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Today, diabetes mellitus is one of the most common diseases that affects the population on a worldwide scale. Patients suffering from this disease are required to control their blood-glucose levels several times a day through invasive methods such as piercing their fingers. Our NaGdF 4 : 5% Er 3+ , 3% Nd 3+ nanoparticles demonstrate a remarkable ability to detect D-glucose levels by analysing alterations in their red-to-green ratio, since this sensitivity arises from the interaction between the nanoparticles and the OH groups present in the D-glucose molecules, resulting in discernible changes in the emission of the green and red bands. These luminescent sensors were implemented and tested on paper substrates, offering a portable, low-cost and enzyme-free solution for D-glucose detection in aqueous solutions with a limit of detection of 22 mg/dL. With this, our study contributes to the development of non-invasive D-glucose sensors, holding promising implications for managing diabetes and improving overall patient well-being with possible future applications in D-glucose sensing through tear fluid., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

In this study, a novel fluorescent nanoprobe (ZIF-90@FSS) was constructed using a zeolite imidazolium ester skeleton (ZIF-90) incorporating sodium fluorescein within its porous structure. Notably, this nanoprobe exhibited regular fluorescence "off" detection performance of Fe 3+ in actual samples and living cells. The concentration range of 0-150 ng/mL exhibited a lowest detection limit of 0.26 ng/mL. A nanofiber paper-based platform (VL78/ZIF-90@FSS) was further developed by coupling the prepared nanoprobe to a multi-dimensional fiber paper via CN bonds, enabling rapid visual white light colorimetric and fluorescence imaging of Fe 3+ within 2 min. The constructed nanoprobe and its paper-based detection platforms demonstrated a stable recovery range in tap water, beer, and soy sauce samples during spiking-recovery assessments. The recovery rates ranged from 98.46 % to 108.24 % for the nanoprobe and from 91.75 % to 108.71 % for the nanofiber paper-based platform. Therefore, the developed nano-fluorescent sensor and paper-based nanofiber sensing platform offer a promising strategy for the visual detection of Fe 3+ , while also presenting novel and valuable methods to investigate the regulatory mechanisms of Fe 3+ in living cells., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Cellulose was isolated from recycled pulp and paper sludge and used to synthesize cellulose nanocrystals. Response surface methodology and Box-Behnken design model were used to predict, improve, and optimize the cellulose isolation process. The optimal conditions were a reaction temperature of 87.5 °C, 180 min with 4% sodium hydroxide. SEM and TEM results revealed that the isolated cellulose had long rod-like structures of different dimensions than CNCs with short rod-like structures. The crystallinity index from XRD significantly increased from 41.33%, 63.7%, and 75.6% for Kimberly mill pulp sludge (KMRPPS), chemically purified cellulose and cellulose nanocrystals, respectively. The TGA/DTG analysis showed that the isolated cellulosic materials possessed higher thermal stability. FTIR analysis suggested that the chemical structures of cellulose and CNCs were modified by chemical treatment. The cellulose surface was highly hydrophilic compared to the CNCs based on the high water holding capacity of 65.31 ± 0.98% and 83.14 ± 1.22%, respectively. The synthesized cellulosic materials portrayed excellent properties for high-end industrial applications like biomedical engineering, advanced materials, nanotechnology, sustainable packaging, personal care products, environmental remediation, additive manufacturing, etc.

In this study, TiO 2 nanoparticle (TiO 2 NP)-coated film was produced to protect manuscripts against microorganisms using ecofriendly benign materials. As a result, a simple method was created that uses poultice biofilm made of carboxymethyl cellulose (CMC) and Phytagel plant cell (PGP) loaded with TiO 2 NPs to preserve manuscripts against microbes in an environmentally responsible way. Three volumes (1, 2, 4 mL) of TiO 2 NPs were put into a biofilm combination to produce the poultices known as CMC/PGP/TiO 2 -1, CMC/PGP/TiO 2 -2, and CMC/PGP/TiO 2 -3. The synthesized TiO 2 NPs were nearly spherical in shape, small in size (98 nm), and stable (zeta potential value - 33 mV). The results showed that the unique deposition of TiO 2 NPs on the biofilm surface gave the produced films loaded with TiO 2 NPs a rough structure. The highest values of mechanical characteristics were determined to be in CMC/PGP/TiO 2 -1 with values of 25.4 g, 6.6 MPa, and 11.4%, for tensile strength, elongation at break, and tear strength, respectively. Based on molecular identification, the fungus Aspergillus sydowii and the bacterium Nevskia terrae, with accession numbers MG991624 and AB806800, respectively, were isolated and identified from an antiquated manuscript formed from cellulosic fibers. Before the experiments, the produced cotton paper samples were aged, and then, one group was infected for 6 months by A. sydowii and the second group with N. terrae. Following the preparation of a CMC/PGP biofilm loaded with various volumes of TiO 2 NPs, poultices were applied to infected cotton paper in order to clean it. The infected cotton paper was placed inside the sandwich-like poultices that were created. The poultice CMC/PGP/TiO 2 -2 demonstrated potential for preventing the growth of A. sydowii and N. terrae-infected cotton paper, when the fibers were saved, cleaned, and coated with CMC/PGP/TiO 2 -2 after absorbing the fungus and the bacterium and exhibiting exceptional antimicrobial activities. Finally, the novel biofilms have demonstrated their capacity to lessen microbial contamination of cotton paper. In order to generalize the usage of these poultices, it is also advised that they be produced on a large scale and tested on a variety of organic materials in the future., (© 2023. The Author(s).)

Detection of the virus is the primary factor to discover and block the occurrence and development of the virus epidemic. Here, an ultrasensitive paper-based virus molecular imprinting sensor is developed to detect two viruses simultaneously in which the detection limit of the influenza virus (H5N1) is 16.0 aM (9.63 × 10 3 particles/mL) while that of the Hepatitis B Virus (HBV) is 129 fM (7.77 × 10 7 particles/mL). This paper-based sensor is low cost and is easy to cut, store, and carry. In addition, the visual semiquantitative detection of two viruses is achieved by using two aptamer-functionalized persistent luminescent nanoparticles as signal probes. These probes and the imprinted cavities on the paper-based material formed sandwich-type double recognition of the target viruses. This sensor has extremely high sensitivity to the H5N1 virus, which is of great value to solve the influenza epidemic with the most outbreaks in history, and also opens up a new way for the prevention and control of other virus epidemics. This cheap and portable visual sensor provides the possibility for self-service detection and can greatly reduce the pressure on medical staff and reduce the risk of virus infection caused by the concentration of people to be tested.

