Temperature-sensitive hydrogel—poly(N-isopropyl acrylamide) (PNIPA) was prepared and applied to protein refolding. PNIPA gel disks and gel particles were synthesized by the solution polymerization and inverse suspens...Temperature-sensitive hydrogel—poly(N-isopropyl acrylamide) (PNIPA) was prepared and applied to protein refolding. PNIPA gel disks and gel particles were synthesized by the solution polymerization and inverse suspension polymerization respectively. The swelling kinetics of the gels was also studied. With these prepared PNIPA gels, the model protein lysozyme was renatured. Within 24h, PNIPA gel disks improved the yield of lysozyme activity by 49.3% from 3375.2U·mg^-1 to 5038.8U·mg^-1. With the addition of faster response PNIPA gel beads, the total lysozyme activity recovery was about 68.98% in 3h, as compared with 42.03% by simple batch dilution. The novel refolding system with PNIPA enables efficient refolding especially at high protein concentrations. Discussion about the mechanism revealed that when PNIPA gels were added into the refolding buffer, the hydrophobic interactions between denatured proteins and polymer gels could prevent the aggregation of refolding intermediates, thus enhanced the protein renaturation.展开更多
Smart functional microgels hold great potential in a variety of applications,especially in drug transportation.However,current drug carriers based on physiological internal stimuli cannot efficiently orientate to desi...Smart functional microgels hold great potential in a variety of applications,especially in drug transportation.However,current drug carriers based on physiological internal stimuli cannot efficiently orientate to designated locations.Therefore,it is necessary to introduce the self-propelled particles to the drug release of the microgels.In order to study self-propulsion of microgels induced by light,it is also a challenge to prepare micronsized microgels so that they can be observed directly under optical microscopes.In this work,phototactic microgels with photoresponsive properties are prepared.The microgel particles can be observed by confocal laser scanning microscopy.The photoresponsive properties of microgels are fully investigated by various instruments.Light can also regulate the state of the microgel solution,making it switch between turbidity and clarity.The phototaxis of particles irradiated by UV light was studied,which may be used for microgels enrichment and drug transportation and release.展开更多
Thiol-stabilized PbS quantum dots （QDs） with dimensions 3-5 nm capped with a mixture of 1-thioglycerol/dithioglycerol （TGL/DTG） were coUoidally prepared at room temperature. Room temperature photoluminescence quan...Thiol-stabilized PbS quantum dots （QDs） with dimensions 3-5 nm capped with a mixture of 1-thioglycerol/dithioglycerol （TGL/DTG） were coUoidally prepared at room temperature. Room temperature photoluminescence quantum efficiency of freshly prepared PbS QDs （7%-11%） remained higher than 5% upon aging for three weeks when the nanocrystals （NCs） were stored in an ice-bath in the dark, and higher than 5%for at least five weeks when extra DTG ligands were introduced into the nanocrystal solution followed by stirring every two weeks. Poly（N-isopropyl acrylamide） （PNIPAM） microgels were produced via precipitation polymerization with dimensions of ca. 230 nm and polydispersity of 3-5%. Incorporation of PbS QDs into PNIPAM microgels indicated that PbS can be incorporated into the interior of microgel particles and not at the microgel interface. The combination of reasonable room temperature quantum efficiency and strong, efficient luminescence covering the 1.3-1.55 μm telecommunication window makes these nanoparticles promising materials in optical devices and telecommunications.展开更多
It is extremely important for photocatalysts to exhibit intelligent responsiveness to their environment. Herein, a poly N-isopropyl acrylamide(PNIPAM)-modified Ag/Ag3PO4-20/CN hybrid material with excellent convertibl...It is extremely important for photocatalysts to exhibit intelligent responsiveness to their environment. Herein, a poly N-isopropyl acrylamide(PNIPAM)-modified Ag/Ag3PO4-20/CN hybrid material with excellent convertible photocatalytic activity is prepared. PNIPAM has good hydrophilicity below the lower critical solution temperature(LCST);this increases the capacity of the photocatalyst for adsorbing tetracycline(TC) molecules. In addition, the