Hyperbranched polyester hydrogels with controlled drug release and cell adhesion properties

Basement Membrane Mimetic Hydrogel Cooperates with Rho-Associated Protein Kinase Inhibitor to Promote the Development of Acini-Like Salivary Gland Spheroids

Successful engineering of functional salivary glands necessitates the creation of cell-instructive environments for ex vivo expansion and lineage specification of primary human salivary gland stem cells (hS/PCs). Herein, basement membrane mimetic hydrogels were prepared using hyaluronic acid, cell adhesive peptides, and hyperbranched polyglycerol (HPG), with or without sulfate groups, to produce "hyperGel+" or "hyperGel", respectively. Differential scanning fluorescence experiments confirmed the ability of the sulphated HPG precursor to stabilize fibroblast growth factor 10. The hydrogels were nanoporous, cytocompatibile and cell-permissive, enabling the development of multicellular hS/PC spheroids in 14 days. Incorporation of sulfated HPG species in the hydrogel enhanced cell proliferation. Culture of hS/PCs in hyperGel+ in the presence of a Rho kinase inhibitor, Y-27632 (Y-27), led to the development of spheroids with a central lumen, increased the expression of acinar marker aquaporin-3 at the transcript level (AQP3), and decreased the expression of ductal marker keratin 7 at both the transcript (KRT7) and the protein levels (K7). Reduced expression of transforming growth factor beta (TGF-β) targets SMAD2/3 was also observed in Y27-treated cultures, suggesting attenuation of TGF-β signaling. Thus, hyperGel+ cooperates with the ROCK inhibitor to promote the development of lumened spheroids with enhanced expression of acinar markers.

Dendritic Polymers in Tissue Engineering: Contributions of PAMAM, PPI PEG and PEI to Injury Restoration and Bioactive Scaffold Evolution

The capability of radially polymerized bio-dendrimers and hyperbranched polymers for medical applications is well established. Perhaps the most important implementations are those that involve interactions with the regenerative mechanisms of cells. In general, they are non-toxic or exhibit very low toxicity. Thus, they allow unhindered and, in many cases, faster cell proliferation, a property that renders them ideal materials for tissue engineering scaffolds. Their resemblance to proteins permits the synthesis of derivatives that mimic collagen and elastin or are capable of biomimetic hydroxy apatite production. Due to their distinctive architecture (core, internal branches, terminal groups), dendritic polymers may play many roles. The internal cavities may host cell differentiation genes and antimicrobial protection drugs. Suitable terminal groups may modify the surface chemistry of cells and modulate the external membrane charge promoting cell adhesion and tissue assembly. They may also induce polymer cross-linking for healing implementation in the eyes, skin, and internal organ wounds. The review highlights all the different categories of hard and soft tissues that may be remediated with their contribution. The reader will also be exposed to the incorporation of methods for establishment of biomaterials, functionalization strategies, and the synthetic paths for organizing assemblies from biocompatible building blocks and natural metabolites.

Progressive use of nanocomposite hydrogels materials for regeneration of damaged cartilage and their tribological mechanical properties

Osteoarthritis (OA) is a non-inflammatory deteriorating debilitating state that bring about remarkable health and economic issues globally. Break down/deterioration of the articular cartilage (AC) is one of the pathologic characteristics of osteoarthritis (OA). Nanocomposite hydrogels (NCH) materials are evolving as a potential class of scaffolds for organ regeneration and tissue engineering. In recent years, innovative hydrogels specifically loaded with nanoparticles have been developed and synthesized with the goal of changing conventional cartilage treatments. The detailed development of a tailored nanocomposite hydrogels (NCH) material utilized for tissue engineering is presented in this review study. Also, the mechanical characteristics, particularly the tribological behavior, of these produced NCH have been highlighted. Large amounts of research and data on the hydrogel substance utilized in cartilage healing are summarized in the current review study. When determining future research gaps in the area of hydrogels for cartilage regeneration, such information will provide researchers an advantage to further develop NCH.

Synthesis of Hydrogels and Their Progress in Environmental Remediation and Antimicrobial Application

As a kind of efficient adsorptive material, hydrogel has a wide application prospect within different fields, owing to its unique 3D network structures composed of polymers. In this paper, different synthetic strategies, crosslinking methods and their corresponding limitations and outstanding contributions of applications in the fields of removing environmental pollutants are reviewed to further provide a prospective view of their applications in water resources sustainability. Furthermore, the applications within the biomedical field, especially in wound dressing, are also reviewed in this paper, mainly due to their unique water retention ability, antibacterial ability, and good biocompatibility. Finally, the development direction of hydrogels in the fields of environmental remediation and biomedicine were summarized and prospected.