Trimethylsilyl cellulose (TMSC) was employed as the coating matrix for the application of zinc oxide nanoparticles (ZnO) onto paper surfaces and the protections of ZnO/TMSC coating against UV-induced damages and fungal spoilage were evaluated. Filter papers were immersed in 2% w/v TMSC solution loaded with ZnO and air-dried. Three ZnO/TMSC suspensions were prepared with 0.1, 0.5, and 1% w/v ZnO NPs. The presences of ZnO/TMSC protective layers were confirmed with ATR-IR spectroscopy. The coated papers exhibited high surface hydrophobicities. After the coated papers were subject to 365-nm UV irradiation at 400 W for 3 h, the contact angles dramatically dropped. The trimethylsilyl (TMS) groups exposed on the surface formed a moisture barrier and were partially removed on UV exposure. ATR-IR revealed that more TMS groups were removed in the protective layer with no ZnO. UV-irradiated papers turned yellow and papers protected with 1% ZnO/TMSC exhibited significantly lower color changes than that of the uncoated one. Compared to the TMSC-coated paper, the addition of ZnO resulted in a significant reduction in tensile strength at maximum. However, after UV irradiation, significant increases in both the strain at break and strength at maximum were only observed in 1% ZnO/TMSC-protected papers. Regarding their anti-fungal properties, the 1% ZnO/TMSC films were effective in growth inhibitions of Aspergillus sp. and Penicillium sp. on the nonirradiated papers. Despite being hydrophilic after UV-irradiation, growths of the molds were severely suppressed on the UV-irradiated paper., (© 2023. The Author(s).)

Near-infrared (NIR)-responsive bioassays based on upconversion nanoparticle (UCNP) incorporating high-performance semiconductors have been developed by researchers, but most lack satisfactory ultrasensitivity for exceedingly trace amounts of target. Herein, for the first time, the CRISPR/Cas13a system is combined with cascade DNA circuits, fluorescent resonance energy transfer (FRET) effect, and luminescence-confined UCNPs-bonded CuInS 2 /ZnO p - n heterostructures-functionalized paper-working electrode to construct dual-signal-on paper-supported NIR-irradiated photoelectrochemical (PEC) (NIR-PEC) and upconversion luminescence (UCL) bioassay for high-sensitive quantification of miRNA-106a (miR-106a). By constructing an ideal FAM-labeled aminating molecular beacon (FAM-H2) model, a relatively good FRET ratio between the UCNP and FAM (≈85.3%) can be achieved. In the existence of miR-106a, the hairpin-structure FAM-H2 was unwound, bringing about the distance increase of UCNP and FAM and the restraint of FRET. Accordingly, both the NIR-PEC signal and the UCL intensity gradually recovered distinctly. Unlike conventional single-mode PEC sensors, with NIR excitation, the designed dual-mode sensing system could implement minimized misdiagnose assay and quantitative miR-106a determination with low detection limits, that is, 76.54 and 51.36 aM for NIR-PEC and UCL detection, respectively. This work not only broadens the horizon of application of the CRISPR/Cas13a strategy toward biosensing but also constructs a new structure of the UCNP-semiconductor in the exploration of efficient NIR-responsive tools and inspires the construction of a no-misdiagnosed and novel biosensor for dual-mode liquid biopsy.

Fluorescence analysis is a fast and sensitive method, and has great potential application in trace detection of environmental toxins. However, many important environmental toxins are non-fluorescent substances, and it is still a challenge to construct a fluorescence detection method for non-fluorescent substances. Here, by means of charge transfer effect and smart molecular imprinting technology, we report a sensitive indirect fluorescent sensing mechanism (IFSM) and microcystin (MC-RR) is selected as a model target. A molecular imprinted thin film is immobilized on the surface of zinc ferrite nanoparticles (ZnFe 2 O 4 NPs) by using arginine, a dummy fragment of MC-RR. By implementation of IFSM on the paper-based microfluidic chip, a versatile platform for the quantitative assay of MC-RR is developed at trace level (the limit of detection of 0.43 μg/L and time of 20 min) in real water samples without any pretreatment. Importantly, the proposed IFSM can be easily modified and extended for the wide variety of species which lack direct interaction with the fluorescent substrate. This work offers the potential possibility to meet the requirements for the on-site analysis and may explore potential applications of molecularly imprinted fluorescent sensors., (© 2023. Springer Nature Limited.)

Health initiatives worldwide demand affordable point-of-care devices to aid in the reduction of morbidity and mortality rates of high-incidence infectious and noncommunicable diseases. However, the production of robust and reliable easy-to-use diagnostic platforms showing the ability to quantitatively measure several biomarkers in physiological fluids and that could in turn be decentralized to reach any relevant environment remains a challenge. Here, we show the particular combination of paper-microfluidic technology, electrochemical transduction, and magnetic nanoparticle-based immunoassay approaches to produce a unique, compact, and easily deployable multiplex device to simultaneously measure interleukin-8, tumor necrosis factor-α, and myeloperoxidase biomarkers in sputum, developed with the aim of facilitating the timely detection of acute exacerbations of chronic obstructive pulmonary disease. The device incorporates an on-chip electrochemical cell array and a multichannel paper component, engineered to be easily aligned into a polymeric cartridge and exchanged if necessary. Calibration curves at clinically relevant biomarker concentration ranges are produced in buffer and artificial sputum. The analysis of sputum samples of healthy individuals and acutely exacerbated patients produces statistically significant biomarker concentration differences between the two studied groups. The device can be mass-produced at a low cost, being an easily adaptable platform for measuring other disease-related target biomarkers.

The proper disposal of disposable synthetic plastic food packaging materials presents a significant challenge for both the environment and the solid waste management community. To address this issue, an antibacterial-based high-strength bio-composite serves as the optimal alternative to conventional packaging materials. This study aims to produce a hybrid material of AgNPs-carboxyl cellulose nanocrystals (AgNPs-CCNCs), obtained from used egg carton boxes (UECBs), through bio acid hydrolysis and an in-situ generation process. Furthermore, AgNPs- carboxyl cellulose nanofibers (AgNPs-CCNFs) will be synthesized through a combination of bio acid hydrolysis and ball milling, followed by an additional in-situ generation step. The AgNPs-carboxyl nanocellulose (AgNPs-CCNCs, and AgNPs-CCNFs) exhibited excellent crystallinity index, morphology, thermal, and antibacterial properties. The morphological analysis was performed by electron microscopy, and the results showed the uniform distribution and spherical form of AgNPs appearing over the carboxyl nanocellulose through the in-situ generation process, which was confirmed through XRD analysis. The study further explores the impact of AgNPs-carboxyl nanocellulose on the mechanical, chemical, antibacterial, and thermal properties of the PVA matrix. The results demonstrate that the bio-nanocomposite film offers opportunities for utilization in active packaging applications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

With the rapid expansion of the flexible electronics market, it is critical to develop high-performance flexible energy storage electrode materials. Cellulose fibers, which are sustainable, low cost, and flexible, fully meet the requirements of flexible electrode materials, but they are electrically insulating and cause a decrease in energy density. In this study, high-performance paper-based flexible electrode materials (PANI:SSA/Zr-CFs) were prepared with cellulose fibers and polyaniline. A high mass loading of polyaniline was wrapped on zirconia hydroxide-modified cellulose fibers under metal-organic acid coordination through a facile in situ chemical polymerization process. The increase in mass loading of PANI on cellulose fibers not only improves the electrical conductivity but also enhances the area-specific capacitance of the flexible electrodes. The results of electrochemical tests show that the area specific capacitance of the PANI:SSA/Zr-CFs electrode is 4181 mF/cm 2 at 1 mA/cm 2 , which is more than two times higher than that of the electrode with PANI on pristine CFs. This work provides a new strategy for the design and manufacture of high-performance flexible electronic electrodes based on cellulose fibers., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

