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IntroductionThis systematic review and meta-analysis present a comprehensive evaluation of paper-based microfluidic devices, focusing on their applications in immunoassays. These devices are emerging as innovative solutions to democratize access to diagnostic technologies, especially in resource-limited settings. Our review consolidates findings from diverse studies to outline advancements in paper-based microfluidic technology, including design intricacies and operational efficacy. Key advantages such as low cost, portability, and ease of use are highlighted.Materials and MethodsThe review categorizes literature based on the design and operational nuances of these diagnostic tools, exploring various methodologies, fabrication techniques, detection methods, and applications, particularly in protein science. The meta-analysis extends to the diverse applications of these technologies, providing a framework for classifying and stratifying their uses in diagnostics.Results and discussionNotable findings include a critical analysis of performance metrics, such as sensitivity and specificity. The review addresses challenges, including the need for further validation and optimization for broader clinical applications. A critical discussion on the validation processes, including cross-validation and rigorous control testing, is provided to ensure the robustness of microfluidic devices. This study offers novel insights into the computational strategies underpinning these technologies and serves as a comprehensive roadmap for future research, potentially broadening the impact across the protein science universe.

Tuberculosis (TB) poses a serious threat to human health and social development. Accurate diagnosis of mycobacterium tuberculosis infection plays a critical role in the prevention and treatment of tuberculosis. Interferon-γ (INF-γ) release assay (IGRA) is currently the only quantitative tuberculosis infection diagnosis method. An accurate, fast, and easily handled INF-γ detection method is the key to obtaining accurate results. Herein, we report a novel paper-based electrochemiluminescence (ECL) method based on lateral flow immunosensors that combines the easy handling characteristics of immunochromatography and the high sensitivity of electrochemiluminescence to detect IFN-γ. To our knowledge this is the first INF-γ detection method that combines immunochromatography with electrochemiluminescence. The paper-based ECL-LFI test consists of a sample pad, conjugation pad (with binding antibody IFN-γ-Ab1 conjugated with ruthenium tripyridine), detection pad (with capture antibody IFN-γ-Ab2 immobilized on nanospheres), absorbent pad, and electrode for signal activation. The ECL signal is obtained by cyclic voltammetry scanning at a speed of 0.1 V/s in the detection area of the paper-based ECL-LFI test. In our experiments, the paper-based ECL-LFI test exhibited a minimum detection limit of 2.57 pg/mL within 12 min, and a broad detection range of 2.57–5,000 pg/mL, with repeatability of 8.10% and stability of 4.97%. With the advantage of high accuracy and sensitivity, easy handling, and low user training requirements, this ECL-LFI test might be used as point-of-care testing (POCT) in the IGRA for tuberculosis diagnosis.

A new generation of rapid, easy to use and robust colorimetric point of care (POC) nanocellulose coated-paper sensors to measure glucose concentration in blood is presented in this study. The cellulose gel containing the enzyme with co-additive is coated and dried onto a paper substrate. Nanocellulose gel is used to store, immobilize and stabilize enzymes within its structure to prolong enzyme function and enhance its availability. Here, we immobilize glucose oxidase within the gel structure to produce a simple colorimetric blood glucose sensor. Increase in blood glucose concentration increases the concentration of reaction product which decreases the system pH detected by the pH indicative dye entrapped in the nanocellulose gel. The sensor produces a color change from red to orange as pH decreases due to the enzymatic reaction of glucose into gluconic acid and hydrogen peroxide. This sensor can measure glucose concentrations of 7–13 mM (medical range for diabetes control) at temperatures of 4°C–40°C. Stability tests confirm that no denaturation of enzyme occurs by measuring enzyme activity after 4 weeks. A prototype device is designed to instantly measure the glucose concentration from blood in a two steps process: 1) red blood cell separation and 2) quantification of glucose by color change. This study demonstrates nanocellulose sensor as an economical, robust, and sensitive diagnostic technology platform for a broad spectrum of diseases.

