Multipurpose smart hydrogel systems

Utilizing Synchrotron-Based X-ray Micro-Computed Tomography to Visualize the Microscopic Structure of Starch Hydrogels In Situ

This study aimed to visualize the microstructures of starch hydrogels using synchrotron-based X-ray micro-computed tomography (μCT). Waxy maize starch (WMS, 3.3% amylose, db), pea starch (PS, 40.3% amylose), and high-amylose maize starch (HMS, 63.6% amylose) were cooked at 95 and 140 °C to prepare starch hydrogels. WMS and HMS failed to form a gel after 95 °C cooking and storage, while PS developed a firm gel. At 140 °C cooking, HMS of a high amylose nature was fully gelatinized and generated a rigid gel with the highest strength. Both scanning electron microscopy (SEM) and μCT revealed the unique structural features of various starch hydrogels/pastes prepared at different temperatures, which were greatly affected by the degree of swelling and dispersity of the starches. As a nondestructive method, μCT showed certain advantages over SEM, including minimal shrinkage of the hydrogels, relatively simple sample preparation, and allowing for three-dimensional reconstruction of the hydrogel microstructure. This study indicated that synchrotron-based μCT could be a useful technique in visualizing biopolymer-based hydrogels.

Exploring the Formulation and Approaches of Injectable Hydrogels Utilizing Hyaluronic Acid in Biomedical Uses

The characteristics of injectable hydrogels make them a prime contender for various biomedical applications. Hyaluronic acid is an essential component of the matrix surrounding the cells; moreover, hyaluronic acid's structural and biochemical characteristics entice researchers to develop injectable hydrogels for various applications. However, due to its poor mechanical properties, several strategies are used to produce injectable hyaluronic acid hydrogel. This review summarizes published studies on the production of injectable hydrogels based on hyaluronic acid polysaccharide polymers and the biomedical field's applications for these hydrogel systems. Hyaluronic acid-based hydrogels are divided into two categories based on their injectability mechanisms: in situ-forming injectable hydrogels and shear-thinning injectable hydrogels. Many crosslinking methods are used to create injectable hydrogels; chemical crosslinking techniques are the most frequently investigated technique. Hybrid injectable hydrogel systems are widely investigated by blending hyaluronic acid with other polymers or nanoparticulate systems. Injectable hyaluronic acid hydrogels were thoroughly investigated and proven to demonstrate potential in various medical fields, including delivering drugs and cells, tissue repair, and wound dressings.

Comparison of Structural, Water-Retaining and Sorption Properties of Acrylamide-Based Hydrogels Cross-Linked by Physical and Chemical Methods

Two series of hydrogels based on acrylamide and its copolymers with acrylonitrile and acrylic acid were synthesized by two cross-linking methods - chemical (using N,N'-methylene bis-acrylamide) and physical (using montmorillonite (MMT)) ones. The structure of the gels was characterized by Fourier Transform Infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The swelling and sorption properties were analyzed as a function of both the monomer composition and the cross-linking method. The shift of the band corresponding to Si-O (995-1030 cm-1 ) confirmed the formation of intercalation structures for MMT-cross-linked gels. Moreover, physically cross-linked gels demonstrated a non-monotonic dependence of the swelling degree on the MMT concentration, and acrylamide-acrylic acid copolymer MMT-cross-linked gels showed pH sensitivity and the highest swelling degree of 150 g/g. The highest sorption capacity towards cadmium(II) ions was demonstrated by acrylamide-acrylic acid copolymer gels, both covalently cross-linked (30 mg/g) and MMT-cross-linked (8.9 mg/g).

Dissolving and Swelling Hydrogel-Based Microneedles: An Overview of Their Materials, Fabrication, Characterization Methods, and Challenges

Polymeric hydrogels are a complex class of materials with one common feature-the ability to form three-dimensional networks capable of imbibing large amounts of water or biological fluids without being dissolved, acting as self-sustained containers for various purposes, including pharmaceutical and biomedical applications. Transdermal pharmaceutical microneedles are a pain-free drug delivery system that continues on the path to widespread adoption-regulatory guidelines are on the horizon, and investments in the field continue to grow annually. Recently, hydrogels have generated interest in the field of transdermal microneedles due to their tunable properties, allowing them to be exploited as delivery systems and extraction tools. As hydrogel microneedles are a new emerging technology, their fabrication faces various challenges that must be resolved for them to redeem themselves as a viable pharmaceutical option. This article discusses hydrogel microneedles from a material perspective, regardless of their mechanism of action. It cites the recent advances in their formulation, presents relevant fabrication and characterization methods, and discusses manufacturing and regulatory challenges facing these emerging technologies before their approval.