This study reports an economical and portable point-of-care (POC) monitoring device based on artificial multi-enzyme cascade systems for multiple detection purposes. The device was made up of a disposable three dimensional microfluidic paper-based analytical device (3D μPAD) with multiple detection zones and a smartphone readout. On-paper synthesis of a multifunctional mimetic composite, based on the CeO 2 nanoparticles embedded in the amino-functionalized Fe metal-organic frameworks (CeO 2 @NH 2 -MIL-88B(Fe)), for cascade reactions was the main achievement of this work. The 3D μPAD was applied for simultaneous quantification of glucose, fructose, sucrose and maltose, and the detection process consisted of the enzymatic reaction of each sugar by anchored enzymes on the metal-organic frameworks (MOF) and successive oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). Utilizing the new artificial mimicking system improved the color development uniformity and resulted in a reliable detection tool, with excellent detection limits in the range of 20-280 μM. It was directly applied to analyze the sugars levels of human total blood, urine, semen, honey and juice samples with the relative errors of less than 7.7% compared with the HPLC method. The cost-effective and easy-to-use μPAD has a great potential to be used in either medical diagnostics or the food industry. Also, it can be considered as a competitive POC method for patients in disadvantaged communities or emergencies., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Cellulosic nanomaterials are in the focus of academia and industry to realize light-weight biobased materials with remarkable strength. While the effect is well known, the distribution of these nanomaterials are less explored, particularly for paper sheets. Here, we explore the 3D distribution of micro and nanosized cellulosic particles in paper sheets and correlate their extent of fibrillation to the distribution inside the sheets and subsequently to paper properties. To overcome challenges with contrast between the particles and the matrix, we attached probes on the cellulose nano/microparticles, either by covalent attachment of fluorescent dyes or by physical deposition of cobalt ferrite nanoparticles. The increased contrast enabled visualization of the micro and nanosized particles inside the paper matrix using multiphoton microscopy, X-ray microtomography and SEM-EDX. The results indicate that fibrillary fines enrich at pores and fiber-fiber junctions, thereby increasing the relative bonded area between fibers to enhance paper strength while CNF seems to additionally form an inner 3D network., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The major obstacle to developing nanozymes which are considered as promising alternatives to natural enzymes is their moderate performance, including poor affinity for substrates, low catalytic activity, and severe pH-dependence. To address these issues, herein, we synthesize ultrathin layered double hydroxide (LDH) nanosheets with a thickness of 1.4 nm and an average lateral size of 23 nm using a fast-precipitation method. Through the rational design of their compositions, it is found that NiMn LDHs exhibit the optimum peroxidase mimicking performance with excellent substrate affinity, high catalytic activity (a limit of detection (LOD) of 0.04 μM H 2 O 2 ) and robustness in a wide pH range (from 2.6 to 9.0), which is superior to that of natural horseradish peroxidase (HRP). The main active centers are identified as Mn sites because of their strong Lewis acidity and low redox potential. Furthermore, a series of disposable paper bioassays based on NiMn LDH nanozymes are designed and used for the highly sensitive detection of H 2 O 2 and ascorbic acid (AA).

The Phenylketonuria (PKU) is an inborn defect of phenylalanine (Phe) metabolism, in which Phe accumulated in the blood causing alterations at the central nervous system. Therefore, the detection of PKU is very important for the early diagnosis of PKU patients. However, existing tests for PKU are time-consuming and require high-resource laboratories. In this study, a novel paper-based biosensor based on phenylalnine ammonia lyase (PAL) hybrid nanoflowers was constructed that provides a semi-quantitative output of the concentration of Phe from urine samples. PAL@Ca 3 (PO 4 ) 2 hybrid nanoflowers (PAL@NF) were first prepared using PAL and Ca 2+ . Synthesis conditions of the PAL@NF on the formation of the PAL@NF were optimized. The PAL@NF exhibited 90% activity recovery under optimal condition. Compared with free PAL, the PAL@NF displayed good storage stability and increased tolerance to proteolysis. After five consecutive operating cycles, the PAL@NF still retained 73% of its initial activity, indicating excellent reusability. Furthermore, the paper-based biosensor was able to detect Phe concentration in urine samples, and exhibited good linearity to the Phe concentrations in the range from 60 to 2400 μM and the response time was only about 10 min. Therefore, the paper-based biosensor can be a promising candidate as a biosensor for the detection of PKU., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In the current work, we present a renewable alternative coating formulation made of durable titania nanoparticles and oxidized nanocellulose (TiO 2 NPs@OCNs) nanocomposites and sodium alginate (SA), to create an environmentally friendly and secure food packaging paper. OCNs sugarcane fibers are firstly hydrolyzed using ammonium persulphate (APS). Then, TiO 2 NPs@OCNs nanocomposites are made in situ with OCNs using a green water-based sol-gel synthesis. Gram (+) microorganisms as well as Gram (-) bacteria are used to test the antibacterial properties of the TiO 2 NPs@OCN dispersions. The results show that the TiO 2 NP@OCNs significantly decreases the growth for all bacterial species. The TiO 2 NP@OCNs nanocomposites are mixed with SA, and the resulting formulations are used to coat paper sheets. The corresponding physicochemical properties are evaluated using FTIR, TGA, AFM, SEM, and EDX. Furthermore, the mechanical strength, air permeability, and water vapor characteristics of the paper sheets treated with SA/TiO 2 NPs@OCN are carried out, resulting in a great improvement of these properties. Finally, the SA/TiO 2 NPs@OCNs coated papers have been used as packaging for strawberries. The findings demonstrate that coated papers could preserve strawberry quality better than unpacked fruit and extend strawberry shelf life from 6 to 18 days., Competing Interests: Declaration of competing interest The authors declare that there are no conflicts of interest., (Copyright © 2023 Elsevier B.V. All rights reserved.)

A portable paper-based microfluidic aptasensor is established to simultaneously and visually detect zearalenone (ZEN) and ochratoxin A (OTA). The targets at the sample zone can migrate to two detection zones through dual-channels and result in green and blue fluorescence recovery. This is due to the specific recognition by a respective aptamer that destroys fluorescence resonance energy transfer (FRET) from dual-color upconversion nanoparticles (UCNPs) to Cu-TCPP nanosheets. By capturing fluorescent images and analyzing the corresponding RGB value via a smartphone, ZEN and OTA can be analyzed with limits of detection down to 0.44 ng/mL and 0.098 ng/mL in the linear ranges of 0.5-100 ng/mL and 0.1-50 ng/mL, respectively. Satisfactory recoveries are also obtained for ZEN (94.5-103.7 %) and OTA (92.2-106.8 %) in corn flour. With the advantages of simple operation, low sample consumption, and broad adaptability, this promising platform allows for the on-site detection of multiple hazards in food., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier Ltd.)

