Biochar from Brewers' Spent Grain: A Green and Low-Cost Smart Material to Modify Screen-Printed Electrodes

Preparation, Modification, and Application of Biochar in the Printing Field: A Review

Biochar is a solid material enriched with carbon produced by the thermal transformation of organic raw materials under anoxic or anaerobic conditions. It not only has various environmental benefits including reducing greenhouse gas emissions, improving soil fertility, and sequestering atmospheric carbon, but also has the advantages of abundant precursors, low cost, and wide potential applications, thus gaining widespread attention. In recent years, researchers have been exploring new biomass precursors, improving and developing new preparation methods, and searching for more high-value and meaningful applications. Biochar has been extensively researched and utilized in many fields, and recently, it has also shown good industrial application prospects and potential application value in the printing field. In such a context, this article summarizes the typical preparation and modification methods of biochar, and also reviews its application in the printing field, to provide a reference for future work.

Carbon Nanomaterials-Based Screen-Printed Electrodes for Sensing Applications

Electrochemical sensors consisting of screen-printed electrodes (SPEs) are recurrent devices in the recent literature for applications in different fields of interest and contribute to the expanding electroanalytical chemistry field. This is due to inherent characteristics that can be better (or only) achieved with the use of SPEs, including miniaturization, cost reduction, lower sample consumption, compatibility with portable equipment, and disposability. SPEs are also quite versatile; they can be manufactured using different formulations of conductive inks and substrates, and are of varied designs. Naturally, the analytical performance of SPEs is directly affected by the quality of the material used for printing and modifying the electrodes. In this sense, the most varied carbon nanomaterials have been explored for the preparation and modification of SPEs, providing devices with an enhanced electrochemical response and greater sensitivity, in addition to functionalized surfaces that can immobilize biological agents for the manufacture of biosensors. Considering the relevance and timeliness of the topic, this review aimed to provide an overview of the current scenario of the use of carbonaceous nanomaterials in the context of making electrochemical SPE sensors, from which different approaches will be presented, exploring materials traditionally investigated in electrochemistry, such as graphene, carbon nanotubes, carbon black, and those more recently investigated for this (carbon quantum dots, graphitic carbon nitride, and biochar). Perspectives on the use and expansion of these devices are also considered.

Nanofibrillar biochar from industrial waste as hosting network for transition metal dichalcogenides. Novel sustainable 1D/2D nanocomposites for electrochemical sensing

Industrial wastes have become elective sustainable sources to obtain materials for electronic/electroanalytical purposes; on the other hand, easy and green strategies to include semiconductor 2D graphene-like materials in conductive networks are highly required. In this work, 1D/2D nanocomposites (NCs) based on nanofibrillar biochar (BH) from paper industry waste and transition metal dichalcogenides (TMDs: MoS₂, WS₂, MoSe₂, and WSe₂), were prepared in water via liquid phase exfoliation (LPE) using sodium cholate as bioderived surfactant. The TMD amount in the NCs has been carefully optimized, searching for the best compromise between electron transfer ability and electroanalytical performances. Four different water-dispersed BH-TMD NCs have been selected and comprehensively studied from the electrochemical point of view and morphologically characterized. The BH-TMDs potentiality have been demonstrated in model solutions and real samples towards different analytes of biological and agri-food interest. The most performing NCs have been selected and used for the simultaneous determination of the neurotransmitters dopamine (DP) and serotonin (SR), and the flavonoids quercetin (QR) and rutin (RT), obtaining good linearity (R² ≥ 0.9956) with limits of detection ranging from 10 to 200 nM. Reproducible quantitative recovery values (90-112%, RSD ≤6%, n = 3) were obtained analyzing simultaneously DP and SR in synthetic biological fluid and drugs, and QR and RT in food supplements, proving the usability of the proposed materials for real analyses. This work proves that BH-nanofibers act as a sustainable conductive hosting network for 2D-TMDs, allowing full exploit their electroanalytical potential. The proposed BH-TMD NCs represent a sustainable, affordable, and captivating opportunity for the electrochemical and (bio)sensoristic field.

