Agarose Film Research Articles

Fluorescent Carbon Dots: Aggregation-Induced Emission Enhancement, Application as Probe for CN- and Cr2O7-2, Sensing Strips and Bio-imaging Agent.

Fluorescent carbon dots (Trp-CDs) were prepared using tryptophan as precursor and were characterized on the basis of elemental analysis, powder-XRD, IR, Raman spectroscopy, 13C-NMR, UV-Vis, fluorescence and TEM. Trp-CDs exhibit poor fluorescence in 100% water but showed strong Aggregation Induced Emission (AIE) in ethanol and higher alcohols. The anion sensing study of Trp-CD revealed that it selectively detects CN- and Cr2O7-2 and from fluorescence quenching titration study, quenching constant, LOD and range of detection were evaluated. The emission life-time of Trp-CD before and after addition of CN- and Cr2O7-2 were measured, the decay curve before addition of anion was best fitted with a bi-exponential function with life-time of τ1 2.79ns (10.74%) and τ2 18.93ns (89.26%). The mechanistic study revealed that for CN-, the fluorescence quenching is due to its interaction with protons attached to surface functional groups and for Cr2O7-2, it is due to inner filter effect (IFE). Sensing strips were prepared by coating Trp-CDs onto various solid surfaces including agarose films and were used for detection of CN- and Cr2O7-. Trp-CD was found to be nontoxic and biocompatible and used as staining agent for Artemia and Bacteria (Bacillus Subtilis, Pseudomonas) and detection of CN- and Cr2O7-.

BIOPOLÍMERO QUITOSANA NA ADSORÇÃO DE GLIFOSATO: USO NO MONITORAMENTO OU REMEDIAÇÃO AMBIENTAL

In this work, low molecular weight chitosan was used to adsorb the herbicide glyphosate in aqueous solution. Considering the possibilities of remediation and monitoring in aquatic environments, chitosan was formatted into thin discs 0.8 mm thick and 2.5 cm in diameter. The films were characterized by SEM, EDS and FTIR. In the adsorption study, a chitosan disc was able to adsorb 100% of a 5 mgL-1 glyphosate solution. Pseudo-first-order, pseudo-second-order and Elovich kinetic models were applied and it was found that chemisorption predominates in the adsorption process. Thus, chitosan films can act very well as a material for remediating water bodies contaminated by glyphosate. For monitoring studies, the possibility of using chitosan films in DGT (Diffusive Gradients in Thin Films) technique was verified and the diffusive material used was 1.5% agarose film (m/v). The diffusion coefficient of glyphosate in the agarose gel was determined 7.94 x 10-10 m2s-1.

Dispersive micro solid-phase extraction combined with laser-induced breakdown spectroscopy for multielement extraction and determination

Dispersive micro solid-phase extraction (DμSPE) is based on efficiently introducing a reduced amount of solid phase into a liquid sample. Due to its large surface area and other desirable characteristics, graphene oxide has found application in the extraction of metal ions. The main objective of the present work is to use DμSPE in the development of an analytical method for the determination of metal ions, such as Al3+, Cu2+, Fe3+, Mn2+, Zn2+, Ti4+, Cd2+, Ni2+, and Cr3+, in liquid samples by laser-induced breakdown spectroscopy (LIBS). Taking full advantage of DμSPE combined with LIBS, graphene oxide containing metal was immobilized on agarose films and cellulose ester membranes. Calibration curves with linear ranges between 200 and 700 μg L−1 using cellulose ester membranes and between 200 and 500 μg L−1 using agarose films were obtained. Finally, the proposed method was applied on certified reference materials of drinking water (EP-H), groundwater (ES-L), and wastewater (EU-L).

Agarose Film-Based Liquid-Solid Conversion for Heavy Metal Detection of Water Samples by Laser-Induced Breakdown Spectroscopy.

