Kinetics of Coil-to-Globule Transition of DansyI-Labeled Poly（N-isopropyl- acrylamide） Chains in Aqueous Solution

The coil-to-globule transition of thermally sensitive linear poly（N-isopropylacrylamide） （PNIPAM） labeled with dansyl group is induced by 1.54 μm laser pulses （widths10 ns）. The dansyl group is used to follow the transition kinetics because its fluorescence intensity is very sensitive to its micro-environment. As the molar ratio of NIPAM monomer to dansyl group increases from 110 to 300, the effect of covalently attached dansyl fluorophores on the transition decreases. In agreement with our previous study in which we used 8-anilino- l-naphthalensulfonic acid ammonium salt free in water as a fluorescent probe, the current study reveals that the transition has two distinct stages with two characteristic times, namely, Tfast≈0.1 ms, which can be attributed to the nucleation and formation of some ＂pearls＂ （locally contracting segments） on the chain, and tslow≈0.5 ms, which is related to the merging and coarsening of the ＂pearls＂.Tfast is independent of the PNIPAM chain length over a wide range （Mw=2.8× 10^6-4.2 × 10^7 g/mol）. On the other hand, Tslow only slightly increases with the chain length.

pH-responsive mesoporous silica nanoparticles employed in controlled drug delivery systems for cancer treatment

In the fight against cancer, controlled drug delivery systems have emerged to enhance the therapeutic efficacy and safety of anti-cancer drugs. Among these systems, mesoporous silica nanoparticles （MSNs） with a functional surface possess obvious advantages and were thus rapidly developed for cancer treatment. Many stimuli-responsive materials, such as nanopartides, polymers, and inorganic materials, have been applied as caps and gatekeepers to control drug release from MSNs. This review presents an overview of the recent progress in the production of pH-responsive MSNs based on the pH gradient between normal tissues and the tumor microenvironment. Four main categories of gatekeepers can respond to acidic conditions. These categories will be described in detail.

Stimuli-responsive Membranes： Smart Tools for Controllable Mass-transfer and Separation Processes

As emerging artificial biomimetic membranes, smart or intelligent membranes that are able to respond to environmental stimuli are attracting ever-increasing interests from various fields. Their permeation properties including hydraulic permeability and diffusional permeability can be dramatically controlled or adjusted self-regulatively in response to small chemical and/or physical stimuli in their environments. Such environmental stimuli-responsive smart membranes could find myriad applications in numerous fields ranging from controlled release to separations. Here the trans-membrane mass-transfer and membrane separation is introduced as the beginning to initiate the requirement of smart membranes, and then bio-inspired design of environmental stimuli-responsive smart membranes and four essential elements for smart membranes are introduced and discussed. Next, smart membrane types and their applications as smart tools for controllable mass-transfer in controlled release and separations are reviewed. The research tooics in the near future are also suggested.

Click-Formed Polymer Gels with Aggregation-Induced Emission and Dual Stimuli-Responsive Behaviors

Stimuli-responsive polymer gels have recently attracted great attention due to their heat/solvent resistance,dimensional stability,and unique sensitivity to external stimuli.In this work,we synthesized thiol-functionalized tetraphenylethylene(TPE)and constructed polymer gels through thiol-ene click reaction.The synthetic process of the polymer gels could be monitored by fluorescence emission of TPE moieties based on aggregation-induced emission mechanism.In addition,due to the dual redox-and acid responsiveness of the polymer gels,in the presence of dithiothreitol and trifluoroacetic acid,fluorescence quenching of the polymer gels can be observed.This stimuli-responsive characteristics endows the polymer gels with potential applications in fluorescent sensing and imaging,cancer diagnosis and selfhealing materials.

Ultrafast Infrared Spectroscopic Study of Microscopic Structural Dynamics in pH Stimulus-Responsive Hydrogels

Hydrogels show versatile properties and are of great interest in the fields of bioelectronics and tissue engineering.Understanding the dynamics of the water molecules trapped in the three-dimensional polymeric networks of the hydrogels is crucial to elucidate their mechanical and swelling properties at the molecular level.In this report,the poly(DMAEMA-co-AA)hydrogels were synthesized and characterized by the macroscopic swelling measurements under different pH conditions.Furthermore,the microscopic structural dynamics of pH stimulus-responsive hydrogels were studied using FTIR and ultrafast IR spectroscopies from the viewpoint of the SCN-anionic solute as the local vibrational reporter.Ultrafast IR spectroscopic measurements showed the time constants of the vibrational population decay of SCN-were increased from 14±1 ps to 20±1 ps when the pH of the hydrogels varied from2.0 to 12.0.Rotational anisotropy measurements further revealed that the rotation of SCNanionic probe was restricted by the three-dimensional network formed in the hydrogels and the rotation of SCN-anionic probe cannot decay to zero especially at the pH of 7.0.These results are expected to provide a molecular-level understanding of the microscopic structure of the cross-linked polymeric network in the pH stimulus-responsive hydrogels.

