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2018 Volume Issue 10
2018, 0(10): 1253-1261
doi: 10.11777/j.issn1000-3304.2018.18120
Abstract:
Enzymes are well-known biological catalysts able to catalyze chemical processes in a mild, efficient and selective manner. Controlled radical polymerization (CRP) techniques have revolutionized the field of polymer chemistry, enabling unprecedented access to various polymer architectures with controlled molar mass, topology, sequence, composition and functionality. The combination of enzyme catalysis and reversible addition-fragmentation chain transfer (RAFT) polymerization is a sustainable strategy for synthesis and functionalization of precision polymers, which has attracted extensive attention in the field of polymer syntheses in recent years. Our group has carried out the following series of work in this field. (i) Enzyme catalysis has been used to initiate RAFT polymerization for synthesis of well-defined polymers with controlled molar mass and low dispersity in benign solvents under mild conditions. (ii) Enzyme cascade catalysis has enabled the synthesis of multiblock and ultrahigh-molecular-weight (UHMW) polymers with oxygen tolerance. (iii) Interestingly, the promiscuity of enzyme can be employed for synthesis and functionalization of well-defined polymers via three different catalytic reactions mediated by one single enzyme. In this feature article, we highlight the recent development on enzyme catalysis for RAFT polymerization and functionalization. At last, perspectives in this field and some future research directions along this exciting theme are proposed.
Enzymes are well-known biological catalysts able to catalyze chemical processes in a mild, efficient and selective manner. Controlled radical polymerization (CRP) techniques have revolutionized the field of polymer chemistry, enabling unprecedented access to various polymer architectures with controlled molar mass, topology, sequence, composition and functionality. The combination of enzyme catalysis and reversible addition-fragmentation chain transfer (RAFT) polymerization is a sustainable strategy for synthesis and functionalization of precision polymers, which has attracted extensive attention in the field of polymer syntheses in recent years. Our group has carried out the following series of work in this field. (i) Enzyme catalysis has been used to initiate RAFT polymerization for synthesis of well-defined polymers with controlled molar mass and low dispersity in benign solvents under mild conditions. (ii) Enzyme cascade catalysis has enabled the synthesis of multiblock and ultrahigh-molecular-weight (UHMW) polymers with oxygen tolerance. (iii) Interestingly, the promiscuity of enzyme can be employed for synthesis and functionalization of well-defined polymers via three different catalytic reactions mediated by one single enzyme. In this feature article, we highlight the recent development on enzyme catalysis for RAFT polymerization and functionalization. At last, perspectives in this field and some future research directions along this exciting theme are proposed.
2018, 0(10): 1262-1278
doi: 10.11777/j.issn1000-3304.2018.18089
Abstract:
With their broad application of polymer materials in optical, packaging, automotive, decorating areas and so on, the demand for their surface quality is becoming higher. Different from frictional wearing, scratching is a special mechanical deformation and failure process caused by a hard tip which is normally compressed on a material and quickly moved across its surface and subsurface. It has been widely demonstrated that the aesthetics, integrity and durability of most polymer materials are susceptible to damage by scratching even under low contact loads. Therefore, the scratch resistance as one of the basic mechanical performances for polymeric materials has caught significant and increasing attention in both academic and industrial areas in recent 15 years. Commonly, the scratching process contains a rapidly changing three-dimensional stress field due to the fast tip movement and can be performed by applying different tip geometries or dimensions. To evaluate and detect the scratch behaviors of a polymeric product qualitatively and quantitatively, several measuring techniques and standards have been established. In general, the scratch deformation can be divided into initial damage (ploughing), periodic damage (wedge formation) and material removal stages. To improve the scratch resistance, it is necessary to comprehensively understand the relationship to the structures and morphologies of the polymeric materials as well as various measuring conditions, such as the scratching rate, normal load, humidity and temperature, etc. In this brief review, the progress in recent studies on scratch behaviors of polymeric materials is presented. The main contents include the measuring and analyzing methodologies for evaluating the scratch resistance, the failure patterns and deformation mechanisms corresponding to different damage stages occurring in a scratch process, the intrinsic and extrinsic factors influencing the scratch behaviors, and the modification strategies for resisting the scratch deformation. At last, the perspective of the fundamental studies in this field is concluded as well.
With their broad application of polymer materials in optical, packaging, automotive, decorating areas and so on, the demand for their surface quality is becoming higher. Different from frictional wearing, scratching is a special mechanical deformation and failure process caused by a hard tip which is normally compressed on a material and quickly moved across its surface and subsurface. It has been widely demonstrated that the aesthetics, integrity and durability of most polymer materials are susceptible to damage by scratching even under low contact loads. Therefore, the scratch resistance as one of the basic mechanical performances for polymeric materials has caught significant and increasing attention in both academic and industrial areas in recent 15 years. Commonly, the scratching process contains a rapidly changing three-dimensional stress field due to the fast tip movement and can be performed by applying different tip geometries or dimensions. To evaluate and detect the scratch behaviors of a polymeric product qualitatively and quantitatively, several measuring techniques and standards have been established. In general, the scratch deformation can be divided into initial damage (ploughing), periodic damage (wedge formation) and material removal stages. To improve the scratch resistance, it is necessary to comprehensively understand the relationship to the structures and morphologies of the polymeric materials as well as various measuring conditions, such as the scratching rate, normal load, humidity and temperature, etc. In this brief review, the progress in recent studies on scratch behaviors of polymeric materials is presented. The main contents include the measuring and analyzing methodologies for evaluating the scratch resistance, the failure patterns and deformation mechanisms corresponding to different damage stages occurring in a scratch process, the intrinsic and extrinsic factors influencing the scratch behaviors, and the modification strategies for resisting the scratch deformation. At last, the perspective of the fundamental studies in this field is concluded as well.
