Search

The development of more efficient and environmentally friendly analytical methods represents a current focus for the fine chemical industry. In particular, microscale methodologies that are free of solvents/reagents. The headspace-GC/MS (HS-GC) methodology was employed in this study as a tool for monitoring a biocatalysed reaction of (4S)-(+)-carvone using Phoma sp., a filamentous fungus from human skin. Biocatalysis provides some advantages, such as high efficiency, high degrees of regioselectivity, chemoselectivity, and enantioselectivity. In order to optimize the small scale biocatalytic reaction of the (4S)-(+)-carvone by the filamentous fungus Phoma sp. was used headspace GC/MS methodology, factorial design of experiments and the response surface methodology (RSM) was performed using the biomass of the fungus, substrate mass and pH as parameters. It was observed that for all reactions conditions tested, forming the products (1 R,4S)-dihydrocarvone and (1S,4S)-dihydrocarvone. The most influential factor was pH, with the highest conversion rate (>95%) and diastereomeric excess (d.e.) (>80%) obtained at pH 5.0. Thus, it was demonstrated that human skin Phoma sp. fungus showed significant bioreduction activity and that headspace GC/MS is an efficient approach for real-time monitoring the biocatalysed reactions.

Palmarosa essential oil (PEO) is an alternative to synthetic fungicides to control the contamination by food-deteriorating fungi, such as Aspergillus nomius. Nonetheless, the low long-term stability and volatility hamper its utilization. Thus, this study aimed to develop nanostructured lipid carriers (NLCs) containing PEO to improve its stability and consequently prolong the activity against A. nomius. A mixture design was applied to find the best preparation conditions for antifungal activity. The characterization analyses included size measurements, zeta potential (ζ-potential), entrapment efficiency (EE), and antifungal activity (by inhibition of mycelial growth (IMG) and/or in situ test (pre-contaminated Brazil nuts) tests). The nanocarriers presented particle sizes smaller than 300 nm, homogeneous size distribution, ζ-potential of −25.19 to −41.81 mV, and EE between 73.6 and 100%. The formulations F5 and F10 showed the highest IMG value (98.75%). Based on the regression model, three optimized formulations (OFs) were tested for antifungal activity (IMG and in situ test), which showed 100% of inhibition and prevented the deterioration of Brazil nuts by A. nomius. The preliminary stability test showed the maintenance of antifungal activity and physicochemical characteristics for 90 days. These results suggest a promising system as a biofungicide against A. nomius.

Modified chondroitin sulfate (p-CdS) microspheres were synthesized by way of crosslinking- copolymerization reaction with N-isopropylacrylamide (NIPAAm), yielding CdS-co-PNIPAAm copolymer net- work. The incorporation of vinyl groups onto the CdS was processed with the use of glycidyl methacrylate (GMA) in an aqueous solution of pH 3.5 under stirring speed of 800 rpm at 50 � C. 13 C NMR and 1 H NMR spectra of CdS treated with the GMA indicated the formation of 3-metha- cryloyl-1-glyceryl ester of p-CdS and 3-methacryloyl-2- glyceryl ester of p-CdS that are the reaction products resultant of an epoxide ring-opening mechanism via. The synthesis of microspheres was performed via radical reac- tion of the vinyl groups at the p-CdS with vinyl groups at the NIPAAm in a waterbenzyl alcohol microemulsion. The formation of spherical structures is the result of the polymerization-crosslinking reaction of the p-CdS with the NIPAAm monomers at the droplets of water, in view that both reactants have hydrophilic characteristics at the tem- perature at which the reaction was processed. The pure CdS hydrogel microspheres showed a slightly cracked structure with a lower diameter range while the CdS-co- PNIPAAm hydrogel microspheres showed a flat and tight structure with a more regular mass distribution. V C 2011

Smart hollow microspheres composed of vinyled-chondroitin sulfate conjugates (CSπ) and magnetite nanoparticles were obtained by the intermediate of a multiple emulsion in absence of a surfactant, attributable to stabilizing properties of the CS. It was formed an oil–water multiple emulsion in which the CS played a role as an anionic stabilizer for magnetite nanoparticles via complexation. Iron oxides were bonded to the microspheres by the formation of a complex of Fe 3+ ions on the crystalline phase with oxygen atoms at the carboxyl groups without their magnetic properties being affected. The average crystal size of embedded magnetite nanoparticles was approximately 16.5 nm, indicative of a good dispersion in microspheres. Furthermore, the introduction of iron oxides resulted in microspheres with a higher diameter and a narrower particle size distribution.

