YingChun Gu

A thermosensitive hydrogel based on biodegradable amphiphilic poly(ethylene glycol)–polycaprolactone–poly(ethylene glycol) block copolymers

A series of low molecular weight poly(ethylene glycol)–polycaprolactone–poly(ethylene glycol) (PEG–PCL–PEG) biodegradable block copolymers were successfully synthesized using isophorone diisocyanate (IPDI) as the coupling agent, and were characterized using 1H NMR and Fourier transform infrared spectroscopy. The aqueous solutions of the PEG–PCL–PEG copolymers displayed a special thermosensitive gel–sol transition when the concentration was above the corresponding critical gel concentration. Gel–sol phase diagrams were recorded using the test-tube-inversion method; they depended on the hydrophilic/hydrophobic balance in the macromolecular structure, as well as some other factors, including the heating history, volume, and the ageing time of the copolymer aqueous solutions and dissolution temperature of the copolymers. As a result, the gel–sol transition temperature range could be altered, which might be very useful for application in injectable drug delivery systems.

Honokiol Nanoparticles in Thermosensitive Hydrogel: Therapeutic Effects on Malignant Pleural Effusion

Honokiol (HK) can efficiently inhibit the growth of tumors. However, its clinical applications have been restricted by its extreme hydrophobicity. We hope to improve its water solubility by nanotechnology. And we wonder whether a novel honokiol nanoparticles-loaded thermosensitive poly(ethylene glycol)-poly(epsilon-caprolactone)-poly(ethylene glycol) (PEG-PCL-PEG, PECE) hydrogel (HK-hydrogel) could improve the therapeutic efficacy on malignant pleural effusion (MPE). To evaluate the therapeutic effects of HK-hydrogel on MPE, MPE-bearing mice were administered intrapleurally with HK-hydrogel, HK nanoparticles (HK-NP), blank hydrogel, or normal saline (NS) at days 4 and 11 after Lewis lung carcinoma (LLC) cells inoculation, respectively. Pleural tumor foci and survival time were observed, and antiangiogenesis of HK-hydrogel was determined by CD31. Histological analysis and assessment of apoptotic cells were also conducted in tumor tissues. HK-hydrogel reduced the number of pleural tumor foci, while prolonging the survival time of MPE-bearing mice, more effectively, as compared with control groups. In addition, HK-hydrogel successfully inhibited angiogenesis as assessed by CD31 (P < 0.05). Histological analysis of pleural tumors exhibited that HK-hydrogel led to the increased rate of apoptosis. This work is important for the further application of HK-hydrogel in the treatment of MPE.

Polymeric matrix for drug delivery: Honokiol‐loaded PCL‐PEG‐PCL nanoparticles in PEG‐PCL‐PEG thermosensitive hydrogel

In this article, we demonstrated a novel injectable polymer matrix: honokiol (HK) loaded poly (epsilon-caprolactone)-poly(ethylene glycol)-poly(epsilon-caprolactone) (PCL-PEG-PCL, PCEC) nanoparticles in thermosensitive poly(ethylene glycol)-poly(epsilon-caprolactone)-poly(ethylene glycol) (PEG-PCL-PEG, PECE) hydrogel for the drug local delivery. First, HK, as a model hydrophobic drug, was loaded into PCL-PEG-PCL nanoparticles by emulsion solvent evaporation method to overcome its poor water solubility. Then, the HK-loaded PCEC nanoparticles (HK-PCEC) were incorporated into thermosensitive PEG-PCL-PEG hydrogel, which was sol at low temperature and could gel as a depot for sustained release of drug in situ after topical injection. The HK-PCEC incorporated PECE hydrogel (HK-PCEC-PECE) was biodegradable and could be gradually eliminated from the injection site in about 2 weeks after subcutaneously injected into mice. The in vitro release studies indicated that HK could be released from HK-PCEC and HK-PCEC-PECE in a sustained manner. Such biodegradable smart drug-delivery system might have great potential application in injectable hydrophobic drug local delivery system.

Synthesis of a novel biodegradable poly(ester amine) (PEAs) copolymer based on low-molecular-weight polyethyleneimine for gene delivery

In this paper, a novel biodegradable poly(ester amine) (PEA) copolymer was successfully prepared from low-molecular-weight polyethyleneimine (PEI, Mn=1800) and poly(epsilon-caprolactone)-Pluronic-poly(epsilon-caprolactone) (PCFC) copolymers. According to the results of agarose gel electrophoresis, particle sizes and zeta potential measurement and transfection efficiency, these PEA copolymers showed great ability to condense plasmid DNA effectively into nano-complexes with small particle size (< or =200 nm) and moderate zeta potential (> or =12 mV) at proper polymeric carrier/DNA weight ratio. Compared with low-molecular-PEI (Mn=1800), the obtained PEAs exhibited higher transfection efficiency as well as lower cytotoxicity. These results indicated that such PEAs might have great potential application in gene delivery system.

