Preparation of biocompatible chitosan grafted poly(lactic acid) nanoparticles

Smart redox-sensitive micelles based on chitosan for dasatinib delivery in suppressing inflammatory diseases

Dasatinib (DAS) exhibits anti-inflammatory effects by retrieving the balance between inflammatory and anti-inflammatory cytokines secreted by macrophages. The aim of this study was the development of redox-responsive micelles with the potential of passive targeting and on-demand drug release for DAS delivery to macrophages. For this purpose, two molecular weights of chitosan (CHIT) were conjugated to DAS at different molar ratios using 3,3'-dithiodipropionic anhydride (DTDPA) as disulfide bond containing linker to synthesize a series of CHIT-S-S-DAS amphiphilic conjugates. Micelles obtained by the sonication method had particle sizes of 129.3-172.2 nm, zeta potentials of +17.5 to +20.9 mV, drug contents of 0.90-7.20 %, CMC values of 35.3-96.6 μg/ml, and exhibited redox-responsive in vitro drug release. Optimized micelles were non-toxic and dramatically more efficient than non-redox responsive micelles in reducing TNF-α and IL-6 and increasing IL-10 secretion from LPS-stimulated RAW264.7 cells. Furthermore, the redox-responsive micelles were able to reduce the mice paw edema, reduce the plasma levels of pro-inflammatory cytokines and increase plasma level of IL-10, considerably more than free DAS and non-redox responsive micelles in carrageenan-induced mice paw edema model of inflammation.

Fabrication and characterization of the H/J-type aggregates astaxanthin/bovine serum albumin/chitosan nanoparticles

Astaxanthin is a natural liposoluble ketocarotenoid with various biological activities. Hydrophobic astaxanthin with C_2h symmetry can self-assembly form H-type aggregates and J-type aggregates in hydrated polar solvents. However, astaxanthin and its aggregates are limited by its water insolubility and chemical instability. Here, the biological macromolecules bovine serum albumin (BSA) and chitosan were chosen as protein-polysaccharides based delivery systems for astaxanthin aggregates by molecular self-assembly method. The precise prepared H-ABC-NPs and J-ABC-NPs suspensions were both near spheres with hydrodynamic size around 281 ± 9 nm and 368 ± 5 nm and zeta potentials around +26 mV and +30 mV, respectively. Two types of astaxanthin aggregates were distinguished, water-dispersible, and stable in nanocarriers through UV-vis spectra observation. The encapsulation efficiency of the astaxanthin in ABC-NPs was above 90 %. Fourier transform infrared spectroscopy (FTIR) and circular dichroism (CD) analyses indicated that the dominant driving forces of ABC-NPs formation mainly included electrostatic, hydrophobic interactions and hydrogen bonding. These results offer an elegant opportunity for the protein-polysaccharides delivery systems, and provide an important perspective for applying novel water-dispersed astaxanthin aggregates products in nutrition and medicine industry.

Development and Characterization of Functional Polylactic Acid/Chitosan Porous Scaffolds for Bone Tissue Engineering

In this study, we developed and characterized various open-cell composite scaffolds for bone regeneration. These scaffolds were made from Polylactic acid (PLA) as the scaffold matrix biopolymeric phase, and chitosan (CS) and chitosan-grafted-PLA (CS-g-PLA) copolymer as the dispersed biopolymeric phase. As a first step, successful grafting of PLA onto CS backbone was executed and confirmed by both FTIR and XPS. Mechanical characterization confirmed that adding CS or CS-g-PLA to the intrinsically rigid PLA made their corresponding PLA/CS and PLA/CS-g-PLA composite scaffolds more flexible under compression. This flexibility was higher for the latter due to the improved compatibility between PLA and CS-g-PLA copolymer. The hydrolytic stability of both PLA/CS and PLA/CS-g-PLA composite scaffolds inside phosphate-buffered saline (PBS) solution, as well as MG-63 osteoblast cell adhesion and proliferation inside both scaffolds, were characterized. The corresponding results revealed that PLA/CS composite scaffolds showed hydrolytic degradation due to the cationic properties of CS. However, modified PLA/CS-g-PLA scaffolds were hydrolytically stable due to the improved interfacial adhesion between the PLA matrix and CS-g-PLA copolymer. Finally, biological characterization was done for both PLA/CS and PLA/CS-g-PLA composite scaffolds. Contrarily to what was observed for uncompatibilized PLA/CS scaffolds, compatibilized PLA/CS-g-PLA scaffolds showed a high MG-63 osteoblast cell proliferation after three and five days of cell culture. Moreover, it was observed that cell proliferation increased with CS-g-PLA content. This suggests that the PLA/CS-g-PLA composite scaffolds could be a potential solution for bone regeneration.

