Cellulose nanowhiskers decorated with silver nanoparticles as an additive to antibacterial polymers membranes fabricated by electrospinning.

Antimicrobial films based on distinct polymer matrices, poly (vinyl alcohol) (PVA) or poly (N-isopropylacrylamide) (PNIPAAm), and silver nanoparticles (AgNPs) immobilized onto cellulose nanowhiskers (CWs) were successfully prepared by either casting or electrospinning. CWs were first functionalized with carboxylate groups (labeled as CWSAc) and later they were immersed in a silver nitrate solution (AgNO3). After Ag+ ions anchored in the COO- groups are chemically reduced to produce AgNPs. The CWSAc/AgNPs biological activity was evaluated against Staphylococcus aureus (S. aureus), Bacillus Subtilis (B. subtilis), Escherichia coli (E. coli), and Candida albicans (C. albicans). The materials were more effective against C. albicans that showed a MIC of 15.6 µg/mL. In the process of AgNPs synthesis, the activity of the stabilizing agent (gelatin) and concentration of precursor and reducing agents were evaluated. The synthesized polymeric films displayed good antimicrobial activity against S. aureus, E. coli, and Pseudomonas aeruginosa (P. aeruginosa) bacteria. The PVA films with CWSAc/AgNPs showed diameter of the inhibition halo of up to 11 mm. The results obtained displayed that the films obtained have a potential application to be used in different fields such as packaging, membrane filtration, wound dressing, clothing and in different biomedical applications.

Cellulose nanowhiskers improve the methylene blue adsorption capacity of chitosan-g-poly(acrylic acid) hydrogel.

Cellulose nanowhiskers (CNWs, 90% crystalline) were used to enhance the adsorption capacity of chitosan-g-poly(acrylic acid) hydrogel. The composites up to 20w/w-% CNWs showed improved adsorption capacity towards methylene blue (MB) as compared to the pristine hydrogel. At 5w/w-% CNWs the composite presented the highest adsorption capacity (1968mg/g). The maximum removal of MB (>98% of initial concentration 2000mg/L) was achieved quickly (60min) at room temperature, pH 6, and at low ionic strength (0.1M). Adsorption mechanism was explained with the Langmuir type I model suggesting the formation of a MB monolayer on the adsorbent surface. The interaction between the adsorbent and MB molecules was explained by chemisorption, as suggested by the pseudo-second-order kinetic model. Desorption experiments showed that 75% of loaded-MB could be recovered from the adsorbent by its immersion in a pH 1 solution. Additional experiments showed the post-utilized composite could be regenerated and reused for at least 5 consecutive adsorption/desorption cycles with minimum efficiency loss (∼2%).

Fast dye removal from water by starch-based nanocomposites.

Robust and efficient methylene blue (MB) adsorbent was prepared based on starch/cellulose nanowhiskers hydrogel composite. Maximum MB adsorption capacity of ∼2050mgperg of dried hydrogel was obtained with the composite at 5wt.% of cellulose nanowhiskers and at pH 5. Adsorption capacity varied from 1450mg/g to 2050mg/g with increasing the initial MB concentration from 1500mg/L to 2500mg/L, respectively. For all the concentrations studied ca. 90% of MB was removed by the adsorbent. Optimal conditions were obtained at pH⩾5 due to the generation of negatively charged groups (COO(-)) in the adsorbent, which can strongly interact with the positive charges from MB. The main advantage of this system over other reported adsorbents, besides the fact of being synthesized from biodegradable polymers (starch and cellulose), is its fast adsorption kinetics that follows the pseudo-second order model, which is based on chimisorption phenomenon. Saturation condition was reached as fast as 1h of experiments owing to the formation of an adsorbed MB monolayer as suggested by the Langmuir isotherm model. Desorption experiments showed 60wt.% of MB loaded can be removed from the adsorbent by immersing it in a pH 1 solution, showing its feasibility to be reused. Therefore, starch/cellulose nanowhiskers hydrogel composite presents outstanding capacity to be employed in the remediation of MB contaminated wastewaters.

N,N-Dimethyl chitosan/heparin polyelectrolyte complex vehicle for efficient heparin delivery.

