Preparation and properties of ionically cross‐linked chitosan nanoparticles

Chitosan nanoparticles were fabricated by a method of tripolyphosphate (TPP) cross‐linking. The influence of fabrication conditions on the physical properties and drug loading and release properties was investigated by transmission electron microscopy (TEM), dynamic light scattering (DLS), and UV–vis spectroscopy. The nanoparticles could be prepared only within a zone of appropriate chitosan and TPP concentrations. The particle size and surface zeta potential can be manipulated by variation of the fabrication conditions such as chitosan/TPP ratio and concentration, solution pH and salt addition. TEM observation revealed a core–shell structure for the as‐prepared nanoparticles, but a filled structure for the ciprofloxacin (CH) loaded particles. Results show that the chitosan nanoparticles were rather stable and no cytotoxicity of the chitosan nanoparticles was found in an in vitro cell culture experiment. Loading and release of CH can be modulated by the environmental factors such as solution pH and medium quality. Copyright © 2008 John Wiley & Sons, Ltd.     

Enhanced two-photon singlet oxygen generation by photosensitizer-doped conjugated polymer nanoparticles

We have prepared photosensitizer-doped conjugated polymer nanoparticles by using a reprecipitation method. The conjugated polymer, poly[9,9-dibromohexylfluorene-2,7-ylenethylene-alt-1,4-(2,5-dimethoxy)phenylene] (PFEMO), was used as the host matrix to disperse tetraphenylporphyrin (TPP). These TPP-doped PFEMO nanoparticles are stable and have a uniform size of ～50 nm. Efficient intraparticle energy transfer from PFEMO to TPP has been observed. The TPP emission of the nanoparticles was found to be enhanced by 21-fold by PFEMO under two-photon excitation. Enhanced two-photon excitation singlet oxygen generation efficiency in the TPP-doped PFEMO nanoparticles has been demonstrated. Our results suggest that these photosensitizer-doped conjugated polymer nanoparticles can act as novel photosensitizing agents for two-photon photodynamic therapy and related applications.     

Modulation of surface charge, particle size and morphological properties of chitosan-TPP nanoparticles intended for gene delivery

This work investigates the polyanion initiated gelation process in fabricating chitosan-TPP (tripolyphosphate) nanoparticles in the size range of 100-250 nm intended to be used as carriers for the delivery of gene or protein macromolecules. It demonstrates that ionic gelation of cationic chitosan molecules offers a flexible and easily controllable process for systematically and predictably manipulating particle size and surface charge which are important properties in determining gene transfection efficacy if the nanoparticles are used as non-viral vectors for gene delivery, or as delivery carriers for protein molecules. Variations in chitosan molecular weight, chitosan concentration, chitosan to TPP weight ratio and solution pH value were examined systematically for their effects on nanoparticle size, intensity of surface charge, and tendency of particle aggregation so as to enable speedy fabrication of chitosan nanoparticles with predetermined properties. The chitosan-TPP nanoparticles exhibited a high positive surface charge across a wide pH range, and the isoelectric point (IEP) of the nanoparticles was found to be at pH 9.0. Detailed imaging analysis of the particle morphology revealed that the nanoparticles possess typical shapes of polyhedrons (e.g., pentagon and hexagon), indicating a similar crystallisation mechanism during the particle formation and growth process. This study demonstrates that systematic design and modulation of the surface charge and particle size of chitosan-TPP nanoparticles can be readily achieved with the right control of critical processing parameters, especially the chitosan to TPP weight ratio.     

