Biomedical exploitation of chitin and chitosan via mechano-chemical disassembly, electrospinning, dissolution in imidazolium ionic liquids, and supercritical drying

Prevention of skin lesions caused by the use of protective face masks by an innovative gelatin-based hydrogel patch: design and in vitro studies

The recent Covid-19 pandemics led to the increased use of facial masks, which can cause skin lesions due to continuous pressure, tension and friction forces on the skin. A preventive approach is the inclusion of dressings between the face and the mask. However, there are still uncertainties about the protective effect of dressings and whether their use compromises the efficiency of masks. The current study aimed to develop and test the efficacy of a gelatin-based hydrogel patch to be placed between the mask and the facial area. Design of Experiment with a Quality by Design approach tools were used in the patch development and in vitro characterization was performed through rheological evaluation, ATR-FTIR and molecular docking studies. Furthermore, tribology studies were performed to test the patch performance. The results showed that the addition of excipients enhanced gelation temperature, elasticity and adhesiveness parameters. The interactions between excipients were confirmed by ATR-FTIR and molecular docking. The tribology assay revealed similar friction values at room and physiological temperature, and when testing different skin types. In conclusion, the physical properties and the performance evaluation reported in this study indicate that this innovative film-forming system can be used to prevent skin lesions caused by the continuous use of protective masks.

Preparation, characterization and properties of three different nanomaterials either alone or loaded with nystatin or fluconazole antifungals

Engineered nanoparticles have enabled the development of novel uses, particularly in disease management. In this investigation, we synthesized and studied three distinct nanomaterials: solid lipid nanoparticles (SLNPs), chitosan nanoparticles (CSNPs), and carbon nanotubes (CNTs), either alone or loaded with two antifungals, nystatin, and fluconazole. The purpose of this study is to investigate the different properties of the produced nanomaterials, either alone or in combination with antifungals. Drug release studies revealed that about 55% from SLNPs, 43% from CSNPs and 97% from CNTs of nystatin drug were released at the longest time point assessed (12 h). In addition, about 89% from SLNPs, 84% from CSNPs and 81% from CNTs of fluconazole drug were released at the longest time point assessed (12 h). This research will expand the understanding of nanomaterials as a viable technique for the management of different fungal diseases that harm several agricultural crops.

pH-Sensitive Drug Delivery System Based on Chitin Nanowhiskers-Sodium Alginate Polyelectrolyte Complex

Polyelectrolyte complexes (PECs), based on partially deacetylated chitin nanowhiskers (CNWs) and anionic polysaccharides, are characterized by their variability of properties (particle size, ζ-potential, and pH-sensitivity) depending on the preparation conditions, thereby allowing the development of polymeric nanoplatforms with a sustained release profile for active pharmaceutical substances. This study is focused on the development of hydrogels based on PECs of CNWs and sodium alginate (ALG) for potential vaginal administration that provide controlled pH-dependent antibiotic release in an acidic vaginal environment, as well as prolonged pharmacological action due to both the sustained drug release profile and the mucoadhesive properties of the polysaccharides. The desired hydrogels were formed as a result of both electrostatic interactions between CNWs and ALG (PEC formation), and the subsequent molecular entanglement of ALG chains, and the formation of additional hydrogen bonds. Metronidazole (MET) delivery systems with the desired properties were obtained at pH 5.5 and an CNW:ALG ratio of 1:2. The MET-CNW-ALG microparticles in the hydrogel composition had an apparent hydrodynamic diameter of approximately 1.7 µm and a ζ-potential of -43 mV. In vitro release studies showed a prolonged pH-sensitive drug release from the designed hydrogels; 37 and 67% of MET were released within 24 h at pH 7.4 and pH 4.5, respectively. The introduction of CNWs into the MET-ALG system not only prolonged the drug release, but also increased the mucoadhesive properties by about 1.3 times. Thus, novel CNW-ALG hydrogels are promising carriers for pH sensitive drug delivery carriers.

