Bacterial Cellulose Nanopaper Research Articles

Transparent Multilayer Acrylic Composites Reinforced with Poly(Acrylated Urethane) Filled Low Grammage Bacterial Cellulose Nanopaper.

Cellulose nanopaper is a material structure that possesses high mechanical performance and is widely regarded as a promising 2D reinforcement for polymer matrix composites. This work explores the use of low grammage bacterial cellulose (BC) nanopaper as reinforcement for poly(acrylated urethane) interlayer adhesive to increase the impact performance of multilayer acrylic composites. The BC nanopaper is impregnated with an acrylated urethane resin and laminated between acrylic sheets to create BC/acrylic composites consisting of one, three, and five layers of BC nanopaper-reinforced poly(acrylated urethane) interlayer adhesive(s). Both the poly(acrylated urethane)-filled BC nanopaper interlayer adhesive and the resulting laminated acrylic composites are optically transparent. The incorporation of BC nanopaper into the poly(acrylated urethane) interlayer adhesive improves the tensile modulus by eightfold and the single-edge notched fracture toughness by 60% compared to neat poly(acrylated urethane). It is also found that using poly(acrylated urethane)-filled BC nanopaper interlayer adhesive proves beneficial to the impact properties of the resulting laminated acrylic composites. In Charpy impact testing, the impact strength of the multilayer acrylic composites increases by up to 130% compared to the "gold-standard" impact-modified monolithic acrylic, with a BC loading of only 1.6wt%.

Flexible, ultrathin and integrated nanopaper supercapacitor based on cationic bacterial cellulose

Cellulose composite nanopaper is extensively employed in flexible energy storage systems owing to their light weight, good flexibility and high specific surface area. Nevertheless, achieving flexible and ultrathin nanopaper supercapacitors with excellent electrochemical performance remains a challenge. Herein, surface cationization of bacterial cellulose (BC) nanofibers was conducted using 2,3-epoxypropyltrimethylammonium chloride (EPTMAC). Anion-doped polypyrrole (PPy) was incorporated onto the surface of the cationic bacterial cellulose (BCE) nanofibers by an interfacial electrostatic self-assembly process. The obtained PPy@BCE electrode exhibited excellent electrochemical performance, including an areal capacitance of 3988 mF cm−2 at 1.0 mA cm−2 and a capacitance retention of 97 % after 10,000 cycles. A laminated paper-forming strategy was adopted to design and fabricate all-in-one integrated flexible supercapacitors (IFSCs) using PPy@BCE nanopaper as electrodes and BC nanopaper as a separator. The IFSCs showed superior areal capacitance (3669 mF cm−2 at 1 mA cm−2), high energy density (193.7 μWh cm−2 at a power density of 827.3 μW cm−2), and outstanding mechanical flexibility (with no significant capacitance attenuation after repeatedly bending for 1000 times). The present strategy paves a way for the large-scale production of paper-based energy storage devices.

Green Synthesis of Sulfur- and Nitrogen-Doped Carbon Quantum Dots for Determination of L-DOPA Using Fluorescence Spectroscopy and a Smartphone-Based Fluorimeter.

Sulfur- and nitrogen-doped carbon quantum dots (S,N-CQDs) were synthesized using feijoa leaves as a green precursor via a novel route. Spectroscopic and microscopic methods such as X-ray photoelectron spectroscopy, fluorescence spectroscopy, and high-resolution transmission electron microscopy were used to analyze the synthesized materials. The blue emissive S,N-CQDs were applied for qualitative and quantitative determination of levodopa (L-DOPA) in aqueous environmental and real samples. Human blood serum and urine were used as real samples with good recovery of 98.4-104.6 and 97.3-104.3%, respectively. A smartphone-based fluorimeter device was employed as a novel and user-friendly self-product device for pictorial determination of L-DOPA. Bacterial cellulose nanopaper (BC) was used as a substrate for S,N-CQDs to make an optical nanopaper-based sensor for L-DOPA determination. The S,N-CQDs demonstrated good selectivity and sensitivity. The interaction of L-DOPA with the functional groups of the S,N-CQDs via the photo-induced electron transfer (PET) mechanism quenched the fluorescence of S,N-CQDs. The PET process was studied using fluorescence lifetime decay, which confirmed the dynamic quenching of S,N-CQD fluorescence. The limit of detection (LOD) of S,N-CQDs in aqueous solution and the nanopaper-based sensor was 0.45 μM in the concentration range of 1-50 μM and 31.05 μM in the concentration range of 1-250 μM, respectively.