Synthesis and Characterization of Maleic Anhydride-Methyl Methacrylate Co-Monomer Grafted Polyethylene Wax for Hot Waxed Wood Process

The beeswax used in Chinese traditional hot waxed wood technology has several drawbacks, such as high price, scarce resources, and poor heat resistance. To expand the application of hot waxing technology in the field of wood decoration and protection, polyethylene wax was modified by a grafted maleic anhydride-methyl methacrylate co-monomer. A type of modified polyethylene wax with low cost, high melting point, high stability, and strong polarity suitable for hot waxed wood was prepared as a replacement for beeswax. The effects of the grafting conditions on the chemical properties, thermal properties, chemical structure, and crystallization properties of modified polyethylene wax were studied and compared to those of beeswax. The results show that maleic anhydride-methyl methacrylate co-monomer grafting can effectively improve the acid value of polyethylene wax. For the ratio of two monomers of 1/1, the total amount of monomer of 8 wt%, the amount of initiator of 2 wt%, the reaction temperature of 150 °C, and the acid value of modified polyethylene wax was consistent with that of beeswax, realizing the simulation of the main chemical properties of beeswax. The thermal stability and melting temperature of the modified polyethylene wax are significantly higher than those of beeswax, its crystal structure is similar to that of beeswax, and the cyclic anhydride groups and ester groups introduced by co-monomer grafting endow it with polar groups that play an important role in the wood hot waxing process.

The Influence of the Polymer Type on the Quality of Newly Developed Oral Immediate-Release Tablets Containing Amiodarone Solid Dispersions Obtained by Hot-Melt Extrusion

The present study aims to demonstrate the influence of the polymer-carrier type and proportion on the quality performance of newly developed oral immediate-release tablets containing amiodarone solid dispersions obtained by hot-melt extrusion. Twelve solid dispersions including amiodarone and different polymers (PEG 1500, PEG 4000; PEG 8000, Soluplus^®, and Kolliphor^® 188) were developed and prepared by hot-melt extrusion using a horizontal extruder realized by the authors in their own laboratory. Only eleven of the dispersions presented suitable physical characteristics and they were used as active ingredients in eleven tablet formulations that contain the same amounts of the same excipients, varying only in solid dispersion type. The solid dispersions’ properties were established by optical microscopy with reflected light, volumetric controls and particle size evaluation. In order to prove that the complex powders have appropriate physical characteristics for the direct compression process, they were subjected to different analyses regarding their flowability and compressibility behavior. Additionally, the Fourier transform infrared spectroscopy and X-ray diffraction analysis were performed on the obtained solid dispersions. After confirming the proper physical attributes for all blends, they were processed into the form of tablets by direct compression technology. The manufactured tablets were evaluated for pharmacotechnical (dimensions–diameter and thickness, mass uniformity, hardness and friability) and in vitro biopharmaceutical (disintegration time and drug release) performances. Furthermore, the influence of the polymer matrix on their quality was determined. The high differences in flow and compression performances of the solid dispersions prove the relevant influence of the polymer type and their concentration-dependent plasticizing properties. The increase in flowability and compressibility characteristics of the solid dispersions could be noticed after combining them with direct compression excipients owning superior mechanical qualities. The influence of the polymer type is best detected in the disintegration test, where the obtained values are quite different between the studied formulations. The use of PEG 1500 alone or combined in various proportions with Soluplus^® leads to rapid disintegration. In contrast, the mixture of PEG 4000 and Poloxamer 188 in equal proportions determined the increase in disintegration time to 120 s. The use of Poloxamer 188 alone and a 3:1 combination of PEG 4000 and Soluplus^® also generates a prolonged disintegration time for the tablets.

Preparation and Evaluation of Poly(lactic acid)/Poly(vinyl alcohol) Nanoparticles Using the Quality by Design Approach

The aim of the study was to prepare and evaluate the potential use of poly(lactic acid)/poly(vinyl alcohol) (PLA/PVA) nanoparticle formulations as a drug delivery system. The nanoparticle formulations were successfully developed by the double emulsification/solvent evaporation method. The developed formulations were optimized using the quality by design approach of the ICH Q8 (Pharmaceutical Development) guideline. In the studies, the effects of emulsifying devices, evaporation technique, centrifugation effect, and polymer concentrations on the physicochemical parameters of the formulations were investigated to obtain the best results. Furthermore, the prepared formulations were evaluated for clarity, particle size, distribution, zeta potential, surface and morphological features, preparation efficiency, and long-term stability. Based on the obtained results, the nanoparticle formulation containing 12.5% PLA, 1% primer, and seconder PVA has a suitable particle size (181.7 ± 2.194 nm) and distribution (0.104 ± 0.049), zeta potential (-0.88 ± 0.45 mV), and high preparation efficiency (65.38%), and nanoparticles were spherical, had a smooth surface, and were stable up to 12 months. In conclusion, this novel formulation can be used as a potential drug delivery system.

