BackgroundThe tumor microenvironment contains a vast array of pro- and anti-inflammatory cytokines that alter myelopoiesis and lead to the maturation of immunosuppressive cells known as myeloid-derived suppressor cells (MDSCs). Incubating bone marrow (BM) precursors with a combination of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-6 (IL-6) generated a tumor-infiltrating MDSC-like population that impaired anti-tumor specific T-cell functions. This in vitro experimental approach was used to simulate MDSC maturation, and the cellular metabolic response was then monitored. A complementary experimental model that inhibited L-arginine (L-Arg) metabolizing enzymes in MSC-1 cells, an immortalized cell line derived from primary MDSCs, was used to study the metabolic events related to immunosuppression.ResultsExposure of BM cells to GM-CSF and IL-6 activated, within 24 h, L-Arg metabolizing enzymes which are responsible for the MDSCs immunosuppressive potential. This was accompanied by an increased uptake of L-glutamine (L-Gln) and glucose, the latter being metabolized by anaerobic glycolysis. The up-regulation of nutrient uptake lead to the accumulation of TCA cycle intermediates and lactate as well as the endogenous synthesis of L-Arg and the production of energy-rich nucleotides. Moreover, inhibition of L-Arg metabolism in MSC-1 cells down-regulated central carbon metabolism activity, including glycolysis, glutaminolysis and TCA cycle activity, and led to a deterioration of cell bioenergetic status. The simultaneous increase of cell specific concentrations of ATP and a decrease in ATP-to-ADP ratio in BM-derived MDSCs suggested cells were metabolically active during maturation. Moreover, AMP-activated protein kinase (AMPK) was activated during MDSC maturation in GM-CSF and IL-6–treated cultures, as revealed by the continuous increase of AMP-to-ATP ratios and the phosphorylation of AMPK. Likewise, AMPK activity was decreased in MSC-1 cells when L-Arg metabolizing enzymes were inhibited. Finally, inhibition of AMPK activity by the specific inhibitor Compound C (Comp-C) resulted in the inhibition of L-Arg metabolizing enzyme activity and abolished MDSCs immunosuppressive activity.ConclusionsWe anticipate that the inhibition of AMPK and the control of metabolic fluxes may be considered as a novel therapeutic target for the recovery of the immunosurveillance process in cancer-bearing hosts.

Demand for long‐lasting antifouling surfaces has steered the development of accessible, novel, biocompatible and environmentally friendly materials. Inspired by lubricin (LUB), a component of mammalian synovial fluid with excellent antifouling properties, three block polymers offering stability, efficacy, and ease of use were designed. The bottlebrush‐structured polymers adsorbed strongly on silica surfaces in less than 10 minutes by a simple drop casting or online exposure method and were extremely stable in high‐salinity solutions and across a wide pH range. Antifouling properties against proteins and bacteria were evaluated with different techniques and ultralow fouling properties demonstrated. With serum albumin and lysozyme adsorption <0.2 ng cm−2, the polymers were 50 and 25 times more effective than LUB and known ultralow fouling coatings. The antifouling properties were also tested under MPa compression pressures by direct force measurements using surface forces apparatus. The findings suggest that these polymers are among the most robust and efficient antifouling agents currently known.

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Collagen-based biomaterials are widely used in the field of tissue engineering; they can be loaded with biomolecules such as growth factors (GFs) to modulate the biological response of the host and thus improve its potential for regeneration. Recombinant chimeric GFs fused to a collagen-binding domain (CBD) have been reported to improve their bioavailability and the host response, especially when combined with an appropriate collagen-based biomaterial. This review first provides an extensive description of the various CBDs that have been fused to proteins, with a focus on the need for accurate characterization of their interaction with collagen. The second part of the review highlights the benefits of various CBD/GF fusion proteins that have been designed for wound healing and bone regeneration.

Growth factors (GFs) are potent signaling molecules that act in a coordinated manner in physiological processes such as tissue healing or angiogenesis. Co-immobilizing GFs on materials while preserving their bioactivity still represents a major challenge in the field of tissue regeneration and bioactive implants. In this study, we explore the potential of an oriented immobilization technique based on two high affinity peptides, namely the Ecoil and Kcoil, to allow for the simultaneous capture of the epidermal growth factor (EGF) and the vascular endothelial growth factor (VEGF) on a chondroitin sulfate coating. This glycosaminoglycan layer was selected as it promotes cell adhesion but reduces non-specific adsorption of plasma proteins. We demonstrate here that both Ecoiltagged GFs can be successfully immobilized on chondroitin sulfate surfaces that had been pre-decorated with the Kcoil peptide. As shown by direct ELISA, changing the incubation concentration of the various GFs enabled to control their grafted amount.Moreover, cell survival studies with endothelial and smooth muscle cells confirmed that our oriented tethering strategy preserved GF bioactivity. Of salient interest, coimmobilizing EGF and VEGF led to better cell survival compared to each GF captured alone, suggesting a synergistic effect of these GFs. Altogether, these results demonstrate the potential of coiled-coil oriented GF tethering for the co-immobilization of macromolecules; it thus open the way to the generation of biomaterials surfaces with fine-tuned biological properties.

Demand for long‐lasting antifouling surfaces has steered the development of accessible, novel, biocompatible and environmentally friendly materials. Inspired by lubricin (LUB), a component of mammalian synovial fluid with excellent antifouling properties, three block polymers offering stability, efficacy, and ease of use were designed. The bottlebrush‐structured polymers adsorbed strongly on silica surfaces in less than 10 minutes by a simple drop casting or online exposure method and were extremely stable in high‐salinity solutions and across a wide pH range. Antifouling properties against proteins and bacteria were evaluated with different techniques and ultralow fouling properties demonstrated. With serum albumin and lysozyme adsorption <0.2 ng cm−2, the polymers were 50 and 25 times more effective than LUB and known ultralow fouling coatings. The antifouling properties were also tested under MPa compression pressures by direct force measurements using surface forces apparatus. The findings suggest that these polymers are among the most robust and efficient antifouling agents currently known.

Biofunctionalized nanomaterials have been extensively studied as a tool for a wide range of applications in biomedical fields. Despite many existing strategies to conjugate proteins to colloidal particles, determining the grafting efficiency that is, the amount of protein conjugated to the surface of a nanoparticle (NP)remains challenging. Formulations for biomedical applications are subjected to strict constraints, and a lack of precise characterization can prevent otherwise promising formulations to be explored further. Here, we propose a simple approach to precisely measure the grafting efficiency of biological molecules on the surface of three types of widely used NPs: polymeric NPs, inorganic NPs, and metallic NPs. This approach relies on the simultaneous hydrolysis of the grafted protein and the NP degradation in acidic conditions, followed by a spectrophotometric quantification of primary amines in solution. This strategy can be applied to any type of protein and does not require any labeling agent. It can be performed in a high-throughput manner as a routine experiment and only requires a conventional oven and a microplate reader.