Silk fibroin/sericin 3D sponges: The effect of sericin on structural and biological properties of fibroin.

Among naturally occurring polymers, silk fibroin and sericin have attracted much attention in the field of tissue engineering; however, clinical application of silk fibroin/sericin scaffolds in a combined form has been questioned due to the possible pro-inflammatory reaction against native silk and fibroin/sericin 3D constructs. The objective of this study was to fabricate 3D spongy fibroin/sericin scaffolds and to explore the structural, biological and immunological properties of different ratios of fibroin and sericin. Structural characterization revealed a highly porous structure (>91%) with a large surface area and water uptake capacity for all different fibroin/sericin scaffolds. Notably, the scaffolds showed enhanced mechanical properties and a higher degradation rate with increasing sericin content. Excellent cell attachment and no significant cytotoxicity were observed in all scaffold types 7 days after seeding of osteoblast-like MG63 cells. Gene expression of pro-inflammatory markers TNF-α, CXCL10 and CD197 as well as TNF-α secretion by THP-1-derived macrophages revealed no significant immune response to all fibroin/sericin scaffold types when compared to sericin-free F1:S0 samples and a TCP (Mɸ) control group. These results demonstrate that spongy fibroin/sericin scaffolds are able to support the growth of osteoblast-like cells without eliciting a pro-inflammatory response, thus being a promising material for bone tissue engineering.

Correction: Silk based scaffolds with immunomodulatory capacity: anti-inflammatory effects of nicotinic acid.

Correction for 'Silk based scaffolds with immunomodulatory capacity: anti-inflammatory effects of nicotinic acid' by Abdollah Zakeri Siavashani et al., Biomater. Sci., 2019, DOI: 10.1039/c9bm00814d.

Mussel-Inspired Injectable Hydrogel Adhesive Formed under Mild Conditions Features Near-Native Tissue Properties.

Injectable hydrogel adhesives, especially those that can strongly adhere to tissues and feature near-native tissue mechanical properties, are desirable biomaterials for tissue repair. Compared to nonadhesive injectable hydrogels for minimally invasive delivery of therapeutic agents, they can better retain the delivered agents at targeted tissue locations and provide additional local physical barriers. However, regardless of recent advances, an ideal injectable hydrogel adhesive with both proper adhesion and mechanical matching between hydrogels and tissues is yet to be demonstrated with cytocompatible and efficient in situ curing methods. Inspired by marine mussels, where different mussel foot proteins (Mfps) function cooperatively to achieve excellent wet adhesion, we herein report a dual-mode-mimicking strategy by modifying gelatin (Gel) biopolymers with a single-type thiourea-catechol (TU-Cat) functionality to mimic two types of Mfps and their mode of action. This strategy features a minor, yet impactful modification of biopolymers, which gives access to collective properties of an ideal injectable hydrogel adhesive. Specifically, with TU-Cat functionalization of only ∼0.4-1.2 mol % of total amino acid residues, the Mfp-mimetic gelatin biopolymer (Gel-TU-Cat) can be injected and cured rapidly under mild and cytocompatible conditions, giving rise to tissue adhesive hydrogels with excellent matrix ductility, proper wet adhesion, and native tissue-like stress relaxation behaviors. Such a set of properties originating from our novel dual-mode-mimicking strategy makes the injectable hydrogel adhesive a promising platform for cell delivery and tissue repair.

Silk based scaffolds with immunomodulatory capacity: anti-inflammatory effects of nicotinic acid.