Fabrication of Multiresponsive Magnetic Nanocomposite Double-Network Hydrogels for Controlled Release Applications

Nanocomposite double-network hydrogels (ncDN hydrogels) have been demonstrated as promising biomaterials to present several desired properties (e.g., high mechanical strength, stimuli-responsiveness, and local therapy) for biomedicine. Here, a new type of ncDN hydrogels featuring definable microstructures and properties as well as multistimuli responsiveness for controlled release applications is developed. Amine-functionalized iron oxide nanoparticles (IOPs_NH₂ ) are used as nanoparticle cross-linkers to simultaneously connect the dual networks of gelatin (Gel) and polydextran aldehyde (PDA) through hydrogen bonding, electrostatic interactions, and dynamic imine bonds. The pH- and temperature-responsive Gel/PDA/IOP_NH₂ ncDN hydrogels present a fast release profile of proteins at acidic pH and high temperature. Besides, IOP_NH₂ also contributes the magnetic-responsiveness to the ncDN hydrogels, allowing the use of magnetic field to generate heat to facilitate the structural change of hydrogels and the subsequent applications. Taken together, a versatile ncDN hydrogel platform capable of multistimuli responsiveness and local heating for controlled release is developed for advanced biomedical applications.

Recent trends in gelatin methacryloyl nanocomposite hydrogels for tissue engineering

Gelatin methacryloyl (GelMA), a photocrosslinkable gelatin-based hydrogel, has been immensely used for diverse applications in tissue engineering and drug delivery. Apart from its excellent functionality and versatile mechanical properties, it is also suitable for a wide range of fabrication methodologies to generate tissue constructs of desired shapes and sizes. Despite its exceptional characteristics, it is predominantly limited by its weak mechanical strength, as some tissue types naturally possess high mechanical stiffness. The use of high GelMA concentrations yields high mechanical strength, but not without the compromise in its porosity, degradability, and three-dimensional (3D) cell attachment. Recently, GelMA has been blended with various natural and synthetic biomaterials to reinforce its physical properties to match with the tissue to be engineered. Among these, nanomaterials have been extensively used to form a composite with GelMA, as they increase its biological and physicochemical properties without affecting the unique characteristics of GelMA and also introduce electrical and magnetic properties. This review article presents the recent advances in the formation of hybrid GelMA nanocomposites using a variety of nanomaterials (carbon, metal, polymer, and mineral-based). We give an overview of each nanomaterial's characteristics followed by a discussion of the enhancement in GelMA's physical properties after its incorporation. Finally, we also highlight the use of each GelMA nanocomposite for different applications, such as cardiac, bone, and neural regeneration.

A Smart Core-Crosslinked Supramolecular Drug Delivery System (SDDS) Enabled by Pendant Cyclodextrins Encapsulation of Drug Dimers via Host-Guest Interaction

Owing to poor aqueous solubility and low delivery efficiency, most of anti-cancer chemodrugs depend on various smart drug delivery platforms to enhance the treatment efficacy. Herein, a stimuli-responsive supramolecular drug delivery system (SDDS) is developed based on polymeric cyclodextrins (PCD) which crosslinked by stimuli-cleavable drug dimers via host-guest interaction. PEGylated PCD was precisely controlled synthesized by ring-opening polymerization and azide-alkyne click chemistry, and two doxorubicins (DOX) were linked with a disulfide bond to form a drug dimer (ss-DOX). They then co-assembled into supramolecular micelles. Drug dimers were utilized as cross-linkers to stabilize the micelles. The drug loading efficiency was very high that could be up to 98%. The size and morphology were measured by DLS and TEM. Owing to the disulfide bonds of drug dimers, these supramolecular micelles were dissociated by treating with dithiothreitol (DTT). In the meanwhile, the free DOXs were recovered and released from cavities of cyclodextrins because of dynamic equilibrium and hydrophilicity changes. The release profile was studied under mimic physiological conditions. Furthermore, in vitro cytotoxicity study showed excellent anti-cancer efficacy of reduced-responsive supramolecular polymeric micelles. Therefore, it can be served as a safe and stimuli-responsive SDDS for cancer therapy.

Enhancing performances of hemp fiber/natural rubber composites via polyhydric hyperbranched polyester

High-performance rubber composites can be obtained by combining the strength of fiber with the high elasticity of rubber. In this article, environmentally friendly natural rubber (NR)/carbon (CB) composites reinforced by maleic anhydride (MAH) grafted hemp fiber (HF) in the presence of polyhydric hyper-branched polyester (PHP) were studied. The grafting of MAH on the surface of HF (HF-MAH) improves the roughness of fibers, the introduced C=C participates in rubber covulcanization with NR matrix at high temperature, thus enhancing the physical locking and chemical crosslinking between HF and NR matrix. The bridge effect was produced between HF-MAH and rubber matrix by PHP, and the interfacial adhesion was further enhanced. As a result, the tensile strength, tear strength, and elongation at break were improved by approximately 14.5, 26.2, and 10.8%, respectively. The 100 and 300% constant elongation stress was increased by 134 and 113%, and the cutting resistance was also improved obviously.

