A pH-responsive bi-MIL-88B MOF coated with folic acid-conjugated chitosan as a promising nanocarrier for targeted drug delivery of 5-Fluorouracil

Cancer has remained one of the leading causes of death worldwide, with a lack of effective treatment. The intrinsic shortcomings of conventional therapeutics regarding tumor specificity and non-specific toxicity prompt us to look for alternative therapeutics to mitigate these limitations. In this regard, we developed multifunctional bimetallic (FeCo) bi-MIL-88B-FC MOFs modified with folic acid-conjugated chitosan (FC) as drug delivery systems (DDS) for targeted delivery of 5-Fluorouracil (5-FU). The bi-MIL-88B nanocarriers were characterized through various techniques, including powder X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, thermogravimetric analysis, and Fourier transform infrared spectroscopy. Interestingly, 5-FU@bi-MIL-88B-FC showed slower release of 5-FU due to a gated effect phenomenon endowed by FC surface coating compared to un-modified 5-FU@bi-MIL-88B. The pH-responsive drug release was observed, with 58% of the loaded 5-FU released in cancer cells mimicking pH (5.2) compared to only 24.9% released under physiological pH (5.4). The in vitro cytotoxicity and cellular internalization experiments revealed the superiority of 5-FU@bi-MIL-88B-FC as a highly potent targeted DDS against folate receptor (FR) positive SW480 cancer cells. Moreover, due to the presence of Fe and Co in the structure, bi-MIL-88B exhibited peroxidase-like activity for chemodynamic therapy. Based on the results, 5-FU@bi-MIL-88B-FC could serve as promising candidate for smart DDS by sustained drug release and selective targeting.

A Bioresponsive Diselenide-functionalized Hydrogel with Cascade Catalytic Activities for Enhanced Local Starvation- and Hypoxia-Activated Melanoma Therapy

Glutathione (GSH) consumption-enhanced cancer therapies represent important potential cancer treatment strategies. Herein, we developed a new multifunctional diselenide-crosslinked hydrogel with glutathione peroxidase (GPx)-like catalytic activity for GSH depletion-enhanced glucose oxidase (GOx)-mediated tumor starvation and hypoxia-activated chemotherapy. By increasing acid and H₂O₂ during GOx-induced tumor starvation, the degradation of the multiresponsive scaffold could be promoted, which led to accelerated release of the loaded drugs. Meanwhile, the overproduced H₂O₂ led to accelerated intracellular GSH consumption under the cascade catalysis of small molecular selenides released from the degraded hydrogel, further enhancing the curative effect of in situ H₂O₂ and subsequent multimodal cancer treatment. Following the GOx-induced amplification of hypoxia, tirapazamine (TPZ) was transformed into the highly toxic benzotriazinyl radical (BTZ·), exhibiting enhanced antitumor activity. This GSH depletion-augmented cancer treatment strategy effectively boosted GOx-mediated tumor starvation and activated the hypoxia drug, leading to significantly enhanced local anticancer efficacy. STATEMENT OF SIGNIFICANCE: There has been a growing interest in depleting intracellular GSH as a potential strategy for improving ROS-based cancer therapy. Herein, a bioresponsive diselenide-functionalized dextran-based hydrogel with GPx-like catalytic activity was developed for GSH consumption-enhanced local starvation- and hypoxia-activated melanoma therapy. Results showed that the overproduced H₂O₂ led to accelerated intracellular GSH consumption under the cascade catalysis of small molecular selenides released from the degraded hydrogel, further enhancing the curative effect of in situ H₂O₂ and subsequent multimodal cancer treatment.

Biomimetic Mineralization for Smart Biostimulant Delivery and Crop Micronutrients Fortification

Sustainable and precise fortification practices are necessary to ensure food security for the increasing human population. Precision agriculture aims to minimize the use of fertilizers and pesticides by developing smart materials for real-life agricultural practices. Here, we show that biomimetic mineralization can be efficiently employed to encapsulate and controllably release plant biostimulants (MiZax-3) to improve the quality and yield of capsicum (Capsicum annum) crops in field experiments. ZIF-8 encapsulation of MiZax-3 (MiZIFs) could significantly enhance its stability up to around 679 times (6p value = 0.0072) at field conditions. Our results demonstrate that the coordinating Zn ions and the MiZax-3 play a vital role in improving Zn content in the produced fruits by 2-fold, which is the first report of this nature on Zn content in fruits. We envision this platform as a starting point to investigate other biocompatible coordination-based platforms for micronutrient delivery in precision agriculture.

Thermo-induced physically crosslinked polypeptide-based block copolymer hydrogels for biomedical applications

Stimuli-responsive synthetic polypeptide-containing block copolymers have received considerable attention in recent years. Especially, unique thermo-induced sol-gel phase transitions were observed for elaborately-designed amphiphilic diblock copolypeptides and a range of poly(ethylene glycol) (PEG)-polypeptide block copolymers. The thermo-induced gelation mechanisms involve the evolution of secondary conformation, enhanced intramolecular interactions, as well as reduced hydration and increased chain entanglement of PEG blocks. The physical parameters, including polymer concentrations, sol-gel transition temperatures and storage moduli, were investigated. The polypeptide hydrogels exhibited good biocompatibility in vitro and in vivo, and displayed biodegradation periods ranging from 1 to 5 weeks. The unique thermo-induced sol-gel phase transitions offer the feasibility of minimal-invasive injection of the precursor aqueous solutions into body, followed by in situ hydrogel formation driven by physiological temperature. These advantages make polypeptide hydrogels interesting candidates for diverse biomedical applications, especially as injectable scaffolds for 3D cell culture and tissue regeneration as well as depots for local drug delivery. This review focuses on recent advances in the design and preparation of injectable, thermo-induced physically crosslinked polypeptide hydrogels. The influence of composition, secondary structure and chirality of polypeptide segments on the physical properties and biodegradation of the hydrogels are emphasized. Moreover, the studies on biomedical applications of the hydrogels are intensively discussed. Finally, the major challenges in the further development of polypeptide hydrogels for practical applications are proposed.

Smart Materials Based on Synthetic Host Molecules: The Role of Host-Guest Chemistry in the Fabrication and Application

Stimuli-responsive or smart materials have recently shown a significant impact on the frontier of materials science and engineering. The exponential development of synthetic host molecules (SHMs) over the last decades and their corresponding host-guest chemistry, have empowered researchers with new opportunities to design and construct tailored or guest-specific smart materials. In this minireview, we present the recent advancements in host based smart materials, ranging from the fabrication strategies to the state-of-art applications including adsorption, separation, luminescence, self-healing and actuation. The role that the host-guest chemistry plays in these systems is highlighted throughout to give a better prospective of the available possibilities for emerging materials of future economies.

