水相中GOx@ZIF-7/PDA的制备及酶学性能研究

原位包埋策略因制备条件温和、操作简单,被普遍应用在酶-金属有机骨架(metal-organic frameworks,MOFs)生物复合材料的制备中。但只有少部分MOFs能在水相中通过原位包埋法合成酶-MOFs生物复合材料。该研究首次在水相中采用原位包埋法将葡萄糖氧化酶(glucose oxidase,GOx)封装在ZIF-7(zeolitic imidazolate frameworks-7)载体中,并在所得的GOx@ZIF-7生物复合材料上合成了亲水性的聚多巴胺(polydopamine,PDA)修饰层,得到GOx@ZIF-7/PDA。采用单因素试验优化了GOx@ZIF-7/PDA的制备条件。结果表明,固定化pH值为7.0,酶质量浓度为5 g/L,苯并咪唑(benzimidazole,Bim)浓度为50 mmol/L,Zn^(2+)与苯并咪唑的摩尔比为1∶9,固定化温度为35℃,固定化时间为40 min,多巴胺的最佳质量浓度为2 g/L的条件下,GOx@ZIF-7/PDA具有最高酶活力回收率为(43.34±2.00)%。与游离酶相比,GOx@ZIF-7/PDA具有高的热稳定性、pH稳定性、贮存稳定性和良好的重复使用性,重复10次后,GOx@ZIF-7/PDA催化活性仍能保持(96.53±2.26)%。以上结果表明,水相原位包埋法制备固定化酶GOx@ZIF-7/PDA策略是高效可行的,有望实现低成本长期稳定的酶催化应用。

Accelerated reconstruction of ZIF-67 with significantly enhanced glucose detection sensitivity

Research on metal-organic framework(MOF)-based non-enzymatic glucose sensors usually ignores the impact of the surface reconstruction degree of MOF on the activity of catalyzing glucose oxidation.In this work,we choose zeolitic imidazolate framework-67(ZIF-67),which is commonly used in glucose sensing,as a representative to investigate the influence of reconstruction degree on its structure and glucose catalytic performance.By employing the electrochemical activation strategy,the activity of ZIF-67 in catalyzing glucose gradually increased with the prolongation of the activation time,reaching the optimum after 2 h activation.The detection sensitivity of the activated ZIF-67 was 19 times higher than that of the initial ZIF-67,and the limit of detection(LOD)was lowered from 7 to 0.4μM.Our findings demonstrate that the oxidation degree of ZIF-67 deepened rapidly with continuously activation and was basically reconstructed to CoOOH after 2 h activation,accompanied by a morphological change from cuboctahedral to flower-like.Simultaneously,theoretical investigation revealed that ZIF-67 is not suitable as a stable glucose sensor electrode since the adsorbed glucose molecules hasten the dissociation of ligands and the breaking of Co-N bond in ZIF-67.Therefore,our work has important implications for the rational design of next-generation MOF-based glucose sensors.

Zeolitic imidazolate framework-8 (ZIF-8) for drug delivery: a critical review

Zeolitie imidazolate framework-8(ZIF-8),composed of Zn ions and imidazolate ligands,is a class of metal-organic frameworks,which possesses a similar structure as conventional aluminosilicate zeolites.This material exhibits inherent porous property,high loading capacity,and pH-sensitive degradation,as well as excep-tional thermal and chemical stability.Extensive research effort has been devoted 10 relevant research aspects ranging from synthesis methods,property characterization to potential applications of ZIF-8.This review focuses on the recent development of ZIF-8 synthesis methods and its promising appications in drug delivery.The potential risks of using ZIF-8 for drug delivery are also summarized.

基于咪唑酯骨架结构材料-7的涡旋辅助微固相萃取

采用漩涡辅助微固相萃取的样品前处理方法,并结合高效液相色谱检测水样中的紫外吸收剂。沸石咪唑酯骨架结构材料-7(ZIF-7)具有大的比表面积,永久性孔道,开放的金属位点,以及较高的化学稳定性及水热稳定性,本文将ZIF-7作为固相萃取剂用于微固相萃取水样中的紫外吸收剂。实验考察了萃取剂用量、萃取时间、洗脱溶剂、洗脱时间、溶液pH值和盐浓度等对萃取效率的影响。最优实验条件为:ZIF-7的质量为15 mg,萃取时间是8 min,洗脱剂是甲醇∶乙腈(体积比3∶7),洗脱时间为5 min,NaCl溶液浓度为0 mg/mL,溶液pH为3。在此条件下,方法在2.5~750 ng/mL的范围内具有良好的线性,检出限为0.2~0.8 ng/mL,定量限为1.0~2.5 mg/mL。采用该方法分析实际水样中的紫外吸收剂,加标回收率为90.3%~111.5%,相对标准偏差为1.4%~7.2%,结果良好。