Fabrication of highly flexible nanochitin film and its composite film with anionic polysaccharide

This study investigated the fabrication of a nanochitin film via the aggregation of scaled-down chitin nanofibers (SD-ChNFs). A self-assembled ChNF film, which was prepared by regeneration from a chitin/ionic liquid ion gel using methanol, followed by filtration, was treated with aqueous NaOH for deacetylation and subsequently disintegrated by cationization and electrostatic repulsion in 1.0 mol/L aqueous acetic acid with ultrasonication to give a SD-ChNF dispersion. Isolation of the SD-ChNFs via filtration of the dispersion resulted in a highly flexible self-assembled ChNF film that bent and twisted easily. The film exhibited superior mechanical properties compared to the parent self-assembled ChNF film, where the flexibility was further enhanced by the compositing the SD-ChNFs with an anionic polysaccharide, namely ι-carrageenan, via multi-point ionic cross-linking. These enhanced mechanical properties and efficient compositing properties were attributed to the scaling down of the ChNFs.

Preparation of Composite Materials from Self-Assembled Chitin Nanofibers

Although chitin is a representative abundant polysaccharide, it is mostly unutilized as a material source because of its poor solubility and processability. Certain specific properties, such as biodegradability, biocompatibility, and renewability, make nanofibrillation an efficient approach for providing chitin-based functional nanomaterials. The composition of nanochitins with other polymeric components has been efficiently conducted at the nanoscale to fabricate nanostructured composite materials. Disentanglement of chitin microfibrils in natural sources upon the top-down approach and regeneration from the chitin solutions/gels with appropriate media, such as hexafluoro-2-propanol, LiCl/N, N-dimethylacetamide, and ionic liquids, have, according to the self-assembling bottom-up process, been representatively conducted to fabricate nanochitins. Compared with the former approach, the latter one has emerged only in the last one-and-a-half decade. This short review article presents the preparation of composite materials from the self-assembled chitin nanofibers combined with other polymeric substrates through regenerative processes based on the bottom-up approach.

Chitosan-Based Anti-Oxidation Delivery Nano-Platform: Applications in the Encapsulation of DHA-Enriched Fish Oil

Refined cobia liver oil is a nutritional supplement (CBLO) that is rich in polyunsaturated fatty acids (PUFAs), such as DHA and EPA; however, PUFAs are prone to oxidation. In this study, the fabrication of chitosan-TPP-encapsulated CBLO nanoparticles (CS@CBLO NPs) was achieved by a two-step method, including emulsification and the ionic gelation of chitosan with sodium tripolyphosphate (TPP). The obtained nanoparticles were inspected by dynamic light scattering (DLS) and showed a positively charged surface with a z-average diameter of between 174 and 456 nm. Thermogravimetric analysis (TGA) results showed the three-stage weight loss trends contributing to the water evaporation, chitosan decomposition, and CBLO decomposition. The loading capacity (LC) and encapsulation efficiency (EE) of the CBLO loading in CS@CBLO NPs were 17.77-33.43% and 25.93-50.27%, respectively. The successful encapsulation of CBLO in CS@CBLO NPs was also confirmed by the Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) techniques. The oxidative stability of CBLO and CS@CBLO NPs was monitored by FTIR. As compared to CBLO, CS@CBLO NPs showed less oxidation with a lower generation of hydroperoxides and secondary oxidation products after four weeks of storage. CS@CBLO NPs are composed of two ingredients that are beneficial for health, chitosan and fish oil in a nano powdered fish oil form, with an excellent oxidative stability that will enhance its usage in the functional food and pharmaceutical industries.

Green Synthesized Chitosan/Chitosan Nanoforms/Nanocomposites for Drug Delivery Applications

Chitosan has become a highlighted polymer, gaining paramount importance and research attention. The fact that this valuable polymer can be extracted from food industry-generated shell waste gives it immense value. Chitosan, owing to its biological and physicochemical properties, has become an attractive option for biomedical applications. This review briefly runs through the various methods involved in the preparation of chitosan and chitosan nanoforms. For the first time, we consolidate the available scattered reports on the various attempts towards greens synthesis of chitosan, chitosan nanomaterials, and chitosan nanocomposites. The drug delivery applications of chitosan and its nanoforms have been reviewed. This review points to the lack of systematic research in the area of green synthesis of chitosan. Researchers have been concentrating more on recovering chitosan from marine shell waste through chemical and synthetic processes that generate toxic wastes, rather than working on eco-friendly green processes-this is projected in this review. This review draws the attention of researchers to turn to novel and innovative green processes. More so, there are scarce reports on the application of green synthesized chitosan nanoforms and nanocomposites towards drug delivery applications. This is another area that deserves research focus. These have been speculated and highlighted as future perspectives in this review.

