Glucose-Sensitive Nanoparticles Based On Poly(3-Acrylamidophenylboronic Acid-Block-N-Vinylcaprolactam) For Insulin Delivery.

BACKGROUND: Compared with random copolymers, block copolymerization is easier to prepare for nanoparticles with core-shell structure, and they will have better glucose sensitivity and higher insulin loading. PURPOSE: In our study, insulin-loaded poly (3-acrylamidophenylboronic acid-block-N-vinyl caprolactam) p(AAPBA-b-NVCL) nanoparticles were successfully prepared and were glucose-sensitive, which could effectively lower the blood sugar levels within 72 hrs. METHODS: The polymer of p(AAPBA-b-NVCL) was produced by reversible addition-fragmentation chain transfer polymerization based on different ratios of 3-acrylamidophenylboronic acid (AAPBA) and N-vinylcaprolactam (NVCL), and its structure was discussed by Fourier transform infrared spectroscopy and 1H-nuclear magnetic resonance . Next, the polymer was manufactured into the nanoparticles, and the characteristics of nanoparticles were detected by dynamic light scattering, lower critical solution temperature, and transmission electron microscopy. After that, the cell and animal toxicity of nanoparticles were also investigated. RESULTS: The results demonstrated that p(AAPBA-b-NVCL) was successfully synthesized, and can be easily self-assembled to form nanoparticles. The new nanoparticles included monodisperse submicron particles, with the size of the nanoparticle ranged between 150 and 300nm and are glucose- and temperature-sensitive. Meanwhile, insulin can be easily loaded by p(AAPBA-b-NVCL) nanoparticles and an effective sustained release of insulin was observed when the nanoparticles were placed in physiological saline. Besides, MTT assay revealed that cell viability was more than 80%, and mice demonstrated no negative impact on blood biochemistry and heart, liver, spleen, lung, and kidney after intraperitoneal injection of 10 mg/kg/d of nanoparticles. This suggested that the nanoparticles were low-toxic to both cells and animals. Moreover, they could lower the blood sugar level within 72h. CONCLUSION: Our research suggested that these p(AAPBA-b-NVCL) nanoparticles might have the potential to be applied in a delivery system for insulin or other hypoglycemic proteins.

Insulin-loaded PLGA microspheres for glucose-responsive release.

Porous poly(lactic-co-glycolic acid) (PLGA) microspheres were prepared, loaded with insulin, and then coated in poly(vinyl alcohol) (PVA) and a novel boronic acid-containing copolymer [poly(acrylamide phenyl boronic acid-co-N-vinylcaprolactam); p(AAPBA-co-NVCL)]. Multilayer microspheres were generated using a layer-by-layer approach depositing alternating coats of PVA and p(AAPBA-co-NVCL) on the PLGA surface, with the optimal system found to be that with eight alternating layers of each coating. The resultant material comprised spherical particles with a porous PLGA core and the pores covered in the coating layers. Insulin could successfully be loaded into the particles, with loading capacity and encapsulation efficiencies reaching 2.83 ± 0.15 and 82.6 ± 5.1% respectively, and was found to be present in the amorphous form. The insulin-loaded microspheres could regulate drug release in response to a changing concentration of glucose. In vitro and in vivo toxicology tests demonstrated that they are safe and have high biocompatibility. Using the multilayer microspheres to treat diabetic mice, we found they can effectively control blood sugar levels over at least 18 days, retaining their glucose-sensitive properties during this time. Therefore, the novel multilayer microspheres developed in this work have significant potential as smart drug-delivery systems for the treatment of diabetes.

Fabrication and investigation of a biocompatible microfilament with high mechanical performance based on regenerated bacterial cellulose and bacterial cellulose.

A high-strength regenerated bacterial cellulose (RBC)/bacterial cellulose (BC) microfilament of potential use as a biomaterial was successfully prepared via a wet spinning process. The BC not only consists of a 3-D network composed of nanofibers with a diameter of several hundred nanometers but also has a secondary structure consisting of highly oriented nanofibrils with a diameter ranging from a few nanometers to tens of nanometers which explains the reason for the high mechanical strength of BC. Furthermore, a strategy of partially dissolving BC was used and this greatly enhanced the mechanical performance of spun filament and a method called post-treatment was utilized to remove residual solvents from the RBC/BC filaments. A comparison of structure, properties, as well as cytocompatibility between BC nanofibers and RBC/BC microfilaments was achieved using morphology, mechanical properties, X-ray Diffraction (XRD) and an enzymatic hydrolysis assay. The RBC/BC microfilament has a uniform groove structure with a diameter of 50-60µm and XRD indicated that the crystal form was transformed from cellulose Iα to cellulose IIII and the degree of crystallinity of RBC/BC (33.22%) was much lower than the original BC (60.29%). The enzymatic hydrolysis assay proved that the RBC/BC material was more easily degraded than BC. ICP detection indicated that the residual amount of lithium was 0.07mg/g (w/w) and GC-MS analysis showed the residual amount of DMAc to be 8.51µg/g (w/w) demonstrating that the post-treatment process is necessary and effective for removal of residual materials from the RBC/BC microfilaments. Also, a cell viability assay demonstrated that after post-treatment the RBC/BC filaments had good cytocompatibility.

Glucose- and temperature-sensitive nanoparticles for insulin delivery.

