Amorphous Chitosan Research Articles

Organized assembly of chitosan into mechanically strong bio-composite by introducing a recombinant insect structural protein OfCPH-1

Chitosan, known for its appealing biological properties in packaging and biomedical applications, faces challenges in achieving a well-organized crystalline structure for mechanical excellence under mild conditions. Herein, we propose a facile and mild bioengineering approach to induce organized assembly of amorphous chitosan into mechanically strong bio-composite via incorporating a genetically engineered insect structural protein, the cuticular protein hypothetical-1 from the Ostrinia furnacalis (OfCPH-1). OfCPH-1 exhibits high binding affinity to chitosan via hydrogen-bonding interactions. Simply mixing a small proportion (0.5 w/w%) of bioengineered OfCPH-1 protein with acidic chitosan precursor induces the amorphous chitosan chains to form fibrous networks with hydrated chitosan crystals, accompanied with a solution-to-gel transition. We deduce that the water shell destruction driven by strong protein-chitosan interactions, triggers the formation of well-organized crystalline chitosan, which therefore offers the chitosan with significantly enhanced swelling resistance, and strength and modulus that outperforms that of most reported chitosan-based materials as well as petroleum-based plastics. Moreover, the composite exhibits a stretch-strengthening behavior similar to the training living muscles on cyclic load. Our work provides a route for harnessing the OfCPH-1-chitosan interaction in order to form a high-performance, sustainably sourced bio-composite.

Mechanical Amorphization of Chitosan with Different Molecular Weights.

Mechanical amorphization of three chitosan samples with high, medium, and low molecular weight was studied. It is shown that there are no significant differences between the course of amorphization process in a planetary ball mill of chitosan with different molecular weights, and the maximum degree of amorphization was achieved in 600 s of high intensity mechanical action. Specific energy consumption was 28 kJ/g, being comparable to power consumption for amorphization of cellulose determined previously (29 kJ/g) and 5–7-fold higher than that for amorphization of starch (4–6 kJ/g). Different techniques for determining the crystallinity index (CrI) of chitosan (analysis of the X-ray diffraction (XRD) data, the peak height method, the amorphous standard method, peak deconvolution, and full-profile Rietveld analysis) were compared. The peak height method is characterized by a broader working range but provides deviated CrI values. The peak deconvolution method (with the amorphous Voigt function) makes it possible to calculate the crystallinity index of chitosan with greater accuracy, but the analysis becomes more difficult with samples subjected to mechanical processing. In order to refine the structure and calculation of CrI by the Rietveld method, an attempt to optimize the structure file by the density functional theory (DFT) method was performed. The averaged profile of amorphous chitosan approximated by an eighth-order Fourier model improved the correctness of the description of the amorphous contribution for XRD data processing. The proposed equation may be used as a universal standard model of amorphous chitosan to determine the crystallinity index both for the amorphous standard method and for peak deconvolution of XRD patterns for arbitrary chitosan samples.

A novel antibacterial and biocompatible wound cover made of gelatin/chitosan with silver nanoparticles of green synthesis