Current Film Coating Designs for Colon-Targeted Oral Delivery

Colon-targeted oral delivery has recently attracted a substantial number of studies on both systemic and local treatments. Among approaches for colonic delivery, film coatings have been demonstrated as effective elements of the drug delivery systems because they can integrate multiple release strategies, such as pH-controlled release, time-controlled release and enzyme-triggered release. Moreover, coating layer modulations, natural film materials and nanoparticle coatings have been vigorously investigated with promising applications. This review aims to describe the primary approaches for improving drug delivery to the colon in the last decade. The outstanding importance of current developments in film coatings will advance dosage form designs and lead to the development of efficient colon-targeted oral delivery systems.

A review on the applications of electrospun chitosan nanofibers for the cancer treatment

In recent years, the incidence of cancer is increasing every day due to poor quality of life (industrialization of life). Therefore, the treatment of cancer has received much attention from therapists. So far, many anticancer drugs have been used to treat cancer patents. However, the direct use of the anticancer drugs has the adverse side effects for patents and several limitations to treat process. Natural chitosan nanofibers prepared by electrospinning method have unique properties such as high surface area, high porosity, suitable mechanical properties, nontoxicity, biocompatibility, biodegradability, biorenewable, low immunogenicity, better clinical functionality, analogue to extracellular model, and easy production in large scale. Therefore, this bio-polymer is a very suitable case to deliver of the anti-cancer drugs to treat cancer patents. In this review summarizes the electrospinning synthesis of chitosan and its therapeutic application for the various cancer treatment.

Chitin nanocrystals based complex fluids: A green nanotechnology

Chitin biopolymer has received significant attention recently by many industries as a green technology. Nanotechnology has been used to make chitin nanocrystals (ChiNCs) that are rod-shaped natural nanomaterials with nanoscale size. Owing to the unique features such as biodegradability, biocompatibility, renewability, rod-shape, and excellent surface and interfacial, physiochemical, and thermo-mechanical properties; ChiNCs have been green and attractive products with wide applications specifically in medical and pharmaceutical, food and packaging, cosmetic, electrical, and electronic, and also in the oil and gas industry. This review aims to give a comprehensive and applied insight into ChiNCs technology. It starts with reviewing different sources of chitin and their extraction methods followed by the characterization of ChiNCs. Furthermore, a detailed investigation into various complex fluids (dispersions, emulsions, foams, and gels) stabilized by ChiNCs and their characterisation have been thoroughly deliberated. Finally, the current status including ground-breaking applications, untapped investigations, and future prospective have been presented.

Cytocompatibility of Bilayer Scaffolds Electrospun from Chitosan/Alginate-Chitin Nanowhiskers

In this work, a bilayer chitosan/sodium alginate scaffold was prepared via a needleless electrospinning technique. The layer of sodium alginate was electrospun over the layer of chitosan. The introduction of partially deacetylated chitin nanowhiskers (CNW) stabilized the electrospinning and increased the spinnability of the sodium alginate solution. A CNW concentration of 7.5% provided optimal solution viscosity and structurization due to electrostatic interactions and the formation of a polyelectrolyte complex. This allowed electrospinning of defectless alginate nanofibers with an average diameter of 200-300 nm. The overall porosity of the bilayer scaffold was slightly lower than that of a chitosan monolayer, while the average pore size of up to 2 μm was larger for the bilayer scaffold. This high porosity promoted mesenchymal stem cell proliferation. The cells formed spherical colonies on the chitosan nanofibers, but formed flatter colonies and monolayers on alginate nanofibers. The fabricated chitosan/sodium alginate bilayer material was deemed promising for tissue engineering applications.

