Stimuli-Responsive Polymers at the Interface with Biology.

There has been growing interest in polymeric systems that break down or undergo property changes in response to stimuli. Such polymers can play important roles in biological systems, where they can be used to control the release of therapeutics, modulate imaging signals, actuate movement, or direct the growth of cells. In this Perspective, after discussing the most important stimuli relevant to biological applications, we will present a selection of recent exciting developments. The growing importance of stimuli-responsive polysaccharides will be discussed, followed by a variety of stimuli-responsive polymeric systems for the delivery of small molecule drugs and nucleic acids. Switchable polymers for the emerging area of therapeutic response measurement in theranostics will be described. Then, the diverse functions that can be achieved using hydrogels cross-linked covalently, as well as by various dynamic approaches will be presented. Finally, we will discuss some of the challenges and future perspectives for the field.

Stimuli-Responsive Polymers for Advanced 19F Magnetic Resonance Imaging: From Chemical Design to Biomedical Applications.

Fluorine magnetic resonance imaging (19F MRI) is a rapidly evolving research area with a high potential to advance the field of clinical diagnostics. In this review, we provide an overview of the recent progress in the field of fluorinated stimuli-responsive polymers applied as 19F MRI tracers. These polymers respond to internal or external stimuli (e.g., temperature, pH, oxidative stress, and specific molecules) by altering their physicochemical properties, such as self-assembly, drug release, and polymer degradation. Incorporating noninvasive 19F labels enables us to track the biodistribution of such polymers. Furthermore, by triggering polymer transformation, we can induce changes in 19F MRI signals, including attenuation, amplification, and chemical shift changes, to monitor alterations in the environment of the tracer. Ultimately, this review highlights the emerging potential of stimuli-responsive fluoropolymer 19F MRI tracers in the current context of polymer diagnostics research.

Stimuli-Responsive Polymersomes: Reshaping the Immunosuppressive Tumor Microenvironment.

The progression of cancer involves mutations in normal cells, leading to uncontrolled division and tissue destruction, highlighting the complexity of tumor microenvironments (TMEs). Immunotherapy has emerged as a transformative approach, yet the balance between efficacy and safety remains a challenge. Nanoparticles such as polymersomes offer the possibility to precisely target tumors, deliver drugs in a controlled way, effectively modulate the antitumor immunity, and notably reduce side effects. Herein, stimuli-responsive polymersomes, with capabilities for carrying multiple therapeutics, are highlighted for their potential in enhancing antitumor immunity through mechanisms like inducing immunogenic cell death and activating STING (stimulator of interferon genes), etc. The recent progress of utilizing stimuli-responsive polymersomes to reshape the TME is reviewed here. The advantages and limitations to applied stimuli-responsive polymersomes are outlined. Additionally, challenges and future prospects in leveraging polymersomes for cancer therapy are discussed, emphasizing the need for future research and clinical translation.

Stimuli-Responsive Polymeric Nanocarriers Accelerate On-Demand Drug Release to Combat Glioblastoma.

Glioblastoma multiforme (GBM) is a highly malignant brain tumor with a poor prognosis and limited treatment options. Drug delivery by stimuli-responsive nanocarriers holds great promise for improving the treatment modalities of GBM. At the beginning of the review, we highlighted the stimuli-active polymeric nanocarriers carrying therapies that potentially boost anti-GBM responses by employing endogenous (pH, redox, hypoxia, enzyme) or exogenous stimuli (light, ultrasonic, magnetic, temperature, radiation) as triggers for controlled drug release mainly via hydrophobic/hydrophilic transition, degradability, ionizability, etc. Modifying these nanocarriers with target ligands further enhanced their capacity to traverse the blood-brain barrier (BBB) and preferentially accumulate in glioma cells. These unique features potentially lead to more effective brain cancer treatment with minimal adverse reactions and superior therapeutic outcomes. Finally, the review summarizes the existing difficulties and future prospects in stimuli-responsive nanocarriers for treating GBM. Overall, this review offers theoretical guidelines for developing intelligent and versatile stimuli-responsive nanocarriers to facilitate precise drug delivery and treatment of GBM in clinical settings.

