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Reactive oxygen species (ROS), acting as essential mediators in the biological system, highly influence the physiologic and pathologic processes of the human body. The aberrant production of ROS, caused by various diseases, may lead to inflammation and cellular damages, as well as homeostasis disruption. In recent years, biomaterials sensitive to biological stimuli have received increasing attention due to their potential for achieving more specific diagnoses and effective treatments. Particularly, ROS-responsive biomaterials could be triggered by ROS in the damaged tissue microenvironment to release their payloads or exert a therapeutically beneficial effect, consequently regulating the elevated ROS level and downregulating the oxidative stress to promote tissue regeneration. In this review, we outline the underlying mechanisms of ROS generation in the tissue microenvironment of various diseases and summarize the cutting-edge advances in developing ROS-responsive biomaterials to expedite inflammation-related diseases, regenerative medicine and tissue engineering applications in various body systems. In particular, we pointed out the challenges and shortcomings that the current ROS-sensitive materials encounter, offer distinctive insights into the field and present solutions or improved strategies.

Shape memory polymers (SMPs) is a type of smart polymers. Shape-memory polymers (SMPs) allow for the development of stimuli-responsive polymer-based materials that can undergo substantial recoverable deformation in response to an external stimulus. Shape-memory effects (SMEs) of these SMP-based materials for task-specific applications are picking the interest of academic and industrial researchers. Significant progress has been gained in the field of shape memory polymers (SMPs) in recent years, with the discovery of new compositions for property tweaking, the discovery of new processes for shape fixing and recovery, and the initiation of phenomenological modelling. The current review will provide a brief account of the history of SMPs, their qualities, their structure and mechanism, classification, biodegradable SMPs and use of SMPs in various fields. Recent advancements in shape memory polymer composites (SMPCs) and shape-memory polymer blends (SMPBs) are also emphasized. This review explains distinct classification criteria of SMPs with a view of polymer type and structure and external stimulation. [ABSTRACT FROM AUTHOR]

Responsive polymeric materials that are sensitive to biological stimuli including temperature, pH, enzymes, or redox conditions have attracted research interest in recent years. Among these, reactive oxygen species (ROS)-responsive polymers are particularly appealing because of the special role of ROS in living organisms. ROS are the indicator and cause of certain diseases, and they are also important signaling molecules. ROS-responsive polymers could possess the following functions: drug carriers, ROS probes, or medications for certain ROS-related diseases. In this review, we analyze the progress about ROS-responsive polymers made in recent years and predict the future trends of ROS-responsive polymers from the above mentioned perspectives. Due to the limited scope of this review, some older articles are not covered here and are left for more comprehensive reviews. [ABSTRACT FROM AUTHOR]

The mechanical addressability of specific chemical bonds holds a high potential for the improvement of polymeric materials. While in many cases, mechanical forces applied to polymers lead to bond scissoring and materials failure, including mechanophores into the polymer structure can lead to stimuli-responsive materials reacting to an applied force in a predefined manner. In this contribution, the mechanical addressability of bis-terpyridine metal complexes embedded into a polymer structure is investigated. The activation of the transition metal complexes in the metallopolymer is monitored by adding a fluorescent sensor molecule to the metallopolymer solution during ultrasonication. Upon sonication, the activation of the complexes leads to fluorescence-quenching of the sensor. The dependency of the metal ion and the type of polymer as well as their molar mass is investigated in detail, showing that this concept could possibly be used in further application of stimuli-responsive or self-healing materials. [ABSTRACT FROM AUTHOR]

Polymers that bear reversible massive, physical or chemical changes in response to little peripheral changes within the environmental conditions are Smart polymers, having versatility and tunable sensitivity. They have very promising applications in the biomedical field. This study will delve into the underlying principles along with entire features of these sensitive polymers and their most current and relevant applications to solve biological problems. [ABSTRACT FROM AUTHOR]

The engineering of human tissues to cure diseases is an interdisciplinary and a very attractive field of research both in academia and the biotechnology industrial sector. Three-dimensional (3D) biomaterial scaffolds can play a critical role in the development of new tissue morphogenesis via interacting with human cells. Although simple polymeric biomaterials can provide mechanical and physical properties required for tissue development, insufficient biomimetic property and lack of interactions with human progenitor cells remain problematic for the promotion of functional tissue formation. Therefore, the developments of advanced functional biomaterials that respond to stimulus could be the next choice to generate smart 3D biomimetic scaffolds, actively interacting with human stem cells and progenitors along with structural integrity to form functional tissue within a short period. To date, smart biomaterials are designed to interact with biological systems for a wide range of biomedical applications, from the delivery of bioactive molecules and cell adhesion mediators to cellular functioning for the engineering of functional tissues to treat diseases. [ABSTRACT FROM AUTHOR]

