials for constructing cell scaffolds for tissue engineering and other reconstructive technologiesСмеси, состоящие из сополимера поли-3-гидроксибутирата-3-гидроксивалерата (ПГБВ) и поли-ε-капролактона (ПКЛ), были использованы для получения полимерных пленок методом испарения из раствора. Исследованы структура, физико-механические и биологические свойства пленок в зависимости от соотношения компонентов смеси. Микроструктура пленок определялась преобладающим компонентом: пленки имели пористую поверхность, если содержание ПГБВ было выше, чем ПКЛ, и относительно гладкими при преобладании ПКЛ. Наибольшее значение удлинения на разрыв (190-368 %) отмечалось для пленок, полученных из смесей с содержанием 5-25 % ПГБВ; при 25 % ПГБВ наблюдались локальные максимумы предела прочности на разрыв (16 МПа) и модуля Юнга (529 МПа). Биосовместимость полученных из смесей пленок была изучена в культуре фибробластов мыши линии NIH 3T3. Результаты растровой электронной микроскопии, окрашивания DAPI, определения численности прикрепленных клеток и MTT-тест показали отсутствие цитотоксических эффектов и высокий уровень адгезии и пролиферации клеток, в ряде случаев превосходившие соответствующие значения для пленок, приготовленных из чистых ПГБВ и ПКЛ. Таким образом, смеси ПГБВ/ПКЛ являются материалами, подходящими для конструирования клеточных матриксов для тканевой инженерии и других реконструктивных технологи

Биодеградация полигидроксиалканоатов в природных почвах

The review reports studies of polyhydroxyalkanoate (PHA) biodegradation behavior in natural soils of different climatic zones. Degradation of different types of PHA is strongly influenced by the temperature, humidity, type of soil, amount of precipitation and the density of microbial populations. Micromycetes are considered to be the most efficient soil PHA degraders, and Penicillium is the most typical genus. But many bacterial species also participate in biodegradation. In all environments most PHA degrading soil microorganisms degrade short-chain PHAs only. Increasing the degrees of crystallinity of degrading PHAs suggests preferential disintegration of their amorphous phase in the soil as compared with crystalline phaseОбзор обобщает результаты исследований по биодеградации полигидроксиалканоатов (ПГА) в природных почвах различных климатических зон. Деградация различных типов ПГА находится под влиянием температуры, влажности и типа почвы, количества осадков и плотности микробной популяции. Наиболее эффективными почвенными деструкторами ПГА являются микромицеты, среди которых широко распространены представители рода Penicillium. Однако значительное количество видов бактерий также принимает участие в биодеградации. Во всех экосистемах микроорганизмы-деструкторы короткоцепочечных ПГА являются значительно более распространенными по сравнению с деструкторами среднецепочечных полимеров. Увеличение степени кристалличности ПГА по мере разрушения свидетельствует о преимущественном разрушении в почве аморфной фазы полимеров по сравнению с кристаллическо

Investigation of Biodegradation of Polylactide Product Samples under Various Temperature and Soil Conditions

In this work, the biodegradation of polylactide films, granules and tapes at temperatures of 23 °C and 8 °C in humus and chernozem soils was investigated. It was found that under the conditions studied, polylactide products are poorly biodegradable – for 84 days of exposure in the soil, the weight loss of all products did not exceed 10%. According to the results of microbiological assessment of the microflora of soils in which destruction occurred, no destructors of this type of biodegradable polymer were identified by inoculation in nutrient media containing polymer as the only carbon source

Comparative study of physical and chemical properties of PLA-based films obtained by solution casting and flat-slot die melt extrusion

In this study the effect of processing methods on physical and chemical properties of polylactide (PLA) (Mn 130 kDa, L-93/ D-7) was investigated. PLA-films were obtained by solution casting and melt extrusion using Bestfiilament extruder equipped with flat-slot die. SEM, AFM, FTIR-spectroscopy and DSC were used for characterization of the films. The films obtained by flat-slot die melt extrusion had a relief surface with prominent strands and inclusions, while the cast films had a smooth surface with pores or gaps ranging in size from 20 to 60 μm. The average roughness (Ra) and root-mean-square roughness (Rq) of the surface of cast films were at the level of 45-48 and 37-39 nm, respectively. Meanwhile, for the melt films these values increased and corresponded to 122 and 65 nm, respectively. According to FTIR, both types of films were characterized by an increase in the absorption peaks at 1800-1700, 1450-1470 and 1350-1320 cm-1, which correspond to stretch vibrations of ester bond and bending vibrations of the C-H bond, respectively. DSC data showed decrease in crystallinity of PLA and change in its internal structure from amorphous-crystalline to amorphous after the processing