Stimuli-Responsive Polymers for Engineered Emulsions.

Emulsions are complex. Dispersing two immiscible phases, thus expanding an interface, requires effort to achieve and the resultant dispersion is thermodynamically unstable, driving the system toward coalescence. Furthermore, physical instabilities, including creaming, arise due to presence of dispersed droplets of different densities to a continuous phase. Emulsions allow the formulation of oils, can act as vehicles to solubilize both hydrophilic and lipophilic molecules, and can be tailored to desirable rheological profiles, including "gel-like" behavior and shear thinning. The usefulness of emulsions can be further expanded by imparting stimuli-responsive or "smart" behaviors by inclusion of a stimuli-responsive emulsifier, polymer or surfactant. This enables manipulation like gelation, breaking, or aggregation, by external triggers such as pH, temperature, or salt concentration changes. This platform generates functional materials for pharmaceuticals, cosmetics, oil recovery, and colloid engineering, combining both smart behaviors and intrinsic benefit of emulsions. However, with increased functionality comes greater complexity. This review focuses on the use of stimuli-responsive polymers for the generation of smart emulsions, motivated by the great adaptability of polymers for this application and their efficacy as steric stabilizers. Stimuli-responsive emulsions are described according to the trigger used to provide the reader with an overview of progress in this field.

Programming colloidal bonding using DNA strand-displacement circuitry.

As a strategy for regulating entropy, thermal annealing is a commonly adopted approach for controlling dynamic pathways in colloid assembly. By coupling DNA strand-displacement circuits with DNA-functionalized colloid assembly, we developed an enthalpy-mediated strategy for achieving the same goal while working at a constant temperature. Using this tractable approach allows colloidal bonding to be programmed for synchronization with colloid assembly, thereby realizing the optimal programmability of DNA-functionalized colloids. We applied this strategy to conditionally activate colloid assembly and dynamically switch colloid identities by reconfiguring DNA molecular architectures, thereby achieving orderly structural transformations; leveraging the advantage of room-temperature assembly, we used this method to prepare a lattice of temperature-sensitive proteins and gold nanoparticles. This approach bridges two subfields: dynamic DNA nanotechnology and DNA-functionalized colloid programming.

Redox Responsive Copolyoxalate Smart Polymers for Inflammation and Other Aging-Associated Diseases.

Polyoxalate (POx) and copolyoxalate (CPOx) smart polymers are topics of interest the field of inflammation. This is due to their drug delivery ability and their potential to target reactive oxygen species (ROS) and to accommodate small molecules such as curcumin, vanilline, and p-Hydroxybenzyl alcohol. Their biocompatibility, ultra-size tunable characteristics and bioimaging features are remarkable. In this review we discuss the genesis and concept of oxylate smart polymer-based particles and a few innovative systemic delivery methods that is designed to counteract the inflammation and other aging-associated diseases (AADs). First, we introduce the ROS and its role in human physiology. Second, we discuss the polymers and methods of incorporating small molecule in oxalate backbone and its drug delivery application. Finally, we revealed some novel proof of concepts which were proven effective in disease models and discussed the challenges of oxylate polymers.

A review on recent advances in polymer and peptide hydrogels.

