Charged Chitosan Research Articles

Thermal-reversible and self-healing hydrogel containing magnetic microspheres derived from natural polysaccharides for drug delivery

Hydrogels with and self-healing properties and responsiveness to external stimuli have been extensively investigated as cell scaffolds and wound dressings, due to their diversity and prolonged lifetime. In this report, we developed magnetic microspheres based on chitosan derivatives through a facile Schiff-base crosslinking procedure. X-Ray diffraction (XRD), scanning electron microscopy (SEM) and thermal gravity (TG) were utilized to characterize the magnetic microspheres. A thermal-reversible and self-healing hydrogel was prepared via electrostatic interactions between positively charged chitosan and negatively charged cellulose. By introducing the magnetic microspheres into polymer hydrogels, hybrid scaffolds were synthesized with facile preparation technology, controllable shape and mobility under magnetic force. Swelling property, degradation rate and morphology of these scaffolds have been investigated. Results revealed that the magnetic microsphere exhibit spherical morphology, good dispersity with narrow size distribution and capability of maintaining structure in physical environment. Rheological study demonstrated the thermal reversibility and self-healing ability of chitosan-cellulose hydrogels. Moreover, the obtained composite hydrogels and lyophilized porous scaffolds exhibited excellent homogeneity, controllable formation, magnetic responsiveness as well as good stability in physiological environment. Moreover, this thermal-reversible and self-healing scaffold showed a controlled in vitro drug release under an external magnetic field. The magnetic gel scaffold suggest an alternative approach to provide intelligent and versatile scaffolds for biomedical applications.

Microfluidic Synthesis of Lignin/Chitosan Nanoparticles for the pH-Responsive Delivery of Anticancer Drugs.

In this work, lignin/chitosan nanoparticles (Lig/Chi NPs) with controlled structures were synthesized in a simple and scalable microfluidic system. When the positively charged chitosan and the negatively charged lignin solution were blended in a microreactor, Lig/Chi NPs were rapidly formed via the electrostatic coassembly between the amino groups of chitosan and the carboxyl groups of lignin. The ζ potential changes from negative (-13 mV) to positive (+54.5 mV) for Lig NPs and Lig/Chi NPs, respectively. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results demonstrated that Lig/Chi NPs have an average particle size of about 180 nm, which can be used as nanocarriers for drug delivery. The anticancer drug nanoparticles with docetaxel (DTX) and curcumin (CCM) were prepared by coassembly with Lig/Chi NPs in a microreactor, which had good drug loading efficiency, biocompatibility, and can release drugs in response to pH in the weakly acidic environment of the tumor. The drug release amounts in acidic solutions that simulated the tumor microenvironment were 51% (DTX@Lig/Chi NPs) and 50% (CCM@Lig/Chi NPs), respectively, which were better than the release amounts at pH 7.4, and have an obvious killing effect on HeLa cells.

Enhanced Thermal Insulation and Flame-Retardant Properties of Polyvinyl Alcohol-Based Aerogels Composited with Ammonium Polyphosphate and Chitosan

Polyvinyl alcohol- (PVA-) based aerogels have attracted widespread attention owing to their low cost, eco-friendliness, and low density. However, the applications of PVA-based aerogels are limited by their flammability. In this study, a flame retardant, ammonium polyphosphate (APP), and a biopolymer, chitosan (CS), were added to polyvinyl alcohol (PVA), and the polymer was further crosslinked using boric acid (H3BO3). In the PVA aerogels, the negatively charged APP and positively charged CS formed a polyelectrolyte complex (PEC) through ionic interaction. Cone calorimetry and vertical burning tests (UL-94) indicated that the PVA composite aerogels have excellent flame retardancy; they could decrease the heat release rate, total heat release rate, and carbon dioxide (CO2) generation. Both PVA/H3BO3 and APP-CS in the composite aerogel could be burned to carbon, and the foamed char layer could act together to impart the PVA composite aerogels with good flame retardancy. Further, the decrease in the temperature at the backside of the aerogels with increasing APP-CS content, as determined by the flame-spraying experiment, indicated that the PVA-based aerogels with APP-CS can also serve as thermal insulation materials. This work provides an effective and promising method for the preparation of PVA-based aerogels with good flame retardancy and thermal insulation property for construction materials.