Cellulomonas biazotea, a Gram-positive cellulolytic bacterium isolated from soil, is capable of producing a complete cellulase complex exhibiting endoglucanase, exoglucanase, and cellobiase activities. Despite the presence of a full complement of all three types of cellulases, samples prepared from both cell lysates and culture media of C. biazotea showed only weak synergistic activities formed among the cellulase components, as reflected by their inefficient performance in filter paper hydrolysis. However, when the five previously characterized recombinant cellobiases of C. biazotea were mixed individually or in different combinations with recombinant enzyme preparations (CenA/Cex) containing an endoglucanase, CenA, and an exoglucanase, Cex, of another Cellulomonas species, C. fimi, the cellulase cocktails exhibited not only much higher but also synergistic activities in filter paper hydrolysis. Among the 5 C. biazotea cellobiases studied, Cba2 was shown to perform 2.8 to 3.8 times better than other homologous isozymes when acting individually with CenA/Cex. More noteworthy is that when Cba2 and Cba4 were added together to the reaction mixture, an even better synergistic effect was achieved. The filter paper activities resulting from Cba2 and Cba4 interacting with CenA/Cex are comparable to those obtained from some commercial fungal cellulase mixtures. To our knowledge, our results represent the first demonstration of synergistic effects on filter paper hydrolysis achieved using recombinant bacterial cellulases.

Greenly synthesized silver nanoparticles (AgNPs) on different cellulosic materials show tremendous potential for colorful, biocidal, and reasonably strong products by replacing the traditional chemical-based synthesis protocols. This study reports on a novel in situ synthesis protocol for synthesizing green and sustainable AgNPs over cellulosic kraft paper substrates using a bio-based stabilizing agent (Cephalotaxus harringtonia fruit extract). The protocol could play a significant role in packaging industries. The aqueous extracts of Cephalotaxus harringtonia fruits have been used to synthesize the metallic silver. The deposited AgNPs values were investigated through XRF (X-ray fluorescence) analysis. The number of deposited nanoparticles (NPs) was 268 ± 7, 805 ± 14, and 1,045 ± 16 PPM, respectively for 0.5, 1.5, and 2.5 mm silver precursors. The developed products were tested with SEM (scanning electron microscopy), SEM-mediated elemental mapping, EDX (energy disruptive X-ray), FTIR (Fourier transform infrared spectroscopy), and XRD (X-Ray diffraction). XRD analysis further confirmed the presence of peaks for elemental AgNP on the deposited papers. Colorimetric values were measured to confirm the colorful appearances of the developed metallic silvers. Mechanical properties were tested in terms of the tensile index and bursting index. Moreover, the statistical analysis of coefficient of variations (R2) and a post-hoc ANOVA test that adopted the Newman-Keul methodology also confirm the significance of developed nanoparticles in the papers. The shielding capacity against UV light was also investigated; all the AgNPs-treated products provided values higher than 40, demonstrating the strong UV resistance capability of the kraft paper material. Overall, the study confirms a successful development of green AgNPs on paper materials.

A key challenge in chemicals biomanufacturing is the maintenance of stable, highly productive microbial strains to enable cost-effective fermentation at scale. A “cookie-cutter” approach to microbial engineering is often used to optimize host stability and productivity. This can involve identifying potential limitations in strain characteristics followed by attempts to systematically optimize production strains by targeted engineering. Such targeted approaches however do not always lead to the desired traits. Here, we demonstrate both ‘hit and miss’ outcomes of targeted approaches in attempts to generate a stable Escherichia coli strain for the bioproduction of the monoterpenoid linalool, a fragrance molecule of industrial interest. First, we stabilized linalool production strains by eliminating repetitive sequences responsible for excision of pathway components in plasmid constructs that encode the pathway for linalool production. These optimized pathway constructs were then integrated within the genome of E. coli in three parts to eliminate a need for antibiotics to maintain linalool production. Additional strategies were also employed including: reduction in cytotoxicity of linalool by adaptive laboratory evolution and modification or homologous gene replacement of key bottleneck enzymes GPPS/LinS. Our study highlights that a major factor influencing linalool titres in E. coli is the stability of the genetic construct against excision or similar recombination events. Other factors, such as decreasing linalool cytotoxicity and changing pathway genes, did not lead to improvements in the stability or titres obtained. With the objective of reducing fermentation costs at scale, the use of minimal base medium containing paper mill wastewater secondary paper fiber as sole carbon source was also investigated. This involved simultaneous saccharification and fermentation using either supplemental cellulase blends or by co-expressing secretable cellulases in E. coli containing the stabilized linalool production pathway. Combined, this study has demonstrated a stable method for linalool production using an abundant and low-cost feedstock and improved production strains, providing an important proof-of-concept for chemicals production from paper mill waste streams. For scaled production, optimization will be required, using more holistic approaches that involve further rounds of microbial engineering and fermentation process development.