In this review, we focus on the very recent developments on the use of the stimuli responsive properties of polymer hydrogels for targeted drug delivery, tissue engineering, and biosensing utilizing their different optoelectronic properties. Besides, the stimuli-responsive hydrogels, the conducting polymer hydrogels are discussed, with specific attention to the energy generation and storage behavior of the xerogel derived from the hydrogel. The electronic and ionic conducting gels have been discussed that have applications in various electronic devices, e.g., organic field effect transistors, soft robotics, ionic skins, and sensors. The properties of polymer hybrid gels containing carbon nanomaterials have been exemplified here giving attention to applications in supercapacitors, dye sensitized solar cells, photocurrent switching, etc. Recent trends in the properties and applications of some natural polymer gels to produce thermal and acoustic insulating materials, drug delivery vehicles, self-healing material, tissue engineering, etc., are discussed. Besides the polymer gels, peptide gels of different dipeptides, tripeptides, oligopeptides, polypeptides, cyclic peptides, etc., are discussed, giving attention mainly to biosensing, bioimaging, and drug delivery applications. The properties of peptide-based hybrid hydrogels with polymers, nanoparticles, nucleotides, fullerene, etc., are discussed, giving specific attention to drug delivery, cell culture, bio-sensing, and bioimaging properties. Thus, the present review delineates, in short, the preparation, properties, and applications of different polymer and peptide hydrogels prepared in the past few years.

In Vitro and in Vivo Optimization of Phase Sensitive Smart Polymer for Controlled Delivery of Rivastigmine for Treatment of Alzheimer's Disease.

PURPOSE: Alzheimer's disease is a neurodegenerative disorder, and most common form of dementia afflicting over 35 million people worldwide. Rivastigmine is a widely used therapeutic for ameliorating clinical manifestations of Alzheimer's disease. However, current treatments require frequent dosing either orally or via transdermal patch that lead to compliance issues and administration errors risking serious adverse effects. Our objective was to develop a smart polymer based delivery system for controlled release of rivastigmine over an extended period following a single subcutaneous injection. METHODS: Rivastigmine release was optimized by tailoring critical factors including polymer concentration, polymer composition, drug concentration, solvent composition, and drug hydrophobicity (rivastigmine tartrate vs base). Optimized in vitro formulation was evaluated in vivo for safety and efficacy. RESULTS: Formulation prepared using PLGA (50:50) at 5% w/v in 95:5 benzyl benzoate: benzoic acid demonstrated desirable controlled drug release characteristics in vitro. The formulation demonstrated sustained release of rivastigmine tartrate for 7 days in vivo with promising biocompatibility and acetylcholinesterase inhibition efficacy for 14 days. CONCLUSION: The results exemplify an easily injectable controlled release formulation of rivastigmine prepared using phase-sensitive smart polymer. The optimized formulation significantly increases the dosing interval, and can potentially improve patient compliance as well as quality of life of patients living with Alzheimer's disease.

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.

Designer Biopolymers: Self-Assembling Proteins and Nucleic Acids.

Nature has evolved sequence-controlled polymers such as DNA and proteins over its long history [...].

Stimuli-Responsive Materials for Tissue Engineering and Drug Delivery.

Smart or stimuli-responsive materials are an emerging class of materials used for tissue engineering and drug delivery. A variety of stimuli (including temperature, pH, redox-state, light, and magnet fields) are being investigated for their potential to change a material's properties, interactions, structure, and/or dimensions. The specificity of stimuli response, and ability to respond to endogenous cues inherently present in living systems provide possibilities to develop novel tissue engineering and drug delivery strategies (for example materials composed of stimuli responsive polymers that self-assemble or undergo phase transitions or morphology transformations). Herein, smart materials as controlled drug release vehicles for tissue engineering are described, highlighting their potential for the delivery of precise quantities of drugs at specific locations and times promoting the controlled repair or remodeling of tissues.

Development of 3D Hepatic Constructs Within Polysaccharide-Based Scaffolds with Tunable Properties.

