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2016 Volume 74 Issue 4
2016, 74(4): 303-311
doi: 10.6023/A16010003
Abstract:
Nanotechnology, with many advantages to engineer new organized nanomaterials, has attracted much attention in recent decades. Smart drug delivery and controlled release system can enhance the effectiveness of chemotherapy at diseased body parts and reduce its side effects of drugs on normal tissues and cells. With high rigidity and surface area, tailored mesoporous structure, and good biocompatibility, mesoporous silica nanoparticles (MSNs) have been proven to be excellent nanocarriers and delivery vehicle. In the mean time, gold nanoparticles (AuNPs) possess a number of advantages of gold-based nanomaterials that make them appealing for controlled drug delivery applications. The novel nanovalve systems based on MSNs (acting as nanocontainers or reservoirs)-AuNPs (acting as gates or switches), combining the good characteristics of the two kinds of nanoparticles in one system, has captured research interests in the fields of chemistry, biomaterials, nanoscience and clinical medicine. This review article introduces important research progress on the single and multiple functions of controllable drug release systems based on MSN-AuNPs hybrids, which will be illustrated from stimulus and applications points of view. In the section of single responsive systems, we introduce the adaptability and responsiveness of the hybrid systems to external environmental stimuli, such as light (UV and NIR), pH, competitive binding, aptamers, and biological signals. In the section of multiple responsive systems, we focus on the design principle and release effect of dual responsive systems and reversible systems. In addition, the challenges and development direction of this type of nanovalve-based drug delivery systems are systematically discussed. Although the nanogate systems based on MSNs capped by AuNPs, employing many different functions, have made tremendous progress in recent years, collaborations between chemists, material scientists, engineers and medical doctors are in urgent need to further advance this research field and realize their final practical applications in the near future.
Nanotechnology, with many advantages to engineer new organized nanomaterials, has attracted much attention in recent decades. Smart drug delivery and controlled release system can enhance the effectiveness of chemotherapy at diseased body parts and reduce its side effects of drugs on normal tissues and cells. With high rigidity and surface area, tailored mesoporous structure, and good biocompatibility, mesoporous silica nanoparticles (MSNs) have been proven to be excellent nanocarriers and delivery vehicle. In the mean time, gold nanoparticles (AuNPs) possess a number of advantages of gold-based nanomaterials that make them appealing for controlled drug delivery applications. The novel nanovalve systems based on MSNs (acting as nanocontainers or reservoirs)-AuNPs (acting as gates or switches), combining the good characteristics of the two kinds of nanoparticles in one system, has captured research interests in the fields of chemistry, biomaterials, nanoscience and clinical medicine. This review article introduces important research progress on the single and multiple functions of controllable drug release systems based on MSN-AuNPs hybrids, which will be illustrated from stimulus and applications points of view. In the section of single responsive systems, we introduce the adaptability and responsiveness of the hybrid systems to external environmental stimuli, such as light (UV and NIR), pH, competitive binding, aptamers, and biological signals. In the section of multiple responsive systems, we focus on the design principle and release effect of dual responsive systems and reversible systems. In addition, the challenges and development direction of this type of nanovalve-based drug delivery systems are systematically discussed. Although the nanogate systems based on MSNs capped by AuNPs, employing many different functions, have made tremendous progress in recent years, collaborations between chemists, material scientists, engineers and medical doctors are in urgent need to further advance this research field and realize their final practical applications in the near future.
2016, 74(4): 312-329
doi: 10.6023/A16010016
Abstract:
Natural products have been widely used in the construction of supramolecular self-assemblies due to not only their abundant resources, unique chiral structures, and multiple reaction sites, but also the good biocompatibility and the controllable degradability. Through the simple chemical modification natural products-based functional molecules would self-assemble into various supramolecular assemblies primarily promoted by non-covalent interactions, such as hydrogen bonding, π-π stacking, van der Waals forces, electrostatic interactions, and charge-transfer interactions. During the assembly process, their unique molecular chirality would be transferred and magnified into supramolecular assemblies, thus providing a facile method to fabricate helical ribbons, nanotubes, and other chiral nanostructures. Furthermore, their good biocompatibility and biological activity endow the assemblies with the ability to be widely applied in tissue engineering, drug delivery, cell imaging, and so on. In this review, recent developments of supramolecular self-assemblies based on amino acids, sugars, nucleosides, steroids, triterpenoids and other natural products were summarized.