Light and temperature dual responsive pesticide release system based on mesoporous silica nanoparticles modified by dopamine

A light and temperature dual responsive copolymer,poly(7-(4-vinylbenzy-loxyl)-4-methylcoumarin-co-N vinyl caprolactam-co-tri(ethylene glycol)methyl ether methacrylate)(PVNM),was grafted on the surface of dopamine based mesoporous silica nanoparticles(MSNs).The resulting polymer brush,MSNs-g-PVNM,was characterized by FT-IR,TEM,TGA and XPS.The dual responsive behaviors of MSNs-g-PVNM were systematically studied.With imidacloprid as the model guest pesticide,the loading percentage and loading efficiency of the polymer brush were determined as 9.2%and 40.6%,respectively.The release efficiency of imidacloprid in MSNs-g-PVNM was the lowest value of 5.4%at 20℃ and 365 nm,and it reached the highest value of 52.4%at 50℃ and 254 nm.The loss percentage of imidacloprid on the leaves contained imidacloprid-loaded MSNs-g-PVNM(8.4%)was much less than that contained only imidacloprid(25.2%)after three rinses.It was confirmed that the release process of imidacloprid was well regulated through changing external conditions such as light and temperature.

环糊精超分子水凝胶

本文综述了近年来基于环糊精包合作用的超分子水凝胶的研究进展,主要包括:环糊精与线性、星型、接枝、超支化聚合物包合形成的多聚(准)轮烷自组装制备超分子物理凝胶及功能化多聚(准)轮烷经交联反应制备超分子化学凝胶;环糊精、环糊精二聚体及其水溶性聚合物与带疏水性侧基的聚合物经"锁-钥匙"包合作用形成超分子物理凝胶;及其在药物、基因释放载体与组织工程支架中的应用。着重介绍了剪切、温度、pH值、光等刺激-响应性超分子水凝胶的设计与制备。

Recent advances in cell imaging and cytotoxicity of intracellular stimuli-responsive nanomaterials

The stimuli-responsive nanomaterials are gaining more and more interest in the biological field,including cell imaging and biosensing etc. Nanomaterials in response to the bio-relevant stimuli(i.e., p H, enzymes and other bioactive molecules) can be utilized to enhance imaging(i.e., optical imaging, MRI, and multi-mode imaging) sensitivity via disease site-specific delivery and controlled release, which helps to diagnose cancer at an early stage or to monitor progression during treatment. In the triggered responsive process, smart nanomaterials undergo changes in physiochemical properties that can cause cytotoxicity or influence on cell functions due to the interactions between nanomaterials and cells. In order to promote the design and fabrication of effective platforms for therapeutics and diagnostics, special attention should be paid to these effects. By taking the advantages of intracellular stimuli, the controlled self-assembly in living cells can be achieved, which has been used for various in situ detections and insights into biological self-assembly. In this review, the recent advances in cell imaging, cytotoxicity and self-assembly of intracellular stimuli-responsive nanomaterials are summarized. Some principles for the further design and applications of intracellular stimuli-responsive nanomaterials and future perspectives are discussed.

Multifunctional devices based on planar microsupercapacitors:Progress and challenges

With the boom of portable,wearable,and implantable smart electronics in the last decade,the demand for multifunctional microscale electrochemical energy storage devices has increased.Owing to their excellent rate performance,high power density,long cycling lifetime,easy fabrication,and integration,multifunctional planar microsupercapacitors(PMSCs)are deemed as one of the ideal micropower sources for next-generation flexible on-chip electronics.Therefore,we offer a comprehensive overview of the recent progress regarding multifunctional devices based on PMSCs,including stretchable,self-healing,stimulus-responsive,thermosensitive,biodegradable,and temperaturetolerant microdevices.We also emphasize the unique applications of multifunctionally integrated PMSCs in the construction of self-powered and sensor-integrated systems in terms of multifunctional operation modes.Finally,the key challenges and future prospects related to these multifunctional devices are discussed to stimulate further research in this flourishing field.

A pH-responsive zinc(Ⅱ) metalated porphyrin for enhanced photodynamic/photothermal combined cancer therapy

The acidic tumor microenvironment is triggered by glycolysis in hypoxic condition, which can motivate the pHresponsive system to build certain triggers for efficiently tumor-targeted phototherapy. Additionally, the metalated porphyrin structures are widely studied in biomedical applications due to the favorable properties of high singlet oxygen quantum yield as well as strong fluorescence imaging ability. Herein, a pH-responsive zinc(II) metalated porphyrin(P-4) was designed and synthesized for amplifying cancer photodynamic/photothermal therapy with excellent fluorescence quantum yield(67.4%), superb singlet oxygen quantum yield(84.3%) and desired photothermal conversion efficiency(30.0%). In vitro, the self-assembled P-4 nanoparticles can specifically target to lysosome subcellular site and realize protonated process of dibutaneaminophenyl(DBAP) groups with high photo toxicity. Under single 660 nm laser illumination, the tumor can be ablated completely with no side effects in vivo. This work demonstrates that the p H-responsive P-4 nanoparticles provide a new avenue for highly efficient cancer combination therapy.