Biomedical subjects

Shuwen Hu

Publications and source records attributed to Shuwen Hu.

6 recordsLinked to original sources

PubMed2026

Transmission dynamics and driving mechanisms of antibiotic resistance genes through a chronosequence of saline-sodic rice cultivation.

Rice cultivation reclaims saline-sodic soils and improves fertility, but may also promote antibiotic resistance genes (ARGs) accumulation and horizontal transfer, posing ecological risks. This study investigated long-term co-evolution of soil properties, microbial communities, ARGs, and mobile genetic elements (MGEs) across a 1-78 year cultivation chronosequence in saline-sodic fields. Results indicated that prolonged cultivation effectively alleviated soil salinization and increased fertility. Microbial communities shifted directionally, with functional taxa enriched, while opportunistic pathogen-containing genera peaked during 5-20 years. ARGs abundance and diversity increased markedly after five years and peaked at 10-20 years. Multidrug efflux pump genes persisted throughout the chronosequence, whereas aminoglycoside resistance genes declined after 30 years. MGEs activity increased over time and was significantly correlated with key ARGs. Path analysis identified improved soil properties as the primary direct driver of ARGs accumulation, while cultivation-induced declines in microbial diversity indirectly promoted ARGs dissemination by weakening the community's suppression of MGEs-mediated horizontal transfer. Collectively, long-term rice cultivation not only ameliorated saline-sodic soils but also created a dynamic, stage-specific resistome, with the 5-20 year period representing a critical risk window for ARGs propagation. These findings highlight the need to integrate ARGs monitoring into soil health assessments for sustainable management of reclaimed saline-sodic lands.

Oryza↗

PubMed2004

Tailoring the surface properties of poly(dimethylsiloxane) microfluidic devices.

Poly(dimethylsiloxane) (PDMS) is an attractive material for microelectrophoretic applications because of its ease of fabrication, low cost, and optical transparency. However, its use remains limited compared to that of glass. A major reason is the difficulty of tailoring the surface properties of PDMS. We demonstrate UV grafting of co-mixed monomers to customize the surface properties of PDMS microfluidic channels in a simple one-step process. By co-mixing a neutral monomer with a charged monomer in different ratios, properties between those of the neutral monomer and those of the charged monomer could be selected. Mixtures of four different neutral monomers and two different charged monomers were grafted onto PDMS surfaces. Functional microchannels were fabricated from PDMS halves grafted with each of the different mixtures. By varying the concentration of the charged monomer, microchannels with electrophoretic mobilities between +4 x 10(-4) cm2/(V s) and -2 x 10(-4) cm2/(V s) were attainable. In addition, both the contact angle of the coated surfaces and the electrophoretic mobility of the coated microchannels were stable over time and upon exposure to air. By carefully selecting mixtures ofmonomers with the appropriate properties, it may be possible to tailor the surface of PDMS for a large number of different applications.

Dimethylpolysiloxanes↗

PubMed2004

Surface-directed, graft polymerization within microfluidic channels.

We demonstrate a simple procedure to coat the surfaces of enclosed PDMS microchannels by UV-mediated graft polymerization. In prior applications, only disassembled channels could be coated by this method. This limited the utility of the method to coatings that could easily and tightly seal with themselves. By preadsorbing a photoinitiator onto the surface of PDMS microchannels, the rate of polymer formation at the surface was greatly accelerated compared to that in solution. Thus, a gel did not form in the lumen of enclosed microchannels. We demonstrate that the photoinitiator benzophenone remained on the surface of PDMS even after extensive washing. After addition of a variety of monomer solutions (acrylic acid, poly(ethylene glycol) monomethoxyl acrylate, or poly(ethylene glycol) diacrylate) and illumination with UV light, a stable, covalently attached surface coating formed in the microchannels. The electroosmotic mobility was stable in response to air exposure and to repeated cycles of hydration-dehydration of the coating. These surfaces also supported the electrophoretic separation of two model analytes. Placement of an opaque mask over a portion of the channel permitted photopatterning of the microchannels with a resolution of approximately 100 microm. By using an appropriate mixture of monomers combined with masks, it should be possible to fabricate PDMS microfluidic devices with distinct surface properties in different regions or channels.

Journal Article↗

PubMed2003

Separation of mixtures of acidic and basic peptides at neutral pH.