Biochar: An environmentally friendly platform for construction of a SARS-CoV-2 electrochemical immunosensor

Waste management is a key feature to ensure sustainable consumption and production patterns, and to combat the impacts of climate change. In this scenario, the production of biochar from different biomasses results in environmental and economic advantages. In this study, biochar was produced from sugarcane bagasse pyrolysis, to immobilize biomolecules, in order to assemble an electrochemical immunosensor to detect antibodies against SARS-CoV-2. For this, screen-printed carbon electrodes (SPCE) were modified with a dispersion of biochar and used to immobilize the receptor-binding-domain (RBD) against virus S-protein, through EDC/NHS crosslinking reaction. Under the best set of experimental conditions, negative and positive serum samples responses distinguished based on a cutoff value of 82.3 %, at a 95 % confidence level. The immunosensor showed selective behavior to antibodies against yellow fever and its performance was stable up to 7 days of storage. Therefore, biochar yielded from sugarcane bagasse is an ecofriendly material that can be used as a platform to immobilize biomolecules for construction of electrochemical biosensors.

A Catechol-Meter Based on Conventional Personal Glucose Meter for Portable Detection of Tyrosinase and Sodium Benzoate

In this study, the personal glucose meter (PGM) was first used as a fast and user-friendly meter for analyzing catechol (CA) based on the reduction of the mediator K₃[Fe(CN)₆] to K₄[Fe(CN)₆] in the glucose test strip. Then, an easy, low-cost, and convenient PGM-based method for detecting tyrosinase (TYR) activity and sodium benzoate (SBA) was developed on the basis of the TYR-catalyzed reaction. In this method, CA is oxidized to form o-benzoquinone by TYR, thereby reducing the residual amount of CA and the PGM readout. On the other hand, SBA can inhibit the oxidation of CA catalyzed by TYR and increase the residual amount of CA after the enzymatic reaction. Therefore, the activity of TYR is proportional to the difference in the PGM readout of CA, and the concentration of SBA is positively correlated with the residual amount of CA. After the relevant experimental conditions were systematically optimized, the proposed PGM-based method for the detection of TYR and SBA was successfully validated. The liner ranges are 1.0-103.3 U/mL and 6.25-1000 ppm, and the quantification limits are 1.0 U/mL and 6.25 ppm for TYR and SBA, respectively. Moreover, the spiked recovery tests in normal human serum and carbonate beverages (i.e., Cola, Sprite, and Fanta) were performed, and the recoveries (91.6-106.8%) further confirm the applicability of the PGM-based method in real sample analysis.

Biochar derived carbonaceous material for various environmental applications: Systematic review

Biochar is the solid material produced from the carbonization of organic feedstock biomass. This material has several unique characteristics such as greater carbon content, good electrical conductivity, high stability and large surface area, which can be applied in several research areas such as generation of power and wastewater treatment. In connection with this, recently, the investigations on biochar significantly focus on the removal of toxic heavy metals since the biochar material is easily available and environmentally friendly. According to an environmental analytical device, biochar-derived carbonaceous material has been additionally applied to the synthesis of an effective, sensitive, and low-cost electrochemical sensor. Biochar with an assessment of electrochemical properties has engaged with different redox reactions in water. In this survey, electrochemical ways of behaving of biochar in light of the electrochemical structures were analytically compiled as well as the impact from biomass sources and manufacturing process including carbonization strategies, pre-treatment/changed techniques. This review emphasizes the various synthesis methods of biochar form organic feedstock, properties and different modulations of biochar for the bioremediation of heavy metals. This review study emphasizes the utilization of biochar as sensing platform and supercapacitor for electrode fabrication in electrochemical biosensor to enhance the remediation of toxic contaminants from water streams and by switching the less ecological traditional materials. Brief information on the techniques employed for packaging biochar as carbon electrode is summarized. Scope in the aspect of environmental concern of biochar, future challenges and prospects are proposed in detail.