In this work, a novel thermo-responsive Fe3O4/poly(methylmethacrylate-b-N-isopropylacrylamide-b-acrylic acid) magnetic composite nanosphere was synthesized for anticancer drug delivery applications. For this propose, the poly(methylmethacrylate-b-N-isopropylacrylamide-b-acrylic acid) [poly (MMA-b-NIPAAm-b-AAc)] was synthesized via reversible addition-fragmentation transfer method. The physic-chemical characterization of the Fe3O4/poly(MMA-b-NIPAAm-b-AAc) magnetic composite nanosphere was investigated by FTIR, HNMR spectroscopies and GPC, FESEM, XRD, VSM and DLS. The thermo-sensitivity of the Fe3O4/P(MMA-b-NIPAAm-b-AAc) magnetic composite nanosphere was confirmed via DLS at 40 °C. DOX encapsulation efficiency was calculated to be 98.2%. The effect of temperature and pH on release behaviors of stimuli responsive DOX-loaded Fe3O4/P(MMA-b-NIPAAm-b-AAc)] magnetic composite nanosphere were investigated. The release rate at pH 7.4, 5.4 and 4 (T = 37 °C) was reached about 24.4, 42.4 and 57.5 wt%, after 4–5 day. The release rate improved at tumor simulated environment (t:40 °C and pH ≤ 5.4). The cytotoxic effects of the magnetic composite nanosphere were appraised by MTT assay and the results indicated that novel developed smart nanocomposite here was nontoxic to MCF-7 cells and can be applied as anti-cancer drug delivery system. Also, the results of the Cellular uptake of MCF7 cells treated with rhodamine labeled DOX-loaded nanocarrier for 2 h have indicated that DOX can be applied as cytotoxic agent and targeting ligand. [ABSTRACT FROM AUTHOR]

A new block copolymer with a temperature-responsive block and a cationic block was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization, with good control of its size and composition. The first block is composed by di(ethylene glycol)methyl ethermethacrylate (DEGMA) and oligo(ethylene glycol) methyl ether methacrylate (OEGMA), with the ratio DEGMA/OEGMA being used to choose the volume phase transition temperature of the polymer in water, tunable from ca. 25 to above 90 °C. The second block, of trimethyl-2-methacroyloxyethylammonium chloride (TMEC), is positively charged at physiological pH values and is used for DNA binding. The coacervate complexes between the block copolymer and a model single strand DNA are characterized by fluorescence correlation spectroscopy and fluorescence spectroscopy. The new materials offer good prospects for biomedical application, for example in controlled gene delivery. [ABSTRACT FROM AUTHOR]

Thermoresponsive polymer-modified microfibers were prepared through electrospinning of poly(4-vinylbenzyl chloride) (PVBC) and subsequent surface-initiated atom transfer radical polymerization for grafting poly( N -isopropylacrylamide) (PIPAAm). Electrospinning conditions were optimized to produce large-diameter (20 μm) PVBC microfibers. The amount of PIPAAm grafted on the microfibers was controlled via the IPAAm monomer concentration. The microfibers exhibited thermally controlled cell separation by selective adhesion of normal human dermal fibroblasts in a mixed cell suspension that also contained human umbilical vein endothelial cells. In addition, adipose-derived stem cells (ADSCs) exhibited thermally modulated cell adhesion and detachment, while adhesion of other ADSC-related cells was low. Thus, ADSCs could be separated from a mixture of adipose tissue-derived cells simply by changing the temperature. Overall, the PIPAAm-modified microfibers are potentially applicable as temperature-modulated cell separation materials. Statement of Significance Thermoresponsive poly( N -isopropylacrylamide) (PIPAAm) polymer-modified poly(4-vinylbenzyl chloride) (PVBC) microfibers were prepared via electrospinning of PVBC, followed by surface-initiated ATRP. They formed effective thermally-modulated cell separation materials with large surface areas. Cells adhered and extended along the modified microfibers; this was not observed on previously reported PIPAAm-modified flat substrates. The cellular adhesion enabled separation of fibroblast cells, as well as that of adipose-derived mesenchymal stem cells, from mixtures of similar cells. Thus, the temperature-controlled thermoresponsive microfibers would be potentially useful as cell separation materials. [ABSTRACT FROM AUTHOR]

