Exploration of hydrophobic modification degree of chitosan-based nanocomplexes on the oral delivery of enoxaparin.

The objective of this paper is to elucidate the influence of lipophilic modification degree of chitosan on the peroral absorption of enoxaparin. A series of novel chitosan grafted glyceryl monostearate (GM) copolymers with different GM substitution degree were synthesized and the successful synthesis was confirmed by (1)H NMR, FTIR and X-ray diffraction. Enoxaparin loaded nanocomplexes with different carriers were prepared by self-assembly process. Influence of GM substitution degree and chitosan molecular weight in the copolymer on the properties of the nanocomplexes was investigated. Morphology of the nanocomplexes was observed by atomic force microscopy. Mucoadhesive properties of the nanocomplexes were characterized using mucin particle method. Initially, mucoadhesion of the nanocomplexes increased with the increase of GM substitution degree and it started to decrease when the substitution degree was up to 18.6%. A good linear relationship between GM substitution degree and in vivo absorption of enoxaparin in fasted rats was established in the substitution degree range of 0-11.1%. In agreement with mucoadhesion data, further increasing GM substitution degree to 18.6% caused a decrease in oral absorption. In conclusion, oral bioavailability of enoxaparin can be enhanced by structure modification of the carriers and the bioavailability is hydrophobic modification degree dependent.

Wang L ，Li L ，Sun Y ，Tian Y ，Li Y ，Li C ，Junyaprasert VB ，Mao S ... -  《-》

In vitro and in vivo evaluation of chitosan graft glyceryl monooleate as peroral delivery carrier of enoxaparin.

In this paper a novel copolymer, chitosan graft glyceryl monooleate (CS-GO) was synthesized and its potential as the nanocarrier for enhancing the peroral delivery of enoxaparin was studied systemically. The successful synthesis was characterized by (1)H NMR. Enoxaparin nanocomplexes were prepared by self-assembly. Mucoadhesive properties of the nanocomplexes were evaluated using mucin particle method. Uptake and transport of the nanocomplexes were investigated in Caco-2 cells. In vivo absorption was studied in rats. The therapeutic effects of the nanocomplexes were evaluated using pulmonary thromboembolism model in mice. This study demonstrated that compared to chitosan based system, hydrophobic modification of CS with GO enhanced the oral absorption of enoxaparin significantly, which is in good agreement with the enhanced mucoadhesion, cellular internalization and transport in cell culture. Cellular uptake of CS-GO based enoxaparin nanocomplexes was incubation time, enoxaparin concentration and incubation temperature dependent. The uptake mechanism was assumed to be adsorptive endocytosis via clathrin- and caveolae-mediated process. Its therapeutic efficacy was further demonstrated by pharmacodynamic study with pulmonary thromboembolism inhibition percentage 47.1%. In conclusion, CS-GO copolymer is a promising nanocarrier for enhancing the oral absorption of enoxaparin.

Wang L ，Li L ，Sun Y ，Ding J ，Li J ，Duan X ，Li Y ，Junyaprasert VB ，Mao S ... -  《-》

Uptake, transport and peroral absorption of fatty glyceride grafted chitosan copolymer-enoxaparin nanocomplexes: influence of glyceride chain length.

The objective of this paper is to elucidate the influence of fatty glyceride chain length in chitosan copolymers on the peroral absorption of enoxaparin. First of all, a series of chitosan copolymers with glyceryl monocaprylate (GM8), glyceryl monolaurate (GM12) and glyceryl monostearate (GM18) as the hydrophobic part were synthesized. The structure of the copolymers was characterized using proton nuclear magnetic resonance. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay demonstrated that all the copolymers were non-toxic. Enoxaparin nanocomplexes were prepared by self-assembly. Mucoadhesion of the nanocomplexes was characterized using the mucin particle method. Nanocomplex uptake and transport were quantified in Caco-2 cells and cellular localization was visualized by confocal laser scanning microscopy. Enoxaparin uptake was enhanced by nanocomplex formation, and was dependent on incubation time, concentration, temperature and glyceride chain length. The GM8 grafted chitosan-enoxaparin nanocomplex exhibited the strongest bioadhesion and the best uptake and transport in both cell culture and in vivo absorption in rats. The uptake mechanism was assumed to be adsorptive endocytosis via clathrin- and caveolae-mediated processes. In conclusion, oral absorption of enoxaparin can be further enhanced by using GM8 grafted chitosan copolymer as the carrier to form nanocomplexes.

Wang L ，Sun Y ，Shi C ，Li L ，Guan J ，Zhang X ，Ni R ，Duan X ，Li Y ，Mao S ... -  《-》

Bioadhesion and oral absorption of enoxaparin nanocomplexes.

Polyelectrolyte complexes (PEC) formed between chitosan derivatives and enoxaparin were prepared by a self-assembly process and were characterized in terms of particle size and surface charge. The morphology was observed by atomic force microscopy (AFM). The colloidal stability and bioadhesion of the PEC were characterized by dynamic light scattering (DLS). The absorption of enoxaparin in rats was evaluated by activated partial thromboplastin time (APTT) assay. It was shown that the prepared PEC had a spherical shape with positive charge and a mean diameter in the range of 200-600 nm. An increase in temperature led to a decrease in particle size (ca. 10%) with an increased kcps value (ca. 10-20%) for the PEC studied, depending on the polymer structure. Thiolation and methylation of chitosan could significantly improve the corresponding PEC's bioadhesion and hence the oral absorption of enoxaparin. A good relationship between bioadhesion and in vivo absorption was established. However, PEC of PEGylated chitosan did not display a significantly enhanced permeation of enoxaparin compared with unmodified chitosan. In conclusion, the oral bioavailability of enoxaparin can be enhanced by improving the bioadhesive properties of PEC via the chemical modification of chitosan employed.

Sun W ，Mao S ，Wang Y ，Junyaprasert VB ，Zhang T ，Na L ，Wang J ... -  《-》

Chitosan based polymer-lipid hybrid nanoparticles for oral delivery of enoxaparin.

In the present study, chitosan based polymer-lipid hybrid nanoparticles (PLNs) were prepared by a self-assembly method and their use as the carrier for oral absorption enhancement of enoxaparin was evaluated. The enoxaparin-loaded nanoparticles were composed of chitosan as the polymer and glyceryl monooleate as the lipid with a lipid/polymer mass ratio ranging from 0 to 0.3, and F127 was added as a stabilizer. It was found that the PLNs showed a higher surface hydrophobicity but mucoadhesive properties similar to those of chitosan based nanocomplexes. Results from DSC experiments and NMR solvent relaxation study indicate that glyceryl monooleate was completely incorporated into the nanoparticles and the lipid/polymer ratio affected the extent of lipid-polymer interaction inside the nanoparticles and the resultant internal structures. The stability of the PLNs in simulated gastrointestinal fluids was also affected by the lipid/polymer ratio; the best stability was shown by nanoparticles with a lipid/polymer ratio of 0.2. Nanoparticles with the optimal composition significantly enhanced the oral bioavailability of enoxaparin with a 4.5-fold increase in AUC in comparison with a solution of enoxaparin. In conclusion, GMO/CS based PLNs can provide a new insight to develop orally applicable delivery system for hydrophilic macromolecules. Their absorption can be enhanced with proposed PLNs and preparation of this PLNs was also found to be easy comparing to other similar methods.

Dong W ，Wang X ，Liu C ，Zhang X ，Zhang X ，Chen X ，Kou Y ，Mao S ... -  《-》