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The emerging demands for healthcare where access is limited due to political, environmental, or socio-economic factors have been driving research into bio-medical devices that perform in both diagnostic and therapeutic roles at lower costs and greater accessibility. Paper microfluidic devices are used in many applications, particularly medical diagnostics and offer an excellent combination of utility and low cost making them particularly valuable in resource-limited applications and point-of-care usage across a wide variety environmental conditions. Microfluidic biological diagnostics continue to mature as researchers discover new ways to exploit the technological possibilities, and address liabilities. The increasing complexity of paper-based microfluidic devices beyond home pregnancy tests is driving the need to produce new tools and methodologies that enable more robust biological diagnostics and potential therapeutic applications. However, the process of developing new paper microfluidic devices is limited due to having to manually design and fabricate designs to research. Often, researchers must design scores of different devices to find a combination of parameters that functions as expected. In this work, a novel software framework to support automated development of paper-based microfluidic devices is introduced to facilitate both research and fabrication to accelerate the investigative process and reduce material utilization and manpower. Unlike to existing lab-on-a-chip technologies, paper-based microfluidics differs in terms of substrate technologies and use a passive flow method to deliver fluids and reagents for assays. While numerous analogies between microfluidics and semiconductor technologies have been espoused, the physical differences between the fluid dynamics and electrical current are significant which suggests that current trends in physical design for microfluidics must change course in order to be of practical use to designers. Within this framework, a methodology is introduced to address design automation such as dynamically placing and routing microfluidic components in a non-discrete design space while avoiding invalid design layouts, accounting for fluid volume usage, surface area utilization, and the timing required to perform specified biological assays and also optimizing device parameters, enabling researchers to focus on the science and thereby accelerating the development of new, low-resource paper microfluidic devices for a developing world.

As early diagnosis is essential for improving patient outcomes when treating both communicable and noncommunicable diseases, it is necessary to develop diagnostic tests that are accessible at the point of care. Thus, there is a need for rapid, robust, and inexpensive diagnostic tests, especially in resource-limited areas where access to healthcare is reduced. One such test is the lateral-flow immunoassay (LFA), which has seen a drastic rise in use during the COVID-19 pandemic. However, the conventional LFA suffers from a couple limitations, which this thesis aims to address. First, we address the limited sensitivity of the LFA by incorporating nanozyme signal enhancement to improve detection of the SARS-CoV-2 nucleocapsid protein in serum. By developing dehydrated signal enhancement reagents and an innovative 3D printed casing to store and deliver reagents at the push of a button, we were able to improve the limit of detection of the LFA by at least 10-fold without introducing additional complexity for the user.Next, we shifted our focus to introducing semi-quantitative results to the LFA through the multicolor etching of gold nanorods (GNRs). We demonstrated the first integration of the LFA with GNRs to produce a multicolor readout for the quantification of digoxin levels in serum. We then expanded upon this work by developing a fully paper-based assay to incorporate both the LFA detection and GNR etching steps together, which involved the design of novel color-changing GNR pads. The color hues generated by GNR etching are easily distinguishable by the naked eye, thus allowing for quantification of target biomarker concentrations at the point of care.

WOS:000967659000009 The utilization of plant extraction products from Oeneanthe pimpinelloides (Apiaceae family) seeds were investigated in terms of their use as an insecticide control of packaging materials. The aim was to investigate their insecticidal effects against the flour beetle Tribolium castaneum. The Oeneanthe pimpinelloides seeds were extracted with methanol. By using the liquid-liquid extraction method, the hexane extract (II) was separated from the methanol extract (I) and hexane and methanol were evaporated. Then, the chemical composition of each sample was determined via gas chromatography–mass spectrometry. The methanol extract predominantly contained tetrahydrofuran, 1-methoxy-2-propanol, 1-methoxy, 2-butoxyethanol, 1-phenylethanone, cyclohexene carboxylate derivative, (3-phenyl-2-propynylidene) cyclopropane, diphenyldiazene, and dihydroxypropyl ester components, while the hexane fraction contained nonane, 1-octanol, decane, undecane, tridecane, alkyl benzene, benzene sulfonic acid, benzoxazine, and hexadecanoic acid components, as well as some derivatives of them. Each fraction was dissolved in DMSO for impregnation on filter paper. The insecticide effects of the paper samples were determined against Tribolium castneum. According to the results, the mortality started after 3 d for each fraction. After 4 d, the hexane fraction indicated total mortality in comparison with the methanol fraction, which showed partial mortality (3/5).

