Biomedical subjects

Wenguang Liu

Publications and source records attributed to Wenguang Liu.

11 recordsLinked to original sources

PubMed2006

Guanidinylated allylamine-N-isopropylacrylamide copolymer nonviral transgene vectors.

N-Isopropylacrylamide and allylamine copolymers (PNIALM) were prepared by radical polymerization method. To endow them with arginine-like cell membrane penetrating function, the aminos in PNIALMs were transformed to guanidinium groups by chemical modification. The formation and guanidinylation PNIALM were confirmed by NMR; the composition of copolymers and the degree of substitution of guanidino in modified copolymer (PNIALM-G) were estimated as well. The electrophoretic assay revealed that PNIALM-G was capable of condensing DNA in spite of lower binding affinity compared to its parent copolymers. The results of particle size analyzer and TEM indicated that at higher copolymer/DNA weight ratios, the copolymer/DNA complexes were condensed to nanoparticles. PNIALM-G1-3 was shown to be very efficient in mediating plasmid DNA transfection to COS-1 cells both in the presence and absence of serum, even superior to PEI.

Acrylamides↗

PubMed2006

A study of thermoresponsive poly(N-isopropylacrylamide)/polyarginine bioconjugate non-viral transgene vectors.

A thermoresponsive poly(N-isopropylacrylamide)/poly(l-arginine)bioconjugate (PNIPArg) was prepared by radical polymerization and EDC-activated coupling. The lower critical solution temperature (LCST) of PNIPArg aqueous solution determined by turbidimetry was around 35.2 degrees Celsius. The transmission electron microscope (TEM) showed that the PNIPArg/DNA complexes appeared uniform nanospheres with size about 50-120nm. Variable temperature circular dichroism (CD) and gel electrophoresis results revealed that the association and dissociation of PNIPArg/DNA complexes could be tuned by varying temperature; polyarginine (PArg) showed no temperature-controllable change of DNA condensate. Incorporation of PNIPAAm considerably decreased the cytotoxicity of PArg. The transfection level of PNIPArg and PArg was evaluated with COS-1 cells using two different reporter genes, pGL3-Control encoding luciferase and pEGP-C1 encoding green fluorescent protein (GFP). The transfection efficiency of PNIPArg incubated at 37 degrees Celsius for 22h, 20 degrees Celsius for 2h and 37 degrees Celsius for 24h was enhanced to a different extent depending on PNIPArg/DNA ratios compared to that incubated at 37 degrees Celsius for 48h. Encouragingly, at PNIPArg/DNA mass ratio of 3/1, the transfection efficiency of PNIPArg obtained with variable temperature route was equivalent to that of Lipofectamine 2000.

Acrylic Resins↗

PubMed2006

Cbf beta regulates Runx2 function isoform-dependently in postnatal bone development.

Runx2 and Cbfbeta are essential for skeletal development during the embryonic stage. Runx2 has two isoforms with different N-termini. We examined the functions of the Runx2 isoforms and Cbfbeta in postnatal bone development. On luciferase and electrophoretic mobility shift assays, Runx2-I was less active than Runx2-II in the absence of Cbfb, but the two Runx2 isoforms had similar activity levels in the presence of Cbfb. We generated Runx2-I transgenic mice under the control of Col1a1 promoter and Runx2-I/Cbfb and Runx2-II/Cbfb double transgenic mice. Runx2-I transgenic mice showed less severe osteopenia and fragility than Runx2-II transgenic mice due to milder inhibition of both osteoblast maturation and transition to osteocytes, even though the former mice showed higher transgene expression. However, Runx2-I/Cbfb and Runx2-II/Cbfb double transgenic mice had enhanced inhibition of osteoblast maturation, resulting in similar severity of osteopenia and fragility, although the latter mice had less osteocytes. These findings indicate that (1) Runx2-II more strongly inhibits osteoblast maturation and transition to osteocytes than Runx2-I; (2) Cbfbeta regulates Runx2 function isoform-dependently; and (3) Runx2-I activity is highly dependent on Cbfbeta. These findings demonstrate that Runx2 isoforms exert their functions through at least partly different mechanisms and Cbfbeta regulates bone development by regulating Runx2 function isoform-dependently.

Animals↗

PubMed2005

An investigation on the physicochemical properties of chitosan/DNA polyelectrolyte complexes.