Pectin was chemically modified with different amounts of trisodium trimetaphosphate (STMP) in aqueous solution (pH = 12), thereby giving a material with reduced water solubility. The physiochemical characterization of this new material was carried out through Fourier transform infrared and thermogravimetric analyses. Phosphated pectin (Pect-STMP) together with prebiotic (oligosaccharide) were incorporated into an aqueous dispersion of polymethacrylate (Eudragit® RS 30 D) in order to obtain free films using a casting process (50 °C) on a Teflon plate. The free films were evaluated using water vapour transmission, average swelling index in simulated gastric fluid (SGF) and simulated intestinal fluid, scanning electron microscopy and a diffusion study with theophylline in buffer solution with and without pectinolytic enzyme. The results suggest that the new material can be used in the coating process for oral solid-reservoir systems, to prevent the premature release of drugs in SGF (pH = 1.2). Furthermore, the presence of both Pect-STMP and oligosaccharide favours the specific degradation of the pellicle by the action of the enzymes produced by colonic microflora. The material obtained in this work has the potential to be applied in devices for drug delivery in the colon, making possible modified release of drugs. Nevertheless, subsequent colon-specific experiments in vivo need to be carried out in order to confirm the possible application of this new material. Copyright © 2009 Society of Chemical Industry

Polysaccharide-structured copolymer hydrogel having excellent pH-sensitivity was developed from N,N-dimethylacrylamide (DMAc) and vinyl-functionalized Pectin (Pec). The Pec was vinyl-functionalized by way of chemical reaction with glycidyl metacrylate (GMA) in water under acidic and thermal stimuli. 13C NMR, 1H NMR, and FT-IR spectra revealed that the vinyl groups coming from the GMA were attached onto backbone of the polysaccharide. The hydrogels were obtained by polymerization of the Pec-vinyl with the DMAc. 13C-CP/MAS NMR and FTIR spectra confirmed that the gelling process occurred by way of the vinyl groups attached on Pec-vinyl backbone. The values of apparent swelling rate constant (k) decreased appreciably for pH greater than 6, demonstrating the swelling process of the hydrogel becomes slower at more alkaline conditions. There was an increase of diffusional exponent (n) with increasing pH of the surrounding liquid. This means the water absorption profile becomes more dependent on the polymer relaxation in basified swelling media. In this condition, a longer water absorption half-time (t1/2) was verified, suggesting the polymer relaxation mechanism of the hydrogel would have a considerable effect on the t1/2.

The synthesis of nanometer and submicrometer hollow particles could be a motivating way to imprint new therapeutic properties into a chondroitin sulfate-based hydrogel formulation. The use of hollowed polymer structures as a formulation strategy is expected to have an impact in the effective therapy in the treatment of rheumatoid arthritis.Chemical modification of the chondroitin sulfate with glycidyl methacrylate (GMA) was performed in water under thermal and acid stimuli. The hydrogel spheres were formed upon cross-linking reaction of modified chondroitin sulfate (CSM) in a water-in-benzyl alcohol nano-droplet emulsion.1H NMR and 13C NMR spectra showed that the carbon-carbon pi-bonds coming from the GMA were incorporated onto backbones of CS. 13C-CP/MAS NMR spectra revealed that the formation of the CSM hydrogel spheres during the dispersion stage occurred by way of carbon-carbon pi-bonds on the CSM structure. The spherical shapes of the particles with diameters in the range of 20 microm to 500 nm were very clearly verified by SEM images where the dark center and edge of the hollow spheres could be identified easily.Nanometer- and submicrometer-sized hydrogel spheres with hollow interior were produced from chondroitin sulfate by using a new strategy of hydrogel synthesis.

