Dynamic Colloidal Photonic Crystal Hydrogels with Self-Recovery and Injectability

Synthesis and thermally-induced gelation of interpenetrating nanogels

Thermally-induced in-situ gelation of polymers and nanogels is of significant importance for injectable non-invasive tissue engineering and delivery systems of drug delivery system. In this study, we for the first time demonstrated that the interpenetrating (IPN) nanogel with two networks of poly (N-isopropylacrylamide) (PNIPAM) and poly (N-Acryloyl-l-phenylalanine) (PAphe) underwent a reversible temperature-triggered sol-gel transition and formed a structural color gel above the phase transition temperature (Tp). Dynamic light scattering (DLS) studies confirmed that the Tp of IPN nanogels are the same as that of PNIPAM, independent of Aphe content of the IPN nanogels at pH of 6.5 ∼ 7.4. The rheological and optical properties of IPN nanogels during sol-gel transition were studied by rheometer and optical fiber spectroscopy. The results showed that the gelation time of the hydrogel photonic crystals assembled by IPN nanogel was affected by temperature, PAphe composition, concentration, and sequence of interpenetration. As the temperature rose above the Tp, the Bragg reflection peak of IPN nanogels exhibited blue shift due to the shrinkage of IPN nanogels. In addition, these colored IPN nanogels demonstrated good injectability and had no obvious cytotoxicity. These IPN nanogels will open an avenue to the preparation and thermally-induced in-situ gelation of novel NIPAM-based nanogel system.

Modeling order-disorder boundaries of colloidal dispersions in organic solvents using interaction force measurements

HYPOTHESIS

The formation of soft colloidal crystals, which are nonclose-packed ordered arrays of colloidal particles suspended in a solvent, is dictated by a single physical factor that yields a fixed threshold at order-disorder boundaries for different experimental conditions such as ion concentration, solvent type, and particle size. Identifying the determinant factor and its threshold value should enable the prediction of the critical concentrations of colloidal particles to form soft colloidal crystals.

EXPERIMENTS

Soft colloidal crystals were fabricated using a series of monohydric alcohols as dispersion media and reflectance spectra were measured to locate order-disorder boundaries. The interaction forces acting between particles were also measured by employing atomic force microscopy.

FINDINGS

The interparticle forces at the order-disorder boundaries exhibited a universal threshold that was independent of the solvent types including alcohols and water. Therefore, the determinant factor for the formation of soft colloidal crystals was determined to be the force acting between the particles. Furthermore, a priori calculation of this critical force and consequently the critical particle concentration in colloidal systems was demonstrated by referring to the pressure at the liquid-to-solid transition in a hard sphere system (Alder transition).

Bioactive Metal Ion-Coordinated Dynamic Hydrogel with Antibacterial, Immunomodulatory, and Angiogenic Activities for Infected Wound Repair

The repair of infected wounds is a complex physiopathologic process. Current studies on infected wound treatment have predominantly focused on infection treatment, while the factors related to delayed healing caused by vascular damage and immune imbalance are commonly overlooked. In this study, an extracellular matrix (ECM)-like dynamic and multifunctional hyaluronic acid (HA) hydrogel with antimicrobial, immunomodulatory, and angiogenic capabilities was designed as wound dressing for the treatment of infected skin wounds. The dynamic network in the hydrogel dressing was based on reversible metal-ligand coordination formed between sulfhydryl groups and bioactive metal ions. In our design, antibacterial silver and immunomodulatory zinc ions were employed to coordinate with sulfhydrylated HA and a vasculogenic peptide. In addition to the desired bioactivities for infected wounds, the hydrogel could also exhibit self-healing and injectable abilities. Animal experiments with infected skin wound models indicated that the hydrogel dressings enabled minimally invasive injection and seamless skin wound covering and then facilitated wound healing by efficient bacterial killing, continuous inflammation inhibition, and improved blood vessel formation. In conclusion, the metal ion-coordinated hydrogels with wound-infection-desired bioactivities and ECM-like dynamic structures represent a class of tissue bionic wound dressings for the treatment of infected and chronic inflammation wounds.

