Fabrication of covalent organic frameworks modified nanofibrous membrane for efficiently enriching and detecting the trace polychlorinated biphenyls in water.

Enriching and detecting the trace pollutants in actual matrices are critical to evaluating the water quality. Herein, a novel nanofibrous membrane, named PAN-SiO2@TpPa, was prepared by in situ growing ß-ketoenamine-linked covalent organic frameworks (COF-TpPa) on the aminated polyacrylonitrile (PAN) nanofibers, and adopted for enriching the trace polychlorinated biphenyls (PCBs) in various natural water body (river, lake and sea water) through the solid-phase micro-extraction (SPME) process. The resulted nanofibrous membrane owned abundant functional groups (-NH-, -OH and aromatic groups), outstandingly thermal and chemical stability, and excellent ability in extracting PCBs congeners. Based on the SPME process, the PCBs congeners could be quantitatively analyzed by the traditional gas chromatography (GC) method, with the satisfactory linear relationship (R2>0.99), low detection limit (LODs, 0.1∼5 ng L-1), high enrichment factors (EFs, 2714∼3949) and multiple recycling (>150 runs). Meanwhile, when PAN-SiO2@TpPa was adopted in the real water samples, the low matrix effects on the enrichment of PCBs at both 5 and 50 ng L-1 over PAN-SiO2@TpPa membrane firmly revealed the feasibility of enriching the trace PCBs in real water. Besides, the related mechanism of extracting PCBs on PAN-SiO2@TpPa mainly involved the synergistic effect of hydrophobic effect, π-π stacking and hydrogen bonding.

Development of nanofiber indicator with high sensitivity for pork preservation and freshness monitoring.

A visual Polyvinylidene Fluoride (PVDF) fibrous film incorporated with Roselle anthocyanin (RS) and Cinnamon essential oil (CEO) (PRC film) was designed via electrospinning technology for pork preservation and freshness monitoring. The PRC film presented well structural integrity and stability in buffer solutions without leaking out RS. And PCR film had well hydrophobic and high permeability with water contact angle (WCA) of 109.52° and water vapor permeability (WVP) of 2.63 × 10-7 g m-1h-1Pa-1. Importantly, PRC film exhibited good antibacterial activity with the inhibition diameter at 29.0 mm and 27.1 mm which against Escherichia coli and staphylococcus aureus, respectively. Finally, the PRC film was employed as a colorimetric sensor for monitoring pork freshness. It presented visible color changes from pink to blue and effectively prolonged the pork shelf-life by 2 days at 4 °C. These results indicate a great potential in intelligent and active packaging.

Preparation and Characterization of Electrospun Polylactic Acid (PLA) Fiber Loaded with Birch Bark Triterpene Extract for Wound Dressing.

Drug-loaded electrospun fibers have attracted increasing attention as a promising wound dressing material due to their capability of preventing from infections and inflammation and maintaining an appropriate environment for wound healing. In this study, polylactic acid (PLA), which is widely used in wound management, was chosen as electrospinnable polymer. A triterpene extract (TE) from the outer bark of birch known for its anti-inflammatory, antiviral, antibacterial, and wound healing effects was chosen to produce TE-loaded PLA electrospun fibers for wound dressing. A binary solvent system of dichloromethane (DCM) and dimethyl sulfoxide (DMSO) was employed, and the ratio of the solvents was optimized for preparing smooth and uniform fibers. The morphology of TE-loaded PLA electrospun fibers was investigated by scanning electron microscopy (SEM). The entrapment of TE in PLA fibers was confirmed by confocal laser scanning microscopy (CLSM). Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were used to analyze the solid state of TE in PLA fibers. The release behavior of TE was assayed by a shaking flask method for a period of 96 h. The results revealed that TE-loaded electrospun PLA microfibers could be reliably prepared and are promising future candidates in wound therapy.

Electrospun orally disintegrating film formulation of telmisartan.

