One-pot synthesis of γ-lactams from ketoaziridines.

The remarkable biological activities of γ-lactams have stimulated the search for efficient synthetic methods to achieve these scaffolds. In this work, we have developed a simple one-pot diastereoselective synthesis of new γ-lactams from ketoaziridines with moderate to good yields via the Horner-Wadsworth-Emmons reaction, followed by an intramolecular ester-aziridine cyclization and its opening in situ. Preliminary efforts towards an enantioselective version of this method are also reported.

Carboxymethylcellulose hydrogels crosslinked with keratin nanoparticles for efficient prednisolone delivery.

Carboxymethylcellulose (CMC) and keratin nanoparticle (KNP) hydrogels were obtained, characterized, and applied as drug delivery systems (DDSs) for the first time. Lyophilized CMC/KNP mixtures containing 10, 25, and 50 wt% of KNPs were kept at 170 °C for 90 min to crosslink CMC chains through a solid-state reaction with the KNPs. The hydrogels were characterized by infrared spectroscopy, thermal analyses, X-ray diffraction, mechanical measurements, and scanning electron microscopy. The infrared spectra indicated the formation of ester and amide linkages between crosslinked CMC and KNPs. The elastic modulus of the hydrogel containing 10 wt% KNPs was 2-fold higher than that of the hydrogel containing 50 wt% KNPs. The mechanical properties influenced the hydrogel stability and water uptake. The anti-inflammatory prednisolone (PRED) drug was incorporated into the hydrogels, and the release mechanism was investigated. The hydrogels supported PRED release by drug desorption for approximately 360 h. A sustained release mechanism was achieved. The CMC/KNP and CMC/KNP/PRED hydrogels were cytocompatible toward mammalian cells. The CMC/KNP/PRED set imparted the highest cell viability after 7 days of incubation. This study showed a straightforward procedure to create DDSs (chemically crosslinked) based on polysaccharides and proteins for efficient PRED delivery.

Improved antioxidant activity of a starch and gelatin-based biodegradable coating containing Tetradenia riparia extract.

The incorporation of plant-based extracts into polymer-based coatings is an efficient alternative to increase the shelf-life of stored fruit and to decrease or even prevent bacterial growth. Considering strawberries, it is also important to preserve their high antioxidant activity. Hence, this work evaluated the efficiency of a coating based on native cassava starch (NCS), gelatin, and sorbitol, containing different concentrations of Tetradenia riparia extract, in delaying the ripening process of strawberries stored under refrigerated conditions, and in preventing bacterial growth and antioxidant activity losses. Both concentrations of extract (500 or 1000 µg mL-1) increased the thickness, opacity, and water vapor transmission rate (WVTR) of the films when compared to the film without extract, but decreased the solubility. Even though the film without extract was expected to create a more efficient barrier to the coated fruits, the films containing the extract led to similar results of soluble solids (SS), titratable acidity (TA), and vitamin C. Nevertheless, the extract incorporation improved the control over bacterial growth, and preserved the high antioxidant activity of the strawberries within ten days of storage.

Effect of gelatin and casein additions on starch edible biodegradable films for fruit surface coating.

Coating fruits surface with biodegradable films obtained from starch is an alternative to delay the fruit ripening process. This study aimed to develop a biodegradable film from a polymer blend consisting of natural cassava starch, casein, and gelatin, and using sorbitol as the plasticizer. Among all the prepared biodegradable films (BFs), the one with desirable results in thickness, opacity, solubility, and water vapor transmission rate (WVTR) analyzes was based on a high concentration of starch, and casein, and low concentration of gelatin. Also, this film had the lowest solubility among all of them. Guava fruit coated with this film showed a two-day increase in shelf-life when compared to non-coated guavas. The increase in shelf-life was due to the extremely low water vapor transmission rate of the films, decreasing the fruits' mass loss, and, consequently, retarding their senescence. These results indicate that the biodegradable film is a promising material for fruit coating.

Synthesis and characterization of a low solubility edible film based on native cassava starch.

Films based on cassava starch have been widely used for fruit coating; however, it is necessary to incorporate other polymers in order to improve mechanical properties, once starch only leads to highly hydrophilic films, compromising their application. In this way, a polymeric blend based on cassava starch, chitosan and gelatin was combined with a plasticizer to produce biodegradable films with satisfactory mechanical and barrier properties, in order to be used as fruit coating. The films were prepared by casting method and a statistical design of 23 was used to evaluate the effect of each polymer and what their combinations would influence over the final product. The formation of a physical blend was confirmed by FTIR. It showed low solubility, varying (10 ±â€¯2) % a (23 ±â€¯4) %, Opacity ranging from (1.06 ±â€¯0.04) to (1.55 ±â€¯0.13) AU x nm/mm, thickness from (0.20 ±â€¯0.01) mm to (0.44 ±â€¯0.03) mm and water vapor transmission rate ranging from 25 ±â€¯0.2 to 30 ±â€¯1.4 g s-1 m-2. Lower amounts of starch led to more flexible, less opaque and soluble films, while the combination of higher levels of starch and chitosan was responsible for lowering films water vapor transmission rate. Thus, the films showed interesting properties for fruit surface coating.

Semiquantitative analysis of mercury in landfill leachates using double-pulse laser-induced breakdown spectroscopy.

Laser-induced breakdown spectroscopy (LIBS) is showing to be a promising, quick, accurate, and practical technique to detect and measure metal contaminants and nutrients in urban wastes and landfill leachates. Although conventional LIBS presents some limitations, such as low sensitivity, when used in the single pulse configuration if compared to other spectroscopic techniques, the use of the double-pulse (DP) configuration represents an adequate alternative. In this work DP LIBS has been applied to the qualitative and quantitative analysis of mercury (Hg) in landfill leachates. The correlation analysis performed between each intensified charge-coupled device pixel and the Hg concentration allowed us to choose the most appropriate Hg emission line to be used for its measure. The normalization process applied to LIBS spectra to correct physical matrix effects and small fluctuations increased from 0.82 to 0.98 the linear correlation of the calibration curve between LIBS and the reference data. The limit of detection for Hg estimated using DP LIBS was 76 mg Kg-1. The cross validation (leave-one-out) analysis yielded an absolute average error of about 21%. These values showed that the calibration models were close to the optimization limit and satisfactory for Hg quantification in landfill leachate.