Synthesis, Characterization, and Evaluation of the Antimicrobial Effects and Cytotoxicity of a Novel Nanocomposite Based on Polyamide 6 and Trimetaphosphate Nanoparticles Decorated with Silver Nanoparticles.

This study aimed to develop a polymeric matrix of polyamide-6 (P6) impregnated with trimetaphosphate (TMP) nanoparticles and silver nanoparticles (AgNPs), and to evaluate its antimicrobial activity, surface free energy, TMP and Ag+ release, and cytotoxicity for use as a support in dental tissue. The data were subjected to statistical analysis (p < 0.05). P6 can be incorporated into TMP without altering its properties. In the first three hours, Ag+ was released for all groups decorated with AgNPs, and for TMP, the release only occurred for the P6-TMP-5% and P6-TMP-10% groups. In the inhibition zones, the AgNPs showed activity against both microorganisms. The P6-TMP-2.5%-Ag and P6-TMP-5%-Ag groups with AgNPs showed a greater reduction in CFU for S. mutans. For C. albicans, all groups showed a reduction in CFU. The P6-TMP groups showed higher cell viability, regardless of time (p < 0.05). The developed P6 polymeric matrix impregnated with TMP and AgNPs demonstrated promising antimicrobial properties against the tested microorganisms, making it a potential material for applications in scaffolds in dental tissues.

Nanoarchitectonic E-Tongue of Electrospun Zein/Curcumin Carbon Dots for Detecting Staphylococcus aureusin Milk.

We report a nanoarchitectonic electronic tongue made with flexible electrodes coated with curcumin carbon dots and zein electrospun nanofibers, which could detect Staphylococcus aureus(S. aureus) in milk using electrical impedance spectroscopy. Electronic tongues are based on the global selectivity concept in which the electrical responses of distinct sensing units are combined to provide a unique pattern, which in this case allowed the detection of S. aureus through non-specific interactions. The electronic tongue used here comprised 3 sensors with electrodes coated with zein nanofibers, carbon dots, and carbon dots with zein nanofibers. The capacitance data obtained with the three sensors were processed with a multidimensional projection technique referred to as interactive document mapping (IDMAP) and analyzed using the machine learning-based concept of multidimensional calibration space (MCS). The concentration of S. aureus could be determined with the sensing units, especially with the one containing zein as the limit of detection was 0.83 CFU/mL (CFU stands for colony-forming unit). This high sensitivity is attributed to molecular-level interactions between the protein zein and C-H groups in S. aureus according to polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS) data. Using machine learning and IDMAP, we demonstrated the selectivity of the electronic tongue in distinguishing milk samples from mastitis-infected cows from milk collected from healthy cows, and from milk spiked with possible interferents. Calibration of the electronic tongue can also be reached with the MCS concept employing decision tree algorithms, with an 80.1% accuracy in the diagnosis of mastitis. The low-cost electronic tongue presented here may be exploited in diagnosing mastitis at early stages, with tests performed in the farms without requiring specialized laboratories or personnel.

Insight into morphological, physicochemical and spectroscopic properties of ß-chitin nanocrystalline structures.

We systematically investigated the effect of ß-chitin (BCH) particle size on the preparation of nanocrystals/nanowhiskers (CWH) by acid hydrolysis. Regardless this variable, CWH aqueous suspension exhibited outstanding stability and the average degree of acetylation remained nearly constant after the acid treatment. In contrast, the morphology, dimensions, crystallinity, and molecular weight of CHW were significantly affect by the particle size. Although needle-like crystals have predominated, BCH particles sizes significantly affected the dimensions and asymmetry of CWH, as confirmed by the rheological and NMR relaxation (T2) behaviors. According to different SSNMR approaches, the acid hydrolysis meaningless affected the local chain conformation, while the spatial freedom of BCH intersheets, rated upon the mobility of methyl segments, was taken as evidence of higher permeability of acid into small particle sizes. Thus, this study demonstrated the importance of standardizing the surface/bulk proportions of ß-chitin aiming to predict and control the CWH morphology and related properties.

N-(2-hydroxy)-propyl-3-trimethylammonium, O-palmitoyl chitosan: Synthesis, physicochemical and biological properties.

Two samples of N-(2-hydroxy)-propyl-3-trimethylammonium, O-palmitoyl chitosan (DPCat) with different average degrees of quaternization named as DPCat35 (DQ¯ = 35%) and DPCat80 (DQ¯ = 80%), were successfully synthesized by reacting glycidyltrimethylammonium chloride (GTMAC) with O-palmitoyl chitosan (DPCh) derivative (DS¯ = 12%). Such amphiphilic derivatives of chitosan were fully water-soluble at 1.0 < pH < 12.0 and showed significant electrostatic stability enhancement of a self-assembly micellar nanostructure (100-320 nm) due to its positively-charged out-layer. In vitro mucoadhesive and cytotoxicity essays toward healthy fibroblast cells (Balb/C 3T3 clone A31 cell), human prostate cancer (DU145) and liver cancer (HepG2/C3A) cell lines revealed that the biological properties of DPCat derivatives were strongly dependent on DQ¯. Additionally, DPCat35 had better interactions with the biological tissue and with mucin glycoproteins at pH 7.4 as well as exhibited potential to be used on the development of drug delivery systems for prostate and liver cancer treatment.

