利用核酸i-motif结构对质子的超敏感特性,选择富含胞嘧啶C的核酸链及其互补链,以及染料SYBR Green Ⅰ对单双链DNA的不同荧光响应特性,研制了一种灵敏的新型pH响应荧光传感器。当pH值从5.0变为7.5时,SYBR Green Ⅰ的荧光强度增大了4倍以...利用核酸i-motif结构对质子的超敏感特性,选择富含胞嘧啶C的核酸链及其互补链,以及染料SYBR Green Ⅰ对单双链DNA的不同荧光响应特性,研制了一种灵敏的新型pH响应荧光传感器。当pH值从5.0变为7.5时,SYBR Green Ⅰ的荧光强度增大了4倍以上,pH传感范围是5.0～7.5,并显示出很高的pH分辨率(0.1个pH单元)。该pH传感器具有简单、快速、成本低等优点,有望用于相关生物过程中微小pH值变化的传感分析。展开更多
i-Motif is formed from two parallel duplexes by intercalating with each other in an antiparallel orientation and each duplex is held together-via-hemiprotonated cytosine+-cytosine base pairs.However,a cell is crowded ...i-Motif is formed from two parallel duplexes by intercalating with each other in an antiparallel orientation and each duplex is held together-via-hemiprotonated cytosine+-cytosine base pairs.However,a cell is crowded with various biomolecules and little is known about the properties of i-Motif under molecular crowding conditions until now.In the present study,we used human telomeric DNA sequence,[C3TA23C3,as a model system to investigate such problem by circular dichroism(CD) and UV absorbance spectroscopy.Based on the CD spectra,we found that there were no changes about the structure of i-Motif in the presence of polyethylene glycol(PEG).CD melting results showed that the thermal stability of i-Motif was increased under molecular crowding conditions compare to that in dilute buffer,which was further demonstrated by UV-melting results.This work suggests that molecular crowding could not affect the structure of i-Motif,which may depend on pH,while could enhance the thermal stability of i-Motif.展开更多
The DNA i-motif is a quadruplex structure formed in tandem cytosine-rich sequences in slightly acidic conditions. Besides being considered as a building block of DNA nano-devices, it may also play potential roles in r...The DNA i-motif is a quadruplex structure formed in tandem cytosine-rich sequences in slightly acidic conditions. Besides being considered as a building block of DNA nano-devices, it may also play potential roles in regulating chromo- some stability and gene transcriptions. The stability of i-motif is crucial for these functions. In this work, we investigated the mechanical stability of a single i-motif formed in the human telomeric sequence 51-（CCCTAA）3CCC, which revealed a novel pH and loading rate-dependent bimodal unfolding force distribution. Although the cause of the bimodal unfolding force species is not clear, we proposed a phenomenological model involving a direct unfolding favored at lower loading rate or higher pH value, which is subject to competition with another unfolding pathway through a mechanically stable inter- mediate state whose nature is yet to be determined. Overall, the unique mechano-chemical responses of i-motif-provide a new perspective to its stability, which may be useful to guide designing new i-motif-based DNA mechanical nano-devices.展开更多
The combination of photothermal therapywith chemotherapy has gradually developed into promising cancer therapy.Here,a synergistic photothermal-chemotherapy nanoplatform based on polydopamine(PDA)-coated gold nanoparti...The combination of photothermal therapywith chemotherapy has gradually developed into promising cancer therapy.Here,a synergistic photothermal-chemotherapy nanoplatform based on polydopamine(PDA)-coated gold nanoparticles(AuNPs)were facilely achieved via the in situ polymerization of dopamine(DA)on the surface of AuNPs.This nanoplatform exhibited augmented photothermal conversion efficiency and enhanced colloidal stability in comparison with uncoated PDA shell AuNPs.The i-motif DNA nanostructure was assembled on PDA-coated AuNPs,which could be transformed into a C-quadruplex structure under an acidic environment,showing a characteristic pH response.The PDA shell served as a linker between the AuNPs and the i-motif DNA nanostructure.To enhance the specific cellular uptake,the AS1411 aptamer was introduced to the DNA nanostructure employed as a targeting ligand.In addition,Dox-loaded NPs(DAu@PDA-AS141)showed the pH/photothermal-responsive release of Dox.The photothermal effect of DAu@PDA-AS141 elicited excellent photothermal performance and efficient cancer cell inhibition under 808 nm near-infrared(NIR)irradiation.Overall,these results demonstrate that the DAu@PDA-AS141 nanoplatform shows great potential in synergistic photothermal-chemotherapy.展开更多