Optically transparent laminated acrylic composites reinforced with mercerised bacterial cellulose nanopaper

Bacterial cellulose (BC) nanopaper is an important material structure for the production of high-performance cellulose nanocomposites. Here, we report the mercerisation of BC nanofibrils as a route to produce ductile BC nanopaper. Mercerised BC nanopaper was found to possess a ductile response under uniaxial tension, albeit with lower tensile modulus and strength compared to neat BC nanopaper due to the presence of large fraction of disordered cellulose. The impregnation of (mercerised) BC nanopaper with an acrylated urethane resin, followed by lamination with impact-modified acrylic produces optically transparent BC/acrylic composites. At a BC loading of only 8 wt%, the mercerised BC/acrylic composite possessed a flatwise and edgewise Charpy impact strength of 19.0 kJ m−2 and 19.5 kJ m−2, respectively; a 62% and 22% increase over monolithic acrylic. The influence of different alkaline treatments on the morphology, crystallography, mechanical and optical properties of the BC nanopaper, as well as the BC/acrylic composites are juxtaposed in this work.

A bacterial cellulose-based LiSrVO4:Eu3+ nanosensor platform for smartphone sensing of levodopa and dopamine: point-of-care diagnosis of Parkinson's disease.

Among the catecholamines, dopamine (DA) is essential in regulating multiple aspects of the central nervous system. The level of dopamine in the brain correlates with neurological diseases such as Parkinson's disease (PD). However, dopamine is unable to cross the blood-brain barrier (BBB). Therefore, levodopa (LD) is used to restore normal dopamine levels in the brain by crossing the BBB. Thus, the control of LD and DA levels is critical for PD diagnosis. For this purpose, LiSr0.0985VO4:0.015Eu3+ (LSV:0.015Eu3+) nanoplates were synthesized by the microwave-assisted co-precipitation method, and have been employed as an optical sensor for the sensitive and selective detection of catecholamines. The synthesized LSV:0.015Eu3+ nanoplates emitted red fluorescence with a high quantum yield (QY) of 48%. By increasing the LD and DA concentrations, the fluorescence intensity of LSV:0.015Eu3+ nanoplates gradually decreased. Under optimal conditions, the linear dynamic ranges were 1-40 μM (R2 = 0.9972) and 2-50 μM (R2 = 0.9976), and the detection limits (LOD) were 279 nM, and 390 nM for LD and DA, respectively. Herein, an instrument-free, rapid quantification visual assay was developed using a paper-based analytical device (PAD) with LSV:0.015Eu3+ fixed on the bacterial cellulose nanopaper (LEBN) to determine LD and DA concentrations with ease of operation and low cost. A smartphone was coupled with the PAD device to quantitatively analyze the fluorescence intensity changes of LSV:0.015Eu3+ using the color recognizer application (APP). In addition, the LSV:0.015Eu3+ nanosensor showed acceptable repeatability and was used to analyze real human urine, blood serum, and tap water samples with a recovery of 96-107%.

GQD embedded bacterial cellulose nanopaper based multi-layered filtration membranes assembly for industrial dye and heavy metal removal in wastewater

GQD embedded bacterial cellulose nanopaper based multi-layered filtration membranes assembly for industrial dye and heavy metal removal in wastewater

Characterization of compressed bacterial cellulose nanopaper film after exposure to dry and humid conditions

This work investigates the effects of two different levels of humidity (RH 50% and 75%) on the characterizations of compressed bacterial cellulose nanopaper film. The film was prepared with different heat treatments; compression at 25 °C for 72 h and then at 100 °C for 24, 72 or 120 h. Maximum tensile strength (250.7 MPa) and tensile modulus (18.6 GPa) were measured on the film treated at 100 °C for 120 h and RH 50%. However, tensile strength and tensile modulus dropped by 53.6% and 75.8% respectively and elongation at break increased by 32% when this film was stored in more humid conditions (RH 75%). FTIR spectra and XRD patterns indicate changes of the deformed chain structure of the cellulose as more water was incorporated between the layers of the lattice after exposure to humidity.

