Development of mucoadhesive thiolated chitosan nanoparticles for biomedical applications

Evolutionary approaches in protein engineering towards biomaterial construction

The tailoring of proteins for specific applications by evolutionary methods is a highly active area of research. Rational design and directed evolution are the two main strategies to reengineer proteins or create chimeric structures. Rational engineering is often limited by insufficient knowledge about proteins' structure-function relationships; directed evolution overcomes this restriction but poses challenges in the screening of candidates. A combination of these protein engineering approaches will allow us to create protein variants with a wide range of desired properties. Herein, we focus on the application of these approaches towards the generation of protein biomaterials that are known for biodegradability, biocompatibility and biofunctionality, from combinations of natural, synthetic, or engineered proteins and protein domains. Potential applications depend on the enhancement of biofunctional, mechanical, or other desired properties. Examples include scaffolds for tissue engineering, thermostable enzymes for industrial biocatalysis, and other therapeutic applications.

Enhanced dual network hydrogels consisting of thiolated chitosan and silk fibroin for cartilage tissue engineering

Thiolated chitosan (CS-NAC) was synthesized and the selected CS-NAC was used together with silk fibroin (SF) to produce dual network CS-NAC/SF hydrogels. The CS-NAC/SF solutions with formulated compositions were able to form hydrogels at physiological temperature and pH. Rheological measurements showed that elastic modulus of some CS-NAC/SF gels could reach around 3 kPa or higher and was much higher than their respective viscous modulus, indicating that they behaved like strong gels. Deformation measurements verified that CS-NAC/SF gels had well-defined elasticity. The optimized CS-NAC/SF gels exhibited jointly enhanced properties in terms of strength, stiffness and elasticity when compared to the gels resulted from either CS-NAC or SF. Examinations of dry CS-NAC/SF gels revealed that they were highly porous with well-interconnected pore features. Cell culture demonstrated that CS-NAC/SF gels supported the growth of chondrocytes while effectively maintaining their phenotype. Results suggest that these dual network gels have promising potential in cartilage repair.

Thiol chitosan-wrapped gold nanoshells for near-infrared laser-induced photothermal destruction of antibiotic-resistant bacteria

Developing new antibacterial nanomaterials and novel therapeutic strategies for the destruction of human pathogenic bacteria that cause infectious diseases is becoming more crucial, because infections caused by antibiotic-resistant bacteria are becoming more and more difficult to be effectively cured with commercially available antibiotics. In this study, we successfully developed new thiol chitosan-wrapped gold nanoshells (TC-AuNSs) as an antibacterial agent for the near-infrared (NIR) laser-triggered photothermal destruction of antibiotic-resistant pathogens, such as Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli), owing to their high water solubility, biocompatibility, strong NIR absorption, and outstanding photothermal properties. More interestingly, TC-AuNSs (115 μg/mL) were capable of completely destroying S. aureus, P. aeruginosa, and E.coli within 5 min of NIR laser irradiation, and no bacterial growth was detected on the tryptic soy agar (TSA) plate after 48 h of laser irradiation, indicating that TC-AuNSs along with laser irradiation are highly efficient and can kill bacteria quickly and prevent bacterial regrowth. We believe that TC-AuNSs deserve much more attention as an antibacterial agent, to be used in effectively combating pathogenic bacteria associated with public health problems and monitoring of environmental pollution for hygiene and safety.

Hyaluronic acid and chitosan-based nanosystems: a new dressing generation for wound care

INTRODUCTION

The main goal in the management of chronic wounds is the development of multifunctional dressings able to promote a rapid recovery of skin structure and function, improving patient compliance.

AREAS COVERED

This review discusses the use of nanosystems, based on hyaluronic acid and chitosan or their derivatives for the local treatment of chronic wounds. The bioactive properties of both polysaccharides will be described, as well as the results obtained in the last decade by the in vitro and in vivo evaluation of the wound healing properties of nanosystems based on such polymers.