Chitin and its derivatives: Structural properties and biomedical applications

Chitin, a polysaccharide that occurs abundantly in nature after cellulose, has attracted the interest of the scientific community due to its plenty of availability and low cost. Mostly, it is derived from the exoskeleton of insects and marine crustaceans. Often, it is insoluble in common solvents that limit its applications but its deacetylated product, named chitosan is found to be soluble in protonated aqueous medium and used widely in various biomedical fields. Indeed, the existence of the primary amino group on the backbone of chitosan provides it an important feature to modify it chemically into other derivatives easily. In the present review, we present the structural properties of chitin, and its derivatives and highlighted their biomedical implications including, tissue engineering, drug delivery, diagnosis, molecular imaging, antimicrobial activity, and wound healing. We further discussed the limitations and prospects of this versatile natural polysaccharide.

Chitosan Grafted with Biobased 5-Hydroxymethyl-Furfural as Adsorbent for Copper and Cadmium Ions Removal

This work investigates the application of 5-hydroxymethyl-furfural (HMF) as a grafting agent to chitosan (CS). The material produced was further modified by cross-linking. Three different derivatives were tested with molecular ratios CS/HMF of 1:1 (CS-HMF1), 2:1 (CS-HMF2) and 10:1 mol/mol (CS-HMF3)) to remove Cu²⁺ and Cd²⁺ from aqueous solutions. CS-HMF derivatives were characterized both before, and after, metal ions adsorption by using scanning electron microscopy (SEM), as well as Fourier-transform infrared (FTIR) spectroscopy thermogravimetric analysis (TGA), and X-Ray diffraction analysis (XRD). The CS-HMF derivatives were tested at pH = 5 and showed higher adsorption capacity with the increase of temperature. Also, the equilibrium data were fitted to Langmuir (best fitting) and Freundlich model, while the kinetic data to pseudo-first (best fitting) and pseudo-second order equations. The Langmuir model fitted better (higher R²) the equilibrium data than the Freundlich equation. By increasing the HMF grafting from 130% (CS-HMF1) to 310% (CS-HMF3), an increase of 24% (26 m/g) was observed for Cu²⁺ adsorption and 19% (20 mg/g) for Cd²⁺. By increasing from T = 25 to 65 °C, an increase of the adsorption capacity (metal uptake) was observed. Ten reuse cycles were successfully carried out without significant loss of adsorption ability. The reuse potential was higher of Cd²⁺, but more stable desorption reuse ability during all cycles for Cu²⁺.

3D Chitin Scaffolds of Marine Demosponge Origin for Biomimetic Mollusk Hemolymph-Associated Biomineralization Ex-Vivo

Structure-based tissue engineering requires large-scale 3D cell/tissue manufacture technologies, to produce biologically active scaffolds. Special attention is currently paid to naturally pre-designed scaffolds found in skeletons of marine sponges, which represent a renewable resource of biomaterials. Here, an innovative approach to the production of mineralized scaffolds of natural origin is proposed. For the first time, a method to obtain calcium carbonate deposition ex vivo, using living mollusks hemolymph and a marine-sponge-derived template, is specifically described. For this purpose, the marine sponge Aplysin aarcheri and the terrestrial snail Cornu aspersum were selected as appropriate 3D chitinous scaffold and as hemolymph donor, respectively. The formation of calcium-based phase on the surface of chitinous matrix after its immersion into hemolymph was confirmed by Alizarin Red staining. A direct role of mollusks hemocytes is proposed in the creation of fine-tuned microenvironment necessary for calcification ex vivo. The X-ray diffraction pattern of the sample showed a high CaCO3 amorphous content. Raman spectroscopy evidenced also a crystalline component, with spectra corresponding to biogenic calcite. This study resulted in the development of a new biomimetic product based on ex vivo synthetized ACC and calcite tightly bound to the surface of 3D sponge chitin structure.