Biocompatible homogeneous particle formation via the self-complexation of chitosan with oleic acid and its application as an encapsulation material for a water-insoluble compound

A simple, precise method for preparing submicrometer-sized homogeneous particles as potential delivery carriers for water-insoluble compounds was developed using self-complexation of chitosan (CHI) and oleic acid (OA). One-step mixing of a CHI aqueous solution and an ethanol solution containing fatty acids provided homogeneously turbid dispersions at ambient conditions. Mean particle diameters measured using dynamic light scattering and laser diffraction measurements ranged from 300 to 1000 nm with narrow diameter distributions (polydispersity index < 0.2, for 600-nm particles), depending on their preparation conditions. Scanning transmission electron microscopy (STEM) also indicated the formation of submicron-sized particles. Based on measurements of Fourier-transform infrared (FT-IR) spectra, fluorescent spectra with pyrene, and small angle X-ray scattering (SAXS), this study proposed particle formation via electrostatic complexation between positively charged CHI and negatively charged oleate ions, and aggregation of hydrophobic interaction between alkyl groups of OA. The diameter distribution of the particles did not change even after storage for three months at room temperature and pH 5.0. Furthermore, the hydrophobic bioactive compound curcumin was successfully encapsulated into complex particles without use of additional emulsifiers as dispersant for curcumin. Particle suspension encapsulating curcumin could be concentrated using evaporation of the aqueous dispersion medium without significant changes in their diameter. These findings demonstrate that CHI-OA complex particles are potentially advantageous for encapsulating/dispersing hydrophobic compounds in aqueous media in order to develop novel liquid-based foods and beverages with improved physicochemical stability and enhanced health functionality. • Biocompatible fine particles were obtained using a one-step procedure. • Homogenous particle size distribution could be maintained for a long time. • Particles formed via non-covalent interactions between chitosan and oleic acid. • Particle size was tunable (300–1000 nm) by adjusting preparation conditions. • Efficient encapsulation of the lipophilic compound curcumin was demonstrated.

Effect of pH adjustment and ratio of oppositely charged polymers on the mechanistic performance and sustained release of volatile perfume in interpolyelectrolyte complex microcapsules

In this study, volatile perfume was encapsulated in microcapsules (MCs) via interpolyelectrolyte complexes (IPECs) of oppositely charged polymers, with high encapsulation efficiency, to be delivered in a sustained manner. Positively charged chitosan (CTS) and negatively charged Eudragit® S100 (ES100) were used as eco-friendly biopolymers. Limonene (LMN) was selected as the model perfume. First, the solution of LMN in ethyl acetate and poloxamer 407 (POX407) in acidic solution was emulsified using ultrasonication. CTS and ES100 were added in that particular order to form o/w emulsion. LMN-loaded microcapsules (LMN-MCs) were prepared by adjusting the pH and freeze-drying for solidification. The electrostatic interactions of CTS and ES100 to form IPECs were highly dependent on pH, changing in the microscopic images of emulsion droplets and zeta potential. The NH3+ group of CTS and the COO– group of ES100 caused the electrostatic interactions at a specific pH. The formation mechanism of LMN-MCs was successfully validated using instrumental analysis, charge density, and energy dispersive X-ray spectrometer (EDS) mapping. Encapsulation efficiency, loading content, and release rates of LMN-MCs varied according to the ratios of CTS and ES100, demonstrating optimal performance at a 1:1 ratio. The current LMN-MCs could provide a simple manufacturing process with high performance in terms of encapsulation efficiency (>94%), drug loading, yield and sustained release of volatile perfume for 120 h.

A Composite Nanosystem as a Potential Tool for the Local Treatment of Glioblastoma: Chitosan-Coated Solid Lipid Nanoparticles Embedded in Electrospun Nanofibers.