EXPERT OPINION

In the last decades, there has been a progressive change in the local treatments of chronic wounds: traditional inert dressings have been replaced by more effective bioactive ones, based on biopolymers taking part in wound healing and able to release the loaded active agents in a controlled way. With the advance of nanotechnologies, the scenario has further changed: nanosystems, characterized by a large area-to-volume ratio, show an improved interaction with the biological substrates, amplifying the activity of the constituent biopolymers. In the coming years, a deeper insight into wound healing mechanisms and the development of new techniques for nanosystem manufacturing will results in the design of new scaffolds with improved performance.

ZnO-NPs embedded biodegradable thiolated bandage for postoperative surgical site infection: In vitro and in vivo evaluation

Post-operative surgical site infections (SSI) present a serious threat and may lead to complications. Currently available dressings for SSI lack mucoadhesion, safety, efficacy and most importantly patient compliance. We aimed to address these concerns by developing a bioactive thiolated chitosan-alginate bandage embedded with zinc oxide nanoparticles (ZnO-NPs) for localized topical treatment of SSI. The FTIR, XRD, DSC and TGA of bandage confirmed the compatibility of ingredients and modifications made. The porosity, swelling index and lysozyme degradation showed good properties for wound healing and biodegradation. Moreover, in-vitro antibacterial activity showed higher bactericidal effect as compared to ZnO-NPs free bandage. In-vivo wound healing in murine model showed significant improved tissue generation and speedy wound healing as compared to positive and negative controls. Over all, thiolated bandage showed potential as an advanced therapeutic agent for treating surgical site infections, meeting the required features of an ideal surgical dressing.

Chitosan-TPP nanoparticles stabilized by poloxamer for controlling the release and enhancing the bioavailability of doxazosin mesylate: in vitro, and in vivo evaluation

Objective: Control the release and enhance the bioavailability of chitosan-doxazosin mesylate nanoparticles (DM-NPs). Significance: Improve DM bioavailability for the treatment of benign prostatic hyperplasia and hypertension. Methods: Plackett-Burman design was utilized to screen the variables affecting the quality of DM-NPs prepared by ionic gelation method. The investigated variables were initial drug load (X₁), chitosan percentage (X₂), tripolyphosphate sodium (TPP) percentage (X₃), poloxamer percentage (X₄), homogenization speed (X₅), homogenization time (X₆) and TPP addition rate (X₇). The prepared DM-loaded NPs have been fully evaluated for particle size (Y₁), Zeta potential (Y₂), production yield (Y₃), entrapment efficiency (Y₄), loading capacity (Y₅), initial burst (Y₆), and cumulative drug release (Y₇). Finally, DM pharmacokinetic has been investigated on healthy albino male rabbits by means of non-compartmental analysis. Results: The combination of variables showed variability of Y₁, Y₂, and Y₃ equal to 122-710 nm, 3.49-23.63 mV, and 47.31-92.96%, respectively. While Y₄ and Y₅, reached 99.87%, and 8.53%, respectively. The prepared NPs revealed that X₂, X₃, and X₄ are the variables that play the important role in controlling the release behavior of DM from the NPs. The in vivo pharmacokinetic results indicated the enhancement in bioavailability of DM by 7 folds compared to drug suspension and the mean residence time prolonged to 23.72 h compared to 4.7 h of drug suspension. Conclusion: The study proved that controlling the release of DM from NPs enhance its bioavailability and improve the compliance of patients with hypertension or benign prostatic hyperplasia.

