Stimuli-responsive surfaces for bio-applications

The development of surfaces that have switchable properties, also known as smart surfaces, have been actively pursued in the past few years. The recent surge of interest in these switchable systems stems from the widespread number of applications to many areas in science and technology ranging from environmental cleanup to data storage, micro- and nanofluidic devices. Moreover, the ability to modulate biomolecule activity, protein immobilisation, and cell adhesion at the liquid-solid interface is important in a variety of biological and medical applications, including biofouling, chromatography, cell culture, regenerative medicine and tissue engineering. Different materials have been exploited to induce such changes in surface biological properties that are mostly based on self-assembled monolayers or polymer films. This critical review focuses on the recent progress in the preparation of these switchable surfaces, and highlights their applications in biological environments. The review is organized according to the external stimuli used to manipulate the properties of the substrate-chemical/biochemical, thermal, electric and optical stimuli. Current and future challenges in the field of smart biological surfaces are addressed (189 references).     

Polymer Nanoassembly as Delivery Systems and Anti‐Bacterial Toolbox: From PGMAs to MSN@PGMAs

Researches on cargo delivery systems have received burgeoning attention and advanced rapidly. For synthetic nanodevices, polymer nanoassemblies and their inorganic‐organic hybrid materials, especially smart mesoporous silica nanoparticle (MSN)‐polymer hybrids (e. g., MSN@PGMAs), have attracted increasing attention in recent years. Their superior characteristics and unique features such as dynamic transition of morphology endow them the ability to efficiently entrap cargo molecules and undergo smart cargo delivery and release in response to various external stimuli. In this Personal Account, we present our recent research progress in the construction of cargo delivery systems based on polymers, poly(glycidyl methacrylate) (PGMA) and its derivatives in particular, ranging from polymer nanoparticles, reverse micelles, to vesicles and reverse vesicles, and their performance in the delivery and controlled release of model molecules and therapeutic agents. Significantly, MSN‐PGMA hybrid nanoassemblies (MSN@PGMAs), constructed with the aid of atom transfer radical polymerization, host‐guest interactions, or layer‐by‐layer self‐assembly techniques, and their potential bio‐related applications and anti‐bacterial applications as new nanocarriers are reviewed. Finally, the prospects and challenges of such nanoplatforms are also discussed.     

基于不同刺激源的刺激响应聚合物体系的构建

刺激响应聚合物是一类具有"智能"行为的大分子体系. 它可以接收外部环境的刺激信号, 如pH值、 光、 温度、 电压、 氧化还原剂和气体等, 使自身大分子结构或状态发生较大改变, 从而影响其物理化学性质, 进而体现出相应的功能. 大量的研究结果表明, 刺激响应聚合物在纳米材料科学、 生命科学及临床医学领域中有着广泛的应用前景. 本文主要介绍了我们课题组在基于不同刺激源的刺激响应性大分子体系研究方面的一些进展.     

Coarse-grained Dynamics Simulation in Polymer Systems: from Structures to Material Properties

Polymers are widely used in our daily life and industry because of their intrinsic characteristics, such as multi-functionality, low cost, light mass, ease of processability, and excellent chemical stability. Polymers have multiscale space-time properties, which are mainly reflected in the fact that the properties of polymer systems depend not only on chemical structure and molecular properties, but also to a large extent on the aggregation state of molecules, that is, phase structure and condensed state structure. Thanks to the continuous development of simulation methods and the rapid improvement of scientific computation, computer simulation has played an increasingly important role in investigating the structure and properties of polymer systems. Among them, coarse-grained dynamics simulations provide a powerful tool for studying the self-assembly structure and dynamic behavior of polymers, such as glass transition and entanglement dynamics. This review summarizes the coarse-grained models and methods in the dynamic simulations for polymers and their composite systems based on graphics processing unit(GPU) algorithms, and discusses the characteristics, applications, and advantages of different simulation methods. Based on recent studies in our group, the main progress of coarse-grained simulation methods in studying the structure, properties and physical mechanism of polymer materials is reviewed. It is anticipated to provide a reference for further development of coarse-grained simulation methods and software suitable for polymer research.     

