Xianghui Liu - Academia.edu (original) (raw)
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Central council for research in Siddha/Siddha Central Research Institute
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Papers by Xianghui Liu
Charge-Shifting Cationic Polymers That Promote Self-Assembly and Self-Disassembly with DNA
Macromolecules, 2005
Chemical Communications, 2010
Supplementary Information Experimental Section General Considerations. 1 H nuclear magnetic reson... more Supplementary Information Experimental Section General Considerations. 1 H nuclear magnetic resonance (NMR) spectra were recorded on Bruker AC+ 250 (250.133 MHz) and Bruker AC+ 300 (300.135 MHz) spectrometers. Chemical shift values are given in ppm and are referenced with respect to residual protons from solvent. Gel permeation chromatography (GPC) was performed using a GPCmax-VE2001 Solvent/Sample module (Viscotek Corp., Houston, TX) and two PlusPore Organic GPC Columns (Polymer Laboratories, Amherst, MA) in series. For the characterization of poly(2vinyl-4,4-dimethylazlactone) (PVDMA), THF was used as the eluent at a flow rate of 1.0 mL/min. For the characterization of polymers P1-P12, THF with 0.1 M triethylamine (TEA) was used as the eluent at a flow rate of 1.0 mL/min. Data were collected using the refractive index detector of a Viscotek TDA 302 triple detector array and processed using the OminiSEC 4.5 software package. Molecular weights and polydispersities are reported relative to monodisperse polystyrene standards. Attenuated total reflectance infrared spectroscopy data were collected on a Bruker TENSOR 27 FTIR instrument (Billerica, MA) outfitted with an ATR transmission cell from Pike Technologies (Madison, WI). Fluorescence microscopy images used to evaluate the expression of enhanced green fluorescent protein in transfection experiments were recorded
Biomacromolecules, 2008
We reported recently that the addition of ester-functionalized, "charge-shifting" side chains to ... more We reported recently that the addition of ester-functionalized, "charge-shifting" side chains to linear poly(ethyleneimine) (LPEI) can be used to design polyamines that promote both self-assembly and self-disassembly with DNA in aqueous environments. This investigation sought to characterize the influence of charge-shifting side chains on the ability of LPEI to mediate cell transfection and understand the extent to which increases (or decreases) in levels of transfection could be understood in terms of time-dependent changes in the net charges of these polymers. We report that the addition of "charge-shifting" side chains to LPEI leads to significant increases in levels of LPEI-mediated transfection. In particular, polymer 1e, functionalized with 20 mol % ester-functionalized side chains, mediates levels of transgene expression in vitro up to 8-fold higher than LPEI. Experiments using an amide-functionalized analog of polymer 1e demonstrated that the esters in polymer 1e play an important role in promoting increased levels of transfection. These results, in combination with the results of additional gel electrophoresis experiments, provide support for the view that increases in transfection result from time-dependent changes in the net charge of polymer 1e and the disruption of ionic interactions in polyplexes. Additional support for this view is provided by the results of confocal microscopy experiments and measurements of fluorescence resonance energy transfer, which suggest that polymer 1e promotes the disruption of polyplexes in intracellular environments effectively. The approach reported here provides a means of addressing one important "late-stage" obstacle to polyplex-mediated transfection (polyplex unpackaging). If integrated successfully with methods that have been developed to address other important barriers to transfection, this general approach could lead to the development of multifunctional polyplexes that mimic more effectively the range of functions of viruses as agents for the delivery of DNA.
Biomacromolecules, 2010
The fungal pathogen Candida albicans can form biofilms on the surfaces of medical devices that ar... more The fungal pathogen Candida albicans can form biofilms on the surfaces of medical devices that are resistant to drug treatment and provide a reservoir for recurrent infections. The use of fungicidal or fungistatic materials to fabricate or coat the surfaces of medical devices has the potential to reduce or eliminate the incidence of biofilm-associated infections. Here, we report on (i) the fabrication of multilayered polyelectrolyte thin films (PEMs) that promote the surfacemediated release of an antifungal β-peptide and (ii) the ability of these films to inhibit the growth of C. albicans on film-coated surfaces. We incorporated a fluorescently labeled antifungal βpeptide into the structures of PEMs fabricated from poly-L-glutamic acid (PGA) and poly-Llysine (PLL) using a layer-by-layer fabrication procedure. These films remained stable when incubated in culture media at 37 °C and released β-peptide gradually into solution for up to 400 hours. Surfaces coated with β-peptide-containing films inhibited the growth of C. albicans, resulting in a 20% reduction of cell viability after two hours and a 74% decrease in metabolic activity after seven hours when compared to cells incubated on PGA/PLL coated surfaces. In addition, β-peptide-containing films inhibited hyphal elongation by 55%. These results, when combined, demonstrate that it is possible to fabricate β-peptide-containing thin films that inhibit the growth and proliferation of C. albicans and provide the basis of an approach that could be used to inhibit the formation of C. albicans biofilms on film-coated surfaces. The layer-by-layer approach reported here could ultimately be used to coat the surfaces of catheters, surgical instruments, and other devices to inhibit drug-resistant C. albicans biofilm formation in clinical settings.
Advanced Materials, 2007
Financial support was provided by the 3M Corporation and the Arnold and Mabel Beckman Foundation.... more Financial support was provided by the 3M Corporation and the Arnold and Mabel Beckman Foundation. We thank Dr. Steven M. Heilmann (3M) for providing samples of poly(2-vinyl-4,4-dimethylazlactone) and for many helpful discussions, and Aaron Lowe for assistance with microcontact printing experiments. M.E.B. was funded in part by an NIH Chemistry Biology Interface Training Grant (NIGMS T32 GM008505). D.M.L.