Telmisartan (TEL) is an antihypertensive BCS class II drug with low solubility at physiological pH. However, the solubility of TEL increases with the presence of an alkalizer. Electrospinning is one of the most recent techniques for the solubility enhancement studies. In this study, an electrospun orally disintegrating film (ODF) formulation of TEL was developed with L-arginine and polyvinylpyrrolidone K90 (PVP), and its characterization studies were performed. Preformulation studies were performed to investigate possible incompatibilities in the components of formulation with differential scanning calorimetry (DSC) and Fourier transform infrared spectrometer (FT-IR) analyses. ODFs were characterized in terms of drug content and uniformity, mechanical properties, fiber shape and diameter and in vitro dissolution profile. Smooth nanofibers without any beads were obtained. The dissolution rate of the TEL significantly increased. The chosen formulation had acceptable mechanical properties with much faster dissolution compared to the commercially available product. Developed ODF and marketed product were compared with a dissolution study in phosphate-buffered solution (pH 7.4). ODF and marketed product both reached 100% release in the 45th minute, and ODF results showed that ODF had much faster release than marketed product. In this study, TEL ODF formulation was successfully produced and characterized.

Enzyme-Instructed Self-Assembly Enabled Monomer-Excimer Transition to Construct Higher Ordered Luminescent Supramolecular Assembly for Activity-based Bioimaging.

It is challenging to construct high-performing excimer-based luminescent analytic tools at low molecular concentrations. We report that enzyme-instructed self-assembly (EISA) enables the monomer-excimer transition of a coumarin dye (Cou) at low molecular concentrations, and the resulting higher ordered luminescent supramolecular assemblies (i.e., nanofibers) efficiently record the spatiotemporal details of alkaline phosphatase (ALP) activity in vitro and in vivo. Cou was conjugated to short self-assembly peptides with a hydrophilic ALP-responsive group. By ALP triggering, EISA actuated a nanoparticles-nanofibers transition at low peptide concentrations followed by monomer-excimer transition of Cou. Analysis of structure-property relationships revealed that the self-assembly motif was a prerequisite for peptides to induce the monomer-excimer transition of Cou. Luminescent supramolecular nanofibers of pYD (LSN-pYD) illuminated the intercellular bridge of cancer cells and distinguished cancer cells (tissues) from normal cells (tissues) efficiently and rapidly, promising potential use for the early diagnosis of cancer. This work extends the functions of EISA and provides a new application of supramolecular chemistry.

Self-assembling nitrilotriacetic acid nanofibers for tracking and enriching His-tagged proteins in living cells.

Specific and expeditious identification and enrichment of target proteins in living cells is often a challenging task. The hexahistidine (6His) tag is frequently used to label artificially engineered proteins produced in prokaryotic or eukaryotic cells. Utilizing the interaction between 6His-tag and nitrilotriacetic acid (NTA) mediated by divalent metal ions (Ni2+, Cu2+, Zn2+ or Co2+), we designed and synthesized a series of Nap-G/Biotin/ANA-FFpYGK-NTA probes that, assisted by alkaline phosphatase (ALP), self-assemble into nanofibers. The probe consists of an NTA group that specifically binds to 6His-tag, an FFpY group that promotes self-assembly facilitated by ALP, and a hydrophobic (Nap-G/ANA/Biotin) capping group for various applications. We demonstrate that the ANA-FFpYGK-NTA(Ni2+) nanofibers are fit for real-time tracking of His-tagged protein in living cells, and the Biotin-FFpYGK-NTA(Ni2+) nanofibers are for isolating His-tagged proteins and other proteins that they interact with.

Effect of gamma irradiation on physico-mechanical and structural properties of active Farsi gum-CMC films containing Ziziphora clinopodioides essential oil and lignocellulose nanofibers for meat packaging.

The objective of this study was to examine the effect of gamma irradiation (0, 2.5, and 5 kGy) on physico-mechanical and structural characteristics of films based on Farsi gum-carboxymethyl cellulose supplemented with Ziziphora clinopodioides essential oil (ZEO; 0%, 1%, and 2%) and lignocellulose nanofibers (LCNF; 0%, 1%, and 2%), and their application on fresh minced beef meat's shelf-life during refrigerated temperature (4 ± 1 °C) for 16 days. Gamma irradiation under the 60 Co source at 2.5 and 5 kGy doses did not have a significant effect on thickness, tensile strength, swelling index, oxygen permeability, and water vapor transmission rate of prepared films (P > 0.05). The best microbiological (total viable count, psychrotrophic bacterial count, Pseudomonas spp., Brochothrix thermosphacta, lactic acid bacteria, and Enterobacteriaceae) and chemical (thiobarbituric acid reactive substances, total volatile base nitrogen content, and peroxide value) properties were recorded for samples packaged with ZEO 2% + LCNF 2%, followed by ZEO 2% + LCNF 1%, ZEO 1% + LCNF 2%, and ZEO 1% + LCNF 1%. These results indicate acceptable extensions of hurdle technology for prolonged refrigeration of minced beef meat. PRACTICAL APPLICATION: The application of active packaging films has received considerable interest in extending the shelf-life of perishable foods during prolonged chilled storage. The effects of active Farsi gum-carboxymethyl cellulose films supplemented with Ziziphora clinopodioides essential oil 2% + lignocellulose nanofibers 2% resulted in delaying lipid oxidation and microbial spoilage growth of refrigerated minced beef meat and consequently extending the shelf-life during storage for at least 16 days.