Preparation and properties of hydrogel photonic crystals assembled by biodegradable nanogels

Thermally induced physical hydrogels formed through the sol-gel transition of nanogels usually lose structural color above phase transition temperature (Tp). Herein, temperature/pH/redox-responsive nanogels that undergo sol-gel transition still keep structural colors above the Tp have been synthesized and studied. N-isopropylacrylamide (NIPAm) was copolymerized with N-tert-butylacrylamide (TBA) and N-acrylamido-l-phenylalanine (Aphe) to form P(NIPAm/TBA/Aphe) nanogel crosslinked with N,N'-bis(acryloyl)cystine (BISS) (referred to as PNTA-BISS). PNTA-BISS nanogel with a broad range of biodegradable crosslinker BISS content can achieve a reversible sol-gel transition above the Tp, surprisingly, while PNTA nanogels with a comparable content of biodegradable N,N'-Bis(acryloyl)cystam (BAC) crosslinker (referred to as PNTA-BAC) didn't form sol-gel transition. Although BISS and BAC possess same disulfide bonds with redox properties, BISS, unlike BAC, is water-soluble and features two carboxyl groups. The mechanism by which PNTA-BISS nanogels form hydrogel photonic crystals has been deeply explored with temperature-variable NMR. The results showed the introduction of Aphe with both steric hindrance and carboxyl groups greatly slowed down the shrinkage of PNTA-BISS nanogels. Therefore, PNTA-BISS nanogels can form sol-gel transition and further structural color of hydrogel photonic crystals due to carboxyl groups above the Tp. Furthermore, the properties of biodegradable hydrogel photonic crystals above the Tp were investigated for the first time, attributed to the presence of the strong reducing agent 1,4-dithiothreitol (DTT). When loaded with doxorubicin (DOX), PNTA-BISS exhibited favorable degradation properties under the influence of DTT. In summary, the PNTA-BISS nanogel, in addition to its in-situ gelation capabilities, demonstrated degradability, potentially providing a novel nanoplatform for applications in drug delivery, biotechnology, and related fields.

Rational multivalency construction enables bactericidal effect amplification and dynamic biomaterial design

The multivalency of bioligands in living systems brings inspiration for not only the discovery of biological mechanisms but also the design of extracellular matrix (ECM)-mimicking biomaterials. However, designing controllable multivalency construction strategies is still challenging. Herein, we synthesized a series of well-defined multivalent antimicrobial peptide polymers (mAMPs) by clicking ligand molecules onto polymers prepared by reversible addition-fragmentation chain transfer polymerization. The multiple cationic ligands in the mAMPs could enhance the local disturbance of the anionic phospholipid layer of the bacterial membrane through multivalent binding, leading to amplification of the bactericidal effect. In addition to multivalency-enhanced antibacterial activity, mAMPs also enable multivalency-assisted hydrogel fabrication with an ECM-like dynamic structure. The resultant hydrogel with self-healing and injectable properties could be successfully employed as an antibacterial biomaterial scaffold to treat infected skin wounds. The multivalency construction strategy presented in this work provides new ideas for the biomimetic design of highly active and dynamic biomaterials for tissue repair and regeneration.

Kartogenin-enhanced dynamic hydrogel ameliorates intervertebral disc degeneration via restoration of local redox homeostasis

INTRODUCTION

Over-activation of oxidative stress due to impaired antioxidant functions in nucleus pulpous (NP) has been identified as a key factor contributing to intervertebral disc degeneration (IVDD). While Kartogenin (KGN) has previously demonstrated antioxidant properties on articular cartilage against osteoarthritis, its effects on NP degeneration have yet to be fully understood.

OBJECTIVES

This study aimed to investigate the protective effects of KGN on nucleus pulpous cells (NPCs) against an inflammatory environment induced by interleukin (IL)-1β, as well as to explore the therapeutic potential of KGN-enhanced dynamic hydrogel in preventing IVDD.

METHODS

NPCs were isolated from rat caudal IVDs and subjected to treatment with KGN at varying concentrations (ranging from 0.01 to 1 ​μM) in the presence of IL-1β. The expression of extracellular matrix (ECM) anabolism markers was quantitatively assessed at both the mRNA and protein levels. Additionally, intracellular reactive oxygen species and antioxidant enzyme expression were evaluated, along with the role of nuclear factor erythroid 2-related factor 2 (NRF2). Based on these findings, a dynamic self-healing hydrogel loaded with KGN was developed through interconnecting networks. Subsequently, KGN-enhanced dynamic hydrogel was administered into rat caudal IVDs that had undergone puncture injury, followed by radiographic analysis and immunohistochemical staining to evaluate the therapeutic efficacy.

RESULTS

In vitro treatments utilizing KGN were observed to maintain ECM synthesis and inhibit catabolic activities in IL-1β-stimulated NPCs. The mechanism behind this protective effect of KGN on NPCs was found to involve the asctivation of NRF2 and downstream antioxidant enzymes, including glutathione peroxidase 1 and heme oxygenase 1. This was further supported by the loss of both antioxidant and anabolic effects upon pharmacological inhibition of NRF2. Furthermore, a self-healing hydrogel was developed and loaded with KGN to achieve localized and sustained release of the compound. The injection of KGN-enhanced hydrogel effectively ameliorated the degradation of NP ECM and mitigated inflammation in a rat model of puncture-induced IVDD.