Synthesis and characterization of a new hydrogel were carried out using a chemically modified starch (starch-M) consisting of coupling CC bounds coming from glycidil methacrylate (GMA) onto the polysaccharide structure. 13C NMR, 1H NMR, and FT-IR spectroscopies were used to confirm the incorporation of such groups onto the starch-M. The hydrogel was prepared by a crosslinking polymerization of starch-M using sodium persulfate as an initiating agent. The starch-M hydrogel shows morphology clearly different from that of the raw starch film due to the presence of voids on its surface. The swelling process of the starch-M hydrogel was not significantly affected by changes on the temperature or on pH of the surrounding liquid, indicating the such behavior can be then understood by a diffusional process, resulting from its physical–chemical interactions with the solvent. The values of the diffusional exponent n were on the order of 0.45–0.49 for the range of pHs investigated, demonstrating that the water transport mechanism of starch-M hydrogel is more dependent on Fickian diffusion, that is, controlled by water diffusion. Such starch-M hydrogel is a promising candidate to be used in transporting and in preserving acid-responsive drugs, such as corticoids, for the treatment of colon-specific diseases, for example, Crohn's disease. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2567–2574, 2008

The loading of solutes onto and their release from hydrogel-based devices can be better understood when they are treated as a partition phenomenon. Partition activity (α) is a parameter that determines the existence of partition phenomena. It expresses the physical chemical affinities of the solute between the solvent and hydrogel phases. When α = 0 , there is no release of the solute from the hydrogel; however, if α > 0 , there is partitioning of the solute between the solvent and the hydrogel phases, and release of the solute from the hydrogel can be observed. The mathematic model proposed here predicts the overall release profile of vitamin B12, methylene blue (MB), and acid orange 7 (AO) from semi-interpenetrating network (semi-IPN) hydrogels composed of PNIPAAm and PAAm. Experimental release tests demonstrated that alterations on variables of the system change both the released fraction and the release rate of such solutes, confirmed by the changes on values of α (an equilibrium parameter) and k R (an kinetic parameter). The modeling of solute release describes the α effects on release of the solute from polymer networks. The solute release mechanism is viewed here as a diffusional transport process and as a partition phenomenon. The partitioning of the solutes occurs between the solvent phase and the hydrogel phase, and the possible physical chemical affinities of the solute between hydrogel and solvent are considered.

This contribution describes the absorption percentage of Pb2+ and Cu2+ from water by a superabsorbent hydrogel matrix (SH) made from an anionic polysaccharide copolymerized with acrylic acid (AAc) and acrylamide (AAm). Metal-absorption tests, upon sequential pH variation, indicated that the SH has pH-sensitivity for the absorption of both metals from solution, attributed to the functional ionic groups (COOH) present in the AAc and arabic gum (AG) segments. At the pH 5.0, the SH exhibited good absorption capacity: 73.10% for Pb2+, 81.99% for Cu2+ in water and 63.64% for Pb2+, and 76.67% for Cu2+ in saline water with 0.1 mol kg−1 ionic strength. A replicated 22 full factorial design with a central point was built to evaluate the maximum absorption capacity of the metals into the SH. It was found that both the interaction and main effects of the pH and the initial concentration of metal solution on absorption percentage of the metals were statistically significant. Surface response plots indicated that the absorption capacity of both metals into the SH may be appreciably improved by using the solutions with lower initial concentration of metal and with higher pH values. Metal-absorption results demonstrated that the SH is a convenient material for absorption of Pb2+ and Cu2+ from pure aqueous and saline aqueous environments. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

A superabsorbent hydrogel (SH) with fast swelling dynamics and good mechanical stability in the swollen state was prepared. The SH was obtained from chemically modified gum arabic (MGA) with glycidyl methacrylate (GMA), acrylic acid (AAc), and acrylamide (AAm). The water-transport mechanisms and equilibrium swelling ratio (SR) were the parameters used to describe the water-absorption profile of SH. A 23 factorial design with a central point was built to evaluate the influence of the chemical modification of gum arabic (GA) on the SH sensitivity to water. The main effects of the temperature and amount of GMA and the interaction effect of the temperature and amount of GMA on the SR responses were statistically significant. It was demonstrated that the amount of GMA had a more prominent effect on gel swelling. Lower elastic modulus values for the SH were found when a decreased amount of GMA was used (0.05 g), which produced an SH with a high SR capacity. The SH matrix consisting of 3.0 g of AAc, 0.5 g of AAm, and 0.5 g of MGA was more suitable to absorb a large amount of water (SR = 503.17 ± 22.65 within 60 min of water immersion) without its mechanical stability being affected. Better GA modifying conditions to produce such an SH were as follows: 60°C for the temperature, 24 h for the time of MGA, and 0.05 g for the amount of GMA. It exhibited a diffusional exponent higher than 0.89, which corresponded to the supercase II type of penetrating transport mechanism, indicating that its water-absorption mechanism exclusively depended on the macromolecular relaxation of the polymer chains. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