2018, 0(10): 1279-1286
doi: 10.11777/j.issn1000-3304.2018.18082
Abstract:
Step-wise self-assembly is a promising strategy to construct assemblies with higher-level hierarchy and complexity. In this self-assembly, the primary assemblies can self-assemble into one-dimensional structures in a way similar to the synthesis of polymers. However, the questions such as whether the principle of polymerization can apply to the one-dimensional growth of the assemblies still need to be clarified. To address this question, Brownian dynamics simulation was used to investigate the self-assembly of the nanorods with two ends capped with hydrophobic polymers such as polystyrenes. In the Brownian dynamics simulation, the amphiphility was simulated by choosing different cutt-off distances of the Lennard-Jones potentials for the nanorods and polymers. It was found that the nanorods associated with each other into chain-like structures via end-to-end connection, due to the hydrophobility of the polymers. The effects of the solvent selectivity, the length of the nanorods, and the concentration of the nanorods on the self-assembly were examined. The self-assembly of the nanorods into chain-like structures resembles the covalent polymerization of the monomers. The kinetics of the polymerization follows the rule of the step-growth polymerization in most of the cases. As the length of the nanorods or the concentration of the nanorods increases, the degrees of the polymerization show a more rapid increase as a function of time. For the effect of the solvent selectivity, the nanorods are found to be " polymerized” more rapidly as the solubility of the polymers decreases. However, as the solubilty of the polymers is low enough, the " polymerization” behavior is remarkedly less influenced by the solvent selectivity. Note that the rule of the step-growth polymerization cannot apply to the one-dimensional self-assembly of the nanorods when the concentration of the nanorods or the solubility of the polymer is higher. In addition, we found that the nanorods can self-assemble into ring-like structures with various numbers of nanorods via designing nanorods with adjustable chamfers at two ends. The observations are well consistent with some available experimental findings regarding the self-assembly of gold nanorods coated with a bilayer of cetyl trimethyl ammonium bromide along its sides and thiol-terminated polystyrene at two ends. The work can help to understand the dynamics of the self-assembly and designing one-dimensional ordered microstructures in future.
Step-wise self-assembly is a promising strategy to construct assemblies with higher-level hierarchy and complexity. In this self-assembly, the primary assemblies can self-assemble into one-dimensional structures in a way similar to the synthesis of polymers. However, the questions such as whether the principle of polymerization can apply to the one-dimensional growth of the assemblies still need to be clarified. To address this question, Brownian dynamics simulation was used to investigate the self-assembly of the nanorods with two ends capped with hydrophobic polymers such as polystyrenes. In the Brownian dynamics simulation, the amphiphility was simulated by choosing different cutt-off distances of the Lennard-Jones potentials for the nanorods and polymers. It was found that the nanorods associated with each other into chain-like structures via end-to-end connection, due to the hydrophobility of the polymers. The effects of the solvent selectivity, the length of the nanorods, and the concentration of the nanorods on the self-assembly were examined. The self-assembly of the nanorods into chain-like structures resembles the covalent polymerization of the monomers. The kinetics of the polymerization follows the rule of the step-growth polymerization in most of the cases. As the length of the nanorods or the concentration of the nanorods increases, the degrees of the polymerization show a more rapid increase as a function of time. For the effect of the solvent selectivity, the nanorods are found to be " polymerized” more rapidly as the solubility of the polymers decreases. However, as the solubilty of the polymers is low enough, the " polymerization” behavior is remarkedly less influenced by the solvent selectivity. Note that the rule of the step-growth polymerization cannot apply to the one-dimensional self-assembly of the nanorods when the concentration of the nanorods or the solubility of the polymer is higher. In addition, we found that the nanorods can self-assemble into ring-like structures with various numbers of nanorods via designing nanorods with adjustable chamfers at two ends. The observations are well consistent with some available experimental findings regarding the self-assembly of gold nanorods coated with a bilayer of cetyl trimethyl ammonium bromide along its sides and thiol-terminated polystyrene at two ends. The work can help to understand the dynamics of the self-assembly and designing one-dimensional ordered microstructures in future.