Chitosan nanoparticles of 5-fluorouracil for ophthalmic delivery: characterization, in-vitro and in-vivo study

The aim of this investigation was to develop 5-fluorouracil (5-FU) loaded chitosan nanoparticles (CH-DNPs) for ophthalmic delivery. CH-DNPs were fabricated by ionotropic gelation mechanism using chitosan (CH) and a polyanion (TPP). The nanoparticles were smooth and spherical, confirmed by scanning electron microscopy (SEM) and atomic force microscope (AFM). CH/TPP mass ratio and TPP significantly changed the particles size morphology and encapsulation efficiency. The nanoparticles size ranged from approximately 114 to 192 nm and had a positive zeta potential (30±4 mV). The encapsulation efficiency, loading capacity and recovery of DNPs were 8.12-34.32%, 3.14-15.24% and 24.22 to 67% respectively. Physical characterization was done by Fourier transform infrared (FT-IR) and X-ray diffraction (XRD). No interaction was observed in between drug and polymer and crystallinity of drug was not changed in drug loaded nanoparticles. In-vitro release study of DNPs showed diffusion controlled release. Bioavailability study of batch CS9 was studied in rabbit eye and compare to 5-FU solution. 5-FU level was significantly higher in aqueous humor of rabbit eye. Ocular tolerance was studied in the eye of New Zealand rabbits and tested formulation was non-irritant with no sign of inflammation.     

Effects of ionic strength on the size and compactness of chitosan nanoparticles

In this work, chitosan nanoparticles were prepared by ionotropic gelation of chitosan with tripolyphosphate (TPP). The effects of the ionic strength of the solvent employed in the particle preparation on the average size and compactness of the particles were investigated. In addition, the effects of the chitosan concentration and the crosslinker to polymer ratio on the particle characteristics were studied. The chitosan–TPP nanoparticles were characterized by dynamic light scattering, zeta potential, and turbidity measurements. The compactness of the nanoparticles was estimated with a method based on the size of the nanoparticles and the turbidity of the nanoparticle suspension. All the investigated preparation parameters, i.e., the ionic strength of the solvent, the chitosan concentration, and the TPP to chitosan ratio, affected the particle characteristics. For instance, smaller and more compact particles were formed in saline solvents, compared to particles formed in pure water. Further, the addition of monovalent salt rendered it possible to prepare particles in the nanometer size range at a higher polymer concentration. Solvent salinity is thus an important parameter to address in the preparation of chitosan nanoparticles crosslinked with TPP.     

肝靶向甘草次酸修饰的壳聚糖纳米粒子的合成和表征

合成了修饰甘草次酸的壳聚糖(GA-CTS), 采用离子交联法制备了GA-CTS纳米粒子. 该材料可能具有肝细胞主动靶向作用, 为进一步的肝靶向药物控释的研究奠定了基础.     

Novel nanoparticles composed of chitosan and β-cyclodextrin derivatives as potential insoluble drug carrier

This research was aim to develop novel cyclodextrin/chitosan(CD/CS) nanocarriers for insoluble drug delivery through the mild ionic gelation method previously developed by our lab. A series of different bcyclodextrin(β-CD) derivatives were incorporated into CS nanoparticles including hydroxypropyl-bcyclodextrin(HP-β-CD), sulphobutylether-β-cyclodextrin(SB-β-CD), and 2,6-di-O-methy-β-cyclodextrin(DM-β-CD). Various process parameters for nanoparticle preparation and their effects on physicochemical properties of CD/CS nanoparticles were investigated, such as the type of CD derivatives,CD and CS concentrations, the mass ratio of CS to TPP(CS/TPP), and p H values. In the optimal condition,CD/CS nanoparticles were obtained in the size range of 215–276 nm and with the zeta potential from30.22 m V to 35.79 m V. Moreover, the stability study showed that the incorporation of CD rendered the CD/CS nanocarriers more stable than CS nanoparticles in PBS buffer at p H 6.8. For their easy preparation and adjustable parameters in nanoparticle formation as well as the diversified hydrophobic core of CD derivatives, the novel CD/CS nanoparticles developed herein might represent an interesting and versatile drug delivery platform for a variety of poorly water-soluble drugs with different physicochemical properties.     

