Side-stream lignins: Potential antioxidant and antimicrobial agents in milk.

In recent years, lignin has drawn increasing attention due to its intrinsic antibacterial and antioxidant activities, biodegradability, and biocompatibility. Yet, like several other biogenic structures, its compositional heterogeneity represents a challenge to overcome. In addition, there are few studies regarding food applications of lignin. Herein, we evaluate the antimicrobial and antioxidant effects of lignin from two different sources. These lignins were characterized by attenuated total reflectance Fourier-transform infrared (ATR-FTIR) and hydrogen nuclear magnetic resonance (1H NMR) spectroscopies. Their antibacterial and antioxidant capacities (DPPH and Folin-Ciocalteu methods) were also investigated. Susceptibility tests were performed with the minimal inhibitory (MIC) and bactericidal (MBC) concentrations using the micro-broth dilution technique. Kraft lignin presented higher radical-scavenging and antibacterial activities than alkali lignin, indicating the dependence of antioxidant and antibacterial activities on the precursor biomass. Scanning electron microscopy shows morphologic changes in the bacteria after exposure to lignin, while confocal microscopy suggests that kraft lignin has affinity towards bacterial surfaces and the ability to cause cell membrane destabilization. Lignin inhibited the growth of Staphylococcus aureus and Salmonella Enteritidis in skimmed milk, herein taken as food model. Our results suggest that lignins are promising candidates for green additives to improve quality and safety within the food chain.

Recent Progress in Stimuli-Responsive Antimicrobial Electrospun Nanofibers.

Electrospun nanofibrous membranes have garnered significant attention in antimicrobial applications, owing to their intricate three-dimensional network that confers an interconnected porous structure, high specific surface area, and tunable physicochemical properties, as well as their notable capacity for loading and sustained release of antimicrobial agents. Tailoring polymer or hybrid-based nanofibrous membranes with stimuli-responsive characteristics further enhances their versatility, enabling them to exhibit broad-spectrum or specific activity against diverse microorganisms. In this review, we elucidate the pivotal advancements achieved in the realm of stimuli-responsive antimicrobial electrospun nanofibers operating by light, temperature, pH, humidity, and electric field, among others. We provide a concise introduction to the strategies employed to design smart electrospun nanofibers with antimicrobial properties. The core section of our review spotlights recent progress in electrospun nanofiber-based systems triggered by single- and multi-stimuli. Within each stimulus category, we explore recent examples of nanofibers based on different polymers and antimicrobial agents. Finally, we delve into the constraints and future directions of stimuli-responsive nanofibrous materials, paving the way for their wider application spectrum and catalyzing progress toward industrial utilization.

Multifunctional bilayer membranes composed of poly(lactic acid), beta-chitin whiskers and silver nanoparticles for wound dressing applications.

Nanomaterial-based wound dressings have been extensively studied for the treatment of both minor and life-threatening tissue injuries. These wound dressings must possess several crucial characteristics, such as tissue compatibility, non-toxicity, appropriate biodegradability to facilitate wound healing, effective antibacterial activity to prevent infection, and adequate physical and mechanical strength to withstand repetitive dynamic forces that could potentially disrupt the healing process. Nevertheless, the development of nanostructured wound dressings that incorporate various functional micro- and nanomaterials in distinct architectures, each serving specific purposes, presents significant challenges. In this study, we successfully developed a novel multifunctional wound dressing based on poly(lactic acid) (PLA) fibrous membranes produced by solution-blow spinning (SBS) and electrospinning. The PLA-based membranes underwent surface modifications aimed at tailoring their properties for utilization as effective wound dressing platforms. Initially, beta-chitin whiskers were deposited onto the membrane surface through filtration, imparting hydrophilic character. Afterward, silver nanoparticles (AgNPs) were incorporated onto the beta-chitin layer using a spray deposition method, resulting in platforms with antimicrobial properties against both Staphylococcus aureus and Escherichia coli. Cytotoxicity studies demonstrated the biocompatibility of the membranes with the neonatal human dermal fibroblast (HDFn) cell line. Moreover, bilayer membranes exhibited a high surface area and porosity (> 80%), remarkable stability in aqueous media, and favorable mechanical properties, making them promising candidates for application as multifunctional wound dressings.

Combining Coaxial Electrospinning and 3D Printing: Design of Biodegradable Bilayered Membranes with Dual Drug Delivery Capability for Periodontitis Treatment.