Exosomes, nanovesicles derived from cells, contain a variety of biomolecules that can be considered biomarkers for disease diagnosis, including microRNAs (miRNAs). Given knowledge and demand, inexpensive, robust, and easy-to-use tools that are compatible with downstream nucleic acid detection should be developed to replace traditional methodologies for point-of-care testing (POCT) applications. This study deploys a paper-based extraction kit for exosome and exosomal miRNA analytical system with some quantifying methods to serve as an easy sample preparation for a possible POCT process. Exosomes concentrated from HCT116 cell cultures were arrested on paper-based immunoaffinity devices, which were produced by immobilizing anti-CD63 antibodies on Whatman filter paper, before being subjected to paper-based silica devices for nucleic acids to be trapped by silica nanoparticles adsorbed onto Whatman filter paper. Concentrations of captured exosomes were quantified by enzyme-linked immunosorbent assay (ELISA), demonstrating that paper-based immunoaffinity devices succeeded in capturing and determining exosome levels from cells cultured in both neutral and acidic microenvironments, whereas microRNA 21 (miR-21), a biomarker for various types of cancers and among the nucleic acids absorbed onto the silica devices, was determined by reverse transcription quantitative polymerase chain reaction (RT-qPCR) to prove that paper-based silica devices were capable of trapping exosomal nucleic acids. The developed paper-based kit and the devised procedure was successfully exploited to isolate exosomes and exosomal nucleic acids from different biological samples (platelet-poor plasma and lesion fluid) as clinical applications.

The COVID-19 pandemic has resulted in significant global social and economic disruption. The highly transmissive nature of the disease makes rapid and reliable detection critically important. Point-of-care (POC) tests involve performing diagnostic tests outside of a laboratory that produce a rapid and reliable result. It therefore allows the diagnostics of diseases at or near the patient site. Paper-based POC tests have been gaining interest in recent years as they allow rapid, low-cost detection without the need for external instruments. In this review, we focus on the development of paper-based POC devices for the detection of SARS-CoV-2. The review first introduces the principles of detection methods that are available to paper-based devices. It then summarizes the state-of-the-art paper devices and their analytical performances. The advantages and drawbacks among methods are also discussed. Finally, limitations of the existing devices are discussed, and prospects are given with the hope to identify research opportunities and directions in the field. We hope this review will be helpful for researchers to develop a clinically useful and economically efficient paper-based platform that can be used for rapid, accurate on-site diagnosis to aid in identifying acute infections and eventually contain the COVID-19 pandemic.

Influenza virus infection is a major worldwide public health problem. Influenza virus infections are associated with a high hospitalization rate in children between the ages of 5 and 14. The predominant reason for poor influenza prognosis is the lack of any effective means for early diagnosis. Early diagnosis of severe illness is critical to improving patient outcome, and could be especially useful in areas with limited medical resources. Accurate, inexpensive, and easy-to-use diagnostic tools could improve early diagnosis and patient outcome, and reduce overall healthcare costs. We developed an interleukin-6 paper-based test strip that used colloidal gold-conjugated antibodies to detect human interleukin-6 protein. These complexes were captured on a paper-based test strip patterned with perpendicular T lines that were pre-coated with anti-human interleukin-6 antibodies. Applied serum samples interacted with these antibodies and presented as colored bands that could be read using a spectrum-based optical reader. The full-spectrum of the reflected light interleukin-6 protein signal could be obtained from the spectral optics module, and the standard could be used to quantitatively analyze interleukin 6 level in serum. We retrospectively evaluated 10 children (23 serum samples) with severe influenza virus infections, 26 children (26 serum samples) with mild influenza virus infections, and 10 healthy children (10 serum samples). Our system, the combined use of a paper-based test strip and a spectrum-based optical reader, provided both qualitative and quantitative information. When used with the optical reader, the detection limit was improved from a qualitative, naked-eye level of 400 pg/ml to a quantitative, optical reader level of 76.85 pg/ml. After monitoring serum interleukin-6 level via our system, we found a high correlation between our system results and those obtainable using a conventional sandwich enzyme-linked immunosorbent assay method (Rho = 0.706, p < 0.001). The sensitivity and specificity for differentiating between severe and mild influenza using our combined method (test strip coupled with optical reader) were 78.3 and 50.0%, respectively. When interleukin-6 was combined with serum C-reaction protein, the sensitivity and specificity were 85.7 and 95.5%, and the receiver operating characteristic area-under-the-curve was quite high (AUC = 0.911, p < 0.001). The potential advantages of our system, i.e., a paper-based test strip coupled with a spectrum-based optical reader, are as follows: 1) simple user operation; 2) rapid turnaround times–within 20 min; 3) high detection performance; and, 4) low-cost fabrication.