Modified Chitosan for Silver Recovery-Kinetics, Thermodynamic, and Equilibrium Studies

The aim of this study is to investigate the silver recovery from aqueous solutions. There are a variety of recovery methods, such as hydrometallurgical, bio-metallurgical, cementation, reduction, electrocoagulation, electrodialysis, ion exchange, etc. Adsorption represents a convenient, environment friendly procedure, that can be used to recover silver from aqueous solutions. In this paper we highlight the silver adsorption mechanism on chitosan chemically modified with active groups, through kinetic, thermodynamic, and equilibrium studies. A maximum adsorption capacity of 103.6 mg Ag(I)/g of adsorbent for an initial concentration of 700 mg/L was noticed by using modified chitosan. Lower adsorption capacity has been noticed in unmodified chitosan—a maximum of 75.43 mg Ag(I)/g. Optimum contact time was 120 min and the process had a maximum efficiency when conducted at pH higher than 6. At the same time, a way is presented to obtain metallic silver from the adsorbent materials used for the recovery of the silver from aqueous solutions.

Extraction and characterization of chitin from sea snail Conus inscriptus (Reeve, 1843)

The chitin was extracted from C. inscriptus and the structure was elucidated. The yield of the C. inscriptus shell chitin was 21.65% on dry weight basis. The ash and moisture content of the chitin was 1.2 and 6.50%. The result of the molecular analysis of the chitin revealed low molecular weight (25 kDa). The crystalline structure (XRD), functional group (FT-IR), elemental analysis (EDAX), surface morphology (SEM) and thermal stability (TG/DTA) results confirmed conus chitin was in α-crystalline form. The crystalline index value (CrI) of the conus chitin was 82.13%. The FT-IR analysis of the conus chitin displayed two bands at around 1730 and 1628 cm^-1. SEM investigation of the commercial chitin and C. inscriptus chitin exposed that it was composed of nanopore and nanofibre structures. Further, the thermal stability of the conus chitin was close to the thermal stability of the commercial chitin. The results show that processing of C. inscriptus shell can lead to a high quality chitin, useful for a broad range of applications.

Synthesis of Novel Chitin Derivatives Bearing Amino Groups and Evaluation of Their Antifungal Activity

Chemical modification is one of the most effective methods to improve the biological activity of chitin. In the current study, we modified C3-OH and C6-OH of chitin (CT) and successfully synthesized 6-amino-chitin (NCT) and 3,6-diamino-chitin (DNCT) through a series of chemical reactions. The structure of NCT and DNCT were characterized by elemental analyses, FT-IR, 13C NMR, XRD, and SEM. The inhibitory effects of CT, NCT, and DNCT against six kinds of phytopathogen (F. oxysporum f. sp. cucumerium, B. cinerea, C. lagenarium, P. asparagi, F. oxysporum f. niveum, and G. zeae) were evaluated using disk diffusion method in vitro. Meanwhile, carbendazim and amphotericin B were used as positive controls. Results revealed that 6-amino-chitin (NCT) and 3,6-diamino-chitin (DNCT) showed improved antifungal properties compared with pristine chitin. Moreover, DNCT exhibited the better antifungal property than NCT. Especially, while the inhibition zone diameters of NCT are ranged from 11.2 to 16.3 mm, DNCT are about 11.4⁻20.4 mm. These data demonstrated that the introduction of amino group into chitin derivatives could be key to increasing the antifungal activity of such compounds, and the greater the number of amino groups in the chitin derivatives, the better their antifungal activity was.

Biopolymer nanofibrils: structure, modeling, preparation, and applications

Biopolymer nanofibrils exhibit exceptional mechanical properties with a unique combination of strength and toughness, while also presenting biological functions that interact with the surrounding environment. These features of biopolymer nanofibrils profit from their hierarchical structures that spun angstrom to hundreds of nanometer scales. To maintain these unique structural features and to directly utilize these natural supramolecular assemblies, a variety of new methods have been developed to produce biopolymer nanofibrils. In particular, cellulose nanofibrils (CNFs), chitin nanofibrils (ChNFs), silk nanofibrils (SNFs) and collagen nanofibrils (CoNFs), as the four most abundant biopolymer nanofibrils on earth, have been the focus of research in recent years due to their renewable features, wide availability, low-cost, biocompatibility, and biodegradability. A series of top-down and bottom-up strategies have been accessed to exfoliate and regenerate these nanofibrils for versatile advanced applications. In this review, we first summarize the structures of biopolymer nanofibrils in nature and outline their related computational models with the aim of disclosing fundamental structure-property relationships in biological materials. Then, we discuss the underlying methods used for the preparation of CNFs, ChNFs, SNF and CoNFs, and discuss emerging applications for these biopolymer nanofibrils.

