Nanobody-Functionalized Cellulose for Capturing SARS-CoV-2

The highly transmissible severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected more than 253 million people, claiming ∼ 5.1 million lives to date. Although mandatory quarantines, lockdowns, and vaccinations help curb viral transmission, there is a pressing need for cost-effective systems to mitigate the viral spread. Here, we present a generic strategy for capturing SARS-CoV-2 through functionalized cellulose materials. Specifically, we developed a bifunctional fusion protein consisting of a cellulose-binding domain and a nanobody (Nb) targeting the receptor-binding domain of SARS-CoV-2. The immobilization of the fusion proteins on cellulose substrates enhanced the capture efficiency of Nbs against SARS-CoV-2 pseudoviruses of the wildtype and the D614G variant, the latter of which has been shown to confer higher infectivity. Furthermore, the fusion protein was integrated into a customizable chromatography with highly porous cellulose to capture viruses from complex fluids in a continuous fashion. By capturing and containing viruses through the Nb-functionalized cellulose, our work may find utilities in virus sampling and filtration towards paper-based diagnostics, environmental tracking of viral spread and reducing viral load from infected individuals. IMPORTANCE The ongoing efforts to address the COVID-19 pandemic center around the development of diagnostics, preventative measures, and therapeutic strategies. In comparison to existing work, we have provided a complementary strategy to capture SARS-CoV-2 by functionalized cellulose materials towards paper-based diagnostics as well as virus filtration in perishable samples. Specifically, we developed a bifunctional fusion protein consisting of both a cellulose-binding domain and a nanobody specific for the receptor-binding domain of SARS-CoV-2. As a proof-of-concept, the fusion protein-coated cellulose substrates exhibited enhanced capture efficiency against SARS-CoV-2 pseudovirus of both wildtype and the D614G mutant variants, the latter of which has been shown to confer higher infectivity. Furthermore, the fusion protein was integrated into a customizable chromatography for binding viruses from complex biological fluids in a highly continuous and cost-effective manner. Such antigen-specific capture can potentially immobilize viruses of interest for viral detection and removal, which contrasts with the common size- or affinity-based filtration devices that bind a broad range of bacteria, viruses, fungi, and cytokines present in blood ( https://clinicaltrials.gov/ct2/show/NCT04413955 ). Additionally, since our work focuses on capturing and concentrating viruses from surfaces and fluids as a means to improve detection, it can serve as an “add-on” technology to complement existing viral detection methods, many of which have been largely focusing on improving the intrinsic sensitivities.

Water intake of cellulose materials monitored by positron annihilation lifetime spectroscopy

In this study, for the first time, the experimental technique of positron annihilation lifetime spectroscopy (PALS) has been applied to monitor in situ the microstructural changes of cellulose-based materials, i.e. paper, during water intake. For three different cellulose samples, bleached fine paper without filler, Kraft paper without filler, and a viscose fiber sheet, the mean positron lifetime $$\Delta \tau _{\mathrm {mean}}$$ Δ τ mean showed a strong increase with time in humid atmosphere, but exhibiting different trends depending on the type of sample. For all the cellulose samples investigated, the mean positron lifetime $$\Delta \tau _{\mathrm {mean}}$$ Δ τ mean shows an initial strong increase simultaneously occurring (t<10 h) to the mass increase of the samples due to water intake. Interestingly, the variations of $$\Delta \tau _{\mathrm {mean}}$$ Δ τ mean of the viscose fiber sheet and the Kraft paper sample both show a second increase on longer timescales (t>60 h in humid atmosphere) during which the mass increase of these samples has already been saturated. The results of this study show that by the means of PALS, water transport in paper can be reliably followed over a long timespan and it is even possible to distinguish between different types of cellulose materials. The second stage increase of the mean positron lifetime after long times in humid atmosphere for the Kraft paper sample and the pure viscose sheets even suggest that not only water intake itself can be monitored but also further atomistic processes in the material are accessible.

POWDERED CELLULOSIC MATERIALS: OVERVIEW, CLASSIFICATION, CHARACTERISTICS AND FIELDS OF APPLICATION

Recently, due to the growing interest in powdered cellulosic materials, a large number of studies have been carried out on various methods of their preparation. The main interest is associated with new opportunities for research on nanocellulose. However, for a complete understanding, it is necessary to have information about all powdered cellulosic materials and the peculiarities of their preparation. This paper provides an overview of powdered cellulosic materials, presents their characteristics, and describes the properties of the materials. It is shown that the morphology of its fiber, as well as the ratio of crystalline and amorphous regions of cellulose, has a significant effect on the properties of the material. Peculiarities of obtaining powdered cellulose materials are discussed, depending on the required properties, and existing research in the field of mechanical, chemical and enzymatic processing of cellulose is presented. The main areas of application of various powdered cellulose materials are described, as well as the current situation on the market, examples of both domestic and foreign manufacturers are given. The information on powdered cellulose materials is generalized, their classification is given, which is consistent with the modern concepts described in the scientific works of researchers from all over the world.

