Formulations based on pullulan and a derivative as coating material for the food sector

Carboxymethylated derivatives of pullulan (PU) were synthesized and evaluated as coating for the postharvest preservation of blueberries. Carboxymethylpullulan was obtained by etherification reaction with the substitution degrees of 0.52, 0.34, and 0.26 for CMP1, CMP2, and CMP3 respectively. Infrared spectroscopy and nuclear magnetic resonance results showed characteristic signals of the carbonyl group belonging to the carboxymethyl group. Thermal analysis showed that CMP1, CMP2, and CMP3 derivatives presented thermal stability values of 209.91 C, 214.73 C, and 225.52 °C, respectively, and were lower with respect to PU with Td of 238.84 °C. Furthermore, an increase in the glass transition temperature due to carboxymethylation was determined. The chemical modification decreased the contact angle with respect to PU (71.34°) with values for CMP1, CMP2, and CMP3 of 39.89°, 53.72° and 60.61°, respectively. The carboxymethylation also increased the water vapor permeability and mechanical properties of the films. In addition, it was found that the CMP molecules affected the optical properties. The application of CMP-based coatings reduced the mass loss and ripening rate of blueberries compared to native pullulan, therefore, packaging from CMP molecules could be used as a coating capable of delaying ripening and extending the shelf life of fruits.

Cancer Treatment Using Nanofibers: A Review

Currently, the number of patients with cancer is expanding consistently because of a low quality of life. For this reason, the therapies used to treat cancer have received a lot of consideration from specialists. Numerous anticancer medications have been utilized to treat patients with cancer. However, the immediate utilization of anticancer medicines leads to unpleasant side effects for patients and there are many restrictions to applying these treatments. A number of polymers like cellulose, chitosan, Polyvinyl Alcohol (PVA), Polyacrylonitrile (PAN), peptides and Poly (hydroxy alkanoate) have good properties for the treatment of cancer, but the nanofibers-based target and controlled drug delivery system produced by the co-axial electrospinning technique have extraordinary properties like favorable mechanical characteristics, an excellent release profile, a high surface area, and a high sponginess and are harmless, bio-renewable, biofriendly, highly degradable, and can be produced very conveniently on an industrial scale. Thus, nanofibers produced through coaxial electrospinning can be designed to target specific cancer cells or tissues. By modifying the composition and properties of the nanofibers, researchers can control the release kinetics of the therapeutic agent and enhance its accumulation at the tumor site while minimizing systemic toxicity. The core-shell structure of coaxial electrospun nanofibers allows for a controlled and sustained release of therapeutic agents over time. This controlled release profile can improve the efficacy of cancer treatment by maintaining therapeutic drug concentrations within the tumor microenvironment for an extended period.

Extracting compositional blocks of alginate-like extracellular polymers (ALE) from conventional activated sludge (CAS)

As a highly added value material, alginate-like extracellular polymers (ALE) can be extracted from extracellular polymeric substances (EPS) from aerobic granular sludge (AGS). In fact, conventional activated sludge (CAS) also contains a certain amount of ALE. As CAS is widely used everywhere, waste activated sludge (WAS) from CAS is huge in its absolute amount. Although the ALE property of CAS was identified not so good as that from AGS, the mechanisms remains unclear. For this reason, it is necessary to unravel the chemically compositional blocks of ALE. Referring to natural alginate, ALE can be separated into three compositional blocks: GGL, GML and MML (like units containing guluronate or mannuronate), associated with other compositions including protein (PN), polysaccharide (PS), phosphorus (P), humic acid (HA). With real WAS from CAS, ALE was extracted and three blocks were separated: GGL = 54 %, GML = 42 % and MML = 4 % in weight, which is similar to the previous study. Moreover, the GGL blocks in CAS were obviously lower than AGS, down to by 1/3-1/2. And the GML and MML blocks in CAS were much higher than AGS, by more than 1/2. Different compositional blocks of ALE in AGS and CAS should be the reason forming different properties in applications. For this reason, a further study will be initiated to dispense/reorganize three blocks of ALE from CAS for expanding its potential applications, based on the compositional blocks of ALE from AGS.