Formation and dissociation mechanisms of C-C＋ base pairs in acidic and alkaline environments are investigated, employing ab initio quantum chemical calculations. Our calculations suggest that, in an acidic environmen...Formation and dissociation mechanisms of C-C＋ base pairs in acidic and alkaline environments are investigated, employing ab initio quantum chemical calculations. Our calculations suggest that, in an acidic environment, a cytosine monomer is first protonated and then dimerized with an unprotonated cytosine monomer to form a C-C＋ base pair; in an alkaline environment, a protonated cytosine dimer is first unprotonated and then dissociated into two cytosine monomers. In addition, the force for detaching a C-C＋ base pair was found to be inversely proportional to the distance between the two cytosine monomers. These results provide a microscopic mechanism to qualitatively explain the experimentally observed reversible formation and dissociation of i-motifs.展开更多
Precise tumor targeting and therapy is a major trend in cancer treatment.Herein,we designed a tumor acidic microenvironment activatable drug loaded DNA nanostructure,in which,we made a clever use of the sequences of A...Precise tumor targeting and therapy is a major trend in cancer treatment.Herein,we designed a tumor acidic microenvironment activatable drug loaded DNA nanostructure,in which,we made a clever use of the sequences of AS1411 and i-motif,which can partially hybridize,and designed a simple while robust DNA D-strand nanostructure,in which,i-motif sequence was designed to regulate the binding ability of the AS1411 aptamer to target tumor.In the normal physiological environment,i-motif inhibits the targeting ability of AS1411.In the acidic tumor microenvironment,i-motif forms a quadruplex conformation and dissociates from AS1411,restoring the targeting ability of AS1411.Only when acidic condition and tumor cell receptor are present,this nanostructure can be internalized by the tumor cells.Moreover,the structure change of this nanostructure can realize the release of loaded drug.This drug loaded A-I-Duplex DNA structure showed cancer cell and spheroid targeting and inhibition ability,which is promising in the clinical cancer therapy.展开更多
The functionality of DNA biomacromolecules has been widely excavated,as therapeutic drugs,carriers,and functionalized modification derivatives.In this study,we developed a series of DNA tetrahedron nanocages(Td),via s...The functionality of DNA biomacromolecules has been widely excavated,as therapeutic drugs,carriers,and functionalized modification derivatives.In this study,we developed a series of DNA tetrahedron nanocages(Td),via synchronous conjugating different numbers of i-(X)and therapeutic siRNA on four vertexes of tetrahedral DNA nanocage(aX-Td@bsiRNA,a+b=4).This i-motif-conjugated Td exhibited good endosomal escape behaviours in A549 tumor cells,and the escape efficiency was affected by the number of i-motif.Furthermore,the downregulating mRNA and protein expression level of epidermal growth factor receptor(EGFR)caused by this siRNA embedded Td were verified in A549 cells.The tumor growth inhibition efficiency of the 2X-Td@2siRNA treated group in tumorbearing mice was significantly higher than that of non-i-motif-conjugated Td@2siRNA(3.14-fold)and free siRNA(3.63-fold).These results demonstrate a general strategy for endowing DNA nanostructures with endosomal escape behaviours to achieve effective in vivo gene delivery and therapy.展开更多
We present here a pH-responsive activatable aptamer probe for targeted cancer imaging based on i-motif-driven conformation alteration. This pH-responsive activatable aptamer probe is composed of two single-stranded DN...We present here a pH-responsive activatable aptamer probe for targeted cancer imaging based on i-motif-driven conformation alteration. This pH-responsive activatable aptamer probe is composed of two single-stranded DNA. One was used for target recognition, containing a central, target specific aptamer sequence at the 3＇-end and an extension sequence at the 5＇-end with 5-carboxytetramethylrhodamine （TAMRA） label （denoted as strand A）. The other （strand ｜）, being competent to work on the formation of i-motif structure, contained four stretches of the cytosine （C） rich domain and was labeled with a Black Hole Quencher 2 （BHQ2） at the 3＇-end. At neutral or slightly alkaline pH, strand ｜ was hybridized to the extension sequence of strand A to form a double-stranded DNA probe, termed i-motif-based activatable aptamer probe （I-AAP）. Because of proximity- induced energy transfer, the I-AAP was in a ＂signal off＇ state. The slightly acidic pH enforced the strand I to form an intramo- lecular i-motif and then initiated the dehybridization of I-AAP, leading to fluorescence readout in the target recognition. As a demonstration, AS1411 aptamer was used for MCF-7 cells imaging. It was displayed that the I-AAP could be carried out for target cancer cells imaging after being activated in slightly acidic environment. The applicability of I-AAP for tumor tissues imaging has been also investigated by using the isolated MCF-7 tumor tissues. These results implied the I-AAP strategy is promising as a novel approach for cancer imaging.展开更多