Cost-effective and disposable label-free voltammetric immunosensor for sensitive detection of interleukin-6

IL-6 detection is highly desirable since can monitor many diseases in humans and assess the response to treatments. Herein, two novel label-free voltammetric immunosensors for rapid and accurate interleukin-6 (IL-6) detection in human serum are presented. The immunosensors are fabricated by immobilising two different IL-6 antibodies, identified as mAb-IL-6 clone-5 and clone-7, on in-house produced screen-printed electrodes modified with inexpensive recycling biochar (Bio-SPEs). To ensure high structural fidelity and performance, an in-depth electrochemical characterization of the layer-by-layer assembly of the immunosensor was conducted by cyclic voltammetry (CV) and sensing was performed using square wave voltammetry (SWV). The two immunosensors showed good analytical performances in human serum, exhibiting a wide linear range (LR) between 26-125 and 30-138 pg/mL, a good limit of detection (LOD) of 4.8 and 5.4 pg/mL and selectivity for IL-6 over other common cytokines, including IL-1β and TNF-α. Performance comparison of IL-6 immunosensors with those of a commercial spectrophotometric ELISA kit (LOD of 20 pg/mL, RSD% of 15%) denotes a better sensitivity and reproducibility of the proposed label-free devices, associated with a reduced detection time (30 min instead of more than 3 h for ELISA test). Furthermore, the proposed immunosensors were successfully applied in blood samples (with only a dilution of 1:100 v/v in PBS and without additional treatments) with good sensitivity (LOD of 14.3 pg/mL) and reproducibility (RSD% < 11%), thus paving the way for their application as viable diagnostic and therapeutic point-of-care tools alternative to the IL-6 detection techniques routinely used (ELISA and Western Blot).

Lignocellulosic residues as supports for enzyme immobilization, and biocatalysts with potential applications

Growing demand for agricultural production means a higher quantity of residues produced. The reuse and recycling of agro-industrial wastes reduce worldwide greenhouse emissions. New opportunities are derived from this kind of residuals in the biotechnological field generating valuable products in growing sectors such as transportation, bioenergy, food, and feedstock. The use of natural macromolecules towards biocatalysts offers numerous advantages over free enzymes and friendliness with the environment. Enzyme immobilization improves enzyme properties (stability and reusability), and three types of supports are discussed: inorganic, organic, and hybrid. Several examples of agro-industrial wastes such as coconut wastes, rice husks, corn residues and brewers spent grains (BSG), their properties and potential as supports for enzyme immobilization are described in this work. Before the immobilization, biological and non-biological pretreatments could be performed to enhance the waste potential as a carrier. Additionally, immobilization methods such as covalent binding, adsorption, cross-linking and entrapment are compared to provide high efficiency. Enzymes and biocatalysts for industrial applications offer advantages over traditional chemical processes with respect to sustainability and process efficiency in food, energy, and bioremediation fields. The wastes reviewed in this work demonstrated a high affinity for lipases and laccases and might be used in biodiesel production and textile wastewater treatment, among other applications.

Sensitive Detection of Industrial Pollutants Using Modified Electrochemical Platforms