Laser-induced breakdown spectroscopy (LIBS) shows promising applications in the analysis of environmental heavy metals. However, direct analysis in water by LIBS faces the problems of droplet splashing and laser energy decay. In this study, a novel liquid-solid conversion method based on agarose films is proposed to provide an easy-to-operate and sensitive detection of heavy metals. First, the water samples were converted into semi-solid hydrogels with the aid of agarose and then dried into agarose films to make the signal intensities stronger. The calibration curves of Cd, Pb and Cr were constructed. The proposed method was validated by standard heavy metal solutions and real water samples. The results showed that the values of R2 were 0.990, 0.989 and 0.975, and the values of the LOD were 0.011, 0.122 and 0.118 mg L-1 for Cd (I) 228.80, Pb (I) 405.78 and Cr (I) 427.48 nm, respectively. The RMSEs of validation were 0.068 (Cd), 0.107 (Pb) and 0.112 mg·L-1 (Cr), and the recovery values were in the range of 91.2-107.9%. The agarose film-based liquid-solid conversion method achieved the desired ease of operation and sensitivity of LIBS in heavy-metal detection, thereby, showing good application prospects in heavy metal monitoring of water.

Alternative Ecosorbent for the Determination of Trihalomethanes in Aqueous Samples in SPME Mode.

A new sorbent material based on modified clay with ionic liquid immobilized into an agarose film was developed as part of this study. It was applied to determine organochlorine pollutants, like disinfection byproducts, through headspace solid-phase microextraction-gas chromatography-electron capture detection (HS-SPME-GC-ECD). The disinfection byproducts determined in this study were used as model molecules because they were volatile compounds, with proven severe effects on human health. Their presence in aquatic environments is in trace concentrations (from pg L-1 to mg L-1). They are classified as emergent pollutants and their determination is a challenge for analytical chemists. The parameters which affected the extraction efficiency, i.e., number and distance between SPME discs, salt concentration, the temperature of extraction, extraction time, and desorption time, were optimized. A wide linear dynamic range of 10-1000 ng mL-1 and coefficients of determination better than 0.997 were achieved. The limits of detection and the limits of quantitation were found in the ranges of (1.7-3.7) ng mL-1 and (5.6-9.9) ng mL-1, respectively. The precision, expressed as relative standard deviation (RSD), was better than 8%. The developed sorbent exhibits good adsorption affinity. The applicability of the proposed methodology for the analysis of trihalomethanes in environmental and water samples showed recoveries in the range of 86-95%. Finally, the newly created method fully complied with the principles of green chemistry. Due to the fact that the sorbent holder was made of agarose, which is a wholly biodegradable material, sorbent clay is a widespread material in nature. Moreover, the reagents intercalated into the montmorillonite are new green solvents, and during the whole procedure, low amounts of organic solvents were used.

The properties of an activated carbon-containing agarose film for the amelioration of 2-amino acetophenone malodour as produced in chronic wounds infected with Pseudomonas aeruginosa

The properties of an activated carbon-containing agarose film for the amelioration of 2-amino acetophenone malodour as produced in chronic wounds infected with Pseudomonas aeruginosa

A highly sensitive PNA-microarray system for miRNA122 recognition.

Surface chemistry is a fundamental aspect of the development of the sensitive biosensor based on microarray technology. Here, an advanced PNA-microarray system for the detection of miRNA, composed by a multilayered Si/Al/Agarose component, is described. A straightforward optical signal enhancement is achieved thanks to a combination of the Al film mirror effect and the positive interference for the emission wavelength of the Cy5 fluorescent label tuned by the agarose film. The PNA-microarray was investigated for the detection of miRNA_122, resulting in a sensitivity of about 1.75μM-1 and Limit of Detection in the range of 0.043nM as a function of the capture probe sequence. The contribution, in terms of H-bonds amounts at 298 and 333 K, of the agarose coating to the dsPNA-RNA interactions was demonstrated by Molecular Dynamic simulations. These results pave the way for advanced sensing strategies suitable for the environmental monitoring and the public safety.

Rosmarinic Acid-Capped Silver Nanoparticles for Colorimetric Detection of CN- and Redox-Modulated Surface Reaction-Aided Detection of Cr(VI) in Water.