Natural products have been widely used in the construction of supramolecular self-assemblies due to not only their abundant resources, unique chiral structures, and multiple reaction sites, but also the good biocompatibility and the controllable degradability. Through the simple chemical modification natural products-based functional molecules would self-assemble into various supramolecular assemblies primarily promoted by non-covalent interactions, such as hydrogen bonding, π-π stacking, van der Waals forces, electrostatic interactions, and charge-transfer interactions. During the assembly process, their unique molecular chirality would be transferred and magnified into supramolecular assemblies, thus providing a facile method to fabricate helical ribbons, nanotubes, and other chiral nanostructures. Furthermore, their good biocompatibility and biological activity endow the assemblies with the ability to be widely applied in tissue engineering, drug delivery, cell imaging, and so on. In this review, recent developments of supramolecular self-assemblies based on amino acids, sugars, nucleosides, steroids, triterpenoids and other natural products were summarized.
2016, 74(4): 330-334
doi: 10.6023/A15120785
Abstract:
In order to overcome the low energy transfer efficiency of the conventional FRET (Förster resonance energy transfer) system, a novel spectra-matching and distance-controllable CIS@ZnS-SQ FRET assembly has been prepared via ultrasonic self-assembly method, by using the synthesized visible CIS@ZnS type I core-shell quantum dots as energy donor and the near infrared SQ dyes as acceptor. Through controllable synthesis of quantum dots, the absorption and fluorescence performance of FRET system were adjusted by the size of CIS@ZnS, while the distance of energy donor-acceptor and the non-valid charge recombination in the FRET system were controlled by the wide-band shell of quantum dots. The excitons transfer and recombination kinetics in CIS@ZnS-SQ assembly were investigated by the pump-probe femtosecond ultrafast transient absorption measurements, with which results in the FRET-type energy transfer mechanism: CIS*+SQ→CIS+SQ* has been proven and a high energy transfer rate of about 5.0×1010 s-1 has been gained between CIS@ZnS and SQ. The excitons' lifetime and FRET energy transfer efficiency were calculated from the fluorescence decay kinetic curves tested by time-resolved fluorescence measurements. The results show that the energy transfer in CIS@ZnS-SQ depends on the size of CIS@ZnS quantum dots. As the size of CIS@ZnS (mainly refers to the ZnS shell thickness) increases from 2.1±0.4 nm to 2.9±0.4 nm, 4.1±0.3 nm, 5.4±0.5 nm and 7.2±0.5 nm, the fluorescence quantum yield of CIS@ZnS improves from 5.4% to 26%, 33%, 38% and 43.3% as well as the distance between CIS@ZnS and SQ (energy donor and acceptor) increases gradually, which makes the FRET energy transfer efficiency (ηFRET) first rise and then decline. As a result, an optimal ηFRET value of 62.8% was gained in the FRET assembly when the reaction time of ZnS shell was 20 min. This research will have a promising theoretical and practical value for the development of the panchromatic and high-efficiency solar cells.