The removal of methylene blue (MB) in water with the superabsorbent hydrogel (SH) formed by modified gum arabic, polyacrylate, and polyacrylamide was investigated. The SH exhibited excellent performance in MB absorption. The maximum absorption capacity was 48 mg of the dye per g of SH, representing 98% of the MB removed. Experimental parameters were used as follows: pH 8, hydrogel mass 50 mg, and initial concentration of MB 50 mg L −1 . In a procedure with an individual solution of orange II, an opposite effect related to the MB was observed: the hydrogel only absorbed water, resulting in an orange II-richer solution. The orange II concentration in solution increased about 50 times (relative to the initial concentration). In another experiment using an aqueous mixture of orange II and MB, the SH absorbed the MB exclusively. Compared to the MB, the orange II is separated from water by SH selectivity-absorption through an inverse process. This effect was attributed to the formation of a ionic complex between the imine groups of MB and the ionized carboxylic groups of SH.

This work describes the preparation of a pH-responsive hydrogel from Arabic gum (AG) chemically modified with glycidyl methacrylate (GMA). This report first describes the chemical modification of AG and next the synthesis and characterization of the hydrogel obtained. An appropriate mixture of water and DMSO was used to dissolve AG and GMA. The presence of GMA groups in the modified structure of Arabic gum (AG-MA) was detected by 13C NMR, 1H NMR, and FT-IR techniques. The cross-linking reaction of AG-MA leads to formation of an AG-MA hydrogel, which was characterized by solid-state 13C-CP/MAS NMR and FT-IR spectroscopy. Morphology was visualized by scanning electron microscopy. It was observed in water uptake tests that AG-MA hydrogels showed significant pH dependence, which affected the water absorption transport mechanism. In the studied pH range, it was found that the transport mechanism of water into AG-MA hydrogel was controlled by Fickian diffusion and polymer relaxation (anomalous transport). At high pH values, the water transport profile became more dependent on polymer relaxation. This effect was attributed to the increase in the ionized groups of glucuronic acid segments, which contributed to electrostatic repulsion among the groups and led the gel polymer network to expand. AG-MA hydrogels exhibited pH-responsive, demonstrating them to be appropriate materials for further tests as drug carriers.

Novel superabsorbent hydrogels were manufactured using chemically modified cashew gum (CGMA) and acrylamide (AAm) as reactants. The route for the synthesis was feasible due to the incorporation of glycidyl methacrylate (GMA) into structure of cashew gum (CG) to form the cashew gum-methacrylated (CGMA), in an appropriate mixture water-DMSO, as solvent, and using TEMED as catalyst. Thereafter, the CGMA was copolymerized with AAm yielding (CGMA-co-AAm) hydrogels. The main characteristics of raw and the modified materials are reported in this paper. 13 C NMR, 1 H NMR and FTIR spectroscopies confirmed the incorporation of vinyl groups, from GMA, into CG structure. By the spectrophotometry analyses, it was found that, ca. 82% of GMA was incorporated to the CG after 24 h of reaction. The cross-linking of CGMA or co-polymerization of CGMA with acrylamide leads to a hydrogel formation. Their gelation was characterized by FT-IR analysis. Alkaline hydrolysis at 40 °C for 3 and 4.5 h increased the water uptake (WU) capacity. Hydrolyzed CGMA-co-AAm hydrogels present higher values of WU (up to 1500) and may be classified as water superabsorbent material. Applications in agriculture, as soil conditioner, and in biomedical field, as biomaterial (scaffold) are being investigated.