Electrospinning of Chitosan-Based Solutions for Tissue Engineering and Regenerative Medicine

Electrospinning has been used for decades to generate nano-fibres via an electrically charged jet of polymer solution. This process is established on a spinning technique, using electrostatic forces to produce fine fibres from polymer solutions. Amongst, the electrospinning of available biopolymers (silk, cellulose, collagen, gelatine and hyaluronic acid), chitosan (CH) has shown a favourable outcome for tissue regeneration applications. The aim of the current review is to assess the current literature about electrospinning chitosan and its composite formulations for creating fibres in combination with other natural polymers to be employed in tissue engineering. In addition, various polymers blended with chitosan for electrospinning have been discussed in terms of their potential biomedical applications. The review shows that evidence exists in support of the favourable properties and biocompatibility of chitosan electrospun composite biomaterials for a range of applications. However, further research and in vivo studies are required to translate these materials from the laboratory to clinical applications.

Aerogels from Chitosan Solutions in Ionic Liquids

Chitosan aerogels conjugates the characteristics of nanostructured porous materials, i.e., extended specific surface area and nano scale porosity, with the remarkable functional properties of chitosan. Aerogels were obtained from solutions of chitosan in ionic liquids (ILs), 1-butyl-3-methylimidazolium acetate (BMIMAc), and 1-ethyl-3-methyl-imidazolium acetate (EMIMAc), in order to observe the effect of the solvent in the structural characteristics of this type of materials. The process of elaboration of aerogels comprised the formation of physical gels through anti-solvent vapor diffusion, liquid phase exchange, and supercritical CO₂ drying. The aerogels maintained the chemical identity of chitosan according to Fourier transform infrared spectrophotometer (FT-IR) spectroscopy, indicating the presence of their characteristic functional groups. The internal structure of the obtained aerogels appears as porous aggregated networks in microscopy images. The obtained materials have specific surface areas over 350 m²/g and can be considered mesoporous. According to swelling experiments, the chitosan aerogels could absorb between three and six times their weight of water. However, the swelling and diffusion coefficient decreased at higher temperatures. The structural characteristics of chitosan aerogels that are obtained from ionic liquids are distinctive and could be related to solvation dynamic at the initial state.

Ulvan-chitosan polyelectrolyte complexes as matrices for enzyme induced biomimetic mineralization

Polyelectrolyte complexes (PEC) of chitosan and ulvan were fabricated to study alkaline phosphatase (ALP) mediated formation of apatitic minerals. Scaffolds of the PEC were subjected to ALP and successful mineral formation was studied using SEM, Raman and XRD techniques. Investigation of the morphology via SEM shows globular structures of the deposited minerals, which promoted cell attachment, proliferation and extracellular matrix formation. The PEC and their successful calcium phosphate based mineralization offers a greener route of scaffold fabrication towards developing resorbable materials for tissue engineering.

On chemistry of γ-chitin

The biological material, chitin, is present in nature in three allomorphic forms: α, β and γ. Whereas most studies have dealt with α- and β-chitin, only few investigations have focused on γ-chitin, whose structural and physicochemical properties have not been well delineated. In this study, chitin obtained for the first time from the cocoon of the moth (Orgyia dubia) was subjected to extensive physicochemical analyses and examined, in parallel, with α-chitin from exoskeleton of a freshwater crab and β-chitin from cuttlebone of the common cuttlefish. Our results, which are supported by¹³C CP-MAS NMR, XRD, FT-IR, Raman spectroscopy, TGA, DSC, SEM, AFM, chitinase digestive test and elemental analysis, verify the authenticity of γ-chitin. Further, quantum chemical calculations were conducted on all three allomorphic forms, and, together with our physicochemical analyses, demonstrate that γ-chitin is distinct, yet closer in structure to α-chitin than β-chitin.