Biodegradable floating hydrogel baits as larvicide delivery systems against mosquitoes

Biological methods for mosquito larvae control are completely biodegradable and have null or limited effects on nontarget organisms. However, commercially available products have a low residual activity, with the consequent need for multiple applications that inevitably increase costs and the risk of resistance phenomena insurgence. Smart delivery systems made of hydrogels proved their efficacy in increasing the action duration of biolarvicides up to several months, but the lack of an efficient baiting mechanism to strongly attract the target pest remains a problem in practical applications. In this work, we investigated two novel hydrogel-based formulations of completely natural composition for baiting and killing larvae of Aedes albopictus mosquitos. The proposed materials consist of charged crosslinked polysaccharides (chitosan and cellulose) and are specifically manufactured to float in water, simulating organic matter usually present at breeding sites. Within the hydrogels' matrix, yeast colonies of Saccharomyces cerevisiae were embedded as phagostimulants alongside a biolarvicide (Bacillus thuringiensis var. israelensis (Bti)). Despite the similar chemical nature and structure, chitosan-based hydrogels exhibited a markedly superior baiting potential compared to those made of cellulose and also succeeded in efficiently killing mosquito larvae just after a few hours from administration. We are confident that the proposed smart delivery hydrogel made of chitosan can be an enabling tool to attract mosquito larvae towards biopesticides of different nature without delocalizing active ingredients away from the breeding site and to simultaneously increase their residual activity, thus holding the potential of minimizing environmental pollution related to pest control and vector-borne disease prevention.

Smart Hydrogel Formed by Alginate-g-Poly(N-isopropylacrylamide) and Chitosan through Polyelectrolyte Complexation and Its Controlled Release Properties

Smart hydrogels that can respond to external stimuli such as temperature and pH have attracted tremendous interest for biological and biomedical applications. In this work, we synthesized two alginate-graft-poly(N-isopropylacrylamide) (Alg-g-PNIPAAm) copolymers and aimed to prepare smart hydrogels through formation of polyelectrolyte complex (PEC) between the negatively charged Alg-g-PNIPAAm copolymers and the positively charged chitosan (Cts) in aqueous solutions. The hydrogels were expected to be able to respond to both temperature and pH changes due to the nature of Alg-g-PNIPAAm and chitosan. The hydrogel formation was determined by a test tube inverting method and confirmed by the rheological measurements. The rheological measurements showed that the PEC hydrogels formed at room temperature could be further enhanced by increasing temperature over the lower critical solution temperature (LCST) of PNIPAAm, because PNIPAAm would change from hydrophilic to hydrophobic upon increasing temperature over its LCST, and the hydrophobic interaction between the PNIPAAm segments may act as additional physical crosslinking. The controlled release properties of the hydrogels were studied by using the organic dye rhodamine B (RB) as a model drug at different pH. The PEC hydrogels could sustain the RB release more efficiently at neutral pH. Both low pH and high pH weakened the PEC hydrogels, and resulted in less sustained release profiles. The release kinetics data were found to fit well to the Krosmyer–Peppas power law model. The analysis of the release kinetic parameters obtained by the modelling indicates that the release of RB from the PEC hydrogels followed mechanisms combining diffusion and dissolution of the hydrogels, but the release was mainly governed by diffusion with less dissolution at pH 7.4 when the PEC hydrogels were stronger and stabler than those at pH 5.0 and 10.0. Therefore, the PEC hydrogels are a kind of smart hydrogels holding great potential for drug delivery applications.

Advances of Stimulus-Responsive Hydrogels for Bone Defects Repair in Tissue Engineering

Bone defects, as one of the most urgent problems in the orthopedic clinic, have attracted much attention from the biomedical community and society. Hydrogels have been widely used in the biomedical field for tissue engineering research because of their excellent hydrophilicity, biocompatibility, and degradability. Stimulus-responsive hydrogels, as a new type of smart biomaterial, have more advantages in sensing external physical (light, temperature, pressure, electric field, magnetic field, etc.), chemical (pH, redox reaction, ions, etc.), biochemical (glucose, enzymes, etc.) and other different stimuli. They can respond to stimuli such as the characteristics of the 3D shape and solid-liquid phase state, and exhibit special properties (injection ability, self-repair, shape memory, etc.), thus becoming an ideal material to provide cell adhesion, proliferation, and differentiation, and achieve precise bone defect repair. This review is focused on the classification, design concepts, and research progress of stimulus-responsive hydrogels based on different types of external environmental stimuli, aiming at introducing new ideas and methods for repairing complex bone defects.