The rapid and sensitive detection of heavy metal ions is important for environment and human health. Hence, the rapid and sensitive detection of multiple heavy metals simultaneously has become a critical issue. Here, we propose a method based on laser-induced breakdown spectroscopy (LIBS) combined with filter paper modified with PtAg bimetallic nanoparticles (BNPs) (LIBS-FP-PtAgBNPs) for the ultrasensitive detection of Hg 2+ , Cr 3+ , and Pb 2+ . The PtAgBNPs-modified filter paper was used to efficiently and specifically adsorb Hg, Cr, and Pb, and LIBS was used to detect the Hg, Cr, and Pb simultaneously. The limits of detection for Hg, Cr, and Pb were 0.5 μg/L (2.5 nM), 8 μg/L (0.15 μM), and 2 μg/L (9 nM), respectively. Furthermore, this method was successfully applied to determine the concentrations of Hg, Cr, and Pb in real spiked water samples. Compared with other methods based on nanoparticle sensing, LIBS-FP-PtAgBNPs is simpler to use and can achieve highly efficient enrichment, rapid separation, and sensitive detection of heavy metal ions. The optimal detections of Hg, Cr, and Pb were achieved in the pH range of 1-6. The developed method provides a new avenue to realize the rapid and sensitive detection of trace heavy metals in the environment., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Bacterial infection has become one of the major threats to human health all over the world, and the development and application of antibacterial materials has drawn great attention. Based on the Schiff-base structure, ZnONPs@ACFs are obtained by loading zinc oxide nanoparticles (ZnONPs) on amino cellulose fibers (ACFs) in-situ through the coordination of amino groups with metal ions. The results of FT-IR, XRD and UV-vis demonstrate that ZnONPs are successfully loaded and uniformly dispersed on ACF surface, and the ACFs maintain intact morphology observed by SEM. Furthermore, the zero-span tensile strength of ZnONPs@ACFs is 66.48 N/cm (ROL: 24.98 N/cm/s) under the optimum conditions, which indicates that ZnONPs@ACFs have a certain strength and can be used to make antibacterial sheet materials via paper-making wet-forming process. Accordingly, the ZnONPs@ACF composites show inhibition zones of 4.95 mm and 1.10 mm against E. coli and S. aureus, respectively. The new cellulose-based antibacterial materials demonstrate potential applications in the field of food packaging and biological medicine etc., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

Nanocelluloses, such as cellulose nanofibers and nanocrystals, are sustainable nanomaterials that are generally extracted from natural raw materials in a top-down manner. These nanomaterials and their assemblies are facilitating new applications of biopolymers. However, creating nanostructures from conventional cellulosic materials including paper and cloth remains challenging. Herein, we report an approach for bottom-up nanostructuring of conventional microfibrous cellulose materials via a molecular self-assembly strategy. As a precursor cellulose material, paper was allowed to swell with aqueous phosphoric acid for the partial dissolution and hydrolysis of cellulose while maintaining its microfibrous structure. The generated cello-oligosaccharides in a dissolved state started to self-assemble upon adding water as a coagulant, resulting in nanospike-like assemblies on the microfiber surfaces. The resultant nanospiked papers were found to serve as a precursor for synthesizing silver nanoparticle-cellulose composites with bactericidal activities. Our findings promote the development of cellulose-based functional materials with nanostructures designed via molecular self-assembly., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Plastic pollution at the nanoscale continues to pose adverse effects on environmental sustainability and human health. However, the detection of nanoplastics (NPLs) remains challenging due to limitations in methodology and instrumentation. Herein, a "green approach" for surface-enhanced Raman spectroscopy (SERS) was exploited to detect polystyrene nanospheres (PSNSs) in water, employing untreated filter paper and a simple syringe-filtration set-up. This SERS protocol not only enabled the filtration of nano-sized PSNSs, which are smaller than the pore size of the ordinary filter paper, but also offered SERS enhancement by utilizing quasi-spherical-shaped silver nanoparticles (AgNPs) as the SERS-active substrate. The filtering of NPLs was accomplished by adding an aggregating agent to the nanoparticle mixture, which caused the aggregation of NPLs and AgNPs, resulting in a larger cluster and more hot spots for SERS detection. The optimal aggregating agent and its concentration, as well as the volume ratio between the AgNPs and NPLs, were also optimized. This SERS method successfully detected and quantified PSNSs of various sizes (i.e., 100, 300, 460, 600, and 800 nm) down to a limit of detection (LOD) of about 0.31 μg mL−1. The method was also validated against the presence of several interferents (i.e., salts, sugars, amino acids, and surfactants) and was proven practical, as evidenced by the detection of 800nm PSNSs in drinking and tap water (LODs of 1.47 and 1.55 μg mL−1, respectively). [ABSTRACT FROM AUTHOR]

China, a big paper-making country, produced hundreds of millions of tons of waste paper which contain a lot of fiber every year. Cellulose nanocrystals were extracted from recycled waste paper which can be a high value utilization of secondary fiber. In this paper, cellulose nanocrystals were successfully extracted from waste paper fibers via two different systems, sulfuric acid hydrolysis (SCNCs) and one-step ammonium persulfate (APS) oxidation (OCNCs). This not only broadened the methods of extracting CNCs from waste paper, but also improved the dispersion and reactivity of CNCs. The CNCs products were investigated by FT-IR spectroscopy for functional group structure, X-ray diffraction for crystal structure, TG-DTG for thermal stability and scanning electron microscope, transmission electron microscope for morphology. The results showed that both OCNCs and SCNCs were a rod-like structure. The crystallinity of OCNCs and SCNCs increased to 72.45 and 77.56, but with a low yield of 22.42% and 41.22%, respectively. The result also suggested H 2 O 2 formed by decomposition of APS, selectively oxidized the hydroxyl on the C 6 in cellulose to carboxyl, introduced 0.57 mmol/g carboxyl. Successful preparation of CNCs extracted from waste paper can effectively utilize the fiber resources in waste paper, thus transforming into higher economic benefits., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Globally, rapid development of antibiotic resistance amongst pathogens has led to limited treatment options and high indirect costs to health management. There is a need to avoid misuse of available antibiotics and to develop rapid, affordable and accessible diagnostic technologies to detect drug resistance even in resource limited settings. This study reports the development of instrument-free point-of-care devices for detection of antibiotic resistance for rapid diagnosis of drug resistance in the penicillin, cephalosporin and carbapenem groups of antibiotics. The simple paper-based devices for flow through assay determine the presence of resistant bacteria in a sample by a visible colour change within 30 minutes. At the center of this technology is the unique sensing nanomaterial comprising of core-shell nanoparticles layered with specific antibiotics. The core is comprised of chitosan nanoparticles of size ∼15 nm coated with the starch-iodine indicator to form a shell increasing the size to ∼47 nm. The test strip is coated with the nanoparticles, air-dried and overlayed with the required antibiotic. In the presence of penicillin, cephalosporin and carbapenem resistant bacteria, the core-shell nanoparticles undergo a visible colour change from blue to white. The core-shell nanoparticles were deposited on paper to form a point-of-care device. Devices were developed to screen for three main classes of antibiotics namely penicillins, cephalosporins and carbapenems. The devices were validated using standard resistant and susceptible ATCC strains in three different sample types, pure colony, broth culture and saline suspensions. The change of colour from blue to white was considered a positive test. The time of detection was found to be 30 min, while the limit of detection was 10 5 cfu ml -1 . The device exhibited 100% sensitivity and specificity with known resistant and susceptible cultures not only from pure colonies but also from direct samples of spiked saline suspensions with graded confounding factors of albumin, glucose, and urea. The inter-device reproducibility and storage stability of the devices was established. The developed point-of-care devices have potential as screening devices for antimicrobial resistance.