Implantation of temporary and permanent biomaterials in the body leads to a foreign body reaction (FBR), which may adversely affect tissue repair processes and functional integration of the biomaterial. However, modulation of the inflammatory response towards biomaterials can potentially enable a favorable healing response associated with functional tissue formation and tissue regeneration. In this work, incorporation of nicotinic acid in 3D silk scaffolds is explored as an immunomodulatory strategy for implantable biomaterials. Silk scaffolds were fabricated from dissolved Bombyx mori silk fibers by freeze-drying, resulting in silk scaffolds with high porosity (>94%), well-connected macropores, a high swelling degree (>550%) and resistance to in vitro degradation. Furthermore, drug-loaded scaffolds displayed a sustained drug release and excellent cytocompatibility could be observed with osteoblast-like MG63 cells. Cultivating M1-like macrophages on the scaffolds revealed that scaffolds loaded with nicotinic acid suppress gene expression of pro-inflammatory markers TNF-α, CXCL10 and CD197 as well as secretion of TNF-α in a concentration dependant manner. Hence, this study provides insights into the possible application of nicotinic acid in tissue engineering to control inflammatory responses towards biomaterials and potentially help minimizing FBR.

Cell-Membrane-Inspired Silicone Interfaces that Mitigate Proinflammatory Macrophage Activation and Bacterial Adhesion.

Biofouling on silicone implants causes serious complications such as fibrotic encapsulation, bacterial infection, and implant failure. Here we report the development of antifouling, antibacterial silicones through covalent grafting with a cell-membrane-inspired zwitterionic gel layer composed of 2-methacryolyl phosphorylcholine (MPC). To investigate how substrate properties influence cell adhesion, we cultured human-blood-derived macrophages and Escherichia coli on poly(dimethylsiloxane) (PDMS) and MPC gel surfaces with a range of 0.5-50 kPa in stiffness. Cells attach to glass, tissue culture polystyrene, and PDMS surfaces, but they fail to form stable adhesions on MPC gel surfaces due to their superhydrophilicity and resistance to biofouling. Cytokine secretion assays confirm that MPC gels have a much lower potential to trigger proinflammatory macrophage activation than PDMS. Finally, modification of the PDMS surface with a long-term stable hydrogel layer was achieved by the surface-initiated atom-transfer radical polymerization (SI-ATRP) of MPC and confirmed by the decrease in contact angle from 110 to 20° and the >70% decrease in the attachment of macrophages and bacteria. This study provides new insights into the design of antifouling and antibacterial interfaces to improve the long-term biocompatibility of medical implants.

Toward Immunocompetent 3D Skin Models.

3D human skin models provide a platform for toxicity testing, biomaterials evaluation, and investigation of fundamental biological processes. However, the majority of current in vitro models lack an inflammatory system, vasculature, and other characteristics of native skin, indicating scope for more physiologically complex models. Looking at the immune system, there are a variety of cells that could be integrated to create novel skin models, but to do this effectively it is also necessary to understand the interface between skin biology and tissue engineering as well as the different roles the immune system plays in specific health and disease states. Here, a progress report on skin immunity and current immunocompetent skin models with a focus on construction methods is presented; scaffold and cell choice as well as the requirements of physiologically relevant models are elaborated. The wide range of technological and fundamental challenges that need to be addressed to successfully generate immunocompetent skin models and the steps currently being made globally by researchers as they develop new models are explored. Induced pluripotent stem cells, microfluidic platforms to control the model environment, and new real-time monitoring techniques capable of probing biochemical processes within the models are discussed.

Diabetic wound regeneration using heparin-mimetic peptide amphiphile gel in db/db mice.

There is an urgent need for more efficient treatment of chronic wounds in diabetic patients especially with a high risk of leg amputation. Biomaterials capable of presenting extracellular matrix-mimetic signals may assist in the recovery of diabetic wounds by creating a more conducive environment for blood vessel formation and modulating the immune system. In a previous study, we showed that glycosaminoglycan-mimetic peptide nanofibers are able to increase the rate of closure in STZ-induced diabetic rats by induction of angiogenesis. The present study investigates the effect of a heparin-mimetic peptide amphiphile (PA) nanofiber gel on full-thickness excisional wounds in a db/db diabetic mouse model, with emphasis on the ability of the PA nanofiber network to regulate angiogenesis and the expression of pro-inflammatory cytokines. Here, we showed that the heparin-mimetic PA gel can support tissue neovascularization, enhance the deposition of collagen and expression of alpha-smooth muscle actin (α-SMA), and eliminate the sustained presence of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) in the diabetic wound site. As the absence of neovascularization and overexpression of pro-inflammatory markers are a hallmark of diabetes and interfere with wound recovery by preventing the healing process, the heparin-mimetic PA treatment is a promising candidate for acceleration of diabetic wound healing by modulating angiogenesis and local immune response.