Ramírez M, Zezza P, Lucío MI, Bañuls MJ, Maquieira Á, Morales-Vidal M, Beléndez A, Pascual I. Processing of Holographic Hydrogels in Liquid Media: A Study by High-Performance Liquid Chromatography and Diffraction Efficiency

The storage of time-stable holographic gratings in hydrogel matrices when the material is immersed in aqueous media is a real challenge at present. The optimization of the storage stages of the holograms must be properly investigated to identify the most suitable development processes. For this reason, this work is focused on the study of the optimization of the washing stages of the hydrogels based on acrylamide and N,N’-methylenebis(acrylamide) once unslanted transmission holograms have been stored. High-performance liquid chromatography and UV-visible measurements have been employed in our system to analyze the composition of the washing solutions. PBST and DMSO:H₂O are used as solvents in the washing stages. The diffraction efficiencies are measured during the washing stages and after the storing of the holograms during several days in PBST. Maximum diffraction efficiencies of 38 and 27.6% are reached when PBST and DMSO:H₂O are employed, respectively, for the washing process. Holograms show temporal stability after being stored immersed in PBST at 4 °C for 4 days.

Current Understanding of Hydrogel for Drug Release and Tissue Engineering

Due to their good absorption, satisfactory biocompatibility, and high safety, hydrogels have been widely used in the field of biomedicine, including for drug delivery and tissue regeneration. In this review, we introduce the characteristics and crosslinking methods of natural and synthetic hydrogels. Then, we highlight the design and principle of intelligent hydrogels (i.e., responsive hydrogels) used for drug release. Moreover, we introduce the application of the application of hydrogels in drug release and tissue engineering, and the limitations and research directions of hydrogel in drug release and tissue engineering are also considered. We hope that this review can provide a reference for follow-up studies in related fields.

Application and Prospects of Hydrogel Additive Manufacturing

Hydrogel has become a commonly used material for 3D and 4D printing due to its favorable biocompatibility and low cost. Additive manufacturing, also known as 3D printing, was originally referred to as rapid prototyping manufacturing. Variable-feature rapid prototyping technology, also known as 4D printing, is a combination of materials, mathematics, and additives. This study constitutes a literature review to address hydrogel-based additive manufacturing technologies, introducing the characteristics of commonly used 3D printing hydrogel methods, such as direct ink writing, fused deposition modeling, and stereolithography. With this review, we also investigated the stimulus types, as well as the advantages and disadvantages of various stimulus-responsive hydrogels in smart hydrogels; non-responsive hydrogels; and various applications of additive manufacturing hydrogels, such as neural catheter preparation and drug delivery. The opportunities, challenges, and future prospects of hydrogel additive manufacturing technologies are discussed.

Cross-Linked Hydrogels Based on PolyNIPAAm and Acid-Activated Laponite RD: Swelling and Tunable Thermosensitivity

The effects of acid activation of Laponite RD (Lap) on the structure and properties of activated Lap nanoparticles (aLap) and the properties of polyNIPAA_m hydrogels physically cross-linked by aLap have been studied. The acid activation of Lap by the sulfuric acid was done using the concentration of sulfuric acid within the interval C_a = 0.525-14.58% for 10 h. For slightly activated samples (C_a ≤ 1.25 wt %), the significant increase of the specific surface area (by ≈1.56 times) was accompanied with a significant decrease in both the values of the specific heat of immersion in water and n-decane. However, the hydrophilic properties of all samples S₀-S₅ were still observed. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) data, Fourier transform infrared (FTIR) spectra, and X-ray diffraction (XRD) patterns demonstrated that the acid activation resulted in the destruction of the crystal lattice of Lap, leaching of magnesium and lithium, and formation of the amorphous phases. Moreover, the acid activation significantly affected aggregation and negative surface charges of the aLap faces in aqueous suspension. The effects of aLap on the swelling properties and cooperativity in the phase transitions of polyNIPAA_m hydrogels cross-linked by aLap are also discussed. It was demonstrated that an increase in C_a resulted in a significant increase in the equilibrium degree of swelling of the hydrogels and a decrease in the hydrogel phase-transition temperature from the swollen phase to the shrunken phase.