Rosmarinic acid-capped silver nanoparticles (Ro-AgNPs) were prepared and applied as a probe for selective colorimetric detection of cyanide (CN–) and chromium(VI) [Cr(VI)] under different conditions in aqueous media. The carbon atom of CN– interacts with the AgNPs, and the carbon atom donates electrons from the HOMO to the vacant orbitals of the coordinatively unsaturated surface atom (Ag0). After donating electrons, CN– attached onto the surface of the nanoparticles becomes very reactive and interacts with dissolved oxygen and generates reactive oxygen species (ROS) such as superoxide (O2–), singlet oxygen (1O2), and so forth. In this process, Ag0 oxidizes to Ag+ and combines with CN– forming water-insoluble AgCN, and the ROS (O2–) formed reacts with Ag/Ag+ to form Ag2O. The oxidation of Ag0 to Ag+ resulted in dissolution of AgNPs, which causes disappearance of the surface plasmon resonance band and color change from yellow to colorless. For detection of Cr(VI), ascorbic acid and CN– were added first; the ascorbic acid replaced the rosmarinic acid and then reduced the added Cr(VI) to Cr(III), and, in this process, ascorbic acid was oxidized to dehydroascorbic acid, which moved away from the nanoparticles’ surface. CN– then interacted with the surface Ag0 atom, got activated, and interacted with dissolved oxygen forming Ag+ and ROS, which then followed the same process as described for CN– to form AgCN and Ag2O with a color change. The limits of detection were found to be 0.01 and 0.03 μM for CN– and Cr(VI), respectively. The material was also used for sensing CN– and Cr(VI) in real samples, and the results obtained were satisfactory. For field application, agarose-based strips were prepared by immobilizing the nanoparticles onto the agarose film and successfully used for the detection of CN– and Cr(VI) in water.

Physicochemical and statistical characterization of gas-sensing behaviors of resonator sensors with carbonaceous films prepared by rf-sputtering of aromatic and hydrophilic biomolecules

Quartz crystal resonators coated with gas-sorptive films were characterized by analyzing their structures and their organic gas-sorption behaviors, which were then studied using statistics and computational molecular simulations. The films had carbonaceous structures that were prepared by radio-frequency (rf) sputtering of aromatic biomolecules, such as cytosine and lignin. These films had been compared with the rf-sputtered films of hydrophilic biopolymer of lignin and gelatin.The composition and morphology of each film governed the organic gas-sorption characteristics of the resonator sensors used for organic gas-sensing. The cytosine film, which was nitrogen-rich and layered, had a moderate affinity for the larger molecules of normal alcohols and acetate esters. The cytosine film is repulsive to positively-charged moieties of adsorbates. In contrast, the agarose film, which was nitrogen-poor and columnar, had a high affinity for small adsorbates with short hydrocarbon chains. Molecular flexibility of the adsorbate played an important role in the gas-sorption ability of the agarose film. Molecular dynamics simulation clarified that the weakly dipolar adsorbate-aggregate were immiscible in the cytosine adsorbent-aggregate because the collision mixture was prone to be instable. In practice, the cytosine-sputtered film had a higher gas-sorption ability for weakly dipolar species that have the longer hydrocarbon chains.

A Humidity-Powered Soft Robot with Fast Rolling Locomotion.

A range of soft robotic systems have recently been developed that use soft, flexible materials and respond to environmental stimulus. The greatest challenge in their design is the integration of the actuator, energy sources, and body of robots while achieving fast locomotion and well-defined programmable trajectories. This work presents such a design that operates under constant conditions without the need for an externally modulated stimulus. By using a humidity-sensitive agarose film and overcoming the isotropic and random bending of the film, the robot, which we call the Hydrollbot, harnesses energy from evaporation for spontaneous and continuous fast self-rolling locomotion with a programmable trajectory in a constant-humidity environment. Moreover, the geometric parameters of the film were fine-tuned to maximize the rolling speed, and the optimised hydrollbot is capable of carrying a payload up to 100% of its own weight. The ability to self-propel fast under constant conditions with programmable trajectories will confer practical advantages to this robot in the applications for sensors, medical robots, actuation, etc.