2018, 0(10): 1287-1296
doi: 10.11777/j.issn1000-3304.2018.18046
Abstract:
The reversible-deactivation radical polymerization (RDRP) of methyl methacrylate (MMA) was carried out utilizing an alkyl iodide in situ formed as initiator and dicyclohexylcarbodiimide (DCC) or N,N′-diisopropylcarbodiimide (DIC) as highly efficient organic catalysts for the first time. Firstly, the catalytic activity of the two catalysts was demonstrated and compared. The control of the polymerization by DCC was better than that by DIC under the same experimental conditions. Then the influence of the amount of catalyst DCC, the amount of traditional initiators and the type of solvents on the polymerization was investigated in detail. The results show that the addition of DCC or DIC catalyst can effectively reduce the polydispersity index (PDI = Mw/Mn), as compared with the reverse iodine chain transfer polymerization (RITP). The catalytic performance is excellent with the ratio of [MMA]0:[I2]0:[ABVN]0:[DCC]0 = 200:1:1.7:4. The measured molecular weight by GPC is consistent with the theoretical molecular weight, and the molecular weight increases linearly with the increase in conversion rate. The molecular weight polydispersity index is small (PDI < 1.26). The polymerizations of MMA in different solvents were carried out. The induction period is shortened and the polymerization rate is increased with the increase of catalyst or initiator amount. The polymerizations have good control effect in toluene, benzene, tetrahydrofuran (THF), anisole. The structure and the iodine-end-capped structure of the obtained PMMA was demonstrated by 1H-NMR spectrum. The calculated Mn,NMR was in good agreement with Mn,GPC, and the fraction of iodine chain end of the PMMA chains was up to 97.5%, and the iodine terminus could be efficiently reactivated for chain extension. Last, the mechanism of the polymerization mediated by carbodiimide is discussed based on free radical trapping experiments and ultraviolet absorption. The high conversion of CP-I to CPo radical catalyzed by DIC and the complexation peak of I2/carbodiimide detected by ultraviolet absorption spectroscopy demonstrate that the polymerization catalyzed by carbodiimide proceeds according to the reversible complexation mediated polymerization mechanism.
The reversible-deactivation radical polymerization (RDRP) of methyl methacrylate (MMA) was carried out utilizing an alkyl iodide in situ formed as initiator and dicyclohexylcarbodiimide (DCC) or N,N′-diisopropylcarbodiimide (DIC) as highly efficient organic catalysts for the first time. Firstly, the catalytic activity of the two catalysts was demonstrated and compared. The control of the polymerization by DCC was better than that by DIC under the same experimental conditions. Then the influence of the amount of catalyst DCC, the amount of traditional initiators and the type of solvents on the polymerization was investigated in detail. The results show that the addition of DCC or DIC catalyst can effectively reduce the polydispersity index (PDI = Mw/Mn), as compared with the reverse iodine chain transfer polymerization (RITP). The catalytic performance is excellent with the ratio of [MMA]0:[I2]0:[ABVN]0:[DCC]0 = 200:1:1.7:4. The measured molecular weight by GPC is consistent with the theoretical molecular weight, and the molecular weight increases linearly with the increase in conversion rate. The molecular weight polydispersity index is small (PDI < 1.26). The polymerizations of MMA in different solvents were carried out. The induction period is shortened and the polymerization rate is increased with the increase of catalyst or initiator amount. The polymerizations have good control effect in toluene, benzene, tetrahydrofuran (THF), anisole. The structure and the iodine-end-capped structure of the obtained PMMA was demonstrated by 1H-NMR spectrum. The calculated Mn,NMR was in good agreement with Mn,GPC, and the fraction of iodine chain end of the PMMA chains was up to 97.5%, and the iodine terminus could be efficiently reactivated for chain extension. Last, the mechanism of the polymerization mediated by carbodiimide is discussed based on free radical trapping experiments and ultraviolet absorption. The high conversion of CP-I to CPo radical catalyzed by DIC and the complexation peak of I2/carbodiimide detected by ultraviolet absorption spectroscopy demonstrate that the polymerization catalyzed by carbodiimide proceeds according to the reversible complexation mediated polymerization mechanism.
2018, 0(10): 1297-1306
doi: 10.11777/j.issn1000-3304.2018.18048
Abstract:
Multiple injections of drugs are generally needed to continuously and effectively kill pathological cells during tumor therapeutic. However, this strategy might induce some side effects. Gold nanoparticles are one kind of photothermal agents that can convert the absorbed light energy into heat energy. This conversion could be used to photo-thermal therapy (PTT), which has property of multiple treatment for killing the tumor cells effectively and completely without other effects. Herein, this study aims to prepare injectable hydrogels with PTT property based on chitosan (CS), β-glycerophosphate (β-GP) and gold nanoparticles (Au NPs) for improving efficiency of anti-tumour. Firstly, CS bio-polymer stabilized Au NPs (CS-Au NPs) were directly reduced in situ by CS. Size of the CS-Au NPs could be controlled at 15 nm. Then, β-glycerophosphate (β-GP) was added into the CS-Au NPs. The mixture of CS-Au NPs and β-GP was sol state at room temperature, which could be injected into the tumor site. And then, at physiological temprature (37 °C), this sol could convert to gel (CGP/Au NPs) via the interactions between CS and β-GP, indicating that the (CGP/Au NPs) gel had the temperature sensitivity. Due to the surface plasmon resonance effect (SPR) of Au NPs, the (CGP/Au NPs) hydrogels showed an excellent photo-thermal property. The temperature of the (CGP/Au NPs) gel rised to above 45 °C and further to approximately 55 °C under Laser irradiation, with increasing amout of Au NPs. Moreover, the photo-thermal ability could be kept for several cycles with repeated laser irradiation. Because of easily fixing CGP hydrogels into biological tissue, Au NPs could be immobilized on the tumor site for a long time for multiple PTT. Thus, the strategies of muiliple drug-injection and blood circulation could be changed with the help of CGP hydrogels. Additionally, Au NPs were distributed evenly in the CGP hydrogels and the (CGP/Au NPs) hydrogels had good stability. Cell viability showed that the gels had excellent biocompatibility to the normal cells, and could kill remarkably the cancer cells with laser irradiation. Meanwhile, the prepared thermo-sensitive hydrogels had good biodegradability. Due to these characteristics, this (CGP/Au NPs) hydrogel might have the potential application to achieve " one time injection, multiple treatments” for tumor therapy.