The effective and cheap production of platform chemicals is a crucial step towards the transition to a bio-based economy. In this work, biotechnological methods using sustainable, cheap, and readily available raw materials bring bio-economy and industrial microbiology together: Microbial production of two platform chemicals is demonstrated [lactic (LA) and succinic acid (SA)] from a non-expensive side stream of pulp and paper industry (fibre sludge) proposing a sustainable way to valorize it towards economically important monomers for bioplastics formation. This work showed a promising new route for their microbial production which can pave the way for new market expectations within the circular economy principles. Fibre sludge was enzymatically hydrolysed for 72 h to generate a glucose rich hydrolysate (100 g·L−1 glucose content) to serve as fermentation medium for Bacillus coagulans A 541, A162 strains and Actinobacillus succinogenis B1, as well as Basfia succiniciproducens B2. All microorganisms were investigated in batch fermentations, showing the ability to produce either lactic or succinic acid, respectively. The highest yield and productivities for lactic production were 0.99 g·g−1 and 3.75 g·L−1·h−1 whereas the succinic acid production stabilized at 0.77 g·g−1 and 1.16 g·L−1·h−1.

Monitoring ferroptosis-related miRNAs is crucial for the treatment and prognosis of patients with intracerebral hemorrhage. In this work, a novel hydrophobic paper (h-paper)-based plasmonic substrate was produced by dropping DS Au nanorods with a narrow range of sizes and morphologies onto h-paper. Raman reporter molecules were adsorbed to the array surface, and surface-enhanced Raman scattering spectra at randomly selected points reveal uniform and significant SERS enhancement. Hairpin DNAs labelled with Raman reporters and hybridized with placeholder DNAs were decorated on SERS substrate to fabricate SERS biosensor. Target miRNAs initiated the “inverse Molecular Sentinel” process. During the process, PHs were removed and the conformation of HPs changed toward the hairpin structure, thus eliciting the proximity of Raman reporter to substrate and a stronger SERS signal. The proposed SERS biosensor performs well in terms of stability, reproducibility, and selectivity. The limits of detection of miR-122-5p and miR-140-5p in serum were 4.17 aM and 4.49 aM, respectively. Finally, the fabricated SERS biosensor was applied to detect miR-122-5p and miR-140-5p in ICH patients and healthy subjects, and the results obtained by SERS were consistent with the results from quantitative real-time polymerase chain reaction, revealing the accuracy of the method. This simple, rapid approach offers great potential for the simultaneous detection of miRNAs in practical clinical applications.

Synthetic organic compounds (SOCs) are reported as xenobiotics compounds contaminating the environment from various sources including waste from the pulp and paper industries: Since the demand and production of paper is growing increasingly, the release of paper and pulp industrial waste consisting of SOCs is also increasing the SOCs’ pollution in natural reservoirs to create environmental pollution. In pulp and paper industries, the SOCs viz. phenol compounds, furans, dioxins, benzene compounds etc. are produced during bleaching phase of pulp treatment and they are principal components of industrial discharge. This review gives an overview of various biotechnological interventions for paper mill waste effluent management and elimination strategies. Further, the review also gives the insight overview of various ways to restrict SOCs release in natural reservoirs, its limitations and integrated approaches for SOCs bioremediation using engineered microbial approaches. Furthermore, it gives a brief overview of the sustainable remediation of SOCs via genetically modified biological agents, including bioengineering system innovation at industry level before waste discharge.