Molecular Springs: Integration of Complex Dynamic Architectures into Functional Devices

Molecular/supramolecular springs are artificial nanoscale objects possessing well‐defined structures and tunable physicochemical properties. Like a macroscopic spring, supramolecular springs are capable of switching their nanoscale conformation as a response to external stimuli by undergoing mechanical spring‐like motions. This dynamic action offers intriguing opportunities for engineering molecular nanomachines by translating the stimuli‐responsive nanoscopic motions into macroscopic work. These nanoscopic objects are reversible dynamic multifunctional architectures which can express a variety of novel properties and behave as adaptive nanoscopic systems. In this Minireview, we focus on the design and structure–property relationships of supramolecular springs and their (self‐)assembly as a prerequisite towards the generation of novel dynamic materials featuring controlled movements to be readily integrated into macroscopic devices for applications in sensing, robotics, and the internet of things.     

Thermally Adjustable Dynamic Disulfide Linkages Mediated by Highly Air‐Stable 2,2,6,6‐Tetramethylpiperidine‐1‐sulfanyl (TEMPS) Radicals

Intrinsically exchangeable dynamic covalent bonds that can be triggered by readily usable stimuli offer easy incorporation of their dynamic properties in various molecular systems, but the library of such bonds is still being developed. Herein, we report the dynamic covalent chemistry of 2,2,6,6‐tetramethylpiperidine‐1‐sulfanyl (TEMPS) dimers derived from thermally reversible homolytic dissociation of disulfide linkages. High air stability of TEMPS was observed even at 100 °C, affording facile employment of thermal dissociation–association equilibria and adjustable bond exchange properties under atmospheric conditions. We also established an efficient synthetic route for a modifiable derivative of the dimer that enabled incorporation of dynamic properties into linear and network polymer structures. The obtained polymers showed controllable molecular weights, temperature‐dependent swelling properties, healing ability, and recyclability, reflecting the thermally tunable dynamics of the dimer.     

Noncovalent water-based materials: robust yet adaptive

The adaptive properties of noncovalent materials allow easy processing, facile recycling, self-healing, and stimuli responsiveness. However, the poor robustness of noncovalent systems has hampered their use in real-life applications. In this Concept Article we discuss the possibility of creating robust noncovalent arrays by utilizing strong hydrophobic interactions. We describe examples from our work on aqueous assemblies based on aromatic amphiphiles with extended hydrophobic cores. These arrays exhibit fascinating properties, including robustness, multiple stimuli-responsiveness, and pathway-dependent self-assembly. We have shown that this can lead to functional materials (filtration membranes) rivaling covalent systems. We anticipate that water-based noncovalent materials have the potential to replace or complement conventional polymer materials in various fields, and to promote novel applications that require the combination of robustness and adaptivity.     

Bioinspired Actuators Based on Stimuli‐Responsive Polymers

Organisms exhibit strong environmental adaptability by controllably adjusting their morphologies or fast locomotion; thus providing constant inspiration for scientists to develop artificial actuators that not only have diverse and sophisticated shape‐morphing capabilities, but can also further transfer dynamic and reversible shape deformations into macroscopic motion under the following principles: asymmetric friction, the Marangoni effect, and counteracting forces of the surrounding conditions. Among numerous available materials for fabricating bioinspired artificial actuators, stimuli‐responsive polymers are superior in their flexible features and the ability to change their physicochemical properties dynamically under external stimuli, such as temperature, pH, light, and ionic strength. Herein, different mechanisms, working principles, and applications of stimuli‐responsive polymeric actuators are comprehensively introduced. Furthermore, perspectives on existing challenges and future directions of this field are provided.     

基于聚醚胺(PEA)动态交联网络的多重响应性表面褶皱图案

刺激响应性表面图案赋予了材料动态可调的表面性能,是智能材料领域研究的热点,然而如何通过简单有效的方法构建这类动态表面图案也是该领域的难点.本文将动态硼酸酯键和光可逆二聚基团引入到聚醚胺(PEA)交联网络中,通过双层褶皱体系构建一系列具有光和湿度刺激响应性表面褶皱图案.在365 nm紫外光照和加热的条件下,蒽基团(AN)的光二聚与硼酸键的形成使得上表层聚醚胺模量变大,产生微米级表面褶皱图案;在254 nm紫外光照射或水蒸气作用下,聚醚胺网络解交联,表面褶皱图案消失;利用光化学时空分辨的特性,通过光掩膜板光照还可以制备多层次动态表面褶皱图案.这种多重刺激响应性表面褶皱图案为构建智能聚合物表面提供了新思路,在传感和防伪等领域具有潜在的应用前景.     