Multiple injections of drugs are generally needed to continuously and effectively kill pathological cells during tumor therapeutic. However, this strategy might induce some side effects. Gold nanoparticles are one kind of photothermal agents that can convert the absorbed light energy into heat energy. This conversion could be used to photo-thermal therapy (PTT), which has property of multiple treatment for killing the tumor cells effectively and completely without other effects. Herein, this study aims to prepare injectable hydrogels with PTT property based on chitosan (CS), β-glycerophosphate (β-GP) and gold nanoparticles (Au NPs) for improving efficiency of anti-tumour. Firstly, CS bio-polymer stabilized Au NPs (CS-Au NPs) were directly reduced in situ by CS. Size of the CS-Au NPs could be controlled at 15 nm. Then, β-glycerophosphate (β-GP) was added into the CS-Au NPs. The mixture of CS-Au NPs and β-GP was sol state at room temperature, which could be injected into the tumor site. And then, at physiological temprature (37 °C), this sol could convert to gel (CGP/Au NPs) via the interactions between CS and β-GP, indicating that the (CGP/Au NPs) gel had the temperature sensitivity. Due to the surface plasmon resonance effect (SPR) of Au NPs, the (CGP/Au NPs) hydrogels showed an excellent photo-thermal property. The temperature of the (CGP/Au NPs) gel rised to above 45 °C and further to approximately 55 °C under Laser irradiation, with increasing amout of Au NPs. Moreover, the photo-thermal ability could be kept for several cycles with repeated laser irradiation. Because of easily fixing CGP hydrogels into biological tissue, Au NPs could be immobilized on the tumor site for a long time for multiple PTT. Thus, the strategies of muiliple drug-injection and blood circulation could be changed with the help of CGP hydrogels. Additionally, Au NPs were distributed evenly in the CGP hydrogels and the (CGP/Au NPs) hydrogels had good stability. Cell viability showed that the gels had excellent biocompatibility to the normal cells, and could kill remarkably the cancer cells with laser irradiation. Meanwhile, the prepared thermo-sensitive hydrogels had good biodegradability. Due to these characteristics, this (CGP/Au NPs) hydrogel might have the potential application to achieve " one time injection, multiple treatments” for tumor therapy.
2018, 0(10): 1307-1314
doi: 10.11777/j.issn1000-3304.2018.18054
Abstract:
Hybrid phenolic resin/silica (PR/SiO2) hybrid aerogels with bicomponent and interpenetrating gel networks were prepared through co-gelating reaction by controlling Sol-Gel reaction and tuning gel time of hybrid solution. In this study, variations of the hybrid aerogels properties, including apparent density, linear shrinkage, pore texture, micromorphology, thermal stability and mechanical performance, with their silica aerogel contents were investigated. The results showed that apparent density of PR/SiO2 hybrid aerogels increased proportionally with increasing content of the silica aerogels. Compared to the pure organic phenolic (PR) aerogels, pore texture for PR/SiO2 hybrid aerogels were remarkably affected by the content of silica aerogels introduced by co-gelating reactions of phenolic resin and tetraethoxysilane (TEOS) monomers. Specific surface area of PR/SiO2 hybrid aerogels was improved and the average pore diameter decreased after incorporation of silica aerogels. As studied in the research, when the concentration of TEOS monomers increased to 1.50 mol/L, the average pore diameter of PR/SiO2 hybrid aerogel extremely decreased to 0.25 μm and the specific surface area increased from 24.6 m2/g for pure PR aerogel to 44 m2/g. Micromorphology detected by scanning electron microscopy (SEM) displayed that larger pores of hybrid aerogels were gradually filled by silica sol particles with increasing content of silica aerogels, which brought forth much more small openings and wider distribution for the pore diameter. Additionally, the skeleton’s strength and thermal stability of PR/SiO2 hybrid aerogels were efficiently enhanced after the incorporation of silica aerogels. As the concentration of TEOS monomers was 1 mol/L, the temperature corresponding to the maximum pyrolysis rate (Tmax) was improved from 539 °C to 602 °C, and the thermal decomposition zone of phenolic resin was evidently widened, which suggested that incorporation of silica aerogels effectively inhibited the pyrolysis of phenolic resins. The big promotion of thermal stability for PR/SiO2 hybrid aerogels was attributed to the thermal barrier and nano-dispersion of SiO2 sol particles in organic skeletons.