Small Molecule-Templated DNA Hydrogel with Record Stiffness Integrates and Releases DNA Nanostructures and Gene Silencing Nucleic Acids

Deoxyribonucleic acid (DNA) hydrogels are a unique class of programmable, biocompatible materials able to respond to complex stimuli, making them valuable in drug delivery, analyte detection, cell growth, and shape-memory materials. However, unmodified DNA hydrogels in the literature are very soft, rarely reaching a storage modulus of 10³  Pa, and they lack functionality, limiting their applications. Here, a DNA/small-molecule motif to create stiff hydrogels from unmodified DNA, reaching 10⁵  Pa in storage modulus is used. The motif consists of an interaction between polyadenine and cyanuric acid-which has 3-thymine like faces-into multimicrometer supramolecular fibers. The mechanical properties of these hydrogels are readily tuned, they are self-healing and thixotropic. They integrate a high density of small, nontoxic molecules, and are functionalized simply by varying the molecule sidechain. They respond to three independent stimuli, including a small molecule stimulus. These stimuli are used to integrate and release DNA wireframe and DNA origami nanostructures within the hydrogel. The hydrogel is applied as an injectable delivery vector, releasing an antisense oligonucleotide in cells, and increasing its gene silencing efficacy. This work provides tunable, stimuli-responsive, exceptionally stiff all-DNA hydrogels from simple sequences, extending these materials' capabilities.

Stimuli-Responsive Silica Silanol Conjugates: Strategic Nanoarchitectonics in Targeted Drug Delivery

The design of novel drug delivery systems is exceptionally critical in disease treatments. Among the existing drug delivery systems, mesoporous silica nanoparticles (MSNs) have shown profuse promise owing to their structural stability, tunable morphologies/sizes, and ability to load different payload chemistry. Significantly, the presence of surface silanol groups enables functionalization with relevant drugs, imaging, and targeting agents, promoting their utility and popularity among researchers. Stimuli-responsive silanol conjugates have been developed as a novel, more effective way to conjugate, deliver, and release therapeutic drugs on demand and precisely to the selected location. Therefore, it is urgent to summarize the current understanding and the surface silanols' role in making MSN a versatile drug delivery platform. This review provides an analytical understanding of the surface silanols, chemistry, identification methods, and their property-performance correlation. The chemistry involved in converting surface silanols to a stimuli-responsive silica delivery system by endogenous/exogenous stimuli, including pH, redox potential, temperature, and hypoxia, is discussed in depth. Different chemistries for converting surface silanols to stimuli-responsive bonds are discussed in the context of drug delivery. The critical discussion is culminated by outlining the challenges in identifying silanols' role and overcoming the limitations in synthesizing stimuli-responsive mesoporous silica-based drug delivery systems.

Stimuli-Responsive and Antibacterial Cellulose-Chitosan Hydrogels Containing Polydiacetylene Nanosheets

Herein, we report a stimuli-responsive hydrogel with inhibitory activity against Escherichia coli prepared by chemical crosslinking of carboxymethyl chitosan (CMCs) and hydroxyethyl cellulose (HEC). The hydrogels were prepared by esterification of chitosan (Cs) with monochloroacetic acid to produce CMCs which were then chemically crosslinked to HEC using citric acid as the crosslinking agent. To impart a stimuli responsiveness property to the hydrogels, polydiacetylene-zinc oxide (PDA-ZnO) nanosheets were synthesized in situ during the crosslinking reaction followed by photopolymerization of the resultant composite. To achieve this, ZnO was anchored on carboxylic groups in 10,12-pentacosadiynoic acid (PCDA) layers to restrict the movement of the alkyl portion of PCDA during crosslinking CMCs and HEC hydrogels. This was followed by irradiating the composite with UV radiation to photopolymerize the PCDA to PDA within the hydrogel matrix so as to impart thermal and pH responsiveness to the hydrogel. From the results obtained, the prepared hydrogel had a pH-dependent swelling capacity as it absorbed more water in acidic media as compared to basic media. The incorporation of PDA-ZnO resulted in a thermochromic composite responsive to pH evidenced by a visible colour transition from pale purple to pale pink. Upon swelling, PDA-ZnO-CMCs-HEC hydrogels had significant inhibitory activity against E. coli attributed to the slow release of the ZnO nanoparticles as compared to CMCs-HEC hydrogels. In conclusion, the developed hydrogel was found to have stimuli-responsive properties and inhibitory activity against E. coli attributed to zinc nanoparticles.

Development of stimuli responsive polymeric nanomedicines modulating tumor microenvironment for improved cancer therapy

The complexity of the tumor microenvironment (TME) severely hinders the therapeutic effects of various cancer treatment modalities. The TME differs from normal tissues owing to the presence of hypoxia, low pH, and immune-suppressive characteristics. Modulation of the TME to reverse tumor growth equilibrium is considered an effective way to treat tumors. Recently, polymeric nanomedicines have been widely used in cancer therapy, because their synthesis can be controlled and they are highly modifiable, and have demonstrated great potential to remodel the TME. In this review, we outline the application of various stimuli responsive polymeric nanomedicines to modulate the TME, aiming to provide insights for the design of the next generation of polymeric nanomedicines and promote the development of polymeric nanomedicines for cancer therapy.

Multi Stimuli-Responsive Aggregation-Induced Emission Active Polymer Platform Based on Tetraphenylethylene-Appended Maleic Anhydride Terpolymers

Multi stimuli-responsive aggregation-induced emission (AIE) active polymers have great application prospects in high-tech innovations. Herein, three types of tetraphenylethylene (TPE)-containing monomers were synthesized and utilized in preparing TPE-appended maleic anhydride terpolymers. After hydrolysis, the produced TPE-appended maleic acid terpolymers have identical linear charge densities but different "primary" structures, which created widely varied microenvironments around the carboxylate and TPE groups. Benefiting from the synergistic interaction of the TPE moiety and the terpolymer conformation change, the TPE-appended maleic acid terpolymers exhibited fluorescence changes in response to multi stimuli, including pH, ionic strength, Ca²⁺, and bovine serum albumin. On both the "signaling" and the "stimuli acceptor" sides, the multi stimuli-responsive fluorescence behavior was influenced markedly by the terpolymer primary structure. The fundamental insights gained in the present work are important for developing an efficient and versatile stimuli-responsive AIE-active polymer platform for chemo-sensing, bioimaging, and so on.

Thermally Programmable Dynamic Capillarity in Nanofluidic Channels Grafted with Smart Elastomeric Layers

This work demonstrates thermally programmable dynamic capillarity in exclusively engineered nanochannels functionalized by grafted smart elastomeric layers onto their inner surfaces. Tunable control of the capillarity is observed over the temperature window of 25-31 °C, deciphering the possibility of a sevenfold alteration in the rate of capillary flow. A simple theory explains the confluence of viscous and capillary interactions as mediated by the non-trivial interplay of the substrate wettability, confinement-induced surface layering of molecules, and thermally activated modulation of surface tension, to bring out this intriguing effect. The technology is demonstrated to be completely reconfigurable over the intended spatial and temporal regimes, via selective grafting of the channel surface and preferential choice of the activation temperature. Such favorable features as opposed to more complex yet non-reconfigurable flow manipulation strategies previously reported are likely to open up new possibilities of highly precise controlled nanofluidic manipulation of temperature-sensitive biological samples and chemical species on-demand, for applications ranging from biomedical technologies to energy harvesting and water purification.

