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Biodegradable and eco-friendly adsorbents composed of natural carbohydrates have been used to replace carbon-based materials. This study presents a natural carbohydrate-based chitosan/pectin (CS/Pec) hydrogel adsorbent to remove Pb(II) from aqueous solutions. The physical CS/Pec hydrogel was prepared by blending aqueous CS and Pec solutions at 65 °C, preventing the use of toxic chemistries (crosslinking agents). The thermosensitive CS/Pec hydrogel was quickly created by cooling CS/Pec blend at room temperature. The used strategy created stable CS/Pec hydrogel against disintegration and water dissolution. The as-prepared hydrogel was characterized by infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The adsorbent had 1.688 mmol -COO− for each gram. These ionized sites bind Pb(II) ions, promoting their adsorption. The adsorption kinetic and equilibrium studies indicated that the Elovich and pseudo-second-order models adjusted well to the experimental data, respectively. The maximum removal capacities (qm) predicted by the Langmuir and Sips isotherms achieved 108.2 and 97.55 mg/g at 0.83 g/L adsorbent dosage (pH 4.0). The hydrogel/Pb(II) pair was characterized by scanning electron microscopy (SEM), X-ray dispersive energy (EDS), and differential scanning calorimetry (DSC). The chemisorption seems to play an essential role in the Pb(II) adsorption. Therefore, the adsorbent was not recovered, showing low potential for reusability.

Here we report a new and straightforward method to yield durable polyelectrolyte complexes (hydrogel PECs) from gellan gum (GG) and chitosan (CS) assemblies, without metallic and covalent crosslinking agents, commonly used to produce GG and CS-based hydrogels, respectively. This new approach overcomes challenges of obtaining stable and durable GG-based hydrogels with structural homogeneity, avoiding precipitation and aqueous instability, typical of PEC-based materials. PECs are created by blending CS:GG solutions (at 60 °C) with GG:CS weight ratios between 80:20 to 40:60. X-ray photoelectron spectroscopy (XPS) analysis shows that CS-GG chains are interacting by electrostatic and intermolecular forces, conferring a high degree of association to the washed PECs, characteristic of self-assembling of polymer chains. The CS:GG weight ratio can be tuned to improve polyelectrolyte complex (PEC) high porosity, stability, porous homogeneity, and degradation rate. Physical and thermosensitive CS/GG-based hydrogels can have advantages over conventional materials produced by chemical processes.

Research in biosensing currently occupies an important role among biomolecular detection techniques, especially with respect to medical diagnoses. Is this sense, the development of biosensors based on the localized surface plasmon resonance (an optical transducer) or electrochemical transductions have been highlighted. However, optical and electrochemical detection working together enable more versatile detections in biosensing. Thus, we propose a dual sensor, which incorporates these two mechanisms on the same platform. The sensor shared the same transducer that was based on a glass-indium thin oxide (ITO) surface covered with gold nanoparticles. The transducer was prepared by the immobilization of gold nanoparticles on (3-aminopropyl)triethoxysilane-activated glass-ITO. The substrate ability to respond to physical surface variations was assessed. For this, measurements of the gold nanoparticles band redshift (plasmonic transduction) and charge transfer resistance from impedance spectra (electrochemical transduction) were performed. The platform was able to detect streptavidin immobilized on the surface by both mechanisms demonstrating its applicability as a device for biodetection in dual detection mode.

NLS was used to prepare holed plasmonic substrates with high sensitivity to streptavidin detection. SEM and AFM characterizations showed substrates with holes distribution of 240.1 ± 27.8 nm and periodicity of 420.2 ± 25.4 nm. These substrates showed a sensitivity of 382.40 ± 11.60 nm/RIU in solutions with different refractive indexes. The sensor has demonstrated high sensitivity in the biosensing of biotin-streptavidin. The immunoassay showed a 1.8 ± 0.3 nm LSPR peak redshift in the protein detection. This work forms a foundation towards the cost-effective plasmonic biosensors.