Synergistic enhancement of tendon-to-bone healing via anti-inflammatory and pro-differentiation effects caused by sustained release of Mg2+/curcumin from injectable self-healing hydrogels

Poor healing response after rotator cuff reconstruction is multifactorial, with the inflammatory microenvironment and deficiency of stem cell differentiation factors at the lesion site being most relevant. However, there is a lack of effective tissue engineering strategies that can simultaneously exert anti-inflammatory and pro-differentiation effects to promote rotator cuff healing.

Methods: In this study, we synthesized and characterized a novel active drug delivery vector that successfully overcame the challenge of simultaneous high-efficiency loading and controlled release of Mg²⁺ and curcumin. The anti-inflammatory and pro-differentiation effects of the composite hydrogel were evaluated in vitro and in vivo. Moreover, healing of the rotator cuff tendon-to-bone interface was studied by histology, immunofluorescence, and biomechanical tests.

Results: The composite hydrogel exhibited excellent biocompatibility and injectability, good adhesiveness, and rapid self-healing. The released curcumin showed obvious anti-inflammatory and antioxidation effects, which protected stem cells and tendon matrix. Furthermore, released Mg²⁺ promoted stem cell aggregation and chondrogenesis. Moreover, biomechanical tests and histological results of a rat rotator cuff tear model at 8 weeks after surgery indicated that the composite hydrogel significantly enhanced tendon-to-bone healing.

Conclusions: The composite hydrogel mediated sustained in situ release of curcumin and Mg²⁺ to effectively promote rotator cuff tendon-to-bone healing via anti-inflammatory and pro-differentiation effects. Therefore, this composite hydrogel offers significant promise for rotator cuff repair.

Dynamic cross-linking of an alginate-acrylamide tough hydrogel system: time-resolved in situ mapping of gel self-assembly

Hydrogels are a popular class of biomaterial that are used in a number of commercial applications (e.g.; contact lenses, drug delivery, and prophylactics). Alginate-based tough hydrogel systems, interpenetrated with acrylamide, reportedly form both ionic and covalent cross-links, giving rise to their remarkable mechanical properties. In this work, we explore the nature, onset and extent of such hybrid bonding interactions between the complementary networks in a model double-network alginate-acrylamide system, using a host of characterisation techniques (e.g.; FTIR, Raman, UV-vis, and fluorescence spectroscopies), in a time-resolved manner. Further, due to the similarity of bonding effects across many such complementary, interpenetrating hydrogel networks, the broad bonding interactions and mechanisms observed during gelation in this model system, are thought to be commonly replicated across alginate-based and broader double-network hydrogels, where both physical and chemical bonding effects are present. Analytical techniques followed real-time bond formation, environmental changes and re-organisational processes that occurred. Experiments broadly identified two phases of reaction; phase I where covalent interaction and physical entanglements predominate, and; phase II where ionic cross-linking effects are dominant. Contrary to past reports, ionic cross-linking occurred more favourably via mannuronate blocks of the alginate chain, initially. Evolution of such bonding interactions was also correlated with the developing tensile and compressive properties. These structure-property findings provide mechanistic insights and future synthetic intervention routes to manipulate the chemo-physico-mechanical properties of dynamically-forming tough hydrogel structures according to need (i.e.; durability, biocompatibility, adhesion, etc.), allowing expansion to a broader range of more physically and/or environmentally demanding biomaterials applications.

Hyperbranched polymer hydrogels with large stimuli-responsive changes in storage moduli and peroxide-induced healing

Hydrogels prepared using hyperbranched polymers with dynamic disulfide bonds show larger changes in moduli upon exposure to chemical stimuli for both softening and stiffening responses compared to linear polymers.

Synthesis and characterization of fully biobased polyesters with tunable branched architectures

A series of sugar-derived triols and biobased diacids were combined to prepare fully biobased branched polyesters with different structural features by melt polycondensation.

A review of the properties and applications of bioadhesive hydrogels

Due to their outstanding properties, bioadhesive hydrogels have been extensively studied by researchers in recent years.