Xylanases have the potential to be used as bio-deinking and bio-bleaching materials and their application will decrease the consumption of the chlorine-based chemicals currently used for this purpose. However, xylanases with specific properties could act effectively, such as having significant thermostability and alkali resistance, etc. In this study, we found that TfXyl10A, a xylanase from Thermobifida fusca, was greatly induced to transcript by microcrystalline cellulose (MCC) substrate. Biochemical characterization showed that TfXyl10A is optimally effective at temperature of 80 °C and pH of 9.0. After removing the carbohydrate-binding module (CBM) and linker regions, the optimum temperature of TfXyl10A-CD was reduced by 10°C (to 70°C), at which the enzyme’s temperature tolerance was also weakened. While truncating only the CBM domain (TfXyl10AdC) had no significant effect on its thermostability. Importantly, polysaccharide-binding experiment showed that the auxiliary domain CBM2 could specifically bind to cellulose substrates, which endowed xylanase TfXyl10A with the ability to degrade xylan surrounding cellulose. These results indicated that TfXyl10A might be an excellent candidate in bio-bleaching processes of paper industry. In addition, the features of active-site architecture of TfXyl10A in GH10 family were further analyzed. By mutating each residue at the -2 and -1 subsites to alanine, the binding force and enzyme activity of mutants were observably decreased. Interestingly, the mutant E51A, locating at the distal -3 subsite, exhibited 90% increase in relative activity compared with wild-type (WT) enzyme TfXyl10A-CD (the catalytic domain of TfXyl110A). This study explored the function of a GH10 xylanase containing a CBM2 domain and the contribution of amino acids in active-site architecture to catalytic activity. The results obtained provide guidance for the rational design of xylanases for industrial applications under high heat and alkali-based operating conditions, such as paper bleaching.

The current international pharmaceutical scenario encompasses several steps in drug production, with complex and extremely long procedures. In the last few decades, scientific research has been trying to offer valid and reliable solutions to replace or support conventional techniques, in order to facilitate drug development procedures. These innovative approaches may have extremely positive effects in the production chain, supplying fast, and cost-effective quality as well as safety tests on active pharmaceutical ingredients (APIs) and their excipients. In this context, the exploitation of electrochemical paper-based analytical devices (ePADs) is still in its infancy, but is particularly promising in the detection of APIs and excipients in tablets, capsules, suppositories, and injections, as well as for pharmacokinetic bioanalysis in real samples.

Reject fines, a waste stream of short lignocellulosic fibers produced from paper linerboard recycling, are a cellulose-rich paper mill byproduct that can be hydrolyzed enzymatically into fermentable sugars. In this study, the use of hydrolyzed reject fines as a carbon source for bacterial biosynthesis of poly(R-3-hydroxyalkanoate) (PHA) and poly(γ-glutamic acid) (PGA) was investigated. Recombinant Escherichia coli harboring PHA biosynthesis genes were cultivated with purified sugars or crude hydrolysate to produce both poly(R-3-hydroxybutyrate) (PHB) homopolymer and medium chain length-containing copolymer (PHB-co-MCL). Wild-type Bacillus licheniformis WX-02 were cultivated with crude hydrolysate to produce PGA. Both PHB and short chain-length-co-medium chain-length (SCL-co-MCL) PHA yields from crude hydrolysate were a 2-fold improvement over purified sugars, and the MCL monomer fraction was decreased slightly in copolymers produced from crude hydrolysate. PGA yield from crude hydrolysate was similarly increased 2-fold. The results suggest that sugars from hydrolyzed reject fines are a viable carbon source for PHA and PGA biosynthesis. The use of crude hydrolysate is not only possible but beneficial for biopolymer production, eliminating the need for costly separation and purification techniques. This study demonstrates the potential to divert a lignocellulosic waste stream into valuable biomaterials, mitigating the environmental impacts of solid waste disposal.

Chemical and biological sensing are crucial tools in science and technology. Plasmonic nanoparticles offer a virtually limitless number of photons for sensing applications, which can be available for visual detection over long periods. Moreover, cellulosic materials, such as paper, represent a versatile building block for implementation of simple, yet valuable, microfluidic analytical devices. This mini review outlines the basic theory of nanoplasmonics and the usability of paper as a nanoplasmonic substrate exploiting its features as a (bio)sensing platform based on different mechanisms depending on localized surface plasmon resonance response. Progress, current trends, challenges and opportunities are also underscored. It is intended for general researchers and technologists who are new to the topic as well as specialist/experts in the field.