Biophysical properties of electrospun chitosan-grafted poly(lactic acid) nanofibrous scaffolds loaded with chondroitin sulfate and silver nanoparticles

The aim of this work was to study the biophysical properties of the chitosan-grafted poly(lactic acid) (CH-g-PLA) nanofibers loaded with silver nanoparticles (AgNPs) and chondroitin-4-sulfate (C₄S). The electrospun CH-g-PLA:AgNP:C₄S nanofibers were manufactured using the electrospinning technique. The microstructure of the CH-g-PLA:AgNP:C₄S nanofibers was investigated by proton nuclear magnetic resonance (¹H-NMR), scanning electron microscopy (SEM), UV-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), and Fourier transform infrared (ATR-FTIR) spectroscopy. ATR-FTIR and ¹H-NMR confirm the CH grafting successfully by PLA with a substitution degree of 33.4%. The SEM measurement results indicated apparently smooth nanofibers having a diameter range of 340 ± 18 nm with porosity of 89 ± 3.08% and an average pore area of 0.27 μm². UV-Vis and XRD suggest that silver nanoparticles with the size distribution of 30 nm were successfully incorporated into the electrospun nanofibers. The water contact angle of 12.8 ± 2.7° reveals the hydrophilic nature of the CH-g-PLA:AgNP:C₄S nanofibers has been improved by C₄S. The electrospun CH-g-PLA:AgNP:C₄S nanofibers are found to release ions Ag+ at a concentration level capable of rendering an antimicrobial efficacy. Gram-positive bacteria (S.aureus) were more sensitive to CH-g-PLA:AgNP:C₄S than Gram-negative bacteria (E. coli). The electrospun CH-g-PLA:AgNP:C₄S nanofibers exhibited no cytotoxicity to the L-929 fibroblast cells, suggesting cytocompatibility. Fluorescence microscopy demonstrated that C₄S promotes the adhesion and proliferation of fibroblast cells onto electrospun CH-g-PLA:AgNP:C₄S nanofibers.

Crucial Role of PLGA Nanoparticles in Mitigating the Amiodarone-Induced Pulmonary Toxicity

BACKGROUND

Amiodarone (AMD) is a widely used anti-arrhythmic drug, but its administration could be associated with varying degrees of pulmonary toxicity. In attempting to circumvent this issue, AMD-loaded polymeric nanoparticles (AMD-loaded NPs) had been designed.

MATERIALS AND METHODS

AMD was loaded in NPs by the nanoprecipitation method using two stabilizers: bovine serum albumin and Kolliphor® P 188. The physicochemical properties of the AMD-loaded NPs were determined. Among the prepared NPs, two ones were selected for further investigation of spectral and thermal analysis as well as morphological properties. Additionally, in vitro release patterns were studied and kinetically analyzed at different pH values. In vitro cytotoxicity of an optimized formula (NP4) was quantified using A549 and Hep-2 cell lines. In vivo assessment of the pulmonary toxicity on Sprague Dawley rats via histopathological and immunohistochemical evaluations was applied.

RESULTS

The developed NPs achieved a size not more than 190 nm with an encapsulation efficiency of more than 88%. Satisfactory values of loading capacity and yield were also attained. The spectral and thermal analysis demonstrated homogeneous entrapment of AMD inside the polymeric matrix of NPs. Morphology revealed uniform, core-shell structured, and sphere-shaped particles with a smooth surface. Furthermore, the AMD-loaded NPs exhibited a pH-dependent and diffusion-controlled release over a significant period without an initial burst effect. NP4 demonstrated a superior cytoprotective efficiency by diminishing cell death and significantly increasing the IC50 by more than threefold above the pure AMD. Also, NP4 ameliorated AMD-induced pulmonary damage in rats. Significant downregulation of inflammatory mediators and free radicle production were noticed in the NP4-treated rats.

CONCLUSION

The AMD-loaded NPs could ameliorate the pulmonary injury induced by the pure drug moieties. Cytoprotective, anti-fibrotic, anti-inflammatory, and antioxidant properties were presented by the optimized NPs (NP4). Future studies may be built on these findings for diminishing AMD-induced off-target toxicities.