PNIPAM-modified Ag/Ag3PO4-20/CN can prevent the loss of Ag3PO4. The dispersity is improved by loading g-C3N4 nanosheets(CN) for enhancing the efficiency of photocatalytic activity. Furthermore, a Z-scheme heterostructure is formed between CN and Ag3PO4, accelerating the separation efficiency of the holes and electrons. Ag nanoparticles can be used as electron-shuttle mediators, and electrons receiving more energy are transferred via the localized surface plasmon resonance(LSPR) effect. Furthermore, the PNIPAM@Ag/Ag3PO4-20/CN photocatalyst exhibits an excellent degradation rate for the degradation of TC when the temperature is lower than the LCST. The photoluminescence spectra and photocurrent curves prove that the carrier-separation efficiency of PNIPAM@Ag/Ag3PO4-20/CN is higher than those of Ag/Ag3PO4/CN and CN. The main active species of ·O2-and h+ are detected to reveal the plausible mechanism of the PNIPAM@Ag/Ag3PO4-20/CN hybrid material system. This work provides a way to develop intelligent materials for switchable photocatalytic applications.展开更多
A series of poly(N-isopropyl acrylamide) (PNIPAM) samples with molecular weight ranging from 2.23 × 104 to 130 × 104 and molecular weight distributionMw/Mn ≤1. 28 were obtained by free radical polymerizatio...A series of poly(N-isopropyl acrylamide) (PNIPAM) samples with molecular weight ranging from 2.23 × 104 to 130 × 104 and molecular weight distributionMw/Mn ≤1. 28 were obtained by free radical polymerization and repeat precipitation fractionation. The molecular weightMw, second virial coefficientA2 as well as the mean-square-root radius of gyration < S2 > for PNIPAM samples in tetrahydrofuran (THF) were determined by light scattering, and the relations were estimated atA2 ∞ M w- 0.25 and S2 1/2 = 1.56 × 10-9 Mw 0.56. The intrinsic viscosity for THF solution and methanol solution of PNIPAM samples was measured and the Mark-Houwink equations were obtained as [η] =6.90x 10-5 M0. 73(THF solution) and [η] = 1.07 × 10-4 M0.71(methanol solution). The above results indicate that both THF and methanol are good solvents for PNIPAM. The limit characteristic ratioC ∞ for PNIPAM in the two solutions was determined to be 10.6 by using Kurata-Stockmayer equation, indicating that the flexibility of PNIPAM chain is close to that of polystyrene. The intrinsic viscosity for the aqueous solution of PNIPAM was measured at 25-30.5°C. The result demonstrates that PNIPAM chain begins to shrink at 25°C, and from about 30°C, onward the molecular chain shrinks much more sharply till the solution becomes macroscopically unstable at 32°C.展开更多
By dynamic viscoelastic measurement for PNIPAM/water solution it has been found that below the phase separation temperature (about 32°C), the system is homogeneous fluid; while upon being heated to about 32°...By dynamic viscoelastic measurement for PNIPAM/water solution it has been found that below the phase separation temperature (about 32°C), the system is homogeneous fluid; while upon being heated to about 32°C, the solution undergoes phase separation and the storage modulus G’ increases sharply and exceeds the loss modulus G”, indicating the physical network formation during the phase separation. Based on the percolation model, the gel points Tgel were obtained by applying the dynamic scaling theory (DST) and Winter’s criterion. The critical exponent n was also obtained to be 0.79 through DST, which is different from 0.67, the critical point of chemically crosslinked network predicted through DST. The obtained n value reflects the special property of physical network being different from chemical network.展开更多
A series of porous intelligent hydrogels, which exhibited appropriate lower critical solution temperature (LCST) and fast response behavior, were synthesized by radiation method. The structure and surface morphology o...A series of porous intelligent hydrogels, which exhibited appropriate lower critical solution temperature (LCST) and fast response behavior, were synthesized by radiation method. The structure and surface morphology of hydrogels were examined by the infrared radiation and the scanning electron microscopy, respectively. The influences of the content of crosslinking agent and relative molecular mass of polyethylene glycol (PEG) on the swelling properties of hydrogels were discussed. The molecular mechanics simulations were performed to investigate the phase transformation mechanism of poly(N-isopropyl