A novel structure of ultra-high-loading small moleculesencapsulated ZIF-8 colloid particles

The safety of nanoparticle-based drug delivery systems(DDSs)for cancer treatment is still a challenge,restricted by the intrinsic cytotoxicity of drug carriers and leakage of loaded drug.Here,we propose a novel nanocarrier’s cytotoxicity avoidance strategy by synthesizing an encapsulation core–shell structure of zeolitic imidazolate framework-8(ZIF-8)-based colloid particles(CPs)with an amorphous ZIF-8 skin.This encapsulation structure achieves an ultra-high loading rate(LR)of 90%(i.e.,9 mg doxorubicin(DOX)per 1 mg ZIF-8)for DOX and the protection of DOX from leaking.Notably,to deliver unit-dose drug,this ultra-high LR of 90%significantly reduces the usage of ZIF-8 to 1.2%(2 orders of magnitude)compared to that of DOX@ZIF-8 with a 10%LR,in which cytotoxicity of ZIF-8 could well below the safety limit and then be relatively ignored.Safety,drug delivery efficacy,scale-up ability,and universality of this encapsulation structure have been further verified.Our findings suggest the great potential of this ZIF-8-based encapsulation core–shell structure in the field of drug delivery.

Metal-organic framework hybrid materials of ZIF-8/RGO for immobilization of D-amino acid dehydrogenase

Immobilization of D-amino acid dehydrogenase(DAADH)by the assembly of peptide linker was studied for the biosynthesis of Dphenylalanine.Hybrid material of zeolitic imidazolate framework-8(ZIF-8)combined with reduced graphene oxide(RGO)was applied for the immobilization of DAADH from Ureibacillus thermosphaericus.The recovery rate of DAADH/ZIF-8/RGO was 165.6%.DAADH/ZIF-8/RGO remained 53.4%of its initial activity at 50°C for 10 h while the free enzyme was inactivated.DAADH/ZIF-8/RGO maintained 70.5%activity in hyperalkaline solution with pH 12.Kinetic parameters indicated that DAADH/ZIF-8/RGO had greater affinity of phenylpyruvate as V_(max)/K_(m)of DAADH/ZIF-8/RGO was 1.27-fold than free enzyme.After seven recycles,the activity of DAADH/ZIF-8/RGO remained 64.3%.Furthermore,one-step separation and in situ immobilization of DAADH by ZIF-8/RGO/Ni was carried out with 1.5-fold activity enhancement.Combining peptide linker and metal-organic framework(MOF)immobilization,thermostability and activity of the immobilized DAADH were significantly improved.

ZIF-8 coated gold nanospheres: A multi-responsive drug delivery system promoting the killing effect of photothermal therapy against osteosarcoma cells

Photothermal therapy(PTT)has been widely used in the treatment of tumors,but its efficacy is greatly limited by the inability of precise drug delivery and the increase of heat shock proteins(HSPs)caused by high temperature.This article describes a therapeutic strategy to enhance PTT with starvation therapy in conjunction with ferroptosis mechanism.A nanoparticle platform ZIF-8@GA was constructed by wrapping together glucose oxidase(GOX)and gold nanospheres(AuNPs)loaded with dihydroartemisinin(DHA)with zeolitic imidazolate framework-8(ZIF-8).This platform can take advantage of the micro-environment of osteosarcoma(OS)cells,featuring low pH and high reactive oxygen species(ROS),for precision drug delivery.GOX can effectively catalyze glucose to produce gluconic acid and H_(2)O_(2),and DHA can also induce ROS production in OS cells.ROS produced by GOX and DHA can further generate lipid peroxidation(LPO)and lead to ferroptosis of OS cells.At the same time,ROS and LPO produced can inhibit the expression of HSPs,thereby increasing the therapeutic effect of PTT.In vitro experiments show that the nanoparticles are pH and ROS responsive.1μg/mL GOX combined with 0.2μg/mL DHA promotes ferroptosis of OS cells,and increases the killing effect of near-infrared(NIR)on OS cells.Further in vivo experiments showed that the nano drug-delivery platform combined with PTT can effectively inhibit the growth of OS cells.Meanwhile,this study provides a new idea for the treatment of OS with biomaterials combined with various treatment methods.