Co-production of xylo-oligosaccharides, xylose and cellulose nanofibrils from sugarcane bagasse.

This work investigated the integration of a two-stage hydrothermal treatment for production of xylooligosaccharides (XOS), a high-value product, into the isolation process of cellulose nanofibrils (CNF) from sugarcane bagasse. Under optimized conditions, the first stage yielded a XOS-rich, high purity hydrolysate and in the second stage only a xylose-rich hydrolysate could be obtained at high purity. The resulting solid cellulosic fraction was delignified and bleached to obtain a cellulose-rich pulp, which was mechanically defibrillated by disc ultra-refining to CNF. Except for the viscosity, the sugarcane CNF showed properties (i.e., thermal stability, crystallinity and diameter size) comparable or superior to the CNF prepared from commercial bleached eucalyptus Kraft pulp. In conclusion, the integration of the two-stage hydrothermal treatment is an efficient and promising strategy to obtain hemicellulose-derived high-value co-products in the process of isolating CNF. In addition, lignin was also recovered as a co-product with yield comparable to other biomass fractionation approaches.

Determination of textural deterioration in fish meat processed with electrospun nanofibers.

Nano-applications are named as one of the novel methods, which provide many advantages like a larger contact area on the surface of fish fillets with less material. The goal of the study was to reveal the textural profile changes correlated with TPB growth of fish fillets coated with nanofibers having 2.47 ± 0.68 mV zeta potential value and 172 nm diameter. The difference of TPB count between control (CS) and the fish fillets treated with nanofibers (NG) reached 3.45 log CFU/g (p < .05) on the sixth day. The hardness value of CS was decreased (p < .05) (the decline: 68%) while the hardness of NG was found to be much more stable (the change: 42%). The highest change in springiness for CS and NG samples was determined as ~24 and ~15%, respectively, for 12 days. Cohesiveness values of CS were slightly increased, but those of the fish fillets coated with nanofibers were remarkably decreased. The coefficient of correlation analysis between TPB count and cohesiveness values was determined as "r = -.026 and r = .796" for CS and NG, respectively. Chewiness values of CS were significantly decreased (p < .05). However, chewiness values of the fish fillets coated with nanofibers were found as much more stable (p > .05). The results revealed that nanofiber coating limited the increase of TPB in fish fillets; it also better kept the textural profile of fish fillets as compared to CS stored at 4°C. The study could play a guiding role in further food nanotechnology applications in the industry and food science.

Association of occupational exposures with ex vivo functional immune response in workers handling carbon nanotubes and nanofibers.

The objective of this study was to evaluate the association between carbon nanotube and nanofiber (CNT/F) exposure and ex vivo responses of whole blood challenged with secondary stimulants, adjusting for potential confounders, in a cross-sectional study of 102 workers. Multi-day exposure was measured by CNT/F structure count (SC) and elemental carbon (EC) air concentrations. Demographic, lifestyle and other occupational covariate data were obtained via questionnaire. Whole blood collected from each participant was incubated for 18 hours with and without two microbial stimulants (lipopolysaccharide/LPS and staphylococcal enterotoxin type B/SEB) using TruCulture technology to evaluate immune cell activity. Following incubation, supernatants were preserved and analyzed for protein concentrations. The stimulant:null response ratio for each individual protein was analyzed using multiple linear regression, followed by principal component (PC) analysis to determine whether patterns of protein response were related to CNT/F exposure. Adjusting for confounders, CNT/F metrics (most strongly, the SC-based) were significantly (p < 0.05) inversely associated with stimulant:null ratios of several individual biomarkers: GM-CSF, IFN-γ, interleukin (IL)-2, IL-4, IL-5, IL-10, IL-17, and IL-23. CNT/F metrics were significantly inversely associated with PC1 (a weighted mean of most biomarkers, explaining 25% of the variance in the protein ratios) and PC2 (a biomarker contrast, explaining 14%). Among other occupational exposures, only solvent exposure was significant (inversely related to PC2). CNT/F exposure metrics were uniquely related to stimulant responses in challenged whole blood, illustrating reduced responsiveness to a secondary stimulus. This approach, if replicated in other exposed populations, may present a relatively sensitive method to evaluate human response to CNT/F or other occupational exposures.