acrylamide) (PNIPA) hydrogel. The results show that macropores are observed in hydrogels, whereas hydrogels prepared without using PEG have a dense surface. LCST of hydrogels increases with the increase of relative molecular mass of PEG. The swelling mechanism of PNIPA porous hydrogels follows non-Fickian diffusion model. The theoretical maximum water absorption S∞ is approximately consistent with experimental value according to the second-order kinetics model established by Schott. The molecule chains of PNIPA hydrogel begin folding and curling, resulting in volume shrinkage at 305 K. There are much intramolecular nonbonding interactions in molecule chains of hydrogels. The porous hydrogels are expected to be applied in the field of artificial intelligence material.展开更多
The effect of cross-linker (methylene-bis-acrylamide) (MBA) on the volume phase transition, mechanical properties and de-swelling of Poly(N-isopropyl acrylamide-co-methylene-bis-acrylamide) hydrogel (PNIPAAm/MBA hydro...The effect of cross-linker (methylene-bis-acrylamide) (MBA) on the volume phase transition, mechanical properties and de-swelling of Poly(N-isopropyl acrylamide-co-methylene-bis-acrylamide) hydrogel (PNIPAAm/MBA hydrogel) was investigated. A new method, namely isothermal thermo-gravimetry was developed for monitoring de-swelling of PNIPAAm/MBA hydrogel. Monomer/ Cross-linker ratio of the initial monomer composition R = moleNIPAAm/moleMBA was introduced. It has been proven earlier that initial monomer composition is close to the copolymer composition;hence R values may be used to express cross-link density. Hydrogels from R10 to R150 were investigated. The results of DSC analysis revealed that the less the cross-linker ratio in the gel (from R10 to R150) the more sharp the temperature range of volume phase transition and the higher its enthalpy. Cross-link density, namely increasing cross-linker content in the copolymer (R from 150 to 10) does not significantly affect the temperature range of volume phase transition. It sets on at 33°C - 34°C, and ends between 35?C and 38?C. Cross-link density has significant effect on compression modulus. By decreasing the ratio of cross-linker (by increasing R from 10 to 150), the compression modulus increases, goes through a maximum, and then decreases. The highest compression modulus was measured for PNIPAAm/MBA hydrogel R20. Hydrogels with cross-linker content between R100 and 30 are strong enough and have their thermoresponsivity. Isothermal thermograms of de-swelling are of similar character for all the gels with different cross-linker content. During the initial stage of de-swelling for gels with higher cross-linker content (R10 - R15) the solute release is quicker than for gels R20 - 150 and the thermograms are drawn out. In the initial stage of de-swelling, i.e. during the first 40 minutes the rate of solute release is the highest for gels R70 - 150. The cross-linker content effects solute release, especially for gels with high cross-linker content. It is noteworthy that gels R10 - 15 release solute quicker than gels R30 - 50 and their rate of de-swelling is comparable to that of gels R100 - 150. The novel thermogravimetric method enables the selection of gels based on the rate of solute release and it can also be applied for other cross-linked gels.展开更多
Six different N-alkyl substituted acrylarnide nonionic hydrogels were prepared and their swelling characteristics were measured. Poly N-isopropyl acrylamide (PNIPA) and poly N-n-propyl-acrylamide (PNNPA) temperature s...Six different N-alkyl substituted acrylarnide nonionic hydrogels were prepared and their swelling characteristics were measured. Poly N-isopropyl acrylamide (PNIPA) and poly N-n-propyl-acrylamide (PNNPA) temperature sensitive hydrogels were chosen as the nonionic temperature sensitive hydrogels for concentration of very dilute aqueous protein solution. The separation properties of PNIPA and PNNPA hydr0gels with different network dimensions were studied and the modification of the hydrogels was surveyed in order to decrease their surface adsorption of protein molecules. The experimental results of the concentration of BSA (Bovin serum albumin) dilute aqueous solution by hydroxylpropyl methacrylate (HPMA) copolymerized PNIPA hydrogel were given. The value and the limitation of concentration of dilute aqueous protein solution by this method was evaluated.展开更多
基金the National Natural Science Foundation of China (No. 20276065).