Photopolymerizable Biomaterials and Light-Based 3D Printing Strategies for Biomedical Applications

Since the advent of additive manufacturing, known commonly as 3D printing, this technology has revolutionized the biofabrication landscape and driven numerous pivotal advancements in tissue engineering and regenerative medicine. Many 3D printing methods were developed in short course after Charles Hull first introduced the power of stereolithography to the world. However, materials development was not met with the same enthusiasm and remained the bottleneck in the field for some time. Only in the past decade has there been deliberate development to expand the materials toolbox for 3D printing applications to meet the true potential of 3D printing technologies. Herein, we review the development of biomaterials suited for light-based 3D printing modalities with an emphasis on bioprinting applications. We discuss the chemical mechanisms that govern photopolymerization and highlight the application of natural, synthetic, and composite biomaterials as 3D printed hydrogels. Because the quality of a 3D printed construct is highly dependent on both the material properties and processing technique, we included a final section on the theoretical and practical aspects behind light-based 3D printing as well as ways to employ that knowledge to troubleshoot and standardize the optimization of printing parameters.

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.

Composite Hydrogels in Three-Dimensional in vitro Models

3-dimensional (3D) in vitro models were developed in order to mimic the complexity of real organ/tissue in a dish. They offer new possibilities to model biological processes in more physiologically relevant ways which can be applied to a myriad of applications including drug development, toxicity screening and regenerative medicine. Hydrogels are the most relevant tissue-like matrices to support the development of 3D in vitro models since they are in many ways akin to the native extracellular matrix (ECM). For the purpose of further improving matrix relevance or to impart specific functionalities, composite hydrogels have attracted increasing attention. These could incorporate drugs to control cell fates, additional ECM elements to improve mechanical properties, biomolecules to improve biological activities or any combinations of the above. In this Review, recent developments in using composite hydrogels laden with cells as biomimetic tissue- or organ-like constructs, and as matrices for multi-cell type organoid cultures are highlighted. The latest composite hydrogel systems that contain nanomaterials, biological factors, and combinations of biopolymers (e.g., proteins and polysaccharide), such as Interpenetrating Networks (IPNs) and Soft Network Composites (SNCs) are also presented. While promising, challenges remain. These will be discussed in light of future perspectives toward encompassing diverse composite hydrogel platforms for an improved organ environment in vitro.

Preparation of Multiwall Carbon Nanotubes Embedded Electroconductive Multi-Microchannel Scaffolds for Neuron Growth under Electrical Stimulation

Objectives

To prepare the conductive MWCNT (multiwall carbon nanotube)-agarose scaffolds with multi-microchannel for neuron growth under electrical stimulation.

Methods

The scaffolds were produced by gradient freeze and lyophilization methods. The synthesized materials were characterized by SEM and near-infrared spectroscopy, and their microstructure, swelling-deswelling, conductivity, biocompatibility, and shape memory behavior were measured. A three-dimensional culture model by implanting cells into scaffolds was built, and the behaviors of RSC96 cells on scaffolds under electrical stimulation were evaluated.

Results

The addition of MWCNT did not affect the pore composition ratio and shape memory of agarose scaffolds, but 0.025% wt MWCNT in scaffolds improved the swelling ratio and water retention at the swelling equilibrium state. Though MWCNTs in high concentration had slight effect on proliferation of RSC96 cells and PC12 cells, there was no difference that the expressions of neurofilament of RSC96 cells on scaffolds with MWCNTs of different concentration. RSC96 cells arranged better along the longitudinal axis of scaffolds and showed better adhesion on both 0.025% MWCNT-agarose scaffolds and 0.05% MWCNT-agarose scaffolds compared to other scaffolds.

Conclusions

Agarose scaffolds with MWCNTs possessed promising applicable prospect in peripheral nerve defects.

Soft and Ion-Conducting Materials in Bioelectronics: From Conducting Polymers to Hydrogels

Bioelectronics devices that directly interface with cells and tissue have applications in neural and cardiac stimulation and recording, electroceuticals, and brain machine interfaces for prostheses. The interface between bioelectronic devices and biological tissue is inherently challenging due to the mismatch in both mechanical properties (hard vs soft) and charge carriers (electrons vs ions). In addition to conventional metals and silicon, new materials have bridged this interface, including conducting polymers, carbon-based nanomaterials, as well as ion-conducting polymers and hydrogels. This review provides an update on advances in soft bioelectronic materials for current and future therapeutic applications. Specifically, this review focuses on soft materials that can conduct both electrons and ions, and also deliver drugs and small molecules. The future opportunities and emerging challenges in the field are also highlighted.

Novozym 435-Catalyzed Synthesis of Well-Defined Hyperbranched Aliphatic Poly(β-thioether ester)

A series of new hyperbranched aliphatic poly(β-thioether ester)s were prepared by the enzymatic ring-opening polycondensation of 1,4-oxathiepan-7-one (OTO) and AB2/ABB' comonomer with acid-labile β-thiopropionate groups. Two kinds of comonomers, methyl 3-((3-hydroxy-2-(hydroxymethyl)propyl)thio)propanoate (HHTP) and methyl 3-((2,3-dihydroxypropyl)thio)propanoate (DHTP), with different primary alcohols and secondary alcohols, were synthesized by thiol-ene click chemistry and thiol-ene Michael addition, respectively. Immobilized lipase B from Candida antarctica (CALB), Novozym 435, was used as the catalyst. The random copolymers were characterized by 1H-NMR, 13C-NMR, GPC, TGA, and DSC. All branched copolyesters had high molecular weights over 15,000 Da with narrow polydispersities in the range of 1.75-2.01 and were amorphous polymers. Their degradation properties under acidic conditions were also studied in vitro. The polymeric nanoparticles of hyperbranched poly(β-thioether ester)s were successfully obtained and showed good oxidation-responsive properties, indicating their potential for biomedical applications.