Trans-resveratrol (t-RESV) is an important and natural polyphenolic antioxidant generally found in grapes and in its derivatives such as red wine and grape juices. The t-RESV has been explored in the pharmaceutical industry for its anti-inflammatory, anti-cancer, and neuroprotective properties. The t-RESV electrochemical determination has basically been carried out using modified electrodes-based sensors. Although these devices show good analytical performance, the electrode preparation can be laborious, and the devices may lack reproducibility. In this sense, it was proposed here a new methodology for the t-RESV electrochemical detection using unmodified screen-printed electrodes and differential pulse voltammetry (DPV). The response of the anodic signal has optimized varying the most important parameters of DPV (pulse time, pulse potential, and pulse step) using the response surface methodology. We showed based on analysis of variance that the new mathematical model developed can predict responses for the t-RESV using DPV. Furthermore, the new analytical method was validated from the limits of detection and quantification. We have still shown that t-RESV can be quantified in commercial drug using DPV with the optimized parameters. The selectivity test also showed that the sensor can be used to determine the antioxidant in other more complex matrices. Additionally, the proposed electrochemical system is completely portable and can work with its own energy, which facilitates point-of-care analysis.

Hydrogels based on alginate and tanfloc (a cationic biopolymer obtained from natural condensed tannins) were successfully prepared. Tanfloc (TN) presents high aqueous solubility at pHs lower than 10; it contains substituted amino sites and molar weight of ca. 600,000gmol-1. A factorial design (22) was used to optimize the yield of alginate/tanfloc polyelectrolyte complexes (PECs). Dialysis recovered the overplus of alginate (AG) no complexed with TN. These materials were characterized by thermal analyses (TGA/DTG and DSC), zeta potential, and FTIR, while SEM technique depicted a rough surface on AG/TN complex, containing non-homogeneous pores. Indeed, the AG and TN were tailored to elicit scaffold materials with outstanding cytocompatibility, mainly upon mouse preosteoblastic cells because of reconstruction of bone tissues (119% at 10days). The AG/TN complex also displayed antioxidant and bactericidal activities against Staphylococcus aureus (S. aureus). Besides, the pristine TN fostered bacteriostatic and bactericidal performances towards S. aureus and Escherichia coli. However, for our best knowledge, no studies were still carried out on TN and TN-based materials for medical purpose.

Thermosensitive hydrogels based on chitosan/pectin (CS/Pec) and CS/Pec/gold nanoparticles (CS/Pec/AuNPs) were successfully prepared with different AuNP levels. Using a tilting method, gelation temperature was demonstrated to decrease when the amount of AuNPs increased and pectin concentrations decreased. The presence of AuNPs in the CS/Pec composite was evaluated via WAXS and UV-vis techniques, while SEM analysis assessed the average size of pores (350-600μm). All samples were extremely cytocompatible with many cell types, such as normal kidney epithelial cells (VERO cells), epithelial colorectal adenocarcinoma cells (HT-29 cells), HPV-16 positive human cervical tumour cells (SiHa cells), kidney epithelial cells (LLCMK2 cells) and murine macrophage cells (J774A1 cells). Cell viability assays using the MTT method upon mouse preosteoblastic cells (MC3T3-E1 cells) showed that CS/Pec and CS/Pec/AuNPs composites had the potential to foster proliferation and growth of bone cells, making them possible stimulators for reconstruction of bone tissues.

Localized surface plasmon resonance (LSPR) is a collective oscillation of free electrons induced by the incident light in nanometric surfaces of conductive materials. Gold nanorods (AuNRs) have been studied for plasmonic devices due to their anisotropic properties. Herein, we report the construction of a specific biosensor using polyacrylamide (PAAm) as the gold nanorods support and test its efficiency with specific streptavidin interaction using biotinylated substrates. First, the hydrogels were synthesized by electropolymerization using cyclic voltammetry on ITO/glass substrates and swallowed with AuNRs. The AuNRs were characterized by visible absorption spectroscopy and transmission electron microscopy. The substrates were characterized by scanning electron microscopy and their plasmonic sensitivities were evaluated using sucrose solutions with different concentrations. The results showed a sensitivity of ca. 226.4 nm RIU-1 with linear correlation of 0.9974. Furthermore, this composite presented reliable detection of the streptavidin biomolecule in the gold surface with good signal-to-noise ratio (SNR).