In order to overcome the low energy transfer efficiency of the conventional FRET (Förster resonance energy transfer) system, a novel spectra-matching and distance-controllable CIS@ZnS-SQ FRET assembly has been prepared via ultrasonic self-assembly method, by using the synthesized visible CIS@ZnS type I core-shell quantum dots as energy donor and the near infrared SQ dyes as acceptor. Through controllable synthesis of quantum dots, the absorption and fluorescence performance of FRET system were adjusted by the size of CIS@ZnS, while the distance of energy donor-acceptor and the non-valid charge recombination in the FRET system were controlled by the wide-band shell of quantum dots. The excitons transfer and recombination kinetics in CIS@ZnS-SQ assembly were investigated by the pump-probe femtosecond ultrafast transient absorption measurements, with which results in the FRET-type energy transfer mechanism: CIS*+SQ→CIS+SQ* has been proven and a high energy transfer rate of about 5.0×1010 s-1 has been gained between CIS@ZnS and SQ. The excitons' lifetime and FRET energy transfer efficiency were calculated from the fluorescence decay kinetic curves tested by time-resolved fluorescence measurements. The results show that the energy transfer in CIS@ZnS-SQ depends on the size of CIS@ZnS quantum dots. As the size of CIS@ZnS (mainly refers to the ZnS shell thickness) increases from 2.1±0.4 nm to 2.9±0.4 nm, 4.1±0.3 nm, 5.4±0.5 nm and 7.2±0.5 nm, the fluorescence quantum yield of CIS@ZnS improves from 5.4% to 26%, 33%, 38% and 43.3% as well as the distance between CIS@ZnS and SQ (energy donor and acceptor) increases gradually, which makes the FRET energy transfer efficiency (ηFRET) first rise and then decline. As a result, an optimal ηFRET value of 62.8% was gained in the FRET assembly when the reaction time of ZnS shell was 20 min. This research will have a promising theoretical and practical value for the development of the panchromatic and high-efficiency solar cells.
2016, 74(4): 335-339
doi: 10.6023/A15120782
Abstract:
Five-ring fused azo-and thio-aromatic compounds 1 and 2 containing imide substituent were designed and synthesized. 3,4-Dibromo-1-(2-ethylhexyl)-1H-pyrrole-2,5-dione reacted with lithium indyl and benzothiophene-3-boronic acid respectively, affording intermediates 3 and 4. Compound 3 was intramolecular cyclized in the presence of PdCl2 to give target compound 1. And compound 2 was prepared through intramolecular cyclization of intermediate 4 by means of photochemical ringclosure reaction and oxidation. The physicochemical properties of compounds 1 and 2 were thoroughly investigated with TGA, UV-vis absorption spectra and cyclic voltammetry. Experimental results showed the introduction of imide substituent not only increased the solubility of compounds 1 and 2, but also decreased their energy levels of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). The HOMO/LUMO energy levels of compounds 1 and 2 are -5.58/-2.25 eV and -6.04/-3.51 eV respectively. Single crystals of compound 1 were grown through solvent evaporation method in the mixture of dichloromethane and petroleum ether. Single crystal structure revealed compound 1 has a planar conjugated core and forms dimmer in the crystal. Strong π-π intermolecular interactions exist in the dimmer, and hydrogen bonds (NH…O＝C) are observed among dimmers. The charge carrier mobilities of compounds 1 and 2 were investigated through thin film transistors. The transistors were fabricated with top-contact/bottom-gate device configurations. And thin films were deposited in vacuum on octadecyltrichlorosilane (OTS)-modified Si/SiO2 substrates. Transistors performance of compound 2 displays obvious p-type performance with a mobility of 2.75×10-3 cm2·V-1·s-1. However, compound 1 exhibited no organic field-effect transistor (OFET) behavior. In order to understand the different device performances of compounds 1 and 2, their thin films were investigated by atomic force microscopy (AFM) and X-ray diffraction (XRD). AFM images showed that compound 1 formed continuous thin film with small size of microstructures, the existence of grain boundaries hindered the transport of charge carriers in the film. XRD curves revealed that compound 2 formed crystalline thin films. Though the continuity of 2 films was worse than that of 1, the larger size of microstructures and the crystalline property of the films facilitated the transport of charge carriers.