In Situ Transformable Supramolecular Nanomedicine Targeted Activating Hippo Pathway for Triple-Negative Breast Cancer Growth and Metastasis Inhibition

As it is closely associated with tumor proliferation, metastasis, and the immunosuppressive microenvironment, the dysfunctional Hippo pathway has become an extremely attractive target for treating multiple cancers. However, to date, the corresponding chemotherapeutic nanomedicines have not been developed. Herein, a supramolecular self-delivery nanomedicine with in situ transforming capacity was tailor-constructed for Hippo-pathway restoration, and its inhibitory effect against tumor growth and metastasis was investigated in a highly aggressive triple-negative breast cancer (TNBC) model. Stimulated by overexpressed glutathione (GSH) and esterase in cancer cells, the self-assembled nanomedicine transformed from inactive nanospheres to active nanofibers conjugating tyrosvaline and spatiotemporally synchronously released the covalently linked flufenamic acid in situ, together activating the maladjusted Hippo pathway by simultaneously acting on different targets upstream and downstream. The transcriptional expression of Yes-associated protein (YAP) and related growth-promoted genes were significantly reduced, finally significantly repressing the proliferation and metastasis of cancer cells. Additionally, the Hippo-pathway restoration showed an excellent radiosensitization effect, making the targeted therapy combined with radiotherapy display a prominent synergistic in vivo anticancer effect against TNBC. This work reports a specifically designed smart nanomedicine to restore the function of the Hippo pathway and sensitize radiotherapy, providing an attractive paradigm for targeted drug delivery and cancer combination therapy.

Development and Evaluation of Novel Leflunomide SPION Bioemulsomes for the Intra-Articular Treatment of Arthritis

Systemic treatments for rheumatoid arthritis are associated with many side effects. This study aimed to minimize the side effects associated with the systemic administration of leflunomide (LEF) by formulating LEF-loaded emulsomes (EMLs) for intra-articular administration. Additionally, EMLs were loaded with supramagnetic nanoparticles (SPIONs) to enhance joint localization, where a magnet was placed on the joint area after intra-articular administration. Full in vitro characterization, including colloidal characteristics, entrapment efficiency, and in vitro release were conducted besides the in vivo evaluation in rats with adjuvant-induced arthritis. In vivo study included joint diameter measurement, X-ray radiographic analysis, RT-PCR analysis, Western blotting, ELISA for inflammatory markers, and histopathological examination of dissected joints. The particle size and entrapment efficiency of the selected LEF SPION EMLs were 198.2 nm and 83.7%, respectively. The EMLs exhibited sustained release for 24 h. Moreover, in vivo evaluation revealed LEF SPION EMLs to be superior to the LEF suspension, likely due to the increase in LEF solubility by nanoencapsulation that improved the pharmacological effects and the use of SPION that ensured the localization of EMLs in the intra-articular cavity upon administration.

Formulating Zwitterionic, Responsive Polymers for Designing Smart Soils

The design of new remediation strategies and materials for treating saline-alkaline soils is of fundamental and practical importantance for many applications. Conventional soil remediation strategies mainly focus on the development of fertilizers or additives for water, nutrient, and heavy metal managements in soils, but they often overlook a soil sensing function for early detection of salinization/alkalization levels toward optimal and timely soil remediation. Here, new smart soils, structurally consisting of the upper signal soil and the bottom hygroscopic bed and chemically including zwitterionic, thermo-responsive poly(NIPAM-co-VPES) and poly(NIPAM-co-SBAA) aerogels in each soil layer are formulated. Upon salinization, the resultant smart soils exhibit multiple superior capacities for reducing the soil salinity and alkalinity through ion exchange, controlling the water cycling, modulating the degradation of pyridine-base ligands into water-soluble, nitrogenous salts-rich ingredients for soil fertility, and real-time monitoring salinized soils via pH-induced allochroic color changes. Further studies of plant growth in smart soils with or without salinization treatments confirm a synergy effect of soil remediation and soil sensing on facilitating the growth of plants and increasing the saline-alkaline tolerance of plants. The esign concept of smart soils can be further expanded for soil remediation and assessment.

The emergence of nanoporous materials in lung cancer therapy

Lung cancer is one of the most common cancers, affecting more than 2.1 million people across the globe every year. A very high occurrence and mortality rate of lung cancer have prompted active research in this area with both conventional and novel forms of therapies including the use of nanomaterials based drug delivery agents. Specifically, the unique physico-chemical and biological properties of porous nanomaterials have gained significant momentum as drug delivery agents for delivering a combination of drugs or merging diagnosis with targeted therapy for cancer treatment. This review focuses on the emergence of nano-porous materials for drug delivery in lung cancer. The review analyses the currently used nanoporous materials, including inorganic, organic and hybrid porous materials for delivering drugs for various types of therapies, including chemo, radio and phototherapy. It also analyses the selected research on stimuli-responsive nanoporous materials for drug delivery in lung cancer before summarizing the various findings and projecting the future of emerging trends. This review provides a strong foundation for the current status of the research on nanoporous materials, their limitations and the potential for improving their design to overcome the unique challenges of delivering drugs for the treatment of lung cancer.

Switched Proton Conduction in Metal-Organic Frameworks

Stimuli-responsive materials can respond to external effects, and proton transport is widespread and plays a key role in living systems, making stimuli-responsive proton transport in artificial materials of particular interest to researchers due to its desirable application prospects. On the basis of the rapid growth of proton-conducting porous metal-organic frameworks (MOFs), switched proton-conducting MOFs have also begun to attract attention. MOFs have advantages in crystallinity, porosity, functionalization, and structural designability, and they can facilitate the fabrication of novel switchable proton conductors and promote an understanding of the comprehensive mechanisms. In this Perspective, we highlight the current progress in the rational design and fabrication of stimuli-responsive proton-conducting MOFs and their applications. The dynamic structural change of proton transfer pathways and the role of trigger molecules are discussed to elucidate the stimuli-responsive mechanisms. Subsequently, we also discuss the challenges and propose new research opportunities for further development.

Microgels Formed by Spontaneous Click Chemistries Utilizing Microfluidic Flow Focusing for Cargo Release in Response to Endogenous or Exogenous Stimuli

Protein therapeutics have become increasingly popular for the treatment of a variety of diseases owing to their specificity to targets of interest. However, challenges associated with them have limited their use for a range of ailments, including the limited options available for local controlled delivery. To address this challenge, degradable hydrogel microparticles, or microgels, loaded with model biocargoes were created with tunable release profiles or triggered burst release using chemistries responsive to endogenous or exogeneous stimuli, respectively. Specifically, microfluidic flow-focusing was utilized to form homogenous microgels with different spontaneous click chemistries that afforded degradation either in response to redox environments for sustained cargo release or light for on-demand cargo release. The resulting microgels were an appropriate size to remain localized within tissues upon injection and were easily passed through a needle relevant for injection, providing means for localized delivery. Release of a model biopolymer was observed over the course of several weeks for redox-responsive formulations or triggered for immediate release from the light-responsive formulation. Overall, we demonstrate the ability of microgels to be formulated with different materials chemistries to achieve various therapeutic release modalities, providing new tools for creation of more complex protein release profiles to improve therapeutic regimens.

Dynamic Anticounterfeiting Through Novel Photochromic Spiropyran-Based Switch@Ln-MOF Composites

Fluorescent materials presenting unique color changes in response to external stimuli have wide applications in information storage and anticounterfeiting. However, developing intelligent fluorescent materials with high security levels and dynamically displaying encrypted information is still a challenge. Herein, we report a new method for constructing excellent fluorescent materials by loading the photochromic molecule spiropyran into a lanthanide metal-organic framework. Controlling the isomerization of the spiropyran unit regulates the fluorescence resonance energy transfer (FRET) mechanism between the spiropyran acceptor and the lanthanide donor, leading to an exceptional reversible absorption/luminescence modulation ability. As the irradiation time is extended, the fluorescent color changes continuously from yellow-greenish to orange and then to red through the FRET process within 60 s. This composite system has great potential in anticounterfeiting because of the following advantages: (1) the materials have different fluorescence emissions and optical colors regulated by ultraviolet radiation, which is convenient for designing complex anticounterfeiting patterns; (2) the system can be repeatedly verified quickly and exhibit dynamic fluorescence color within 60 s, having great potential in advanced anticounterfeiting, where time is key in encryption/decryption. These unique advantages will greatly enhance the reliability of anticounterfeiting measures and increase the difficulty of anticounterfeiting.