壳聚糖纳米粒子荧光探针的制备和表征

通过低分子量的壳聚糖(LCS)聚阳离子与三聚磷酸钠(TPP)的静电作用制备纳米级壳聚糖微球,并利用壳聚糖链上丰富的氨基与荧光素异硫氰酸酯(FITC)反应从而制备纳米壳聚糖微球荧光探针(NFCS)。结果表明,当壳聚糖分子量为60000,LCS与TPP的质量比为6∶1时,可得到粒度均一的球形纳米粒子,平均粒径为40±3 nm。荧光倒置显微镜观察证实FITC结合到壳聚糖微球上。荧光光谱分析显示NFCS的最大激发波长、最大发射波长与游离态FITC无显著差异。光漂白实验证实NFCS的稳定性比游离态FITC有显著提高。     

Chitosan nanoparticles crosslinked by glycidoxypropyltrimethoxysilane for pH triggered release of protein

pH-responsive-chitosan nanoparticles for the control release of protein drug were prepared by combining two-step crosslinking method,in which chitosan was subsequently crosslinked by sodium tripolyphosphate(TPP)and glycidoxypropyltrimethoxysilane (GPTMS).Compared with TPP crosslinked chitosan particles,the two-step crosslinked nanoparticles were not only pH-responsive but also more stable in wide pH range.Fluorescein isothiocyanate(FITC)labeled anti-human-IgG antibody was used as a model protein drug for...     

Synthesis, structure, and unusual reactivity of beta-halovinyl cobalt porphyrin complexes

The preparation, structures, and reactivity of tetraphenylporphyrin (TPP) cobalt halovinyl complexes are reported. Beta-halovinyl complexes of (TPP)Co(E-CHCHX) (X = Br and I) were prepared from the insertion of acetylene into the cobalt halide bonds of the corresponding halide complexes. The reactivity of these compounds and of the previously reported (TPP)Co(E-CHCHCl), was studied in depth, and it was found that complex reactivity increased with the leaving group ability of the halide. A trans-dichlorovinyl cobalt porphyrin complex, (TPP)Co(Z-CClCHCl), was also prepared through the reaction of (TPP)CoNa and TCE. The structures of (TPP)Co(E-CHCHBr), (TPP)Co(Z-CClCHCl), and (TPP)Co(C(2)H) are reported. The C-C bond length of the vinyl group was found to vary for the beta-halovinyl complexes (TPP)Co(E-CHCHX) from 1.211 A for X = Br to 1.234 A for X = Cl and 1.320 A for (TPP)Co(Z-CClCHCl). A comparison of these structures to many chlorovinyl cobalt complexes shows that trans-2-halo substitution results in a dramatically decreased vinyl C-C bond length. The mechanism of halide substitution for the beta-halovinyl complexes was investigated with kinetic experiments that indicated a dissociative mechanism and supported the intermediacy of a cobalt acetylene complex.     

Chitosan and silver nanoparticles as pudding with raisins with antimicrobial properties

Chitosan nanoparticles (CS-NP) containing small silver nanoparticles are reported (Ag@CS-NP). CS-NP was synthesized using tripolyphosphate (TPP) as a polyanionic template. TPP also served to electrostatically attract Ag(+) inside CS-NP, where it was reduced by the terminal glucosamine units of the biopolymer. This procedure is environmental friendly, inexpensive, and permits the synthesis of very small AgNP (0.93-1.7 nm), with only a discrete dependence from the amount of silver nitrate used (5-200mg). The obtained hybrid nanocomposites Ag@CS-NP were characterized by DLS, HRTEM, and HAADF-STEM presenting a mean hydrodynamic diameter of 78 nm. The antimicrobial activity of Ag@CS-NP against Candida glabrata, Sacharomyces cerevisiae, Escherichia coli, Klebsiella pneumoniae, Salmonella, Staphylococcus aureus, and Bacillus cereus corresponded to MIC values lower than for AgNO(3).     