Hydrogels for Treatment of Oral and Maxillofacial Diseases: Current Research, Challenge, and Future Directions

Oral and maxillofacial diseases such as infection and trauma often involve various organs and tissues, resulting in structural defects, dysfunctions and/or adverse effects on facial appearance. Hydrogels have been applied...

Advanced biomedical hydrogels: molecular architecture and its impact on medical applications

Hydrogels are cross-linked polymeric networks swollen in water, physiological aqueous solutions or biological fluids. They are synthesized by a wide range of polymerization methods that allow for the introduction of linear and branched units with specific molecular characteristics. In addition, they can be tuned to exhibit desirable chemical characteristics including hydrophilicity or hydrophobicity. The synthesized hydrogels can be anionic, cationic, or amphiphilic and can contain multifunctional cross-links, junctions or tie points. Beyond these characteristics, hydrogels exhibit compatibility with biological systems, and can be synthesized to render systems that swell or collapse in response to external stimuli. This versatility and compatibility have led to better understanding of how the hydrogel's molecular architecture will affect their physicochemical, mechanical and biological properties. We present a critical summary of the main methods to synthesize hydrogels, which define their architecture, and advanced structural characteristics for macromolecular/biological applications.

Marine Polysaccharides for Wound Dressings Application: An Overview

Wound dressings have become a crucial treatment for wound healing due to their convenience, low cost, and prolonged wound management. As cutting-edge biomaterials, marine polysaccharides are divided from most marine organisms. It possesses various bioactivities, which allowing them to be processed into various forms of wound dressings. Therefore, a comprehensive understanding of the application of marine polysaccharides in wound dressings is particularly important for the studies of wound therapy. In this review, we first introduce the wound healing process and describe the characteristics of modern commonly used dressings. Then, the properties of various marine polysaccharides and their application in wound dressing development are outlined. Finally, strategies for developing and enhancing marine polysaccharide wound dressings are described, and an outlook of these dressings is given. The diverse bioactivities of marine polysaccharides including antibacterial, anti-inflammatory, haemostatic properties, etc., providing excellent wound management and accelerate wound healing. Meanwhile, these biomaterials have higher biocompatibility and biodegradability compared to synthetic ones. On the other hand, marine polysaccharides can be combined with copolymers and active substances to prepare various forms of dressings. Among them, emerging types of dressings such as nanofibers, smart hydrogels and injectable hydrogels are at the research frontier of their development. Therefore, marine polysaccharides are essential materials in wound dressings fabrication and have a promising future.

Hemostatic dressings based on poly(vinyl formal) sponges

The development of novel hemostatic agents is related to the fact that severe blood loss due to hemorrhage continues to be the leading cause of preventable death of patients with military trauma and the second leading cause of death of civilian patients with injuries. Herein we assessed the hemostatic properties of porous sponges based on biocompatible hydrophilic polymer, poly(vinyl formal) (PVF), which meets the main requirements for the development of hemostatic materials. A series of composite hemostatic materials based on PVF sponges with different porosities and fillers were synthesized by acetalization of poly(vinyl alcohol) with formaldehyde. Nano-sized aminopropyl silica, micro-sized calcium carbonate, and chitosan hydrogel were used to modify PVF matrixes. The physicochemical properties (pore size, elemental composition, functional groups, hydrophilicity, and acetalization degree) of the synthesized composite sponges were studied by gravimetrical analysis, optical microscopy, scanning electron microscopy combined with energy dispersive x-ray spectroscopy, infrared spectroscopy, and nuclear magnetic resonance. Hemostatic properties of the materials were assessed using a model of parenchymal bleeding from the liver of white male Wistar rat with a gauze bandage as a control. All investigated PVF-based porous sponges showed high hemostatic activity: upon the application of PVF-samples the bleeding decreased within 3 min by 68.4-94.4% (р < 0.001). The bleeding time upon the application of PVF-based composites decreased by 78.3-90.4% (p < 0.001) compared to the application of well-known commercial product Celox™.