Recent developments in intelligent biomedical polymers

Intelligent polymers or stimuli-responsive polymers may exhibit distinct transitions in physical-chemical properties, including conformation, polarity, phase structure and chemical composition in response to changes in environmental stimuli. Due to their unique 'intelligent' characteristics, stimuli-sensitive polymers have found a wide variety of applications in biomedical and nanotechnological fields. This review focuses on the recent developments in biomedical application of intelligent polymer systems, s...     

Supramolecular polymeric hydrogels

The supramolecular crosslinking of polymer chains in water by specific, directional and dynamic non-covalent interactions has led to the development of novel supramolecular polymeric hydrogels. These aqueous polymeric networks constitute an interesting class of soft materials exhibiting attractive properties such as stimuli-responsiveness and self-healing arising from their dynamic behaviour and that are crucial for a wide variety of emerging applications. We present here a critical review summarising the formation of dynamic polymeric networks through specific non-covalent interactions, with a particular emphasis on those systems based on host-guest complex formation, as well as the characterisation of their physical characteristics. Aqueous supramolecular chemistry has unlocked a versatile toolbox for the design and fine-tuning of the material properties of these hydrogels (264 references).     

Dynamic Hydrogels from Host–Guest Supramolecular Interactions

Hydrogel biomaterials are pervasive in biomedical use. Applications of these soft materials range from contact lenses to drug depots to scaffolds for transplanted cells. A subset of hydrogels is prepared from physical cross‐linking mediated by host–guest interactions. Host macrocycles, the most recognizable supramolecular motif, facilitate complex formation with an array of guests by inclusion in their portal. Commonly, an appended macrocycle forms a complex with appended guests on another polymer chain. The formation of poly(pseudo)rotaxanes is also demonstrated, wherein macrocycles are threaded by a polymer chain to give rise to physical cross‐linking by secondary non‐covalent interactions or polymer jamming. Host–guest supramolecular hydrogels lend themselves to a variety of applications resulting from their dynamic properties that arise from non‐covalent supramolecular interactions, as well as engineered responsiveness to external stimuli. These are thus an exciting new class of materials.     

基于环糊精包结络合作用的大分子自组装

本文综述了基于环糊精包结络合作用的大分子自组装的研究进展,包括：（1) 线型、梳型、多臂星型或超支化聚合物与环糊精或其二聚体自组装形成多聚轮烷（分子项链）、多聚准轮烷、双多聚（准）轮烷、分子管、双分子管、超分子凝胶及其应用;（2）桥联环糊精与桥联客体分子自组装制备线型或超支化超分子聚合物;（3）温度、pH值、光及客体分子刺激响应智能体系; （4) 通过亲水性的环糊精线型均聚物与含金刚烷的疏水性聚合物之间的包结络合作用来制备高分子胶束及其空心球等。     

Multi‐Stimuli‐Responsive Polymer Materials: Particles,Films, and Bulk Gels

Stimuli‐responsive polymers have received tremendous attention from scientists and engineers for several decades due to the wide applications of these smart materials in biotechnology and nanotechnology. Driven by the complex functions of living systems, multi‐stimuli‐responsive polymer materials have been designed and developed in recent years. Compared with conventional single‐ or dual‐stimuli‐based polymer materials, multi‐stimuli‐responsive polymer materials would be more intriguing since more functions and finer modulations can be achieved through more parameters. This critical review highlights the recent advances in this area and focuses on three types of multi‐stimuli‐responsive polymer materials, namely, multi‐stimuli‐responsive particles (micelles, micro/nanogels, vesicles, and hybrid particles), multi‐stimuli‐responsive films (polymer brushes, layer‐by‐layer polymer films, and porous membranes), and multi‐stimuli‐responsive bulk gels (hydrogels, organogels, and metallogels) from recent publications. Various stimuli, such as light, temperature, pH, reduction/oxidation, enzymes, ions, glucose, ultrasound, magnetic fields, mechanical stress, solvent, voltage, and electrochemistry, have been combined to switch the functions of polymers. The polymer design, preparation, and function of multi‐stimuli‐responsive particles, films, and bulk gels are comprehensively discussed here.     