Electrogenicity, or bacterial electron transfer capacity, is an important application which offers environmentally sustainable advances in the fields of biofuels, wastewater treatment, bioremediation, desalination, and biosensing. Significant boosts in this technology can be achieved with the growth of synthetic biology that manipulates microbial electron transfer pathways, thereby potentially significantly improving their electrogenic potential. There is currently a need for a high-throughput, rapid, and highly sensitive test array to evaluate the electrogenic properties of newly discovered and/or genetically engineered bacterial species. In this work, we report a single-sheet, paper-based electrofluidic (incorporating both electronic and fluidic structure) screening platform for rapid, sensitive, and potentially high-throughput characterization of bacterial electrogenicity. This novel screening array uses (i) a commercially available wax printer for hydrophobic wax patterning on a single sheet of paper and (ii) water-dispersed electrically conducting polymer mixture, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate, for full integration of electronic and fluidic components into the paper substrate. The engineered 3-D, microporous, hydrophilic, and conductive paper structure provides a large surface area for efficient electron transfer. This results in rapid and sensitive power assessment of electrogenic bacteria from a microliter sample volume. We validated the effectiveness of the sensor array using hypothesis-driven genetically modified Pseudomonas aeruginosa mutant strains. Within 20 min, we observed that the sensor platform successfully measured the electricity-generating capacities of five isogenic mutants of P. aeruginosa while distinguishing their differences from genetically unmodified bacteria.

Introduction: Regular and rapid large-scale screening for pathogens is crucial for controlling pandemics like Coronavirus Disease 2019 (COVID-19). In this study, we present the development of a digital point-of-care testing (POCT) system utilizing microfluidic paper-based analytical devices (μPADs) for the detection of SARS-CoV-2 gene fragments. The system incorporates temperature tuning and fluorescent detection components, along with intelligent and autonomous image acquisition and self-recognition programs.Methods: The developed POCT system is based on the nucleic acid amplification test (NAAT), a well-established molecular biology technique for detecting and amplifying nucleic acids. We successfully detected artificially synthesized SARS-CoV-2 gene fragments, namely ORF1ab gene, N gene, and E gene, with minimal reagent consumption of only 2.2 μL per readout, representing a mere 11% of the requirements of conventional in-tube methods. The power dissipation of the system was low, at 6.4 W.Results: Our testing results demonstrated that the proposed approach achieved a limit of detection of 1000 copies/mL, which is equivalent to detecting 1 copy or a single RNA template per reaction. By employing standard curve analysis, the quantity of the target templates can be accurately determined.Conclusion: The developed digital POCT system shows great promise for rapid and reliable detection of SARS-CoV-2 gene fragments, offering a cost-effective and efficient solution for controlling pandemics. Its compatibility with other diagnostic techniques and low reagent consumption make it a viable option to enhance healthcare in resource-limited areas.

The transformation of modern industries towards enhanced sustainability is facilitated by green technologies that rely extensively on rare earth elements (REEs) such as cerium (Ce), neodymium (Nd), terbium (Tb), and lanthanum (La). The occurrence of productive mining sites, e.g., is limited, and production is often costly and environmentally harmful. As a consequence of increased utilization, REEs enter our ecosystem as industrial process water or wastewater and become highly diluted. Once diluted, they can hardly be recovered by conventional techniques, but using cyanobacterial biomass in a biosorption-based process is a promising eco-friendly approach. Cyanobacteria can produce extracellular polymeric substances (EPS) that show high affinity to metal cations. However, the adsorption of REEs by EPS has not been part of extensive research. Thus, we evaluated the role of EPS in the biosorption of Ce, Nd, Tb, and La for three terrestrial, heterocystous cyanobacterial strains. We cultivated them under N-limited and non-limited conditions and extracted their EPS for compositional analyses. Subsequently, we investigated the metal uptake of a) the extracted EPS, b) the biomass extracted from EPS, and c) the intact biomass with EPS by comparing the amount of sorbed REEs. Maximum adsorption capacities for the tested REEs of extracted EPS were 123.9–138.2 mg g−1 for Komarekiella sp. 89.12, 133.1–137.4 mg g−1 for Desmonostoc muscorum 90.03, and 103.5–129.3 mg g−1 for Nostoc sp. 20.02. A comparison of extracted biomass with intact biomass showed that 16% (Komarekiella sp. 89.12), 28% (Desmonostoc muscorum 90.03), and 41% (Nostoc sp. 20.02) of REE adsorption was due to the biosorption of the extracellular EPS. The glucose- rich EPS (15%–43% relative concentration) of all three strains grown under nitrogen-limited conditions showed significantly higher biosorption rates for all REEs. We also found a significantly higher maximum adsorption capacity of all REEs for the extracted EPS compared to cells without EPS and untreated biomass, highlighting the important role of the EPS as a binding site for REEs in the biosorption process. EPS from cyanobacteria could thus be used as efficient biosorbents in future applications for REE recycling, e.g., industrial process water and wastewater streams.