Disulfide bond reconstruction: A novel approach for grafting of thiolated chitosan onto wool

Chitosan, a natural biopolymer, is used as a multifunctional agent for modification of wool either through chemical crosslinking or physical coating. For the first time, wool fabric has been modified with chitosan through disulfide bond breaking and reforming reactions. The chitosan was thiolated and then grafted onto the reduced wool fibers through disulfide bonds. In order to understand the mechanism of the grafting of thiolated chitosan onto wool, glutathione was used as a model compound for wool in the research. The structures of thiolated chitosan reacted with glutathione and wool fabrics grafted with thiolated chitosan were investigated by FTIR, ¹³CNMR, XPS, XRD, SEM. The dyeability, shrink-resistance and biocompatibility were also tested. The results suggested that glutathione reacted with thiolated chitosan and formed disulfide bond. The thiolated chitosan-grafted wool fabric had good shrink-resistance and dyeability. Hydrophilicity and antibacterial properties were also improved compared with untreated wool fabric. The results provide a novel approach for modification of wool through fiber-intrinsic groups like disulfide bonds.

Carvacrol and linalool co-loaded in β-cyclodextrin-grafted chitosan nanoparticles as sustainable biopesticide aiming pest control

Pesticides are the main tactics for pest control because they reduce the pest population very fast and their efficiency does not depend on abiotic factors. However, the indiscriminate use of these substances can speed up the development of resistant populations and causing environmental contamination. Therefore, alternative methods of pest control are sought, such as the use of botanical compounds. Nanoencapsulation of volatile compounds has been shown to be an important tool that can be used to overcome the lack of stability of these compounds. In this work, we describe the preparation and characterization of chitosan nanoparticles functionalized with β-cyclodextrin containing carvacrol and linalool. The toxicity and biological activity were evaluated. Decreases of toxicity were observed when the compounds were nanoencapsulated. The nanoparticles presented insecticidal activity against the species Helicoverpa armigera (corn earworm) and Tetranychus urticae (spider mite). In addition, repellent activity and reduction in oviposition were observed for the mites.

Synthesis of thiolated arabinoxylan and its application as sustained release mucoadhesive film former

The present work aimed to synthesize thiolated arabinoxylan (TAX), and to evaluate its mucoadhesive potential. Synthesis of TAX was accomplished by esterification of arabinoxylan (AX) with thioglycolic acid (TGA). The appearance of a characteristic peak at 2516 cm^-1 in the FTIR spectrum of TAX, and presence of 6.01 ± 1.03 m moles of thiol per gram of the polymer confirmed successful thiolation of AX. The incorporation of the thiol group considerably promoted mucoadhesive strength of the polymer-viz. 3.99-fold. Moreover, in vivo safety analysis in albino rats revealed TAX to be safe in the concentration range of 750-1000 mg kg^-1 body weight. Synthesized TAX was utilized to prepare Tizanidine HCl (TZN HCl) loaded sustained release (SR) mucoadhesive buccal films using a solvent casting technique. Results proved that the prepared films were of uniform thickness, good mechanical strength (with folding endurance >300), acceptable moisture contents (5%-7%) and surface pH (6.23 ± 0.81 to 6.43 ± 0.49) compatible to that of the buccal cavity. Presence of greater that 90% of drug contents indicated the excellent drug loading ability of the prepared films. Results of in vitro dissolution studies and ex vivo permeation studies conducted respectively by USP dissolution apparatus II and Franz diffusion cell indicated that sustained effect of TAX was achieved for 8 h. These results have conclusively proven that TAX has the potential to improve the bioavailability of TZN HCl due to enhanced mucoadhesion in buccal cavity, hence signifying its suitability as a mucoadhesive buccal film former.

Multimodal tumor-homing chitosan oligosaccharide-coated biocompatible palladium nanoparticles for photo-based imaging and therapy

Palladium, a near-infrared plasmonic material has been recognized for its use in photothermal therapy as an alternative to gold nanomaterials. However, its potential application has not been explored well in biomedical applications. In the present study, palladium nanoparticles were synthesized and the surface of the particles was successfully modified with chitosan oligosaccharide (COS), which improved the biocompatibility of the particles. More importantly, the particles were functionalized with RGD peptide, which improves particle accumulation in MDA-MB-231 breast cancer cells and results in enhanced photothermal therapeutic effects under an 808-nm laser. The RGD peptide-linked, COS-coated palladium nanoparticles (Pd@COS-RGD) have good biocompatibility, water dispersity, and colloidal and physiological stability. They destroy the tumor effectively under 808-nm laser illumination at 2 W cm⁻² power density. Further, Pd@COS-RGD gives good amplitude of photoacoustic signals, which facilitates the imaging of tumor tissues using a non-invasive photoacoustic tomography system. Finally, the fabricated Pd@COS-RGD acts as an ideal nanotheranostic agent for enhanced imaging and therapy of tumors using a non-invasive near-infrared laser.