Herein,a dual-signal electrochemical biosensor has been developed by self-assembly of pH-activatable i-motif probes on magnetic microparticles(MMPs)coupled with DNA walker for signal amplification.In this study,the cy...Herein,a dual-signal electrochemical biosensor has been developed by self-assembly of pH-activatable i-motif probes on magnetic microparticles(MMPs)coupled with DNA walker for signal amplification.In this study,the cytosine(C)-rich single-stranded DNAs are hybridized with DNA initiators to obtain the long-nicked duplexes with repeated units,which are further captured on MMPs to form the magnetic i-motif containers.The resulting duplexes contain abundant G-C base pairs,thus providing extensive binding sites for doxorubicin(DOX).At acidic pH,the C-rich sequences are folded into i-motif structure,resulting in the release of DOX and walker initiators.In this case,the liberated DOX is adsorbed on gra-phene quantum dots-modified glassy carbon electrode viaπ-πinteraction,while the walker initiators as a moving part can catalyze the hybridization between MB-modified fueler DNA and tracker DNA on electrode,contributing to the generation of dual electrochemical signals induced by MB and DOX.Importantly,the magnetic separation can effectively reduce the background,achieving sensitive biosensing of pH ranging from 4.0 to 7.4 with excellent stability.Moreover,the proposed dual-signal electrochemical biosensor has been successfully applied for accurate monitoring of pH in human serum,which holds great potential in pH-dependent bioassays,especially in ultra-micro analysis for clinical applications.展开更多
文摘利用核酸i-motif结构对质子的超敏感特性,选择富含胞嘧啶C的核酸链及其互补链,以及染料SYBR Green Ⅰ对单双链DNA的不同荧光响应特性,研制了一种灵敏的新型pH响应荧光传感器。当pH值从5.0变为7.5时,SYBR Green Ⅰ的荧光强度增大了4倍以上,pH传感范围是5.0～7.5,并显示出很高的pH分辨率(0.1个pH单元)。该pH传感器具有简单、快速、成本低等优点,有望用于相关生物过程中微小pH值变化的传感分析。
文摘i-Motif is formed from two parallel duplexes by intercalating with each other in an antiparallel orientation and each duplex is held together-via-hemiprotonated cytosine+-cytosine base pairs.However,a cell is crowded with various biomolecules and little is known about the properties of i-Motif under molecular crowding conditions until now.In the present study,we used human telomeric DNA sequence,[C3TA23C3,as a model system to investigate such problem by circular dichroism(CD) and UV absorbance spectroscopy.Based on the CD spectra,we found that there were no changes about the structure of i-Motif in the presence of polyethylene glycol(PEG).CD melting results showed that the thermal stability of i-Motif was increased under molecular crowding conditions compare to that in dilute buffer,which was further demonstrated by UV-melting results.This work suggests that molecular crowding could not affect the structure of i-Motif,which may depend on pH,while could enhance the thermal stability of i-Motif.
基金the Natural Science Foundation of China(21735002,21874035,21675046,22174044)Postgraduate Scientific Research Innovation Project of Hunan Province(CX20210396)。
基金supported by Grants from the National Research Foundation through the Mechanobiology Institute Singapore and the Ministry of Education of Singapore(Grant No.MOE2012-T3-1-001)[to Yan J]the National Basic Research Program of China(Grant No.2013CB932800)+1 种基金the Major Research Plan of the National Natural Science Foundation of China(Grant Nos.91027046 and 91027045)the Fundamental Research Funds for the Central Universities(Grant No.2013121005)
文摘The DNA i-motif is a quadruplex structure formed in tandem cytosine-rich sequences in slightly acidic conditions. Besides being considered as a building block of DNA nano-devices, it may also play potential roles in regulating chromo- some stability and gene transcriptions. The stability of i-motif is crucial for these functions. In this work, we investigated the mechanical stability of a single i-motif formed in the human telomeric sequence 51-（CCCTAA）3CCC, which revealed a novel pH and loading rate-dependent bimodal unfolding force distribution. Although the cause of the bimodal unfolding force species is not clear, we proposed a phenomenological model involving a direct unfolding favored at lower loading rate or higher pH value, which is subject to competition with another unfolding pathway through a mechanically stable inter- mediate state whose nature is yet to be determined. Overall, the unique mechano-chemical responses of i-motif-provide a new perspective to its stability, which may be useful to guide designing new i-motif-based DNA mechanical nano-devices.