Thermoresponsive Smart Gating Wood Membranes

Smart membranes that can open and/or close their pores in a controlled manner by external stimuli possess potential in various applications, such as water flow manipulation, indoor climate regulation, and sensing. The design of smart gating membranes with high flux, immediate response, and mechanical robustness is still an open challenge, limiting their versatility and practical applicability. Inspired by the controlled opening and closure of plant stomata, we have developed a smart gating wood membrane, taking advantage of the unique wood scaffold with its hierarchical porous structure to carry thermoresponsive hydrogel gates. Laser drilling was applied to cut channels in the wood scaffold with well-aligned pores to incorporate the smart gating membranes. In situ polymerization of poly(N-isopropylacrylamide) above its lower critical solution temperature inside the channels resulted in a hydrogel with a heterogeneous microstructure acting as a thermoresponsive gate. The wood-based smart gating membranes exhibited reversible and stable pore opening/closing under heating/cooling stimuli. The achieved rapid response and feasibility of scale-up open the venue for various practical applications. In this work, we demonstrated their potential for indoor light regulation and as a water flow manipulator.

Freestanding Helical Nanostructured Chiro-Photonic Crystal Film and Anticounterfeiting Label Enabled by a Cholesterol-Grafted Light-Driven Molecular Motor

Design and fabrication of freestanding chiro-photonic crystal film with the ability to change color over the whole visible light spectrum is appealing for anticounterfeiting technology and smart labels. Utilizing a newly synthesized light-responsive molecular motor functionalized with cholesterol (chol-MM) on the rotor, novel light-controlled photonic crystal is prepared by doping the novel chol-MM into liquid crystals (LCs). Thanks to the liquid crystalline cholesterol substituent, the chol-MM can be triggered by visible light (420 nm). At the same time, the miscibility of chol-MM in LC matrix is significantly enhanced. Integrating the chol-MM with thermochromic hydrogen-bonded LC matrix, thermal and light dual-responsive cholesteric LC (CLC) material is prepared, in which the nanoscale helical pitch is tunable by photo-induced molecular motions of chol-MM. More importantly, utilizing UV-initiated polymerization of the visible light-modulated CLC material, structural colored photonic crystal films with arbitrary colorful patterns are fabricated. Such freestanding helical nanostructured labels have potential in the application of encrypted communication and anticounterfeiting.

Controlling Synthetic Cell-Cell Communication

Synthetic cells, which mimic cellular function within a minimal compartment, are finding wide application, for instance in studying cellular communication and as delivery devices to living cells. However, to fully realise the potential of synthetic cells, control of their function is vital. An array of tools has already been developed to control the communication of synthetic cells to neighbouring synthetic cells or living cells. These tools use either chemical inputs, such as small molecules, or physical inputs, such as light. Here, we examine these current methods of controlling synthetic cell communication and consider alternative mechanisms for future use.

Near-infrared probes for luminescence lifetime imaging

Biomedical luminescence imaging in the near-infrared (NIR, 700-1700 nm) region has shown great potential in visualizing biological processes and pathological conditions at cellular and animal levels, owing to the reduced tissue absorption and scattering compared to light in the visible (400-700 nm) region. To overcome the background interference and signal attenuation during intensity-based luminescence imaging, lifetime imaging has demonstrated a reliable imaging modality complementary to intensity measurement. Several selective or environment-responsive probes have been successfully developed for luminescence lifetime imaging and multiplex detection. This review summarizes recent advances in the application of luminescence lifetime imaging at cellular and animal levels in NIR-I and NIR-II regions. Finally, the challenges and further directions of luminescence lifetime imaging are also discussed.

Stimuli Responsive Materials Supported by Orthogonal Hydrogen and Halogen Bonding or I···Alkene Interaction

Smart materials represent an elegant class of (macro)-molecules endowed with the ability to react to chemical/physical changes in the environment. Herein, we prepared new photo responsive azobenzenes possessing halogen bond donor groups. The X-ray structures of two molecules highlight supramolecular organizations governed by unusual noncovalent bonds. In azo dye I-azo-NO₂, the nitro group is engaged in orthogonal H···O···I halogen and hydrogen bonding, linking the units in parallel undulating chains. As far as compound I–azo–NH–MMA is concerned, a non-centrosymmetric pattern is formed due to a very rare I···π interaction involving the alkene group supplemented by hydrogen bonds. The Cambridge Structural Database contains only four structures showing the same I···CH₂=C contact. For all compounds, an ¹⁹F-NMR spectroscopic analysis confirms the formation of halogen bonds in solution through a recognition process with chloride anion, and the reversible photo-responsiveness is demonstrated upon exposing a solution to UV light irradiation. Finally, the intermediate I–azo–NH₂ also shows a pronounced color change due to pH variation. These azobenzenes are thereby attractive building blocks to design future multi-stimuli responsive materials for highly functional devices.

Rational Design of Peptide-based Smart Hydrogels for Therapeutic Applications

Peptide-based hydrogels have captivated remarkable attention in recent times and serve as an excellent platform for biomedical applications owing to the impressive amalgamation of unique properties such as biocompatibility, biodegradability, easily tunable hydrophilicity/hydrophobicity, modular incorporation of stimuli sensitivity and other functionalities, adjustable mechanical stiffness/rigidity and close mimicry to biological molecules. Putting all these on the same plate offers smart soft materials that can be used for tissue engineering, drug delivery, 3D bioprinting, wound healing to name a few. A plethora of work has been accomplished and a significant progress has been realized using these peptide-based platforms. However, designing hydrogelators with the desired functionalities and their self-assembled nanostructures is still highly serendipitous in nature and thus a roadmap providing guidelines toward designing and preparing these soft-materials and applying them for a desired goal is a pressing need of the hour. This review aims to provide a concise outline for that purpose and the design principles of peptide-based hydrogels along with their potential for biomedical applications are discussed with the help of selected recent reports.

Stimuli Responsive Nitric Oxide-Based Nanomedicine for Synergistic Therapy

Gas therapy has received widespread attention from the medical community as an emerging and promising therapeutic approach to cancer treatment. Among all gas molecules, nitric oxide (NO) was the first one to be applied in the biomedical field for its intriguing properties and unique anti-tumor mechanisms which have become a research hotspot in recent years. Despite the great progress of NO in cancer therapy, the non-specific distribution of NO in vivo and its side effects on normal tissue at high concentrations have impaired its clinical application. Therefore, it is important to develop facile NO-based nanomedicines to achieve the on-demand release of NO in tumor tissue while avoiding the leakage of NO in normal tissue, which could enhance therapeutic efficacy and reduce side effects at the same time. In recent years, numerous studies have reported the design and development of NO-based nanomedicines which were triggered by exogenous stimulus (light, ultrasound, X-ray) or tumor endogenous signals (glutathione, weak acid, glucose). In this review, we summarized the design principles and release behaviors of NO-based nanomedicines upon various stimuli and their applications in synergistic cancer therapy. We also discuss the anti-tumor mechanisms of NO-based nanomedicines in vivo for enhanced cancer therapy. Moreover, we discuss the existing challenges and further perspectives in this field in the aim of furthering its development.