Studies report the production of gold nanoparticles (AuNPs) and polysaccharides-based composites. However, there are few reports about AuNPs synthesis in-situ followed by the formation of hydrogel composites. Here, we show AuNPs synthesis in-situ into the pectin solutions to yield cytocompatible pectin-capped AuNPs/chitosan hydrogel composites. Visible spectroscopy and dynamic light scattering measurements confirm the AuNPs synthesis. The hydrodynamic radius of the pectin-capped AuNPs ranges from approximately 510 to 721 nm, while the Zeta potential is around −43 mV. Scanning electron microscopy shows that the composites present compact structures. Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy characterize the composites as well. Hydrogels (with or without AuNPs) containing the highest pectin content (at 4.12 pectin/chitosan weight ratio) have low stability (disintegrates approximately 60% after 14 days in phosphate buffer). Composites obtained at 3.75 pectin/chitosan weight ratio disintegrate between 25 and 30% after 14 days in phosphate buffer (physiological condition = pH 7.4). The AuNPs reinforce the hydrogel structures, increasing the elastic modulus (from 3.5 to 7.6 Pa) and decreasing the water uptake from 4465 to 2976%. 3.75 PT/CS weight ratio and 3.0 × 10−4 M Au(III) content provide a durable, cytocompatible, and superabsorbent hydrogel composite. These properties can support materials for drug delivery purposes.

The aim of this work was to improve the nutritional quality of Nile tilapia meat through enriched diets with conjugated isomers of linolenic acid from tung oil. The transfer process of conjugated fatty acids (CFAs) into fish muscle tissue was evaluated by gas chromatography-flame ionization detection (GC-FID) and easy ambient sonic-spray ionization mass spectrometry (EASI-MS).; Results: The results showed that conjugated fatty acids were transferred from enriched diet for muscle tissue of Nile tilapia. Conjugated linoleic acids biosynthesis from conjugated linolenic acids was also observed after 10 days. Other important fatty acids such as docosahexaenoic (DHA), eicosapentaenoic (EPA) and arachidonic (AA) acids were also identified over time; however, DHA showed the highest concentration when compared with EPA and AA compounds.; Conclusion: Therefore, the nutritional quality of Nile tilapia was improved through feeding with enriched diets. The ingestion of these fish may contribute to reaching adequate levels of daily CFA consumption. Furthermore, other important substances which play an important role in human metabolism, such as EPA, DHA and AA, can also be ingested together with CFA. © 2016 Society of Chemical Industry.; © 2016 Society of Chemical Industry.

Nanoparticles (NPs) based on N,N-dimethyl chitosan (DMC) and N,N,N-trimethyl chitosan (TMC), physical crosslinked with sodium tripolyphosphate (TPP) were successful obtained, using water/benzyl alcohol emulsion system. NPs morphologies were evaluated by Scanning Electron Microscopy and Transmission Electron Microscopy. NPs were characterized by Infrared Spectroscopy (FTIR), Thermogravimetric Analysis, Zeta Potential, Differential Scanning Calorimetry and Wide-angle X-ray Scattering. Curcumin (CUR) was loaded onto NPs and controlled release studies were evaluated in simulated intestinal fluid and in simulated gastric fluid. Cytotoxicity assays showed only loaded TMC/TPP particles containing CUR were slightly cytotoxic on human cervical tumor cells (SiHa cells), concerning unloaded TMC/TPP particles. Conversely, loaded NPs (TMC/TPP/CUR and DMC/TPP/CUR), especially TMC/TPP/CUR sample presented greater biocompatibility toward healthy VERO cells than unloaded NPs (TMC/TPP and DMC/TPP).

Tumor necrosis factor-alpha (TNF-α) is a signaling protein of inflammatory processes. TNF-α overexpression triggers inflammatory processes related to various diseases such as rheumatoid arthritis, Crohn’s disease, Chagas, and others. For this reason, the TNF-α has been used as an important biological biomarker for prognosis, understanding, and disease treatment. Surface plasmon resonance (SPR)-based biosensors are a good alternative for TNF-α detection because they are more sensitive than other techniques and have the ability to be developed miniaturized systems. Then we developed a nanohole array on gold nanofilm-based SPR biosensor for TNF-α detection. A biological biorecognition system (cysteamine/biotin/streptavidin/TNF-α antibody) was formed and TNF-α antigen was detected by transmitted light intensity monitoring. TNF-α antigen at 17 pg mL − 1 was detected from fungus Paracoccidioides brasiliensis-infected rat blood serum. This concentration is far below those found in similar studies in the literature. This plasmonic device opens new opportunities for TNF-α detection.