Polysaccharide-based device for oral delivery of heparin (HP) was successfully prepared. Previously synthesized N,N-dimethyl chitosan (DMC) (86% dimethylated by (1)H NMR spectroscopy) was complexed with HP by mixing HP and DMC aqueous solutions (both at pH 3.0). The polyelectrolyte complex (PEC) obtention was confirmed by infrared spectroscopy (FTIR), thermogravimetric analysis (TGA/DTG) and wide-angle X-ray scattering (WAXS). In vitro controlled release assays of HP from PEC were investigated in the simulated intestinal fluid (SIF) and simulated gastric fluid (SGF). The PEC efficiently protected the HP in SGF condition in which HP is degraded. On the other hand, in SIF PEC promoted the releasing of 80 ± 1.5% of loaded HP. The promissory results indicated that the PEC based on DMC/HP presented potential as drug-carrier matrix, since biological activity of HP was improved at pH close to physiological condition.

Antimicrobial activity of chitosan derivatives containing N-quaternized moieties in its backbone: a review.

Chitosan, which is derived from a deacetylation reaction of chitin, has attractive antimicrobial activity. However, chitosan applications as a biocide are only effective in acidic medium due to its low solubility in neutral and basic conditions. Also, the positive charges carried by the protonated amine groups of chitosan (in acidic conditions) that are the driving force for its solubilization are also associated with its antimicrobial activity. Therefore, chemical modifications of chitosan are required to enhance its solubility and broaden the spectrum of its applications, including as biocide. Quaternization on the nitrogen atom of chitosan is the most used route to render water-soluble chitosan-derivatives, especially at physiological pH conditions. Recent reports in the literature demonstrate that such chitosan-derivatives present excellent antimicrobial activity due to permanent positive charge on nitrogen atoms side-bonded to the polymer backbone. This review presents some relevant work regarding the use of quaternized chitosan-derivatives obtained by different synthetic paths in applications as antimicrobial agents.

Starch-based microspheres for sustained-release of curcumin: preparation and cytotoxic effect on tumor cells.

Curcumin (CUR) has been proved to be highly cytotoxic against different tumor cell lines. However, its poor solubility in aqueous medium and fast degradation in physiological pH are the common drawbacks preventing its efficient practical use. Herein, we report the development of original microspheres based on the biopolymer starch crosslinked with N,N-methylenebisacrylamide (MBA) to be applied as an efficient delivering system for CUR. The starch-based microspheres showed high loading efficiency even in loading solution with different CUR concentrations. In vitro release assays data showed that the CUR release is governed by anomalous transport (n=0.73) and it is pH-dependent. Cytotoxicity assays showed that starch microspheres could improve the cytotoxicity of CUR toward Caco-2 and HCT-116 tumor cell lines up to 40 times than that found for pure CUR. This behavior was attributed to the slowly and sustained release of CUR from the microspheres.

Chitosan/TPP microparticles obtained by microemulsion method applied in controlled release of heparin.

This work deals with the preparation of chitosan/tripolyphosphate microparticles (CHT/TPP) using microemulsion system based on water/benzyl alcohol. The morphology of the microparticles was evaluated by scanning electron microscopy (SEM). The microparticles were also characterized through infrared spectroscopy (FTIR) and wide-angle X-ray scattering (WAXS). The morphology and crystallinity of microparticles depended mainly on CHT/TPP ratio. Studies of controlled release of HP were evaluated in distilled water and in simulated gastric fluid. Besides, the profile of HP releasing could be tailored by tuning the CHT/TPP molar ratio. Finally, these prospective results allow the particles to be employed as site-specific HP controlled release system.

Natural polymer-based magnetic hydrogels: Potential vectors for remote-controlled drug release.

The preparation and characterization of natural polymer-based hydrogels that contain 50-nm diameter magnetite (i.e., FeO:Fe(2)O(3)) nanoparticles are described herein. Fourier-transform infrared spectroscopy (FTIR) analysis confirmed the efficiency of the polysaccharide-modifying process. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and compressive moduli demostrate that the presence of magnetite improves thermal and mechanical resistance. Transient diffusion of water in magnetic hydrogels was analyzed via boundary layer mass transfer across an expaning interface, and the degree of swelling of these polysaccharide hydrogels decreases in the presence of magnetite, with no variation in the binary diffusion mechanism. The absence of hysteresis loops and coercivity observed via magnetometry suggests that magnetic hydrogels are useful for remote-controlled drug release, as demonstrated by magnetic-field-induced release of curcumin. Experiments reveal that magnetic hydrogels with greater magnetic susceptibility have the potential to release larger concentrations of drugs from the hydrogel network.