Mixtures of acidic and basic peptides composed of the phosphorylated and nonphosphorylated forms of peptide substrates for kinases and a phosphatase were separated by capillary electrophoresis (CE) in buffer conditions compatible with live mammalian cells. The separation of such mixtures was especially challenging given the high salt and neutral pH of the requisite physiologic buffers. Due to poor peak reproducibility in bare capillaries, several strategies were implemented to improve the electrophoretic separation of the peptide mixtures. Covalent coating of the capillary with the neutral polymer poly(dimethylacrylamide) (PDMA) resulted in a 2-fold improvement in the migration time RSD, but required the use of hydrodynamic flow to overcome the differing electrophoretic mobilities (microeo) of the peptides at neutral pH. This parabolic fluid flow diminished separation efficiency almost 5-fold. Polarity switching during the CE run was used to overcome the opposed microeo, but required the retention of hydrodynamic flow and consequent reduction in separation efficiency. The most efficient separations were seen with the use of covalently-linked, charged polymer coatings to maintain electroosmotic flow and to reduce wall interactions. Two such coatings were tested in the current study. Relative to the PDMA coating, an anionic poly(acrylate) improved the average migration time RSD of six peptides from 1.3 to 0.85% and average separation efficiency from 4.8 to 18.0 (x 10(4) plates/m). Likewise, cationic poly([3-(methacryloylamino)propyl]-trimethylammonium) improved the average migration time RSD of eight peptides from 1.2 to 1.1% and average separation efficiency from 4.8 to 33.9 (x 10(4) plates/m). These findings will be of value to the growing number of applications for analytical techniques utilizing CE for cellular analysis and biochemical studies.

Amino Acid Sequence↗

PubMed2003

Cross-linked coatings for electrophoretic separations in poly(dimethylsiloxane) microchannels.

We have developed a strategy using ultraviolet light to polymerize mixed monomer solutions onto the surface of a poly(dimethylsiloxane) (PDMS) microdevice. By including monomers with different chemical properties, electrophoretic separations were optimized for a test set of analytes. The properties of surfaces grafted with a single neutral monomer, a neutral and a negative monomer, or a neutral, negative, and cross-linking monomer were assessed. The highest quality separations were achieved in channels with cross-linked coatings. The separation efficiency for biologically relevant peptides (kinase substrates) on these surfaces was as high as 18 600 theoretical plates in a 2.5 cm channel. The test peptides were fluorescein-AEEEIYGEFEAKKKK, fluorescein-GRPRAATFAEG, fluorescein-GRPRAA(T-PO(3))FAEG, fluorescein-DLDVPIP GRFDRRVSVAAE, and fluorescein-DLDVPIPGRFDRRV(S-PO(3))VAAE. Separations between two different peptides occurred in as little as 400 ms after injection into the separation channel. The simultaneous separation of five kinase and phosphatase substrates was also demonstrated. By carefully selecting mixtures of monomers with the appropriate properties, it may be possible to tailor the surface of PDMS for a large number of different electrophoretic separations.

Amino Acid Sequence↗

PubMed2002

Surface modification of poly(dimethylsiloxane) microfluidic devices by ultraviolet polymer grafting.

Poly(dimethylsiloxane) (PDMS)-based microfluidic devices are increasing in popularity due to their ease of fabrication and low costs. Despite this, there is a tremendous need for strategies to rapidly and easily tailor the surface properties of these devices. We demonstrate a one-step procedure to covalently link polymers to the surface of PDMS microchannels by ultraviolet graft polymerization. Acrylic acid, acrylamide, dimethylacrylamide, 2-hydroxylethyl acrylate, and poly(ethylene glycol)monomethoxyl acrylate were grafted onto PDMS to yield hydrophilic surfaces. Water droplets possessed contact angles as low as 45 degrees on the grafted surfaces. Microchannels constructed from the grafted PDMS were readily filled with aqueous solutions in contrast to devices composed of native PDMS. The grafted surfaces also displayed a substantially reduced adsorption of two test peptides compared to that of oxidized PDMS. Microchannels with grafted surfaces exhibited electroosmotic mobilities intermediate to those displayed by native and oxidized PDMS. Unlike the electroosmotic mobility of oxidized PDMS, the electroosmotic mobility of the grafted surfaces remained stable upon exposure to air. The electrophoretic resolution of two test peptides in the grafted microchannels was considerably improved compared to that in microchannels composed of oxidized PDMS. By using the appropriate monomer, it should be possible to use UV grafting to impart a variety of surface properties to PDMS microfluidics devices.

Dimethylpolysiloxanes↗