Appraisal of amiodarone-loaded PLGA nanoparticles for prospective safety and toxicity in a rat model

AIMS

Amiodarone (AM) is a highly efficient drug for arrhythmias treatment, but its extra-cardiac adverse effects offset its therapeutic efficacy. Nanoparticles (NPs)-based delivery system could provide a strategy to allow sustained delivery of AM to the myocardium and reduction of adverse effects. The primary purpose was to develop AM-loaded NPs and explore their ameliorative effects versus off-target toxicities.

MATERIALS AND METHODS

Polymeric NPs were prepared using poly lactic-co-glycolic acid and their physicochemical properties were characterized. Animal studies were conducted using a rat model to compare exposure to AM versus that of the AM-loaded NPs. Biochemical evaluation of liver enzymes, lipid profile, and thyroid hormones was achieved. Besides, histopathological changes in liver and lung were studied.

KEY FINDINGS

Under optimal experimental conditions, the AM-loaded NPs had a size of 186.90 nm and a negative zeta potential (-14.67 mV). Biochemical evaluation of AM-treated animal group showed a significant increase in cholesterol, TG, LDL, T4, and TSH levels (ρ < 0.05). Remarkably, the AM-treated group exhibited a significant increase of liver enzymes (ρ < 0.05) coupled with an obvious change in liver architecture. The AM-loaded NPs displayed a reduction of liver damage and enzyme levels. Lung sections of the AM-treated group demonstrated thickening of interalveolar septa, mononuclear cellular infiltration with congested blood vessels, and heavy collagenous fibers deposition. Conversely, less cellular infiltration and septal thickening were observed in the animal lungs treated with the AM-loaded NPs-treated.

SIGNIFICANCE

Our findings demonstrate the competence of the AM-loaded NPs to open several exciting avenues for evading the AM-induced off-target toxicities.

Chitosan/carboxymethylcellulose-stabilized poly(lactide-co-glycolide) particles as bio-based drug delivery carriers

Poly(lactide-co-glycolide) (PLGA) colloidal particles stabilized by complexes of two oppositely charged polysaccharides, chitosan (cationic, CS) and sodium carboxymethylcellulose (anionic, NaCMC), were fabricated. Dichloromethane containing dissolved PLGA was first emulsified in an aqueous phase containing mixtures of CS and NaCMC. Evaporation of dichloromethane from the resulting emulsion led to CS/NaCMC-covered-PLGA particles. CS and NaCMC contents affected the short-term stability of PLGA particles and also their intrinsic characteristics. The particles displayed pH-dependent characteristic. Zeta potential varied from +54 to -50 mV when pH was varied from 3 to 10. CS/NaCMC-covered-PLGA particles showed colloidal stability, over a wider pH range as compared to CS-covered-PLGA particles. Curcumin, a model hydrophobic drug, was encapsulated into the particles up to 10 wt% of PLGA. The CS/NaCMC-covered-PLGA particles loaded with curcumin showed delayed release in mildly acidic conditions and faster release in neutral and basic conditions. Cytotoxicity experiments were carried out with human colorectal carcinoma cells.

Self-assembling cashew gum-graft-polylactide copolymer nanoparticles as a potential amphotericin B delivery matrix

Amphotericin B is an antibiotic used in the treatment of fungal disease and leishmania; however, it exhibits side effects to patients, hindering its wider application. Therefore, nanocarriers have been investigated as delivery systems for amphotericin B (AMB) in order to decrease its toxicity, besides increase bioavailability and solubility. Amphiphilic copolymers are interesting materials to encapsulate hydrophobic drugs such as AMB, hence copolymers of cashew gum (CG) and l-lactide (LA) were synthesized using two different CG:LA molar ratios (1:1 and 1:10). Data obtained revealed that copolymer nanoparticles present similar figures for particle sizes and zeta potentials; however, particle size of encapsulated AMB increases if compared to unloaded nanoparticles. The 1:10 nanoparticle sample has better stability although higher polydispersity index (PDI) if compared to 1:1 sample. High amphotericin (AMB) encapsulation efficiencies and low hemolysis were obtained. AMB loaded copolymers show lower aggregation pattern than commercial AMB solution. AMB loaded nanoparticles show antifungal activities against four C. albicans strains. It can be inferred that cashew gum/polylactide copolymers have potential as nanocarrier systems for AMB.