Five-ring fused azo-and thio-aromatic compounds 1 and 2 containing imide substituent were designed and synthesized. 3,4-Dibromo-1-(2-ethylhexyl)-1H-pyrrole-2,5-dione reacted with lithium indyl and benzothiophene-3-boronic acid respectively, affording intermediates 3 and 4. Compound 3 was intramolecular cyclized in the presence of PdCl2 to give target compound 1. And compound 2 was prepared through intramolecular cyclization of intermediate 4 by means of photochemical ringclosure reaction and oxidation. The physicochemical properties of compounds 1 and 2 were thoroughly investigated with TGA, UV-vis absorption spectra and cyclic voltammetry. Experimental results showed the introduction of imide substituent not only increased the solubility of compounds 1 and 2, but also decreased their energy levels of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). The HOMO/LUMO energy levels of compounds 1 and 2 are -5.58/-2.25 eV and -6.04/-3.51 eV respectively. Single crystals of compound 1 were grown through solvent evaporation method in the mixture of dichloromethane and petroleum ether. Single crystal structure revealed compound 1 has a planar conjugated core and forms dimmer in the crystal. Strong π-π intermolecular interactions exist in the dimmer, and hydrogen bonds (NH…O＝C) are observed among dimmers. The charge carrier mobilities of compounds 1 and 2 were investigated through thin film transistors. The transistors were fabricated with top-contact/bottom-gate device configurations. And thin films were deposited in vacuum on octadecyltrichlorosilane (OTS)-modified Si/SiO2 substrates. Transistors performance of compound 2 displays obvious p-type performance with a mobility of 2.75×10-3 cm2·V-1·s-1. However, compound 1 exhibited no organic field-effect transistor (OFET) behavior. In order to understand the different device performances of compounds 1 and 2, their thin films were investigated by atomic force microscopy (AFM) and X-ray diffraction (XRD). AFM images showed that compound 1 formed continuous thin film with small size of microstructures, the existence of grain boundaries hindered the transport of charge carriers in the film. XRD curves revealed that compound 2 formed crystalline thin films. Though the continuity of 2 films was worse than that of 1, the larger size of microstructures and the crystalline property of the films facilitated the transport of charge carriers.
2016, 74(4): 340-350
doi: 10.6023/A15120781
Abstract:
90 kinds of dinitrogen binuclear transition-metal complexes at singlet and triplet states in Group 4~10 from Period 4 to 6 based on the biomimetic dinitrogen fixation species were studied using DFT method, [Cp*Fe(μ-η2:η2-bdt)- (μ-η1:η1-MeN＝NMe)FeCp*] and [Cp*Fe(μ-SEt)2(μ-η1:η1-MeN＝NMe)FeCp*], in order to investigate the transition-metal effect in N-N activation. The calculated results indicate that N-N bond activation is strongly related to the period of transition metal. N-N activation by transition metals in Period 6 is stronger than those in Period 5 and Period 4. For transition metals in the same period, N-N activation ability decreases from Group 4 to Group 10. The odd-even electron number of transition metal center also shows certain influence on the N-N activation. In addition, side-on coordination mode is more favorable than end-on mode for thiolate-bridged dinuclear transition-metal complexes on N-N bond activation. The type of ligands (BDT ligand or ethyl ligand) in this system has little impact on N-N activation.
90 kinds of dinitrogen binuclear transition-metal complexes at singlet and triplet states in Group 4~10 from Period 4 to 6 based on the biomimetic dinitrogen fixation species were studied using DFT method, [Cp*Fe(μ-η2:η2-bdt)- (μ-η1:η1-MeN＝NMe)FeCp*] and [Cp*Fe(μ-SEt)2(μ-η1:η1-MeN＝NMe)FeCp*], in order to investigate the transition-metal effect in N-N activation. The calculated results indicate that N-N bond activation is strongly related to the period of transition metal. N-N activation by transition metals in Period 6 is stronger than those in Period 5 and Period 4. For transition metals in the same period, N-N activation ability decreases from Group 4 to Group 10. The odd-even electron number of transition metal center also shows certain influence on the N-N activation. In addition, side-on coordination mode is more favorable than end-on mode for thiolate-bridged dinuclear transition-metal complexes on N-N bond activation. The type of ligands (BDT ligand or ethyl ligand) in this system has little impact on N-N activation.