Self-Healing Polymer Composites: Prospects,Challenges, and Applications

Self-healing polymer composites possess the inherent ability to heal the damage event autonomically or non-autonomically with external intervention. These advanced materials can be commercialized if the challenges and limitations of different self-healing mechanisms are well known and considered. These include capsule-based healing systems, vascular healing systems, and intrinsic healing systems. To date, most of the reviews have studied and reported on different self-healing mechanisms including their response to impact, fatigue, and corrosion tests. This review focuses mostly on extrinsic and intrinsic self-healing polymer composites which have been reported during the past five years by comparing their healing efficiency, advantages, and challenges in the prospect of their future development as well as their possible applications across various industries such as aerospace, automobile, coating, electronics, energy, etc.     

Recent advances in starch–clay nanocomposites

Biological nanocomposites are a valuable addition to the existing nanocomposite materials and eventually can substitute petroleum-based composite materials in numerous applications due to their inherent advantages such as biodegradability, eco-friendliness, low cost, and easy availability to name a few. Recently, polymer–clay nanocomposites have achieved much more attention due to their enhanced properties such as size dispersion and significant enhancement in physicochemical and mechanical properties in comparison to the pure polymer systems. Among various biopolymers, starch is one of the most abundant natural polymers on the earth and is highly valuable due to its chemical and physical properties. Starch polymer has highly increased potential as an alternative to petroleum-based materials. However, starch cannot be used alone and starch–clay nanocomposite has emerged as a new potential green sustainable material. This article focuses on recent progress in starch-based nanocomposites with particular emphasis on starch–clay nanocomposite preparation, properties, and applications.     

Dynamic modeling of the morphology of multiphase waterborne polymer particles

Multiphase waterborne polymer particles provide advantages in more demanding applications, and their performance depends on particle morphology. Currently, no dynamic model for the prediction of the development of the morphology of multiphase latex particles is available. In this work, a model was developed for the prediction of the dynamic development of the morphology of multiphase waterborne systems, such as polymer–polymer and polymer–polymer–inorganic hybrids.     

热适性形状记忆聚合物

动态共价交联聚合物的研究具有悠久的历史,其早期的工作着眼于如何解决应力松弛带来的聚合物材料力学性能降低的问题.20世纪90年代以来,利用动态共价键来主动设计聚合物网络的特殊可适性逐渐成为研究主流,其中包括自修复和重加工性.然而,受到动态共价键的种类、通用性及所实现功能的特异性等限制,对于动态共价交联聚合物网络的研究尚停留在基础阶段.本文以本课题组近期在动态共价交联形状记忆聚合物的研究为基础,结合其他相关工作,展示了通用共价键(酯键及氨酯键)的动态可逆性,并利用其设计了具有特殊性能和潜在商业化价值的形状记忆聚合物.在此基础上,我们提出分子结构设计及宏观性能均不同于传统热塑性和热固性形状记忆聚合物的第3类形状记忆聚合物,即热适性形状记忆聚合物.     

Advances in Polymeric Systems for Tissue Engineering and Biomedical Applications

The characteristics of tissue engineered scaffolds are major concerns in the quest to fabricate ideal scaffolds for tissue engineering applications. The polymer scaffolds employed for tissue engineering applications should possess multifunctional properties such as biocompatibility, biodegradability and favorable mechanical properties as it comes in direct contact with the body fluids in vivo. Additionally, the polymer system should also possess biomimetic architecture and should support stem cell adhesion, proliferation and differentiation. As the progress in polymer technology continues, polymeric biomaterials have taken characteristics more closely related to that desired for tissue engineering and clinical needs. Stimuli responsive polymers also termed as smart biomaterials respond to stimuli such as pH, temperature, enzyme, antigen, glucose and electrical stimuli that are inherently present in living systems. This review highlights the exciting advancements in these polymeric systems that relate to biological and tissue engineering applications. Additionally, several aspects of technology namely scaffold fabrication methods and surface modifications to confer biological functionality to the polymers have also been discussed. The ultimate objective is to emphasize on these underutilized adaptive behaviors of the polymers so that novel applications and new generations of smart polymeric materials can be realized for biomedical and tissue engineering applications.

     

由聚合物门控的介孔二氧化硅基刺激响应性药物递送系统

本文主要介绍了以聚合物体系作为门控构筑的基于介孔二氧化硅纳米粒子的刺激响应性药物控释体系, 并根据聚合物类别将门控体系分为聚合物刷、 聚合物交联网络和聚合物包裹层三类. 根据聚合物“阀门”与无机纳米粒子的共价或非共价连接方式, 综述了这些杂化材料在不同外界刺激作用下的药物控制释放行为, 并给出该领域所面临的机遇和挑战.