文摘Temperature-sensitive hydrogel—poly(N-isopropyl acrylamide) (PNIPA) was prepared and applied to protein refolding. PNIPA gel disks and gel particles were synthesized by the solution polymerization and inverse suspension polymerization respectively. The swelling kinetics of the gels was also studied. With these prepared PNIPA gels, the model protein lysozyme was renatured. Within 24h, PNIPA gel disks improved the yield of lysozyme activity by 49.3% from 3375.2U·mg^-1 to 5038.8U·mg^-1. With the addition of faster response PNIPA gel beads, the total lysozyme activity recovery was about 68.98% in 3h, as compared with 42.03% by simple batch dilution. The novel refolding system with PNIPA enables efficient refolding especially at high protein concentrations. Discussion about the mechanism revealed that when PNIPA gels were added into the refolding buffer, the hydrophobic interactions between denatured proteins and polymer gels could prevent the aggregation of refolding intermediates, thus enhanced the protein renaturation.
基金supported by the National Natural Science Foundation of China(No.21274135,No.21871243 and No.51673181)。
文摘Smart functional microgels hold great potential in a variety of applications,especially in drug transportation.However,current drug carriers based on physiological internal stimuli cannot efficiently orientate to designated locations.Therefore,it is necessary to introduce the self-propelled particles to the drug release of the microgels.In order to study self-propulsion of microgels induced by light,it is also a challenge to prepare micronsized microgels so that they can be observed directly under optical microscopes.In this work,phototactic microgels with photoresponsive properties are prepared.The microgel particles can be observed by confocal laser scanning microscopy.The photoresponsive properties of microgels are fully investigated by various instruments.Light can also regulate the state of the microgel solution,making it switch between turbidity and clarity.The phototaxis of particles irradiated by UV light was studied,which may be used for microgels enrichment and drug transportation and release.
基金NSFC(No.50543007)Scientific Research Foundation for the Returned Overseas Chinese Scholars (State Education Ministry)+1 种基金NSF of Guangdong Province (No.07006838)Tianhe Bureau of Sci. & Techno., Guangzhou.
文摘Thiol-stabilized PbS quantum dots （QDs） with dimensions 3-5 nm capped with a mixture of 1-thioglycerol/dithioglycerol （TGL/DTG） were coUoidally prepared at room temperature. Room temperature photoluminescence quantum efficiency of freshly prepared PbS QDs （7%-11%） remained higher than 5% upon aging for three weeks when the nanocrystals （NCs） were stored in an ice-bath in the dark, and higher than 5%for at least five weeks when extra DTG ligands were introduced into the nanocrystal solution followed by stirring every two weeks. Poly（N-isopropyl acrylamide） （PNIPAM） microgels were produced via precipitation polymerization with dimensions of ca. 230 nm and polydispersity of 3-5%. Incorporation of PbS QDs into PNIPAM microgels indicated that PbS can be incorporated into the interior of microgel particles and not at the microgel interface. The combination of reasonable room temperature quantum efficiency and strong, efficient luminescence covering the 1.3-1.55 μm telecommunication window makes these nanoparticles promising materials in optical devices and telecommunications.