Polymer film based on pH-dependent Eudragit FS 30 D acrylic polymer in association with arabinoxylane, a polysaccharide issued from gum psyllium, was produced by way of solvent casting. Physical-chemical characterization of the polymer film samples was performed by means of thermogravimetry (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Furthermore, water-equilibrium swelling index (I(s)) and weight loss of the films in KCl buffer solution of pH 1.2, in KH(2)PO(4) buffer solution of pH 5.0, or in KH(2)PO(4) buffer solution of pH 5.0 consisting of 4% enzyme Pectinex 3X-L (w/v) were also carried out for the film characterization. No chemical interactions between the Eudragit FS 30 D and the arabinoxylane polymer chains were evidenced, thus suggesting that the film-forming polymer structure was obtained from a physical mixture of both polymers. The arabinoxylane-loader films showed a more pronounced weight loss after their immersion in buffer solution containing enzyme Pectinex 3X-L. The introduction of the arabinoxylane makes the film more susceptible to undergo an enzymatic degradation. This meant that the enzyme-dependent propriety issued from the arabinoxylane has been imprinted into the film formulation. This type of polymer film is an interesting system for applications in colon-specific drug delivery system.

A pectin-based hydrogel was used as a remover of Cu2+ and Pb2+ ions from water and wastewater and in the release of phosphate, potassium, and urea. The swelling studies in either aqueous or saline solutions were analyzed at different pressures, and the prediction of profile of water and solute transports was further analyzed on basis of transport process by diffusion in swellable polymer networks. The hydrogel composed of 0.10 g mL−1 final polymer concentration showed an excellent absorption capacity for removal of Cu2+ and Pb2+ from the solution: 120 mg Cu2+ and 130 mg Pb2+ per g hydrogel, both at pH 5.5. The hydrogel help to conserve water in a pressure range in which a variety of horticultural plants can absorb it. The release process of urea, phosphate, and potassium from the hydrogels is controlled by non-Fickian mechanism with a tendency to macromolecular relaxation. This type of hydrogel is an interesting system for applications in which the efficient use of water is required and release of fertilizers for agriculture. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Transesterification and epoxide ring-opening reactions are two mechanism routes that explain chemical modifications of macromolecules by glycidyl methacrylate (GMA). Although the coupling reaction of the GMA with macromolecules has widely been investigated, there are still mechanisms that remain to be explained when GMA is processed in an aqueous solution at different pH conditions. To this end, reaction mechanisms of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAAc) by GMA in water in acidic and basic conditions were investigated thoroughly. The presence of hydroxyl groups in PVA and carboxyl groups in PAAc allowed for a better evaluation of the reaction mechanisms. The analysis of the (1)H and (13)C NMR spectra clearly demonstrated that the chemical reactions of GMA with carboxyl groups and alcohols of the macromolecules in an aqueous solution are dependent on pH conditions. At pH 3.5, the GMA reacts with both the carboxylic and the hydroxyl groups through an epoxide ring-opening mechanism. At pH 10.5, the GMA undergoes a hydrolysis process and reacts with hydroxyl groups by way of both the transesterification and the epoxide ring-opening mechanisms, whereas the ring-opening reaction is the preferential pathway.

Hollow-structured nano- and microspheres with diameters ranging from 24 microm to 160 nm were successfully produced from chemically modified pectin (Ma-Pec) through a two-step synthesis. In a first step, the Pec was modified with glycidyl methacrylate (GMA) in a heterogeneous phase system, indeed consisting of water-soluble Pec and water-insoluble GMA, via an interfacial reaction at the interface of the GMA-water phase system after 12 h under continuous stirring of 1000 rpm at 60 degrees C. In a second step, the spheres were prepared in a water-in-benzyl alcohol nanodroplet emulsion at 12000 rpm under a bubbling stream of nitrogen in the presence of sodium persulfate, as initiator, and TEMED, as catalytic agent. FT-IR spectra revealed that the vinyl groups (CC) coming from the GMA were attached onto backbone of the polysaccharide. 13C-CP/MAS NMR spectra demonstrated that the spheres were formed via carbon-carbon pi-bonds on Ma-Pec in the water phase, for the duration of the dispersion stage. The dark center (an empty core) and edge of the hollow spheres could be easily identified by SEM micrographs. This type of polymer structure represents a class of unique material with particular importance in terms of state-of the-art applications in both nano- and microencapsulation of drugs, for example, protection shields of biologically active agents.