TRIBOLOGICAL ASPECT OF ASSESSMENT OF EFFICIENCY OF FILTRATION USING MULTI-LAYER MATERIALS

This study presents the results of testing for the efficiency and effectiveness of filtration using multi-layer filter materials, and briefly presents a new technology for manufacturing filter media using these materials. The first part of the article describes the causes of the formation of impurities in operating fluids and the tribological effects of their impact. The second part is dedicated to testing for filtration efficiency and effectiveness for different filter materials. The third part of the article briefly describes the technology for manufacturing filter media using efficient but difficult-to-form materials. The testing results showed significant differences in filtering efficiency and effectiveness between the cellulose samples and the samples of filter materials based on glass microfibre layers. All of the tested multi-layer materials allow filtration effectiveness of over 90% to be achieved over the entire range of impurity sizes included in the experiment. The results of a comparative test for pressure change during filtration also indicate that glass microfibre materials have a considerably longer operating life than cellulose materials. The time after which a sharp increase in pressure occurs (due to the filter layer being filled with impurities) is nearly four times longer for multi-layer materials than for cellulose materials. The methods for cutting, forming, and joining filter materials have been developed by the author of this article and implemented at the EXMOT company.

Degradation of lignocelluloses in straw using AC-1, a thermophilic composite microbial system

In composting, the degradation of lignocellulose in straw is problematic due to its complex structures such as lignin. A common solution to this problem is the addition of exogenous inoculants. AC-1, a stable thermophilic microbial composite, was isolated from high temperature compost samples that can decompose lignocellulose at 50–70 °C. AC-1 had a best degradation efficiency of rice straw at 60 °C (78.92%), of hemicellulose, cellulose and lignin were 82.49%, 97.20% and 20.12%, respectively. It showed degrad-ability on both simple (filter paper, absorbent cotton) and complex (rice straw) cellulose materials. It produced acetic and formic acid during decomposition process and the pH had a trend of first downward then upward. High throughput sequencing revealed the main bacterial components of AC-1 were Tepidimicrobium, Haloplasma, norank-f-Limnochordaceae, Ruminiclostridium and Rhodothermus which provides major theoretical basis for further application of AC-1.

MODIFICATION OF THE METHOD FOR DETERMINING THE WETTABILITY OF CELLULOSE FIBROUS RAW MATERIALS FOR POLYMER COMPOSITE MATERIALS