Thiolated Chitosan Masked Polymeric Microspheres with Incorporated Mesocellular Silica Foam (MCF) for Intranasal Delivery of Paliperidone

In this study, mesocellular silica foam (MCF) was used to encapsulate paliperidone, an antipsychotic drug used in patients suffering from bipolar disorder. MCF with the drug adsorbed was further encapsulated into poly(lactic acid) (PLA) and poly(lactide-co-glycolide) (PLGA) 75/25 w/w microspheres and these have been coated with thiolated chitosan. As found by TEM analysis, thiolated chitosan formed a thin layer on the polymeric microspheres' surface and was used in order to enhance their mucoadhesiveness. These microspheres aimed at the intranasal delivery of paliperidone. The DSC and XRD studies showed that paliperidone was encapsulated in amorphous form inside the MCF silica and for this reason its dissolution profile was enhanced compared to the neat drug. In coated microspheres, thiolated chitosan reduced the initial burst effect of the paliperidone dissolution profile and in all cases sustained release formulations have been prepared. The release mechanism was also theoretically studied and three kinetic models were proposed and successfully fitted for a dissolution profile of prepared formulations to be found.

Nano cellulose dispersed chitosan film with Ag NPs/Curcumin: An in vivo study on Albino Rats for wound dressing

With an aim to develop chitosan film with controllable swelling behavior and maximum antimicrobial efficacy, we hereby report cellulose nano crystals loaded chitosan films with Curcumin/Ag nano particles embedded as strong antimicrobial agents. The CNC had average size of 40-90nm with poly dispersity index of 3.641. The TEM analysis of Ag NPs, produced via DMF reduction, revealed a particle size range of 15-25nm. The Surface Plasmon resonance (SPR) of these Ag NPs shifted from 380 to 440nm, with the increase in concentration of Ag (I). The TGA of the film samples Ch/CNC, and Ch/CNC (Ag₄₆₃/Cur₄₅₀) exhibited% weight loss of around 95 and 80 respectively, thus indicating higher stability due to presence of Ag NPs. In XRD analysis 2θ reflections at 38.12, 44.28 and 66.46°^, confirmed the presence planes (1 1), (2 0) and (2 0) respectively. In skin irritation test, the mean Erythema scores observed after 72h was zero for both the Curcumin and Ag NPs/Curcumin loaded films. The percent wound reduction, observed for the film samples Ch/CNC (Cur₄₅₀) and Ch/CNC (Ag NP₄₆₃/Cur₄₅₀) was 57.8 and 97.2 respectively, indicating better suitability of Ag NPs/Curcumin loaded film.

Fabrication and evaluation of chitosan/NaYF4:Yb3+/Tm3+ upconversion nanoparticles composite beads based on the gelling of Pickering emulsion droplets