Peptide-Based Drug Delivery Systems

Peptide-based drug delivery systems have many advantages when compared to synthetic systems in that they have better biocompatibility, biochemical and biophysical properties, lack of toxicity, controlled molecular weight via solid phase synthesis and purification. Lysosomes, solid lipid nanoparticles, dendrimers, polymeric micelles can be applied by intravenous administration, however they are of artificial nature and thus may induce side effects and possess lack of ability to penetrate the blood-brain barrier. An analysis of nontoxic drug delivery systems and an establishment of prospective trends in the development of drug delivery systems was needed. This review paper summarizes data, mainly from the past 5 years, devoted to the use of peptide-based carriers for delivery of various toxic drugs, mostly anticancer or drugs with limiting bioavailability. Peptide-based drug delivery platforms are utilized as peptide–drug conjugates, injectable biodegradable particles and depots for delivering small molecule pharmaceutical substances (500 Da) and therapeutic proteins. Controlled drug delivery systems that can effectively deliver anticancer and peptide-based drugs leading to accelerated recovery without significant side effects are discussed. Moreover, cell penetrating peptides and their molecular mechanisms as targeting peptides, as well as stimuli responsive (enzyme-responsive and pH-responsive) peptides and peptide-based self-assembly scaffolds are also reviewed.

Peptide-Assisted Nucleic Acid Delivery Systems on the Rise

Concerns associated with nanocarriers' therapeutic efficacy and side effects have led to the development of strategies to advance them into targeted and responsive delivery systems. Owing to their bioactivity and biocompatibility, peptides play a key role in these strategies and, thus, have been extensively studied in nanomedicine. Peptide-based nanocarriers, in particular, have burgeoned with advances in purely peptidic structures and in combinations of peptides, both native and modified, with polymers, lipids, and inorganic nanoparticles. In this review, we summarize advances on peptides promoting gene delivery systems. The efficacy of nucleic acid therapies largely depends on cell internalization and the delivery to subcellular organelles. Hence, the review focuses on nanocarriers where peptides are pivotal in ferrying nucleic acids to their site of action, with a special emphasis on peptides that assist anionic, water-soluble nucleic acids in crossing the membrane barriers they encounter on their way to efficient function. In a second part, we address how peptides advance nanoassembly delivery tools, such that they navigate delivery barriers and release their nucleic acid cargo at specific sites in a controlled fashion.

Informative and corrective responsive packaging: Advances in farm-to-fork monitoring and remediation of food quality and safety

Microbial growth and fluctuations in environmental conditions have been shown to cause microbial contamination and deterioration of food. Thus, it is paramount to develop reliable strategies to effectively prevent the sale and consumption of contaminated or spoiled food. Responsive packaging systems are designed to react to specific stimuli in the food or environment, such as microorganisms or temperature, then implement an informational or corrective response. Informative responsive packaging is aimed at continuously monitoring the changes in food or environmental conditions and conveys this information to the users in real time. Meanwhile, packaging systems with the capacity to control contamination or deterioration are also of great interest. Encouragingly, corrective responsive packaging attempting to mitigate the adverse effects of condition fluctuations on food has been investigated. This packaging exerts its effects through the triggered release of active agents by environmental stimuli. In this review, informative and corrective responsive packaging is conceptualized clearly and concisely. The mechanism and characteristics of each type of packaging are discussed in depth. This review also summarized the latest research progress of responsive packaging and objectively appraised their advantages. Evidently, the mechanism through which packaging systems respond to microbial contamination and associated environmental factors was also highlighted. Moreover, risk concerns, related legislation, and consumer perspective in the application of responsive packaging are discussed as well. Broadly, this comprehensive review covering the latest information on responsive packaging aims to provide a timely reference for scientific research and offer guidance for presenting their applications in food industry.

Emerging Role of Hydrogels in Drug Delivery Systems, Tissue Engineering and Wound Management

The popularity of hydrogels as biomaterials lies in their tunable physical properties, ability to encapsulate small molecules and macromolecular drugs, water holding capacity, flexibility, and controllable degradability. Functionalization strategies to overcome the deficiencies of conventional hydrogels and expand the role of advanced hydrogels such as DNA hydrogels are extensively discussed in this review. Different types of cross-linking techniques, materials utilized, procedures, advantages, and disadvantages covering hydrogels are tabulated. The application of hydrogels, particularly in buccal, oral, vaginal, and transdermal drug delivery systems, are described. The review also focuses on composite hydrogels with enhanced properties that are being developed to meet the diverse demand of wound dressing materials. The unique advantages of hydrogel nanoparticles in targeted and intracellular delivery of various therapeutic agents are explained. Furthermore, different types of hydrogel-based materials utilized for tissue engineering applications and fabrication of contact lens are discussed. The article also provides an overview of selected examples of commercial products launched particularly in the area of oral and ocular drug delivery systems and wound dressing materials. Hydrogels can be prepared with a wide variety of properties, achieving biostable, bioresorbable, and biodegradable polymer matrices, whose mechanical properties and degree of swelling are tailored with a specific application. These unique features give them a promising future in the fields of drug delivery systems and applied biomedicine.

Interfacial Photo-Cross-Linking: Simple but Powerful Approach for Fabricating Capsule Polymer Particles with Tunable pH-Responsive Controlled Release Capability

Herein, we describe capsule polymer particles with precisely controlled pH-responsive release properties prepared directly via the interfacial photo-cross-linking of spherical poly(2-diethylaminoethyl methacrylate-co-2-cinnamoylethyl methacrylate) (P(DEAEMA-CEMA)) particles. In the interfacial photo-cross-linking, photoreactive cinnamoyl groups in the polymer particles were cross-linked via [2π + 2π] cycloaddition reactions at the polymer/water interface, showing that the shell-cross-linked hollow polymer particles can be directly prepared from spherical polymer particles. The approach has fascinating advantages such as using minimal components, simplicity, and not requiring sacrificial template particles and toxic solvents. The following important observations are made: (I) encapsulated materials were stably retained in the capsule particles under neutral pH conditions; (II) encapsulated materials were released from the capsule particles under acidic pH conditions; (III) the release kinetics of encapsulated materials were controlled by the pH conditions; i.e., immediate and sustained release was achieved by varying the acidity of the aqueous media; (IV) the photoirradiation time did not significantly affect the release kinetics under different pH conditions; and (V) the pH-responsive release properties were regulated by changing the polymer composition in P(DEAEMA-CEMA). Furthermore, by exploiting the pH-responsiveness, capsule particles are successfully obtained via an all-aqueous process from spherical polymer particles. The advantages of the all-aqueous encapsulation process allowed the water-soluble biomacromolecules such as DNA and saccharides to be successfully encapsulated in the P(DEAEMA-CEMA) hollow particles. With this simple interfacial photo-cross-linking strategy, we envision the ready synthesis of sophisticated particulate materials for broad application in advanced research fields.

