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Radical anions are important for various uses. However, their generation and stabilization under ambient conditions, which are essential for actual applications, are challenging. A photogenerated N...

Rational molecular design enables the development of stimuli-responsive supramolecular hydrogels. Biocompatible supramolecular hydrogels have great potential for medicinal and pharmaceutical applic...

With the incessant improvement of requirements for optical anti-counterfeiting technology, it is essential to develop multifunctional luminescent materials with multiple models and adjustable lumin...

Over the past few decades, advanced polymeric materials have gained popularity in the development of sustainable agricultural applications. Smart polymeric systems have extensively contributed to the agricultural industry by increasing the efficiency of pesticides, herbicides, and fertilizers by facilitating controlled release systems and, therefore, enabling lower doses to be used. Superabsorbent polymeric materials have been used as soil conditioners to control the impact of drought, whereas polycationic polymers have been utilized for plant bioengineering. These functions in the environment are complemented by applications within plants as part of the developing range of tools for genetically transforming plants in order to increase productivity and disease resistance. This Review will summarize and discuss the recent developments in the design and application of advanced polymeric systems for precision agriculture related applications. The design criteria of the polymers employed to date, such as polymer structure, as well as the properties of polymer nanoparticles including shape and size will be discussed, and the key findings in the related area will be highlighted. Finally, we will identify future directions for the exploration of functional polymers with the ultimate aim of advancing sustainable agriculture.\ud \ud

Diabetes is a serious global disease that threatens more than 400 million people’s health. Therefore, timely detection of body’s glucose level becomes extremely important for control, diagnosis and treatment of diabetes. Based on the feature of stimuli-responsive volume phase transition of hydrogel materials, this review will provide a systematic summary of glucose detection devices in recent years, including hydrogel preparation methods based on glucose-sensitive pattern, detection mechanisms based on signal transduction, current and emerging devices based on different body fluids and discuss the challenge, prospect the future development trend in the end.

This study presents dual-responsive colloidal microgels to repair nonwoven fiber mats (NWFs) and recover their native morphological and functional properties. The formulation comprises poly(N-isopr...

A wide variety of synthetic molecular machines has been designed and synthesized to construct nanometer-scale assemblies whose molecular motions can be precisely controlled by external stimuli. A h...

Hydrogels serving as a drug carrier was realized by entrapping small-sized drug molecules within their cross-linked interstitial networks. After covering the targeted location, hydrogels interact with the physiological fluids and swell, resulting in an increased interspace between networks for the outside diffusion of drugs. However, inevitable in vivo inflammatory responses or bacterial infection on the implant materials and persistent cargo release are still challenging. Herein, we report the fabrication of dual-responsive hydrogels based on acid-sensitive poly(ethylenimine) (PEI) derivative (PEI(-COOH/-vinyl)), thiol-responsive camptothecin prodrug monomer (CPTM), and hydrophilic oligo(ethylene glycol) methyl ether acrylate (OEGMA) by a conventional radical polymerization. Curcumin was then solubilized into the hydrogels to endow them with antimicrobial and cancer resistance properties. The in vitro experiments exhibited sustained hydrogel dissolution and CPT release in a simulated physiological environment. The antimicrobial and cytotoxicity tests of drug-loaded hydrogels using methicillin-resistant

An easy one-pot method is utilized for the synthesis of carbon nanodots, which has been investigated primarily from material perspectives. However, this preferred one-pot synthesis method suffers f...

Nanomedicines afford unique advantages in therapeutic intervention against tumors. However, conventional nanomedicines have failed to achieve the desired effect against cancers because of the presence of complicated physiological fluids and the tumor microenvironment. Stimuli-responsive drug-delivery systems have emerged as potential tools for advanced treatment of cancers. Versatile nano-carriers co-triggered by multiple stimuli in different levels of organisms (eg, extracorporeal, tumor tissue, cell, subcellular organelles) have aroused widespread interest because they can overcome sequential physiological and pathological barriers to deliver diverse therapeutic “payloads” to the desired targets. Furthermore, multiple stimuli-responsive drug-delivery systems (MSR-DDSs) offer a good platform for co-delivery of agents and reversing multidrug resistance. This review affords a comprehensive overview on the “landscape” of MSR-DDSs against tumors, highlights the design strategies of MSR-DDSs in recent years, discusses the putative advantage of oncotherapy or the obstacles that so far have hindered the clinical translation of MSR-DDSs.