A Gelatin-Hyaluronic Acid Double Cross-Linked Hydrogel for Regulating the Growth and Dual Dimensional Cartilage Differentiation of Bone Marrow Mesenchymal Stem Cells

Owing to its unique physiochemical properties similar to the extracellular matrix (ECM), three-dimensional (3D) crosslinked hydrogels are widely studied materials for tissue engineering. In this study, to mimic the ECM microenvironment, a two-step covalent cross-linking with hyaluronic acid and gelatin was performed to form an interpenetrating polymer network structure. Gelatin as the first network greatly improved the mechanical strength of the hydrogels, while a hyaluronic acid network as the second network improved the tenacity and biological activity. Compared with a single network hydrogel, the interpenetrating hydrogel system can further regulate the mechanical properties of the hydrogel by adjusting the ratio of the two components, thereby changing the proliferation, activity, and direction of cartilage differentiation of bone marrow mesenchymal stem cells (BMSCs). Not only that, with two culture methods for BMSCs on the surface and 3D wrapped in the double cross-linked hydrogels, they exhibited their potential to induce BMSCs to cartilage differentiation under the condition of 3D encapsulation of BMSCs and contact with BMSCs on its surface. As a scaffold material for cartilage tissue engineering, this double cross-linked hydrogel demonstrated its high feasibility and applicability in delivering BMSCs in vivo and repairing defects.

Review of Contemporary Self-Assembled Systems for the Controlled Delivery of Therapeutics in Medicine

The novel and unique design of self-assembled micro and nanostructures can be tailored and controlled through the deep understanding of the self-assembly behavior of amphiphilic molecules. The most commonly known amphiphilic molecules are surfactants, phospholipids, and block copolymers. These molecules present a dual attraction in aqueous solutions that lead to the formation of structures like micelles, hydrogels, and liposomes. These structures can respond to external stimuli and can be further modified making them ideal for specific, targeted medical needs and localized drug delivery treatments. Biodegradability, biocompatibility, drug protection, drug bioavailability, and improved patient compliance are among the most important benefits of these self-assembled structures for drug delivery purposes. Furthermore, there are numerous FDA-approved biomaterials with self-assembling properties that can help shorten the approval pathway of efficient platforms, allowing them to reach the therapeutic market faster. This review focuses on providing a thorough description of the current use of self-assembled micelles, hydrogels, and vesicles (polymersomes/liposomes) for the extended and controlled release of therapeutics, with relevant medical applications. FDA-approved polymers, as well as clinically and commercially available nanoplatforms, are described throughout the paper.

Enzyme-Regulated Healable Polymeric Hydrogels

The enzyme-regulated healable polymeric hydrogels are a kind of emerging soft material capable of repairing the structural defects and recovering the hydrogel properties, wherein their fabrication, self-healing, or degradation is mediated by enzymatic reactions. Despite achievements that have been made in controllable cross-linking and de-cross-linking of hydrogels by utilizing enzyme-catalyzed reactions in the past few years, this substrate-specific strategy for regulating healable polymeric hydrogels remains in its infancy, because both the intelligence and practicality of current man-made enzyme-regulated healable materials are far below the levels of living organisms. A systematic summary of current achievements and a reasonable prospect at this point can play positive roles for the future development in this field. This Outlook focuses on the emerging and rapidly developing research area of bioinspired enzyme-regulated self-healing polymeric hydrogel systems. The enzymatic fabrication and degradation of healable polymeric hydrogels, as well as the enzymatically regulated self-healing of polymeric hydrogels, are reviewed. The functions and applications of the enzyme-regulated healable polymeric hydrogels are discussed.

Thermoresponsive hydrogels physically crosslinked with magnetically modified LAPONITE® nanoparticles

Recently, considering the potential applications of hydrogel nanocomposites in biomedical engineering, there has been a growing interest in the synthesis of hydrogels with improved mechanical properties. Among magnetic materials, iron oxides are of particular interest due to their magnetic properties and biocompatibility. At the same time, LAPONITE®, a synthetic clay, can be used to improve the mechanical properties of polymer-based nanocomposites. In this study we report the effects of hydrogel composition and structure on its thermoresponsive properties and hydrogel sorption and release of a model anticancer drug - 5-fluorouracil. Using one-step coprecipitation method we synthesized magnetic LAPONITE® (LAM) nanoparticles with magnetite-to-LAPONITE® weight ratios from 2 : 1 to 1 : 8. With increase in magnetite concentration the ferrofluidic properties of LAM nanoparticles are getting improved, while fluorouracil absorptivity - decreases. Exfoliation of the clay is observed when the magnetite content exceeds the LAPONITE® content. Physical crosslinking of poly(N-isopropylacrylamide) with LAM nanoparticles yields magnetic thermosensitive hydrogel nanocomposites with controllable temperature-induced drug release. All hydrogel nanocomposites have a distinct volume phase transition from a swollen state to a collapsed state upon heating within the physiologically acceptable temperature range of 33-36 °C.