Modulation of physicochemical properties of magnetic agarose microspheres by hydrolysis-suppressive sequential crosslinking

Separation and purification of target proteins are essential for drug discovery and development. A magnetic separation has been exploited due to its high efficiency. Despite many studies on chemical crosslinking of a magnetic agarose microsphere (MAM), the study on a crosslinking reaction preventing MAM from hydrolytic degradation during the reaction and the effects of the crosslinks on the physicochemical and electrochemical properties of the crosslinked MAM (CL-MAM) has rarely been reported. In our study, CL-MAM was prepared using a sequential crosslinking by which MAM was crosslinked using epichlorohydrin (ECH) in DMSO after crosslinking the MAM by 1,3-dichloro-2-propanol (DCP) for a short time. Such a crosslinking prevented the hydrolytic degradation of DCP-crosslinked MAM ( D -CL-MAM) and DCP and ECH-crosslinked MAM (DE-CL-MAM). MAM had a mean diameter of 110 ± 57.42 µm and its morphology was not affected by the crosslinking. In FT-IR analysis, increase of peak intensity at 1037 cm −1 confirmed newly formed C-O-C bonds in the agarose of CL-MAM. Thermal stability of MAM increased by both DCP crosslinking and subsequent ECH crosslinking of the agarose. While T g of MAM was not shifted by the crosslinking, the onset temperatures of glass transition and thermal decomposition increased by DCP crosslinking and further increased by DCP and ECH-crosslinking. Stiffness (S) and elastic modulus (E) of MAM were enhanced by DCP crosslinking and subsequent ECH crosslinking, indicating a half of ECH formed crosslinks between agarose mainchains while the other half crosslinked adjacent pyranose rings in the agarose mainchain. Permittivity analysis revealed that α relaxation temperature of the agarose film corresponded to T g determined by DSC analysis and the relaxation intensity decreased with increasing crosslink density of the agarose. The higher swelling ratio of DE-CL-MAM compared to D -CL-MAM was attributed to greater S and E values of DE-CL-MAM. The hydrolysis-repressive sequential crosslinking of MAM using DCP and ECH can be a feasible approach to modulate physicochemical and electrochemical properties of MAM. • Hydrolysis-suppressive crosslinkings by DCP and ECH were effective to crosslink MAM. • DCP-crosslinked MAM had enough stability to be crosslinkable by ECH in DMSO. • The sequential crosslinkings did not induce morphological changes of the MAM. • The crosslinking improved thermal stability of MAM, not influencing T g . • Mechanical and swelling properties of crosslinked MAM depended on degree of crosslinks.

Hydrogen-Bonding-Induced H-Aggregation of Charge-Transfer Complexes for Ultra-Efficient Second Near-Infrared Region Photothermal Conversion

Hydrogen-Bonding-Induced H-Aggregation of Charge-Transfer Complexes for Ultra-Efficient Second Near-Infrared Region Photothermal Conversion

Photoinitiated Free-Radical Polymerization of 4,5,6,7-Tetrahalogenated Fluoresceins.

We demonstrated the photoredox catalytic performances of fluorescein derivatives, bearing heavy halogen atoms (Br or I) on a benzoic acid group, using photoinitiated free-radical polymerization. 4,5,6,7-Tetrabromofluorescein and 4,5,6,7-tetraiodofluorescein were used as visible-light-photoredox catalysts to initiate polymerization of poly(ethylene glycol) diacrylate and N-vinylpyrrolidone in the presence of triethanolamine under aerobic conditions. Their photocatalytic performances were evaluated by the hydrogelation of photopolymerization both on the surface of an agarose film and in a liquid solution. The polymerization degree increased considerably in the following order: tetraiodofluorescein<tetrabromofluorescein<fluorescein. This result was different from fluorescein derivatives containing the heavy halogen atoms on a xanthene core ring. Consequently, the location of the heavy halogen atoms was crucial in the photocatalytic performance of fluorescein derivatives.