Synthesis and characterization of pH and temperature sensitive hydrogel based on poly(N-isopropylacrylamide), poly(ɛ-caprolactone), methylacrylic acid, and methoxyl poly(ethylene glycol)

AbstractIn this paper, a novel biodegradable and pH/thermo-sensitive hydrogel based on poly(ɛ-caprolactone), methoxyl poly(ethylene glycol), methylacrylic acid and N-isopropylacrylamide was prepared by UV-initiated free radical polymerization. The hydrogels were characterized by Fourier transforms infrared ray. The thermal responsibility was investigated with the help of differential scanning calorimetry. Swelling behavior in aqueous medium with different pH value was studied in detail. When the pH value of the aqueous medium was increased from 1.2 to 7.2, the swelling ratio of the hydrogels increased accordingly. The morphology was observed by scanning electron microscopy, and the hydrolytic degradation behavior in different aqueous media (pH 1.2 and pH 7.2) was also investigated in detail. The prepared biodegradable pH/thermo-sensitive hydrogel based on poly(ɛ-caprolactone), methoxyl poly(ethylene glycol), methylacrylic acid and N-isopropylacrylamide hold great promise in the development of a smart drug delivery system.

Preparation, Characterization, and Self-assembly Behavior of a Novel MPEG/PCL-g-Chitosan Copolymer

In this article, MPEG/PCL-g-Chitosan (MPEG/PCL-g-CS) was successfully prepared via free‐radical polymerization method. MPEG/PCL copolymer was first synthesized from MPEG and ϵ‐caprolactone. Then, the double bond ended MPEG/PCL (MPEG/PCL macromonomer) was obtained by reaction with acryloyl chloride at 40oC in pre-dried dichloromethane. MPEG/PCL-g-CS copolymer was characterized by 1H-nuclear magnetic resonance (1H-NMR), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and differential scanning calorimeter (DSC), respectively. The obtained amphiphilic MPEG/PCL-g-CS copolymer could self-assemble into nanoparticles in aqueous solution. The critical micellar concentration (CMC) of MPEG/PCL-g-CS copolymer is about 1.78 mg/L determined by the fluorescence robe technique. In vitro cytotoxicity test revealed that MPEG/PCL-g-CS nanoparticles were low cytotoxicity against HEK293 cells after incubated for 24 h. The coupling of CS with MPEG/PCL endowed the pH sensitivity and cationic characteristics to MPEG/PCL nanoparticles. Size distribution and zeta potential of nanoparticles were greatly influenced by pH values.

Nano titanium dioxide/PAoQ-coated polybenzoxazol fibers for enhancing anti-ultraviolet performance

Inspired by the composition of adhesive in mussels, polydopamine has been widely used for surface modification of various materials. In accord with the formation mechanism of polydopamine coating, the catechol containing two o-phenol groups and triethylenetetramine (TETA) containing two primary amine groups were used to copolymerize and deposit a polyamine-o-benzoquinone polymers (PAoQ) film on the polybenzoxazol (PBO) fibers. In order to enhance the anti-ultraviolet performance of PBO fibers, rutile nano titanium dioxide particles (TiO2) were also decorated on the PBO fibers by the layer-by-layer self-assembling technique. The optimum modification conditions were obtained by orthogonal method. Morphological structure and chemical composition of the modified fibers were studied using scanning electron microscopy with energy dispersive X-ray, and Fourier transform infrared spectroscopy. The UV-aging test results showed that under 144 h UV-light exposure at 340 nm, the modified PBO fibers’ strength retention was promoted to 80.8%, 34.4% higher than that of the original PBO fiber. The thermal stability of the modified fibers had no obvious change after modification with TiO2/PAoQ, while their carbon residue rate increased slightly.

Core/shell structured halloysite/polyaniline nanotubes with enhanced electrochromic properties

Novel halloysite (HNT)/polyaniline (PANI) nanocomposites are fabricated by controllable in situ chemical polymerization for electrochromic applications. The nanocomposites with different morphologies can be obtained simply by controlling the relative proportions of aniline (ANI) monomers and HNTs in the chemical polymerization system. “Adsorption” is proposed to account for the preferential growth of PANI along HNT nanotubes to form a core/shell structure. The films casted by the nanocomposites exhibited remarkably enhanced electrochromic performances. When compared with pure polyaniline, nanocomposite films possess a faster response time (1.0 s for bleaching and 3.0 s for coloring), higher optical contrast (60.5%), and more remarkable switching stability (over 500 cycles). The unique nanocomposites pave the way for developing new functional materials with enhanced properties for new applications.