基金This work was financially supported by National Natural Sciences Foundation of China(31971308 and 82102767)National S&T Major Project(2019ZX09301-147)+1 种基金Sichuan Science and Technology Program(2021YFS0081)Luzhou Science and Technology Plan(2018CDLZ-10).
文摘The combination of photothermal therapywith chemotherapy has gradually developed into promising cancer therapy.Here,a synergistic photothermal-chemotherapy nanoplatform based on polydopamine(PDA)-coated gold nanoparticles(AuNPs)were facilely achieved via the in situ polymerization of dopamine(DA)on the surface of AuNPs.This nanoplatform exhibited augmented photothermal conversion efficiency and enhanced colloidal stability in comparison with uncoated PDA shell AuNPs.The i-motif DNA nanostructure was assembled on PDA-coated AuNPs,which could be transformed into a C-quadruplex structure under an acidic environment,showing a characteristic pH response.The PDA shell served as a linker between the AuNPs and the i-motif DNA nanostructure.To enhance the specific cellular uptake,the AS1411 aptamer was introduced to the DNA nanostructure employed as a targeting ligand.In addition,Dox-loaded NPs(DAu@PDA-AS141)showed the pH/photothermal-responsive release of Dox.The photothermal effect of DAu@PDA-AS141 elicited excellent photothermal performance and efficient cancer cell inhibition under 808 nm near-infrared(NIR)irradiation.Overall,these results demonstrate that the DAu@PDA-AS141 nanoplatform shows great potential in synergistic photothermal-chemotherapy.
基金Project supported by the National Basic Research Program of China (973 Program,Grant No.2013CB932804)the National Natural Science Foundation of China (Grant Nos.91227115 and 11121403)the Hundred Talent Program of the Chinese Academy of Sciences (CAS)
文摘Formation and dissociation mechanisms of C-C＋ base pairs in acidic and alkaline environments are investigated, employing ab initio quantum chemical calculations. Our calculations suggest that, in an acidic environment, a cytosine monomer is first protonated and then dimerized with an unprotonated cytosine monomer to form a C-C＋ base pair; in an alkaline environment, a protonated cytosine dimer is first unprotonated and then dissociated into two cytosine monomers. In addition, the force for detaching a C-C＋ base pair was found to be inversely proportional to the distance between the two cytosine monomers. These results provide a microscopic mechanism to qualitatively explain the experimentally observed reversible formation and dissociation of i-motifs.
基金funded by the National Natural Science Foundation of China(No.32271464)the Hunan Provincial Natural Science Foundation for Distinguished Young Scholars(No.2022JJ10086)+2 种基金the Innovation-Driven Project of Central South University(No.2020CX048)Hunan Provincial High-Level Health Talents(No.20240304088)Fund of the Hunan Provincial Natural Science Foundation and the Hunan Medical Products Administration(No.2023JJ60501)。
文摘Precise tumor targeting and therapy is a major trend in cancer treatment.Herein,we designed a tumor acidic microenvironment activatable drug loaded DNA nanostructure,in which,we made a clever use of the sequences of AS1411 and i-motif,which can partially hybridize,and designed a simple while robust DNA D-strand nanostructure,in which,i-motif sequence was designed to regulate the binding ability of the AS1411 aptamer to target tumor.In the normal physiological environment,i-motif inhibits the targeting ability of AS1411.In the acidic tumor microenvironment,i-motif forms a quadruplex conformation and dissociates from AS1411,restoring the targeting ability of AS1411.Only when acidic condition and tumor cell receptor are present,this nanostructure can be internalized by the tumor cells.Moreover,the structure change of this nanostructure can realize the release of loaded drug.This drug loaded A-I-Duplex DNA structure showed cancer cell and spheroid targeting and inhibition ability,which is promising in the clinical cancer therapy.