Preparation, characterization and adhesive properties of di- and tri-hydroxy benzoyl chitosan nanoparticles

Modified chitosans with 3,4-di-hydroxy benzoyl groups (CS-DHBA) and 3,4,5-tri-hydroxy benzoyl groups (CS-THBA) were synthesized and their nanoparticles were prepared via ionic crosslinking by tripolyphosphate (TPP). The chemical structure and degree of substitution (DS) of di-and tri-hydroxy benzoyl chitosans are determined by FTIR and 1H-NMR spectroscopy. The morphology of particles, size distribution and zeta potential of nanoparticles were studied using transmission electron microscopy (TEM) and dynamic light scattering (DLS), respectively. The mean diameters of particles of CS-DHBA and CS-THBA nanoparticles were 144 nm and 112 nm, respectively. It was found that the particles size decreased slightly with decreasing the degree of substitution and increasing degree of deacetylation (DD), due to increasing of ionic crosslinking of ammonium ions and polyanions of tripolyphosphate. The TEM photographs of CS-DHBA show that these particles are spherical in shape, but the particles of CS-THBA show some aggregation. In addition, the solubility and the mechanical properties of the prepared modified chitosans and their nanoparticles were evaluated for bio-adhesive and biomedical application. The results of solubility tests indicated that, the CS-DHBA and CS-THBA have higher solubility at pH > 7 comparing to CS. Also the CS-DHBA, CS-THBA and their nanoparticles showed a significant adhesive capacity and enhanced tensile strength and tensile modulus.     

Monovalent salt enhances colloidal stability during the formation of chitosan/tripolyphosphate microgels

Chitosan micro- and nanoparticles are routinely prepared through ionotropic gelation, where sodium tripolyphosphate (TPP) is added as a cross-linker to dilute chitosan solutions. Despite the wide use of these gel-like particles, their preparation currently relies on trial and error. To address this, we used isothermal titration calorimetry (ITC), dynamic light scattering (DLS), transmission electron microscopy (TEM), and ζ-potential measurements to investigate how the formation, structure, and colloidal stability of chitosan microgels are linked to the molecular interactions that underlie their self-assembly. The strength of the chitosan/TPP interactions was systematically varied through the addition of monovalent salt (NaCl). Remarkably, and contrary to other colloidal systems, this revealed that moderate amounts of NaCl (e.g., 150 mM) enhance the colloidal stability of chitosan/TPP microgels during their formation. This stems from the weakened chitosan/TPP binding, which apparently inhibits the bridging of the newly formed microgels by TPP. The enhanced colloidal stability during the ionic cross-linking process yields microgels with dramatically narrower size distributions, which hitherto have typically required the deacetylation and fractionation of the parent chitosan. Conversely, at high ionic strengths (ca. 500 mM) the chitosan/TPP binding is weakened to the point that the microgels cease to form, thus suggesting the existence of an optimal ionic strength for ionotropic microgel preparation.     

Preparation of chitosan nanoparticles as carrier for immobilized enzyme

This work investigated the preparation of chitosan nanoparticles used as carriers for immobilized enzyme. The morphologic characterization of chitosan nanoparticles was evaluated by scanning electron microscope. The various preparation methods of chitosan nanoparticles were discussed and chosen. The effect of factors such as molecular weight of chitosan, chitosan concentration, TPP concentration, and solution pH on the size of chitosan nanoparticles was studied. Based on these results, response surface methodology was emploved. The results showed that solution pH, TPP concentration, and chitosan concentration significantly affected the size of chitosan nanoparticles. The adequacy of the predictive model equation for predicting the magnitude orders of the size of chitosan nanoparticles was verified effectively by the validation data. Immobilization conditions were investigated as well. The minimum particles size was about 42±5 nm under the optimized conditions. The optimal conditions of immobilization were as follow: one milligram of neutral proteinase was immobilized on chitosan nanoparticles for about 15 min at 40°C. Under the optimized conditions, the enzyme activity yield was 84.3%.     