Redox-Responsive Nanocarrier for Controlled Release of Drugs in Inflammatory Skin Diseases

A synthetic route for redox-sensitive and non-sensitive core multi-shell (CMS) carriers with sizes below 20 nm and narrow molecular weight distributions was established. Cyclic voltammetric measurements were conducted characterizing the redox potentials of reduction-sensitive CMS while showcasing its reducibility through glutathione and tris(2-carboxyethyl)-phosphine as a proof of concept. Measurements of reduction-initiated release of the model dye Nile red by time-dependent fluorescence spectroscopy showed a pronounced release for the redox-sensitive CMS nanocarrier (up to 90% within 24 h) while the non-sensitive nanocarriers showed no release in PBS. Penetration experiments using ex vivo human skin showed that the redox-sensitive CMS nanocarrier could deliver higher percentages of the loaded macrocyclic dye meso-tetra (m-hydroxyphenyl) porphyrin (mTHPP) to the skin as compared to the non-sensitive CMS nanocarrier. Encapsulation experiments showed that these CMS nanocarriers can encapsulate dyes or drugs with different molecular weights and hydrophobicity. A drug content of 1 to 6 wt% was achieved for the anti-inflammatory drugs dexamethasone and rapamycin as well as fluorescent dyes such as Nile red and porphyrins. These results show that redox-initiated drug release is a promising strategy to improve the topical drug delivery of macrolide drugs.

Protein and mRNA Delivery Enabled by Cholesteryl-Based Biodegradable Lipidoid Nanoparticles

Developing safe and efficient delivery systems for therapeutic biomacromolecules is a long-standing challenge. Herein, we report a newly developed combinatorial library of cholesteryl-based disulfide bond-containing biodegradable cationic lipidoid nanoparticles. We have identified a subset of this library which is effective for protein and mRNA delivery in vitro and in vivo. These lipidoids showed comparable transfection efficacies but much lower cytotoxicities compared to the Lpf2k in vitro. In vivo studies in adult mice demonstrated the successful delivery of genome engineering protein and mRNA molecules in the skeletal muscle (via intramuscular injection), lung and spleen (via intravenous injection), and brain (via lateral ventricle infusion).

Stimuli-responsive composite biopolymer actuators with selective spatial deformation behavior

Bioinspired actuators with stimuli-responsive and deformable properties are being pursued in fields such as artificial tissues, medical devices and diagnostics, and intelligent biosensors. These applications require that actuator systems have biocompatibility, controlled deformability, biodegradability, mechanical durability, and stable reversibility. Herein, we report a bionic actuator system consisting of stimuli-responsive genetically engineered silk-elastin-like protein (SELP) hydrogels and wood-derived cellulose nanofibers (CNFs), which respond to temperature and ionic strength underwater by ecofriendly methods. Programmed site-selective actuation can be predicted and folded into three-dimensional (3D) origami-like shapes. The reversible deformation performance of the SELP/CNF actuators was quantified, and complex spatial transformations of multilayer actuators were demonstrated, including a biomimetic flower design with selective petal movements. Such actuators consisting entirely of biocompatible and biodegradable materials will offer an option toward constructing stimuli-responsive systems for in vivo biomedicine soft robotics and bionic research.

Effects of Chemical Modifications on the Thermoresponsive Behavior of a PDMAEA-b-PNIPAM-b-POEGA Triblock Terpolymer

In this work, the synthesis, selective chemical modifications, and self-assembly behavior in aqueous media of a novel poly(2-(dimethylamino)ethyl acrylate)₂₀-b-poly(N-isopropylacrylamide)₁₁-b-poly(oligo ethylene glycol methyl ether acrylate)₁₈ (PDMAEA₂₀-b-PNIPAM₁₁-b-POEGA₁₈) dual-responsive (pH and temperature) and triply hydrophilic amino-based triblock terpolymer are reported. The amine functional triblock terpolymer was synthesized by sequential reversible addition fragmentation chain transfer polymerization (RAFT) polymerization and molecularly characterized by size exclusion chromatography (SEC) and ¹H-NMR spectroscopy that evidenced the success of the three-step polymerization scheme. The tertiary amine pendant groups of the PDMAEA block were chemically modified in order to produce the Q₁PDMAEA₂₀-b-PNIPAM₁₁-b-POEGA₁₈ as well as the Q₆PDMAEA₂₀-b-PNIPAM₁₁-b-POEGA₁₈ quaternized triblock terpolymers (Q₁ and Q₆ prefixes show the number of carbon atoms (C1 and C6) attached on the PDMAEA groups) using methyl iodide (CH₃I) and 1-iodohexane (C₆H₁₃I) as the quaternizing agents and the SPDMAEA₂₀-b-PNIPAM₁₁-b-POEGA₁₈ sulfobetainized triblock terpolymer using 1,3 propanesultone (C₃H₆O₃S) as the sulfobetainization agent. The self-assembly properties of the triblock terpolymers in aqueous solutions upon varying temperature and solution pH were studied by light scattering and fluorescence spectroscopy experiments. The novel triblock terpolymers self-assemble into nanosized aggregates upon solution temperature rise above the nominal lower critical solution temperature (LCST) of the temperature-responsive PNIPAM block. The remarkable stimuli-responsive self-assembly behavior of the novel triblock terpolymers in aqueous media make them interesting candidates for biomedical applications in the fields of drug and gene delivery.

Multimodal Decorations of Mesoporous Silica Nanoparticles for Improved Cancer Therapy

The presence of leaky vasculature and the lack of lymphatic drainage of small structures by the solid tumors formulate nanoparticles as promising delivery vehicles in cancer therapy. In particular, among various nanoparticles, the mesoporous silica nanoparticles (MSN) exhibit numerous outstanding features, including mechanical thermal and chemical stability, huge surface area and ordered porous interior to store different anti-cancer therapeutics with high loading capacity and tunable release mechanisms. Furthermore, one can easily decorate the surface of MSN by attaching ligands for active targeting specifically to the cancer region exploiting overexpressed receptors. The controlled release of drugs to the disease site without any leakage to healthy tissues can be achieved by employing environment responsive gatekeepers for the end-capping of MSN. To achieve precise cancer chemotherapy, the most desired delivery system should possess high loading efficiency, site-specificity and capacity of controlled release. In this review we will focus on multimodal decorations of MSN, which is the most demanding ongoing approach related to MSN application in cancer therapy. Herein, we will report about the recently tried efforts for multimodal modifications of MSN, exploiting both the active targeting and stimuli responsive behavior simultaneously, along with individual targeted delivery and stimuli responsive cancer therapy using MSN.

On-Demand Release of Protective Agents Triggered by Environmental Stimuli

The aim of this study was to develop smart materials with stimuli-responsive properties for the long-term protection of steel. The idea was to obtain a tailored and controlled release of protective agents in response to the environment stimuli. First, the protective efficacy of three inhibitors containing a carboxylic moiety, such as p-aminobenzoic (pAB), succinic (SA), and caffeic (CA) acids, was investigated in alkaline chloride solutions. The results revealed that pAB is the most effective protective agent, significantly better than SA and CA. It is surprising that the steel surface in the pAB solution remains unchanged even after 5 months of corrosion treatment, whereas the formation of degradation products in the SA and CA solutions was observed after only 6 days. Based on these findings, pAB was selected and used for the functionalization of silica nanoparticles and layered double hydroxides (LDHs) that can act as delivery vehicles and as an inhibitor reservoir. Specifically, pAB was chemisorbed on silica amino groups via an amide bond, and this makes possible a gradual inhibitor release induced by an alkaline environment. The intercalation of pAB in its anionic form into the LDHs structure is responsible for a completely different behavior since the release is induced by chloride ions and occurs by an anionic exchange reaction. Thus, these materials play a dual role by acting as an inhibitor reservoir and by capturing chlorides. These findings reveal that it is possible to create a reservoir of corrosion inhibitors gradually released on demand based on the chemical environment. The stimuli-responsive properties and the complementary protective action of inhibitor-loaded silica and LDHs make them attractive for the long-term protection of steel and open the way for innovative solutions in the preservation of concrete cultural heritage.