Photoactive Hybrid Catalysts Based on Natural and Synthetic Polymers: A Comparative Overview

In the present review, we would like to draw the reader's attention to the polymer-based hybrid materials used in photocatalytic processes for efficient degradation of organic pollutants in water. These inorganic-organic materials exhibit unique physicochemical properties due to the synergistic effect originating from the combination of individual elements, i.e., photosensitive metal oxides and polymeric supports. The possibility of merging the structural elements of hybrid materials allows for improving photocatalytic performance through (1) an increase in the light-harvesting ability; (2) a reduction in charge carrier recombination; and (3) prolongation of the photoelectron lifetime. Additionally, the great majority of polymer materials exhibit a high level of resistance against ultraviolet irradiation and improved corrosion resistance. Taking into account that the chemical and environmental stability of the hybrid catalyst depends, to a great extent, on the functional support, we highlight benefits and drawbacks of natural and synthetic polymer-based photocatalytic materials and pay special attention to the fact that the accessibility of synthetic polymeric materials derived from petroleum may be impeded due to decreasing amounts of crude oil. Thus, it is necessary to look for cheap and easily available raw materials like natural polymers that come from, for instance, lignocellulosic wastes or crustacean residues to meet the demand of the "plastic" market.

An Experimental and Molecular Dynamics Study of Red Fluorescent Protein mCherry in Novel Aqueous Amino Acid Ionic Liquids

The search for biocompatible ionic liquids (ILs) with novel biochemical and biomedical applications has recently gained greater attention. In this report, we characterize the effects of two novel amino acid-based aqueous ILs composed of tetramethylguanidinium (TMG) and amino acids on the structure and stability of a widely used red fluorescent protein (mCherry). Our experimental data shows that while the aspartic acid-based IL (TMGAsp) has effects similar to previously studied conventional ILs (BMIBF4, EMIAc, and TMGAc), the alanine-based IL (TMGAla) has a much stronger destabilization effect on the protein structure. Addition of 0.30 M TMGAla to mCherry decreases the unfolding temperature from 83 to 60 °C. Even at 25 °C, TMGAla results in a blue shift of the mCherry absorbance and fluorescence peaks and an increased Stokes shift. Molecular dynamics simulations show that the chromophore conformation and its interaction with mCherry with TMGAla are changed relative to those with TMGAsp or in the absence of ILs. Protein-ILs contact analysis indicates that the mCherry-Asp interactions are hydrophilic but the (fewer) mCherry-Ala interactions are more hydrophobic and may modulate the TMG interaction with the protein. Hence, the anion hydrophobicity may explain the special TMGAla destabilization of mCherry.

Effect of the electrical conductivity of core solutions on the morphology and structure of core–shell CA-PCL/CS nanofibers

CA-PCL/CS nanofibers with controllable core to shell ratios were prepared by altering the electrical conductivities of core solutions.

Dopamine Modified Organic-Inorganic Hybrid Coating for Antimicrobial and Osteogenesis

A hybrid coating composed of hydroxyapatite (HA), Ag nanoparticles (NPs), and chitosan (CS) was successfully prepared on a Ti substrate by a layer-by-layer assembly process. A polydopamine-assisted (PDA-assisted) coating showed a good bond with HA. Ag NPs were uniformly distributed into the hybrid coating through a solution method and ultraviolet light reduction. A CS nanofilm was deposited via spin-coating to control the release of Ag⁺ from the hybrid coating. The results disclosed that the 3-layer CS coating could efficiently control the release of Ag⁺ from the hybrid coating via the Fickian diffusion mechanism and that the PDA/HA/Ag/CS-1 coating exhibited antibacterial ratios of 63.0% and 51.8% against E. coli and S. aureus, respectively. Furthermore, the normal structure of E. coli was obviously destroyed by two types of Ag doped coatings. The cell viability assay showed that CS effectively reduced the cytotoxicity of the hybrid coating after a 7 day incubation. The hybrid coating presented high ALP activities at days 3 and 14. The results reveal that hybrid coatings can endow Ti implants with good antibacterial capability as well as cell viability and osteogenic activity.