The preparation of pH and GSH dual responsive thiolated heparin/DOX complex and its application as drug carrier

The complicated preparation procedure and carrier's suspicious biocompatibility are two major limitations for traditional drug carrier. In this manuscript, a novel polyion complex (PIC) was prepared by simply mixing two biocompatible components, thiolated heparin and doxorubicin (DOX), and subsequently crosslinking under atmosphere, so that it can overcome the above limitations. The PIC's particle size kept stable for one week storage in PBS, and the particles wouldn't decomposed by the dilution, indicating excellent storage and anti-dilution stability resulting from the crosslinking. The PIC can release the larger amount of DOX in acidic environment than psychological environment, and largest amount in acidic and glutathione (GSH) environment, showing the pH and GSH dual sensitive drug release behavior. Furthermore, the PIC exhibited obvious tumor inhibition effect in vivo as well as long circulation ability and low heart toxicity by anti-tumor tests on tumor-bearing mice. Consequently, as-prepared PIC shows promising potential in drug carrier application.

Heparin-based and heparin-inspired hydrogels: size-effect, gelation and biomedical applications

Heparin is the highest negatively charged biomolecule, which is a polysaccharide belonging to the glycosaminoglycan family, and its role as a regulator of various proteins, cells and tissues in the human body makes it an indispensable macromolecule. Heparin-based hydrogels are widely investigated in various applications including implantation, tissue engineering, biosensors, and drug-controlled release due to the 3D-constructs of hydrogels. However, heparin has supply and safety problems because it is usually derived from animal sources, and has the clinical limitations of bleeding and thrombocytopenia. Therefore, analogous heparin-mimicking polymers and hydrogels derived from non-animal and/or totally synthetic sources have been widely studied in recent years. In this review, the progress and potential biomedical applications of heparin-based and heparin-inspired hydrogels are highlighted. We classify the forms of these hydrogels by their size including macro-hydrogels, injectable hydrogels, and nano-hydrogels. Then, we summarize the various fabrication strategies for these hydrogels including chemical covalent bonding, physical conjugation, and the combination of chemical and physical interactions. Covalent bonding includes free radical polymerization of vinyl-containing components, amide bond formation reaction, Michael-type addition reaction, click-chemistry, divinyl sulfone crosslinking, and mussel-inspired coating. Hydrogels physically conjugated via host-guest interaction, electrostatic interaction, hydrogen bonding, and hydrophobic interaction are also discussed. Finally, we conclude with the challenges and future directions for the fabrication and the industrialization of heparin-based and heparin-inspired hydrogels. We believe that this review will attract more attention toward the design of heparin-based and heparin-inspired hydrogels, leading to future advancements in this emerging research field.

Graphene-based advanced nanoplatforms and biocomposites from environmentally friendly and biomimetic approaches

Environmentally friendly and biomimetic approaches to fabricate graphene-based advanced nanoplatforms and biocomposites for biomedical applications are summarized in this review.

Inflammation-responsive self-regulated drug release from ultrathin hydrogel coating

Heterotopic ossification(HO) is a potential severe complication after many biomaterial implanting surgeries, and the inflammation environment caused by the implanting-associated infections is considered as the main nosogenesis. Herein, an inflammation-responsive drug release system was designed by chemically conjugating indometacin (via ester group) onto hydrogel coating to realize local self-regulated drug release to prevent HO. In our strategy, poly(3-mercaptopropyl)trimethoxysilane-co-acrylic acrylate and polyvinyl alcohol (providing anchoring sites for drug molecules) were firstly synthesized and functionalized with ene-groups, then a hydrogel layer was formed and covalently attached onto thiol-modified substrate via thiol-ene click chemistry, followed by grafting indometacin. A porous structure of the attached hydrogel layer was observed by scanning electron microscopy, and the presence of drug molecules in the hydrogel layer was confirmed by X-ray photoelectron spectroscopy and UV-vis absorption spectra. The drug release could be triggered under the mimicking inflammation environment, and the release rate was responsive to the inflammation degree. In addition, after attaching the hydrogel coating, the substrate showed low cytotoxicity, and high promotion for cell adhesion and proliferation. The excellent hemocompatibility of the hydrogel coating was also demonstrated by prolonged clotting time and suppressed platelet adhesion. This work suggests that the inflammation-responsive indometacin conjugated hydrogel coating has great potential to be used for prophylaxis HO.