With the overarching aim for the development of sustainable, nontoxic wet strength agents for paper, a novel polymer gel system based on oxidized hydroxypropyl cellulose (keto-HPC) cross-linked with polyamines was investigated in detail to gain a deeper insight into the wet strength mechanism. When applied to paper, this wet strength system significantly increases the relative wet strength by using only low amounts of polymer, and it is therefore comparable with established wet strength agents based on fossil resources, such as polyamidoamine epichlorohydrin resins. With the help of ultrasonic treatment, keto-HPC was degraded with respect to its molecular weight and further cross-linked in paper using polymeric amine-reactive counterparts. The resulting polymer-cross-linked paper mechanical properties were analyzed with respect to the dry and wet tensile strength, respectively. In addition, we analyzed the polymer distribution using fluorescence confocal laser scanning microscopy (CLSM). If high-molecular-weight samples are being used for cross-linking, we do find accumulation of the polymer mainly on the surface of the fibers and at fiber crossing points, accompanied with enhancing strong effects on paper’s wet tensile strength. In contrast, if low-molecular-weight (i.e., degraded) keto-HPC is being applied, the macromolecules are capable of entering the inner porous structure of the paper fibers, and almost no accumulation at the fiber crossing points is observed, which also results in a lowered wet paper tensile strength, respectively. This insight into wet strength mechanisms of the keto-HPC/polyamine system can thus lead to new opportunities for the development of alternative biobased wet strength agents where molecular weight dependence of the wet tensile properties allows for a fine tuning of mechanical properties in the wet state.

The clinical diagnosis of urinary tract infections (UTIs) faces challenges characterized by prolonged test results, contributing to over-prescription of antibiotics, and missed diagnoses. Point-of-care (POC) tests such as the lateral-flow immunoassay (LFA) attempt to alleviate this issue by providing patients with rapid results; however, their effectiveness is limited by low sensitivity. To improve the performance of the LFA, this thesis focuses on the development of an automated device that enables the addition of a sample preconcentration step at the POC using an aqueous two-phase system (ATPS). The device utilizes a photoresistor-based interface detection algorithm to selectively extract the bottom phase of the ATPS, containing concentrated biomarker, thereby avoiding the dispensing of the undesired top phase onto an LFA. The device incorporates a custom syringe pump module to apply the sample fluid to the LFA, and a gravity-based buffer dispensing module to facilitate the application of running buffer following sample addition. The affordability of the device is ensured through the use of reusable electrical components and cost- effective consumables, making it accessible to physician offices and mobile clinics at the POC. Experimental results demonstrate the successful automation of ATPS application onto the LFA, effectively extracting the bottom phase without any of the top phase. This advancement brings sample preconcentration using an ATPS one step closer to clinical adoption, offering a sensitive, rapid, and user-friendly UTI diagnostic solution.

Environmental toxic pollutants and pathogens that enter the ecosystem are major global issues. Detection of these toxic chemicals/pollutants and the diagnosis of a disease is a first step in efficiently controlling their contamination and spread, respectively. Various analytical techniques are available to detect and determine toxic chemicals/pathogens, including liquid chromatography, HPLC, mass spectroscopy, and enzyme-linked immunosorbent assays. However, these sensing strategies have some drawbacks such as tedious sample pretreatment and preparation, the requirement for skilled technicians, and dependence on large laboratory-based instruments. Alternatively, biosensors, especially paper-based sensors, could be used extensively and are a cost-effective alternative to conventional laboratory testing. They can improve accessibility to testing to identify chemicals and pollutants, especially in developing countries. Due to its low cost, abundance, easy disposal (by incineration, for example) and biocompatible nature, paper is considered a versatile material for the development of environmentally friendly electrochemical/optical (bio) sensor devices. This review presents an overview of sensing platforms constructed from paper, pointing out the main merits and demerits of paper-based sensing systems, their fabrication techniques, and the different optical/electrochemical detection techniques that they exploit.

Microfibrillated cellulose (MFC) was prepared from post-consumer old corrugated container (OCC) material, which was first disintegrated in water, cleaned to remove impurities, and then fibrillated by grinding. Those processed MFCs were treated with in-situ formation of calcium carbonate by adding calcium oxide and injecting carbon dioxide into the mixture up to the ratio of 1:40 (MFC : calcium carbonate) by weight. The MFCs had a dark brown color initially but turned into high brightness materials similar to commercial ground calcium carbonate (GCC) after the in-situ formation process. The MFCs that had calcium carbonate attached on their surfaces, which were lengthy and flexible, were called flexible calcium carbonate from OCC (FCCO). Paper containing FCCO gave higher bulk, higher stiffness, and higher tensile index without lowering smoothness when compared to the paper containing commercial GCC. However, brightness was slightly lowered because of initial low brightness of the OCC. This study also demonstrated the feasibility to substitute wood fibers up to 5% with FCCO without lowering essential properties for printing paper. Benefits of the waste paper are savings of both wood resources and production cost.