Formation of Monolithic Ion-Selective Transport Media Based on "Click" Cross-Linked Hyperbranched Polyglycerol

In the emerging field of organic bioelectronics, conducting polymers and ion-selective membranes are combined to form resistors, diodes, transistors, and circuits that transport and process both electronic and ionic signals. Such bioelectronics concepts have been explored in delivery devices that translate electronic addressing signals into the transport and dispensing of small charged biomolecules at high specificity and spatiotemporal resolution. Manufacturing such "iontronic" devices generally involves classical thin film processing of polyelectrolyte layers and insulators followed by application of electrolytes. This approach makes miniaturization and integration difficult, simply because the ion selective polyelectrolytes swell after completing the manufacturing. To advance such bioelectronics/iontronics and to enable applications where relatively larger molecules can be delivered, it is important to develop a versatile material system in which the charge/size selectivity can be easily tailormade at the same time enabling easy manufacturing of complex and miniaturized structures. Here, we report a one-pot synthesis approach with minimal amount of organic solvent to achieve cationic hyperbranched polyglycerol films for iontronics applications. The hyperbranched structure allows for tunable pre multi-functionalization, which combines available unsaturated groups used in crosslinking along with ionic groups for electrolytic properties, to achieve a one-step process when applied in devices for monolithic membrane gel formation with selective electrophoretic transport of molecules.

Cellular Behavior of RAW264.7 Cells in 3D Poly(ethylene glycol) Hydrogel Niches

Although macrophages undergo dynamic cellular responses in diverse extracellular environments, macrophage research has mostly relied on conventional culture methodologies such as two-dimensional and suspension cultures. In contrast, recent efforts have revealed evidence of the characteristic cellular behaviors of macrophages in actual tissues using a three-dimensional (3D) culture matrix. In this work, we exploited a poly(ethylene glycol)-based hydrogel as a macrophage culture matrix and observed cellular behaviors in 3D by manipulating the matrix properties. In the 3D microenvironment, macrophage-like RAW264.7 cells proliferated and formed spherical clusters by degrading the surrounding hydrogel network. Interestingly, we observed the significant upregulation of matrix metalloproteinases (MMPs) (i.e., MMP9 and MMP14) as well as M1 polarization markers (i.e., iNOS, COX2, TNF-α) in 3D, whereas M2 polarization markers (i.e., CD206, Arg1, TGF-β) were downregulated. Specifically, the expressions of both M1 and M2 markers were simultaneously increased in a stiff matrix compared to those of a soft matrix. In addition, matrix degradability significantly influenced the TNF-α secretion of encapsulated RAW264.7 cells. The MMP sensitivity of the hydrogel decreased TNF-α expression in a soft matrix, whereas it upregulated TNF-α in a stiff matrix compared to those of MMP-insensitive hydrogel. These findings suggest that the highly tunable poly(ethylene glycol) hydrogels can dictate macrophage behavior by altering the surrounding 3D microenvironment.

Mechanically enhanced nested-network hydrogels as a coating material for biomedical devices

Well-organized composite formations such as hierarchical nested-network (NN) structure in bone tissue and reticular connective tissue present remarkable mechanical strength and play a crucial role in achieving physical and biological functions for living organisms. Inspired by these delicate microstructures in nature, an analogous scaffold of double network hydrogel was fabricated by creating a poly(2-hydroxyethyl methacrylate) (pHEMA) network in the porous structure of alginate hydrogels. The resulting hydrogel possessed hierarchical NN structure and showed significantly improved mechanical strength but still maintained high elasticity comparable to soft tissues due to a mutual strengthening effect between the two networks. The tough hydrogel is also self-lubricated, exhibiting a surface friction coefficient comparable with polydimethylsiloxane (PDMS) substrates lubricated by a commercial aqueous lubricant (K-Y Jelly) and other low surface friction hydrogels. Additional properties of this hydrogel include high hydrophilicity, good biocompatibility, tunable cell adhesion and bacterial resistance after incorporation of silver nanoparticles. Firm bonding of the hydrogel on silicone substrates could be achieved through facile chemical modification, thus enabling the use of this hydrogel as a versatile coating material for biomedical applications.