Dual crosslinked chondroitin sulfate injectable hydrogel formed via continuous Diels-Alder (DA) click chemistry for bone repair

In the present work, a thermosensetive copolymer with a low gelation concentration under 37°C, F127@ChS (F127 crosslinked chondroitin sulfate) was synthesized via DA click chemistry between F127-AMI (maleimido terminated F127) and ChS-furan (furfurylamine grafted chondroitin sulfate). Then, dual crosslinked hydrogels were prepared based on F127@ChS and PEG-AMI (maleimido terminated polyethylene glycol). The physical crosslinking of F127@ChS affords the hydrogel fast gelation behavior, while in situ DA click reaction occurred between F127@ChS and PEG-AMI affords the hydrogel system covalent crosslinking. The dual crosslinked injectable hydrogel was applied as scaffold to load BMP-4 for rat cranial defect repair. As indicated by X-ray imaging, cranial digital images and histological (HE and Masson) staining analysis, new bone tissues were formed in the defected area after 12 weeks repair. The results demonstrate that the novel dual crosslinked injectable hydrogel offer an interesting option for cranial bone tissue engineering.

Functional Graphene Nanomaterials Based Architectures: Biointeractions, Fabrications, and Emerging Biological Applications

Functional graphene nanomaterials (FGNs) are fast emerging materials with extremely unique physical and chemical properties and physiological ability to interfere and/or interact with bioorganisms; as a result, FGNs present manifold possibilities for diverse biological applications. Beyond their use in drug/gene delivery, phototherapy, and bioimaging, recent studies have revealed that FGNs can significantly promote interfacial biointeractions, in particular, with proteins, mammalian cells/stem cells, and microbials. FGNs can adsorb and concentrate nutrition factors including proteins from physiological media. This accelerates the formation of extracellular matrix, which eventually promotes cell colonization by providing a more beneficial microenvironment for cell adhesion and growth. Furthermore, FGNs can also interact with cocultured cells by physical or chemical stimulation, which significantly mediate their cellular signaling and biological performance. In this review, we elucidate FGNs-bioorganism interactions and summarize recent advancements on designing FGN-based two-dimensional and three-dimensional architectures as multifunctional biological platforms. We have also discussed the representative biological applications regarding these FGN-based bioactive architectures. Furthermore, the future perspectives and emerging challenges will also be highlighted. Due to the lack of comprehensive reviews in this emerging field, this review may catch great interest and inspire many new opportunities across a broad range of disciplines.

Direct catechol conjugation of mussel-inspired biomacromolecule coatings to polymeric membranes with antifouling properties, anticoagulant activity and cytocompatibility

TheO-sulfated chitosan andN,O-sulfated chitosan coatings were prepared by direct catechol conjugation to enrich the biological applications of polymeric membranes.

Hydrogels based on poly(ethylene glycol) as scaffolds for tissue engineering application: biocompatibility assessment and effect of the sterilization process

Hydrogels are suitable materials to promote cell proliferation and tissue support because of their hydrophilic nature, porous structure and sticky properties. However, hydrogel synthesis involves the addition of additives that can increase the risk of inducing cytotoxicity. Sterilization is a critical process for hydrogel clinical use as a proper scaffold for tissue engineering. In this study, poly(ethylene glycol) (PEG), poly(ethylene glycol)-chitosan (PEG-CH) and multi-arm PEG hydrogels were synthesized by free radical polymerization and sterilized by gamma irradiation or disinfected using 70 % ethanol. The biocompatibility assessment in human fibroblasts and hemocompatibility studies (hemolysis, platelet aggregation, morphology of mononuclear cells and viability) in peripheral blood from healthy volunteers (ex vivo), were performed. The sterilization or disinfection effect on hydrogel structures was evaluated by FT-IR spectroscopy. Results indicated that hydrogels do not induce any damage to fibroblasts, erythrocytes, platelets or mononuclear cells. Moreover, there was no significant difference in the biocompatibility after the sterilization or disinfection treatment. However, after gamma irradiation, several IR spectroscopic bands were shifted to higher or lower energies with different intensity in all hydrogels. In particular, several bands associated to carboxyl or hydroxyl groups were slightly shifted, possibly associated to scission reactions. The disinfection treatment (70 % ethanol) and γ-irradiation at 13.83 ± 0.7 kGy did not induce morphological damages and yielded sterile and biocompatible PEG hydrogels potentially useful for clinical applications.