Stimuli-activatable nanomedicines for chemodynamic therapy of cancer

Chemodynamic therapy (CDT) takes the advantages of Fenton-type reactions triggered by endogenous chemical energy to generate highly cytotoxic hydroxyl radicals. As a novel modality for cancer treatment, CDT shows minimal invasiveness and high tumor specificity by responding to the acidic and the highly concentrated hydrogen peroxide microenvironment of tumor. The CDT approach for spatiotemporal controllable reactive oxygen species generation exhibits preferable therapeutic performance and satisfying biosafety. In this review article, we summarized the recent advances of stimuli-activatable nanomedicines for CDT. We also overviewed the strategies for augmenting CDT performance, including increasing the catalytic efficacy through rational design of the nanomaterials, modulating the reaction condition, inputting external energy field, and regulating the tumor microenvironment. Furthermore, we discussed the potential and challenges of stimuli-activatable nanomedicine for clinical translation and future development of CDT. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

Harnessed Dopant Block Copolymers Assist Decorating Membrane Pores: A Dissipative Particle Dynamics Study

Self-assembly of asymmetric block copolymers (BCPs) around active pore edges has emerged as an important strategy to produce smart membranes with tunable pathways for solute transport. However, thus far, it is still challenging to manipulate pore shape and functionality for directional transformation under external stimuli. Here, a versatile strategy by mesoscale simulations to design stimuli-responsive pores with various edge decorations in hybrid membranes is reported. Dopant BCPs are used as decorators to stabilize pore edges and extend their function in reconfiguring pores in response to repeated membrane stretching/shrinking caused by external stimuli. The decoration morphologies are predictable since the assemblies of dopant BCPs around pore edges are closely related to their self-assemblies in solution. The coassembly between different BCPs in the hybrid membrane for the control of pore morphology is featured, and the parameter settings, including block incompatibility and molecular architecture for the construction of a specific pore, are determined. Results show that harnessed dopant BCPs in the hybrid membrane can enhance pore formation and induce directional pore shape and functionality transformation. Diversified pore decorations exhibit potential that can be further explored in selective solute transport and the design of stimuli-responsive smart nanodevices.

Recent Advances and Future Prospects on Adaptive Biomaterials for Antimicrobial Applications

Bacterial infection is becoming the biggest threat to human health. The scenario is partly due to the ineffectiveness of the conventional antibiotic treatments against the emergence of multidrug-resistant bacteria and partly due to the bacteria living in biofilms or cells. Adaptive biomaterials can change their physicochemical properties in the microenvironment of bacterial infection, thereby facilitating either their interactions with bacteria or drug release. The trends in treating bacterial infections using adaptive biomaterials-based systems are flourishing and generate innumerous possibility to design novel antimicrobial therapeutics. This feature article aims to summarize the recent developments in the formulations, mechanisms, and advances of adaptive materials in bacterial infection diagnosis, contact killing of bacteria, and antimicrobial drug delivery. Also, the challenges and limitations of current antimicrobial treatments based on adaptive materials and their clinical and industrial future prospects are discussed.

Injectable Hydrogels for Localized Cancer Therapy

Traditional intravenous chemotherapy is relative to many systemic side effects, including myelosuppression, liver or kidney dysfunction, and neurotoxicity. As an alternative method, the injectable hydrogel can efficiently avoid these problems by releasing drugs topically at the tumor site. With advantages of localized drug toxicity in the tumor site, proper injectable hydrogel as the drug delivery system has become a research hotspot. Based on different types and stages of cancer, a variety of hydrogel drug delivery systems were developed, including thermosensitive, pH-sensitive, photosensitive, and dual-sensitive hydrogel. In this review, the latest developments of these hydrogels and related drug delivery systems were summarized. In summary, our increasing knowledge of injectable hydrogel for localized cancer therapy ensures us that it is a more durable and effective approach than traditional chemotherapy. Smart release system reacting to different stimuli at different time according to the micro-environment changes in the tumor site is a promising tendency for further studies.

Design of a pH-Responsive Conductive Nanocomposite Based on MWCNTs Stabilized in Water by Amphiphilic Block Copolymers

Homogeneous water dispersions of multi-walled carbon nanotubes (MWCNTs) were prepared by ultrasonication in the presence of an amphiphilic polystyrene-block-poly(acrylic acid) (PS-b-PAA) copolymer. The ability of PS-b-PAA to disperse and stabilize MWCTNs was investigated by UV-vis, SEM and zeta potential. The results show that the addition of a styrene block to PAA enhances the dispersion efficiency of the graphitic filler compared to pure PAA, possibly due to the nanotube affinity with the polystyrene moiety. Notably, the dispersions show an evident pH-responsive behavior, being MWCNTs reaggregation promoted in basic environment. It is worth noting that the responsive character is maintained in solid composites obtained by drop casting, thus indicating potential applications in sensing.

Enabling Robust Self-Folding Origami by Pre-Biasing Vertex Buckling Direction

Self-folding is a powerful approach to fabricate materials with complex 3D forms and advanced properties using planar patterning steps, but suffers from intrinsic limitations in robustness due to the highly bifurcated nature of configuration space around the flat state. Here, a simple mechanism is introduced to achieve robust self-folding of microscale origami by separating actuation into two discrete steps using different thermally responsive hydrogels. First, the vertices are pre-biased to move in the desired direction from the flat state by selectively swelling one of the two hydrogels at high temperature. Subsequently, the creases are folded toward their target angles by activating swelling of the second hydrogel upon cooling to room temperature. Since each vertex can be individually programmed to move upward or downward, it is possible to robustly select the desired branch even in multi-vertex structures with reasonably high complexity. This strategy provides key new principles for designing shaping-morphing materials that avoid undesired distractor states, expanding their potential applications in areas such as soft robotics, sensors, mechanical metamaterials, and deployable devices.

Elaboration and Characterization of Conductive Polymer Nanocomposites with Potential Use as Electrically Driven Membranes

In this work, a general, facile, and relatively low-cost method to produce electrically driven non-porous membranes by revalorization of recycled polyolefins is proposed. The polymer matrices are poly(propylene) (PP) and poly(ethylene) (PE) and their corresponding recycled samples, which are respectively mixed with carbon nanotubes (CNT). The performances of the elaborated nanocomposites are studied by morphological, rheological, and electrical conductivity tests. The Joule heating effect is evaluated by applying an electric field and recording the corresponding temperature rise. An increase of 90 °C is obtained in certain cases, which represents the highest temperature enhancement reached so far by the Joule effect in thermoplastics, to our knowledge. The work shows a route to develop stimulus (voltage)-response (temperature) materials with low cost and with potential applications in many fields. As an example, the increase of the permeability with temperature of membranes made of the indicated nanocomposites, is analyzed.