STATEMENT OF SIGNIFICANCE

In this study, we developed a tough hydrogel by crosslinking HEMA monomers in alginate hydrogels and forming a well-organized structure of hierarchical nested network (NN). Different from most reported stretchable alginate-based hydrogels, the NN hydrogel shows higher compressive strength but retains comparable softness to alginate counterparts. This work further demonstrated the good integration of the tough hydrogel with silicone substrates through chemical modification and micropillar structures. Other properties including surface friction, biocompatibility and bacterial resistance were investigated and the hydrogel shows a great promise as a versatile coating material for biomedical applications.

Thermo- and redox-responsive dendronized polymer hydrogels

Unique supramolecular coordination of Fe²⁺ with terpyridine afford these hydrogels redox-responsive sol–gel transitions, while characteristic thermoresponsive properties from OEG-based first generation dendronized polymers render these hydrogels thermally-induced macroscopical volume changes and enhanced mechanical properties.

Novel fluorinated hyperbranched polyimides with excellent thermal stability, UV-shielding property, organosolubility, and low dielectric constants

A novel fluorinated aromatic triamine, named 1,3,5-tris (4-(2-trifluoromethyl-4-aminophenoxy)phenyl) benzene (TTFAPOPB), with several –CF3 groups, prolonged chain segments, and ether bonds was first successfully synthesized via a three-step reaction. Then a series of fluorinated hyperbranched polyimides (FHBPIs) with terminal amino or anhydride groups were prepared by condensation polymerization, which were derived from three commercial dianhydrides and the obtained triamine. The prepared FHBPIs showed excellent optical properties with the transmittance reaching 94.5% at 800 nm, favorable ultraviolet (UV)-shielding property with only 27% photodegradation of methylene blue solution after intense UV irradiation for 50 min, good thermal stability with glass transition temperature between 225°C and 264°C, and 10% weight loss temperature of 520–555°C and 509–541°C, respectively, in nitrogen and air atmosphere. They also exhibited relatively good mechanical properties with tensile strength, tensile modulus, and elongation at break values of 64.2–84.2 MPa, 1.2–1.5 GPa, and 6–10%, respectively. Moreover, the introduction of –CF3 and hyperbranched architecture reduced the dielectric constants of the FHBPIs to 2.69–2.92 and increased the surface contact angles to more than 98°. Thus, the FHBPIs are promising dielectric or UV-shielding materials.

A Bioinspired Alginate-Gum Arabic Hydrogel with Micro-/Nanoscale Structures for Controlled Drug Release in Chronic Wound Healing

Biopolymeric hydrogels have drawn increasing research interest in biomaterials due to their tunable physical and chemical properties for both creating bioactive cellular microenvironment and serving as sustainable therapeutic reagents. Inspired by a naturally occurring hydrogel secreted from the carnivorous Sundew plant for trapping insects, here we have developed a bioinspired hydrogel to deliver mitsugumin 53 (MG53), an important protein in cell membrane repair, for chronic wound healing. Both chemical compositions and micro-/nanomorphological properties inherent from the natural Sundew hydrogel were mimicked using sodium alginate and gum arabic with calcium ion-mediated cross-linking. On the basis of atomic force microscopy (AFM) force measurements, an optimal sticky hydrogel scaffold was obtained through orthogonal experimental design. Imaging and mechanical analysis showed the distinct correlation between structural morphology, adhesion characteristics, and mechanical properties of the Sundew-inspired hydrogel. Combined characterization and biochemistry techniques were utilized to uncover the underlying molecular composition involved in the interactions between hydrogel and protein. In vitro drug release experiments confirmed that the Sundew-inspired hydrogel had a biphasic-kinetics release, which can facilitate both fast delivery of MG53 for improving the reepithelization process of the wounds and sustained release of the protein for treating chronic wounds. In vivo experiments showed that the Sundew-inspired hydrogel encapsulating with rhMG53 could facilitate dermal wound healing in mouse model. Together, these studies confirmed that the Sundew-inspired hydrogel has both tunable micro-/nanostructures and physicochemical properties, which enable it as a delivery vehicle for chronic wounding healing. The research may provide a new way to develop biocompatible and tunable biomaterials for sustainable drug release to meet the needs of biological activities.