2016, 74(4): 351-355
doi: 10.6023/A16010001
Abstract:
As well-known, traditional luminescent dyes such as dicyanomethylene-4H-pyran (DCM) luminogens used in biological diagnosis and therapy still exit several limitations due to their inherent molecular structures. One of the most notorious phenomena is "aggregation caused quenching" (ACQ), namely that the fluorescence can be easily observed in dilute solution, but quenched in high concentration or aggregated state. Therefore, how to understand the aggregation environment formed by dye molecules and further utilize the aggregate itself as a potential pattern for biomedical application is highly desirable. Since the intriguing discovery of the aggregation-induced emission (AIE) phenomenon, much effort has been paid to exploration of AIE systems and their applications. These AIE chromophores exhibit highly bright fluorescence when aggregated, and weak fluorescence when dissolved in solution, making them beneficial for improving the sensitivity of biosensors and bioimaging in situ or in vivo. Herein we set out to construct a novel AIE-active quinoline-malononitrile (QM) building block, by merely replacing the oxygen atom in DCM moiety with N-ethyl group, thoroughly solving the fluorescence quenching problems of DCM derivatives in aggregation. Five QM derivatives (QM-H, QM-F, QM-Br, QM-I and QM-N) with different substituent groups have been successfully synthesized by Knoevenagel reaction, extending the AIE wavelength from 528 to 614 nm in the aggregated state. A series of experiments were performed to examine the photoluminescence properties of QM-H, QM-F, QM-Br, QM-I and QM-N. As expected, all these AIE-active compounds show weak or no fluorescence in molecular state when dissolved in THF solution, but enhanced emission in solid or aggregate state along with an increasing volume fraction of water in tetrahydrofuran/water (THF/H2O) mixtures. Moreover, their AIE-active fluorescent properties are dependent upon the different aggregated microenvironment affected by substituent groups of QM derivatives. Notably, the halogen atoms of QM-F, QM-Br and QM-I play important role in AIE quantum yield, while introducing electron donor group shifts the solid fluorescence of QM-N into red emission. The substituent effect of QM derivatives with excellent AIE properties can provide a platform to develop NIR AIE materials.
As well-known, traditional luminescent dyes such as dicyanomethylene-4H-pyran (DCM) luminogens used in biological diagnosis and therapy still exit several limitations due to their inherent molecular structures. One of the most notorious phenomena is "aggregation caused quenching" (ACQ), namely that the fluorescence can be easily observed in dilute solution, but quenched in high concentration or aggregated state. Therefore, how to understand the aggregation environment formed by dye molecules and further utilize the aggregate itself as a potential pattern for biomedical application is highly desirable. Since the intriguing discovery of the aggregation-induced emission (AIE) phenomenon, much effort has been paid to exploration of AIE systems and their applications. These AIE chromophores exhibit highly bright fluorescence when aggregated, and weak fluorescence when dissolved in solution, making them beneficial for improving the sensitivity of biosensors and bioimaging in situ or in vivo. Herein we set out to construct a novel AIE-active quinoline-malononitrile (QM) building block, by merely replacing the oxygen atom in DCM moiety with N-ethyl group, thoroughly solving the fluorescence quenching problems of DCM derivatives in aggregation. Five QM derivatives (QM-H, QM-F, QM-Br, QM-I and QM-N) with different substituent groups have been successfully synthesized by Knoevenagel reaction, extending the AIE wavelength from 528 to 614 nm in the aggregated state. A series of experiments were performed to examine the photoluminescence properties of QM-H, QM-F, QM-Br, QM-I and QM-N. As expected, all these AIE-active compounds show weak or no fluorescence in molecular state when dissolved in THF solution, but enhanced emission in solid or aggregate state along with an increasing volume fraction of water in tetrahydrofuran/water (THF/H2O) mixtures. Moreover, their AIE-active fluorescent properties are dependent upon the different aggregated microenvironment affected by substituent groups of QM derivatives. Notably, the halogen atoms of QM-F, QM-Br and QM-I play important role in AIE quantum yield, while introducing electron donor group shifts the solid fluorescence of QM-N into red emission. The substituent effect of QM derivatives with excellent AIE properties can provide a platform to develop NIR AIE materials.