New Biocompatible Nanohydrogels of Predefined Sizes for Complexing Nucleic Acids

The advent of protein expression using m-RNA applied lately for treating the COVID pandemic, and gene editing using CRISPR/Cas9 technology for introducing DNA sequences at a specific site in the genome, are milestones for the urgent need of developing new nucleic acid delivery systems with improved delivery properties especially for in vivo applications. We have designed, synthesized, and characterized novel cross-linked monodispersed nanohydrogels (NHG's) with well-defined sizes ranging between 50-400 nm. The synthesis exploits the formation of self-assemblies generated upon heating a thermo-responsive mixture of monomers. Self-assemblies are formed and polymerized at high temperatures resulting in NHGs with sizes that are predetermined by the sizes of the intermediate self-assemblies. The obtained NHGs were chemically reduced to lead particles with highly positive zeta potential and low cell toxicity. The NHGs form complexes with DNA, and at optimal charge ratio the size of the complexes is concomitant with the size of the NHG's. Thus, the DNA is fully embedded inside the NHGs. The new NHGs and their DNA complexes are devoid of cell toxicity which together with their tunned sizes, make them potential tools for gene delivery and foreign protein expression.

A molecular simulation study on amine-functionalized silica/polysulfone mixed matrix membrane for mixed gas separation

Polysulfone (PSF) based mixed matrix membranes (MMMs) are one of the most broadly studied polymeric materials used for CO₂/CH₄ separation. The performance of existing PSF membranes encounters a bottleneck for widespread expansion in industrial applications due to the trade-off amongst permeability and selectivity. Membrane performance has been postulated to be enhanced via functionalization of filler at different weight percentages. Nonetheless, the preparation of functionalized MMMs without defects and its empirical study that exhibits improved CO₂/CH₄ separation performance is challenging at an experimental scale that needs prior knowledge of the compatibility between the filler and polymer. Molecular simulation approaches can be used to explore the effect of functionalization on MMM's gas transport properties at an atomic level without the challenges in the experimental study, however, they have received less scrutiny to date. In addition, most of the research has focused on pure gas studies while mixed gas transport properties that reflect real separation in functionalized silica/PSF MMMs are scarcely available. In this work, a molecular simulation computational framework has been developed to investigate the structural, physical properties and gas transport behavior of amine-functionalized silica/PSF-based MMMs. The effect of varying weight percentages (i.e., 15-30 wt.%) of amine-functionalized silica and gas concentrations (i.e., 30% CH₄/CO₂, 50% CH₄/CO₂, and 70% CH₄/CO₂) on physical and gas transport characteristics in amine-functionalized silica/PSF MMMs at 308.15 K and 1 atm has been investigated. Functionalization of silica nanoparticles was found to increase the diffusion and solubility coefficients, leading to an increase in the percentage enhancement of permeability and selectivity for amine-functionalized silica/PSF MMM by 566% and 56%, respectively, compared to silica/PSF-based MMMs at optimal weight percentage of 20 wt.%. The model's permeability differed by 7.1% under mixed gas conditions. The findings of this study could help to improve real CO₂/CH₄ separation in the future design and concept of functionalized MMMs using molecular simulation and empirical modeling strategies.

Alginate as a Promising Biopolymer in Drug Delivery and Wound Healing: A Review of the State-of-the-Art

Biopolymeric nanoparticulate systems hold favorable carrier properties for active delivery. The enhancement in the research interest in alginate formulations in biomedical and pharmaceutical research, owing to its biodegradable, biocompatible, and bioadhesive characteristics, reiterates its future use as an efficient drug delivery matrix. Alginates, obtained from natural sources, are the colloidal polysaccharide group, which are water-soluble, non-toxic, and non-irritant. These are linear copolymeric blocks of α-(1→4)-linked l-guluronic acid (G) and β-(1→4)-linked d-mannuronic acid (M) residues. Owing to the monosaccharide sequencing and the enzymatically governed reactions, alginates are well-known as an essential bio-polymer group for multifarious biomedical implementations. Additionally, alginate’s bio-adhesive property makes it significant in the pharmaceutical industry. Alginate has shown immense potential in wound healing and drug delivery applications to date because its gel-forming ability maintains the structural resemblance to the extracellular matrices in tissues and can be altered to perform numerous crucial functions. The initial section of this review will deliver a perception of the extraction source and alginate’s remarkable properties. Furthermore, we have aspired to discuss the current literature on alginate utilization as a biopolymeric carrier for drug delivery through numerous administration routes. Finally, the latest investigations on alginate composite utilization in wound healing are addressed.