Hybrid phenolic resin/silica (PR/SiO2) hybrid aerogels with bicomponent and interpenetrating gel networks were prepared through co-gelating reaction by controlling Sol-Gel reaction and tuning gel time of hybrid solution. In this study, variations of the hybrid aerogels properties, including apparent density, linear shrinkage, pore texture, micromorphology, thermal stability and mechanical performance, with their silica aerogel contents were investigated. The results showed that apparent density of PR/SiO2 hybrid aerogels increased proportionally with increasing content of the silica aerogels. Compared to the pure organic phenolic (PR) aerogels, pore texture for PR/SiO2 hybrid aerogels were remarkably affected by the content of silica aerogels introduced by co-gelating reactions of phenolic resin and tetraethoxysilane (TEOS) monomers. Specific surface area of PR/SiO2 hybrid aerogels was improved and the average pore diameter decreased after incorporation of silica aerogels. As studied in the research, when the concentration of TEOS monomers increased to 1.50 mol/L, the average pore diameter of PR/SiO2 hybrid aerogel extremely decreased to 0.25 μm and the specific surface area increased from 24.6 m2/g for pure PR aerogel to 44 m2/g. Micromorphology detected by scanning electron microscopy (SEM) displayed that larger pores of hybrid aerogels were gradually filled by silica sol particles with increasing content of silica aerogels, which brought forth much more small openings and wider distribution for the pore diameter. Additionally, the skeleton’s strength and thermal stability of PR/SiO2 hybrid aerogels were efficiently enhanced after the incorporation of silica aerogels. As the concentration of TEOS monomers was 1 mol/L, the temperature corresponding to the maximum pyrolysis rate (Tmax) was improved from 539 °C to 602 °C, and the thermal decomposition zone of phenolic resin was evidently widened, which suggested that incorporation of silica aerogels effectively inhibited the pyrolysis of phenolic resins. The big promotion of thermal stability for PR/SiO2 hybrid aerogels was attributed to the thermal barrier and nano-dispersion of SiO2 sol particles in organic skeletons.
2018, 0(10): 1315-1327
doi: 10.11777/j.issn1000-3304.2018.18066
Abstract:
Hydrogel is an excellent candidate for drug delivery and tissue regeneration. However, hydrogel used as drug carriers is facing some problems, including limited optional drug and burst drug release. In addition, hydrogel is still confronting some challenges in the area of mechanical property. Cholecalciferol is a type of vitamin able to promote ossification. However, as a lipophilic drug, it should be taken according to the recommended dosage. That means the carriers must be capable of making hydrophobic drug homodispersed with controlling drug release. In this study, we designed a novel hydrogen bond based mechanical reinforced hydrogel, modified by release-controlling cholecalciferol liposome, as an multifunctional scaffold for promoting osteogenesis during the process of bone regeneration. Specifically, drug-loaded liposome was fabricated and the characteristics of the liposomes were investigated. Further, photo-crosslinkable gelatin derivative (GelMA) was combined with drug loaded liposome by micro-cross linking double network, generated by the interaction between hydrogen bond and hydrogel network, leading to double enhancement in mechanical property both for compression and streching. Furthermore, the ability to control release and support uniform distribution of hydrophobic drug (cholecalciferol) was observed in the composite hydrogel, specifically the sustained release of cholecalciferol lasted for three weeks at least without significant brust release. In vitro study also revealed that, this composite hydrogel was proved to have excellent biocompatibility without significant influence on MC3T3-E1 cell adhesion, proliferation, compared with GelMA hydrogel and control groups. After 21 days cultivation, MC3T3-E1 cells cultured with this composite hydrogel exhibited remarkably facilitated osteogenic differentiation, according to the result of ALP stain, ALP analysis and Alizarin red staining. Thus, it is reasonable to believe that this liposome composite hydrogel could provide a promising strategy for extending the application of hydrogel in drug delivery and tissue reconstruction.
Hydrogel is an excellent candidate for drug delivery and tissue regeneration. However, hydrogel used as drug carriers is facing some problems, including limited optional drug and burst drug release. In addition, hydrogel is still confronting some challenges in the area of mechanical property. Cholecalciferol is a type of vitamin able to promote ossification. However, as a lipophilic drug, it should be taken according to the recommended dosage. That means the carriers must be capable of making hydrophobic drug homodispersed with controlling drug release. In this study, we designed a novel hydrogen bond based mechanical reinforced hydrogel, modified by release-controlling cholecalciferol liposome, as an multifunctional scaffold for promoting osteogenesis during the process of bone regeneration. Specifically, drug-loaded liposome was fabricated and the characteristics of the liposomes were investigated. Further, photo-crosslinkable gelatin derivative (GelMA) was combined with drug loaded liposome by micro-cross linking double network, generated by the interaction between hydrogen bond and hydrogel network, leading to double enhancement in mechanical property both for compression and streching. Furthermore, the ability to control release and support uniform distribution of hydrophobic drug (cholecalciferol) was observed in the composite hydrogel, specifically the sustained release of cholecalciferol lasted for three weeks at least without significant brust release. In vitro study also revealed that, this composite hydrogel was proved to have excellent biocompatibility without significant influence on MC3T3-E1 cell adhesion, proliferation, compared with GelMA hydrogel and control groups. After 21 days cultivation, MC3T3-E1 cells cultured with this composite hydrogel exhibited remarkably facilitated osteogenic differentiation, according to the result of ALP stain, ALP analysis and Alizarin red staining. Thus, it is reasonable to believe that this liposome composite hydrogel could provide a promising strategy for extending the application of hydrogel in drug delivery and tissue reconstruction.