Water pollution is nowadays a global problem and the effective detection of pollutants is of fundamental importance. Herein, a facile, efficient, robust, and rapid (response time < 2 min) method for the determination of important quinone-based industrial pollutants such as hydroquinone and benzoquinone is reported. The recognition method is based on the use of screen-printed electrodes as sensing platforms, enhanced with carbon-based nanomaterials. The enhancement is achieved by modifying the working electrode of such platforms through highly sensitive membranes made of Single- or Multi-Walled Carbon Nanotubes (SWNTs and MWNTs) or by graphene nanoplatelets. The modified sensing platforms are first carefully morphologically and electrochemically characterized, whereupon they are tested in the detection of different pollutants (i.e., hydroquinone and benzoquinone) in water solution, by using both cyclic and square-wave voltammetry. In particular, the sensors based on film-deposited nanomaterials show good sensitivity with a limit of detection in the nanomolar range (0.04 and 0.07 μM for SWNT- and MWNT-modified SPEs, respectively) and a linear working range of 10 to 1000 ppb under optimal conditions. The results highlight the improved performance of these novel sensing platforms and the large-scale applicability of this method for other analytes (i.e., toxins, pollutants).

Exploring the Adsorption of Pb on Microalgae-Derived Biochar: A Versatile Material for Environmental Remediation and Electroanalytical Applications

Biochar, a carbon material obtained by pyrolysis of biomasses, is increasingly applied in environmental remediation and sensing thanks to its functional properties, cost-effectiveness and eco-friendliness. The adsorption capacity of biochar, strictly dependent on its specific surface area, heteroatom doping and surface functional groups, is crucial for these applications. Here, biochar produced at low temperature (350 °C) from a marine microalga (Nannochloropsis sp.) is proposed as an efficient adsorbent of lead (II) ions in aqueous solution; this production strategy promotes the natural self-doping of biochar without requiring harsh conditions. The kinetics and thermodynamics of the adsorption process, as well as the effect of pH, ionic strength and dissolved organic matter on the adsorption efficiency were systematically assessed. The microalgae-derived biochar shows superior adsorption performances compared to a nutshell-derived one (used as a reference of lignocellulosic feedstocks) under all the tested conditions. The microalgae-derived biochar was finally used to decorate screen-printed carbon electrodes to improve the electroanalytical performances towards the voltammetric detection of lead (II) ions. A two-fold increase in sensitivity was obtained compared to the unmodified electrode thanks to the enhanced electron transfer and adsorption properties provided by biochar. These results highlight the potentialities of microalgae-derived biochar for environmental and sensing applications.

Electrochemical sensors based on sewage sludge-derived biochar for the analysis of anthocyanins in berry fruits

The reutilization of waste and the reduction of the general environmental impact of every production are fundamental goals that must be achieved in the framework of a circular economy. Recycled carbon-rich materials may represent a promising alternative to other less-sustainable carbonaceous materials used in the production of electrochemical sensing platforms. Herein, we propose an innovative carbon paste electrode (CPE) composed of biochar derived from biological sludge obtained from municipal and industrial wastewater treatment plants. The physicochemical properties of the biochar after a chemical treatment with an acidic solution obtained from industrial by-products were investigated. The electrode surface characterization was carried out by analyzing common redox probes and multiple phenols bearing varying numbers of –OH and –OCH₃ groups in their structure. Furthermore, the CPE was also tested on the evaluation of the phenolic fingerprints of Vaccinium myrtillus, Vaccinium uliginosum subsp. gaultherioides, and Fragaria × ananassa. Standard anthocyanin mixtures and extracts of the aforementioned fruits were analyzed to provide a phenolic characterization of real samples. The obtained results show that the sewage sludge–derived biochar can be a promising material for the development of electroanalytical sensors.

Monitoring of alcohol-based hand rubs in SARS-CoV-2 prevention by HS-GC/MS and electrochemical biosensor: A survey of commercial samples