Fast-forward approach of time-domain NMR relaxometry for solid-state chemistry of chitosan.

Chitosans with different average degrees of acetylation and weight molecular weight were analyzed by time-domain NMR relaxometry using the recently proposed pulse sequence named Rhim and Kessemeier - Radiofrequency Optimized Solid-Echo (RK-ROSE) to acquire 1H NMR signal of solid-state materials. The NMR signal decay was composed of faster (tenths of µs) and longer components, where the mobile-part fraction exhibited an effective relaxation transverse time assigned to methyl hydrogens from N-acetyl-d-glucosamine (GlcNAc) units. The higher intrinsic mobility of methyl groups was confirmed via DIPSHIFT experiments by probing the 1H-13C dipolar interaction. RK-ROSE data were modeled by using Partial Least Square (PLS) multivariate regression, which showed a high coefficient of determination (R2 > 0.93) between RK-ROSE signal profile and average degrees of acetylation and crystallinity index, thus indicating that time-domain NMR consists in a promising tool for structural and morphological characterization of chitosan.

Tuning the properties of carboxymethylchitosan-based porous membranes for potential application as wound dressing.

Wound repair is a complex process that calls for strategies to allow a rapid and effective regeneration of injured skin, which has stimulated the research of advanced wound dressings. Herein, highly porous membranes of N,O-carboxymethylchitosan (CMCh), and poly (vinyl alcohol) (PVA) were successfully prepared via a green and facile freeze-drying method of blend solutions containing CMCh/PVA at weight ratio 25/75. Membranes composed only by CMCh were also prepared and genipin was used for crosslinking. Different contents of TiO2 nanoparticles were incorporated to both type of membranes, which were characterized in terms of morphology, porosity (Φ), swelling capacity (S.C.), mechanical properties, susceptibility to lysozyme degradation and in vitro cytotoxicity toward human fibroblast (HDFn) and keratinocytes (HaCaT) cells. Larger apparent pores were observed in the surface of the genipin-crosslinked CMCh membrane, which resulted in higher porosity (Φ ≈ 76%) and swelling capacity (S.C. ≈ 1720%) as compared to CMCh/PVA membrane (Φ ≈ 68%; S.C. ≈ 1660%). The porosity of both types of membranes decreased upon the addition of TiO2 nanoparticles while swelling capacity increased. Due to their high porosity and swelling capacity, adequate mechanical properties, controlled degradability, and cytocompatibility, such carboxymethylchitosan-based membranes are potentially useful as wound dressings.

Microwave irradiation to the rapid extraction of Stryphnodendron adstringens (Barbatimão) compounds by statistical planning.

Stryphnodendron adstringens is a typical tree from Brazilian Savanah used in medicine as an anti-inflammatory and antiseptic agent. It is secondary metabolites has biological activities, so the development of efficient extraction methods is essential. Microwave irradiation through assisted extraction is innovative and highly efficient for bioactive compounds. The aim of this study was to optimize an extractive method for phenolics compounds, as tannins, from the stem bark of "barbatimão" by microwave irradiation using a statistical planning and to evaluate its consistency with conventional extraction. Microwave irradiation extraction, 16.36-22.12% of phenols and 15.91-18.69% of tannins, has a better yield when compared to conventional extraction, 14.99% of phenols and 16.70% of tannins. The method by microwave irradiation is consistent with the conventional one. However, extraction by microwave irradiation had a reduction in reaction time, reagent volume, samples amount and energy consumption when compared to conventional extraction.

Soybean hulls: Optimization of the pulping and bleaching processes and carboxymethyl cellulose synthesis.

Soybean hulls, a co-product generated in high volumes, were used to obtain pulp and CMC. The pulping process was optimized with the aid of 1%, 2%, and 2.5% NaOH solutions at 90 °C for 2 h. A 22 central composite design was used in order to optimize the bleaching process and the CMC synthesis. Volumes of bleaching solution (VS) of between 55 and 65 mL/g at temperatures between 85 and 95 °C and VS of 70 and 75 mL/g at 95 °C were applied in the pulp bleaching process. The factors considered in the carboxymethylation were the chloroacetic acid mass (1.2-2.1 g/g) and the reaction time (192-228 min), at 63 °C. The soybean hulls contain 40.62% of cellulose and have a low lignin content. The pulping process was optimized when 1% NaOH was used at 90 °C/2 h and bleaching process applying VS = 75 mL at 95 °C/4 h. The pulps showed low lignin content (<6%) and the cellulose had a high degree of crystallinity. The SEM, 1H NMR, XRD, FTIR and TGA/DTG analysis results demonstrated that it is possible to synthesize CMC (DS = 1.45) by acetylating the bleached pulp with 2.1 g of chloroacetic acid for 192 min, at 63 °C.