Therapeutic proteins and peptides have become notable in the drug delivery arena for their compatibility with the human body as well as their high potency. However, their biocompatibility and high potency does not negate the existence of challenges resulting from physicochemical properties of proteins and peptides, including large size, short half-life, capability to provoke immune responses and susceptibility to degradation. Various delivery routes and delivery systems have been utilized to improve bioavailability, patient acceptability and reduce biodegradation. The ocular route remains of great interest, particularly for responsive delivery of macromolecules due to the anatomy and physiology of the eye that makes it a sensitive and complex environment. Research in this field is slowly gaining attention as this could be the breakthrough in ocular drug delivery of macromolecules. This work reviews stimuli-responsive polymeric delivery systems, their use in the delivery of therapeutic proteins and peptides as well as examples of proteins and peptides used in the treatment of ocular disorders. Stimuli reviewed include pH, temperature, enzymes, light, ultrasound and magnetic field. In addition, it discusses the current progress in responsive ocular drug delivery. Furthermore, it explores future prospects in the use of stimuli-responsive polymers for ocular delivery of proteins and peptides. Stimuli-responsive polymers offer great potential in improving the delivery of ocular therapeutics, therefore there is a need to consider them in order to guarantee a local, sustained and ideal delivery of ocular proteins and peptides, evading tissue invasion and systemic side-effects. [ABSTRACT FROM AUTHOR]

ABSTRACT Similar to shape memory, the stress in a stimulus responsive polymer can also be programmed, stored, and retrieved reversibly upon an external stimulus, and known as stress memory. Herein, the stress analysis in a semicrystalline polyurethane is investigated to unveil the total stress-strain components of the memory polymer. The evolution of stress under different temperature and strain levels is determined experimentally. A constitutive model based on phase transition was further used to predict and characterize the individual stress components during the thermomechanical process. In contrast to earlier models, a new approach of using relaxed modulus (RM) has been proposed to predict the stress components in tensile programming condition. The predicted results are having significant agreement with the experimental data. The quantitative stress analysis can help in engineering the products more precisely, where the controllable stimulus responsive stress is needed in multidisciplinary arenas such as pressure garments, massage devices, and artificial muscles etc. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 941-947 [ABSTRACT FROM AUTHOR]

ABSTRACT Like shape memory polymers, a novel phenomenon of stress memory was shown in which the stress of a material can respond to an external stimulus. This concept was further enlightened by a switch-spring-frame model that would eliminate the limitation of existing models which overlooked the stimulus responsive nature of such polymers. The discovery being reported in this article was stemmed from a real case study into shape memory polymer fibers in compression stocking for varicose veins. The breakthrough of stress memory enabled researchers to develop applications needing stimuli-responsive forces, which can broaden the horizon of such smart polymers in emerging smart products in many multidisciplinary fields such as sensors, stress garments, and massage devices, electronic skins, and artificial muscles. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 893-898 [ABSTRACT FROM AUTHOR]

• Fluorescent sensing label TPE/PMAA/Rh B was developed for fish freshness monitoring. • Sensing label showed ratiometric fluorescence changing from pink to blue during the spoilage trial. • Aggregation-induced emissive TPE/PMAA polymer is a key factor for the sensing process. • Sensing label is suitable for real-time fish freshness monitoring by naked eyes. • Sensing label is capable of evaluating TVB-N content based on delta E values. Freshness is an important parameter of fish quality. This study aims to develop a ratiometric fluorescent sensing label that is responsive to volatile amines, affording real-time and visual detection of fish freshness. For developing of the sensing label, an aggregation-induced emissive (AIE) polymer was prepared from the stimuli-responsive polymer polymethacrylic acid and the AIE molecule tetraphenylethylene and coated on to filter paper with rhodamine B as an internal reference. By exploiting the ratiometric response, the freshness of fish could be identified clearly and easily according to the color of on-package label, which changes from pink (fresh) to dark blue. The difference was linearly correlated with the total volatile basic nitrogen (TVB-N, R2 = 0.995 and 0.994 at 25 °C and 4 °C, respectively) in the range of 15–25 mg/100 g for the salmon samples, which indicated that the sensing label feasibly and non-destructively quantified TVB-N. [ABSTRACT FROM AUTHOR]