Alcohol-based hand rubs (ABHRs) have found large diffusion during the Severe Acute Respiratory Syndrome Coronavirus 2, SARS-CoV-2, thus becoming the most widespread means for hand hygiene. Whereby, it is fundamental to assess the alignment of commercial ABHRs to the indications provided by the principal health agencies regarding alcohol content and possible impurities. In this work, a novel improvement of previous existent methods for the determination of alcohol content in such products was reported. In particular, two alternative sensitive and reproducible methods, such as an electrochemical screen-printed based enzymatic (alcohol oxidase) biosensor and a Headspace Gas Chromatography coupled with Mass Spectrometry (HS-GC/MS) were proposed. The electrochemical device represents a rapid, low-cost and accurate fraud screening method for alcohol-based hand rubs. The second technique confirms, identifies and simultaneously determines ethyl alcohol, isopropyl alcohol, n-propyl alcohol and methyl alcohol, improving their extraction through acidification in the sample pre-treatment step. The developed specific HS-GC/MS method was in-house validated according to ISO/IEC 17025 requirements. Analytical parameters such as limit of detection (LoD 0.13%v/v - 0.17%v/v), limit of quantification (LoQ 0.44% v/v - 0.57% v/v), inter-day repeatability (RSD_R 2.1–10.7%) and recovery (80–110%) were assessed. The relative expanded uncertainties range (between 0.1%v/v and 3.4%v/v) for all the analytes were evaluated. Results obtained using the different analytical approaches were compared and indicated that the two data sets were comparable (median; HS-GC/MS, 56%v/v; electrochemical biosensor, 62%v/v) and were not statistically different (one-way ANOVA test; p = 0.062). In addition, a good correlation (95%) was found. This study noticed that only 39% of the tested hand sanitiser products had the recommended average alcohol content, thus highlighting the need for analytical controls on this type of products.

Powerful Electron-Transfer Screen-Printed Platforms as Biosensing Tools: The Case of Uric Acid Biosensor

The use of carbon nanomaterials (CNMs) in sensors and biosensor realization is one of the hottest topics today in analytical chemistry. In this work, a comparative in-depth study, exploiting different nanomaterial (MWNT-CO₂H, -NH₂, -OH and GNP) modified screen-printed electrodes (SPEs), is reported. In particular, the sensitivity, the heterogeneous electron transfer constant (k⁰), and the peak-to-peak separation (ΔE) have been calculated and analyzed. After which, an electrochemical amperometric sensor capable of determining uric acid (UA), based on the nano-modified platforms previously characterized, is presented. The disposable UA biosensor, fabricated modifying working electrode (WE) with Prussian Blue (PB), carbon nanotubes, and uricase enzyme, showed remarkable analytical performances toward UA with high sensitivity (CO₂H 418 μA μM^-1 cm^-2 and bare SPE-based biosensor, 33 μA μM^-1 cm^-2), low detection limits (CO₂H 0.5 nM and bare SPE-based biosensors, 280 nM), and good repeatability (CO₂H and bare SPE-based biosensors, 5% and 10%, respectively). Moreover, the reproducibility (RSD%) of these platforms in tests conducted for UA determination in buffer and urine samples results are equal to 6% and 15%, respectively. These results demonstrate that the nanoengineered electrode exhibited good selectivity and sensitivity toward UA even in the presence of interfering species, thus paving the way for its application in other bio-fluids such as simple point-of-care (POC) devices.

Synergetic Co-Production of Beer Colouring Agent and Solid Fuel from Brewers’ Spent Grain in the Circular Economy Perspective

Brewers’ Spent Grain is a by-product of the brewing process, with potential applications for energy purposes. This paper presents the results of an investigation aiming at valorization of this residue by torrefaction, making product for two purposes: a solid fuel that could be used for generation of heat for the brewery and a colouring agent that could replace colouring malt for the production of dark beers. Decreased consumption of malt for such purposes would have a positive influence on the sustainability of brewing. Torrefaction was performed at temperatures ranging between 180 °C and 300 °C, with a residence time between 20 and 60 min. For the most severe torrefaction conditions (300 °C, 60 min), the higher heating value of torrefied BSG reached 25 MJ/kg. However, the best beer colouring properties were achieved for mild torrefaction conditions, i.e., 180 °C for 60 min and 210 °C for 40 min, reaching European Brewery Convention colours of 145 and 159, respectively. From the solid fuel properties perspective, the improvements offered by torrefaction in such mild conditions were modest. Overall, the obtained results suggest some trade-off between the optimum colouring properties and optimum solid fuel properties that need to be considered when such dual-purpose torrefaction of BSG for brewery purposes is implemented.