Nanocarriers are nanoscale delivery systems composed of natural or synthetic polymers, which are advantageous in reducing drug toxicity while improving drug targeting and utilization. With the advancement of biomedical technology, it is revealed that reactive oxygen species (ROS), a class of oxidative metabolites, show abnormal overexpression in disease-related parts of the body. Hence, ROS stimuli-responsive nanocarriers have gained increasing attention, and recent developments are expected to realize controllable drug release. Based on linkers with different ROS-responsive mechanisms, a series of ROS-responsive nanocarriers have been designed to achieve specific controlled drug release under the stimulation of the ROS at the disease site. This article mainly focuses on ROS-responsive linkers, which have been commonly used for the synthesis of nanocarriers in recent years. Accordingly, the linkers are classified as chalcogen-containing responsive linkers (thioether, thioketal, selenide, diselenide, and telluride) and responsive linkers containing other elements (arylboronic ester, ferrocene, and peroxalate ester). ROS stimuli-responsive nanocarriers are fabricated by introducing ROS-responsive linkers in different design principles. Owing to the ROS-responsive linkers, the nanocarriers follow different responsive mechanisms, including hydrophobic-to-hydrophilic phase transition and cleavage. This article discusses the degree of responsiveness of nanocarri-ers and the specific release of drugs from nanocarriers upon ROS-stimuli, as well as their applications in vivo. In particular, on the basis of intelligent drug release and precision medicine, this article also emphasizes the importance of the biocompatibility and biodegradability of nanocarriers.

Stimuli-responsive emulsifiers have emerged as a class of smart agents that can permit regulated stabilization and destabilization of emulsions, which is essential for food, cosmetic, pharmaceutical, and petroleum industries. Here, we report the synthesis of novel "smart" hydroxyapatite (HaP) magnetic nanoparticles and their corresponding stimuli-responsive Pickering emulsions and explore their movement under confined spaces using a microfluidic platform. Pickering emulsions prepared with our magnetic stearic acid-functionalized Fe2O3@HaP nanoparticles exhibited pronounced pH-responsive behavior. We observed that the diameter of emulsion droplets decreases with an increase in pH. Swift demulsification was achieved by lowering the pH, whereas the reformation of emulsions was achieved by increasing the pH; this emulsification-demulsification cycling was successful for at least ten cycles. We used a microfluidic platform to test the stability of the emulsions under flowing conditions and their response to a magnetic field. We observed that the emulsion stability was diminished and droplet coalescence was enhanced by the application of the magnetic field. The smart nanoparticles we developed and their HaP-based emulsions present promising materials for pharmaceutical and petroleum industries, where responsive emulsions with controlled stabilities are required.

Epilepsy is a common but a complex neurological disorder with limited practices for successful management due to the complicated neuronal network and lack of knowledge of epileptic pathophysiology. Theranostic systems such as implantable devices and biodegradable nanomaterials offer better tailor‐made methods for the detection and treatment using nanotechnology‐based approaches for patients with epilepsy. Miniaturized nano‐implantable devices and biosensors equipped with operations to mimic neurostimulation demonstrate excellent opportunities in profiling the disease and assist in comprehension of the relationship between the disease and host. This strategy is developed for diagnoses and mapping brain activities to integrate and target therapeutic nanosystems in epilepsy. Non‐invasive class of nanotheranostics such as biodegradable and stimuli‐responsive polymers includes nanomaterials that utilize bio‐physico‐chemical processes or stimuli as a source for detecting the state and progress of the disease. The superior form of nanotheranostics encompasses in‐situ diagnostics with triggered release at the specific site. This review article focuses on the nanotheranostic strategies for epilepsy, their implications, challenges and new potentials for detection and therapy in personalized medicine. The concept of “on‐demand” release of drugs at the site of action using bio‐responsive theranostic approach reveals a potential for developing a point of primary care for epilepsy in the future.