Design Considerations for Hydrogel Wound Dressings: Strategic and Molecular Advances

Wound dressings are traditionally used to protect a wound and to facilitate healing. Currently, their function is expanding. There is an urgent need for new smart products that not only act as a protective barrier but also actively support the wound healing process. Hydrogel dressings are an example of such innovative products and typically facilitate wound healing by providing a hospitable and moist environment in which cells can thrive, while the wound can still breathe and exudate can be drained. These dressings also tend to be less painful or have a soothing effect and allow for additional drug delivery. In this review, various strategic and molecular design considerations are discussed that are relevant for developing a hydrogel into a wound dressing product. These considerations vary from material choice to ease of use and determine the dressing's final properties, application potential, and benefits for the patient. The focus of this review lies on identifying and explaining key aspects of hydrogel wound dressings and their relevance in the different phases of wound repair. Molecular targets of wound healing are discussed that are relevant when tailoring hydrogels toward specific wound healing scenarios. In addition, the potential of hydrogels is reviewed as medicine advances from a repair-based wound healing approach toward a regenerative-based one. Hydrogels can play a key role in the transition toward personal wound care and facilitating regenerative medicine strategies by acting as a scaffold for (stem) cells and carrier/source of bioactive molecules and/or drugs. Impact statement Improved wound healing will lead to a better quality of life around the globe. It can be expected that this coincides with a reduction in health care spending, as the duration of treatment decreases. To achieve this, new and modern wound care products are desired that both facilitate healing and improve comfort and outcome for the patient. It is proposed that hydrogel wound dressings can play a pivotal role in improving wound care, and to that end, this review aims to summarize the various design considerations that can be made to optimize hydrogels for the purpose of a wound dressing.

An Environmentally Sensitive Silk Fibroin/Chitosan Hydrogel and Its Drug Release Behaviors

To fabricate environmentally sensitive hydrogels with better biocompatibility, natural materials such as protein and polysaccharide have been widely used. Environmentally sensitive hydrogels can be used as a drug carrier for sustained drug release due to its stimulus responsive performance. The relationship between the internal structure of hydrogels and their drug delivery behaviors remains indeterminate. In this study, environmentally sensitive hydrogels fabricated by blending silk fibroin/chitosan with different mass ratios were successfully prepared using 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide (EDC)/N-Hydroxysuccinimide (NHS) cross-linking agent. Scanning-electron microscopy (SEM) images showed the microcosmic surface of the gel had a 3-D network-like and interconnected pore structure. The N2 adsorption-desorption method disclosed the existence of macroporous and mesoporous structures in the internal structure of hydrogels. Data of compression tests showed its good mechanical performance. The swelling performance of hydrogels exhibited stimuli responsiveness at different pH and ion concentration. With the increase of pH and ion concentration, the swelling ratios of hydrogels (silk fibroin (SF)/ chitosan (CS) = 8/2 and 7/3) decreased. Methylene blue (MB) was loaded into the hydrogels to confirm the potential of sustained drug release and pH-responsive behavior. Therefore, due to the porous structure, stable mechanical strength, stimuli responsive swelling performance, and drug release behaviors, the SF/CS composite hydrogels have potential applications in controlled drug release.

Composite Materials Design: Biomineralization Proteins and the Guided Assembly and Organization of Biomineral Nanoparticles

There has been much discussion of the role of proteins in the calcium carbonate biomineralization process, particularly with regard to nucleation, amorphous stabilization/transformation, and polymorph selection. However, there has been little if any discussion of the potential role that proteins might play in another important process: the guided assembly and organization of mineral nanoparticles into higher-ordered structures such as mesocrystals. This review discusses particle attachment theory and recent evidence of mineral-associated proteins forming hydrogels that assemble and organize mineral clusters into crystalline phase. From this discussion we postulate a mechanism by which biomineralization protein hydrogel aggregation assists in mineral nanoparticle assembly and organization within calcium carbonate skeletal elements and discuss potentials ways for harnessing this process in materials design.

A pH-induced self-healable shape memory hydrogel with metal-coordination cross-links

A 4-armed PEG–DA hydrogel was fabricated, which showed regulated shape memory and self-healing properties at different pH values.