Synthesis and quantitative analyses of acrylamide-grafted poly(lactide-co-glycidyl methacrylate) amphiphilic copolymers for environmental and biomedical applications

Bio-degradable/bio-compatible poly(lactide-co-glycidyl methacrylate), P(LA-co-GMA), a copolymer has been synthesized. The material contains curable CC groups, which enable its self-curing and grafting reactions with other vinyl monomers. The copolymer was grafted with a pH-responsive polyacrylamide (PAAm), by UV-assisted reactions using acrylamide (AAm) and N,N'-methylene bisacrylamide monomers, and various photoinitiator systems. The original copolymer and its partially-cured counterpart were employed in the grafting reaction. Chemical structures and properties of the resulting materials were characterized. Standard quantitative analysis techniques for measurement of the grafted AAm content and the degree of CC conversion have been developed by ¹H NMR and FTIR spectroscopy. FTIR offers more advantages, in terms of non-destructive analysis, ease of operation, and lower cost of analysis. The results show that the grafted products from pre-cured P(LA-co-GMA) copolymers contain higher grafted AAm contents than their uncured counterparts. The highest grafted AAm content was obtained by using benzophenone (BP) as an initiator, while camphorquinone (CQ) led to the lowest content. In contrast, the degree of CC conversion of the copolymer from the two initiator systems shows a reverse trend. These amphiphilic and pH-responsive grafted copolymers with tunable AAm contents have a high potential for use in various applications, especially in biomedical and environmental fields.

Gadolinium-doped mesoporous calcium silicate/chitosan scaffolds enhanced bone regeneration ability

Chitosan (CTS) and mesoporous calcium silicate (MCS) have been developed for bone defect healing; however, their bone regeneration capacity still does not satisfy the patients with bone diseases. Gadolinium (Gd) is accumulated in human bones, and plays a beneficial role in regulating cell performance and bone regeneration. We firstly constructed Gd-doped MCS/CTS (Gd-MCS/CTS) scaffolds by a lyophilization technology. The interconnected arrangement of CTS films lead to forming macropores by using ice crystals as templates during the lyophilization procedure, and the Gd-MCS nanoparticles dispersed uniformly on the macropore walls. The biocompatible chemical components and hierarchical pores facilitated the attachment and spreading of rat bone marrow-derived mesenchymal stem cells (rBMSCs). Interestingly, the Gd dopants in the scaffolds effectively activated the Wnt/β-catenin signaling pathway, resulting in excellent cell proliferation and osteogenic differentiation capacities. The osteogenic-related genes such as alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2) and collagen type1 (COL-1) were remarkably up-regulated by Gd-MCS scaffolds as compared with MCS scaffolds, and their expression levels increased in a positive correlation with Gd doping amounts. Moreover, in vivo rat cranial defect tests further confirmed that Gd-MCS/CTS scaffolds significantly stimulated collagen deposition and new bone formation. The exciting finding suggested the beneficial effects of Gd³⁺ ions on osteogenic differentiation and new bone regeneration, and Gd-MCS/CTS scaffolds can be employed as a novel platform for bone defect healing.

3D Printed scaffolds with hierarchical biomimetic structure for osteochondral regeneration

Osteochondral defects resulting from trauma and/or pathologic disorders are critical clinical problems. The current approaches still do not yield satisfactory due to insufficient donor sources and potential immunological rejection of implanted tissues. 3D printing technology has shown great promise for fabricating customizable, biomimetic tissue matrices. The purpose of the present study is to investigate 3D printed scaffolds with biomimetic, biphasic structure for osteochondral regeneration. For this purpose, nano-hydroxyapatite and transforming growth factor beta 1 nanoparticles were synthesized and distributed separately into the lower and upper layers of the biphasic scaffold, which was fabricated using 3D stereolithography printer. Our results showed that this scaffold design successfully promoted osteogenic and chondrogenic differentiation of human bone marrow mesenchymal stem cells, as well as enhanced gene expression associated with both osteogenesis and chondrogenesis alike. The finding demonstrated that 3D printed osteochondral scaffolds with biomimetic, biphasic structure are excellent candidates for osteochondral repair and regeneration.

Super-hydrophilic and high strength polymeric foam dressings of modified chitosan blends for topical wound delivery of chloramphenicol

In the present study polymer blends based on chitosan (CS) and its derivatives with trans-aconitic (t-Acon) acid and another with trimellitic (TRM) anhydride, were prepared for topical wound delivery of chloramphenicol (CHL). FT-IR spectroscopy revealed the successful grafting of t-Acon acid or TRM anhydride into CS macromolecules at molar ratios 1:1 and 1:0.5, while powder X-ray diffraction (XRD) analysis showed that the prepared materials were amorphous. Neat chitosan and its grafted derivatives were mixed in different ratios (25/75, 50/50 and 75/25 w/w) in order to prepare suitable blends. Scanning electron microscopy (SEM) showed that the formed blends after freeze-drying had a sponge-like structure, while thermogravimetric analysis (TGA) verified their thermal stability. All blends are miscible in studied compositions and have extensive swelling and much better mechanical properties than neat CS. In a further step, the obtained porous sponges prepared from CS/CS-derivatives 50/50 w/w were loaded with Chloramphenicol (10, 20 and 30 wt%), a broad-spectrum antibiotic, and the prepared dressings were evaluated in terms of FT-IR, XRD, SEM, and in vitro drug dissolution. An initial burst release followed by a quasi-Fickian diffusion driven sustained release phase was observed while the addition of chloramphenicol gives high antimicrobial properties to all dressings.