Abstract: Synthesis, characterization, and applications of novel thermoresponsive polymeric coatings for quantum dots (QDs) are presented. Comb-copolymers featuring hydrophobic alkyl groups, carboxylic groups and poly(N-isopropylacrylamide) (PNIPAM) side chains with molar masses ranging from 1000g/mol to 25,400g/mol were obtained. The amphiphilic comb-copolymers were shown to efficiently transfer the QDs to aqueous media. The PNIPAM-coated QD materials display a lower critical solution temperature (LCST). The absorbance, luminescence emission, size of the assemblies, and electrophoretic mobility were followed as a function of temperature and the reversibility of the temperature induced changes is demonstrated by cyclic heating and cooling. [Copyright &y& Elsevier]

Sensitive polymers with external physical, chemical, and electrical stimuli are termed as ‘intelligent materials’ and currently have been used in variety fields of engineering, and medicine. Numerous research papers utilizing stimuli-responsive intelligent materials are found in the literature to date. In this manuscript, the authors described several applications of surfaces and interfaces modified with stimuli-responsive polymers for stimuli-responsive surface property alteration and their application for the separation sciences. The special attention is paid to the temperature responsive polymers, poly(N-isopropylacrylamide) (PIPAAm) and its derivatives as surface modifiers for novel ‘green’ chromatography in which only aqueous mobile phase was utilized for separation of bioactive compounds. Several factors were investigated and discussed the effects on separation of bioactive compounds; these include the effects of the temperature-responsive hydrophilic/hydrophobic changes, copolymer composition, graft polymer molecular architecture and the incorporation of charged groups. Furthermore, application of PIPAAm-grafted surfaces for affinity separation of proteins will be discussed. The technique has superior characteristics in reducing organic wastes and costs to run chromatographic separation, and thus must be an environmentally friendly separation tool. [Copyright &y& Elsevier]

In the current study, an acrylic polymer binder applicable to road signs was successfully developed by mixing various acrylic, acrylate-type, and photoinitiator-based monomer species at different acrylate series/silicone acrylate ratios. An amorphous acrylic monomer was used, and the distance between the polymers was increased to improve transparency. The binder was designed with the purpose of reducing the yellowing phenomenon due to resonance by excluding the aromatic ring structure, which is the main cause of yellowing. The optical properties of the binder were determined according to the content of n-butyl methacrylate/methyl methacrylate and the composition of the crosslinking agent in the formulation. Allyl glycidyl ether and dilauroyl peroxide were used to improve the yellowing problem of benzoyl peroxide, an aromatic photoinitiator. Adding a silicone-based trivalent acrylic monomer, 3-(trimethoxysilyl)propyl methacrylate (TMSPMA), was also found to have a significant effect on the transparency, shear properties, and water resistance of the binder. When 15 wt% TMSPMA was added, the best water repellency and mechanical properties were exhibited. The surface morphology of the improved binder and the peeling part were confirmed using field emission scanning electron microscopy. The acrylic polymer developed in this study can be applied in the coating and adhesive industries.