Lots of beetles, moths, and birds in the natural world present stunning unique structural colors as well as excellent hydrophobic performances. Herein, a novel bioinspired variable structural-color film with organic-solvent responsiveness and surface hydrophobicity was fabricated. Cellulose nanocrystals (CNCs) provided structural color with left-handed helicity. PEG-PPG-PEG triblock copolymers (PPPTCs) were blended with CNCs, giving rise to the organic-solvent-responsive structural color and wider red-shift window of the reflectance peak. The color of the film could be regulated repeatedly under the stimulus of cyclohexanone with an obvious red shift up to 107 nm, corresponding to a macroscopic color change from blue to yellow. Low-surface-energy compound hexadecyltrimethoxysilane (HDTMS) was covalently grafted on the surface in a one-step method to introduce hydrophobicity, successfully preventing the effect of water on the ordered nanostructure. Based on the bionics principle, the as-prepared CNC/PPPTC nanocomposite films with variable structural colors and hydrophobicity are beneficial to their prospective applications in display screens, rewritable hydrophobic structural-color-changing paper, biomimetic sensors, and so forth.

Nanocellulose has received enormous scientific interest for its abundance, easy manufacturing, biodegradability, and low cost. Cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) are ideal candidates to replace plastic coating in the textile and paper industry. Thanks to their capacity to form an interconnected network kept together by hydrogen bonds, nanocelluloses perform an unprecedented strengthening action towards cellulose- and other fiber-based materials. Furthermore, nanocellulose use implies greener application procedures, such as deposition from water. The surface chemistry of nanocellulose plays a pivotal role in influencing the performance of the coating: tailored surface functionalization can introduce several properties, such as gas or grease barrier, hydrophobicity, antibacterial and anti-UV behavior. This review summarizes recent achievements in the use of nanocellulose for paper and textile coating, evidencing critical aspects of coating performances related to deposition technique, nanocellulose morphology, and surface functionalization. Furthermore, beyond focusing on the aspects strictly related to large-scale coating applications for paper and textile industries, this review includes recent achievements in the use of nanocellulose coating for the safeguarding of Cultural Heritage, an extremely noble and interesting emerging application of nanocellulose, focusing on consolidation of historical paper and archaeological textile. Finally, nanocellulose use in electronic devices as an electrode modifier is highlighted., (© 2022 The Authors. ChemPlusChem published by Wiley-VCH GmbH.)

Herein, novel fluorescein mono-acrylate (Flu-Ac) was synthesized and copolymerized with methyl methacrylate and glycidyl methacrylate to produce epoxy-functionalized latex nanoparticles. Fluorescent cellulose paper was then obtained by dip-coating and subsequent heat treatment. Synthesis of Flu-Ac, its incorporation efficiency into the epoxy-functionalized nanoparticles (almost 92 %), spherical morphology of the particles and their sizes (89-93 nm), and optical properties were studied comprehensively. SEM micrographs showed effective wetting of the cellulose fibers with uniform diffusion and deposition of the prepared functional nanoparticles through the establishment of physical and chemical interactions. Visual and spectroscopic emission intensity of the impregnated cellulose paper (λ max of 529 nm) were enhanced by increasing pH of the solution (from 2 to14) as a consequence of the transformation of cationic fluorescein to its neutral and anionic form. These observations depicted that such fluorescent cellulose substrates could be exploited in reusable indicators with good ability for sensing pH of solutions with diverse acidity or basicity., Competing Interests: Declaration of competing interest There is no conflict of interest to declare with this work., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The rapid development of and the large market for medical diagnostics necessitate point-of-care testing (POCT) with superior sensitivity, miniaturization, multiple functionalities and high integration. Thus, flexible substrates with complex structures that provide multiple functions are in demand. Herein, we present multistructured pseudo-papers (MSPs) as a platform for building flexible microfluidics. Flexible and freestanding MSPs are generated by the self-assembly of colloidal silica crystals or core-shell copolymer elastic colloidal crystals on microcavity PDMS molds to form photonic crystals (PCs). Nitrocellulose (NC) multistructured pseudo-papers (NC MSPs) were obtained by etching SiO 2 PCs after NC precursor infiltration, while elastic copolymer (EC) multistructured pseudo-papers (EC MSPs) were directly peeled off the mold; both types of freestanding MSPs have ordered micropillars and nanocrystal structures and presented unique properties such as pumpless liquid transport and fluorescence and chemiluminescence (CL) enhancement. MSPs with designed patterns were fabricated by patterned PDMS molds, and complicated microfluidic chips were used to generate MSPs by utilizing these patterns as liquid channels. The MSPs were used for fabricating microfluidic sensors for human cardiac marker and cancer marker sensing; the features of these bioinspired MSPs indicate their potential for sensitive sensing, which will enable them to find broader applications in many fields.

Up-converting nanoparticles can be a demand for requirements in many areas, including bioimaging and conversion of energy, but also in the battle against counterfeiting. The properties of lanthanide ions make falsification difficult or even impossible using appropriately designed systems. The proposition of such an approach is the NaErF 4 :Tm 3+ @NaYF 4 core@shell up-converting nanoparticles combined with transparent varnishes. Given the spectroscopic properties of Er 3+ ions present in the fluoride matrix, the obtained up-converting nanoparticles absorb light by 808 and 975 nm wavelengths. The intentionally co-doped Tm 3+ ions enable tuning characteristic green Er 3+ emission to red luminescence, particularly desirable in anti-counterfeiting applications. The article includes a thorough analysis of structural and morphological properties. Moreover, this work shows that exclusive luminescent properties of NaErF 4 :Tm 3+ @NaYF 4 NPs can be given to the transparent varnish, providing an excellent anti-counterfeiting system, revealing red emission under two different excitation wavelengths., (© 2022. The Author(s).)