A dressing material based on the combination of gelatine, chitosan and silver nanoparticles with a suitable proportion has been developed and can be successfully applied in biomedical fields. The new gelatin/chitosan membranes were prepared using the chitosan suspension mixed with gelatin and silver nanoparticles (AgNPs), resulting in a biocompatible and antibacterial product. AgNPs were obtained by the reduction of silver nitrate with chitosan solution and added to chitosan/gelatin (GCs) blend solutions to obtain membranes by the casting method. Thus, membranes with three different AgNPs concentrations were produced: 30 mM, 20 mM and 10 mM AgNPs. To evaluate the characteristics of the membranes, physicochemical and morphological tests were carried out, such as infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission (TEM), and in vitro cytotoxicity and bacterial assays. The formation of AgNPs was confirmed by Visible Ultraviolet to Ultraviolet to Visible (UV–vis) and TEM, where the nanoparticles were observed by the formation of the peak spectrum at a wavelength at 560 nm. According to the TEM images, polymorphic nanoparticles with an average size of 30 nm were obtained. Furthermore, the results of scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) indicated the presence of silver evenly distributed within the membranes. The results obtained by (FTIR) showed spectral peaks characteristic of the membrane materials, that is, typical spectra of gelatin, chitosan and silver. These results could be explained by addition of free −OH, −NH2 and −NHOCOCH3 groups of the amorphous chitosan in the blends and a network structure through electrostatic interactions between the ammonium ions (−NH3+) of the chitosan and the carboxylate ions (−COO−) of the gelatin. The concentrations of AgNPs 30 mM and 20 mM in the membranes attributed to them a high hydration rate and high water vapor permeability (WVP). Membranes with 30 mM AgNPs showed bacterial effect against Staphylococcus aureus and Pseudomonas aeruginosa, concentrations of 20 mM AgNPs and 10 mM AgNPs, bacteriostatic effect against Staphylococcus aureus and bacterial effect against Pseudomonas aeruginosa. In the results of the in vitro assays, 10 mM AgNPs membranes were not cytotoxic. With the results obtained, GC membranes with up to 10 mM AgNPs are candidates for use in the fields of biomaterials and biomedicine.

Surfactant-free amorphous solid dispersion with high dissolution for bioavailability enhancement of hydrophobic drugs: a case of quercetin

At present, saccharides as hydrophilic matrixes, have been gradually used in amorphous solid dispersions (ASD) for dispersing poorly water-soluble drugs without surfactants. In this study, an amorphous chitosan oligosaccharide (COS) was applied as a water-soluble matrix to form surfactant-free ASD via the ball milling to vitrify quercetin (QUE) and enhance the dissolution and bioavailability. Solid-state characterization (DSC, XRPD, FTIR, SEM and PLM) and physical stability assessments verified that the prepared ASDs showed excellent physical stability with complete amorphization due to potential interactions between QUE and COS. In vitro sink dissolution tests suggested all QUE-COS ASDs (w:w, 1:1, 1:2 and 1:4) significantly enhanced the dissolution rate of QUE. Meanwhile, in vitro non-sink dissolution exhibited that the maximum supersaturated concentration ranged from 112.62 to 138.00 µg/mL for all QUE-COS ASDs, which was much higher than that of pure QUE. Besides, the supersaturation of QUE-COS ASD kept for at least 24 h. In rat pharmacokinetics, the oral bioavailability of QUE-COS ASDs showed 1.64 ∼ 2.25 times increase compared to the pure QUE (p < .01). Hence, the present study confirms the amorphous COS could be applied as a promising hydrophilic matrix in QUE-COS ASDs for enhancing dissolution performance and bioavailability of QUE.

Glycine-Chitosan-Based Flexible Biodegradable Piezoelectric Pressure Sensor.

This paper presents flexible pressure sensors based on free-standing and biodegradable glycine–chitosan piezoelectric films. Fabricated by the self-assembly of biological molecules of glycine within a water-based chitosan solution, the piezoelectric films consist of a stable spherulite structure of β-glycine (size varying from a few millimeters to 1 cm) embedded in an amorphous chitosan polymer. The polymorphic phase of glycine crystals in chitosan, evaluated by X-ray diffraction, confirms formation of a pure ferroelectric phase of glycine (β-phase). Our results show that a simple solvent-casting method can be used to prepare a biodegradable β-glycine/chitosan-based piezoelectric film with sensitivity (∼2.82 ± 0.2 mV kPa–1) comparable to those of nondegradable commercial piezoelectric materials. The measured capacitance of the β-glycine/chitosan film is in the range from 0.26 to 0.12 nF at a frequency range from 100 Hz to 1 MHz, and its dielectric constant and loss factor are 7.7 and 0.18, respectively, in the high impedance range under ambient conditions. The results suggest that the glycine–chitosan composite is a promising new biobased piezoelectric material for biodegradable sensors for applications in wearable biomedical diagnostics.