Coaxial Spinning of All-Cellulose Systems for Enhanced Toughness: Filaments of Oxidized Nanofibrils Sheathed in Cellulose II Regenerated from a Protic Ionic Liquid.

Hydrogels of TEMPO-oxidized nanocellulose were stabilized for dry-jet wet spinning using a shell of cellulose dissolved in 1,5-diazabicyclo[4.3.0]non-5-enium propionate ([DBNH][CO2Et]), a protic ionic liquid (PIL). Coagulation in an acidic water bath resulted in continuous core-shell filaments (CSFs) that were tough and flexible with an average dry (and wet) toughness of ∼11 (2) MJ·m-3 and elongation of ∼9 (14) %. The CSF morphology, chemical composition, thermal stability, crystallinity, and bacterial activity were assessed using scanning electron microscopy with energy-dispersive X-ray spectroscopy, liquid-state nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermogravimetric analysis, pyrolysis gas chromatography-mass spectrometry, wide-angle X-ray scattering, and bacterial cell culturing, respectively. The coaxial wet spinning yields PIL-free systems carrying on the surface the cellulose II polymorph, which not only enhances the toughness of the filaments but facilities their functionalization.

Preparation and characterization of naftifine-loaded poly(vinyl alcohol)/sodium alginate electrospun nanofibers

In this study, naftifine (a topical antifungal drug) loaded poly(vinyl) alcohol (PVA)/sodium alginate (SA) nanofibrous mats were prepared using the single-needle electrospinning technique. The produced nanofibers were crosslinked with glutaraldehyde (GTA) vapor. The morphology and diameter of the electrospun nanofibers were studied by scanning electron microscopy (SEM). SEM images showed the smoothness of the nanofibers and indicated that the fiber diameter increased with crosslinking and drug loading. Atomic force microscopy (AFM) images confirmed the uniform production of the scaffolds, and elemental mapping via energy dispersive X-ray spectroscopy (EDS) showed the uniform distribution of the drug within the nanofibers. An attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy study demonstrated that naftifine has sufficient secondary interactions with the polymer blend. The crosslinking treatment decreased the burst drug release effectively and the release mechanism followed Korsmeyer-Peppas Super Case-II transport. Overall, these findings suggest the potential use of naftifine-loaded PVA/SA nanofibers as a topical antifungal drug delivery system.

Synthetic Genetic Circuits for Self-Actuated Cellular Nanomaterial Fabrication Devices.

Genetically controlled synthetic biosystems are being developed to create nanoscale materials. These biosystems are modeled on the natural ability of living cells to synthesize materials: many organisms have dedicated proteins that synthesize a wide range of hard tissues and solid materials, such as nanomagnets and biosilica. We designed an autonomous living material synthesizing system consisting of engineered cells with genetic circuits that synthesize nanomaterials. The circuits encode a nanomaterial precursor-sensing module (sensor) coupled with a materials synthesis module. The sensor detects the presence of cadmium, gold, or iron ions, and this detection triggers the synthesis of the related nanomaterial-nucleating extracellular matrix. We demonstrate that when engineered cells sense the availability of a precursor ion, they express the corresponding extracellular matrix to form the nanomaterials. This proof-of-concept study shows that endowing cells with synthetic genetic circuits enables nanomaterial synthesis and has the potential to be extended to the synthesis of a variety of nanomaterials and biomaterials using a green approach.

Predicting Occupational Exposures to Carbon Nanotubes and Nanofibers Based on Workplace Determinants Modeling.