We outline the fabrication of a highly sensitive biosensor for phytic acid (PA) determination using the extract of rice sprout and SBA@DABCO nanoparticles. The nanoparticles were first added to the surface of small paper disks. After drying, the extract of rice sprout in phosphate buffered saline was immobilized on the paper disks. FT-IR spectroscopy, XRD, and SEM were employed for the characterization of the nanoparticles. The assembly process of the modified paper disks on top of graphite screen-printed electrodes was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. PA measurements were performed by differential pulse voltammetry (DPV) with a small amount of sample (7 μL) for analysis. The cooperation of the rice sprout extract and the nanostructure of this biosensor led to the selective and sensitive electrochemical determination of PA. The limit of detection (S/N = 3) and linear dynamic range for PA determination by DPV were obtained at 0.04 μM and 0.1-10.0 μM, respectively. The biosensor showed excellent sensitivity for the determination of PA in real samples such as biscuits and wheat flour.

A molecularly imprinted paper-based analytical device (MIP-μPAD) was developed for the sensing of bisphenol A (BPA). The platform was screen-printed onto a filter paper support, where the electrodes and the fluorescence μPADs were designed. Owing to its dual electrochemical and fluorescence responses, molecularly imprinted curcumin nanoparticles were used to sense BPA. The μPAD design was characterized by transmission electron microscopy, scanning electron microscopy, fluorescence spectroscopy, and electrochemical techniques. The sensor design comprised a wide linear range from 1 to 200 μg L -1 with limits of detection of 0.47 ± 0.2 and 0.62 ± 0.3 μg L -1 (LOD, S/N = 3) for electrochemical and fluorescence sensing, respectively. Furthermore, the system showed good analytical performance such as selectivity, stability, and reproducibility. The feasibility of the MIP-μPAD was demonstrated for the sensing of BPA in seawater, foods, and polycarbonate plastic packaged water with recovery values of 97.2 and 101.8%.

The fabrication of fully ink-drawn fluidic electrochemical paper-based analytical devices (ePADs) is reported for the determination of trace Pb(II) and Cd(II) by differential pulse anodic stripping voltammetry (DPASV). The fluidic pattern was formed on the paper substrate using an inexpensive computer-controlled x-y plotter and a commercial hydrophobic marker pen. Then, electrodes were deposited on the devices using a second x-y plotting step with a commercial technical pen filled with a graphite-based conductive ink prepared in house. The fabrication parameters of the ePADs were studied by cyclic voltammetry using the ferro/ferri couple as a probe and by scanning electron microscopy. The ePADs, featuring a bismuth nanoparticle-modified working electrode, were applied to the determination of Pb(II) and Cd(II) by DPASV. The chemical and instrumental conditions were studied. The limits of detection were 3.1 μg L -1 for Cd(II) and 4.5 μg L -1 for Pb(II) whereas the between-device reproducibility (expressed as the % relative standard deviation of the response at 6 different ePADs) was < 14%. Each ePAD requires 120 s to fabricate and costs less than 0.15 € in terms of consumables. The ePADs are suitable for the on-site determination of Pb(II) and Cd(II) in environmental and food samples., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Preservation of paper-based historical artifacts against deterioration due to the presence of bacteria and fungi colonies has been one of the major issues for the importance of protecting the cultural heritage of humankind. Advances in nanotechnology have enabled the implementation of nanomaterials for this purpose. In this work, calcium/chitosan nanoparticles (Ca/CS NPs) were prepared and well-characterized to investigate their potential as a novel approach for preserving paper-based documents. Following the fundamental characterizations, it was found that Ca/CS NPs are spherical nanoparticles with ~65 nm average size and homogenous dispersion (PdI: 0.2). Besides, minimum inhibition concentration results revealed that Ca/CS NPs show a superior antimicrobial effect against specific bacteria and fungi strains commonly found on paper documents compared to the effect of bare chitosan nanoparticles (CS NPs). After the deposition of Ca/CS NPs onto the paper the pH level was increased and stabilized, and only a limited amount of microbial colony formation was observed for up to 20 days. Moreover, molecular docking analysis provided a better insight into the antibacterial and antifungal activities of these nanoparticles. The antimicrobial activity of CS NPs and Ca/CS NPs was investigated through their interactions with E. coli DNA gyrase B and C. albicans dihydrofolate reductase. The binding modes and all possible interactions of active sites were confirmed by in silico molecular docking method. Collectively, our findings revealed that the formulated Ca/CS NPs are promising candidates for preserving paper documents., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Chiral nematic papers (CNPs) with mesopores structure based on cellulose nanocrystals (CNCs) were fabricated successfully via a swelling and freeze-drying method. The order of the original chiral nematic cellulose nanocrystals film was preserved in CNPs, which was proved by scanning electron microscopy (SEM), polarized optical microscopy (POM) measurements and circular dichroism (CD) spectra. The CNPs exhibited excellent optical responsive properties to different solvents. Inspired by this feature, a colorable ink containing amounts of gel particles was prepared by pulverizing CNPs/water mixture into a suspension. Patterns written in suspension ink with various colors can be formed when soaked with different solvents. Moreover, CNPs displayed an irreversible color response to compression. Additionally, the hydrophilicity of CNPs was tuned by polyethyleneimine. Modified CNPs exhibited different colors under the identical solvent environment when compared to the original one. Aqueous PEI can be used as an ink to depict responsive photonic patterns on CNPs., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

We report results of the studies relating to the fabrication of a label-free, flexible, light weight and disposable conducting paper based immunosensing platform comprising of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and nanostructured iron oxide (nFe 2 O 3 @PEDOT:PSS) nanocomposite for detection of carcinoembryonic antigen (CEA), a cancer biomarker. The effect of various solvents such as sorbitol, ethanol, propanol, n-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO) on the electrical conductivity of Whatman filter paper (WP) modified with nFe 2 O 3 @PEDOT:PSS/WP was investigated. The electrical conductivity of the PEDOT:PSS/WP electrode was found to be enhanced by two orders of magnitude (from 6.8× 10 -4 to 1.92 × 10 -2 Scm -1 ) after its treatment with DMSO. Further, nFe 2 O 3 doped PEDOT:PSS/WP electrode exhibited the electrical conductivity as 2.4 × 10 -2 Scm -1 . Besides this, the incorporation of iron oxide nanoparticles (nFe 2 O 3 ) into PEDOT:PSS/WP resulted in improved electrochemical performance and signal stability. This nFe 2 O 3 @PEDOT:PSS/WP based platform was used for immobilization of the anti-carcinoembronic antigen (anti-CEA) protein for quantitative estimation of cancer biomarker (CEA). The results of electrochemical response studies revealed that this conducting paper based immunoelectrode had a sensitivity of 10.2 μAng -1 mLcm -2 in the physiological range (4-25 ngmL -1 ) and shelf life of 34 days. Further, the proposed immunoelectrode was validated with conventional ELISA for the detection of CEA in serum samples of cancer patients., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Paper-based sensors and assays have been highly attractive for numerous biological applications, including rapid diagnostics and assays for disease detection, food safety, and clinical care. In particular, the paper immunoassay has helped drive many applications in global health due to its low cost and simplicity of operation. This review is aimed at examining the fundamentals of the technology, as well as different implementations of paper-based assays and discuss novel strategies for improving their sensitivity, performance, or enabling new capabilities. These innovations can be categorized into using unique nanoparticle materials and structures for detection via different techniques, novel biological species for recognizing biomarkers, or innovative device design and/or architecture.