The rare earth ion doped upconversion nanoparticles (UCNPs) synthesized by hydrophobic organic ligands possess poor solubility and low fluorescence quantum yield in aqueous media. To conquer this issue, NaYF₄:Yb³⁺/Tm³⁺ UCNPs, synthesized by a hydrothermal method, were coated with F127 and then assembled with chitosan to fabricate the chitosan/NaYF₄:Yb³⁺/Tm³⁺ composite beads (CS/NaYF₄:Yb³⁺/Tm³⁺ CBs) by Pickering emulsion system. The characterization results revealed that the as-synthesized NaYF₄:Yb³⁺/Tm³⁺ UCNPs with an average size of 20nm exhibited spherical morphology, high crystallinity and characteristic emission upconversion fluorescence with an overall blue color output. The NaYF₄:Yb³⁺/Tm³⁺ UCNPs were successfully conjugated on the surface of chitosan beads by the gelling of emulsion droplets. The resultant CS/NaYF₄:Yb³⁺/Tm³⁺ CBs showed good upconversion luminescent property, drug-loading capacity, release performance and excellent biocompatibility, exhibiting great potentials in targeted drug delivery and tissue engineering with potential tracking capability and lasting release performance.

A review on chitosan-cellulose blends and nanocellulose reinforced chitosan biocomposites: Properties and their applications

Chitin is one of the most abundant natural polymers in world and it is used for the production of chitosan by deacetylation. Chitosan is antibacterial in nature, non-toxic, and biodegradable thus it can be used for the production of biodegradable film which is a green alternative to commercially available synthetic counterparts. However, their poor mechanical and thermal properties restricted its wide spread applications. Chitosan is highly compatible with other biopolymers thus its blending with cellulose and/or incorporation of nanofiber isolated from cellulose namely cellulose nanofiber and cellulose nanowhiskers are generally useful. Cellulosic fibers in nano scale are attractive reinforcement in chitosan to produce environmental friendly composite films with improved physical properties. Thus chitosan based composites have wide applicability and potential in the field of biomedical, packaging and water treatment. This review summarises properties and preparation procedure of chitosan-cellulose blends and nano size cellulose reinforcement in chitosan bionanocomposites for different applications.

Polymeric nanoparticles for colon cancer therapy: overview and perspectives

Colorectal cancer (CRC) is the third-most common malignant tumour and is associated with high morbidity and mortality worldwide.

Hydrophobically Modified Keratin Vesicles for GSH-Responsive Intracellular Drug Release

Redox-responsive polymersomes were prepared by self-assembly of a hydrophobically modified keratin and employing a water addition/solvent evaporation method. Polyethylene glycol-40 stearate (PEG40ST) was chosen as hydrophobic block to be coupled to keratin via radical grafting. The amphiphilic polymer exhibited low critical aggregation concentration (CAC; 10 μg/mL), indicating a good thermodynamic stability. The polymeric vesicles loaded both hydrophilic methotrexate and hydrophobic curcumin with high entrapment efficiencies, and showed a GSH-dependent drug release rate. Confocal studies on HeLa cells revealed that the obtained polymersomes were efficiently internalized. Biocompatibility properties of the proposed delivery vehicle were assessed in HET-CAM test and Balb-3T3 mouse fibroblasts. Polymersomes loaded with either methotrexate or curcumin inhibited HeLa and CHO-K1 cancer cells proliferation. Overall, the proposed keratin polymersomes could be efficient nanocarriers for chemotherapeutic agents.

Glucose cryoprotectant affects glutathione-responsive antitumor drug release from polysaccharide nanoparticles

The aim of this work was to prepare polysaccharide-based nanoparticles (NPs) sensitive to glutathione (GSH), and to elucidate the effect of the concentration of glucose used as cryoprotectant during freeze-drying on the GSH-responsiveness. NPs were obtained via ionic interaction between negatively charged polysaccharides, chondroitin sulfate and dermatan sulfate, and the positively charged thiolated chitosan (CSSH), and crosslinking of CSSH before or after the nanoparticles formation with a disulfide-bond containing crosslinker, N,N'-bis(acryloyl)cystamine (BAC). NPs were freeze-dried with glucose at two different concentrations (0.5 and 5.0%w/w) and then characterized as methotrexate delivery systems, studying the effect of GSH concentration on drug release, efficacy against tumor cells and cellular internalization. Non-loaded NPs were highly compatible with murine fibroblasts and showed a suitable size for being used in anticancer therapy. When methotrexate-loaded NPs were freeze-dried with the highest glucose concentration, they lost their responsiveness to GSH concentration in vitro. Drug-loaded NPs were shown to inhibit the growth of tumor cells (HeLa and CHO-K1) with greater efficiency than free methotrexate, disregarding the concentration of glucose used for freeze-drying. Nevertheless, confocal microscopy studies revealed that cellular internalization of NPs freeze-dried with 5.0% glucose is more difficult than for NPs freeze-dried with lower glucose concentration. Thus, concentration of glucose cryoprotectant should be taken into account during development of NPs intended to release the drug as a function of GSH levels, due to the specific interactions of glucose with GSH.