Mesoporous silica nanoparticles (MSNs) primed with RAFT agent were synthesized via co-condensation of tetraethoxysilane (TEOS) and organoalkoxysilane based RAFT agent. The nature of the R group in organoalkoxysilane based RAFT agent was varied in order to control the preferential location of polymer grafting. Two different RAFT agents were prepared, one RAFT agent contained phenyl ethyl as R group, and other RAFT agent contained isobutyric acid as R group. The stability of the organoalkoxysilane based RAFT agents was confirmed employing UV–Visible spectroscopy and 1H solution NMR spectroscopy techniques. Succeeding this RAFT functionalized MSNs preparation, surface-initiated RAFT polymerization was carried out using N -isopropylacrylamide (NIPAM). RAFT and polymer functionalized MSNs were then characterized by diverse techniques such as FT-IR, TGA, UV–Visible spectroscopy, surface area measurement, X-ray photoelectron spectroscopy (XPS), 13C and 29Si solid-state NMR spectroscopy. The outcome of utilizing different types of organoalkoxysilane based RAFT agent on the morphology was examined using SEM and TEM. Spherical and cuboid shape was observed in the case of RAFT–COOH–MSNs and RAFT-Ph-MSNs respectively. Higher percentage of polymer grafting was observed in case of PNIPAM–COOH–MSNs in comparison to PNIPAM-Ph-MSNs. The realization of preferential grafting of polymer on exterior or interior surface of RAFT MSNs was established using pore size/volume analysis by BET as well as by XPS. The characteristic resonances in 13C and 29Si solid-state NMR and characteristic vibrations in FT-IR, confirms successful synthesis of organic-inorganic hybrids. The analysis of thermoresponsiveness of PNIPAM grafted MSNs was experimented by drug loading and release studies at different temperatures as well as by confocal laser scanning microscopy. Image 1 • MSNs primed with RAFT agent were synthesized via co-condensation of TEOS and organoalkoxysilane RAFT agent. • The nature of the R group was varied in order to control the preferential location of polymer grafting as well as morphology. • RAFT agent and polymer functionalized MSNs were characterized using variety of techniques. • Thermoresponsiveness of PNIPAM grafted MSNs was experimented by drug loading and release studies at different temperatures. [ABSTRACT FROM AUTHOR]

Shape memory polymers represent an interesting class of stimuli-responsive polymers. With their ability to memorize and recover their original shape, they could be useful in almost every area of our daily life. We herein present the synthesis of shape-memory metallopolymers in which the switching unit is designed by using bis(pyridine–triazole) metal complexes. The polymer networks were synthesized via free radical polymerization of methyl-, ethyl- or butyl-methacrylate, tri(ethylene glycol) dimethacrylate and a methacrylate moiety of the triazole–pyridine ligand. By the addition of zinc(II) or cobalt(II) acetate it was possible to achieve metallopolymer networks featuring shape-memory abilities. The successful formation of the metal-ligand complex was proven by Fourier transform infrared (FT-IR) spectroscopy and by 1H NMR spectroscopy. Furthermore, the shape-recovery behavior was studied in detailed fashion and even triple-shape memory behavior could be revealed. [ABSTRACT FROM AUTHOR]

In this study, we show that codeposition of temperature responsive microgels in the foulant cake layer and cleaning of the cake upon stimuli-induced size change of the microgels is an effective method of fouling removal. Humic acid in CaCl 2 solution was used as a model foulant and poly( n-isopropylacrylamide) (p(NIPAm)) and poly( n-isopropylacrylamide- co-sulfobetainemethacrylate) (p(NIPAm- co-SBMA)) were used as temperature responsive microgels. Filtrations were done below the lower critical solution temperature (LCST) and temperature was increased to above the LCST for cleaning. As an extra cleaning a temperature swing of above, below and then again above the LCST was applied. P(NIPAm) was found to be ineffective in cleaning the foulant deposit despite the 20-fold change in its volume with temperature change at LCST. P(NIPAm- co-SBMA) microgels, on the other hand, provided high fouling reversibility on hydrophilic poly(ether sulfone)(PES)/poly(vinylpyrrolidone) (PVP) and hydrophobic PES membranes. Better fouling reversibility with these microgels was observed at low and high solution ionic strength. While the use of microgels alone increased fouling reversibility to some extent, even in the absence of temperature stimulus, 100% reversibility could only be obtained when a temperature switch was applied in the presence of microgels, showing the effect of microgels' volume change in cleaning.

Implantation of a scaffold into the body in a safe and convenient manner remains a challenge in the repair of patient bone defect. In the present study, a strategy for fabrication of the redox-sensitive nanofibers with a core-shell structure that can deliver the growth factors in a tunable manner is presented. Poly(ethylene oxide) (PEO) and bone morphogenetic protein 2 (BMP-2) forms the inner core region, and a mixture of poly(epsilon-caprolactone) (PCL) and redox-responsive c-6A PEG-PCL nanogel with -S-S- bond forms the outer shell. The redox-sensitive shell of the nanofibers can respond the change of the GSH (glutathione) concentration and thus regulate the BMP-2 release behavior in vitro and in vivo. In vitro cytotoxicity results indicated that the redox-sensitive nanofiber had good osteoinduction. The in vivo results demonstrated that the nanofibers exhibited a capacity of prompting new bone generation in the bone defect. Therefore, the redox-responsive nanofiber in the present study may be of great potential for application in bone reconstruction.