Pectina fosfatada (Pect-TMFT) juntamente com o α-Gluco-oligossacarídeo (Bioecolians®) foram incorporados à dispersão aquosa de polimetacrilato (Eudragit® RS 30 D) para obtenção de filmes isolados pelo processo "casting" (50 ºC) em placa de Teflon®. A Pect-TMFT e o Bioecolians® foram adicionados à dispersão de Eudragit® RS 30 D nas concentrações: 90: 05: 05, 80: 10: 10 e 70: 20: 10 (4 % p/v). Citrato de trietila (TEC) foi utilizado como plastificante (20 % da massa do polimetacrilato). As dispersões propostas apresentaram habilidades filmogênicas. Os filmes isolados foram caracterizados pela determinação da permeabilidade ao vapor d'água (TVA), pelo índice de intumescimento (Ii %) em fluidos de simulação gástrica (FSG) e intestinal (FSI) e por microscopia eletrônica de varredura (MEV). O aumento do polissacarídeo modificado e do Bioecolians® nos filmes favoreceram a permeabilidade ao vapor d'água e o grau de hidratação quando em FSI (pH= 6,8). Dessa forma, o filme 70: 20: 10, poderá impedir a liberação prematura do fármaco em regiões superiores do TGI quando aplicado como revestimento de sistemas sólidos orais. Além disso, a presença da Pect-TMFT e do Bioecolians®, poderá favorecer a degradação específica da película por enzimas produzidas pela microflora colônica, possibilitando uma cinética de liberação modificada de fármacos apesar das variações inter-individuais de pH que possam existir. Phosphated pectin (Pect-TMFT) together with α-gluco-oligossacaride (Bioecolians®) were incorporated into aqueous dispersion of polymethacrylate (Eudragit® RS 30 D) to obtain free films by the casting process (50ºC) in Teflon® plate. Pect-TMFT and Bioecolians® were added into dispersions of Eudragit ® RS 30 D at different rates: 90:05:05, 80:10:10 and 70:20:10 (4% p/v). Triethyl citrate (TEC) was used as plasticizer (20% of mass of the polymethacrylate). The proposed dispersions showed film formation ability. The free films were characterized by the determination of water vapour transmission (WVT), by the swelling index (Ii%) in fluids of gastric simulation (FGS) and intestinal (FIS) and by scanning electron microscopy (SEM). The increase of modified polysaccharide and Bioecolians® in the films favored their permeability to the water vapour and their hydration degree when in FIS (pH = 6.8). In that way, the obtained film in the concentration 70:20:10, can prevent the premature release of the drug in the up GIT when applied to develop oral solid systems coating. Besides, the presence of Pect-TMFT and Bioecolians® can contribute to the specific membrane degradation by colonic microflora enzymes, making possible a modified release kinetics of drugs even with the existence of inter-individual variations of pH.

In this work, low-methoxyl pectin was chemically modified by reaction with glycidyl methacrylate (GMA) to give a material with low hydrosolubility. After physio-chemical characterization by FT-IR, DSC, and TGA analyses, the methacrylated/modified pectin (Pect-GMA) was crosslinked after the addition of sodium persulfate (SP), that actuates as initiator, at 50 degrees C for 24 and 48h either in the presence or not of aqueous polymethacrylate dispersion (Eudragit RS 30 D) to obtain free films by Teflon plate "casting" process. Different Pect-GMA/Eudragit RS 30 D ratios and SP concentrations were used. The free films were characterized by the determination of water vapor transmission (WVT), the swelling index (Ieq%) in simulated gastric (SGF) and intestinal (SIF) fluids, and by scanning electron microscopy (SEM). The presence of ionized groups in Pect-GMA turned the films pH-dependent because Ieq% of swollen crosslinked Pect-GMA films was larger at pH 6.8 than at pH 1.2. This was confirmed by the large pore size observed in the micrographs of SIF-swollen lyophilized films. In this way, films containing Pect-GMA and Eudragit RS 30 D, a time-dependent polymer, may present a synergistic action that favors specific biodegradation of the film in distal end of the gastrointestinal tract (GIT) by enzymes produced by the colonic microflora, enabling the modification of the release kinetics of drugs.