Для полимерных композиционных материалов (ПКМ) с армирующим наполнителем из натуральных волокон одними из проблем являются оценка качества подготовки волокон и определение динамики взаимодействия волокон и полимерной матрицы. Актуальность проблем обусловлена расширяющимся объёмом исследований ПКМ с растительными волокнами и разнообразными видами и глубиной предварительной обработки растительных волокон. Предметом исследования выступил стандартный метод определения смачиваемости целлюлозных материалов. Цель экспериментального исследования – предложить модифицированный метод определения смачиваемости, потенциально пригодный для оценки качества подготовки армирующих наполнителей ПКМ из растительных волокон. Использован стандартный по ГОСТ и модифицированный метод определения смачиваемости. В качестве пробного материала использовали целлюлозу древесную, полубелёную сульфитную из хвойной древесины в форме целлюлозной папки. Образцы целлюлозы механически разрыхляли до элементарных волокон и испытывали на смачиваемость. Использовали три схемы испытаний – взвешивание стаканчика с навеской, погруженного в воду (схема 1), взвешивание сосуда с водой (схема 2), стандартную методику по ГОСТ (схема 3). По схемам 1 и 2 измерения проводили в течение до 120 секунд, по схеме 3 – 30 секунд. Эксперименты проводили в трёхкратной повторности. Сущность модифицированного метода определения смачиваемости основана на постоянном контроле массы навески по мере сорбции водной влаги. Полученные закономерности кинетики процесса показали, что количество водной влаги, впитываемой образцами, нелинейно меняется во времени. Величины смачиваемости, определённых по различным схемам, с учётом отклонений, соответствуют друг другу. Определение смачиваемости по модифицированному методу предложено проводить в течение 120 секунд, периодически контролируя показания весов. Предложенный модифицированный метод может быть использован в исследовательских целях для изучения динамики впитывания воды и сравнения поведения различных целлюлозных материалов для ПКМ с матрице на основе гидрофильных полимеров. For polymer composite materials (PCM) with a reinforcing filler made of natural fibers, one of the problems is to assess the quality of fiber preparation and determine the dynamics of the interaction of fibers and a poly-dimensional matrix. The urgency of the problems is due to the expanding volume of research on PCM with plant fibers and various types and depth of pretreatment of plant fibers. The subject of the study was a standard method for determining the wettability of cellulose materials. The purpose of the experimental study is to propose a modified method for determining wettability, potentially suitable for assessing the quality of preparation of reinforcing fillers of PCM from plant fibers. The standard GOST and modified method for determining wettability were used. As a test material, wood cellulose, semi-green sulfite from coniferous wood in the form of a cellulose folder was used. Cellulose samples were mechanically loosened to elementary fibers and tested for wettability. Three test schemes were used – weighing a cup with a suspension immersed in water (scheme 1), weighing a vessel with water (scheme 2), standard procedure according to GOST (scheme 3). According to schemes 1 and 2, measurements were carried out for up to 120 seconds, according to scheme 3 – 30 seconds. The experiments were carried out in threefold repetition. The essence of the modified method for determining the permeability is based on the constant control of the weight of the suspension as the sorption of water moisture. The obtained laws of the kinetics of the process showed that the amount of water moisture absorbed by the samples varies non-linearly over time. The wettability values determined according to various schemes, taking into account deviations, correspond to each other. The determination of wettability by the modified method is proposed to be carried out within 120 seconds, periodically monitoring the readings of the scales. The proposed modified method can be used for research purposes to study the dynamics of water absorption and compare the behavior of various cellulose materials for PCM with a matrix based on hydrophilic polymers.

Fracture toughness as an alternative approach to quantify the ageing of insulation paper in oil

Oil-immersed transformers use paper and oil as insulation system which degrades slowly during the operation of these machines. Cellulose materials are used generally as insulation solid in power transformers. The degree of polymerization (DP), defined as number of repeating β-glucose residues in the cellulose molecule, is a critical property of cellulosic insulation material used in transformers, since it provides information about paper ageing and its mechanical strength. The fast-developing electric power industry demanding superior performance of electrical insulation materials has led to the development of new materials, as well as different drying techniques performed during transformer manufacturing and service when required. Both developments have caused some practical difficulties in the DP measurement. Moreover, the increasing interest in synthetic dielectric materials replacing cellulose materials requires measuring alternative properties to the DP to quantify the degradation of insulation solids over time. In this sense, this paper proposes the possibility of analyzing paper degradation through fracture toughness. This approach is different from the study of mechanical properties such as tensile strength or strain because it provides a tool for solving most practical problems in engineering mechanics, such as safety and life expectancy estimation of cracked structures and components which cannot to be considered through the traditional assessment of the mechanical resistance of the material. An accelerated thermal ageing of Kraft paper in mineral oil was carried out at 130 °C during different periods of time, to obtain information on the kinetics of the ageing degradation of the paper. Double-edged notched specimens were tested in tension to study their fracture toughness. The evolution of the load–displacement curves obtained for different ageing times at the ageing temperature of 130 °C was utilized to the determination of the stress intensity factor. Furthermore, different kinetic models based on this stress intensity factor were applied to relate its evolution over time as a function of the temperature. Finally, the correlation between the DP and stress intensity factor, which depends on the fiber angle, was also defined. Graphic abstract

The effect of the time process of enzymatic hydrolysis on nanocellulose properties

The effect of the time process of enzymatic hydrolysis on nanocellulose properties - the aim of the study was to evaluate the effect of enzymatic hydrolysis time on the properties of obtained nanocellulose. Two cellulose materials were tested as a raw material for nanocellulose production in the experiment: Avicel and Whatman. The cellulolytic enzyme obtained from the fungus Trichoderma reesei was used to carry out the enzymatic hydrolysis reaction. Enzymatic hydrolysis was performed on cellulose using the reaction times of 0.5, 1, 2 and 4 hours. In order to characterize the obtained materials, the following analyses were used: infrared spectroscopy, X-ray diffraction and dynamic light scattering. The recorded results showed that cellulose after enzymatic hydrolysis showed similar parameters (particle size, XRD patterns and degree of crystallinity) after all the applied reaction times.