Inhibition of VEGF mediated corneal neovascularization by anti-angiogenic peptide nanofibers.

Atypical angiogenesis is one of the major symptoms of severe eye diseases, including corneal neovascularization, and the complex nature of abnormal vascularization requires targeted methods with high biocompatibility. The targeting of VEGF is the most common approach for preventing angiogenesis, and the LPPR peptide sequence is known to strongly inhibit VEGF activity by binding to the VEGF receptor neuropilin-1. Here, the LPPR epitope is presented on a peptide amphiphile nanofiber system to benefit from multivalency and increase the anti-angiogenic function of the epitope. Peptide amphiphile nanofibers are especially useful for ocular delivery applications due to their ability to remain on the site of interest for extended periods of time, facilitating the long-term presentation of bioactive sequences. Consequently, the LPPR sequence was integrated into a self-assembled peptide amphiphile network to increase its efficiency in the prevention of neovascularization. Anti-angiogenic effects of the peptide nanofibers were investigated by using both in vitro and in vivo models. LPPR-PA nanofibers inhibited endothelial cell proliferation, tube formation, and migration to a greater extent than the soluble LPPR peptide in vitro. In addition, the LPPR-PA nanofiber system led to the prevention of vascular maturation and the regression of angiogenesis in a suture-induced corneal angiogenesis model. These results show that the anti-angiogenic activity exhibited by LPPR peptide nanofibers may be utilized as a promising approach for the treatment of corneal angiogenesis.

Norrin mediates angiogenic properties via the induction of insulin-like growth factor-1.

Norrin is an angiogenic signaling molecule that activates canonical Wnt/ß-catenin signaling, and is involved in capillary formation in retina and brain. Moreover, Norrin induces vascular repair following an oxygen-induced retinopathy (OIR), the model of retinopathy of prematurity in mice. Since insulin-like growth factor (IGF)-1 is a very potent angiogenic molecule, we investigated if IGF-1 is a downstream mediator of Norrin's angiogenic properties. In retinae of transgenic mice with an ocular overexpression of Norrin (ßB1-Norrin), we found at postnatal day (P)11 a significant increase of IGF-1 mRNA compared to wild-type littermates. In addition, after treatment of cultured Müller cells or dermal microvascular endothelial cells with Norrin we observed an increase of IGF-1 and its mRNA, an effect that could be blocked with DKK-1, an inhibitor of Wnt/ß-catenin signaling. When OIR was induced, the expression of IGF-1 was significantly suppressed in both transgenic ßB1-Norrin mice and wild-type littermates when compared to wild-type animals that were housed in room air. Furthermore, at P13, one day after the mice had returned to normoxic conditions, IGF-1 levels were significantly higher in transgenic mice compared to wild-type littermates. Finally, after intravitreal injections of inhibitory α-IGF-1 antibodies at P12 or at P12 and P14, the Norrin-mediated vascular repair was significantly attenuated. We conclude that Norrin induces the expression of IGF-1 via an activation of the Wnt/ß-catenin signaling pathway, an effect that significantly contributes to the protective effects of Norrin against an OIR.

Angiogenic Peptide Nanofibers Improve Wound Healing in STZ-Induced Diabetic Rats.