TEMPO-oxidised nanocellulose hydrogels and self-standing films derived from bacterial cellulose nanopaper.

Hydrogels derived from TEMPO-oxidised cellulose nanofibrils (TOCNs) are not robust and inherently water unstable if the TOCNs are not crosslinked or coated with a water-swellable polymer. Furthermore, the manufacturing of self-standing TOCN films is still a challenge due to the small TOCN diameter and the viscosifying effect of TOCNs. Here, we report the TEMPO-mediated oxidation of bacterial cellulose (BC) nanopaper as a route to produce robust and water stable TOCN hydrogels without the need of additional additives or crosslinking steps. Pristine BC pellicle was first press-dried into a dried and well-consolidated BC nanopaper, followed by TEMPO-oxidation at various NaClO concentrations. The oxidation reaction introduced carboxylate moieties onto the exposed BC nanofibrils within the nanopaper network structure. This then led to the expansion and swelling of the nanopaper into a hydrogel. A swelling ratio of up to 100 times the original thickness of the BC nanopaper was observed upon TEMPO-oxidation. The water retention value of the TEMPO-oxidised BC hydrogels was also found to increase with increasing carboxylate content. These TEMPO-oxidised BC hydrogels were found to be robust and water-stable, even under prolonged (>1 month) magnetic stirring in water. We further showed that high grammage self-standing TOCN films (100 g m−2) can be fabricated as simple as press-drying these water stable TEMPO-oxidised BC hydrogels without the need of vacuum-assisted filtration or slow-drying, which is typically the rate-limiting step in the manufacturing of TOCN films.

Bacterial nanocellulose papers with high porosity for optimized permeance and rejection of nm-sized pollutants

Access to clean potable water is increasingly becoming a struggle for whole humankind, thus water treatment to remediate wastewater and fresh water sources is an important task. Pollutants in the nanoscale, such as viruses and macromolecules, are usually removed by means of membrane filtration processes, predominantly nanofiltration or ultrafiltration. Cellulose nanopapers, prepared from renewable resources and manufactured by papermaking, have recently been demonstrated to be versatile alternatives to polymer membranes in this domain. Unfortunately, so far nanopaper filters suffer from limited permeance and thus efficiency. We here present nanopapers made from bacterial cellulose dispersed in water or different types of low surface tension organic liquids (alcohol, ketone, ether) through a simple papermaking process. Nanopapers prepared from organic liquids (BC-org) exhibited 40 times higher permeance, caused by a lower paper density hence increased porosity, compared to conventional nanopapers produced from aqueous dispersions, ultimately enhancing the efficiency of bacterial cellulose nanopaper membranes. Despite their higher porosity, BC-org nanopapers still have pore sizes of 15–20 nm similar to BC nanopapers made from aqueous dispersions, thus enabling removal of contaminants the size of viruses by a size-exclusion mechanism at high permeance.

Anomalous tensile response of bacterial cellulose nanopaper at intermediate strain rates

Nanocellulose network in the form of cellulose nanopaper is an important material structure and its time-dependent mechanical response is crucial in many of its potential applications. In this work, we report the influences of grammage and strain rate on the tensile response of bacterial cellulose (BC) nanopaper. BC nanopaper with grammages of 20, 40, 60 and 80 g m−2 were tested in tension at strain rates ranging from 0.1% s−1 to 50% s−1. At strain rates le 2.5% s−1, both the tensile modulus and strength of the BC nanopapers stayed constant at ~ 14 GPa and ~ 120 MPa, respectively. At higher strain rates of 25% s−1 and 50% s−1 however, the tensile properties of the BC nanopapers decreased significantly. This observed anomalous tensile response of BC nanopaper is attributed to inertial effect, in which some of the curled BC nanofibres within the nanopaper structure do not have enough time to uncurl before failure at such high strain rates. Our measurements further showed that BC nanopaper showed little deformation under creep, with a secondary creep rate of only ~ 10–6 s−1. This stems from the highly crystalline nature of BC, as well as the large number of contact or physical crosslinking points between adjacent BC nanofibres, further reducing the mobility of the BC nanofibres in the nanopaper structure.