Preparation of Thermoresponsive Polymer Nanogels of Oligo(Ethylene Glycol) Diacrylate-Methacrylic Acid and Their Property Characterization

Stimuli-responsive polymers have received growing attention in recent years owing to their wide applications in diverse fields. A novel stimuli-responsive polymer, based on oligo(ethylene glycol) diacrylate (OEGDA) and methacrylic acid (MAA), P(OEGDA-MAA), is prepared by precipitation polymerization and is shown to have a LCST-type VPTT (volume phase transition temperature) at 33 °C in water and a UCST-type VPTT at 43 °C in ethanol, all at concentration of 1 mg/mL. Both VPTTs are strongly concentration and pH dependent, providing an easy way to tune the phase transition temperature. The polymer is characterized with regard to its composition and its morphology in water and in ethanol at different concentration. The two transitions are studied and interpreted based on the results. This work provides a novel way for the preparation of a new type of stimuli-responsive polymer with great potential for different applications, particularly those in biomedical areas because PEG-based stimuli-responsive polymers are known to be nontoxic and non-immunogenic.

Chitosan-based hydrogels: From preparation to biomedical applications

The advances in the field of biomaterials have led to several studies on alternative biocompatible devices and to their development focusing on their properties, benefits, limitations, and utilization of alternative resources. Due to their advantages like biocompatibility, biodegradability, and low cost, polysaccharides have been widely used in the development of hydrogels. Among the polysaccharides studied on hydrogels preparation, chitosan (pure or combined with natural/synthetic polymers) have been widely investigated for use in biomedical field. In view of potential applications of chitosan-based hydrogels, this review focuses on the most recent progress made with respect to preparation, properties, and their salient accomplishments for drug delivery and tissue engineering.

Potassium-sensitive poly(N-isopropylacrylamide)-based hydrogels for sensor applications

In situcrosslinking polymerization of potassium sensitive hydrogels for advancedin vivosensor applications is studied in detail.

Synthesis and Characterization of Nanofunctionalized Gelatin Methacrylate Hydrogels

Given the importance of the extracellular medium during tissue formation, it was wise to develop an artificial structure that mimics the extracellular matrix while having improved physico-chemical properties. That is why the choice was focused on gelatin methacryloyl (GelMA), an inexpensive biocompatible hydrogel. Physicochemical and mechanical properties were improved by the incorporation of nanoparticles developed from two innovative fabrication processes: High shear fluid and low frequencies/high frequencies ultrasounds. Both rapeseed nanoliposomes and nanodroplets were successfully incorporated in the GelMA networks during the photo polymerization process. The impact on polymer microstructure was investigated by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and enzymatic degradation investigations. Mechanical stability and viscoelastic tests were conducted to demonstrate the beneficial effect of the functionalization on GelMA hydrogels. Adding nanoparticles to GelMA improved the surface properties (porosity), tuned swelling, and degradability properties. In addition, we observed that nanoemulsion didn't change significantly the mechanical properties to shear and compression solicitations, whereas nanoliposome addition decreased Young's modulus under compression solicitations. Thus, these ways of functionalization allow controlling the design of the material by choosing the type of nanoparticle (nanoliposome or nanoemulsion) in function of the application.

Sea Urchin Spicule Matrix Proteins Form Mesoscale "Smart" Hydrogels That Exhibit Selective Ion Interactions

In the sea urchin embryo spicule, there exists a proteome of >200 proteins that are responsible for controlling the mineralization of the spicule and the formation of a fracture-resistant composite. In this report, using recombinant proteins, we identify that two protein components of the spicule, SM30B/C and SM50, are hydrogelators. Because of the presence of intrinsic disorder and aggregation-prone regions, these proteins assemble to form porous mesoscale hydrogel particles in solution. These hydrogel particles change their size, organization, and internal structure in response to pH and ions, particularly Ca(II), which indicates that these behave as ion-responsive or "smart" hydrogels. Using diffusion-ordered spectroscopy NMR, we find that both hydrogels affect the diffusion of water, but only SM50 affects the diffusion of an anionic solute. Thus, the extracellular matrix of the spicule consists of several hydrogelator proteins which are responsive to solution conditions and can control the diffusion of water and solutes, and these proteins will serve as a model system for designing ion-responsive, composite, and smart hydrogels.

Functionalized Textile Based Therapy for the Treatment of Atopic Dermatitis

Atopic dermatitis (AD) is a common chronic inflammatory skin condition characterized by intense puritus and skin dryness. The pathogenesis for AD has not been fully understood to date. Complementary therapies are very popular as effective treatment for AD among clinical practitioners. This study presents a comprehensive review of published works associated with textiles-based complementary therapies for AD treatment such as wet-wrap dressing, functionalized textiles, and the application of hydrogel techniques in the textile industry to provide a better understanding of the development and design of new textiles-based transdermal therapies.