The binding capacities of chitin (CT) and chitosan (CS) produced from silkworm chrysalides were investigated aiming at their future application in the removal of Pb2+ and Ni2+ from wastewaters. CS with 75% deacetylation degree (DD) exhibited good binding performance for Pb2+, but bad efficiency for Ni2+. The maximum binding capacity obtained from isotherms for CS Pb was 141.10 mg g−1 and 52.81 mg g−1 for CS Ni. The binding capacities for CT were 32.01 mg g−1 for Pb2+ and 61.24 mg g−1 for Ni2+. The authors attribute these behaviors to two main factors: (i) the large ionic size of Pb2+ and (ii) the steric hindrance due to CT acetyl groups. Metal binding onto CS was evaluated by the Freundlich and Langmuir isotherm models. The parameter values obtained from the isotherm analysis confirmed that Pb2+ and Ni2+ interact differently with CS and that various factors influence their adsorption. Thermogravimetric analysis (TGA) showed that the thermal behavior of CS with 75% deacetylation degree was in the same profile of standard CS; however, the binding of the metals onto its structure affects the curve profile.

In this contribution, maximum capacity for adsorption of Pb(2+), Ni(2+), and Cu(2+) by silkworm chrysalides (SC) was determined. The raw silkworm chrysalides (SC(r)) and chrysalides after acidic washing (SC(w)) were used. Chitin (CT), extracted from SC, and chitosan (CS), with 85% deacetylation, were employed as reference samples. Adsorption tests showed that all the studied adsorbents exhibited excellent performance in removal of metals. The choice of a more appropriate adsorbent is related to its efficiency for removal of a specific metal. The studied materials presented different intensities for metal adsorption as follows: (i) Ni(2+)>Cu(2+)>Pb(2+) for SC(r); (ii) Pb(2+)>Cu(2+)>Ni(2+) for SC(w); (iii) Ni(2+)>Cu(2+)>Pb(2+) for CT; and (iv) Cu(2+)>Pb(2+)>Ni(2+) for CS. Metal adsorption onto SC(r) and CS was analyzed by Freundlich and Langmuir isotherm equations. Adsorption values for CS-Pb and SC(r)-Ni were provided by the Freundlich model, while the adsorption values for CS-Cu, CS-Ni, SC(r)-Pb, and SC(r)-Cu were provided by the Langmuir model. The studied adsorbents are suitable for use in treatment of wastewater. From the economic point of view, the use of SC(r) as an adsorbent of heavy metals (mainly Ni(2+)) on the large industrial scale would be more appropriate.

The present investigation describes a procedure for the synthesis of a glycidyl methacrylated derivative from galactomannan, GA-MA, and the respective hydrogel formation. The galactomannan (GA), raw material, was purified and dissolved in DMSO. After dissolution, 4-dimethyl-amino-pyridine (DMAP) and glycidyl methacrylate (GMA) were added. The modified polymer, quoted as GA-MA, was purified by precipitation in ethanol. Hydrogels were obtained from GA-MA in aqueous solution by polymerization of GA-MA using sodium persulfate (SP), as initiator, and N,N,N′,N′-tetramethylethylenediamine (TEMED), as catalyst. For this, the cross-linking process was trigged by the addition of TEMED and sodium persulfate aqueous solutions. Two different concentrations of TEMED and SP were used. GA, GMA and GA-MA were characterized by FT-IR and NMR ( 13 C and 1 H ) spectroscopy. The addition of GMA on GA molecules was confirmed through FT-IR results by appearing of a band at ν=1717 cm−1 and also by the cleavage of CC groups of GA-MA (band at ν=1636 cm−1) during the cross-linking process. The signals attributed to vinyl carbon of methacrylate (δ 138.52, 130.06 ppm), to carbonyl (δ 171.87 ppm) and to methyl group (δ 20.19 ppm) were observed in the 13 C NMR spectra of GA-MA. The addition of methacrylate on GA was also confirmed through the signals present in 1 H NMR spectra of GA-MA. The formation of hydrogel was observed by complete gelation. The hydrogels were characterized by FT-IR and by measuring the equilibrium water content (EWC) in pH=7.0 and 1.0. The hydrogels contain 83 wt.% of water at 25 °C and 85 wt.% at 37 °C. Good resistance to degradation in acidic conditions, pH=1.0, was observed at 37 °C up to 48 h. These properties suggest that the GA-MA hydrogels may be a new material for pharmaceutical use, mainly for drug delivery system.