Biodegradable Polyphosphazenes for Regenerative Engineering

Regenerative engineering is a field that seeks to regenerate complex tissues and biological systems, rather than simply restore and repair individual tissues or organs. Since the first introduction of regenerative engineering in 2012, numerous research has been devoted to the development of this field. Biodegradable polymers such as polyphosphazenes in particular have drawn significant interest as regenerative engineering materials for their synthetic flexibility in designing into materials with a wide range of mechanical properties, degradation rates, and chemical functionality. These polyphosphazenes can go through complete hydrolytic degradation and provide harmlessly and pH neutral buffering degradation products such as phosphates and ammonia, which is crucial for reducing inflammation in vivo. Here, we discuss the current accomplishments of polyphosphazene, different methods for synthesizing them, and their applications in tissue regeneration such as bones, nerves, and elastic tissues.

Translating Therapeutic Microgels into Clinical Applications

Microgels are crosslinked, water-swollen networks with a 10 nm to 100 µm diameter and can be modified chemically or biologically to render them biocompatible for advanced clinical applications. Depending on their intended use, microgels require different mechanical and structural properties, which can be engineered on demand by altering the biochemical composition, crosslink density of the polymer network, and the fabrication method. Here, the fundamental aspects of microgel research and development, as well as their specific applications for theranostics and therapy in the clinic, are discussed. A detailed overview of microgel fabrication techniques with regards to their intended clinical application is presented, while focusing on how microgels can be employed as local drug delivery materials, scavengers, and contrast agents. Moreover, microgels can act as scaffolds for tissue engineering and regeneration application. Finally, an overview of microgels is given, which already made it into pre-clinical and clinical trials, while future challenges and chances are discussed. This review presents an instructive guideline for chemists, material scientists, and researchers in the biomedical field to introduce them to the fundamental physicochemical properties of microgels and guide them from fabrication methods via characterization techniques and functionalization of microgels toward specific applications in the clinic.

A Molecular Simulation Study of Silica/Polysulfone Mixed Matrix Membrane for Mixed Gas Separation

Polysulfone-based mixed matrix membranes (MMMs) incorporated with silica nanoparticles are a new generation material under ongoing research and development for gas separation. However, the attributes of a better-performing MMM cannot be precisely studied under experimental conditions. Thus, it requires an atomistic scale study to elucidate the separation performance of silica/polysulfone MMMs. As most of the research work and empirical models for gas transport properties have been limited to pure gas, a computational framework for molecular simulation is required to study the mixed gas transport properties in silica/polysulfone MMMs to reflect real membrane separation. In this work, Monte Carlo (MC) and molecular dynamics (MD) simulations were employed to study the solubility and diffusivity of CO₂/CH₄ with varying gas concentrations (i.e., 30% CO₂/CH₄, 50% CO₂/CH₄, and 70% CO₂/CH₄) and silica content (i.e., 15–30 wt.%). The accuracy of the simulated structures was validated with published literature, followed by the study of the gas transport properties at 308.15 K and 1 atm. Simulation results concluded an increase in the free volume with an increasing weight percentage of silica. It was also found that pure gas consistently exhibited higher gas transport properties when compared to mixed gas conditions. The results also showed a competitive gas transport performance for mixed gases, which is more apparent when CO₂ increases. In this context, an increment in the permeation was observed for mixed gas with increasing gas concentrations (i.e., 70% CO₂/CH₄ > 50% CO₂/CH₄ > 30% CO₂/CH₄). The diffusivity, solubility, and permeability of the mixed gases were consistently increasing until 25 wt.%, followed by a decrease for 30 wt.% of silica. An empirical model based on a parallel resistance approach was developed by incorporating mathematical formulations for solubility and permeability. The model results were compared with simulation results to quantify the effect of mixed gas transport, which showed an 18% and 15% percentage error for the permeability and solubility, respectively, in comparison to the simulation data. This study provides a basis for future understanding of MMMs using molecular simulations and modeling techniques for mixed gas conditions that demonstrate real membrane separation.