In this work, to eliminate the effect of the hydrophobicity of N-acetyl groups in chitosan on the interaction between chitosan and DNA, a water soluble chitosan with molecular weight of 5000 and deacetylated degree of 99% was selected to complex with DNA at varied charged ratios. The physicochemical properties of chitoplexes were investigated by means of FTIR, circular dichroism (CD), static fluorescence spectroscopy, and atomic force microscopy (AFM). The results indicated that upon interacting with chitosan, the DNA molecules saved a B conformation, and the binding affinity of chitosan to DNA was dependent on pH of media. At pH 5.5, highly charged chitosan had a strong binding affinity with DNA; whereas in pH 12.0 medium, only weak interactions existed. The CD spectra of Hoechst 33258 competitive displacement revealed that chitosan was partially bound to the minor groove of DNA. The morphology of chitosan/DNA complexes was strongly dependent upon the charge ratios. At charge ratio (+/-) of 1:4, not all DNA could be entrapped in the complex; at ratio of 8:1, the spherical complexes with mean size of nanoscale were formed without free DNA, but no typical toroid patterns were observed, which might stem from the strong compact of DNA caused by highly charged chitosan. It was supposed that the strong interaction of chitosan with DNA possibly prevented gene unpacking from chitosan vector, consequently restraining gene expression in nucleus.

Chitosan↗

PubMed2005

Thermosensitive N-isopropylacrylamide-N-propylacrylamide-vinyl pyrrolidone terpolymers: synthesis, characterization and preliminary application as embolic agents.

In this article, thermosensitive N-isopropylacrylamide (NIPAAm)-N-propylacrylamide (NPAAm)-vinyl pyrrolidone (VP) terpolymers (PNINAVP) were prepared by varying feed ratios with free radical copolymerization method. The composition ratios and molecular weights of PNINAVP were examined by NMR and GPC. The thermo-responsive behaviors of copolymer solutions in the absence and with addition of Iohexol, a radiopaque agent, were investigated by differential scanning calorimetry (DSC) and rheometer. The sol-gel transition of the copolymer solutions occurred reversibly within 1 min in response to temperature. Incorporation of Iohexol increased the transition time and transition temperature of PNINAVP solutions; the rheological properties were also influenced. It was observed that at body temperature, PNINAVP and Iohexol could form an integrated bulky hydrogel presumably due to the hydrogen bonding between them, which was favorable for the clinical follow-up and reducing toxic side effects. In vitro embolic model experiment indicated that 5 wt% 16:16:1H PNINAVP solution containing Iohexol displayed a satisfactory embolization effect. This solution was injected into the rete mirabiles (RM) of six swines through a microcatheter. The angiographical results obtained immediately after the operation showed a complete occlusion of the RM, and no recanalization was observed at postoperative month 1. The histological examination demonstrated no acute inflammatory reaction inside the RM and surrounding tissue. This work could provide a beneficial guidance for designing a new temperature-sensitive polymer-based embolic agent.

Acrylamides↗

PubMed2004

A rapid temperature-responsive sol-gel reversible poly(N-isopropylacrylamide)-g-methylcellulose copolymer hydrogel.

Poly(N-isopropylacrylamide) (PNIPAAm) was grafted to methylcellulose (MC) with various feeding ratios using ammonium persulfate and N,N,N',N'-tetramethyl ethylene diamine as an initiator. FTIR results confirm the formation of PNIPAAm-g-MC copolymers. The temperature responsiveness of copolymer gels was investigated by turbidimetry, dynamic contact angle (DCA), differential scanning calorimetry and dynamic mechanical analysis (DMA). The results indicate that PNIPAAm-g-MC hydrogels are strongly temperature responsive. At lower contents of MC, the lower critical solution temperature (LCST) is decreased, whereas further increasing MC contents raises the LCSTs. It is observed that the phase transition of the hydrogels occurs reversibly within 1 min, and near body temperature, a rigid gel can be generated in a certain range of MC content. What is more, the incorporation of MC prevents the syneresis of copolymer hydrogel. DMA measurement reveals that the storage moduli (E') of the gels increase upon increasing MC contents, and moreover the values of E' go up markedly above LCST. The copolymer hydrogels hold a promise as a blood vessel barrier by tuning gelation temperature, gelation time and mechanical strength.

Acrylic Resins↗

PubMed2004

Unpolymerized nuclear actin is involved in the activation of CSF-1 gene transcription.

Nuclear actin is a nuclear component in many kinds of eukaryotic cells but its function is still not clear. In this study, we overexpressed actin in nuclei and found that it promoted transcription of the CSF-1 gene, both exogenous and endogenous, approximately two-fold. Cytochalasin B did not affect this function of nuclear actin. Our results suggest that nuclear actin plays a role in regulating CSF-1 gene transcription, and this role does not depend on actin polymerization.

Actins↗

PubMed2003

Self-aggregation behavior of alkylated chitosan and its effect on the release of a hydrophobic drug.

Chitosan (CS) was hydrophobically modified with butyl bromide and dodecyl bromide. The self-aggregation in acetic acid solution was characterized by fluorescence spectroscopy and dynamic light-scattering method. The results indicate that introducing butyl and dodecyl moieties leads to the formation of self-aggregates. Along with the enhancement in the hydrophobicity of chitosan the self-association occurs at a lower concentration, and the mean size of self-aggregates increases. The loading capacity of butylated chitosan (4-CS) and dodecylated chitosan (12-CS) for vitamin B2 are markedly increased compared to that of chitosan, and the release of drug from alkylated chitosans is somewhat hindered due to its increased affinity for hydrophobic carriers.