Metal substrates beneath polymeric coatings are susceptible to localized corrosion, which could result in lifetime reduction and catastrophic failure without timely repair treatment. In situ detection of corrosion and repair coating defects are in high demand yet challenging to fulfill so far. Herein, we report a smart polymeric coating by integrating nanosensors into the coating matrix, which is capable of efficient corrosion sensing and active anticorrosion protecting. The nanosensors were constructed by zeolitic imidazolate framework encapsulated with the polyethylene glycol-tannic acid complex. The morphology, chemical constitution, and stimulus responsiveness of nanosensors were systematically analyzed. The generation of local corrosion beneath coating can be promptly sensed and reported by a conspicuous purple color derived from tannic-iron ion coordinates. Meanwhile, local electrochemical impedance spectroscopy results proved that the metal degradation process at the defected interface can be largely inhibited, exhibiting active anticorrosion property. Furthermore, the constructed smart coating possessed superior impermeability and long-term protective performance under simulated seawater and harsh salts spray conditions. This feasible and effective strategy based on simple nanosensors to engineer smart coatings paves a new way to develop high environmental adaptability protective materials with protecting, corrosion sensing, and self-healing functions.

A simple-structured super gelator with self-healability and multi-stimuli responses was reported herein, which exhibited multiple visual molecular recognition abilities. Multifunctional applications such as effective lubricants, safe fuels, high-efficient propellants, dyes adsorbents, enhanced fluorescence emission and separation of aldehydes from aqueous solutions are integrated into a single organogelator, which was rarely reported.

Targeted release of drugs is important for precision treatment at the desired site and preventing the indiscriminate release of drugs. Incorporating stimuli-responsiveness into drug carriers has been proposed to enable the carriers to have the ability to perform targeted release at specific sites. However, a vast majority of the many established carriers are not stimuli-responsive. The current methods used for the synthesis of stimuli-responsive carriers are mostly highly specific and ineffective (e.g., they either leak or cannot release completely). This manuscript describes a novel class of stimuli-responsive attachments that can be attached flexibly onto any type of soft carrier (i.e., loaded with chemicals or drugs), thus transforming the non-responsive carrier into a stimuli-responsive carrier. The attachment consists of a layer of stimuli-responsive hydrogel around the carrier and a partial rigid coating on the exterior. The attachment is general: non-responsive carrier materials of different types (e.g., liposomes and polymeric carriers) and different sizes (e.g., nanoscale and macroscopic) are shown to become stimuli-responsive for different types of stimuli. Importantly, the attachment is capable of exerting a large pressure for rupturing carriers with rigid and impermeable shells (e.g., highly crosslinked shells). Hence, these carriers with stimuli-responsive attachment effectively exhibit a full range of stimuli-responsiveness: they are not leaky due to their rigid shells, but can release their contents completely via rupture of their shells under the influence of the stimulus. The approach of using this novel class of stimuli-responsive attachments is thus general, simple, and effective. The large number and diverse range of well-established soft non-responsive drug carriers can be transformed into stimuli-responsive carriers conveniently without the constant need to find specific methods for different types of carriers.

Stimuli-responsive crystals have aroused tremendous interest due to their potential as smart materials. However, endowing mono-component crystals with multiple stimuli-responsive and multifunction properties is still a great challenge. Here, we report an anthracene derivative, 9-anthraldehyde, which can respond to mechanical force and light. It possesses two-dimensional (2D) elastic bending, plastic twisting and photoinduced bending properties. Unusual elastic bending of the plastic twisted crystal was achieved in one crystal. The crystal obtained in this work is a multi-dimensional elastic crystal, which is different from reported twistable materials. To reveal the mechanisms of the properties of 2D elastic bending, plastic twisting and photoinduced bending, nanoindentation tests, energy framework analysis and Hirshfeld surface analysis were used to study the property–structure relationship at the molecular level. It was found that these properties can be ascribed to the unique intermolecular interactions and types of molecular arrangement.