2016, 74(4): 356-362
doi: 10.6023/A16010008
Abstract:
Large quantities of particulate pollutants are emitted into the atmosphere during biomass burning processes. In China, large amounts of agricultural residues are burned in the field during harvest seasons, which influence regional air quality and human health. Corn and wheat are two major crops grown in China, whose burning was simulated in this study. The controlled laboratory simulation of straw burning was performed in the Laboratory of Biomass Burning Simulation at Peking University Shenzhen Graduate School. The burning simulation system was improved and verified. Straw burning aerosols (PM2.5) samples were collected and measured by gravimetric method. Organic carbon (OC) and elemental carbon (EC) were measured by thermal/optical method. Water-soluble inorganic ions and organic matter were measured by ion chromatography. Emission level, characterization and influence factors of crop straw burning aerosols are discussed. PM2.5 emission factors of corn and wheat straw burning are 1082.8 and 835.7~897.3 mg/kg, respectively. Organic matter (OM), which is calculated by multiplying organic carbon (OC) by 1.3, is the major component of PM2.5, accounting for 42%~66% of the total mass. Nearly half (37%~50%) of OM are water soluble. Cl- and K+are two major components among water-soluble inorganic ions, accounting for 4%~15% and 2%~14% of total particle mass, respectively. The K+/EC ratio is 0.5~3.8. The proportions of these species in PM2.5 are comparable to previous studies. Straw moisture content and burning temperature influence the emission level and characterization of straw burning aerosols. Emission factors of PM2.5 and OC increase with the increase of straw moisture content because of incomplete burning. With higher moisture content, more thermal energy is used for the evaporation of water, lowering the burning temperature. Then less proportion of K+and Cl- are released from biomass into the smoke. Therefore, their contributions to the particle mass decrease with the increase of straw moisture content. The emissions of PM2.5 and OC/EC by crop straw burning in the field are estimated based on the emission factors obtained in this study. Corn and wheat burning in the field yield 92.7 Gg PM2.5 and 47.5 Gg OC every year in China, accounting for important fractions among the total mass.
Large quantities of particulate pollutants are emitted into the atmosphere during biomass burning processes. In China, large amounts of agricultural residues are burned in the field during harvest seasons, which influence regional air quality and human health. Corn and wheat are two major crops grown in China, whose burning was simulated in this study. The controlled laboratory simulation of straw burning was performed in the Laboratory of Biomass Burning Simulation at Peking University Shenzhen Graduate School. The burning simulation system was improved and verified. Straw burning aerosols (PM2.5) samples were collected and measured by gravimetric method. Organic carbon (OC) and elemental carbon (EC) were measured by thermal/optical method. Water-soluble inorganic ions and organic matter were measured by ion chromatography. Emission level, characterization and influence factors of crop straw burning aerosols are discussed. PM2.5 emission factors of corn and wheat straw burning are 1082.8 and 835.7~897.3 mg/kg, respectively. Organic matter (OM), which is calculated by multiplying organic carbon (OC) by 1.3, is the major component of PM2.5, accounting for 42%~66% of the total mass. Nearly half (37%~50%) of OM are water soluble. Cl- and K+are two major components among water-soluble inorganic ions, accounting for 4%~15% and 2%~14% of total particle mass, respectively. The K+/EC ratio is 0.5~3.8. The proportions of these species in PM2.5 are comparable to previous studies. Straw moisture content and burning temperature influence the emission level and characterization of straw burning aerosols. Emission factors of PM2.5 and OC increase with the increase of straw moisture content because of incomplete burning. With higher moisture content, more thermal energy is used for the evaporation of water, lowering the burning temperature. Then less proportion of K+and Cl- are released from biomass into the smoke. Therefore, their contributions to the particle mass decrease with the increase of straw moisture content. The emissions of PM2.5 and OC/EC by crop straw burning in the field are estimated based on the emission factors obtained in this study. Corn and wheat burning in the field yield 92.7 Gg PM2.5 and 47.5 Gg OC every year in China, accounting for important fractions among the total mass.
