Search

Multifunctional alginate microspheres encapsulated with in situ-formed bismuth sulfide nanoparticles (denoted as Bi2S3@BCA) were developed in this work. In comparison with conventional hybrid polymer microspheres usually involved in complicate preparation process, Bi2S3@BCA microspheres can be easily one-step prepared using a droplet-based microfluidic technique with alginate as a soft template and microspheric matrix. As-prepared Bi2S3@BCA microspheres has unique nano-in-micro structure. The obtained wet microspheres show good uniform size with approximately 170 μm in diameter. Scanning electron microscopy images show that Bi2S3 nanoparticles with a size of 300 nm were homogeneously distributed in the microspheres. In addition, Bi2S3@BCA microspheres exhibit strong absorption of near-infrared (NIR) light and excellent photothermal effect in vitro. Furthermore, anti-cancer drug (doxorubicin)-loaded Bi2S3@BCA microspheres show sustained drug release behavior and enhanced release rate under NIR laser irradiation. The in vitro cytotoxicity experiments confirm that chemotherapy combined with NIR-induced hyperthermia can act synergistic effect to kill more tumor cells. Therefore, the as-prepared drug-loaded Bi2S3@BCA microspheres may potentially be used as a novel embolic material for tumor therapy due to their multifunction including embolization, hyperthermia and controlled local chemotherapy.

Due to the very poor mechanical strength of polyaniline-poly(styrene sulfonate) (PANI-PSS) conducting hydrogels, we explored the possibility to improve the strength of PANI-PSS hydrogels using supramolecular nanofibers formed by self-assembly of sorbitol derivatives (DBS). The compressive strength of these reinforced hydrogels was found to be 11 times higher than that of the unreinforced one. SEM studies indicated that the in-situ formed DBS nanofibers and PANI-PSS chains are entangled, leading to improvement of the hydrogel strength. The conductivity of reinforced hydrogels measured by impedance was found to be 10−4 S/cm, rather similar to that of the unreinforced hydrogels. In addition, the spectra of cyclic voltammetry for the reinforced and unreinforced hydrogels were almost the same. These results reveal that the presence of DBS nanofibers does not affect the electric properties of PANI-PSS hydrogels. As drug carriers with electric-driven release, the release rate of model drug Rhodamine B loaded within reinforced PANI-PSS hydrogels distinctly increased when an increase of voltage was applied. Furthermore, a pulse release could be realized when the voltage was alternatively applied.

A novel drug carrier was synthesized through grafting polymerization of hydroxyethyl starch (HES) and d,l-lactide. By changing the molar ratio of HES and d,l-lactide, HES-g-PLA copolymers with different chain lengths of PLA can be obtained. Their chemical structures were characterized by FT-IR and 1H NMR. Through self-emulsification combined with solvent evaporation, HES-g-PLAs self-assembled into micelles with uniform sizes ranging from 65 to 130 nm, depending upon the chain length of PLA. In vitro release profiles of docetaxel-loaded HES-g-PLAs meet first-order release kinetics via a mechanism of diffusion and polymer chain relaxation. The size of the micelles and the amount of drug loading can be controlled by varying the chain length of PLA. Another significant result is that release rates of docetaxel can be also modulated by changing the chain lengths of the PLA segments.

Triptolide (TP), which has immunosuppressive effect, anti-neoplastic activity, anti-fertility function and severe toxicities on digestive, urogenital, blood circulatory system, was used as a model drug in this study. TP-loaded poly ( d , l -lactic acid) (PLA) nanoparticles were prepared by the modified spontaneous emulsification solvent diffusion method (modified-SESD method). Dynamic light scattering system (DLS), transmission electron microscope (TEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC), X-ray powder diffractometry and Fourier transform infra-red spectroscopy (FT-IR) were employed to characterize the nanoparticles fabricated for size and size distribution, surface morphology, the physical state of drug in nanoparticles, and the interaction between the drug and polymer. Encapsulation efficiency (EE) and the in vitro release of TP in nanoparticles were measured by the reverse phase high-performance liquid chromatography (RP-HPLC). The produced nanoparticles exhibited a narrow size distribution with a mean size of approximately 150 nm and polydispersity index of 0.088. The morphology of the nanoparticles exhibited a fine spherical shape with smooth surfaces without aggregation or adhesion. TP-entrapped in nanoparticles was found in the form of amorphous or semicrystalline. It was found that a weak interaction existed between the drug and polymer. In all experiments, more than 65% of EE were obtained. The in vitro release profile of TP from nanoparticles exhibited a typical biphasic release phenomenon, namely initial burst release and consequently sustained release. In this case, the particle size played an important role for the drug release. The modified-SESD method was a potential and advantage method to produce an ideal polymer nanoparticles for drug delivery system (DDS).

Hydrogels based on n-alkyl methacrylate esters (n-AMA) of various chain lengths, acrylic acid, and acrylamide cross-linked with 4,4-di(methacryloylamino)azobenzene were synthesized. The equilibrium swelling degree of the hydrogels in buffered solutions at pH 7.4 was shown to be very low in the pH range of the stomach. The entire swelling processes of the gels in the gastrointestinal tract were mainly dependent on those in the small intestine. In the buffered solution of pH 7.4 the diffusion of water into the gel slabs was discussed on the stress relaxation model of polymer chains. The results obtained are in good agreement with Schott's second-order diffusion kinetics. The biodegradability in vivo of their azobenzene cross-linking groups as well as the mechanism of degradation by cecal bacteria was studied. The gels are stable in the stomach but degradable by ananerobes present in the colon. The extent of degradation was considerably related to the equilibrium degree of swelling. The factors influencing the swelling degree were shown to influence the in vivo degradation of the gels. By changing these factors such as the degree of cross-linking, the length and content of the n-AMA side chains, it is possible to control both the degree of swelling and the degradation of the hydrogels.