Selective detection and quantification of biomarkers related to human diseases are essential for preventive healthcare. Surface-enhanced Raman scattering (SERS) spectroscopy is a powerful analytical tool offering high sensitivity. However, the success of this promising analytical tool relies on the ability to effectively fabricate SERS substrate. Herein we have demonstrated a plasmonic paper-based flexible substrate (PPFS) for SERS sensing. In situ growth of silver nanostructures (AgNS) on the paper-based substrate was achieved by using a simple one-step silver mirror reaction (SMR). FESEM and TEM results depicts that the increasing silver ion content influences the morphology (growth of multifacets), as well as size of AgNS. Further, the PPFS substrate was tested with Rhodamine-6G (Rh-6G) dye and an attomole sensitivity with a LOD of 4.54 x 10-18 M was achieved. Further, two biomarkers, lactic acid (LA) and uric acid (UA) were detected on the PPFS substrate, with μM and pM sensitivity, having LOD values of 0.6 x 10-6 and 0.3 x 10-12 M respectively. Above detection levels for UA on PPFS is two orders better than reported values, whereas for LA it is comparable with reported substrates. Finally, UA, LA and their mixtures were tested on PPFS and results compared with commercial substrate. The performance of PPFS were found better in all cases, thus, multifaceted AgNS paper based PPFS offers the potential to be used as a biosensor for detection of various biomarkers from body fluids, responsible for the detection of the critical disease for preventive health care.

The prevalence of diabetes has increased over the past years. Therefore, developing minimally invasive, user-friendly and cost-effective glucose biosensors is necessary especially in low-income and developing countries. Cellulose paper-based analytical devices have attracted the attention of many researchers due to affordability, not requiring trained personnel, and complex equipment. This paper describes a microfluidic paper-based analytical device for the detection of glucose in tear with the naked eye. The paper-based biosensor fabricated by laser CO2, and GOx/HRP enzymatic solution coupled with TMB was utilized as reagents. A sample volume of 10 µl was needed for the biosensor operation and the results were observable within 5 minutes. To evaluate the device performance, color intensity-based and distance-based results were analyzed by ImageJ and Tracker. Distance-based results showed a linear behavior in the range of 0.1–0.6 mM with an R2 = 0.967 and LOD of 0.2 mM. The results could be perceived by the naked eye without any need to further equipment or trained personnel in a relatively short time (3–5 minutes). Moreover, glucose concentration could be obtained non-invasively by tears collected by this µPAD.

Paper, which is in fact a very complex cellulose-based product derived from different lignocellulosic resources, is usually regarded as a simple omnipresent commodity in our lives. Wood fibers derived from trees are the most employed sources for papermaking purposes. From an environmental protection perspective, and for their essential role in our life (they give us the life itself through their foliar system supporting the photosynthesis process), trees should not be extensively cut down and they should be used less and less for papermaking. Thus, employment of non-woody alternative sources for papermaking could be exploited more as an attractive and feasible option.

Access to medical care is a significant challenge facing developing countries. The World Health Organization developed the ASSURED criteria, which specifies requirements for the ideal diagnostic. ASSURED stands for Affordable, Sensitive, Specific, Rapid/Robust, Equipment-free and Deliverable. Traditional microfluidic diagnostics (comprised of glass/PDMS) require expensive fabrication procedures and user-intervention to manipulate fluids on the device. For those reasons, paper shows great promise as a substrate for an ASSURED microfluidic diagnostic. It is affordable and does not require external pumping to move fluids. Initially, microfluidic paper-based analytical devices (μPADs) performed simple, colorimetric assays. However, the field has evolved rapidly. Modern μPADs have been developed for a plethora of applications such as nucleic acid amplification. Wider adaptation of μPADs relies on the incorporation of more complicated assays (i.e. involving multiple fluids), which would allow μPADs to replace more expensive benchtop equipment. This requires more robust fluid control. Typically, fluid control on μPADs has been achieved by slowing fluid down to create delays between different channels. However, adding delays increases overall assay time and creates other complications such as fluid loss due to evaporation. Instead, creating ‘delays’ by accelerating wicking (relative to native paper) is being investigated. Previous approaches include sandwiching the paper between polymer films or creating ‘macro capillaries’ within the paper for the liquid to flow through. Of particular interest is the etching of grooves onto paper channels using either a plotter or a CO2 laser. These grooves create hollow regions in the paper which lead to faster wicking speeds. This study aims to characterize the behavior of grooved channels in paper and assess their performance as ‘delay’ mechanisms for a multi-fluid paper-based sensor.Typically, μPAD designs evolve in a trial-and-error basis, where devices are fabricated, tested and updated. Having accurate models that characterize the imbibition process could streamline development by allowing direct translation of in-silico designs to fully-functioning paper-based tools. Current imbibition models do not adequately describe the complex transport phenomena occurring within the paper matrix. This study also aims to develop an in-silico simulation that can reliably predict imbibition in both native paper and grooved channels.