Sorghum straw: Pulping and bleaching process optimization and synthesis of cellulose acetate.

The process employed for the pulping and bleaching of sorghum straw was optimized prior to the synthesis of cellulose acetate. A 22 factorial central composite design was carried out. The variables considered were cooking time (1.5 to 2.5 h) and dilute alkali concentration (0.75 to 1.25%) for the pulping and bleaching time (30 to 35 min) and bleach volume (20 to 25 mL) for the bleaching. The sorghum straw was comprised of 49.43% α-cellulose, 19.18% hemicellulose and 30.42% lignin. The optimum conditions that maximize these processes were 2.5 h and 1.25% (dilute alkali concentration) at 90 °C, and 35 min and 25 mL (bleach volume) at 80 °C, respectively, providing pulps with a low Kappa number (<3) and lignin content, and cellulose with a high degree of crystallinity. The 1H NMR, XRD, FTIR spectroscopy, SEM and thermal analysis demonstrated that it is possible to synthetize cellulose acetate (with 2.62 degrees of substitution) by acetylating bleached pulp for 16 h at 25 °C.

Biodegradation of anthracene and different PAHs by a yellow laccase from Leucoagaricus gongylophorus.

Laccases produced by Leucoagaricus gongylophorus act in lignocellulose degradation and detoxification processes. Therefore, the use of L. gongylophorus laccase (Lac1Lg) was proposed in this work for degradation of anthracene and others polycyclic aromatic hydrocarbons without the use of mediators. Degradation reactions were performed in buffer aqueous solution with 10 ppm of anthracene and other PAHs, Tween-20 in 0.25% v/v and a laccase preparation of 50 U. The optimum condition (pH 6.0 and 30 °C) was determined by response surface methodology with an excellent coefficient of determination (R2) of 0.97 and an adjusted coefficient of determination (R2adj) of 0.93. In addition, the employment of the mediator ABTS decreased the anthracene biodegradation from 44 ± 1% to 30 ± 1%. This optimum pH of 6.0 suggests that the reaction occurs by a hydrogen atom transfer mechanism. Additionally, in 24 h Lac1Lg biodegraded 72 ± 1% anthracene, 40 ± 3% fluorene and 25 ± 3% phenanthrene. The yellow laccase from L. gongylophorus biodegraded anthracene and produced anthrone and anthraquinone, which are interesting compounds for industrial applications. Moreover, this enzyme also biodegraded the PAHs phenanthrene and fluorene justifying the study of Lac1Lg for bioremediation of these compounds in the environment.

Characterization and physical-chemistry of methoxypoly(ethylene glycol)-g-chitosan.

Methoxypoly(ethyleneglycol)-graft-chitosan (PEG-g-Ch) was prepared by grafting polyethyleneglycol into chitosans (Ch) exhibiting different average degree of deacetylation (60% < DD¯â€¯< 95%). 1H NMR showed that PEG-g-Ch derivatives presented high average degree of N-substitution (DS¯â€¯≈ 40%) and such derivatives exhibited full water solubility at 1.0 < pH < 11.0. The mPEG-g-Ch derivatives displayed much lower intrinsic viscosity (20 mL g-1 < [η] < 110 mL g-1) as compared to the parent chitosans (440 mL g-1 < [η] < 1650 mL g-1) due to extensive exposition of PEG chains to the aqueous medium and compact coiling of the chitosan backbone. The presence of numerous PEG chains grafted into chitosan also determined the crystalline arrangement and the thermal stability of PEG-g-Ch derivatives. The rheological study showed that the concentrated aqueous solutions of PEG-g-Ch derivatives displayed pseudoplastic behavior regardless of the parent chitosans´ characteristics and no dependence of dynamic viscosity on the temperature. However, PChD2 (DD¯â€¯≈ 76%; [η] ≈ 1201 mL g-1) showed a distinct rheological behavior as it formed a physically cross-linked hydrogel that exhibited a thermo-induced sol-gel transition at ≈38 °C.

Nanostructured electrospun nonwovens of poly(ε-caprolactone)/quaternized chitosan for potential biomedical applications.