BACKGROUND: Recent cross-sectional epidemiologic studies have examined the association between human health effects and carbon nanotube and nanofiber (CNT/F) workplace exposures. However, due to the latency of many health effects of interest, cohort studies with sufficient follow-up will likely be needed. The objective of this study was to identify workplace determinants that contribute to exposure and develop predictive models to estimate CNT/F exposures for future use in epidemiologic studies. METHODS: Exposure measurements were compiled from 15 unique facilities for the metrics of elemental carbon (EC) mass at both the respirable and inhalable aerosol size fractions as well as a quantitative analysis performed by transmission electron microscopy (TEM). These metrics served as the dependent variables in model development. Repeated personal samples were collected from most of the 127 CNT/F worker participants for 252 total observations. Determinants were categorized as company-level or worker-level and used to describe the exposure relationship within the dependent variables. The influence of determinants on variance components was explored using mixed linear models that utilized a backwards stepwise selection process with a lowering of the AIC for model determinant selection. Additional ridge regression models were created that examined predictive performance with and without all two-way interactions. Cross-validation was performed on each model to evaluate the generalizability of its predictive capabilities while predictive performance was evaluated according to the corresponding R2 value and root mean square error (RMSE). RESULTS: Determinants at the company-level that increased exposure included an inadequate or semi-adequate engineering control rating, increasing average CNT/F diameter/length, daily quantities of material handled from 101 g to >1 kg and >1 kg, the use of CNF materials, the industry type of hybrid producer/user, and the expert assessment of a high exposure potential. Worker-level determinants associated with higher exposure included handling the dry-powdered form of CNT/F, handling daily quantities of material >1 kg, direct/indirect exposure, having the job title of engineer, using a respirator, using a ventilated or unventilated enclosure, and the job task of powder handling. The mixed linear models explained >60% of the total variance when using all company- and worker-level determinants to create the three exposure models. The cross-validated RMSE values for each of the three mixed models ranged from 2.50 to 4.23. Meanwhile, the ridge regression models, without all two-way interactions, estimated cross-validated RMSE values of 2.85, 2.23, and 2.76 for the predictive models of inhalable EC, respirable EC, and TEM, respectively. CONCLUSIONS: The ridge regression models demonstrated the best performance for predicting exposures to CNT/F for each exposure metric, although they only provided a modest predictive capability. Therefore, it was concluded that the models alone would not be adequate in predicting workplace exposures and would need to be integrated with other methods.

Amphotericin-B and vancomycin-loaded chitosan nanofiber for antifungal and antibacterial application

In the present study, a mucoadhesive non-woven fiber mat (d= 116 nm) was fabricated by the electrospinning method using chitosan (80% Wt), polyethylene oxide (10% Wt), cysteine (4% Wt) and drugs (6% Wt), respectively. In addition, a comparative study was conducted to define effect of drugs and mucoadhesive agent on the nanofiber formation. FTIR, SEM, DSC and DMA were used to investigate the chemical and physical properties of the nanofibers. In vitro release of the drugs was assessed over a 48-hour period by the total immersion method. Release data were fitted to kinetic models, including the zero-order, first-order, Higuchi matrix, and Hixson-Crowell. Zone inhibition investigations were used to describe the inhibition content of vancomycin and amphotericin B loaded in the mats. The SEM images displayed a slight decrease in the fiber diameter with adding drugs and mucoadhesive agents. FTIR spectra confirmed that any undesirable reaction between VAN-AMB and CS-PEO was not observed. DSC test recognized the uniform distribution of drugs in the polymeric bead of the fiber without any crystal form. The elasticity modulus of the nanofiber was in an acceptable range for oral mucosa (approximately 5 Mpa). The results indicated that biodegradable mucoadhesive nanofibrous membranes released high concentrations of VAN in the first 24 hours, but the AMB release was affected in more controlled phenomena

Preparation and Characterization of Tetrahydrocurcumin-Loaded Cellulose Acetate Phthalate/Polyethylene Glycol Electrospun Nanofibers.

A simple composite electrospun nanofiber of cellulose acetate phthalate (CAP)-polyethylene glycol (PEG) loaded with tetrahydrocurcumin (THC) was developed in this study, and the in vitro diffusion of THC was evaluated. The nanofibers were characterized by scanning electron microscopy, powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FT-IR), and differential scanning calorimetry (DSC). The formulated nanofiber (NF) with THC has smooth morphology with diameter of around 300-500 nm. The complete entrapment and dispersion of THC was observed from the results of PXRD and DSC due to the loss of THC crystalline property. Further, FT-IR demonstrated that the vibration bands for the polymers used were dominant over the THC, and the vibrational bands of THC were not observed from the final formulation. The drug entrapment by the final CAP + PEG NF was found to be 95.5% with the high swelling index. From the in vitro release study, it was found that the formulated THC-loaded CAP + PEG NF has followed anomalous mechanism, demonstrating both diffusion and swelling controlled modes. The drug release extended up to 12 h with a final cumulative release of 94.24%.