2018, 0(10): 1328-1335
doi: 10.11777/j.issn1000-3304.2018.18063
Abstract:
Recently, protein-polymer conjugates, which combine protein molecules with one or more specific polymer chains at certain position, have attracted a great deal of attention due to their unique properties of both the proteins and the polymers. Therefore, the objective of this work is to study the self-assembly behavior of protein-polymer conjugates on a planar gold substrate, in which bovine serum albumin (BSA) is employed as the anchoring point for self-assembly process. We first prepare an initiator, 2-bromo-2-methylpropionic acid-2-aminooxy ethyl ester (ABM), which can be linked to the N-terminal of BSA modified by pyridoxal-5-phosphate (PLP), giving rise to a macroinitiator (i.e., BSA-Br). Then BSA-POEGMA conjugate is obtained by atom transfer radical polymerization (ATRP) using oligo(ethylene glycol) methacrylate (OEGMA) as monomer and the BSA-Br as macroinitiator, respectively. All products are characterized by Fourier-transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis) and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). FTIR and MALDI-TOF-MS results indicate that one POEGMA chain with a polymerization degree of 218 is coupled to the N-terminal of BSA. The adsorption behaviors of both the BSA and the BSA-POEGMA conjugate on gold surfaces are studied by using surface plasmon resonance spectroscopy (SPR). The data suggest that the BSA-POEGMA conjugate could be adsorbed to the gold substrate at the same way as the pure BSA molecule as expected, while the hydrophilic POEGMA chain is directed to the opposite of gold surface. At last, the adsorption behaviors of two model proteins (i.e., lysozyme, Lys and fibrinogen, Fib) on the BSA-POEGMA conjugate are also investigated. SPR data indicate that there is a decrease in Lys adsorption on the BSA-POEGMA compared to pure BSA layer. In contrast, Fib adsorption on the BSA-POEGMA conjugate increase slightly in comparison with that on pure BSA. The results clearly show the influence of POEGMA chain on the surface property of BSA molecule, which may be attributed to the water layer associated with the POEGMA chains.
Recently, protein-polymer conjugates, which combine protein molecules with one or more specific polymer chains at certain position, have attracted a great deal of attention due to their unique properties of both the proteins and the polymers. Therefore, the objective of this work is to study the self-assembly behavior of protein-polymer conjugates on a planar gold substrate, in which bovine serum albumin (BSA) is employed as the anchoring point for self-assembly process. We first prepare an initiator, 2-bromo-2-methylpropionic acid-2-aminooxy ethyl ester (ABM), which can be linked to the N-terminal of BSA modified by pyridoxal-5-phosphate (PLP), giving rise to a macroinitiator (i.e., BSA-Br). Then BSA-POEGMA conjugate is obtained by atom transfer radical polymerization (ATRP) using oligo(ethylene glycol) methacrylate (OEGMA) as monomer and the BSA-Br as macroinitiator, respectively. All products are characterized by Fourier-transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis) and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). FTIR and MALDI-TOF-MS results indicate that one POEGMA chain with a polymerization degree of 218 is coupled to the N-terminal of BSA. The adsorption behaviors of both the BSA and the BSA-POEGMA conjugate on gold surfaces are studied by using surface plasmon resonance spectroscopy (SPR). The data suggest that the BSA-POEGMA conjugate could be adsorbed to the gold substrate at the same way as the pure BSA molecule as expected, while the hydrophilic POEGMA chain is directed to the opposite of gold surface. At last, the adsorption behaviors of two model proteins (i.e., lysozyme, Lys and fibrinogen, Fib) on the BSA-POEGMA conjugate are also investigated. SPR data indicate that there is a decrease in Lys adsorption on the BSA-POEGMA compared to pure BSA layer. In contrast, Fib adsorption on the BSA-POEGMA conjugate increase slightly in comparison with that on pure BSA. The results clearly show the influence of POEGMA chain on the surface property of BSA molecule, which may be attributed to the water layer associated with the POEGMA chains.
2018, 0(10): 1336-1344
doi: 10.11777/j.issn1000-3304.2018.18042
Abstract:
Fluorenyl polyphosphazene (PZFP) microspheres were facilely prepared through a one-step precipitation copolymerization of hexachlorocyclotriphosphazene (HCCP) and 4,4′-(9-fluorenylidene)diphenol under ultrasonic. PZFP microspheres were incorporated into polybenzoxazine resins to improve the flame properties of the polymers. The results of thermogravimetric analysis (TGA), cone calorimeter (CONE) and dynamic thermal mechanical analysis (DMA) showed that incorporation of PZFP microspheres enhanced the char residues amount of PBa during thermal degradation process, reduced the heat release rate (HRR), delayed the time to ignition (TTI) and increased the fire performance index (FPI) of PBa in fire. Interestingly, PBa/PZFP-10% showed the relatively best flame retardant properties among a series of PBa/PZFP composites with different PZFP contents. In comparison to pure PBa, the HRR value in the composite PBa/PZFP-10% was reduced to 214 kW·m−2 from 566 kW·m−2 for pure PBa, and FPI value was enhanced to 0.243 from 0.087. The glass transition temperature (Tg) and storage modules of PBa/PZFP-10% were increased slightly, with the introduction of 10% PZFP microspheres. The Tg of PBa and PBa/PZFP-10% was 222 and 226 °C, respectively. It is believed that PZFP microspheres offered PBa resins good flame retardant properties, without affecting the application temperature of PBa. The char residue analysis using scanning electron microscopy (SEM) suggested the formation of high-quality char layer with compact outer surfaces and polyphorous inner structure. The volatile products formed in the thermal degradation process of PBa and PBa/PZFP composites were detected by a TGA-Fourier transform infrared spectrometer (TGA-FTIR). The improved flame retardancy of PBa/PZFP composites was mainly attributed to a combination of the greatly increased melt viscosity of PBa and matrix fast swelling due to the pyrolytic gases. Additionally, PZFP microspheres was found to greatly reduce the amount of pyrolytic gases containing N―H and ―C＝C＝C― groups. Instead, it released phosphorous-containing species to achieve flame retardancy in the gas phase. PZFP microspheres contributed a synergistic condensed phase and gas phase flame retardant mechanism for PBa resins.