2016, 74(4): 363-368
doi: 10.6023/A16010038
Abstract:
Near-infrared (NIR) fluorescence facilitates noninvasive bio-imaging because it involves less interference from blood and tissue auto-fluorescence and high transparency. Nowadays, the research of new NIR fluorescent probes with favorable biocompatibility, high quantum yield, high stability and long-wavelength emission band has become the focus of bio-nanotechnology. Herein, we introduced NIBC enantiomers onto the surface of gold nanoclusters and synthesized chiral gold nanoclusters anchored with N-isobutyryl-L-cysteine (L-NIBC-AuNCs) and N-isobutyryl-D-cysteine (D-NIBC-AuNCs), respectively. Transmission electron microscopy (TEM images) of the L-NIBC-AuNCs and D-NIBC-AuNCs reveal that the particle sizes of both two AuNCs are around 1.9±0.7 nm. The UV-Vis absorption spectra of L-NIBC-AuNCs and D-NIBC-AuNCs are basically identical and both two AuNCs have characteristic absorption peaks at 580 nm and 680 nm. Compared with the FT-IR spectra of NIBC, the vanishing of the S—H stretching vibration at the 2500~2600 cm-1 in the FT-IR spectra of L-NIBC-AuNCs and D-NIBC-AuNCs indicate that L-NIBC and D-NIBC have successfully anchored on to the surface of Au core by Au—S bond. The circular dichroism (CD) spectra of L-NIBC-AuNCs and D-NIBC-AuNCs show nearly a mirror image relationship at 230~360 nm, which means the chirality signal transmitted from molecular level to nanoscale level. Most important of all, both two water-soluble nanoclusters have fluorescence emission bands between 900~1000 nm which belong to the near infrared bands. And the fluorescence quantum yields of L-NIBC-AuNCs and D-NIBC-AuNCs are 6.9% and 8.2%, respectively. Cell toxicity experiments show that both two kinds of gold nanoclusters have no cytotoxicity even at the high concentration of 100 mg/L. Moreover, these gold nanoclusters also have unique chiroptical activity and potential chiral recognition ability. Based on the experiment mentioned above, these kinds of chiral gold nanoclusters can be used as a new kind of near-infrared fluorescent probe, which may have promising application in the near-infrared fluorescent imaging. These findings provide an interesting insight in the near-infrared fluorescence (NIRF) imaging techniques.
Near-infrared (NIR) fluorescence facilitates noninvasive bio-imaging because it involves less interference from blood and tissue auto-fluorescence and high transparency. Nowadays, the research of new NIR fluorescent probes with favorable biocompatibility, high quantum yield, high stability and long-wavelength emission band has become the focus of bio-nanotechnology. Herein, we introduced NIBC enantiomers onto the surface of gold nanoclusters and synthesized chiral gold nanoclusters anchored with N-isobutyryl-L-cysteine (L-NIBC-AuNCs) and N-isobutyryl-D-cysteine (D-NIBC-AuNCs), respectively. Transmission electron microscopy (TEM images) of the L-NIBC-AuNCs and D-NIBC-AuNCs reveal that the particle sizes of both two AuNCs are around 1.9±0.7 nm. The UV-Vis absorption spectra of L-NIBC-AuNCs and D-NIBC-AuNCs are basically identical and both two AuNCs have characteristic absorption peaks at 580 nm and 680 nm. Compared with the FT-IR spectra of NIBC, the vanishing of the S—H stretching vibration at the 2500~2600 cm-1 in the FT-IR spectra of L-NIBC-AuNCs and D-NIBC-AuNCs indicate that L-NIBC and D-NIBC have successfully anchored on to the surface of Au core by Au—S bond. The circular dichroism (CD) spectra of L-NIBC-AuNCs and D-NIBC-AuNCs show nearly a mirror image relationship at 230~360 nm, which means the chirality signal transmitted from molecular level to nanoscale level. Most important of all, both two water-soluble nanoclusters have fluorescence emission bands between 900~1000 nm which belong to the near infrared bands. And the fluorescence quantum yields of L-NIBC-AuNCs and D-NIBC-AuNCs are 6.9% and 8.2%, respectively. Cell toxicity experiments show that both two kinds of gold nanoclusters have no cytotoxicity even at the high concentration of 100 mg/L. Moreover, these gold nanoclusters also have unique chiroptical activity and potential chiral recognition ability. Based on the experiment mentioned above, these kinds of chiral gold nanoclusters can be used as a new kind of near-infrared fluorescent probe, which may have promising application in the near-infrared fluorescent imaging. These findings provide an interesting insight in the near-infrared fluorescence (NIRF) imaging techniques.