Adsorption performance of Cd(II), Cr(III), Cu(II), Ni(II), Pb(II) and Zn(II) by aminated solution-blown polyacrylonitrile micro/nanofibers.

In this work, we prepared amidoxime-functionalized polyacrylonitrile (APAN) micro/nanofibers by modifying solution-blown PAN fibers with hydroxylamine hydrochloride, and investigated the adsorption performance of the APAN fibers for Cd(II), Cr(III), Cu(II), Ni(II), Pb(II) and Zn(II) from aqueous solutions. Batch experiments and quantitative analysis were conducted considering initial pH and contact time as controlling parameters. The equilibrium data were better explained by the Langmuir model with maximum adsorption capacities of 185, 204, 105, 104, 345 and 91 mg/g for Cd(II), Cr(III), Cu(II), Ni(II), Pb(II) and Zn(II), respectively. The adsorption kinetics were found to follow the pseudo-second-order kinetic model. The calculated thermodynamic parameters demonstrated that the adsorption of metal ions onto APAN fibers is feasible, spontaneous and endothermic. The five adsorption-desorption cycle experiments showed that APAN micro/nanofiber adsorbent exhibits good reusability, and has a potential application for the removal of heavy metals from wastewater.

Association of pulmonary, cardiovascular, and hematologic metrics with carbon nanotube and nanofiber exposure among U.S. workers: a cross-sectional study.

BACKGROUND: Commercial use of carbon nanotubes and nanofibers (CNT/F) in composites and electronics is increasing; however, little is known about health effects among workers. We conducted a cross-sectional study among 108 workers at 12 U.S. CNT/F facilities. We evaluated chest symptoms or respiratory allergies since starting work with CNT/F, lung function, resting blood pressure (BP), resting heart rate (RHR), and complete blood count (CBC) components. METHODS: We conducted multi-day, full-shift sampling to measure background-corrected elemental carbon (EC) and CNT/F structure count concentrations, and collected induced sputum to measure CNT/F in the respiratory tract. We measured (nonspecific) fine and ultrafine particulate matter mass and count concentrations. Concurrently, we conducted physical examinations, BP measurement, and spirometry, and collected whole blood. We evaluated associations between exposures and health measures, adjusting for confounders related to lifestyle and other occupational exposures. RESULTS: CNT/F air concentrations were generally low, while 18% of participants had evidence of CNT/F in sputum. Respiratory allergy development was positively associated with inhalable EC (p=0.040) and number of years worked with CNT/F (p=0.008). No exposures were associated with spirometry-based metrics or pulmonary symptoms, nor were CNT/F-specific metrics related to BP or most CBC components. Systolic BP was positively associated with fine particulate matter (p-values: 0.015-0.054). RHR was positively associated with EC, at both the respirable (p=0.0074) and inhalable (p=0.0026) size fractions. Hematocrit was positively associated with the log of CNT/F structure counts (p=0.043). CONCLUSIONS: Most health measures were not associated with CNT/F. The positive associations between CNT/F exposure and respiratory allergies, RHR, and hematocrit counts may not be causal and require examination in other studies.

Hand-Held Volatilome Analyzer Based on Elastically Deformable Nanofibers.

This study reports on a hand-held volatilome analyzer for selective determination of clinically relevant biomarkers in exhaled breath. The sensing platform is based on electrospun polymer nanofiber-multiwalled carbon nanotube (MWCNT) sensing microchannels. Polymer nanofibers of poly(vinylidene fluoride) (PVDF), polystyrene (PS), and poly(methyl methacrylate) (PMMA) incorporated with MWCNT exhibits a stable response to interferences of humidity and CO2 and provides selective deformations upon exposure of exhaled breath target volatilomes acetone and toluene, exhibiting correlation to diabetes and lung cancer, respectively. The sensing microchannels "P1" (PVDF-MWCNT), "P2" (PS-MWCNT), and "P3" (PMMA-MWCNT) are integrated with a microfluidic cartridge (µ-card) that facilitates collection and concentration of exhaled breath. The volatilome analyzer consists of a conductivity monitoring unit, signal conditioning circuitries and a low energy display module. A combinatorial operation algorithm was developed for analyzing normalized resistivity changes of the sensing microchannels upon exposure to breath in the concentration ranges between 35 ppb and 3.0 ppm for acetone and 1 ppb and 10 ppm for toluene. Subsequently, responses of volatilomes from individuals in the different risk groups of diabetes were evaluated for validation of the proposed methodology. We foresee that proposed methodology provides an avenue for rapid detection of volatilomes thereby enabling point of care diagnosis in high-risk group individuals.