文摘It is extremely important for photocatalysts to exhibit intelligent responsiveness to their environment. Herein, a poly N-isopropyl acrylamide(PNIPAM)-modified Ag/Ag3PO4-20/CN hybrid material with excellent convertible photocatalytic activity is prepared. PNIPAM has good hydrophilicity below the lower critical solution temperature(LCST);this increases the capacity of the photocatalyst for adsorbing tetracycline(TC) molecules. In addition, the PNIPAM-modified Ag/Ag3PO4-20/CN can prevent the loss of Ag3PO4. The dispersity is improved by loading g-C3N4 nanosheets(CN) for enhancing the efficiency of photocatalytic activity. Furthermore, a Z-scheme heterostructure is formed between CN and Ag3PO4, accelerating the separation efficiency of the holes and electrons. Ag nanoparticles can be used as electron-shuttle mediators, and electrons receiving more energy are transferred via the localized surface plasmon resonance(LSPR) effect. Furthermore, the PNIPAM@Ag/Ag3PO4-20/CN photocatalyst exhibits an excellent degradation rate for the degradation of TC when the temperature is lower than the LCST. The photoluminescence spectra and photocurrent curves prove that the carrier-separation efficiency of PNIPAM@Ag/Ag3PO4-20/CN is higher than those of Ag/Ag3PO4/CN and CN. The main active species of ·O2-and h+ are detected to reveal the plausible mechanism of the PNIPAM@Ag/Ag3PO4-20/CN hybrid material system. This work provides a way to develop intelligent materials for switchable photocatalytic applications.
基金Project supported by the State Outstanding Talent Fund adn by the Higher Education Bureau of Guangdong Province.
文摘A series of poly(N-isopropyl acrylamide) (PNIPAM) samples with molecular weight ranging from 2.23 × 104 to 130 × 104 and molecular weight distributionMw/Mn ≤1. 28 were obtained by free radical polymerization and repeat precipitation fractionation. The molecular weightMw, second virial coefficientA2 as well as the mean-square-root radius of gyration < S2 > for PNIPAM samples in tetrahydrofuran (THF) were determined by light scattering, and the relations were estimated atA2 ∞ M w- 0.25 and S2 1/2 = 1.56 × 10-9 Mw 0.56. The intrinsic viscosity for THF solution and methanol solution of PNIPAM samples was measured and the Mark-Houwink equations were obtained as [η] =6.90x 10-5 M0. 73(THF solution) and [η] = 1.07 × 10-4 M0.71(methanol solution). The above results indicate that both THF and methanol are good solvents for PNIPAM. The limit characteristic ratioC ∞ for PNIPAM in the two solutions was determined to be 10.6 by using Kurata-Stockmayer equation, indicating that the flexibility of PNIPAM chain is close to that of polystyrene. The intrinsic viscosity for the aqueous solution of PNIPAM was measured at 25-30.5°C. The result demonstrates that PNIPAM chain begins to shrink at 25°C, and from about 30°C, onward the molecular chain shrinks much more sharply till the solution becomes macroscopically unstable at 32°C.
文摘By dynamic viscoelastic measurement for PNIPAM/water solution it has been found that below the phase separation temperature (about 32°C), the system is homogeneous fluid; while upon being heated to about 32°C, the solution undergoes phase separation and the storage modulus G’ increases sharply and exceeds the loss modulus G”, indicating the physical network formation during the phase separation. Based on the percolation model, the gel points Tgel were obtained by applying the dynamic scaling theory (DST) and Winter’s criterion. The critical exponent n was also obtained to be 0.79 through DST, which is different from 0.67, the critical point of chemically crosslinked network predicted through DST. The obtained n value reflects the special property of physical network being different from chemical network.