Aqueous Modification of Chitosan with Itaconic Acid to Produce Strong Oxygen Barrier Film

In this study, the chemical modification of chitosan using itaconic acid as a natural-based unsaturated dicarboxylic acid was investigated. In an aqueous environment, the amine group of chitosan reacts with itaconic acid to produce a chitosan derivative with pyrrolidone-4-carboxylic acid group. On the basis of the elemental analysis, 15% of the amine groups of chitosan reacted, thus creating modified chitosan with amine and carboxylic acid functionalities. Due to the presence of amine and carboxylic acid groups, the surface charge properties of the chitosan were notably altered after itaconic acid modification. In an aqueous solution, the modified chitosan exhibited zwitterionic properties, being cationic at low pH and turning anionic when the pH was increased over 6.5, whereas the original chitosan remained cationic until pH 9. Furthermore, it was demostrated that the modified chitosan was suitable for the preparation of a self-standing film with similarly high transparency but notably higher mechanical strength and oxygen barrier properties compared to a film made from the original chitosan. In addition, the thermal stability of the modified chitosan film was higher than that of the original chitosan film, and the modified chitosan exhibited flame-retardant properties.

An alginate-PHMB-AgNPs based wound dressing polyamide nanocomposite with improved antibacterial and hemostatic properties

Wound dressing should be impenetrable against microorganisms and it should keep the wound wet. Gauze and polyamide (PA) substrate were treated with various concentrations of AgNPs (25, 50, 75, and 100 ppm), PHMB (0.2, 0.4, 0.6, 0.8, and 1% w/v), and constant concentration of alginate (0.5% W/V) using a simple dipping method. Prepared samples were characterized by various techniques including Fourier transform infrared spectroscopy and scanning electron microscopy. The results indicated that the particles were successfully applied onto both substrates with an average diameter of particle size of 78 nm on gauze and 172 nm on the PA substrate surface (based on 50 nanoparticles). Antibacterial activity of the prepared nanocomposite against Staphylococcus aureus (gram-positive) bacteria on PA substrate and gauze were evaluated using the disc diffusion method. The results indicated that the prepared nanocomposites offer favorable antibacterial properties and bacteria would not grow in culture media. The water uptake capacity test of the treated samples was assessed and the data demonstrated that the water absorption rate significantly increases on both treated substrates (gauze and PA substrate) due to the presence of alginate polymer. Also, observing the results of the coagulation test showed that treated samples caused blood clots on the dressing. This is due to the presence of alginate polymer. The present work demonstrates that the prepared samples offer excellent antibacterial properties and good water uptake capacity that capable of being a potential candidate for wound dressings. Due to the results, the produced PA substrate could be an appropriate replacement for the cotton gauze as a wound dressing.

Composite Hydrogel of Poly(acrylamide) and Starch as Potential System for Controlled Release of Amoxicillin and Inhibition of Bacterial Growth

Novel composite hydrogels of poly(acrylamide) (PAAm) and starch, at different ratios, were studied as potential platforms for controlled release of amoxicillin. The composite hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and swelling kinetic measurements. The morphology analysis revealed the presence of starch granules well embedded within the PAAm network. The increase in starch content increased the rate of water uptake and the swelling degree at equilibrium. The amoxicillin release kinetics was sensitive to pH and temperature conditions. The in vitro bacterial growth inhibition of antibiotic-loaded hydrogels was tested though disc diffusion assays with Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, and a carbapenemase producer Pseudomonas aeruginosa strain. The optimal release profile at physiological conditions and the powerful bacteria growth inhibition effects of amoxicillin-loaded hydrogels evidenced its potential for biomedical applications, particularly in oral administration and the local treatment of bacterial infections.

A Novel Method to Increase Tumor Ablation Zones With RFA by Injecting the Cationic Polymer Solution to Tissues: In Vivo and Computational Studies

OBJECTIVE

This study aims to examine, for the first time, the introduction of cationic polymer solutions to improve radiofrequency ablation (RFA) in terms of a potentially enlarged ablation zone.

METHODS

By using in vivo and computational RFA studies, two cationic polymers, Chitooligosaccharides (COS) and carboxymethyl chitosan (CMC), diluted in deionized water, were injected into tissues separately surrounding the RF bipolar electrode prior to power application. A total of 9 rabbits were used to 1) measure the increase in electrical conductivity of tissues injected with the cationic polymer solutions, and 2) explore the enhancement of the ablation performance in RFA trials. A computer model of RFA comprising a model of the solution diffusion with an RF thermal ablation model was also built, validated by the in vivo experiment, to quantitatively study the effect of cationic polymer solutions on ablation performances.