Fluorenyl polyphosphazene (PZFP) microspheres were facilely prepared through a one-step precipitation copolymerization of hexachlorocyclotriphosphazene (HCCP) and 4,4′-(9-fluorenylidene)diphenol under ultrasonic. PZFP microspheres were incorporated into polybenzoxazine resins to improve the flame properties of the polymers. The results of thermogravimetric analysis (TGA), cone calorimeter (CONE) and dynamic thermal mechanical analysis (DMA) showed that incorporation of PZFP microspheres enhanced the char residues amount of PBa during thermal degradation process, reduced the heat release rate (HRR), delayed the time to ignition (TTI) and increased the fire performance index (FPI) of PBa in fire. Interestingly, PBa/PZFP-10% showed the relatively best flame retardant properties among a series of PBa/PZFP composites with different PZFP contents. In comparison to pure PBa, the HRR value in the composite PBa/PZFP-10% was reduced to 214 kW·m−2 from 566 kW·m−2 for pure PBa, and FPI value was enhanced to 0.243 from 0.087. The glass transition temperature (Tg) and storage modules of PBa/PZFP-10% were increased slightly, with the introduction of 10% PZFP microspheres. The Tg of PBa and PBa/PZFP-10% was 222 and 226 °C, respectively. It is believed that PZFP microspheres offered PBa resins good flame retardant properties, without affecting the application temperature of PBa. The char residue analysis using scanning electron microscopy (SEM) suggested the formation of high-quality char layer with compact outer surfaces and polyphorous inner structure. The volatile products formed in the thermal degradation process of PBa and PBa/PZFP composites were detected by a TGA-Fourier transform infrared spectrometer (TGA-FTIR). The improved flame retardancy of PBa/PZFP composites was mainly attributed to a combination of the greatly increased melt viscosity of PBa and matrix fast swelling due to the pyrolytic gases. Additionally, PZFP microspheres was found to greatly reduce the amount of pyrolytic gases containing N―H and ―C＝C＝C― groups. Instead, it released phosphorous-containing species to achieve flame retardancy in the gas phase. PZFP microspheres contributed a synergistic condensed phase and gas phase flame retardant mechanism for PBa resins.
2018, 0(10): 1345-1350
doi: 10.11777/j.issn1000-3304.2018.18029
Abstract:
In recent years, both academia and industry have focused their efforts on better utilization of natural fibers and synthetic bio-based fibers. Agar, extracted from red algae, has good biocompatibility, excellent moisturizing ability and biodegradability. Agar fibers were usually fabricated via wet spinning by extruding agar solution into a barium chloride coagulation bath due to the unique gel properties of agar. However, the phenomenon of " fibers bundle adhesion” and the mechanical properties of agar fibers need to be improved. In this study, we use different post-processing solutions (amino silicones and sodium tetraborate) to get excellent agar fibers. The structures, mechanical properties and thermal properties of the agar fibers ontained were evaluated by scanning electron microscopy (SEM), single fiber tensile strength tester, contact angle tester, thermogravimetric tester, and Fourier transform infrared spectroscopy (FTIR). The results show that the phenomenon of " fibers bundle adhesion” disappeared whether agar fibers were immersed in amino silicones or sodium tetraborate. Agar fibers immersed in amino silicones form a hydrophobic film on the surface, therefore, the contact angle increased to 106.4°. The linear intensity increased to 0.69 cN/dtex and the elongation at break increased to 104.89% when the agar fibers were immersed in amino silicones. The contact angle decreased to 68.3° while the agar fibers were immersed in sodium tetraborate because their surface became rough and the mechanical strength decreased. However, the agar fibers immersed in sodium tetraborate showed a certain degree of flame retardancy. The results of limit oxygen index (LOI) indicate that the agar fibers immersed in sodium tetraborate were combustible while the agar fibers were flammable by thermogravimetric test. The change of chemical structure of the agar fibers by different post-processing was analyzed by FTIR. Owing to excellent biological properties and outstanding moisturizing capacity, it still requires further study to accelerate the development of these agar products.
In recent years, both academia and industry have focused their efforts on better utilization of natural fibers and synthetic bio-based fibers. Agar, extracted from red algae, has good biocompatibility, excellent moisturizing ability and biodegradability. Agar fibers were usually fabricated via wet spinning by extruding agar solution into a barium chloride coagulation bath due to the unique gel properties of agar. However, the phenomenon of " fibers bundle adhesion” and the mechanical properties of agar fibers need to be improved. In this study, we use different post-processing solutions (amino silicones and sodium tetraborate) to get excellent agar fibers. The structures, mechanical properties and thermal properties of the agar fibers ontained were evaluated by scanning electron microscopy (SEM), single fiber tensile strength tester, contact angle tester, thermogravimetric tester, and Fourier transform infrared spectroscopy (FTIR). The results show that the phenomenon of " fibers bundle adhesion” disappeared whether agar fibers were immersed in amino silicones or sodium tetraborate. Agar fibers immersed in amino silicones form a hydrophobic film on the surface, therefore, the contact angle increased to 106.4°. The linear intensity increased to 0.69 cN/dtex and the elongation at break increased to 104.89% when the agar fibers were immersed in amino silicones. The contact angle decreased to 68.3° while the agar fibers were immersed in sodium tetraborate because their surface became rough and the mechanical strength decreased. However, the agar fibers immersed in sodium tetraborate showed a certain degree of flame retardancy. The results of limit oxygen index (LOI) indicate that the agar fibers immersed in sodium tetraborate were combustible while the agar fibers were flammable by thermogravimetric test. The change of chemical structure of the agar fibers by different post-processing was analyzed by FTIR. Owing to excellent biological properties and outstanding moisturizing capacity, it still requires further study to accelerate the development of these agar products.