Alkylation↗

PubMed2002

Modulation of osteoblast function using poly(D,L-lactic acid) surfaces modified with alkylation derivative of chitosan.

Poly(D,L-lactic acid) (PDLLA) was modified with alkylated chitosan (N-butyl chitosan and N-cetyl chitosan), and the effects of modified films on the functions of rat osteoblasts were investigated. The characteristics of surfaces (both modified and control) were examined by water contact angle measurement and electron spectroscopy for chemical analysis (ESCA). Cell morphologies on these surfaces were taken using scanning electron microscopy (SEM). Cell attachment and proliferation were used to assess cell behavior on modified surface and control. MTT assay was used to determined cell viability, and alkaline phosphatase (ALP) activity was taken to evaluate differentiated cell function. Compared with the untreated films, no significant difference in cell attachment of osteoblasts was found on the modified films at a period of 8 h (p > 0.05). However, cell proliferation of N-butyl chitosan rather than N-cetyl chitosan modified PDLLA films was significantly higher than that found on control one (p < 0.05) at the end of the 4th and 7th days. The cell viability of osteoblasts on N-butyl chitosan modified PDLLA films were found higher than that on control (p < 0.05). These results suggested that N-butyl chitosan contributed greater than N-cetyl chitosan when used to modify PDLLA films for improving its biocompatibility.

Alkaline Phosphatase↗

PubMed2002

Impaired vascular invasion of Cbfa1-deficient cartilage engrafted in the spleen.

Chondrocyte maturation and vascular invasion of cartilage are essential in the process of endochondral ossification. Cbfal-deficient (Cbfa1-/-) mice displayed a complete absence of osteoblast and osteoclast maturation as well as severely inhibited chondrocyte maturation in most parts of the skeleton. Although chondrocyte maturation and mineralization were observed in restricted areas of Cbfa1-/- mouse skeleton, vascular invasion of calcified cartilage was never noted. To investigate the possibility of chondrocyte maturation and vascular invasion in Cbfal-/- cartilage and the role of the hematopoietic system in the process of vascular invasion, we transplanted embryonic day 18.5 (E18.5) Cbfa1-/- femurs, which are composed of immature chondrocytes, into spleens of normal mice. One week later, the transplanted femurs contained terminally differentiated chondrocytes expressing osteopontin, bone sialoprotein (BSP), and matrix metalloproteinase (MMP) 13. In the diaphyses of the transplants, the cartilage matrix was mineralized and the cartilage was invaded by vascular vessels and osteoclasts. However, chondrocyte maturation and vascular invasion were severely retarded in comparison with transplants of E14.5 wild-type femurs, in which the cartilage was rapidly replaced by bone, and neither mature osteoblasts nor bone formation were observed. In primary culture of Cbfa1-/- chondrocytes, transforming growth factor (TGF) beta1, platelet-derived growth factor (PDGF), interleukin (IL)-1beta, and thyroid hormone (T3) induced osteopontin and MMP-13 expression. These findings indicated that factors in the hematopoietic system are able to support vascular invasion of cartilage independent of Cbfal but are less effective without it, suggesting that Cbfal functions in cooperation with factors from bone marrow in the process of growth plate vascularization.

Animals↗

PubMedDate not supplied

A thermoresponsive chitosan-NIPAAm/vinyl laurate copolymer vector for gene transfection.

A carboxyl-terminated N-isopropylacrylamide/vinyl laurate (VL) copolymer was prepared and coupled with chitosan (molecular weight = 2000) to produce a chitosan-NIPAAm/VL copolymer (PNVLCS) vector. The aqueous solution of PNVLCS displayed an obvious thermoresponsive behavior with a lower critical solution temperature (LCST) about 26 degrees C. The transmission electron microscopy (TEM) showed that the size of PNVLCS/DNA complexes varied with charge ratios (+/-), and the smaller nanoparticles were formed at higher charge ratios. DLS revealed that the size of complex particles was dependent on temperature. The results of temperature-variable circular dichroism (CD), UV, and electrophoresis retardation indicated that at lower charge ratios, DNA in the complexes assume a B conformation, whereas increasing charge ratios caused B --> C type conformation transformation; the dissociation-formation of PNVLCS/DNA complexes could be tuned by varying temperature: at 37 degrees C, the collapse of PNIPAAm in PNVLCS was favorable for the formation of compact complexes, shielding more DNA from exposure; at 20 degrees C, the hydrated and extended PNIPAAm chains facilitated the unpacking of DNA from PNVLCS, increasing the exposure of DNA. PNVLCS was used to transfer plasmid-encoding beta-galactosidase into C2C12 cells. The level of gene expression could be controlled by varying incubation temperature. The transfection efficiency of PNVLCS was well improved by temporarily reducing culture temperature to 20 degrees C, whereas naked DNA and Lipofectamine 2000 did not demonstrate the characteristics of thermoresponsive gene transfection.

Acetanilides↗