Synthesis and Application of Injectable Bioorthogonal Dendrimer Hydrogels for Local Drug Delivery

We developed novel dendrimer hydrogels (DH)s on the basis of bioorthogonal chemistry, in which polyamidoamine (PAMAM) dendrimer generation 4.0 (G4) functionalized with strained alkyne dibenzocyclooctyne (DBCO) via PEG spacer (M_n = 2,000 g/mol) underwent strain-promoted azide-alkyne cycloaddition (SPAAC) with polyethylene glycol bisazide (PEG-BA) (M_n= 20,000 g/mol) to generate a dendrimer-PEG cross-linked network. This platform offers a high degree of functionality and modularity. A wide range of structural parameters including dendrimer generation, degree of PEGylation, loading density of clickable DBCO groups, PEG-BA chain length as well as the ratio of clickable dendrimer to PEG-BA and their concentrations can be readily manipulated to tune chemical and physical properties of DHs. We used this platform to prepare an injectable liquid DH. This bioorthogonal DH exhibited high cytocompatibility and enabled sustained release of the anticancer drug 5-fluorouracil (5-FU). Following intratumoral injection, the DH/5-FU formulation significantly suppressed tumor growth and improved survival of HN12 tumor-bearing mice by promoting tumor cell death as well as by reducing tumor cell proliferation and angiogenesis.

Patterning Three-Dimensional Hydrogel Microenvironments Using Hyperbranched Polyglycerols for Independent Control of Mesh Size and Stiffness

The extracellular matrix is an environment rich with structural, mechanical, and molecular signals that can impact cell biology. Traditional approaches in hydrogel biomaterial design often rely on modifying the concentration of cross-linking groups to adjust mechanical properties. However, this strategy provides limited capacity to control additional important parameters in 3D cell culture such as microstructure and molecular diffusivity. Here we describe the use of multifunctional hyperbranched polyglycerols (HPGs) to manipulate the mechanical properties of polyethylene glycol (PEG) hydrogels while not altering biomolecule diffusion. This strategy also provides the ability to separately regulate spatial and temporal distribution of biomolecules tethered within the hydrogel. The functionalized HPGs used here can also react through a copper-free click chemistry, allowing for the encapsulation of cells and covalently tethered biomolecules within the hydrogel. Because of the hyperbranched architecture and unique properties of HPGs, their addition into PEG hydrogels affords opportunities to locally alter hydrogel cross-linking density with minimal effects on global network architecture. Additionally, photocoupling chemistry allows micropatterning of bioactive cues within the three-dimensional gel structure. This approach therefore enables us to tailor mechanical and diffusive properties independently while further allowing for local modulation of biomolecular cues to create increasingly complex cell culture microenvironments.

In Situ-Forming Polyamidoamine Dendrimer Hydrogels with Tunable Properties Prepared via Aza-Michael Addition Reaction

In this work, we describe synthesis and characterization of novel in situ-forming polyamidoamine (PAMAM) dendrimer hydrogels (DHs) with tunable properties prepared via highly efficient aza-Michael addition reaction. PAMAM dendrimer G5 was chosen as the underlying core and functionalized with various degrees of acetylation using acetic anhydride. The nucleophilic amines on the dendrimer surface reacted with α, β-unsaturated ester in acrylate groups of polyethylene glycol diacrylate (PEG-DA, Mn = 575 g/mol) via aza-Michael addition reaction to form dendrimer hydrogels without the use of any catalyst. The solidification time, rheological behavior, network structure, swelling, and degradation properties of the hydrogel were tuned by adjusting the dendrimer surface acetylation degree and dendrimer concentration. The DHs were shown to be highly cytocompatible and support cell adhesion and proliferation. We also prepared an injectable dendrimer hydrogel formulation to deliver the anticancer drug 5-fluorouracil (5-FU) and demonstrated that the injectable formulation efficiently inhibited tumor growth following intratumoral injection. Taken together, this new class of dendrimer hydrogel prepared by aza-Michael addition reaction can serve as a safe tunable platform for drug delivery and tissue engineering.

Nanocomposite Hydrogels and Their Applications in Tissue Engineering

Nanocomposite (NC) hydrogels, organic-inorganic hybrid materials, are of great interest as artificial three-dimensional (3D) biomaterials for biomedical applications. NC hydrogels are prepared in water by chemically or physically cross-linking organic polymers with nanomaterials (NMs). The incorporation of hard inorganic NMs into the soft organic polymer matrix enhances the physical, chemical, and biological properties of NC hydrogels. Therefore, NC hydrogels are excellent candidates for artificial 3D biomaterials, particularly in tissue engineering applications, where they can mimic the chemical, mechanical, electrical, and biological properties of native tissues. A wide range of functional NMs and synthetic or natural organic polymers have been used to design new NC hydrogels with novel properties and tailored functionalities for biomedical uses. Each of these approaches can improve the development of NC hydrogels and, thus, provide advanced 3D biomaterials for biomedical applications.

S-nitrosothiol-modified hyperbranched polyesters

Hyperbranched polyesters with a range of exterior thiol modifications were synthesized through a Michael addition thiol-ene reaction. S-Nitrosothiol nitric oxide (NO) donors were subsequently introduced onto the scaffolds to yield NO-releasing polyesters with total NO storage of ~2.0 μmol mg^-1. Multiple decomposition pathways (i.e., use of light, copper ions, and heat) triggered S-nitrosothiol NO donor breakdown and NO release under physiological conditions (37 °C, pH 7.4). The NO-releasing polyesters were characterized as a function of chemical modification and scaffold size or generation. The approaches described herein expand the scope of biodegradable NO-releasing materials with large NO payloads.