CRISPR-Cas9 promotes changes in identity or abundance of nucleic acids in live cells and is a programmable modality of broad biotechnological and therapeutic interest. To reduce off-target effects, tools for conditional control of CRISPR-Cas9 functions are under active research, such as stimuli-responsive guide RNA (gRNA). However, the types of physiologically relevant stimuli that can trigger gRNA are largely limited due to the lack of a versatile synthetic approach in chemistry to introduce diverse labile modifications into gRNA. In this work, we developed such a general method to prepare stimuli-responsive gRNA based on site-specific derivatization of 2′-O-methylribonucleotide phosphorothioate (PS-2′-OMe). We demonstrated CRISPR-Cas9-mediated gene editing in human cells triggered by oxidative stress and visible light, respectively. Our study tackles the synthetic challenge and paves the way for chemically modified RNA to play more active roles in gene therapy., Conditional control of CRISPR-Cas9 activity by reactive oxygen species and visible light is achieved using stimuli-responsive guide RNA synthesized by a general method based on RNA 2′-O-methylribonucleotide phosphorothioate.

Stimuli-responsive luminescent materials have received much attention as next-generation smart materials for various applications, including their use as biomedical probes, for the visualization of pollutants and sensing toxic gases. Boron-containing luminophores have been widely utilized to achieve such sensing materials because of their vacant 2pz orbital, which is responsible for their Lewis acidity, electron-accepting properties, and ability to form complexes. In addition, polymeric structures often enhance stimuli-responsivity because slight environmental changes around the molecules can dramatically affect their molecular motions, shapes and physical properties. This review describes the development of stimuli-responsive materials using various kinds of luminescent boron compounds, focusing on the mechanisms of the sensing abilities and the molecular designs.

Controlled drug delivery systems, which could release loaded therapeutics upon physicochemical changes imposed by physiological triggers in the desired zone and during the required period of time, offer numerous advantages over traditional drug carriers including enhanced therapeutic effects and reduced toxicity. A polypeptide is a biocompatible and biodegradable polymer, which can be conveniently endowed with stimuli-responsiveness by introducing natural amino acid residues with innate stimuli-responsive characteristics or introducing responsive moieties to its side chains using simple conjugating methods, rendering it an ideal biomedical material for controlled drug delivery. This feature article summarizes our recent work and other relevant studies on the development of polypeptide-based drug delivery systems that respond to single or multiple physiological stimuli (e.g., pH, redox potential, glucose, and hypoxia) for controlled drug delivery applications. The material designs, synthetic strategies, loading and controlled-release mechanisms of drugs, and biomedical applications of these stimuli-responsive polypeptides-based drug delivery systems are elaborated. Finally, the challenges and opportunities in this field are briefly discussed.

Stimuli-responsive temporary adhesives constitute a rapidly developing class of materials defined by the modulation of adhesion upon exposure to an external stimulus or stimuli. Engineering these materials to shift between two characteristic properties, strong adhesion and facile debonding, can be achieved through design strategies that target molecular functionalities. This perspective reviews the recent design and development of these materials, with a focus on the different stimuli that may initiate debonding. These stimuli include UV light, thermal energy, chemical triggers, and other potential triggers, such as mechanical force, sublimation, electromagnetism. The conclusion discusses the fundamental value of systematic investigations of the structure–property relationships within these materials and opportunities for unlocking novel functionalities in future versions of adhesives., Stimuli-responsive temporary adhesives emerge as next-generation multifunctional materials with advantages that include strong temporary adhesion, debonding on demand, and tunable reactivity.

Smart fibers with reversible optical properties have received extensive attention due to their wide potential for application in human health monitoring and wearable devices. However, achieving multi-stimuli-responsive luminescent fibers via a facile manufacturing process is challenging. Herein, novel independent multi-stimuli-responsive luminescent fibers are successfully fabricated via a facile wet-spinning process. The color of the fibers responds to ultraviolet (UV) and heat independently and in combination. The fibers emit bright red light emission (λem = 627 nm) after excitation (λex = 330 nm) which is attributed to Y2O2S:Eu3+,Mg2+,Ti4+ ceramics. The as-prepared fibers possess a tensile strength of around 9.39 MPa. The experimental results demonstrate that the multi-stimuli-responsive persistent luminescent fibers coupled with the facile preparation process make the multi-stimuli-responsive luminescent fibers a potential candidate for application in anti-counterfeiting and UV/heat detection devices.