A simple strategy in enhancing moisture and thermal resistance and tensile properties of disintegrated bacterial cellulose nanopaper

Cellulose-based nanopaper with high moisture and thermal resistance and high tensile properties has many applications in the food packaging industry, electronics, and biosensors. The objective of the present work is to produce and characterize the disintegrated bacterial cellulose-based nanopaper film and its ZnO bionanocomposite prepared without and with compression. Addition of ZnO nanoparticles into nanopaper and compression improved the tensile and thermal properties and moisture resistance of the bionanocomposite. Compressed nanopaper film with 1.2 wt% ZnO had the highest tensile strength (TS) of 94.2 MPa and tensile modulus (TM) of 10.1 GPa. These TS and TM values were 109% and 172% higher than those of non-compressed film due to an increase in the crystal structure. Surprisingly this bionanocomposite also demonstrates higher elongation at break in comparison to the nanopaper film. All samples show good rollability and bendability. Compressed bionanocomposite had higher moisture resistance than non-compressed one. This work promotes an environmentally friendly bionanocomposite film which has good potential for food packaging applications.

Nanopaper-based screen-printed electrodes: a hybrid sensing bioplatform for dual opto-electrochemical sensing applications.

Given the importance of developing easy-to-use, disposable, affordable, and portable hybrid opto-electrochemical sensing devices, for the first time, we have developed a nanopaper-based screen-printed electrode (SPE) by taking advantage of the high optical transparency, affordability, biocompatibility, printability, flexibility, and other unrivaled physicochemical properties of bacterial cellulose (BC) nanopaper in screen printing technology. To fabricate the BC-SPE platform, a screen-printed three-electrode system was transferred onto the dried film of a pre-printed BC nanopaper-based substrate. Because of the optical transparency of the BC nanopaper, the fabricated BC-SPE platform can be used as a hybrid sensing platform for simultaneous optical and electrochemical (bio)sensing applications. A portable photometer was also assembled to measure the optical signals of the fabricated BC-SPE. The opto-electrochemical tunable properties of Prussian blue and their application in the dual optical and electrochemical sensing of acetaminophen as a model analyte were investigated using the fabricated BC-SPE to demonstrate the sensing applicability of the developed hybrid bioplatform. Moreover, we prove that our fabricated BC-SPE can be potentially exploited as a smartphone-based electrochemiluminescence (ECL) sensing platform. We envisage that our developed BC-SPE platform will find promising practical application in the detection of a wide range of (bio)chemicals, and also would be inspirational for the development of novel hybrid opto-electrochemical (bio)sensing devices.

Spectrophotometric and visual determination of zoledronic acid by using a bacterial cell-derived nanopaper doped with curcumin.

A nanopaper-based analytical device (NAD) is described for a colorimetric metal-complexing indicator-displacement assay (M-IDA) for zoledronic acid (ZA). Bacterial cellulose nanopaper was doped with curcumin to obtain a chemosensor on which hydrophilic test zones were patterned via laser printing of hydrophobic walls. The color intensity of the test zones decreases in the presence of Fe(III) due to the formation of Fe(III)-curcumin complex. However, upon addition of ZA, Fe(III) ions preferably binds ZA. Subsequently, the color of the zone changes from light yellow to dark yellow. The changes in the absorption (measured at 427nm) and of the color of the test stripe can be monitored visually, by using a digital camera, or by a spectrophotometer. Under optimal conditions, the analytical signals increase linearly in the 0.01-100μM ZA concentration range, and the detection limits are 8.8 and 8.0nM for smartphone and spectrophotometer-based methods, respectively. The method was employed to the determination of ZA in (spiked) urine, serum, saliva, and in pharmaceutical samples. Graphical abstract Schematic representation of a nanopaper-based analytical device based on curcumin-doped BC nanopaper (CDBC) integrated with smartphone for metal-complexing indicator-displacement assay of zoledronic acid (ZA). High affinity of ZA to Fe(III) on the NAD/CDBC leads to color change.