Microfluidic paper-based analytical devices (microPADs) are emerging as simple-to-use, low-cost point-of-care testing platforms. Such devices are mostly fabricated at present by creating hydrophobic barriers using wax or photoresist patterning on porous paper sheets. Even though devices fabricated using these methods are used and tested with a wide variety of analytes, still they pose many serious practical limitations for low-cost automated mass fabrication for their widespread applicability. We present an affordable and simple two-step process - cut and heat (CH-microPADs) - for the selective fabrication of hydrophilic channels and reservoirs on a wide variety of porous media such as tissue/printing/filter paper and cloth types, such as cotton and polyester, by a lamination process. The technique presents many advantages as compared to existing commonly used methods. The devices possess excellent mechanical strength against bending, folding and twisting, making them virtually unbreakable. They are structurally flexible and show good chemical resistance to various solvents, acids and bases, presenting widespread applicability in areas such as clinical diagnostics, biological sensing applications, food processing, and the chemical industry. Fabricated paper media 96 well-plate CH-microPAD configurations were tested for cell culture applications using mice embryonic fibroblasts and detection of proteins and enzymes using ELISA. With a simple two-step process and minimal human intervention, the technique presents a promising step towards mass fabrication of inexpensive disposable diagnostic devices for both resource-limited and developed regions.

A surface profilometry technique was used to characterize the surfaces of paper products. A stylus-contact type profilometer capable of simultaneously generating both surface roughness- and friction-profiles was used. As a stylus for the profilometer, a conical shape whose tip was rounded to have a 0.5 mm curvature radius was designed and successfully employed in both printing & writing (P&W) papers and hygiene papers such as bathroom tissues and kitchen towel. From the profiles, the mean absolute deviation (MAD) from the averages, i.e., R-MAD from the roughness average and F-MAD from the average coefficient of friction, were suggested as the new surface characterization parameters. To elucidate the surface roughness profiles by fractal dimension analysis, the variogram method was applied to get the fractal dimensions of the paper products. Generally, the value of the fractal dimension increased as the surface roughness increased. The surface profilometry technique with the fractal dimension analysis with the variogram method looks promising to gain additional insight on the surface characteristics of paper products.

Fold cracking, which reduces the economic feasibility of paper-making, is a localized surface deformation caused by extreme bending stress. Most paper products, such as base paper and coated paper, generate fold cracking during folding processing. To control fold cracking, the mechanical properties of the base paper can be strengthened, and the flexibility of the structure can be increased by controlling the modification in pulp fibers and stock preparation conditions. This study analyzed the changes in the mechanical properties of high-grammage paper in response to the addition of precipitated calcium carbonate (PCC) and cationic starch (C-starch). The application of inorganic filler (PCC) drastically reduced the internal bond strength and tensile strength, causing fold cracking, whereas C-starch increased the bond strength between fibers, which improved the tensile strength, internal bond strength, and elongation. However, when applied independently, fold cracking occurred because of extreme increase or decrease in strength. Therefore, the combined application of C-starch and PCC made it possible to form a paper-based structure with high fold cracking resistance. Moreover, when the fold cracking resistance was excellent, the mechanical properties were balanced without being biased in one direction even under conditions of relatively low mechanical properties.

Microfluidic paper-based analytical devices (μPADs) have attracted great attention as potential candidates for point-of-care testing (POCT). Nevertheless, only a limited number of μPADs expected to satisfy the standard of Clinical Laboratory Improvement Amendments (CLIA) waived tests as issued by the US Food and Drug Administration (FDA) have been reported. This work introduces a "traffic light type μPAD", enabling highly intuitive semi-quantitative equipment-free naked-eye readout with no need for calibration, subjective interpretation or calculation. Assay results are displayed as traffic light colours reporting 5 analyte concentration levels (green/greenyellow/yellow/yellowred/red). The device has been designed to never display all three colours simultaneously, eliminating any risk for misinterpretation. The mechanism relies on the modulation of sample flow through a network of paperfluidic channels modified with a hydrophobic to hydrophilic phase-switching substance responsive to H

Bacterial meningitis, an infection of the membranes (meninges) and cerebrospinal fluid (CSF) surrounding the brain and spinal cord, is one of the major causes of death and disability worldwide. Higher case-fatality rates and short survival times have been reported in developing countries. Hence, a quick, straightforward, and low-cost approach is in great demand for the diagnosis of meningitis. In this research, a microfluidic fully paper-based analytical device (μFPAD) integrated with loop-mediated isothermal amplification (LAMP) and ssDNA-functionalized graphene oxide (GO) nano-biosensors was developed for the first time for a simple, rapid, low-cost, and quantitative detection of the main meningitis-causing bacteria