Cancer is a multifactorial disease that involves unique tumor microenvironment (TEM) and abnormal organs with complex structures. Conventional anticancer drugs require high doses and systemic administration, and nonspecific tissue distribution causing serious side effects. Nanomaterials have far-reaching influences in cancer treatment, theranostics and imaging. Specifically, anticancer drug-loading into nanocarriers can avoid unnecessary systemic toxicity and achieve sustained drug release in response to all kinds of exogenous or endogenous stimuli. Nanocarriers can be stimulated by external (light irradiation and magnetic fields) or internal (pH, glutathione, enzymes and oxidative stress) elements, which have attracted growing attention in the field of drug delivery systems. On the basis of this powerful concept, environment-responsive nanocarriers have been designed to ensure delivery of the anticancer drug to the targeting lesion sites and effective release, which can overcome the biological barriers that limit conventional treatments and reduce the administered drug dose. Herein, this review will discuss the fundamentals of environment-responsive nanocarriers to enhance the permeability and retention (EPR) effect, and improve cancer therapy outcomes.

Photoacoustic imaging (PAI) relies on the use of contrast agents with high molar absorptivity in the NIR-I/NIR-II region. Expanded porphyrins, synthetic analogues of natural tetrapyrrolic pigments (e.g. heme and chlorophyll), constitute as potentially attractive platforms due to their NIR-II absorptivity and their ability to respond to stimuli. Here, we evaluate two expanded porphyrins, naphthorosarin (1) and octaphyrin (4), as stimuli responsive PA contrast agents for functional PAI. Both undergo proton-coupled electron transfer to produce species that absorb well in the NIR-II region. Octaphyrin (4) was successfully encapsulated into 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-poly(ethylene glycol) (DSPE-PEG2000) nanoparticles to afford OctaNPs. In combination with PAI, OctaNPs allowed changes in the acidic environment of the stomach to be visualized and cancerous versus healthy tissues to be discriminated., In this study, two expanded porphyrins, octaphyrin and naphthorosarin were evaluated as potential PA agents. The nanoparticle encapsulation of octaphyrin successfully enabled the visualization of acidic environments and the discrimination between cancerous and healthy tissues.

Multifunctional nanocomposites have drawn great attention in clinical applications because of their ability to integrate diagnostic and therapeutic functions. Manganese dioxide (MnO2), owing to its biocompatibility and magnetic resonance imaging (MRI) properties, has been widely applied in biomedical research. Our previous work on biogenic MnO2 nanoparticles (Bio-MnO2 NPs) revealed that intrinsic photothermal properties and stimuli-responsive MRI imaging are particularly promising for the development of theranostic systems. However, further improvement in the photothermal therapy (PTT) performance of Bio-MnO2 NPs is still required. Herein, we have improved the PTT efficiency of Bio-MnO2 NPs by in situ synthesis of fluorescent polydopamine (PDA) while generating additional stimuli responsive fluorescence properties in this system, thus further broadening the scope of their theranostic functions. These synthesis conditions are mild and green. The fluorescence of PDA was quenched by capping Bio-MnO2 NPs and could be recovered upon degradation of Bio-MnO2 NPs inside tumour cells. Additionally, Mn2+ released from the nanoparticles can support T1-weighted MR imaging. Compared to the Bio-MnO2 NPs alone, the integration of Bio-MnO2 NPs and PDA significantly enhances the photothermal performance in vitro and in vivo. With their high biocompatibility, these multifunctional composite nanodevices hold great potential for fluorescence imaging and MRI-guided photothermal therapy.

Molecular self-assembly is a widespread natural phenomenon and has inspired several researchers to synthesize a compendium of nano/microstructures with widespread applications. Biomolecules like proteins, peptides and lipids are used as building blocks to fabricate various nanomaterials. Supramolecular peptide self-assembly continue to play a significant role in forming diverse nanostructures with numerous biomedical applications; however, dipeptides offer distinctive supremacy in their ability to self-assemble and produce a variety of nanostructures. Though several reviews have articulated the progress in the field of longer peptides or polymers and their self-assembling behavior, there is a paucity of reviews or literature covering the emerging field of dipeptide-based nanostructures. In this review, our goal is to present the recent advancements in dipeptide-based nanostructures with their potential applications.