基金supported by Double First-Class Innovation Team of China Pharmaceutical University(CPU2018GY40,China)National Mega-project for Innovative Drugs(2019ZX09721001,China)。
文摘The functionality of DNA biomacromolecules has been widely excavated,as therapeutic drugs,carriers,and functionalized modification derivatives.In this study,we developed a series of DNA tetrahedron nanocages(Td),via synchronous conjugating different numbers of i-(X)and therapeutic siRNA on four vertexes of tetrahedral DNA nanocage(aX-Td@bsiRNA,a+b=4).This i-motif-conjugated Td exhibited good endosomal escape behaviours in A549 tumor cells,and the escape efficiency was affected by the number of i-motif.Furthermore,the downregulating mRNA and protein expression level of epidermal growth factor receptor(EGFR)caused by this siRNA embedded Td were verified in A549 cells.The tumor growth inhibition efficiency of the 2X-Td@2siRNA treated group in tumorbearing mice was significantly higher than that of non-i-motif-conjugated Td@2siRNA(3.14-fold)and free siRNA(3.63-fold).These results demonstrate a general strategy for endowing DNA nanostructures with endosomal escape behaviours to achieve effective in vivo gene delivery and therapy.
基金supported by the Key Project of National Natural Science Foundation of China (21175039, 21322509, 21305035, 21190044, 21221003, 21305038, 2015JJ3044)
文摘We present here a pH-responsive activatable aptamer probe for targeted cancer imaging based on i-motif-driven conformation alteration. This pH-responsive activatable aptamer probe is composed of two single-stranded DNA. One was used for target recognition, containing a central, target specific aptamer sequence at the 3＇-end and an extension sequence at the 5＇-end with 5-carboxytetramethylrhodamine （TAMRA） label （denoted as strand A）. The other （strand ｜）, being competent to work on the formation of i-motif structure, contained four stretches of the cytosine （C） rich domain and was labeled with a Black Hole Quencher 2 （BHQ2） at the 3＇-end. At neutral or slightly alkaline pH, strand ｜ was hybridized to the extension sequence of strand A to form a double-stranded DNA probe, termed i-motif-based activatable aptamer probe （I-AAP）. Because of proximity- induced energy transfer, the I-AAP was in a ＂signal off＇ state. The slightly acidic pH enforced the strand I to form an intramo- lecular i-motif and then initiated the dehybridization of I-AAP, leading to fluorescence readout in the target recognition. As a demonstration, AS1411 aptamer was used for MCF-7 cells imaging. It was displayed that the I-AAP could be carried out for target cancer cells imaging after being activated in slightly acidic environment. The applicability of I-AAP for tumor tissues imaging has been also investigated by using the isolated MCF-7 tumor tissues. These results implied the I-AAP strategy is promising as a novel approach for cancer imaging.
基金supported by the National Natural Science Foundation of China(22076087)the Special Funds of the Taishan Scholar Program of Shandong Province(tsqn20161028)+2 种基金the Science Foundation for Distinguished Young Scholars of Shandong Province(ZR2020JQ08)the Youth Innovation Technology Program of Shandong Province(2019KJC029)the Collaborative Innovation Program of Jinan(2018GXRC033).
文摘Herein,a dual-signal electrochemical biosensor has been developed by self-assembly of pH-activatable i-motif probes on magnetic microparticles(MMPs)coupled with DNA walker for signal amplification.In this study,the cytosine(C)-rich single-stranded DNAs are hybridized with DNA initiators to obtain the long-nicked duplexes with repeated units,which are further captured on MMPs to form the magnetic i-motif containers.The resulting duplexes contain abundant G-C base pairs,thus providing extensive binding sites for doxorubicin(DOX).At acidic pH,the C-rich sequences are folded into i-motif structure,resulting in the release of DOX and walker initiators.In this case,the liberated DOX is adsorbed on gra-phene quantum dots-modified glassy carbon electrode viaπ-πinteraction,while the walker initiators as a moving part can catalyze the hybridization between MB-modified fueler DNA and tracker DNA on electrode,contributing to the generation of dual electrochemical signals induced by MB and DOX.Importantly,the magnetic separation can effectively reduce the background,achieving sensitive biosensing of pH ranging from 4.0 to 7.4 with excellent stability.Moreover,the proposed dual-signal electrochemical biosensor has been successfully applied for accurate monitoring of pH in human serum,which holds great potential in pH-dependent bioassays,especially in ultra-micro analysis for clinical applications.