Heparin-Mimicking Polymers: Synthesis and Biological Applications

Heparin is a naturally occurring, highly sulfated polysaccharide that plays a critical role in a range of different biological processes. Therapeutically, it is mostly commonly used as an injectable solution as an anticoagulant for a variety of indications, although it has also been employed in other forms such as coatings on various biomedical devices. Due to the diverse functions of this polysaccharide in the body, including anticoagulation, tissue regeneration, anti-inflammation, and protein stabilization, and drawbacks of its use, analogous heparin-mimicking materials are also widely studied for therapeutic applications. This review focuses on one type of these materials, namely, synthetic heparin-mimicking polymers. Utilization of these polymers provides significant benefits compared to heparin, including enhancing therapeutic efficacy and reducing side effects as a result of fine-tuning heparin-binding motifs and other molecular characteristics. The major types of the various polymers are summarized, as well as their applications. Because development of a broader range of heparin-mimicking materials would further expand the impact of these polymers in the treatment of various diseases, future directions are also discussed.

Graphene oxide and sulfonated polyanion co-doped hydrogel films for dual-layered membranes with superior hemocompatibility and antibacterial activity

GO based dual-layered membranes with superior hemocompatibility and antibacterial activity have potential application for clinical hemodialysis and many other biomedical therapies.

Highly hemo-compatible, mechanically strong, and conductive dual cross-linked polymer hydrogels

Novel hydrogels with highly hemo-compatible, mechanically strong and conductive properties are developed as promising candidates for a wide range of biomedical applications.

Graphene oxide-based polyethersulfone core–shell particles for dye uptake

Graphene oxide (GO), a graphene nanomaterial with great application potential, possesses promising adsorption abilities towards various water contaminants due to the ultra-large surface area and the nature of electric charge on the surface.

Stimulus-responsive hydrogels reinforced by cellulose nanowhisker for controlled drug release

Hybrid hydrogels (W–C gels), composed of PDMAEMA, cellulose nanowhisker (CNW) and carboxymethyl chitosan (CMCS), were prepared for developing a stimuli-responsive drug-release system.

Graphene oxide linked sulfonate-based polyanionic nanogels as biocompatible, robust and versatile modifiers of ultrafiltration membranes

A GO linked sulfonate-based polyanionic nanogel as a membrane modifier has application potential in clinical hemodialysis and other biomedical therapies.

Highly swellable and biocompatible graphene/heparin-analogue hydrogels for implantable drug and protein delivery

The GO/heparin-analogue hydrogels with hemo- and cyto-compatibility could be used in various biomedical fields, such as drug and protein delivery, tissue regeneration scaffold, and other biomedical systems.

Development of novel hydrogels based on Salecan and poly(N-isopropylacrylamide-co-methacrylic acid) for controlled doxorubicin release

We designed a novel semi-interpenetrating polymer network hydrogel for the controlled delivery of doxorubicin.

Substrate-Independent Robust and Heparin-Mimetic Hydrogel Thin Film Coating via Combined LbL Self-Assembly and Mussel-Inspired Post-Cross-linking

In this work, we designed a robust and heparin-mimetic hydrogel thin film coating via combined layer-by-layer (LbL) self-assembly and mussel-inspired post-cross-linking. Dopamine-grafted heparin-like/-mimetic polymers (DA-g-HepLP) with abundant carboxylic and sulfonic groups were synthesized by the conjugation of adhesive molecule, DA, which exhibited substrate-independent adhesive affinity to various solid surfaces because of the formation of irreversible covalent bonds. The hydrogel thin film coated substrates were prepared by a three-step reaction: First, the substrates were coated with DA-g-HepLP to generate negatively charged surfaces. Then, multilayers were obtained via LbL coating of chitosan and the DA-g-HepLP. Finally, the noncovalent multilayers were oxidatively cross-linked by NaIO4. Surface ATR-FTIR and XPS spectra confirmed the successful fabrication of the hydrogel thin film coatings onto membrane substrates; SEM images revealed that the substrate-independent coatings owned 3D porous morphology. The soaking tests in highly alkaline, acid, and concentrated salt solutions indicated that the cross-linked hydrogel thin film coatings owned high chemical resistance. In comparison, the soaking tests in physiological solution indicated that the cross-linked hydrogel coatings owned excellent long-term stability. The live/dead cell staining and morphology observations of the adhered cells revealed that the heparin-mimetic hydrogel thin film coated substrates had low cell toxicity and high promotion ability for cell proliferation. Furthermore, systematic in vitro investigations of protein adsorption, platelet adhesion, blood clotting, and blood-related complement activation confirmed that the hydrogel film coated substrates showed excellent hemocompatibility. Both the results of inhibition zone and bactericidal activity indicated that the gentamycin sulfate loaded hydrogel thin films had significant inhibition capability toward both Escherichia coli and Staphylococcus aureus bacteria. Combined the above advantages, it is believed that the designed heparin-mimetic hydrogel thin films may show high potential for applications in various biological and clinical fields, such as long-term hemocompatible and drug-loading materials for implants.