Chaoxing Li

Chitosan-NAC nanoparticles as a vehicle for nasal absorption enhancement of insulin.

The purpose of this work was to investigate chitosan-N-acetyl-L-cysteine (chitosan-NAC) nanoparticles as a potential carrier system for the nasal delivery of insulin. For the study, we used insulin-loaded chitosan-NAC nanoparticles (140-210 nm in diameter) prepared by in situ gelation with tripolyphosphate (TPP), with positive zeta potential values of +19.5-31.7 mV and insulin loading capacities of 13-42%. The physicochemical properties of the nanoparticles were affected by the number of thiol groups present. Mucoadhesive properties, which were evaluated by measuring the in vitro absorbed mass of mucin, of chitosan-NAC nanoparticles were >1.8-fold that of unmodified chitosan nanoparticles. In aqueous solution, chitosan-NAC nanoparticles exhibited fast swelling behavior. Insulin was released from chitosan-NAC nanoparticles in vitro in an initial burst followed by slow release. Intranasal administration of chitosan-NAC nanoparticles in rats enhanced the absorption of insulin by the nasal mucosa compared with unmodified chitosan nanoparticles and control insulin solution. In light of these observations, the novel thiolated chitosan nanoparticles represent a promising vehicle for nasal insulin administration.

Gradient cross-linked biodegradable polyelectrolyte nanocapsules for intracellular protein drug delivery

Gradient shell cross-linked hollow polyelectrolyte nanocapsules composed of cysteamine conjugated chitosan and dextran sulfate were prepared by layer-by-layer adsorption on beta-cyclodextrin (beta-CD) functionalized silica spheres followed by cross-linking thiols and removal of silica core. This disulfide bond gradient cross-linked nanocapsules combined reduction and pH sensitive. Gradually increased from the inside to the outside of the cross-linking degree, one purpose is to ensure that cross-linking disulfide bond after reduction cleavage still has pH sensitive, on the other hand is to avoid cross-linked contraction of internal damage the crystal and bioactivity of protein drugs. Disulfide cross-linked nanocapsules were used to enhance the physical stability against acidic pH conditions compared to the un-cross-linked ones. Bovine serum albumin, as a model protein drug, was loaded inside nanocapsules. The disulfide bond cross-linked nanocapsules are intended to remain more stable in physiological pH and decrease the loss of protein drugs caused by the gastric cavity, and can release the drugs in the intracellular environment after glutathione reduction.

Amphiphilic Random Glycopolymer Based on Phenylboronic Acid: Synthesis, Characterization, and Potential as Glucose-Sensitive Matrix

This study is devoted to developing amphiphilic, random glycopolymers based on phenylboronic acid, which self-assemble to form nanoparticles (NPs), as a glucose-sensitive agent. Maleimide-glucosamine was copolymerized with 3-acryl aminophenylboronic acid in methanol at 70 degrees C. Using the nanoprecipitation method, NPs with a narrow size distribution were successfully generated. Transmission electron microscopic analysis showed that the NPs were well dispersed as individual, spherically shaped particles. The swelling behavior of the NPs and the in vitro release profiles of insulin at different glucose concentrations revealed definite glucose sensitivity of the glycopolymers. Further, circular dichroism spectroscopy demonstrated that the overall tertiary structure of the released insulin was not altered compared with standard insulin. The analysis of relative cell proliferation suggested that the glycopolymer NPs had good biocompatibility. The glycopolymers that responded to changes in the glucose concentration of the surrounding environment are being aimed for use in self-regulated insulin delivery.