The applicability of paper mulberry fiber (PM-FB), which is bast fiber, for manufacturing cellulose nanocrystals (CNCs) with high-yield was investigated. The PM-FB and hardwood bleached kraft pulp (Hw-BKP) were hydrolyzed under different sulfuric acid concentrations, reaction times, and reaction temperatures. The dependence of the CNC yield on the hydrolysis conditions and crystallinity of the raw materials was analyzed. The functional groups of the CNCs and their zeta potentials were determined. The fiber length and width of the individual CNCs were determined by transmission electron microscopy image analysis. The PM-FB showed a higher crystallinity of 86.8% compared to that of Hw-BKP and exhibited a high CNC yield of 55% under strong hydrolysis conditions. The sulfate group was introduced into the CNCs, which increased their negative charge. The fiber width of PM-FB-based CNCs (PM-CNCs) was larger than that of Hw-BKP-based CNCs (Hw-CNCs), and the aspect ratio ranged from 29.0 to 12.2 depending on the hydrolysis conditions. The yield of PM-CNCs was higher than that of Hw-CNCs under the same hydrolysis conditions. In addition, both CNCs exhibited similar quality. Therefore, PM-FB is a promising raw material for efficient CNC manufacturing.

The prevalence of malaria across the globe creates the need for the development of diagnostic devices, as many deaths caused by malaria could be prevented by early diagnosis and treatment. Since typical symptoms of malaria, such as fever and chills, are challenging to distinguish from other diseases, diagnostic tests are crucial for allowing patients to receive the appropriate medical care. While current gold-standard methods such as microscopy are able to identify the presence and species of malaria parasites, the sensitivity achieved with these methods depends on the microscopist’s training, as well as access to resources such as lab equipment and power. Disparities in supplies and training lead to late or incorrect diagnosis in resource-limited areas across the globe. This has led to the development of point-of-care devices, which provide more rapid results without the need for expensive lab equipment or training. One example of such a device is the lateral-flow immunoassay (LFA), which has commonly found use as at-home pregnancy tests and recently as COVID-19 tests. Although the LFA is simple to use and provides easy-to-read results, currently available LFAs for malaria detection suffer from lower sensitivity compared to laboratory tests. In this thesis, I investigate methods for improving the detection of the malaria antigen Plasmodium falciparum lactate dehydrogenase (pLDH).Methods to improve the detection of the LFA include biomarker preconcentration and signal enhancement. Biomarker preconcentration can be achieved using aqueous two-phase systems (ATPSs), which are liquid-liquid extraction systems composed mostly of water. Molecules that are added into an ATPS can be concentrated into the smaller of the two phases. In addition, the sensitivity of the LFA can be improved through the use of signal enhancement, which aims to increase the intensity at the detection zone with the use of additional or modified colorimetric indicators.In Chapter 2, we focus on using a polymer-salt ATPS to purify the serum sample and concentrate pLDH into the smaller salt-rich phase of the ATPS via colorimetric probes to capture the biomarker. In addition, we used signal enhancement via platinum-coated gold nanozyme probes (PtGNPs) to improve the test line intensity, allowing us to detect pLDH at concentrations as low as 0.01 ng/mL in serum. This LFA with improved detection has the potential for early detection of malaria when parasite concentrations are low, which can help patients receive access to treatment before their symptoms worsen.

The pulp and paper industry is highly energy-intensive. In mills that use chemical pulping, roughly half of the higher heating value of the cellulosic material used to manufacture the product typically is incinerated to generate steam and electricity that is needed to run the processes. Additional energy, much of it non-renewable, needs to be purchased. This review considers publications describing steps that pulp and paper facilities can take to operate more efficiently. Savings can be achieved, for instance, by minimizing unnecessary losses in exergy, which can be defined as the energy content relative to a standard ambient condition. Throughout the long series of unit operations comprising the conversion of wood material to sheets of paper, there are large opportunities to more closely approach a hypothetical ideal performance by following established best-practices.

Aβ42 is one of the most extensively studied blood and Cerebrospinal fluid (CSF) biomarkers for the diagnosis of symptomatic and prodromal Alzheimer’s disease (AD). Because of the heterogeneity and transient nature of Aβ42 oligomers (Aβ42Os), the development of technologies for dynamically detecting changes in the blood or CSF levels of Aβ42 monomers (Aβ42Ms) and Aβ42Os is essential for the accurate diagnosis of AD. The currently commonly used Aβ42 ELISA test kits usually mis-detected the elevated Aβ42Os, leading to incomplete analysis and underestimation of soluble Aβ42, resulting in a comprised performance in AD diagnosis. Herein, we developed a dual-target lateral flow immunoassay (dLFI) using anti-Aβ42 monoclonal antibodies 1F12 and 2C6 for the rapid and point-of-care detection of Aβ42Ms and Aβ42Os in blood samples within 30 min for AD diagnosis. By naked eye observation, the visual detection limit of Aβ42Ms or/and Aβ42Os in dLFI was 154 pg/mL. The test results for dLFI were similar to those observed in the enzyme-linked immunosorbent assay (ELISA). Therefore, this paper-based dLFI provides a practical and rapid method for the on-site detection of two biomarkers in blood or CSF samples without the need for additional expertise or equipment. Graphical Abstract