Development of a Novel Electrochemical Biosensor Based on Carbon Nanofibers-Cobalt Phthalocyanine-Laccase for the Detection of p-Coumaric Acid in Phytoproducts

The present paper developed a new enzymatic biosensor whose support is a screen-printed electrode based on carbon nanofibers modified with cobalt phthalocyanine and laccase (CNF-CoPc-Lac/SPE) to determine the p-coumaric acid (PCA) content by cyclic voltammetry and square wave voltammetry. Sensor modification was achieved by the casting and cross-linking technique, using glutaraldehyde as a reticulation agent. The biosensor’s response showed the PCA redox processes in a very stable and sensitive manner. The calibration curve was developed for the concentration range of p-coumaric acid of 0.1–202.5 μM, using cyclic voltammetry and chronoamperometry. The biosensor yielded optimal results for the linearity range 0.4–6.4 μM and stood out by low LOD and LOQ values, i.e., 4.83 × 10⁻⁷ M and 1.61 × 10⁻⁶ M, respectively. PCA was successfully determined in three phytoproducts of complex composition. The results obtained by the voltammetric method were compared to the ones obtained by the FTIR method. The amount of p-coumaric acid determined by means of CNF-CoPc-Lac/SPE was close to the one obtained by the standard spectrometric method.

Feasibility Analysis of Brewers’ Spent Grain for Energy Use: Waste and Experimental Pellets

Waste production is increasing every day as a consequence of human activities; thus, its valorization is becoming more important. For this purpose, the usage of wastes as biofuels is one of the most important aspects of sustainable strategies. This is the case of the main waste generated in brewing industries: brewers’ spent grain (BSG). In this sector, microbreweries are not able to properly manage the wastes that they generate due to lack of space. Consequently, the transformation of BSG to a high-quality biofuel might be an interesting option for this kind of small industry. In this work, we carried out a physical-energy characterization of BSG, as well as pellets from this waste. The initial characterization showed slightly unfavorable results concerning N and ash, with values of 3.76% and 3.37% db, respectively. Nevertheless, the physical characterization of the pellets was very good, with acceptable bulk density (662.96 kg·m−3 wb) and low heating value (LHV; 17.65 MJ·kg−1 wb), among others. This situation is very favorable for any of the intended uses (for energy use or animal feed, among others).

Brewer's Spent Grains-Valuable Beer Industry By-Product

The brewing sector is a significant part of the global food industry. Breweries produce large quantities of wastes, including wastewater and brewer’s spent grains. Currently, upcycling of food industry by-products is one of the principles of the circular economy. The aim of this review is to present possible ways to utilize common solid by-product from the brewing sector. Brewer’s spent grains (BSG) is a good material for sorption and processing into activated carbon. Another way to utilize spent grains is to use them as a fuel in raw form, after hydrothermal carbonization or as a feedstock for anaerobic digestion. The mentioned by-products may also be utilized in animal and human nutrition. Moreover, BSG is a waste rich in various substances that may be extracted for further utilization. It is likely that, in upcoming years, brewer’s spent grains will not be considered as a by-product, but as a desirable raw material for various branches of industry.