Disulfide-crosslinked chitosan hydrogel for cell viability and controlled protein release

Synthetic hydrogel mimics of the extracellular matrix (ECM) were prepared by cross-linking a thiol-modified chitosan (CS). CS was chemically modified using N-acetyl-l-cysteine (NAC). To minimize interference with biological function, the degree of substitution of thiol groups was kept below 50%. Solution of thiolated CS was prepared in pH 7.4 phosphate buffered saline (PBS) and crosslinked by disulfide bond formation in air. The gelation mainly depended on the content of thiol groups on thiolated CS, concentration of thiolated CS and the molecular weight of CS. Thermogravimetric analysis showed the thermal stabilities of CSS-S hydrogels. Results from SEM observation showed a porous 3D hydrogel structure with pores ranging from 5 to 30microm. In vitro release showed that insulin and BSA release could be controlled by choosing the composition, loading and disulfide bond contents. In vitro cell compatibility of the hydrogels on NIH 3T3 cells was evaluated, indicating that the hydrogels were biocompatible and the cells could migrate into the hydrogels. Moreover, cells were viable and preserved 3D cell morphology inside the hydrogels. These results demonstrate that disulfide-crosslinked CS hydrogels, a new type of macroporous, biocompatible, synthetic polymers, are promising applications in tissue engineering, drug delivery, and cell culture.

Hollow and degradable polyelectrolyte nanocapsules for protein drug delivery

Biodegradable hollow capsules encapsulating protein drugs were prepared via layer-by-layer assembly of water-soluble chitosan and dextran sulfate on protein-entrapping amino-functionalized silica particles and the subsequent removal of the silica. In order to enhance the encapsulated efficiency and decrease its burst release, we designed this new system to fulfill these two goals. Bovine serum albumin (BSA), which was used as model protein, was entrapped in the nanocapsules. This system demonstrated a good capacity for the encapsulation and loading of BSA. The burst release was decreased to less than 10% in phosphate-buffered saline within 2h. No significant conformation change was noted from the released BSA in comparison with native BSA by using circular dichroism spectroscopy. Cell viability study suggested that the nanocapsules had good biocompatibility. The drug release kinetics mechanism is Fickian diffusion. These kinds of novel composite nanocapsules may offer a promising delivery system for water-soluble proteins and peptides.

Polyelectrolyte nanoparticles based on water-soluble chitosan–poly(l-aspartic acid)–polyethylene glycol for controlled protein release

Water-soluble chitosan (WSC)-poly(L-aspartic acid) (PASP)-polyethylene glycol (PEG) nanoparticles (CPP nanoparticles) were prepared spontaneously under quite mild conditions by polyelectrolyte complexation. These nanoparticles were well dispersed and stable in aqueous solution, and their physicochemical properties were characterized by turbidity, FTIR spectroscopy, dynamic light scattering (DLS), transmission electron microscope (TEM), and zeta potential. PEG was chosen to modify WSC-PASP nanoparticles to make a protein-protective agent. Investigation on the encapsulation efficiency and loading capacity of the bovine serum albumin (BSA)-loaded CPP nanoparticles was also conducted. Encapsulation efficiency was obviously decreased with the increase of initial BSA concentration. Furthermore, its in vitro release characteristics were evaluated at pH 1.2, 2.5, and 7.4. In vitro release showed that these nanoparticles provided an initial burst release, followed by a slowly sustained release for more than 24 h. The BSA released from CPP nanoparticles showed no significant conformational change compared with native BSA, which is superior to the BSA released from nanoparticles without PEG. A cell viability study suggested that the nanoparticles had good biocompatibility. This nanoparticle system was considered promising as an advanced drug delivery system for the peptide and protein drug delivery.

Bioconjugated nanoparticles for attachment and penetration into pathogenic bacteria.

As an antimicrobial agent, silver nanoparticles functionalized with both bacitracin A and polymyxin E (AgNPs-BA&PE) were designed and synthesized with complementary antibacterial functions to act against gram-positive and gram-negative bacteria. AgNPs-BA&PE could easily get attached and penetrate into the bacterial cell membrane through surface-immobilized BA and PE with a membrane target, resulting in up to 10-fold increase in the antibacterial activity, without the emergence of bacterial resistance. Analysis of the antimicrobial mechanism confirmed that the synthesized nanoparticles caused disorganization of the bacterial cytomembrane and leakage of cytoplasmic contents. This antimicrobial agent with better biocompatibility can promote healing of infected wounds, and has promising and useful applications in biomedical devices and antibacterial control systems.