Chitin, chitosan, and its derivatives for wound healing: old and new materials

Chitin (β-(1-4)-poly-N-acetyl-d-glucosamine) is widely distributed in nature and is the second most abundant polysaccharide after cellulose. It is often converted to its more deacetylated derivative, chitosan. Previously, many reports have indicated the accelerating effects of chitin, chitosan, and its derivatives on wound healing. More recently, chemically modified or nano-fibrous chitin and chitosan have been developed, and their effects on wound healing have been evaluated. In this review, the studies on the wound-healing effects of chitin, chitosan, and its derivatives are summarized. Moreover, the development of adhesive-based chitin and chitosan are also described. The evidence indicates that chitin, chitosan, and its derivatives are beneficial for the wound healing process. More recently, it is also indicate that some nano-based materials from chitin and chitosan are beneficial than chitin and chitosan for wound healing. Clinical applications of nano-based chitin and chitosan are also expected.

Exploring the Preparation of Albendazole-Loaded Chitosan-Tripolyphosphate Nanoparticles

The objective of this study was to improve the solubility of albendazole and optimize the preparation of an oral nanoparticle formulation, using β-cyclodextrin (βCD) and chitosan-tripolyphosphate (TPP) nanoparticles. The solubility of albendazole in buffers, surfactants, and various concentrations of acetic acid solution was investigated. To determine drug loading, the cytotoxic effects of the albendazole concentration in human hepatocellular carcinoma cells (HepG2) were investigated. The formulations were prepared by mixing the drug solution in Tween 20 with the chitosan solution. TPP solution was added dropwise with sonication to produce a nanoparticle through ionic crosslinking. Then the particle size, polydispersity index, and zeta potential of the nanoparticles were investigated to obtain an optimal composition. The solubility of albendazole was greater in pH 2 buffer, Tween 20, and βCD depending on the concentration of acetic acid. Drug loading was determined as 100 µg/mL based on the results of cell viability. The optimized ratio of Tween 20, chitosan/hydroxypropyl βCD, and TPP was 2:5:1, which resulted in smaller particle size and proper zeta positive values of the zeta potential. The chitosan-TPP nanoparticles increased the drug solubility and had a small particle size with homogeneity in formulating albendazole as a potential anticancer agent.

Curcumin/cellulose micro crystals/chitosan films: water absorption behavior and in vitro cytotoxicity

A new technique, called vapor induced phase inversion (VIPI), has been employed to fabricate cellulose micro crystals (CMC)-loaded chitosan (Ch) films. The method involves immediate exposure of CMC-dispersed chitosan solution to NH3 gas. The films were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) analysis. The swelling ratio (SR) of films showed negative dependence on the cellulose content in the films. The dynamic water uptake data were interpreted by various kinetic models. Finally, the release of curcumin from the films was investigated. The CMC-loaded chitosan film showed slower release as compared to the plain chitosan film, suggesting that cellulose micro crystals acted as diffusion barrier. The films were non-cytotoxic, non-thrombogenic and non-hemolytic.