Polysaccharide-based composite materials (beads) containing silver nanoparticles (AgNPs) were successfully prepared. Hydrogel beads acted as an efficient vehicle for Ag+ delivery. Beads promoted the AgNPs protection and inhibited their aggregation. Antimicrobial assays showed that the beads/AgNPs concentration can be modulated to deliver an amount of Ag+ necessary for kill Escherichia coli cells.

Polyelectrolyte complex (beads) based on N , N , N -trimethyl chitosan/alginate was successful obtained and silver nanoparticles (AgNPs) were loaded within beads. In vitro cytotoxicity assays using beads/silver nanoparticles (beads/AgNPs) provided results, indicating that this material significantly inhibited the growth of colon cancer cells (Caco-2). In vitro release studies showed that the beads stabilized AgNPs and repressed Ag 0 oxidation under gastric conditions (pH 2.0). On the other hand, at physiological condition (pH 7.4) the beads/AgNPs released 3.3 μg of Ag + per each beads milligram. These studies showed that the concentration of Ag + released (3.3 μg) was cytotoxic for the Caco-2 cells and was not cytotoxic on healthy VERO cells. This result opens new perspectives for the manufacture of biomaterials based on beads/AgNPs with anti-tumor properties.

Biosensors based on surface plasmon resonance (SPR), operating with the Kretschmann conventional arrangement, have been employed for biomolecular detection of tumor markers. However, the traditional SPR configuration presents some experimental inconveniences that are overcome by using plasmonic substrates based on nanohole arrays manufactured in metallic films. This SPR configuration exhibits the extraordinary optical transmission (EOT) phenomenon, which is explored in the monitoring of binding events that occur on the metal surface. In this work, we proposed a plasmon biosensor based on nanohole arrays built on gold film operating in collinear transmission mode by using spectral investigation for signal transduction. The SPR substrate was coupled to a microfluidic system and showed good sensitivity and linearity. A concentration of 30 ng mL−1 of human epidermal receptor protein-2 (HER2) antigen (associated with breast cancer) was detected using the integrated device; this showed its great potential to be used in tumor diagnosis.

Background: Gold nanoparticles (AuNPs) have enormous potential for application in imaging, diagnosis, and therapies in the medical field. AuNPs are renowned for their localized surface plasmon resonance (LSPR) properties, large surface area, and biocompatibility with body fluids. Further, AuNPs have featured prominently in new methodologies for cancer treatments, like photothermal and imaging therapies. Although AuNPs present enormous potential for application in the medical field, their instability under physiological conditions prevents further uses. However, this limitation may be overcome by associating AuNPs with biopolymers. To the best of our knowledge, a revision paper rationalizing the structure/property relationship and applications of AuNPs-polysaccharide composites in the medical field has not been published yet. Methods: This manuscript discusses the most relevant aspects of and state-of-art concepts surrounding the synthesis of AuNPs based on green chemistry and their association with polysaccharides that can efficiently function both as stabilizing and reducing agents of Au nanoparticles. Even more, polysaccharide devices may inhibit non-specific interactions between AuNPs and biological macromolecules, suppressing unsuitable “protein corona” formations on AuNP surfaces, thereby increasing the potential of AuNP composites of being employing as drug delivery matrices and wound-healing devices as well as in photothermal/imaging purposes for cancer treatments and biosensors.