Organoids production is a key tool for in vitro studies of physiopathological conditions, drug-induced toxicity assays, and for a potential use in regenerative medicine. Hence, it prompted studies on hepatic organoids and liver regeneration. Numerous attempts to produce hepatic constructs had often limited success due to a lack of viability or functionality. Moreover, most products could not be translated for clinical studies. The aim of this study was to develop functional and viable hepatic constructs using a 3D porous scaffold with an adjustable structure, devoid of any animal component, that could also be used as an in vivo implantable system. We used a combination of pharmaceutical grade pullulan and dextran with different porogen formulations to form crosslinked scaffolds with macroporosity ranging from 30 µm to several hundreds of microns. Polysaccharide scaffolds were easy to prepare and to handle, and allowed confocal observations thanks to their transparency. A simple seeding method allowed a rapid impregnation of the scaffolds with HepG2 cells and a homogeneous cell distribution within the scaffolds. Cells were viable over seven days and form spheroids of various geometries and sizes. Cells in 3D express hepatic markers albumin, HNF4α and CYP3A4, start to polarize and were sensitive to acetaminophen in a concentration-dependant manner. Therefore, this study depicts a proof of concept for organoid production in 3D scaffolds that could be prepared under GMP conditions for reliable drug-induced toxicity studies and for liver tissue engineering.

Long-Term Physical Aging Tracked by Advanced Thermal Analysis of Poly(N-Isopropylacrylamide): A Smart Polymer for Drug Delivery System.

Poly(N-isopropylacrylamide) (PNIPA), as a smart polymer, can be applied for drug delivery systems. This amorphous polymer can be exposed on a structural recovery process during the storage and transport of medicaments. For the physical aging times up to one year, the structural recovery for PNIPA was studied by advanced thermal analysis. The structural recovery process occurred during the storage of amorphous PNIPA below glass transition and could be monitored by the differential scanning calorimetry (DSC). The enthalpy relaxation (recovery) was observed as overshoot in change heat capacity at the glass transition region in the DSC during heating scan. The physical aging of PNIPA was studied isothermally at 400.15 K and also in the non-isothermal conditions. For the first time, the structural recovery process was analyzed in reference to absolute heat capacity and integral enthalpy in frame of their equilibrium solid and liquid PNIPA.

Design of high-performance curling mascara through utilization of smart thermoresponsive polymer.

OBJECTIVE: In this study, methoxy poly(ethylene glycol)-b-poly(D,L-lactide), or mPEG-PLA, was used as the smart thermoresponsive polymer in our mascara formulation. The utility of mPEG-PLA in a mascara formulation was investigated by a stepwise build-up in an oil in water (O/W) emulsion. The experimental results may pave the way to a strategy of developing more cosmetic formulation with thermoresponsive shape memory polymers (SMPs). METHOD: mPEG-PLA was first incorporated in a simple emulsion for rheological evaluation such as shear flow viscosity and small deformation oscillation measurements over the relevant temperature settings to mascara application. Then, wax and pigment were incorporated to complete the basic formulation as an O/W mascara and evaluated rheologically as before. Finally, the formulation was applied by a heated mascara applicator to false lashes to evaluate its curing and lifting effect. RESULTS: With 0.8% concentration of mPEG-PLA, the viscosity was able to increase from 0.20 Pas·s to 1.00 Pas·s. At 1.0% concentration of mPEG-PLA, the emulsion samples with mineral oil were evaluated from 55°C to 25°C for its storage modulus (G') and were found to have a consistent shear-thinning characteristic across all temperature range. The sample containing the polymer (M-1) arrived at a markedly higher elasticity when compared against the sample without (M-0). The same result holds true for the set of samples formulated with beeswax instead of mineral oil. When the formulations were applied with a heated mascara applicator on false eyelashes, the formulation containing mPEG-PLA was found to produce a more pronounced and longer-lasting curl. CONCLUSION: This preliminary rheological study of an O/W mascara containing mPEG-PLA demonstrated that thermoresponsive SMP can be added to enhance the curl and lifting effect of a mascara formulation.