Thiomers: A Blessing to Evaluating Era of Pharmaceuticals

Thiomers are the polymers modified for the mucoadhesive properties and other additive properties by incorporating thiol moieties in the backbone of the unmodified polymeric chain by substitution reactions or simple oxidation reactions. Drugs that are less soluble and permeable can be complexed with thiomers for their increased absorption through the mucosal membranes by increase in contact time and prolonged stay in body due to mucoadhesion. Immobilization of thiol group therefore increases the mucoadhesive properties of the modified polymer by 2–140-folds. The prepared thiomers are characterized and made stable by different techniques. Thiomers also give the controlled delivery of the active pharmaceutical ingredients in the body. Different polymers that are modified by thiolation are chitosan, polyacrylic acid, sodium alginate, sodium carboxy methyl cellulose, guar gum, and so forth. Thiomeric formulations are a challenge to deliver drugs with low therapeutic compatibility. Micro- and nanopreparations containing thiomers can be prepared by different techniques such as covalent crosslinking, in situ gelation, radical emulsion polymerization, and emulsification. Nowadays thiomers have wide range of applications as a promising pharmaceutical excipient in the evaluating era of pharmaceutical technology.

Synthesis and Characterization of New Thiolated Chitosan Nanoparticles Obtained by Ionic Gelation Method

We derivatized low molecular weight chitosan (LMWC) with 3-mercaptopropanoic acid (3-MPA) by a coupling reaction. The chemical modification of LMWC was characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance,1HNMR. We researched the influence of 3-MPA on the nanoparticles formation by ionic gelation method using sodium tripolyphosphate (TPP) as cross-linker reagent. In order to optimize the nanoparticles formation, we studied the effect of the pH solution and molar ratio on nanoparticles stability. Analyses of particle size, morphology, and surface charge were determined by dynamic light scattering, Atomic Force Microscopy, and zeta potential, respectively. It was found that formation of semispherical and stable nanoparticles was improved due to the chemical modification of chitosan. Optimized semispherical nanoparticles of thiolated chitosan were synthesized with the parameters (pH 4.7, molar ratios 1 : 106). Additionally, we reported the thermodynamic profile of the nanoparticles formation determined by isothermal titration calorimetry (ITC). The aggregation process achieved to form nanoparticles of thiolated and nonmodified chitosan consisted of two stages, considering one binding site model. Gibbs free energy(ΔG)and binding constant (Ka) describe the aggregation process of thiolated chitosan/TPP, which is an initial reaction and followed by an endothermic stage. These results are promising for the possible application of these nanoparticles as nanocarriers and delivery systems.

Biomimetic multi-layered hollow chitosan–tripolyphosphate rod with excellent mechanical performance

Design of hollow and multi-layered features in chitosan–tripolyphosphate rod and the resulting excellent mechanical performance.

Biocompatibility of a self-assembled glycol chitosan nanogel

The research of chitosan-based nanogel for biomedical applications has grown exponentially in the last years; however, its biocompatibility is still insufficiently reported. Hence, the present work provides a thorough study of the biocompatibility of a glycol chitosan (GC) nanogel. The obtained results showed that GC nanogel induced slight decrease on metabolic activity of RAW, 3T3 and HMEC cell cultures, although no effect on cell membrane integrity was verified. The nanogel does not promote cell death by apoptosis and/or necrosis, exception made for the HMEC cell line challenged with the higher GC nanogel concentration. Cell cycle arrest on G1 phase was observed only in the case of RAW cells. Remarkably, the nanogel is poorly internalized by bone marrow derived macrophages and does not trigger the activation of the complement system. GC nanogel blood compatibility was confirmed through haemolysis and whole blood clotting time assays. Overall, the results demonstrated the safety of the use of the GC nanogel as drug delivery system.