Fabrication and in vitro behavior of dual-function chitosan/silver nanocomposites for potential wound dressing applications

We report the synthesis and in vitro evaluation of dual-function chitosan-silver nanoparticles (CTS-AgNPs) films with potential applications as wound dressings. We attempted to formulate nanocomposite films with appropriate AgNPs concentrations to simultaneously display antibacterial activity and suitability for cell culture. Nanocomposites were obtained by CTS-mediated in situ chemical reduction of AgNO₃. Circular-shape AgNPs (sizes ca. 7-50 nm) well distributed within the CTS matrices were obtained in concentrations from 0.018 to 0.573 wt%. Efficacy (bacteriostatic and bactericidal properties) of CTS-AgNPs films to decrease planktonic and biofilm bacterial growth was AgNPs concentration- and bacteria strain-dependent. Films showed significant antibacterial activity against Gram-negative E. coli and P. aeruginosa and Gram-positive S. aureus. Antibacterial activity against S. epidermidis was moderated. Films suitability for cell culture was characterized using primary human fibroblasts (HF). HF displayed cell viability higher than 90% and the characteristic fusiform morphology of adhered fibroblast upon culture on films with AgNPs concentration ≤ 0.036 wt%. HF cultured on these films also showed positive expression of tropoelastin, procollagen type I and Ki-67, characteristic proteins of extracellular matrix and proliferative cells, respectively. In vitro assays demonstrated that cytocompatibility/antibacterial properties decreased/increased as silver concentration increased, suggesting that CTS-AgNPS nanocomposite films with ≈0.04-0.20 wt% might be considered as potential temporary dual-function wound dressings.

Chitosan/gelatin as a new nano-carrier system for calcium hydroxide delivery in endodontic applications: Development, characterization and process optimization

The main aim of this study is preparation, optimization and in vitro characterization of Chitosan/Gelatin nano-carriers (NCs) for calcium hydroxide (CH) to improve its therapeutic potential. The designed system can be used in the endodontic applications demanding a sustained release of calcium and hydroxyl ions. Modeling and optimization of CH loaded polymeric NCs were performed using response surface methodology (RSM) based on central composite surface statistical design. The effect of Chitosan concentration (0.1-1% w/v), Gelatin concentration (0.1-1% w/v) and CH concentration (0.05-0.4% w/v) on the particle size, polydispersity index (PDI), drug loading (DL) and encapsulation efficiency (EE) of CH loaded polymeric NCs were investigated. Optimized CH loaded polymeric NCs formulation which obtained using RSM showed spherical and smooth surface with a particle size of 292 nm, PDI of 0.32, DL of 88.8% and EE of 99%. Optimized formulation was evaluated for in vitro calcium ion release in phosphate buffer solution (PBS) at pH 7.4 for 14 days. The presence of hydrogen bonding and some intermolecular interactions between Chitosan/Gelatin polymeric materials were confirmed using Fourier transform infrared (FTIR) analysis. These interactions enable Chitosan/Gelatin NCs to load CH and maintain sustained release of Calcium ions from CH during experimental period.

Fabrication of aqueous nanodispersion from natural DNA and chitosan as eminent carriers for water-insoluble bioactives

For high-valued application of natural DNA as raw materials, we prepared nanocarriers by using salmon sperm DNA and chitosan to encapsulate water-insoluble bioactives. Here, water dispersible astaxanthin/DNA/chitosan nano-aggregates (ADC-NAs) were prepared by co-assemble evaporation method. The key point for preparing well formed ADC-NAs was specifically discussed. The resultant ADC-NAs were spherical with 100-300 nm diameter measured by dynamic light scattering (DLS) and transmission electron microscopy (TEM), and their homogeneous dispersions were sufficiently stable at room temperature. One important feature of these nanocarriers is enormously high loading amount of cargo (about 40 wt%). According to the UV-Vis spectra of the nanosuspension, we deduced that astaxanthin was encapsulated as uniquely structured J-aggregates. Fourier transform infra-red (FTIR) spectroscopy proved fabrication was successfully and astaxanthin was embedding in DNA/chitosan nanocarriers. Cytotoxicity was examined in vitro using cell culture in L929 cell lines. When necessary, these nano-aggregates can be degraded by DNase I. Homogeneous dispersions of other non-charged guest molecules are also prepared by using DNA/chitosan nanocarriers. These dispersions are cheaply and easily obtainable from naturally occurring DNA and chitosan, and should be useful for versatile applications.