Charge-Shifting Cationic Polymers That Promote Self-Assembly and Self-Disassembly with DNA
Macromolecules, 2005
Chemical Communications, 2010
Supplementary Information Experimental Section General Considerations. 1 H nuclear magnetic reson... more Supplementary Information Experimental Section General Considerations. 1 H nuclear magnetic resonance (NMR) spectra were recorded on Bruker AC+ 250 (250.133 MHz) and Bruker AC+ 300 (300.135 MHz) spectrometers. Chemical shift values are given in ppm and are referenced with respect to residual protons from solvent. Gel permeation chromatography (GPC) was performed using a GPCmax-VE2001 Solvent/Sample module (Viscotek Corp., Houston, TX) and two PlusPore Organic GPC Columns (Polymer Laboratories, Amherst, MA) in series. For the characterization of poly(2vinyl-4,4-dimethylazlactone) (PVDMA), THF was used as the eluent at a flow rate of 1.0 mL/min. For the characterization of polymers P1-P12, THF with 0.1 M triethylamine (TEA) was used as the eluent at a flow rate of 1.0 mL/min. Data were collected using the refractive index detector of a Viscotek TDA 302 triple detector array and processed using the OminiSEC 4.5 software package. Molecular weights and polydispersities are reported relative to monodisperse polystyrene standards. Attenuated total reflectance infrared spectroscopy data were collected on a Bruker TENSOR 27 FTIR instrument (Billerica, MA) outfitted with an ATR transmission cell from Pike Technologies (Madison, WI). Fluorescence microscopy images used to evaluate the expression of enhanced green fluorescent protein in transfection experiments were recorded
Biomacromolecules, 2008
We reported recently that the addition of ester-functionalized, "charge-shifting" side chains to ... more We reported recently that the addition of ester-functionalized, "charge-shifting" side chains to linear poly(ethyleneimine) (LPEI) can be used to design polyamines that promote both self-assembly and self-disassembly with DNA in aqueous environments. This investigation sought to characterize the influence of charge-shifting side chains on the ability of LPEI to mediate cell transfection and understand the extent to which increases (or decreases) in levels of transfection could be understood in terms of time-dependent changes in the net charges of these polymers. We report that the addition of "charge-shifting" side chains to LPEI leads to significant increases in levels of LPEI-mediated transfection. In particular, polymer 1e, functionalized with 20 mol % ester-functionalized side chains, mediates levels of transgene expression in vitro up to 8-fold higher than LPEI. Experiments using an amide-functionalized analog of polymer 1e demonstrated that the esters in polymer 1e play an important role in promoting increased levels of transfection. These results, in combination with the results of additional gel electrophoresis experiments, provide support for the view that increases in transfection result from time-dependent changes in the net charge of polymer 1e and the disruption of ionic interactions in polyplexes. Additional support for this view is provided by the results of confocal microscopy experiments and measurements of fluorescence resonance energy transfer, which suggest that polymer 1e promotes the disruption of polyplexes in intracellular environments effectively. The approach reported here provides a means of addressing one important "late-stage" obstacle to polyplex-mediated transfection (polyplex unpackaging). If integrated successfully with methods that have been developed to address other important barriers to transfection, this general approach could lead to the development of multifunctional polyplexes that mimic more effectively the range of functions of viruses as agents for the delivery of DNA.
Biomacromolecules, 2010
The fungal pathogen Candida albicans can form biofilms on the surfaces of medical devices that ar... more The fungal pathogen Candida albicans can form biofilms on the surfaces of medical devices that are resistant to drug treatment and provide a reservoir for recurrent infections. The use of fungicidal or fungistatic materials to fabricate or coat the surfaces of medical devices has the potential to reduce or eliminate the incidence of biofilm-associated infections. Here, we report on (i) the fabrication of multilayered polyelectrolyte thin films (PEMs) that promote the surfacemediated release of an antifungal β-peptide and (ii) the ability of these films to inhibit the growth of C. albicans on film-coated surfaces. We incorporated a fluorescently labeled antifungal βpeptide into the structures of PEMs fabricated from poly-L-glutamic acid (PGA) and poly-Llysine (PLL) using a layer-by-layer fabrication procedure. These films remained stable when incubated in culture media at 37 °C and released β-peptide gradually into solution for up to 400 hours. Surfaces coated with β-peptide-containing films inhibited the growth of C. albicans, resulting in a 20% reduction of cell viability after two hours and a 74% decrease in metabolic activity after seven hours when compared to cells incubated on PGA/PLL coated surfaces. In addition, β-peptide-containing films inhibited hyphal elongation by 55%. These results, when combined, demonstrate that it is possible to fabricate β-peptide-containing thin films that inhibit the growth and proliferation of C. albicans and provide the basis of an approach that could be used to inhibit the formation of C. albicans biofilms on film-coated surfaces. The layer-by-layer approach reported here could ultimately be used to coat the surfaces of catheters, surgical instruments, and other devices to inhibit drug-resistant C. albicans biofilm formation in clinical settings.
Advanced Materials, 2007
Financial support was provided by the 3M Corporation and the Arnold and Mabel Beckman Foundation.... more Financial support was provided by the 3M Corporation and the Arnold and Mabel Beckman Foundation. We thank Dr. Steven M. Heilmann (3M) for providing samples of poly(2-vinyl-4,4-dimethylazlactone) and for many helpful discussions, and Aaron Lowe for assistance with microcontact printing experiments. M.E.B. was funded in part by an NIH Chemistry Biology Interface Training Grant (NIGMS T32 GM008505). D.M.L.