OBJECTIFS: Dans cette étude, le méthoxy poly (éthylène glycol) -b-poly (D, L-lactide), ou mPEG-PLA, a été utilisé comme polymère thermosensible intelligent dans notre formulation de mascara. L'utilité du mPEG-PLA dans une formulation de mascara a été étudiée par une accumulation progressive dans une émulsion huile dans l'eau (H/E). Les résultats expérimentaux pourraient ouvrir la voie à une stratégie de développement des formulations cosmétiques avec des polymères à mémoire de forme thermosensibles (SMP). MÉTHODES: Le mPEG-PLA a d'abord été incorporé dans une émulsion simple pour l'évaluation rhéologique telle que la viscosité de l'écoulement de cisaillement et les mesures d'oscillation de petite déformation sur les réglages de température pertinents pour l'application du mascara. Ensuite, la cire et le pigment ont été incorporés pour compléter la formulation de base en tant que mascara H/E et évalués rhéologiquement comme auparavant. Enfin, la formulation a été appliquée par un applicateur de mascara chauffé sur les faux cils pour évaluer son effet durcissant et liftant. RÉSULTATS: Avec une concentration de 0,8% de mPEG-PLA, la viscosité a pu augmenter de 0,20 Pas · s à 1,00 Pas · s. À une concentration de 1,0% de mPEG-PLA, les échantillons d'émulsion avec de l'huile minérale ont été évalués de 55°C à 25°C pour son module de stockage (G') et se sont avérés avoir une caractéristique de cisaillement-amincissement cohérente dans toute la plage de températures. L'échantillon contenant le polymère (M-1) est arrivé à une élasticité nettement supérieure par rapport à l'échantillon sans (M-0). Le même résultat est vrai pour l'ensemble d'échantillons formulés avec de la cire d'abeille au lieu d'huile minérale. Lorsque les formulations ont été appliquées avec un applicateur de mascara chauffé sur de faux cils, la formulation contenant du mPEG-PLA s'est révélée produire une boucle plus prononcée et plus durable. CONCLUSION: Cette étude rhéologique préliminaire d'un mascara H/E contenant du mPEG-PLA a démontré que le SMP thermoréactif peut être ajouté pour améliorer l'effet de recourbement et de lifting d'une formulation de mascara.

Protein Assemblies: Nature-Inspired and Designed Nanostructures.

Ordered protein assemblies are attracting interest as next-generation biomaterials with a remarkable range of structural and functional properties, leading to potential applications in biocatalysis, materials templating, drug delivery and vaccine development. This Review covers ordered protein assemblies including protein nanowires/nanofibrils, nanorings, nanotubes, designed two- and three-dimensional ordered protein lattices and protein-like cages including polyhedral virus-like cage structures. The main focus is on designed ordered protein assemblies, in which the spatial organization of the proteins is controlled by tailored noncovalent interactions (including metal ion binding interactions, electrostatic interactions and ligand-receptor interactions among others) or by careful design of modified (mutant) proteins or de novo constructs. The modification of natural protein assemblies including bacterial S-layers and cage-like and rod-like viruses to impart novel function, e.g. enzymatic activity, is also considered. A diversity of structures have been created using distinct approaches, and this Review provides a summary of the state-of-the-art in the development of these systems, which have exceptional potential as advanced bionanomaterials for a diversity of applications.

Polymeric Carriers for Nucleic Acid Delivery: Current Designs and Future Directions.

Within the last two decades, a series of novel therapeutic nucleic acids entered research and clinical evaluation. Their differences both in biophysical properties as well as in mode and site of biological action provide polymer-based carriers with new delivery challenges. Recent tailor-made designs of polymeric carriers are reviewed that were optimized for nucleic acid cargos such as plasmid DNA, siRNA, and micro RNA, mRNA, or genome-modifying nucleic acids. The specific requirements for the various therapeutic cargos are discussed. Future directions include dynamic bioresponsive polymers as components of nanomachines, multifunctional sequence-defined carriers for evolution-based selective optimization, and organic-inorganic multicomponent nanoassemblies.