How Defects Control the Out-of-Equilibrium Dissipative Evolution of a Supramolecular Tubule

Supramolecular architectures that work out-of-equilibrium or that can change in specific ways when absorbing external energy are ubiquitous in nature. Gaining the ability to create via self-assembly artificial materials possessing such fascinating behaviors would have a major impact in many fields. However, the rational design of similar dynamic structures requires to understand and, even more challenging, to learn how to master the molecular mechanisms governing how the assembled systems evolve far from the equilibrium. Typically, this represents a daunting challenge due to the limited molecular insight that can be obtained by the experiments or by classical modeling approaches. Here we combine coarse-grained molecular models and advanced simulation approaches to study at submolecular (<5 Å) resolution a supramolecular tubule, which breaks and disassembles upon absorption of light energy triggering isomerization of its azobenzene-containing monomers. Our approach allows us to investigate the molecular mechanism of monomer transition in the assembly and to elucidate the kinetic process for the accumulation of the transitions in the system. Despite the stochastic nature of the excitation process, we demonstrate how these tubules preferentially dissipate the absorbed energy locally via the amplification of defects in their supramolecular structure. We find that this constitutes the best kinetic pathway for accumulating monomer transitions in the system, which determines the dynamic evolution out-of-equilibrium and the brittle behavior of the assembly under perturbed conditions. Thanks to the flexibility of our models, we finally come out with a general principle, where defects explain and control the brittle/soft behavior of such light-responsive assemblies.

Metal-Organic Framework-Based Stimuli-Responsive Systems for Drug Delivery

With the rapid development of nanotechnology, stimuli-responsive nanomaterials have provided an alternative for designing controllable drug delivery systems due to their spatiotemporally controllable properties. As a new type of porous material, metal-organic frameworks (MOFs) have been widely used in biomedical applications, especially drug delivery systems, owing to their tunable pore size, high surface area and pore volume, and easy surface modification. Here, recent progress in MOF-based stimuli-responsive systems is presented, including pH-, magnetic-, ion-, temperature-, pressure-, light-, humidity-, redox-, and multiple stimuli-responsive systems for the delivery of anticancer drugs. The remaining challenges and suggestions for future directions for the rational design of MOF-based nanomedicines are also discussed.

Dielectric and Resistive Heating of Polymeric Media: Toward Remote Thermal Activation of Stimuli-Responsive Soft Materials

Stimuli-responsive soft materials are becoming increasingly important in a wide range of contemporary technologies, and methods by which to promote thermal stimulation remotely are of considerable interest for controllable device deployment, particularly in inaccessible environments such as outer space. Until now, remote thermal stimulation of responsive polymers has relied extensively on the use of nanocomposites wherein embedded nanoparticles/structures are selectively targeted for heating purposes. In this study, an alternative remote-heating mechanism demonstrates that the dielectric and resistive thermal losses introduced upon application of an alternating current generate sufficient heat to raise the temperature of a neat polyimide by over 70 °C within ≈10 s. Thermal imaging is used here to measure current-induced temperature changes of polymeric media, and a proposed analytical model yields predictions that compare reasonably well with experimental data, confirming that such remote heating is viable. Conditions permitting a shape-memory polymer possessing a melting transition and susceptible to dielectric actuation to achieve continuous electrostrain-temperature cycling are identified.

Endogenous Stimuli-Responsive Nucleus-Targeted Nanocarrier for Intracellular mRNA Imaging and Drug Delivery

Drug resistance arising from overexpressed efflux transporters increases the efflux of drugs and accordingly restricts the efficacy of chemotherapy. Advances in nanocarriers have provided potential strategies to cope with drug resistance. Herein, endogenous stimuli-responsive nucleus-targeted nanocarrier is developed for intracellular multidrug resistance protein 1 (MRP1) mRNA imaging and drug delivery. This nanocarrier (AuNP-mRS-DSs) is composed of three parts: (i) gold nanoparticle (AuNP), for loading DNA and quenching fluorescence; (ii) mRNA recognition sequence (mRS) modified on the surface of gold nanoparticle by gold-thiol bond, for the specific recognition of MRP1 mRNA; (iii) detachable subunit (DS), hybridized with Cy5-labeled DNA linker and nucleolin recognition motif and grafted onto mRS via the DNA linker for loading doxorubicin (Dox), binding to nucleolin, and reporting signal. First, nucleolin recognition motif of this nanocarrier targets nucleolin, which is overexpressed on cancer cells surface; subsequently, the whole nanocarrier enters the cell via nucleolin-mediated internalization. Subsequently, mRS will specifically recognize overexpressed MRP1 mRNA, leading to the release of trapped DS and followed by AuNP-quenched Cy5 fluorescence recovery. Finally, by translocation of nucleolin from cytoplasm to nucleus, the DS targets nucleus to delivery Dox. By intracellular fluorescence imaging, the differentiation of drug-resistant and nondrug-resistant cells could be achieved. Compared with free Dox (IC50 > 8.00 μM), Dox-loaded AuNP-mRS-DSs (IC50 = 2.20 μM) performed superior suppression efficacy toward drug-resistant cancer cells. Such a nanocarrier provides an effective strategy to synergistically sense and circumvent drug resistance, which may be exploited as a candidate for personalized medicine.

Chemical Tuning of Zwitterionic Ionic Liquids for Variable Thermophysical Behaviours, Nanostructured Aggregates and Dual-Stimuli Responsiveness

The design and synthesis of a series of zwitterionic ionic liquids (ZILs) to understand the structure-property relationship towards an increase of the thermal stability, a variation of the glass transition temperature, the shape-tuning of nanostructured aggregates and the tuning of the stimuli responsiveness are demonstrated. The substitution reaction of imidazole with various aliphatic and aromatic bromides followed by the reaction of the corresponding substituted imidazoles with bromoalkyl carboxylic acids of varying spacer length produces the ZILs. In aqueous solution, a ZIL molecule either exist in its ionic liquid (substituted imidazolium bromide) form or its zwitterionic (substituted imidazolium alkyl carboxylate) form with an isoelectric point (pI) depending on the pH value of the solution. Upon changing the pH to near or above the pI, the aqueous ZIL solution undergoes transition from a transparent to a turbid phase due to the formation of insoluble hierarchical nanostructured aggregates of various morphologies, such as spheres, tripods, tetrapods, fern-like, flower-like, dendrites etc. depending on the pH of the solution and the nature of the alkyl/vinyl/aryl substituents. Upon heating the solution a phase transition occurs from turbid to transparent, exhibiting a distinct reversible upper critical solution temperature (UCST)-type cloud point (T_cp ). It is observed that the cloud point varies with the nature of the substituent, an increase of the concentration of the ZIL as well as with changes of the pH of the solution.

Stimuli Responsive Polymeric Systems for Cancer Therapy

Nanoscale polymers systems have dominated the revolution of drug delivery advancement. Their potential in the fight against cancer is unrivalled with other technologies. Their functionality increase, targeting ability and stimuli responsive nature have led to a major boom in research focus. This review article concentrates on the use of these smart polymers in cancer therapy. Nanotechnologies have shown potential as drug carriers leading to increased drug efficacy and penetration. Multifunctional smart carriers which can release their payload upon an external or internal trigger such as pH or temperature are proving to be major frontrunners in the development of effective strategies to overcome this disease with minimal patient side effects.