Cellulose fiber/paper-based surface-enhanced Raman scattering (SERS) is considered as a promising food safety detection technology due to its non-toxicity, low cost, flexibility, and hygroscopicity for possible rapid on-site agricultural product contaminant detection. However, it faces the problems of poor noble metal adhesion and toxic noble metal reducing agent. In this study, a natural macromolecule—xylan was used as both a reducing agent and a stabilizing agent to prepare stable Au-Ag bimetal nanoparticles, which were anchored on the paper surface by xylans in order to fabricate a paper-based Au-Ag bimetallic SERS substrate. The results show that the SERS substrate has a high Raman enhancement performance and reproductively. The substrate can effectively detect trace pesticide, i.e., thiram, and the limit of detection is as low as 1 × 10–6 mol/L (0.24 ppm). In addition, the paper-based SERS substrate can be used for direct detection of pesticide residues on the surface of fruit. The paper-based SERS substrate developed in this study has great potential in applications for rapid food safety detection.

Biosorption of metal ions by phototrophic microorganisms is regarded as a sustainable and alternative method for bioremediation and metal recovery. In this study, 12 cyanobacterial strains, including 7 terrestrial and 5 aquatic cyanobacteria, covering a broad phylogenetic diversity were investigated for their potential application in the enrichment of rare earth elements through biosorption. A screening for the maximum adsorption capacity of cerium, neodymium, terbium, and lanthanum was conducted in which Nostoc sp. 20.02 showed the highest adsorption capacity with 84.2–91.5 mg g-1. Additionally, Synechococcus elongatus UTEX 2973, Calothrix brevissima SAG 34.79, Desmonostoc muscorum 90.03, and Komarekiella sp. 89.12 were promising candidate strains, with maximum adsorption capacities of 69.5–83.4 mg g-1, 68.6–83.5 mg g-1, 44.7–70.6 mg g-1, and 47.2–67.1 mg g-1 respectively. Experiments with cerium on adsorption properties of the five highest metal adsorbing strains displayed fast adsorption kinetics and a strong influence of the pH value on metal uptake, with an optimum at pH 5 to 6. Studies on binding specificity with mixed-metal solutions strongly indicated an ion-exchange mechanism in which Na+, K+, Mg2+, and Ca2+ ions are replaced by other metal cations during the biosorption process. Depending on the cyanobacterial strain, FT-IR analysis indicated the involvement different functional groups like hydroxyl and carboxyl groups during the adsorption process. Overall, the application of cyanobacteria as biosorbent in bioremediation and recovery of rare earth elements is a promising method for the development of an industrial process and has to be further optimized and adjusted regarding metal-containing wastewater and adsorption efficiency by cyanobacterial biomass.

With the outbreak and pandemic of COVID-19, point-of-care testing (POCT) systems have been attracted much attention due to their significant advantages of small batches of samples, user-friendliness, easy-to-use and simple detection. Among them, flexible biosensors show practical significance as their outstanding properties in terms of flexibility, portability, and high efficiency, which provide great convenience for users. To construct highly functional flexible biosensors, abundant kinds of polymers substrates have been modified with sufficient properties to address certain needs. Paper-based biosensors gain considerable attention as well, owing to their foldability, lightweight and adaptability. The other important flexible biosensor employs textiles as substrate materials, which has a promising prospect in the area of intelligent wearable devices. In this feature article, we performed a comprehensive review about the applications of flexible biosensors based on the classification of substrate materials (polymers, paper and textiles), and illustrated the strategies to design effective and artificial sensing platforms, including colorimetry, fluorescence, and electrochemistry. It is demonstrated that flexible biosensors play a prominent role in medical diagnosis, prognosis, and healthcare.