Periodontitis is a chronic inflammatory disease that can lead to significant destruction of tooth-supporting tissues, compromising dental function and patient's health. Although the currently employed treatment approaches can limit the advance of the disease, the development of multifunctional and hierarchically structured materials is still in demand for achieving successful tissue regeneration. Here, we combine coaxial electrospinning and 3D printing techniques to prepare bilayered zein-based membranes as a potential dual drug delivery platform for periodontal tissue regeneration. A layer of core-sheath electrospun nanofibers consisting of poly(ethylene oxide) (PEO)/curcumin (Curc)/tetracycline hydrochloride (TH) as the core and zein/poly(ε-caprolactone)(PCL)/ß-glycerolphosphate (ß-GP) as the sheath was deposited over a 3D printed honeycomb PLA/zein/Curc platform in order to render a bilayered structure that can mimic the architecture of periodontal tissue. The physicochemical properties of engineered constructs as well as the release profiles of distinct drugs were mainly controlled by varying the concentration of zein (10, 20, 30%, w/w relative to dry PCL) on the sheath layer of nanofibers, which displayed average diameters ranging from 150 to 400 nm. In vitro experiments demonstrated that the bilayered constructs provided sustained release of distinct drugs over 8 days and exhibited biocompatibility toward human oral keratinocytes (Nok-si) (cell viability >80%) as well as antibacterial activity against distinct bacterial strains including those of the red complex such as Porphyromonas gingivalis and Treponema denticola, which are recognized to elicit aggressive and chronic periodontitis. Our study reveals the potential of zein-based bilayered membranes as a dual drug delivery platform for periodontal tissue regeneration.

Advances in Functional Polymer Nanofibers: From Spinning Fabrication Techniques to Recent Biomedical Applications.

Functional polymeric micro-/nanofibers have emerged as promising materials for the construction of structures potentially useful in biomedical fields. Among all kinds of technologies to produce polymer fibers, spinning methods have gained considerable attention. Herein, we provide a recent review on advances in the design of micro- and nanofibrous platforms via spinning techniques for biomedical applications. Specifically, we emphasize electrospinning, solution blow spinning, centrifugal spinning, and microfluidic spinning approaches. We first introduce the fundamentals of these spinning methods and then highlight the potential biomedical applications of such micro- and nanostructured fibers for drug delivery, tissue engineering, regenerative medicine, disease modeling, and sensing/biosensing. Finally, we outline the current challenges and future perspectives of spinning techniques for the practical applications of polymer fibers in the biomedical field.

Impedimetric electronic tongue based on molybdenum disulfide and graphene oxide for monitoring antibiotics in liquid media.

Antibiotics are considered emerging pollutants which indiscriminate use has led to the development of antibiotic-resistant bacteria, while their improper disposal has caused adverse effects to the environment and human health. Thus, the development of devices or techniques capable of detecting antibiotics with high sensitivity, low detection limits, and reasonable cost becomes of prime importance. In this work, an electronic tongue (e-tongue) based on molybdenum disulfide (MoS2) and graphene oxide (GO) was developed and employed to detect four distinct antibiotics, namely cloxacillin benzathine, erythromycin, streptomycin sulfate, and tetracycline hydrochloride. The five sensing units of the e-tongue were obtained using the drop-casting method to modify gold interdigitated electrodes with MoS2 and GO. Using Principal Component Analysis to process the experimental data allowed the e-tongue to recognize samples contaminated with distinct antibiotics at varied concentrations from 0.5 to 5.0 nmol L-1. Analyses with real samples were also performed using river water and human urine and the electronic tongue was able to differentiate the samples at a nanomolar level. The proposed system represents a sensitive and low-cost alternative for antibiotic analyses in different liquid media.

Tracking Sulfonated Polystyrene Diffusion in a Chitosan/Carboxymethyl Cellulose Layer-by-Layer Film: Exploring the Internal Architecture of Nanocoatings.