Aqueous Synthesis of Triphenylphosphine-Modified Gold Nanoparticles for Synergistic In Vitro and In Vivo Photothermal Chemotherapy

Triphenylphosphine (TPP) surface-functionalized and F-108 Pluronic-stabilized gold nanoparticles (F-108@TPP-AuNPs) have been synthesized through a one-step approach, leading to well-defined (9.6±1.6 nm) and water-soluble nanoparticles by microwave heating an aqueous solution of TPP-Au^ICl in the presence of a Pluronic polymer under basic conditions. TPP release was negligible under physiological conditions, but enhanced significantly at an acidic pH (5.4) mimicking that of a cancer cell. Laser irradiation (532 nm) raised the temperature of an aqueous solution of F-108@TPP-AuNPs to 51.7 °C within 5 min, confirming efficient light-to-heat conversion capabilities without significant photodegradation. TEM confirmed intracellular localization of F-108@TPP-AuNPs in the cytosol, endosomes and lysosomes of HeLa cells. F-108@TPP-AuNPs were well tolerated by HeLa cells and zebrafish embryos at ambient temperatures and became toxic upon heat activation, suggesting synergistic interactions between heat and cytotoxic action by TPP.     

Physical and chemical characterization insulin-loaded chitosan-TPP nanoparticles

The purpose of this study was to develop and characterize insulin nanoparticles systems using chitosan. Insulin-loaded nanoparticles were prepared by ionic gelation of chitosan with tripolyphosphate anions (TPP). The interactions between insulin and chitosan were evaluated by differential scanning calorimetry (DSC), thermogravimetry/derivative thermogravimetry (TG/DTG), and Fourier-transform infrared (FTIR) spectroscopy. Besides, particle size distribution, polydispersity index (PDI), zeta potential, and association efficiency (AE%) of the nanoparticles were evaluated. In general, inert nanoparticles and insulin-loaded nanoparticles showed an average size of 260.56 nm (PDI 0.502) and 312.80 nm (PDI 0.481), respectively. Both nanoparticles showed positive charge, but after insulin incorporation the zeta potential was reduced, evidencing its incorporation. Nanoparticles obtained also showed AE% around 70%, measured by high-performance liquid chromatography (HPLC). The results of FTIR, DSC, and TG/DTG corroborated the data presented suggesting that insulin was successfully encapsulated. However, drug incorporation seems to be related not only to electrostatic interactions, but also to physical process and/or adsorption phenomena.     

Synthesis,crystal structures,and redox potentials of 2,3,12,13-tetrasubstituted 5,10,15,20-tetraphenylporphyrin zinc(II) complexes

Zinc(II) complexes of antipodal beta-tetrasubstituted meso-tetraphenylporphyrin with trifluoromethyl (Zn(TPP(CF(3))(4)) (1a)), bromine (Zn(TPPBr(4)) (2a)), and methyl groups (Zn(TPP(CH(3))(4)) (3a)) were synthesized in order to examine the steric and the electronic effects of trifluoromethyl groups on the macrocycle. The analysis of X-ray crystal structures of the five-coordinate complexes Zn(TPP(CF(3))(4))(EtOH)(3) (1b), Zn(TPPBr(4))(MeOH)(DMF) (2b), and Zn(TPP(CH(3))(4))(THF)(1.6)(CHCl(3))(0.4) (3b) revealed distorted macrocyclic cores where significant differences in the Zn-N distance between the beta-substituted and the non-beta-substituted side were observed. The difference was significant in 1b due to the strong steric interactions among the peripheral substituents and the electronic effects of trifluoromethyl groups. The macrocycles of 1b-3b are saddle-distorted and slightly ruffled due to the five-coordination of zinc(II) and the peripheral substitution. Distortion of the macrocycles of 2b and 3b were modest. On the other hand, distortion in 1b was severe due to the peripheral strain. Cyclic voltammetric measurements of the four-coordinate complexes Zn(TPP) and 1a-3a were performed and their redox potentials were analyzed together with previously reported potentials of Zn(TPP(CN)(4)). The oxidation potential of 1a did not gain as much as expected from the electron-withdrawing effect of the four trifluoromethyl groups. The HOMO-LUMO gap of 1a was very small (1.5 V) and cannot just be explained by macrocyclic distortion. The magnitude of this gap is very similar to that of Zn(TPP(CN)(4)). Compound 2a also exhibited a modest gap contraction. Compound 3a was easier to oxidize and harder to reduce than Zn(TPP), even though the HOMO-LUMO gap of 3a was similar to that of Zn(TPP).     