Application of response surface methodology to tailor the surface chemistry of electrospun chitosan-poly(ethylene oxide) fibers

Chitosan is a promising biocompatible polymer for regenerative engineering applications, but its processing remains challenging due to limited solubility and rigid crystalline structure. This work represents the development of electrospun chitosan/poly(ethylene oxide) blend nanofibrous membranes by means of a numerical analysis in order to identify and tailor the main influencing parameters with respect to accessible surface nitrogen functionalities which are of importance for the biological activity as well as for further functionalization. Depending on the solution composition, both gradient fibers and homogenous blended fiber structures could be obtained with surface nitrogen concentrations varying between 0 and 6.4%. Response surface methodology (RSM) revealed chitosan/poly(ethylene oxide) ratio and chitosan molecular weight as the main influencing factors with respect to accessible nitrogen surface atoms and respective concentrations. The model showed good adequacy hence providing a tool to tailor the surface properties of chitosan/poly(ethylene oxide) blends by addressing the amount of accessible chitosan.

Quantitative Analysis of Polyacrylamide Grafted on Polylactide Film Surfaces Employing Spectroscopic Techniques

Standard techniques for quantitative measurement of polyacrylamide (PAm) contents grafted on polylactide (PLA) film substrates, P(LA- g-Am- co-MBAm), which are commonly used as cell culture substrates or scaffolds, and pH-sensitive absorbents have been developed with X-ray photoelectron (XPS), proton-nuclear magnetic resonance (¹H-NMR), and Fourier transform infrared (FT-IR) spectroscopy. The techniques are then applied to examine P(LA- g-Am- co-MBAm) samples prepared from two separate photo-initiator/co-initiator systems. Efficiency and accuracy of the techniques are compared. The results from all techniques are in good agreement, indicating high analysis precisions, although FT-IR technique provides additional advantages, in terms of short analysis time, ease of sample preparation, and accessibility of a machine. The results indicate that the riboflavin (RF) initiator system has higher grafting efficiency than its camphorquinone (CQ) counterpart. These standard techniques can be applied in the analysis of these materials and further modified for quantitative analysis of other grafting systems.

PAA-g-PLA amphiphilic graft copolymer: synthesis, self-assembly, and drug loading ability

This article reports the synthesis of a PAA-g-PLA amphiphilic polymer by the combination of RAFT polymerization and organocatalytic ROP, which could self-assemble into spheres in aqueous media for sustained release of doxorubicin.

Synthesis of an amphiphilic graft copolymer bearing a hydrophilic poly(acrylate acid) backbone for drug delivery of methotrexate

This article reports the synthesis of a PAA-g-PLA amphiphilic graft polymer, which could self-assemble into large compound micelles in aqueous media for sustained release of MTX.

pH-Responsive Polyethylene Glycol Monomethyl Ether-ε-Polylysine-G-Poly (Lactic Acid)-Based Nanoparticles as Protein Delivery Systems

The application of poly(lactic acid) for sustained protein delivery is restricted by the harsh pH inside carriers. In this study, we synthesized a pH-responsive comb-shaped block copolymer, polyethylene glycol monomethyl ether-ε-polylysine-g-poly (lactic acid) (PEP)to deliver protein (bovine serum albumin (BSA)). The PEP nanoparticles could automatically adjust the internal pH to a milder level, as shown by the quantitative ratio metric results. The circular dichroism spectra showed that proteins from the PEP nanoparticles were more stable than those from poly(lactic acid) nanoparticles. PEP nanoparticles could achieve sustained BSA release in both in vitro and in vivo experiments. Cytotoxicity results in HL-7702 cells suggested good cell compatibility of PEP carriers. Acute toxicity results showed that the PEP nanoparticles induced no toxic response in Kunming mice. Thus, PEP nanoparticles hold potential as efficient carriers for sustained protein release.