A novel hydrochloride-free chitosan oligosaccharide production method to improve taste

Chitosan oligosaccharide hydrochloride (COS-HCl) has an unpleasant taste. To improve this taste, we used an enzymatic hydrolysis with chitosan to manufacture hydrochloride-free chitosan oligosaccharide (HFCOS). We found that HFCOS powder with weight-average molecular weight (Mw) of approximately 1000 and a high degree of deacetylation can be obtained from amorphous chitosan in carbonated water by enzymatic hydrolysis because amorphous chitosan slightly dissolves in carbonated water. HFCOS was stable enough to be atomized by spray-drying. However, HFCOS yield was quite low (15.7%). There were few chloride ions in HFCOS (0.1% ± 0.1%), in contrast to the number of chloride ions in COS-HCl (16.6% ± 0.6%) with statistical significance (p < 0.01). The molar ratio of anion/amino group of HFCOS was only 0.05. Therefore, it appeared that the amino groups of HFCOS were mostly free bases. In sensory evaluations, 5% w/w HFCOS was significantly sweeter than 5% w/w COS-HCl (p < 0.01); saltiness, acidity, bitterness were significantly weak (p < 0.01); and aftertaste and overall taste were significantly improved (p < 0.01). These results suggest that HFCOS can be obtained by a novel method of enzymatically hydrolyzing amorphous chitosan dissolved in carbonated water and this is one way to improve its taste.

Osteoblast studied on gelatin based biomaterials in rabbit Bone Bioengineering.

The bone-derived-osteoblast seeded biomaterials scaffold in tissue engineering, have displayed prominence in the treatment of the osseous medical condition. In vitro osteogenesis of rabbit osteoblast cell (rOb) from bone tissue (rT) and MSC-derived rOb from bone marrow (rM) on Gelatin-Hydroxyapatite (HG) based biomaterials was investigated. In this work, lyophilized biomaterial was prepared by the addition of amorphous chitosan ('C') to 'H' dispersed in 'G' matrix, to find its role in biomaterials biocompatibility. Isolated rOb seeded biomaterials were studied using CLSM and flow cytometry for proliferation potential. The biomaterial's core and surface morphology was studied from SEM-EDX and AFM respectively. Upon co-culture with HCG, rT over rM showed rabbit bone extracellular matrix (ECM) mimicking properties both in in vitro studies and biomaterials micro architecture. The in vitro metabolic behaviour was studied by Alamar Blue (AB) assay, DNA content using Hoechst 33258, potency via the activity of Alkaline Phosphatase (ALP), Calcium's relative content by Alizarin Red S (ARS) assay. A novel combination of biomaterials-cell interaction was observed when rT was co-cultured with HCG and proved effective in osteogenesis with regard to Bone Bioengineering.

Surfactant-free solid dispersion of BCS class IV drug in an amorphous chitosan oligosaccharide matrix for concomitant dissolution in vitro - permeability increase

Saccharides have been applied as a water-soluble matrix for dispersing hydrophobic drugs homogeneously without the need to use surfactants in amorphous solid dispersions (ASD). Up to now, concomitant permeability improvement of BCS Class IV drug by such matrices have not been much appreciated. Herein, an amorphous chitosan oligosaccharide (COS) was used as matrix to prepare surfactant-free ASD of BCS class IV drug by the ball milling method, with curcumin (CUR) as a model drug. The DSC, XRPD, FTIR and physical stability experiments indicated that CUR was in an amorphous state with high physical stability and exhibited potential interactions with COS in the ASD. Non-sink dissolution in vitro studies showed the maximum dissolution concentration of all CUR-COS ASD (CUR and COS at weight ratios of 1:1, 1:2 and 1:4) reached ranging from 97.85 to 101.21 μg/mL, far above that of pure CUR. The supersaturated concentration remained for at least 24 h under non-sink condition. Caco-2 cell model revealed that, compared to the pure CUR group, the apparent permeability coefficients were increased by 1.72–4.44-fold in all three CUR-COS ASD, which was mainly attributed to opening the tight junctions of Caco-2 cells by COS. The pharmacokinetic study showed that all CUR-COS ASD groups exhibited significant enhancements in AUC0-∞, with 1.55–3.01-fold that of pure CUR (p < 0.01). Tmax of CUR was shortened after oral administration of all three ASD. The current study demonstrates the amorphous COS could be used as a promising matrix in ASD for enhancing the oral bioavailability of BCS class IV drug by improving dissolution behavior and membrane permeability.