A nanocellulose-based colorimetric assay kit for smartphone sensing of iron and iron-chelating deferoxamine drug in biofluids

The current work describes the development of a “nanopaper-based analytical device (NAD)”, through the embedding of curcumin in transparent bacterial cellulose (BC) nanopaper, as a colorimetric assay kit for monitoring of iron and deferoxamine (DFO) as iron-chelating drug in biological fluids such as serum blood, urine and saliva. The iron sensing strategy using the developed assay kit is based on the decrease of the absorbance/color intensity of curcumin-embedded in BC nanopaper (CEBC) in the presence of Fe(III), due to the formation of Fe(III)-curcumin complex. On the other hand, releasing of Fe(III) from Fe(III)-CEBC upon addition of DFO as an iron-chelating drug, due to the high affinity of this drug to Fe(III) in competition with curcumin, which leads to recovery of the decreased absorption/color intensity of Fe(III)-CEBC, is utilized for selective colorimetric monitoring of this drug. The absorption/color changes of the fabricated assay kit as output signal can be monitored by smartphone camera or by using a spectrophotometer. The results of our developed sensor agreed well with the results from a clinical reference method for determination of Fe(III) concentration in human serum blood samples, which revealed the clinical applicability of our developed assay kit. Taken together, regarding the advantageous features of the developed sensor as an easy-to-use, non-toxic, disposable, cost-effective and portable assay kit, along with those of smartphone-based sensing, it is anticipated that this sensing bioplatform, which we name lab-on-nanopaper, will find utility for sensitive, selective and easy diagnosis of iron-related diseases (iron deficiency and iron overload) and therapeutic drug monitoring (TDM) of iron-chelating drugs in clinical analysis as well.

Lab-on-nanopaper: An optical sensing bioplatform based on curcumin embedded in bacterial nanocellulose as an albumin assay kit

Herein, we introduce a nanopaper-based analytical device (NAD) or “lab-on-nanopaper” device for visual sensing of human serum albumin (HSA) in human blood serums, which relies on embedding of curcumin within transparent bacterial cellulose (BC) nanopaper. BC nanopaper is an appropriate candidate to be an excellent platform for the development of optical (bio)sensors due to having exceptional properties such as optical transparency, high flexibility, porosity, biodegradability, and printability. The hydrophilic test zones were created on the fabricated bioplatform through creating the hydrophobic walls via laser printing technology. The color changes of curcumin embedded in BC nanopaper (CEBC) due to the inhibitory effect of HSA on the curcumin degradation in alkaline solutions, which can be monitored visually (naked eye/Smartphone camera) or spectroscopically using a spectrophotometer, were linearly proportional to the HSA concentration in the range of 10–300 μM and 25–400 μM, respectively. The developed NAD/CEBC as a novel albumin assay kit was successfully utilized to the determination of HSA in human blood serum samples with satisfactory results. Building upon the fascinating features of BC nanopaper as a very promising bioplatform in optical (bio)sensing applications we are confident “lab-on-nanopaper” devices/NADs, which take the advantages of the nanopaper and also meet the ASSURED criteria, could be considered as a new generation of optical (bio)sensing platforms that are currently based on paper, glass or plastic substrates.

Easy Diagnosis of Jaundice: A Smartphone-Based Nanosensor Bioplatform Using Photoluminescent Bacterial Nanopaper for Point-of-Care Diagnosis of Hyperbilirubinemia.