Preparation of Polystyrene/Triphenyl Phosphate Composites by Suspension Polymerization and Melt Extrusion Method——A Comparative Study

Polystyrene (PS)/triphenyl phosphate (TPP) composites were prepared by both suspension polymerization and melt extrusion, and a comparative study of the flame retardance and mechanical properties was carried out. The results showed that suspension polymerization was a better technique than melt extrusion for obtaining good dispersity of the PS/TPP composite. The TPP nanoparticles, which were approximately 50 nm in size, were homogenously and uniformly dispersed in the PS matrix by suspension polymerization in one-step. However, the PS/TPP composite was partially agglomerated, exhibiting irregularly shaped micron-scale particles as a result of melt extrusion. In contrast to the melt extrusion, the limited oxygen index (LOI) of the PS/TPP nanocomposite by suspension polymerization increased to 22.6% from 21.8%, and time to ignition (TTI) increased by 12.3%, the peak heat release rate (PHRR) decreased by 8.5%, and the total heat release (THR) decreased by 11.0%. The mechanical properties of the PS/TPP nanocomposite by suspension polymerization also increased. The tensile strength, elongation at break, and flexural strength increased by 36.4%, 8.5%, and 108%, respectively.     

细胞色素P-450模拟体系的活性中间体-氧配位铬(V)四苯基卟啉 配合物的分离、 表征和氧化反应

氮气保护下二氯甲烷中铬(III)四苯基卟啉衍生物在-40℃与亚碘酰苯反应,分离得氧配位铬(V)四苯基卟啉配合物:O=Cr(V)TPP(Cl)PhI,O=Cr(V)TPP(N~30PhI,O=Cr(V)TPP(p-CH~3O-C~6H~4O)(1/2)PhI。已经元素分析、可见、红外、顺磁、核磁和质谱法结构表征。这些配合物能氧化苯乙烯,环己醇,环己烯和环己烷,可作为细胞色素P-450模拟体系的活性中间体。     

Poly(L‐Glutamic Acid)‐Drug Conjugates for Chemo‐ and Photodynamic Combination Therapy

Despite the polymeric vascular disrupting agent (poly(_L‐glutamic acid)‐graft‐methoxy poly(ethylene glycol)/combretastatin A4) nanoparticles can efficiently inhibit cancer growth, their further application is still a challenge owing to the tumor recurrence and metastasis after treatment. In this study, two poly(_L‐glutamic acid)‐drug conjugates for chemo‐and photodynamic combination therapy are fabricated. PLG‐g‐mPEG‐CA4 nanoparticles are prepared by combretastatin A4 (CA4) and poly(_L‐glutamic acid)‐graft‐methoxy poly(ethylene glycol) (PLG‐g‐mPEG) using the Yamaguchi esterification reaction. PLG‐g‐mPEG‐TPP (TPP: 5, 10, 15, 20‐tetraphenylporphyrin) nanoparticles are constructed using PLG‐g‐mPEG and amine porphyrin through condensation reaction between carboxyl group of PLG‐g‐mPEG and amino group of porphyrin. The results showed that PLG‐g‐mPEG‐CA4 nanoparticles have good antitumor ability. PLG‐g‐mPEG‐TPP nanoparticles can produce singlet oxygen under the laser irradiation. Moreover, the combined therapy of PLG‐g‐mPEG‐CA4 and PLG‐g‐mPEG‐TPP nanoparticles has higher antitumor effect than the single chemotherapy or the single photodynamic therapy in vitro. The combination of CA4 nondrug and photodynamic therapy provides a new insight for enhancing the tumor therapeutic effect with vascular disrupting agents and other therapy.