FTIR spectroscopy studies on the spontaneous neutralization of chitosan acetate films by moisture conditioning

The influence of moisture ambiance on the spontaneous neutralization of amorphous chitosan acetate films during storage at 30°C and water activities (aw) in the range of 0.11 to 0.84 is studied by Fourier transform infrared (FTIR) spectroscopy. Three ranges of relative humidity affecting the chitosan acetate films are identified: i) 0.11≤aw≤0.32, produces dehydration and partial neutralization; ii) aw=0.44 and 0.55, spontaneous neutralization and rearrangement of OH bonds; iii) 0.64≤aw≤0.85, prevalence of films in the acetate form and moisture absorption. Acetate content of films as function of water activity and storage time is assessed from the band accounting for the electrostatic interaction of protonated amine groups (–NH3+) in chitosan and carboxylate ions (–COO−) of acetic acid. FTIR spectroscopy results are correlated with the equilibrium properties determined from moisture sorption isotherm. The simple method presented may help to produce chitosan acetate films with tuned protonation degree that are relevant in many applications such as biomedical, food, cosmetics, and pharmaceutical.

Influence of the electrophoretic deposition route on the microstructure and properties of nano-hydroxyapatite/chitosan coatings on the Ti-13Nb-13Zr alloy

In this work, nanocomposite HA/chitosan coatings were electrophoretically deposited (EPD) on a near-β Ti-13Nb-13Zr alloy. The influence of the state of the HA particles introduced to the colloidal solution of chitosan (nc-HA-p as a nanopowder and nc-HA-s as nanoparticles suspended in ethanol), as well as the chemical composition of a multi-component HA-chitosan suspension and EPD parameters, on the homogeneity of coatings has been studied. It was established that the pH value and the chemical composition of the suspension have a substantial effect on the electrokinetic properties of suspended HA and chitosan particles. These are also influenced by the deposition kinetics of EPD and the uniformity of as-deposited coatings. The thickness of the nc-HA-p/chitosan and nc-HA-s/chitosan coatings was up to 750nm and 1.5μm, respectively. The nc-HA-s/chitosan coating microstructure consisted of HA nanoparticles, homogeneously embedded in an amorphous chitosan matrix. The nc-HA-p/chitosan coating microstructure was non-homogeneous, composed of HA agglomerates in a chitosan matrix. The presence of thin oxide layer was observed on the coatings/titanium alloy interface. The nc-HA-s/chitosan coating exhibited better adhesion to the titanium alloy substrate than the nc-HA-p/chitosan coating. It was found that the nc-HA-s/chitosan coating improves the electrochemical corrosion resistance of the Ti-13Nb-13Zr alloy in Ringer's solution, as well as its bioactivity and other biological properties.