Paper-based fluorescence devices, with smartphone aids, bring considerable operation convenience for tetracycline (TC) sensing. Nevertheless, they must meet the challenge in real determination against complicated backgrounds. Considering that, we present a programmable-printing paper-based device and then apply it to TC determination for various natural samples. MoS2 NPs and Gmp/Eu-Cit are synthetized as composite probes. A static quenching process is found with MoS2 NP fluorescence at 430 nm, while significant magnification of Gmp/Eu-Cit emission is obtained at 617 nm, establishing a valuable ratiometric indicator. Remarkably, two-stage programmable printing maximizes the proposed sensing capability. A transitive device, containing a gradually changing amount of a certain probe, is prepared to sense TC. With a homemade smartphone application and 3D-printed measurement chamber, the corresponding signals are examined to explore optimal setups. These setups are automatically processed to prepare the final-version device, not requiring manual operations. Benefitting from this interesting feature, the proposed device gains many rewards in performances. It effectively senses TC in a wide range from 12.7 nM to 80 μM and simultaneously provides naked eye-legible signals and smartphone-based readouts with confident selectivity and stability. This device is consequently applied for various samples of soil, river water, milk, and serum and meets well with HPLC-MS and recovery tests.

The pulp and paper industry discharges massive amount of wastewater containing hazardous organochlorine compounds released during different processing stages. Therefore, some cost-effective and nonpolluting practices such as enzymatic treatments are required for the potential mitigation of effluents released in the environment. Various xylanolytic enzymes such as xylanases, laccases, cellulases and hemicellulases are used to hydrolyse raw materials in the paper manufacturing industry. These enzymes are used either individually or in combination, which has the efficient potential to be considered for bio-deinking and bio-bleaching components. They are highly dynamic, renewable, and high in specificity for enhancing paper quality. The xylanase act on the xylan and cellulases act on the cellulose fibers, and thus increase the bleaching efficacy of paper. Similarly, hemicellulase enzyme like endo-xylanases, arabinofuranosidase and β-d-xylosidases have been described as functional properties towards the biodegradation of biomass. In contrast, laccase enzymes act as multi-copper oxidoreductases, bleaching the paper by the oxidation and reduction process. Laccases possess low redox potential compared to other enzymes, which need some redox mediators to catalyze. The enzymatic process can be affected by various factors such as pH, temperature, metal ions, incubation periods, etc. These factors can either increase or decrease the efficiency of the enzymes. This review draws attention to the xylanolytic enzyme-based advanced technologies for pulp bleaching in the paper industry.

Xylan is the primary hemicellulose in most hardwood species, especially in birch. Research has highlighted the exploitation of xylans as a strength-enhancing additive to paper due to the current trend for the effective utilization of biomass. In this paper, a new pulping process was proposed, which involved the extraction of xylan prior to pulping, followed by the re-adsorption of the pulp after the final stage in the digester, followed by a suitable bleaching process. The aim of this work was to bleach hardwood kraft pulp (brown pulp) with adsorbed birch xylan via hydrogen peroxide and study the effect of the bleaching parameters on the paper properties. The results showed that the optical properties of paper decreased; however, the mechanical properties increased after the brown pulp adsorbed birch xylan. During the bleaching process, better mechanical properties were obtained with shorter bleaching times and lower bleaching temperatures, initial pHs, and MgSO4 dosages. However, the optical properties were improved as the bleaching time, temperature, initial pH, and MgSO4 dosage were increased. The adsorption of birch xylan could effectively modify the mechanical properties of paper made from brown pulp under various phases.

The spread of Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2), resulting in a global pandemic with around four million deaths. Although there are a variety of nucleic acid-based tests for detecting SARS-CoV-2, these methods have a relatively high cost and require expensive supporting equipment. To overcome these limitations and improve the efficiency of SARS-CoV-2 diagnosis, we developed a microfluidic platform that collected serum by a pulling-force spinning top and paper-based microfluidic enzyme-linked immunosorbent assay (ELISA) for quantitative IgA/IgM/IgG measurements in an instrument-free way. We further validated the paper-based microfluidic ELISA analysis of SARS-CoV-2 receptor-binding domain (RBD)-specific IgA/IgM/IgG antibodies from human blood samples as a good measurement with higher sensitivity compared with traditional IgM/IgG detection (99.7% vs 95.6%) for early illness onset patients. In conclusion, we provide an alternative solution for the diagnosis of SARS-CoV-2 in a portable manner by this smart integration of pulling-force spinning top and paper-based microfluidic immunoassay.