Filtration is a promising water treatment method to purify drinking water. To develop highly efficient drinking water filter paper, water-resistant cellulose foam paper with a high wet strength property was fabricated using diverse metal oxide (e.g., copper oxide (CuO), zinc oxide (ZnO), and silver oxide (Ag 2 O)) nanoparticles. These nanoparticles were synthesized using the hydrothermal reaction method. Their morphological structures were studied using a field emission scanning electron microscope (FESEM). The presence of coated nanoparticles on the cellulose foam filter was verified by energy dispersive X-ray spectroscopy (EDX) methods. The antibacterial performance of different types of modified cellulose foam filters was studied against E. coli, P. aeruginosa, B. subtilis, and B. cereus strains using the zone of inhibition test. The antibacterial profile of the cellulose foam filter impregnated with Ag 2 O nanoparticles, when tested against different types of bacteria, exhibited higher antibacterial activity than the cellulose foam filter impregnated with ZnO and CuO nanoparticles., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Deacidification and surface self-cleaning are of great significance for the long-term preservation of historic literature. Herein, a superhydrophobic self-cleaning coating, derived from nanocellulose coated with CaCO 3 particles is constructed via chemical vapor deposition (CVD) for the first time for the preservation of historic paper. The static contact angle of superhydrophobic paper reached more than 150° and the minimum sliding angle was 6.4°. Deacidification effect was achieved with a desired pH value in the range from 7.50 to 7.77 and the maximum alkali storage was up to 1.235 mol/kg. It is found that the low-cost CaCO 3 nanoparticles can not only remove the acid substances, but also gave the paper function of self-cleaning, which is very great significant for the protection of paper-based relics., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Lanthanide coordination polymer nanoparticles (LML-Eu 3+ -GMP CPNPs) were fabricated as a ratiometric fluorescence sensor for real-time and visual assays of tetracycline (TC). The LML-Eu 3+ -GMP CPNPs were prepared by spontaneous self-assembly of Eu 3+ , luminol (LML) and guanosine 5'-monophosphate (GMP) at room temperature, which only emitted blue fluorescence dominated by LML, and no red characteristic fluorescence of Eu 3+ was observed. In the presence of TC, TC can trigger the antenna effect (AE) and inner filter effect (IFE), the blue fluorescence of LML-Eu 3+ -GMP CPNPs is quenched by TC via IFE, and the red characteristic fluorescence of Eu 3+ can be turned on through AE. When sodium citrate (Cit) is added to the sensing system, it can further enhance the red fluorescence of Eu 3+ . The dual-ligand CPNP sensor has a rapid fluorescence response, noticeable fluorescence color change, good selectivity, and high sensitivity with a detection limit of 3.4 nM. It was successfully applied to detect TC in honey, milk, lake water and tap water. Meanwhile, the portable smartphone and test paper were applied to develop POCT devices for real-time and visual detection of TC, which could offer a promising application for real-time and semiquantitative assays of TC., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Surging interests in point-of-care diagnostics have led to the development of many lightweight and cost-effective paper-based sensors. Particularly, sensors using colorimetric readouts are considered highly advantageous because no additional detector or device is required for signal display. Herein, we introduce an electrochemically operated colorimetric sensor that can compensate for the disadvantages of traditional colorimetry, hence enhancing response time, reusability and color uniformity. On a single paper substrate, carbon/graphite paste was screen printed to form the working and counter electrodes, and Ag/AgCl ink was applied for the reference electrode. Prussian blue and Glucose oxidase were employed on the one of the carbon electrodes for the detection of analytes, hydrogen peroxide and glucose. For the colorimetric readout, indium tin oxide nanoparticles and polyaniline were consecutively introduced on the other carbon electrode, which is used as the counter electrode. The color change of electrochromic polyaniline could be clearly observed, and its application as a colorimetric sensor was demonstrated by the quantitative analyses of hydrogen peroxide and glucose. This paper-based electrochromic glucose sensor showed a short response time of 30 s and exhibited a detection limit of 126 μM for glucose. Along with its rapid and easy detection by incorporating the merits of electrochemical sensing and colorimetry, the paper-based electrochromic sensor could potentially contribute to the development of point-of-care devices by combination with portable power sources., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Fluorescent nanoparticles are widely exploited as probes in cell tracking, drug delivery systems and high-performance security devices nowadays. Herein, we report the synthesis of novel 7-acryloxycoumarin (7-AC) through modification reaction of 7-hydroxycoumarin with acryloyl chloride and its copolymerization with methyl methacrylate and glycidyl methacrylate to produce epoxy-functionalized fluorescent polymer nanoparticles through emulsion polymerization. Chemical modification of cellulose pulp papers with the as-prepared fluorescent latex nanoparticles was also assessed. Spherical nanoparticles with average particle size of 40-93 nm and their diffusion into cellulosic fibers with excellent wetting and coating were monitored. Fluorimetery analysis demonstrated that immobilization of 7-AC into the hydrophobic acrylic copolymer substrate enhanced its emission intensity significantly with respect to its molecularly solution due to the elimination of unwanted environmental effects and non-radiative processes such as probable internal conversions. The obtained products exhibited intensified fluorescence emission with potentiality of being used in anticounterfeiting inks and security documents., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Point-of-care testing (POCT) devices represent a growing field that aims to develop low-cost, rapid, sensitive diagnostic testing platforms that are portable and self-contained. Surface-enhanced Raman spectroscopy (SERS) is an approach has shown high potential in POCT technology. However, the specificity or ability to uniquely detect a desired biomarker in complex biological samples is a key factor for translating SERS technologies to POCT. Herein, we fabricated cellulose SERS strips (CS) decorated with novel plasmonic nanoparticles, termed graphene-isolated-Au-nanocrystals (GIANs), for the portable detection of complex biological samples. This CS@GIANs SERS strip was used to detect free bilirubin (BR) in the blood of newborns, a biomarker of jaundice, without sample labeling or prepreparation. CS@GIANs showed superior affinity to hydrophobic BR molecules compared to typical SERS substrate, which reduced the steric hindrance effect from the nonspecific binding of BR with serum albumin in blood and improved sensitivity. Meanwhile, with the separation property of cellulose chromatography papers, CS@GIANs showed superior anti-interference to other biomolecules that had been previously adsorbed on the SERS strip. Moreover, the SERS signal from the graphitic shell of GIANs could be used as a stable internal calibration standard, which improved the reproducibility and accuracy of Raman analysis. Such a cellulose SERS strip holds high potential for enhancing current efforts in the development of rapid and low-cost point-of-care diagnostic testing.