Stable dual-emissive fluorescin@UiO-67 metal-organic frameworks for visual and ratiometric sensing of Al3+ and ascorbic acid

Encapsulation of fluorophore in metal organic framework (MOF) is an effective method to construct multi-emissive composites. Unfortunately, the small molecules loaded in MOF pores are easy to leak. To overcome this difficulty, fluorescin (FL) is proposed to be encapsulated tightly in the cage of the small tetrahedron of UiO-67, as one of the organic ligands coordinated with the central ion Zr. Finally, stable multi-emission fluorescence was successfully achieved, and Förster resonance energy transfer (FRET) occurred between FL and UiO-67. Ascorbic acid (AA) can dynamically quench the fluorescence of FL@UiO-67 nanoclusters (NCs) through internal filtering effect, photoinduced electron transfer (PET). The detection limit of the probe for AA was as low as 0.20 μM, and the detection range was 0.67 μM-0.36 mM. The probe was further employed to detect Al3+ due to the coordination between Al3+ and the carboxyl group in the FL@UiO-67 NCs. The detection limit for Al3+ was 3.3 nM, and the linear range was 11 nM-5 μM agarose film and test paper were both prepared successfully for visual detection of AA and Al3+. This work provides new ideas for low-cost and convenient real-time detection method.

Controlling Surface-Induced Platelet Activation by Agarose and Gelatin-Based Hydrogel Films.

Platelet-surface interaction is of paramount importance in biomedical applications as well as in vitro studies. However, controlling platelet-surface activation is challenging and still requires more effort as they activate immediately when contacting with any nonphysiological surface. As hydrogels are highly biocompatible, in this study, we developed agarose and gelatin-based hydrogel films to inhibit platelet-surface adhesion. We found promising agarose films that exhibit higher surface wettability, better controlled-swelling properties, and greater stiffness compared to gelatin, resulting in a strong reduction of platelet adhesion. Mechanical properties and surface wettability of the hydrogel films were varied by adding magnetite (Fe3O4) nanoparticles. While all of the films prevented platelet spreading, films formed by agarose and its nanocomposite repelled platelets and inhibited platelet adhesion and activation stronger than those of gelatin. Our results showed that platelet-surface activation is modulated by controlling the properties of the films underneath platelets and that the bioinert agarose can be potentially translated to the development of platelet storage and other medical applications.

Drug Release from Polymer Thin Films and Gel Pellets: Insights from Programmed Microplate Electroanalysis.

Robotic electroanalysis in 24-well microplates was used to determine Paracetamol (PCT) release from thin films of chitosan and two pH-sensitive synthetic polymers as well as blends of the polymers with each other and with agarose. Square-wave voltammograms were recorded automatically in a potential window of 0.35 V-0.85 V vs. Ag/AgCl/0.1 M KCl and their evaluation revealed time-dependent PCT release into acidic and basic media. Comparison of the release profiles showed that pure chitosan layers released PCT quickly in a single-phase process while liberation from synthetic polymer thin films was slower with a sigmoidal shape at pH 1.2 and pH 8.0 with a maximum release of PCT after approximately 150 and 140 min, respectively. The release profile from thicker agarose films was between those of the thin films. Agarose blended with chitosan or synthetic polymers formed films with biphasic release behavior. Chitosan linearized the initial section of the release profile in chitosan/polymer blends. The automated procedure for release testing offers the advantage of low-cost, labor-effective and error-free data acquisition. The procedure has been validated as a useful microplate assay option for release profile testing.

Micropatterned Biphasic Nanocomposite Platform for Maintaining Chondrocyte Morphology.