Development of a Novel Electrochemical Biosensor Based on Carbon Nanofibers-Gold Nanoparticles-Tyrosinase for the Detection of Ferulic Acid in Cosmetics

The present paper deals with the electrochemical behavior of three types of sensors based on modified screen-printed electrodes (SPEs): a sensor based on carbon nanofibers (CNF/SPE), a sensor based on nanofibers of carbon modified with gold nanoparticles (CNF-GNP/SPE) and a biosensor based on nanofibers of carbon modified with gold nanoparticles and tyrosinase (CNF-GNP-Ty/SPE). To prepare the biosensor, the tyrosinase (Ty) was immobilized on the surface of the electrode already modified with carbon nanofibers and gold nanoparticles, by the drop-and-dry technique. The electrochemical properties of the three electrodes were studied by cyclic voltammetry in electroactive solutions, and the position and shape of the active redox peaks are according to the nature of the materials modifying the electrodes. In the case of ferulic acid, a series of characteristic peaks were observed, the processes being more intense for the biosensor, with the higher sensitivity and selectivity being due to the immobilization of tyrosinase, a specific enzyme for phenolic compounds. The calibration curve was subsequently created using CNF-GNP-Ty/SPE in ferulic acid solutions of various concentrations in the range 0.1-129.6 μM. This new biosensor allowed low values of the detection threshold and quantification limit, 2.89 × 10-9 mol·L-1 and 9.64 × 10-9 mol·L-1, respectively, which shows that the electroanalytical method is feasible for quantifying ferulic acid in real samples. The ferulic acid was quantitatively determined in three cosmetic products by means of the CNF-GNP-Ty/SPE biosensor. The results obtained were validated by means of the spectrometric method in the infrared range, the differences between the values of the ferulic acid concentrations obtained by the two methods being under 5%.

The role of microorganisms on biotransformation of brewers' spent grain

Brewers' spent grain (BSG) is the most abundant by-product of brewing. Due to its microbiological instability and high perishability, fresh BSG is currently disposed of as low-cost cattle feed. However, BSG is an appealing source of nutrients to obtain products with high added value through microbial-based transformation. As such, BSG could become a potential source of income for the brewery itself. While recent studies have covered the relevance of BSG chemical composition in detail, this review aims to underline the importance of microorganisms from the stabilization/contamination of fresh BSG to its biotechnological exploitation. Indeed, the evaluation of BSG-associated microorganisms, which include yeast, fungi, and bacteria, can allow their safe use and the best methods for their exploitation. This bibliographical examination is particularly focused on the role of microorganisms in BSG exploitation to (1) produce enzymes and metabolites of industrial interest, (2) supplement human and animal diets, and (3) improve soil fertility. Emerging safety issues in the use of BSG as a food and feed additive is also considered, particularly considering the presence of mycotoxins.Key points• Microorganisms are used to enhance brewers' spent grain nutritional value.• Knowledge of brewers' spent grain microbiota allows the reduction of health risks. Graphical abstract.

Vegetable waste scaffolds for 3D-stem cell proliferating systems and low cost biosensors

Vegetable wastes represent an inexpensive and sustainable source of valuable bioproducts for several applications. Natural micro-porous and fibrous materials can be obtained from a very cheap and abundant cellulosic bio-waste. Here we demonstrated that vegetable waste derivatives can be suitable as scaffolds for biosensors and 3D cell growth. Many studies have been addressed to fabricate biocompatible 3D scaffolds for mammalian stem cells cultures and develop novel systems able to reproduce the complexity of the in vivo microenvironment. Many of these products are proprietary, expensive or require chemical synthesis. The recycling and revaluation of vegetable derived tissues to fabricate scaffolds for analytical biosensors 3D stem cell cultures platforms may represent a very low-cost approach for toxicological and environmental analyses. In this approach, potential applications of vegetable-derived tissue for biosensing and 3D stem cell cultures were investigated. Micro-structured scaffolds from stalk of broccoli, named BrcS, were either functionalized for production of enzymatic 3D-biosensors or preconditioned to be used them as 3D-scaffolds for human mesenchymal stem cells cultures. The conditions to fabricate 3D-biosensors and scaffolds for cell growth were here optimized studying all analytical parameters and demonstrating the feasibility to combine these two properties for an innovative solution to ennoble vegetable wastes.