2018, 0(10): 1351-1358
doi: 10.11777/j.issn1000-3304.2018.18072
Abstract:
We performed Brownian dynamics simulations with implicit solvent to study the self-assembly of polymer-grafted nanoparticle amphiphiles in selective solvents. Each model amphiphile consists of one hydrophobic nanoparticle (H) bead and one hydrophilic polymer chain composed of P-beads. The diameter of each H-bead is varied from one to several times that of each P-bead. The influences of experimental conditions on the self-assembled morphologies are investigated. The experimental conditions studied include the amphiphile concentration, the size of the hydrophobic head, the interaction parameters between the hydrophilic bead and hydrophobic bead, the polymer chain length and the solvent. Various self-assembled morphologies are obtained, including conventional spherical micelles, cylindrical micelles, cylindrical networks, large compound micelles, thin sheets, spherical vesicles, and novel ones of tubular vesicles, cylindrical multicompartment vesicles, and spherical multicompartment vesicles. The morphological phase diagrams are constructed as a function of different parameters. Mechanisms of morphological formation are discussed. Two pathways, mechanisms I and II, of vesicle formation are identified. In mechanism I, the model amphiphiles first self-assemble into spherical micelles, which transform into cylindrical micelles, further into bilayer-sheets, and finally the sheets bend around and close up to form vesicles. In mechanism II, in the initial stage of simulation, the model amphiphiles first self-assemble into many small spherical aggregates, inside which the hydrophilic P-beads are mixing with hydrophobic H-beads. Subsequently, neighboring aggregates coalesce together, and microphase separation between H and P beads occurs in the interior of the aggregates, resulting in a concentration of P-beads at the center of the aggregates, i.e., the formation of semivesicles. As simulation proceeds further, the semivesicles grow larger, and more and more P-beads enter into the inner of the semivesicles, and finally semivesicles expand outward, forming vesicles. Furthermore, transition from mechanism II to mechanism I can occur by increasing amphiphile concentration. At low amphiphile concentration, the attractions among the hydrophobic H-beads are dominant in the system. In this case, mechanism II occurs during vesicle formation. At high amphiphile concentration, repulsion among the hydrophilic P-beads dominates the system where bilayer-sheets occur as an intermediate state of the vesicle formation and thus mechanism I occurs. The simulation results are compared with available experimental and simulation results obtained from related systems.
We performed Brownian dynamics simulations with implicit solvent to study the self-assembly of polymer-grafted nanoparticle amphiphiles in selective solvents. Each model amphiphile consists of one hydrophobic nanoparticle (H) bead and one hydrophilic polymer chain composed of P-beads. The diameter of each H-bead is varied from one to several times that of each P-bead. The influences of experimental conditions on the self-assembled morphologies are investigated. The experimental conditions studied include the amphiphile concentration, the size of the hydrophobic head, the interaction parameters between the hydrophilic bead and hydrophobic bead, the polymer chain length and the solvent. Various self-assembled morphologies are obtained, including conventional spherical micelles, cylindrical micelles, cylindrical networks, large compound micelles, thin sheets, spherical vesicles, and novel ones of tubular vesicles, cylindrical multicompartment vesicles, and spherical multicompartment vesicles. The morphological phase diagrams are constructed as a function of different parameters. Mechanisms of morphological formation are discussed. Two pathways, mechanisms I and II, of vesicle formation are identified. In mechanism I, the model amphiphiles first self-assemble into spherical micelles, which transform into cylindrical micelles, further into bilayer-sheets, and finally the sheets bend around and close up to form vesicles. In mechanism II, in the initial stage of simulation, the model amphiphiles first self-assemble into many small spherical aggregates, inside which the hydrophilic P-beads are mixing with hydrophobic H-beads. Subsequently, neighboring aggregates coalesce together, and microphase separation between H and P beads occurs in the interior of the aggregates, resulting in a concentration of P-beads at the center of the aggregates, i.e., the formation of semivesicles. As simulation proceeds further, the semivesicles grow larger, and more and more P-beads enter into the inner of the semivesicles, and finally semivesicles expand outward, forming vesicles. Furthermore, transition from mechanism II to mechanism I can occur by increasing amphiphile concentration. At low amphiphile concentration, the attractions among the hydrophobic H-beads are dominant in the system. In this case, mechanism II occurs during vesicle formation. At high amphiphile concentration, repulsion among the hydrophilic P-beads dominates the system where bilayer-sheets occur as an intermediate state of the vesicle formation and thus mechanism I occurs. The simulation results are compared with available experimental and simulation results obtained from related systems.