Design of novel RGO/2D strip-like ZIF-8/DMAOP ternary hybrid structure towards high-efficiency microwave absorption, active and passive anti-corrosion, and synergistic antibacterial performance

In order to meet the requirements of the marine environment for microwave absorption(MA)materials,we put forward the strategy of constructing multi-functional composite materials,which integrate microwave absorption,anti-corrosion,and antibacterial properties.Herein,graphene oxide(GO)was used as a template to induce the growth of zeolitic imidazolate framework-8(ZIF-8),simultaneously as a two-dimensional(2D)nanocontainers to load corrosion inhibitors to achieve pH-responsive and self-healing properties.Finally,quaternary ammonium salt(dimethyl octadecyl(3-trimethoxylsilyl propyl)ammonium chloride(DMAOP))and sodium ascorbate(VCNa)were introduced to achieve synergistic antibacterial activity and the reduction of GO.The 2D strip-like structure of ZIF-8 was due to the confined growth induced by the electrostatic attraction between ZIF-8 and GO sheets.The as-obtained reduced GO(RGO)/ZIF-8/DMAOP5 exhibited excellent microwave absorption(MA)properties,with a minimum reflection loss(RL)value of-47.08 dB at 12.73 GHz when the thickness was 2.8 mm.Moreover,the effective absorption bandwidth reached 6.84 GHz.After soaking in 3.5%NaCl solution for 35 days,the RGO/ZIF-8/DMAOP5-0.7%coating still achieved an impedance value of 4.585×107Ω·cm^(2) and a protective efficiency of 99.994%,providing superior anti-corrosion properties.In addition,fantastic antibacterial activity was obtained,with the antibacterial rates of RGO/ZIF-8/DMAOP_(10) reaching 99.39%and 100%against Escherichia coli and Staphylococcus aureus.This work could open new avenues towards the development of a new generation of multifunctional MA materials.

The“mediated molecular”-assisted construction of Mo_(2)N islands dispersed on Co-based nanosheets for high-efficient electrocatalytic hydrogen evolution reaction

The rational design of the catalysts with easily-accessible surface and high intrinsic activity is desirable for electrocatalytic hydrogen evolution reaction(HER).Here,we reported the construction of two-dimensional(2D)Co-Mo nitrides based heterojunctional catalyst for efficient HER based on a“mediated molecular”assisted route.The 2D Co(OH)_(2)sheet reacted partially with the“mediated molecular”(2-methylimidazole(2-MIM))to form zeolitic imidazolate framework(ZIF)-67 at surface,giving ZIF-67/Co(OH)_(2)sheets.The ZIF-67 combines with[PMo_(12)O_(40)]^(3−)cluster(PMo_(12))due to the interaction of mediated molecular with PMo_(12),producing 2D Mo-Co-2MIM/Co(OH)_(2)bimetallic precursor.After controlled nitriding,the Mo_(2)N islands dispersed on 2D porous Co-based sheets were formed.A series of characterizations and density functional theory(DFT)calculation indicated the formation of a close contact interface,which promotes the electron transfer between Mo and Co components,enhances the electron migration/redistribution and redistribution and down-shift of d-band center and thus gives a high intrinsic activity.The 2D characteristics make the catalyst more accessible contact sites,which is favourable to promot the HER.The tests showed that the optimized catalyst exhibits an onset potential of 0 mV and an overpotential of 10 mA·cm^(−2)at 35.0 mV,which is quite close to that of Pt/C catalyst.It also exhibits an activity superior to Pt/C at high current density(>100 mA·cm^(−2)).A good stability of the catalyst was achieved with no significant decay for 100 h of continuous operation.The electrolytic cell composed of optimized catalyst and P-NiFe-layered double hydroxide(LDH)can be driven by low voltage(only 1.47 V)to reach a current density of 10 mA·cm^(−2).

Laccase-functionalized magnetic framework composite enabled chlorophenols degradation,a potential remediation for fungicides residues in leather

Chlorophenols,used as the fungicides in leather,are strictly limited in leather products.In this work,a metal-organic framework material,zeolitic metal azolate framework-7(MAF-7),was first used to encapsulate laccase(Lac)to prepare MAF-7/Lac bio-composites with 98.5%immobilization yield.Afterward,Lac/MNP@MOM was formed by introducing the magnetic nanoparticles(MNPs)into the Lac@MOM.MAF-7 with better hydrophilicity and stronger pH buffering ability,exhibits good compatibility with laccase,which can reserve the activity of laccase after immobilization.Moreover,the porous structure of MAF-7 is favorable for the sufficient contact between laccase and substrates.Lac/MNP@MOM exhibited excellent activity when exposed to high temperature,extreme pH,and organic solvents,which also simplified complex recovery steps.Furthermore,the degradation rate of 2,4-dichlorophenol(2,4-DCP)could reach as high as 97%within 24 h by immobilized laccase,and after nine consecutive cycles of operation,enzyme activity could remain over 80%,which gives it the potential for practical applications.