Electrophoretic deposition and characterization of composite chitosan-based coatings incorporating bioglass and sol-gel glass particles on the Ti-13Nb-13Zr alloy

Composite bioglass/chitosan and sol-gel glass/chitosan coatings were electrophoretically deposited (EPD) on a near-β Ti-13Nb-13Zr alloy. The influence of EPD parameters, such as chemical composition and suspension pH as well as potential difference and deposition time, on the uniformity of coatings has been studied. It was found that the pH value of the suspension and chemical composition have a significant impact on the electrokinetic properties of suspended chitosan molecules and glass particles, which in turn affect the deposition rate of EPD and the uniformity of as-deposited coatings. The thicknesses of the bioglass/chitosan and sol-gel glass/chitosan coatings were up to 2μm and 860nm, respectively. The microstructure of the coatings was characterized by scanning and transmission electron microscopy as well as X-ray diffractometry. The coating microstructure was composed of sol-gel glass particles or amorphous bioglass separate particles or agglomerates, homogeneously embedded in an amorphous chitosan matrix. The sol-gel particles consisted of hydroxyapatite (hp), CaSiO3 (tp) phases. The sol-gel glass/chitosan coating exhibited better adhesion to the titanium alloy substrate than the bioglass/chitosan coating. It was found that both types of coating improve the electrochemical corrosion resistance of the Ti-13Nb-13Zr alloy in Ringer's solution and are cytocompatible with osteoblast-like cells.

Microstructure formation in porous calcium phosphate-chitosan bone cements

We have studied the microstructure formation in composite cement materials consisting of amorphous calcium phosphate and chitosan and reinforced with sodium alginate granules, their compressive strength, and the kinetics of their dissolution in an isotonic solution. Hardening in air allowed us to obtain a cement stone with a strength of up to 18 MPa and limiting strain of 6–8%. During hardening in simulated body fluid, the maximum strength decreased to 0.8 MPa, and the strain increased to 25–30%, which was due to the dissolution of the granules and the increase in the elasticity of the chitosan framework. The calcium ion release to the isotonic solution varied nonmonotonically, with a maximum in the initial stage of hardening. The cements are intended for the fabrication of porous matrices in bone tissue regeneration.

Enhanced proton conductivities of nanofibrous composite membranes enabled by acid–base pairs under hydrated and anhydrous conditions

Herein, a series of nanofibrous composite membranes (NFCMs) are designed and prepared by incorporating chitosan (CS) matrix into electrospun sulfonated poly(ether ether ketone) (SPEEK) nanofiber mats with controllable structures. Fourier transform infrared results suggest that the −SO3H groups of SPEEK and the −NH2 groups of CS assemble into acid–base pairs along the nanofiber surface. The electrostatic attractions within the pairs inhibit the chain mobility of CS and SPEEK, endowing NFCMs with reinforced thermal and structural stabilities. Besides, the attractions drive the enrichment of acid/base groups near the nanofiber surface, thus providing more proton-hopping sites in the perpendicular direction of NFCMs. Together with the conducting groups in the amorphous CS phase, these sites donate significant enhancement in proton conduction via a low-energy-barrier manner. Particularly, a hydrated conductivity of 0.153Scm−1 is achieved by the NFCM, much higher than those of CS (0.024Scm−1) and SPEEK (0.037Scm−1) casting membranes. Meanwhile, the formed acid–base pairs display unique anhydrous transfer ability, affording the NFCM a high anhydrous conductivity (59.6mScm−1) at 120°C. Moreover, the influence of sulfonation degree and diameter of SPEEK nanofiber on proton conductivity is systematically investigated.

Effects of sodium acetate buffer on chitosan sponge properties and in vivo degradation in a rat intramuscular model.

Chitosan sponges were developed for adjunctive local antibiotic delivery to reduce bacteria in wounds. There is a need to increase sponge degradation for rapid clearance from the wound site during initial wound care. This work examined the effect of using 0.25 M sodium acetate buffers, at pH 4.6 or 5.6, to fabricate sponges with an amorphous chitosan polymer structure. Sponges were evaluated for their crystallinity, thermal, spectroscopic, and morphological properties, in addition to in vitro degradation, and cytocompatibility analysis using normal human dermal fibroblasts. In vivo degradation and biocompatibility were also examined after 4 and 10 days in rat intramuscular tissues. Both buffered chitosan sponge variations exhibited decreases in crystallinity and thermal decomposition temperatures, and increases in surface roughness, which resulted in over 40% increases in degradation over 10 days in vitro compared to the neutral sponges. There were no significant differences between sponges during in vivo degradation over 10 days with respect to histomorphometric analysis of the recovered sponges. These results demonstrated that the acetate buffer did change characteristic chitosan sponge material properties, and increasing the in vivo sponge degradation rate will require balancing material characteristics and processing.