CONCLUSIONS

Our results indicate that KGN exhibits potential as a therapeutic agent for NP degeneration, and that KGN-enhanced dynamic hydrogel represents a novel approach for treating IVDD by restoring redox homeostasis in NP.The translational potential of this article: The dysregulation of oxidant and antioxidant balance has been shown to impede the repair and regeneration of NP, thereby hastening the progression of IVDD following injury. The present investigation has demonstrated that the sustained release of KGN promotes the synthesis of ECM in vitro and mitigates the progression of IVDD in vivo by restoring redox equilibrium, thereby presenting a novel therapeutic candidate based on the antioxidant properties of KGN for the treatment of IVDD.

Ionic Microgel Colloidal Crystals: Responsive Chromism in Dual Physical and Chemical Colors for High-End Information Security and Encryption

Chromic materials play a decisive and escalating role in information security. However, it is challenging to develop chromic materials for encryption technologies that can hardly be imitated. Inspired by versatile metachrosis in nature, a series of coumarin-based 7-(6-bromohexyloxy)-coumarin microgel colloidal crystals (BrHC MGCC) with multiresponsive chromism are able to be assembled by ionic microgels in poly(vinyl alcohol) (PVA) solution followed by two cycles of freezing-thawing. The ionic microgels can be finely tailored by in situ quaternization with tunable size under varied temperatures and hydration energies of counterions as well as quenched luminescence under UV irradiation, which endows BrHC MGCC with intriguing chromism in the dual-channel coloration of physical structural color and chemical fluorescent color. Three types of BrHC MGCC exhibit various change ranges in structural coloration and similar quenching in fluorescence emission, which can be utilized for the development of the static-dynamic combined anticounterfeiting system with dual coloration. The information conveyed by the BrHC MGCC array presents dynamic variation versus temperature, while the static information can be only integrally read in both sunlight and a 365 nm UV lamp. The fabrication of a microgel colloidal crystal with dual coloration opens a facile and ecofriendly window for multilevel information security, camouflage, and a cumbersome authentication process.

Advances in the Design of Phenylboronic Acid-Based Glucose-Sensitive Hydrogels

Diabetes, characterized by an uncontrolled blood glucose level, is the main cause of blindness, heart attack, stroke, and lower limb amputation. Glucose-sensitive hydrogels able to release hypoglycemic drugs (such as insulin) as a response to the increase of the glucose level are of interest for researchers, considering the large number of diabetes patients in the world (537 million in 2021, reported by the International Diabetes Federation). Considering the current growth, it is estimated that, up to 2045, the number of people with diabetes will increase to 783 million. The present work reviews the recent developments on the hydrogels based on phenylboronic acid and its derivatives, with sensitivity to glucose, which can be suitable candidates for the design of insulin delivery systems. After a brief presentation of the dynamic covalent bonds, the design of glucose-responsive hydrogels, the mechanism by which the hypoglycemic drug release is achieved, and their self-healing capacity are presented and discussed. Finally, the conclusions and the main aspects that should be addressed in future research are shown.

Structural Color Ionic Hydrogel Patches for Wound Management

Ionic hydrogels have attracted extensive attention because of their wide applicability in electronic skins, biosensors, and other biomedical areas. Tremendous effort is dedicated to developing ionic hydrogels with improved detection accuracy and multifunctionality. Herein, we present an inverse opal scaffold-based structural color ionic hydrogel with the desired features as intelligent patches for wound management. The patches were composed of a polyacrylamide-poly(vinyl alcohol)-polyethylenimine-lithium chloride (PAM-PVA-PEI-LiCl) inverse opal scaffold and a vascular endothelial growth factor (VEGF) mixed methacrylated gelatin (GelMA) hydrogel filler surface. The scaffold imparted the composite patches with brilliant structural color, conductive property, and freezing resistance, while the VEGF-GelMA surface could not only prevent the ionic hydrogel from the interference of complex wound conditions but also contribute to the cell proliferation and tissue repair in the wounds. Thus, the hydrogel patches could serve as electronic skins for in vivo wound healing and monitoring with high accuracy and reliability. These features indicate that the proposed structural color ionic hydrogel patches have great potential for clinical applications.