Glioblastoma multiforme (GBM) is one of the most prevalent and aggressive brain tumors for which there is currently no cure. A novel composite nanosystem (CN), consisting of chitosan-coated Solid Lipid Nanoparticles (c-SLN) embedded in O-carboxymethyl chitosan (O-CMCS)-containing nanofibers (NFs), was proposed as a potential tool for the local delivery of lipophilic anti-proliferative drugs. Coacervation was selected as a solvent-free method for the preparation of stearic acid (SA) and behenic acid (BA)-based SLN (SA-SLN and BA-SLN respectively). BA-SLN, containing 0.75% w/w BA sodium salt and 3% w/w poly(vinyl alcohol) (PVA), were selected for the prosecution of the work since they are characterized by the lowest size functional to their subsequent coating and incorporation in nanofibers. BA-SLN were coated with chitosan (CS) by means of a two-step coating method based on the physical absorption of positively charged CS chains on the SLN negative surface. Nile Red (NR), chosen as the hydrophobic model dye, was dissolved in a micellar solution of BA sodium salt and then added with a coacervating solution until pH ≅ 2.5 was reached. Immunocytochemistry analyses highlighted that CS-coated BA-SLN (c-BA-SLN) exhibited a higher accumulation in human glioblastoma cells (U-373) after 6 h than CS-free BA-SLN. Finally, the c-BA-SLN dispersion was blended with a solution consisting of freely soluble polymers (O-CMCS, poly(ethylene oxide) and poloxamer) and then electrospun to obtain NFs with a mean diameter equal to 850 nm. After the NFs dissolution in an aqueous media, c-BA-SLN maintained their physicochemical properties and zeta potential.

Enhanced cellular compatibility of chitosan/collagen multilayers LBL modified nanofibrous mats

Developing novel, lightweight and biocompatible mesh for pelvic organ prolapse, a gynecological disease, has attracted the global interest of biomedical researchers. In our study, polycaprolactone and nylon 6 mats with excellent mechanical properties were fabricated via co-electrospinning. Positively charged chitosan with antimicrobial properties and negatively charged collagen with good biocompatibility were then assembled on the nanofiber mats via layer by layer (LBL) technology. SEM and mechanical property tests showed that LBL deposition increased the nanofibers’ diameter and elastic modulus. To evaluate the successful deposition process, the zeta potential, The Fourier-transform infrared, X-ray diffraction, and X-ray photoelectron spectroscopy analyses were conducted to systematically study the mats’ chemical characterization. The results indicated that the mats’ composition and structure significantly changed after LBL modification. Cell biology experiments demonstrated that the LBL-structured mats can facilitate cell growth, proliferation, and adhesion. Antibacterial tests confirmed their excellent antibacterial activity. Chitosan/Collagen-coated Polycaprolactone/Nylon 6 mats demonstrate considerable potential as implant materials for pelvic reestablishment in pelvic organ prolapse patients.

Engineered Protein Photo-Thermal Hydrogels for Outstanding In Situ Tongue Cancer Therapy.

Surgical excision is the main choice for tongue cancer treatment. However, the physiological functions of oral and maxillofacial regions might be severely impaired and high risk of tongue tumor recurrence cannot be avoided. It is thus becoming urgently important to develop alternative strategies for tongue cancer therapy. In this regard, a new class of near-infrared (NIR) light-responsive and peritumoral injectable hydrogel is fabricated with extraordinary photothermal therapy (PTT) for in situ tongue tumors. The as-prepared soft material exhibits good biocompatibility and ultra-strong photothermal effect due to the formed network by negatively charged proteins, chitosan molecules, and Ag3 AuS2 nanoparticles (NPs). In a well-constructed in situ tongue tumor model, tumors can be efficiently eradicated by one-time PTT treatment. Importantly, there are no side effects on surrounding normal tissues and potential tumor recurrence is inhibited. In stark contrast to traditional surgical excision, such biomaterials hold great potential for clinical treatment of oral cancers.

The immunostimulatory effects of hydroxypropyltrimethyl ammonium chloride chitosan-carboxymethyl chitosan nanoparticles