Low expressions of angiogenic growth factors delay the healing of diabetic wounds by interfering with the process of blood vessel formation. Heparin mimetic peptide nanofibers can bind to and enhance production and activity of major angiogenic growth factors, including VEGF. In this study, we showed that heparin mimetic peptide nanofibers can serve as angiogenic scaffolds that allow slow release of growth factors and protect them from degradation, providing a new therapeutic way to accelerate healing of diabetic wounds. We treated wounds in STZ-induced diabetic rats with heparin mimetic peptide nanofibers and studied repair of full-thickness diabetic skin wounds. Wound recovery was quantified by analyses of re-epithelialization, granulation tissue formation and blood vessel density, as well as VEGF and inflammatory response measurements. Wound closure and granulation tissue formation were found to be significantly accelerated in heparin mimetic gel treated groups. In addition, blood vessel counts and the expressions of alpha smooth muscle actin and VEGF were significantly higher in bioactive gel treated animals. These results strongly suggest that angiogenic heparin mimetic nanofiber therapy can be used to support the impaired healing process in diabetic wounds.

Design of a Gd-DOTA-phthalocyanine conjugate combining MRI contrast imaging and photosensitization properties as a potential molecular theranostic.

The design and synthesis of a phthalocyanine--Gd-DOTA conjugate is presented to open the way to novel molecular theranostics, combining the properties of MRI contrast imaging with photodynamic therapy. The rational design of the conjugate integrates isomeric purity of the phthalocyanine core substitution, suitable biocompatibility with the use of polyoxo water-solubilizing substituents, and a convergent synthetic strategy ended by the use of click chemistry to graft the Gd-DOTA moiety to the phthalocyanine. Photophysical and photochemical properties, contrast imaging experiments and preliminary in vitro investigations proved that such a combination is relevant and lead to a new type of potential theranostic agent.

Designing an intracellular fluorescent probe for glutathione: two modulation sites for selective signal transduction.

A selective probe for glutathione was designed and synthesized. The design incorporates spatial and photophysical constraints for the maximal emission signal. Thus, pHs, as well as the intracellular thiol concentrations, determine the emission signal intensity through a tight control of charge-transfer and PeT processes. The probe works satisfactorily inside the human breast adenocarcinoma cells, highlighting GSH distribution in the cytosol.

Pluronic polymer capped biocompatible mesoporous silica nanocarriers.

A facile self-assembly method is described to prepare PEGylated silica nanocarriers using hydrophobic mesoporous silica nanoparticles and a pluronic F127 polymer. Pluronic capped nanocarriers revealed excellent dispersibility in biological media with cyto- and blood compatibilities.

Cytotoxic and bioactive properties of different color tulip flowers and degradation kinetic of tulip flower anthocyanins.

This study was conducted to determine the potential use of anthocyanin-based extracts (ABEs) of wasted tulip flowers as food/drug colorants. For this aim, wasted tulip flowers were samples and analyzed for their bioactive properties and cytotoxicity. Total phenolic contents of the extracts of the claret red (126.55 mg of gallic acid equivalent (GAE)/g dry extract) and orange-red (113.76 mg GAE/g dry extract) flowers were the higher than those of the other tulip flowers. Total anthocyanin levels of the violet, orange-red, claret red and pink tulip flower extracts were determined as 265.04, 236.49, 839.08 and 404.45 mg pelargonidin 3-glucoside/kg dry extract, respectively and these levels were higher than those of the other flowers. The extracts were more effective for the inhibition of Listeria monocytogenes, Staphylococcus aureus and Yersinia enterocolitica compared to other tested bacteria. Additionally, the cytotoxic effects of five different tulip flower extracts on human breast adenocarcinoma (MCF-7) cell line were investigated. The results showed that the orange red, pink and violet extracts had no cytotoxic activity against MCF-7 cell lines while yellow and claret red extracts appeared to be toxic for the cells. Overall, the extracts of tulip flowers with different colors possess remarkable bioactive and cytotoxic properties.