Blend solutions of poly(ε-caprolactone) (PCL) and N-(2-hydroxy)-propyl-3-trimethylammonium chitosan chloride (QCh) were successfully electrospun. The weight ratio PCL/QCh ranged in the interval 95/5-70/30 while two QCh samples were used, namely QCh1 (DQ¯â€¯= 47.3%; DPv¯â€¯= 2218) and QCh2 (DQ¯â€¯= 71.1%; DPv¯â€¯= 1427). According to the characteristics of QCh derivative and to the QCh content on the resulting PCL/QCh nonwoven, the nanofibers displayed different average diameter (175 nm-415 nm), and the nonwovens exhibited variable porosity (57.0%-81.6%), swelling capacity (175%-425%) and water vapor transmission rate (1600 g m-2 24 h-2500 g m-2 24 h). The surface hydrophilicity of nonwovens increases with increasing QCh content, favoring fibroblast (HDFn) adhesion and spreading. Tensile tests revealed that the nonwovens present a good balance between elasticity and strength under both dry and hydrated state. Results indicate that the PCL/QCh electrospun nonwovens are new nanofibers-based biomaterials potentially useful as wound dressings.

PDLLA honeycomb-like scaffolds with a high loading of superhydrophilic graphene/multi-walled carbon nanotubes promote osteoblast in vitro functions and guided in vivo bone regeneration.

Herein, we developed honeycomb-like scaffolds by combining poly (d, l-lactic acid) (PDLLA) with a high amount of graphene/multi-walled carbon nanotube oxides (MWCNTO-GO, 50% w/w). From pristine multi-walled carbon nanotubes (MWCNT) powders, we produced MWCNTO-GO via oxygen plasma etching (OPE), which promoted their exfoliation and oxidation. Initially, we evaluated PDLLA and PDLLA/MWCNTO-GO scaffolds for tensile strength tests, cell adhesion and cell viability (with osteoblast-like MG-63 cells), alkaline phosphatase (ALP, a marker of osteoblast differentiation) activity and mineralized nodule formation. In vivo tests were carried out using PDLLA and PDLLA/MWCNTO-GO scaffolds as fillers for critical defects in the tibia of rats. MWCNTO-GO loading was responsible for decreasing the tensile strength and elongation-at-break of PDLLA scaffolds, although the high mechanical performance observed (~600MPa) assures their application in bone tissue regeneration. In vitro results showed that the scaffolds were not cytotoxic and allowed for osteoblast-like cell interactions and the formation of mineralized matrix nodules. Furthermore, MG-63 cells grown on PDLLA/MWCNTO-GO significantly enhanced osteoblast ALP activity compared to controls (cells alone), while the PDLLA group showed similar ALP activity when compared to controls and PDLLA/MWCNTO-GO. Most impressively, in vivo tests suggested that compared to PDLLA scaffolds, PDLLA/MWCNTO-GO had a superior influence on bone cell activity, promoting greater new bone formation. In summary, the results of this study highlighted that this novel scaffold (MWCNTO-GO, 50% w/w) is a promising alternative for bone tissue regeneration and, thus, should be further studied.

Response surface methodology applied to the study of the microwave-assisted synthesis of quaternized chitosan.

A quaternized derivative of chitosan, namely N-(2-hydroxy)-propyl-3-trimethylammonium chitosan chloride (QCh), was synthesized by reacting glycidyltrimethylammonium chloride (GTMAC) and chitosan (Ch) in acid medium under microwave irradiation. Full-factorial 2(3) central composite design and response surface methodology (RSM) were applied to evaluate the effects of molar ratio GTMAC/Ch, reaction time and temperature on the reaction yield, average degree of quaternization (DQ) and intrinsic viscosity ([η]) of QCh. The molar ratio GTMAC/Ch was the most important factor affecting the response variables and RSM results showed that highly substituted QCh (DQ = 71.1%) was produced at high yield (164%) when the reaction was carried out for 30min. at 85°C by using molar ratio GTMAC/Ch 6/1. Results showed that microwave-assisted synthesis is much faster (≤30min.) as compared to conventional reaction procedures (>4h) carried out in similar conditions except for the use of microwave irradiation.

Microwave-assisted carboxymethylation of cellulose extracted from brewer's spent grain.

Cellulose was extracted from brewer's spent grain (BSG) by alkaline and bleaching treatments. The extracted cellulose was used in the preparation of carboxymethyl cellulose (CMC) by reaction with monochloroacetic acid in alkaline medium with the use of a microwave reactor. A full-factorial 2(3) central composite design was applied in order to evaluate how parameters of carboxymethylation process such as reaction time, amount of monochloroacetic acid and reaction temperature affect the average degree of substitution (DS) of the cellulose derivative. An optimization strategy based on response surface methodology has been used for this process. The optimized conditions to yield CMC with the highest DS of 1.46 follow: 5g of monochloroacetic acid per gram of cellulose, reaction time of 7.5min and temperature of 70°C. This work demonstrated the feasibility of a fast and efficient microwave-assisted method to synthesize carboxymethyl cellulose from cellulose isolated of brewer's spent grain.