Glucose- and temperature-sensitive polymers of a phenylboronic acid derivative and diethylene glycol dimethacrylate (poly(3-acrylamidophenyl boronic acid-b-diethylene glycol methyl ether methacrylate); p(AAPBA-b-DEGMA)) were prepared by reversible addition-fragmentation chain transfer polymerization. Successful polymerization was evidenced by 1H nuclear magnetic resonance and infrared spectroscopy, and the polymers were further explored in terms of their glass transition temperatures and by gel permeation chromatography (GPC). The materials were found to be temperature sensitive, with lower critical solution temperatures in the region of 12°C-47°C depending on the monomer ratio used for reaction. The polymers could be self-assembled into nanoparticles (NPs), and the zeta potential and size of these particles were determined as a function of temperature and glucose concentration. Subsequently, the optimum NP formulation was loaded with insulin, and the drug release was studied. We found that insulin was easily encapsulated into the p(AAPBA-b-DEGMA) NPs, with a loading capacity of ~15% and encapsulation efficiency of ~70%. Insulin release could be regulated by changes in temperature and glucose concentration. Furthermore, the NPs were non-toxic both in vitro and in vivo. Finally, the efficacy of the formulations at managing blood glucose levels in a murine hyperglycemic diabetes model was studied. The insulin-loaded NPs could reduce blood glucose levels over an extended period of 48 h. Since they are both temperature and glucose sensitive and offer a sustained-release profile, these systems may comprise potent new formulations for insulin delivery.

Phenylboronic acid-diol crosslinked 6-O-vinylazeloyl-d-galactose nanocarriers for insulin delivery.

A new block polymer named poly 3-acrylamidophenylboronic acid-b-6-O-vinylazeloyl-d-galactose (p(AAPBA-b-OVZG)) was prepared using 3-acrylamidophenylboronic acid (AAPBA) and 6-O-vinylazeloyl-d-galactose (OVZG) via a two-step procedure involving S-1-dodecyl-S-(α', α'-dimethyl-α″-acetic acid) trithiocarbonate (DDATC) as chain transfer agent, 2,2-azobisisobutyronitrile (AIBN) as initiator and dimethyl formamide (DMF) as solvent. The structures of the polymer were examined by Fourier transform infrared spectroscopy (FT-IR) and 1H NMR and the thermal stability was determined by thermal gravimetric analysis (TG/DTG). Transmission electron microscopy (TEM) and dynamic light scattering (DLS) were utilized to evaluate the morphology and properties of the p(AAPBA-b-OVZG) nanoparticles. The cell toxicity, animal toxicity and therapeutic efficacy were also investigated. The results indicate the p(AAPBA-b-OVZG) was successfully synthesized and had excellent thermal stability. Moreover, the p(AAPBA-b-OVZG) nanoparticles were submicron in size and glucose-sensitive in phosphate-buffered saline (PBS). In addition, insulin as a model drug had a high encapsulation efficiency and loading capacity and the release of insulin was increased at higher glucose levels. Furthermore, the nanoparticles showed a low-toxicity in cell and animal studies and they were effective at decreasing blood glucose levels of mice over 96h. These p(AAPBA-b-OVZG) nanoparticles show promise for applications in diabetes treatment using insulin or other hypoglycemic proteins.

Synthesis and evaluation of temperature- and glucose-sensitive nanoparticles based on phenylboronic acid and N-vinylcaprolactam for insulin delivery.

Poly N-vinylcaprolactam-co-acrylamidophenylboronic acid p(NVCL-co-AAPBA) was prepared from N-vinylcaprolactam (NVCL) and 3-acrylamidophenylboronic acid (AAPBA), using 2,2-azobisisobutyronitrile (AIBN) as initiator. The synthesis and structure of the polymer were examined by Fourier Transform infrared spectroscopy (FT-IR) and (1)H-NMR. Dynamic light scattering (DLS), lower critical solution temperature (LCST) and transmission electron microscopy (TEM) were utilized to characterize the nanoparticles, CD spectroscopy was used to determine if there were any changes to the conformation of the insulin, and cell and animal toxicity were also investigated. The prepared nanoparticles were found to be monodisperse submicron particles and were glucose- and temperature-sensitive. In addition, the nanoparticles have good insulin-loading characteristics, do not affect the conformation of the insulin and show low-toxicity to cells and animals. These p(NVCL-co-AAPBA) nanoparticles may have some value for insulin or other hypoglycemic protein delivery.

A novel multifunctional biomedical material based on polyacrylonitrile: Preparation and characterization.

Wet spun microfibers have great potential in the design of multifunctional controlled release materials. Curcumin (Cur) and vitamin E acetate (Vit. E Ac) were used as a model drug system to evaluate the potential application of the drug-loaded microfiber system for enhanced delivery. The drugs and polyacrylonitrile (PAN) were blended together and spun to produce the target drug-loaded microfiber using an improved wet-spinning method and then the microfibers were successfully woven into fabrics. Morphological, mechanical properties, thermal behavior, drug release performance characteristics, and cytocompatibility were determined. The drug-loaded microfiber had a lobed "kidney" shape with a height of 50-100 µm and width of 100-200 µm. The addition of Cur and Vit. E Ac had a great influence on the surface and cross section structure of the microfiber, leading to a rough surface having microvoids. X-ray diffraction and Fourier transform infrared spectroscopy indicated that the drugs were successfully encapsulated and dispersed evenly in the microfilament fiber. After drug loading, the mechanical performance of the microfilament changed, with the breaking strength improved slightly, but the tensile elongation increased significantly. Thermogravimetric results showed that the drug load had no apparent adverse effect on the thermal properties of the microfibers. However, drug release from the fiber, as determined through in-vitro experiments, is relatively low and this property is maintained over time. Furthermore, in-vitro cytocompatibility testing showed that no cytotoxicity on the L929 cells was found up to 5% and 10% respectively of the theoretical drug loading content (TDLC) of curcumin and vitamin E acetate. This study provides reference data to aid the development of multifunctional textiles and to explore their use in the biomedical material field.