2016, 74(4): 369-374
doi: 10.6023/A15120755
Abstract:
Responsive polymers have attracted great interests in many application fields. Thermoresponsive polymers are especially appealing, and have been applied in biomedical and biotechnological fields. A thermoresponsive polymer, 2-hydroxy-3-isopropoxypropyl hydroxyethyl cellulose (HIPEC), was prepared by etherification reaction, which grafted isopropyl glycidyl ether (IPGE) onto hydroxyethyl cellulose (HEC). The HIPEC was characterized by 1H NMR, 13C NMR, and 2D HSQC NMR, and the molar substitution (MS) of HIPEC was determined by 1H NMR. The lower critical solution temperature (LCST) of HIPEC can be tuned from 17.0~43.0 ℃ by changing MS of hydrophobic groups from 1.21~2.88. The salt concentration has a significant influence on LCST, the experiment results indicated that the LCST of HIPEC decreased with increasing NaCl concentration. Amphiphilic, thermoresponsive polymers can form micelles in aqueous solution and encapsulate guest molecules. Fluorescence spectroscopy and dynamic light scattering (DLS) showed that HIPEC can assemble into micelles, and micelles diameter significantly increase with increasing temperature. It is indicated that the morphologies of the HIPEC micelles can be varied by changing temperature. The critical micelle concentrations (CMC) of HIPEC which were measured by fluorescence spectroscopy decreased with increasing of the MS of hydrophobic groups. Additionally, using Nile Red as a probe, fluorescence spectroscopy and confocal laser scan microscope (CLSM) were applied to the HIPEC aqueous solution to examine the encapsulation of Nile Red aqueous solutions of the HIPEC. The research results show that Nile Red can be encapsulated and stabilized in the hydrophobic core of HIPEC micelles. The fluorescence intensity of Nile Red increased with increasing of HIPEC concentration, and there is a sharp increase in the number of HIPEC micelles above CMC. Because the morphologies of HIPEC micelles were disrupted when the temperature reached the LCST, the Nile Red which was capsulated in HIPEC micelles can be slowly released from HIPEC micelles over a much longer period of time, and the release process can be controlled by changing temperature.
Responsive polymers have attracted great interests in many application fields. Thermoresponsive polymers are especially appealing, and have been applied in biomedical and biotechnological fields. A thermoresponsive polymer, 2-hydroxy-3-isopropoxypropyl hydroxyethyl cellulose (HIPEC), was prepared by etherification reaction, which grafted isopropyl glycidyl ether (IPGE) onto hydroxyethyl cellulose (HEC). The HIPEC was characterized by 1H NMR, 13C NMR, and 2D HSQC NMR, and the molar substitution (MS) of HIPEC was determined by 1H NMR. The lower critical solution temperature (LCST) of HIPEC can be tuned from 17.0~43.0 ℃ by changing MS of hydrophobic groups from 1.21~2.88. The salt concentration has a significant influence on LCST, the experiment results indicated that the LCST of HIPEC decreased with increasing NaCl concentration. Amphiphilic, thermoresponsive polymers can form micelles in aqueous solution and encapsulate guest molecules. Fluorescence spectroscopy and dynamic light scattering (DLS) showed that HIPEC can assemble into micelles, and micelles diameter significantly increase with increasing temperature. It is indicated that the morphologies of the HIPEC micelles can be varied by changing temperature. The critical micelle concentrations (CMC) of HIPEC which were measured by fluorescence spectroscopy decreased with increasing of the MS of hydrophobic groups. Additionally, using Nile Red as a probe, fluorescence spectroscopy and confocal laser scan microscope (CLSM) were applied to the HIPEC aqueous solution to examine the encapsulation of Nile Red aqueous solutions of the HIPEC. The research results show that Nile Red can be encapsulated and stabilized in the hydrophobic core of HIPEC micelles. The fluorescence intensity of Nile Red increased with increasing of HIPEC concentration, and there is a sharp increase in the number of HIPEC micelles above CMC. Because the morphologies of HIPEC micelles were disrupted when the temperature reached the LCST, the Nile Red which was capsulated in HIPEC micelles can be slowly released from HIPEC micelles over a much longer period of time, and the release process can be controlled by changing temperature.