Despite previous efforts, the fabrication of superhydrophobic substrate via an environment friendly and easy approach remains a great challenge. In this study, a low cost, simple, and green procedure was developed to prepare a superhydrophobic paper surface that is acceptable for the papermaking industry. First, a wax mixture (beeswax & carnauba wax) was emulsified and coated on the filter paper surface. Then, the coated paper was annealed at different temperatures. The further heat-treatment-rendered wax-coated paper hydrophobic or superhydrophobic because submicrometer or micrometer wax structures were present on the paper surface. The water contact angle of the annealed filter paper sample reached 151.5° at 60 °C, and the sliding angle was under 10°. Further, the relationship between surface composition and the hydrophobic properties of the coated paper samples was discussed. The obtained paper samples showed great potential in water/oil separation, as they had an efficiency over 99%. This work proposed a new simple and mild approach to fabricate superhydrophobic filter papers and explored the hydrophobicity and water/oil separation properties.

This work introduces the concept of a counting-based measurement on paper analytical devices (cPADs) to improve the utilization of numerous reactions. The design of cPADs consists of two layers of paper substrates; the first layer contains a central sample zone combined with a radial surrounded by 12 detection zones that are predeposited with the various reagents, and the second layer acts as a connection channel between the sample zone and each detection zone. The solution can vertically flow from the first to the second layer and then move through the area to each subsequent detection zone. The analyte level can be evaluated by counting the number of detection zones that change color from a blank signal. Furthermore, our cPADs exhibit a capability of implementation for a broad series of reactions. Compared to the dPAD technique, some reactions that are possibly difficult to apply in such devices can be wholly enabled in our devices. The final color reaction on cPADs can apparently occur due to its identity. We applied this technique to the monitoring of carbaryl (CBR) and copper ions (Cu

Research into paper-based devices and ionic liquids has increased considerably in the past few years. Thus, the combination of paper-based devices with ionic liquids is also becoming an increasingly frequent research subject. However, the influence of the ionic liquid on the paper properties has been hardly considered. In this paper, the influence of a hydrophobic ionic liquid (1-butyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl)imide) on the mechanical properties of laboratory paper, isotropic and oriented, made from eucalyptus sulfate and cotton linters, is investigated. The tensile strength, elastic modulus, and breaking strain of papers saturated with ionic liquid were about 60 to 90% of the dry paper characteristics. In contrast to water, the breaking strain did not increase in the presence of the ionic liquid. This is because the ionic liquid only slightly swelled the fibers.

Recycled fibers used in the manufacturing of paper and board are associated with strength deficiencies. This study investigated the use of TEMPO-oxidized nanocellulose from oil palm empty fruit bunch (OPEFB-TEMPO) for reinforcing papers made from such fibers. Strength properties of tensile and tear were enhanced with the addition of OPEFB-TEMPO, with strong correlations, as indicated by the R2 values. The reinforcement capability was supported by the scattering coefficient-percent relationship. The only drawback of the nanocellulose addition is that it reduces pulp drainability, which can be minimized by adding drainage aids. Because only a relatively small amount is required, OPEFB-TEMPO has the potential to be used as paper strengthening agent, particularly in the production of low grammage papers.

Cervical cancer is a leading cause of cancer death for women in low-resource settings. The World Health Organization recommends that cervical cancer screening programs incorporate HPV DNA testing, but available tests are expensive, require laboratory infrastructure, and cannot be performed at the point-of-care. We developed a two-dimensional paper network (2DPN), hybrid-capture, signal amplification assay and a point-of-care sample preparation protocol to detect high-risk HPV DNA from exfoliated cervical cells within an hour. The test does not require expensive equipment and has an estimated cost of$3 per test without the need for batching. We evaluated performance of the paper HPV DNA assay with short synthetic and genomic HPV DNA targets, HPV positive and negative cellular samples, and two sets of clinical samples. The first set of clinical samples consisted of 16 biobanked, provider-collected cervical samples from a study in El Salvador previously tested with careHPV and subsequently tested in a controlled laboratory environment. The paper HPV DNA test correctly identified eight of eight HPV-negative clinical samples and seven of eight HPV-positive clinical samples. We then performed a field evaluation of the paper HPV DNA test in a hospital laboratory in Mozambique. Cellular controls generated expected results throughout field testing with fully lyophilized sample preparation and 2DPN reagents. When evaluated with 16 residual self-collected cervicovaginal samples previously tested by the GeneXpert HPV assay ("Xpert"), the accuracy of the HPV DNA paper test in the field was reduced compared to testing in the controlled laboratory environment, with positive results obtained for all eight HPV-positive samples as well as seven of eight HPV-negative samples. Further evaluation showed reduction in performance was likely due in part to increased concentration of exfoliated cells in the self-collected clinical samples from Mozambique compared with provider-collected samples from El Salvador. Finally, a formal usability assessment was conducted with users in El Salvador and Mozambique; the assay was rated as acceptable to perform after minimal training. With additional optimization for higher cell concentrations and inclusion of an internal cellular control, the paper HPV DNA assay offers promise as a low-cost, point-of-care cervical cancer screening test in low-resource settings.