Preparation and characterization of porous scaffold composite films by blending chitosan and gelatin solutions for skin tissue engineering

AbstractBiodegradable polymers have significant potential in biotechnology and bioengineering. However, for some applications, they are limited by their inferior mechanical properties and unsatisfactory compatibility with cells and tissues. In the present investigation blends of chitosan and gelatin with various compositions were produced as candidate materials for biomedical applications. Fourier transform infrared spectral analysis showed good compatibility between these two biodegradable polymers. The composite films showed improved tensile properties, highly porous structure, antimicrobial activities, low water dissolution, low water uptake and high buffer uptake compared to pure chitosan or gelatin films. These enhanced properties could be explained by the introduction of free OH, NH2 and NHOCOCH3 groups of the amorphous chitosan in the blends and a network structure through electrostatic interactions between the ammonium ions (NH3+) of the chitosan and the carboxylate ions (COO−) of the gelatin. Scanning electron microscopy images of the blend composite films showed homogeneous and smooth surfaces which indicate good miscibility between gelatin and chitosan. The leafy morphologies of the scaffolds indicate a large and homogeneous porous structure, which would cause increased ion diffusion into the gel that could lead to an increase in stability in aqueous solution, buffer and temperature compared to the gelatin/chitosan system. In vivo testing was done in a Wistar rat (Rattus norvegicus) model and the healing efficiencies of the scaffolds containing various compositions of chitosan were measured. The healing efficiencies in Wistar rat of composites with gelatin to chitosan ratios of 10:3 and 10:4 were compared with that of a commercially available scaffold (Eco‐plast). It was observed that, after 5 days of application, the scaffold with a gelatin to chitosan ratio of 10:3 showed 100% healing in the Wistar rat; however, the commercial Eco‐plast showed only a little above 40% healing of the dissected rat wound. Copyright © 2012 Society of Chemical Industry

Understanding of the Plasticizing Effects of Glycerol and PEG 400 on Chitosan Films Using Solid-State NMR Spectroscopy

Differences were found in the plasticizing effects of two commonly used softening materials on amorphous chitosan films. The plasticizing efficiencies for glycerol and PEG 400 were found to be similar in mechanical tests, but the changes in the three-dimensional H-bonded structure monitored by solid-state NMR spectroscopy were different. The analysis of Lee−Goldburg cross-polarization build-up curves demonstrated that, while glycerol decreases the mobility of the acetamide groups, PEG 400 increases it. Further, while glycerol molecules are immobilized in chitosan films, PEG 400 remains mobile in them. The results of two-dimensional (2D) 1H−13C frequency-switched Lee−Goldburg (FSLG) HETCOR experiments supported the mobility difference of the chitosan chains and suggested a specific interaction between the glycerol and the glucosamine units. Our findings were supported by density functional theory calculations. Overall, PEG 400 acts as an external plasticizer, while glycerol acts as an internal plasticizer.

Microwave technique for efficient deacetylation of chitin nanowhiskers to a chitosan nanoscaffold

A chitosan nanoscaffold in the form of a colloidal solution was obtained from the deacetylation of chitin whiskers under alkaline conditions by using a microwave technique in only 1/7 of the treatment time of the conventional method. Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance ( 1H NMR) techniques confirm the degree of deacetylation to be above 90% within 3 h. The wide-angle X-ray diffraction (WAXD) pattern clearly shows that the highly crystalline chitin whiskers are changed to amorphous chitosan. SEM micrographs show the aggregation of branched nanofibers, whereas the TEM micrographs reveal the scaffold morphology.

Preparation, swelling and electro-mechano-chemical behaviors of a gelatin-chitosan blend membrane.