A method for the synthesis of DNA-based acrylamide hydrogel microcapsules loaded with quantum dots as a readout signal is introduced. The shell of DNA-acrylamide hydrogel microcapsules is encoded with microRNA-responsive functionalities, being capable of the detection of cancer-associated microRNA. The microRNA-141 (miR-141), a potential biomarker in prostate cancer, was employed as a model target in the microcapsular biosensor. The sensing principle of the microcapsular biosensor is based on the competitive sequence displacement of target miR-141 with the bridging DNA in the microcapsule's shell, leading to the unlocking of DNA-acrylamide hydrogel microcapsules and the release of the readout signal provided by fluorescent quantum dots. The readout signal is intensified as the concentration of miR-141 increases. While miR-141 was directly measured by DNA-acrylamide hydrogel microcapsules, the linear range for the detection of miR-141 is 2.5 to 50 μM and the limit of detection is 1.69 μM. To improve the sensitivity of the microcapsular biosensor for clinical needs, the isothermal strand displacement polymerization/nicking amplification machinery (SDP/NA) process was coupled to the DNA-acrylamide hydrogel microcapsule sensor for the microRNA detection. The linear range for the detection of miR-141 is improved to the range of 102 to 105 pM and the limit of detection is 44.9 pM. Compared to direct microcapsular biosensing, the detection limit for miR-141 by microcapsules coupled with strand-displacement amplification is enhanced by four orders of magnitude.

Stimuli-responsive polymers (SRPs) are capable of changing their solubility, conformation, and volume in response to external stimuli. By understanding the nature of the responsivity and the synthetic challenges, new SRPs can be synthesized with enhanced responsivities at scales that will allow their use in the real world. In this review, many fundamental concepts and recent advances in SRPs for sensing and actuation are presented. A variety of sensors that can respond to physiologically relevant species and stimuli are reviewed, including temperature/pH, proteins, glucose and ions. The review also includes examples of the use of SRPs for artificial muscles, soft robots, cell culture, and drug delivery.

The combination of polymerization-induced self-assembly (PISA) and post-polymerization modification is a versatile route to prepare core-functionalized nanoaggregates. PISA is a useful approach for preparing in situ self-assembled nano-objects, in which morphological nanostructures are tunable with a high solid concentration that can afford scale-up syntheses. Herein, the preparation via PISA of diblock copolymers that have functional groups in their structures to be further post-functionalized using active modifiers has been reviewed. The resulting multifunctional nanoaggregates exhibit great potential for use in a wide range of applications, for example, crosslinked nano-objects having improved stability, stimuli responsive vehicles for drug delivery, and fluorescent nanomaterials for bioimaging.

Traditional textiles with hydrophilic properties can absorb sweat secreted from the skin, but cause an undesirable cold sensation and adhere to the skin. Textiles with an effect similar to an air conditioner and sensing properties have attracted great interest because of their desirable performance, comfort, and energy-saving properties. However, fabricating functional textiles with moisture management and pH identification properties remains a difficult challenge. Herein, we demonstrate a fluorine-free hydrophobic loofah fabric with embedded thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) microspheres as microplugs, which endowed it with directional liquid transport and body temperature regulation depending on the temperature. Based on the phase separation of the microplugs and capillary gradients, the microplugs of the self-venting textile are opened and generate drying and cooling effects via high moisture transport in hot weather, whereas the pores of the microplugs close to retain heat in cold weather. Moreover, the multifunctional loofah textile exhibits hydrophobic or hydrophilic behaviour for droplets with different pH values, which can provide real-time liquid signal detection. The water repellency and the wicking, permeability, and mechanical properties of the hydrophobic outer surface of the loofah textile are not affected by harsh conditions. This study not only provides ideas for the design and preparation of textiles for personal comfort, but also environmentally friendly and acid/alkali-protective clothing with great potential applications in demanding situations.