Development of novel electrically conductive scaffold based on hyperbranched polyester and polythiophene for tissue engineering applications

A novel electrically conductive scaffold containing hyperbranched aliphatic polyester (HAP), polythiophene (PTh), and poly(ε-caprolactone) (PCL) for regenerative medicine application was succesfully fabricated via electrospinning technique. For this purpose, the HAP (G4; fourth generation) was synthesized via melt polycondensation reaction from tris(methylol)propane and 2,2-bis(methylol)propionic acid (bis-MPA). Afterward, the synthesized HAP was functionalized with 2-thiopheneacetic acid in the presence of N,N-dicyclohexyl carbodiimide, and N-hydroxysuccinimide as coupling agent and catalyst, respectively, to afford a thiophene-functionalized G4 macromonomer. This macromonomer was subsequently used in chemical oxidation copolymerization with thiophene monomer to produce a star-shaped PTh with G4 core (G4-PTh). The solution of the G4-PTh, and PCL was electrospun to produce uniform, conductive, and biocompatible nanofibers. The conductivity, hydrophilicity, and mechanical properties of these nanofibers were investigated. The biocompatibility of the electrospun nanofibers were evaluated by assessing the adhesion and proliferation of mouse osteoblast MC3T3-E1 cell line and in vitro degradability to demonstrate their potential uses as a tissue engineering scaffold. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2673-2684, 2016.

Emerging translational research on magnetic nanoparticles for regenerative medicine

Regenerative medicine, which replaces or regenerates human cells, tissues or organs, to restore or establish normal function, is one of the fastest-evolving interdisciplinary fields in healthcare. Over 200 regenerative medicine products, including cell-based therapies, tissue-engineered biomaterials, scaffolds and implantable devices, have been used in clinical development for diseases such as diabetes and inflammatory and immune diseases. To facilitate the translation of regenerative medicine from research to clinic, nanotechnology, especially magnetic nanoparticles have attracted extensive attention due to their unique optical, electrical, and magnetic properties and specific dimensions. In this review paper, we intend to summarize current advances, challenges, and future opportunities of magnetic nanoparticles for regenerative medicine.

Forming Spacers in Situ by Photolithography to Mechanically Stabilize Electrofluidic-Based Switchable Optical Elements

Electro-Fluidic Displays (EFD) have been demonstrated to be an attractive technology for incorporation into portable display devices. EFDs have excellent optical efficiency and fast switching enabling video content. Ensuring mechanical stability of EFD display cells is a key challenge and essential for developing large area as well as flexible displays. Although the electro-optic performance of an EFD, unlike a liquid crystal display (LCD), is insensitive to cell-gap, extreme changes in cell-gap can result in irreversible collapse of the cell. Here we use photolithography to develop spacers to prevent cell-gap collapse and provide the required mechanical stability for EFD devices. The spacer is formed directly on the cover plates (ITO/glass) after cell assembly with UV light induced phase separation polymerization in the illuminated area. Phase separation behavior between polar aqueous solution and polymer is closely related to the solubility of acrylate monomers. In this work, polyethylene glycol diacrylate (PEGDA) as cross-linker, 2-hydroxyethyl acrylate (HEA) and acrylic acid or acrylamide as co-monomers are investigated for fabricating the spacers. PEGDA was added to the mixtures in order to increase the mechanical strength of the spacer. The spacers showed excellent performance for cell-gap control in EFD devices.

Recent Advances in Dendritic Macromonomers for Hydrogel Formation and Their Medical Applications

Hydrogels represent one of the most important classes of biomaterials and are of interest for various medical applications including wound repair, tissue engineering, and drug release. Hydrogels possess tunable mechanical properties, biocompatibility, nontoxicity, and similarity to natural soft tissues. The need for hydrogels with specific properties, based on the design requirements of the in vitro, in vivo, or clinical application, motivates researchers to develop new synthetic approaches and cross-linking methodologies to form novel hydrogels with unique properties. The use of dendritic macromonomers represents one elegant strategy for the formation of hydrogels with specific properties. Specifically, the uniformity of dendrimers combined with the control of their size, architecture, density, and surface groups make them promising cross-linkers for hydrogel formation. Over the last two decades, a large variety of dendritic-based hydrogels are reported for their potential use in the clinic. This review describes the state of the art with these different dendritic hydrogel formulations including their design requirements, the synthetic routes, the measurement and determination of their properties, the evaluation of their in vitro and in vivo performances, and future perspectives.