In this study, we generated chitosan nanoparticles by exploiting the electrostatic interactions between positively charged hydroxypropyltrimethyl ammonium chloride chitosan (HACC) and negatively charged carboxymethyl chitosan (CMC), and examined the effects of altering the molecular weight and carboxymethyl substitution sites of the chitosan molecules. Particle size, potential, and encapsulation efficiency of the various chitosan nanoparticles were examined; the particle size range was 162.40–332.80 nm, the charge range was 19.50–40.60 mV, and the encapsulation efficiency range was 48.4–70.7%. We then examined the immunostimulatory effects of the nanoparticle variants on dendritic cells (DCs); we found that the site of carboxymethyl substitution significantly affected the immunostimulatory effects of the nanoparticles. Two nanoparticle types, 200 kDa N,O-carboxymethyl chitosan-HACC (NO-CMC-HACC) and N-carboxymethyl chitosan-HACC (N-CMC-HACC), greatly promoted the expression of interleukin-6, tumor necrosis factor, and interleukin-1β in DCs. Moreover, NO-CMC-HACC nanoparticles caused an increase in major histocompatibility complex-II (MHC-II), CD11c, CD80, and CD86 secretion in DCs, indicating that these nanoparticles promoted antigen presentation. We then examined chitosan nanoparticle uptake by DCs using laser confocal microscopy; we found that the NO-CMC-HACC nanoparticles were more readily absorbed by DCs compared to the N-CMC-HACC nanoparticles. Therefore, we concluded that 200 kDa NO-CMC-HACC nanoparticles exhibited strong potential as immunological adjuvants.

β-Cyclodextrin-containing chitosan-oligonucleotide nanoparticles improve insulin bioactivity, gut cellular permeation and glucose consumption.

The main objective of the present study was to develop a nanoparticulate drug delivery system that can protect insulin against harsh conditions in the gastrointestinal (GI) tract. The effects of the following employed techniques, including lyophilisation, cross-linking and nanoencapsulation, on the physicochemical properties of the formulation were investigated. We herein developed a nanocarrier via ionotropic gelation by using positively charged chitosan and negatively charged Dz13Scr. The lyophilised nanoparticles with optimal concentrations of tripolyphosphate (cross-linking agent) and β-cyclodextrin (stabilising agent) were characterised by using physical and cellular assays. The addition of cryoprotectants (1% sucrose) in lyophilisation improved the stability of nanoparticles, enhanced the encapsulation efficiency, and ameliorated the pre-mature release of insulin at acidic pH. The developed lyophilised nanoparticles did not display any cytotoxic effects in C2C12 and HT-29 cells. Glucose consumption assays showed that the bioactivity of entrapped insulin was maintained post-incubation in the enzymatic medium. Freeze-drying with appropriate cryoprotectant could conserve the physiochemical properties of the nanoparticles. The bioactivity of the entrapped insulin was maintained. The prepared nanoparticles could facilitate the permeation of insulin across the GI cell line.

Polysaccharide dual coating of yeast capsules for stabilization of anthocyanins

The dual coated yeast capsules for anthocyanin encapsulation and stabilization were fabricated. Anthocyanins were preloaded in hollow yeast capsules, and then the dual coating was performed by deposition of opposite charged polysaccharides using layer-by-layer technique. The combination of positively charged chitosan and negatively charged chondroitin sulfate was found to confer the yeast capsules with the highest encapsulation efficiency and retention rate of anthocyanins. Additionally, the coated yeast capsules featured high tolerance to environmental stresses (i.e., oxygen, ascorbic acid, and heat) and therefore effectively inhibited the degradation of anthocyanins. These stabilizing effects were related to the formation of high penetration barrier provided by the double layers of polysaccharides, as well as the enhanced hydrophobic microenvironment in the capsules. Further development of the polysaccharide-coated yeast capsules may hold promise for the controlled delivery of other water-soluble bioactive components.

Preparation of zinc phthalocyanine-loaded amphiphilic phosphonium chitosan nanomicelles for enhancement of photodynamic therapy efficacy

To increase the solubility and the encapsulation of zinc phthalocyanine (ZnPc) photosensitizer for photodynamic therapy (PDT), a positively charged amphiphilic phosphonium chitosan nanomicelle with multi-benzene structure was developed, and its application to PDT was explored. N-acetyl-l-phenylalanine-(4-carboxybutyl) triphenylphosphonium bromide chitosan (CTPB-CS-NAP), a chitosan derivative with tunable amphiphilicity, was synthesized first. ZnPc was encapsulated in CTPB-CS-NAP at the critical micelle concentration (CMC) of 4.898 mg/L by a hydrophobic self-assembly method to form ZnPc-loaded nanomicelles (ZnPc@CTPB-CS-NAP). The method gives the highest encapsulation efficiency and drug loading of 89.4 % and 22.3 %, respectively. ZnPc@CTPB-CS-NAP is stably dispersed in aqueous solution and shows the average particle size of 103±5 nm. PDT experiments suggest the phototoxicity of ZnPc@CTPB-CS-NAP is much higher than that of ZnPc, but no obvious dark cytotoxicity is observed. Our study has provided a new strategy for improving the photodynamic therapy efficacy of hydrophobic photosensitizer by the encapsulation with chitosan derivative carriers.