Swelling, states of water, morphology, stability in the aqueous solution, and electro-mechano-chemical bending behaviors of the gelatin-chitosan blend system were studied in order to clarify the potential use of this blend system as an actuator. The gelatin-chitosan blend system was prepared in order to avoid dissolution of the pure chitosan in an aqueous medium and the rigidity and easy degradation of the pure gelatin in the swollen state. The blend systems showed improved material properties: the vacuum-dried blend sample at the G75/C25 (w/w, gelatin-chitosan) ratio showed ∼6 times swelling (in distilled water, at neutral pH and room temperature), ∼5 times stability (in distilled water), and ∼6 times bending (at 6 V/53 mm and in a 0.02 M NaCl aqueous solution) as compared to pure gelatin. These enhanced properties could be explained by the introduction of free -OH, -NH2, and -NHOCOCH3 groups of the amorphous chitosan in the blend and the network structure through the electrostatic interactions between the ammonium (-NH3+) ions of the chitosan and the carboxylate (-COO-) ions of the gelatin. The scanning electron microscopy (SEM) micrographs of the surfaces of the blend films showed homogeneous and smooth surfaces due to the good miscibility between gelatin and chitosan. However, a different morphology from the fractured surface was found between the pure gelatin and blend systems which showed condensed and foliaceous morphologies, respectively. The leafy morphology indicates a large and homogeneous pore structure, which would cause increased ion diffusion into the gel and might lead to increased bending.

Morphology controllable nanostructured chitosan matrix and its cytocompatibility

It is becoming clear that surface nanotopography of underlying substrates can influence cell behavior such as adhesion, proliferation, and orientation of mammalian cells. Nanofabrication methods such as electron beam lithography are, however, expensive and time consuming. In this study, a simple and cost-effective approach, heterogeneous seeded growth, was developed to create nanostructured chitosan matrix (CSM) from amorphous chitosan nanoparticles (CNPs). The physiochemical properties of CSM were characterized followed by an evaluation of CSM cytocompatibility. Shape-controllable morphology of CSM from nanoparticles to three-dimensional urchin-like architectures was achieved by using varying amounts of seeds. CSM was found to be cytocompatible with human foreskin fibroblasts suggesting that the nanofibrous surface morphology and crystalline structure of CSM could favor cell spread and growth.

Selective reactivity of biochemically relevant quinones towards chitosans

Biologically significant quinones, such as menadione (vitamin K), plumbagin, ubiquinone (CoQ 10) and CoQ 3 were examined along with 1,2-naphthoquinone and 1,4-naphthoquinone for their capacity to react with five chitosans in freeze-dried or film form. The chitosans tested were: chitosan acetate salt, re-acetylated chitosan, amorphous chitosan, 5-methylpyrrolidinone chitosan and N-carboxymethyl chitosan. It was surprisingly found that CoQ 10 and CoQ 3 do not react with the chitosans, whilst menadione and even more 1,4-naphthoquinone are reactive and yield deeply coloured modified chitosans. The reactivities of plumbagin and 1,2-naphthoquinone are modest or nil, depending on the chitosan tested. The maximum capacity of chitosans for 1,4-naphthoquinone corresponded to an amine/quinone molar ratio close to 2, indicative of saturation over a 12 h contact period: the relevant infrared spectra did not show the typical bands of 1,4-naphthoquinone. Uv–vis measurements on methanol solutions indicated that chitosan acetate salt and re-acetylated chitosan were most reactive with menadione. Menadione-treated chitosans gave infrared spectra containing typical quinone bands, and the films had altered surface properties, their contact angles with saline being much higher than for controls. The absence of reactivity between ubiquinone and N-carboxymethyl chitosan, both widely accepted functional cosmetic ingredients, could constitute the basis for the formulation of toot-pastes and gingival gels, possessing enhanced reparative properties due to the synergistic actions of intact ubiquinone and N-carboxymethyl chitosan.