Low toxicity and long circulation time of polyampholyte-coated magnetic nanoparticles for blood pool contrast agents

Polyampholyte-coated (poly(acrylic acid) (PAA)-co-3-(diethylamino)-propylamine (DEAPA)) magnetite nanoparticles (PAMNPs) have been prepared as contrasting agent used in magnetic resonance imaging (MRI). Excellent biocompatibility is required for contrasting agents used in high-resolution magnetic resonance angiography. To evaluate the biocompatibility of PAMNPs, some experiments have been conducted. The hemolysis, plasma recalcification, dynamic blood clotting, prothrombin time, inflammatory cytokine release and complement system activation assays were carried out to investigate the hemocompatibility. To evaluate the toxicity to vessel, MTT test and vascular irritation tests were conducted. Tissue toxicity test was also performed to investigate the biocompability in vivo. We also looked into the biodistribution. The results showed that PAMNPs at the working concentration (0.138 mM) present similar hemocompatibility with negative control, thus have no significant effect to vessels. PAMNPs were mainly distributed in the liver and the blood. The circulation time in blood was considerably long, with the half-time of 3.77 h in plasma. This property is advantageous for PAMNPs' use in angiography. PAMNPs could be metabolized rapidly in mice and were not observed to cause any toxic or adverse effect. In short, these results suggest that the PAMNPs have great potential to serve as safe contrast agents in magnetic resonance imaging (MRI).

PLA architectures: the role of branching

Biobased and biodegradable polymers have become more and more interesting in view of waste management and crude oil depletion.

Antimicrobial activity of chitosan derivatives containing N-quaternized moieties in its backbone: a review

Chitosan, which is derived from a deacetylation reaction of chitin, has attractive antimicrobial activity. However, chitosan applications as a biocide are only effective in acidic medium due to its low solubility in neutral and basic conditions. Also, the positive charges carried by the protonated amine groups of chitosan (in acidic conditions) that are the driving force for its solubilization are also associated with its antimicrobial activity. Therefore, chemical modifications of chitosan are required to enhance its solubility and broaden the spectrum of its applications, including as biocide. Quaternization on the nitrogen atom of chitosan is the most used route to render water-soluble chitosan-derivatives, especially at physiological pH conditions. Recent reports in the literature demonstrate that such chitosan-derivatives present excellent antimicrobial activity due to permanent positive charge on nitrogen atoms side-bonded to the polymer backbone. This review presents some relevant work regarding the use of quaternized chitosan-derivatives obtained by different synthetic paths in applications as antimicrobial agents.

Progress in the characterization of bio-functionalized nanoparticles using NMR methods and their applications as MRI contrast agents

Significant progress has been made over the last three decades in the field of NMR, a technique which has proven to have a variety of applications in many scientific disciplines, including nanotechnology. Herein we describe how NMR enables the characterization of nanosystems at different stages of their formation and modification (raw materials, bare or functionalized nanosystems), even making it possible to study in vivo nanoparticle interactions, thereby importantly contributing to nanoparticle design and subsequent optimization. Furthermore, the unique characteristics of nanosystems can open up new prospects for site-targeted, more specific contrast agents, contributing to the development of certain nuclear magnetic resonance applications such as MRI.

Self-aggregated nanoparticles based on amphiphilic poly(lactic acid)-grafted-chitosan copolymer for ocular delivery of amphotericin B

Background

The purpose of this study was to develop a self-aggregated nanoparticulate vehicle using an amphiphilic poly(lactic acid)-grafted-chitosan (PLA-g-CS) copolymer and to evaluate its potential for ocular delivery of amphotericin B.

Methods

A PLA-g-CS copolymer was synthesized via a “protection-graft-deprotection” procedure and its structure was confirmed by Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance, and X-ray diffraction spectra. Amphotericin B-loaded nanoparticles based on PLA-g-CS (AmB/PLA-g-CS) were prepared by the dialysis method and characterized for particle size, zeta potential, and encapsulation efficiency. Studies of these AmB/PLA-g-CS nanoparticles, including their mucoadhesive strength, drug release properties, antifungal activity, ocular irritation, ocular pharmacokinetics, and corneal penetration were performed in vitro and in vivo.

Results

Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance, and X-ray diffraction spectra showed that the PLA chains were successfully grafted onto chitosan molecules and that crystallization of chitosan was suppressed. The self-aggregated PLA-g-CS nanoparticles had a core-shell structure with an average particle size of approximately 200 nm and zeta potentials higher than 30 mV. Amphotericin B was incorporated into the hydrophobic core of the nanoparticles with high encapsulation efficiency. Sustained drug release from the nanoparticles was observed in vitro. The ocular irritation study showed no sign of irritation after instillation of the PLA-g-CS nanoparticles into rabbit eyes. The minimal inhibitory concentration of the AmB/PLA-g-CS nanoparticles showed antifungal activity similar to that of free amphotericin B against Candida albicans. The in vivo ocular pharmacokinetic study suggested that the PLA-g-CS nanoparticles have the advantage of prolonging residence time at the ocular surface. The corneal penetration study showed that the PLA-g-CS nanoparticles could penetrate into the cornea.

Conclusion

Our results suggest that this nanoparticulate vehicle based on a PLA-g-CS copolymer might be a promising system for effective ocular delivery of amphotericin B.