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Exploiting exogenous and endogenous stimulus-responsive degradable nanoparticles as drug carriers can improve drug delivery systems (DDSs). The use of hollow nanoparticles may facilitate degradation, and combination of DDS with photodynamic therapy (PDT) and photothermal therapy (PTT) may enhance the anticancer effects of treatments. Here, a one-pot synthetic method is presented for an anticancer drug (doxorubicin [DOX]) and photosensitizer-containing hollow hybrid nanoparticles (HNPs) with a disulfide and siloxane framework formed in response to exogenous (light) and endogenous (intracellular glutathione [GSH]) stimuli. The hollow HNPs emit fluorescence within the near-infrared window and allow for the detection of tumors in vivo by fluorescence imaging. Furthermore, the disulfides within the HNP framework are cleaved by intracellular GSH, deforming the HNPs. Light irradiation facilitates penetration of GSH into the HNP framework and leads to the collapse of the HNPs. As a result, DOX is released from the hollow HNPs. Additionally, the hollow HNPs generate singlet oxygen (1O2) and heat in response to light; thus, fluorescence imaging of tumors combined with trimodal therapy consisting of DDS, PDT, and PTT is feasible, resulting in superior therapeutic efficacy. Thus, this method may have several applications in imaging and therapeutics in the future.

“Liquid marbles” are liquid-in-gas dispersed systems stabilized by hydrophobic solid particles adsorbed at the gas-liquid interface. The structure, stability and movement of these liquid marbles can be controlled by external stimuli such as pH, temperature, light, magnetic and electric fields, ultrasonic, mechanical stress and organic solvents. Stimuli-responsive modes can be categorized into five classes: (i) liquid marbles whose stability can be controlled by adsorption/desorption of solid particles to/from liquid surfaces, (ii) liquid marbles that can open and close their particle-coated surface by moving particles to and from the gas-liquid surface, (iii) liquid marbles that can move, (iv) liquid marbles that can change their shape and (v) liquid marbles that can be split. As a result of these stimuli-responsive characteristics, liquid marbles offer potential in the areas of controlled encapsulation, delivery and release.

The need for dynamic, elastomeric polymeric biomaterials remains high, with few options with tunable control of mechanical properties, and environmental responses. Yet the diversity of these types of protein polymers pursued for biomaterials-related needs remains limited. Robust high-throughput synthesis and characterization methods will address the need to expand options for protein-polymers for a range of applications. To address this need, a combinatorial library approach with high throughput screening is used to select specific examples of dynamic protein silk-elastin-like polypeptides (SELPs) with unique stimuli responsive features, including tensile strength, and adhesion. Using this approach 64 different SELPs with different sequences and molecular weights are selected out of over 2,000 recombinant E. coli colonies. New understanding of sequence-function relationships with this family of proteins is gained through this combinatorial-screening approach and can provide a guide to future library designs. Further, this approach yields new families of SELPs to match specific material functions.

Stimuli-responsive materials are so named because they can alter their physicochemical properties and/or structural conformations in response to specific stimuli. The stimuli can be internal, such as physiological or pathological variations in the target cells/tissues, or external, such as optical and ultrasound radiations. In recent years, these materials have gained increasing interest in biomedical applications due to their potential for spatially and temporally controlled release of theranostic agents in response to the specific stimuli. This article highlights several recent advances in the development of such materials, with a focus on their molecular designs and formulations. The future of stimuli-responsive materials will also be explored, including combination with molecular imaging probes and targeting moieties, which could enable simultaneous diagnosis and treatment of a specific disease, as well as multi-functionality and responsiveness to multiple stimuli, all important in overcoming intrinsic biological barriers and increasing clinical viability.

Gut dysbiosis is involved in the pathogenesis of energy metabolic disorders and represents a new strategy for treating these ailments. In this study, a pH/gut microflora dual stimuli‐responsive system, berberine (BBR)‐CS/PT‐NP with colon‐homing and microbiota‐targeting characteristics, is investigated to enhance the interaction between BBR and the gut microbiota. It provides a novel proof‐of‐concept for drug delivery targeting gut microbiota to ameliorate metabolic diseases.

Stimuli-responsive polymer brushes are smart materials for the design of bio-interactive and responsive interfaces. The “grafting-to” approach is a convenient preparation procedure that allows the modification of surfaces with preformed and most notably well-defined functionalized macromolecules. However, the shortcoming of this approach is an intrinsic limitation of the grafting density, which in turn affects the stimuli-responsive properties of the brush system. Here, a general strategy to overcome this limitation and to simultaneously improve the switching behavior of a temperature-responsive poly(N-isopropylacrylamide) (PNiPAAm) brush is reported. A technically simple processing step is used in combination with the thermal azide–alkyne cycloaddition to perform the chain extension of alkyne-functionalized PNiPAAm brushes with azide-functionalized PNiPAAm molecules.