In this Feature, the most recent developments as well as "pros and cons" in smartphone sensing, which have been developed using various functional nanoparticles in paper-based sensing systems, will be discussed. Additionally, smart phone sensing and POC combination as a potential tool that opens a gate for knowledge flow "from lab scale data to public use" will be evaluated.

The detection of drugs containing hydrochloric salt with conventional methods is time consuming and expensive. In this work, upon exposure to ciprofloxacin hydrochloride at different concentrations, the emission from CsPbBr 3 NCs shifts to the blue from 513 nm to 442 nm. CsPbBr (3- x ) Cl x NCs are formed by the ion exchange and substitution of Br - and Cl - ions from surface to core of NCs. The first-principles calculations suggest that the substitution of Br - by Cl - ions plays a critical role in the tuning of the energy bandgap. The color of paper test strips changes immediately after exposure to different Ciproxan solutions. We propose that this rapid and portable method has a high potential application in other chloride salts for food safety., (© 2022 IOP Publishing Ltd.)

The homeostatic control of Sodium (Na + ) ion in the human body assumes paramount relevance owing to its physiological importance. Any deviation from the normal level causes serious health problems like hypernatremia, hyponatremia, stroke, kidney problems etc. Therefore, quantification of Na + levels in body fluids has significant diagnostic and prognostic importance. However, interfering ions like Potassium ion (K + ) is the major hurdle in sodium detection. In this work, we synthesized the clusters of 3-9 nm-sized highly stable and pure Copper nanoparticles surface functionalised with curcumin, through chemical reduction method. Each cluster of particles is encapsulated in a curcumin layer which is clearly visible in TEM images. The results show that these curcumin functionalized Cu NPs (CuC) are highly selective to the colorimetric detection of Na + . The ions like K + , Mg 2+ and Zn 2+ did not interfere with the Na + in this sensing technique. Low-cost paper-based sensor strips are fabricated and calibrated for the sensing of sodium in the physiological range and shade cards were developed as a calorimetric guide for estimation of Na + which makes them ideal point of care diagnostic platform. We demonstrate that the proposed CuC paper strip can be used for detecting Na + concentration within the whole physiological range in both blood serum and urine., (© 2022. The Author(s).)

Many lanthanide ions-based probes have been widely used for detecting anthrax spores biomarker-dipicolinic acid (DPA). However, little work has realized detection of bacillus anthrax spores in real environmental samples. In this work, a novel ratiometric fluorescent nanoprobe based on europium (Eu)-doped silicon nanoparticles (Eu@SiNPs) was fabricated for the first time by one-pot method without post-modification for determination of the DPA in bacillus subtilis spores (simulant bacillus anthrax spores). Based on Eu(III) in the Eu@SiNPs could be sensitized by DPA to emit intrinsic fluorescence and the fluorescence intensity of SiNPs in the Eu@SiNPs almost remained stable, a new ratiometric fluorescent method for determination of micro DPA in bacillus subtilis spores and bacillus subtilis spores in real environmental samples, such as Yellow river water, tap water and soil was established. Under the optimum conditions, the limit of detection (LOD) of the method toward bacillus subtilis spores was as low as 2.38×10 4 spore/mL. Simple, fast and visual DPA and bacillus subtilis spores determination was also achieved by the Eu@SiNPs-based test paper. Therefore, the newly established method was expected to be a powerful tool for efficiently determination of bacillus anthrax spores to avoid anthrax threats., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier B.V. All rights reserved.)

We report the use of a laser-based fabrication process in the creation of paper-based flow-through filters that when combined with a traditional lateral flow immunoassay provide an alternative pathway for the detection of a pre-determined analyte over a wide concentration range. The laser-patterned approach was used to create polymeric structures that alter the porosity of the paper to produce porous flow-through filters, with controllable levels of porosity. When located on the top of the front end of a lateral flow immunoassay the flow-through filters were shown to block particles (of known sizes of 200 nm, 500 nm, 1000 nm and 3000 nm) that exceed the effective pore size of the filter while allowing smaller particles to flow through onto a lateral flow immunoassay. The analyte detection is based on the use of a size-exclusive filter that retains a complex (∼3 μm in size) formed by the binding of the target analyte with two antibodies each of which is tagged with different-sized labels (40 nm Au-nanoparticles and 3 μm latex beads), and which is larger than the effective pore size of the filter. This method was tested for the detection of C-reactive protein in a broad concentration range from 10 ng/ml to 100,000 ng/ml with a limit-of-detection found at 13 ng/ml and unlike other reported methods used for analyte detection, with this technique we are able to counter the Hook effect which is a limiting factor in many lateral flow immunoassays., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The advent of 3D printing technology has spurred innovation, particularly in healthcare and biosensing. One notable application is the creation of wearable biosensors for detecting substances like ketamine, a potent anesthetic and pain reliever with medical and recreational uses. Monitoring ketamine levels is crucial due to potential misuse and health risks. Utilizing 3D printing, manufacturers can produce intricate and customizable wearable biosensors designed for ketamine detection. This flexibility permits the incorporation of various sensor types, enhancing accuracy. Traditional detection methods are often cumbersome, making 3D printing a transformative tool for real-time monitoring. The application of 3D printing in wearable biosensors has the potential to revolutionize personalized healthcare, ensuring the safe and effective usage of ketamine. In this paper 3D printed paper-based wearable aptamer cassette (3DP-PWC) has been developed by immobilizing Ketamine Aptamer on ZnO-NPs electrodes. Electrochemical techniques such as cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were employed for validating results. The sensor’s versatility was demonstrated across beverages encompassing both alcoholic and non-alcoholic options. Two prototypes—a bracelet and a pendant—were developed and compared, showing promising results. Here, we reported a 3D-printing paper based wearable aptasensor for the ketamine detection. This pioneering developed sensor showed a low limit detection (LOD) of 0.01 μg/mL (lower than the physiological detection threshold 0.084 μg/mL) with linear-range was between 0.01 and 5 μmL and an optimal response time of 25 s.

Microorganisms such as bacteria, fungi, algae and moulds are highly proficient at colonizing artistic and architectural heritage. The irreparable damage they cause to unique artefacts results in immeasurable cultural and societal losses to our shared cultural heritage, which represent an important social and economic resource for Europe. With the overall aim of preventing fungal deterioration of paper artefacts, we report the use of magnesium oxide nanoparticles (MgO NPs) of average diameter 12 nm as potent antifungal agents against fungi commonly found colonising paper heritage: A. niger, C. cladosporioides and T. reesei. Dispersions of MgO NPs on original 18th century paper samples from the Archives of the Spanish Royal Botanic Garden were effective at preventing fungal colonisation without altering the appearance of the paper artefacts. Importantly, MgO NPs also inhibit cellulase activity in the filamentous fungi T. resei and A. niger, two of the principle biodeteriogens of cellulosic materials. In addition, our report provides three simple new procedures for studying the fungal colonisation prevention properties of nanomaterials on paper samples. Overall this opens the door to the use of colourless, low-cost, and scalable nanomaterials for preventing biodeterioration in cellulose-based artefacts.