Bioperspectives for Shape-Memory Polymers as Shape Programmable, Active Materials.

Within the natural world, organisms use information stored in their material structure to generate a physical response to a wide variety of environmental changes. The ability to program synthetic materials to intrinsically respond to environmental changes in a similar manner has the potential to revolutionize material science. By designing polymeric devices capable of responsively changing shape or behavior based on information encoded into their structure, we can create functional physical behavior, including a shape-memory and an actuation capability. Here we highlight the stimuli-responsiveness and shape-changing ability of biological materials and biopolymer-based materials, plus their potential biomedical application, providing a bioperspective on shape-memory materials. We address strategies to incorporate a shape-memory (actuation) function in polymeric materials, conceptualized in terms of its relationship with inputs (environmental stimuli) and outputs (shape change). Challenges and opportunities associated with the integration of several functions in a single material body to achieve multifunctionality are discussed. Finally, we describe how elements that sense, convert, and transmit stimuli have been used to create multisensitive materials.

Spirocyclic Acetal-Modified Dextran as a Flexible pH-Sensitive Solubility-Switching Material.

Bioresponsive polymers can enable the development of more effective drug delivery vehicles and medical materials. Acetal-modified polysaccharides allow pH-triggered solubility switching in a versatile and effective manner, but prior work has been limited to a combination of acyclic alkoxyisopropyl and cyclic isopropylidene acetals. We describe here the preparation and characterization of spirocyclic acetal-modified dextran (SpAc-Dex), which comprises dextran decorated with cyclopentyl, cyclohexyl, or cycloheptyl acetals (SpAc5-, SpAc6-, and SpAc7-Dex, respectively). A library of materials with varying acyclic and cyclic acetal contents was synthesized, and organic-soluble materials were formed into microparticles and assessed for degradability and cytocompatibility. At high levels of modification, SpAc5-Dex degraded most quickly and SpAc7-Dex degraded most slowly. SpAc6-Dex features lower degrees of substitution but spans a wide range of degradability. These materials were found to be noncytotoxic and may find future use in biomedical applications.

Enzymatic Activity in Fractal Networks of Self-Assembling Peptides.

The tissue environment is exceptionally complex, with well-controlled biochemical communication occurring between similar and dissimilar cells as well as between these cells and local extracellular matrices (ECM). To build an artificial ECM that can directly affect regional cell populations, a designer system should allow for controlled degradation, molecular release, and reorganization as related to local cellular function. (RADA)4 self-assembling peptide (SAP) hydrogels are excellent candidates for precisely tuned ECMs, or nanoscaffolds, with several beneficial qualities. They are a class of materials with uncomplicated fabrication and potentially allow for a diverse set of release strategies for many types of bioactive ligands. Enzyme-induced degradation and release of peptide sequences, synthesized within the SAP for on-demand cell signaling, could prove impactful to a plethora of human health applications. However, the degradation products and their release kinetics from these nanoscaffolds may greatly affect the overall system. To address this, enzyme kinetics in self-assembled hydrogels were studied by tethering matrix metalloproteinase 2 (MMP-2) cleavable peptide substrates of differing activities to the C-terminus of (RADA)4. High and low activity sequences, GPQG+IASQ (CP1) and GPQG+PAGQ (CP2), were respectively chosen for tunable release. When incubated with 5 nM MMP-2, over 3 days, both CP1 and CP2 sequences showed product formation values of ∼32% and ∼9% of the original substrate, respectively. On-demand product formation was found to be dependent upon both SAP composition and enzyme concentrations and could be tuned over the course of several days and weeks. Despite the fact that the self-assembling peptides are not directly cleavable by MMP-2, the CP1 and CP2 nanoscaffold morphology was visibly degraded by the protease. This degradation yielded a lower fractal dimensions for the matrix and suggested clearance of these materials may be possible over time.