Active motion is intrinsic to all kinds of living organisms from unicellular ones to humans and inspires development of synthetic actively moving materials. Hydrogels, which are three dimensional polymer networks imbibed with aqueous solutions, mimic the swelling/shrinking behavior of plant cells and produce macroscopic actuation upon swelling and shrinking. This Feature Article covers basic principles of design as well as recent advances in the development of hydrogel based actuating systems. It is discussed how simply swelling can be used to generate very complex multistep motion, which can be used to develop new optical devices, sensors, biomaterials, smart surface, etc.

Remote-controlled drug depots represent a highly valuable tool for the timely controlled administration of pharmaceuticals in a patient compliant manner. Here, the first pharmacologically controlled material that allows for the scheduled induction of a medical response in mice is described. To this aim, a novel, humanized biohybrid material that releases its cargo in response to a small-molecule stimulus licensed for human use is developed. The functionality of the material in mice is demonstrated by the remote-controlled delivery of a vaccine against the oncogenic human papillomavirus type 16. It is shown that the biohybrid depot-mediated immunoprotection is equivalent to the classical multi-injection-based vaccination. These results indicate that this material can be used as a universal remote-controlled vehicle for the patient-compliant delivery of vaccines and pharmaceuticals.

The surface nanoarchitecture provides spatially and temporally resolved stimuli response of the material, and offers defined control over the behavior of biomolecules and cells at the solid-liquid interface. Here, the focus is on metal-based systems that are interesting for biomedical applications. Intelligence of the surface is suggested to be achieved through its nanostructuring for stimuli responsive properties. Spatial and temporal cell performance at the surface, provided by the surface nanoarchitecture, offers advanced bio-applications of metal-based materials, such as implantation, lab-on-chip and organ-on-chip, biosensors, smart biomaterials and drug delivery systems. Spatial control is achieved by surface patterning. Temporal control is accessed through the application of stimuli responsive switchable surface chemistry, sensitive to external parameters: temperature, pH, light, electric and magnetic field, ionic strength, surrounding medium (hydrogels in water), multi-trigger response, and response to products of the cell metabolism. The key issue is the prospect in the formation of self-regulating “intelligent” surface cell interactions: biomimetic of natural systems.

An important goal and major challenge of material science and nanotechnology is building nanomotors for manipulating the motion of nanoparticles (NPs). Here, it is demonstrated that patterned, stimulus-responsive polymer brush microstructures can be used as motor arrays to manipulate the movement of gold NP aggregates in response to external stimuli that induce a conformational change in the brushes as the driving force. The motion of NP aggregates in the out-of-plane direction is achieved with displacements ranging from nanometers to sub-micrometers. These patterned polymerbrush microstructures can fi nd applications as effi cient motor arrays and nanosensors, and benefi t the design of more complex nanodevices.

Cell transplantation has emerged as the most promising therapy for restoring the scarred myocardium in the treatment of heart failure. However, clinical efficacy of (stem) cell therapies is still limited by poor retention rate and survival of injected cells in the ischemic tissue. Here we present a new strategy to deliver microtissues in the treatment of heart dysfunction in order to improve the retention, survival, and integration of the delivered cells. For this purpose, we developed stimuli responsive biodegradable polymer constructs consisting of a thin film of thermosensitive hydrogel coupled to a thin film of non-responsive polymer. Due to the temperature responsive swelling behavior of the hydrogel layer, the bilayer polymer constructs can roll or unroll at will. Therefore they can potentially be used for efficient encapsulation and protection of cell clusters during delivery, while under physiological conditions, the constructs, named cell wraps, can unroll and expose the delivered microtissue to the ischemic tissue.

Many emerging interfacial technologies, such as self-cleaning surfaces, oil/water separation, water collection, and microfluidics, are essentially liquid manipulation processes. In this regard, micro-nanostructures of the living organisms are highly preferable, by virtue of the evolutionary pressure and the adaptation to the specific environments, to inspire the optimization of man-made interfaces. With the increasing demands of modern life, research, and industry, intelligent materials with stimuli-responsive liquid manipulation functions have gained substantial attention from interfacial scientists. This review introduces the recent progress in the development of stimuli-responsive liquid-manipulating materials with bioinspired structures and surface chemistry according to two classified manipulation modes: (i) smart manipulation of liquid wetting behaviors, including lyophobic/lyophilic and superlyophobic/superlyophilic, and (ii) smart manipulation of liquid motion behaviors, including coalescence, transportation, rolling/adhesion, and sliding/pinning. At the beginning of the presentation of each classification, the theoretical basis and the sources of inspiration are introduced comprehensively to ensure a better understanding. This review mainly focuses on the mechanisms, fabrication, and applications of the state-of-the-art works related to smart and biomimetic liquid-manipulating materials. Finally, conclusions and future prospects are provided, and the remaining problems and promising breakthroughs in fabricating large-scale, cost-effective, and efficient smart liquid-manipulating materials are outlined.