Rational Design of Intelligent and Multifunctional Dressing to Promote Acute/Chronic Wound Healing

Currently, the clinic's treatment of acute/chronic wounds is still unsatisfactory due to the lack of functional and appropriate wound dressings. Intelligent and multifunctional dressings are considered the most advanced wound treatment modalities. It is essential to design and develop wound dressings with required functions according to the wound microenvironment in the clinical treatment. This work summarizes microenvironment characteristics of various common wounds, such as acute wound, diabetic wound, burns wound, scalded wound, mucosal wound, and ulcers wound. Furthermore, the factors of transformation from acute wounds to chronic wounds were analyzed. Then we focused on summarizing how researchers fully and thoroughly combined the complex microenvironment with modern advanced technology to ensure the usability and value of the dressing, such as photothermal-sensitive dressings, microenvironment dressing (pH-sensitive dressings, ROS-sensitive dressings, and osmotic pressure dressings), hemostatic dressing, guiding tissue regeneration dressing, microneedle dressings, and 3D/4D printing dressings. Finally, the revolutionary development of wound dressings and how to transform the existing advanced functional dressings into clinical needs as soon as possible have carried out a reasonable and meaningful outlook.

The Efficient and Convenient Extracting Uranium from Water by a Uranyl-Ion Affine Microgel Container

Uranium is an indispensable part of the nuclear industry that benefits us, but its consequent pollution of water bodies also makes a far-reaching impact on human society. The rapid, efficient and convenient extraction of uranium from water is to be a top priority. Thanks to the super hydrophilic and fast adsorption rate of microgel, it has been the ideal adsorbent in water; however, it was too difficult to recover the microgel after adsorption, which limited its practical applications. Here, we developed a uranyl-ion affine and recyclable microgel container that has not only the rapid swelling rate of microgel particles but also allows the detection of the adsorption saturation process by the naked eye.

Two-dimensional colloidal crystal of soft microgel spheres: Development, preparation and applications

Two-dimensional (2D) colloidal crystals are ordered monolayer arrays of colloidal sphere particles assembled on the substrates or at phase interfaces. Owing to their unique periodic structure and fascinating properties, 2D colloidal crystals have aroused considerable interest because of their potential applications. Among them, 2D colloidal crystals self-assembled from soft microgel spheres stand out particularly. The 2D colloidal crystals of soft microgel spheres combine the advantages of monolayer colloidal crystals and sensitive microgels, which have a good application prospect in biomedical area. In this article, we provide a systematic overview of 2D colloidal crystals of soft microgel spheres related to their development, preparation and applications. First, various preparation methods of 2D colloidal crystal of microgels are introduced, including dip-coating, drop-coating, spin-coating, interface assembly, surface reaction-assisted assembly, and so forth. Second, representative biomedical applications consisting of optical sensor, drug delivery, antibacterial coating, cell culture, and colloidal template are also exemplified to show the high performance of 2D colloidal crystals of soft microgel spheres. In addition, we also present prospects of future developments of 2D microgel colloidal crystals.

Bio-inspired shape-memory structural color hydrogel film

Structural colors, derived from existing natural creatures, have aroused widespread attention in the materials regulation for different applications. Here, inspired by the color adjusting mechanism of hummingbird, we present a novel shape-memory structural color hydrogel film by introducing shape memory polymers (SMPs) into synthetic inverse opal scaffold structure. The excellent flexibility as well as the inverse opal structure of the hydrogel films imparts them with stable stretchability and brilliant structural colors. Benefiting from the transient structural anisotropy of copolymers, the hybrid films are possessed with shape-morphing behaviors capability. Based on the shape transformations and color responsiveness performance, we have demonstrated diverse structural color actuators with complex shapes for different tasks. Notably, as the photothermal responsive graphene quantum dots were integrated into the hydrogel, the hybrid films could also be endowed with the feature of light-controlled reversible deformation with synchronous structural color variation. These features demonstrate that the presented shape-memory structural color hydrogel film is valuable for soft robotics with multi-functions of sensing, communication and disguise.

Emerging Theranostic Nanomaterials in Diabetes and Its Complications

Diabetes mellitus (DM) refers to a group of metabolic disorders that are characterized by hyperglycemia. Oral subcutaneously administered antidiabetic drugs such as insulin, glipalamide, and metformin can temporarily balance blood sugar levels, however, long-term administration of these therapies is associated with undesirable side effects on the kidney and liver. In addition, due to overproduction of reactive oxygen species and hyperglycemia-induced macrovascular system damage, diabetics have an increased risk of complications. Fortunately, recent advances in nanomaterials have provided new opportunities for diabetes therapy and diagnosis. This review provides a panoramic overview of the current nanomaterials for the detection of diabetic biomarkers and diabetes treatment. Apart from diabetic sensing mechanisms and antidiabetic activities, the applications of these bioengineered nanoparticles for preventing several diabetic complications are elucidated. This review provides an overall perspective in this field, including current challenges and future trends, which may be helpful in informing the development of novel nanomaterials with new functions and properties for diabetes diagnosis and therapy.