One major limitation hindering the translation of in vitro osteoarthritis research into clinical disease-modifying therapies is that chondrocytes rapidly spread and dedifferentiate under standard monolayer conditions. Current strategies to maintain rounded morphologies of chondrocytes in culture either unnaturally restrict adhesion and place chondrocytes in an excessively stiff mechanical environment or are impractical for use in many applications. To address the limitations of current techniques, we have developed a unique composite thin-film cell culture platform, the CellWell, to model articular cartilage that utilizes micropatterned hemispheroidal wells, precisely sized to fit individual cells (12-18 μm diameters), to promote physiologically spheroidal chondrocyte morphologies while maintaining compatibility with standard cell culture and analytical techniques. CellWells were constructed of 15-μm-thick 5% agarose films embedded with electrospun poly(vinyl alcohol) (PVA) nanofibers. Transmission electron microscope (TEM) images of PVA nanofibers revealed a mean diameter of 60.9 ± 24 nm, closely matching the observed 53.8 ± 29 nm mean diameter of human ankle collagen II fibers. Using AFM nanoindentation, CellWells were found to have compressive moduli of 158 ± 0.60 kPa at 15 μm/s indentation, closely matching published stiffness values of the native pericellular matrix. Primary human articular chondrocytes taken from ankle cartilage were seeded in CellWells and assessed at 24 h. Chondrocytes maintained their rounded morphology in CellWells (mean aspect ratio of 0.87 ± 0.1 vs three-dimensional (3D) control [0.86 ± 0.1]) more effectively than those seeded under standard conditions (0.65 ± 0.3), with average viability of >85%. The CellWell's design, with open, hemispheroidal wells in a thin film substrate of physiological stiffness, combines the practical advantages of two-dimensional (2D) culture systems with the physiological advantages of 3D systems. Through its ease of use and ability to maintain the physiological morphology of chondrocytes, we expect that the CellWell will enhance the clinical translatability of future studies conducted using this culture platform.

Novel ABTS-dot-blot method for the assessment of antioxidant properties of food packaging

Abstract The new ABTS-dot-blot method for the direct determination of antioxidant activity of active packaging that is in contact with foodstuffs has been developed. The usefulness of the new method was verified with the use of agarose, pork gelatin, bacterial cellulose and cellulose-chitosan films with incorporated standard antioxidant – Trolox or plant phytochemicals derived from three types of berry juices (chokeberry, blue-berried honeysuckle, rowanberry) or green tea. The plant components used for preparation of films were characterized by antioxidant profiling with the use of HPLC coupled with post-column derivatization with ABTS. The most abundant antioxidants were polyphenols, mainly anthocyanins, hydroxycinnamates and flavan-3-ols. The antioxidant properties of different types of films studied were evaluated by typical cuvette spectrophotometric ABTS test or by the novel method employing ABTS radical stabilised in an agarose gel. The results obtained for the Trolox containing films showed quantitative linear relationship between antioxidant content and the degree of ABTS bleaching in agarose gel. The results of both standard spectrophotometric method as well as ABTS-dot-blot approach indicated that gelatin, bacterial cellulose and chitosan on their own possessed antioxidant activity, which was substantially increased (6–10 times) by the addition of phytochemicals during film preparation. The highest antioxidant activity was observed for microbial cellulose films, which were prepared on the basis of material obtained during the kombucha drink production.

Surface Functionalization of Plastic Surfaces with Non-Biofouling Agarose Film to Develop a Chip-Based Platform.

We chemically functionalized several plastic surfaces using an agarose film for applying a protein chip. The chip performance was affected by the surface energy of each plastic after oxygen-plasma cleaning; as a result, polystyrene and polyethylene terephthalate showed a higher signal-to-noise ratio than did polypropylene. We envision that this study will help to develop a way to build biochips.

Raman and Fluorescence Imaging of Polyoxometalate Composite Agarose Films

Composite agarose films were prepared with EuIII containing polyoxometalates, in particular the organic‐inorganic hybrid [Eu(W5O18)2(pic)4]13– (Hpic = 3‐hydroxypicolinic acid) and a Mo blue EuIII derivative. The latter compound shows interesting EuIII based photoluminescence properties, described for a molybdenum blue compound for the first time. Imaging of optical properties and morphology of the films was explored by Raman and fluorescence measurements in a confocal microscopy system, together with the AFM profile. Raman and fluorescence imaging are powerful tools for the characterization of the films, in particular their chemical composition and homogeneity at the micrometric scale.