An injectable and glucose-sensitive nanogel for controlled insulin release

Glucose-responsive polymer gels provide an attractive option for the design of a self-regulated insulin delivery system. Here, this paper reported the biocompatibility, glucose-sensitive behavior, and in vivo application of a dispersion of nanogels with three interpenetrating polymer networks of poly(N-isopropylacrylamide), dextran and poly(3-acrylamidophenylboronic acid) (P(NIPAM–Dex–PBA)). The nanogels had an average hydrodynamic radius of about 150 nm, and particle size increased with increasing content of dextran. The swelling behavior of the nanogels at different glucose concentrations revealed definite glucose sensitivity of P(NIPAM–Dex–PBA) particles. Furthermore, the analysis of relative cell proliferation suggested that the nanogels had good biocompatibility with L-929 mouse fibroblast cells. The loading amount of insulin, as a model drug, was up to 16.2%, and the drug release was dependent on the composition of dextran in the particles and the concentration of glucose present in release medium. In vivo experiments revealed that insulin-loaded nanogels decreased the blood glucose levels in diabetic rats and maintained 51% of the baseline level for almost 2 hours. The hypoglycemic effect of the drug-loaded nanogels was similar to that of free insulin after administration. Importantly, the drug-loaded nanogels could keep blood glucose levels stable and avoided blood sugar fluctuations compared with free insulin.

A pH gated, glucose-sensitive nanoparticle based on worm-like mesoporous silica for controlled insulin release.

This study prepares a kind of core-shell hybrid nanoparticles, which is worm-like, pH gated, and glucose-sensitive. It has a mesoporous silica nanoparticle (MSN) core and polymer shell (cross-linked and non-cross-linked), bearing 3-acrylamidophenylboronic acid (AAPBA) and N-isopropylacrylamide (NIPAM) as sensor moieties. The shell of the nanoparticles has presented a distinct transition from swollen state to collapsed state as the temperature increases, which offers easy access to drug loading. Here, insulin is applied as a model drug and the behaviors of its loading/release are investigated. Insulin loading is up to 15% via mesoporous silica core. In vitro experiment shows that the cumulative release of insulin is dependent on glucose concentration, and the glucose sensitivity could be adjusted simply by different pH values. Simultaneously, compared with the non-cross-linked shell, the cross-linked shell, using dextran-maleic acid (Dex-Ma) as a macromolecule cross-link, enables insulin to release more persistently. Also, cell viability assay indicates that these nanoparticles have good biocompatibility. Consequently, the novel, pH gated, glucose-sensitive core-shell nanoparticles may have potential applications as a vehicle of self-regulated insulin delivery system.

Amphiphilic glycopolymer nanoparticles as vehicles for nasal delivery of peptides and proteins.

Nasal drug delivery system has been a very promising route for delivery of proteins and peptides for the reason that it can avoid degradation in gastrointestinal tract and metabolism by liver enzymes. However, the bioavailability of proteins and peptides is still low due to the rapid clearance of mucociliary. Here, to prolong the residence time of drugs and improve their absorption, we prepared amphiphilic glycopolymer poly(2-lactobionamidoethyl methacrylate-random-3-acrylamidophenylboronic acid) (p(LAMA-r-AAPBA), and the glycopolymer could assemble into the nanoparticles with narrow size distribution. Insulin, as a model drug, was efficiently encapsulated within the nanoparticles, and loading capacity was up to 12%. In vitro study revealed that the insulin release could be controlled by modifying the composition of glycopolymers. Cell viability showed that p(LAMA-r-AAPBA) nanoparticles had good cytocompatibility. Moreover, the mechanism of nanoparticle internalization into Calu-3 cells was a combination mechanism of clathrin-mediated endocytosis and lipid raft/caveolae-mediated endocytosis. Importantly, there was a significant decrease in the blood glucose levels after the nasal administration of p(LAMA-r-AAPBA) nanoparticles to diabetic rats. Therefore, p(LAMA-r-AAPBA) glycopolymers have a potential application as a nasal delivery systems for proteins and peptides.