Supramolecular Structuring of Hyaluronan-Lactose-Modified Chitosan Matrix: Towards High-Performance Biopolymers with Excellent Biodegradation.

Non-covalent interactions in supramolecular chemistry provide useful systems to understand biological processes, and self-assembly systems are suitable assets to build-up innovative products for biomedical applications. In this field, polyelectrolyte complexes are interesting, especially when polysaccharides are involved, due to their non-toxicity and bio-absorbability. In this work, we investigated a polyelectrolyte formed by hyaluronic acid (HA), a negatively charged linear polysaccharide, with Chitlac (Ch), a positively charged lactose-modified chitosan. The aim of the study was the investigation of a novel Ch–HA polyelectrolyte complex, to understand the interaction between the two polysaccharides and the stability towards enzymatic activity. By means of gel permeation chromatography–triple detector array (GPC–TDA), nuclear magnetic resonance (NMR), dynamic viscosity, Zeta Potential and scanning electron microscopy (SEM), the polyelectrolyte complex properties were identified and compared to individual polysaccharides. The complex showed monodisperse molecular weight distribution, high viscosity, negative charge, and could be degraded by specific enzymes, such as hyaluronidase and lysozyme. The results suggest a close interaction between the two polysaccharides in the complex, which could be considered a self-assembly system.

Chitosan based controlled release drug delivery of mycophenolate mofetil loaded in nanocarriers system: synthesis and in-vitro evaluation

Background: Organ transplantation is an important and critical procedure, which requires the suppression of immunity, and to suppress the immunity, a constant plasma concentration of immunosuppressant is required. Objectives: The said objective can be achieved by formulating a controlled release drug delivery system of the drug. Chitosan (CHT) nanoparticles (NPs) have been revolutionizing the conventional drug delivery system, for the past two decades. The aim of the current research work was to develop and evaluate CHT-based mycophenolate mofetil (MMF) loaded nanoparticles (CHT/MMF-NPs) using different drug to polymer ratios. Methods: The challenge was to entrap a lipophilic drug within NPs by the ionic gelation method of the positively charged CHT, using tripolyphosphate (TPP) as the crosslinking agent. The prepared CHT/MMF-NPs were evaluated for physical and chemical characterizations, including particle size, surface charge, entrapment efficiency (EE), surface morphology by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) for chemical compatibilities, X-ray diffractometry (XRD) and in-vitro dissolution studies. Results: Outcomes of the studies revealed that particles were 260 ± 17 nm in diameter, with the smooth and regular surface. Satisfactory values of EE (99%) have indicated the suitability of selected ingredients and employed methodology. Moreover, FTIR has confirmed the chemical compatibilities of the formulations. In-vitro dissolution studies have indicated diffusion type of controlled and sustained drug release during 24 h, with zero-order, as best fit kinetic model. Conclusion: Conclusively, the successful achievement of objectives has indicated the suitability of excipients and methodology to prepare CHT/MMF-NPs for better therapeutic outcomes.

Evaluation of polymer choice on immunogenicity of chitosan coated PLGA NPs with surface-adsorbed pneumococcal protein antigen PspA4Pro