Design, synthesis, fabrication and in vitro evalution of mucoadhesive 5-amino-2-mercaptobenzimidazole chitosan as low water soluble drug carriers

Mucoadhesive thiolated chitosan suitable as a carrier for low water soluble drugs was designed and synthesized by conjugating 5-amino-2-mercaptobenzimidazole (MBI) using methylacrylate (MA) as the linking agent. A 14.4% degree of substitution of MA, as determined by (1)H NMR analysis, and 11.86±0.01μmol thiol groups/g of polymer, as determined by Ellman's method, was obtained. The MBI-MA-chitosan had an 11-fold stronger mucoadhesive property compared to unmodified chitosan at pH 1.2, as determined by the periodic acid: Schiff colorimetric method. Chitosan, MA-chitosan and MBI-MA-chitosan were fabricated as well-formed microspheres using electrospray ionization, including an entrapment efficiency of simvastatin (SV) of over 80% for the MBI-MA-chitosan. The mucoadhesiveness of the SV-loaded MBI-MA-CS microspheres was still higher than that for SV-loaded chitosan at pH 1.2 and 6.4. The SV-loaded MBI-MA-CS microspheres revealed a reduced burst effect and an increased release rate (more than fivefold higher than pure SV) of SV over 12h.

pH-responsive thiolated chitosan nanoparticles for oral low-molecular weight heparin delivery: in vitro and in vivo evaluation

The aim of present study was to investigate a pH-responsive and mucoadhesive nanoparticle system for oral bioavailability enhancement of low-molecular weight heparin (LMWH). The thioglycolic acid (TGA) was first covalently attached to chitosan (CS) with 396.97 ± 54.54 μmol thiol groups per gram of polymer and then the nanoparticles were prepared with thiolated chitosan (TCS) and pH-sensitive polymer hydroxypropyl methylcellulose phthalate (HPMCP) by ionic cross-linking method. The obtained nanoparticles were characterized for the shape, particle size, zeta potential, drug entrapment efficiency and loading capacity. In vitro results revealed the acid stability of pH-responsive nanoparticles, which had a significant control over LMWH release and could effectively protect entrapped drugs in simulated gastric conditions. By the attachment of the thiol ligand, an improvement of permeation-enhancing effect on freshly excised carp intestine (1.86-fold improvement) could be found. The mucoadhesive properties were evaluated using fluorescently labeled TCS or CS nanoparticles. As compared with the controls, a significant improvement of mucoadhesion on rat intestinal mucosa was observed in TCS/HPMCP nanoparticles via confocal laser scanning microscopy. The activated partial thromboplastin time (APTT) was significantly prolonged and an increase in the oral bioavailability of LMWH was turned out to be pronounced after oral delivered LMWH-loaded TCS/HPMCP nanoparticles in rats, which suggested enhanced anticoagulant effects and improved absorption of LMWH. In conclusion, pH-responsive TCS/HPMCP nanoparticles hold promise for oral delivery of LMWH.

In vitro combinatorial anticancer effects of 5-fluorouracil and curcumin loaded N,O-carboxymethyl chitosan nanoparticles toward colon cancer and in vivo pharmacokinetic studies

Colon cancer is the third most leading causes of death due to cancer worldwide and the chemo drug 5-fluorouracil's (5-FU) applicability is limited due to its non-specificity, low bioavailability and overdose. The efficacy of 5-FU in colon cancer chemo treatment could be improved by nanoencapsulation and combinatorial approach. In the present study curcumin (CUR), a known anticancer phytochemical, was used in combination with 5-FU and the work focuses on the development of a combinatorial nanomedicine based on 5-FU and CUR in N,O-carboxymethyl chitosan nanoparticles (N,O-CMC NPs). The developed 5-FU-N,O-CMC NPs and CUR-N,O-CMC NPs were found to be blood compatible. The in vitro drug release profile in pH 4.5 and 7.4 showed a sustained release profile over a period of 4 days. The combined exposure of the nanoformulations in colon cancer cells (HT 29) proved the enhanced anticancer effects. In addition, the in vivo pharmacokinetic data in mouse model revealed the improved plasma concentrations of 5-FU and CUR which prolonged up to 72 h unlike the bare drugs. In conclusion, the 5-FU and CUR released from the N,O-CMC NPs produced enhanced anticancer effects in vitro and improved plasma concentrations under in vivo conditions.