Since chitosan presents the ability to interact with a wide range of molecules, it has been one of the most popular natural polymers for the construction of layer-by-layer thin films. In this study, depth-profiling X-ray photoelectron spectroscopy (XPS) was employed to track the diffusion of sulfonated polystyrene (SPS) in carboxymethyl cellulose/chitosan (CMC/Chi) multilayers. Our findings suggest that the CMC/Chi film does not constitute an electrostatic barrier sufficient to block diffusion of SPS, and that diffusion can be controlled by adjusting the diffusion time and the molecular weight of the polymers that compose the CMC/Chi system. In addition to monitoring the diffusion, it was also possible to observe a process of preferential interaction between Chi and SPS. Thus, the nitrogen N 1s peak, due to functional groups found exclusively in chitosan chains, was the key factor to identifying the molecular interactions involving chitosan and the different polyanions. Accordingly, the presence of a strong polyanion such as SPS shifts the N 1s peak to a higher level of binding energy. Such results highlight that understanding the fundamentals of polymer interactions is a major step to fine-tuning the internal architecture of LbL structures for specific applications (e.g., drug release).

Core-sheath nanostructured chitosan-based nonwovens as a potential drug delivery system for periodontitis treatment.

Core-sheath nanofibers were successfully prepared via coaxial electrospinning by using chitosan with well-defined structural characteristics as the shell layer and poly (vinyl alcohol) (PVA) containing tetracycline hydrochloride (TH) as the core layer. The effects of the average degree of deacetylation (DD‾) of chitosan and the post-electrospinning genipin crosslinking on physicochemical and biological properties of resulting nonwovens were evaluated. Defect-free and geometrically uniform nanofibers with diameters predominantly in the range of 100-300 nm were prepared, and transmission electron microscopy (TEM) revealed the core-sheath structures and its preservation after crosslinking. The mechanical properties, as well as the stability of nonwovens in aqueous medium, were greatly improved by genipin-crosslinking, which enabled a sustained release of TH over 14 days. Results also revealed that the release profile of TH in the presence of lysozyme was affected by the composition of the shell layer, as the TH release rate increases with decreasing of DD‾. Further in vitro antimicrobial activity demonstrated that the cross-linked nonwovens containing TH showed strong activity against bacterial strains associated with periodontal disease. Additionally, the nonwovens did not demonstrate cytotoxic toward fibroblast (HDFn) cells, hence showing their potential for applications as a novel drug delivery platform for periodontitis treatment.

Investigation of the Internal Chemical Composition of Chitosan-Based LbL Films by Depth-Profiling X-ray Photoelectron Spectroscopy (XPS) Analysis.

Chitosan-based thin films were assembled using the layer-by-layer technique, and the axial composition was accessed using X-ray photoelectron spectroscopy with depth profiling. Chitosan (CHI) samples possessing different degrees of acetylation ([Formula: see text]) and molecular weight ([Formula: see text]) produced via the ultrasound-assisted deacetylation reaction were used in this study along with two different polyanions, namely, sodium polystyrenesulfonate (PSS) and carboxymethylcellulose (CMC). When chitosan, a positively charged polymer in aqueous acid medium, was combined with a strong polyanion (PSS), the total positive charge of chitosan, directly related to its [Formula: see text], was the key factor affecting the film formation. However, for CMC/CHI films, the pH of the medium and [Formula: see text] of chitosan strongly affected the film structure and composition. Consequently, the structure and the axial composition of chitosan-based films can be finely adjusted by choosing the polyanion and defining the chitosan to be used according to its DA and [Formula: see text] for the desired application, as demonstrated by the antibacterial tests.

Optimization of carboxymethyl chitosan synthesis using response surface methodology and desirability function.

In this paper, chitosan was reacted with monochloroacetic acid under alkaline conditions to prepare carboxymethyl chitosan. A 2(3) full-factorial central composite design was applied to evaluate the effect of molar ratio sodium hydroxide (NaOH)/Chitosan (Ch), time and molar ratio monochloroacetic acid (MCA)/Chitosan (Ch) on the reaction yield and on the characteristics of carboxymethyl chitosan such as average degree of substitution (DS¯) and solubility. An optimization strategy based on response surface methodology was used together with the desirability function approach to optimize this process. The occurrence of carboxymethylation was evidenced by FTIR and (1)H NMR spectroscopy. The optimum conditions for carboxymethylation process were found to be 12.4, 10.6h and 5 for molar ratio sodium hydroxide (NaOH)/Chitosan (Ch), time and molar ratio monochloroacetic acid (MCA)/Chitosan (Ch), respectively. Under these optimal conditions, it was possible to obtain carboxymethyl chitosan with DS¯ of 1.86 and solubility of 99.6%. X-ray diffraction and thermogravimetry analysis showed that crystallinity and thermal stability of derivatives was lower than chitosan and decreased with increase of DS¯.