In analogy to higher plants, eukaryotic microalgae are thought to be incapable of utilizing green light for growth, due to the “green gap” in the absorbance profiles of their photosynthetic pigments. This study demonstrates, that the marine chlorophyte Picochlorum sp. is able to grow efficiently under green light emitting diode (LED) illumination. Picochlorum sp. growth and pigment profiles under blue, red, green and white LED illumination (light intensity: 50–200 μmol m−2 s−1) in bottom-lightened shake flask cultures were evaluated. Green light-treated cultures showed a prolonged initial growth lag phase of one to 2 days, which was subsequently compensated to obtain comparable biomass yields to red and white light controls (approx. 0.8 gDW L−1). Interestingly, growth and final biomass yields of the green light-treated sample were higher than under blue light with equivalent illumination energies. Further, pigment analysis indicated, that during green light illumination, Picochlorum sp. formed unknown pigments (X1-X4). Pigment concentrations increased with illumination intensity and were most abundant during the exponential growth phase. Mass spectrometry and nuclear magnetic resonance data indicated, that pigments X1-X2 and X3-X4 are derivatives of chlorophyll b and a, which harbor C=C bonds in the phytol side chain similar to geranylgeranylated chlorophylls. Thus, for the first time, the natural accumulation of large pools (approx. 12 mg gDW−1) of chlorophyll intermediates with incomplete hydrogenation of their phytyl chains is demonstrated for algae under monochromatic green light (Peak λ 510 nm, full width at half maximum 91 nm). The ability to utilize green light offers competitive advantages for enhancing biomass production, particularly under conditions of dense cultures, long light pathways and high light intensity. Green light acclimation for an eukaryotic microalgae in conjunction with the formation of new aberrant geranylgeranylated chlorophylls and high efficiency of growth rates are novel for eukaryotic microalgae. Illumination with green light could enhance productivity in industrial processes and trigger the formation of new metabolites–thus, underlying mechanisms require further investigation.

In this study water soluble compounds that form complexes with Rare Earth Elements (REE) and other metals were isolated from Calothrix brevissima biomass with chromatographic methods for the first time. Molecular characterization showed that the isolated compounds are most likely polysaccharides comprised of arabinose, xylose, mannose, galactose and glucose. FT-IR analysis revealed functional groups involved in the binding mechanism of Tb are likely sulfate- and to a lesser extend hydroxyl-groups. The binding specificity of the isolated compounds was investigated with different metal solutions. Here, ions of the alkali and alkaline earth metals Na, K, Mg and Ca showed no competition for Tb-binding even at 10-fold excess concentration. Ions of the elements Co and Pb on the other hand replaced Tb at higher concentrations. Addition of the isolated compounds significantly reduced the precipitation of Eu at pH-values between 6.7 and 9.5, indicating that the interaction between the isolated chelators and Rare Earth Metals is stable even at high pH-values.

Interleukin-6 (IL-6) is a pro/anti-inflammatory cytokine, the quantitative detection of which has been extensively considered for diagnosis of inflammatory associated diseases. However, there has not yet been a reliable, low-cost, and user-friendly platform developed for point-of-care (POC) detection of IL-6, which will eliminate the conventional costly, time-consuming, and complex assays. In this work, we developed a lateral flow assay for colorimetric detection of IL-6, using anti-IL-6 antibodies conjugated to gold nanoparticles (AuNPs) as the detection probes. Silver amplification technique was incorporated with the newly developed assay in order to enhance the obtained colorimetric signals, allowing sensitive detection of IL-6 in human serum in the desired physiological ranges (i.e., 5–1000 pg/mL). A limit of detection of 5 pg/mL could be achieved for IL-6 detection in serum with the amplification step which was not achievable in the standard assay. The corresponding specificity and reproducibility tests were all preformed to confirm the reliability of this assay for quantitative measurement of IL-6 in a POC manner.