K. J. Zhu
Zhejiang University
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Featured researches published by K. J. Zhu.
Polymer International | 1999
H L Jiang; K. J. Zhu
Poly(ethylene glycol) (PEG) segments were introduced into a polyanhydride main chain by copolymerization of terminal-carboxylated poly(ethylene glycol) with diacidic monomers (sebacic acid and trimellitylimidoglycine). IR and 1H NMR spectroscopy confirmed the copolymer structures. DSC analysis showed that these polyanhydrides have low Tg and low crystallinity. In vitro degradation tests indicated that introducing PEG segments accelerated the degradation rate of these polymers and the degradation duration could be manipulated from 3 days to 3 weeks. The pH of the environment caused by the polymer degradation was lower than 5.0; therefore, the polyanhydrides could be used as components of a newly designed pulsed-release device for peptide and protein delivery. © 1999 Society of Chemical Industry
Polymer International | 1997
Cai Jie; K. J. Zhu
Poly(D,L-lactide-co-1,3-trimethylene carbonate) (PLCA) has been synthesized by ring-opening polymerization of 1,3-trimethylene carbonate (CA) and D,L-lactide (LA) using stannous octoate as catalyst. The copolymers were characterized by 1H nuclear magnetic resonance (NMR), 13C NMR and differential scanning calorimetry. Water content and static contact angle of distilled water on the polymer surface were used to evaluate hydrophobicity of the polymers. It was found that the hydrophobicity increased with increasing CA fractions in the copolymers. Biodegradation experiments were conducted in vitro and in vivo. The results indicated that the biodegradation behaviour changed from surface to bulk degradation when the LA content exceeded 30mol% in the copolymers. These properties of PLCA may be useful in protein delivery systems.
Polymer International | 1996
Cai Jie; K. J. Zhu; Yang Shilin
Poly(1,3-trimethylene carbonate-co-glycolide) (PGCA) has been synthesized by ring-opening polymerization of 1,3-trimethylene carbonate (CA) and glycolide (GA) with stannous octoate as catalyst. The copolymers were characterized by 1 H nuclear magnetic resonance (NMR), 13 C NMR and differential scanning calorimetry. Water content and static contact angle of distilled water on the polymer surface were used to evaluate the hydrophobicity of the copolymers. There was no apparent difference in hydrophobicities of copolymers containing up to 30mol% GA. The biodegradation of PGCA was conducted in phosphate buffer solution at 37°C and in rats. The results indicated that the degradation rates of PGCA were higher than that of PCA and depended on the GA fraction in the copolymers. Furthermore, degradation occurred in the bulk when the GA content exceeded 20mol%. With less GA units the degradation became a surface reaction both in vitro and in vivo. These properties of PGCA may be useful in protein delivery systems.
Journal of Applied Polymer Science | 2000
Liyan Qiu; K. J. Zhu
Novel biodegradable polyphosphazenes containing glycine ethyl ester and benzyl ester of amino acethydroxamic acid as cosubstituents (PGBP) were synthesized by further modifying poly[bis(glycine ethyl ester)phosphazene] (PGP). The polymers were characterized by IR, 1H-NMR, DSC, and elemental analysis. Degradation experiments were conducted in vitro at varied pH conditions. The results indicated that the degradation of PGBP was pH-sensitive. The sample dissoluted after 1.5 days under a physiological condition (pH 7.4) but took more than 20 days under an acidic condition (pH 5–6), which was related to the content of the benzyl ester of amino acethydroxamic acid in the polymer. The “two-stage” degradation mechanism of PGBP was proposed: that the polymer first degraded to a water-soluble polymeric product with the fast break of side groups, followed by the relatively slow scission of the backbone. This property of PGBP may be useful in controlled drug-delivery systems.
Polymer International | 2000
L Y Qiu; K. J. Zhu
Poly[bis(glycine ethyl ester)phosphazene] (PGP) was blended with poly(D,L-lactide) (PLA), poly(D,L-lactide-co-glycolide) (80:20 by mole) (PLGA), poly(sebacic anhydride) (PSA) and poly(sebacic anhydride-co-trimellitylimidoglycine)-block-poly(ethylene glycol) (30:50:20 by mole) (PSTP) in various ratios using a solvent-mixing technique. The compatibility of these blends has been evaluated by DSC, FTIR and phase contrast microscopy. The results indicated that PGP is completely incompatible with PLA, but partially compatible with PLGA and PSTP, which may be attributed to a hydrogen bonding effect. Degradation experiments have been conducted in distilled water at 37 °C and show that the blend degradation rate can be regulated by adjusting the PLGA or PSTP content of the blends. PGP/PLGA (70:30 by wt) slabs took 120 days to disappear completely, while PGP/PSTP (70:30 by wt) slabs needed only 20 days. These findings suggest that blends of PGP and PLGA or PSTP may be used as matrices for drug controlled release and for other potential biomedical applications. © 2000 Society of Chemical Industry
Journal of Applied Polymer Science | 2000
Guping Tang; K. J. Zhu; Q. Q. Chen
Poly-α,β-(3-hydroxypropyl)-DL-aspartamide (PHPA) was synthesized by the ring-open reaction of polysuccinimide (PSI) and 3-hydroxypropylamine. The polymer was characterized by 1 H-NMR, 13 C-NMR, FTIR, and GPC. Mark-Houwink coefficients were obtained from viscometry and GPC measurements, K = 5.53 x 10 3 and a = 0.78 in water. The acute toxicity of PHPA was examined and it revealed no death in ICR mice up to the dose treated of 15.3 kg/kg, and hematological parameters showed no significant difference between treated and control animals. The potential use of PHPA as a drug carrier was also investigated. In a typical case, a contraceptive drug, norethindrone (NET), was bonded to PHPA, and the drug sustained released as long as 120 days an in vitro test.
Journal of Applied Polymer Science | 1990
K. J. Zhu; Lin Xiangzhou; Yang Shilin
Journal of Applied Polymer Science | 2001
Hongliang Jiang; K. J. Zhu
Journal of Applied Polymer Science | 2006
Hongliang Jiang; K. J. Zhu
Chinese Journal of Chemistry | 2007
K. J. Zhu; Weipu Zhu; Yan-Bo Gu; Zhiquan Shen; Wei Chen; Gui-Xiang Zhu