The outbreak of new viral strains promotes advances in universal diagnostic techniques for detecting infectious diseases with unknown viral sequence. Long double-stranded RNA (dsRNA), a hallmark of infections, serves as a virus marker for prompt detection of viruses with unknown genomes. Here, we report on-chip paper electrophoresis for ultrafast screening of infectious diseases. Negatively charged RNAs pass through the micro and nanoscale pores of cellulose in order of size under an external electric field applied to the paper microfluidic channel. Quantitative separation of long dsRNA mimicking poly I:C was analyzed from 1.67 to 33 ng·μL−1, which is close to the viral dsRNA concentration in infected cells. This paper-based capillary electrophoresis chip (paper CE chip) can provide a new diagnostic platform for ultrafast viral disease detection at the point-of-care (POC) level.

An approach of green in situ synthesis single-step method was applied to produce antibacterial paper. The objective was to investigate the effect of precursor addition on the formation of zinc oxide particles using an in situ single-step method. Zinc chloride concentrations of 0.1, 0.3, 0.5, and 0.7 M were prepared and added into a solution of algae extract and bamboo pulp. The prepared pulps were tested and made into handsheets using a papermaking machine based on TAPPI T205 (2006). Morphological observation of treated papers was conducted using a field emission scanning electron microscope (FESEM). An average of 400 to 570 nm zinc oxide spherical-shaped particle was observed on the fibers of paper. The percentage of element composition of the treated paper were 15.08% to 34.08% of zinc and 17.45% to 32.59% of oxygen captured via scanning electron microscopy with energy dispersive X-ray (SEM-EDX) analysis. The crystallinity test was performed using X-ray dispersion (XRD). A higher percentage of precursors exhibited a more amorphous structure. A measurement of more than 30% increment of inhibition zone was obtained from 10.00 to 25.00 mm against S. aureus, S. choleraesuis, and E. coli. Precursors addition of more than 0.3 M would have the most potential to enhance the growth of zinc oxide via in situ preparation, hence providing better antibacterial properties of the prepared papers.

Lignin/tannin/ZnONP composite coatings were designed for paper-based green packaging. Multiple functions, such as high strength, moisture resistance, low air permeance, heat endurance, UV aging resistance, and antibacterial/mold properties, were successfully integrated into one biobased coating. Prepolymerization improved the physical properties of coatings at high lignin contents. The best ingredient ratio was: 40% lignin, 15% tannin, and 10% ZnONPs (based on tannin weight), and the as-prepared biocoating was labeled LTZn-10. After coated with LTZn-10, the tensile strength and bursting strength of the packaging were efficiently enhanced by more than 3 times and were dramatically increased by 51.6 and 5.6 times at the wet state, respectively, which reveals that the packaging has favorable moisture resistance and it can be used in high humidity environments. Scanning electron microscopy (SEM) proved that most of the pores on the paper were blocked by the coatings, which helped to decrease the air permeance by 10.3 times. Meanwhile, ZnONPs were evenly spread on the coatings, which endowed the packaging with excellent antibacterial/mold performance. No colony or mycelium was found in the test against Gram-negative/positive bacteria and eight common molds. Besides, antibacterial activity is only available while the bacteria come in contact with the coating and no active substances were released into the culture medium, which is a good property that can keep the cargo from contamination of antibacterial agents. In addition, the coated paper presented an improved Tg and thermal degradation temperature, indicating that the coated package has favorable thermostability and can maintain its outstanding physical properties in a wider temperature range. Lignin and tannin promoted the UV stability and service life of the coated paper, as a rare physical decrease was observed after UV aging for 72 h. The function-integrated biobased coating with favorable sustainability is a good candidate to be widely used in paper-based green packaging fields.

A new coating method was developed, based on cellulose regenerated from an N-methylmorpholine N-oxide (NMMO) solution applied to paper. In particular, the purpose of this study was to compare the effectiveness of the “deep coating” method using cellulose regenerated from NMMO solution and the classic pulp refining process as methods to improve paper mechanical properties and overall quality. The “deep coating” name comes from the fact that the coating process is combined with subsequent heating of the coating before its final solidification. As a result of this operation, deep penetration of the cellulosic solution into the paper structure occurs. This increases the contact surface of the solution with the cellulosic fibers, which increases the strength properties of the paper structure. It was found that the cellulosic coating increased the apparent density of the paper, the tensile strength, the elongation, the resistance to bursting, and the double fold number. However, the coating also decreased the air permeability and the tear resistance of the paper samples. Despite some technological difficulties, this method could be an attractive solution in the case of a need for additional functionalization of a paper structure.