Polymeric nanoparticles (NPs) are recognized as potential delivery vehicles for vaccines. PLGA is a biocompatible polymer synonymous with polymeric NPs, which can be coated with other polymers such as chitosan that has intrinsic adjuvant properties as well as mucoadhesive properties. Numerous modifications and variations exist for PLGA and chitosan, which can influence the NP characteristics and the resulting immunogenicity. The current study investigated variations for making chitosan coated PLGA NPs incorporating recombinant pneumococcal surface protein A from family 2, clade 4 (PspA4Pro) antigen as a vaccine targeting the vast majority of pneumococcal strains and determine the effect of the polymers on particle size, surface charge, and surface marker upregulation on a dendritic cell (DC) line in vitro. PLGA variations tested with the ester-terminal group had the greatest detriment for prospective vaccine use, due to the lowest PspA4Pro adsorption and induction of CD40 and CD86 cell surface markers on DCs. The negatively charged chitosans exhibited the lowest surface marker expressions, similar to the uncoated NP, supporting the commonly accepted notion that positive surface charge augments immunogenic effects of the NPs. However, the study indicated that NPs made from PLGA with an acid terminated group, and chitosan HCl salt, exhibit particle characteristics, antigen adsorption efficiency and immunogenicity, which could be most suitable as a vaccine formulation.

Fiber template approach toward preparing one-dimensional silica nanostructure with rough surface

Silica nanofibers were grown on the surface of chitosan nanofibers used as templates by coating the surface with silica derived from the hydrolysis and condensation of tetraethoxysilane using ammonium hydroxide as a catalyst. This was followed by the decomposition of the chitosan template. The relationship between different processing factors (type of templates as well as amounts of catalyst and template) and the formation of silica nanofibers was examined. Varying the processing factors was found to be effective in controlling the morphology of the silica nanofibers. The use of chitosan nanofibers effectively led to the formation of one-dimensional silica nanofibers as the positively charged chitosan nanofibers promoted the deposition of the negatively charged silica nanoparticles through electrostatic attractive forces. Therefore, the chitosan nanofibers acted as good deposition sites for interacting with silica nanoparticles. Although a large amount of catalyst promoted the sol-gel reaction, the silica nanoparticles grew excessively in the solvent. Therefore, the surface structure of the prepared silica nanofibers could be controlled by varying the amount of chitosan template as this also varied the formation mechanism of the silica nanofibers. The resultant samples had a rough silica wall composed of densely assembled silica nanoparticles, with a high specific surface area (338 m2/g).

Carbon electrode with cross-linked and charged chitosan binder for enhanced capacitive deionization performance

Capacitive deionization (CDI) has emerged an energy-efficient and operation-simple electrochemical desalination processes among water treatments. Polymeric binder as an important component of CDI electrode is desired to have good adhesion, wettability and stability. In order to reduce the chemical uses and further enhance the CDI performance, we have designed the preparation of the crosslinked chitosan (CS) with glutaraldehyde (GA), and coated it on the activated carbon (AC) electrodes for desalination. By adjusting different GA contents, the CS crosslinked with GA (CS + 3GA) binder with stable three-dimensional (3D) networks were fabricated due to the utilization of tertiary amines (C=N), which exhibited strong adhesive property. Moreover, the CS + 3GA not only possessed good hydrophilicity, but also carried more positive charges that function as ion anion exchange membrane. In the electrosorption tests, an asymmetric CDI system (CS + 3GA//PVDF) was assembled via pairing a composite carbon anode coated with CS + 3GA binder, and a PVDF-bound carbon cathode. The studies demonstrated that CS + 3GA//PVDF cell showed excellent salt adsorption capacity (SAC) of 16.0 mg g−1 over 2 times higher than PVDF//PVDF, and good charge efficiency (CE) of 62.5% at 1.2 V. More importantly, CS + 3GA//PVDF displayed a remarkable regeneration performance that retention rate of 82.8% and approached that of PVDF//PVDF-M (83.2%) over 80 regeneration cycles. In addition, CS + 3GA//PVDF cell could be implemented at 1.4 V for desalination, which showed the unprecedented SAC of 18.4 mg g−1. The cross-linked and charged CS + 3GA binder coated with the carbon anode possesses the merits of being inexpensive, green and stable, making it a promising candidate for future CDI applications.