RESULTS

Compared to the control group, the electrical conductivity of rabbit liver tissues was increased by 42.20% (0.282 ± 0.006 vs. 0.401 ± 0.048 S/m, P = 0.001) and 43.97% (0.282 ± 0.006 vs. 0.406 ± 0.042 S/m, P = 0.001) by injecting the COS and CMC solution at the concentration of 100 mg/mL into the tissues, denoted COS_DW100 and CMC_DW100, respectively. Consequently, the in vivo experiments show that the ablation zone was enlarged by 95% (47.6 ± 6.3 vs. 92.6 ± 11.5 mm², P < 0.001) and 87% (47.6± 6.3 vs. 88.8 ± 9.6 mm², P < 0.001) by COS_DW100 and CMC_DW100, respectively. The computer simulation shows that the ablation zone was enlarged by 71% (51.9 vs. 88.7 mm²) and 63% (51.9 vs. 84.7 mm²) by COS_DW100 and CMC_DW100, respectively.

CONCLUSION

The injection of the cationic solution can greatly improve the performance of RFA treatment in terms of enlarging the ablation zone, which is due to the increase in the electrical conductivity of liver tissues surrounding the RF electrode.

SIGNIFICANCE

This study contributes to the improvement of RFA in the treatment of large tumors.

Sorption of copper onto low molecular weight chitosan derivative from aqueous solution

In this study, sorption of copper onto low molecular weight chitosan derivative was studied. Experimental parameters such as pH of the solution (A), temperature (B), dose of the sorbent (C), and concentration of solution (D) were considered. The statistical results indicated that the dose of sorbent (C) and Cu (II) concentration (D) influenced removal efficiency at 5% significance level. Also, some interactions such as ABCD, ACD, ABC and AC affected the removal process. The sorbent was characterized with FTIR, SEM and TG/DSC. Freundlich isotherm model was the best isotherm model. The kinetic study results correlated well with the pseudo-second-order model. The thermodynamic studies revealed that the nature of copper sorption was spontaneous and endothermic. Strong affinity of the sorbent for copper (II) was revealed by the Isothermal Titration Calorimetry (ITC) technique.

Sorption of heavy metal ions onto carboxylate chitosan derivatives--a mini-review

Chitosan is of importance for the elimination of heavy metals due to their outstanding characteristics such as the presence of NH2 and -OH functional groups, non-toxicity, low cost and, large available quantities. Modifying a chitosan structure with -COOH group improves it in terms of solubility at pH ≤7 without affecting the aforementioned characteristics. Chitosan modified with a carboxylic group possess carboxyl, amino and hydroxyl multifunctional groups which are good for elimination of metal ions. The focal point of this mini-review will be on the preparation and characterization of some carboxylate chitosan derivatives as a sorbent for heavy metal sorption.

Removal of cadmium from aqueous solution using low molecular weight chitosan derivative

A 2(3) factorial design was used to examine the sorption of Cd(2+) onto cross-linked low molecular weight chitosan pyruvic acid derivative. Three factors and two levels of solution pH (A) (6.0 or 10.0), temperature (B) (45 or 70 °C) and Cd(II) concentration (C) (1 or 3 mg/L) were considered. Batch mode system was employed with 0.05 g of the sorbent and 25 mL of Cd(II) solution. The efficiency of cadmium removal during an exposition time of 4h was then evaluated. The factors and their interaction effect on the cadmium removal efficiency followed the order: Cd(II) concentration > solution pH > interaction between solution pH and Cd(II) concentration>interaction between solution pH, temperature and Cd(II) concentration. Langmuir isotherm model was the best isotherm model. The Pseudo second order fitted well the kinetic data. The thermodynamic studies revealed the nature of the cadmium sorption.

The Preparation and Characterization of Carboxymethyl Chitosan Wound Dressings

In order to improve the absorption properties of chitosan wound dressings, this paper used chloro-acetic acid to convert chitosan fibers into partially carboxymethylated chitosan fibers. Fibers with various degrees of carboxymethylation were prepared by controlling the ratio between the weight of fiber and chloro-acetic acid. Results showed that the carboxymethylated chitosan fibers can absorb a large amount of liquid into the fiber structure. When the degree of carboxymethylation is below 50%, the carboxymethylated chitosan fibers can absorb a large amount of liquid whilst maintaining its fibrous struture at the same time.