Evaluation of Mechanical Properties of Various Nanofibre Reinforced Bis-GMA/TEGDMA Based Dental Composite Resins / Evaluación de las propiedades mecánicas de varias resinas compuestas dentales basadas en Bis-GMA/TEGDMA reforzadas con nanofibras

ABSTRACT Objective: To investigate the mechanical properties of various mass fractions of Nylon 6 (N6), polymethyl-metacrylate (PMMA) and polyvinylidene-difluoride (PVDF) nanofibres reinforced bisphenol A-glycidyl methacrylate (Bis-GMA) and tri-ethylene glycol dimethacrylate (TEGDMA) based dental composite resins and to evaluate the penetration characteristics of the nanofibres into the resin. Methods: Nylon 6, PMMA and PVDF nanofibres were produced using the electrospinning method. The morphologies of the fabricated nanofibres were evaluated with a scanning electron microscope (SEM). The nanofibres were placed into the resin matrix at different mass fractions (3%, 5% and 7%). The three-point bending test was applied to nanofibre-reinforced dental composite resins and neat resin specimens. The flexural strength (Fs), flexural modulus (EY) and work of fracture (WOF) of the groups were found. The analysis of variance was used for the statistical analysis of the acquired data. Tukey 's multiple test was performed to compare the Fs, EY and WOF means. Fractured surfaces of the samples were observed by SEM, and fracture morphologies were evaluated. Results: Polymethyl-metacrylate nanofibres dissolved in the matrix, and a polymer alloy took place in the matrix. Fibre pull-out and fibre bridging mechanisms were observed by SEM images of the N6 and PVDF nanofibre-reinforced dental composites. The produced nanofibres enhanced the mechanical properties of the dental composite resins. Conclusion: Fibre pull-out and fibre bridging mechanisms on the fractured surfaces of samples may play a key role in the reinforcement of dental composite resins. However, polymer alloy of PMMA nanofibres increased the mechanical properties of the resin matrix.

RESUMEN Objetivo: Investigar las propiedades mecánicas de resinas compuestas dentales basadas en bisfenol A-diglicidildimetacrilato (Bis-GMA) y dimetacrilato trietilen-glicol (TEGDMA) reforzadas con nanofibras de fracciones de masa de Nylon 6 (N6), polimetilmetacrilato (PMMA) y fluoruro de polivinilideno (PVDF), y evaluar las características de la penetración de las nanofibras en la resina. Métodos: Se produjeron nanofibras de Nylon 6, PMMA y PVDF utilizando el método de electrohilado (electrospinning). Las morfologías de las nanofibras fabricadas fueron evaluadas con un microscopio electrónico de barrido (MEB). Las nanofibras fueron introducidas en la matriz de resina en diferentes fracciones de masa (3%, 5% y 7%). La prueba de flexión de tres puntos fue aplicada a las resinas compuestas dentales reforzadas por nanofibras y a las muestras de resina pura. La resistencia a la flexión (Rf), el módulo de flexión (EY) y el trabajo de fractura (WOF) de los grupos fueron halladas. El análisis de varianza se usó para el análisis estadístico de los datos adquiridos. Se realizó la prueba de comparaciones múltiples de Tukey con el propósito de comparar las medidas de Rf, EY y WOF. Las superficies fracturadas de las muestras fueron observadas mediante un MEB, y se evaluaron las morfologías de fractura. Resultados: Las nanofibras de polimetilmetacrilato se disolvieron en la matriz, y tuvo lugar una aleación de polímeros en la matriz. Los mecanismos de desprendimiento de fibras y puenteo de fibras fueron observados mediante imágenes de MEB de los compuestos dentales reforzados con nanofibras de N6 y PVDF. Las nanofibras producidas realzaron las propiedades mecánicas de las resinas compuestas dentales. Conclusión: Los mecanismos de desprendimiento de fibras y puenteo de fibras en las superficies fracturadas de las muestras pueden desempeñar un papel clave en el reforzamiento de las resinas de los compuestos dentales. Sin embargo, la aleación polimérica de las nanofibras de PMMA aumentó las propiedades mecánicas de la matriz de resina.