A study on chitosan-coated liposomes as a carrier of bovine serum albumin as oral protein drug

The development of protein drug liposomes was limited due to the instability of the structure of liposomes, such as easy aggregation, easy fusion, and drug leakage. The object of this work was to prepare bovine serum albumin (BSA) loaded liposomes (BSA-Lip) using BSA as a protein model drug and then BSA-Lip was further coated with chitosan (CH-BSA-Lip) in order to improve the stability of phospholipid bilayer membrane. It was found that the particle size of BSA-Lip increased after being coated with chitosan and the surface potential changed from negative charge to positive charge due to the electrostatic interaction between liposomes and chitosan. After chitosan coating, the encapsulation efficiency of liposomes also increased due to the interaction between positively charged chitosan and negatively charged BSA. Fourier transform infrared spectroscopy analysis confirmed that BSA was encapsulated into liposomes and chitosan was successfully coated on the surface of liposomes. Transmission electron microscopy showed that the particles were nanosized and spherical. The physical stability and in vitro digestion stability of liposomes were examined by observing the changes of particle size and potential. It was found that chitosan coating enhanced the stability of liposomes significantly. The in vitro release profile of CH-BSA-Lip possessed a slow release behavior, and BSA release was governed by both diffusion and dissolution from phospholipid bilayer.

Rate-dependent fracture behavior of tough polyelectrolyte complex hydrogels from biopolymers

Tough bio-based hydrogels based on the association of physical bonds are promising materials for use in biomedical applications due to their biocompatibility, biomimicry and biodegradability. Understanding the mechanical mechanisms at work during the fracture in such applications is indispensable. Using tough and self-healing bio-based hydrogels attained by the complexation of the negatively charged sodium hyaluronate (HA) and positively charged chitosan as a model system, an investigation of the tensile and fracture behavior over five decades of stretch velocities in physically and chemically crosslinked HA/chitosan hydrogels was systematically performed. In this study, the tensile analysis shows that the both of physically and chemically crosslinked hydrogels at small deformation are viscoelastic at a low stretch velocity, while they exhibit quasi-elastic character at a relatively high stretch velocity. In comparison to the physically and lightly chemically crosslinked HA/chitosan hydrogels exhibiting plastic-like behavior, the highly chemically crosslinked hydrogels demonstrate strong finite chain extensibility before fracture. The fracture analysis shows that the fracture energy of the highly chemically crosslinked hydrogels scales with the crack velocity as a power law relation Γ∝Vca (a= 0.15), where the exponent a can be well predicted from the viscoelastic spectrum of the bulk sample. These findings indicate that the viscoelastic energy dissipation around the crack tip dominates the fracture energy of the highly chemically crosslinked hydrogels. On the other hand, the fracture energy of the physically and lightly chemically crosslinked hydrogels is noted to increase with the crack velocity as a complex growth function, which can be effectively predicated by a viscoplastic model. The observed finding shows that the fracture energy of the physically and lightly chemically crosslinked hydrogel is dominated by the unzipping of the polyion complex structure and viscous energy dissipation due to the pulled out chains from the polymer network structure.

A Potential Quorum-Sensing Inhibitor for Bronchiectasis Therapy: Quercetin-Chitosan Nanoparticle Complex Exhibiting Superior Inhibition of Biofilm Formation and Swimming Motility of Pseudomonas aeruginosa to the Native Quercetin.

Quercetin (QUE)—a plant-derived flavonoid, is recently established as an effective quorum sensing (QS) inhibiting agent in Pseudomonas aeruginosa—the main bacterial pathogen in bronchiectasis lungs. Successful clinical application of QUE, however, is hindered by its low solubility in physiological fluids. Herein we developed a solubility enhancement strategy of QUE in the form of a stable amorphous nanoparticle complex (nanoplex) of QUE and chitosan (CHI), which was prepared by electrostatically driven complexation between ionized QUE molecules and oppositely charged CHI. At its optimal preparation condition, the QUE–CHI nanoplex exhibited a size of roughly 150 nm with a 25% QUE payload and 60% complexation efficiency. The complexation with CHI had no adverse effect on the antibacterial and anticancer activities of QUE, signifying the preservation of QUE’s bioactivities in the nanoplex. Compared to the native QUE, the QUE–CHI nanoplex exhibited superior QS inhibition in suppressing the QS-regulated swimming motility and biofilm formation of P. aeruginosa, but not in suppressing the virulence factor production. The superior inhibitions of the biofilm formation and swimming motility afforded by the nanoplex were attributed to (1) its higher kinetic solubility (5-times higher) that led to higher QUE exposures, and (2) the synergistic QS inhibition attributed to its CHI fraction.