Physical kappa-carrageenan-based hydrogels are often prepared from dilute aqueous kappa-carrageenan (κ-carrageenan) solutions at the presence of metallic ions or by mixing these solutions with proteins and other polysaccharides. The κ-carrageenan hydrogels have been used for technological purposes; however, there are no reports about the properties of a commercial GENUGEL® κ-carrageenan produced by the CP Kelco. The flame atomic absorption spectrometry shows that the commercial κ-carrageenan comprises a high content of metallic ions (K+ = 216.1 g kg−1, Na+ = 6.3 g kg−1 and Ca2+ = 12.5 g kg−1). The X-ray photoelectron spectroscopy (XPS) indicates the presence of sodium, calcium, and potassium atoms on the as-received κ-carrageenan and its physical hydrogel surfaces. XPS supports the occurrence of a low protein content onto the sample surfaces, as well. The metallic level (especially for K+) in the commercial κ-carrageenan plays an essential role in the preparation of durable hydrogels. These materials are prepared by cooling aqueous κ-carrageenan solutions at 4.0 and 5.0 wt%. The gelation temperature is determined by measuring G′ & G″ as a function of the temperature. The gelation behavior depends on the κ-carrageenan concentration, as well as the metallic content in the commercial sample. Scanning electron microscopy shows that hydrogels have porous and smooth surfaces. The dried materials swell from 2400 to 3100%, while the disintegration/dissolution test confirms that the samples present high stability in distilled water throughout 14 days. These hydrogels are superabsorbent materials and can be applied in agriculture as soil conditioners.

HER2 antigen is a marker used for breast cancer diagnosis and prevention. Its determination has great importance since breast cancer is one of the most insidious types of cancer in women. HER2 antigen assessment in human serum is traditionally achieved by enzyme-linked immunosorbent assay (ELISA method), but it has some disadvantages, such as suppressing the thermodynamic–kinetic studies regarding the antibody–antigen interaction, and the use of labeled molecules that can promote false positive responses. Biosensors based on surface plasmon resonance (SPR) are sensitive optical techniques widely applied on bioassays. The plasmonic devices do not operate with labeled molecules, overcoming conventional immunoassay limitations, and enabling a direct detection of target analytes. In this way, a new SPR biosensor to assess HER2 antigen has been proposed, using nanohole arrays on a gold thin film by signal transduction of transmitted light measurements from array image acquisitions. These metallic nanostructures may couple the light directly on surface plasmons using a simple collinear arrangement. The proposed device reached an average sensitivity for refractive index (RI) variation on a metal surface of 4146 intensity units/RIU (RIU = RI units). The device feasibility on biomolecular assessment was evaluated. For this, 3 ng ml−1 known HER2 antigen concentration was efficiently flowed (using a microfluidic system) and detected from aqueous solutions. This outcome shows that the device may be a powerful apparatus for bioassays, particularly toward breast cancer diagnosis and prognosis.

The aim of this work was to improve the nutritional quality of Nile tilapia meat through enriched diets with conjugated isomers of linolenic acid from tung oil. The transfer process of conjugated fatty acids (CFAs) into fish muscle tissue was evaluated by gas chromatography-flame ionization detection (GC-FID) and easy ambient sonic-spray ionization mass spectrometry (EASI-MS).The results showed that conjugated fatty acids were transferred from enriched diet for muscle tissue of Nile tilapia. Conjugated linoleic acids biosynthesis from conjugated linolenic acids was also observed after 10 days. Other important fatty acids such as docosahexaenoic (DHA), eicosapentaenoic (EPA) and arachidonic (AA) acids were also identified over time; however, DHA showed the highest concentration when compared with EPA and AA compounds.Therefore, the nutritional quality of Nile tilapia was improved through feeding with enriched diets. The ingestion of these fish may contribute to reaching adequate levels of daily CFA consumption. Furthermore, other important substances which play an important role in human metabolism, such as EPA, DHA and AA, can also be ingested together with CFA. © 2016 Society of Chemical Industry.

Stimuli-resposive hydrogels, such as poly(acrylamide), are smart materials that can be loaded with gold nanoparticles to explore the localized surface plasmon resonance effect to develop an optical device. Here we used electropolymerized poly(acrylamide) hydrogel for entrapped gold nanoparticles into gel structure (composite) to prepare a plasmonic device. Sensing tests were performed; for this bovine serum albumin molecules were placed into the composite by diffusion from an aqueous solution. The presence of the molecules alters the refractive index around the gold nanoparticles, changing its resonance conditions. The plasmonic band shifted ∼3.8 nm when the composite was incubated at the 20 µg/mL bovine serum albumin solution, which is a result comparable to reports elsewhere using gold nanoparticles on glass substrates. The device showed that it was possible to detect significantly low concentrations up to 10 ng/mL of protein in aqueous solution. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42449.