Gels prepared from low-molecular-weight gelators (LMWGs) represent versatile soft materials. Self-assembly of LMWGs forms nanofibers and above critical gelation concentrations, the entanglement of which leads to self-supporting gels. Owing to the dynamic properties of the self-assembly process, stimuli-responsive LMWGs have prospered in the last decade. In addition, incorporating multiple LMWGs into one system brings the opportunity to achieve sophisticated designs and functions. This review covers recent advances in the field of supramolecular gels, from stimuli-responsive gelators to multicomponent systems that are self-sorting and/or co-assembling.

Stimuli-responsive metal-organic framework nanoparticles, NMOFs, provide a versatile platform for the controlled release of drugs and biomedical applications. The porous structure of NMOFs, their biocompatibility, low toxicity, and efficient permeability turn the NMOFs into ideal carriers for therapeutic applications. Two general methods to gate the drug-loaded NMOFs and to release the loads were developed: by one method, the loaded NMOFs are coated or surface-modified with stimuli-responsive gates being unlocked in the presence of appropriate chemical (e.g., ions or reducing agents), physical (e.g., light or heat), or biomarker (e.g., miRNA or ATP) triggers. By a second approach, the drug-loaded NMOFs include encoded structural information or co-added agents to induce the structural distortion or stimulate the degradation of the NMOFs. Different chemical triggers such as pH changes, ions, ATP, or redox agents, and physical stimuli such as light or heat are applied to degrade the NMOFs, resulting in the release of the loads. In addition, enzymes, DNAzymes, and disease-specific biomarkers are used to unlock the gated NMOFs. The triggered release of drugs for cancer therapy, anti-blood clotting, and the design of autonomous insulin-delivery systems ("artificial pancreas") are discussed. Specifically, multi-drug carrier systems and functional NMOFs exhibiting dual and cooperative therapeutic functions are introduced. The future perspectives and applications of stimuli-responsive particles are addressed.

Herein, we report the first example of two pure organic polymorphs with stimuli-responsive single/dual phosphorescence transformation. By analyzing the crystal structures and theoretical results, it could be understood that efficient intermolecular interactions could restrict the molecular movements and lock distinct molecular conformations, leading to different phosphorescence behaviors. Besides, single/dual phosphorescence could transform into each other by heating or under solvent vapor conditions. Considering such unique properties, logical sensors (AND gate and OR gate) were built by providing different emission colors as inputs. Our work provides not only important information for understanding the dual RTP mechanism but also unique stimuli-responsive pure organic phosphorescent materials to enrich material fields.

Stimuli responsiveness has long been a fascinating feature of smart material design. Polydopamine (PDA), a nature inspired polymeric pigment, exhibits excellent photo-responsive properties and has active surface functionality for loading various responsive motifs, making it a promising candidate for the construction of stimuli-responsive smart functional materials. PDA has long been considered as a robust coating material, but its responsive feature has rarely been emphasized in the past reviews. Herein, we present the first effort to summarize recent advances in the design strategies, responsive mechanisms, and diverse applications of stimuli-responsive PDA-based smart materials; the stimuli include light, pH, chemicals, temperature, humidity, electric fields, mechanical force, magnetic fields, and ultrasound. Moreover, the current trends, challenges, and future directions of stimuli-responsive PDA-based materials are also elaborated.

The functionality of multi-stimuli-responsive hydrogels in physiological states is the reason for the increased attention of hydrogels nowadays. Multi-stimuli-responsive hydrogels exhibit tunable changes in swelling or mechanical properties in response to predetermined combinations of stimuli such as pH, temperature, ionic strength, electric field, magnetic field, light, chemical triggers, enzyme concentration, redox species, reactive oxygen species (ROS), and glucose levels. This review summarizes the recent advances in multi-stimuli-responsive hydrogels used in medical approaches. The first part of the review highlights the medical applications of polymer-based and supramolecular hydrogels and emphasizes the priority of multi-stimuli hydrogels over single-stimuli hydrogels. Also, recent studies in medical applications of multi-stimuli-responsive hydrogels are collected with a focus on self-healing hydrogels, anti-bacterial materials, and drug-delivery systems.