Electrochemiluminescence Biosensors Using Screen-Printed Electrodes

Electrogenerated chemiluminescence (also called electrochemiluminescence (ECL)) has become a great focus of attention in different fields of analysis, mainly as a consequence of the potential remarkably high sensitivity and wide dynamic range. In the particular case of sensing applications, ECL biosensor unites the benefits of the high selectivity of biological recognition elements and the high sensitivity of ECL analysis methods. Hence, it is a powerful analytical device for sensitive detection of different analytes of interest in medical prognosis and diagnosis, food control and environment. These wide range of applications are increased by the introduction of screen-printed electrodes (SPEs). Disposable SPE-based biosensors cover the need to perform in-situ measurements with portable devices quickly and accurately. In this review, we sum up the latest biosensing applications and current progress on ECL bioanalysis combined with disposable SPEs in the field of bio affinity ECL sensors including immunosensors, DNA analysis and catalytic ECL sensors. Furthermore, the integration of nanomaterials with particular physical and chemical properties in the ECL biosensing systems has improved tremendously their sensitivity and overall performance, being one of the most appropriates research fields for the development of highly sensitive ECL biosensor devices.

Development of an Electrochemical Immunosensor for Specific Detection of Visceral Leishmaniasis Using Gold-Modified Screen-Printed Carbon Electrodes

Visceral leishmaniasis is a reemerging neglected tropical disease with limitations for its diagnosis, including low concentration of antibodies in the serum of asymptomatic patients and cross-reactions. In this context, this work proposes an electrochemical immunosensor for the diagnosis of visceral leishmaniasis in a more sensitive way that is capable of avoiding cross-reaction with Chagas disease (CD). Crude Leishmania infantum antigens tested in the enzyme-linked immunosorbent assay (ELISA) were methodologically standardized to best engage to the sensor. The antibodies anti-Trypanosoma cruzi and anti-Leishmania sp. Present in serum from patients with diverse types of CD or leishmaniasis were chosen. A screen-printed carbon electrode modified with gold nanoparticles was the best platform to guarantee effective adsorption of all antigens so that the epitope of specific recognition for leishmaniasis occurred efficiently and without cross-reaction with the evaluated CD. The current peaks reduced linearly after the recognition, and still were able to notice the discrimination between different kinds of diseases (digestive, cardiac, undetermined Chagas/acute and visceral chronic leishmaniasis). Comparative analyses with ELISA were performed with the same groups, and a low specificity (44%) was verified due to cross-reactions (high number of false positives) on ELISA tests, while the proposed immunosensor presented high selectivity and specificity (100%) without any false positives or false negatives for the serum samples from isolated patients with different types of CD and visceral leishmaniasis. Furthermore, the biosensor was stable for 5 days and presented a detection limit of 200 ng mL⁻¹.

HTC of Wet Residues of the Brewing Process: Comprehensive Characterization of Produced Beer, Spent Grain and Valorized Residues

Steady consumption of beer results in a steady output of residues, i.e., brewer’s spent grain (BSG). Its valorization, using hydrothermal carbonization (HTC) seems sensible. However, a significant knowledge gap regarding the variability of this residue and its influence on the valorization process and its potential use in biorefineries exists. This study attempted to fill this gap by characterization of BSG in conjunction with the main product (beer), taking into accounts details of the brewing process. Moreover, different methods to assess the performance of HTC were investigated. Overall, the differences in terms of the fuel properties of both types of spent grain were much less stark, in comparison to the differences between the respective beers. The use of HTC as a pretreatment of BSG for subsequent use as a biorefinery feedstock can be considered beneficial. HTC was helpful in uniformization and improvement of the fuel properties. A significant decrease in the oxygen content and O/C ratio and improved grindability was achieved. The Weber method proved to be feasible for HTC productivity assessment for commercial installations, giving satisfactory results for most of the cases, contrary to traditional ash tracer method, which resulted in significant overestimations of the mass yield.