One of the concerns of parents in the first days of their baby's birth is the baby's risk of jaundice/hyperbilirubinemia. This is because more than 60% of babies are born with jaundice that, if not timely diagnosed and subsequently treated, can lead to serious damage to their health. On the other hand, despite recent progress in sensor technology for clinical applications, the development of easy-to-use, cost-effective, sensitive, specific, and portable diagnostic devices, which use nontoxic and biodegradable materials in their design and fabrication, is still in high demand. Herein we present an easy-to-use, cost-effective, selective, nontoxic, and disposable photoluminescent nanopaper-based assay kit with a smartphone readout for easy diagnosis of neonatal jaundice through visual determination of Bilirubin (BR) in infants' blood samples. The developed BR assay kit comprises highly photoluminescent carbon dot (CD) sensing probes embedded in a bacterial cellulose (BC) nanopaper substrate (CDBN). The photoluminescence (PL) of the developed BR sensor is quenched in the presence of BR as a PL quencher and then selectively recovered upon blue light (λ = 470 nm) exposure, due to conversion of the unconjugated BR to the colorless oxidation products (non-PL quencher) through BR photoisomerization and photooxidation, that subsequently leads to selective PL enhancement of CDBN. The recovered PL intensity of the developed BR assay kit, which was monitored by integrated smartphone camera, was linearly proportional to the concentration of BR in the range of 2-20 mg dL-1. The feasibility of real application of the fabricated smartphone-based BR assay kit was also confirmed via comparing the results of our method with a clinical reference method for determination of BR concentration in infant's blood samples. With the advantages of nontoxicity and the extraordinary physicochemical properties of photoluminescent BC nanopaper as the sensing substrate, along with those of smartphone technology, we believe that our developed smartphone-based BR assay kit, as an easy-to-use, cost-effective (∼0.01 Euro per test), portable and novel sensing bioplatform, can be potentially exploited for sensitive, specific, rapid, and easy BR detection and jaundice diagnosis at the point of care (POC) and in routine clinical laboratories as well.

Preparation and Characterization of Bacterial Cellulose-Carbon Dot Hybrid Nanopaper for Potential Sensing Applications

Green and facile approaches aiming at the manufacture of biocompatible paper-based optical sensors reporting the presence of photoluminescence (PL) modulating compounds is an emerging field of research. This study investigates the preparation of bacterial cellulose nanopaper containing covalently immobilized carbon dots for potential biosensing applications. Preliminary work of this feasibility study included TEMPO-mediated ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl-mediated) oxidation and nanofibrillation of bacterial cellulose (TOBC) on the one hand as well as synthesis and comparative analysis of different types of carbon dots (CDs) on the other hand. The two source materials of the targeted functional nanopaper were finally linked to each other by two different N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride/ N-hydroxysuccinimide (EDC/NHS) coupling approaches to clarify whether grafting of CDs prior to or after TOBC paper formation would be the method of choice. Synthesis of the carbon nanodots was accomplished by microwave-assisted co-hydrothermolysis of appropriate precursor compounds. After isolation and purification by dialysis particles in the single-digit nanometer-range were obtained and characterized with regard to their photoluminescence properties in terms of emission wavelength, pH stability, and quantum yield. All types of synthesized CDs reached their PL maxima (450–480 nm; light blue) in a narrow excitation wavelength range of 340–360 nm. Variation of molar (C/N) ratio of the CD precursors and substitution of the nitrogen donor EDEA by urea increased PL and quantum yield (QY), respectively. The highest relative QY of nearly 32% was obtained for CDs synthesized from citric acid and urea. PL of all CDs was virtually insensitive to pH changes in the range of 4–10. Tensile testing of hybrid nanopaper prepared after EDC/NHS-mediated grafting of GEA-type CDs onto TOBC (0.52 mmol·g−1 COOH) in dispersion state revealed that both stiffness and strength are not compromised by incorporation of carbon dots, while plastic deformation and elongation at break increased slightly compared to nanopaper formed prior to decoration with CDs. Water contact angle of the nanopaper is unaffected by introduction of carbon dots which is supposedly due to the presence of surface amino- and amide groups compensating for the loss of carboxyl groups by grafting.

Thinner and better: (Ultra-)low grammage bacterial cellulose nanopaper-reinforced polylactide composite laminates