The vinyl caprolactam (VCL) based microgel system has become the center of great attention due to its versatile properties. Copolymerization of VCL with an ionic monomer imparts pH responsive properties into the microgel system in addition to thermo-sensitivity. Stimuli responsive behavior of VCL-based microgels makes them prospective and appealing candidates for practical applications covering the fields of drug delivery, catalysis and optical devices. In the last few years, VCL-based microgels have been used as microreactors and stabilizers for the synthesis and stabilization of inorganic nanoparticles to obtain hybrid microgels. The present review article provides a summary of the present-day progress of fabrication, stabilization, categorization and analysis of VCL-based microgels and their hybrids with different morphologies. The stimuli responsive properties and applications of VCL-based hybrid microgels have been reviewed critically. The remaining problems which need to be addressed have been pointed out for further advancement in this field.

Graphene possesses a set of unique physicochemical properties including exceptional mechanical, thermal, and electrical properties, making it an excellent candidate for constructing materials for a wide range of applications including the vast field of separation technology using membranes. Separation membranes based on graphene and its derivatives have shown satisfactory results over the years when applied to environmental systems such as wastewater treatment and gas purification, which is a great contribution in sustainable development. However, membrane separation research is generally performed using conventional membranes with fixed driving force and separation properties that suffer from fouling and decline in performance upon long-term use or when a change in the environmental conditions occur. These issues can be solved by employing an emerging technology that makes use of graphene and its derivatives combined with polymeric materials to construct stimuli-responsive or “smart” membranes that respond to the changes in their environment such as chemical cues, temperature, pressure, and external fields, and have a self-regulated separation performance due to reversible physicochemical properties. In this review, we present a report on the recent advancements on graphene-based separation technology including a concise discussion on the basic structure and properties of graphene and its derivatives, various membrane fabrication methods, and their employment on the different areas of membrane separation. More importantly, the main focus of this paper is to evaluate the design and utilization of graphene-based smart separation membranes.

Many physiological processes involve multiple coordinated chemical and/or biological events. Therefore, it is considered urgent to develop dual-responsive probes for a more comprehensive understanding of the synergistic effects between multiple analytes in complex cellular environments. In this study, we developed a dual-responsive probe βgal-BP-PMB (β-galactosyl–3, 3′-dihydroxy-2, 2′-bipyridyl–p-methoxybenzyl), the photoluminescence of which can be activated by β-galactosidase (β-gal) and acidic conditions. The overexpression of β-gal is an important feature of senescent and ovarian cancer cells. Single-input activatable probes for detecting β-gal activity in ovarian cancer cells can induce a false positive response from senescent cells. Because the lysosomal pH in senescent cells is increased, probe βgal-BP-PMB can be specifically activated in ovarian cancer cells, but silenced in senescent cells. Probe βgal-BP-PMB has a small molecular size, high sensitivity towards targeted stimuli and unique ratiometric properties, thereby enabling the quantification of both pH and enzyme activity. Such dual-responsive probes could earn a unique place in the field of bioimaging, where multiple analytes should be accurately and simultaneously monitored.

Responsive polymers with properties designed to interact with their surrounding environment are enabling “smart” design features for custom biomaterials. Numerous applications are being innovated, ranging from diagnostics and imaging to tissue engineering and drug delivery. Herein, I feature a collection of research articles published in ACS Macro Letters that highlight an array of innovative chemical attributes such as pH-triggered hydrolytic degradation, reduction-based release, photomodulation, glucose responsiveness, thermal sensitivity, and membrane permeating peptides. The chemical, physical, mechanical, and morphological properties of polymeric structures can be custom tailored to enhance numerous features such as biological delivery, pharmaceutical potency and safety, disease diagnosis, and antigen/biomaker detection.

Horseradish peroxidase (HRP)-mediated oxidation of tyrosine-conjugated biodynamer containing acylhydrazone linkages and ovalbumin (OVA)/reduced ovalbumin (rOVA) generated protein nanogels through simultaneous tyrosine coupling and thiol cross-linking in the presence of H