Functional calcium phosphate composites in nanomedicine

Calcium phosphate (CaP) materials have many peculiar and intriguing properties. In nature, CaP is found in nanostructured form embedded in a soft proteic matrix as the main mineral component of bones and teeth. The extraordinary stoichiometric flexibility, the different stabilities exhibited by its different forms as a function of pH and the highly dynamic nature of its surface ions, render CaP one of the most versatile materials for nanomedicine. This review summarizes some of the guidelines so far emerged for the synthesis of CaP composites in aqueous media that endow the material with tailored crystallinity, morphology, size, and functional properties. First, we introduce very briefly the areas of application of CaP within the nanomedicine field. Then through some selected examples, we review some synthetic routes where the presence of functional units (small templating molecules like surfactants, or oligomers and polymers) assists the synthesis and at the same time impart the functionality or the responsiveness desired for the end-application of the material. Finally, we illustrate two examples from our laboratory, where CaP is decorated by biologically active polymers or prepared within a thermo- and magneto-responsive hydrogel, respectively.

Lanthanide-Organic Gels as a Multifunctional Supramolecular Smart Platform

A multifunctional smart supramolecular platform based on a lanthanide-organic hydrogel is presented. This platform, which provides unique biocompatibility and tunable optical properties, is synthesized by a simple, fast, and reproducible eco-friendly microwave-assisted route. Photoluminescent properties enable the production of coated light-emitting diodes (LED), unique luminescent barcodes dependent on the excitation wavelength and thin-films for use in tamper seals. Moreover, piroxicam entrapped in hydrogel acts as a transdermal drug release device efficient in inhibiting edemas as compared to a commercial reference.

Controlling the 3D architecture of Self-Lifting Auto-generated Tissue Equivalents (SLATEs) for optimized corneal graft composition and stability

Ideally, biomaterials designed to play specific physical and physiological roles in vivo should comprise components and microarchitectures analogous to those of the native tissues they intend to replace. For that, implantable biomaterials need to be carefully designed to have the correct structural and compositional properties, which consequently impart their bio-function. In this study, we showed that the control of such properties can be defined from the bottom-up, using smart surface templates to modulate the structure, composition, and bio-mechanics of human transplantable tissues. Using multi-functional peptide amphiphile-coated surfaces with different anisotropies, we were able to control the phenotype of corneal stromal cells and instruct them to fabricate self-lifting tissues that closely emulated the native stromal lamellae of the human cornea. The type and arrangement of the extracellular matrix comprising these corneal stromal Self-Lifting Analogous Tissue Equivalents (SLATEs) were then evaluated in detail, and was shown to correlate with tissue function. Specifically, SLATEs comprising aligned collagen fibrils were shown to be significantly thicker, denser, and more resistant to proteolytic degradation compared to SLATEs formed with randomly-oriented constituents. In addition, SLATEs were highly transparent while providing increased absorption to near-UV radiation. Importantly, corneal stromal SLATEs were capable of constituting tissues with a higher-order complexity, either by creating thicker tissues through stacking or by serving as substrate to support a fully-differentiated, stratified corneal epithelium. SLATEs were also deemed safe as implants in a rabbit corneal model, being capable of integrating with the surrounding host tissue without provoking inflammation, neo-vascularization, or any other signs of rejection after a 9-months follow-up. This work thus paves the way for the de novo bio-fabrication of easy-retrievable, scaffold-free human tissues with controlled structural, compositional, and functional properties to replace corneal, as well as other, tissues.

Real-Space, in Situ Maps of Hydrogel Pores

We characterize the porosity of hydrogels by imaging the displacement trajectories of embedded tracer particles. This offers the possibility of characterizing the size and projected shape of individual pores as well as direct, real-space maps of heterogeneous porosity and its distribution. The scheme shows that when fluorescent spherical particles treated to avoid specific adsorption are loaded into the gel, their displacement trajectories from Brownian motion report on the size and projected shape in which the pore resides, convoluted by the particle size. Of special interest is how pores and their distribution respond to stimuli. These ideas are validated in agarose gels loaded with latex particles stabilized by adsorbed bovine serum albumin. Gels heated from room temperature produced an increasingly more monodisperse pore size distribution because increasing temperature preferentially enlarges smaller pores, but this was irreversible upon cooling, and shearing agarose gels beyond the yield point destroyed larger pores preferably. The method is considered to be generalizable beyond the agarose system presented here as proof of concept.