One of the rate-limiting steps in the large-scale production of cellulose nanopaper-reinforced polymer composites is the time consuming dewatering step to produce the reinforcing cellulose nanopapers. In this work, we show that the dewatering time of bacterial cellulose (BC)-in-water suspension can be reduced by reducing the grammage of BC nanopaper to be produced. The influence of BC nanopaper grammage on the tensile properties of BC nanopaper-reinforced polylactide (PLLA) composites is also investigated in this work. BC nanopaper with grammages of 5, 10, 25 and 50 g m−2 were produced and it was found that reducing the grammage of BC nanopaper from 50 g m−2 to 5 g m−2 led to a three-fold reduction in the dewatering time of BC-in-water suspension. The porosity of the BC nanopapers, however, increased with decreasing BC nanopaper grammage. While the tensile properties of BC nanopapers were found to decrease with decreasing BC nanopaper grammage, no significant difference in the reinforcing ability of BC nanopaper with different grammages for PLLA was observed. All PLLA composite laminates reinforced with BC nanopapers possessed similar tensile modulus of 10.5–11.8 GPa and tensile strength of 95–111 MPa, respectively, at a BC loading fraction vf,BC = 39–53 vol.-%, independent of the grammage and tensile properties of the reinforcing BC nanopaper.

A rainbow ratiometric fluorescent sensor array on bacterial nanocellulose for visual discrimination of biothiols.

Considering the crucial role of biothiols in many biological processes, which turns them into highly valuable biomarkers for the early diagnosis of various diseases, the development of an affordable, sensitive and portable probe for the identification and discrimination of these compounds is of great importance. Herein, we developed a ratiometric fluorescent (RF) sensor array with a wide color emissive variation, on a bacterial cellulose (BC) nanopaper substrate for the visual discrimination of biothiols. To this aim, RF sensing elements including N-acetyl l-cysteine capped green CdTe quantum dots-rhodamine B (GQDs-RhB) and red CdTe QDs-carbon dots (RQDs-CDs) at two different NaOH concentrations (0 and 5 mM) were utilized as sensor elements for the discrimination of biothiols. Owing to the high affinity of the thiol group (SH) to the surface of CdTe QDs and the aggregation of the QDs, the fluorescence (FL) emission of the QDs changed while the emission of the CDs and rhodamine B remained almost unchanged upon the addition of biothiols. Accordingly, characteristic rainbow-like FL fingerprint patterns were created for each biothiol which were then distinguished both visually and spectroscopically. Hierarchical cluster analysis (HCA) and linear discriminant analysis (LDA) pattern recognition techniques were employed for the identification and discrimination of biothiols. Based on the designed RF sensor array, convenient test strips were fabricated on BC nanopaper for the visual discrimination of biothiols. It has been shown that this probe can successfully identify biothiols in human plasma as well. Altogether, the developed nanopaper-based sensor array offers an efficient biothiol discrimination tool that can be potentially exploited in the near future in theranostic and point-of-care applications.

A nanopaper-based artificial tongue: a ratiometric fluorescent sensor array on bacterial nanocellulose for chemical discrimination applications.

In the present study, a ratiometric fluorescent sensor array as an artificial tongue has been developed on a nanopaper platform for chemical discrimination applications. The bacterial cellulose (BC) nanopaper was utilized for the first time as a novel, flexible, and transparent substrate in the optical sensor arrays for developing high-performance artificial tongues. To fabricate this platform, the hydrophobic walls on the BC nanopaper substrates were successfully created using a laser printing technology. In addition, we have used the interesting photoluminescence (PL) properties of an immobilized ratiometric probe (carbon dot-Rhodamine B (CD-RhB) nanohybrids) on the nanopaper platform to improve the visual discrimination analysis. Heavy metal ions were utilized as model analytes to verify the applicability of the fabricated nanopaper-based ratiometric fluorescent sensor array (NRFSA). Using the color variation of the NRFSA platform upon the addition of heavy metal ions, which have been obtained by a smartphone (under an UV irradiation), five heavy metal ions (i.e., Hg(ii), Pb(ii), Cd(ii), Fe(iii), and Cu(ii)) have been well-distinguished through the RGB analysis via production of the characteristic PL fingerprint-like response patterns for each of them. Moreover, the developed optical sensor array was successfully exploited to identify the heavy metal ions in the water and fish samples. We have also found that the PL spectra, which have been obtained by a spectrofluorometer, of the developed NRFSA can be exploited for discrimination applications. We believe that the nanopaper-based artificial tongues will provide innovative insights into the development of optical sensor arrays towards advanced (bio)chemical discrimination applications and can revolutionize the conventional optical sensor array technology.