基金Project(102101210100) supported by the Key Science and Technology Project of Henan Province,ChinaProjects(2011B430023,12B430021) supported by the Natural Science Foundation of Henan Province,China
文摘A series of porous intelligent hydrogels, which exhibited appropriate lower critical solution temperature (LCST) and fast response behavior, were synthesized by radiation method. The structure and surface morphology of hydrogels were examined by the infrared radiation and the scanning electron microscopy, respectively. The influences of the content of crosslinking agent and relative molecular mass of polyethylene glycol (PEG) on the swelling properties of hydrogels were discussed. The molecular mechanics simulations were performed to investigate the phase transformation mechanism of poly(N-isopropyl acrylamide) (PNIPA) hydrogel. The results show that macropores are observed in hydrogels, whereas hydrogels prepared without using PEG have a dense surface. LCST of hydrogels increases with the increase of relative molecular mass of PEG. The swelling mechanism of PNIPA porous hydrogels follows non-Fickian diffusion model. The theoretical maximum water absorption S∞ is approximately consistent with experimental value according to the second-order kinetics model established by Schott. The molecule chains of PNIPA hydrogel begin folding and curling, resulting in volume shrinkage at 305 K. There are much intramolecular nonbonding interactions in molecule chains of hydrogels. The porous hydrogels are expected to be applied in the field of artificial intelligence material.
文摘The effect of cross-linker (methylene-bis-acrylamide) (MBA) on the volume phase transition, mechanical properties and de-swelling of Poly(N-isopropyl acrylamide-co-methylene-bis-acrylamide) hydrogel (PNIPAAm/MBA hydrogel) was investigated. A new method, namely isothermal thermo-gravimetry was developed for monitoring de-swelling of PNIPAAm/MBA hydrogel. Monomer/ Cross-linker ratio of the initial monomer composition R = moleNIPAAm/moleMBA was introduced. It has been proven earlier that initial monomer composition is close to the copolymer composition;hence R values may be used to express cross-link density. Hydrogels from R10 to R150 were investigated. The results of DSC analysis revealed that the less the cross-linker ratio in the gel (from R10 to R150) the more sharp the temperature range of volume phase transition and the higher its enthalpy. Cross-link density, namely increasing cross-linker content in the copolymer (R from 150 to 10) does not significantly affect the temperature range of volume phase transition. It sets on at 33°C - 34°C, and ends between 35?C and 38?C. Cross-link density has significant effect on compression modulus. By decreasing the ratio of cross-linker (by increasing R from 10 to 150), the compression modulus increases, goes through a maximum, and then decreases. The highest compression modulus was measured for PNIPAAm/MBA hydrogel R20. Hydrogels with cross-linker content between R100 and 30 are strong enough and have their thermoresponsivity. Isothermal thermograms of de-swelling are of similar character for all the gels with different cross-linker content. During the initial stage of de-swelling for gels with higher cross-linker content (R10 - R15) the solute release is quicker than for gels R20 - 150 and the thermograms are drawn out. In the initial stage of de-swelling, i.e. during the first 40 minutes the rate of solute release is the highest for gels R70 - 150. The cross-linker content effects solute release, especially for gels with high cross-linker content. It is noteworthy that gels R10 - 15 release solute quicker than gels R30 - 50 and their rate of de-swelling is comparable to that of gels R100 - 150. The novel thermogravimetric method enables the selection of gels based on the rate of solute release and it can also be applied for other cross-linked gels.
基金This project sponsored by the National Natural Science Foundation of China.
文摘Six different N-alkyl substituted acrylarnide nonionic hydrogels were prepared and their swelling characteristics were measured. Poly N-isopropyl acrylamide (PNIPA) and poly N-n-propyl-acrylamide (PNNPA) temperature sensitive hydrogels were chosen as the nonionic temperature sensitive hydrogels for concentration of very dilute aqueous protein solution. The separation properties of PNIPA and PNNPA hydr0gels with different network dimensions were studied and the modification of the hydrogels was surveyed in order to decrease their surface adsorption of protein molecules. The experimental results of the concentration of BSA (Bovin serum albumin) dilute aqueous solution by hydroxylpropyl methacrylate (HPMA) copolymerized PNIPA hydrogel were given. The value and the limitation of concentration of dilute aqueous protein solution by this method was evaluated.
